Abstract
IEEE 802.11ad specifies a hybrid medium access control (MAC) protocol consisting of contention as well as noncontention-based channel access mechanisms. Further, it also employs directional antennas to compensate for the high freespace path loss observed in 60GHz frequency band. Therefore, it significantly differs from other IEEE 802.11(b/g/n/ac) MAC protocols and thus requires new methods to analyze its performance. In this paper, we propose a new analytical model for performance analysis of IEEE 802.11ad employing a threedimensional Markov chain considering all the features of IEEE 802.11ad medium access mechanisms including the presence of non-contention access and the different number of sectors due to the use of directional antennas. We show that the number of sectors has a high impact on the network throughput. We also show that the MAC packet delay is significantly affected by the duration of the contention period. Our results indicate that a suitable choice of the number of sectors and contention period can illustriously improve the channel utilization and MAC delay performance.
Highlights
Due to the availability of large bandwidth, millimeter wave frequency band (30 GHz to 300 GHz) has become a key enabler for the multi-Gb/s connectivity envisaged under 5G
The high free-space path loss and limited ability to diffract around obstacles require high-gain and steerable directional antennas at mmWave frequencies, which significantly impacts the design of medium access control (MAC) mechanisms [1]
We propose a three-dimensional Markov chain to model the IEEE 802.11ad MAC protocol which allows us to investigate the impact of different factors attributed to the use of directional antennas and the hybrid access mechanism
Summary
Due to the availability of large bandwidth, millimeter wave (mmWave) frequency band (30 GHz to 300 GHz) has become a key enabler for the multi-Gb/s connectivity envisaged under 5G. There are several modified versions of Bianchi’s model considering various factors such as finite retransmission limit [5], busy channel conditions [6] and differentiated quality-ofservice [7], etc These models are not directly applicable in case of the IEEE 802.11ad MAC due to the provision for hybrid medium access and the use of directional antennas. We propose a three-dimensional Markov chain to model the IEEE 802.11ad MAC protocol which allows us to investigate the impact of different factors attributed to the use of directional antennas and the hybrid access mechanism. According to the IEEE 802.11ad MAC protocol, when j ∈ [2, Wi − 1], STAs jump to non-contention state if CBAP time counter reaches zero. Let pb be the state transition probability of channel being busy during the contention period, ,
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