Improving User Experience of Internet Services in Cellular Networks

University dissertation from Karlstad : Karlstads universitet

Abstract: The Internet has grown enormously since the introduction of the World Wide Web in the early 90's. The evolution and wide spread deployment of cellular networks have contributed to make the Internet accessible to more people in more places. The cellular networks of today offer data rates high enough for most Internet services. Even so, the service quality experienced by the users is often lower than in wired networks.The performance of TCP has a large impact on user experience. Therefore, we investigate TCP in cellular networks and propose functionality to improve the situation for TCP. We have studied sources of delay and data loss, such as link layer retransmissions, queuing, and handover. Measurements were conducted in a GSM/GPRS testbed. The results indicate that TCP interact efficiently with the GSM link layer protocol in most cases. From experiments of queuing in GPRS, we conclude that with a smaller buffer delay is reduced significantly, but that TCP throughput is about the same as with a larger buffer. Furthermore, we propose an improved buffer management when a connection loses all its resources to traffic with higher priority. We also propose a scheme for data forwarding to avoid negative impact on TCP during handover for WINNER, a research system that was used to test ideas for LTE.The achievable data rates in cellular networks are limited by inter-cell interference that vary over the cell. Inter-cell interference can be mitigated with Coordinated Multipoint techniques (CoMP), techniques that currently are being standardized for LTE-Advanced. System wide CoMP is, however, not an option, since it would be too resource consuming. In order to limit the required resources for CoMP, we propose an approach to select a subset of users for CoMP that is based on user experience. Simulation results indicate that user experience, represented with application utility,  and fairness are improved compared to if only rate is considered in the user selection.