NHK OPEN HOUSE 2012 | Exhibition

24 Space-Time Trellis Coded MIMO Transmission System

The FPUs * 1 currently being used for mobile relays of outdoor sports events such as road races operate in the 700-MHz band. In response to the frequency reorganization plan of the Japanese Ministry of Internal Affairs and Communication, our laboratories have developed an FPU mobile relay system operating in other bands that uses the space-time trellis coded MIMO(STTC-MIMO) transmission * 2 scheme.


System requirements Free-space transmission loss, diffraction loss, etc., are much greater in the candidate frequencies of the 1.2-GHz and 2.3-GHz bands than in the 700-MHz band. The losses must be compensated by, for example, increasing the transmission power, improving the transmission scheme, or improving the receiving system by using macro-diversity * 3 Two-transmitter, two-receiver space-time trellis coded MIMO transmission system We developed two-transmitter, two-receiver space-time trellis coded MIMO transmitting equipment for QPSK, 8PSK and 16QAM. This equipment has twice the transmission capacity (44.7 Mbps for 16QAM) of the current FPU OFDM system. The required CNR for a quasi error-free state was also improved by about 6.0 dB in case of the same transmission capacity. Reed-Solomon outer error correction code (204,166) Reed-Solomon code (204,166) uses 38 parity bytes and has an error correction capability about 2.5 times greater than the currently used Reed-Solomon code (204,188). This code improves the required CNR by about 1.0 dB.

We will conduct field tests to verify the system’s effectiveness in the 1.2-GHz and 2.3G-Hz bands and investigate the technical requirements related to a switch-over of FPU frequencies.

* 1 FPU (Field Pick-up Unit) : Wireless system for transmitting video material * 2 Space-time trellis coded MIMO(STTC-MIMO) transmission : A MIMO method in which two transmitting branches perform convolutional coding with distant mapping points for different data and two receiving branches are used in Viterbi decoding to reconstruct the transmitted data. * 3 Macro-diversity : A method that gathers, selects, and combines the signals received by multiple distant base stations. It greatly improves the diversity effect in comparison with the previous method of selection after demodulation for each base station.