A new diversity code for high spectrum occupancy applications

The resurgent use of HF, the increase in VHF/UHF usage and in particular the employment of data transmission has meant that the newer enabling technologies such as digital signal processing (DSP) have found a fertile ground in these mature electronic technologies. The main reason is the ability of DSP to overcome the problems that have dogged earlier users. For example, adaptive modem techniques have permitted us to negate the vagaries of the single ionospheric path. DSP techniques can also improve systems by means of real time channel evaluation (RTCE), which allows a rapid choice to be made of the best out of a number of assigned channels. Although both these approaches work exceedingly well in the single path situation, they are less effective in the case of multiple-user networks as each link is unique in terms of transmission conditions and each node is susceptible to a separate set of interference conditions! The authors discuss some 'operational realities', then lead on to a highly effective code, which (a) offers not only a greater data throughput than conventional ASCII codes (and thus makes it applicable to the whole of the radio spectrum as well as line communications) but (b) also offers a bit error correction technique, having the capability of tolerating high levels of interference-a daunting problem at HF-and it is the latter that provides the special solutions for networked systems, which neither the adaptive nor the RTCE methods appear able to tackle effectively. The proposed solution arises from a code based on the Fibonacci series, as opposed to codes based on standard binary progressions. This structure offers an 'intrinsic RTCE method', thus providing independence to the receiving systems.