Abstract: A structure (24) includes a plurality of repeaters (34), each having a primary transceiver (36) and a secondary transceiver (38) electromagnetically located upon a clear side (30) and a blocked side (32), respectively, of a barrier (26). Each primary transceiver (36) and secondary transceiver (38) communicate using an intra-repeater signal (46). Each intra-repeater signal (46) is output from its respective primary transceiver (36), combined with other intra-repeater signals (46) by a combiner (50), passed over a communication infrastructure (22), separated from other intra-repeater signals (46) by a separator (54), and input to its respective secondary transceiver (38). Optionally, each intra-repeater signal (46) may be retrieved from the communication infrastructure (22), separated from other intra-repeater signals (46) by a separator (62), amplified by a bandpass amplifier (64), combined with other intra-repeater signals (46) by a combiner (66), and inserted back into the communication infrastructure (22).

Abstract: A wireless transmitter is disclosed that mitigates the 3 MPH effect, which is the phenomenon of poor received signal quality at a wireless receiver because neither transmit power control nor data interleaving are capable of overcoming the effects of Rayleigh fading. Some of the wireless transmitters disclosed mitigate the 3 MPH effect by having the transmit antenna move mechanically, as on a turntable. Other transmitters achieve the same effect by moving the phase center of the transmitted signal between two or more stationary antennas. The phase center of the transmitted signal can be made to move between stationary antennas by electronically manipulating and varying the amount of signal radiated by each antenna. In an illustrative embodiment of the present invention, a signal to be transmitted is switched back and forth between two stationary antennas at a rate that creates virtual motion as observed by the wireless terminal sufficient to remove the wireless terminal from the depths of the 3 MPH effect.

Abstract: A radio communication system between a mobile station on a vehicle and a stationary station in which a uniform field intensity is obtained in a direction of a width of a road so that a good communication can be performed irrespective of a position of the vehicle on the road. A mobile station is provided on the vehicle. A stationary station communicating with the mobile station includes at least one pair of antennas located with the road therebetween so that the antennas generate an electric field having a substantially uniform intensity in a direction of a width of the road.

Abstract: A radiating coaxial cable comprises an inner conductor, a layer of cellular foam dielectric material surrounding the inner conductor, and a single, continuous, corrugated outer conductor surrounding the dielectric foam layer in direct contact with it. The outer conductor forms at least one row of slots which are configured to produce a radiated field polarized perpendicularly to the axis of the cable to substantially avoid the radiation of a field polarized parallel to the axis of the cable and to provide coupling energy between the interior of the cable and the slots. In this way a substantially constant near-field pattern is produced along the length of the cable across the bandwidth of the cable.

Abstract: Realistic models and processes for simulation of wireless information transport systems are provided which replicate all time and frequency dynamics effects on stationary and mobile communications systems. The preferred embodiment is a realsitic modeling apparatus for simulation of wireless information transport systems comprising a data entry module, a communications traffic selection module, a driver database, and voice and data input modules furnishing a simulation input to a network simulation module. The network simulation module having communications realism effects, a DIS structure, a channel error-burst model to transmit random errors, and a multipath modeling module to integrate deterministic and stochastic effects.

Abstract: A radio transmission system comprises a phased-array radio apparatus for optimizing reception in a multipath transmission environment. In the phased-array radio apparatus, phase shifting is performed after down-conversion of received RF signals. Phase control and beam-forming are simple. By applying a zero-IF or low-IF receiver structure, the complete structure can easily be fully integrated.

Abstract: A multiple access digital transmission system including a transmitter for transmitting at least one modulated data stream, and at least one receiver for receiving, via a multipath transmission channel, a transmitted signal which includes the modulated data streams. The receiver includes a resolver for resolving at least one path for at least one multipath received modulated data stream and a channel estimator for estimating channel path delays in the received modulated data streams. The receiver includes a generator for generating an interference reduced signal from the received signal, the interference reduced signal being fed to the channel estimator.

