Cross-layer optimisation for uplink transmission in OFDMA cellular networks with fixed relays

Abstract

In this paper, we consider a cross-layer design aimed to enhance performance for uplink transmission in an orthogonal frequency division multiple-access (OFDMA)-based cellular network with fixed relay stations. Because mobile stations (MSs) spend most of the power on the uplink transmission, power efficiency resource allocation becomes very important to MSs. We develop a cross-layer optimisation framework for two types of uplink flows (inelastic and elastic flows) that have different quality-of-service requirements. For inelastic flows with fixed-rate requirement, we formulate the cross-layer optimisation problem as the minimisation of the sum transmission power of MSs under the constraints of flow conservation law, subcarrier assignment, relaying path selection and power allocation. For elastic flows with flexible-service-rate requirement, we consider the cross-layer trade-off between uplink service rate and power consumption of MSs and pose the optimisation problem as the maximisation of a linear combination of utility (of service rates) and power consumption (of MSs). Different trade-offs can be achieved by varying the weighting parameters. Dual decomposition and subgradient methods are used to solve the problems optimally with reduced computational complexity. The simulation results show that, through the proposed cross-layer resource optimisation framework and algorithms, significant benefits of deployment of multiple fixed relays in an OFDMA cellular network can be fully obtained such as reduction in power consumption, increase in service rate and energy savings in the uplink transmission of MSs.

Relay Selection Fairness and Resource Allocation for OFDMA Networks

“…Power allocation with total and individual power constraints was considered for the OFDM DF relaying systems in [6] but multiple users were not studied. The QoS requirements of users were considered in several works [7][8]. In [9], QoS-aware optimal joint relay selection and resource allocation under a total power constraint were proposed.…”

Relay Selection and Resource Allocation for Multi-User Cooperative OFDMA Networks

“…The duality gap of any optimization problem satisfying the time sharing condition is negligible as the number of subcarriers becomes sufficiently large [28]. Since our optimization problem obviously satisfies the time-sharing condition, it can be solved by using the dual method and the solution is optimal [16], [28].…”

“…However, resource allocation schemes designed for the downlink may not be applicable for the uplink due to the distributive nature of power constraints [16]. A multi-user joint distributed resource allocation scheme for uplink cooperative OFDMA system is proposed in [17].…”

“…However, the problem is solved heuristically. A cross layer approach for uplink OFDMA based cellular networks supporting heterogeneous services is introduced in [16]. The authors formulated two different optimization problems to support two types of uplink flows and determined cross-layer trade-off between uplink service rate and power consumption of users.…”

“…However, homogeneous users with same service and demand are considered. Resource allocation supporting each user's QoS requirements has been considered in several works [16], [19], [20]. In [20], a rate adaptive joint subcarrier and power allocation algorithm under interference and QoS constraints is proposed for cooperative OFDMA based broadband wireless access networks.…”