) Mostly, the benefits of AAS at SS do not outweigh the complexity and
cost associated with it.
WiMAX MAC and OFDM/OFDMA PHY provide support for AAS use at the BS. The
hardware and algorithm support for AAS, however, is considered an implementation
detail and left to be vendor specific.
WiMAX Mesh
Much of our discussion of WiMAX in this chapter has been centered on PMP operations,
whose underlying restriction is that SSs have to communicate with only a central BS.
This restriction poses several limitations on a BWA network. For example, range of a
BS is limited to a certain geographic region, extension of the network beyond which
would require deployment of another BS which is significantly more complex and perhaps
significantly more expensive than an SS.
In Mesh networks, if physical conditions allow for it, any two devices (called nodes),
including a pair of SSs, can directly communicate with each other. If channel conditions
are such that more than two pairs of nodes can communicate with each other, they are
WiMAX 483
allowed to communicate with each other simultaneously. Finally, each node is capable of
relaying data packets from one node to another.
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