Spacetime division multiple access (SDMA) for mobile, multihop, broadcast packet radio networks

Abstract

Many transmission-scheduling algorithms have been proposed to maximize the spatial reuse and minimize the time-division multiple-access (TDMA) frame length in multihop packet radio networks. None of these algorithms uses knowledge of the physical location. We propose a new concept. Spacetime division multiple access. In spacetime division multiple access (SDMA), space is divided into slots (space slots) that are grouped into periodically repenting frames (space frames), and time slots are assigned to space slots (hence, spacetime). The space slots are constructed such that the probability of more than one node being in the same space slot is minimized, and the space frame is constructed such that spatial reuse is minimized, thus minimizing the TDMA frame length. Therefore, given that each node in the network has a means of determining its location, all nodes can instantaneously determine at all times, the time slot that they should transmit at, without exchanging any information with any other node in the network. Next, we derive the time frame length for mobile, multi-hop, broadcast packet radio networks using SDMA, as a function of the network density and the maximum transmission range. Finally, we show how SDMA can be utilized as the access scheme for the control channel of a reservation TDMA MAC protocol.