Channel division multiple access

Ultra-WideBand (UWB) has been recently presented as a promising radio technology due to the large bandwidth available. This feature enables point to point high data rates at short range as well as high temporal resolution with long channel impulse reponses (CIR). In this paper, we present an original multiple access scheme called Channel Division Multiple Access (ChDMA), where we use the CIR as a user signature. The signature code is given by the channel and the users are separated by their position: this signature is uniquely determined by the user's position, which changes from one position to another. This signature location-dependent property provides decentralized flexible multiple access as the codes are naturally generated by the radio channel. The results derived can be straightforwardly applied to UWB ad-hoc networks. To analyze the multiple access scheme performance, we evaluate the channel capacity in a wideband power limited regime by the tradeoff of the spectral efficiency (b/s/hz) versus the ratio between the number of users and the system resolution. The framework is analyzed and validated by capacity assessments using UWB measurements performed at Eurecom and compared with classical CDMA schemes with random spreading. The following receivers are considered: optimal joint processing, single-user matched filter and MMSE receiver.