如何解决WCDMA上下行链路不平衡问题
WCDMA常见问题及解决思路
4．2．5．1覆盖优化首先让手机在idle状态进行覆盖测试，来优化PCCPCH RSCP 的覆盖范围和PCCPCH_C/I，然后再做拨打测试，可以达到事半功倍的效果。
因为在PCCPCH RSCP弱和PCCPCH_C/I较差的地方，寻呼成功率、拨打成功率等也必然很差。
当PCCPCH_RSCP 和PCCPCH_C/I优化达到指标后，那么在对拨打状态的优化时就可以去除这方面的影响，可以专注于对切换、寻呼等参数的优化以及对设备故障的排查，达到事半功倍的效果。
问题分类：常见的PCCPCH RSCP覆盖问题主要有如下几种情况：（1）邻区缺失引起的弱覆盖（2）参数设置不合理引起的弱覆盖（3）缺少基站引起的弱覆盖（4）越区覆盖（5）背向覆盖（6）天馈实际安装与规划不一致引起的覆盖问题（7）基站GPS故障引起的弱覆盖解决思路：对于不同的覆盖问题，有着不同的优化方法，以下是常见覆盖问题的优化方法：（1）对于由于邻区缺失引起的弱覆盖，应添加合理的邻区（2）对于由于参数设置不合理引起的弱覆盖（包括小区功率参数以及切换、重选参数），根据具体情况调整相关参数（3）对于由于缺少基站的弱覆盖，应通过在合适点新增基站以提升覆盖（4）对于由于越区覆盖导致的覆盖问题，应通过调整问题小区天馈的方位角/俯仰角或者降低小区发射功率解决，但是降低小区发射功率将影响小区覆盖范围内所欲区域的覆盖情况，不建议此种方法解决越区（5）对于背向覆盖，大部分由于建筑物反射导致，合理调整方位角/下倾角（6）对于天馈安装与规划不一致（包括同一基站小区间天馈接反或者天馈下倾角/方位角不合适等）引起的覆盖问题，应对天馈进行调整（7）对于由于基站GPS故障引起的弱覆盖，应及时上站更换故障模块总结：对于网络中存在的各种覆盖问题，我们应仔细分析并找出问题的根源。
有些问题的现象可能是相似或者相同的，但是问题的根源却有着本质的区别，应采取不同的解决方案。
4．2．5．2切换优化无线网络特有的用户移动性，为了保证用户移动过程中同样享有业务就必须使网络具备正确的切换。
GSM网无线网络优化中上下行问题分析
GSM网无线网络优化中上下行问题分析提要GSM网无线网络优化工作中,设备上下行平衡问题往往容易被忽略,但实际工作中,上行明显弱于下行的问题存在较多,如何处理该类问题,一直是网络优化工程师比较关心的。
本文针对这一问题进行详细分析和介绍,以供大家参考。
关键词:上下行平衡;平衡等级;接收灵敏度中图分类号:F49文献标识码:A一、引言从网管上局取出话务统计数据见表1、表2、表3,依据数据分析得出上下行平衡性能,具体为一级至五级占比例合平均为25%左右,而七级至十一级占用比例合为59%左右,并且BTS312、BTS30、BTS3012、BTS3001C和BTS3002C基站均如此,如果以6为标准则为上行偏弱,需要分析该问题原因,下两表分别为各等级统计次数和比例。
(表1、表2、表3)二、问题原因分析按照协议规定,手机的接收灵敏度为-102dBm,而基站接收灵敏度为-110dBm,考虑到一般手机的灵敏度可能会比协议好2dB左右。
所以,一般取手机灵敏度为-104dBm。
这样上下行灵敏度的差别就是6dB。
所以,在上下行平衡的统计项中,当下行接收电平(手机上报)大于上行接收电平(基站上报)6dB时候,我们认为是最理想的平衡状态。
所以,在上下行平衡统计中,等级6就是下行接收电平恰好大于上行接收电平6dB的情况。
表4就是具体的各个统计区间说明。
(表4)上下行平衡话统在BSC侧的计算公式为:下行功率电平-上行功率电平-6dB(灵敏度补偿)=平衡等级上下行不平衡的原因有:(一)基站各个载频中间上报电平有一定的波动。
GSM协议0508规定,测量基站接收机的接收信号电平RMS(均方根值),在正常条件下,从-110dBm～-70dBm,其绝对精度为±4dB,在正常条件和极端温度下,从-110dBm～-48dBm之间,绝对精度为±6dB。
GSM协议这样的规定是从三方面考虑:(1)射频器件的幅频特性(也就是随着频率的变化,射频器件的增益会有些变化,这是射频器件的特性);(2)整个接收通道器件的增益离散性;(3)这种上报精度是不会影响网络指标的。
上下行不平衡处理方法及案例
一、链路不平衡简介链路不平衡基站主要分为室分基站和宏站的链路不平衡。
而一般情况下室分基站都是上行电平明显强于下行电平。
而引起室分基站上行电平强于下行电平的原因是这些室分基站都挂有直放站和干放，由于直放站和干放对上行信号有放大作用，导致上行电平明显强于下行电平。
处理方法是调整直放站和干放的上行增益，减小上行信号放大的倍数，达到链路平衡的目的。
宏站链路不平衡的问题比较复杂，原因也比较多。
宏站的链路不平衡的可能是由于载频故障引起。
载频故障可能引起链路不平衡，需要更换载频。
天馈系统问题是引起宏站链路不平衡的主要原因。
载频的小钢跳质量不好，或者链接不牢固可能引起接收信号偏弱，导致下行信号过强，处理方法是更换小跳线。
馈线存在驻波告警或者接头部分做工不好都会导致驻波告警。
馈线接成鸳鸯线会造成链路不平衡。
馈线接成鸳鸯线的基站一般情况会有两个小区的载频同时出现链路不平衡现象。
鸳鸯线可以通过信令跟踪发现，通常情况下存在鸳鸯线的小区，主集接收电平和分集接收电平值会相差6个dB以上。
基站数据配置与实际链接不一致也会导致链路不平衡。
一般情况下，如果数据配置错误，跟踪信令会发现上行电平值时时为-110dBM，如果出现这种情况，基本可以判断实际连接与数据配置不一致。
二、典型案例分析：1、海盐泾塘-2上下链路不平衡处理。
海盐泾塘-2基站TCH载频上下行电平强于上行电平。
代维到达现场检查显现馈线连接，基站为2、2、2配置。
2扇区实际连接接收为分集接收模式。
跟踪信令发现，海盐泾塘-2分集载频上行电平值时时为-110dBM。
由此可以判断海盐泾塘-2数据配置可能跟实际连接不一致，检查海盐泾塘-2基站数据配置，发现海盐泾塘-2接收模式为独立接收，与实际连接模式不同。
将海盐泾塘的接收模式由独立接收改为分集接收。
修改之后，海盐泾塘-2上下链路平衡。
起始时间对象名称上下行平衡因子S462A:上下行平衡等级1的次数S462K:上下行平衡等级11的次数1和11比例10/03/2010 00:00:00 海盐泾塘-2 10.78 0 39 78.00% 10/03/2010 01:00:00 海盐泾塘-2 11 0 190 100.00% 10/03/2010 02:00:00 海盐泾塘-2 11 0 399 100.00% 10/03/2010 04:00:00 海盐泾塘-2 11 0 3 100.00% 10/03/2010 05:00:00 海盐泾塘-2 10.984 0 309 98.41% 10/03/2010 06:00:00 海盐泾塘-2 10.931 0 2531 93.43% 10/03/2010 07:00:00 海盐泾塘-2 10.956 0 3501 96.26% 10/03/2010 08:00:00 海盐泾塘-2 10.931 0 2642 94.97% 10/03/2010 09:00:00 海盐泾塘-2 10.941 0 7410 95.01% 10/03/2010 10:00:00 海盐泾塘-2 10.885 0 5990 90.35% 10/03/2010 11:00:00 海盐泾塘-2 10.89 0 3187 91.11% 10/03/2010 12:00:00 海盐泾塘-2 10.956 0 4890 96.05%10/03/2010 13:00:00 海盐泾塘-2 10.984 0 62 98.41%10/03/2010 14:00:00 海盐泾塘-2 11 0 389 100.00% 10/03/2010 15:00:00 海盐泾塘-2 11 0 1531 100.00% 10/03/2010 16:00:00 海盐泾塘-2 7.275 13 273 5.73%10/03/2010 17:00:00 海盐泾塘-2 6.585 31 36 1.36%10/03/2010 18:00:00 海盐泾塘-2 6.537 43 398 4.88%10/03/2010 19:00:00 海盐泾塘-2 6.676 19 242 2.69%10/03/2010 20:00:00 海盐泾塘-2 7.521 1 268 2.75%10/03/2010 21:00:00 海盐泾塘-2 6.905 39 179 2.48%10/03/2010 22:00:00 海盐泾塘-2 4.723 185 1 7.23%10/03/2010 23:00:00 海盐泾塘-2 7.605 1 40 3.13%11/03/2010 00:00:00 海盐泾塘-2 7.214 0 0 0.00%11/03/2010 01:00:00 海盐泾塘-2 7.763 0 0 0.00%11/03/2010 03:00:00 海盐泾塘-2 6.646 0 0 0.00%11/03/2010 04:00:00 海盐泾塘-2 7.28 0 0 0.00%11/03/2010 05:00:00 海盐泾塘-2 8.547 4 39 6.83%11/03/2010 06:00:00 海盐泾塘-2 7.329 0 5 0.80%11/03/2010 07:00:00 海盐泾塘-2 6.821 11 58 1.99%11/03/2010 08:00:00 海盐泾塘-2 6.657 6 27 1.15%11/03/2010 09:00:00 海盐泾塘-2 6.91 11 25 0.95%11/03/2010 10:00:00 海盐泾塘-2 6.004 22 183 1.91%11/03/2010 11:00:00 海盐泾塘-2 7.197 11 66 0.84%11/03/2010 12:00:00 海盐泾塘-2 5.697 15 17 0.95%11/03/2010 13:00:00 海盐泾塘-2 5.095 10 1 0.42%11/03/2010 14:00:00 海盐泾塘-2 4.794 48 5 1.77%11/03/2010 15:00:00 海盐泾塘-2 5.359 89 8 1.17%11/03/2010 16:00:00 海盐泾塘-2 4.994 132 15 4.72%2、海盐香溢大酒店上下链路处理。
