• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.501-515
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• 2006

The IEEE 802.11 protocol is the most mature technology for WLANs(Wireless Local Area Networks). However, as the number of stations increases, the delay and throughput performance of IEEE 802.11 MAC(Medium Access Control) degrades severely. In this paper, we present the comprehensive performance analysis of IEEE 802.11 MAC protocol by investigating the MAC layer packet service time when arrival packet sizes have a general probability distribution. We obtain the discrete probability distribution of the MAC layer service time. By using this, we analyze the system throughput and the MAC layer packet service time of IEEE 802.11 MAC protocol in wireless LAN environment. We take some numerical examples for the system throughput and the mean packet service time for several special distributions of arrival packet sizes.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.2
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• pp.89-95
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• 2011

The distributed coordination function (DCF) and point coordination function (PCF) protocols are the basic MAC protocols for legacy IEEE 802.11, IEEE 802.11a, IEEE 802.11b, IEEE 802.11e, IEEE 802.11g and IEEE 802.11n wireless LANs. When the DCF protocol is used for the various versions of IEEE 802.11 wireless LANs, the MAC performance seriously degrades due to the collisions among the stations (STAs) as more and more STAs attempt to transmit their data frames. On the other hand, the PCF MAC performance becomes poor when many STAs exist in IEEE 802.11 wireless LANs, however, only small number of STAs actually attempt to transmit their data frames. In this paper, we propose the algorithm for improving the MAC performance by selectively using the DCF and PCF protocols according to the state of IEEE 802.11 wireless LANs. Numerical examples are presented to show the MAC performance improvement by the selective use of the DCF and PCF protocols according to the network state.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.640-647
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• 2009

IEEE 802.11i is an amendment to the original IEEE 802.11/b,a,g standard specifying security mechanism by stipulating RSNA for tighter security. The RSNA uses TKIP(Temporal Key Integrity Protocol) and CCMP(Counter with CBC-MAC Protocol) instead of old-fashioned WEP(Wired Equivalent Privacy) for data encryption. This paper describes a design of a communication security engine for IEEE 802.11i MAC layer. The design includes WEP and TKIP modules based on the RC4 encryption algorithm, and CCMP module based on the AES encryption algorism. The WEP module suffices for compatibility with the IEEE 802.11 b,a,g MAC layer. The CCMP module has about 816.7Mbps throughput at 134MHz, hence it satisfies maximum 600Mbps data rate described in the IEEE 802.11n specifications. We propose a pipelined AES-CCMP cipher core architecture, which has lower hardware cost than existing AES cores, because CBC mode and CTR mode operate at the same time.

• Journal of Korean Institute of Industrial Engineers
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• v.40 no.5
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• pp.520-525
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• 2014

When the PCF (Point Coordinated Function) MAC protocol is combined with the frame aggregation method to enhance the MAC performance in IEEE 802.11 wireless LANs, the formulae for the optimal frame aggregation level for best PCF MAC performance were derived in our previous study. We extend the formulae for the PCF protocol to derive the optimal frame aggregation level for the connectivity-based multipolling MAC protocol in IEEE 802.11 wireless LANs. By simulations, we compare the performances of IEEE 802.11 wireless LANs with the optimal and random frame aggregation levels. Compared with the random frame aggregation level, the optimal frame aggregation level significantly improves the performance of IEEE 802.11 wireless LANs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1A
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• pp.62-69
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• 2005

Efforts for standardization of medium access control (MAC) protocol in IEEE802.11e have been made to support quality of service (QoS) in IEEE802.11e MAC protocol. Enhanced disoibuted coordination function (EDCF) of 802.11e MAC protocol is modified to support QoS for packets that have differentiated priority. However, EDCF still has the problem of throughput optimization and priority support. Therefore, we have proposed a scheme called adaptive EDCF for both supporting priority of packets and throughput optimization. We have derived the relation between the number of nodes and contention window size for throughput optimization. Based on the analytic results, we have evaluated the performance of the proposed scheme using OPNET simulations. The simulation results show that using the proposed scheme can improve the overall throughput regardless of the number of nodes and the decrement of the throughput with increasing the number of nodes can be alleviated. Additionally, we have shown that the adaptive EDCF can support priority of packets more effectively than existing EDCF.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12A
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• pp.1367-1374
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• 2004

Efforts for standardization of medium access control (MAC) protocol in IEEE802.11e have been made to support quality of service (QoS) in IEEE802.11 MAC protocol. Enhanced distributed coordination function (EDCF) of 802.11e MAC protocol is modified to support QoS for packets that have differentiated priority. However, EDCF still has e problem of throughput optimization and priority support. Therefore, we have proposed a scheme called adaptive EDCF for both supporting priority of packets and throughput optimization. We have derived the relation between the number of nodes and contention window size for throughput optimization. Based on the analytic results, we have evaluated the performance of the proposed scheme using OPNET simulations. The simulation results show that using the proposed scheme can Improve the overall throughput regardless of the number of nodes and the decrement of the throughput with increasing the number of nodes can be alleviated. Additionally, we have shown that the adaptive EDCF can support priority of packets more effectively than existing EDCF.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.467-469
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• 2006

In wireless network environments, as users' demands on high-speed data communications due to increase of multi-media services, the necessity of new high-speed WLAN technologies has appeared. Nowaday, IEEE is standardizing a new WLAN protocol caned as IEEE 802.11n. To effectively use wireless resources, IEEE 802.11n introduces MAC aggregation function which is similar to that in IEEE 802.11e. In case of transmitting several frames without MAC aggregation, the frames include individual frame header and trailer, and their corresponding acknowledgement frames can appear on wireless link. However, if they are aggregated into single MAC frame, we can reduce the number of used bits due to frame headers/trailers and also remove redundant acknowledgement frames. In this paper, we explain two different MAC frame aggregation methods for IEEE 802.11e and IEEE 802.11n and evaluate their throughput by simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1320-1328
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• 2007

In recent year, the popularity of WLAN has generated much interests on improvement and performance analysis of the IEEE 802.11 protocol. In this paper, we analyze two medium access methods of the IEEE 802.11 MAC protocol by investigating the MAC layer packet service times when arrival packet sizes have a general probability distribution. We use the M/G/1/K queueing model to analyze the throughput and the delay performance of IEEE 802.11 MAC protocol in a wireless LAN. We compare the performances of Basic access method and RTS/CTS access method. We take some numerical examples for the system throughput and the queue dynamics including the mean packet delay and packet blocking probability.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.469-471
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• 2002

This paper presents analysis of the IEEE802.11 MAC protocol and implementation of the asynchronous communication portion of the IEEE802.11 MAC protocol. we have used PRISM2 chipsets from intertsil to build physical layer and PCI controller from PLX to interface LLC layer. This study is shown to be able to apply to MAC implementation in high speed LAN.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.8
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• pp.492-499
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• 2003

This paper presents the analysis and the implementation of the asynchronous communication portion of the IEEE 802.11 MAC protocol. We have used PRISM2 chipsets from INTERSIL to build baseband, IF, and RF parts and PCI controller from PLX to interface LLC Layer. We have implemented DCF(Distributed Coordination Function) service using CSMA/CA(Carrier Sense Multiple Access with Collision Acoidance) with backoff algorithm and RTS/CTS protocol. Also, we have implemented TSF(Timing Synchronization Function) which can be used for power management frequency hop synchronization, and other management function. This study can be used as a reference for the MAC protocol implementation and MAC controller design in very high speed wireless LAN which complies with the IEEE 802.11 standard.