Distributed multiple antenna carrier- and sampling-frequency synchronization for OFDM

Abstract

IJ Multiple antenna systems have been shown to provide significant performance improvements for network nodes; however, the vast majority of nodes in military networks will be limited to single channel devices due to mobility (size and power) and ease of use considerations. In this paper we apply a new joint synchronization-pilot sequence (JSPS) optimization design technique to multiple transmitter OFDM systems. We consider the cases where the transmitters could be co-located or distributed (i. e. multiple single-channel transmitters) in space. Independent JSPSs are designed for each transmitter in a multiple antenna system and can be utilized to estimate the carrier frequency offset (CFO) and sampling frequency offset (SFO) of each antenna independently. We study the mean square error (MSE) for the estimation of CFO and SFO and compare the performance of our estimators to a closed form solution for A WGN channels. We show that the performance of our proposed iterative estimators for distributed CFO and SFO estimation is approximately equivalent to the estimation performance in the co-located CFO and SFO estimation case. The iterative estimator for the distributed case is also found to be of low complexity, with only a linear complexity increase over the co-located estimator. We have also measured, via simulation, the performance of the CFO estimator for distributed Rayleigh fading multipath channels.

Self-Cancellation of Sampling Frequency Offsets in STBC-OFDM Based Cooperative Transmissions

“…In OFDM based CTs, because the oscillator for DAC on each relay is independent, multiple SFOs exist at the receiver, which is a very difficult problem to cope with (Kleider et al, 2009). The common used correction method for single SFO is interpolation/decimation (or named re-sampling), which is a energy consuming procedure.…”

“…And what is more important is that, because the re-sampling of the received signal can only correct single SFO, it seems helpless to multiple SFOs in the case of OFDM based CTs. Although the estimation of multiple SFOs in OFDM-based CT systems has been addressed by several researchers (Kleider et al, 2009;, few contributions have addressed the correction of multiple SFOs in OFDM-based CT systems so far to our knowledge. One related work is the tracking problem in MIMO-OFDM systems (Oberli, 2007), but it is assumed that all transmitting branches are driven by a common sampling clock, so there is still only one SFO at the receiver.…”

Energy Efficiency in Communications and Networks

“…However, OFDM systems are sensitive to sampling frequency offset (SFO), which may lead to severe performance degradation (Pollet, 1994). In OFDM based CTs, because the oscillator for DAC on each relay is independent, multiple SFOs exist at the receiver, which is a very difficult problem to cope with (Kleider et al, 2009). The common used correction method for single SFO is interpolation/decimation (or named re-sampling), which is a energy consuming procedure.…”