LTE网络优化方案上下行链路不均衡的优化分析
LTE网络优化方案上下行链路不均衡的优化分析
上下行链路不均衡会导致以下问题：
2.下行带宽浪费：由于下行链路带宽过剩，但上行链路带宽不足，导致下行带宽没有得到有效利用，浪费网络资源。
3.QoS差异：上下行链路不均衡可能导致不同服务质量等级的差异，进一步影响用户体验。
为了解决上下行链路不均衡问题，可以采取以下优化方案：
一、网络规划优化：
1.基站规划：合理规划基站的布局和密度，使得上行链路和下行链路能够平衡地覆盖用户，避免上行链路过于拥塞。
2.频谱分配：根据实际需求，合理分配上行和下行的频谱资源，确保上行链路和下行链路能够得到均衡的利用。
二、上行链路优化：
1.增加上行带宽：通过增加小区的上行带宽或者组播通道的带宽，提高上行链路的传输速度和容量。
3.优化调度算法：采用合适的调度算法，根据不同用户的业务需求和网络状况，合理分配上行传输资源，提高上行链路的利用率。
三、下行链路优化：
1.QoS保证：根据用户的优先级和业务需求，对下行链路上的数据进行合理的调度和优先级控制，确保重要数据的传输质量。
2.缓存技术：使用缓存技术对热门数据进行缓存，减少对下行链路的
请求，提高用户对数据的响应速度。
3.增加下行带宽：根据网络负载和用户需求，增加下行链路的带宽，
提高传输速度和容量。
四、终端优化：
1.充分利用终端设备的资源：通过优化终端设备的协议栈和传输机制，减少协议开销，提高上行链路的利用率。
2.功率控制：根据终端设备的信号质量和覆盖范围，合理控制终端设
备的功率，确保信号的质量和传输的稳定性。
上下行不平衡的影响及问题处理
上下行不平衡的影响及问题处理上下行不平衡，指目标覆盖区域内，上下行对称业务出现下行覆盖良好而上行覆盖受限（如UE的发射功率达到最大仍不能满足上行BLER要求），或上行覆盖良好而下行覆盖受限（表现为下行专用信道码发射功率达到最大仍不能满足下行BLER要求）的情况。
上下行不平衡的覆盖问题比较容易导致掉话。
这类问题通常包括以下原因：上行干扰（比如直放站和干放等设备上下行增益设置存在问题），天馈系统问题，NodeB硬件原因等。
主要的解决方法是对设备硬件与设备设置进行检查上下行功率不平衡造成单通、掉话[现象描述]路测过程中发现以下现象：手机占上某小区，但不能呼出；单向通话；在距离小区一定距离处总是掉话；频繁的切换后掉话现象。
[处理过程]无线链路分上行和下行两个方向，实际的覆盖范围应由信号较弱的方向决定。
如果上行信号覆盖大于下行信号覆盖，那么小区边缘下行信号较弱，容易被其它小区的强信号“淹没”；如果下行信号覆盖大于上行信号覆盖，那么移动台被迫驻留在该强信号下，但上行信号太弱，手机不能呼出，或造成通话后话音质量差、单向通话，甚至掉话。
当然，平衡并不是绝对的相等，由于基站灵敏度好于移动台的灵敏度，所以下行信号将大于上行信号。
上面提到的路测现象多是缘于上行信号低于下行信号太多而造成的功率不平衡，特别是打开上行功控时。
测试时让手机往小区边缘方向移动，同时用MA10信令分析仪在基站侧跟踪抓取数据，比较BTS和MS各自的接收电平，观察当上行信号达到最低接收门限电平时，下行信号是否还好得足以让手机驻留该小区。
检查上下行功率是否平衡，但从下图可以看出，其差异已近30dB；若出现多个这样的测量结果，肯定是上行接收存在问题，需要检查TRX板、分路器、塔放电流和天馈的驻波比。
当上行功控打开时，功控参数设置不当也会造成明显的功率不平衡。
首先应保证手机静态功率等级设置正确（900为等级5，1800为等级0），曾发现1800手机因上下行功率不平衡造成单通。
WCDMA网络语音业务上下行功率不平衡问题分析与优化
２．２功率控制策略和算法
在了解功率控制基本原理后，我ｃｒｌｘ寸语音业务功率控制的策略和算法进行分析。上 下行功率平衡指标主要考察手机在接收信号强度良好情况下，手机的上行发射功率，所 以本文重点对ＷＣＤＭＡ系统上行链路功率控制策略进行介绍。上行功控主要包括以下几 个部分：
关键词 ＷＣＤＭＡ；语音业务；上下行功率不平衡；功率控制
小区内干扰。 功率控制的作用是在保证物理信道传输质量要求前提下，尽可能的限制基站或移动
台的发射功率，从而尽可能降低对其他用户信号的干扰。用户所面临的通信环境是不同 的，如移动台与发射台的远近，周围的地理环境，干扰噪声的强度等，对于每一个用户 而言，特定服务所要求信道传输质量也不相同，这些不同也就决定了分配给特定用户的 物理信道环功率控制的实时性和准确性
大连ＷＣＤＭＡ网络外环功率控制的算法采用的是门限算法，ＲＮＣ侧指根据上行传输 信道ＣＲＣＩ值统计误块数，若误块容忍周期未到时，但误块数已超过了误块门限，此时就 要上调ＳＩＲＴａｒｇｅｔ；当误块容忍计数器大于等于误块容忍周期时，若收到的误块数小于误 块门限则下调整ＳＩＲＴａｒｇｅｔ，等于误块门限则不调整。
（１）外环功控环节，调整ＲＮＣ侧为基站没定的外环功控ＳＩＲＴａｒｇｅｔ。 （２）外环功控环节，调整ＲＮＣ侧外环功控算法，提高外环功率控制的实时性和 准确性。
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上下行链路平衡
关于上下行链路不平衡的一些说明1) 理论计算一个无线扇区允许的最大半径取决于发信端和收信端之间所允许的最大路径损耗。
也就是取决于发射天线端的最大输出功率EIRP(emitted isotropic radiation power)和接收天线端的最低输入功率(为正确接收解调必须达到的输入功率) RIPL(required input power level) 的差值。
在计算上下行无线链路的最大允许路径损耗之前，让我们来看看BTS和MS各自的EIRP 和RIPL：1-1) BTS的输出:EIRP BTS = Power Amplifier Output - Combiner Loss - Downlink Cable Loss + Antenna Gain注，公式中各参数的含义：a)Power Amplifier Output: PA的输出功率b)Combiner Loss: 合路器(DUCOM, HYCOM, FICOM)衰减c)Downlink Cable Loss: 从机柜到天线方向的电缆损耗d)Antenna Gain: 天线本身的增益一般这些参数的取值为：a) Power Amplifier Output:PA25 或 MPA: 25 Watt = 44 dBm (GSM900)HPAG: 50Watt = 47dBmb) Combiner Loss:c) Downlink Antenna Cable Loss: 3 dB (example)e)Antenna Gain: 15.5 dB (650度方向性天线的典型值)南宁市区天线天线为15.5 dBi郊区为17dBi1-2) MS的输出:手机的电缆损耗(cable loss)和天线增益(antenna gain)都为0。
手机的最大输出功率取决于它的功率等级：摘自 GSM: 05.05通常我们的900兆无线扇区都是为 Power Class=4 (输出功率为33dBm)的手机设计的，但考虑到要保证网内可能还存在的Power Class为2或3的手机的上下行平衡，我们在BSC 数据库中设置：MSTXPMAX=5 (33dBm)。
LTE网络优化方案：上下行链路不均衡的优化分析
