Performance Evaluation of DSSS and FHSS Using Modulation Technique
The technique which has the bandwidth of the transmitted signal is much greater than the bandwidth of the original message is called Spread Spectrum modulation techniques and the bandwidth of the transmitted signal is determined by the message to be transmitted. In this modulation technique, Linear Feedback Shift Register (LFSR) is the basic unit or element, which produces Maximal length PN sequence. Linear Feedback Shift Register represented by a primitive polynomial. In this system each user has a pseudo noise sequence (PN) which is helpful in spreading as well as de-spreading. Thus PN-sequence generation is the heart of Spread Spectrum system. The maximal length PNsequence (m-sequence) is the best PN-sequence whose length is same as its period. Various PN-codes can be generated using Linear Feedback Shift register (LFSR).The generator polynomial gives the necessary feedback taps for the LFSR circuit. Performance evaluation of DSSS and FHSS using modulation technique is implemented in VHDL and simulated and synthesized on Xilinx 13.1 tool.