Frequency Hopping Spread Spectrum: An Effective Way to Improve Wireless Communication Performance
Naser Hossein · InTech eBooks · 2011
IntroductionTo improve the performance of short-range wireless communications, channel quality must be improved by avoiding interference and multi-path fading.Frequency hopping spread spectrum (FHSS) is a transmission technique where the carrier hops from frequency to frequency.For frequency hopping a mechanism must be designed so that the data can be transmitted in a clear channel and avoid congested channels.Adaptive frequency hopping is a system which is used to improve immunity toward frequency interference by avoiding using congested frequency channels in hopping sequence.Mathematical modelling is used to simulate and analyze the performance improvement by using frequency hopping spread spectrum with popular modulation schemes, and also the hopping channel situations are investigated.In this chapter the focus is to improve wireless communication performance by adaptive frequency hopping which is implemented by selecting sets of communication channels and adaptively hopping sender's and receiver's frequency channels and determining the channel numbers with less interference.Also the work investigates whether the selected channels are congested or clear then a list of good channels can be generated and in practice to use detected frequency channels as hopping sequence to improve the performance of communication and finally the quality of service.The Fourier transform mathematical modules are used to convert signals from time domain to frequency domain and vice versa.The mathematical modules are applied to represent the frequency and simulate them in MATLAB and as result the simulated spectrums are analysed.Then a simple two-state Gilbert-Elliot Channel Model (Gilbert, 1960;Elliott, 1963) in which a two-state Markov chain with states named "Good" and "Bad" is used to check if the channels are congested or clear in case of interference.Finally, a solution to improve the performance of wireless communications by choosing and using "Good" channels as the next frequency hopping sequence channel is proposed. Review of related theories Spread spectrumSpread spectrum is a digital modulation technology and a technique based on principals of spreading a signal among many frequencies to prevent interference and signal detection.As www.intechopen.comHow to reference In order to correctly reference this scholarly work, feel free to copy and paste the following: Naser Hossein Motlagh (2011).Frequency Hopping Spread Spectrum: An Effective Way to Improve Wireless Communication Performance, Advanced Trends in Wireless Communications, Dr