This book was born from the perception that there is much more to spectrum use
and sharing than one sees reflected in publications, whether academic, commercial
or political. the former – in good research style – tend towards reductionism and
concentrate on specific, detailed aspects. commercial publications tend to empha-
size the positive aspects and they tend to put promise above practice. Given the ever
increasing pace of technology development and recent successes of new wireless
technologies, some pundits predict large-scale spectrum scarcity, potentially lead-
ing to economic catastrophe. Although economic theory has a hard time explaining
recent events that shook the world economy, the notion of spectrum scarcity is intui-
tively acceptable, even if not correct or immediately relevant.
The radio spectrum is one of the most precious resources which must be managed
to ensure efficient access for the wireless communication services which use it. The
allocation and management of spectrum are administered by the regulatory
authorities. Traditionally, spectrum allocation is carried out exclusively of its use in
large geographic areas and assigning frequency bands to specific users or service
providers is proved to be inefficient. Recently, substantial knowledge about
dynamic spectrum access scheme has been accumulated to enable efficient spectrum
sharing.
Radio frequency spectrum is a scarce and critical natural resource that is utilized for
many services including surveillance, navigation, communication, and broadcast-
ing. Recent years have seen tremendous growth in the use of spectrum especially by
commercial cellular operators. Ubiquitous use of smartphones and tablets is one
of the reasons behind an all-time high utilization of spectrum. As a result, cellular
operators are experiencing a shortage of radio spectrum to meet bandwidth
demands of users. On the other hand, spectrum measurements have shown that
much spectrum not held by cellular operators is underutilized even in dense urban
areas. This has motivated shared access to spectrum by secondary systems with no
or minimal impact on incumbent systems. spectrum sharing is a promising
approach to solve the problem of spectrum congestion as it allows cellular operators
access to more spectrum in order to satisfy the ever-growing bandwidth demands of
commercial users.
The goal of this book is to provide a concise but lucid explanation and deriva-
tion of the fundamentals of spread-spectrum communication systems. Although
spread-spectrum communication is a staple topic in textbooks on digital com-
munication, its treatment is usually cursory, and the subject warrants a more
intensive exposition. Originally adopted in military networks as a means of
ensuring secure communication when confronted with the threats of jamming
and interception, spread-spectrum systems are now the core of commercial ap-
plications such as mobile cellular and satellite communication.
Spread-spectrum communication is a core area within the field of digital
communication. Originally used in military networks as countermeasures against
the threats of jamming and interception, spread-spectrum systems are now widely
used in commercial applications and are part of several wireless and mobile
communication standards. Although spread-spectrum communication is a staple
topic in textbooks on digital communication, its treatment is usually cursory. This
book is designed to provide a more intensive examination of the subject that is
suitable for graduate students and practicing engineers with a solid background
in the theory of digital communication. As the title indicates, this book stresses
principles rather than specific current or planned systems, which are described in
manyotherbooks.My goal in this bookis to providea concisebut lucidexplanation
of the fundamentals of spread-spectrum systems with an emphasis on theoretical
principles.
The continuing vitality of spread-spectrum communication systems and the devel-
opment of new mathematical methods for their analysis provided the motivation to
undertake this new edition of the book. This edition is intended to enable readers
to understand the current state-of-the-art in this field. Almost twenty percent of the
materialinthiseditionisnew, includingseveralnewsections, anewchapteronadap-
tive arrays and filters, and a new chapter on code-division multiple-access networks.
The remainder of the material has been thoroughly revised, and I have removed a
considerable amount of material that has been superseded by more definitive results.
A light-emitting diode (LED) is a semiconductor device that emits narrow-spectrum incoherent light when forward-biased.The color of the emitted light depends on the chemical composition of the semiconductor material used, and can benear-ultraviolet, visible or infrared. LEDs are more prevalent today than ever before, replacing traditional incandescent andfluorescent bulbs in many lighting applications. Incandescents use a heated filament, are subject to breakage and burnoutand operate at a luminous efficiency of 2% to 4%. Fluorescents are more efficient, at 7% to 12%, but require highdrive voltage and contain mercury, a toxic substance that may be eventually banned in certain countries. LEDs, however,produce light directly through electroluminescence, operate at low voltage and can deliver over 20% luminous efficiency.
為了使音頻信號分析儀小巧可靠，成本低廉，設計了以2片MSP430F1611單片機為核心的系統。該系統將音頻信號送入八階巴特沃茲低通濾波器，對信號進行限幅放大、衰減、電平位移、緩沖，并利用一單片機負責對前級處理后的模擬信號進行采樣，將采集得到的音頻信號進行4 096點基2的FFT計算，并對信號加窗函數提高分辨率，另一單片機負責對信號的分析及控制顯示設備。此設計精確的測量了音頻信號的功率譜、周期性、失真度指標，達到較高的頻率分辨率，并能將測量結果通過紅外遙控器顯示在液晶屏上。
Abstract:
o make the audio signal analyzer cheaper， smaller and more reliable， this system sends the audio signal to the eight-order butterworth filter， and then amplifies， attenuates， buffers it in a limiting range， transfers the voltage level of the signal before utilizing two MSP430F1611 MCU to realize the audio analysis. One is charged for sampling and dealing with the processed audio signal collected by the 4096 point radix-2 FFT calculation and imposes the window function to improve the frequency resolution. The other one controls the display and realizes the spectrum， periodicity， power distortion analysis in high resolution which is displayed in the LCD screen through the infrared remote control.
This application report discusses the design of non-invasive optical plethysmographyalso called as pulsoximeter using the MSP430FG437 Microcontroller (MCU). Thepulsoximeter consists of a peripheral probe combined with the MCU displaying theoxygen saturation and pulse rate on a LCD glass. The same sensor is used for bothheart-rate detection and pulsoximetering in this application. The probe is placed on aperipheral point of the body such as a finger tip, ear lobe or the nose. The probeincludes two light emitting diodes (LEDs), one in the visible red spectrum (660nm) andthe other in the infrared spectrum (940nm). The percentage of oxygen in the body isworked by measuring the intensity from each frequency of light after it transmitsthrough the body and then calculating the ratio between these two intensities.
