Performance Study of Hybrid Spread Spectrum Techniques

This thesis focuses on the performance analysis of hybrid direct sequence/slow frequency hopping (DS/SFH) and hybrid direct sequence/fast frequency hopping (DS/FFH) systems under multi-user interference and Rayleigh fading. First, we analyze the performance of direct sequence spread spectrum (DSSS), slow frequency hopping (SFH) and fast frequency hopping (FFH) systems for varying processing gains under interference environment assuming equal bandwidth constraint with Binary Phase Shift Keying (BPSK) modulation and synchronous system. After thorough literature survey, we show that hybrid DS/FFH systems outperform both SFH and hybrid DS/SFH systems under Rayleigh fading and multi-user interference. Also, both hybrid DS/SFH and hybrid DS/FFH show performance improvement with increasing spreading factor and decreasing number of hopping frequencies

Power allocation of multi-rate transmissions over a jammed broadcast channel

Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaf 40).by John L. Benko.S.B.and M.Eng

Techniques for improving the performance of frequency-hopped multiple-access communication systems

Imperial Users onl

Improvement in the Spread Spectrum System in DSSS, FHSS, AND CDMA

© ASEE 2009In this paper, we introduce spread spectrum links that can be used to overcome intentional jamming. The problem of communicating in the presence of jamming is very much akin to the problem of communicating over fading channels. Hence, by finding out how to defeat jamming by spread spectrum will also reveal how to overcome fading. Today, spread spectrum links are also used in many civilian systems to overcome non-intentional jamming (or interference), and the report is concluded with an overview of current commercial spread spectrum systems. In addition to the traditional coherent spread-spectrum systems, the definition of an ideal modified version is introduced and this model is analyzed from an information theoretic viewpoint. The project uses a simple point-to-point communication system with fully synchronized transmitter and receiver in a simple channel with white Gaussian noise and arbitrary jamming signal. We prove that in traditional systems the channel converges to a Gaussian noisy channel in the limit in the case of almost any jamming signal, and in our new ideal modified system the channel converges to a white Gaussian noisy channel in the limit in the case of any jamming signal when the processing gain goes to infinity

Simulated Assessment of Interference Effects in Direct Sequence SpreadSpectrum (DSSS) QPSK Receiver

This research developed and validated a generic simulation for a direct sequence spread spectrum (DSSS), using differential phase shift keying (DPSK) and phase shift keying (PSK) modulations, providing the flexibility for assessing intentional interference effect using DSSS quadrature phase shift keying receiver (QPSK) with matched filtering as a reference. The evaluation compares a comprehensive pool of jamming waveforms at pass-band that include continuous wave (CW) interference, broad-band jamming, partial-band interference and pulsed interference. The methodology for jamming assessment included comparing the bit error rate (BER) versus required jamming to signal ratio (JSR) for different interferers using the Monte Carlo approach. This thesis also analyzes the effect of varying the jammer bandwidth for broad-band jammers including broad-band noise (BBN), frequency hopping interference (FHI), comb- spectrum interference (CSI), multi-tone jamming (MTJ), random frequency modulated interference (RFMI) and linear frequency modulated interference (LFMI). Also, the effect of changing the duty cycle for pulsed CW waveforms is compared with the worst case pulsed jamming equation. After the evaluation of different interferers, the research concludes that pulsed binary phase shift keying (BPSK) jamming is the most effective technique, whereas the CW tone jamming and CW BPSK interference result are least effective. It is also concluded that by finding an optimum bandwidth, FHI and BBN improves the required JSR by approximately 2.1 dB, RFMI and LFMI interference by 0.9 and 1.5 dB respectively. Alternately, MTJ and CSI improves their effectiveness in 4.1 dB and 3.6 dB respectively, matching the performance of the pulsed BPSK jammer

Performance analysis of FFH/BPSK receivers with convolutional coding and soft decision Viterbi decoding over channels with partial-band noise interference

