A threshold-based opportunistic MAC protocol for MIMO wireless sensor networks

In this paper, we consider a single-hop wireless sensor network where both the sensor nodes and the controller node have multiple antennas. We focus on single beam opportunistic communication and propose a threshold-based medium access control (MAC) scheme for uplink packet transmission which exploits multiuser diversity gain without feedback in a decentralized manner. Packet transfer from sensor nodes to the controller node is initiated when the channel quality of any node exceeds the predefined threshold based on the effective signal-to-noise ratio (ESNR) measurements at the sensor nodes through linear combining techniques. The +is determined to maximize the probability of successful packet transmission where only one sensor node transmits its packet in one time-slot. Computer simulations confirm that the use of multiple antennas at the sensor nodes can improve the throughput of proposed scheme compared with our previous scheme without implementing the spatial diversity at the SNs assuming Rayleigh fading channel model.