Throughput Dependence on SNR in IEEE802.11 WLAN Systems

Throughput Dependence on SNR in IEEE802.11 WLAN Systems

Copyright: © 2018 |Pages: 12
DOI: 10.4018/978-1-5225-2255-3.ch574
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This chapter seeks to present the dependence of Throughput on Signal to Noise Ratio (SNR) in IEEE802.11 WLAN Systems. High throughput and low delays are presented as the requirements for indicating good performance of WLAN systems. The multiple communication data rates specified by the physical layer of IEEE802.11 WLANs which vary depending on the SNR observed is shown to appreciably influence the throughput experienced by the users. Cross layer modelling principles which simplifies the process of estimating the dependence of throughput on SNR is presented. Recent research findings which apply cross layer modelling principles to model the dependence of throughput on SNR only is presented along with future research directions.
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Background Of Study

IEEE 802.11 WLANs

The first IEEE802.11 WLAN standard which supported data rates up to 2 Mbps was released in 1997 (Obaidat et al, 2008). The standard defined both the physical layer and the medium access control (MAC) layer. Other IEEE802.11standards such as IEEE802.11a, IEEE802.11b, IEEE802.11g, IEE802.11n, (with higher data rates), IEEE802.11e (for better quality of service support) and IEEE802.11i (for security), IEEE802.11ac, IEEE802.11ax have been developed since then.

At the physical layer IEEE 802.11n can provide data rates up to 54Mbps in a 20MHz band with at least 100Mbps at the MAC data services access point using only mandatory features specified in the standard (Metreaud, 2006). Newer standards such as IEEE802.11ac and IEEE802.11ax offer up to 1,300Mbps and 2Gbps respectively (Jamie, 2015). The popularity of the IEEE802.11 “family of standards” has continued to increase due to their convenience and the reduction in prices of their hardware. The discussion in this chapter is however limited to the base standards because available in literature are throughput models which predict throughput directly from observed SNR only for these base standards.

Radio frequency (RF) based WLANs (which are more common than the IR-based ones) operate in the International Scientific and Medical (ISM) band which does not require any licensing from the US FCC (Obaidat et al., 2008). They use RF signals which can pass through obstacles to transmit and receive data through the air without any connecting cables thus providing freedom and flexibility unmatched by Wired LAN.

Key Terms in this Chapter

Throughput: It is a measurement of the average rate that data (in bits) can be sent between one user and another.

Cross Layer Modelling: It is a type of modelling that involves three basic stages namely: (i) wireless channel modelling, (ii) cross-layer extension of the wireless channel of interest to the layer of interest (iii) performance evaluation at the layer of interest.

Signal to Noise Ratio (SNR): It is a network metric measured in decibel (dB) and is equal to the signal level (in dBm) minus the noise level (in dBm).

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