Evaluating and Reducing Multipath Transport Latency

Access to the Internet is a very significant part of everyday life with increasing online services such as news delivery, banking, gaming, audio and high quality movies. Applications require different transport guarantees with some requiring higher bandwidth and others low latency. Upgrading access link capacity does not guarantee faster access to the Internet as it offers higher bandwidth but may not offer low latency. With increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G,..), there is a need to analyse the impact of using multiple such technologies at the same time. Legacy transport protocols such as TCP or SCTP are only able to connect to one access network at a time to create an end-to-end connection. When more than one access technology is used, there may be a large difference in the data rate offered by each technology. This asymmetry might impact latency sensitive applications by creating out of order delivery. In this thesis, we focus on the latency aspect of multipath transport protocol performance. We consider CMT-SCTP and Multipath TCP as available multipath protocols that were designed for exploiting multiple paths for better throughput and reliability. We consider various real world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. We perform simulations, emulations and experiments using heterogeneous network settings involving access networks with different bandwidth, delay and loss characteristics. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. However, MPTCP does not perform well in asymmetric scenarios with latency sensitive traffic. This analysis provides insights in to various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses to reduce latency. Tail losses are the losses that occur at the end of a packet stream. Recovering such losses is of higher significance to latency sensitive applications. We propose a modification to the use of TLP, a mechanism in TCP for tail loss recovery. We evaluate the performance of proposed TLP modification, first using emulations and with real world network experiments. Our results show significant improvements in latency for specific loss scenarios in emulations and up to 50% improvement in experiments.With an increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G), there is a need to analyse the impact of using multiple such technologies at the same time. The inherent asymmetry among these technologies might affect latency sensitive applications by creating out of order delivery. In this thesis, we consider CMT-SCTP and Multipath TCP as available multipath protocols designed to exploit multiple paths for better throughput and reliability.  We perform simulations, emulations and experiments using various real-world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. This analysis provides insights into various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses (losses that occur at the end of a packet stream) to reduce latency. This thesis presents a modification to the use of Tail Loss Probe (TLP) in MPTCP that provides improvements in latency for specific loss scenarios in emulations and upto 50% improvement in experiments

A Dynamic Pricing Method for Efficient Radio Resource Management in Wireless Access Networks

Radio Resource Management(RRM) has become critical with the current growth in the development of new technologies and services in the field of cellular communications. Efficient management of available radio resources and the possibility of dynamically selling unused spectrum are crucial challenges for the telecom operators. We propose an auction model for efficiently marketing radio resources and a dynamic pricing method for setting the prices of communication resources for sale. Simulation results demonstrate the effectiveness of the proposed pricing method in maximizing the revenue and success rate of the bid compared to the random pricing

Load Balancing Combining Fractional Frequency Reuse with Unrestricted User Association

Maximizing system throughput and bandwidth utilization while guaranteeing fairness among users is a core technical challenge in the design of next generation cellular networks. In this context, fractional frequency reuse (FFR) is a helpful tool if it is flexible in terms of resource and power allocation as well as scheduling. Complementary to this tool, a well-chosen association of users to base station sectors can yet be another important factor, particularly when users are distributed unevenly in space. Here we propose a load balancing scheme that combines flexible FFR with an unrestricted association of users to sectors or base stations, thereby effectively increasing the user data rates in the dense regions of the network. In a first step, we perform virtual joint power allocation and scheduling so as to determine the best sectors for maximizing the throughput for a given user. In a second step, users are actually associated to the best sectors, which are not necessarily the ones providing the strongest signal. Simulation results show that our proposed mechanism provides fairness by load balancing while still maintaining the throughput over all users