Saewoong Bahk

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The fairness concept has been widely studied in the area of data networks. The most well-known fairness criterion (max–min fairness) gives priority to the minimum-rate session. Kelly questioned its appropriateness in his works on the bandwidth sharing among the end-to-end flows and proposed another fairness criterion preferring short-distance flows to(More)
Orthogonal frequency-division multiple access (OFDMA) systems are considered promising candidates for implementing next-generation wireless communication systems. They provide multiple channels that can be accessed via random access schemes. However, traditional random access schemes could result in an excessive amount of access delay. To address this(More)
Mobile stations in the cell boundary experience poor spectral efficiency due to the path loss and interference from adjacent cells. Therefore, satisfying QoS requirements of each MS at the cell boundary has been an important issue. To resolve this spectral efficiency problem at the cell boundary, deploying fixed relay stations has been actively considered.(More)
It was recently shown that 802.11b MAC has an “anomaly” that the throughput of high bit-rate terminals in good channel condition is down-equalized to that of the lowest bit-rate peer in the network. In this letter, we analytically prove that the phenomenon can be cleanly resolved through configuring the initial contention window size inversely proportional(More)
The OFDMA systems are emerging for future cellular networks. Creating multiple data channels, they can support the flexible frequency reuse factor (FRF). Although FRF 1 is the best choice in terms of cell throughput, it causes intercell interference at the cell boundary, thereby being unable to serve the whole cell area. Therefore it was proposed to use the(More)
In this paper we describe briefly a dynamic multi-path routing scheme that has been considered for connection oriented homogeneous high speed networks. The fundamental objective of the scheme is to bridge the gap between routing and congestion control as the network becomes congested. Because propagation delay far out shadows queueing and transmission delay(More)
This paper considers some scheduler structures that are executable in environments of multiple traffic classes and multiple frequency channels. In designing a scheduler structure for multiple traffic classes, we first propose a scheduler selection rule that uses the priority of traffic class and the urgency level of each packet. Then we relax the barrier of(More)
An important quality-of-service (QoS) issue in wireless multimedia networks is how to control handoff drops. In this paper, we propose admission-control algorithms that adaptively control the admission threshold in each cell in order to keep the handoff-dropping probability below a predefined level. The admission threshold is dynamically adjusted based on(More)
Opportunistic scheduling provides a good chance to improve wireless system performance by exploiting the underlying channel condition. There has been a lot of work on opportunistic scheduling, but the problem of finding the right feedback mechanism to convey channel information has largely been untouched. In emerging multichannel systems, the perchannel(More)
센서 네트워크에서 노드들의 한정된 전력량을 이유로 에너지 효율성은 MAC 프로토콜을 설계하는 데 있어서 중요한 요소이다. 센서 네트워크를 위한 MAC 프로토콜들은 전력 소모를 최소화하기 위해 낮은 듀티 사이클(Duty Cycle)을 사용한다. 그 중에서 RMAC [4]의 경우 Pioneer(PION) 프레임을 이용하여 한 주기 내에 여러 홉을 전송한다. 본 논문에서는 RMAC 과는 달리 한 주기 내에 전달될 수 있는 최대 홉 수 정보가 포함된 Explorer(EXP)를 이용하여 데이터 전송을 하는 HE-MAC 프로토콜을 제안한다. EXP 의 정보와 Ready-to-Receive(RTR) 상태를 이용하여 RMAC 에 비해 2 홉을(More)