Mutual-information based rate-adaptation for Multi-User TH-IR-UWB coded system

In this paper we present a coding rate adaptation technique for a Time-Hopping Impulse-Radio Ultra-Wide Band (TH-IR-UWB) system assuming that the Multi-User Interference (MUI) is modeled as an additive interference noise following a Generalized Gaussian Distribution (GGD). The shape parameter induced by the GGD model is in general time-variant since it strongly depends on the essential UWB system parameters and the received signal power of the active users. In this paper, we show that the performance of a TH-IR-UWB LDPC coded system is quite independent of the GGD shape parameter when we consider the mutual information between the soft input to the decoder and the transmitted sequence, especially for medium to high-rate regimes. This allows to derive a simple and efficient link adaptation scheme based on a rate-compatible protograph-based LDPC code. Simulated results are provided to evaluate the performance of the described coding rate adaptation algorithm for a TH-IR-UWB multi-user system.