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. 2018 Dec 10;18(12):4351.
doi: 10.3390/s18124351.

Clustering Transmission Opportunity Length (CTOL) Model over Cognitive Radio Network

Mas Haslinda Mohamad  1   2 , Aduwati Sali  3 , Fazirulhisyam Hashim  4 , Rosdiadee Nordin  5 , Osamu Takyu  6
Affiliations

Clustering Transmission Opportunity Length (CTOL) Model over Cognitive Radio Network

Mas Haslinda Mohamad et al. Sensors (Basel). .

Abstract

This paper investigated the throughput performance of a secondary user (SU) for a random primary user (PU) activity in a realistic experimental model. This paper proposed a sensing and frame duration of the SU to maximize the SU throughput under the collision probability constraint. The throughput of the SU and the probability of collisions depend on the pattern of PU activities. The pattern of PU activity was obtained and modelled from the experimental data that measure the wireless local area network (WLAN) environment. The WLAN signal has detected the transmission opportunity length (TOL) which was analyzed and clustered into large and small durations in the CTOL model. The performance of the SU is then analyzed and compared with static and dynamic PU models. The results showed that the SU throughput in the CTOL model was higher than the static and dynamic models by almost 45% and 12.2% respectively. Furthermore, the probability of collisions in the network and the SU throughput were influenced by the value of the minimum contention window and the maximum back-off stage. The simulation results revealed that the higher contention window had worsened the SU throughput even though the channel has a higher number of TOLs.

Keywords: WLAN; cognitive radio; opportunistic access; primary user; secondary user; transmission opportunity length.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of the CTOL system.
Figure 2
Figure 2
Secondary user (SU) frame structure.
Figure 3
Figure 3
The experimental setup of the WLAN networks.
Figure 4
Figure 4
The number of idle times detected (tRB) with different threshold values: (a) 10−4, (b) 10−5 and (c) 10−6.
Figure 5
Figure 5
The analysed WLAN signal using the spectrum analyzer.
Figure 6
Figure 6
The PU’s traffic model of the CTOL model.
Figure 7
Figure 7
The effect of sensing the duration of the normalized throughput for the secondary user when increasing the sensing time: (a) τ=0.1 ms; (b) τ=1 ms and (c) τ=10 ms.
Figure 8
Figure 8
The probability of collisions for the CTOL model, dynamic model, and static model.
Figure 9
Figure 9
The normalized throughput for the CTOL model with the different numbers of TOL.
See this image and copyright information in PMC

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