Power Minimization for OFDM Transmission with Subcarrier-Pair Based Opportunistic DF Relaying

Abstract

This paper develops a sum-power minimized resource allocation (RA) algorithm subject to a sum-rate constraint for cooperative orthogonal frequency division modulation (OFDM) transmission with subcarrier-pair based opportunistic decode-and-forward (DF) relaying. The improved DF protocol first proposed in [1] is used with optimized subcarrier pairing. Instrumental to the RA algorithm design is appropriate definition of variables to represent source/relay power allocation, subcarrier pairing and transmission-mode selection elegantly, so that after continuous relaxation, the dual method and the Hungarian algorithm can be used to find an (at least approximately) optimum RA with polynomial complexity. Moreover, the bisection method is used to speed up the search of the optimum Lagrange multiplier for the dual method. Numerical results are shown to illustrate the power-reduction benefit of the improved DF protocol with optimized subcarrier pairing. Index Terms-Cooperative communication, resource allocation, decode and forward, OFDM.

Distributed algorithms for sum rate maximization in multi-cell downlink OFDMA with opportunistic DF relaying

“…During the second TS, except for the relay, the source might also transmit symbols on subcarriers unused by the relay. Adopting the DF relaying, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] have investigated intensively the RA problems for downlink OFDMA.…”

“…Considering the case when the S-D link is available, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] have studied RA in systems with opportunistic relaying (sometimes termed as selection relaying). To start with, [8][9][10][11][12][13] have studied a low spectrum efficiency (LSE) protocol, when only the relay transmits symbols during the second TS.…”

“…Note that, with the LSE protocol, subcarriers unused by the relay during the second TS are actually wasted. To address this issue, [14][15][16][17][18][19][20][21][22] have proposed and studied improved high spectrum efficiency (HSE) protocols which allow new symbols to be transmitted on the subcarriers unused by the relay during the second TS.…”

Power allocation and subcarrier pairing in OFDM-based Decode-and-Forward relay networks based on a genetic approach

“…For example, Boostanimehr and Bhargava [8] proposed a selective subcarrier pairing and power allocation scheme by KTT condition in DF OFDM relay systems. Li et al [9] and Wang et al [10] solved the joint subcarrier pairing and power allocation by the dual iterative method, where the pairing scheme is resolved by the hungarian method [11]. The optimization of power allocation and subcarrier pairing in [9], [10], however, were treated separately, so the solution appears to be only suboptimal.…”

“…Li et al [9] and Wang et al [10] solved the joint subcarrier pairing and power allocation by the dual iterative method, where the pairing scheme is resolved by the hungarian method [11]. The optimization of power allocation and subcarrier pairing in [9], [10], however, were treated separately, so the solution appears to be only suboptimal. In light of this, Hsu et al [12] proposed an amendment algorithm to jointly solve the subcarrier pairing and power allocation problem by continuously relaxing the subcarrier pairing constraints, and solving the problem in the dual domain.…”