Product Info

WipLL Radio Technology - Physical Layer System Description
2-28 Airspan Networks Inc. 25030311-08
2.6.4. Frequency Allocation
Frequency allocation includes the following issues:
 Synchronized vs. Unsynchronized operation
 Frequency Reuse
 Frequency Allocation template
2.6.4.1. Synchronized vs. Unsynchronized Operation
The frequency allocation scheme in WipLL depends on the mode of operation.
Three main options exist:
 Unsynchronized Frequency Hopping
 Synchronized Frequency Hopping
 Fix Sub-Channel Assignment
2.6.4.1.1. Unsynchronized Frequency Hopping
A scenario may exist whereby the operator does not want to synchronize base
stations due to cost or regulatory issues. For example, the FCC prohibits
synchronization between base stations when operating in the unlicensed band. In
such a scenario, the BSRs (and SPRs) are assigned pseudo-random frequency tables,
and, therefore, collisions between transceivers are possible, resulting in some level
of retransmissions. However, implementing orthogonal frequency tables (hopping
sequences) reduces collisions.
In this mode of operation, the available set of sub-channels, which must include a
prime number of sub-channels, is organized into several different hopping sequences
that are orthogonal to each other. Each BSR in the coverage area is assigned a
different sequence (until there is a need to start reusing the tables). The degradation
level in performance due to collisions will be a random number, depending on the
length of the frequency tables (the number of available sub-channels).