Signal space cooperative communication

Abstract

In this paper, a single-hop single-relay system with a direct link between the source and the destination is considered when the relay operates in the half-duplex mode. Motivated by the concept of signal space diversity, this paper introduces signal space cooperation, in which cooperation between the source and the relay is achieved using a novel constellation design approach. In this approach, the original constellation is expanded so that each member of the new constellation inherits its components from at least two members of the original constellation. The expanded constellation enables the relay to extract the required information in order to cooperate in the relay phase, and it helps the destination to effectively combine received signals during the broadcast phase and the relay phase. The analytical study of the proposed scheme leads to the development of two design criteria for the constellation expansion approach. The proposed design criteria aim at maximizing the relay role in the cooperative scheme by increasing the performance of the source-relay link. In this way, the source and the relay can effectively cooperate in order to maximize the overall performance of the system. The signal space cooperative scheme can be used for any constellation size without incurring significant complexity overhead to the system. Numerical results depict superior performance in comparison with other cooperative schemes such as the adaptive decode and forward and the distributed turbo code schemes.

Two-way decode-and-forward cooperative systems with signal space diversity

“…The analytical results are validated using Monte Carlo simulations, which were performed with 10 9 trials for each simulation point for accuracy and correctness. The SSD scheme is using 4-QAM modulation with rotation angle of 26.6 • [31]. The path loss exponent is set as ν = 3 and the variances are σ 2 h = σ 2 a = σ 2 b = 1.…”

“…The rotation angle θ is chosen carefully to ensure that each signal point in the rotated constellation carries enough information in one component, either I or Q, and uniquely represents the original signal [28,31]. A list of θ for various modulation schemes can be found in [34,35], such as the rotation angle θ of 26.6 • , 14.0 • , and 7.1 • , is chosen for 4-, 16-, and 64-QAM constellations, respectively.…”

“…Hereafter, this proposed scheme will be referred to as SSD-based two-way cooperative system, can also called as two-way signal space cooperative system (SSC-2W). SSD has been utilized in one-way relaying systems [31][32][33] to improve system performance. In [31], SSD is introduced into a one-way single-relay DF cooperative system, where the source and the relay cooperate to transmit different symbols to the destination.…”

“…SSD has been utilized in one-way relaying systems [31][32][33] to improve system performance. In [31], SSD is introduced into a one-way single-relay DF cooperative system, where the source and the relay cooperate to transmit different symbols to the destination. A similar cooperative scheme with one-way single relay is analyzed in [32], where a tight closed-form upper bound on the error probability is derived.…”

System analysis of relaying with modulation diversity

“…In fact, by using MD, the undesirable impact of the channel fading can be reduced [1], [2]. Current techniques in MD involve mapping the information bits into multiple symbols of a typical constellation, e.g., quadrature phase-shift keying (QPSK), and grouping them into vectors [1], [2], [3]. Then, to distinguish any two vectors by their distinct components, the vectors are rotated by a square spreading matrix.…”