Junichi Suga

Centralized mobility load balancing scheme in LTE systems

MLB (Mobility Load Balancing) is one of the use cases of SON (Self-Organizing Network) discussed in NGMN and 3GPP. The objective of MLB is to reduce the number of low throughput users and the call blocking rate, when cell loads such as radio resources are unbalanced among cells, by adjusting handover parameters. In this paper, we focus on adjusting the HO margin which is one of the handover parameters and propose a centralized solution for MLB where a central server decides optimal HO margins considering load distribution among cells. In addition, we also present simulations results to demonstrate that our proposed solution reduces the number of low throughput users compared with a distributed solution.

Implementation and performance evaluation of keyword-based content retrieval

Information-Centric Networking (ICN) is receiving attention as an emerging network technology. Due to its attractive features, such as accessing content by its name, in-network caching, etc., ICN is expected to apply essentially to the Internet of Things (IoT). IoT applications typically collect a large amount of data widely distributed in various locations. For such usage, we proposed the architecture of Keyword-Based Content Retrieval (KBCR) in a previous paper, as an extension of ICN. In KBCR, a requester sends one request with some keywords, and can receive related content in one response. In this paper, we describe the implementation and performance evaluation of KBCR, and show the feasibility and efficiency of it. For implementation, we implemented KBCR protocol in our testbed system to confirm its functions and developed a demonstration application to show its effectiveness. For performance evaluation, we compared KBCR and NDN by queueing analysis using measured data on the prototype, and showed that KBCR provides better performance both in a requester load and the network delay/throughput.

A Method of Introducing Multipath TCP to Mobile Core Networks and Its Evaluations

The number of mobile terminals that have both a cellular interface and a Wi-Fi interface has been growing in the recent years. Meanwhile, Multipath TCP (MPTCP) that enables the simultaneous use of multiple paths with multiple TCP flows while showing just one regular TCP connection with the application has been standardized by the IETF and has drawn more attention recently. One feature of MPTCP is that it can be realized only by operating system layers supporting multipath communication without any modifications of the application. However, it might be difficult to install MPTCP in all server operating systems. In this paper, we propose a method for applying a proxy that forwards TCP communication from a server to MPTCP communication on a mobile core network, and show the results of evaluation with the existing equipment.

Optimal policy for joint spectrum resource management in multi-band cognitive radio networks

Cognitive Radio (CR) has been recognized as a promising solution to solve the current spectrum inefficiency problem. We consider a CR Base Station (CR-BS) has multiple spectrum bands over a wide frequency range and uses channel-dependent data rates to communicate with the Secondary Users (SUs). To maximize the spectrum utilization while supporting the Quality of Service (QoS) of the SUs, various decisions needs to be made during the operational period of the CR system taking into account not only the behavior of Primary Users (PUs) and SUs but also the current utilization of each spectrum band. In this paper, we propose an optimal policy for joint spectrum resource management in multi-band CR networks, which consists of admission control, spectrum band selection, spectrum handover and eviction control. The problem is formulated as a Semi-Markov Decision Process (SMDP) and the optimal decision for each system state is derived to reduce the SU blocking probability while keeping the SU dropping probability upper-bounded. Performance evaluation shows that the proposed policy outperforms other three policies in terms of both the SU blocking probability and the SU dropping probability.