Baseband processor prototype for low bit rate communication in tactical radio

Digital communication system is an important part in the development of communications. A notable form of communication systems is voice communication, which is needed in various areas including the military. A widely used type of military communication systems is the tactical communication. Indonesia is currently developing digital communication systems to meet national military demand, to communicate using multichannel high frequency (HF) band. Each channel has a limited bandwidth of 40 kHz. This bandwidth limit inquires a compression/decompression routine from the digital voice acquisition coder to lower the digital voice bit rate. Low bit rate speech coding and modulation with a narrow bandwidth is the goal of this project. The algorithms for compression and modulation are implemented in C with PC to model the processor. Reconstructed voice from the baseband processor prototype is tested subjectively by taking sample respondents to conduct mean opinion scoring (MOS) method. The MOS perception testing score gives an average score ranging from 3 (sufficiently decent with tolerable minor disturbances) to 4 (good).