Abstract: The present invention provides a device and method in multi-access communications system for reliably receiving burst transmissions from users in the presence of narrow band interference. The adaptive interference suppresser incorporates adaptive elements that are updated using a predetermined adaptation algorithm. These adaptive elements are stored in memory at the end of the burst transmission for reuse in receiving a next burst transmission.

Abstract: A radio frequency communication system utilizing a radiating transmission line is disclosed. During normal operation, a mobile communication unit near the radiating transmission line can communicate with other mobile communication units near the transmission line as well as with the base station. The communication system is redundant in that if a portion of the communication system fails such that communication signals cannot be communicated through the fault the communication system will continue to operate and communication signals from any mobile communication units near the radiating transmission line will be transmitted and received from the base station. The communication system is particularly suited for use in underground mines in which event the base station can be located at the surface, and the mobile communication units are generally located in the mine shafts.

Abstract: Method and apparatus for using a plurality of correlators to improve an estimate of direct signal arrival time by identifying features of a correlation function at and adjacent to the correlation peak. In a first embodiment, the errors in location of the center point of a correlation function R(.tau.), formed by the incoming composite signal and a stored copy of the expected signal, are assumed to be strongly correlated for narrow sample spacing and wide sample spacing of the correlation function. In a second embodiment, multipath signal strengths and phases are estimated, using multiple sampling of the correlation function R(.tau.). This approach assumes that path delays of the direct signal and of the multipath signals can be determined separately.

Abstract: Briefly described, the present invention is a circuit for detecting and indicating a level of interference on a high frequency angular modulated signal. This circuit includes a logarithmic amplifier for receiving high frequency angular modulated signals and for providing a logarithmic amplifier output in response thereto. Next, the angular modulated signals are detected to determine a level of associated FM modulation thereof. Finally, a processor, programmed to distinguish those high frequency spectrum components due to interference from those due to other sources, determines a carrier to interference ratio. Of note, when the level of FM modulation at the logarithmic amplifier input exceeds a predetermined threshold, however, the associated carrier to interference ratio is ignored.

Abstract: Mobile radio receivers in a broadcasting system having more than one transmission channel sending the same programs use time diversity to prevent service outages during periods when none of the channels can be received.

Abstract: A low complexity model based channel estimator is disclosed for use by a receiver in Rayleigh fading environments. The receiver contains at least one channel state estimator which uses an auto regressive model for channel variations. The channel state estimates are initialized by using at least preliminarily detected symbols. The receiver also contains a data detector which uses the received signal and the channel estimate, or a function thereof, delivered by at least one channel estimator to detect the transmitted symbols.

Abstract: A system for mitigating the effect of fading in a digital communication system. Deep signal nulls occur when signals from multiple paths are precisely aligned in amplitude and phase canceling the signal at the receiving antenna and creating a fade. In an indoor system, moving either transmitter or receiver a short distance can shift a fade away from the frequency of interest. This invention provides an actual or perceived movement of an antenna such that the effects of fading can be averaged over a time interval. The signal processing capability of modern digital transceivers can correct errors due to the time varying fades using the present invention. Thus, a dual-antenna element using the system of this invention can provide diversity receive and transmit paths to maintain capacity. The present invention may also provide improved capacity to due enhanced stability in power control.

Abstract: A cellular base station (10) in a digital cellular system employs transmitting circuitry in which voice signals (15) are processed at a low frequency level (12) into two separate paths. A first of the low frequency signals is variably delayed (20), and the first and the other low frequency signals are upconverted to radio frequency level (16,22) for transmission over independent time-spaced transmission paths (26,28) to cellular receivers. A receiver downconverts and demodulates the radio frequency diversity signals, and then combines the demodulated diversity signals to generate an equalized combination diversity signal for receiver output processing.

