导频信道使得用户站能够获得前向码分多址信道时限

1、导频信道使得用户站能够获得前向码分多址信道时限,提供相干解调相位参考,并且为各基站提供信号强度比较以确定何时进行切换。 Pilot-frequency channel allows users to gain/get channel time-limit of forward CDMA,provides phase reference for Coherent demodulation and offers BTS comparison regarding signal intensity.As a result ,it can define when to switch. CDMA

2、技术在中国商用已经三年，得到了飞速的发展。目前中国CDMA网络的用户突破了2300万用户，成为世界第二大CDMA网。  It has been three years since CDMAs commercial ulitilization，rapid development has already been achieved .By far,in China,the subscribers who ultilize the network of CDMA has beyond 23 million,making it the second largest CDMA network

3、in the world. 随着网络规模的扩大和用户的不断增加，CDMA网络建设由开始的以扩大覆盖面积为目标，转移到加强网络优化，提高信号质量上来。  As the size of CDMA networks expands and its subscribers increasingly grow,its construction target has transferred from expanding its coverage into intensity the networking optimization so as to improve the quality of s

4、ignal. 在一些城市地区，一个载频的容量逐渐不够，开始增加新的载频。相邻的小区之间载频数量不平衡的现象越来越多，不同的频率之间切换的问题开始显露。  As the capacity of a single carrier gradually (insufficient)，so in some urban areas operators start to add new carriers.The signs of carriers imbalance are getting more and more,the switching problems among different f

5、requencies come to light. CDMA的软切换技术在降低掉话率方面作用明显，但它仅在相同载频之间的切换才能发挥作用。CDMAs soft-handoff technology plays an evident/obvious role in reducing calldroprate,however,this technology can switch only owns same carriers.对于不同载频之间的切换，只能采用硬切换实现。Hard-handoff is the only way for those different carriers to achi

6、eve handoff.硬切换的成功率相对较低，尤其是不同基站不同载频之间的硬切换，很容易造成掉话。The possibility of success is comparatively low for hard-handoff, which was realized among different BTS&carries.In particular,it is very easy to cause calldrops in the process of hard-handoff.伪导频技术可以有效提高不同载频之间的切换成功率，是网络优化的重要手段之一。  Pseudo-pi

7、lot technology can effectively improve/enhance the possibilities of success and it is also one of the important means/way of networking optimization.伪导频切换的原理 handoff principles on pseudo pilot-frequency导频信号是基站连续发射未经调制的直接序列扩频信号Pilot-frequency is a direct sequence, spreading-frequence and unmodul

8、ated signal which is transmitted continuously/continual from BTS.在没有伪导频设备的情况时，手机漫游在A基站下，使用载频FA2通信。In the absence of pseudo-pilot facilities/equipment,cellphone will communicate by way of carrier FA2 when roaming in the site A.当手机逐渐远离A基站，靠近B基站，B基站则只有载频FA1提供服务。When a cellphone gradually gets far away

9、from base station A and gets closer to base station B. Then it is only base station Bs carrier FA1 that serves the communications.手机收到的A基站FA2的信号越来越弱，而B基站FA1信号逐渐增强，只能采用硬切换的方式进行切换，而且会产生30毫秒的中断。When a cellphone receives signal of FA2 from stationA and the signal gets weaker and weaker,however,the signa

10、l of FA1 from station B gets stronger and stronger.Under this circumstances,hard handoff is the only solution/way and the interruption will last for 30 milli-seconds. 不同基站的异频硬切换的成功率很低，非常容易形成掉话的现象。 If the process of hard-handoff of pilot-frequencys deploys among different base-stations, the poss

11、ibility of success will be very low and the phenomenon of calldrop will be easily created/generated/formed.如果我们在B基站安装了伪导频设备，并且手机处于载频FA2服务之下，从A基站移动到B基站时，手机会不断检测附近基站的导频信号强度。If the pseudo pilot-frequency equipment was installed in Station B,and Carrier FA2 serves cellphone.The cellphone will always det

