Showing papers by "Qualcomm published in 1991"

On the capacity of a cellular CDMA system

Abstract: It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

Abstract: It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

System and method for generating signal waveforms in a CDMA cellular telephone system

Abstract: A system and method for communicating information signals using spread spectrum communication techniques. PN sequences are constructed that provide orthogonality between the users so that mutual interference will be reduced, allowing higher capacity and better link performance. With orthogonal PN codes, the cross-correlation is zero over a predetermined time interval, resulting in no interference between the orthogonal codes, provided only that the code time frames are time aligned with each other. In an exemplary embodiment, signals are communicated between a cell-site and mobile units using direct sequence spread spectrum communication signals. In the cell-to-mobile link, pilot, sync, paging and voice channels are defined. Information communicated on the cell-to-mobile link channels are, in general, encoded, interleaved, bi-phase shift key (BPSK) modulated with orthogonal covering of each BPSK symbol along with quadrature phase shift key (QPSK) spreading of the covered symbols. In the mobile-to-cell link, access and voice channels are defined. Information communicated on the mobile-to-cell link channels are, in general, encoded, interleaved, orthogonal signaling along with QPSK spreading.

Cdma microcellular telephone system and distributed antenna system therefor

Abstract: A code division multiple access (CDMA) communication system in which cellular techniques are utilized in a wireless Private Branch Exchange (PBX) environment. A microcellular arrangement is defined in which a base station (10) communicates user information signals using CDMA communication signals with subscriber terminals. A distributed antenna system (26) is utilized in the system to provide multipath signals which facilitate signal diversity for enhanced system performance.

Adaptive block size image compression method and system

Abstract: An image compression system and method for compressing image data for transmission Each block and corresponding sub-blocks of pixel data is subjected to a discrete cosine transform (DCT) operation Varying levels of sub-blocks of resulting corresponding transform coefficients are selected for construction into a composite transform coefficient block corresponding to each input block of pixel data The selection of transform coefficient block size for the composite block is determined by a comparison process between transform block and sub-block coding efficiency The composite block is variable length coded to further reduce bit count in the compressed data

On the system design aspects of code division multiple access (CDMA) applied to digital cellular and personal communications networks

Abstract: A breadboard CDMA digital cellular system was developed by QUALCOMM and demonstrated in San Diego in November 1989. In February 1990, an extensive technical field trial was carried out in midtown Manhattan with NYNEX Mobile. For the purposes of carrying out the CDMA trials and demonstrations, a total of three cell-site and two mobile prototype units were built. In each case, the demonstration system utilized two actual cell sites and one mobile and included A/B comparisons with the commercial analog system. The fundamental features of CDMA, such as power control and soft handoff, were tested and proven in a variety of field conditions. The authors describe the CDMA signal and waveform design, the CDMA system design, CDMA power control, and additional features of CDMA. >

Spread spectrum transmitter power control method and system

Abstract: A power control system for a cellular mobile telephone system in which system users communicate information signals between one another via at least one cell site using code division multiple access spread spectrum communication signals. The power control system controls transmission signal power for each cellular mobile telephone in the cellular mobile telephone system wherein each cellular mobile telephone has an antenna, transmitter and receiver and each cell-site also has an antenna, transmitter and receiver. Cell-site transmitted signal power is measured as received at the mobile unit. Transmitter power is adjusted at the mobile unit in an opposite manner with respect to increases and decreases in received signal power. A power control feedback scheme may also be utilized. At the cell-site communicating with the mobile unit, the mobile unit transmitted power is measured as received at the cell-site. A command signal is generated at the cell-site and transmitted to the mobile unit for further adjusting mobile unit transmitter power corresponding to deviations in the cell site received signal power. The feedback scheme is used to further adjust the mobile unit transmitter power so as to arrive at the cell-site at a desired power level.

