A novel load-balancing scheme for cellular-WLAN heterogeneous systems with cell-breathing technique

This paper proposes a novel load-balancing scheme for an operator-deployed cellular-wireless local area network (WLAN) heterogeneous network (HetNet), where the user association is controlled by employing a cell-breathing technique for the WLAN network. This scheme eliminates the complex coordination and additional signaling 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 optimizing the system throughput. In addition, a cellular-WLAN interworking architecture and signaling procedures are proposed for implementing the proposed load-balancing schemes in an operator-deployed cellular-WLAN HetNet

Energy efficiency in heterogeneous wireless access networks

In this article, 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

Adaptive stochastic radio access selection scheme for cellular-WLAN heterogeneous communication systems

This study proposes a novel adaptive stochastic radio access selection scheme for mobile users in heterogeneous cellular-wireless local area network (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 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 with the mainstream network selection schemes: namely, WLAN-first and load balancing

Efficient network selection schemes for an operator deployed cellular-WLAN heterogeneous networks.

The HetNet architecture is considered to be one of the promising solutions for the problem of capacity crunch and increasing energy consumption of wireless communication networks. Hence, it is expected to be one of the key aspects in the realisation of the future wireless communication networks. Moreover, future wireless communication networks are characterised by the co-existence of multiple radio access technologies called multi-RAT HetNets. In this context, the integrated cellular-WLAN HetNet attracts considerable interest among the mobile network operators. One of the major challenges of such HetNet is the optimal selection of serving network. In this regard, this thesis focuses on the efficient network selection schemes for an operator deployed cellular-WLAN HetNet. Firstly, a novel load balancing scheme is proposed for an operator deployed cellular-WLAN HetNet, where the user association is controlled by employing cell-breathing technique for the WLAN network. In this scheme, the coverage of each WiFi AP is dynamically optimised to achieve desired load balancing. Since this is a network controlled traffic steering scheme, users can simply associate to the available strongest WiFi AP, without making any complex network selection decisions. Thus, can be easily implemented in an existing cellular-WLAN HetNet. Subsequently, performance analysis of cellular-WLAN HetNet is carried out for a saturated downlink scenario, in order to investigate the effect of deploying CRE technique for WLAN network in the cellular-WLAN HetNet. In addition, a cellular-WLAN interworking architecture and detailed signalling procedures are proposed for implementing CRE scheme in an operator deployed cellular-WLAN HetNet. Finally, a novel Adaptive Stochastic Radio Access Selection scheme is proposed for an operator deployed cellular-WLAN HetNet. This scheme implements a stochastic network selection policy that assigns certain probability for selecting WLAN according to the status of the network in terms of load and signal quality. The proposed scheme helps to improve the system performance in terms of network throughput, energy efficiency, and call blocking probability

Performance Analysis of Cellular-WLAN Heterogeneous Network Based on Continuous Time Markov Chain

This paper proposes an analytical model for performance evaluation of Cellular-WLAN Heterogeneous Networks (HetNets) based on Continuous Time Markov Chain (CTMC) for variable-bit-rate (VBR) data services. This model considers system specific overheads and limitations such as limited number of supported modulation and coding scheme (MCS) of each network. Moreover, this model includes the traffic density variation between hot-spot (where the WLAN access point are usually deployed) and non-hot-spot areas. The proposed analytical model is used to evaluate the system performance of two mainstream network association schemes; namely, WLAN-first and Load Balancing, in terms of total system throughput. In addition, the proposed analytical model is thoroughly validated against extensive system level simulation results obtained from the Network Simulator 3 (NS3) platform

Analysis of Energy Efficiency on the Cell Range Expansion for Cellular-WLAN Heterogeneous Network

In this paper, we analyse the total network en- ergy efficiency (EE) of cellular-WLAN heterogeneous network (HetNet) that employs cell range expansion (CRE) technique, in order to control the user association to either WLAN or cellular network. To this end, we model the system with OFDM based cellular macro-cells and WiFi access points for a saturated (i.e., full-buffer) downlink scenario, considering practical aspects of each type of access technology. Then we evaluate the EE of network by considering realistic power consumption models for each access network type. We compare the performance of the CRE scheme with two benchmark user association schemes; namely, WLAN-first and Max-RSRP (Reference Signal Receive Power). The results demonstrate that CRE with negative biasing performs best in terms of network EE, while the WLAN-first scheme demonstrates the worst performance. However, the CRE with negative biasing lacks fairness in terms of user throughput, while the WLAN-first scheme shows better fairness. Hence, there is a trade-off between the user fairness and the system EE. We show that by optimising the bias factor of each APs individually, with appropriate utility function, a better balance of this trade-off can be achieved

Performance analysis of Cellular-WLAN Heterogeneous Network based on Continuous Time Markov Chain

This paper proposes an analytical model for performance evaluation of Cellular-WLAN Heterogeneous Networks (HetNets) based on Continuous Time Markov Chain (CTMC) for variable-bit-rate (VBR) data services. This model considers system specific overheads and limitations such as limited number of supported modulation and coding scheme (MCS) of each network. Moreover, this model includes the traffic density variation between hot-spot (where the WLAN access point are usually deployed) and non-hot-spot areas. The proposed analytical model is used to evaluate the system performance of two mainstream network association schemes; namely, WLAN-first and Load Balancing, in terms of total system throughput. In addition, the proposed analytical model is thoroughly validated against extensive system level simulation results obtained from the Network Simulator 3 (NS3) platform