12、ect the intensity of pilot-frequency signal from Base-station around.当T_ ADD参数超过门限值时，手机会主动向A基站发送PSMM(功率强度测量)消息。When parameters of T_ ADD exceed thresholds,the cellphone will send the message of PSMM actively.A基站收到消息后，查询相邻基站的配置信息，发现B基站的FA2的导频信号实际上是伪导频信号，不具备提供业务信道的可能，但B基站的FA1可以提供服务信道。Having received t

13、he message of PSMM, stationA desks/checks message regarding configuration in the neighbouring base-stations. Its message finds out that pilot-frequency of FA2 from base-stationB ,in practice, is pseudo-pilot signal.So it has no possibilities of providing traffic channel,however, FA1 of base-stationB

14、 can provide service channel.A基站向手机发送EHDM(增强型切换定向)消息，通知手机切换到载频FA1，同时将切换参数发送给手机。Base-stationA transmits the message of EHDM to cellphone ,informs cellphone of switching into carrier FA1 and sends switching parameters to cellphone.手机首先立刻切换到A基站的载频FA1下，然后按照软切换的方式从A基站的载频FA1切换到B基站的载频FA1，从而保证切换的顺利进行。 

15、At first,the cellphone will be handoffed to carrier FA1 in base-stationA,and then it will be handoffed carrier FA1 in base-stationA to carrier FA1 in base-stationB by way of soft handoff so as to make sure/guarantee the smooth handoff.几种常用的伪导频实现方案 (Several common solutions to realize pseudo-pil

16、ot):伪导频技术由CDMA技术标准拥有者高通公司提出之后，由于对有效降低掉话率，作用非常明显，因而得到了广泛的应用。根据使用方式的不同，大致可以分为以下三类： Pseudo-pilot technologies was raised by corporation of Qualcom who is the owner of standard CDMA.It was widely used due to playing an very obvious role in reducing droprates. According to different application ways

17、, generally it was divided into three categories.一、基站自提供方式 way of base-stations self-offering基站在设计的时候就考虑到伪导频切换功能。The switching function of pilot-frequency was taken into consideration when designing base-stations.在数字基带处理时，从正常载频信道中提取出导频信号，用于伪导频的发射。When processing digital base-band, the signal of

18、 pilot-frequency was taken out from normal carrier channel and it would be used for transmitting pseudo pilot-frequency.这样可以保证伪导频信号只包括导频信号，而且和正常载频导频信号保持高度一致。By doing so it can guarantee pilot-frequency alone which was/is included in pseudo-pilot signal.And it can also maintains a high degree of cons

19、istency with normal carrier &pilot signal. 这种方式显然是最佳的实现方式。Obviously,this is the best way to realize pseudo-pilot.但遗憾的是，不少厂家的基站并不支持。However,it is a pity that many base-stations (providers/suppliers)factories dont support this way, especially /in particular,micro-cellular as a representative.尤其是微蜂

20、窝基站为代表，为了减少成本，厂家往往省去伪导频的功能。In order to reduce costs, eliminating/taking aside the function of pseudo-pilot is what factories/manufacturers always do. 也为后面两种方式留下了市场空间。 By doing so,market space has been left for two ways following.二、纯导频方式 way of pure pilot-frequency纯导频方式是采用专门的信道发生器模拟出纯粹的导频信号

21、。The way of pure pilot-frequency is one that adopts dedicated-channel generator to simulate pure pilot signal.由于只发射纯导频，对伪导频所在的载频的干扰减小。Due to the single transmission of pure pilot-frequency,by doing so it can reduce carrier interference where pseudo-pilot lies in.但由于导频信号需要自己产生，要使用一些昂贵的modem芯片，而且内部结构比

22、较复杂。 However,because the pilot-signal is for itself to generate,it will use some expensive modem-chips.And their structures are comparatively complicated.三、移频方式 way of frequency-shifting移频方式实现起来相对简单，具体地说从基站射频信号处将所有信号(包括同步、寻呼和业务信道信号)都耦合到新载频上进行发射。 Frequency-shifting is a relatively simp

23、le way to realize pilot-frequency ,specifically speaking, including signal in/on/through synchronous,paging and traffic channel. All of these signals will be transmitted by way of coupling to new carriers.伪导频设备不仅发射导频信号，而且还要发射同步信号、寻呼信号和业务信道信号，这样为保证伪导频的覆盖范围与基站的覆盖范围相似，所需要发射的功率将与基站的发射功率保持同步。 Pseudo

