Opportunities and Challenges in OFDMA-Based Cellular Relay Networks: A Radio Resource Management Perspective

Abstract

Abstract-The opportunities and flexibility in relay networks and orthogonal frequency-division multiple access (OFDMA) make the combination a suitable candidate network and air-interface technology for providing reliable and ubiquitous high-data-rate coverage in next-generation cellular networks. Advanced and intelligent radio resource management (RRM) schemes are known to be crucial toward harnessing these opportunities in future OFDMA-based relay-enhanced cellular networks. However, it is not very clear how to address the new RRM challenges (such as enabling distributed algorithms, intra-cell/inter-cell routing, intense and dynamic co-channel interference (CCI), and feedback overhead) in such complex environments comprising a plethora of relay stations (RSs) of different functionalities and characteristics. Employment of conventional RRM schemes in such networks will highly be inefficient if not infeasible. The next-generation networks are required to meet the expectations of all wireless users, irrespective of their locations. High-data-rate connectivity, mobility, and reliability, among other features, are examples of these expectations. Therefore, fairness is a critical performance aspect that has to be taken into account in the design of prospective RRM schemes. This paper reviews some of the prominent challenges involved in migrating from the conventional cellular architecture to the relay-based type and discusses how intelligent RRM schemes can exploit the opportunities in relay-enhanced OFDMA-based cellular networks. We identify the role of multiantenna systems and explore the current approaches in literature to extend the conventional schedulers to next-generation relay networks. This paper also highlights the fairness aspect in such networks in the light of the recent literature, provides some example fairness metrics, and compares the performances of some representative algorithms.

A Survey of Self Organisation in Future Cellular Networks

“…In addition to the approaches discussed above, relay assisted cellular networks have also been extensively investigated as possible LB tools [67], [79], [87]- [97]. This is due to the fact that relay nodes can help achieve LB via at least three different means.…”

Radio resource management for user-relay assisted OFDMA-based wireless networks

“…The problem formulation may differ significantly in optimization objectives (rate maximization, power minimization), optimization constraints (fairness, load balancing), relaying protocols (amplify and forward (AF), decode and forward (DF)), relaying modes (full-duplex, half-duplex), relay types (fixed, mobile), antenna numbers of the source, destination and relay (single antenna/multiple antennas) and system architectures (downlink/uplink, single-cell/multi-cell). The RRM problem has been examined in numerous research works for OFDMA-based fixed relay networks [19][20][21][22][23][24][25][26][27][28][29]. The opportunities and challenges of the OFDMA-based fixed relay networks have been discussed in detail in [19,20].…”

“…The RRM problem has been examined in numerous research works for OFDMA-based fixed relay networks [19][20][21][22][23][24][25][26][27][28][29]. The opportunities and challenges of the OFDMA-based fixed relay networks have been discussed in detail in [19,20]. In [21], RRM problem for sum rate maximization has been examined for single-cell OFDMA system.…”

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

“…With multi-cell DF relay-aided OFDMA systems, [27] and [28] have discussed RA algorithms when the powers are uniformly allocated to all stations. For multicell OFDMA systems without DF relaying, several RA algorithms have been proposed in [29][30][31][32].…”