Cross-layer performance in cellular WCDMA/3G networks: modelling and analysis

Dynamic radio link adaptation is a key component in WCDMA/3G wireless networks to improve the spectral efficiency while meeting the radio link level QoS (quality of service) requirements, such as the BER (bit error rate) requirements, for the different wireless services. Again, performance of an end-to-end protocol, such as TCP (Transmission Control Protocol), depends on the performance of the underlying radio link adaptation technique. A multilayer modeling of the WCDMA/3G radio interface is therefore necessary to understand better the interlayer protocol interactions and identify suitable transport and radio link layer mechanisms to improve TCP performance in a wide-area cellular WCDMA/3G network. We present such a multilayer system model to analyze TCP performance under joint rate and power adaptation with constrained BER requirements for downlink data transmission in a cellular VSF (variable spreading factor) WCDMA/3G network. To this end, we present the outline of a more general model which can completely describe the interaction between TCP and the radio link adaptation and error control protocol.