Abstract: The invention relates to a method and an arrangement for improving the communication between a base station and a number of mobile units belonging to it in a microcell system. In greater detail, the invention has the aim of reducing the fading which is a problem when the mobile units are moving slowly or are standing still. According to the invention, the problem is solved by introducing diversity on the downlink in the system. The antenna pattern of the base station is turned so that a wave pattern varying with time is produced with spatially separated fading points. The communication preferably utilizes time-division multiple access (TDMA), the turning of the antenna pattern being effected step by step between suitable time slots, preferably between TDMA frames. The turning of the antenna pattern is advantageously produced by controlling a sectoral antenna (7, 7').

Abstract: A receiver (100) that includes an antenna (101) employs a method and apparatus for producing diversity gain of a signal (106) received by the antenna (101), wherein the signal (106) is subject to a time-variant fading condition. Upon receiving the signal (106), the receiver (100) determines a signal quality metric of the signal (106) and compares the signal quality metric to a quality threshold. When the signal quality metric is below the quality threshold, the receiver (100) orients a predetermined antenna pattern (304) of the antenna (101) to improve the signal quality metric, thereby producing the diversity gain.

Abstract: Signals from multiple signal paths are received using a multi-element antenna and a beam-forming network. Signals from each of the antenna elements are sampled to form a sample vector. Several sample vectors are used to form an auto-covariance matrix. A singular value decomposition of the auto-covariance matrix is used to form three matrices. The first matrix is used to determine the number of signal paths and the second matrix is used to form several polynomials. The polynomial roots that are on or near the unit circle are used to determine points on the unit circle that are associated with each signal path. Each point on the unit circle is used to calculate weights for a beam-forming network that forms a receive beam for each signal path.

Abstract: A distributed antenna system is utilized in a system for providing multipath signals which facilitate signal diversity for enhanced system performance. Each node of the antenna comprises more than one antenna. Each antenna at a common node provides a path having a different delay to the base station.

Abstract: Closure system remotely controllable by transmitter signals (I) for one or more locks (L) of one or more openings (T), having a portable transmitter (S) as key (S) for radiating the transmitter signals (I), namely the UNLOCK transmitter signals (I) which (I) initiate the unlocking (Z) of the relevant lock or locks (L), and/or the LOCK transmitter signals (I) which initiate the locking (Z) of these locks (L), having a receiver (E) which (E), if it is within range (W) of the transmitter (S), triggers a control signal (Z) after the reception of the transmitter signals (I), and having a locking element (B) which can be controlled by the control signal (Z), by means of which (B) the relevant lock (L) can be locked and/or unlocked.

Abstract: A first transmitter (103) reduces an interference in a time division duplex (TDD) communication system (100). The first transmitter (103) alternates from a transmit state in which a first information signal (130) is transmitted to a standby state in which a residual signal (132) is transmitted. The first transmitter (103) includes a transmitter section (142) and a controller (141). The transmitter section (142 transmits the first information signal (130) and the residual signal (132). The transmitter section (142) includes a power amplifier (144) to amplify the first information signal (130) and the residual signal (132) to a power level; and an exciter (143) to control a carrier frequency of the first information signal (130) and the residual signal (132). The controller (141) is coupled to the power amplifier (144) and the exciter (143), for adjusting the power level and setting the carrier frequency.

Abstract: A cable equalizer (10) receives signals transmitted over a coaxial cable (12) at a multi-path simulator (14). The multi-path simulator (14) includes a splitter (16) that places the signal along a first path (26) and a second path (28), wherein the signal on the first path (26) is 180.degree. out of phase with the signal along the second path (28). The signal along the first path (26) propagates to a combiner circuit (18). The signal along the second path (28) propagates through a delay circuit (20) having a delay value of .tau. that determines the notch spacing of the equalized signal. The signal along second path 28 propagates from delay circuit 20 to a variable attenuator circuit (22) that determines the notch depth for the equalized signal. The combiner (18) receives the signal along the first path (26) and the second path (28) and generates an equalized signal at the output of the multi-path simulator (14).

