Throughput maximization in UWB-based ad-hoc networks

In this paper, we study the problem of radio resource allocation, both transmission rates and transmission powers, so as to maximize the throughput of UWB wireless ad-hoc networks. Our analysis is based on the packet-success function (PSF), which is defined as the probability of a data packet being successfully received as a function of the receiver's signal-to-interference-and-noise-ratio (SINR). We find an optimal link transmission rate, which maximizes the link's throughput and is dependent on the all active links transmission powers. If each link transmission rate is adapted to this optimal link transmission rate, then, with single-link operation (i.e., no other interference sources are present), the link's throughput is directly proportional to the transmitter's power and increases indefinitely with increasing transmission power. However, with multiplelinks operation and interference each other, as each link transmitting power increases, so does the interference level, and the total network throughput approaches a constant other than infinite. Thus, for sufficiently small transmission power, the total network throughput of the multiple-links case exceeds the throughput of the single-link case, but the reverse happens for high power. In addition, this paper reveals that, as the number of concurrently transmitting links increases, regardless of the power level, the maximal total network throughput approaches a constant, with each link's throughput approaching zero. To maximize the network throughput, for the case of small maximal transmission power with weak interference levels, the optimal transmission scheduling allocates simultaneous transmissions of multiple links, but for the case of large maximal transmission power with strong interference levels, the optimal policy assigns separate time for transmission on each link. The breakpoint of when to use one link or multiple links is termed the critical power. As an example of the analytical calculation of the critical link's power, we present here solutions for a two-link case and an N-link case. In contrast with previous studies, our results imply that the design of optimal MAC is dependent on the choice of a routing scheme.