3GPP TSG RAN WG2 #58bis Tdoc-R2-072721 Orlando, U.S.A., 25th – 29th June 2007Agenda item: 4.5.1Source: NTT DoCoMo, Telecom Italia, T-MobileTitle: Use of cell specific offsets and reading neighbour BCHDocument for: Discussion1. IntroductionIn RAN2#58 in Kobe, RAN2 has decided that, to allow for sufficient mobility control without NCL, an offset value shall be included in BCH, and that the UE shall read the neighbour cell BCH to obtain this offset value both in ACTIVE and IDLE modes [1]. The offset value biases the measured quantity of the corresponding cell for mobility control. It was expressed by operators that this offset is necessary primarily to control the cell boudaries considering the DL and UL coverage imbalance, caused by DL/UL feeder cable loss difference (due to TMA) and eNBs having different transmission powers adjoining in the network [2]. However, in RAN Plenary #36 in Busan, the decision was taken back after some vendors expressed concerns on the handover/cell reselection delays and UE battery consumption [3]. Revisiting this issue, this document explains why cell specific offsets are thought necessary, summarises concerns of reading neighbour BCH, and presents our position on the issue.Note that the support for optional NCL for intra-frequency cells has already been agreed in RAN2, and this has not been reopened. The optional NCL should serve purposes such as to set serving-neighbour pairwise specific offsets or to blacklist certain cells. It can also be used to speed up cell detection, although relevance of this is pending RAN4 response. Hence, the only open question that needs to be addressed is “whether UE reads neighbour BCH and obtains the offset value included therewith,” and this is the exact focus of this paper.2. Use of cell specific offsets2.1 DL/UL imbalance problemAs mentioned in [2], the need for a cell specific offset is mainly motivated by the fact that eNBs of different power classes can be adjoining in many places throughout the network, and that each cell has different DL and UL feeder cable losses (i.e., DL/UL feeder loss difference due to TMA). By setting approprite offset values, the DL/UL imbalance can be mitigated. Before going into how offsetting works, the DL/UL imbalance problem has to be understood.Figure 1 shows the principle of DL/UL imbalance caused by cable loss difference. Assuming two base stations, having the same antennas and propagation coefficients, the cell boundary will be at the centre (equidistant) based on path loss (UL oriented). However, if the two base stations have different cable losses (or different transmission powers), the cell boundary will deviate from the centre based on Ec/N0 (DL oriented), hence causing DL/UL imbalance.Fig. 1 DL/UL imbalance principle.2.2 Mitigating DL/UL imbalanceThe DL/UL imbalance problem can be mitigated/tolerated in a number of ways:Alt.1: Mobility control based on Ec/N0 (do nothing)Alt.2: Adjust DL total transmission power based on the UL coverage (DL/UL balancing)Alt.3: Adjust DL pilot transmission power based on the UL coverageAlt.4: Use cell specific offsetsEach solution is described in detail in the sequel. Note that these solutions are not exclusive, and can be combined if so desired.To simplify the discussion, the traffic distribution aspect is omitted for the qualitative assessment below. However in practice, cell planning has to take into account real traffic distributions, which can be far from ideal uniform. It should be noted that this adds another dimension to network planning, which can be quite complicated.2.2.1 Alt.1: Ec/N0 based mobility control (do nothing)The first solution is to do nothing special, and just rely on Ec/N0 to control mobility (Fig.2). This can be optimum for the DL, however, the UL will deteriorate especially at cell edge. If the UE has sufficient transmission power (typ. small cells), it will transmit at a larger power to satisfy its QoS (i.e., the required SIR for a desired rate). If the UE did not have enough power (typ. large cells), the likely consequence in a scheduler based system as in LTE is that it