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CDMA truy cập và chuyển mạch P2

Overview In this chapter we study the structures and properties of orthogonal and pseudoorthogonal sequences. Firstly, we examine several types of pseudo-orthogonal (PN) and Quasi-Orthogonal (QO) sequences, and present their cross-correlation properties under synchronous and asynchronous conditions. Secondly, we survey basic methods of constructing orthogonal code sets. Orthogonal binary (Hadamard) codes may exist for lengths 1, 2 and 4k (for k = 1, 2, 3, .). Methods for generating all lengths up to 256 are presented. | CDMA Access and Switching For Terrestrial and Satellite Networks Diakoumis Gerakoulis Evaggelos Geraniotis Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-49184-5 Hardback 0-470-84169-9 Electronic 2 Spreading Sequences 2.1 Overview In this chapter we study the structures and properties of orthogonal and pseudoorthogonal sequences. Firstly we examine several types of pseudo-orthogonal PN and Quasi-Orthogonal QO sequences and present their cross-correlation properties under synchronous and asynchronous conditions. Secondly we survey basic methods of constructing orthogonal code sets. Orthogonal binary Hadamard codes may exist for lengths 1 2 and 4k for k 1 2 3 . . Methods for generating all lengths up to 256 are presented. We also present complex polyphase and other orthogonal code designs. In particular we focus our attention on Kronecker product of orthogonal matrices called extended orthogonal sequences and their applications in the design of CDMA systems. Thirdly we examine the properties of orthogonal and quasi-orthogonal sequences when there is timing jitter or misalignment amongst them. That is we investigate the performance impact on a system when the time-pulses representing binary 1 code entries are not perfectly aligned to a common time reference. Performance results indicate that the inter-user interference power is parabolically proportional to the time jitter as a percentage of the code-symbol or the chip length. Finally we examine the impact of band-limited pulse-phases on interference. That is when the code-symbol or chip waveform is not an ideal square-pulse time-limited but is the result of a band-limit filtering. In this case we evaluate the inter-chip and inter-user interference when there is an equalizing inal.cliod filter. Tlie hit.crif rc rice is evaluated when we have orthogonal or PN-sequences and under synchronous and asynchronous conditions. 2.2 Orthogonal and Pseudo-Orthogonal Sequences 2.2.1 Definitions A binary sequence is defined as a .