无线通信基础-毕业论文外文翻译
毕设外文原文及译文
北京联合大学毕业设计（论文）任务书题目：OFDM调制解调技术的设计与仿真实现专业：通信工程指导教师：张雪芬学院：信息学院学号：2011080331132班级：1101B姓名：徐嘉明一、外文原文Evolution Towards 5G Multi-tier Cellular WirelessNetworks:An Interference ManagementPerspectiveEkram Hossain, Mehdi Rasti, Hina Tabassum, and Amr AbdelnasserAbstract—The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, e.g., higher data rates, excellent end-to-end performance and user-coverage in hot-spots and crowded areas with lower latency, energy consumption and cost per information transfer. To address these challenges, 5G systems will adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g., power control, cell association) in these networks with shared spectrum access (i.e., when the different network tiers share the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multitier networks where users in different tiers have different priorities for channel access. In this context, a survey and qualitative comparison of the existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems.Index Terms—5G cellular wireless, multi-tier networks, interference management, cell association, power control.I. INTRODUCTIONTo satisfy the ever-increasing demand for mobile broadband communications, the IMT-Advanced (IMT-A) standards have been ratified by the International Telecommunications Union (ITU) in November 2010 and the fourth generation (4G) wireless communication systems are currently being deployed worldwide. The standardization for LTE Rel-12, also known as LTE-B, is also ongoing and expected to be finalized in 2014. Nonetheless, existing wireless systems will not be able to deal with the thousand-fold increase in total mobile broadband data [1] contributed by new applications and services such as pervasive 3D multimedia, HDTV, VoIP, gaming, e-Health, and Car2x communication. In this context, the fifth generation (5G) wireless communication technologies are expected to attain 1000 times higher mobile data volume per unit area,10-100 times higher number of connecting devices and user data rate, 10 times longer battery life and 5 times reduced latency [2]. While for 4G networks the single-user average data rate is expected to be 1 Gbps, it is postulated that cell data rate of theorder of 10 Gbps will be a key attribute of 5G networks.5G wireless networks are expected to be a mixture of network tiers of different sizes, transmit powers, backhaul connections, different radio access technologies (RATs) that are accessed by an unprecedented numbers of smart and heterogeneous wireless devices. This architectural enhancement along with the advanced physical communications technology such as high-order spatial multiplexing multiple-input multiple-output (MIMO) communications will provide higher aggregate capacity for more simultaneous users, or higher level spectral efficiency, when compared to the 4G networks. Radio resource and interference management will be a key research challenge in multi-tier and heterogeneous 5G cellular networks. The traditional methods for radio resource and interference management (e.g., channel allocation, power control, cell association or load balancing) in single-tier networks (even some of those developed for two-tier networks) may not be efficient in this environment and a new look into the interference management problem will be required.First, the article outlines the visions and requirements of 5G cellular wireless systems. Major research challenges are then highlighted from the perspective of interference management when the different network tiers share the same radio spectrum. A comparative analysis of the existing approaches for distributed cell association and power control (CAPC) is then provided followed by a discussion on their limitations for5G multi-tier cellular networks. Finally, a number of suggestions are provided to modifythe existing CAPC schemes to overcome these limitations.II. VISIONS AND REQUIREMENTS FOR 5G MULTI-TIERCELLULAR NETWORKS5G mobile and wireless communication systems will require a mix of new system concepts to boost the spectral and energy efficiency. The visions and requirements for 5G wireless systems are outlined below.·Data rate and latency: For dense urban areas, 5G networks are envisioned to enable an experienced data rate of 300 Mbps and 60 Mbps in downlink and uplink, respectively, in 95% of locations and time [2]. The end-to- end latencies are expected to be in the order of 2 to 5 milliseconds. The detailed requirements for different scenarios are listed in [2].·Machine-type Communication (MTC) devices: The number of traditional human-centric wireless devices with Internet connectivity (e.g., smart phones, super-phones, tablets) may be outnumbered by MTC devices which can be used in vehicles, home appliances, surveillance devices, and sensors.·Millimeter-wave communication: To satisfy the exponential increase in traffic and the addition of different devices and services, additional spectrum beyond what was previously allocated to 4G standard is sought for. The use of millimeter-wave frequency bands (e.g., 28 GHz and 38 GHz bands) is a potential candidate to overcome the problem of scarce spectrum resources since it allows transmission at wider bandwidths than conventional 20 MHz channels for 4G systems.·Multiple RATs: 5G is not about replacing the existing technologies, but it is about enhancing and supporting them with new technologies [1]. In 5G systems, the existing RATs, including GSM (Global System for Mobile Communications), HSPA+ (Evolved High-Speed Packet Access), and LTE, will continue to evolve to provide a superior system performance. They will also be accompanied by some new technologies (e.g., beyondLTE-Advanced).·Base station (BS) densification: BS densification is an effective methodology to meet the requirements of 5G wireless networks. Specifically, in 5G networks, there will be deployments of a large number of low power nodes, relays, and device-to-device (D2D) communication links with much higher density than today’s macrocell networks.Fig. 1 shows such a multi-tier network with a macrocell overlaid by relays, picocells, femtocells, and D2D links. The adoption of multiple tiers in the cellular networkarchitecture will result in better performance in terms of capacity, coverage, spectral efficiency, and total power consumption, provided that the inter-tier and intratier interferences are well managed.·Prioritized spectrum access: The notions of both trafficbased and tier-based Prioriti -es will exist in 5G networks. Traffic-based priority arises from the different requirements of the users (e.g., reliability and latency requirements, energy constraints), whereas the tier-based priority is for users belonging to different network tiers. For example, with shared spectrum access among macrocells and femtocells in a two-tier network, femtocells create ―dead zones‖ around them in the downlink for macro users. Protection should, thus, be guaranteed for the macro users. Consequently, the macro and femtousers play the role of high-priority users (HPUEs) and lowpriority users (LPUEs), respectively. In the uplink direction, the macrocell users at the cell edge typically transmit with high powers which generates high uplink interference to nearby femtocells. Therefore, in this case, the user priorities should get reversed. Another example is a D2D transmission where different devices may opportunistically access the spectrum to establish a communication link between them provided that the interference introduced to the cellular users remains below a given threshold. In this case, the D2D users play the role of LPUEs whereas the cellular users play the role of HPUEs.·Network-assisted D2D communication: In the LTE Rel- 12 and beyond, focus will be on network controlled D2D communications, where the macrocell BS performs control signaling in terms of synchronization, beacon signal configuration and providing identity and security management [3]. This feature will extend in 5G networks to allow other nodes, rather than the macrocell BS, to have the control. For example, consider a D2D link at the cell edge and the direct link between the D2D transmitter UE to the macrocell is in deep fade, then the relay node can be responsible for the control signaling of the D2Dlink (i.e., relay-aided D2D communication).·Energy harvesting for energy-efficient communication: One of the main challenges in 5G wireless networks is to improve the energy efficiency of the battery-constrained wireless devices. To prolong the battery lifetime as well as to improve the energy efficiency, an appealing solution is to harvest energy from environmental energy sources (e.g., solar and wind energy). Also, energy can be harvested from ambient radio signals (i.e., RF energy harvesting) with reasonable efficiency over small distances. The havested energy could be used for D2D communication or communication within a small cell. Inthis context, simultaneous wireless information and power transfer (SWIPT) is a promising technology for 5G wireless networks. However, practical circuits for harvesting energy are not yet available since the conventional receiver architecture is designed for information transfer only and, thus, may not be optimal for SWIPT. This is due to the fact that both information and power transfer operate with different power sensitivities at the receiver (e.g., -10dBm and -60dBm for energy and information receivers, respectively) [4]. Also, due to the potentially low efficiency of energy harvesting from ambient radio signals, a combination of different energy harvesting technologies may be required for macrocell communication.III. INTERFERENCE MANAGEMENT CHALLENGES IN 5GMULTI-TIER NETWORKSThe key challenges for interference management in 5G multi-tier networks will arise due to the following reasons which affect the interference dynamics in the uplink and downlink of the network: (i) heterogeneity and dense deployment of wireless devices, (ii) coverage and traffic load imbalance due to varying transmit powers of different BSs in the downlink, (iii) public or private access restrictions in different tiers that lead to diverse interference levels, and (iv) the priorities in accessing channels of different frequencies and resource allocation strategies. Moreover, the introduction of carrier aggregation, cooperation among BSs (e.g., by using coordinated multi-point transmission (CoMP)) as well as direct communication among users (e.g., D2D communication) may further complicate the dynamics of the interference. The above factors translate into the following key challenges.·Designing optimized cell association and power control (CAPC) methods for multi-tier networks: Optimizing the cell associations and transmit powers of users in the uplink or the transmit powers of BSs in the downlink are classical techniques to simultaneously enhance the system performance in various aspects such as interference mitigation, throughput maximization, and reduction in power consumption. Typically, the former is needed to maximize spectral efficiency, whereas the latter is required to minimize the power (and hence minimize the interference to other links) while keeping theFig. 1. A multi-tier network composed of macrocells, picocells, femtocells, relays, and D2D links.Arrows indicate wireless links, whereas the dashed lines denote the backhaul connections. desired link quality. Since it is not efficient to connect to a congested BS despite its high achieved signal-to-interference ratio (SIR), cell association should also consider the status of each BS (load) and the channel state of each UE. The increase in the number of available BSs along with multi-point transmissions and carrier aggregation provide multiple degrees of freedom for resource allocation and cell-selection strategies. For power control, the priority of different tiers need also be maintained by incorporating the quality constraints of HPUEs. Unlike downlink, the transmission power in the uplink depends on the user’s batt ery power irrespective of the type of BS with which users are connected. The battery power does not vary significantly from user to user; therefore, the problems of coverage and traffic load imbalance may not exist in the uplink. This leads to considerable asymmetries between the uplink and downlink user association policies. Consequently, the optimal solutions for downlink CAPC problems may not be optimal for the uplink. It is therefore necessary to develop joint optimization frameworks that can provide near-optimal, if not optimal, solutions for both uplink and downlink. Moreover, to deal with this issue of asymmetry, separate uplink and downlink optimal solutions are also useful as far as mobile users can connect with two different BSs for uplink and downlink transmissions which is expected to be the case in 5G multi-tier cellular networks [3].