transmits (is scheduled) more frequently so that the desired rate can be met. In either case, this will create larger interference at the neighbour cell, and hence decreases system capacity in the UL.Fig. 2 Ec/N0 based mobility control (do nothing).2.2.2 Alt.2: DL total Tx power adjusting (balancing)The second solution is to adjust the total DL transmission power of the base station such that the DL boundary matches the UL boundary, while the power ratio of the pilot symbols used for mobility measurements is maintained. An example case is shown in Fig. 3. The total power of the base station having a smaller cable loss is reduced, such that the emitted power from the antenna is equal to that of the neighbour having a larger cable loss. This will balance the DL/UL boundaries, hence resolving imbalance, and will be the optimum in terms of the UL. This has a benefit in that it limits DL interference at the neighbour, and generally improves Ior/(Ioc+N0) at cell boundaries. However, it has some drawbacks as the cell with the reduced power now has limited capacity due to reduced power. It may also reduce channel estimation and cell detection performances due to reduced pilot power. This will be more evident in noise limited deployements (e.g., large cells).Fig. 3 DL total Tx power adjusting (balancing).2.2.3 Alt.3: DL pilot Tx power adjustingInstead of adjusting the total transmission power, the transmission power of the pilot symbols can be reduced, while maintaining the total power (Fig. 4). This would also resolve DL/UL imbalance. Since the total power is maintained and data transmissions can be allocated larger powers, the cell can provide larger capacity compared to Alt.2. However, this will create larger interference at the neighbour cell, and will reduce channel estimation and cell detection performance due to reduced pilot power. This alternative will also require some further adjustments e.g.,The transmission powers of other DL common channels (such as BCH) also need to be adjusted considering the channel estimation quality.The pilot/data symbol power ratio must be adjusted and signalled to the UE so that it can correctly demodulate 16QAM or 64QAM signals.These adjustments will have to be performed for each cell, which can incur extensive efforts on operators.Fig. 4 DL pilot Tx power adjusting.2.2.4 Alt.4: Use cell specific offsetsAnother alternative is to use cell specific offsets (Fig. 5). With this alternative, the total and pilot powers do not have to be modified, and the DL/UL imbalance can be mitigated by instead, setting a cell specific offset at each cell. The offset value can be set such that it reflects the cable loss (DL/UL difference). By having the UE take into account the offset value in making mobility decisions, the imbalance can be resolved.The offset can be used to optimise cell boundary for the UL, DL, or anywhere in between, by setting the appropriate offset value. If the offset is used to optimise boundary for the UL, for the cell transmitting at a higher power (left in Fig.5) the DL quality/capacity improves (1), however, the neighbour cell (right in Fig.5) will suffer degraded DL quality/capacity (2) and degraded DL common channel (CCH) quality (3). Note that if the cell boundary is optimised for the DL (offset = 0), the performance will be the same as for Alt.1.Since the pilot power is not reduced as in Alt.3, the channel estimation quality does not degrade with this alternative. The pilot power is usually adjusted considering the optimum (tradeoff) allocation between the pilot and data, and in that sense, this alternative allows to maintain the optimum power allocation settings (i.e., it should not require power adjustments per cell). Although signalling of the offsets incur some additional overhead, this overhead can be trivial considering the entire system bandwidth. As such, it offers