Ki Jun Han

Performance analysis of the IEEE 802.16 wireless metropolitan area network

In this paper, we propose a new QoS architecture for the IEEE 802.16a MAC protocol and present a bandwidth allocation and admission control policy for the architecture. Our architecture provides QoS support to real-time traffic with high priority while maintaining throughput performance to an acceptable level for low priority traffic. Analytical and simulation results assure advantages of our architecture.

Analysis of Latency Performance of Bluetooth Low Energy (BLE) Networks

Bluetooth Low Energy (BLE) is a short-range wireless communication technology aiming at low-cost and low-power communication. The performance evaluation of classical Bluetooth device discovery have been intensively studied using analytical modeling and simulative methods, but these techniques are not applicable to BLE, since BLE has a fundamental change in the design of the discovery mechanism, including the usage of three advertising channels. Recently, there several works have analyzed the topic of BLE device discovery, but these studies are still far from thorough. It is thus necessary to develop a new, accurate model for the BLE discovery process. In particular, the wide range settings of the parameters introduce lots of potential for BLE devices to customize their discovery performance. This motivates our study of modeling the BLE discovery process and performing intensive simulation. This paper is focused on building an analytical model to investigate the discovery probability, as well as the expected discovery latency, which are then validated via extensive experiments. Our analysis considers both continuous and discontinuous scanning modes. We analyze the sensitivity of these performance metrics to parameter settings to quantitatively examine to what extent parameters influence the performance metric of the discovery processes.

A power efficient routing protocol based on balanced tree in wireless sensor networks

A wireless sensor network consisting of a large number of nodes with limited battery power should minimize energy consumption at each node to prolong the network lifetime. In this paper, we propose a routing protocol based on a balanced tree, called BATR (balanced aggregation tree routing), which uses near optimal minimal spanning tree for balancing the power consumptions over all nodes. Our key idea is that a near optimal data aggregation can be achieved in terms of network lifetime when power consumption at each node can be nicety balanced. Simulation results show that the BATR can lengthen system lifetime as compared with the conventional data aggregation protocols.

An adaptive probabilistic broadcast scheme for ad-hoc networks

Broadcast service in ad hoc networks is elementary operation to support various important functions such as route discovery procedure. In this paper, we propose several adaptive probabilistic broadcast schemes to alleviate the broadcast storm problem. Our schemes dynamically determine the rebroadcast probability at each node based on the neighbor information within two-hop span. Simulation results are presented, which show our schemes have a better performance over the deterministic flooding approach.

An adaptive energy saving mechanism for the IEEE 802.15.4 LR-WPAN

In this paper, an energy saving mechanism is proposed for the IEEE 802.15.4 Low-Rate Personal Area Network (LR-PAN). In the current version of IEEE 802.15.4 standard, each node can enter the sleep mode only during the inactive portion of superframe. In our scheme, the coordinator dynamically determines duty cycle and adjusts the interval of sleep mode by varying BO (Beacon Order) based on the arrival rate of packets in the network observed. Analytical results show that our scheme with a proper adjustment of BO can increase the average sleep time and shorten the energy consumption.

Multicast handoff agent mechanism for all-IP mobile network

This paper proposes a mechanism called a Multicast Handoff Agent (MHA) to reduce handoff latency for IP multicast. The MHA acts as a proxy for the Internet Group Management Protocol (IGMP) of mobile nodes and keeps information for members of multicast groups in a cell. When a mobile node moves to other cell, the MHA immediately sends unsolicited reports without waiting for the IGMP query. In addition, our mechanism may conserve battery power since it does not need to reply to a query.The mechanism is evaluated through simulation and analysis and compared with the IGMPv2 for mobility and IGMP traffic. Simulation results show that handoff latency can be largely reduced and the IGMP control traffic can be eliminated on the wireless links during the duration of membership.

An enhanced bandwidth balancing mechanism of the DQDB MAN

The bandwidth balancing (BWB) mechanism of the distributed queue dual bus (DQDB) protocol has several drawbacks, such as inefficiency of the priority scheme and unfairness in the multiple priority implementation. An enhanced BWB mechanism is proposed here to solve these problems. In the proposed mechanism, a separate BWB is applied to each priority level. Simulation indicates that the enhanced version not only may provide more efficient priority transmissions but may also offer fairer access opportunities among nodes.<<ETX>>

A partition prediction algorithm for group mobility in ad-hoc networks

One of important issues associated with group mobility in ad-hoc networks is predicting the partition time. The existing algorithms predict the partition time assuming that the partitioned groups move to opposite direction with the same speed and the same coverage. So, these algorithms could not accurately predict partition time in practical situation. In this paper, we propose a partition prediction algorithm considering network partition in any direction, at any speed, and with different coverage of group. To validate the proposed algorithm, we carried out a simulation study. We observe a sound agreement between numerical results obtained by our algorithm and computer simulation. Our algorithm can predict the partition time more accurately in real situations.

An architecture for efficient qos support in the IEEE 802.16 broadband wireless access network

In this paper, we propose a new QoS architecture for the IEEE802.16a MAC protocol and present a bandwidth allocation and admission control policy for the architecture. Our architecture provides QoS support to real-time traffic with high priority while maintaining throughput performance to an acceptable level for low priority traffic. Analytical and simulation results assure advantages of our architecture.

Throughput Analysis of IEEE 802.11e EDCA Protocol

The Medium Access Control (MAC) protocol standardized by the IEEE 802.11e supports multimedia applications such as voice and video using QoS enhancement at medium access control level. In this paper, we present an analytical model for throughput of contention-based channel access function called Enhanced Distributed Coordination Function (EDCF) used for IEEE 80 2.11e MAC protocol. We observed a sound agreement between numerical results obtained by our analytical model and simulation.