Gang Uk Hwang

Learn More
In this paper, we propose an analytical Markov chain model of the slotted carrier-sense multiple-access/collision-avoidance (CSMA/CA) protocol for IEEE 802.15.4 under unsaturated traffic conditions. Our proposed Markov chain model reflects the characteristics of the IEEE 802.15.4 medium-access control (MAC) protocol, such as a superframe structure,(More)
In this paper, we consider a time slotted cognitive radio network where multiple secondary users (SUs) contend to access wireless channels. We propose and analyze a channel access policy where each secondary user stochastically determines whether to access a wireless channel (or not) based on a given access probability. In our analysis we consider two(More)
In this paper, we propose a useful framework for the cross-layer design and analysis of wireless networks where ARQ (Automatic Repeat reQuest) and AMC (Adaptive Modulation and Coding) schemes are employed. To capture the joint effect of the packet transmission error rate at the PHY layer and the packet loss probability at the MAC layer, we introduce the(More)
In this paper, we propose an analytic model to analyze a wireless sensor network (WSN) operating the IEEE 802.15.4 slotted CSMA/CA protocol with ACK mode. Based on the renewal approximation, we first develop an analytic model for a homogeneous WSN where all nodes in the network have the same traffic characteristic. Using our analytical model, we obtain(More)
We analyze a multiserver queue with a discrete autoregressive process of order 1 (DAR(1)) as an input. DAR(1) is a good mathematical model for VBR-coded teleconference traffic. Based on matrix analytic methods and the theory of Markov regenerative processes, we obtain the stationary distributions of the system size and the waiting time of an arbitrary(More)
We analyze a multi-server priority queueing system with partial buffer sharing, where the input is a discrete autoregressive process of order 1 (DAR(1)) which is known as a good mathematical model for a VBR-coded teleconference video traffic. We assume that arriving packets are classified into two priority classes, say, high priority class and low priority(More)
In this paper, we focus on a packet scheduling algorithm exploiting multiuser diversity in wireless networks. We compare the delay performance of individual user under the scheduling algorithm exploiting multiuser diversity with that under the round-robin scheduling algorithm in order to reveal the characteristics of the scheduling algorithm exploiting(More)
In this letter, we propose a new downlink fair scheduling scheme exploiting the multiuser diversity to enhance the transmission capacity. In the proposed scheme, only the MSs (mobile stations) whose normalized SNR (signal-to-noise ratio) values are larger than a given threshold feed back one-bit information to the BS (base station). As a result, while(More)