• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12C
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• pp.1164-1174
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• 2007

Antenna selection based MIMO schedulers are proposed to achieve the optimal performance with low complexity in uplink multiuser MIMO/FDD system. In this paper, three heuristic schedulers are proposed to approach the optimal performance which is achieved by the optimal Brute-Force Scheduler. Two search methods called sub-set and full-set way are also discussed to set up the antenna channels to be the candidates of the scheduler. Simulation results show that the sum rate and BER performance of the proposed CSS and SOAS schemes are about the same to that of the brute-force scheduler with affordable complexity, while RC-SOAS with further reduced complexity achieves almost the optimal performance in the case of small number of antennas. Moreover, the complexity can be additionally reduced by the sub-set search method when the number of transmit and receive antennas are 2 respectively, which is applicable in the realistic systems.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.717-724
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• 2005

In this paper, we Propose an efficient scheduler well suited for the next-generation wireless networks that can support multimedia traffic having various requirements. The scheduler is designed to provide each of multimedia classes with differentiated services. In particular, the scheduler is intended to maximize throughput and minimize packet loss ratio. To apply the scheduler, we suppose that the wireless network is based on TDD/CDMA system The scheduler assigns a packet in a dedicated uplink-slot to the user within a frame to operate scheduling of packets transmitted by the users belonging to the specific class in an efficient manner. Such a manner also enables the scheduler to meet different QoS requirements. The paper also includes performance comparison with other schemes and analysis of the proposed scheduling algorithm by using simulation. We also analyze the proposed scheme by using simulation. The simulation compares the proposed scheduling algerian with previously proposed schemes in terms of the performance.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.57-66
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• 2010

In this paper, we propose the reliability constrained resource allocation scheduling algorithm in cellular network for uplink transmission, where uplink transmission is supported via packet switching schemes without the dedicated uplink circuit links. We evaluate the performance of the proposed algorithm, and compared with the conventional works to identify the pros and cons. The proposed uplink scheduling algorithm is to satisfy the constraints requirements of the MTC services which is considered as the core technology for future mobile wireless networks. It is different to conventional works which target to maximize the link capacity. The proposed algorithm provides reliable uplink transmission independent to the location and the quality of the wireless link of the mobile terminal. Based on the performance evaluation results, we conclude that the proposed method provides enhanced reliability performance than conventional works.

• Journal of Communications and Networks
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• v.10 no.1
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• pp.28-37
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• 2008

In this paper, we investigate the problem of minimizing the average transmission power of users while guaranteeing the average delay constraints in time-varying uplink channels. We design a scheduler that selects a user for transmission and determines the transmission rate of the selected user based on the channel and backlog information of users. Since it requires prohibitively high computation complexity to determine an optimal scheduler for multi-user systems, we propose a low-complexity scheduling scheme that can achieve near-optimal performance. In this scheme, we reduce the complexity by decomposing the multiuser problem into multiple individual user problems. We arrange the probability of selecting each user such that it can be determined only by the information of the corresponding user and then optimize the transmission rate of each user independently. We solve the user problem by using a dynamic programming approach and analyze the upper and lower bounds of average transmission power and average delay, respectively. In addition, we investigate the effects of the user selection algorithm on the performance for different channel models. We show that a channel-adaptive user selection algorithm can improve the energy efficiency under uncorrelated channels but the gain is obtainable only for loose delay requirements in the case of correlated channels. Based on this, we propose a user selection algorithm that adapts itself to both the channel condition and the backlog level, which turns out to be energy-efficient over wide range of delay requirement regardless of the channel model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.145-152
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• 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 IEEK Conference
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• 2002.06a
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• pp.93-96
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• 2002

Fair Queueing has been studied only on wired network. When it is applied to wireless netowork, the collision phenomenon makes a problem.'rho information of queue of MT cannot be transferred to fair queueing algorithm In real time easily. We propose wireless fair queueing scheduler that protects short term farirness and long term fairness. We developed it in TDMA/TDD enviroment. Our scheme also supports uplink and downlink at the same time. And it can make subframe boundary based on fair scheduling algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9B
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• pp.775-785
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• 2008

We identify the problem of the current IEEE 802. lie HCCA (Hybrid Coordination Function Controlled Channel Access) scheduler and its numerous variations, that the queue information cannot be notified to the Hybrid Coordinator (HC) timely, therefore the uplink delay lengthens unnecessarily. We suggests a simple solution and a couple of implementation practices, namely the Adaptive Scheduler with RTS/CTS (ASR) and Adaptive Scheduler with Data/Ack (ASD). They are both further elaborated to emulate the Deficit Round Robin (DRB) scheduler. They are finally compared with existing exemplary schedulers through simulations, and shown to perform well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.786-793
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• 2004

Autonomous data rate control scheme of current IxEV-DO uplink networks can not supper the various QoS requirements of heterogeneous traffics nor hold rise-over-thermal OtoT) constraints. In this paper, an uplink resource management scheme called the modified weighted g-fair (MWGF) scheduler with RoT filling is proposed and evaluated for heterogeneous traffics in cdma2000 type uplink networks. The proposed scheme belongs to a family of centralized resource management schemes and offers QoS guarantee by using priority metrics as well as lower system loading by holding RoT constraints using RoT filling method. With some case-study simulations, the proposed algorithms shows lower average delays of real time users compared to that of autonomous rate control by 29 - 40 ％. It also shows the 1.0 - 1.3 dB lower received RoT level than autonomous rate control schemes, leading to lower network loading.

• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.430-436
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• 2007

In this paper, we assume the uplink multiuser MIMO system based on FDD. Considering the implementation of practical system, Antenna selection and Transmit Beamforming scheme are suggested. System model of both two schemes are introduced and the scheduling algorithm which approaches the optimal performance with affordable computational complexity is proposed for each transmission scheme. Simulation results show that the sum-rate of the proposed low complexity scheduler approaches the performance of brute-force scheduler which is believed to be the optimal scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.899-906
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• 2003

In this paper, a channel access control algorithm and a slot allocation algorithm are proposed as MAC protocol for multimedia services in TDMA/TDD-based wireless ATM networks. In the proposed protocol, VBR terminals that require real-time services transmit a reservation request through a random access minislot. VBR terminals, which are successfully transmitted the reservation request, transmits the dynamic parameters through a dynamic parameter minislot without contention. On the other hand, ABR terminals transmit a reservation request with contention basis whenever a non-real-time traffic burst is generated. Based on the received dynamic parameters and the number of requested slots, the base station scheduler allocates a dynamic parameter minislot as well as uplink data slots into VBR terminals. Also the scheduler allocates uplink data slots into ABR terminals in proportion to the number of requested slots.