A medium access control protocol for ultra-wideband wireless ad hoc networks

In the past few years, ultra-wideband (UWB) has emerged as a radio transmission scheme for short-range wireless communications. Its various benefits have attracted interests in studying UWB technologies in both academia and industry. Currently, several MAC protocols are being proposed for UWB networks. A number of these protocols are direct adaptations from the existing MAC protocols that have been designed for narrowband systems, and thus do not make use of the UWB´s unique characteristics. In contrary, there are UWB MAC protocols that incorporate dynamic channel coding after revealing that it is unique for UWB channels to exhibit a linear Shannon capacity function with respect to signal-to-noise ratio (SNR) at the receiver. We show in this paper another characteristic of a UWB channel. Specifically, for a given bit error rate and a transmission rate, the optimal ratio of interfering distance to transmitting distance may become less than unity in a UWB channel as compared to a value larger than unity in a narrowband system. This implies UWB can effectively support concurrent transmissions within the receiving range of a receiver node as long as they are outside an exclusion region given by the optimal distance ratio. In view of this, this paper further propose a CSMA/CA based MAC protocol called medium access control with concurrent transmissions (CT-MAC) to capitalize on this UWB characteristic. Simulation results indicate that CT-MAC improve the throughput-delay performance by allowing concurrent transmissions without compromising the bit error rate requirement.