·Designing efficient methods to support simultaneous association to multiple BSs: Compared to existing CAPC schemes in which each user can associate to a singleBS, simultaneous connectivity to several BSs could be possible in 5G multi-tier network. This would enhance the system throughput and reduce the outage ratio by effectively utilizing the available resources, particularly for cell edge users. Thus the existing CAPCschemes should be extended to efficiently support simultaneous association of a user to multiple BSs and determine under which conditions a given UE is associated to which BSs in the uplink and/or downlink.·Designing efficient methods for cooperation and coordination among multiple tiers: Cooperation and coordination among different tiers will be a key requirement to mitigate interference in 5G networks. Cooperation between the macrocell and small cells was proposed for LTE Rel-12 in the context of soft cell, where the UEs are allowed to have dual connectivity by simultaneously connecting to the macrocell and the small cell for uplink and downlink communications or vice versa [3]. As has been mentioned before in the context of asymmetry of transmission power in uplink and downlink, a UE may experience the highest downlink power transmission from the macrocell, whereas the highest uplink path gain may be from a nearby small cell. In this case, the UE can associate to the macrocell in the downlink and to the small cell in the uplink. CoMP schemes based on cooperation among BSs in different tiers (e.g., cooperation between macrocells and small cells) can be developed to mitigate interference in the network. Such schemes need to be adaptive and consider user locations as well as channel conditions to maximize the spectral and energy efficiency of the network. This cooperation however, requires tight integration of low power nodes into the network through the use of reliable, fast andlow latency backhaul connections which will be a major technical issue for upcoming multi-tier 5G networks. In the remaining of this article, we will focus on the review of existing power control and cell association strategies to demonstrate their limitations for interference management in 5G multi-tier prioritized cellular networks (i.e., where users in different tiers have different priorities depending on the location, application requirements and so on). Design guidelines will then be provided to overcome these limitations. Note that issues such as channel scheduling in frequency domain, timedomain interference coordination techniques (e.g., based on almost blank subframes), coordinated multi-point transmission, and spatial domain techniques (e.g., based on smart antenna techniques) are not considered in this article.IV. DISTRIBUTED CELL ASSOCIATION AND POWERCONTROL SCHEMES: CURRENT STATE OF THE ARTA. Distributed Cell Association SchemesThe state-of-the-art cell association schemes that are currently under investigation formulti-tier cellular networks are reviewed and their limitations are explained below.·Reference Signal Received Power (RSRP)-based scheme [5]: A user is associated with the BS whose signal is received with the largest average strength. A variant of RSRP, i.e., Reference Signal Received Quality (RSRQ) is also used for cell selection in LTE single-tier networks which is similar to the signal-to-interference (SIR)-based cell selection where a user selects a BS communicating with which gives the highest SIR. In single-tier networks with uniform traffic, such a criterion may maximize the network throughput. However, due to varying transmit powers of different BSs in the downlink of multi-tier networks, such cell association policies can create a huge traffic load imbalance. This phenomenon leads to overloading of high power tiers while leaving low power tiers underutilized.·Bias-based Cell Range Expansion (CRE) [6]: The idea of CRE has been emerged as a remedy to the problem of load imbalance in the downlink. It aims to increase the downlink coverage footprint of low power BSs by adding a positive bias to their signal strengths (i.e., RSRP or RSRQ). Such BSs are referred to as biased BSs. This biasing allows more users to associate with low power or biased BSs and thereby achieve a better cell load balancing. Nevertheless, such off-loaded users may experience unfavorable channel from the biased BSs and strong interference from the unbiased high-power BSs. The trade-off between cell load balancing and system throughput therefore strictly depends on the selected bias values which need to be optimized in order to maximize the system utility. In this context, a baseline approach in LTE-Advanced is to ―orthogonalize‖ the transmissions of the biased and unbiased BSs in time/frequency domain such that an interference-free zone is created.·Association based on Almost Blank Sub-frame (ABS) ratio [7]: The ABS technique uses time domain orthogonalization in which specific sub-frames are left blank by the unbiased BS and off-loaded users are scheduled within these sub-frames to avoid inter-tier interference. This improves the overall throughput of the off-loaded users by sacrificing the time sub-frames and throughput of the unbiased BS. The larger bias values result in higher degree of offloading and thus require more blank subframes to protect the offloaded users. Given a specific number of ABSs or the ratio of blank over total number of sub-frames (i.e., ABS ratio) that ensures the minimum throughput of the unbiased BSs, this criterion allows a user to select a cell with maximum ABS ratio and may even associate with the unbiased BS if ABS ratio decreases significantly. A qualitative comparison amongthese cell association schemes is given in Table I. The specific key terms used in Table I are defined as follows: channel-aware schemes depend on the knowledge of instantaneous channel and transmit power at the receiver. The interference-aware schemes depend on the knowledge of instantaneous interference at the receiver. The load-aware schemes depend on the traffic load information (e.g., number of users). The resource-aware schemes require the resource allocation information (i.e., the chance of getting a channel or the proportion of resources available in a cell). The priority-aware schemes require the information regarding the priority of different tiers and allow a protection to HPUEs. All of the above mentioned schemes are independent, distributed, and can be incorporated with any type of power control scheme. Although simple and tractable, the standard cell association schemes, i.e., RSRP, RSRQ, and CRE are unable to guarantee the optimum performance in multi-tier networks unless critical parameters, such as bias values, transmit power of the users in the uplink and BSs in the downlink, resource partitioning, etc. are optimized.B. Distributed Power Control SchemesFrom a user’s point of view, the objective of power control is to support a user with its minimum acceptable throughput, whereas from a system’s point of view it is t o maximize the aggregate throughput. In the former case, it is required to compensate for the near-far effect by allocating higher power levels to users with poor channels as compared to UEs with good channels. In the latter case, high power levels are allocated to users with best channels and very low (even zero) power levels are allocated to others. The aggregate transmit power, the outage ratio, and the aggregate throughput (i.e., the sum of achievable rates by the UEs) are the most important measures to compare the performance of different power control schemes. The outage ratio of a particular tier can be expressed as the ratio of the number of UEs supported by a tier with their minimum target SIRs and the total number of UEs in that tier. Numerous power control schemes have been proposed in the literature for single-tier cellular wireless networks. According to the corresponding objective functions and assumptions, the schemes can be classified into the following four types.·Target-SIR-tracking power control (TPC) [8]: In the TPC, each UE tracks its own predefined fixed target-SIR. The TPC enables the UEs to achieve their fixed target-TABLE IQUALITATIVE COMPARISON OF EXISTING CELL ASSOCIATION SCHEMESFOR MULTI-TIER NETWORKSSIRs at minimal aggregate transmit power, assuming thatthe target-SIRs are feasible. However, when the system is infeasible, all non-supported UEs (those who cannot obtain their target-SIRs) transmit at their maximum power, which causes unnecessary power consumption and interference to other users, and therefore, increases the number of non-supported UEs.·TPC with gradual removal (TPC-GR) [9], [10], and [11]:To decrease the outage ra -tio of the TPC in an infeasiblesystem, a number of TPC-GR algorithms were proposedin which non-supported users reduce their transmit power[10] or are gradually removed [9], [11].·Opportunistic power control (OPC) [12]: From the system’s point of view, OPC allocates high power levels to users with good channels (experiencing high path-gains and low interference levels) and very low power to users with poor channels. In this algorithm, a small difference in path-gains between two users may lead to a large difference in their actual throughputs [12]. OPC improves the system performance at the cost of reduced fairness among users.·Dynamic-SIR tracking power control (DTPC) [13]: When the target-SIR requirements for users are feasible, TPC causes users to exactly hit their fixed target-SIRs even if additional resources are still available that can otherwise be used to achieve higher SIRs (and thus better throughputs). Besides, the fixed-target-SIR assignment is suitable only for voice service for which reaching a SIR value higher than the given target value does not affect the service quality significantly. In contrast, for data services, a higher SIR results in a better throughput, which is desirable. The DTPC algorithm was proposed in [13] to address the problem of system throughput maximization subject to a given feasible lower bound for the achieved SIRs of all users in cellular networks. In DTPC, each user dynamically sets its target-SIR by using TPC and OPC in a selective manner. It was shown that when the minimum acceptable target-SIRs are feasible, the actual SIRs received by some users can be dynamically increased (to a value higher than their minimum acceptabletarget-SIRs) in a distributed manner so far as the required resources are available and the system remains feasible (meaning that reaching the minimum target-SIRs for the remaining users are guaranteed). This enhances the system throughput (at the cost of higher power consumption) as compared to TPC. The aforementioned state-of-the-art distributed power control schemes for satisfying various objectives in single-tier wireless cellular networks are unable to address the interference management problem in prioritized 5G multi-tier networks. This is due to the fact that they do not guarantee that the total interference caused by the LPUEs to the HPUEs remain within tolerable limits, which can lead to the SIR outage of some HPUEs. Thus there is a need to modify the existing schemes such that LPUEs track their objectives while limiting their transmit power to maintain a given interference threshold at HPUEs. A qualitative comparison among various state-of-the-art power control problems with different objectives and constraints and their corresponding existing distributed solutions are shown in Table II. This table also shows how these schemes can be modified and generalized for designing CAPC schemes for prioritized 5G multi-tier networks.C. Joint Cell Association and Power Control SchemesA very few work in the literature have considered the problem of