Multi-layer reuse pattern is a gradual process for TCH frequency planning. In other words, the reuse is rather loose in TCH1 layer and it is quite close in the last TCH layer .The reason for this pattern is that base band hopping is used in the Multi-layer reuse pattern.
When there are rather few frequency carriers, the hopping gain is small. Therefore, more frequency carriers should be allocated for the layer with small TCH and then the reuse coefficient is relatively large. When RF hopping is used in the Multi-layer reuse pattern and there are a large number of frequency carriers, the hopping gain is high and the reuse coefficient can be very small.
In addition, the Multi-layer reuse pattern is of a free pattern. It is different from base band hopping, in which the reuse must be loose in the first TCH layer and more close in inner layers.
Comparison between Multi layer Reuse and 1*3
- For Multi-layer reuse pattern, either Base band hopping or RF hopping can be used. But for 1×3 reuse, only RF hopping can be used.
- The frequency planning for the 1×3 mode is simple and it is easy to plan the frequency for new added BTS.
- 1×3 mode requires a rather regular BTS location distribution.
- For the cells with fixed number of TRX, when the traffic is heavy, the 1×3 provides higher service quality than that of Multi-layer reuse pattern.
- TRX can be easily added to the 1×3 network, but TRX number of hopping should not exceed the product of the allocated hopping frequency number and the max RF load ratio.
- BCCH of Multi-layer reuse pattern can take part in the frequency hopping, while BCCH in 1×3 mode can not.