Code Division Multiple Access (CDMA) by Mike Buehrer, William Tranter

By Mike Buehrer, William Tranter

This e-book covers the fundamental facets of Code department a number of entry or CDMA. It starts off with an advent to the fundamental rules at the back of mounted and random entry structures so that it will reveal the adaptation among CDMA and the extra generally understood TDMA, FDMA or CSMA. Secondly, a overview of uncomplicated unfold spectrum innovations are awarded that are utilized in CDMA structures together with direct series, frequency-hopping and time-hopping ways. the fundamental inspiration of CDMA is gifted, by way of the 4 simple rules of CDMA structures that impression their functionality: interference averaging, common frequency reuse, gentle handoff, and statistical multiplexing. the point of interest of the dialogue will then shift to functions. the commonest software of CDMA at the moment is mobile platforms. an in depth dialogue on mobile voice platforms in keeping with CDMA, particularly IS-95, is gifted. The means of such structures should be tested in addition to functionality enhancement thoughts resembling coding and spatial filtering. additionally mentioned are 3rd new release CDMA mobile structures and the way they range from moment iteration platforms. A moment software of CDMA that's coated is unfold spectrum packet radio networks. eventually, there's an exam of multi-user detection and interference cancellation and the way such suggestions effect CDMA networks. This publication can be of curiosity and cost to engineers, complex scholars, and researchers in communications.

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Additional info for Code Division Multiple Access (CDMA)

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1 Slow Versus Fast Hopping As mentioned earlier, the hop period (also called the chip period, Tc ) may be greater or less than the symbol duration. The bandwidth expansion factor is related only to the number of hop frequencies N, not the hop period. Thus, we are free to choose the hop period based on other considerations. Specifically, the hop frequency should be chosen on the basis of implementation and performance considerations. First, let us consider the case where Tc > Ts , or slow hopping.

Data demodulation is then accomplished as in standard digital communications. cls September 28, 2006 15:54 SPREAD SPECTRUM TECHNIQUES FOR CODE DIVISION MULTIPLE ACCESS b(t) Data modulator sd(t) s(t) X 37 Filter η(t) 2P cos(ωct) Frequency generator Code generator pseudo-randomly chooses one of N hop frequencies. k bits are used to choose one of 2k k Code generator frequencies. 8: Typical frequency-hopping transmitter architecture. the number of hop frequencies N. Unlike in DS/SS, the bandwidth expansion is independent of the chip period Tc .

However, it is often advantageous to use long pseudo-random codes that do not repeat each bit. The performance of these codes (often called long codes) depends on the partial correlation properties of the codes, which are more difficult to bound. 3 FREQUENCY HOPPING The goal of spread spectrum systems is to increase the dimensionality of the signal. By increasing the dimensionality, we make eavesdropping and/or jamming more difficult since there are more dimensions of the signal to consider. In commercial applications, this means that the increased dimensionality provides robustness in the presence of other signals and less interference caused to those same signals.

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