Opportunistic and cooperative spatial multiplexing in MIMO ad hoc networks
Proceedings of the 9th ACM international symposium on Mobile ad hoc networking and computing
Taking the sting out of carrier sense: interference cancellation for wireless LANs
Proceedings of the 14th ACM international conference on Mobile computing and networking
Enabling MAC protocol implementations on software-defined radios
NSDI'09 Proceedings of the 6th USENIX symposium on Networked systems design and implementation
Optimal training design for MIMO OFDM systems in mobile wireless channels
IEEE Transactions on Signal Processing
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A PHY and MAC protocol for MIMO concurrent transmissions, called Contrabass, is presented. Concurrent transmissions, also referred to as multi-user MIMO, are simultaneous transmissions by multiple interfering nodes over the same carrier frequency. Concurrent transmissions technique has the potential of mitigating the overhead of MAC protocols by amortizing protocol overhead among multiple packets. However, existing proposals for concurrent transmissions could not achieve this as MIMO channel training and collision avoidance typically involve an expensive process of coordination and control message exchanges. This overhead has made MIMO concurrent transmission Impractical and thus unused in real applications. Contrabass implements simultaneous channel training and optimal transmission control without any coordination. As a result, Contrabass achieves very high aggregate throughput, low delays and scalability even under dynamic environments and outperforms the existing MIMO protocols. This is the first practical implementation of MIMO-based concurrent transmissions. We implemented Contrabass in GNU radios and also in NS-2.