Abstract: A dual locked loop is disclosed comparing preferably a GPS signal with an E1 signal and the E1 signal with the output of the loop. The GPS signal is low pass filtered to provide a low pass filtered GPS versus E1 signal that is used as a calibration for a closed loop having a second low pass filter for filtering the comparisons of the E1 and the output signal. By appropriately selecting the filter parameters, the output stability can track the stability of the local oscillator driving the NCO for short term stability, the medium term stability of the E1 signal and the long term stability of the GPS signal.

Abstract: A system that allows multiple bundles of plesiochronous digital hierarchy (PDH) payload data streams to be synchronously trasmitted from one point to another is described. The system multiplexes multiple stages of the PDH using a single clock signal. This removes the need to perform stuffing and de-stuffing of the data streams at the various stages of the multiplexing.

Abstract: The invention relates to a method and to an arrangement for effecting base orthogonal channel hopping between mobile stations (MS1-MS3) and a base station in a radio communications system. Connections (F1-F3) having low attenuation are allotted a number of channels having high interference I (channel, t). Connections (F1-F3) that have higher attenuation are allocated a number of channels that have lower interference I (channel, t). A channel allocation means (211) in the base station functions to produce channel hopsequences which are transferred to hopsequence lists (204-206) in the mobile stations (MS1-MS3), via a control channel SACCH. The channel hopsequences are also transferred to corresponding hopsequence lists (201-203) in the base station. Attenuation of the connections (F1-F3) and interference on the channels I (channel, t) are measured continuously in the channel allocating means (211), wherein the best channels with respect to interference are used.

Abstract: A cordless telephone system connectable to the public switched telephone network having a base station and one or more handsets communicating with the base station by an RF link using a time division duplex direct sequence spread spectrum quadrature modulation technique, having a gain imbalance compensation system for balancing the gain between the I and Q channels. Gain imbalance estimation is performed as part of a calibration cycle when the handset is in the cradle of the base station. The controller of the unit causes another unit to send a data signal with a frequency error. The baseband receiver performs the operation .vertline.I.vertline.-.vertline.Q.vertline., which is an indication of gain error. The results are stored in an accumulator over a set period of time. The controller reads the accumulator and uses an iterative process, increasing or decreasing the gain link compensation until no gain imbalance error is obtained.

Abstract: In a method and terminal apparatus for automatic modem type recognition and adaptation thereto within a communication mode, a microprocessor in a control unit of the terminal apparatus, is programmed to enter into a communication mode with a remote central data station in order to enter into a modem preselect value setting mode. The control unit is programmed so that the communication mode is exited after an automatic setup of the communication and after the execution of the communication. For automatic modem type recognition, modem-specific transmission sequences are stored in a program memory or in a modem initialization memory contained in a non-volatile memory of the terminal apparatus and are transmitted successively to the associated modem in steps, and the modem transmits its modem-specific response (transmission sequence) back to the microprocessor. The microprocessor then executes, in steps, a comparison of the response signals with the stored response signals for automatic modem type recognition.

Abstract: A novel and improved method and apparatus for high rate CDMA wireless communication is described. In accordance with one embodiment of the invention, a set of individually gain adjusted subscriber channels are formed via the use of a set of orthogonal subchannel codes having a small number of PN spreading chips per orthogonal waveform period. Data to be transmitted via one of the transmit channels is low code rate error correction encoded and sequence repeated before being modulated with one of the subchannel codes, gain adjusted, and summed with data modulated using the other subchannel codes. The resulting summed data is modulated using a user long code and a pseudorandom spreading code (PN code) and upconverted for transmission. The use of the short orthogonal codes provides interference suppression while still allowing extensive error correction coding and repetition for time diversity to overcome the Raleigh fading commonly experienced in terrestrial wireless systems.

Abstract: This invention discloses a frequency hopping cellular LAN system including a LAN, a plurality of access points each operatively connected to the LAN, the plurality of access points including at least a first access point and a second access point, and a station which communicates with at least some of the plurality of access points using frequency hopping spread spectrum wireless communication, wherein the first access point and the second access point each communicate with the station using a first and second predetermined sequence of frequencies respectively, and wherein, during a neighbor beacon interval, the second access point communicates with the station using the first predetermined sequence of frequencies, and wherein the station chooses an access point with which to communicate based, at least in part, on a transmission received from the second access point during the neighbor beacon interval.

Abstract: A maximum likelihood detection of a convolution code Yn obtained by coupling a transversal equalizer to a code Zn of a recording and reproducing channel. A branch metric is arithmetically operated by changing a weight of a data train of a convolution code corresponding to multiplication coefficients of a filter by a distributor with respect to a reproduction signal Rn. On the basis of the branch metric, an ACS circuit judges a maximum likelihood path at every path node and the results are stored into a path memory 56. Simultaneously with the maximum likelihood detection, metrics of the maximum likelihood paths judged with respect to the path nodes are compared by a maximum likelihood path comparing circuit, thereby deciding the maximum likelihood path node. A maximum inclination arithmetic operating circuit calculates a maximum inclination of the multiplication coefficients of the filter. The next multiplication coefficients are updated by an updating circuit.

Abstract: For use in a direct sequence spread spectrum ("DSSS") receiver adapted to receive a differential phase shift keyed ("DPSK") packet on a channel, the DPSK packet having a training preamble and a data portion, a system to improve detection of the packet under degraded channel conditions, comprising: (1) a detection circuit that derives phase information from symbols in the packet and a weight that is a function of an estimated power profile for the channel and (2) a computation circuit that computes a weighted average for the phase information using the weight, the weighted average being power profile-based to allow the receiver to detect the data contained in the packet more reliably under the degraded channel conditions.

