Wireless Infrared CommunicationsThe demand for wireless access to network services is growing in virtually all communications and computing applications. Once accustomed to unteathered opera tion, users resent being tied to a desk or a fixed location, but will endure it when there is some substantial benefit, such as higher resolution or bandwidth. Recent technolog ical advances, however, such as the scaling of VLSI, the development of low-power circuit design techniques and architectures, increasing battery energy capacity, and advanced displays, are rapidly improving the capabilities of wireless devices. Many of the technological advances contributing to this revolution pertain to the wireless medium itself. There are two viable media: radio and optical. In radio, spread-spectrum techniques allow different users and services to coexist in the same bandwidth, and new microwave frequencies with plentiful bandwidth become viable as the speed of the supporting low-cost electronics increases. Radio has the advantage of being available ubiquitously indoors and outdoors, with the possibility of a seam less system infrastructure that allows users to move between the two. There are unan swered (but likely to be benign) biological effects of microwave radiation at higher power densities. Optical communications is enhanced by advances in photonic devices, such as semiconductor lasers and detectors. Optical is primarily an indoor technology - where it need not compete with sunlight - and offers advantages such as the immediate availability of a broad bandwidth without the need for regulatory approval. |
Contents
Introduction | 1 |
11 Comparison of Infrared and Radio Communications | 2 |
12 The Wireless Infrared Communications | 3 |
13 History of Wireless Infrared Communications | 6 |
14 A HighSpeed Wireless LAN | 10 |
15 Optoelectronic Components | 11 |
16 Outline | 12 |
Link Analysis and Optics Design | 15 |
43 MultipleBounce Impulse Response | 84 |
44 Simulation and Experimental Results | 87 |
45 MultipathInduced Power Penalty | 102 |
46 Summary | 107 |
Modulation and Equalization | 109 |
52 Binary Modulation | 112 |
53 MultiLevel Modulation | 120 |
54 Discussion | 133 |
22 ThinFilm Optical Filters | 17 |
23 Truncated Spherical Concentrators | 24 |
24 Joint Optimization of Transmitter and Filter | 37 |
25 Summary and Conclusions | 46 |
Receiver Design | 49 |
32 Limitations on Photodetector Bandwidth | 51 |
33 Analysis of CurrentFeedback Pair | 52 |
34 Optimal Filtering for Quadratic Noise Spectrum | 57 |
35 Choosing the Right Transistor and Filter | 59 |
36 Design Procedures | 60 |
37 Optional Design Embellishments | 68 |
38 Summary and Conclusions | 77 |
Modeling Multipath Dispersion | 79 |
42 Models for Diffuse Reflectors and Transmitters | 81 |
55 ML Sequence Detection and Equalization for PPM | 135 |
56 Coherent Optical Communication | 146 |
57 Summary | 147 |
SystemLevel Issues | 149 |
62 SingleCell Architectures | 150 |
63 Overlapping Cells | 153 |
64 Summary | 158 |
Conclusions and Future Work | 161 |
72 Future Work | 162 |
167 | |
Power Efficiency on the Linear Gaussian Noise Channel | 175 |
179 | |
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Common terms and phrases
achieve angle of incidence approximation assume background light bandwidth bandwidth efficiency bandwidth requirement base station baseband BDFE bit rate BPSK capacitance cell chapter cm² concentrator radius configuration conventional channel curve defined detected detector area diode equal experimental feedback frequency response front end Gaussian given high-speed IEEE impulse response infrared links input intensity-modulation channel intersymbol interference L-PAM L-PPM Lambertian Mb/s ML sequence modulation schemes multi-subcarrier multipath dispersion multiple multiplexing N-L-QAM optical filter optical gain optical power optimal output photodetector photodiode planar filter portable unit power efficiency power requirement preamplifier pulse shape pulse-position modulation radiation pattern received optical reflectors scalar shot noise shown in Fig signal power simulation slicer spherical filter subcarrier subcarrier frequency thermal noise thin-film thin-film optical filter tion transmission transmitter and receiver transmitter radiation pattern wavelength wireless LAN zero
Popular passages
Page 174 - P. Rabinowitz: Coherent Detection of Light Scattered from a Diffusely Reflecting Surface.