Performance analysis and robustness of the ATM adaptation layer 2 over wireless ATM networks.

The wireless and personal communication systems are experiencing an enormous growth due to recent advancements in wireless networking technologies. At the same time the cellular network infrastructure around the world is being upgraded to support the 3rd generation wireless communication networks, as defined by the International Mobile Telecommunications for the year 2000 (IMT-2000) and the Universal Mobile Telecommunication Systems (UMTS) standards. As a result there is great interest in evaluating diverse technologies that can be used to handle the heterogeneous traffic types and at the same time be able to provide quality of service guarantees and ATM has been identified as an ideal transport technology for this type of networks. The research presented in this thesis details the use of the ATM Adaptation Layer 2 (AAL2) standard, which is used to adapt low data rate and delay sensitive traffic in ATM networks. In this work we are interested in evaluating the performance of the AAL2 standard over error-prone wireless links. Therefore we are interested in proposing a mechanism to improve the performance that is observed at the AAL2 layer. The study begins by evaluating diverse analytical models to characterize the bit error process at the physical layer over error-prone links. This study has identified that the Finite State Markov Chain (FSMC) models provide a suitable analytical work frame to evaluate the impact of bit errors at the higher protocol layers, such as the AAL2. Based on the FSMC models we derive analytical expressions to evaluate the impact of bit errors at the AAL2 layer and numerical results are obtained to evaluate the performance of the AAL2 standard over the error-prone links. Later the analytical expressions are used to evaluate the performance improvements at the AAL2 layer when implementing diverse techniques that are commonly used to improve system performance. Such techniques include the use of Forward Error Correction codes and diversity techniques. Finally, a robust frame format is proposed for the AAL2 standard. The proposed frame format improves the performance of the AAL2 standard by introducing a robust mechanism for the delineation of AAL2 packets. In addition, the proposed mechanism can reduce the overhead introduce by the header fields that are required to achieve the delineation of the AAL2 packets inside the payload of the ATM cells