Abstract: A CSK modulation is applied to transmit input data for transmission by using N PN code series. A modulator for N series synthesizes a predetermined number (n) of PN code series selected from N PN code series in response to m bits in the input data, and the synthesized code series is transmitted onto a transmission medium through a transmitting interface. The PN code series which is actually transmitted has a maximum value of the absolute magnitude of auto-correlation which is always greater than a maximum value of the absolute value of cross-correlations between the remaining synthesized PN code series.

Abstract: The effect of the multipath distortions on the carrier phase measurements is reduced by using the weighted correlation functions. The generators of both periodic and dynamic weighted functions are used. The apparatus and method employing generators of such weighted functions can comprise the standard correlators and/or the weighted function correlators.

Abstract: A method and apparatus is disclosed that receives a multi-channel digital serial encoded signal and converting it signal into a synchronized set of binary characters. A charge pump phase-locked loop receives a transmitted reference clock and derives a multi-phase clock from the reference clock. The multi-phase clock is used to control a plurality of multi-bit block assembly circuits. Each assembly circuit receives one channel of the digital signal and produces a multi-bit block or character. The multi-bit block assembly circuit includes an oversampler, a digital phase-locked loop and a byte synchronizer. The oversampler oversamples the received digital signal under control of the multiphase clock and produces a sequence of oversampled binary data. The digital phase-locked loop receives the oversampled data and selects samples from it depending on the skew characteristics of the sample. The byte synchronizer assembles a sequence of selected bits into a bit block, or character.

Abstract: A reception method of a multicarrier system is one in which a phase-modulated data is transmitted by using each of a plurality of subcarriers, and includes a random data generating step of generating a phase shift data randomly changed, a multiplying step for multiplying each of the received subcarriers with an output obtained in the random data generating step, and a state detection signal generating step for monitoring a state of an output obtained in the multiplying step and for generating a predetermined state detection signal when a predetermined state is detected.

Abstract: An adaptive filter or equalizer for digital data communication includes, a first cascade circuit connected to operate as a digital finite-impulse-response (FIR) filter, the first cascade circuit having a respective first single input for receiving samples of complex input data, a respective second input composed of a first plurality of input taps for receiving filter weighting signals, and a respective output for producing samples of filtered data. An error signal generator responds to samples supplied from the output of first cascade circuit to generate samples of an error signal.

Abstract: A communication device (107) employs a method for determining signal quality of a communication channel (117) in a communication system (100). Upon receipt of a radio signal, a communication device (107), such as a portable radio, determines the signal quality of at least two portions (121, 124) of the communication channel (117) over which the radio signal was transmitted. The communication device (107) then determines which of the determined signal qualities is lowest and selects the lowest determined signal quality as the signal quality of the communication channel (117). The communication device (107) can then use the selected channel quality in the handoff decision-making process.

Abstract: Compensation measurements can be made of the transmit and receive path circuitry of a dual FDD/TDD system which can be selectively operated in either the FDD mode or alternately in the TDD mode. BY selectively controlling the switches coupling low frequency and high frequency receivers and coupling low frequency and high frequency transmitters to a diplexer, compensation measurements can be made for both FDD and TDD modes of operation.

Abstract: A clock reproduction circuit for reproducing a data clock from a data signal is disclosed. The clock reproduction circuit includes a voltage controlled oscillator, a phase detector, a frequency error detection circuit and a charge pump whose output is controlled by the outputs of the phase detector and the frequency error detection circuit. A VCO clock output from the voltage controlled oscillator is synchronized with the data clock by the feedback loop consisting of these elements. The frequency error detection circuit detects a frequency error between the VCO clock and the data clock by detecting changes in the phases of the VCO clock at the transition edges of the data signal. Analog and digital frequency error detection circuits are disclosed. Further, improved circuit elements in the clock reproduction circuit are disclosed.

Abstract: A base station receiver and a method for receiving a signal in a base station receiver the service area of which is divided into sectors, the signal including multipath propagated signal components. To provide a preferred base station structure, the signal components received in each sector are converted in the method to an intermediate frequency and to digital form, the digitalized signal components are supplied by use of a sector-specific multiplexed bus to a plural number of correlation and spectrum assembling elements, in which each signal component is demodulated and assembled to narrowband form, and the demodulated signal components are supplied by connecting elements to a plural number of receiver-specific combining elements, in which the signals obtained from the different sectors are combined and detected.

Abstract: The spread spectrum communication system of the present invention is intended to equalize link capacity by taking deterioration of link quality so as to enable reliable communication which enhances the frequency diversity effect even if it is affected by the frequency selective fading or the like. Then, between a base station and a mobile station in a code division multiple access communication system which multiplexes the hopping frequencies by varying them with hopping series different for each channel, a same frequency band is used for a forward-link and a reverse-link, and the number of hopping frequencies and/or the number of hops per one data symbol being assigned is varied according to line quality. There is provided means for performing communication by multiplexing the forward- and reverse-links using the different hopping frequencies for transmission and receiving, so that the link capacity is equalized for the forward- and reverse-links.

Abstract: A block interleaver (212) suitable for communication over fading channels with convolutionally coded signals as input is disclosed. The block interleaver (212) implements multiple interleaving distances which are matched to the particular convolutional code to provide better performance than conventional block interleavers.