roaming process happen together. In this case, LMRs must be able to decide the
priority whether to deal with leaving process first and then roaming process or
visa versa.
For each type of the previously discussed signalling messages a specific task is carried
out. In the next section there will be a detailed discussion of the role of these messages.
5.4.2 Roaming messages roles in MoSReM
The tasks held by roaming messages are to guarantee the change of point of attachment
for mobile receiver in MoSReM. These tasks can be divided into two types as discussed
in the next two subsections.
5.4.2.1 Registration/ De-registration process
Registration and de-registration of receiver node with the multicast source is done by
LMRs on behalf of mobile receivers decide to join/leave the multicast group in the
ordinary case (no roaming). In contrast, when a mobile receiver is roaming, further
consideration is needed. The new LMRs in the existing multicast session do not need to
re-register mobile receivers. However, the new LMRs should recognize the incoming
receiver and register this incoming receiver with the new LMR for multicast service. To
solve this issue, it is needed for the new LMR to be able to obtain information (from the
Rm_in message) about incoming receivers’ qualification to receive multicast packets.
For this, the Rm_in message should carry an identity field for the roaming in receiver to
prove that it is authorized to receive multicast data packets without re-registering with the
source.
5.4.2.2 Roaming process
The third type of messages discussed in Section 4.3.2 is involved in roaming process in
MoSReM. Additionally, it is important to understand that we assume that the actual
physical layer handover over process is handled by the appropriate mobile network
protocols. Examples of such protocols are HAWAII [55], Cellular IP [15] and Helmy [34,
35]. The process of implementing the movement is out of the scope of this thesis. Briefly,
the following steps are to satisfy the roaming process procedure:
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