Effective bandwidth in wireless ATM networks

Wireless ATM sums at extending ATM services to the wire-less environment. In contrast to wireline ATM, which is pri-marily based on reliable fiber optic, wireless ATM will have to cope with an unreliable radio channel. This poses a host of technical challenges related to the provisioning of qual-ity of service (QoS). Key issues include incorporating the characteristics of the wireless channel in the provisioning of cell-level QoS, and improving the perceived quality by using error control mechanisms. In this study, we propose a model for analyzing the cell loss statistics due to buffer overflow in a wireless ATM environment. This model incorporates the service disruption caused by the unreliable radio channel as well as the impact of error control schemes, e.g., automatic repeat request (ARQ) and forward error correction (FEC) mechanisms. The main theme of this study is to investigate the cell loss behavior of a wireless ATM link as a function of the assigned bandwidth and error control schemes. Using fluid analysis, we present an approximate expression for the cell loss rate (CLR). This expression is used to derive a closed-form expression for the wireless effective bandwidth. It is also used to investigate the optimal FEC code rate that guarantees a given CLR while maximizing the utilization of the wireless bandwidth. The validity of our analytical results are tested by contrasting them to simulation results. Our observations indicate that the proposed expression of CLR is quite accurate over a range of moderate bit error rates.