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Spread Spectrum Techniques and Applications, 1994. IEEE ISSSTA '94., IEEE Third International Symposium on

Date 4-6 July 1994

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  • Proceedings of IEEE 3rd International Symposium on Spread Spectrum Techniques and Applications (ISSSTA'94)

    Publication Year: 1994
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  • A new scheme for the coded SSMA systems

    Publication Year: 1994 , Page(s): 560 - 563 vol.2
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    A new scheme for coded spread spectrum multiple access (SSMA) systems is presented. The new scheme employs a four-dimensional modulation which combines the FSK and PSK modulation. The corresponding receiver structure is discussed and a realization method is given. The bandwidth expansion and performance comparisons show that the scheme presented is more attractive over the coded MPSK SSMA systems View full abstract»

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  • The performance of GMSK as a modulation scheme for direct sequence CDMA

    Publication Year: 1994 , Page(s): 554 - 559 vol.2
    Cited by:  Papers (1)  |  Patents (1)
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    The processing gain of a direct sequence spread spectrum communications system using GMSK modulation is analysed. Multiple access interference is considered, rather than broadband white noise. Monte-Carlo methods are used. It is shown that the processing gain in a GMSK based system is lower than is possible in an equivalent system using QPSK. It is further shown that this processing gain need not be lost if adjacent systems are allowed to overlap in frequency. The optimum time-bandwidth product is found to be between 0.1 and 0.2 View full abstract»

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  • An overview of TU Delft research on CDMA

    Publication Year: 1994 , Page(s): 319 - 324 vol.1
    Cited by:  Papers (3)
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    This paper presents an overview of the research work carried out by the faculty members and students of the Delft University of Technology (TU Delft), The Netherlands in the field of code division multiple access. They have investigated CDMA systems considering direct sequence (DS), slow frequency hopping (SFH), hybrid SFH/DS, hybrid CDMA/inhibit sense multiple access (ISMA), multi-carrier (MC)-CDMA, interference cancellation, dynamic code channel allocation, synchronization, receiver structure and overlay CDMA/TDMA systems for macro-, micro- and pico-cellular systems as well as for land mobile satellite systems. The effect of forward error correction (FEC) coding and of diversity techniques on CDMA systems performance is also analyzed. Computer simulation has been performed to verify the basic assumptions, such as approximating by multi-users interference by a Gaussian random variable, in the analysis. Results of these investigations are summarized and discussed View full abstract»

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  • Carrier frequency offset-spread spectrum multiple access (CFO-SSMA) method

    Publication Year: 1994 , Page(s): 314 - 318 vol.1
    Cited by:  Papers (2)  |  Patents (1)
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    A novel spread spectrum multiple access method employing only a single PN code is proposed. This new method, named “CFO-SSMA (carrier frequency offset-spread spectrum multiple access)”, utilizes a single PN code commonly assigned to all users with different carrier frequencies. The amount of the frequency offset between carriers is determined by the information rate, which is very small as compared with the bandwidth of the spread spectrum signal. CFO-SSMA employs a receiver using a surface acoustic wave (SAW) matched filter, which has an advantage of rapid signal acquisition over the conventional receiver, but has a disadvantage of difficulty to change the PN code pattern. CFO-SSMA defeats this disadvantage, because there is no need to change the matched filer in accordance with the channel to be recovered. The concept and basic performance of CFO-SSMA is discussed in this paper. The optimum bandwidth of the receive filter as well as the BER performance of CFO-SSMA are also shown View full abstract»

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  • 4-phase DS-CDMA mobile radio receiver in non-Gaussian environment

    Publication Year: 1994 , Page(s): 440 - 444 vol.2
    Cited by:  Papers (2)
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    The aim of the paper is to investigate the performance of digital mobile radio communications using the RAKE receiver under impulsive environments. The performances studies are carried out in terms of spectral efficiency and bit error probability. The assumed modulation technique is QPSK. The signature sequences used for spreading the signal are complex valued and characterized by different correlation properties; the possible choices lead to a performance comparison based on the properties of the sequences in order to maximize the number of users per cell View full abstract»

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  • Bit error probability for an adaptive diversity receiver in a Rayleigh fading channel

    Publication Year: 1994 , Page(s): 450 - 454 vol.2
    Cited by:  Papers (2)
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    The bit error probability is determined for an adaptive diversity receiver using decision directed feedforward channel estimation. The channel is assumed to be a nonselective Rayleigh fading channel with AWGN. The analysis is valid for all feedforward estimation structures which use an FIR-type estimation filter. The analysis can be applied also to Rake receivers in a frequency selective Rayleigh fading channel. Numerical results are presented for an adaptive diversity receiver which uses either an FIR-type minimum mean-square error (MMSE) filter or a moving average (MA) filter as the estimation filter. The results show that the MA filter performs poorly compared to the MMSE filter at large signal-to-noise ratios and large Doppler spreads. However, at small signal-to-noise ratios and Doppler spreads the filters do not show any remarkable difference in the performance View full abstract»

