A system and method for wireless communication between a plurality of subscriber units and a base station, the base station communicating information signals from an originating source to a destination subscriber unit over a channel at an assigned one of a plurality of frequencies using repetitive time frames, each said time frame comprising a sequence of time slots. The channel is defined as having the same one or more time slots from the sequence of time slots in one or more of the time frames. The base station includes a central processing unit capable of assigning a duration of time for the information signals being sent to the destination subscriber unit. The duration equals the duration of one or more time slots in the same frame. The central processing unit maintains a memory of which time slots of each time frame have been assigned and provides the time slot assignment, and therefore channel assignment, by consulting said memory. The system includes a multiplexer for multiplexing the information signals onto the assigned channel; and a transmitter for transmitting the information signals to the destination subscriber unit using the assigned channel.

Subscriber RF telephone system for providing multiple speech and/or data signals simultaneously over either a single or a plurality of RF channels

The combination of trellis coding and MPSK signaling with asymmetry (nonuniform spacing) to the signal set is disclosed with regard to its suitability for a fading mobile satellite communication channel. For MPSK signaling, introducing nonuniformity in the phase spacing between signal points provides an improvement in performance over that achievable with trellis codes symmetric MPSK signaling, all this without increasing the average or peak power, or changing the bandwidth constraints imposed on the system. Block interleaving may be used to reduce error and pilot tone(s) may be used for improving the error correction performance of the trellis decoder in the presence of channel fading.

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Trellis coded modulation for transmission over fading mobile satellite channel

A power-conserving time division multiple access (TDMA) radio telephone system is disclosed in which a cluster of subscriber stations, remote from a base station, employs a common pool of frequency-agile modems each of which digitally synthesizes, on a timeSlot-by-timeSlot basis, the different channel-identifying intermediate frequencies needed to support communications between several of the subscriber stations and the base station. Power conservation is facilitated inter alia by controlling the assignment of modems to calls, maintaining unassigned modems in a powered-down state and by controlling the number of calls using the same time slot. Delay in assigning a powered-down modem to a call is eliminated by making available to all modems the highest quality synchronization information obtained by any of the active modems.

Modularly clustered radiotelephone system

A modem for a digital data transmission system in which binary-coded data at up to 9.6 Kbit/sec is transmitted over a telephone line pair circuit, as phase and amplitude modulation (QAM) of a carrier signal at a frequency of 1800 Hz, at a line symbol rate of 2400 bauds. The modem utilizes two data signal processors (4 and 5) and two gate arrays (6 and 7), controlled by a microprocessor (8), to carry out digitally all the processes required to convert binary coded data signals into PCM coded samples of the required carrier signal for transmission and to recover binary coded data signals from PCM coded samples of a received carrier signal.

Data transmission systems

Methods and apparatus for data communication are disclosed. An example method includes encoding a first plurality of transmitting frames, where a header segment of each frame is encoded in accordance with a fixed set of header encoding parameters and a payload segment of each frame is encoded in accordance with a first set of a variable set of payload encoding parameters. The example method also includes transmitting the first plurality of transmitting frames to a receiving station and receiving a request from the receiving station to change the first set of payload encoding parameters to a second set of the variable set of payload encoding parameters. The example method further includes selecting the second set of payload encoding parameters based on the request and encoding a second plurality of transmitting frames, where a header segment of each frame of the second plurality of transmitting frames is encoded in accordance with the fixed set of header encoding parameters and a payload segment of each frame of the second plurality of transmitting frames is encoded in accordance with the second set of payload encoding parameters. The example method still further includes transmitting the second plurality of transmitting frames to the receiving station.

Method for providing dynamic adjustment of frame encoding parameters in a frame-based communications network

Data in the form of multi-value symbols is transmitted at a symbol rate 1/ΔT At the receiver a decision circuit supplies estimates of the transmitted symbols on the basis of the received symbols The present invention concerns compensating phase noise after equalization, if any, of the received symbols and before application of the received symbols to the decision circuit (38, 39) The received symbols are in complex form with in-phase and quadrature components yk ' and yk " respectively Phase noise is compensated by complex multiplication in a multiplier (36) of the received symbols by a complex coefficient mk mk+1 =[mk -λ(vk -ak)yk *]exp[-iFk (ej)] where: λ is a real coefficient; yk * is the complex conjugate of the symbol received at instant kΔT+to (where to is the instant taken as the origin of time measurements); vk is the symbol applied to the decision circuit at said instant; ak is the estimated value of the received symbol; ej is an error signal derived from the phase difference between the symbol applied to the decision circuit and the symbol estimated by the decision circuit at instant jΔT+to ; and Fk (ej) is a linear function of at least the error signals ej The invention is particularly applicable to quadrature modulation systems, but if only one channel is transmitted the quadrature channel can be simulated using the Hilbert transform of the one channel

