求助：CDMA容量-接入控制

lemonlemon

专家好，
      这2个图是从论坛下载资料里取到的，是爱立信WCDMA资料第三个胶片中的。
看不太明白。第一个图中的2个接入失败例子，（文字部分是胶片的备注），备注中只说明，第一个MS3接入失败是由于上行干扰将会显著增加，所以连接失败。 为什么呢？（有公式解释吗）
第二个例子说基站功率不足以建立与UE2的连接。
感激感激

The diagram above shows two scenarios where these ratios have limited the capacity of the base station.

Cell 1 cannot accommodate MS3 because the increase in interference in the uplink by adding this connection would be too great. In this example the uplink interference has limited the capacity of the cell.

In the second scenario we can see that Cell 2 cannot accommodate UE2 because it is using all its available power resources to maintain the connections to the other mobiles. In other words the base station has not enough power to achieve the required Eb/No ratio required at UE2. Another way to understand this is to imagine that the base station has a total power output of 10 W and allocates 5 W to broadcasting common channels leaving 5 W available for traffic. In this instance it requires 1 W for each of the 5 ongoing connections and has no available power to accommodate UE2. This time the capacity is limited by the downlink

Eb/N0  Energy per bit to noise ratio

As the noise in the system increases the energy per bit must be increased to maintain the required Eb/N0 hence this will be limited by the transmit power.  Since all base station transmissions share the same power source some connections that require a lot of power to maintain an acceptable Eb/N0 ratio will use valuable resources that could be used for more connections.  

• Eb/I0  Energy per bit - to Interference Ratio

This ratio will be affected differently in the uplink and downlink. It can be drastically affected by interference associated with imperfect power control.

On the other hand as spread spectrum processing gain is reduced at higher data rates the Eb/Io ratio will have to be increased to maintain an error free connection.

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