Pakistan Research Repository

Multirate Signal Processing For Software And Cognitive Radios

Sheikh, Hafiz Faheem (2010) Multirate Signal Processing For Software And Cognitive Radios. PhD thesis, Lahore University of Management Science, Lahore.



Multirate signal processing has widespread applications in digital communications.It features prominently as an integral part of next generation wireless systems.Two promising technologies for future communication systems are, (i) software radio and (ii) cognitive ra-dio. In both these domains multirate systems perform key signal processing operations.In the area of multi-standard software radios, this thesis explores the role of multirate signal processing in sample rate conversion lter design as well as programmable digital IF imple-mentation. While for cognitive radios, multirate solutions for wideband spectrum sensing and performance-enhancing detection techniques are investigated. In the context of sample rate conversion (SRC) lters for software radios; this thesis makes two key contributions. Firstly, a practical, iterative factorization algorithm has been formulated that assigns rate change factors to ltering stages of a proposed multi-standard SRC architecture. This multistage architecture is composed of multiplexed cascaded in- tegrator comb (CIC) lters, Farrow interpolators and half-band lters.Secondly, a novel frequency domain technique for joint CIC compensation lter and Farrow interpolator de- sign has been proposed. This scheme saves the cost of an FIR lter normally required for compensation in high decimation devices. Based on these developments, a programmable and computationally e cient SRC lter design scheme for utilization in the digital IF stage of a software radio, has been derived.The results of this chapter are corroborated through simulations using parameters corresponding to various commercial wireless communications standards including GSM, IS-95, UMTS and the emerging WiMax IEEE 802.16 standard. On the cognitive radio front, this thesis makes advances in wideband spectrum sensing from a signal processing perspective. Initially, the drawback of using simple harmonic power detection in wideband cognitive radios has been demonstrated.This is followed by a dis-cussion of preprocessing the received signal to improve detection performance.The impact of preprocessing and its trade-o with complexity and consequent delays in cognitive radio networks is investigated.This thesis includes the derivation of detection probability for si-multaneous sensing of multiple primary user channels.It has been shown that a polyphase DFT lter bank with an optimal window as a prototype lter results in a reliable and e - cient sensing architecture, with minimal overhead in cognitive radios.A detailed account of performance limits and computational complexity comparisons for various spectrum sensing solutions is also provided.In addition to addressing wideband sensing in dynamic spectrum access radios, three techniques to improve detection performance for corresponding sensing methods, are also presented. These include proposed schemes to utilize channel history for minimizing the detection error, subband detection of unknown bandwidth signals and detection performance improvement in multi-antenna con gurations. In summary this thesis establishes multirate signal processing as a mathematical foundation for software and cognitive radios.The study is supported through simulations with parameters corresponding to the wireless regional area network (IEEE 802.22 ) standard.

Item Type:Thesis (PhD)
Uncontrolled Keywords:Conversion, Delay, Processing, Software, Digital, Technique, Frequency, Wideband, Cognitive, Comparisons, Parameters, Multirate, Sample, Radios, Signal, Software, Prototype, Performance, Limits
Subjects:Engineering & Technology (e) > Engineering(e1) > Computer Engineering(e1.10)
ID Code:6971
Deposited By:Mr. Javed Memon
Deposited On:18 Aug 2011 09:55
Last Modified:18 Aug 2011 09:55

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