• 한국통신학회논문지
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• 제37권1B호
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• pp.15-20
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• 2012

본 논문에서는 밀리미터파 대역을 사용하는 개인영역 무선통신 네트워크 표준의 하나인 IEEE 802.15.3c에서 지향성 CSMA/CA의 성능을 향상시킬 수 있는 알고리즘을 제안한다. 제안한 알고리즘은 saturation 환경에서 No-ACK 모드를 고려하여 마코프 체인으로 모델링하여 분석하였다. 마코프 체인 모델에서는 공간을 재활용하는 지향성 안테나의 특성과 IEEE 802.15.3c의 특성이 고려되었다. 분석실험을 통하여 경쟁윈도우 크기의 최적값을 얻었다. 제안한 성능향상 지향성 CSMA/CA 알고리즘이 기존의 지향성 CSMA/CA에 비해 훨씬 좋은 성능을 보여주는 결과를 얻었으며 이는 시뮬레이션으로 검증되었다. 얻은 결과는 밀리미터파 대역 개인영역 무선통신 네트워크의 성능을 향상시키는 모수의 선택과 MAC 프로토콜의 개발에 지침을 제공할 것으로 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권4호
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• pp.1293-1316
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• 2021

Using directional antennas in wireless Ad hoc networks has many superiorities, including reducing interference, extending transmission range, and increasing space division multiplexing. However, directional transmission introduces two problems: deafness and directional hidden terminals problems. We observe that these problems result in saturation throughput disparity among the competing flows in directional CSMA/CA based Ad hoc networks and bring challenges for modeling the saturation throughput of the flows. In this article, we concentrate on how to model and analyze the saturation throughput disparity of different flows in directional CSMA/CA based Ad hoc networks. We first divide the collisions occurring in the transmission process into directional instantaneous collisions and directional persistent collisions. Then we propose a four-dimensional Markov chain to analyze the transmission state for a specific node. Our model has three different kinds of processes, namely back-off process, transmission process and freezing process. Each process contains a certain amount of continuous time slots which is defined as the basic time unit of the directional CSMA/CA protocols and the time length of each slot is fixed. We characterize the collision probabilities of the node by the one-step transition probability matrix in our Markov chain model. Accordingly, we can finally deduce the saturation throughput for each directional data stream and evaluate saturation throughput disparity for a given network topology. Finally, we verify the accuracy of our model by comparing the deviation of analytical results and simulation results.

• ETRI Journal
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• 제34권1호
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• pp.24-34
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• 2012

In this paper, the directional carrier sense multiple access/collision avoidance (CSMA/CA) protocol in the immediate acknowledgement mode for IEEE 802.15.3c is analyzed under saturation environments. For the analysis, a sensing region and an exclusive region with a directional antenna are computed probabilistically and a Markov chain model in which the features of IEEE 802.15.3c and the effects of using directional antennas are incorporated is analyzed. An algorithm to find the maximal number of concurrently transmittable frames is proposed. The system throughput and the average transmission delay are obtained in closed forms. The numerical results show the impact of directional antennas on the CSMA/CA media access control (MAC) protocol. For instance, the throughput with a small beamwidth of antenna is more than ten times larger than that for an omnidirectional antenna. The overall analysis is verified by a simulation. The obtained results will be helpful in developing an MAC protocol for enhancing the performance of mmWave wireless personal area networks.