Capacity comparison between alamouti and cooperative VAA with EF and AF Relays

Abstract

It is widely recognized that the use of multiple antennas will be a key point for the implementation of future wireless systems. However, in a large number of cases, due to size and complexity constraints, it is impractical to implement multiple antenna transceivers. In this paper we analyze a Virtual MIMO system with 2 transmit antennas, 1 receive antenna and 2 cooperative relays, using Alamouti coding. Two types of relays are studied when applied to this scheme: ‘Equalize and Forward’ and ‘Amplify and Forward’. The instantaneous capacity for both systems are derived, average and outage capacities are compared with the Alamouti scheme applied with collocated antennas and conventional SISO system. Numerical results show that virtual Alamouti is better when using EF relays, in most realistic scenarios. With AF relays, VAA is still be better than the Alamouti scheme, for scenarios with slightly higher values of path loss exponent.