a considerably simpler solution to resolving DL/UL imbalance, especially if the offset is read from the neighbour BCH.Fig. 5 DL/UL imbalance mitigation by use of cell specific offsets.2.2.5 Qualitative comparisonTable 1 summarises qualitative comparison of the four alternatives.Table 1 Qualitative comparison.2.2.6 Capacity comparisonHere, two extreme scenarios, i.e., Alt.2 (balancing, hereafter) and Alt.4 (offsetting, hereafter), both optimised for UL,are compared. Note that Alt.3 is expected to perform somewhat similarly as Alt.4, although any difference cannot be assessed without detailed analysis. (It can be expected that Alt.3 performs worse due to poorer channel estimation quality.) The deployment Cases 1 (ISD = 500 m) and 3 (ISD = 1,732 m) in TR 25.814 [4] are assumed, with vertical antenna patterns and tilting also taken into account. The feeder cable loss was modelled as log-normal with [-5 dB, +5 dB] limits, with the sectors of the same eNB having the same cable loss. The log-normal std. deviation was set in a range 1-4 dB, and the median was set such that the resulting gain on average is equal to that assumed in Cases 1 and 3. Snapshot system level simulations were performed to obtain the Ior/(Ioc+N0) distribution, and from this, the normalised capacity was derived considering two factors: CCH overhead according to the Ior/(Ioc+N0) at 2% coverage, and DL-SCH capacity scaling according to the average Ior/(Ioc+N0). For the CCH factor, it was assumed that a 2 dB degradation in Ior/(Ioc+N0) incurs a 3 dB larger overhead for CCH (based on our internal analysis).Figures 6 and 7 compare the Ior/(Ioc+N0) distribution of offsetting (Alt.4) and balancing (Alt.2). It can be observed that offsetting produces worse Ior/(Ioc+N0) in Case 1 (Fig. 6(a), 7(a)). This is due to increased interference at cell edge. However, in Case 3, offsetting produces better Ior/(Ioc+N0) even at around cell edge (Fig. 6(b), 7(b)). This is because balancing (Alt.2) reduces the total transmission power and increases the impact of thermal noise throughout the entire cell.00.20.40.60.81Ior/(Ioc+N0) [dB]00.20.40.60.81Ior/(Ioc+N0) [dB](a) (b)Fig. 6 Ior/(Ioc+N0) distribution for (a) Case 1 and (b) Case 3.Ior/(Ioc+N0) [dB]00.020.040.060.080.1Ior/(Ioc+N0) [dB](a) (b)Fig. 7 Ior/(Ioc+N0) distribution (cell edge) for (a) Case 1 and (b) Case 3.Figure 8 compares the system capacity. As shown in Fig. 8(a), offsetting provides less capacity in Case 1 when some CCH overhead is considered. This is mainly due to the larger CCH overhead caused by Ior/(Ioc+N0) degradation at around cell edge. However, as shown in Fig. 8(b), offsetting provides larger capacity than balancing in Case 3. The capacity is about 20% larger at 2 dB imbalance and 10% CCH overhead. This is because balancing reduces the total power and hence increases the impact of thermal noise. With offsetting, the impact of thermal noise is kept at minimum. Therefore, offsetting is beneficial in providing larger capacity in moderate/large cell scenarios (more evident in thermal noise limited scenarios).Log-normal std. dev. of DL/UL imbalance [dB]Log-normal std. dev. of DL/UL imbalance [dB](a) (b)Fig. 8 Normalised capacity for (a) Case 1 and (b) Case 3.2.2.7 Benefits of cell specific offsetsSummarising above discussions and analysis, the benefits of cell specific offsets are:Offsetting provides larger system capacity when cell size is moderate/large (i.e., more evident in thermal noise limited scenarios);Offsetting allows the operator to flexibly choose between UL optimised and DL optimised;Easy to operate as the offset is just a parameter on BCCH (or DCCH), and does not involve complicated power adjustments.Note that balancing by DL transmission power adjusting is anyway possible, regardless of support for an offset mechanism. The mechanism to utilise cell specific offsets allows the operator to