What Is Spread Spectrum?

Spread-spectrum is a technique by which the energy produced at or by one or more discrete frequencies is deliberately spread out or directed towards specific time or frequency spheres. This technique of spread spectrum is adopted for a number of specific reasons. The reasons for adopting the technique include the establishment of secure and user specific communication, increasing the natural resistance to interference and jamming and to prevent detection of source.

The technology of spread spectrum was commercialised in 1976 via a dedicated publication of 'Spread Spectrum Systems' by Robert Dixon. The published work helped to take the concept beyond the confines of transcript and was a notable milestone in the marketing of the technology. Previously, the concept was either classified under 'military reports' or 'academic papers'. However, the concept of spread spectrum, in a way, set the rostrum for increasing research within the sphere of commercial applications. Spread spectrum is a kind of wireless connectivity where the frequency of the transmitted signal is purposely varied. As a result of this deliberation, there is a much greater bandwidth created than the signal would ever have, if its frequency were not varied. The technology is extensively applied today and is part and parcel of the wireless industry.

Spread spectrum is highly efficient technique that is being utilized for the transformation of signal and its sidebands over a very wide band width. Traditionally the efficiency of modulation and multiplexing methods is calculated by how small spectrum they consume. The concept of Spread spectrum is not so new. In fact it was developed primarily by the military after World War II. At that time is was restricted just for military purpose communication application because it offers a secure communication that is prime necessity in case of military communication.

Spread spectrum technique has two types.
1. Frequency Hopping Spread Spectrum (FHSS)
2. Direct Sequence Spread Spectrum (DSSS).

In frequency hopping, the frequency of the carrier the transmitter is changed randomly at a rate bigger than that of the serial binary data modulating the carrier, in direct sequence, the serial binary is mixed with a higher – frequency Pseudorandom binary code at faster rate and the result is used to phase modulate a carrier.

There are several advantages of spread spectrum communication. It is secured; eavesdropping is almost impossible, unless the receiver has very wide span of bandwidth, accurate pseudorandom code and type of modulation technique, the signals will not be received. Spread spectrum is fast growing technique in data and telecommunication transmissions.