Abstract: A wireless communication system includes a plurality of stations each having a plurality of antennas. A first packet, containing a training signal portion is transmitted from a transmitting station using a first selected antenna and received at a receiving station using a second selected antenna which is selected as the antenna giving the best received signal quality, determined during the training signal period. Following transmission of the first packet, a control signal (ACKCNTL) is generated in both the transmitting station and the receiving station to condition these stations for the transmission from the receiving station of a response packet via the same antenna pair used for the information packet transmission. Thus, the response packet need have only a relatively short training signal portion.

Abstract: The present invention discloses a wireless LAN, a peer-to-peer wireless LAN, a wireless transceiver and a method of transmitting data, all of which are capable of operating at frequencies in excess of 10 GHz and in multipath transmission environments. This is achieved by a combination of techniques which enable adequate performance in the presence of multipath transmission paths where the reciprocal of the information bit rate of the transmission is short relative to the time delay differences between significant ones of the multipath transmission paths. In the LANs the mobile transceivers are each connected to, and powered by, a corresponding portable electronic device with computational ability.

Abstract: A system for mitigating the effect of fading in a digital communication system. Deep signal nulls occur when signals from multiple paths are precisely aligned in amplitude and phase canceling the signal at the receiving antenna and creating a fade. In an indoor system, moving either transmitter or receiver a short distance can shift a fade away from the frequency of interest. This invention provides an actual or perceived movement of an antenna such that the effects of fading can be averaged over a time interval. The signal processing capability of modern digital transceivers can correct errors due to the time varying fades using the present invention. Thus, a dual-antenna element using the system of this invention can provide diversity receive and transmit paths to maintain capacity. The present invention may also provide improved capacity to due enhanced stability in power control.

Abstract: An invention for providing diversity for direct sequence spread spectrum wireless communication systems is presented. The invention provides a transmitting technique for communicating a first signal comprising one or more segments to a receiver with use of a plurality of M antennas. The first signal includes one or more signal segments. The technique comprises forming M copies of the first signal; for a segment of a signal copy, weighting each of two or more sub-segments of the segment with a distinct signal, wherein a sequence of the distinct weighting signals for the segment is distinct from sequences of signals weighting the same segment of one or more other signal copies; and for each of M weighted signal copies, transmitting a signal to the receiver using a distinct antenna, the transmitted signal based on the weighted signal copy. Illustratively, the first signal is a spread spectrum signal. Moreover, the process of weighting comprises applying a phase shift to a sub-segment.

Abstract: An adaptive digital filter uses a weight adjustment unit for adjusting the weights of an adaptive digital filter according to one or more input signals to the digital filter and according to an error signal indicative of the difference between the actual and desired outputs of the digital filter. The weight adjustment unit has a first low-pass filter for low-pass filtering a signal indicative of the product of the error signal and the one or more input signals, a squarer for squaring the output of the first low-pass filter, a second low-pass filter for low-pass filtering the output of the squarer to extract the D.C. component thereof, a third low-pass filter for low-pass filtering a signal indicative of the output of the error signal squared to extract the D.C.

Abstract: An automotive radio system employs a plurality of corrective actions in response to the detection of multipath interference to reduce distortion audible to a listener. The speed of the vehicle is determined since the number of multipath events per unit time and the expected duration of each multipath event vary according to vehicle speed. The corrective action taken in response to detection of multipath interference depends upon the vehicle speed. In a diversity antenna system, antenna switching is suspended at high vehicle speed while filtering of the audio output to reduce noise is suspended at lower vehicle speeds.

Abstract: The invention provides a fading simulator method and a fading simulator by which the attenuation ratio is not varied and the fading characteristic of a wide band can be realized stably even when the notch frequency sweeps. A fading simulator is interposed between a transmitter and a receiver, and a signal from the transmitter is inputted to first and second path artificial circuits of the fading simulator. In the first path artificial circuit, the attenuation amount of a first variable attenuator is controlled to control the amplitude of the signal passing therethrough, and the signal is delayed by a first delay circuit.

