Analysis of subcarrier pairing in a cellular OFDMA relay link

Riihonen, Taneli; Wichman, Risto; Hämäläinen, Jyri; Hottinen, A.

doi:10.1109/wsa.2008.4475544

Cited by 20 publications

(23 citation statements)

References 11 publications

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“…The performance of the last user is the same as that of the random allocation (RA) whereas the first users gets good channel at high probability. However, the capacity variation between users is smaller than that of the system in [10] with optimal pairing where the worst SR channel is paired with the worst RD channel resulting performance for the last user remarkably lower than that of the RA. As already demonstrated at the previous study [9], AS outperforms STBC also with imperfect feedback link.…”

Section: Performance Resultsmentioning

confidence: 93%

“…Analytical study in [10] shows that the optimal subcarrier pairing provides some performance gain when the subchannels from the RNs to user equipments (UEs) are fixed. In this paper, we assume that feedback information is conveyed from the UE to the RN so that RBs can be dynamically allocated according to the strictly limited channel knowledge.…”

Section: Introductionmentioning

confidence: 99%

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Subchannel Allocation in Relay-Enhanced OFDMA Downlink with Imperfect Feedback

Leinonen

Riihonen²,

Hämäläinen³

et al. 2009

GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference

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Abstract-This paper studies the resource allocation for orthogonal frequency division multiple access (OFDMA) in a fixed amplify-and-forward (AF) relay link. We express closed-form average capacity results for the system when frequency allocation is based on limited and imperfect feedback information and multiple antennae are assumed at the relay node (RN) and the user equipment (UE). Feedback strategies based on the best-M method and resource block (RB)-wise one bit quantization are analyzed and compared. Capacity expressions are presented for space-time block coding (STBC) and transmit antenna selection (AS) schemes. The capacity results with imperfect feedback path are of particular interest. The results illustrate that promising tradeoff between the system performance, feedback overhead, and robustness against feedback errors can be achieved by using AS and limited feedback in frequency allocation.

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Section: Performance Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Subchannel Allocation in Relay-Enhanced OFDMA Downlink with Imperfect Feedback

Leinonen

Riihonen²,

Hämäläinen³

et al. 2009

GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference

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“…The RN can either amplify the BS-RN subcarriers and forward them to the RN-UE subcarriers, or it can decode the BS-RN symbols and encode the data again for the RN-UE hop. In this paper, we concentrate on DF protocols, whereas reference results considering AF protocols are available in [8].…”

Section: B Relay Functionalities and Relaying Protocolsmentioning

confidence: 99%

“…Then we compare the capacities of the relaying protocols with different functionalities by applying the parameters to the formulas derived in the previous section. The system setup is similar to that of [8] and the performance results for the AF protocol are taken directly from there as an additional reference.…”

Section: Numerical Evaluationmentioning

confidence: 99%

Capacity Evaluation of DF Protocols for OFDMA Infrastructure Relay Links

Riihonen¹,

Wichman²,

Werner³

2009

GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference

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Abstract-We consider a downlink OFDMA transmission system in which an infrastructure-based relay node is deployed for extending the coverage of a base station. Focusing on decode-andforward (DF) operation, we study how different relay functionalities affect the system performance. The functionalities include fixed or adaptive subcarrier pairing, information redistribution, buffering, and adjustment of the time shares allocated for the two hops. In particular, it is of great interest for system design to be able to evaluate the performance gains due to each functionality, because they come at the expense of increased complexity and cost of the relay architecture. The main contribution of the paper is to analyze the performance of the proposed protocols by deriving new closed-form expressions for the average end-to-end capacity. The calculated expressions facilitate the performance comparison between the different functionalities.

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“…To fully exploit the spectral and spatial degrees of freedom, different OFDM relaying protocols have been proposed in the literature, e.g., [7]- [18]. Specifically, for AF OFDM(A) relay systems, power allocation and subcarrier pairing (SP) schemes have been studied in [8] and [9]- [12], respectively, and have been jointly exploited in [13] and [14]. These power allocation and SP schemes have also been studied for DF OFDM relay systems in [15], [16] and [11], [17], respectively, and a scheme that utilizes joint coding across subcarriers has also been developed in [18] as an alternative for SP.…”

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confidence: 99%

Feedback-Aided Pilot Placement and Subcarrier Pairing for AF OFDM Relay Channels

Sung

Hong

Chao

2013

IEEE Trans. Veh. Technol.

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Abstract-This paper examines the use of channel feedback to adaptively determine pilot placement among subcarriers in amplify-and-forward (AF) orthogonal frequency-division multiplexing (OFDM) relay systems. With feedback of the previous channel estimate, pilot subcarriers at the source and relay can be reassigned to reduce channel estimation error and ensure that good subcarriers are made available for data transmission. The minimum effective signal-to-noise ratio (SNR) among data subcarriers is utilized as the performance metric for the optimization of the pilot locations. The effective SNR is defined as the receive SNR at the destination, taking into consideration the source-to-relay (SR) and relay-to-destination (RD) channels, as well as their respective channel estimation errors. The feedback gain, which is defined as the ratio between the minimum effective SNR achieved with the optimal feedback-aided pilot placement and that achieved with the equal-spaced pilot placement, is used to measure the gains achieved through feedback. In this paper, we first derive an analytic lower bound on the optimal feedback gain and show its rate of increase with respect to the number of subcarriers. These studies are performed for systems both without and with subcarrier pairing (SP) at the relay. Specifically, in systems without SP, the relay forwards each datum on the same subcarrier on which it is received. In systems with SP, the relay is allowed to reassign the subcarriers used to forward the data received from the source. With the goal of maximizing the minimum effective SNR, the optimal SP scheme is shown to be an inverse mapping between the SR and RD subcarriers with respect to their channel gains. Due to the complexity of finding the optimal placement, a suboptimal but efficient algorithm called the iterative pilot relocation (IterPR) scheme is then proposed. The effectiveness of the proposed IterPR schemes is demonstrated through numerical simulations.Index Terms-Channel estimation, feedback, orthogonal frequency-division multiplexing (OFDM), pilot placement, relaying, subcarrier pairing (SP).

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Analysis of subcarrier pairing in a cellular OFDMA relay link

Cited by 20 publications

References 11 publications

Subchannel Allocation in Relay-Enhanced OFDMA Downlink with Imperfect Feedback

Subchannel Allocation in Relay-Enhanced OFDMA Downlink with Imperfect Feedback

Capacity Evaluation of DF Protocols for OFDMA Infrastructure Relay Links

Feedback-Aided Pilot Placement and Subcarrier Pairing for AF OFDM Relay Channels

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