Sungkwan Youm

Asynchronous inter-network interference avoidance for wireless body area networks

This paper considers the internetwork interference problem in environments with multiple wireless body area networks (WBANs). We propose an asynchronous internetwork interference avoidance scheme (abbreviated as AIIA), which is based on the hybrid multiple access of carrier sense multiple access with collision avoidance (CSMA/CA) and time division multiple access (TDMA). In AIIA, the gateway device of each WBAN maintains a table, called an AIIA table, which includes the timing offset and TDMA transmission schedule information corresponding to the interfering WBANs. By referring to the table, the conflicting TDMA schedule can be checked and updated by itself, in asynchronous and distributed manners. Extensive simulations are conducted to demonstrate the feasibility and effectiveness of AIIA.

Machine-to-machine platform architecture for horizontal service integration

Nowadays, machine-to-machine (M2M) communication is being considered as the most promising solution for revolutionizing the future intelligent pervasive applications. This article presents the design of an M2M service platform architecture and prototype implementation of a home automation system based on the designed M2M platform. The proposed service platform consists of three subsystems: M2M service enablement, M2M device management, and M2M communication management. These subsystems include the essential function blocks and interact with each other to horizontally accommodate various M2M applications. The prototype implementation of the full “smart home automation” system, including the M2M service platform, M2M area network, and user/administrator domains, shows the feasibility of the proposed M2M platform architecture.

Selective Cooperative Transmission in Ad Hoc Networks with Directional Antennas

This paper presents a selective cooperative transmission scheme (abbreviated SCT) for ad hoc network with directional antennas that leverages the benefits of directional-only antenna approach and cooperative communication. The main feature of SCT is its adaptability to the channel condition in the network. In other words, when the node sends data, SCT determines its transmission strategy on either direct or cooperative transmission via a relay node called a forwarder, depending on the transmission time. Simulation results are provided to validate the effectiveness of the proposed scheme.

Queuing Analysis for IEEE 802.11e Networks in Non-Saturation Environments

This paper presents an analytical model for the performance evaluation of an IEEE 802.11e network in non-saturation environments. We first characterize the probability distribution of the MAC layer...

Integrated multicast routing algorithms considering traffic engineering for broadband IPTV services

With the rapid growth of broadband network deployment and multimedia streaming development, Internet protocol (IP) multicast networks have become a delivery mechanism for Internet protocol television (IPTV). IPTV provides a two-way interactive service to the viewers, which generates the path request for IP multicast network. Thus, it is essential to evaluate the path rejection probability accurately and further to reduce it. In this paper, we propose a new dynamic multicast routing algorithm for broadband IPTV services and apply it to three legacy algorithms. These integrated multicast routing algorithms support the minimum cost and the traffic engineering features, in order to maximize the acceptance rate for bandwidth constraint path request under IPTV service environments. Furthermore, we compare their network performances in terms of the acceptance rate and delay by experimental simulations. The simulation result gives us that the nearest node first Dijkstra algorithm can be the optimal solution of multicast connection for IPTV service delivery.

Stable pairwise time synchronization in the application layer for capillary machine-to-machine networks

This paper presents the design and performance evaluation of a stable pairwise time synchronization protocol (abbreviated SPS) for capillary machine-to-machine (M2M) networks that provides underlying platform independence and operational stability, even under harsh conditions. SPS achieves the first criterion using a novel technique whereby the M2M device captures incoming or outgoing moments of timing messages. The second criterion is achieved by adaptively adjusting the resynchronization interval. Extensive simulations are conducted to demonstrate the validity and effectiveness of SPS.

Energy-Efficient BOP-Based Beacon Transmission Scheduling in Wireless Sensor Networks

Many applications in wireless sensor networks (WSNs) require the energy efficiency and scalability. Although IEEE 802.15.4/Zigbee which is being considered as general technology for WSNs enables the low duty-cycling with time synchronization of all the nodes in network, it still suffer from its low scalability due to the beacon frame collision. Recently, various algorithms to resolve this problem are proposed. However, their manners to implement are somewhat ambiguous and the degradation of energy/communication efficiency is serious by the additional overhead. This paper describes an Energy-efficient BOP-based Beacon transmission Scheduling (EBBS) algorithm. EBBS is the centralized approach, in which a resource-sufficient node called as Topology Management Center (TMC) allocates the time slots to transmit a beacon frame to the nodes and manages the active/sleep schedules of them. We also propose EBBS with Adaptive BOPL (EBBS-AB), to adjust the duration to transmit beacon frames in every beacon interval, adaptively. Simulation results show that by using the proposed algorithm, the energy efficiency and the throughput of whole network can be significantly improved. EBBS-AB is also more effective for the network performance when the nodes are uniformly deployed on the sensor field rather than the case of random topologies.

Performance Analysis of Reliable Multicast Protocols Using Transparent Proxy Servers on Wired and Wireless Networks

This paper considers the reliable multicast transport protocols used in hybrid networks that include wired and wireless networks and transparent proxy servers. We present four analytic performance models of two extreme reliable multicast transport protocols, sender-initiated and receiver-initiated, and supported and unsupported by transparent proxy servers are considered in each reliable multicast protocol. We analyze the throughputs of these four different models mathematically. Numerical results show that transparent proxy servers give good effects to overall performance. Furthermore, the receiver-initiated reliable multicast supported by transparent proxy servers gives better performances of total throughput than sender-initiated reliable multicast supported by transparent proxy servers. We provide efficiency criterion of the optimal number of transparent proxy servers for each protocol under varying wireless loss probabilities. Numerical results are verified by simulations.