Cooperative Bandwidth Sharing for Relaying in

Manuscript received April 25, 2013; revised June 8, 2014; accepted July 15, 2014. Date of publication July 24, 2014; date of current version June 16, 2015. The review of this paper was coordinated by Dr. C. Yuen. The authors are with the MEDIATRON Laboratory, Communication Engineering School of Tunis (Sup’Com), 2083 Ariana, Tunisia (e-mail: soumaya.hamouda@supcom.rnu.tn; benchaab@ties.itu.int; sami.tabbane@ supcom.rnu.tn). Color versions of one or more of the figures in this paper are available online at . Digital Object Identifier 10.1109/TVT.2014.2342791
Fig. 1.
Downlink subframe structure in LTE-AdON A. Background and Related Work O further improve the performance of the LTE-Advanced system, the Third-Generation Partnership Project (3GPP) has recently introduced new network architecture, i.e., the Heterogeneous network (HetNet). As it involves a diverse set of short-range, low-power, and low-cost base stations (e.g., picocells, relays, and femtocells), the HetNet is likely to provide ubiquitous access to mobile broadband services [1]. Each small cell actually targets a different environment in the network so that the spectral efficiency per unit area is enhanced. In this paper, we are interested in the deployment of small cells for range expansion purposes and the improvement of the system performance at the cell edge. Therefore, we consider a HetNet composed of an eNodeB (eNB) coexisting with different relay nodes (RNs) situated at the cell border. Typically, relays help in forwarding data, and based on their roles, they have been categorized into two types [2], [3]. The first type is exclusively
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used to extend the coverage to remote user equipment (UE), beyond the service range of the eNB in LTE-Advanced. These relays are called type-I relays by LTE-Advanced specifications. In addition to providing extended coverage, they also help in the deployment of cells in areas where the cost of wired backhaul is prohibitive. Layer-3 functions are performed by these RNs. On the other hand, the second category of relays is used to help the UE within the service range of the base station to improve its service quality and link capacity. These are called type-II relays by LTE-Advanced (L2 relays). In our paper, we consider type-I relays. To fully benefit from relay technology and achieve better cell-edge users’ throughputs, efficient radio resource management between the eNB and the RNs is much needed. In downlink communications, the LTE-Advanced system supports the orthogonal frequency-division multiple access (OFDMA) technique, which offers high flexibility in radio resource allocation. The backhaul link and the access link are time division, and the radio resources for both eNB and RNs are fully multiplexed. According to the 3GPP, the RN performs in half-duplex mode. In the first orthogonal frequency-division multiplexing (OFDM) time slot, all the physical resource blocks (PRBs) are allocated to the eNB while the RNs remain silent. In the second slot, both eNB and RN operate within the same frequency bandwidth (see Fig. 1) [4]. Different radio resource allocation algorithms were proposed in the literature, aiming at optimizing the frequency bandwidth sharing in a dual-hop OFDMA-based network (e.g., [2], [5]–[7]). In [2], Krishnan et al. investigated bandwidth sharing jointly with the power allocation problem in relaying networks under rate constraints. They solved the optimal bandwidth to be allocated to the different relays and examined the weighted power minimization problem with single and multiple users. In [5], Hou et al. proposed to divide the available frequency bands into subbands to optimize the spectrum sharing in
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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 64, NO. 6, JUNE 2015
Cooperative Bandwidth Sharing for Relaying in LTE-Advanced Using Game Theory
Soumaya Hamouda, Imen Ben Chaabane, and Sami Tabbane
Abstract—Heterogeneous networks (HetNets) are likely to provide ubiquitous access to mobile broadband services as they involve various small cells, each targeting a different environment in the network. In this paper, we are interested in improving the system performance at the cell edge. Hence, we consider a HetNet composed of an eNodeB (eNB) coexisting with different relay nodes (RNs) situated at the cell border. We propose a cooperative physical resource blocks (PRBs) sharing scheme in a dual-hop LTE-Advanced in which every node can transmit on some of the PRBs assigned to a coexisting node without causing it harmful interference. To do so, we use a powerful mathematical tool, i.e., game theory. First, we consider two nodes in the macrocell and define a new repeated game in which a selfish node is encouraged to cooperate under the threat of punishment. Then, we enlarge the number of RNs in the network and find the optimal pairs of nodes that will cooperate, due to a new coalition formation game. Simulation results show that the proposed cooperative PRB sharing scheme significantly improves the utilization of the spectrum and the achieved total throughput in the system. We also demonstrate that both games rapidly attain Pareto efficiency. Index Terms—Coalitional game, cooperative spectrum sharing, game theory, LTE-Advanced, relaying, repeated game.