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  • On narrowband interference suppression using DFB filter in DSSS systems under impulsive channel conditions

    Publication Year: 1994 , Page(s): 530 - 533 vol.2
    Cited by:  Papers (1)
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    In this paper the extension analysis of the recently proposed direct sequence spread spectrum (DSSS) receiver using decision feedback filter (DFB) under narrowband interference (NBI) and impulsive channel conditions is presented. The results, obtained by theoretical analysis and computer simulation in term of the output signal to interference ratio (SIR), show that the impulsive noise does not deteriorate the excellent performance of the DFB receiver in the NBI suppression. The impulsive noise influence on the receiver performance can be adequately expressed through the increase of the total noise power View full abstract»

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  • Optimum PN sequences for CDMA systems

    Publication Year: 1994 , Page(s): 27 - 35 vol.1
    Cited by:  Papers (5)
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    Most known methods for the design of hopping patterns for frequency-hopped code-division multiple-access (CDMA) systems and for the design of signature sequences for direct-sequence CDMA systems provide sequences that can be viewed as codewords (or the images of codewords) from low-rate Reed-Solomon codes. This paper surveys sequence designs for CDMA systems from this viewpoint View full abstract»

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  • Prediction, smoothing and interpolation in adaptive diversity reception

    Publication Year: 1994 , Page(s): 475 - 478 vol.2
    Cited by:  Papers (3)  |  Patents (2)
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    Adaptive channel estimators based on linear prediction, or smoothing and interpolation are analyzed and compared in a flat fading channel. Data modulation is removed by using decision feedback before the estimator based on prediction. In the estimator based on smoothing and interpolation known training symbols are exploited. It is shown how the estimators can adaptively be “matched” to the Doppler power spectrum of the channel by using the well-known algorithms such as the LMS and RLS algorithms. The method has potential applications in mobile communications, e.g. in spread-spectrum RAKE receivers and in other diversity receivers View full abstract»

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  • Experimental investigation of CDMA mobile satellite communication system

    Publication Year: 1994 , Page(s): 435 - 439 vol.2
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    The performance of a direct sequence spread spectrum CDMA communication system in an actual land mobile satellite channel is experimentally evaluated. Field test results using the ETS-V satellite in urban and suburban environments at L-band frequency show that this land mobile satellite channel of 3 MHz bandwidth can be seen as a non-frequency selective Rician fading channel as well as a shadowing channel. The bit error performance can be estimated using signal power measurements as if they were narrow band modulation signals. Based on the experimental results of the ETS-V, a prototype system for the personal satellite communication is proposed and field tests are planned on the S-band frequency using the ETS-VI satellite which will be launched in August 1994 View full abstract»

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  • Performance of the forward link of a CDMA cellular network

    Publication Year: 1994 , Page(s): 213 - 217 vol.1
    Cited by:  Papers (6)
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    In this paper we study the performance of a point-to-multipoint CDMA communication system operating in an environment with multipath propagation. Rake receivers are used by the mobile terminals to receive the multipath signals. Analytical expressions for signal-to-noise ratios (SNR) are derived for both orthogonal and non-orthogonal spreading sequences. Analytical results are obtained assuming signal paths have amplitudes that are Rayleigh distributed. Also, multipath delay profile measurements, made in the Toronto area, are used to study how the SNR varies in urban and suburban environments View full abstract»

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  • Throughput and delay analysis of a cellular slotted DS CDMA system with imperfect power control and sectorization

    Publication Year: 1994 , Page(s): 420 - 424 vol.2
    Cited by:  Papers (2)
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    An analytical model is developed to evaluate the performance of a cellular slotted DS CDMA system in terms of throughput and delay for a multiple cell system. The effect of both imperfect power control and sectorization on the performance is investigated. It is shown that imperfections of the power control and sectorization scheme have a considerable influence on the performance View full abstract»

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  • Modeling and performance evaluation of different CDMA schemes for terrestrial and satellite communication systems

    Publication Year: 1994 , Page(s): 338 - 342 vol.1
    Cited by:  Papers (1)
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    The paper deals with the modeling and performance evaluation of different code division multiple access schemes suitable for applications in terrestrial and satellite mobile communication networks. The paper is focused on the use of particular propagation channel models and the relative sensitivity of different demodulation schemes to their parameters. The main goal is to analyze how the increased interference level, typical of a multipath environment, can influence different demodulator architectures in different propagation conditions. Some issues concerning the characterization of the propagation channel models in the case of the RAKE receiver are also investigated and discussed View full abstract»

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  • Frequency and time division duplex techniques for CDMA cellular radio

