The focus of this dissertation is the performance analyses of two classes of frequency-hopped spread-spectrum multiple access (FH-SSMA) systems in various fading environments. The capacity of Viterbi’s FH-SSMA system is evaluated under three types of fading, namely Rician, shadowed Rician, and Nakagami fading. The results of recent experiments have indicated that these fading phenomena occur in various environments where the FH-SSMA system may be implemented. In this dissertation, the deletion probability for each fading scenario is derived. Subsequently, the system capacity is analyzed in terms of maximum number of users versus average bit error rate. The effect of a change in the signal-to-noise ratio level on the system capacity is also demonstrated. For Rician fading, it is found that the capacity of the system with a Rician factor of 2 dB is reduced by 13 percent as compared to the capacity of the non-fading case. For shadowed Rician fading, three shadowing scenarios are considered: light, average, and heavy. It is shown that the light and the average shadowing scenarios provide only a slight decrease in the capacity, while the heavy shadowing scenario renders a capacity identical to that for the Rayleigh fading case. Finally, for Nakagami fading the capacity is found to decrease by 50 percent as the fading parameter is reduced to 0.5. The performance of a cellular frequency-hopped spread-spectrum multiple access system is studied under an indoor environment. It is demonstrated how the system capacity, given in terms of the number of users per cell, is affected by the number of cells in the system. Also, the influence of the delay spread, which is the result of multipath propagation, is investigated. The analysis focuses on a worst-case scenario where a user receives both the desired and interfering signals with equal power levels. This scenario applies to both the downlink and the uplink. It is shown that the system capacity is reduced drastically as the number of adjacent interfering cells increases from one to three. Previous work concerning the indoor multipath propagation assumed that the number of paths is fixed, the path delays are uniformly distributed, and the path gains are equal. In this dissertation, a more realistic channel model derived from actual impulse response measurements by Saleh and Valenzuela is employed. The model consists of clusters of rays with constant cluster and ray arrival rates and power-delay time constants. The system performance is shown to be affected strongly by the change in the power-delay time constants, yet only slightly influenced by the variation in the arrival rates of the rays and clusters. In addition, the degradation in the system performance due to the delay spread becomes more severe as the transmission rate increases. / Graduate

No description available.

Thesis (PhD)--University of South Australia, 1997

Report (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Abstract. Includes bibliographical references (leaves 42-43). Also available via the Internet.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Charles G. Boncelet, Dept. of Computer & Information Sciences. Includes bibliographical references.

This dissertation is concerned with performance analysis of diversity combining schemes in frequency-hop spread spectrum communications under the worst case partial-band noise and multitone jamming. Performance of a ratio-threshold diversity combining scheme in fast frequency hop spread spectrum systems with M-ary frequency shift keying modulation (FFH/MFSK ) under partial-band noise (PBN) and band multitone jamming without and with the additive white Gaussian noise (AWGN) is analyzed. The analysis is based on exact bit error probabilities, instead of bounds on the bit error probabilities. A method to compute the bit error probability for ratio-threshold combining on jamming channel is developed. Relationship between the system performance and the system parameters, such as ratio-threshold, diversity order, and thermal noise level, is illustrated. The performances under band multitone jamming and under partial-band noise jamming are compared. For binary FSK modulation, the performance under the two types of jamming is almost the same, but for 8-ary FSK modulation, tone jamming is more effective against communications. The structure of the combiner is very simple and easy to implement. Another merit of this combiner is that its output can be directly fed to a soft-decision FEC decoder. Maximum-likelihood diversity combining for an FFH/MFSK spread spectrum system on a PBN interference channel is investigated. The structure of maximum likelihood diversity reception on a PBN channel with AWGN is derived. It is shown that signal-to-noise ratio and the noise variance at each hop have to be known to implement this optimum diversity combining. Several sub-optimum diversity combining schemes, which require the information on noise variance of each hop to operate, are also considered. The performance of the maximum-likelihood combining can be used as a standard in judging the performance of other suboptimum, but more practical diversity combining schemes. The performance of the optimum combining scheme is evaluated by simulations. It is shown that the Adaptive Gain Control (AGC) diversity combining actually achieves the optimum performance when interference is not very weak. But the performance difference between some of the known diversity combining schemes, which do not require channel information to operate, and the optimum scheme is not small when the diversity order is low. An error-correction scheme is proposed for an M-ary symmetric channel characterized by a large error probability Pe. Performance of the scheme is analyzed. The value of Pe can be close to, but smaller than, 1 – 1/M for which the channel capacity is zero. Such a large Pe may occur, for example, in a jamming environment. The coding scheme considered consists of an outer convolutional code and an inner repetition code of length m which is used for each convolutional code symbol. At the receiving end, the m inner code symbols are used to form a soft-decision metric, which is subsequently passed to a soft-decision decoder for the convolutional code. Emphasis is placed on using a binary convolutional code due to the consideration that there exist commercial codecs for such a code. New methods to generate binary metrics from M-ary (M > 2) inner code symbols are developed. For the binary symmetric channel, it is shown that the overall code rate is larger than O.6R0, where R0 is the cutoff rate of the channel. New union bounds on the bit error probability for systems with a binary convolutional code on 4-ary and 8-ary orthogonal channels are presented. Owing to the variable m which has no effect on the decoding procedure, this scheme has a clear operational advantage over some other schemes. For a BSC and a large m, a method presented for BER approximation based on the central limit theorem. / Graduate

