3 edition of susceptibility of direct sequence and frequency hopped spread spectrum to interference found in the catalog.
susceptibility of direct sequence and frequency hopped spread spectrum to interference
by Hewlett-Packard Laboratories, Technical Publications Department in Palo Alto, CA
Written in English
|Statement||David Purle, John Waters.|
|Series||HP Laboratories technical report -- HPL-96-86.|
|Contributions||Waters, John., Hewlett-Packard Laboratories.|
|The Physical Object|
|Pagination||6 p. :|
Two Popular Spread Spectrum Techniques 17 Direct Sequence 17 Frequency Hopped 18 Comparison of DS andFH Systems 19 Summary 19 3. Direct Sequence Spread Spectrum 21 Basic Concepts of DSSS 22 Block Diagram 22 Modulation 23 Demodulation 26 Characteristics of DSSS the transmission energy over some spectrum, Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS). The rst one, DSSS, uses a xed transmission frequency, but a wider bandwidth. This is achieved by encoding each bit with a sequence of so-called chips obtained from pseudonoise.
Frequency Hopping Spread Spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and is used as a multiple access method in the frequency-hopping code division multiple access (FH-CDMA) scheme.. FHSS is a wireless technology that spreads its signal over . Mullins B, Davis N and Midkiff S () An adaptive wireless local area network protocol that improves throughput via adaptive control of direct sequence spread spectrum parameters, ACM SIGMOBILE Mobile Computing and Communications Review, , (), Online publication date: 1-Sep
Originally the standard defined three physical (PHY) layer standards. These are infra-red and two spread spectrum systems - frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). No products have really been developed for infra-red possibly because of its limited applications. Direct-Sequence Spread Spectrum DSSS (direct-sequence spread spectrum) is another type of SSR most commonly used for wide-band communications such as wireless Ethernet, including increasingly common wireless networks. The DSSS data signal is spread over the band/channel according to a spreading ratio. The code includes a redundant bit.
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Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral changes are controlled by a code known to both transmitter and is used to avoid interference, to prevent eavesdropping, and to enable code-division multiple access (CDMA).
Direct-sequence spread spectrum (DSSS) and frequency-hopping spread spectrum (FHSS) have different physical mechanisms for reject- ing narrowband interference. Because of these physical differences, they perform differently in the presence of the same levels of narrowband : Earl McCune.
Frequency hopping spread spectrum (FHSS) is a method of transmitting radio signals by shifting carriers across numerous channels with pseudorandom sequence which is already known to the sender and receiver. Frequency hopping spread spectrum is defined in the GHz band and operates in around 79 frequencies ranging from GHz to GHz.
Direct or Hopping Direct sequence and frequency hopping are the most commonly used methods for the spread spectrum technology.
Although the basic idea is the same, these two methods have many distinctive characteristics that result in complete different radio performances. The carrier of the direct-sequence radio stays at a fixed frequency. By definition, a spread-spectrum system uses a process other than the information signal to expand, or spread, the bandwidth of the signal.
In frequency hopping, data is directly modulated and the Author: Earl Mccune. Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and/or multiple functions.
Because of this choice of frequency band, b/g/n equipment may occasionally suffer interference in the GHz band from microwave ovens, cordless telephones, and Bluetooth devices. Introduction This paper discusses the relative susceptibility of both Direct Sequence and Frequency Hopped spread spectrum to interference.
It is based upon, and extends, a previous analysis and uses the performance of a Differential Phase Shift Keying modem as a benchmark for comparison.
Different devices can share the same band and their spectra can overlap; the receiver selects the desired signal by means of the PN code, which will de-spread only the desired signal. Frequency Hopping. The spread-spectrum technique that we have discussed so far is called direct-sequence spread spectrum.
A hybrid frequency-hopping direct-sequence system ; A frequency-hopping system that uses direct-sequence spreading during each dwell interval ; Or, equivalently, a direct-sequence system in which the carrier frequency changes periodically.
34 (No Transcript) Hops occur periodically after a fixed number of sequence chips. The type of spread spectrum system illustrated here is called direct sequence spread spectrum. There exists another practical spread spectrum technique, known as frequency hopping spread spectrum.
In this technique, the frequency on which the digital signal is transmitted is moved multiple times during the transmission of one bit.
Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver.
A spread-spectrum transmission offers three main advantages over a fixed-frequency transmission: # Spread-spectrum signals are highly resistant to narrowband interference. This book will provide the reader with a concise introduction to the use of spread spectrum waveforms in multiple user systems, often termed code division multiple access or CDMA.
Code Division Multiple Access (CDMA) is appropriate for courses on spread spectrum, advanced digital communication or multiple access, and also for professional engineers in need of a basic understanding of CDMA 5/5(1). This paper presents performance evaluation and comparison analysis of Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS) systems.
The evaluation and analysis are done based on the systems performance against wideband interferences. A Comparison of Frequency Hopping and Direct Sequence Spread Spectrum Modulation for IEEE Applications at GHz Carl Andren Harris Semiconductor Palm Bay, Florida Abstract Two types of spread spectrum have been approved for use by the FCC in the unlicensed ISM band.
The WLAN committee establishing a global standard for wireless. Spread-spectrum clock generation (SSCG) is used in some synchronous digital systems, especially those containing microprocessors, to reduce the spectral density of the electromagnetic interference (EMI) that these systems generate.
A synchronous digital system is one that is driven by a clock signal and, because of its periodic nature, has an unavoidably narrow frequency spectrum. Interference Susceptibility C. Broadband Rating D.
Maximum Segment Length. Bandwidth rating Is susceptible to electrical interference. Has a distance limitation of meters D. Is susceptible to electrical interference C.
Frequency Hopping D. Direct-Sequence Spread Spectrum. Other methods of spread spectrum sweep the carrier frequency up or down the amateur band with specified timing and shift the phase of the carrier, and yet others use a repeating sequence rather than a continuing pseudo-randomized algorithm.
A pulsed RF carrier can also be used to affect time multiplexed signals, often combined with frequency hopping in a hybrid technique of spread spectrum. The Correlated Hopping Enhanced Spread Spectrum (CHESS) waveform is introduced as an improved approach to high-speed, HF digital communications.
In general terms, frequency hopping (FH) avoids narrowband interference better than direct sequence (DS) spread spectrum. Direct sequence (DS) and frequency hopped (FH) systems each have their strengths and weaknesses with respect to the above criteria, and these are often manifested in different ways.
There is no universal agreement on whether DS or FH systems have inherently. Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS) systems.
The evaluation and analysis are done based on the systems performance against wideband interferences. The interferences are signals with similar spectrum characteristic to the transmitted signals of DSSS and FHSS systems.
SAMEER-Centre for Electromagnetics has developed both Direct Sequence (DS) and Frequency Hopping (FH) based Spread Spectrum (SS) Communication systems for different applications.
The DS and FH systems adopt different methodology for rejecting the narrow band interference. This paper describes the performance of both DS and FH based spread spectrum systems and the mechanism of interference.synchronize the received modulated ncy-hopping spread-spectrum (FHSS) systems have been extensively used in military communications.
Frequency Hoppers (FH) are a more sophisticated and arguably better family of spread spectrum techniques than the simpler Direct Sequence (DS) systems.
However, performance comes with.If the other users of the frequency band are near the frequency hop receiver and a frequency hop transmitter is far away, a frequency hop system can more easily reject the nearby interference than a direct sequence system can.