    Publication Year: 1994 , Page(s): 309 - 313 vol.1
    Cited by:  Papers (3)  |  Patents (3)
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    A time division duplex (TDD) technique for use in code division multiple access (CDMA) cellular radio systems is investigated and compared with the performance results for frequency division duplex (FDD) CDMA systems. The TDD base station measures the impulse response of the channel (on the uplink) and uses a matched filter to the channel. It then pre-matches the signal it wishes to transmit on the downlink since its impulse response is identical. This eliminates any channel matched filter operations in the mobile unit and so reduces its complexity, although the base station complexity is increased slightly. Results indicate that FDD techniques provide a higher cell capacity than the equivalent TDD techniques. The advantage of a reduction in mobile station complexity, by using TDD, is offset by the poor error rate and cell capacity performances found for high speed mobile operation View full abstract»

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  • Receiver techniques for direct sequence spread spectrum ISM band radio LANs

    Publication Year: 1994 , Page(s): 376 - 380 vol.2
    Cited by:  Papers (1)
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    This paper presents the results of an investigation into the performance of DS spread spectrum ISM band radio LANs using BPSK modulation and matched filter receivers with short spreading sequences (one sequence per symbol). Differential and quasi-coherent systems were considered. The BER against normalised delay spread was estimated using Monte-Carlo techniques for the two receiver types. The results show that the use of quasi-coherent rather than differential techniques gives a significant increase in the maximum tolerable delay spread from 0.7 to 0.9 for combining diversity. However, for selection diversity the increase is insignificant, the maximum tolerable delay spread being around 0.4. The results also show that optimum system performance in noise is achieved when the normalised delay spread is between 0.05 and 0.3. For a transmission rate of 1 Mbit/s this is equivalent to a range in delay spread from 50 ns to 300 ns. This means that these systems will work well in all indoor environments View full abstract»

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  • Modulation and coding schemes for TDM/SS packet radio

    Publication Year: 1994 , Page(s): 549 - 553 vol.2
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    A novel frequency hopped spread spectrum packet radio communication system suitable for time division multiplexed, high speed indoor office wireless networks is proposed. The hopping is carried out at a logical level on the bit stream rather than physical hopping of the carriers. This on one hand eliminates phase problems associated with differential modulation along hopped carriers in frequency-selective fading channels, and on the other circumvents the need for agile frequency synthesizers. A coding strategy has been developed to provide the best error-rate performance under given channel conditions. System design issues are discussed and an example design is presented View full abstract»

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  • Spatial and temporal filtering for co-channel interference in CDMA

    Publication Year: 1994 , Page(s): 51 - 60 vol.1
    Cited by:  Papers (7)  |  Patents (2)
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    This paper provides a review of the challenges and opportunities that arise for improving the user capacity of spread spectrum multiple access (SSMA) or code division multiple access (CDMA) based on spread spectrum techniques. Co-channel interference (CCI) in CDMA is the most dominant factor in the limitation of user capacity, while the capacities of FDMA and TDMA capacities are primarily bandwidth limited. From an information theoretical viewpoint, however, an optimum multi-user receiver for CDMA can be derived by utilizing CCI as redundant information distributed among multiple accessing users. In practical channels such as personal, indoor, mobile radio communication channels, more feasible receivers are required to combat the multipath fading that causes estimation errors of the channel characteristics due to time variance. An overview of several CCI cancellation schemes for sub-optimum but practical multi-user receivers for CDMA is provided by classifying them in the temporal domain, the spatial domain, or in both domains View full abstract»

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  • Frequency hopped systems for PCS

    Publication Year: 1994 , Page(s): 105 - 114 vol.1
    Cited by:  Papers (3)
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    The application of frequency hopping methods to cellular and personal communication systems (PCS) is studied. The performance enhancements due to the use of frequency hopping (FH) is initially reviewed followed by a brief summary of previously designed cellular/PCS systems that have incorporated FH methods. A slow frequency hop (SFH) prototype (which incorporated a hybrid form of multiple access, in particular slow frequency hopping CDMA combined with time division multiple access (TDMA)) was developed for PCS applications is then described. Performance results using the SFH prototype in laboratory and field trials are provided. These results demonstrate the excellent performance that may be obtained in PCS environments using a SFH architecture which has a complexity level that is suitable for PCS implementation View full abstract»

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  • A novel, on-board satellite spread spectrum correlator

    Publication Year: 1994 , Page(s): 362 - 366 vol.2
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    Currently, there is much research activity in the area of satellite on-board signal processing. This interest stems from the potential to use the space segment as more than just a transponder. On-board processing would improve the overall link budget and allow such features as signal re-routing to be exploited. Typically, most multiple access schemes to the satellite use either time or frequency division techniques. However, spread spectrum multiple access techniques are gaining in popularity and can, in certain instances, provide a viable alternative to the above methods. As with any spread spectrum system, the implementation of the correlator dictates, to an extent, the overall system performance. This paper describes a novel implementation of the correlation function which would be suited to space payloads and in addition considers the various design constraints and benefits. It then reports on the experimental results obtained using a prototype device operating in the C-band region with a spreading code rate of up to 500 Mbit/s. Implementation of the design in high temperature superconducting (HTS) technology is then discussed and results for an HTS delay line fabricated on a 50 mm diameter wafer presented View full abstract»

