CDSK Transmitter and receiver
Chaos signal has following characteristics:
• broadband signal
• easy implementation
This chaos communication system is based on initial vector generated using chaos signal generator as shown in the figure below.
CDSK stands for correlative differential shift keying. It is a modulation technique employed to modulate and transmit the information bits 'bi' as shown.
In CDSK transmitter, preamble is not being transmitted unlike most of the communication systems and hence the system has less overhead but its BER is poor in noisy channel environment. Preamble is the known pattern transmitted along with the data frame in most of the system. As preamble is known on the other side of the system i.e. at receiver it helps in correlation and identifying the start of the frame as well as in doing front end synchronization.Few examples of the system employing preamble based transmissions are wimax,wlan,lte and so on.
In CDSK same signal is delayed and transmitted and hence correlation is done using the same signal and delayed version of itself. After that threshold is being determined based on sum and average of the signal samples received. This threshould is used to find the start of the frame. Later decoding process is being employed.
In order to improve BER, STBC based MIMO technique is employed in CDSK system. Popular techniques are 2x1,2x2 and 4x4 MIMO based on the requirement is being used.