Field experiments on TDMA mobile radio signal transmissions

An experimental 1.45-GHz-band TDMA (time-division multiple-access) signal transmission system is described. The system is characterized by a TDMA structure with three time slots per carrier (combination of common access channel (CACH) and two traffic channels (TCH)), narrowband n/4-shift QPSK (quadrature phase-shift keying) with differential detection, two-branch postdetection selection diversity reception, rate-2/3 and rate-1/2 block error correction to protect CACH data and associated control channel (ACCH) data, respectively, and fast bit timing recovery for reception of CACH bursts at the base station. Experimental results on the bit error rate (BER) performance for TCH data transmission due to additive white Gaussian noise (AWGN), cochannel interference, and multipath channel delay spread are presented. Field experiments were also conducted in the Yokohama area to assess the BER performance in a real fading environment. With diversity reception, a BER of 10^-2 can be achieved at a median E_b/N₀ of about 12 dB and at an average signal to interference ratio (SIR) of about 15 dB.