QoE Based Vertical Handover Schemes For Indoor VLC-RF Heterogeneous Networks

Communication systems in the fourth generation(4G)and beyond consist of different variety of wireless access standards,coverage,network availability and Quality of Experience(QoE).The standard may quickly change relative to velocity and motion of the user equipment(UE).Delivery of seamless connectivity comprises the development of intelligent proactive mechanisms for efficiently predicting and executing vertical handover(VHO).The complexity of the challenge increases a lot more with consideration of haphazard UE movement patterns.Geographical topologies such as indoor or outdoor environments also exert further constraints on the network coverage and the movement of the UE.Another challenge specifically for visible light communication(VLC)is the light-of-sight(LOS)propagation.The main aim of this research is how to find a seamless connection between a number of VLC hotspots and RF when the VLC link is blocked.In order to enhance the quality of experience(QoE)of the UE,reduce handover delay cost and minimize handover failure probability.The ability of a VHO scheme to perform handover at the right time to the neighboring network greatly affects the QoE of the user.The advantages of VLC and its complementary role with RF in both coverage and capacity have made it essential for their combined use in wireless communication as employed in this dissertation;this,therefore,has an advantage over a sole media.However,technical challenges in VHO exist for such integration.In order to solve these challenges mention above,three main VHO schemes have been proposed in the next three paragraphs as follows.1).A VLC heterogeneous network(VLC-HetNet)that combines VLC and existing radio networks,in VHO scheme that provides continuous transmission has been proposed to solve these problems.Specifically,the proposed VHO scheme maximizes the quality of experience(QoE)of a user.When a user makes a handover between VLC and the RF network,the influence on the user's QoE may be positive(defined as the QoE profit)or negative(the reduced QoE value is defined as the handover cost).The handover decision is made in order to enhance the QoE and reduce the handover cost of the user,by formulating the problem as a Markov decision process(MDP).The simulation results show that the proposed VHO scheme is adaptive to user movement and achieves a relatively high average QoE,low handover failure probability,and few handover times.2).In addition,we propose a fuzzy logic approach termed estimated quality of experience fuzzy logic(EQFL-VHO)scheme to estimate the quality of experience of the user.Our method fuses four input metrics variables,namely estimated QoE in RF,handover failure probability,delay cost and velocity of the UE to determine whether handover needs to be triggered.After fuzzification,the handover factor(HF)is used which indicates whether handover to RF would enhance the user's QoE or not.Our scheme couples the advantages of the Mamdani fuzzy logic system and QoE estimation for good system performance.Given the different traffic modes and interruption types,the traditional methods;immediate VHO(I-VHO)and dwell VHO(D-VHO)can be deployed as the two benchmark VHO schemes.A heterogeneous environment is considered where a user moves between two-tier networks.The simulation result shows that the EQFL generally outperforms the traditional methods and the fuzzy logic methods.The analysis further shows that our scheme can provide the least handover failure probability as well as low delay cost with the same HF decision method.In addition,our scheme handover initiation frequency is reduced effectively.3).Furthermore,we propose a dynamic quality of experience fuzzy logic(QFL)scheme,which combines the advantages of VLC with the advantages of RF.The QFL scheme enables the QoE of the user equipment(UE)to be enhanced when VHO is performed from one network to another,taking into consideration the data rate and the bandwidth of the networks.Our proposed scheme has the ability to handle any variation and indecision that might have arisen out of the handover input metric.The handover process is less complex and easy to implement.The simulation result shows that the proposed scheme outperformed other VHO schemes,with a better QoE performance,lesser queuing of packets in the uplink,and least handover failure probability to RF.In addition,it provides good performance for short interruption and excellent performance in relation to VHO execution delay.