distributed CAPC jointly (e.g., [14]) with guaranteed convergence. For single-tier networks, a distributed framework for uplink was developed [14], which performs cell selection based on the effective-interference (ratio of instantaneous interference to channel gain) at the BSs and minimizes the aggregate uplink transmit power while attaining users’ desire d SIR targets. Following this approach, a unified distributed algorithm was designed in [15] for two-tier networks. The cell association is based on the effective-interference metric and is integrated with a hybrid power control (HPC) scheme which is a combination of TPC and OPC power control algorithms.Although the above frameworks are distributed and optimal/ suboptimal with guaranteed convergence in conventional networks, they may not be directly compatible to the 5G multi-tier networks. The interference dynamics in multi-tier networks depends significantly on the channel access protocols (or scheduling), QoS requirements and priorities at different tiers. Thus, the existing CAPC optimization problems should be modified to include various types of cell selection methods (some examples are provided in Table I) and power control methods with different objectives and interference constraints (e.g., interference constraints for macro cell UEs, picocell UEs, or D2Dreceiver UEs). A qualitative comparison among the existing CAPC schemes along with the open research areas are highlighted in Table II. A discussion on how these open problems can be addressed is provided in the next section.V. DESIGN GUIDELINES FOR DISTRIBUTED CAPCSCHEMES IN 5G MULTI-TIER NETWORKSInterference management in 5G networks requires efficient distributed CAPC schemes such that each user can possibly connect simultaneously to multiple BSs (can be different for uplink and downlink), while achieving load balancing in different cells and guaranteeing interference protection for the HPUEs. In what follows, we provide a number of suggestions to modify the existing schemes.A. Prioritized Power ControlTo guarantee interference protection for HPUEs, a possible strategy is to modify the existing power control schemes listed in the first column of Table II such that the LPUEs limit their transmit power to keep the interference caused to the HPUEs below a predefined threshold, while tracking their own objectives. In other words, as long as the HPUEs are protected against existence of LPUEs, the LPUEs could employ an existing distributed power control algorithm to satisfy a predefined goal. This offers some fruitful direction for future research and investigation as stated in Table II. To address these open problems in a distributed manner, the existing schemes should be modified so that the LPUEs in addition to setting their transmit power for tracking their objectives, limit their transmit power to keep their interference on receivers of HPUEs below a given threshold. This could be implemented by sending a command from HPUEs to its nearby LPUEs (like a closed-loop power control command used to address the near-far problem), when the interference caused by the LPUEs to the HPUEs exceeds a given threshold. We refer to this type of power control as prioritized power control. Note that the notion of priority and thus the need of prioritized power control exists implicitly in different scenarios of 5G networks, as briefly discussed in Section II. Along this line, some modified power control optimization problems are formulated for 5G multi-tier networks in second column of Table II.To compare the performance of existing distributed power control algorithms, let us consider a prioritized multi-tier cellular wireless network where a high-priority tier consisting of 3×3 macro cells, each of which covers an area of 1000 m×1000 m, coexists with a low-priority tier consisting of n small-cells per each high-priority macro cell, each。
网络工程 英文 毕业 设计 论文 文献翻译 无线技术
毕业论文（文献翻译）单位代码01学号_080114601_分类号_ TN92 _密级__________文献翻译无线技术，低功耗传感器网络无线技术，低功耗传感器网络译文正文：加里莱格在发掘无线传感器的潜在应用方面我们几乎没遇见任何困难。
比如说在家庭安全系统方面，无线传感器比有线传感器更易安装。
而无线传感器的安装费用通常只占有线传感器安装费用的80%，这一点用于工业环境方面同样合适。
并且相对于有线传感器而言，无线传感器应用性更强。
虽然，无线传感器需要消耗更多能量，也就是说所需电池的数量会随之增加或更换过于频繁。
再加上对无线传感器由空气传送的数据可靠性的怀疑论，所以无线传感器看起来并不是那么吸引人。
一个被称为ZigBee的低功率无线技术，它是无线传感器方程重写，但是，通过的IEEE 802.15.4无线标准（图1），ZigBee承诺，把无线传感器的一切，从工厂自动化系统延伸到家庭安全系统，消费电子产品中。
与802.15.4的合作下，ZigBee提供的电池寿命可比普通小型电池长几年。
ZigBee设备预计也便宜，有人估计销售价格最终不到3美元每节点，。
由于价格低，他们应该也能适用于无线交换机，无线自动调温器，烟雾探测器等产品。
图1：ZigBee将网络安全和应用服务层添加到PHY和IEEE811.15.4网络通信的MAC层虽然还没有正式规范的ZigBee存在，但ZigBee的前景似乎一片光明。
技术研究公司In-Stat/MDR在它所谓的“谨慎进取”的预测中预测，802.15.4节点和芯片销售将从今天基本上为零，增加到2010年的165万台。
不是所有这些单位都将与ZigBee结合，但大多数可能会。
世界研究公司预测，到2010年射频模块无线传感器出货量4.65亿美量，其中77％是与ZigBee相关的。
从某种意义上说，ZigBee的光明前途在很大程度上是由于其较低的数据速率（20 kbps到250 kbps），而这些数据率则取决于频段频率（图2）。
TheCapacityofWirelessNetworks中文翻译-22页精选文档
无线网络的容量The Capacity of Wireless Networks(Piyush Gupta, Student Member, IEEE, and P.R. Kumar, Fellow, IEEE)翻译：陈海强学号：08110607摘要：固定范围内的n 个随机放置同类节点构成一个无线网络，每个节点传输能力为W bit/s ，在使用无干扰协议，且每个节点的目的节点是随机选择时，可获得网络吞吐量λ(n)是 )log (n n WΘ bit/s 。
如果节点以最优的方式放置在单位面积的圆盘上，业务模式、传输范围都是最优化的配置，在这种情况下，网络每秒钟能够传输的比特-距离乘积是 )(An WΘ bit •m/s 。
因此，即便是在最优环境下，每个节点获得的吞吐量也只能是)(n WΘ bit/s 。
对于一个物理模型可选的网络也具有类似的结果。
在这种网络中，为了保证成功接收，需要一个特定的信干比（信号干扰比SIR ：Signal-to-Interference Ratio ）。
实际上，在整个网络覆盖区域内，每个节点都需要和它的本地相邻节点共享一定比例的无线信道，这是网络容量产生瓶颈的原因。
把信道分割成多个子信道不改变这个结果。
论文得到的一些概念和启示对设计者来说可能具有一定的价值。
既然分配到每个用户的吞吐量会随着用户数目的增多而逐渐下降至零，因此设计一个用户数目较少的网络或者配置连接特性，使得节点主要与邻近节点相连接是一种可行的方案。
关键词：Ad hoc 网络，容量，多跳无线通信网，吞吐量，无线网络Ⅰ 引言无线网络由众多使用无线信道通信的节点构成。
某些无线网络的主干网使用有线连接，而在最后一跳使用无线连接，比如蜂窝语音和数据通信网以及移动IP 等。
也有一些网络，它所有的连接都是无线的，如多跳无线通信网以及ad hoc 网络等。
此外，一些比较新潮的例子[1]，例如“智能住宅”，它把计算机、微波炉、门锁、洒水机以及其它的“信息设备”通过无线网络连接起来。
[最新]通信专业的外文及外文翻译
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Research,,,,,on,,,,,Carrier,,,,,T racking,,,,,in,,,,,Hybrid,,, ,,DS/FH,,,,,Spread,,,,,Spectrum,,,,,TT&C,,,,,SystemAbstractBecause,,,,,of,,,,,the,,,,,effect,,,,,of,,,,,carrier,,,,,frequency,,,,,hopping,,,,,,the,,,,,inp ut,,,,,IF,,,,,signal,,,,,of,,,,,carrier,,,,,tracking,,,,,loop,,,,,in,,,,,DS/FHSS,,,,,(Direct,,,,,Sequ ence/Frequency,,,,,Hopping,,,,,Spread,,,,,Spectrum),,,,,TT&C,,,,,(Telemetry,,,,,,Trackin g,,,,,&,,,,,Command),,,,,System,,,,,is,,,,,characterized,,,,,by,,,,,the,,,,,Doppler,,,,,frequen cy,,,,,agile.,,,,,The,,,,,tracking,,,,,loop,,,,,will,,,,,shift,,,,,to,,,,,the,,,,,frequency,,,,,step,,,,, response,,,,,state,,,,,ceaselessly,,,,,and,,,,,the,,,,,measurement,,,,,resolution,,,,,severely,,, ,,decline,,,,,,even,,,,,the,,,,,loop,,,,,is,,,,,likely,,,,,to,,,,,be,,,,,unlocked.,,,,,This,,,,,paper,,,, ,presents,,,,,a,,,,,carrier,,,,,tracking,,,,,loop,,,,,aided,,,,,by,,,,,frequency,,,,,hopping,,,,,pat tern.,,,,,In,,,,,order,,,,,to,,,,,keep,,,,,the,,,,,stability,,,,,of,,,,,the,,,,,tracking,,,,,loop,,,,,,the,, ,,,Doppler,,,,,frequency,,,,,agility,,,,,in,,,,,the,,,,,next,,,,,frequency,,,,,hopping,,,,,dwell,,,, ,is,,,,,estimated,,,,,and,,,,,timely,,,,,compensated,,,,,to,,,,,the,,,,,frequency,,,,,adjustment, ,,,,of,,,,,carrier,,,,,NCO,,,,,according,,,,,to,,,,,the,,,,,preset,,,,,frequency,,,,,hopping,,,,,pat tern,,,,,and,,,,,current,,,,,spacecraft,,,,,velocity.,,,,,Simulation,,,,,results,,,,,show,,,,,that,,, ,,this,,,,,method,,,,,effectively,,,,,eliminates,,,,,the,,,,,instability,,,,,due,,,,,to,,,,,carrier,,,,, frequency,,,,,hopping,,,,,,and,,,,,the,,,,,resolution,,,,,of,,,,,loop,,,,,meets,,,,,the,,,,,require ment,,,,,of,,,,,TT&C,,,,,system.,,,,,Keywords：carrier,,,,,tracking；DS/FHSS；frequency,,,,,agility；aided；TT&CI．INTRODUCTIONThe,,,,,main,,,,,function,,,,,of,,,,,TT&C,,,,,(Telemetry,,,,,,Tracking,,,,,and,,,,,Com mand),,,,,system,,,,,is,,,,,ranging,,,,,and,,,,,velocity,,,,,measurement.,,,,,Presently,,,,,,the, ,,,,most,,,,,common,,,,,used,,,,,TT&C,,,,,systems,,,,,are,,,,,unit,,,,,carrier,,,,,system,,,,,an d,,,,,unit,,,,,spread,,,,,spectrum,,,,,system.,,,,,For,,,,,the,,,,,unit,,,,,carrier,,,,,TT&C,,,,,sys tem,,,,,,ranging,,,,,is,,,,,realized,,,,,by,,,,,measuring,,,,,the,,,,,phase,,,,,difference,,,,,betw een,,,,,transmitted,,,,,and,,,,,received,,,,,tones,,,,,,and,,,,,for,,,,,the,,,,,unit,,,,,spread,,,,,sp ectrum,,,,,TT&C,,,,,system,,,,,,according,,,,,to,,,,,the,,,,,autocorrelation,,,,,properties,,,,, of,,,,,PN,,,,,code,,,,,,ranging,,,,,is,,,,,realized,,,,,by,,,,,measuring,,,,,the,,,,,phase,,,,,delay, ,,,,between,,,,,the,,,,,received,,,,,and,,,,,local,,,,,pseudonoise,,,,,(PN),,,,,code.,,,,,V elocity ,,,,,measurement,,,,,in,,,,,both,,,,,of,,,,,TT&C,,,,,systems,,,,,depends,,,,,on,,,,,extracting,, ,,,the,,,,,frequency,,,,,difference,,,,,resulting,,,,,from,,,,,the,,,,,Doppler,,,,,phenomena,,,,, between,,,,,the,,,,,transmitted,,,,,and,,,,,received,,,,,carrier.,,,,,While,,,,,all,,,,,the,,,,,proc esses,,,,,mentioned,,,,,above,,,,,are,,,,,finished,,,,,on,,,,,the,,,,,ground,,,,,of,,,,,high,,,,,res olution,,,,,carrier,,,,,tracking,,,,,,and,,,,,the,,,,,phase,,,,,lock,,,,,loop,,,,,is,,,,,the,,,,,comm on,,,,,used,,,,,method,,,,,to,,,,,implement,,,,,it,,,,,in,,,,,TT&C,,,,,system.,,,,,As,,,,,the,,,,,s pace,,,,,electromagnetism,,,,,environment,,,,,become,,,,,more,,,,,and,,,,,more,,,,,complic ated,,,,,,the,,,,,capability,,,,,of,,,,,anti-jamming,,,,,is,,,,,required,,,,,by,,,,,the,,,,,future,,,,, TT&C,,,,,system,,,,,[1].,,,,,So,,,,,we,,,,,consider,,,,,using,,,,,the,,,,,hybrid,,,,,DS/FHSS,,,, ,(Direct,,,,,Sequence/Frequency,,,,,Hopping,,,,,Spread,,,,,Spectrum),,,,,technology,,,,,to ,,,,,build,,,,,a,,,,,more,,,,,robust,,,,,TT&C,,,,,system.,,,,,,,,,,For,,,,,many,,,,,ordinary,,,,,hybrid,,,,,DS/FHSS,,,,,communication,,,,,systems,,,,,,th e,,,,,most,,,,,important,,,,,function,,,,,is,,,,,demodulating,,,,,data,,,,,but,,,,,not,,,,,measuri ng,,,,,,so,,,,,it,,,,,is,,,,,not,,,,,necessary,,,,,to,,,,,measure,,,,,the,,,,,carrier,,,,,frequency,,,,,p recisely.,,,,,However,,,,,,in,,,,,hybrid,,,,,DS/FHSS,,,,,TT&C,,,,,system,,,,,,measuring,,,,, and,,,,,tracking,,,,,the,,,,,carrier,,,,,precisely,,,,,is,,,,,the,,,,,foundation,,,,,of,,,,,system,,,,, ,so,,,,,some,,,,,special,,,,,problem,,,,,needs,,,,,to,,,,,be,,,,,solved.,,,,,In,,,,,the,,,,,hybrid,,,, ,DS/FHSS,,,,,TT&C,,,,,system,,,,,,even,,,,,the,,,,,received,,,,,signal,,,,,has,,,,,been,,,,,de hopped,,,,,by,,,,,the,,,,,pattern,,,,,synchronization,,,,,module,,,,,,due,,,,,to,,,,,the,,,,,Dopp ler,,,,,Effect,,,,,and,,,,,carrier,,,,,frequency,,,,,hopping,,,,,,the,,,,,input,,,,,frequency,,,,,of, ,,,,tracking,,,,,loop,,,,,contains,,,,,frequency,,,,,agility,,,,,severely.,,,,,As,,,,,a,,,,,result,,,,,, the,,,,,loop,,,,,is,,,,,likely,,,,,to,,,,,shift,,,,,to,,,,,the,,,,,frequency,,,,,step,,,,,responses,,,,,state,,,,,again,,,,,and,,,,,again,,,,,,and,,,,,it,,,,,seems,,,,,to,,,,,be,,,,,impossible,,,,,for,,,,,freq uency,,,,,measurement,,,,,and,,,,,carrier,,,,,tracking.,,,,,,,,,,The,,,,,paper,,,,,is,,,,,organize d,,,,,as,,,,,follows.,,,,,In,,,,,section,,,,,I,,,,,,the,,,,,frequency,,,,,hopping,,,,,pattern,,,,,sync hronization,,,,,module,,,,,in,,,,,the,,,,,DS/FHSS,,,,,TT&C,,,,,system,,,,,is,,,,,introduced., ,,,,In,,,,,section,,,,,II,,,,,,we,,,,,analyze,,,,,how,,,,,the,,,,,carrier,,,,,frequency,,,,,hopping,,, ,,influences,,,,,the,,,,,performance,,,,,of,,,,,the,,,,,carrier,,,,,tracking,,,,,loop.,,,,,In,,,,,sect ion,,,,,III,,,,,,a,,,,,carrier,,,,,tracking,,,,,loop,,,,,aided,,,,,by,,,,,frequency,,,,,hopping,,,,,pat tern,,,,,and,,,,,current,,,,,spacecraft,,,,,velocity,,,,,is,,,,,proposed.,,,,,In,,,,,section,,,,,IV,,,, ,,a,,,,,simulation,,,,,mode,,,,,on,,,,,the,,,,,ground,,,,,of,,,,,actual,,,,,requirement,,,,,of,,,,,T T&C,,,,,system,,,,,is,,,,,built,,,,,and,,,,,the,,,,,results,,,,,of,,,,,simulation,,,,,show,,,,,that,,, ,,this,,,,,method,,,,,is,,,,,very,,,,,simple,,,,,and,,,,,effective,,,,,for,,,,,DS/FHSS,,,,,TT&C,, ,,,system.,,,,,Finally,,,,,,some,,,,,conclusions,,,,,are,,,,,drawn,,,,,in,,,,,section,,,,,V.II．