Product Info

WipLL Radio Technology - Physical Layer System Description

2-40 Airspan Networks Inc. 25030311-08

2.6.6.4. System Capacity

The modulation for each link in the WipLL system is adaptively determined

according to the signal strength and the BER. When evaluating system capacity, it

should be taken into account that the intermediate 4-FSK modulation is not

supported when operating at 1.33 Msps.

Assume a WipLL deployment where subscribers are located at various distances

from the base stations. In general, three coverage circles can be expected around

each base station:

 Inner circle—supporting 8-level FSK

 Intermediate circle—supporting 4-level FSK

 Outer circle—supporting 2-level FSK

Let pi, pm, and po represent the percentages of subscribers located at the inner,

intermediate, and outer coverage circles, respectively. The average capacity of the

system (without taking into account advanced features like fairness) for each of the

possible modes can be given by the following formulas:

()

33.14][

123][

33.1

⋅++⋅=

⋅

omiMsps

pppMbpsCapacity

Radio planning can provide estimations for p

, p

, and p

so that the WipLL operator

can determine which option provides the highest system capacity.

2.6.6.5. Conclusion

The 1.33 Msps mode provides superior bit rate, but at the expense of a possible

reduction in radio coverage (FCC), and/or increase in interference. A certain amount

of radio planning is required to determine the preferable mode to maximize the

overall capacity of the access network.