24、-pilot equipment can transmit not only pilot signal,but also synchronous,paging and traffic signal.By doing so it will guarantee the similar coverage area between pseudo-pilot and base-stations.Power (pseudo-pilot) needs to transmit will be synchronized with base-station power.分析比较(analysis and comp

25、are) 基站自提供方式和纯导频方式从技术本质上看属于同一种技术，我们重点分析一下纯导频方式和移频方式的优缺点。 Base-stations self-offering way and pure pilot way altogether belong to the same technology in terms of technical essence.Here,we will attach great importance to pure pilot and frequency-shifting to analyze their advantages and disad

26、vantages.纯导频方式结构复杂，导频信号发生器设备成本也较高，但其所需发射的信号纯粹，对发射功率的要求也减少到最小，一般不超过4w。Pure-pilot mode/way owns a complicated structure and pilot-signal generators priceis comparatively high.However,what the signal of this mode needs to transmit is pure.So minimize the power transmission,generally speaking , to less

27、than 4w.而对于移频方式，伪导频设备转发了正常载频的全部信号，因此所需要发射的功率将与基站正常载频的发射功率相同，在国内基站的发射功率通常为20w，这样，伪导频的发射需要20w的高功放，成本较高，因此移频方式和纯导频方式综合成本相差不多。 As for mode of frequency-shifting,pseudo-pilot equipment/device transmits all signals of normal carrier frequencies.So the power needs to transmit will be the same as base-

28、stations normal carrier frequencies. Power transmits from base-station,in our country,usually 20w.20ws high power amplifier is needed for transmission of pseudo-pilot and its cost is coparatively high.So the comprehensive cost will be closer to each other/almost the same.纯导频方式的覆盖范围相对固定，而CDMA基站的信号是有呼

29、吸效应的，实际的覆盖范围会随着用户数量不断变化，纯导频方式的信号覆盖范围不能保持和原基站载频的同步，对切换的成功率产生负面影响。Mode of pure pilot owns a relatively stable coverage area,the signal of CDMAs base-station owns cellbreathing effect.So the real area of coverage will change as subscribers numbers.Coverage of signal is not capable of synchronizing with

30、 the original base station carrier frequency.The mode will have a side effect on handoffs possibility of success移频方式却恰恰很好地解决了这个问题。 However,the way/mode of frequency-shifting well handles this problem.移频方式在发射伪导频的同时，也发射了业务信道等信号。Mode of frequency-shifting transmits pseudo-pilot signal and traffic

31、signal as well.这些不需要的信号会对周围的基站产生不必要的干扰，降低了周围基站的信号质量和用户容量。Those unwanted signals will cause unnecsssary interference to surrounding base-stations,as a result of it,the signal quality and subscriber capacity of (?)will be reduced.而纯导频方式则对周围基站的干扰降到了最小。 The mode of pure-pilot,however, will minimize

32、 interference to surrounding base-stations.综合起来，我们认为纯导频方式对网络影响小，适合在基站密集的地区使用。Comprehensively speaking,we believe the approach of pure-pilot has a small impact on the network,so it is suitable for using in areas which deploy dense base-stations.移频方式对网络一定的影响，但切换成功率较好，适合在城市边缘地区使用。Approach of frequency-

33、shifting will have an effect on network.However,its possibility of success is better.So it is suitable for areas locating the edge of the city to use.一点多址微波通信系统(one point to multipoint access microwave systems)一点多址微波通信系统利用微波信道传输实现多个分散用户群接入电话网络的通信系统。one point to multipoint access microwave system is

34、a communication system that uses microwave channel to transmit so as to make distributed subscribers group access to telecommunication network. 该网络分布为点对多点，因此，又称一点对多点微波通信系统。This kind of network distribution is point to multipoints,so it also names as one point to multipoints microwave system.整个系统由中心站

35、（基站 ）和不同方向的若干个外围站（用户站、远端站）组成，外围站也可作为中继站，以便将中心站发来的信号传送至远处的用户群。The whole system is made up of user/subscriber station,far-end station and peripheral station in different directions. Peripheral station also acts as repeater,which enables signal from central stations to transmits to subscribers in the far-end.用户只需接到这些外围站，就可接入本地交