In wireless networks without nodes equipped with multiple antennas, cooperative Multiple Input Multiple Output (MIMO) transmissions may be used to harness diversity gains. In general, diversity gains are larger if more nodes are involved in the transmission. However, a transmission policy that maximizes the diversity gain or throughput need not maximize the stability region, since queues at the nodes may grow while waiting for a sufficient number of nodes to become available. To address this issue, this paper develops a mechanism for maximizing the throughput while reducing the energy consumption and maintaining queue stability. We develop a sufficient condition that ensures the throughput optimality of a stable transmission policy and then use it to design a distributed, dynamic threshold based Medium Access Control (MAC) protocol for cooperative MIMO transmissions. The MAC protocol requires only limited local information for its operation. Simulation results are provided to evaluate the performance of the proposed protocol and compare it against regular point-to-point and existing cooperative MIMO MAC protocols. The results show that the proposed scheme can provide considerable gains in the throughput and energy savings compared to cooperative MIMO based on fixed number of cooperating nodes.

This paper develops a distributed, threshold based MAC protocol for cooperative multi input multi output (MIMO) transmissions in distributed wireless systems. The protocol uses a thresholding scheme that is updated dynamically based on the queue length at the sending node to achieve low power transmissions while ensuring stability of the transmission queues at the nodes. Simulation results are provided to evaluate the performance of the proposed protocol and compare it against regular point to point as well as fixed group size cooperative MIMO MAC protocols.

In this paper we propose a distributed system for facilitating cooperative MIMO transmissions in networks without multiple antenna devices. MIMO diversity is achieved by employing groups of nodes in the vicinity of the source and destination to help with the transmission. The distributed sending nodes are assumed to have different carrier frequency offsets (CFO). Space-time block codes (STBC) and code combining are used to utilize spatial diversity. The estimation of multiple CFO and detector for STBC-coded data under multiple CFO are provided. The BER of the proposed system is shown and discussed. We also consider the energy consumption and compare it with other cooperative designs.

Cooperative MIMO can achieve higher energy savings and lower delays in distributed systems by allowing nodes to transmit and receive information jointly. In this paper, we develop a new MAC protocol for enabling packet transmissions using cooperative MIMO. The paper also develops analytical models for evaluating the packet error probability, energy consumption and packet delays associated with the proposed MAC protocol. The analysis is validated against simulation results using the NS- 2 simulator. Our results show that the proposed MAC protocol has lower delays and lower energy consumption as compared to regular point to point MAC protocols.