• Proceedings of the IEEK Conference
• /
• 2007.07a
• /
• pp.111-112
• /
• 2007

IEEE 802.16j의 목적은 기존의 IEEE 802.16e에 중계기를 도입하여 커버리지 확장과 데이터 처리율 향상에 있다. IEEE 802.16j시스템에서 두 개 이상의 중계기를 상호 협조적으로 사용함으로써 공간 다이버시티 이득을 얻을 수 있다. 이 논문에서는 상호 협조 중계 방식을 사용하는 IEEE 802.16j의 성능을 링크 레벨 모의 실험을 통해 구하고, 그 방식이 기존의 단일 중계 방식보다 우수한 성능을 가짐을 보인다.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.11 s.353
• /
• pp.95-117
• /
• 2006

In this paper, we describe the optimization of the link-level performance and the complexity of floating-point and fixed-point methods in IEEE 802.16e OFDMA/TDD mobile modem. In floating-point design, we propose the channel estimation methods for downlink traffic channel and select the optimized method using computer simulation. So we also propose efficent algorithms for time and frequency synchronization, Digital Front End and CINR estimation scheme to optimize the system performance. Furthermore, we describe fixed-point method of uplink traffic and control channels. The superiority of the proposed algorithm is validated using the performances of Detection, False Alarm, Missing Probability and Mean Acquisition Time, PER Curve, etc. For fixed-point design, we propose an efficient methodology for optimized fixed-point design from floating-point At last, we design fixed-point of traffic channel, time and frequency synchronization, DFE block in uplink and downlink. The tradeoff between performance and complexity are optimized through computer simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.10a
• /
• pp.722-725
• /
• 2010

In this paper, BER performance and error convergence speed of layered LDPC(Low Density Parity Check) decoder which supports IEEE 802.16e WiMAX standard is analyzed, and optimal design conditions for hardware implementation are derived. A LDPC decoder is modeled and simulated at AWGN channel with QPSK modulation by Matlab. The parity check matrix(PCM) for IEEE 802.16e standard which has block lengths of 576, 1440, 2304 and code rates of 1/2, 2/3A, 2/3B, 3/4A, 3/4B, 5/6 are used. Fixed-point simulation results show that fixed-point bit-width should be more than 8 bits for acceptable decoding performance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.6A
• /
• pp.445-457
• /
• 2009

Recently, there are growing interests in femto-cell for providing indoor users with various broadband multimedia services more efficiently. The technical issues regarding femto-cell such as interference management, self-organization, and resource allocation are now being intensively studied and investigated by researchers worldwide. In this paper, two novel schemes of neighboring cell list(NCL) management are proposed for the IEEE 802.16e system where a macro-cell and huge number of femto-cells coexist. The proposed schemes, named MS location-based neighboring cell list management and BS type-based neighboring cell list management, enable a mobile station(MS) to perform fast scanning and efficient handover by means of preselecting the candidate target femto-cells with high possibility for handover. The simulation result shows that the proposed schemes improve the MS's handover-related performance in terms of scanning power and scanning time compared with the conventional managements scheme of IEEE 802.16e system.

• Proceedings of the KIEE Conference
• /
• 2007.04a
• /
• pp.270-272
• /
• 2007

인터넷의 급속한 성장에 따라 사용자들은 이동중에도 인터넷을 이용하고자 하는 수요가 증하고 있다. IEEE 802.16 시스템은 이러한 사용자들의 요구를 충족할 수 있는 시스템으로 이동중에도 인터넷을 사용할 수 있도록 하는 기술이다. 하지만 이동 중에 발생하는 핸드오프에 대한 QoS는 보장되고 있지 못하다. 본 논문에서는 핸프오프시에 등록걸차를 간소화 시켜줌으로써 지연시간을 줄여주고, 데이터 손실과 약간의 끊김현상을 줄여주고자 한다. 이 메커니즘으로 핸프오프가 발생할 때 BS간 전환을 보다 빨라게 해주어 사용자들은 이동중에도 다양한 서비스를 끊김없이 받을 수 있으며. 핸프오프 전에 받고 있던 QoS도 그대로 유지할 수 있어 보다 나은 무선 인터넷 사용을 할 수 있을 것이라 사료된다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.10
• /
• pp.1875-1882
• /
• 2008

Nowadays, usage of mobile unit which has a characteristic of low cost and high efficiency is being generalized because of frequent use of internet-based variable service and application in IEEE 802.16 WiMAX. A study for handling a security problem of high speed internet service is rising while the use of a mobile is being generalized. This paper suggests a security mechanism which provides safety from certification load of SS and a security attack as well as a basic function which is provided from IEEE 802.16e standard to satisfy security demand of IEEE802.16 WiMAX. The proposed mechanism exchangeskey material information for TEK and data code by using 난수(?) and secret value created by SS and BS, also reduces capacity load of BS not to perform an additional certificate procedure of BS by using the early certification information and certificate of SS.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.2
• /
• pp.1-8
• /
• 2010

Multi antenna techniques using space-time codes can achieve diversity gains in a multi-path environment without additional bandwidth requirement. Most of the 4G candidate standards including the IEEE 802.16e adopt multi-input multi-output (MIMO) schemes to achieve either high throughput performance or diversity gains. In these 4G candidate standards, turbo codes using an iterative decoder with soft input soft output are used to overcome serious channel fading. For this reason, the estimated signal values from MIMO detectors should be soft decision detection values. In this paper, we propose efficient methods to estimate soft decision detection values for various space time coding schemes, and provide the simulation results of turbo coded space time coding scheme over an IEEE 802.16e link.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.1
• /
• pp.145-152
• /
• 2009

IEEE 802.16e standard, a kind of WMAN standard, was established to support data services with cheaper cost to mobile users than traditional mobile communications system and wireless LAN system can do. In this paper, we propose an uplink QoS packet-scheduler for VoIP service which can be installed in IEEE 802.16 system and evaluate its performance with NS-2 network simulator. The proposed QoS packet-scheduler consists of three procedures: determining scheduler interval, determining the amount of resource assignment, and deciding which mobile station the base station should serve first among multiple mobile stations. According to numerical results, the proposed QoS packet-scheduler can provide more increased system capacity by 220% than UGS service scheme does and by 25 % than ertPS service scheme does.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2007.10a
• /
• pp.355-358
• /
• 2007

In wireless mobile communication systems, priority of voice service through high speed data and multimedia transmission requires increased service diversification. Research is being carried out in this environment, on the call admission control techniques to guarantee the diversified service's QoS. SRN (Stochastic Reward Net) is an extended version of Petri nets, well know modeling and analysis tool. In this paper, we develop SRN call admission control model considering the 4 classes of services in the 4th generation IEE 802.16e mobile communication Technology.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.3A
• /
• pp.221-229
• /
• 2007

In this paper, we propose and analyze the optimized sleep mode for a mobile node (MN) in IEEE 802.16e wireless metropolitan area networks. Because a MN in a sleep mode specified in 802.16e specification should maintain state information with the base station currently attached, it must renew sleep state with a new base station after handover which leads to unnecessary waste of battery power. Noting that the mobility pattern of a MN is independent of call arrival patterns, we propose an optimized sleep mode to eliminate unnecessary standby period of a MN in sleep state after handover. We also propose an analytical model for the proposed scheme in terms of power consumption and the initial call response time. Simulation studies that compare the performance between the sleep mode and the optimized sleep mode show that our scheme marginally increases initial call response delay with the huge reduction in power consumption.