Rob Otte

Low-Power Wireless Infrared Communications

Today, wireless infrared transmission has entered our homes, offices, industry and health care, with applications in the field of remote control, telemetry and local communication. Low-Power Wireless Infrared Communications is about the underlying technology. As most equipment is battery-powered, the emphasis is on power optimization of the infrared transmission system. System parameters as well as environmental parameters that determine the eventual transmission quality are identified, to facilitate well-reasoned system design. Many design rules, based on calculations, measurements and simulations, are presented to help the designer push the performance close to the limits set by nature and the available technology. Firstly, the basic transmission link is introduced, and strategies to optimize its signal-to-noise ratio are discussed. Lighting flicker is identified as a possible source of interference. Then, receiver noise and bandwidth are discussed. It is argued that noise optimization and bandwidth optimization do not necessarily conflict. The following chapters provide the reader with an overview of modulation and synchronization techniques. Pulse position modulation is recognized as an attractive technique for low-power purposes. As receiver synchronization in those systems is a subject hardly covered by literature, an in-depth discussion of possible synchronization subsystems is included. This book is essential reading for researchers and designers of infrared communication systems and those who are involved in standardization activities (Infrared Data Association, IrDA). For those who are new to the area, the first chapter serves as an ideal introduction.

Advanced Signal Processing for the Blu-ray Disc System.

Advanced signal processing techniques enable higher capacities for the Blu-ray Disc (BD) system. A signal-to-noise analysis of a Limit Equalizer circuit in the BD system is performed. Limit equalizer (LE) and adaptive controlled partial response maximum likelihood (PRML) bit detection schemes are compared on the basis of system margins. Measurements with an adaptive equaliser were also performed to improve tangential tilt margin.

Evaluation of adaptive PRML/Viterbi bit detection for DVD and beyond

Two adaptive PRML/Viterbi bit detectors have been evaluated based on DVD. They are able to handle non-linearities. It is shown that adaptive PRML/Viterbi detection can help to improve the tangential tilt margin or to increase the possible density.

Transition detector for CD and DVD

This bit detector for d=2 modulation codes is remarkably simple, supports very high data rates, can be adaptive, and is capable of handling nonlinearities. The performance approaches that of a full-fledged maximum-likelihood sequence detector.

Asynchronous LMS adaptive equalization

Digital data receivers often operate at a fixed sampling rate 1/Ts that is asynchronous to the baud rate 1/T. A digital equalizer that processes the incoming signal will also operate in the asynchronous clock domain. Existing adaptation techniques for this equalizer involve an error sequence ek that is produced in the synchronous clock domain, and converted to the asynchronous domain via an inverse sampling-rate converter. Several disadvantages of this approach may be avoided by means of an alternative topology that is developed and analyzed in this paper. Numerical results for an idealized optical storage channel serve to illustrate the merits of the approach.

Advanced signal processing for the Blu-ray Disc system

Advanced signal processing enables high capacities for the BD system. Measurements show that data detection with a conventional equalizer does not give sufficient system margins. Both a Viterbi decoder and the limit equalizer give a significant improvement of the signal-to-noise ratio and therefore sufficiently large margins. An adaptive equalizer is able to correct the distortions introduced by tangential tilt. The performance of the limit equalizer and a Viterbi decoder are comparable; only in the tangential tilt situation does a Viterbi decoder perform slightly better. For high data rates the limit equalizer may be preferred over the Viterbi decoder due to its simple hardware structure.

Synchronization in PPM receivers

In the previous chapter, PPM was proposed as a means to minimize the required transmitter power. It was assumed that the timing of the PPM slot and frames is ‘known’ by the receiver. The recovery of these timing signals is the subject of this chapter.

Link design — electronic considerations

Considering the transmitter and the receiver, the circuit that mainly determines the achievable transmission quality is the receiver front end. Here, the signal level is the lowest in the entire system, necessitating very low-noise operation. Further, the front end should combine a large gain and a large bandwidth, two requirements that are essentially conflicting. For these reasons, this chapter is entirely devoted to the front end. Throughout this chapter, it is assumed that the front end is a low-pass overall feedback amplifier. However, in principle, the design procedures are applicable to bandpass overall feedback amplifiers as well. Since the information-carrying signal is a current, the front end is either a transimpedance amplifier or a current amplifier. Because the general design philosophy has been published several times before, by Nordholt [66] and Verhoeven [67], this work only concentrates on those aspects essential to the design of wireless optical receivers.

Link design — optical considerations

As a first step towards low-power optical transmission, the properties of the transmission channel have to be investigated. Then the signal-to-noise ratio has to be maximized.

Maximum–likelihood PPM frame synchronization

This paper presents an improved method for retrieving frame synchronization from a, possibly noisy, pulse-position modulated (PPM) signal. It does not require synchronization patterns to be inserted in the data stream, but uses all information already present in the signal. Theory is accompanied by simulations, a circuit design and implementation, and measurement results.