Satellite communication providers and space agencies are constantly trying to utilize better the bandwidth in the communication link due to high bit-rate applications and the lack of bandwidth resources. Another point is that satellite communication providers are dealing with cost reductions. One way of increasing bandwidth efficiency is to use modulation forms with a high spectral efficiency (high modulation order), another option is reducing exceed bandwidth (also known as roll-off factor) that required for signal shaping filters. First method is widely used among satellite communication equipment vendors - currently existing technologies allowing increasing modulation order up to 32APSK. However the second option is less known and therefore need to be investigated.
Raised cosine filtering is used to minimize ISI. According to definition of DVB-S2 satellite communication standard pulse shaping based on the raised cosine filtering requires at least 20% of additional bandwidth. Nyquist limit states that the number of symbols we can safely transmit through a channel of bandwidth 1 Hz that has inter-symbol interference is 2 symbols per second. But to achieve this bandwidth efficiency we need a brick wall filter, which is not physically realizable.
There is another technique generally named partial response signaling that allows increasing symbol rate transmission up to Nyquist bandwidth by allowing for a controlled amount of ISI. This concept first time was proposed by Adam Lender in 1964.
Partial response signals of class I also called duo-binary signals and partial response class IV signals sometimes named modified duo-binary signals. This research investigates possibility of using duo-binary and modified duo-binary signaling for transmission over satellite communication channel.
In this work investigated two methods for detecting the information symbols at the receiver when received signal contains controlled ISI. First method uses the symbol-by-symbol detection approach that is relatively easy to implement because it ignoring inherent memory containing in the received signal. However a significant disadvantage of symbol-by-symbol detection method is degradation in bit error rate performance. The second method is based on the maximum-likelihood criterion for detecting a sequence of symbols and named maximum likelihood sequence detection (MLSD). The latter method minimizes error probability but is relatively complex to be implemented. MLSD detector searches through the trellis for the most probable transmitted sequence. Complexity significantly reduced by using Viterbi Algorithm (VA) through a recursive elimination procedure. At each stage of the search process detector compares the metrics of paths that merge at each of the nodes and selects the path that is most probable.
Literature review was done and showed that there was no any research performed and published on this subject, therefore this work is not based on any existing paper.
The simulation uses the MATLAB tool and designed to verify usage of partial response signaling over satellite communication. Non-linear amplifier model of satellite transponder are simulated according to ETSI recommendations and its effect on partial response signals verified. Bit error rate performance, peak to average power ratio and EVM results compared for raised cosine and partial response signals.