Field Experiments on Ultimate Frequency Efficiency Exceeding 30 Bit/Second/Hz Using MLD Signal Detection in MIMO-OFDM Broadband Packet Radio Access

This paper presents indoor and field experimental results on extremely high-speed packet transmissions of 4.92 Gbps in a 100-MHz channel bandwidth, i.e., the frequency efficiency of approximately 50 bit/second/Hz, in the downlink orthogonal frequency division multiplexing (OFDM) radio access. The required received signal-to-noise power ratio (SNR) is less than 30 dB, which approaches the almost upper limit in cellular environments near a cell site even with a light channel load, with the aim of the application to future universal broadband packet radio access. We apply 12-by-12 MIMO multiplexing using the maximum likelihood detection employing QR decomposition and the M-algorithm (QRM-MLD) with adaptive selection of the surviving symbol replica candidates (ASESS), 64QAM data modulation, and turbo coding with the coding rate of R = 8/9 to achieve an extremely high frequency efficiency level. In the field experiments conducted in the Yokosuka Research Park (YRP) district of Yokosuka city, we show that the measured throughput of 4.92 Gbps is achieved at the average received SNR per receiver antenna of approximately 28.0 and 28.5 dB when the receiver antenna spacing is 40 cm (6.2lambda), and 10 cm (1.5lambda) at the average speed of 10 km/h, respectively.