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and helped set the platform for the major 3G mobile radio specifications UMTS and

CDMA2000, whose variations are still used in modern cell phone networks [7]. The

development of CDMA was pioneered at about the same time as other spread spectrum

technologies like Time Division Multiple Access (TDMA) and Frequency Division Multiple

Access (FDMA). The main drawback in developing spread spectrum technologies for non-

military use before the 1990‟s was the lack of enabling technologies. When high speed Digital

Signal Processing (DSP) chips became readily available, there was a rapid acceleration in the

development of spread spectrum based systems [8]. These rapid developments have led to the

adoption of spread spectrum technologies into everyday life. Hybrid systems (systems that

combine a few different spreading techniques) can be found in the ubiquitous IEEE 802.11

standard, hand held and car GPS navigation system, and virtually any other modern wireless

communication device.

Spread spectrum refers to a telecommunications technique in which a signal is

transmitted in a bandwidth considerably greater than the frequency content of the original

information. The main signal structuring techniques are frequency hopping and direct sequence,

but there are also many different forms of each as well as hybrids that combine multiple

techniques. These techniques can be used for multiple access and offer multiple functions. First,

they decrease the potential interference to other receivers while achieving privacy. Second, they

increase the immunity of spread spectrum receivers to noise and interference. Lastly, spread

spectrum makes use of a sequential noise-like signal structure to spread the normally narrowband

information signal over a relatively wide band of frequencies. The receiver correlates the signals

to retrieve the original information signal. In frequency hopping the signal power is spread over

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