hyongwoo lee - Academia.edu (original) (raw)

Papers by hyongwoo lee

2007 IEEE International Conference on Communications, 2007

... Hyong-Woo Lee and Jun-Bae Seo Department of Electronics and Information Engineering ... B. ... more ... Hyong-Woo Lee and Jun-Bae Seo Department of Electronics and Information Engineering ... B. Queueing Analysis In this subsection, we assume the transmission success probability of a PN-code for an SS, ps, and the retransmission probability that an SS transmits its PN-code ...

IEEE Globecom 2006, 2006

In this paper, we consider the queueing performance of periodic polling services for VoIP in an I... more In this paper, we consider the queueing performance of periodic polling services for VoIP in an IEEE802.16 system, which is modeled by an MIGIC type queue with periodic batch service. We carry out an analysis for this system, using a generating function approach with supplementary variable technique. As a service discipline, the size of batch, the transmission duration in units of frames, i.e., contiguous frames, and the vacation period correspond to the bandwidth assigned to a subscriber station and the period to poll other subscriber stations, respectively. In numerical examples, the mean queue lengths are given, according to various system parameters.

IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004

ABSTRACT In this work, the performance of queues for handover calls in both a micro- and a macroc... more ABSTRACT In this work, the performance of queues for handover calls in both a micro- and a macrocell is analysed by varying the number of microcells under a macrocell, arrival rates of new calls in micro- and macrocells, cell dwell times, signal degradation interval, and queue size of both micro- and macrocells. In the model, the role of a macrocell is as a secondary server for handover calls overflowed from microcells and the overflow process of handover calls from microcells is modelled by Poisson and Markov modulated Poisson process (MMPP) approximations. In the numerical examples, it is found that Poisson approximation optimistically estimates call performance compared to MMPP, and that queues in a macrocell are more effective than those in microcells.

Advances in Multimedia Information Processing - PCM 2004, 2004

HIPERLAN/2 is one of the standards for high-speed wireless LANs developed by ETSI BRAN. A mobile ... more HIPERLAN/2 is one of the standards for high-speed wireless LANs developed by ETSI BRAN. A mobile terminal(MT), when it has messages to send in the uplink channel, may use contention slots, called random access channels (RCHs), to send the resource request messages. Based on successful resource request messages from the MTs, the access point(AP) allocates uplink channel resources dynamically. The number of RCHs in one MAC frame should be adjusted in such way that the access delay for request messages is kept small without underutilizing the RCHs. In this paper, we propose a new RCH allocation scheme using the splitting algorithm, which dynamically adjusts the number of RCHs according to the current traffic situation. The simulation results show that our scheme performs well in terms of channel throughput, access delay and delay jitter compared with previously proposed RCH allocation schemes.

Canadian Conference on Electrical and Computer Engineering, 2005.

ABSTRACT In this paper, the queueing performance of an adaptive type-I hybrid automatic repeat re... more ABSTRACT In this paper, the queueing performance of an adaptive type-I hybrid automatic repeat request (ARQ) with a generalized Markovian source is studied for a TDMA/TDD system over a Markovian channel. In the adaptive type-I hybrid ARQ of our interest, the pay load size for information in a packet (or ARQ block) and the coding rate of ARQ block vary, according to the channel state, e.g., high coding rate and small payload size for information in a bad state of channel. We assume that an arriving message over a medium access control (MAC) layer consists of a number of information units of fixed size. We analyze the delay of a message, which is composed of its queueing delay and its transmission time, and the message dropping probability. In the numerical examples, we have shown that the correlation of either traffic source or radio channel affects the queueing performance in a similar way, due to its Markovian structure. The analytical work presented here can be used to control physical parameters, such as coding rate, in order to meet QoS requirements in a higher layer which is over the MAC layer

The Journal of Korea Information and Communications Society, 2012

In the presence of a high power cellular network, picocells are added to a Macro-cell layout aimi... more In the presence of a high power cellular network, picocells are added to a Macro-cell layout aiming to enhance total system throughput from cell-splitting. While because of the different transmission power between macrocell and picocell, and co-channel interference challenges between the existing macrocell and the new low power node-picocell, these problems result in no substantive improvement to total system effective throughput. Some works have investigated on these problems. Pico Cell Range Expansion (CRE) technique tries to employ some methods (such as adding a bias for Pico cell RSRP) to drive to offload some UEs to camp on picocells. In this work, we propose two solution schemes (including cell selection method, channel allocation and serving process) and combine new adaptive frequency partitioning reuse scheme to improve the total system throughput. In the simulation, we evaluate the performances of heterogeneous networks for downlink transmission in terms of channel utilization per cell (pico and macro), call blocking probability, outage probability and effective throughput. The simulation results show that the call blocking probability and outage probability are reduced remarkably and the throughput is increased effectively.

