Apple Inc.

Nortel Networks Corporation

Northern Telecom Limited

Rockstar Bidco, LP

Paul Murray Row

Graham Dolman

Dorian Thomas Charles Davies

David G Steer

Howard Martin Sandler

Martin O'Flaherty

Jastinder Singh Jawanda

Mark Watkins

Fraser Murray Edwards

David Michael Priest

Keith Daniel O'Neill

Christopher J Adams

Jorge Alberto Del Rio

William John Newman

Christopher Sean Reece

Dorian Thomas Davies

Correction of quadrature errors associated with digital communications systems. A correction network may correct a difference between a transmission characteristic of an in-phase signal path and a transmission characteristic of a quadrature signal path. The quadrature signal path may be for the transmission of in-phase and quadrature parts of a signal and the signal comprising frequency components within a baseband. The correction network may include an in-phase input port, a quadrature input port, an in-phase output port and a quadrature output port. Each input port may be connected to each output port by a digital filter network, which may include a set of filter tap coefficients and configuration means for configuring values of the coefficients. Frequency dependent quadrature impairments, e.g., due to the analogue components of a quadrature up-converter or down-converter, may be corrected by suitable control of the coefficients.

Correction of quadrature errors

A transmit chain comprises a transmit path with a quadrature up-converter which up-converts quadrature signal components to RF. An observation path samples a portion of the RF signal and a quadrature down-converter down-converts the RF signal to baseband quadrature signal components. A local oscillator signal source provides the up-converter and the down-converter with a local oscillator signal and is operable in two states. In a second of the states the local oscillator signal is applied to the up-converter and the down-converter and a phase shift is made to the signal applied to up-converter or the down-converter compared to the first of the states. A processor monitors properties of the down-converted signal while the local oscillator signal source is operating in the first state and the second state. The processor calculates a correction to apply to the baseband observation signal to correct for errors introduced by the observation path. The processor also calculates a correction to apply to the input signal to correct for errors introduced in the transmit path.

Measuring and correcting errors in a transmit chain with an IQ up-converter and IQ down-converter

Embodiments of the invention are concerned with correction of quadrature errors associated with digital communications systems, and in particular in a wireless transmit chain in which an up-converter and a down-converter both have a direct conversion architecture. One embodiment comprises a correction network for correcting a difference between a transmission characteristic of an in-phase signal path and a transmission characteristic of a quadrature signal path, said quadrature signal path being for the transmission of in-phase and quadrature parts of a signal and the signal comprising frequency components within a base band, wherein the correction network comprises an in-phase input port, a quadrature input port, an in-phase output port and a quadrature output port, wherein each input port is connected to each output port by a digital filter network, the digital filter network comprising a set of filter tap coefficients and configuration means for configuring values of said set of filter tap coefficients. Since each input port is connected to each output port by a digital filter network comprising a set of filter tap coefficients and having configuration means for configuring values of said set of filter tap coefficients, frequency dependent quadrature impairments, for example due to the analogue components of a quadrature up-converter or down-converter, may be corrected by suitable control of the coefficients.

A cellular radio communication system for transmitting blocks of data over transmission links in which the quality of the transmission links are monitored. The system comprises a data storage means for storing sets of modulation scheme and forward error correction coding level pairs to give an optimum data rate at a predetermined bit error rate and a predetermined symbol rate for different quality transmission links. The database is interrogated and a modulation scheme and forward error correction coding level pair is allocated and applied to the blocks of data transmitted over a transmission link dependent on the monitored quality of the transmission link.

Cellular radio communications system

This invention provides a communication network with a method and apparatus for interrupting the transmission of an existing stream of data to insert interrupting packets which may have a higher priority than the existing data stream. The interrupting packets are inserted in the data stream by making use of unused pointer values in common transmission schemes known as the Data Over Cable Service Interchange Specification (DOCSIS) or the Asynchronous Transfer Mode (ATM) adaptation layer 2 (AAL2) format of the International Telecommunications Union (ITU) recommendation I363.2. Advantageously, the scheduling of packets is significantly simplified and the packet jitter is better controlled which results in a significant improvement in transmission performance.

Method and apparatus for inserting packets into a data stream

A wireless telephone system is adapted for serving portable telephone sets of itinerant users. The wireless telephone system is provided with a plurality of radio base stations being organized in at least two groups or paging areas. Each group has a boundary, a portion of each boundary being overlapped by at least one other boundary, and at least two of the at least two groups having at least two radio base stations, one of which is in common with the other group. From time to time in relation to each group, a beacon signal is radio transmitted from a radio base station exclusive to the group for soliciting a recordation response from a portable telephone set of an itinerant user within a beacon zone. When the presence of a respondent portable set is recorded as being within a service area of one of the groups, the portable set is instructed not to respond to subsequent occurrences of the same beacon signal for some hours to avoid cluttering the wireless spectrum with undue supervisory signalling. A call request wherein the itinerant user is a called party, results in the recorded portable set being paged via at least an idle one of the radio base stations of the group within which the portable set is recorded as being present, whereby the itinerant user may be called via the wireless telephone system without any requirement for the user to have prior knowledge of or to have taken any action in relation to the wireless telephone service.

Telephone system for mobile wireless telephone services

Growing community of inventors

Bishops Stortford, United Kingdom

Paul Murray Row