Bounds on the Maximum Number of Concurrent Links in MIMO Ad Hoc Networks with QoS Constraints

摘要

Multiple-Input Multiple-Output (MIMO) based Medium Access Control (MAC)protocols have received a good deal of attention as researchers look to enhanceoverall performance of Ad Hoc networks by leveraging multi antenna enablednodes. To date such MAC protocols have been evaluated through comparativesimulation based studies that report on the number of concurrent links theprotocol can support. However, a bound on the maximum number of concurrentlinks (MNCL) that a MIMO based MAC protocol should strive to achieve hashitherto been unavailable. In this paper we present a theoretical formulationfor calculating the bound on the MNCL in a Mobile Ad Hoc Network (MANET) wherethe nodes have multiple antenna capability, while guaranteeing a minimumQuality of Service (QoS). In an attempt to make our findings as practical andrealistic as possible, the study incorporates models for the following PHYlayer and channel dependent elements: (a) path loss and fast fading effects, inorder to accurately model adjacent link interference; (b) a Minimum MeanSquared Error (MMSE) based detector in the receiver which provides a balancebetween completely nulling of neighboring interference and hardware complexity.In calculating the bound on the MNCL our work also delivers the optimal powercontrol solution for the network as well as the optimal link selection. Theresults are readily applicable to MIMO systems using Receive Diversity, SpaceTime Block Coding (STBC), and Transmit Beamforming and show that with a 4element antenna system, as much as 3x improvement in the total number ofconcurrent links can be achieved relative to a SISO based network. The resultsalso show diminishing improvement as the number of antennas is increased beyond4, and the maximum allowable transmit power is increased beyond 10 dBm (for thesimulated parameters).