• Journal of Korea Multimedia Society
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• v.12 no.11
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• pp.1521-1529
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• 2009

There is a serious unfairness problem between upstream and downstream flows of AP in IEEE 802.11 Wireless LAN. This problem is because Wireless LAN's DCF MAC protocol provides AP with equal channel access priority to mobile noded. Also, it makes this problem worse that the TCP's Data segment loss is more effective on throughput than the TCP's ACK segment. In this paper, we first make several simulations to analysis the unfairness in the various point of view and to find reasons of the unfairness. Also, this paper presents AP's scheduling scheme to alleviate the unfairness problem and evaluate the scheme through ns2 simulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1229-1238
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• 1999

To maximize the statistical multiplexing gain in wireless ATM MAC, a centralized scheduling function must be provided for the dynamic slot assignment in the wireless ATM access point. Exploiting the dynamic parameters received in the wireless ATM access point, the centralized scheduler will execute a dynamic slot assignment to determine bandwidth required for individual wireless terminal. In this paper, we propose a new scheduling algorithm, which can effectively reduce a burden of the explicit signaling requirement of transmitting the dynamic parameters in a timely manner. We have demonstrated that the proposed approach outperforms the existing schemes in terms of the timeliness of transmitting the dynamic parameters, which is a critical factor to the performance of delay-sensitive service classes, and works as an effective means of dynamic slot assignment without heavily relying on the dynamic parameters in the wireless ATM networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1704-1709
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• 2016

In this paper, we propose efficient uplink data transmission method in ultra dense wireless networks as in intra-aircraft, where large-scale APs and wireless sensors are deployed. In the ultra dense wireless networks, a performance degradation is inevitable due to the inter-AP interference. However, the performance degradation can be avoided if a scheduling algorithm can estimate the amount of interference caused by each wireless sensor and reflects it. SGIR (Signal-to-Generating Interference Ratio) based scheduling algorithms is a typical example. Unfortunately, the scheduling algorithms based on the interference caused by wireless sensors necessarily yield large scale exchange of information through backhaul which connects APs. Therefore, we, in this paper, propose a novel scheme which can dramatically reduce the amount of information which are exchanged through backhaul connection. Monte-Carlo simulation results show that the proposed scheme can reduce the amount of backhaul traffic by 27% without loss of data transmission rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.512-519
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• 2016

This paper presents spectrum utilization strategies in cognitive radio (CR) networks powered by multi-antenna based wireless energy transfer. Secondary access point (AP) with multiple antennas should transfer the energy to the secondary sensor nodes with energy beamforming and simultaneously induces no interference to PUs. In addition, sensor nodes can transmit information to the secondary AP using the harvested energy, only when the spectrum is not utilized by PUs. We analyze the achievable rate of the CR sensor networks and propose an interference nulling energy beamforming method to maximize the achievable rate. Finally, we also propose a frame scheduling algorithm in which the durations of wireless energy transfer/information transfer frames (phases) are optimized.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1B
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• pp.11-17
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• 2003

In this paper, we presented the dynamic random access channel allocation method under the priority based scheduling policy in order to improve the system performance of HIPERLAN/2 standardized by ETSI According to the scheduling policy, AP scheduler primarily allocates the resource to the collision MT This scheduling policy bring about decreasing the transmission delay of collision MT Dynamic RCH(random access channel) allocation method decreases the collision probability by increasing the number of RCH slots in case of low traffic. While it increases the maximum throughput by increasing the number of the data transmission slots in case of high traffic Therefore dynamic allocation method of RCH slots decreases the scheduling delay and increases the throughput When we evaluate the performance of presented method based on standards, we saw that the presented method improve the performance of the MAC protocol in terms of throughput and transmission delay.