An analysis of the performance of a binary phase shift keying (BPSK) communication system employing fast frequency hopped (FFH) spread spectrum modulation under conditions of hostile partial band noise interference is performed in this thesis. The data are assumed to be encoded using convolutional coding and the receivers are assumed to use soft decision Viterbi decoding. The receiver structures to be examined are the conventional FFH/BPSK receiver with diversity the conventional FFH/BPSK receiver with diversity and the assumption of perfect side information and the noise normalized FFH/BPSK combining receiver with diversity. The FFH/BPSK noise normalized receiver with diversity minimizes the effects of hostile partial band noise interference and alleviates the effects of fading. The effect of inaccurate measurement of the noise power present in each hop is also examined and it is found that noise measurement error does not significantly degrade receiver performance. For the conventional FFH/BPSK receiver with perfect side information the effect of a Ricean fading channel is also examined.http://archive.org/details/performancenalys1094532141NAHellenic Navy authorApproved for public release; distribution is unlimited

Study of spread spectrum multiple access systems for satellite communications with overlay on current services

The feasibility of using spread spectrum techniques to provide a low-cost multiple access system for a very large number of low data terminals was investigated. Two applications of spread spectrum technology to very small aperture terminal (VSAT) satellite communication networks are presented. Two spread spectrum multiple access systems which use a form of noncoherent M-ary FSK (MFSK) as the primary modulation are described and the throughput analyzed. The analysis considers such factors as satellite power constraints and adjacent satellite interference. Also considered is the effect of on-board processing on the multiple access efficiency and the feasibility of overlaying low data rate spread spectrum signals on existing satellite traffic as a form of frequency reuse is investigated. The use of chirp is examined for spread spectrum communications. In a chirp communication system, each data bit is converted into one or more up or down sweeps of frequency, which spread the RF energy across a broad range of frequencies. Several different forms of chirp communication systems are considered, and a multiple-chirp coded system is proposed for overlay service. The mutual interference problem is examined in detail and a performance analysis undertaken for the case of a chirp data channel overlaid on a video channel

Surface elastic wave detectors

The potential applications of acoustic surface wave technology to multiplex communication systems such as data-bus, are examined. The goals are primarily to characterize certain aspects of surface wave trapped delay lines, surface wave modulation techniques, and surface wave applications that are relevant to the evaluation of surface wave devices in multiplex systems. The results indicate that there is a potential for the application of surface wave technology in data-bus type systems

Multicarrier Frequency Hopping Spread Spectrum Techniques With Quasi-Cyclic Low Density Parity Check Codes Channel Coding

This work presents a new proposed Multicarrier Frequency Hopping Spread Spectrum (MCFH-SS) system employing Quasi-Cyclic Low Density Parity Check (QC-LDPC) codes instead of the conventional LDPC codes. A new technique for constructing the QC-LDPC codes based on row division method is proposed. The new codes offer more flexibility in terms of high girth, multiple code rates and block length. Moreover, a new scheme for channel prediction in MCFH-SS system is proposed. The technique adaptively estimates the channel conditions and eliminates the need for the system to transmit a request message prior to transmitting the packet data. The ready-to-use channel will be occupied with a Pseudonoise (PN) code and use for transmission or else, it will be banned

FH/MFSK performance in multitone jamming

The performance of frequency-hopped (FH) M-ary frequency-shift keyed (MFSK) signals in partial-band noise was analyzed in the open literature. The previous research is extended to the usually more effective class of multitone jamming. Some objectives researched are: (1) To categorize several different multitone jamming strategies; (2) To analyze the performance of FH/MSFK signaling, both uncoded with diversity, assuming a noncoherent energy detection metric with linear combining and perfect jamming state side information, in the presence of worst case interference for each of these multitone categories; and (3) To compare the effectiveness of the various multitone jamming techniques, and contrast the results with the partial band noise jamming case