Shared medium
networks such as PMP RF-wireless networks also provide an ideal ground for
providing multicasting services, and WiMAX is no exception.
WiMAX supports multicast connections that can be used for multicast services on
the downlink (transmission from BS to SS). The BS does so by associating a connection
(and a CID) with the multicast service and associating all the SSs in the multicast
group with the connection. The CID used for the multicast service is the same for all
the SSs in the same channel that are in the multicast group. The standard does not
WiMAX 477
specify a separate group of CIDs for multicast services, and the CIDs do not need to be
distinguished in any way from the CID used for unicast traffic. In fact, each SS does
not need to be aware of the fact that it is receiving multicast traffic in the connection.
The BS ???broadcasts??? the multicast data, with the multicast CID, and is received by all
the SSs sharing the same channel. However, only those associated with the CID would
accept it.
The WiMAX standard allows for per-service encryption techniques (to be discussed in
the next section). which enable effective encryption of multicast services such that SSs
that are not in the multicast group are not able to decrypt the multicast packet even if
they are able to receive it.
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