in this paper, the performance of IEEE 802.Ilb and 802.1 l g Wireless Local Area Networks (WLANs) performance under barrage jamming is evaluated theoretically and using measurements. Single WLAN ad-hoc link performance is measured when receiver station is jammed. W M link vulnerability assessment is based on throughput and Packet Error Rate (PER), which depends on d$-ferent Physical (PHY) layer characteristic. WLAN system is found to be more tolerant to narrow-band jamming than tu wideband-band jamming. In 802.1 I b WLAN, processing gain increases the tolerance to jamming whereus coding and diferent modulations are used to improve the link performance in 802.1 l g WLAN. Measured link throughputs are far from theuretical values, especially when high datu rate modes are used.
This paper investigates how the performance and capacity of the IEEE 802.11 medium access control (MAC) layer is affected by pulse jamming, using a time-driven simulation program in C language implemented at the Communications Laboratory of the Helsinki University of Technology. The simulations demonstrate the effect of pulse duration and pulse repetition interval on the IEEE 802.11 wireless local area network (WLAN) capacity, defined in terms of simultaneous Voice over IP (VoIP) connections. Under normal conditions (i.e., no jamming), the WLAN can support a certain number of real-time VoIP connections, taking into account the fact that VoIP traffic cannot tolerate excessive delays caused by multiple retransmissions or the build-up of VoIP packets in the transmission buffers of the wireless stations. The simulations show that during severe pulse jamming, the number of supported VoIP connections is substantially decreased.
The effect of terminal movement on the performance of the IEEE 802.11 g wireless LAN (WLAN) system is evaluated using a measurement set-up including a radio channel simulator. The evaluation is based on laboratory measurements of WLAN PC cards in different simulated radio environments. In the measurements, two different radio channel models are used; the exponential channel model and the UMTS vehicular channel model. The measurement results indicate promising operation of IEEE 802.11 g WLAN systems as such. However, the use of different packet sizes has a significant effect on the system behaviour. With large packets the terminal is more likely to experience channel estimation errors than with small packets. This is due to the fact that the IEEE 802.11 g receiver estimates the channel only once per frame, and uses this estimation over the entire frame. Based on the measurement results we suggest a modification to the medium access control (MAC) layer operation that overcomes this problem: the use of optimized fragmentation.
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