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  • Performance analysis of mobile positioning using existing CDMA network

    Publication Year: 1994 , Page(s): 190 - 192 vol.1
    Cited by:  Papers (2)
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    Using spread spectrum signals transmitted from each cell in the CDMA network it is possible to estimate a mobile's location. This location information may be used for directing users to a required destination. Possible uses are emergency calls and fleet management. The performance of a mobile positioning application using the CDMA (code division multiple access) network is investigated through the use of simulation. A CDMA network was first proposed by QUALCOMM and performance tests have been successful. As an additional feature, mobile positioning can be applied to the network at no major hardware cost View full abstract»

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  • New technology and radio regulation

    Publication Year: 1994 , Page(s): 1 - 3 vol.1
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    Historical and current examples show dependence of growth of radiocommunication and new services on international radio regulations for allocation of frequency bands and control of interference. Recent ITU World Radiocommunication Conferences allocated frequency bands for future growth of mobile services, new mobile satellite applications and digital sound broadcasting. An increasingly congested spectrum and complex communication environment challenge the catalytic role of radio regulation. Spread spectrum technology may represent a critical contribution providing its performance and benefits for spectrum use are well understood View full abstract»

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  • Error-correcting coding for CDMA systems

    Publication Year: 1994 , Page(s): 22 - 26 vol.1
    Cited by:  Papers (6)
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    The preselected title of this paper highlights the misconception that most engineers, sometimes even communication specialists, still harbor concerning the central role of channel coding in communication system performance. More properly descriptive terms are “error-preventing”, “error-protecting”, or the more common “error control.” The reason is that in modern communication systems, designed according to the norms of information theory, coding is an integral part of the modulation process and the optimum modulator and demodulator combine the coding and modulation, as well as the decoding and demodulation, processes into one function at both the transmitter and the receiver. This viewpoint has become commonplace for modulation systems which operate in additive Gaussian noise, with relatively high signal-to-noise ratios, at bit rates considerably greater than their transmission bandwidth. For such systems and channels, the evolution and general acceptance of trellis coded modulation (TCM) has demonstrated how modulation and channel coding can be integrated to provide superior performance View full abstract»

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  • Rake reception for a CDMA mobile communication system with multipath fading

    Publication Year: 1994 , Page(s): 98 - 104 vol.1
    Cited by:  Papers (1)  |  Patents (2)
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    The performance of a rake receiver for direct-sequence (DS) spread spectrum communications on multipath fading channels depends on the number and type of multipath components present at the channel output. The focus in this paper is on noncoherent combining of the outputs of the taps of the rake receiver in a code-division multiple-access (CDMA) system that employs DS spread spectrum with binary DPSK data modulation. It is shown that the advantages and disadvantages of a rake receiver, as compared with a standard correlation receiver, depend greatly on the fading characteristics of the individual multipath components. In general, rake receivers are more appropriate for DS systems with a smaller number of chips per data symbol and for channels that have only diffuse, Rayleigh fading multipath components. On the other hand, a correlation receiver is preferred for DS systems with a large number of chips per data symbol if the channel has a strong specular multipath component in addition to one or more diffuse components. The probability of error on the channel is determined as a function of the chip rate for doubly selective fading channels, and the pairwise error probability is evaluated for a CDMA system with binary convolutional encoding and Viterbi decoding. The effects of the Doppler spread and the interleaving depth on the performance of the system and the choice of chip rate are discussed View full abstract»

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  • Novel magic-square codes for hiding DS/SS signals from intercept receivers

    Publication Year: 1994 , Page(s): 484 - 488 vol.2
    Cited by:  Papers (1)
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    The interest in operating spread spectrum (SS) modulation systems for quiet or covert co-channel communications is growing rapidly. The military require good low probability of intercept (LPI) performance whilst the civil mobile radio community is actively seeking additional spectrum utilisation efficiency through techniques such as co-channel DS/SS multiple access. Previously reported statistically-based chip coding showed considerable promise in its ability to suitably smear the PSDF of the output from a delay-and-multiply (DM) processing receiver thus hiding the chip-line structure. A novel code set has now been investigated in which DS/SS reference sequences are taken from selected numerical vector components of “magic square” arrays. Computer simulation shows that these magic codes produce excellent spectral sidelobe and chip-rate line suppression in a DM receiver. These results are compared with those previously obtained with temporal and/or spectral domain statistical chip code designs View full abstract»

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