High dynamic range closed loop automatic gain control circuit

Abstract: A closed loop automatic gain control (AGC) circuit with high dynamic range capabilities having an amplifier circuit for receiving an input signal, which is susceptible to variations in signal power, and a control signal. The amplifier circuit is responsive to the control signal for amplifying the input signal at a gain level corresponding to the control signal so as to provide a corresponding output signal. A measurement circuit is coupled to the amplifier means for measuring logarithmic signal power of the amplified input signal and providing a corresponding linear measurement signal. An integration circuit is included for receiving the measurement signal, and a reference signal which corresponds to a desired signal power of the output signal. The integration circuit integrates with respect to time the difference between the measurement signal and the reference signal, and generates the control signal which corresponds to the result of the integration.

Dual satellite navigation system and method

Abstract: A system and method for determining the position of an airborne object, using a fixed station and a pair of earth orbit satellites whose positions are known. Separate periodic signals are transmitted from the fixed station via the first and second satellites to the object whose position is to be determined. The phase offset in periodic characteristics of the periodic signals as received from the first and second satellites is measured at the object. The phase offset corresponds to a realtive time difference in propagation of the signals traveling two different paths to the object. The object transmits via the first satellite a return signal indicative of the measured relative time difference. This return signal is activated some time in the future according to the object local time, which is slaved to receipt of the periodic signal sent through the first satellite. This future time is the start of the particular time period as decided by the fixed station's schedule. At the fixed station, an instantaneous round trip delay, determined by the time offset of the current transmission clock time relative to the receive clock time of reception of the return signal, along with the measured relative time difference sent back on the return signal, is used to calculate the distances between the first and second satellites to the object. From these distances, along with the combined altitude of the object with the distance from the surface of the earth to the center of the earth, the position of the object is calculated.

Viterbi decoder bit efficient chainback memory method and decoder incorporating same

Abstract: A decoder for decoding trellis coded data in which the received signal is assigned a sector value corresponding to the phase of the signal in accordance with a predetermined signal space sectorization format. A Viterbi decoder is used to reconstruct from the received signal an estimate of a data bit that was coded for transmission. This estimate is re-encoded and provided to a trellis output mapper along with the sector value. The trellis mapper in response to the input re-encoded estimate and sector value provides an estimate of an an uncoded data bit transmitted with the coded data bit.

Efficient motion planners for nonholonomic mobile robots

Abstract: Deals with the problem of motion planning for a car-like robot (i.e. a nonholonomic mobile robot whose turning radius is lower bounded). The authors present a fast and exact planner based upon recursive subdivisions of a collision-free path generated by a lower-level geometric planner which ignores the motion constraints. The resultant trajectory is optimized to give a path which is of near-minimal length in its homotopy class. The claims of high speed are supported by experimental results for several implementations which assume different geometric models of the robot. >

Linear gain control amplifier

Abstract: An amplification circuit having a compensation circuit (10) for receiving a control signal and generating a corresponding compensation signal according to predetermined compensation characteristics. An input amplification circuit (12) is provided for, receiving an input signal and the compensation signal, amplifying the input signal at an input gain level determined by the compensation signal and providing a corresponding input amplification circuit output signal. A filter element (14) receives and filters unwanted frequency components from the input amplification circuit output signal. An output amplification circuit (16) is provided for, receiving the filtered input amplification circuit output signal and the compensation signal, amplifying the filtered input amplification circuit output signal at an output gain level determined by the compensation signal and providing a corresponding output amplification circuit output signal.