INPUT,,,,,SIGNAL,,,,,OF,,,,,CARRIER,,,,,TRACKING,,,,,LOOPAs,,,,,the,,,,,traditional,,,,,TT&C,,,,,and,,,,,communication,,,,,system,,,,,,the,,,,,inp ut,,,,,signal,,,,,of,,,,,carrier,,,,,tracking,,,,,loop,,,,,must,,,,,be,,,,,a,,,,,monotonous,,,,,inter mediate,,,,,frequency,,,,,signal,,,,,,so,,,,,the,,,,,received,,,,,RF,,,,,signal,,,,,should,,,,,be,,,, ,dehopped,,,,,by,,,,,the,,,,,frequency,,,,,hopping,,,,,patternsynchronization,,,,,module.,,,, ,In,,,,,FH,,,,,communication,,,,,system,,,,,,the,,,,,signal,,,,,during,,,,,a,,,,,hop,,,,,dwell,,,,, time,,,,,is,,,,,a,,,,,narrowband,,,,,signal,,,,,and,,,,,the,,,,,general,,,,,power,,,,,detector,,,,,is ,,,,,commonly,,,,,used,,,,,to,,,,,detect,,,,,the,,,,,frequency,,,,,hopping,,,,,signal,,,,,[2].,,,,,B ut,,,,,in,,,,,the,,,,,hybrid,,,,,DS/FHSS,,,,,TT&C,,,,,system,,,,,,the,,,,,signal,,,,,is,,,,,subme rged,,,,,in,,,,,the,,,,,noise,,,,,,it,,,,,is,,,,,impossible,,,,,to,,,,,acquire,,,,,signal,,,,,directly,,,,, by,,,,,power,,,,,detector,,,,,such,,,,,as,,,,,FH,,,,,communication,,,,,system.,,,,,However,,,, ,,the,,,,,signal,,,,,during,,,,,a,,,,,hop,,,,,dwell,,,,,time,,,,,in,,,,,the,,,,,system,,,,,just,,,,,is,,,,, a,,,,,direct,,,,,sequence,,,,,spread,,,,,spectrum,,,,,signal,,,,,,so,,,,,we,,,,,can,,,,,acquire,,,,,i t,,,,,based,,,,,on,,,,,the,,,,,acquisition,,,,,of,,,,,direct,,,,,sequence,,,,,spread,,,,,spectrum,,,, ,signal.,,,,,The,,,,,acquisition,,,,,methods,,,,,,such,,,,,as,,,,,serial-search,,,,,acquisition,,,,, ,parallel,,,,,acquisition,,,,,and,,,,,rapid,,,,,acquisition,,,,,based,,,,,on,,,,,FFT,,,,,have,,,,,be en,,,,,discussed,,,,,in,,,,,a,,,,,lot,,,,,of,,,,,papers,,,,,[3-5],,,,,,so,,,,,we,,,,,won’t,,,,,discuss,,, ,,the,,,,,problem,,,,,detailedly,,,,,in,,,,,this,,,,,paper.,,,,,In,,,,,our,,,,,system,,,,,,since,,,,,one,,,,,hop,,,,,dwell,,,,,time,,,,,is,,,,,very,,,,,short,,,,,,the,,,,,rapid,,,,,acquisition,,,,,based,,,,, on,,,,,FFT,,,,,which,,,,,can,,,,,extract,,,,,the,,,,,phase,,,,,delay,,,,,and,,,,,carrier,,,,,frequen cy,,,,,at,,,,,one,,,,,time,,,,,will,,,,,be,,,,,the,,,,,best,,,,,way,,,,,for,,,,,acquisition.,,,,,The,,,,,s cheme,,,,,of,,,,,the,,,,,frequency,,,,,hopping,,,,,patters,,,,,acquisition,,,,,,i.e.,,,,,,coarse,,,,, synchronization,,,,,,could,,,,,be,,,,,shown,,,,,as,,,,,Fig,,,,,1.Figure,,,,,1.,,,,,Scheme,,,,,of,,,,,frequency,,,,,hopping,,,,,pattern,,,,,synchronizationThe,,,,,synchronization,,,,,of,,,,,frequency,,,,,hopping,,,,,pattern,,,,,is,,,,,realized,,,,, by,,,,,the,,,,,local,,,,,frequency,,,,,synthesizer,,,,,rapid,,,,,searching,,,,,and,,,,,the,,,,,two,,, ,,dimension,,,,,rapid,,,,,acquisition,,,,,of,,,,,Direct,,,,,Sequence,,,,,PN,,,,,code,,,,,phase,,, ,,and,,,,,carrier,,,,,frequency.,,,,,At,,,,,the,,,,,beginning,,,,,,the,,,,,link,,,,,switch,,,,,is,,,,,o n,,,,,the,,,,,location,,,,,1,,,,,,and,,,,,the,,,,,output,,,,,signal,,,,,of,,,,,local,,,,,frequency,,,,,s ynthesizer,,,,,with,,,,,higher,,,,,hop,,,,,speed,,,,,than,,,,,the,,,,,received,,,,,one,,,,,is,,,,,mi xed,,,,,with,,,,,the,,,,,received,,,,,signal.,,,,,Then,,,,,,via,,,,,the,,,,,band,,,,,pass,,,,,filter,,,,, ,the,,,,,output,,,,,signal,,,,,of,,,,,mixer,,,,,is,,,,,fed,,,,,into,,,,,the,,,,,acquisition,,,,,module, ,,,,of,,,,,PN,,,,,code,,,,,and,,,,,carrier.,,,,,If,,,,,the,,,,,output,,,,,of,,,,,correlator,,,,,in,,,,,acq uisition,,,,,module,,,,,is,,,,,less,,,,,than,,,,,the,,,,,preset,,,,,threshold,,,,,,the,,,,,direct,,,,,se quence,,,,,spread,,,,,spectrum,,,,,signal,,,,,is,,,,,not,,,,,acquired,,,,,during,,,,,this,,,,,hop,,, ,,dwell,,,,,time,,,,,and,,,,,the,,,,,local,,,,,frequency,,,,,synthesizer,,,,,steps,,,,,the,,,,,next,,, ,,frequency.,,,,,By,,,,,contrast,,,,,,if,,,,,detection,,,,,variable,,,,,of,,,,,acquisition,,,,,modul e,,,,,is,,,,,more,,,,,than,,,,,the,,,,,preset,,,,,threshold,,,,,,it,,,,,means,,,,,that,,,,,the,,,,,freque ncy,,,,,hopping,,,,,signal,,,,,is,,,,,acquired,,,,,and,,,,,the,,,,,mixer,,,,,outputs,,,,,a,,,,,stable, ,,,,district,,,,,spread,,,,,spectrum,,,,,signal.,,,,,After,,,,,that,,,,,,the,,,,,switch,,,,,is,,,,,on,,,,, the,,,,,location,,,,,2,,,,,and,,,,,the,,,,,local,,,,,frequency,,,,,synthesizer,,,,,will,,,,,timely,,,,, change,,,,,the,,,,,output,,,,,frequency,,,,,according,,,,,to,,,,,the,,,,,frequency,,,,,hopping,,, ,,pattern.,,,,,After,,,,,the,,,,,coarse,,,,,synchronization,,,,,mentioned,,,,,above,,,,,,the,,,,,D S/FHSS,,,,,signal,,,,,have,,,,,being,,,,,dehopped,,,,,is,,,,,fed,,,,,to,,,,,PN,,,,,code,,,,,tracking,,,,,loop,,,,,and,,,,,a,,,,,fine,,,,,alignment,,,,,between,,,,,the,,,,,received,,,,,PN,,,,,code,,,,,and,,,,,local,,,,,PN,,,,,code,,,,,is,,,,,achieved,,,,,by ,,,,,a,,,,,code,,,,,tracking,,,,,loop,,,,,na mely ,,,,,the,,,,,delay-locked,,,,,loop.,,,,,Then,,,,,,the,,,,,output,,,,,of,,,,,code,,,,,tracking,,,,,loop,,,,,,i.e.,,,,,,a,,,,,duplicate,,,,,of,,,,,received,,,,,PN,,,,,code,,,,,,is,,,,,mixed,,,,,to,,,,,th e,,,,,IF,,,,,direct,,,,,sequence,,,,,spread,,,,,spectrum,,,,,signal,,,,,dehopped,,,,,by ,,,,,coarse ,,,,,synchronization,,,,,,and,,,,,a,,,,,monotonous,,,,,intermediate,,,,,frequency ,,,,,narrowb and,,,,,,,,,,signal,,,,,which,,,,,will,,,,,be,,,,,fed,,,,,to,,,,,carrier,,,,,tracking,,,,,loop,,,,,is,,,,,o btained.III.,,,,,CHARACTERISTIC,,,,,OF,,,,,DS/FHSS,,,,,CARRIER,,,,,TRA CKING,,,,,LOOPCompared,,,,,with,,,,,the,,,,,carrier,,,,,tracking,,,,,loop,,,,,in,,,,,ordinarycommunica tion,,,,,system,,,,,,because,,,,,of,,,,,the,,,,,high,,,,,dynamic,,,,,of,,,,,the,,,,,spacecraft,,,,,,e specially,,,,,during,,,,,the,,,,,landing,,,,,,accelerating,,,,,and,,,,,decelerating,,,,,,the,,,,,car rier,,,,,tracking,,,,,loop,,,,,of,,,,,hybrid,,,,,DS/FHSS,,,,,TT&C,,,,,system,,,,,will,,,,,be,,,,,i nfluenced,,,,,more,,,,,severely ,,,,,by,,,,,the,,,,,Doppler,,,,,Effect,,,,,(up,,,,,to,,,,,100KHz).,,,,,Addition,,,,,to,,,,,that,,,,,,a,,,,,Doppler,,,,,frequency ,,,,,agility ,,,,,resulted,,,,,from,,,,,th e,,,,,carrier,,,,,frequency ,,,,,hopping,,,,,won’t,,,,,be,,,,,eliminated,,,,,by ,,,,,dehopping,,,,,t he,,,,,frequency ,,,,,hopping,,,,,carrier,,,,,,and,,,,,which,,,,,becomes,,,,,the,,,,,main,,,,,fact or,,,,,influencing,,,,,the,,,,,performance,,,,,of,,,,,carrier,,,,,tracking,,,,,loop,,,,,in,,,,,DS/F HSS,,,,,TT&C,,,,,system.,,,,,The,,,,,frequency ,,,,,of,,,,,downlink,,,,,signal,,,,,of,,,,,DS/F HSS,,,,,TT&C,,,,,system,,,,,may ,,,,,be,,,,,described,,,,,as:)()(1)()()()(000i v i f c i f i f i f i f d +=+= where,,,,,i,,,,,is,,,,,the,,,,,sequence,,,,,number,,,,,of,,,,,carrier,,,,,frequency ,,,,,,)(0i f is,,,,,the,,,,,,,,,,ith,,,,,carrier,,,,,frequency ,,,,,,,,,,,)(i f d is,,,,,the,,,,,Doppler,,,,,frequency ,,,,,offset,,,,,during,,,,,the,,,,,,,,,,ith,,,,,hop,,,,,dwell,,,,,time,,,,,and,,,,,,,,,,)(i v ,,,,,is,,,,,the,,,,,current,,,,,speed,,,,,of,,,,,spacecraft.,,,,,We,,,,,can,,,,,assume,,,,,that,,,,,the,,,,,synchroniz ation,,,,,of,,,,,frequency ,,,,,hopping,,,,,pattern,,,,,has,,,,,been,,,,,completed,,,,,,and,,,,,the,,,,,output,,,,,frequency ,,,,,of,,,,,local,,,,,frequency ,,,,,synthesizer,,,,,is)()()(i f i f i f o lo ∆-=,,,,,,,,,,,where,,,,,)(i f ∆is,,,,,the,,,,,frequency ,,,,,difference,,,,,between,,,,,the,,,,,received,,,,,and,,,,,local,,,,,frequency ,,,,,,i.e.,,,,,,the,,,,,intermediate,,,,,freque ncy ,,,,,of,,,,,input,,,,,signal,,,,,of,,,,,carrier,,,,,tracking,,,,,loop.,,,,,Passing,,,,,a,,,,,IF,,,,,ba nd,,,,,pass,,,,,filter,,,,,,a,,,,,IF,,,,,signal,,,,,,the,,,,,frequency ,,,,,of,,,,,which,,,,,is,,,,,)(i f ∆,,,,,,is,,,,,obtained.,,,,,According,,,,,to,,,,,the,,,,,relation,,,,,among,,,,,the,,,,,velocity ,,,,,,carrier,,,,,frequen cy ,,,,,and,,,,,Doppler,,,,,frequency ,,,,,offset,,,,,,the,,,,,input,,,,,frequency ,,,,,of,,,,,carrier,,,,,tracking,,,,,loop,,,,,is,,,,,derived,,,,,easily,,,,,as,,,,,follow:,,,,,)()(1)()()()(0i v i f c i f i f i f i f d in +=+=∆∆ Then,,,,,,between,,,,,the,,,,,interval,,,,,of,,,,,the,,,,,,,,,,ith,,,,,frequency ,,,,,and,,,,,the,,,,,(i+i)th,,,,,frequency ,,,,,,the,,,,,Doppler,,,,,frequency ,,,,,agility ,,,,,)(i f d ∆,,,,,is,,,,,genera ted,,,,,,and,,,,,can,,,,,be,,,,,expressed,,,,,as:,,,,,)]()()1()1([1)(00i v i f i v i f c i f d -++=∆ Generally,,,,,speaking,,,,,,we,,,,,assume,,,,,that,,,,,the,,,,,velocity ,,,,,of,,,,,spacecraft ,,,,,during,,,,,two,,,,,adjacent,,,,,frequency ,,,,,won’t,,,,,change,,,,,,i.e.)()1(i v i v =+,,,,,,s o )()(1)(0i f i v ci f d ∆∆=,,,,,,which,,,,,shows,,,,,,,,,,that,,,,,the,,,,,frequency,,,,,agility,,,,,is,,,,,a,,,,,function,,,,,of,,,,,the,,,,,frequency ,,,,,difference,,,,,of,,,,,two,,,,,adjacent,,,,,hop,,,,,a nd,,,,,the,,,,,current,,,,,speed,,,,,of,,,,,spacecraft.,,,,,,,,,,Then,,,,,,the,,,,,input,,,,,signal,,,,,of,,,,,the,,,,,carrier,,,,,tracking,,,,,loop,,,,,can,,,,,be ,,,,,expressed,,,,,as:,,,,,,,,,, )(])()()(1222sin[)(2)(0t n nT t p n f n v c t f t f t R P t s n ab +++-++∙=∑∞∞→∆∆τσπππ where,,,,,P,,,,,is,,,,,the,,,,,carrier,,,,,power,,,,,after,,,,,the,,,,,synchronization,,,,,of,,,,,freq uency ,,,,,hopping,,,,,pattern,,,,,,)(t R ,,,,,is,,,,,the,,,,,modulated,,,,,data,,,,,,∆f ,,,,,is,,,,,the,,,,,intermediate,,,,,frequency ,,,,,,d f and,,,,,τ,,,,,are,,,,,the,,,,,rudimental,,,,,frequency ,,,,,o ffset,,,,,and,,,,,rudimental,,,,,phase,,,,,offset,,,,,brought,,,,,from,,,,,acquisition,,,,,module ,,,,,respective.,,,,,;1)(,10=≤≤t p t otherwise,,,,,0)(=t p ,,,,,,T,,,,,is,,,,,one,,,,,hop,,,,,dw ell,,,,,time,,,,,,σ,,,,,,,,,,is,,,,,the,,,,,timing,,,,,error,,,,,of,,,,,the,,,,,synchronization,,,,,of,,,,,f requency ,,,,,hopping,,,,,patterns,,,,,,n(t),,,,,is,,,,,the,,,,,additive,,,,,white,,,,,Gaussian,,,,,noise,,,,,with,,,,,two-side,,,,,power,,,,,spectral,,,,,density ,,,,,2N W/Hz,,,,,and,,,,,c,,,,,is,,,,,t he,,,,,velocity ,,,,,of,,,,,light.,,,,,The,,,,,tracking,,,,,resolution,,,,,is,,,,,the,,,,,basic,,,,,description,,,,,of,,,,,the,,,,,loop,,,,,performance,,,,,,and,,,,,we,,,,,can,,,,,obtain,,,,,it,,,,,by ,,,,,the,,,,,error,,,,,transfer,,,,,fun ction,,,,,as,,,,,follow:,,,,,where,,,,,,F(s),,,,,is,,,,,the,,,,,transfer,,,,,function,,,,,of,,,,,loop,,,,,filter,,,,,,K,,,,,is,,,,,the,,,,,gain,,,,,of,,,,,open,,,,,loop.,,,,,Then,,,,,we,,,,,can,,,,,apply,,,,,the,,,,,limit,,,,,theorem,,,,,,which,,,,,is,,,,,expressed,,,,,as,,,,,)()()(0100lim s H s s s Θ=∞→θ,to,,,,,derive,,,,,the,,,,,steady-state,,,,,tracking,,,,,error.,,,,,Unfortunately ,,,,,,the,,,,,derivation,,,,,of,,,,,Laplacian,,,,,transfer,,,,,of,,,,,,,,,,is,,,,,seen,,,,,to,,,,,be,,,,,impossible,,,,,,so,,,,,we,,,,,can’t,,,,,calcula te,,,,,the,,,,,measuring,,,,,error,,,,,precisely ,,,,,and,,,,,only,,,,,analyze,,,,,it,,,,,by ,,,,,simula tion.,,,,,For,,,,,the,,,,,2edorder,,,,,loop,,,,,,the,,,,,acquisition,,,,,time,,,,,can,,,,,be,,,,,expre ssed,,,,,as:3202nT ξωωρ∆= where,,,,,,0ω,,,,,is,,,,,the,,,,,initial,,,,,frequency ,,,,,offset,,,,,,n ω,,,,,and,,,,,ξ,,,,,are,,,,,the,,,,,natural,,,,,frequency ,,,,,and,,,,,damping,,,,,factor,,,,,of,,,,,the,,,,,tracking,,,,,loop.,,,,,In,,,,,the,,,,,hybrid,,,,,DS/FHSS,,,,,TT&C,,,,,system,,,,,,0ω,,,,,just,,,,,is,,,,,the,,,,,freque ncy ,,,,,agility ,,,,,which,,,,,is,,,,,a,,,,,function,,,,,of,,,,,time,,,,,according,,,,,to,,,,,the,,,,,fre quency ,,,,,hopping,,,,,pattern.,,,,,Thereby ,,,,,,three,,,,,cases,,,,,are,,,,,discussed.,,,,,Case,,,,,1:,,,,,Tp<Tc,,,,,,,,,,,i.e.,,,,,,hop,,,,,dwell,,,,,time,,,,,is,,,,,more,,,,,than,,,,,the,,,,,loop,,,,,acquisition,,,,,time.The,,,,,carrier,,,,,tracking,,,,,loop,,,,,is,,,,,able,,,,,to,,,,,acqu ire,,,,,and,,,,,track,,,,,the,,,,,DS/FHSS,,,,,TT&C,,,,,signal,,,,,,but,,,,,shift,,,,,the,,,,,unlock ,,,,,state,,,,,immediately ,,,,,when,,,,,the,,,,,next,,,,,frequency ,,,,,signal,,,,,is,,,,,fed,,,,,to,,,,,the,,,,,loop.,,,,,The,,,,,loop,,,,,steps,,,,,to,,,,,lock,,,,,,unlock,,,,,,re-lock,,,,,,re-unlock,,,,,s tate,,,,,repeatedly,,,,,for,,,,,all,,,,,time,,,,,,and,,,,,the,,,,,Doppler,,,,,offset,,,,,can’t,,,,,be,,,,,extracted,,,,,accurately .Case,,,,,2:,,,,,Tp>Tc,,,,,,i.e.,,,,,,hop,,,,,dwell,,,,,time,,,,,is,,,,,less,,,,,than,,,,,the,,,,,lo op,,,,,acquisition,,,,,time.,,,,,During,,,,,the,,,,,acquisition,,,,,state,,,,,of,,,,,loop,,,,,,the,,,,,f requency ,,,,,of,,,,,input,,,,,signal,,,,,is,,,,,likely ,,,,,to,,,,,step,,,,,up,,,,,suddenly ,,,,,,and,,,,,t hen,,,,,the,,,,,loop,,,,,steps,,,,,to,,,,,the,,,,,acquisition,,,,,state,,,,,once,,,,,again.,,,,,For,,,,,t he,,,,,case,,,,,,the,,,,,tracking,,,,,loop,,,,,will,,,,,step,,,,,to,,,,,acquisition,,,,,state,,,,,again,,,,,and,,,,,again,,,,,for,,,,,all,,,,,time.,,,,,,,,,,Case,,,,,3:,,,,,For,,,,,the,,,,,non-ideal,,,,,2ed,,,,,or,,,,,high-degree,,,,,order,,,,,loop,,,,,,the,,,,,acquisition,,,,,band,,,,,p ω∆,,,,,is,,,,,limited,,,,,,and,,,,,the,,,,,hopping,,,,,frequenc y ,,,,,agility,,,,,)(i f d ∆,,,,,also,,,,,influences,,,,,the,,,,,performance,,,,,of,,,,,loop.,,,,,When )(i f d ∆<p ω∆,,,,,,,,,,,the,,,,,conclusion,,,,,is,,,,,same,,,,,as,,,,,the,,,,,analysis,,,,,,,,,,mentio ned,,,,,above,,,,,,and,,,,,when )(i f d ∆>p ω∆,,,,,,,,,,,the,,,,,tracking,,,,,loop,,,,,won’t,,,,,loc ked,,,,,the,,,,,signal,,,,,forever.The,,,,,simulation,,,,,result,,,,,of,,,,,2ed,,,,,order,,,,,tracking,,,,,loop,,,,,used,,,,,com monly,,,,,in,,,,,TT&C,,,,,field,,,,,is,,,,,shown,,,,,in,,,,,Fig,,,,,2.,,,,,The,,,,,Doppler,,,,,agilit y ,,,,,is,,,,,plotted,,,,,by ,,,,,broken,,,,,line,,,,,and,,,,,the,,,,,time,,,,,response,,,,,is,,,,,denoted ,,,,,by ,,,,,real,,,,,line.,,,,,Fig.,,,,,2(a),,,,,shows,,,,,the,,,,,tracking,,,,,performance,,,,,witho ut,,,,,Doppler,,,,,offset,,,,,agility;,,,,,the,,,,,time,,,,,response,,,,,as,,,,,Tp<Tc,,,,,is,,,,,descr ibed,,,,,in,,,,,Fig.,,,,,2(b),,,,,,the,,,,,loop,,,,,state,,,,,is,,,,,alternating,,,,,between,,,,,locked,,,,,and,,,,,,,,,,unlocked.,,,,,In,,,,,Fig.,,,,,2(c),,,,,,the,,,,,loop,,,,,is,,,,,acquiring,,,,,signal,,,,,f orever.,,,,,Because,,,,,the,,,,,frequency ,,,,,is,,,,,changed,,,,,before,,,,,stepping,,,,,to,,,,,the ,,,,,locked,,,,,state,,,,,,the,,,,,loop,,,,,won’t,,,,,acquire,,,,,any ,,,,,signal,,,,,at,,,,,all,,,,,time.,,,,,In,,,,,Fig,,,,,2(d),,,,,,when )(i f d ∆>p ω∆,,,,,,the,,,,,tracking,,,,,capability ,,,,,of,,,,,the,,,,,loop,,,,,is,,,,,invalid,,,,,entirely .Figure,,,,,2.,,,,,Time,,,,,response,,,,,of,,,,,tracking,,,,,loop,,,,,with,,,,,Doppler,,,,,offset,,,,,agility:,,,,,,,,,,,,,,,(a) No,,,,,hopping,,,,,,(b),,,,,Tp<Tc,,,,,,,,,,,,,,,,(c),,,,,Tp>T c,,,,,,(d),,,,,)(i f d ∆>pω∆IV.,,,,,THE,,,,,SCHEME,,,,,OF,,,,,CARRIER,,,,,TRACKING,,,,,LOO P,,,,,AIDED,,,,,BY,,,,,HOPPING,,,,,PA TTERNThe,,,,,structure,,,,,of,,,,,the,,,,,carrier,,,,,track,,,,,loop,,,,,aided,,,,,by,,,,,the,,,,,hoppi ng,,,,,frequency,,,,,pattern,,,,,is,,,,,shown,,,,,in,,,,,Fig,,,,,3.,,,,,Generally,,,,,speaking,,,,,, we,,,,,can,,,,,assume,,,,,that,,,,,the,,,,,velocity,,,,,during,,,,,the,,,,,interval,,,,,time,,,,,betw een,,,,,two,,,,,adjacent,,,,,frequency,,,,,will,,,,,keep,,,,,a,,,,,fixed,,,,,value,,,,,,then,,,,,the,,,,,doppler,,,,,frequency,,,,,offset,,,,,,,,,,in,,,,,the,,,,,next,,,,,frequency,,,,,interval,,,,,c an,,,,,be,,,,,calculated,,,,,by,,,,,the,,,,,current,,,,,velocity,,,,,of,,,,,spacecraft,,,,,combined,,,,,with,,,,,carrier,,,,,frequency.,,,,,The,,,,,is,,,,,added,,,,,timely,,,,,to,,,,,the,,,,,adjust ment,,,,,value,,,,,of,,,,,the,,,,,carrier,,,,,NCO,,,,,when,,,,,the,,,,,new,,,,,frequency,,,,,signa l,,,,,is,,,,,fed,,,,,to,,,,,the,,,,,loop.,,,,,So,,,,,the,,,,,output,,,,,frequency,,,,,of,,,,,NCO,,,,,also ,,,,,changes,,,,,synchronal,,,,,as,,,,,the,,,,,frequency,,,,,changing,,,,,of,,,,,input,,,,,signal,,, ,,,and,,,,,the,,,,,loop,,,,,keeps,,,,,stable.,,,,,Deserve,,,,,to,,,,,mentioned,,,,,,before,,,,,the,,,, ,loop,,,,,stepped,,,,,to,,,,,steady,,,,,state,,,,,,the,,,,,spacecraft,,,,,velocity,,,,,used,,,,,by,,,,,t he,,,,,scheme,,,,,is,,,,,given,,,,,from,,,,,the,,,,,acquisition,,,,,module.,,,,,After,,,,,having,,, ,,being,,,,,locked,,,,,state,,,,,,then,,,,,the,,,,,velocity,,,,,should,,,,,be,,,,,extracted,,,,,from,, ,,,the,,,,,loop,,,,,itself,,,,,directly.,,,,,By,,,,,this,,,,,way,,,,,,the,,,,,loop,,,,,is,,,,,able,,,,,to,,,,, keep,,,,,stable,,,,,even,,,,,on,,,,,the,,,,,high,,,,,dynamic,,,,,condition.,,,,,Figure,,,,,3.,,,,,Carrier,,,,,tracking,,,,,loop,,,,,aided,,,,,by,,,,,frequency,,,,,hopping,,,,,patternBesides,,,,,the,,,,,thermal,,,,,noise,,,,,jitter,,,,,,the,,,,,main,,,,,error,,,,,of,,,,,carrier,,,, ,tracking,,,,,loop,,,,,aided,,,,,by,,,,,the,,,,,frequency,,,,,hopping,,,,,pattern,,,,,is,,,,,the,,,,,f requency,,,,,jitter,,,,,of,,,,,the,,,,,frequency,,,,,synthesizer,,,,,and,,,,,timing,,,,,error,,,,,due ,,,,,to,,,,,frequency,,,,,pattern,,,,,synchronization.,,,,,The,,,,,former,,,,,one,,,,,depends,,,,, on,,,,,the,,,,,resolution,,,,,of,,,,,frequency,,,,,synthesizer,,,,,as,,,,,other,,,,,communication,,,,,and,,,,,we,,,,,only,,,,,discuss,,,,,the,,,,,latter,,,,,one.,,,,,Briefly,,,,,,when,,,,,the,,,,,local, ,,,,frequency,,,,,changing,,,,,of,,,,,the,,,,,local,,,,,frequency,,,,,synthesizer,,,,,is,,,,,advanc ed,,,,,or,,,,,retarded,,,,,to,,,,,the,,,,,one,,,,,of,,,,,receive,,,,,signal,,,,,,the,,,,,aiding,,,,,modu le,,,,,will,,,,,provide,,,,,a,,,,,frequency,,,,,offset,,,,,to,,,,,the,,,,,carrier,,,,,NCO,,,,,at,,,,,the, ,,,,wrong,,,,,time,,,,,and,,,,,the,,,,,loop,,,,,will,,,,,step,,,,,to,,,,,the,,,,,unlocked,,,,,state,,,,, at,,,,,once,,,,,,i.e.,,,,,,response,,,,,of,,,,,frequency,,,,,step.,,,,,Fortunately,,,,,,when,,,,,the,, ,,,frequency,,,,,of,,,,,input,,,,,signal,,,,,changes,,,,,actually,,,,,,the,,,,,loop,,,,,will,,,,,retur n,,,,,to,,,,,the,,,,,steady,,,,,state,,,,,rapidly.,,,,,But,,,,,as,,,,,the,,,,,increase,,,,,of,,,,,synchro nization,,,,,error,,,,,,it,,,,,also,,,,,be,,,,,likely,,,,,to,,,,,become,,,,,too,,,,,severe,,,,,to,,,,,me et,,,,,the,,,,,resolution,,,,,requirement,,,,,of,,,,,the,,,,,TT&C,,,,,system.V.,,,,,SIMULA TIOMThe,,,,,model,,,,,of,,,,,carrier,,,,,tracking,,,,,loop,,,,,of,,,,,hybrid,,,,,DS/FHSS,,,,,sys tem,,,,,is,,,,,shown,,,,,in,,,,,Fig,,,,,3,,,,,,which,,,,,is,,,,,built,,,,,in,,,,,the,,,,,simulink,,,,,of,, ,,,Matlab.,,,,,The,,,,,tracking,,,,,loop,,,,,is,,,,,the,,,,,standard,,,,,costas,,,,,loop,,,,,commo nly,,,,,used,,,,,in,,,,,the,,,,,TT&C,,,,,field,,,,,,which,,,,,is,,,,,able,,,,,to,,,,,eliminate,,,,,the,, ,,,inference,,,,,resulted,,,,,form,,,,,the,,,,,polarity,,,,,change,,,,,of,,,,,the,,,,,modulated,,,,, data,,,,,[9].,,,,,To,,,,,adapt,,,,,the,,,,,Doppler,,,,,frequency,,,,,change,,,,,due,,,,,to,,,,,the,,,, ,spacecraft,,,,,movement,,,,,,the,,,,,loop,,,,,is,,,,,designed,,,,,as,,,,,a,,,,,2ed,,,,,order,,,,,loo p,,,,,,and,,,,,the,,,,,loop,,,,,filter,,,,,is,,,,,a,,,,,1st,,,,,order,,,,,filter.,,,,,The,,,,,simulation,,,,, parameter,,,,,is,,,,,set,,,,,according,,,,,to,,,,,the,,,,,actual,,,,,TT&C,,,,,task,,,,,as,,,,,follow s:,,,,,Carrier,,,,,frequency:,,,,,2.2GHz~2.3GHz,,,,,Amount,,,,,of,,,,,frequencies:,,,,,128,,,,,Frequency,,,,,hopping,,,,,pattern:,,,,,based,,,,,on,,,,,m-sequence,,,,,Rudimental,,,,,frequency,,,,,offset,,,,,after,,,,,acquisition:,,,,,300Hz,,,,,Intermediate,,,,,frequency,,,,,of,,,,,the,,,,,carrier,,,,,tracking,,,,,loop:,,,,,4.8MHz,,,,,Sampling,,,,,frequency:,,,,,16.3Mbps,,,,,Noise,,,,,Bandwidth,,,,,of,,,,,the,,,,,loop:,,,,,10Hz,,,,,A.,,,,,The,,,,,time,,,,,response,,,,,on,,,,,uniform,,,,,motion,,,,,and,,,,,,,,,,uniformly,,,, ,accelerated,,,,,motionWe,,,,,assume,,,,,the,,,,,spacecraft,,,,,speed,,,,,is,,,,,7.9km/s,,,,,,by,,,,,the,,,,,relation ,,,,,among,,,,,the,,,,,Doppler,,,,,frequency,,,,,,carrier,,,,,frequency,,,,,and,,,,,velocity,,,,,,t he,,,,,frequency,,,,,offset,,,,,of,,,,,the,,,,,input,,,,,IF,,,,,signal,,,,,of,,,,,loop,,,,,is,,,,,obtaine d,,,,,as,,,,,Fig,,,,,4(a).,,,,,The,,,,,max,,,,,frequency,,,,,agility,,,,,is,,,,,up,,,,,to,,,,,2.3KHz.,,, ,,The,,,,,time,,,,,response,,,,,without,,,,,aid,,,,,is,,,,,shown,,,,,in,,,,,the,,,,,Fig,,,,,4(b),,,,,an d,,,,,the,,,,,one,,,,,with,,,,,aid,,,,,by,,,,,hopping,,,,,pattern,,,,,is,,,,,shown,,,,,in,,,,,Fig4(c)., ,,,,The,,,,,results,,,,,show,,,,,that,,,,,the,,,,,loop,,,,,without,,,,,aid,,,,,is,,,,,unlocked,,,,,com pletely,,,,,,while,,,,,the,,,,,one,,,,,with,,,,,aid,,,,,can,,,,,track,,,,,the,,,,,carrier,,,,,accurately .,,,,,When,,,,,the,,,,,spacecraft,,,,,is,,,,,on,,,,,the,,,,,uniformly,,,,,accelerated,,,,,motion,,,,, (the,,,,,initial,,,,,speed,,,,,is,,,,,7.9km/s,,,,,,and,,,,,speed,,,,,accelerator,,,,,is,,,,,30g),,,,,,th e,,,,,time,,,,,response,,,,,is,,,,,shown,,,,,in,,,,,Fig,,,,,5.,,,,,The,,,,,same,,,,,conclusion,,,,,is, ,,,,obtained,,,,,as,,,,,pre-paragraph.,,,,,Figure,,,,,4.,,,,,,,,,,The,,,,,time,,,,,response,,,,,on,,,,,uniform,,,,,,,,,,,,,,,motion:,,,,,(a)doppler,,,,,frequency,(b)without,,,,,aid,,,,,,(c),,,,,with,,,,,aid.Figure,,,,,5.,,,,,Time,,,,,response,,,,,on,,,,,uniformly,,,,,accelerated,,,,,motion:(a)doppler,,,,,frequency,(b)without,,,,,aid,,,,,(c),,,,,with,,,,,aidB.,,,,,Tracking,,,,,resolution,,,,,on,,,,,different,,,,,hopping,,,,,speedIn,,,,,this,,,,,simulation,,,,,,the,,,,,resolution,,,,,of,,,,,carrier,,,,,tracking,,,,,loop,,,,,is, ,,,,obtained,,,,,by,,,,,calculating,,,,,variance.,,,,,The,,,,,relation,,,,,between,,,,,tracking,,,, ,resolution,,,,,and,,,,,hopping,,,,,speed,,,,,is,,,,,shown,,,,,in,,,,,Fig,,,,,6,,,,,on,,,,,different,, ,,,input,,,,,SNR,,,,,and,,,,,the,,,,,minimum,,,,,value,,,,,insuring,,,,,the,,,,,demodulating,,,, ,correctly,,,,,in,,,,,TT&C,,,,,system,,,,,is,,,,,13,,,,,dB.,,,,,The,,,,,result,,,,,of,,,,,simulation ,,,,,testified,,,,,that,,,,,the,,,,,resolution,,,,,is,,,,,not,,,,,sensitive,,,,,to,,,,,the,,,,,hopping,,,,, speed,,,,,and,,,,,the,,,,,scheme,,,,,is,,,,,very,,,,,robust,,,,,for,,,,,different,,,,,hopping,,,,,spe ed.Figure,,,,,6.,,,,,Stead-state,,,,,tracking,,,,,resolution,,,,,vs,,,,,hopping,,,,,speedC.,,,,,Tracking,,,,,resolution,,,,,on,,,,,different,,,,,timing,,,,,error,,,,,of,,,,,frequency, ,,,,,,,,,pattern,,,,,,,,,,synchronization,,,,,,,,,,For,,,,,carrier,,,,,tracking,,,,,loop,,,,,aided,,,,,by,,,,,the,,,,,frequency,,,,,hopping,,,,,p attern,,,,,,according,,,,,to,,,,,the,,,,,above,,,,,discussion,,,,,the,,,,,main,,,,,factor,,,,,impact ing,,,,,the,,,,,stability,,,,,of,,,,,loop,,,,,is,,,,,the,,,,,timing,,,,,error,,,,,caused,,,,,by,,,,,the,,,,, patterns,,,,,synchronization.,,,,,Fig,,,,,7,,,,,shows,,,,,the,,,,,stead-state,,,,,tracking,,,,,acc uracies,,,,,on,,,,,different,,,,,timing,,,,,error,,,,,of,,,,,synchronization,,,,,pattern,,,,,on,,,,,d ifferent,,,,,input,,,,,SNR.,,,,,The,,,,,measuring,,,,,error,,,,,is,,,,,increase,,,,,as,,,,,increasin g,,,,,of,,,,,timing,,,,,error,,,,,and,,,,,the,,,,,measurement,,,,,error,,,,,resulted,,,,,from,,,,,the ,,,,,SNR,,,,,even,,,,,can,,,,,be,,,,,ignored,,,,,when,,,,,the,,,,,time,,,,,error,,,,,is,,,,,up,,,,,to,,, ,,some,,,,,specified,,,,,value.,,,,,Consequently,,,,,,we,,,,,can,,,,,infer,,,,,that,,,,,the,,,,,trac k,,,,,accuracy,,,,,won’t,,,,,meet,,,,,the,,,,,requirement,,,,,of,,,,,TT&C,,,,,system,,,,,finally ,,,,,,and,,,,,the,,,,,problem,,,,,needs,,,,,to,,,,,be,,,,,researched,,,,,in,,,,,the,,,,,future.Figure,,,,,7.,,,,,Stead-state,,,,,tracking,,,,,resolution,,,,,vs,,,,,timing,,,,,error,,,,,of,,,,,,,,,,pattern,,,,,synchronization。
无线调频发射器的毕业设计论文(内有外文翻译资料)
无线调频发射器的设计The Design of Wireless Frequency Modulation Transmitter摘要利用无线通信信道的远距离语音传输业务，是近年来发展很快的一门技术。
由于语音业务对误码不敏感，可以采用调频方式发送信息。
调频发射器可以使音频信息传送到附近的任意FM接收机。
本设计中使用AT89S52控制调频发射的频率，选择了数码管显示发射的频率状态。
选择了ROHM BH1415F集成电路产生调频调制发射信号的频率。
芯片的主要特征:体积小，准确性高，而且容易产生发射频率。
这个系统的各个部分可以进行深入的独立设计研究，现在把它们组合成一个典型的调频发射系统。
本设计使用模拟调频技术，在88MHz--98MHz的频段上，实现了线路输入语音信号的小功率远距离单工发送。
系统发射功率大约20mW，发射距离大于20m，本系统可实现无明显失真的语音传输。
关键词：调频；语音传输；ROHM BH1415ABSTRACTThe remote audio service code through wireless communication channels is a fast developing technology in recent years. As the audio service code is not sensitive to the mistaken code, the frequency modulation can be used to send information.The FM Transmitter will allow almost any audio source to be transmitted to any nearby FM receiver. The A T89S52 to be used to control the transmission frequency.The LED was chosen, providing enough space for all output situations. The ROHM BH1415F integrated circuit was chosen to create the frequency modulated audio output signal. Chip features include: small size, accuracy, and easily programmed transmission frequency. These system components have been thoroughly researched separately and are now in the process of being integrated to produce a working prototype FM Transmitter. The simulating frequency modulation technique was adopted in the design .In the frequency interval of 88MHz---98 MHz, the audio signals can be sent out and received with the small power in a long distance .The emissive power of the system is about 20mW and the emissive distance is more than 20m.There is no obvious distortion in the audio transmission.Key Words：frequency modulation；audio transmission；ROHM BH1415F目录1 引言 (1)1.1 通信的发展 (1)1.2 广播的发展现状 (1)1.3 设计思路 (2)2系统概述 (3)2.1 系统功能要求 (3)2.2系统组成 (3)3 方案论证与比较 (5)3.1 无线调频发射电路设计方案论证与选择 (5)3.2 压控振荡器方案论证与选择 (6)4 系统硬件电路的设计 (7)4.1 单片机控制电路 (7)4.1.1 内部结构 (7)4.1.2 引脚功能 (9)4.2 调频调制发射电路 (11)4.2.1 调频调制电路的特点 (11)4.2.2 结构图 (11)4.2.3 允许的最大值 (12)4.2.4 工作范围 (12)4.2.5 调频调制发射电路的组成 (12)4.3 键盘部分 (14)4.3.1 单片机键盘和键盘接口概述 (14)4.3.2 单片机键盘接口和键功能的实现 (15)4.4 LC振荡电路 (16)4.5 调频放大电路 (17)4.6 电源模块设计 (17)4.6.1 单元电源电路设计 (17)4.6.2 直流稳压电源的检测 (17)5 系统程序的设计 (18)5.1 主程序 (18)5.2 延时子程序 (19)5.3 LED动态扫描子程序 (19)5.4 频率数据转换子程序 (19)5.5 控制命令合成子程序 (19)5.6 BH1415F字节写入子程序 (20)5.7 查键子程序 (21)6 系统调试及性能分析 (23)6.1 硬件调试 (23)6.2 软件调试 (23)6.3 发射频率的调试 (23)6.4 性能分析 (23)结论 (24)参考文献 (25)附录1：原理图 (26)附录2：程序源代码 (28)附录3：英文原文 (41)附录4：中文译文 (52)致谢 (59)1 引言1.1 通信的发展人类社会的发展可视为一部信息传播技术的发展史。
计算机科学与技术专业无线局域网毕业论文外文文献翻译及原文
毕业设计（论文）外文文献翻译文献、资料中文题目：无线局域网文献、资料英文题目：文献、资料来源：文献、资料发表（出版）日期：院（部）：专业：计算机科学与技术专业班级：姓名：学号：指导教师：翻译日期： 2017.02.14毕业设计(论文)外文资料翻译外文出处：Chris Haseman. Android-essential(用外文写)s[M].London:Spring--Verlag,2008.8-13.附件： 1.外文资料翻译译文；2.外文原文。
指导教师评语：签名：年月日注：请将该封面与附件装订成册。
