Synchronization using an adaptive early-late algorithm for IR-TH-UWB transmission in multipath scenarios

Ultra-wide band (UWB) radio transmits data using sub-nanosecond pulses with a very low duty cycle. It is a promising candidate for short-range communications in dense multipath environments. However, due to the short length of the impulse signal, a very precise synchronization control is vital for the whole system. In this paper an adaptive algorithm using an Early-Late delay locked loop (DLL) is proposed to achieve frame synchronization in a multiuser multipath scenario. This concept has been studied by Gardner [2] [3]. Our main contribution is to extend the use of this DLL to a wide band signal. In this extension, instead of using the received signal as the input of the DLL, the output of an analog matched filter to the transmitted reference impulse is used. Consequently implementation is simplified. We investigate using I bit and 2 bit resolution samples in DLL. Simulation results indicate that the performance of DLL for 2 bit resolution is degraded by only 1dB at SNR of -20dB for 2 active users. It is also shown that the loop can maintain lock with the incoming signal at very low signal-to-noise ratio. In a dense multipath channel, performance is equivalent to that of a classical algorithm. It is also able to track variable timing delay.