IP Multimedia Access between 3G/4G Mobile Radio and Fixed Packet Switched Networks

This thesis addresses the problem of managing voice, image and data traffic in a single low bandwidth, interference limited wireless access network where handover takes place The aims of the thesis are to produce a model to enhance the understanding of network traffic behaviour, to produce a model that optimises the allocation of radio channels for different applications and to provide a new approach for reducing the probability of losing a radio connection when changing the connection point to the fixed network.

A mathematical model was developed that predicts queue latency and size using Markov models and was compared to a simulation model produced for voice, file transfer, web browsing, database and email applications. This was found to agree with the simulation model for all applications in non-congested networks.

A wireless channel allocation algorithm was modelled which helped in the understanding and optimising of channel allocation techniques. This increased the channel capacity, by allowing flexible data rates and bandwidths for different applications. Real-time applications were shown to have the lowest latencies in a mixed application environment, whilst non-real time applications had higher bandwidth requirements due to high instantaneous throughput values. These translate to efficient code allocation and de-allocation. The optimum number of channel request attempts per application was found by heuristic methods.

Finally to allow seamless handover, the Cellular IP protocol in conjunction with the novel semi-soft handover algorithm designed was modelled. The semi-soft handover algorithm allows a user to request a channel from a new base station (BS) whilst receiving packets from both the old BS and new BS simultaneously. This model allows users to handover without having an adverse effect on throughput and latency whilst having a very flat hierarchy compared to Universal Mobile Telecommunications System (UMTS) solutions. The semi-soft mechanism can also be used for vertical handovers to other access methods making this a truly fourth generation (4G) solution.