cope with DL/UL imbalance in various ways, providing flexible countermeasures depending on the deployment scenario. Without the offsetting mechanism, the operator is restricted to either tolerating UL losses, or to engage a complicated process of adjusting DL transmission powers. Therefore, the offsetting mechanism should be supported in LTE.3. Reading neighbour BCH3.1 Ways of signalling cell specific offsetsIn section 2, the need for cell specific offsets has been justified. The question then becomes how the offset values are signalled to the UE. As discussed in [2], there are two ways:Alt.1: UE reads offset included in neighbour BCH-The offset is set for its own cell in BCH (no need to care about neighbours).-The same offset applies to all the neighbouring cells (1-to-all).-The UE has to read the neighbour BCH to avoid any ping-pongs [5].-This was decided as mandatory in RAN2#58 in Kobe, but reopened in RAN Plenary #36.Alt.2: Use NCL-The offsets applicable to the relevant neighbours are broadcast by NCL.-The offset can be specific to certain serving-neighbour relationship (1-to-1).-The use of NCL causes larger overhead compared to Alt.1.-NCL needs to be planned and set by OAM, which can be complicated.-This is already supported optionally in LTE (RAN2 decision).The only question that needs to be addressed is whether LTE shall support Alt.1 or not.3.2 Concerns of reading neighbour BCHAs discussed in detail in [2] and above in section 2, the offset can be used primarily to mitigate DL/UL imbalance. As such it is prevalent that each cell requires a different offset value, and that it is sufficient for most cases if the offset is 1-to-all. That is, the 1-to-1 granularity is not necessary to cope with DL/UL imbalance, but only necessary in irregular cases like tunnels. Hence, it would be preferable, from OAM aspects, that Alt.1 is adopted. However, as expressed by [2] and in particular [3], there are several concerns of mandating the UE to read neighbour BCH:UE will have to read BCH for each cell detected;-It can be battery consuming if the UE cannot decode BCH and repeatedly tries decoding for a detected cell;-This problem is more evident if the BCH error rate does not match (is worse than) the cell detection performance;Note: This may be prevented to some extent by specifying UE behaviours, e.g., UE only reads BCH if RSRP > threshold, and/or UE considers offset = 0 if it fails reading BCH after some attempts.UE implementation may be more complex.-UE may have to decide whether to read BCH or not upon detecting a cell, e.g., UE does not have to read for cells indicated in NCL or if RSRP < threshold, etc.Larger BCH overhead to make it robust.- E.g., by reducing the coding rate, increasing Tx power, repetition, soft combining, etc.These aspects need to be discussed in RAN WGs, and comments from UE vendors are especially valuable in this respect. If these concerns are serious, LTE should certainly not support reading of neighbour BCH.3.3 Other aspects of reading neighbour BCHIn discussing the pros/cons of reading neighbour BCH, another aspect that might be worth considering is the CSG cell (home-eNB) scenario. The requirements of CSG cells [6] state notably:7.It shall be possible to minimise the quantity of measurements which UEs perform on CSG Cells, if the UEdoes not belong to the User Group of a specificCSG Cell.8.The mobility procedures shall allow a large number of (small) CSG Cells to be deployed within the coverageof e-UTRAN, UTRAN and GERAN macro-layer cells. Deployment of (additional) CSG Cells shall not require reconfiguration of other eNodeB (E-UTRAN) or RNC (UTRAN) or BSS (GERAN).This could be easily achieved if the UE reads the BCH of a detected cell, and finds out that the cell is not open to public through some simple indicators or cell id included in BCH. This will allow the UE to omit measurements on that