The application of a novel two-way mobile satellite communications and vehicle tracking system to the transportation industry

Abstract: A two-way mobile satellite communications and vehicle position reporting system currently operational in the US and Europe is described. The system characteristics and service operations are described in detail, and technical descriptions of the equipment and signal processing techniques are provided. The application of this technology to the land transportation industry, specifically the over-the-road truckload motor carrier segment, and the types of benefits being derived by the current users are described. >

Process for fabricating a MMIC hybrid device and a transceiver fabricated thereby

Abstract: The substrate for implementation of MMIC devices comprises alumina with feedthrough holes drilled therein to provide conduct ion paths from the top surface of the substrate to the bottom surface. A high-temperature to low-temperature fabrication process is used to form circuit traces and components upon the substrate. Each of the thick film deposition processes is followed by a firing process to remove organic materials from the deposited material and to secure the material to the substrate or previous layer. A Ku-band transceiver constructed using the process includes the attachment of six discrete, unpackaged MMIC's and one HEMT. All other devices and traces are patterned on the substrate and the discrete components are directly attached to pads on the substrate.

Specifying Local Oscillator Phase Noise Performance: How Good is Good Enough?

Abstract: Definitive criteria are provided for specifying local oscillator phase noise performance for use in communication systems. In the absence of such criteria, many oscillators tend to be either under or over-specified. The emphasis is on digital modulation and demodulation, but analog communications are also considered. LO phase noise is analyzed for loss in demodulator performance, and also for impact on the modulation process. The results may be used to select an appropriate oscillator, or to tailor the noise characteristics of a frequency synthesizer design.

Synchronization issues in ocean telemetry

Abstract: The synchronization problem over fading dispersive channels is discussed. Although stated in general terms, the results are equally applicable to sonar and undersea problems in which the propagation medium has significant multipath spread and fluctuation rate. Optimum detection over such channels requires a perfect knowledge of the channels' scattering functions, which completely characterize the behavior of fading dispersive channels. Lack of such knowledge may result in performance degradation. A closed-form expression for the probability of false alarm and probability of detection is given, and a set of curves is provided to demonstrate the amount of degradation due to mismatch conditions. A parallel structure to achieve acquisition is suggested, and its performance is investigated. A performance measure for the synchronizer in this mode is defined. Upper and lower bounds on the performance measure are derived. The effect of various parameters, such as the signal-to-noise ratio, pulse width and modulation, number of pulses, spread of the channel, and the size of the resolution cell on the performance of the synchronizer is investigated. After achieving acquisition, the system needs to switch to the tracking mode. An optimum closed-loop symbol synchronizer is developed. >

Ku-Band MMIC Transceiver for Mobile Satellite Communications

Abstract: A fully integrated Ku-Band transceiver utilizing state-of-the-art GaAs MMIC components has been developed for use in a commercial two-way mobile satellite communication system. The current transceiver, with over 500 discrete components requiring an area of 50 square inches, has been reduced to six MMIC chips and an area of 4.2 square inches. The extensive use of integration maximizes the inherent advantages of size, weight, cost, and reliability. The MMIC's are integrated onto an alumina substrate to eliminate the cost associated with individual microwave quality packages. To further reduce the cost, state-of-the art techniques in thick film are being used for the metallization of the substrate. After a brief description of the OmniTRACS® mobile communication system, this paper will describe the Ku-Band transceiver, the alumina substrate, and the individual GaAS MMIC's.

Universal frequency reuse: the CDMA advantage in capacity for digital cellular radio

Abstract: Summary form only given, as follows. Interference among simultaneous users presents the primary limitation on capacity of all multiple access communication systems. In frequency-division-multiple-access (FDMA) and time-division-multiple-access (TDMA) cellular systems, interference is controlled by assigning disjoint frequency or time slots to all users in the same cell and disjoint frequency bands to adjacent cells, but to increase capacity, frequency bands are reused for sufficiently separated cells. These techniques lead to a hard limit on capacity and a tradeoff between frequency reuse and the C/I levels which can be tolerated. With direct sequence spread spectrum CDMA, frequency reuse is universal, with the same band utilized by all users over all cells with all user signals appearing as noise to all other users' receivers, progressively more attenuated with the distances involved. Careful analyses of both forward and reverse link interference lead to capacity estimates considerably higher than those for FDMA and TDMA systems, as well as a soft capacity limit unattainable with the more conventional systems. >

"On-wafer Testing Issues for the 90's and Beyond."

