Low-overhead symbol timing and carrier recovery for TDMA portable radio systems

Simulation and experimental results for a hardware implementation of a low-overhead digital coherent burst demodulator for time-division multiple-access (TDMA) radio systems using short bursts are analyzed. This implementation is based on digitizing a receiving signal after a low-frequency IF amplifier and performing all demodulation functions using digital signal processing techniques. Demodulation with very low overhead for TDMA is made possible by storing a burst in memory. A novel forward loop plus backward loop structure performs carrier recovery. Symbol-timing and carrier-frequency-offset estimations are performed by block processes, using the error signal resulting from differential demodulation. Bursts as short as 32 symbols can be demodulated without overhead. Since the demodulator is entirely digital and has the potential for low-power VLSI implementation, it is suitable for a portable radio system. Other advantages of this implementation include the availability of a channel quality measure derived from symbol timing estimation and the possibility of providing differential detection when it is desirable