S-TFRC: An efficient rate control scheme for multimedia handovers

The integration of heterogeneous wireless access technologies has numerous issues for multimedia applications, such as to smoothly continue over new connections without any service disruption during vertical handovers. We propose State-Aware Feedback extension to Datagram Congestion Control Protocol (DCCP) that meets QoS requirements of multimedia applications throughout the handover process. We consider movement of mobile subscribers among heterogeneous access technologies from highly unstable to more stable environment and model their mobility patterns as Uniform, Pareto, and Exponentially distributed. We present detailed analysis on the performance of proposed mechanism in terms of resuming transmissions during the handover process. In particular, we propose Markov model of TFRC capturing TCP timeouts, loss rates, and no-feedback timer expirations. We validate the proposed analytical model through simulations and show that it accurately predicts various congestion events that may happen during the handover process. We then evaluate the performance of S-TFRC via both simulations and analytical model and observe the sender rates and throughputs achieved. We also consider transmission delays and transmission rates as performance metrics and compare performance of S-TFRC with the standard TFRC. Our results show that S-TFRC is capable of providing better QoS to multimedia applications than standard TFRC by significantly reducing transmission delays and provides better throughput to multimedia applications.

Exploring the Open Problems and Future Trends Concerning Handovers in Heterogeneous Wireless Networks: A Review

The advancements in the telecoms industry have led to the emergence of many new technologies to meet communication requirements worldwide. Consumers have largely been using GSM, CDMA and WiFi. New developments have given birth to more robust communication systems including WiMax and LTE. Lay users are not aware of the technicalities, advantages and disadvantages of these technologies. Therefore, there is a state of great confusion among the users of this generation as to which technology is the best for them to use. Each of these technologies has pros and cons over one another. For example, LTE covers a large area and offers the highest speed, but the user has to pay for it; however, WiFi covers only hotspots but the use is free. Future heterogeneous networks (HetNets) will enable users to achieve seamless connectivity through vertical handovers while providing them the beneficial features of each technology. For HetNets many issues still need to be addressed. This paper explores some of the open problems and future trends related to the handovers in heterogeneous wireless networks. The dynamics with respect to handovers and the network load of cellular architecture in the coming era in the field of wireless communications are also presented. In addition, first a foundation is laid on the IEEE media independent handover and its importance and then the problem of load balancing and its impact on the realization of future HetNets is explained. Finally, an important problem during vertical handovers, known as the ping-pong effect is explained. The open problems for researchers have been identified for the aforementioned issues.

Investigation of a New Handover Approach in LTE and WiMAX

Nowadays, one of the most important challenges in heterogeneous networks is the connection consistency between the mobile station and the base stations. Furthermore, along the roaming process between the mobile station and the base station, the system performance degrades significantly due to the interferences from neighboring base stations, handovers to inaccurate base station and inappropriate technology selection. In this paper, several algorithms are proposed to improve mobile station performance and seamless mobility across the long-term evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) technologies, along with a minimum number of redundant handovers. Firstly, the enhanced global positioning system (GPS) and the novel received signal strength (RSS) prediction approaches are suggested to predict the target base station accurately. Then, the multiple criteria with two thresholds algorithm is proposed to prioritize the selection between LTE and WiMAX as the target technology. In addition, this study also covers the intercell and cochannel interference reduction by adjusting the frequency reuse ratio 3 (FRR3) to work with LTE and WiMAX. The obtained results demonstrate high next base station prediction efficiency and high accuracy for both horizontal and vertical handovers. Moreover, the received signal strength is kept at levels higher than the threshold, while maintaining low connection cost and delay within acceptable levels. In order to highlight the combination of the proposed algorithms’ performance, it is compared with the existing RSS and multiple criteria handover decision algorithms.