Transmitter identification using embedded spread spectrum sequences

A transmitter identification system using embedded spread spectrum sequence is proposed in this paper. Principles of the proposed technique is illustrated through an example of digital TV (DTV) transmitters identification. Code generators in Matlab are developed to study the auto-correlation and cross-correlation properties of the Gold and Kasami sequences. Spread spectrum sequences with different periods are generated and simulated. To speed-up the identification process, the embedded spread spectrum sequence is preferred to be time-synchronized with the DTV signal. By doing so, code length has to be truncated before it is fitted into each field of the ATSC DTV signal. The impact of truncation noise and in-band DTV interference on transmitter identification is also investigated in this paper. It is shown that the auto-correlation and cross-correlation properties are only slightly affected by truncation noise. It is also shown that the dominant interference to the transmitter identification is the in-band DTV signal. The signal to truncation noise ratio and signal to DTV interference ratio in the correlation output are derived and verified form the simulation results. It is further recognized that in-band DTV interference can only be mitigated by increasing the code length or by time-domain averaging technique to smoothen out the in-band interference.