Asynchronous Transmission Schemes for Digital Information

Some coding schemes of binary signals into ternary signals for asynchronous transmission of digital information are presented. First, an application of differentiated ternary return to zero signals, where every signal is associated with a particular separation signal, to asynchronous transmission is introduced and discussed. Second, coding schemes where successive signals are alike are introduced and also discussed. In these schemes signals may have large intersymbol interferences. Third, in order to minimize intersymbol interference a coding scheme where no two successive pulses may have the same polarity is introduced. The number of code points Nmof lengthmis given by,N_{m} = 2(F_{m} + F_{m-1}), where Fmis in a Fibonacci series{F_{i}}, i = 1,2,...,m,starting withF_{1} = 1andF_{2} = 2. Thus we call this Fibonacci coding. If the Fibonacci coding is performed on a bit-by-bit basis, the code words derived do not generally have equal length. To avoid this, word-by-word coding is proposed. The power spectrum of the Fibonacci coded signals is calculated theoretically. In all cases, any single error may cause a succession of errors. In order to prevent these errors caused by an error, it is required to achieve stable block or frame synchronization.