Energy-Efficient Channel-Dependent Cooperative Relaying for the Multiuser SC-FDMA Uplink

Abstract

Abstract-In this contribution we exploit the benefits of combining the diversity gains arising from cooperation, multiple propagation paths and from the opportunistic relaying of multiple users. Our goal is to improve the energy-efficiency of the amplify-and-forward single-relay assisted single-carrier frequency-division multiple-access uplink, where the single relay considered may support a single user or may be shared by multiple users communicating over dispersive channels subject to large-scale fading. Based on the proposed amalgam of single-tap frequency-domain equalisation and a diversity combining aided receiver relying on the minimum mean-square error criterion, three different relay selection schemes designed for either singleuser or multi-user relaying scenarios are investigated, when combined with source/relay power sharing, which employ imperfect power control. Our results demonstrate that at a bit error ratio of 10 −4 , the proposed receiver is capable of saving 2dB power by achieving a higher cooperative diversity gain than the conventional receiver. Moreover, a beneficial energy-efficiency improvement may be achieved, when the cooperative regime operates at E b /N0 < 0. Most importantly, when the shadowing variance is increased from 4dB to 8dB, the energy consumption gain gleaned from our multi-user and multi-access relay selection schemes may increase to 4∼9 compared to the direct transmission in the absence of shadowing at E b /N0 = −10dB.

Energy-Efficient Dynamic Resource Allocation for Opportunistic-Relaying-Assisted SC-FDMA Using Turbo-Equalizer-Aided Soft Decode-and-Forward

“…Following the subband mapping operations, the resulting U -element FD symbol vector is transformed to the TD by the U -point inverse discrete Fourier transform (IDFT), which is similar to the action of the OFDM transmitter [29]. Consequently, the U -symbol baseband-equivalent discrete-time signal s S,t k transmitted by the kth source MT before inserting the cyclic prefix (CP) may be expressed as [20] …”

“…Although IFDMA may also invoke DSA, the achievable selection diversity gain may be lower than that of LFDMA operating through DSA, which is a consequence of the frequency selectivity of the IFDMA symbol spectrum. received by the jth relay is first transformed to the FD by the U -point DFT operation and then demapped to the appropriate N subbands through the matrix (P (2), yielding its equivalent FD representation in the form of [20] …”

“…Although both the dynamic relay selection (DRS) [19], [20] and dynamic subband/subcarrier allocation (DSA) techniques [21] can provide a power gain, conventional DSA-aided OR may not exploit both. The main reason is that the two hops of the relay channel limit the capacity to that of the lower capacity link of the two hops.…”

“…• In contrast to the aforementioned solutions, our focus is mainly on the energy efficiency of the DRA-aided OR-assisted SC-FDMA system, where the energy efficiency is quantified in terms of the energy consumption gain (ECG) and the energy reduction gain (ERG) [20], [25]. In addition, we evaluated the impact of the channel estimation overhead and the MWR-aided CQI exchange overhead on the energy efficiency.…”

Variable packet splitting transmission in multi-relay cooperative communications with DF and DAF for SC-FDMA

“…In recent years, cooperative communications are widely studied [6][7][8][9]. Cooperative communications use the relay node except the source and destination nodes.…”