Differential Space-Time Network Coding for Multi-Source Cooperative Communications

Abstract

Abstract-Due to the asynchronous nature of cooperative communications, simultaneous transmissions from two or more nodes are challenging in practice. The existing cooperative communications employing successive transmission from one user node to the other can avoid the synchronization problem but results in large transmission delay. In addition, channel estimation in multisource cooperative communications is a challenging and costly task due to the amount of training, especially when the number of cooperative users is large. Considering these practical challenges in multi-source cooperative communications, this paper proposes a differential space-time network coding (DSTNC) scheme for narrowband multi-source cooperative communications to overcome the problems of imperfect synchronization and complex channel estimation without introducing large transmission delay. Each user in the network linearly combines the correctly decoded symbols via network coding and transmits its packet in time division multiple access (TDMA) mode. The pairwise error probability is analyzed and the design criteria of the DSTNC are derived to achieve full diversity. For broadband cooperative communications, distributed differential space-timefrequency network coding (DSTFNC), which is differentially encoded within each orthogonal frequency-division multiplexing (OFDM) block, is designed through mapping from the proposed DSTNC. When the statistical channel power-delay profile is known at the corresponding user node, each node can permutate its channel independently to improve the performance of the DSTFNC scheme. Simulation results are presented to verify the performance of the proposed schemes.

Distributed Widely Linear Kalman Filtering for Frequency Estimation in Power Networks

“…Statistical signal processing in the complex-domain underpins a number of disciplines, including wireless communications [31], [32] and power systems [16]. Although it may be convenient to process complex-valued data by representing the real and imaginary parts as a bivariate signal in the real domain, any intuition and physical meaning inherent in processing in the complex domain would be obscured.…”

“…From (35), notice that when the system is balanced (B i,n = 0), the coefficient g i,n = 0, and the widely linear frequency estimate in (36) is identical to its strictly linear counterpart in (31). While the strictly linear AR(2) model in (33) is identical for both balanced and unbalanced voltages, the widely linear model provides an intuitive advantage as the coefficient g i,n represents the negative sequence which characterises the imbalance of the system voltage.…”

Cooperative adaptive estimation of distributed noncircular complex signals

“…Moreover, distributed systems offer numerous advantages compared with centralised systems, such as robustness to link and node failures, and lower communication overheads. In this work, we address the problem of adaptive estimation of noncircular complex signals within a framework of cooperative distributed networks; this has recently attracted plenty of interest, as complex signals are the backbone in distributed applications such as wireless communication networks and seismic sensing [3].…”

“…The estimator in (2) is optimal for the generality of complex signals, both circular and noncircular. Further, the full second order information is contained in the augmented covariance matrix (3) and as such, estimation based on R� incorporates both the covariance and pseudocovariance.…”

Space-Time Network Coding With Transmit Antenna Selection and Maximal-Ratio Combining

“…In [8], [9], it was assumed that the channel state information (CSI) is known at the receivers. To avoid the requirement of channel estimation, the differential space-time network coding (DSTNC) and distributed differential spacetime-frequency network coding (DSTFNC) schemes were designed for narrowband and broadband cooperative communication systems, respectively, in [11]. Similarly to STNC, both the DSTNC and DSTFNC schemes provide the full diversity.…”