A Pulsed-Index Technique for Single-Channel, Low-Power, Dynamic Signaling

Abstract

The most common operation of an IoT sensor is that of short activity bursts separated by long time intervals in sleep or listen modes. During the data bursts, sensed information has to be reliably communicated in real time without draining the energy resources of the sensor node. One way to save such resources is to efficiently code the data burst, use single-channel communication, and adopt ultra-low-power communication circuit techniques. Clock-data recovery (CDR) circuits are typically significant consumers of energy on traditional single-channel communication protocols. In this paper, we present a novel single-channel protocol that does not require any CDR circuitry. The protocol is based on the novel concept of a pulsed index where data is encoded to minimize the number of ON bits, move them to the LSB end of the packet, and transmit the ON bit indices in the form of a pulse stream. The pulse count is equal to the index of the ON bit. We call this protocol Pulsed Index Communication (PIC). Beside the elimination of CDR, we show that the implementation of PIC is very area-efficient, low-power and highly tolerant of clocking differences between transmitter and receiver. We present both an FPGA and an ASIC implementation of the protocol and use them to illustrate the performance, reliability and power consumption features of PIC signaling. In particular, we show that for an ASIC implementation on 65nm technology, PIC can reduce area by more than 80% and power by more than 70% in comparison with a CDR-based serial bit transfer protocol.