附件1：外文资料翻译译文无线局域网一、为何使用无线局域网络对于局域网络管理主要工作之一，对于铺设电缆或是检查电缆是否断线这种耗时的工作，很容易令人烦躁，也不容易在短时间内找出断线所在。
再者，由于配合企业及应用环境不断的更新与发展，原有的企业网络必须配合重新布局，需要重新安装网络线路，虽然电缆本身并不贵，可是请技术人员来配线的成本很高，尤其是老旧的大楼，配线工程费用就更高了。
因此，架设无线局域网络就成为最佳解决方案。
二、什么情形需要无线局域网络无线局域网络绝不是用来替代有限局域网络，而是用来弥补有线局域网络之不足，以达到网络延伸之目的，下列情形可能须要无线局域网络。
●无固定工作场所的使用者●有线局域网络架设受环境限制●作为有线局域网络的备用系统三、无线局域网络存取技术目前厂商在设计无线局域网络产品时，有相当多种存取设计方式，大致可分为三大类：窄频微波技术、展频(Spread Spectrum)技术、及红外线(Infrared)技术，每种技术皆有其优缺点、限制及比较，接下来是这些技术方法的详细探讨。
1.技术要求由于无线局域网需要支持高速、突发的数据业务，在室内使用还需要解决多径衰落以及各子网间串扰等问题。
具体来说，无线局域网必须实现以下技术要求：1)可靠性：无线局域网的系统分组丢失率应该低于10-5，误码率应该低于10-8。
关于下一代无线通信网络的详细综述(论文谷歌翻译)
计算机无线网络前沿理论与技术课程报告关于下一代无线通信网络的详细综述（论文谷歌翻译）学院：计算机与信息技术学院专业：计算机科学与技术专业学号：姓名：教师：摘要相对比当前4G LTE网络。
下一代5G无线通信的愿景在于提供非常高的数据速率(通常为Gbps数量级)，极低的延迟，基站容量的增加以及用户感知的服务质量(QoS)的显着改善。
智能设备的不断增加，新兴的多媒体应用的引入，以及无线数据(多媒体)需求和使用的指数增长已经对现有蜂窝网络造成了重大负担。
5G无线系统，具有改进的数据速率，容量，延迟和QoS预期是当前蜂窝网络的大多数问题的灵丹妙药。
在本次调查中，我们对5G网络的无线演进做了详尽的回顾。
我们首先讨论与无线接入网(RAN)设计相关的新架构变化，包括空中接口，智能天线，云和异构RAN。
随后，我们对基础的新型毫米波物理层技术进行深入调查，包括新的信道模型估计，定向天线设计，波束成形算法和大规模MIMO技术。
接下来，讨论有效支持这个新物理层所需的MAC层协议和复用方案的细节。
我们还研究了杀手级应用程序，被认为是5G背后的主要驱动力。
为了了解改进的用户体验，我们提供与5G演进相关的新的QoS，QoE和SON功能的亮点。
为了减少增加的网络能耗和运营成本，我们对能源意识和成本效率进行了详细审查。
因为了解5G实施的当前状态对于其最终的商业化是重要的，我们还讨论相关的现场试验，驱动测试和模拟实验。
最后，我们指出现有的主要研究问题，并确定未来的研究方向。
关键字：5G毫米波波束成型信道模型 C-RANSDNHetNets大规模MIMO，SDMA，IDMA，D2D，M2M，IoT，QoE，SON，可持续性，实验1.引言移动无线通信始于第一代，纯语音系统已经有几十年了。
在过去几十年中，世界已经目睹了移动无线通信逐渐向第二，第三和第四代无线网络演进的趋势。
引入数字调制，有效的频率复用，基于分组的因特网的渗透以及诸如WCDMA，OFDMA，MIMO，HARQ等物理层技术的快速发展已经对这种逐渐演进做出了重大贡献。
无线网络_外文翻译_外文文献_英文文献_无线局域网技术
毕业外文翻译无线局域网技术最近几年，无线局域网开始在市场中独霸一方。
越来越多的机构发现无线局域网是传统有线局域网不可缺少的好帮手,它可以满足人们对移动、布局变动和自组网络的需求，并能覆盖难以铺设有线网络的地域。
无线局域网是利用无线传输媒体的局域网。
就在前几年，人们还很少使用无线局域网.原因包括成本高、数据率低、职业安全方面的顾虑以及需要许可证。
随着这些问题的逐步解决,无线局域网很快就开始流行起来了.无线局域网的应用局域网的扩展在20世纪80年代后期出现的无线局域网早期产品都是作为传统有线局域网替代品而问世的。
无线局域网可以节省局域网缆线的安装费用，简化重新布局和其他对网络结构改动的任务。
但是，无线局域网的这个动机被以下一系列的事件打消。
首先，随着人们越来越清楚地认识到局域网的重要性，建筑师在设计新建筑时就包括了大量用于数据应用的预先埋设好的线路.其次，随着数据传输技术的发展，人们越来越依赖于双绞线连接的局域网。
特别是3类和5类非屏蔽双绞线。
大多数老建筑中已经铺设了足够的3类电缆，而许多新建筑里则预埋了5类电缆。
因此，用无线局域网取代有线局域网的事情从来没有发生过。
但是,在有些环境中无线局域网确实起着有线局域网替代品的作用。
例如，象生产车间、股票交易所的交易大厅以及仓库这样有大型开阔场地的建筑；没有足够双绞线对，但又禁止打洞铺设新线路的有历史价值的建筑;从经济角度考虑,安装和维护有线局域网划不来的小型办公室。
在以上这些情况下，无线局域网向人们提供了一个有效且更具吸引力的选择.其中大多数情况下，拥有无线局域网的机构同时也拥有支持服务器和某些固定工作站的有线局域网。
因此，无线局域网通常会链接到同样建筑群内的有线局域网上。
所以我们将此类应用领域成为局域网的扩展。
建筑物的互连无线局域网技术的另一种用途是邻楼局域网之间的连接，这些局域网可以是无线的也可以是有线的。
在这种情况下，两个楼之间采用点对点的无线链接.被链接的设备通常是网桥或路由器。
无线红外通信-外文翻译
原文：Wireless Infrared CommunicationsI. IntroductionWireless infrared communications refers to theuse of free-space propagation of light waves in thenear infrared band as a transmission medium forcommunication(1-3), as shown in Figure 1. The communication can be between one portable communication device and another or between a portable device and a tethered device, called an access pointor base station. Typical portable devices includelaptop computers, personal digital assistants, andportable telephones, while the base stations are usually connected to a computer with other networkedconnections. Although infrared light is usually usedother regions of the optical spectrum can be used (sothe term wireless optical communications" insteadof wireless infrared communications" is sometimesused).Wireless infrared communication systems can becharacterized by the application for which they aredesigned or by the link type, as described below.A.ApplicationsThe primary commercial applications are as follows:²short-term cable-less connectivity for informationexchange (business cards, schedules, file sharing) between two users. The primary example is IrDA systems (see Section 4).²wireless local area networks (WLANs) provide network connectivity inside buildings. This can eitherbe an extension of existing LANs to facilitate mobility, or to establish “ad hoc”networks where there isno LAN. The primary example is the IEEE 802.11standard (see Section 4).²building-to-building connections for high-speednetwork access or metropolitan- or campus-area net-works.²wireless input and control devices, such as wirelessmice, remote controls, wireless game controllers, andremote electronic keys.B. Link TypeAnother important way to characterize a wirelessinfrared communication system is by the “link type”which means the typical or required arrangement ofreceiver and transmitter. Figure 2 depicts the twomost common configurations: the point-to-point system and the diffuse system.The simplest link type is the point-to-pointsystem. There, the transmitter and receiver must bepointed at each other to establish a link. The line-of-sight (LOS) path from the transmitter to the receivermust be clear of obstructions, and most of the transmitted light is directed toward the receiver. Hence,point-to-point systems are also called directed LOS systems. The links can be temporarily created for adata exchangesession between two users, or established more permanently by aiming a mobile unit ata base station unit in the LAN replacement application.In diffuse systems, the link is always maintainedbetween any transmitter and any receiver in the samevicinity by reflecting or |“bouncing”the transmittedinformation-bearing light off reflecting surfaces suchas ceilings, walls, and furniture. Here, the transmitter and receiver are non-directed; the transmitteremploys a wide transmit beam and the receiver hasa wide field-of-view. Also, the LOS path is not required. Hence, diffuse systems are also called non-directed non-LOS systems. These systems are wellsuited to the wirelessLAN application, freeing theuser from knowing and aligning with the locations ofthe other communicating devices.C. Fundamentals and OutlineMost wireless infrared communications systemscan be modeled as having an output signal Y (t) andan input signal X(t) which are related bywhere denotes convolution, C(t) is the impulse response of the channel and N(t) is additive noise.This article is organized around answering key questions concerning the system as represented by thismodel.In Section 2, we consider questions of optical design. What range of wireless infrared communications systems does this model apply to? How does C(t) depend on the electrical and optical properties ofthe receiver and transmitter? How does C(t) dependon the location, size, and orientation of the receiverand transmitter? How do X(t) and Y (t) relate to optical processes? What wavelength is used for X(t)?What devices produce X(t) and Y (t)? What is thesource of N(t)? Are there any safety considerations?In Section 3, we consider questions of communications design. How should a data symbol sequence bemodulated onto the input signal X(t)? What detection mechanism is best for extracting the informationabout the data from the received signal Y (t)? Howcan one measure and improve the performance of thesystem? In Section 4, we consider the design choicesmade by existing standards such as IrDA and 802.11.Finally, in Section 5, we consider how these systemscan be improved in the future.II. Optical DesignA. Modulation and demodulationWhat characteristic of the transmitted wave willbe modulated to carry information from the transmitter to the receiver? Most communication systemsare based on phase, amplitude, or frequency modulation, or some combination of these techniques.However, it is difficult to detect such a signal following nondirected propagation, and more expensivenarrow-linewidth sources are required(2). An effective solution is to use intensity modulation, wherethe transmitted signal's intensity or power is proportional to the modulating signal.At the demodulator (usually referred to as a detector in optical systems) the modulation can be extracted by mixing the received signalwith a carrierlight wave. This coherent detection technique is bestwhen the signal phase can be maintained. However,this can be difficult to implement and additionally, innondirected propagation, it is difficult to achieve therequired mixing efficiency. Instead, one can use directdetection using a photodetector. The photodetectorcurrent is proportional to the received optical signalintensity, which for intensity modulation, is also theoriginal modulating signal. Hence, most systems useintensity modulation with direct detection (IM/DD)to achieve optical modulation and demodulation.In a free-space optical communication system, thedetector is illuminated by sources of light energyother than the source. These can include ambientlighting sources, such as natural sunlight, fluorescent lamp light, and incandescent lamp light. Thesesources cause variation in the received photocurrentthat is unrelated to the transmitted signal, resultingin an additive noise component at the receiver.We can write the photocurrent at the receiver aswhere R is the responsivity of the receiving photodiode (A/W). Note that the electrical impulse responsec(t) is simply R times the optical impulse responseh(t). Depending on the situation, some authors use(t) and some use h(t) as the impulse response.B. Receivers and TransmittersA transmitter or source converts an electrical signal to an optical signal. The two most appropriatetypes of device are the light-emitting diode (LED)and semiconductor laser diode (LD).LEDs havea naturally wide transmission pattern, and so aresuited to nondirected links. Eye safety is much simpler to achieve for an LED than for a laser diode,which usually have very narrow transmit beams.The principal advantages of laser diodes are theirhigh energy-conversion efficiency, their high modulation bandwidth, and their relatively narrow spectral width. Although laser diodes offer several advantages over LEDs that could be exploited, mostshort-range commercial systems currently use LEDs.A receiver or detector converts optical power intoelectrical current by detecting the photon flux incident on the detector surface. Silicon p-i-n photodiodes are ideal for wireless infrared communications asthey have good quantum efficiency in this band andare inexpensive(4). Avalanche photodiodes are notused here since the dominant noise source is back-ground light-induced shot noise rather than thermalcircuit noise.C. Transmission W avelength and NoiseThe most important factor to consider whenchoosing a transmission wavelength is the availability of effective, low-cost sources and detectors. Theavailability of LEDs and silicon photodiodes operating in the 800 nm to 1000 nm range is the primaryreason for the use of this band. Another importantconsideration is the spectral distribution of the dominant noise source: background lighting.The noise N(t) can be broken into four components: photon noise or shot noise, gainnoise, receiver circuit or thermal noise, and periodic noise.Gain noise is only present in avalanche-type devices,so we will not consider it here.Photon noise is the result of the discreteness ofphoton arrivals. It is due to background lightsources, such as sun light, fluorescent lamplight,and incandescent lamp light, as well as the signaldependent source X(t) - c(t). Since the backgroundlight striking the photodetector is normally muchstronger than the signal light, we can neglect the dependency of N(t) on X(t) and consider the photonnoise to be additive white Gaussian noise with two-sided power spectral density where qis the electron charge, R is the responsivity, and Pnis the optical power of the noise (background light).Receiver noise is due to thermal effects in the receiver circuitry, and is particularly dependent on thetype of preamplifier used. With careful circuit design, it can be made insignificant relative tothe photon noise(5).Periodic noise is the result of the variation of fluorescent lighting due to the method of driving thelamp using the ballast. This generates an extraneous periodic signal with a fundamental frequency of44 kHz with significant harmonics to several MHz.Mitigating the effect of periodic noise can be doneusing high-pass filtering in combination with baselinerestoration(6), or by careful selection of the modulation type, as discussed in Section 3.1.D. SafetyThere are two safety concerns when dealing withinfrared co mmunication systems. Eye safety is a concern because of a combination of two effects: thecornea is transparent from the near violet to the nearIR. Hence, the retina is sensitive to damage from light sources transmitting in these bands. However,the near IR is outside the visible range of light, andso the eye does not protect itself from damage byclosing the iris or closing the eyelid. Eye