Method of compensating phase noise at the receiver end of a data transmission system

An echo canceller for a full-duplex carrier modulation transmission system terminal. The echo canceller includes a digital time-domain complex transversal filter with controlled weighting coefficients and an offset equal to a submultiple l of a Baud period Δ related to a rate at which a stream of complex symbols is received at the input of the filter. These complex symbols include complex symbols outputted by a coder of a transmitter of the terminal at the rate l/Δ interleaved with l-1 null symbols. The transversal filter output is connected to a digital modulator operated at the transmitter carrier frequency with instantaneous values updated at intervals equal to the Baud period to generate a passband echo copy signal. The invention is of particular benefit in transmission systems in which the product of the transmission carrier frequency and the Baud period is an integral multiple of l/4, as digital implementation of the modulator is then extremely simple.

Adaptive echo canceller for full-duplex transmission of data

PRECIS DE LA DIVULGATION: ABSTRACT OF THE DISCLOSURE: La presente invention a pour objet un circuit de correction des bruits de phase pour un systeme de transmission synchrone de donnees par l'intermediaire de symboles ayant en reception un circuit de decision fournissant une estimation des symboles emis. The present invention relates to a phase noise correction circuit for a synchronous data transmission system via reception symbols having a decision circuit providing an estimate of the transmitted symbols. Ce circuit de correction comporte un circuit de dephasage place This correction circuit includes a phase shifting circuit placed devant le circuit de decision et muni d'une boucle d'asservissement de phase du troisieme ordre comprenant un generateur d'angle de dephasage muni d'une entree d'incrementation, un detecteur d'erreur de phase four-nissant au rythme des symboles recus la valeur d'une erreur de phase subsistant aux bornes du circuit de decision entre chaque symbole recu et son estimation, et un filtre intercale entre l'entree d'incrementation du generateur d'angle de dephasage et le detecteur d'erreur de phase , ce filtre ayant une fonction de transfert qui exprimee par la transformee en za pour expression: before the decision circuit and provided with a third order phase locked loop comprising a phase angle generator provided with an increment input, a phase error detector oven-ning the symbol timing the received value of a phase error remaining at the terminals of the decision circuit between each received symbol and its estimate, and a filter interposed between the phase angle generator incrementing input and the phase error detector , this filter having a transfer function expressed by transform za expression: a,b,c et d etant des coefficients non nuls positifs et les termes z-1 des numerateurs pouvant etre supprimes. a, b, c and d are non-zero coefficients and the positive z-1 terms numerators can be removed. Ce circuit de correction des bruits de phase est avanta-geusement utilise avec une modulation d'amplitude en quadrature. This correction circuit is phase noise avanta-suitably used with a quadrature amplitude modulation.

Phase noise correction circuit for a data transmission system

A subscriber card includes a controller for concentrating Internet frames so as not to occupy a telephone circuit for each call to an Internet service provider. The subscriber card is connected to a switching matrix that facilitates transmission of the concentrated Internet frames to a data transmission network. The subscriber card handles multiple subscriber inputs and statistically multiplexes data from the multiple subscriber inputs in order to increase throughput.

Subscriber card, subscriber connecting unit and relay centre for concentrating internet frames

In a QPSK system using one cycle of a squared-off sinusoid per Baud period to represent the data dibits, the following are disclosed: (1) a direct detection circuit using samples taken only during the second and third quarters of the Baud period; (2) timing recovery by recognition of the opposite polarity of any QPSK signal compared to a half-Baud-delayed version of itself; and (3) an encoding scheme wherein only one of the two dibits is differentially encoded

Michel Levy

Papers

Method of compensating phase noise at the receiver end of a data transmission system

Adaptive echo canceller for full-duplex transmission of data

Phase noise correction circuit for a data transmission system

Subscriber card, subscriber connecting unit and relay centre for concentrating internet frames

QPSK system with one cycle per Baud period