IrDA-VFIr (16 Mb/s): modulation code and system design

Abstract

Devices for convenient information exchange over the wireless infrared channel are commonly found in many of today's mobile platforms for computing, communicating, and imaging. Most devices comply with the international standards promoted by the Infrared Data Association for data rates of up to 4 Mb/s. With the recent approval of a 16 Mb/s data rate option called Very Fast Infrared, IrDA's point-to-point usage model is extendable to applications requiring wireless connectivity beyond 4 Mb/s. In this article we describe the design and the properties of a new modulation code specifically developed for VFIr, and discuss related system design aspects. After defining basic system requirements and modulation constraints imposed by the WIrC, we introduce a rate-2/3 run-length-limited code designed to meet these criteria. The Boolean expressions for encoding and decoding are given, and their implementation is discussed together with various aspects of system design such as scrambling, invalid sequence detection, and error propagation. Furthermore, it is shown that the specific composite nature of the new RLL modulation code enables simple and efficient generation of VFIr packet frames by encoding an equivalent packet frame assembled entirely in the code's input data domain.