Abstract-In this paper, we bring forward the important aspect of energy savings in wireless access networks. We specifically focus on the energy saving opportunities in the recently evolving heterogeneous networks (HetNets), both Single-RAT and Multi-RAT. Issues such as sleep/wakeup cycles and interference management are discussed for co-channel Single-RAT HetNets. In addition to that, a simulation based study for LTE macro-femto HetNets is presented, indicating the need for dynamic energy efficient resource management schemes. Multi-RAT HetNets also come with challenges such as network integration, combined resource management and network selection. Along with a discussion on these challenges, we also investigate the performance of the conventional WLAN-first network selection mechanism in terms of energy efficiency (EE) and suggest that EE can be improved by the application of intelligent call admission control policies.

Abstract-This paper proposes a novel load balancing scheme, for an operator-deployed cellular-WLAN heterogeneous network (HetNet), where the user association is controlled by employing cell breathing technique for the WLAN network. This scheme, eliminates the complex coordination and additional signalling overheads between the users and the network, by allowing the users to simply associate with the available WLAN networks similar to the traditional WLAN-first association, without making complex association decisions. Thus, this scheme can be easily implemented in an existing operator-deployed cellular-WLAN HetNet. The performance of the proposed scheme is evaluated in terms of load distribution between cellular and WLAN networks, user fairness, and system throughput, which demonstrates the superiority of the proposed scheme in load distribution and user fairness while optimising the system throughput. In addition, a cellular-WLAN interworking architecture and signalling procedures are proposed for implementing the proposed load balancing schemes in an operator-deployed cellular-WLAN HetNet.

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This paper proposes a novel Adaptive Stochastic Radio Access Selection (ASRAS) scheme for mobile users in heterogeneous Cellular-WLAN systems. In this scheme, a mobile user located in dual coverage area randomly selects WLAN with probability of ω when there is a need for downloading a chunk of data. The value of ω is optimised according to the status of both networks in terms of network load and signal quality of both cellular and WLAN networks. An analytical model, based on Continuous Time Markov Chain (CTMC) is proposed to optimise the value of ω and compute the performance of proposed scheme in terms of energy efficiency, throughput, and call blocking probability. Both analytical and simulation results demonstrate the superiority of the proposed scheme compared to the mainstream network selection schemes, namely, WLAN-first and Load Balancing.

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