• Scientech Technologies Private Limited

CDMA-DSSS Communication System with BER Measurement

The Wireless mobile communication systems provide access to the capabilities of the global network at any time, irrespective of the location or mobility of the user. The Direct Sequence Spread Spectrum (DS-SS) technique, incorporated into CDMA can accommodate large number of users in one radio channel depending on the voice activity level. This feature also provides immunity to jamming signals and enables resolution of multi-path components in a time dispersive radio propagation channel. Spread Spectrum is a type of modulation that spreads data transmission across available frequency band, in excess of minimum bandwidth required to send the information. Spreading makes Signal resistive to noise and other interference. Spread Spectrum is commonly used with personal communication devices such as cell phones and LAN`s. Spread Spectrum has many unique properties that cannot be found in other techniques like the ability to eliminate or alleviate multi-path interference, communication privacy due to unknown random codes, multi user handling capacity over a single frequency, and low power Spectral density since Signal is spread over a large frequency band. Scientech 2131B TechBooks provide a detailed understanding of the concepts behind CDMA-DSSS, and various points that need to be considered in the design of a Direct Sequence Spread Spectrum System. They include generation of various pseudorandom (PN) codes like Gold, MLS & Barker with user selectable tappings, variable Chip rate, and baseband modulations BPSK, QPSK, OQPSK & Digital AWGN noise with Root Raised Cosine filter (RRC) FIR low pass filter. Bit Error Rate (BER) measurement with known data sequence, overall data rate dependency parameters, spreading & despreading with DSSS, SNR control, offset control & so on can be performed on Scientech 2131B.