A Hybrid Communication System Using Pulse Position and Width Modulation

The digital revolution has emerged the need for storing, processing and communicating data in digital format. Accordingly, all-digital systems have become popular, where no analogue components are included in the circuitry. As the output of these systems is digital, pulse code modulation is employed to establish communications without the need for analogue components. A certain characteristic of the pulse, such as its width, position or amplitude, is adjusted based on the input value. The number of bits transmitted in the channel depends on the number of bits modulated per pulse and the number of pulses outputted from the system per second. However, these parameters are limited by the capabilities of the digital system and communication channel. In this study, a new hybrid communications technique is proposed to allow increasing the bandwidth of digital communication systems, without the need for significant modification to the system. The bits of the input data is split into two sets, one modulated using Pulse Width Modulation and the other is modulated using Pulse Position Modulation. The outputs from these modulators are encoded to the output signal, using one of two possible encoding techniques, amplitude or frequency, depending on the characteristics of the communications channel. The evaluation results show that the proposed method has been able to provide twice the bandwidth the digital system can establish using each of these techniques, solely.