Development of multi user TDMA based DSSS systems

Direct sequence spread spectrum (DSSS) is a state-of-the-art technology evolved over the last 3-4 decades. The inherent features of DSSS such as anti-jamming, multiple access, low probability of intercept (LPI) and above all ease of deployment makes it an ideal transmission scheme for defense as well as commercial applications. Most of the modern remote control units (RCUs) control small UAVs or helicopter, send command and control data using DSSS as a standard technique. As the number of users or aircraft to control increase, the DSSS alone may not be sufficient enough to provide multiple accesses. Therefore, a hybrid approach should be opted by using another multiple access scheme such as time division multiple accesses (TDMA) in conjunction with DSSS to obtain an efficient multiple accesses. Other multiple access schemes such as Frequency Division Multiple Access (FDMA) can also be used. However, they require more resources such as frequency and require broadband RF front ends. Hence, TDMA with DSSS is a viable solution. The hybrid form allows to transmit data in a collision-free manner and takes advantage of the broadband property of DSSS. This paper implements the IEEE 802.11b standard DSSS and makes it hybrid with TDMA by designing a complete frame structure and finds the BER performance results of the final design. The results of BER are simulated at different spreading factors of codes by using MATLAB.