This paper illustrates a large-scale MIMO propagation channel measurement in a real life environment and evaluates throughput performance of various MIMO schemes in that environment. For that purpose, 44 MIMO transceivers and a novel spatial scanner are fabricated for wideband MIMO channel measurements in the 5 GHz band. A total of more than 50,000 spatial samples in an area of 150 m2, which includes a bedroom, a Japanese room, a hallway, and the living and dining areas, are taken in a real residential home environment. Statistical properties of the propagation channel and throughput performance of various MIMO schemes are evaluated by using measured data. Propagation measurement results show large dynamic channel variations occurring in a real environment in which statistical properties of the channel, such as frequency correlation and spatial correlation are not stationary any more, and become functions of the SNR. Furthermore, evaluation of throughput shows that although MIMO schemes outperform the SISO system in most areas, open loop systems perform badly in the far areas with low SNR. Paying for the cost of CSI or partial CSI at Tx, closed loop and hybrid systems have superior performance compared to other schemes, especially in reasonable SNR areas ranging from 10 dB to 30 dB. Spatial correlation, which is common in Japanese wooden residences, is also found to be a dominant factor causing throughput degradation of the open loop MIMO schemes.

It is well known that deploying a proxy at the boundary of wireless networks and the Internet is able to improve the performance of transmission control protocol (TCP) over wireless links. Snoop protocol, acting like a transport layer proxy, performs local retransmissions for packets corrupted by wireless channel errors. In this letter, an improvement for the Snoop protocol is proposed to shorten the time spent on local recovery by sending extra copies in every local retransmission attempt. This enables TCP to quickly return to normal, effectively eliminating several of the problems that may cause throughput degradation.

In this paper, the CSK/SSMA ALOHA system with nonorthogonal sequences which combines the ALOHA system with Code Shift Keying (CSK) using nonorthogonal sequences is proposed. The throughput performance was evaluated by theoretical analysis. Moreover, the throughput performance of the system is compared with those of the DS/SSMA ALOHA and M-ary/SSMA ALOHA systems. It is found that the throughput performance of our system to be better than those of the other two systems.

To improve the throughput efficiencies of ARQ protocols over a high random packet-error channel, contiguous multiple copy-transmission (CMCT) strategy for which each packet is (re-)transmitted by sending its multiple copies in contiguous slots has been used so far. However, in burst error environments, all copies may be damaged in an error burst resultting the performance degradation of CMCT. To cope with this situation, we propose, in this paper, a new strategy called intermittent multiple copy-transmission (IMCT) whereby multiple copies are sent at a fixed interval. The throughput efficiency of go-back-N ARQ using CMCT or IMCT is analyzed and considered under a two-state Markov channel model expressing burst error property of a channel. As a result, it is shown that (i) the degree of improvement of throughput efficiency by CMCT or IMCT depends on the degree of error burst and (ii) the proposed IMCT can improve the throughput efficiency of go-back-N ARQ for high and burst error channels.

The throughput performance of the non-persistent carrier sense spread spectrum with overload detection (NP-CSSS/OD) protocol is analysed and compared with that of the conventional non-persistent and one-persistent carrier sense multiple access with collision detection (NP-CSMA/CD and 1P-CSMA/CD) and the one-persistent carrier sense spread spectrum with overload detection (1P-CSSS/OD) protocols. We also introduced utilization measurements and did some performance comparisons between these protocols. At high offered loads, the NP-CSSS/OD protocol is found to offer the best throughput and utilization performances amongst them.