Abstract: The panel session had a theme "On-wafer Testing Issues f o r the 90's and Beyond." member on what they feel are some of the most important on-wafer testing issues that remain, and what solution approaches they andlor their company may be involved with. We try to look into the future and predict on-wafer testing issues and methods that we will be facing through the turn of the century. explore just how mature on-wafer testing is (now that sessions have been devoted to the subject), and to identify key problem areas that conference attendees may want to consider addressing in their own future work. The format was a f ive minute presentation by each panel

A hybrid approach toward model-based texture segmentation

Abstract: The authors develop a hybrid texture segmentation algorithm, combining statistical (maximum likelihood/maximum a posteriori) and structural (local consensus) classification techniques. This algorithm exhibits several advantages over traditional algorithms based solely on statistical models; (i) homogeneity and integrity of each region in the texture mosaic can be included implicitly by a local voting scheme, in addition to explicit modeling through Gibbs random fields, and (ii) modified maximum likelihood solution of the hybrid segmentation algorithm provides a better initial estimate of region boundaries which can be used in a maximum a posteriori segmentation algorithm. With this initial estimate, an iterative, semideterministic relaxation algorithm, called mean field annealing, is used to locate the nearly global optimum solution efficiently. >

Image data compression using adaptive block size selection

Abstract: Systeme et procede de compression d'images permettant de comprimer des donnees d'images destinees a etre transmises. System and image compression method for compressing image data to be transmitted. Chaque bloc et les sous-blocs correspondants de donnees de pixel sont soumis a une operation (10, 12) de transformation en cosinus discrete (TCD). Each block and corresponding sub-blocks of pixel data are subjected to an operation (10, 12) of discrete cosine transform (DCT). Des niveaux variables de sous-blocs (QC16, QC8, QC4, QC2) de coefficients de transformation correspondants obtenus sont selectionnes afin de permettre la construction d'un bloc de coefficients (QC) de transformation composite correspondant a chaque bloc d'entree de donnees de pixels. Varying levels of sub-blocks (QC16, QC8, QC4, QC2) corresponding transform coefficients obtained are selected to allow the construction of a coefficient block (QC) of composite processing corresponding to each data input block pixel. La selection de la dimension du bloc de coefficient de transformation permettant d'obtenir le bloc composite est determinee selon un procede de comparaison entre un bloc de transformation et l'efficacite de codage des sous-blocs (20, 26, 32). The selection of the dimension of the transform coefficient block to obtain the composite block is determined according to a comparison process between a processing block and the coding efficiency of sub-blocks (20, 26, 32). Le bloc composite est code en longueur variable (56) afin de reduire davantage le nombre de bits dans les donnees comprimees. The composite block is coded in variable length (56) to further reduce the number of bits in the compressed data.

On a consistency issue in multiresolution stereo

Abstract: The authors address an important problem in the multiresolution (pyramid) approach to the correspondence problem in computational vision: the consistency between the domain and range (disparity) pyramids. Consistency guarantees the validity of pyramidal implementation. The authors investigate some previous approaches in stereo vision and present a general framework in multiresolution stereo. Simulations on natural stereo pairs exhibit results that are superior with this consistency check. >

System for generating signal waveforms in a CDMA cellular telephone system

Abstract: A modulation system for use in a system of spread spectrum communication employing a scheme soft handover capable of switching between cell sites (12, 14) as dictated by the signal intensity, wherein said intensity signal is derived from a pilot signal, the system comprising: means (200) for generating a first orthogonal sequence signal corresponding to one of a plurality of orthogonal binary sequences; means (196, 198) for generating a pseudonoise signal corresponding to a binary PN sequence (PN); means (202, 204) for combining orthogonal sequence signal and said signal and said first PN providing a first signal resulting modulation for said pilot signal.