The Interactive Video Data Service (IVDS) system allows consumers to browse the Internet, request information on products or services, make purchases, indicate preferences, and perform other interactive applications. To provide this service, the IVDS system has three subsystems: Consumer Control (CC), Cell Repeater (CR), and Host subsystem. In the CC subsystem, an IVDS transceiver box is placed near a television set. Once the consumer sends a command to the transceiver box using a standard television/VCR/Cable remote control, the transceiver box receives information embedded in the television audio, and then transmits the information to the CR subsystem as a radio frequency (RF) spread spectrum message. The CR subsystem decodes the spread spectrum message and forwards it to the Host subsystem for processing. Located in the CR subsystem, a custom designed circuit board, called the decoder board, uses surface mounted components to decode and packetize the spread spectrum message for transfer to the CR main processor. This paper provides a functional description of the hardware components on the decoder board, and describes the hardware/software developed for interfacing the decoder board to the radio receiver and to the CR main processor. Hardware modifications were needed to correct timing problems between components. Software was developed to initialize the components for downconverting, despreading, and demodulating spread spectrum messages, and to packetize them for transfer to the CR main processor. This paper also discusses the tests used to verify both the performance of the decoder board software and the operation of the hardware components. / Master of Science

No description available.

A Gold code sequence generator suitable for use in a code division multiple access spread spectrum communication application is designed. A dual, single return shift register configuration is used to generate Gold code sequences. The code sequences are generated by the mod-2 addition of two linear maximal length pseudo-random noise codes, each of which corresponds to a sixth-order primitive polynomial. A computer model of the design is used to generate all 65 possible members of the Gold code sequence family. A tabulation of all sequences and their initial condition “keys” is provided, along with a designation as to which code sequences are balanced. The mathematical basis of maximal length sequence generation is developed, using first the matrix characterization of a shift register generator, and then switching to the alternate treatment of a shift register generator as a polynomial division engine. The link between the matrix representation and the polynomial representation via the characteristic equation, the use of the generating function, and the three mathematical properties required of polynomials which are capable of generating maximal length sequences are described. Gold’s algorithm for selecting preferred polynomial pairs is presented, as is his technique for determining the characteristic phase of a maximal length sequence. The actual Gold code generator is then designed and modeled in software. All Gold code sequences output from the generator are tabulated. The family of sequences is evaluated in terms of its randomness properties. Finally, the results of computer analysis of the auto and cross-correlation characteristics of the family is summarized.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / A MIMO radar system for target localization is presented which uses direct-sequence CDMA (DS-CDMA) waveforms. The received DS-CDMA signal at each antenna is expressed directly in terms of the target positions. The waveforms employed are Gold sequences, and hence are not exactly orthogonal. A generalized successive interference cancellation (GSIC) approach is used to resolve multiple scatterers and reduce clutter. Simulation results are presented which suggest the capability to detect weak scatterers in the presence of clutter using the cancellation method.