Showing papers by "Qualcomm published in 1990"

Very low rate convolution codes for maximum theoretical performance of spread-spectrum multiple-access channels

Abstract: A spread-spectrum multiple-access (SSMA) communication system is treated for which both spreading and error control is provided by binary PSK modulation with orthogonal convolution codes. Performance of spread-spectrum multiple access by a large number of users employing this type of coded modulation is determined in the presence of background Gaussian noise. With this approach and coordinated processing at a common receiver, it is shown that the aggregate data rate of all simultaneous users can approach the Shannon capacity of the Gaussian noise channel. >

Diversity receiver in a cdma cellular telephone system

Abstract: A spread spectrum receiver subsystem for utilization in a CDMA cellular telephone having a searcher receiver (44) for scanning the time domain so as to use the PN processing gain and time discrimination properties of spread spectrum coding to determine the location in the time domain and the received signal strength of multiple receptions of a pilot signal traveling upon one or more physical propagation paths to reception The searcher receiver (44) provides a control signal indicative of the received pilot signals of greatest strength and corresponding time relationship A data receiver (40, 42) receives spread spectrum communication signals accompanying each received pilot signal and is responsive to the searcher control signal for acquiring and demodulating a spread spectrum communication signal, concomitant with the pilot signal of greatest signal strength, and thus providing a corresponding encoded output signal bearing information

Increased capacity using CDMA for mobile satellite communication

Abstract: The performance of a spread-spectrum CDMA (code-division multiple access) system in a mobile satellite environment is analyzed. Comparisons to single-channel-per-carrier FDMA systems are presented which show that the CDMA approach provides greater capacity. Results from computer simulations, laboratory tests, and field tests of a prototype modem are also presented. The tests results show excellent performance of the modem in the mobile environment and also the feasibility of the spread-spectrum approach to satellite mobile communications. >

Current carrier tractor-trailer data link

Abstract: An apparatus and method for providing communication of information between a truck tractor and trailer via existing truck wiring At least one transmitter is located in each trailer for generating a unique identification signal representative of trailer identification information corresponding to the trailer in which the transmitter is located, modulating the identification signal, and providing the modulated identification on an existing truck power bus coupling the tractor and trailer A receiver is located in the tractor for receiving each modulated identification signal on the power bus, demodulating each modulated identification signal and providing each demodulated identification signal to a mobile communications terminal located in the tractor for transmission to a central facility The system may further include the transmission of trailer status or load status information by the transmitter to the receiver in a similar manner as the identification information

Direct digital synthesizer driven phase lock loop frequency synthesizer with hard limiter.

Abstract: Synthetiseur de frequence (100, 200) utilisant un synthetiseur numerique direct (SND) (102, 216) dont le signal de sortie est filtre par un filtre passe-bande (110, 218) et dont l'amplitude peut etre limitee par un limiteur (111, 219) pour reduire le bruit parasite. Frequency synthesizer (100, 200) using a direct digital synthesizer (DDS) (102, 216) whose output signal is filtered by a bandpass filter (110, 218) and the amplitude can be limited by a limiter (111, 219) to reduce the noise. Dans une variante, le SND (102) est relie a une boucle de verrouillage de phase (114) qui recoit le signal de reference genere par le SND et un signal de division par N pour generer une frequence de sortie determinee par un signal de division par N. Dans une deuxieme variante, le SND (216) est incorpore dans la voie de reaction d'une boucle de verrouillage de phase (202) ayant une frequence de sortie determinee par une frequence de reference d'entree et par la dimension de l'etape SND commandee par un signal de regulation de frequence. Alternatively, the SND (102) is connected to a phase locked loop (114) which receives the reference signal generated by the DDS and a division signal by N to generate an output frequency determined by a signal dividing N. In a second variant, the SND (216) is incorporated in the feedback path of a phase lock loop (202) having an output frequency determined by an input reference frequency and the size of the DDS step controlled by a frequency control signal. Des diviseurs en option (112, 214, 219) peuvent etre ajoutes, dans les deux variantes, a la voie de reaction pour modifier encore la frequence de sortie du syhthetiseur (100, 200). Optional dividers (112, 214, 219) can be added, in both variants, the reaction path to further modify the syhthetiseur output frequency (100, 200).

Method and apparatus for generating super-orthogonal convolutional codes and the decoding thereof

Abstract: An encoder and decoder for generating and decoding convolutional codes of enhanced orthogonality. In an exemplary embodiment the encoder includes a K bit length shift register for receiving an input serial stream of information bits and providing for each input bit a K bit parallel output to an orthogonal code sequence generator where one of 2 K-1 symbol sequences is generated with each symbol sequence of a K-2 symbol length. The encoded symbol stream is decoded using an orthogonal function generator driven by a K-2 binary counter to generate all possible symbol sequences for comparison with each received symbol sequence. The output of the comparison is Viterbi decoded to provide the original stream of information bits. Corresponding methods of encoding the information bits and decoding of the symbol sequences are included.

The OmniTRACS/sup R/ Mobile Satellite Communications and Positioning System

Abstract: The OmniTRACS two-way mobile satellite communications and position reporting system is described. This system provides message communications between moving vehicles and their operations centers. Me mobile unit directly communicates with a central hub facility which provides system control, message processing and archival, and point-to-point communications with the operations centers. QASPR, a dual satellite positioning system giving accuracies in the United States to about 1/4 mile, is described. Experiences and benefits to the trucking industry are also highlighted.