safety canbe ensured by restricting the transmit beam strengthaccording to IEC or ANSI standards(7,8).Skin safety is also a possible concern. Possibleshortterm effects such as heating of the skin are accounted for by eye safety regulations (since the eyerequires lower power levels than the skin). Longtermexposure to IR light is not a concern, as the ambientlight sources are constantly submitting our bodies tomuch higher radiation levels than these communication systems do.III. Communications DesignEqually important for achieving the design goals ofwireless infrared systems are communications issues.In particular, the modulation signal format togetherwith appropriate error control coding is critical toachieving power efficiency. Channel characterizationis also important for understanding performance limits.A. Modulation TechniquesTo understand modulation in IM/DD systems, wemust look again at the channelmodeland consider its particular characteristics. First,since we are using intensity modulation, the channel input X(t) is optical intensity and we have theconstraint X(t). The average transmitted optical power PT is the time average of X(t). Our goalis to minimize the transmitted power required to attain a certain probability of bit error Pe, also knownas a bit error rate (BER).It is useful to define the signal-to-noise ratio SNRaswhere H(0) is the d.c. gain of the channel, i.e. itis the Fourier transform of h(t) evaluated at zerofrequency, soThe transmitted signal can be represented asThe sequence represents the digital informationbeing transmitted, whereis one of L possible datasymbols from 0 to L-1. The function Si(t) representsone of L pulse shapes with duration Ts, the symboltime. The data rate (or bit rate) Rb, bit time T,symbol rate Rs, and symbol time Ts are related asfollows:.There are three commonly used types of modulation schemes: on-off keying (OOK) with non-return-to-zero pulses, OOK with return-to-zero pulses ofnormalized width and pulse position modulation with L pulses (L-PPM). OOK and aresimpler to implement at both the transmitter and receiver than L-PPM. The pulse shapes for these modulation techniques are shown in Figure 3. Representative examples of the resulting transmitted signalX(t) for a short data sequence areshown in Figure4.We compare modulation schemes in Table 1 bylooking at measures of power efficiency and bandwidth efficiency. Bandwidth efficiency is measuredby dividing the zero-crossing bandwidth by the datarate. Bandwidth efficient schemes have severaladvantages—the receiver and transmitter electronicsare cheaper, and the modulation scheme is less likelyto be affected by multipath distortion. Power efficiency is measured by comparing the required transmit power to achieve a target probability of error Pefor different modulation techniques. Both andPPM are more power efficient than OOK, but at thecost of reduced bandwidth efficiency. However, for agiven bandwidth efficiency, PPM is more power efficient than,and so PPM is most commonlyused. OOK is most useful at very high data rates,say 100 Mb/s or greater. Then, the effect of multipath distortion is the most significant effect andbandwidth efficiency becomes of paramount importance(9).B. Error Control CodingError control coding is an important technique forimproving the quality of any digital communicationsystem. We concentrate here on forward error correction channel coding, as this specifically relates to wireless infrared communications; source coding andARQ coding are not considered here.Trellis-coded PPM has been found to be an effective scheme for multipath infrared channels(10,11).The key technique is to recognize that although ona distortion-free channel, all symbols are orthogonal and equidistant in signal space, this is not trueon a distorting channel. Hence, trellis-coding usingset partitioning designed to separate the pulse positions of neighboring symbols is an effective codingmethod. Coding gains of 5.0 dB electrical have beenreported for rate 2/3-coded 8-PPM over uncoded 16-PPM, which has the same bandwidth(11).C. Channel impulse response characterizationImpulse response characterization refers to theproblem of understanding how the impulse response C(t) in Equation (1) depends on the location, size,and orientation of the receiver and transmitter.There are basically three classes of techniques foraccomplishing this: measurement, simulation, andmodeling. Channel measurements have been described in several studies(9,12,2), and these formthe fundamental basis for understanding the channel properties. A particular study might generate a collection of hundreds or thousands of example impulse responses Ci(t) for configuration i. The collection of measured impulse responses Ci(t) can thenbe studied by looking at scatter plots of path lossversus distance, scatter plots of delay spread versusdistance, the effect of transmitter and receiver orientations, robustness to shadowing, and so on.Simulation methods have been used to allow directcalculation of a particular impulse response based ona site-specific characterization of the propagation environment(13,14). The transmitter, receiver, and thereflecting surfaces are described and used to generatean impulse response. The basic assumption is thatmost interior surfaces reflect light diffusely in a Lambertian pattern, i.e. all incident light, regardless ofincident angle, is reflected in all directions with anintensity proportional to the cosine of the angle ofthe reflection with the surface normal. The difficultywith existing methods is that accurate modeling requires extensive computation.A third technique attempts to extract knowledge gained from experimental and simulation-basedchannel estimations into a simple-to-use model. In (15), for example, a model using two parameters (onefor path loss, one for delay spread) is used to providea general characterization of all diffuse IR channels.Methods for relating the parameters of the modelto particular room characteristics are given, so thatsystem designers can quickly estimate the channelcharacteristics in a wide range of situations.翻译:无线红外通信I.导言无线红外通信指的是使用近红外波段的光作为通信传输介质的一种通讯方式（1-3），如图1所示。
蜂窝无线通信系统的研究英文翻译
郑州轻工业学院本科毕业设计〔论文〕——英文翻译题目蜂窝无线通信系统的研究学生姓名耿永鹏专业班级信息工程07-1班学号 2院〔系〕计算机与通信工程学院指导教师〔职称〕张娜〔讲师〕完成时间 2011 年 5 月 30日英文原文RESEARCH OF CELLULAR WIRELESS COMMUNATIONSYSTEMAbstractCellular communication systems allow a large number of mobile users to seamlessly and simultaneously communicate to wireless modems at fixed base stations using a limited amount of radio frequency (RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to baseband, or to a wideband microwave link, and relayed to mobile switching centers (MSC), which connect the mobile transmissions with the Public Switched Telephone Network (PSTN). Similarly, communications from the PSTN are sent to the base station, where they are transmitted to the mobile. Cellular systems employ either frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), or spatial division multiple access (SDMA).1 IntroductionA wide variety of wireless communication systems have been developed to provide access to the communications infrastructure for mobile or fixed users in a myriad of operating environments. Most of today’s wireless systems are based on the cellular radio concept. Cellular communication systems allow a large number of mobile users to seamlessly and simultaneously communicate to wireless modems at fixed base stations using a limited amount of radio frequency (RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to baseband, or to a wideband microwave link, and relayed to mobile switching centers (MSC), which connect the mobile transmissions with the Public Switched Telephone Network (PSTN). Similarly, communications from the PSTN are sent to the base station, where they are transmitted to the mobile. Cellular systems employ either frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), or spatial division multiple access (SDMA) .Wireless communication links experience hostile physical channel characteristics, such as time-varying multipath and shadowing due to large objects in the propagation path.In addition, the performance of wireless cellular systems tends to be limited by interference from other users, and for that reason, it is important to have accurate techniques for modeling interference. These complex channel conditions are difficult to describe with a simple analytical model, although several models do provide analytical tractability with reasonable agreement to measured channel data . However, even when the channel is modeled in an analytically elegant manner, in the vast majority of situations it is still difficult or impossible to construct analytical solutions for link performance when error control coding, equalization, diversity, and network models are factored into the link model. Simulation approaches, therefore, are usually required when analyzing the performance of cellular communication links.Like wireless links, the system performance of a cellular radio system is most effectively modeled using simulation, due to the difficulty in modeling a large number of random events over time and space. These random events, such as the location of users, the number of simultaneous users in the system, the propagation conditions, interference and power level settings of each user, and the traffic demands of each user,combine together to impact the overall performance seen by a typical user in the cellular system. The aforementioned variables are just a small sampling of the many key physical mechanisms that dictate the instantaneous performance of a particular user at any time within the system. The term cellular radio system,therefore, refers to the entire population of mobile users and base stations throughout the geographic service area, as opposed to a single link that connects a single mobile user to a single base station. To design for a particular system-level performance, such as the likelihood of a particular user having acceptable service throughout the system, it is necessary to consider the complexity of multiple users that are simultaneously using the system throughout the coverage area. Thus, simulation is needed to consider the multi-user effects upon any of the individual links between the mobile and the base station.The link performance is a small-scale phenomenon, which deals with the instantaneous changes in the channel over a small local area, or small time duration, over which the average received power is assumed constant . Such assumptions are sensible in the design of error control codes, equalizers, and other components that serve to mitigatethe transient effects created by the channel. However, in order to determine the overall system performance of a large number of users spread over a wide geographic area, it is necessary to incorporate large-scale effects such as the statistical behavior of interference and signal levels experienced by individual users over large distances, while ignoring the transient channel characteristics. One may think of link-level simulation as being a vernier adjustment on the performance of a communication system, and the system-level simulation as being a coarse, yet important, approximation of the overall level of quality that any user could expect at any time.Cellular systems achieve high capacity (e.g., serve a large number of users) by allowing the mobile stations to share, or reuse a communication channel in different regions of the geographic service area. Channel reuse leads to co-channel interference among users sharing the same channel, which is recognized as one of the major limiting factors of performance and capacity of a cellular system. An appropriate understanding of the effects of co-channel interference on the capacity and performance is therefore required when deploying cellular systems, or when analyzing and designing system methodologies that mitigate the undesired effects of co-channel interference. These effects are strongly dependent on system aspects of the communication system, such as the number of users sharing the channel and their locations. Other aspects, more related to the propagation channel, such as path loss, shadow fading (or shadowing), and antenna radiation patterns are also important in the context of