Enhanced channels access methods in hetbands for single and multi-rat femtocell networks

Abstract

To handle the spectrum scarcity, Mobile Network Operators (MNOs) offloaded data traffic of macrocell via licensed and unlicensed bands simultaneously using conventional methods named Dual Band Femtocell (DBF) and Integrated Femto Wi-Fi (IFW). The existing procedures to manage coexistence in unlicensed band led to low throughput. Moreover, both DBF and IFW also not efficient due to inappropriate selection criteria for the values of channel access scheme parameters which were pre-assigned. In addition, an efficient strategy is needed for optimal traffic balancing over both bands according to traffic loads. The main objective is to propose enhanced channels access methods in Heterogeneous Bands (HetBands) for single and multi-RAT femtocell networks using Enhanced DBF (EDBF) and Enhanced IFW (EIFW), where both enhance BS's performance in unlicensed band in terms of optimal throughput and fair sharing. Initially, the conceptual system model was built for EDBF and EIFW small cells. In an analytical model, two approaches to obtain unlicensed channel and manage coexistence were formulated and validated, then Home enhanced Node-B (HeNB) performance been analyzed in terms of throughput, fair sharing, and traffic balancing. The simulation model represents a suburban scenario using DBF, IFW, EDBF, and EIFW. The performance evaluations considered unlicensed channel access schemes including a new procedure to access unlicensed band and dynamic algorithm control data traffic for optimal traffic balancing over HetBands, thus EDBF and EIFW against conventional methods. Simulation results show that the proposed methods successfully enhance performance, where the throughput results at UE using EDBF and DBF were 88.32Mbps and 80.02Mbps, and from EIFW and IFW were 80.80Mbps and 72.86Mbps. Thus, EDBF and EIFW outperformed conventional methods by 1.103 and 1.108 times, respectively. These results reveal that EDBF outperformed EIFW in terms of UE's throughput, also in whole system throughput as their results were 5209Mbps and 4847Mbps, respectively. However, both enhanced methods had the same influence on macrocell and Wi-Fi networks’ throughput. The Wi-Fi throughput and fractions of channel time ( and ) revealed that both enhanced methods achieved fair sharing in unlicensed band. In addition, both methods control data traffic, where unlicensed band was used as a supplementary band. Under high traffic loads, unlicensed band was equally shared between cellular and Wi-Fi networks where as fairness metric was 0.475, which is half of the maximum fraction of channel time that the channel can be used by both networks. The main contributions of this thesis are enhanced channels access methods in HetBands, a new formulation for fair sharing management, a new procedure to access unlicensed band, and an optimized dynamic algorithm. In the future, thorough investigation on the total energy efficiency utilizing unlicensed band in femtocell is essential.