Issues in wireless communication networks

Future-generation personal communication systems are expected to support multimedia traffic including voice, video, images, files, or data, or combinations of these. Extension of these ATM services to the low bandwidth and high error rate wireless networks introduces a series of challenging issues. Two of the key issues are addressed in this dissertation.; In the first part techniques to capture the behavior of realistic wireless channels with mathematically tractable models are presented. Different state-space aggregattion techniques to reduce a large number of states of a Markov chain to a fewer number of states are examined. The property of strong and weak lumpability is discussed and the necessary and sufficient conditions for lumpability are stated. A new, finite algorithm is developed to determine if the aggregrated process satisfies the lumpability condition. We introduce a stochastic bounding technique to handle those aggregated processes that fail to meet the lumpability conditions. The aggregated process can be stochastically lower and upper bounded by another Markov processes via the study of its failure rate functions of the sojourn time probability distributions in the aggregated states. These techniques are applied to three different types of previously published channel models for mobile VHF, wireless indoor, and Rayleigh fading channels. Results show that our stochastic bounding technique can produce a simpler yet still accurate upper and lower bounds for the original channel model. We find that the bounds perform well when the higher-layer error control protocols such as stop-and-go and Transmission Control Protocol (TCP) are considered.; Future wireless networks catering to mobile communication and computing are expected to accommodate traffic from heterogeneous sources of voice, data, video, or multimedia with a specified Quality of Service (QoS). In order to support multi-media services with a specified QoS requires future wireless networks allocate radio resources to multimedia services in a fair, flexible, and efficient manner. The second part of the dissertation proposes a wireless packet cellular network infrastructure and a resource allocation scheme to achieve that objective. The increase in efficiency of packet transfer mode over the radio interface when there are multiple overlapping cells is investigated. Protocols are proposed for accessing to a multiplicity of base stations to increase efficiency and system throughput, achieve flexibility in handling multi-rate traffic and provide macrodiversity against the error-prone wireless channel. Performance results indicate that the multiple packet links access protocols significantly improve system performance under both uniform and non-uniform traffic loading conditions.