Blind Timing and Carrier Synchronization in Decode and Forward Cooperative Systems

Abstract

Abstract-Synchronization in Decode and Forward (DF) cooperative communication systems is a complex and challenging task requiring estimation of many independent timing and carrier offsets at each relay in the broadcasting phase and multiple timing and carrier offsets at the destination in the relaying phase. This paper presents a scheme for blind channel, timing and carrier offset estimation in a DF cooperative system with one source, M relays and one destination equipped with N antennas. In particular, we exploit blind source separation at the destination to convert the difficult problem of jointly estimating multiple synchronization parameters in the relaying phase into more tractable sub-problems of estimating many individual timing and carrier offsets for the independent relays. We also modify and propose a criterion for best relay selection at the destination. Simulation results demonstrate the excellent end-toend Bit Error Rate (BER) performance of the proposed blind scheme with relay selection, which is shown to achieve the maximum diversity order with M = 4 relays using N = 5 antennas at the destination. The presented work is a complete solution to blind synchronization and channel estimation in DF cooperative communication systems.

Performance of Multi-Hop Cooperative Networks Subject to Timing Synchronization Errors

“…First, each node transmits its distinct training sequence to the next hop, where the nodes, upon receiving the training sequence use, the ML-based algorithms such as presented in [19]- [21] to compute the timing delays. After the training is completed, the actual data is transmitted.…”

“…The k th node in the first cluster pre-synchronizes its clock according to the estimated timing offsetτ (1) k and samples the received signal at τ (1) k . Thisτ (1) k is estimated by using an ML-based estimator for a generic SISO link as described in [19] and [21]. The 1 in the superscript ofτ (1) k denotes the first hop.…”

“…Several schemes have been proposed for the synchronization of cooperative diversity systems. These schemes can be categorized as transmit time synchronization [17], [18] or receiver synchronization [19]- [21]. The transmit time synchronization schemes are aimed to synchronize the nodes in a cluster such that all the nodes can transmit simultaneously.…”

“…On the other hand, the receiver synchronization at each node can be achieved by employing either the data-aided schemes [19], [20], and [22] or non-data-aided schemes [21]. The dataaided schemes are generally preferred for the synchronization of the distributed MIMO systems, which use a single distinct training sequence for the single-input single-output (SISO) and orthogonal set of sequences for the multiple-input single-output (MISO).…”

Semi-blind multiple-frequency-offset estimation for decode-and-forward OFDM cooperative networks

“…These methods only handle point-to-point MIMO systems in [9] [10] and thus could not apply to cooperative systems directly. The use of blind synchronization and channel estimation by N antennas at the destination in decode-and-forward (DF) cooperative communication systems is proposed in [11]. The blind method requires a more complex system structure.…”