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Reliable multicast applications such as software distribution, data distribution and replication and mailing list delivery, etc.[1] are getting more and more interests from network and service providers. The conventional error/loss recovery schemes are not efficient when they are applied to multicast scenarios in wireless networks. The reason lies in the unreliable wireless channel, the limited wireless bandwidth and resource, the battery powered wireless devices, and others. To have an effective error/loss recovery scheme for reliable multicast in wireless networks, we advocate a new communication architecture. It is referred to as cellular controlled peer-topeer network [2], where the mobile devices communicate directly with each other to perform cooperative retransmissions using their short-range communication capabilities in addition to their cellular links. Based on the cooperative architecture a novel retransmission scheme is proposed exploiting the shortrange retransmission in this paper. The state of the art, the non-cooperative error recovery schemes (e.g., ARQ, Layered FEC and Integrated FEC II) and the proposed scheme are compared with each other in terms of energy consumption to show the benefit of the newly introduced scheme.

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Hierarchical overlay structure is an alternative solution to integrate the existing and future heterogeneous wireless networks for providing subscribers with better mobile broadband services. Traffic loss performance in such integrated heterogeneous networks is necessary for operator's network dimensioning and planning. This paper investigates the computationally efficient loss performance modeling for multiservice in hierarchical heterogeneous wireless networks. A speed-sensitive call admission control scheme is considered in our model in order to assign overflowed calls to the appropriate tiers. This approach avoids unnecessary and frequent handoff between cells and reduces signaling overheads. An approximation model with guaranteed accuracy and low computational complexity is presented for the loss performance of multiservice traffic. The accuracy of the numerical results is validated by comparing the results from the approximation with the simulations.

Abstrzict ' Elenientary congestion models sornetimes require analysis of G/Gfl systems with hyperexponentially distributed interarrival time and service time distributions. It is shown that for such systems, the ergodic waiting time distribution is itself hyperexponentially distributed, A siinple computational procedure is provided to find the parameters needed, Green's function methods are employed to motivate the factorization required, The releyance of these results to the delay in the overflow process of MIM!S is dis¢ ussed.