cell, and avoid reporting on CSG cells that it has no access to. If the UE does not read neighbour BCH, other means must be thought of, although approaches such as blacklisting seems to contradict with requirement #8 above.4. ConclusionsThe need for cell specific offset mechanism and concerns of reading neighbour BCH have been discussed. Following the discussions above and in [2], we see only two viable alternatives shown in Table 2.Table 2. Viable alternatives [2].After revisiting the issue, our current position is as below:An offset mechanism is necessary.The current RAN2 WA to support optional NCL to set serving-neighbour pairwise specific offsets should be kept.The optional NCL should also be supported for inter-frequency/RA T neighbour cells [2].The solutions for ACTIVE/IDLE mobility should be aligned [2], i.e., the choice should only be between Alt.1 and Alt.2 in Table 2.If reading of neighbour BCH has serious impacts on UE complexity/battery and system performance, Alt.2 in Table 2 should be adopted. Otherwise Alt.1 should be adopted.To progress this issue and reach a firm decision in Orlando, we propose the following way forward:RAN4 should discuss this issue first and provide to RAN2 during the Orlando meeting a consolidated view on reading of neighbour BCH.The final decision shall be made during RAN2#58bis in Orlando, taking into account the comments received from RAN4, and the decision shall be informed to RAN1 and RAN4.References[1] R2-072188, “LS on neighbour cell lists and reading of neighbour cell P-BCH,” RAN WG2.[2] R2-072010, “Operator’s view on neighbour cell information,” NTT DoCoMo, V odafone, Telecom Italia, T-Mobile,Orange.[3] RP-070464, “LTE mobility consideration,” Nokia, Nokia Siemens Networks.[4] TR 25.814, “Physical layer aspects for E-UTRA,” V7.1.0.[5] R2-071296, “Consideration on 1-to-all Qoffset,” NTT DoCoMo, Inc.[6] R2-072139, “Report of email discussion on Home-eNB requirement (point 8),” V odafone Group.。
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表 1 上下行链路不平衡的判定方法
RSCP+UE TX Power 的对数值之和/dBm ＞-85
-95~-85 ＜-95
结论 上行受限 不存在上下行链路不平衡 下行受限
2 上下行链路不平衡的原因分析
上下行链路不平衡的原因可从上行受限和下行受 限 2 方面进行分析。 2.1 上行受限原因分析
在实际网络优化中， 可通过数据来判定上下行链 路不平衡。
首先分析上下行链路不平衡的 2 种情况。 a） 下行覆盖良好而上行受限，即下行的各项指标 均在正常值范围内，上行的指标异常。 UE 侧 RSCP 正 常，UE TX Power 偏大； 基站侧基站发射功率正常，接 收 SIR 偏低。 b） 上行覆盖良好而下行受限，即上行的各项指标
N
Y
是否为基站内干扰
Y 是否为系统内干扰
对干扰源小区
N
进行负荷分担
找出外部干扰源 并降低其影响
检查基站 内部连接
图 1 上下链路不平衡分析流程
发射功率）、基础数据（天馈数据）、MR 数据（弱 覆 盖 、 过 覆 盖 分 析 ）、路 测 数 据 （RSCP、UE TX Power、外 部 干 扰分析），从覆盖、干扰、参数、工程、外部因素等多方面 查找问题的原因，给出了相应的解决方案。
提升本小区在 该区域的覆盖
开始
Y
RSCP+UE TX
Power<-95 dBm
N
RSCP+UE TX
N
Power>-85 dBm
下行受限
Y 上行受限
Y 导频发射功率
<门限 Y
调整参数：导 频发射功率
是否过覆盖 N
Y
现场查看地物 过覆盖分析
调整该区域 主服务小区
调整该区域 主服务小区
结束
N RTWP <门限
这种情况主要是由上行干扰引起的。 上行干扰可 以分为基站内干扰、系统内干扰和系统外干扰。
a） 基站内干扰主要是由馈线接头、连接器、耦合 器等元件安装不当造成，只要工程人员现场排查即可。
b） 系统内干扰主要是指系统内其他小区对该小 区的干扰，如周围基站负载过重，发射功率较大，造成 这一区域的底噪抬升。这种情况一般只出现在忙时，所 以通过网管侧的指标分析， 进行忙时和闲时的比较就 可以找到干扰源， 对干扰源小区进行部分负荷分担即 可消除其影响。
上 行 受 限 主 要 体 现 在 UE TX Power 很 大 的 情 况 下，基站侧的 SIR 依然很差，导致上行 BLER 很大。 造 成 基 站 侧 的 SIR 差 的 原 因 不 外 乎 基 站 接 收 信 号 强 度 弱，或基站接收底噪 RTWP 太强 2 种情况。
2.1.1 基站接收信号强度弱 在功率控制的作用下，如果基站接收信号强度弱，
在上下行链路不平衡的情况下， 从 RSCP 和 UE TX Power 的异常变化趋势来看，上行受限和下行受限 完全是将 RSCP 与 UE TX Power 之和从正常值向 2 个 相反的方向变化，高于正常值则为上行受限，低于正常 值则为下行受限。
所以， 只要给出 RSCP+UE TX Power 的对数值之 和的正常值达到上下行链路平衡即可。 但对于无线指 标来说，波动是不可避免的，在此只能根据经验给出一 个合理的范围：当 RSCP 介于-85~-80 dBm 时 ，则 UE TX Power 一 般 介 于-10~-5 dBm， 那 么 RSCP+UE TX Power 的 对 数 值 之 和 的 合 理 范 围 应 该 是 在 -95 ~-85 dBm。
Abstract：
It dis cus s es the determ ination m ethod of the im balance of uplink and dow nlink w hich generally exis ts in WCDMA w ireles s netw ork. Through us ing configuration data, KPI data, param eter data, MR data and DT data, it analyzes the reas ons on the im balance of uplink and dow nlink. Finally, it pres ents the procedure for s olving the im balance of uplink and dow nlink in netw ork optim ization.