Abstract: A CDMA communication system using a spreading code has a plurality of mobile stations and at least one base station. The mobile stations and the base station are provided with respective receiving sections, each of which has a path diversity function for reducing multipath fading. The base station includes an array antenna having a plurality of integrated antenna elements spaced by a distance substantially equal to one to several wavelengths from each other so as to produce a space diversity effect. A plurality of delay devices are coupled with the respective antenna elements, for applying time delays to signals which pass through the respective antenna elements. The time delay are different from each other by a one symbol period of the spreading code or more.

Abstract: In a digital radio communications system, a transmit signal is delayed and sent on a first diversity channel and a nondelayed version of the signal sent on a second diversity channel. At the receiving site, first and second diversity channel signals are recovered and normalized into first and second constant-amplitude signals. Predominant components of the constant-amplitude signals are phase-and-amplitude aligned with each other by feedback loops including phase-and-amplitude alignment circuits, an adder and an AGC amplifier. The output of the AGC amplifier or the output of the subtracter is selected and applied to a matched filter to which a decision feedback equalizer is coupled.

Abstract: An invention for providing diversity for direct sequence spread spectrum wireless communication systems is presented. The invention provides a transmitting technique for communicating a first signal comprising one or more segments to a receiver with use of a plurality of M antennas. The first signal includes one or more signal segments. The technique comprises forming M copies of the first signal; for a segment of a signal copy, weighting each of two or more sub-segments of the segment with a distinct signal, wherein a sequence of the distinct weighting signals for the segment is distinct from sequences of signals weighting the same segment of one or more other signal copies; and for each of M weighted signal copies, transmitting a signal to the receiver using a distinct antenna, the transmitted signal based on the weighted signal copy. Illustratively, the first signal is a spread spectrum signal. Moreover, the process of weighting comprises applying a phase shift to a sub-segment.

Abstract: When communication is established using a mobile radio terminal, the speed at which the terminal is moving is measured by monitoring the Rayleigh fading of the signal strength. Using this velocity indicative parameter, a threshold level which is used to determine if a handoff is required or not, can be adjusted in a manner which renders the decision process more accurate and minimizes the number of unwarranted handoffs.

Abstract: The invention relates to a method for transmitting in a time multiplex radio communication system, for instance, a GSM-type mobile telephony system, different commands from a movable station to a fixed station with respect to the selection of transmitter antenna in the fixed station. Each transmission sequence from the movable station includes a synchronizing word which consists of a predetermined number of binary bits. The different commands are transmitted by using different synchronizing words in dependence on the command to be transmitted. The movable station has access to at least two different synchronizing words. The synchronizing words used in addition to a standard synchronizing word are formed by the binary bits from the standard synchronizing word being shifted laterally to mutually different extents and/or in mutually different directions in order to generate different, new synchronizing words.

Abstract: The gain of a recursive integrator is controlled so as to be adaptive to the quality of a received signal by comparing the magnitude of its emphasized information component with a reference voltage and controlling the gain of the integrator's feedback delay path in accordance with the difference between the peak value of the emphasized information component and the reference voltage. As a result, when the signal to noise ratio of the input signal is high, the gain can be reduced, so that the recursive loop will adapt quickly to changes in a multipath profile.

Abstract: Fading channel effects on a transmitted communication signal are simulated with both frequency and time variations using a channel scattering function to affect the transmitted signal. A conventional channel scattering function is converted to a series of channel realizations by multiplying the square root of the channel scattering function by a complex number of which the real and imaginary parts are each independent variables. The two-dimensional inverse-FFT of this complex-valued channel realization yields a matrix of channel coefficients that provide a complete frequency-time description of the channel. The transmitted radio signal is segmented to provide a series of transmitted signal and each segment is subject to FFT to generate a series of signal coefficient matrices. The channel coefficient matrices and signal coefficient matrices are then multiplied and subjected to inverse-FFT to output a signal representing the received affected radio signal.

Abstract: A spread spectrum receiver subsystem for utilization in a CDMA cellular telephone having a searcher receiver 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 provides a control signal indicative of the received pilot signals of greatest strength and corresponding time relationship. A data receiver 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 information bearing encoded output signal.