MAC layer: resource sharing principles and algorithms

"This document aims at laying out a modelling framework and a quantitative approach to the resource sharing issue in an UWB air interface, where the main issues are: i) multiplexing of best effort traffic with reservation based traffic with QoS (in terms of delay); ii) distributed algorithms. Therefore, we assume that traffic offered to the UWB air interface (MAC layer) falls into two categories: i) Reservation Based (RB) traffic; ii) Best Effort (BE) traffic. The RB traffic serves those services requiring some guarantees as to throughput (hence transfer delay). As seen by the MAC entities, the terminal to be addressed (among those that are “connected”, i.e. reachable) and the bit rate of the MAC layer communication to be set up are given as input, while the decision variables are the power levels to be used under the constraints on the maximum transmittable average power and the communication quality (BER). The BE traffic offers a transfer resource that adapts itself to the available bandwidth at a given time and in a given point in space. The aim here is to achieve the maximum possible overall throughput, possibly with fairness constraints, but no guarantees are offered as to achievable throughput and transfer delay. The resource sharing among the UWB terminodes requires both signalling and local measurements. The rest of the document is structured as follows. Section 2 summarizes with some detail the derivation of the bit error probability for the UWB air interface under the fundamental hypothesis of ideal channel with Gaussian additive noise (AWGN channel). Moreover, unsynchronised randomly coded time hopping sequences are assumed for the co-existing communications. Section 3 lays down the principles of the resource sharing starting out from the expression of the SNR and of the BER derived in the previous Section. A theoretical framework is assessed, and hints are given as to how a distributed algorithm can exploit the theoretical results. Section 4 presents a distributed algorithm based on the approach outlined in the previous Section, by specifying signalling flows for RB and BE traffic. Section 5 reports the analysis of the proposed algorithms based on simulations"