李德屹，郭景赞，张晓荣 无线通信
WCDMA 上下行链路不平衡问题研究 Radio Communication
WCDMA 上下行链路不平衡问题研究
Research on the Imbalance of WCDMA Uplink and Downlink
李德屹 1，郭景赞 1，张晓荣 2（1. 中讯邮电咨询设计院有限公司，北京 100048；2. 中国移动通信集团天津有限公司，天津 300143） Li Deyi1，Guo Jingzan1，Zhang Xiaorong2 （1. China Information Technology Designing&Consulting Institute Co.Ltd.，Beijing 10004，China；2.China Telecom Tianjin Branch，Tianjin 300143，China ）
摘 要： 探讨了 WCDMA 无线网络中普遍存在的上下行链路不平衡问题的判定方法，通过对 基础数据、性能数据、参数数据、MR 数据、路测数据的综合关联分析，得出了造成上 下行链路不平衡的各种原因，最终给出网络优化工作中解决该问题的分析流程。
关键词： WCDMA；上下行链路不平衡；覆盖 中 图 分 类 号 ：TN9 2 9 .5 文 献 标 识 码 ：A 文章编号：1007- 3043（2012）01- 0037- 03
c） 系统外干扰是指与本系统使用频段相近的其 他通信系统发出的信号对本系统产生的干扰，如 CDMA1900、部 分 军 用 通 信 系 统 等 。 对 于 这 些 问 题 ，由 于 定 位干扰源需要大量的路测才能完成，而且，因不是自己 局方的设备，协调起来难度也很大，所以一般的方案是 在不影响覆盖的情况下，调整受干扰的天线，使其天线 口不与干扰源正对，以减少干扰源的影响。 2.2 下行受限原因分析
3 上下行链路不平衡分析流程
实际网优工作中分析上下行链路不平衡问题的大 致流程如图 1 所示。
图 1 中使用了性能数据（RTWP）、参数数据（导频
38 2012/01/DTPT
李德屹，郭景赞，张晓荣 无线通信
WCDMA 上下行链路不平衡问题研究 Radio Communication
N 弱覆盖分析
Keywords：
WCDMA; Im balance of uplink and dow nlink; Coverage; Interference
0 前言
随着 3G 网络规模的扩大及用 户 的 迅 猛 发 展 ，网 络问题日益显现。 在网络优化所面对的诸多问题中， 有些问题的原因比较单一（如过覆盖、弱覆盖、导频污 染等），且已形成了固定的解决方案，但有些问题的原 因相对复杂，必须通过对多种数据进行综合、深入的 分析，才能找到问题的症结，上下行链路不平衡就是 这样一个问题。
4 结束语
上下行链路不平衡问题比较复杂， 涉及的方面也 比较多，本文讨论的解决方案，难免有所疏漏，还需要 在今后的工作实践中继续完善。在此希望能抛砖引玉， 给大家提供一些参考。
参考文献：
［1］ 蔡瑞瑱. 浅析华为上下行链路不 平 衡 故 障 ［J］. 广 东 通 信 技 术 ，2009 （11）.
［2］ 付斐. WCDMA 网络覆盖问题分析与优化［J］. 电信工程技术与标准 化 ，2009 （10 ）.
1 上下行链路不平衡的现象与判定方法
1.1 上下行链路不平衡的现象 上下行链路不平衡一般是指目标覆盖区域内，上
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下行对称链路出现下行覆盖良好而上行受限 （表现为 UE TX Power 达到最大 仍 不 能 满 足 上 行 业 务 的 BLER 要求），或上行覆盖良好而下行受限（表现为下行专用 信道码发射功率达到最大仍不能满足下行业务的 BLER 要求）。 上下行链路不平衡的覆盖问题容易导致 接入失败、掉话等。 1.2 上下行链路不平衡的判定方法
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无线通信 李德屹，郭景赞，张晓荣
Radio Communication WCDMA 上下行链路不平衡问题研究
均 在 正 常 值 范 围 内 ， 下 行 的 各 项 指 标 异 常 。 UE 侧 RSCP 偏低，UE TX Power 正常； 基站侧基站发射功率 很大。
必然会要求手机增大发射功率，也就是说，在手机发射 功率达到最大时，基站接收到的信号仍然很弱。这说明 信号的路径损耗很大，要么是手机离基站较远，小区过 覆盖造成；要么是受到地物遮挡。 总之，这一区域覆盖 不合理， 可以通过调整其他小区的天馈或相关参数实 现对该区域的良好覆盖，避免手机驻留在原来的小区。 2.1.2 基站接收底噪 R TWP 太强
作者简介： 李德屹，毕业于西安电子科技大学，硕士，工程师，主要从事无线网络优化工作；郭景 赞，毕业于西北工业大学，硕士，高级工程师，主要从事 3G 规划优化研究工作；张晓荣， 毕业于西安邮电学院，高级工程师，长期从事城域网工程的规划、设计、项目管理工作。
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下行受限主要体现在基站专用业务信道发射功率 很大的情况下， 手机解调后的业务 Eb/No 无法满足要 求，导致下行业务 BLER 很大。 对于该问题，可能存在 2 方面原因：天线本身发射的导频强度就弱，或者仅仅 只是该手机接收到的 RSCP 低。