Development of TDMA cellular base station equipment

The system configuration and base station equipment developed to realize a three-channel TDMA cellular system based on the Japanese standard is described. The frequency band is 900 MHz and, the interleave carrier spacing is 25 kHz. The modulation scheme is π/4-shift QPSK. Developed technologies include extremely low-distortion multicarrier power amplification, modulation/demodulation with diversity reception, and speech processing incorporating VOX control for reducing the power consumption of portable sets. These technologies increase the capacity remarkably, and reduce the size of the base station equipment to one-fifth that of existing analog systems. The cost is also reduced considerably. To ensure high-quality radio transmission performance, a BER of 10^-2 is achieved at a median E_b/ N₀ of less than 11 dB in fading environments. This ensures robust speech and nonspeech (facsimile/data) transmissions