Real Life Application

The most common application of spread systems is in mobile phones (in general multiple access communication systems). They use a particular type of direct sequence spread spectrum transmission called Code Division Multiple Access or CDMA in short. In this all users are given a unique pseudo noise code. When they transmit signals the signals are multiplied by this code and hence only a receiver having the same code sequence can recover data from the signal. The signals sent by other users will be equivalent to noise. The main advantage of this technique is that the users can use the whole of the bandwidth assigned and there is no frequency or time restriction as observed in FDMA or TDMA techniques.(refer Glossary)

CDMA is not exclusively restricted to DSSS. Frequency Hopping technique can also be incorporated in the signal transmission so as to increase the security and resistance to interference. Spread Spectrum techniques are also used in Wireless Networks and the recently developed Bluetooth technology.

Advantages of CDMA over others:

· Capacity: Because of its unique SS technology, mobile phone service providers can handle more customers on a CDMA network than previous networks.

· Quality: Improved call quality, with better and more consistent sound. Dropped calls are minimized.

· Enhanced Privacy: Data bits used to convey information are mixed with PN code that is known only to the base station and the individual mobile phone.

· Improved Coverage, allowing for the possibility of fewer cell sites.

· Increased talk time for mobile phones.

· Bandwidth on Demand: When one mobile phone is using less bandwidth, more is available for others.

Conclusion: