Ec/Io与Eb/No概念与区别

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Eb/N每比特能量比噪声电平
Ec/I每码片能量比干扰电平
在WCDMA里面,Eb/No研究对象主要是业务,Ec/Io研究对象主要是导频,这时候无须有转换之说.
干扰电平和噪声电平区别   在这里两者基本相当,只是噪声还比干扰多了一些由于设备引起的热噪声
I=No+Ec  
eb是比特能量，ec是码片能量。  
How to calculate UL Eb/No : 上行公式为： UL Eb/No=W/R.Prx/I
其中:   signal received at constant power is Prx         received interference power is I.   due to fast feedback loop (1500Hz) this is fairly successful. It means that for a chose service, chose channel condition and chose required BLER, the received power on the traffic channel divided by the interfering power is approximately constant.. How to calculate DL Eb/No :  Because the synchronized orthogonal code reduce the interference from the serving cell (or cell ,in soft handover) : DL the Eb/No is calculated by the model:    下行公式为:Eb/No=W/R.Prx/Iown(1-α)+ Ioth+Pn  
其中:Where Iown is the total power received from the serving cell ,Ioth is the total power received from the surrounding cells, and Pn is noise power (thermal and equipment).the factorαis the call orthogonal factor, which depends on the multipath Condition. The codes are fully orthogonal. Thus in the case of no multipath the interference from the serving cell is cancelled andα=1.if there are instantaneously two equally strong propagation path, then only half of the interference is cancelled from the receiver point of view and α=0.5 at this instant. Ec/I   Ec/Io is received chip energy relative to the total power spectral density. In UL this is the same as Eb/No divided by the processing gain. I.e.  by W/R. in DL the Io is the totol  received power spectral density,thus the  orthogonality effects are not taken into account.   Notice that the notation of CPICH Ec/No is actually the Ec/Io of the CPICH channel.Ec/Io is typically used as a link performance indicator for the signals, which have no information bits in the usual meaning. Such signals are for, e.g., CPICH,AICH and PICH.    Eb/N 举例：UL:如果12.2 kbps voice 3km/h 　　4db                  　　　PS 3km/h 64kbps 2db                 DL: 12.2 kbps voice 3km/h 　　　　6.5db                     PS 3km/h 64kbps  　　　　　 5.5db     　一般在实际测试中我们都把Eb/No＝Eb/Ｉo．
Ec/I0是解扩后而没解调的信噪比所以信号是淹没在噪声中的，所以是负值!
Eb/No是解调后的比特能量/噪声密度，所以信号的强度要比噪声强，所以较好的情况是正值。
Ec/Io是模拟信号的概念,Eb/No是数字信号的概念.其中作为模拟信号的Ec代表功率,在频域有范围,但时域是无限的,因此只能够测量功率(其能量是无限的),单位为dBm,具体代表了收到的导频的功率.;Eb作为数字信号的概念,其在频域是无限的,时域有范围(bit),因此只能测能量,没有功率,单位为dBm*s,具体代表了接收信号每比特的能量.
同理,Io代表接收到的干扰的功率(电平);而No是输入干扰的频率谱密度(dBm/Hz).
Ec是高频端 解扩前的
Eb是解扩后的
Ec/Io是解扩和解编码前的宽带的信干比，等同于GSM中的C/I。
Eb/No是解扩后信号功率密度（每BIT能量即功率密度）与干扰噪声功率密度之比，叫解调门限。
由于扩频/解扩、编码/去编码带来了处理增益，所以Ec/Io一般是负数，即信号功率可以比干扰噪声功率低。
Ec/Io+处理增益=Eb/No

[ 本帖最后由 zibeikehome 于 2010-1-14 22:01 编辑 ]