Multipacket reception in MIMO-OFDM systems

The medium access control (MAC) layer in many wireless systems is designed to serve one user at a slot when conventional slotted ALOHA protocol is applied. However, the problem of packet collisions can be solved at the physical (PHY) layer by using signal processing technique. By exploiting orthogonal frequency division multiple access (OFDMA) and spatial division multiple access (SDMA), a decentralized MAC strategy with multi-packet reception (MPR) is proposed for MIMO-OFDM systems. First, employing receive beamforming, we study the possible optimal number of users which are likely to transmit at the same subcarrier and slot to maximize the separable packets subject to their BER (SINR) requirements. Then the transmission probability is designed to achieve the desired number of users. The performance and benefits of the proposed strategy is analyzed analytically and evaluated through simulations.