Abstract
Wireless communication technologies divide their available spectrum into pre-defined channels. Some wireless technologies, such as the IEEE 802.11b/g, define their channels in such a way that adjacent channels share the spectrum. When two distinct channels share some part of their spectrum, simultaneous transmissions on these channels cause what is known as the adjacent channel interference. For problems that consider adjacent channel interference, such as the channel assignment problem for multi-channel wireless mesh networks, we need a model that quantitatively describes adjacent channel interference. The interference factor is a concept defined to quantify the amount of the overlap, hence the interference, between two wireless channels. Analytical and experimental methods have been proposed in the literature to define the interference factors among channels of a wireless technology. In this article, we propose a physical-layer-measurement-based, technology-independent and generic approach that is capable of determining interference factors between the channels of a wireless technology and also between the channels of two different wireless technologies, such as IEEE 802.11 and IEEE 802.15.4. We also report our measurement results for interference factors among 802.11b DSSS channels and between 802.15.4 and 802.11b channels. Our results show that our approach is practical, accurate and generic enough to compute the interference factors of radio channels belonging to various wireless communication technologies.
Highlights
Interference factor (I-factor) [1] is used to model the amount of interference between two channels of a wireless communication standard, such as the IEEE 802.11 family of standards or the IEEE 802.15.4 standard
Spectral bands are allocated to wireless communication standards by regulation and standardization bodies such as the US Federal Communications Commission (FCC) or the European Telecommunications Standards Institute (ETSI)
The method we propose above defines I-factor as the ratio of the area below the intersection of two frequency domain signal traces to the total area below the trace that belongs to the interferer signal
Summary
Interference factor (I-factor) [1] is used to model the amount of interference between two channels of a wireless communication standard, such as the IEEE 802.11 family of standards or the IEEE 802.15.4 standard. One such approach for the interference factor of 802.11 DSSS channels appears in [1] According to this model, the I-factor for two (overlapping) 802.11 channels is calculated as a function of the power spectral distribution of the DSSS signal and the receiver filter’s frequency response, as follows: Itheory(i, j) = IF(T,R)(5 i − j ). The authors define the carrier sensing range as “the maximum distance that these two can affect each other’s communications” [7] They give statistical and numerical models of capacity improvements when overlapping channels are used compared to using only orthogonal channels in one-hop and multi-hop wireless networks. The authors measure the packet delivery ratios of the 802.15.4 network They use the spectrum analyzer to report the average power spectral densities of the 802.11n signals for different alignments of the 802.11n nodes.
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