Direct digital synthesizer/direct analog synthesizer hybrid frequency synthesizer

Abstract: A digital/analog hybrid frequency synthesizer having a digital frequency synthesizer for digitally generating an analog output signal of a predetermined frequency within a frequency range of f to f+Δf; an input stage analog frequency synthesizer for, receiving the digital frequency synthesizer output signal and I analog input stage input signals, each input stage input signal separated in frequency from a next one by a frequency increment of Δf wherein a first one and a last one of the input stage input signals are respectively of a frequency of f A and f A +(I-1)Δf, selecting one input stage input signal from the input stage input signals, mixing the selected input stage input signal with the digital frequency synthesizer output signal and providing a resultant input stage output signal; and an output stage analog frequency synthesizer for, receiving the input stage output signal and K analog output stage input signals, each output stage input signal separated in frequency from a next one by a frequency increment of IΔf wherein a first one and a last one of the output stage input signals are respectively of a frequency of f N and f N +(K-1)IΔf, selecting one output stage input signal from the output stage input signals, mixing the selected output stage input signal with the input stage output signal and providing a resultant output stage output signal. Additional intermediate frequency stages may be employed to facilitate greater bandwidth expansion.

Soft handoff in a cdma cellular telephone system

Abstract: In a cellular telephone system a system for directing communications between a mobile user (18) and cell-sites (12, 14, 16) as a mobile user (18) changes cell-site service areas. The mobile user (18) includes an apparatus (40, 46) for, while in communication with another system user via one cell-site, determining a transition of the mobile user (18) from the cell-site service area to the service area of another cell-site. The system includes circuitry (78) responsive to the indication for coupling communications between the mobile user and the other system user via the new cell-site while the mobile user also remains in communication with the system user via the first cell-site. The system further includes apparatus (78) responsive to the coupling of the communications between the mobile user and the other system user via the new cell-site for terminating the communications between the mobile user and another system user via cell-site with communications continuing between the mobile user and the system user via the new cell-site.

Practical applications of TCM

Abstract: The first VLSI implementation of a decoder for multiple-signal (pragmatic) trellis-coded modulation (TCM) is described. Integrated on the same device is an encoder and a decoder for a variable rate binary code. The IC discussed is a 64-state rate 2/3 or 3/4 (used in conjunction with 8 and 16 PSK modulation) TCM decoder. The decoder is also accompanied by a K=7 trellis encoder. Integrated on the TCM decoder is a variable-rate Viterbi decoder (rates 1/2, 3/4, 7/8, 1/3). The chip has been manufactured and tested. The performance in rate 2/3 8 PSK and rate 3/4 16 PSK is shown graphically. Included in each figure is the uncoded performance in addition to the simulated and measured data of the chip. The performance of the chip in the rest of the models is shown. The die size is 320 mils on a side. The device contains 17800 transistors and was fabricated in a state-of-the art 1.0 mu m process. The device has attained clock speeds above 30 MHz under nominal conditions. The power consumption at 10 Mbit/s is less than 0.75 W. >

A 25 MHz Viterbi FEC codec

Abstract: An implementation of a single-chip Viterbi codec which incorporates many features into a single device is described. The device also implements a unified trellis decoder using the industry standard convolutional codes to achieve good coding gain using phase-shift keying (PSK) trellis encoding. The level of integration and the device speeds present a new upper bound on system performance based on convolutional coding systems. The device was produced by silicon-compiler-based tools in 15 months. >

A second anniversary operational review of the OmniTRACS(R): The first two-way mobile Ku-band satellite communications system

Abstract: A novel two-way mobile satellite communications and vehicle position reporting system that is currently operational in the United States and Europe is described. The system characteristics and service operations are described in detail. Technical descriptions of the equipment and signal processing techniques are provided.

Ku-band MMIC upconverter for mobile satellite communications

Abstract: A complete Ku-band MMIC (monolithic microwave IC) upconverter is developed for use in a high-volume commercial two-way mobile satellite communication system. Both FET and diode mixer topologies were explored. An output power of 20 dBm is achieved for the diode mixer topology, and 19 dBm is achieved for the FET mixer topology. Both achieved LO (local oscillator) rejection >25 dB and 2IF+LO rejection >20 dB. This single chip replaces 80 discrete components. The area occupied by the upconverter function has been reduced from 4700 mm/sup 2/ to 7.6 mm/sup 2/. >

Dual satellite navigation method and system

Abstract: A method and system for determining the position of an object (12) using a fixed station (10) and a plurality of earth orbit satellites (S1, S2) whose positions are known. Separate periodic signals (20, 22) are transmitted from the fixed station (10) via first and second satellites (S1, S2) to the object (12) 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 relative time difference in propagation of the signals traveling two different paths to the object. The object (12) transmits via the first satellite (S1) a return signal (24) 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 (10), 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 (24), along with the measured relative time difference sent back on the return signal (24), is used to calculate the distances between the first and second satellites (S1, S2) to the object (12). From these distances the position of the object (12) is calculated.

A description of QUALCOMM Automatic Satellite Position Reporting (QASPR(R)) for mobile communications

Abstract: Two satellite position reporting has been introduced into the OmniTRACS mobile satellite communication system This system significantly improves position reporting reliability and accuracy while simplifying the terminal's hardware The positioning technique uses the original OmniTRACS TDMA timing signal formats in the forward and return link directions plus an auxiliary, low power forward link signal through a second satellite to derive distance values The distances are then converted into the mobile terminal's latitude and longitude in real time A minor augmentation of the spread spectrum profile of the return link allowed the resolution of periodic ambiguities The system also locates the two satellites in real time with fixed platforms in known locations using identical mobile terminal hardware Initial accuracies of 1/4 mile have been realized uniformly throughout the USA using a satellite separation of 22 degrees and there are no dead zones, skywaves, or cycle slips as found in terrestrial systems like LORAN-C