In April 2010, NTT DOCOMO began WIDESTAR II, mobile satellite communications service (MSS) covering all of the Japan landmass and the surrounding maritime area. WIDESATR II is the next stage in the evolution of the Japanese domestic MSS system and is the successor to WIDESTAR, using four beams of the N-STAR c/d geostationary satellites. The new WIDESTAR II system provides all of the previous WIDESTAR services and higher speed data communications at a lower cost. Base station equipment and mobile stations were newly developed, and core node equipment was efficiently developed to add only functions specific to MSS. The IP multimedia subsystem (IMS) and other general-purpose IP technologies were incorporated as the software is commonly used in the MSS and 3G/Long Term Evolution (LTE) cellular system. WIDESTAR II can provide diverse high-speed MSS services.

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 OFDM radio access. The required received signal-to-noise power ratio (SNR) is less than 30dB, which is almost the upper limit in cellular environments near a cell site even with a light channel load, with the aim of 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 respective receiver antenna separation is 40 cm (6.2lambda) and 10 cm (1.5lambda) and the transmitter antenna separation is 70 cm (10.9lambda) at the average speed of 10 km/h under non-line-of-sight (NLOS) conditions.

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.