system performance, since these effects also vary with the locations of particular users. In this chapter, we will discuss the application of system-level simulation in the analysis of the performance of a cellular communication system under the effects of co-channel interference. We will analyze a simple multiple-user cellular system, including the antenna and propagation effects of a typical system. Despite the simplicity of the example system considered in this chapter, the analysis presented can easily be extended to include other features of a cellular system.2 Cellular Radio SystemSystem-Level Description：Cellular systems provide wireless coverage over a geographic service area by dividingthe geographic area into segments called cells as shown in Figure 2-1. The available frequency spectrum is also divided into a number of channels with a group of channels assigned to each cell. Base stations located in each cell are equipped with wireless modems that can communicate with mobile users. Radio frequency channels used in the transmission direction from the base station to the mobile are referred to as forward channels, while channels used in the direction from the mobile to the base station are referred to as reverse channels. The forward and reverse channels together identify a duplex cellular channel. When frequency division duplex (FDD) is used, the forward and reverse channels are split in frequency. Alternatively, when time division duplex (TDD) is used, the forward and reverse channels are on the same frequency, but use different time slots for transmission.Figure 2-1 Basic architecture of a cellular communications system High-capacity cellular systems employ frequency reuse among cells. This requires that co-channel cells (cells sharing the same frequency) are sufficiently far apart from each other to mitigate co-channel interference. Channel reuse is implemented by covering the geographic service area with clusters of N cells, as shown in Figure 2-2, where N is known as the cluster size.Figure 2-2 Cell clustering:Depiction of a three-cell reuse pattern The RF spectrum available for the geographic service area is assigned to each cluster, such that cells within a cluster do not share any channel . If M channels make up the entire spectrum available for the service area, and if the distribution of users is uniform over the service area, then each cell is assigned M/N channels. As the clusters are replicated over the service area, the reuse of channels leads to tiers of co-channel cells, and co-channel interference will result from the propagation of RF energy between co-channel base stations and mobile users. Co-channel interference in a cellular system occurs when, for example, a mobile simultaneously receives signals from the base station in its own cell, as well as from co-channel base stations in nearby cells from adjacent tiers. In this instance, one co-channel forward link (base station to mobile transmission) is the desired signal, and the other co-channel signals received by the mobile form the total co-channel interference at the receiver. The power level of the co-channel interference is closely related to the separation distances among co-channel cells. If we model the cells with a hexagonal shape, as in Figure 2-2, the minimum distance between the center of two co-channel cells, called the reuse distance ND, is〔2-1〕R3D N Nwhere R is the maximum radius of the cell (the hexagon is inscribed within the radius).Therefore, we can immediately see from Figure 2-2 that a small cluster size (small reuse distance ND), leads to high interference among co-channel cells.The level of co-channel interference received within a given cell is also dependent on the number of active co-channel cells at any instant of time. As mentioned before, co-channel cells are grouped into tiers with respect to a particular cell of interest. The number of co-channel cells in a given tier depends on the tier order and the geometry adopted to represent the shape of a cell (e.g., the coverage area of an individual base station). For the classic hexagonal shape, the closest co-channel cells are located in the first tier and there are six co-channel cells. The second tier consists of 12 co-channel cells, the third, 18, and so on. The total co-channel interference is, therefore, the sum of the co-channel interference signals transmitted from all co-channel cells of all tiers. However, co-channel cells belonging to the first tier have a stronger influence on the total interference, since they are closer to the cell where the interference is measured.Co-channel interference is recognized as one of the major factors that limits the capacity and link quality of a wireless communications system and plays an important role in the tradeoff between system capacity (large-scale system issue) and link quality (small-scale issue). For example, one approach for achieving high capacity (large number of users), without increasing the bandwidth of the RF spectrum allocated to the system, is to reduce the channel reuse distance by reducing the cluster size N of a cellular system . However, reduction in the cluster sizeincreases co-channel interference, which degrades the link quality.The level of interference within a cellular system at any time is random and must be simulated by modeling both the RF propagation environment between cells and the position location of the mobile users. In addition, the traffic statistics of each user and the type of channel allocation scheme at the base stations determine the instantaneous interference level and the capacity of the system.The effects of co-channel interference can be estimated by the signal-tointerference ratio (SIR) of the communication link, defined as the ratio of the power of the desired signal S, to the power of the total interference signal, I. Since both power levels S and I are random variables due to RF propagation effects, user mobility and traffic variation, the SIRis also a random variable. Consequently, the severity of the effects of co-channel interference on system performance is frequently analyzed in terms of the system outage probability, defined in this particular case as the probability that SIR is below a given threshold 0SIR . This isdx p ]SIR Pr[SIR P )x 0SIR 0SIR 0outpage （⎰=<= 〔2-2〕Where is the probability density function (pdf) of the SIR. Note the distinction between the definition of a link outage probability, that classifies an outage based on a particular bit error rate (BER) or Eb/N0 threshold for acceptable voice performance, and the system outage probability that considers a particular SIR threshold for acceptable mobile performance of a typical user.Analytical approaches for estimating the outage probability in a cellular system, as discussed in before, require tractable models for the RF propagation effects, user mobility, and traffic variation, in order to obtain an expression for . Unfortunately, it is very difficult to use analytical models for these effects, due to their complex relationship to the received signal level. Therefore, the estimation of the outage probability in a cellular system usually relies on simulation, which offers flexibility in the analysis. In this chapter, we present a simple example of a simulation of a cellular communication system, with the emphasis on the system aspects of the communication system, including multi-user performance, traffic engineering, and channel reuse. In order to conduct a system-level simulation, a number of aspects of the individual communication links must be considered. These include the channel model, the antenna radiation pattern, and the relationship between Eb/N0 (e.g., the SIR) and the acceptable performance. SIR(x)p SIR(x)p英文翻译蜂窝无线通信系统的研究摘要蜂窝通信系统允许大量移动用户无缝地、同时地利用有限的射频〔radio frequency，RF〕频谱与固定基站中的无线调制解调器通信。
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毕业设计（论文）的外文文献翻译 原始资料的题目/来源： Fundamentals of wireless
communications by David Tse 翻译后的中文题目： 无线通信基础
专 业 通信工程 学 生 学 号 班 号 指导教师 翻译日期 2015年6月15日 外文文献的中文翻译 7．mimo：空间多路复用与信道建模
本书我们已经看到多天线在无线通信中的几种不同应用。在第3章中，多
天线用于提供分集增益，增益无线链路的可靠性，并同时研究了接受分解和发射分解，而且，接受天线还能提供功率增益。在第5章中，我们看到了如果发射机已知信道，那么多采用多幅发射天线通过发射波束成形还可以提供功率增益。在第6章中，多副发射天线用于生产信道波动，满足机会通信技术的需要，改方案可以解释为机会波束成形，同时也能够提供功率增益。 章以及接下来的几章将研究一种利用多天线的新方法。我们将会看到在合适的信道衰落条件下，同时采用多幅发射天线和多幅接收天线可以提供用于通信的额外的空间维数并产生自由度增益，利用这些额外的自由度可以将若干数据流在空间上多路复用至MIMO信道中，从而带来容量的增加：采用n副发射天线和接受天线的这类MIMO信道的容量正比于n。 过去一度认为在基站采用多幅天线的多址接入系统允许若干个用户同时与基站通信，多幅天线可以实现不同用户信号的空间隔离。20世纪90年代中期，研究人员发现采用多幅发射天线和接收天线的点对点信道也会出现类似的效应，即使当发射天线相距不远时也是如此。只要散射环境足够丰富，使得接受天线能够将来自不同发射天线的信号分离开，该结论就成立。我们已经了解到了机会通信技术如何利用信道衰落，本章还会看到信道衰落对通信有益的另一例子。 将机会通信与MIMO技术提供的性能增益的本质进行比较和对比是非常的有远见的。机会通信技术主要提供功率增益，改功率增益在功率受限系统的低信噪比情况下相当明显，但在宽带受限系统的高信噪比情况下则很不明显。正如我们将看到的，MIMO技术不仅能够提供功率增益，还可以提供自由度增益，因此，MIMO技术成为在高信噪比情况下大幅度增加容量的主要工具。 MIMO通信是一个内容非常丰富的主题，对它的研究将覆盖本书其余章节。本章集中研究能够实现空间多路复用的物理环境的属性，并阐明如何在MIMO统计信道模型中简明扼要地俘获这些属性。具体分析过程如下：首先通过容量分析，明确确定确定性MIMO信道多路复用容量的关键参数，之后介绍一系列MIMO物理信道，评估其空间多路复用性能；根据这些实例的结果，我们认为在角域对MIMO信道进行建模是非常自然地，同时讨论了基于该方法的统计模型。本章采用的方法与第2章的方法是平行的，第2章就是从多径无线信道的几个理想实例着手进行分析，从中了解了基本物理现象，进而研究更适用于通信方案设计与性能分析的统计衰落模型。实际上，在特定的信道建模技术中，我们将会看到大量的类似方法。 我们贯穿始终的研究焦点是平坦衰落MIMO信道，但也可以直接扩展到频率选择性MIMO信道，这方面的内容会在习题中加以介绍。
7.1确定性mimo信道的多路复用容量 包括nt副发射天线和nt接受天线的窄带时不变无线信道可以用一个nt*nt阶确定性矩阵H描述，H具有哪些决定信道空间多路复用容量的重要属性呢？我们通过对信道容量的分析来回答这个问题。 7.1.1通过奇异值分解分析容量 时不变信道可以表示为：y = Hx+w_ 其中x、y与w分别表示一个码元时刻的发射信号、接受信号与高斯白噪声（为简单起见省略了时标），信道矩阵H为确定性的，并假定在所有时刻都保持不变，而且对于发射机和接收机是已知的。这里的hij为发射天线j到接受天线i的信道增益，对发射天线的信号的总功率约束为P。 这就是矢量高斯信道，将矢量信道分解为一组并行的、相互独立的标量高斯子信道就可以计算出该信道的容量。油线性代数的基本原理可知，每个线性变换都能够表示为三种运算的组合：旋转运算、比例运算和另一次旋转运算。用矩阵符号表示，矩阵H具有如下奇异值分解（SVD）：
其中，与为（旋转）酉矩阵1，是对角元素为非负实数、非对角线元素为零的矩形矩阵2。对角线元素为矩阵H的有序奇异值，其中nmin：=min（nt，nr）。因为
所以平方奇异值为矩阵HH*的特征值，同时也是矩阵H*H的特征值。注意，奇异值共有nmin个，可以将SVD重新写成为：
SVD分解可以解释为2个坐标变换：即如果输入用V的各种定义的坐标系统表示，并且输出用U的各列定义的坐标系统表示，那么输入/输出关系是非常简单的。 我们已经在第5章讨论时不变频率选择性信道以及具有完整CSI的时变衰落信道时看到了高斯并并行信道的例子。时不变MIMO信道也是另外一个例子，这里空间维所起的作用与其他问题中时间维和频率维的作用是相同的。大家熟知的容量表达式为：
其中，P1*,…,Pnmin*为注水功率分配：
通过选择满足总功率约束，各对应于信道的一个特征模式（也称特征信道）。各非零特征信道能够支持一路数据流，因此，MIMO信道能够支持多路数据流的空间多路复用。基于SVD的可靠通信结构与第三章介绍的OFDM系统之间存在明显的相似之处，在这2种情况下，都是利用变换将矩阵信道转换为一组并行的独立子信道。在OFDM系统中，矩阵信道由上式中的轮换矩阵C给出，该矩阵由ISI信道和加在输入码元上的循环前缀定义，ISI信道与MIMO信道的重要区别在于，前者的U、V矩阵不依赖与ISI信道的特定实现，而后者的U、V矩阵则依赖与MIMO信道的特定实现。
7.2 MIMO信道的物理建模 通过本节的内容我们将了解到MIMO信道的空间多路复用性能对于物理环境的依赖程度，为此，我们将研究一系列理想化实例并分析骑信道矩阵的秩和条件数，这些确定性实例同时表明了下一节中讨论的MIMO信道统计建模的常规方法。具体地讲，本节的讨论局限于均匀线性天线阵列，即天线一均匀的间隔分布于一条直线上，分析的细节取决于特定的天线结构，但是我们要表达的概念于此无关。 7.2.1 视距SIMO信道 最简单的SIMO信道只有一条视距信道（如下所示），图中为不存在任何反射体和散射体的自由空间，并且各天线对之间仅存在直接信号路径，天线间隔为
，其中为载波波长，为归一化接受天线间隔，即归一化为载波波长的单位，天线阵列的尺寸比发射机与接收机之间的距离小得多。 发射天线与第i副接受天线之间信道的连续时间冲激响应为： 其中，di为发射天线与第i副接受天线之间的距离，c为光速，a为路径衰减，假定路径衰减对所有天线对都相同。设di/c《1/W,其中W为传输带宽，则可得基带信道增益为：
其中，fc为载波频率。SIMO信道可以写成：y=hx+w。其中，x为发射码元，w为噪声，y为接受矢量。有时将信道增益矢量h=[h1,…hnt]t称为信号方向或由发射信号在接收天线阵列上感应出的空间特征图。 由于发射机与接收机之间的距离远大于接收天线阵列的尺寸，所以从发射天线到各接收天线的路径为1阶并行的，并且
其中，d为从发射天线到第一副接收天线之间的距离，为视距路径到接收天线 阵列的入射角，为在视距方向上接收天线i相对于接受天线1的位移。并且 通常被称为相对于接收天线阵列的方向余弦。因此，空间特征图h=[h1,…hnt]t为
即有相对时延引起的相位差为的连续天线处的接收信号。为了符号表示方便，定义
为方向余弦上的单位空间特征图。 最佳接收机只是将有噪声接收信号投影到该信号方向上，也就是最大比合并或接收波束成形，对不同的时延进行调整，从而使天线的接收信号能够进行相长合并，得到nt倍的功率增益，所获取的容量为：
于是，SIMO信道提供了功率增益，但没有提供自由度增益。 在介绍视距信道时，有时将接收天线阵列称为相位阵列天线。
8. MIMO:容量与多路复用结构 本章研究MIMO衰落信道的容量，讨论能够从信道中提取所期望的多路复用增益的收发信机结构，特别是集中研究发射机未知信道的情况。在快衰落MIMO信道中，可以证明： 1 在高信噪比时，独立同分布瑞利快衰落信道的容量有nminlogSNRb/s/Hz确定，其中nmin为发射天线数nt与接收天线数nr的最小值，这是自由度增益。 2 在低信噪比时，容量近似为nrSNRlog2eb/s/Hz，这是接收波束成形功率增益。 3 在所有信噪比时，容量与nmin呈线性比例关系，这是由于功率增益与自由度增益合并造成的。 此外，如果发射机也能够跟踪信道，那么还存在发射波束成形增益以及机会通信增益。 利用确定性时不变MIMO信道的容量获取收发信机，其结构比较简单：在适当的坐标系统中对独立数据流进行多路复用，接收机将接收矢量变换到另一个适当的坐标系统中，分别对不同的数据流进行译码。如果发射机未知信道，那么必须事先固定独立数据流被多路复用所选取的坐标系统。连同联合译码，这种发射机结构实现了快衰落信道的容量，在文献中也将改结构称为V-BLAST结构1。 8．3节讨论比独立数据流的联合最大似然译码更简单的接收机结构，虽然可以支持信道全部自由度的接收机结构有若干种，其中的一种特殊结构是合并使用最小均方误差估计与串行干扰消除，即MMSE-SIC接收机可以获取容量。 慢衰落MIMO信道的性能可以通过中断概率和相应的中断容量来表征。在低信噪比时，一个时刻利用一副发射天线就可以获取中断容量，实现满分集增益ntnr和功率增益nr。 另一方面，高信噪比时的中断容量还受益于自由度增益，要简洁地刻画其特征更加困难，此问题留到第9章再分析。 虽然采用V-BLAST结构可以实现快衰落信道的容量，但该结构对于慢衰落信道则是严格次最优的，实际上，它甚至还没有实现MIMO信道期望的满分集增益。为了说明这一问题，考虑通过发射天线直接发送独立数据流，在这种情况下，各数据流的分集仅限于接收分集，为了从信道中获取满分集，须对发射天线进行编码。将发射天线编码与MMSE-SIC结合起来的一种修正结构D-BLAST2不仅能够从信道中获取满分集，而且其性能还接近于中断容量。
8.1 V-BLAST结构 首先考虑时不变信道y[m]=Hx[m]+w[m] m=1,2,…当发射机已知信道矩阵H时，有7.1.1节可知，最优策略是在H*H的特征矢量的方向上发射独立数据流，即在由矩阵V定义的坐标系统中发射，该坐标系统与信道有关。考虑到要处理发射机未知信道矩阵时的衰落信道，归纳出入如下图所示的结构，图中nt个独立的数据流在由酉矩阵Q确定的任意坐标系统中进行多路复用，该酉矩阵未必与信道矩阵H有关，这就是V-BLAST结构。对数据流进行联合译码，为第k个数据流分配的功率为Pk（使得功率之和P1+…+Pnt等于P，即发射总功率约束），并利用速率为Rk的容量获取高斯码进行编码，总的速率为