The Journal of Korea Information and Communications Society, 2013

IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008

ABSTRACT In this paper we consider a playout buffer with two thresholds based on its occupancy. P... more ABSTRACT In this paper we consider a playout buffer with two thresholds based on its occupancy. Playout begins when the occupancy exceeds one threshold, say L o, while it slows down the playout rate in order to prevent buffer starvation whenever the occupancy drops below the other threshold, say L u(les L o). The design parameters here are two thresholds and the reduction factor of the playout rate whose optimal values are sought by minimizing a cost function with constraints. The cost function consists of queueing performance metrics, such as starvation probability, frame loss probability and the quality degradation probability by slowing down playout rate, while the constraints are given as excess preroll delay distribution, excess slow-down playout time distribution and the coefficient of variation of the departure process from the playout buffer. In numerical studies, we present optimal values of those parameters.

In this paper, we propose new cell structures using multi-hop Relay Station(RS) based on IEEE802.... more In this paper, we propose new cell structures using multi-hop Relay Station(RS) based on IEEE802.16j in Narrow-Beam Trisector Cell (NBTC) and Wide-Beam Trisector Cell (WBTC), which are two methods for cell sectorization using 3-sector directional antennas. Then, we analyze our proposed structures compared with the existing system which does not use any RS about the numbers of optimized Base Station (BS) and multi-hop relay, the extended BS coverage, and the deployment cost according to the traffic density using optimization model. According to the results, we know the reduction of total deployment cost of the proposed systems and that WBTC is suitable when the traffic density is high and NBTC is suitable when the traffic density is low in our proposed multi-hop based NBTC and WBTC structures.

Mobile multi-hop relaying (MMR) technology is being considered as a promising solution capable to... more Mobile multi-hop relaying (MMR) technology is being considered as a promising solution capable to enhance coverage, user throughput, and system capacity of the current wired backbone dependent wireless access networks. Since the relaying nodes do not need a wired backbone access, MMR technology offers easy and low-cost deployment, flexible cell planning, and adaptive traffic handling performance. In this paper, we investigate performance and cost effectiveness of the MMR technology deployment in the IEEE802.16j based WiBro/WiMAX systems. We first introduce standardization activities and research issues of MMR WiBro/ WiMAX systems. Since the coverage extension problem may occur in metropolitan areas as well as suburban or rural areas where user density is relatively low or moderate, we introduce several MMR topologies and analyze cost-effectiveness of MMR based coverage extension with respect to the user traffic density. Then, we argue cost effect on MMR technology deployment and throughput performance, Finally, we introduce further study issues including sectorized base station based MMR deployment approaches and the single and multi-frame structure MMR approaches.

In this paper, we propose the structures of the NBTC (Narrow-Beam Trisector Cell) and the WBTC(Wi... more In this paper, we propose the structures of the NBTC (Narrow-Beam Trisector Cell) and the WBTC(Wide-Beam Trisector Cell) in which directional antennas both at the base station and at the relay station are used. We analyze and compare total capacity of the both systems taking the co-channel interference into consideration for two channel models. Through analysis, we find the effect of LOS (Lind of Sight) path to the total capacity of NBTC structure and that of WBTC structure. Our work may be useful as a guideline to control the interference for the next generation mobile communication and WiBro systems using multi-hop relays.

Proceedings of 15th International Conference on Computer Communications and Networks, 2006

In this paper, we consider the queueing performance of IEEE802.16 random access protocol for spor... more In this paper, we consider the queueing performance of IEEE802.16 random access protocol for sporadic data transmission with a binary exponential backoff algorithm. The random access protocol of IEEE 802.16 is physically based on orthogonal frequency-division-multiple-access and code- division-multiple-access with time division duplexing mode, i.e., multichannel- and multicode- slotted Aloha. In a medium access control layer, the protocol is a

2008 International Conference on Information Networking, 2008

2010 IEEE 72nd Vehicular Technology Conference - Fall, 2010

2006 IEEE 63rd Vehicular Technology Conference

A Fast handover protocols for Mobile IPv6 networks can support seamless service by reducing hando... more A Fast handover protocols for Mobile IPv6 networks can support seamless service by reducing handover latency to mobile nodes. To gain advantage derived from the fast handover in IEEE 802.16e networks, we propose a new fast handover protocol using a multiple simultaneous binding mechanism and a handover protocol based on trigger event for IEEE 802.21 in order to integrate IEEE 802.16e handover protocol and FMIPv6 handover protocol using link layer trigger. Through the numerical analysis, we compare performance of the proposed protocol and FMIPv6 protocol.

In this paper, we propose a scheduling algorithm to improve the performance of IEEE 802.16 based ... more In this paper, we propose a scheduling algorithm to improve the performance of IEEE 802.16 based wireless mesh networks using directional antenna. The performance is presented in terms of throughput of system and delay between each node by varying number of users. The result show that proposed scheduling algorithm improving the performance by reducing the delay of mesh network system. Our work may be useful as a guideline to control the fairness between SSs for multi-hop systems such as multi-hop relay and mesh networks.

2005 International Conference on Wireless Networks, Communications and Mobile Computing