Nortel Networks Corporation

Apple Inc.

Gregory Carleton

Charles Tremlett Nicholls

Steve Andre Beaudin

Somsack Sychaleun

Philippe Wu

Adrian John Bergsma

Eric Gagnon

Brian James Lehman

Yu Yang

The present invention facilitates the reduction of cabling required in a base station environment. When receive diversity is employed, main and diversity antennas are used to receive common signals at different locations. The signals received at the main and diversity antennas are combined with one another in the masthead and transmitted over a single feeder cable to a base housing for further processing. Thus, signals that were normally sent over separate feeder cables and combined in the base housing are combined in the masthead and sent over a single feeder cable. The technique can be replicated for each sector provided by the base station environment.

Feeder cable reduction

Systems and methods are disclosed to maintain synchronous communications that uses a global positioning system satellite, a primary communication unit, and a secondary communication unit. The satellite based time reference broadcasts a reference signal to the primary communication unit and the secondary communication unit. The primary communication unit contains a high quality oscillator, and operates a virtual model of a secondary oscillator which is located in the secondary communication unit. The primary and secondary units have synchronous communications with each other by using a global positioning system satellite broadcast as a reference signal. If the secondary unit loses its signal from the global positioning system, the secondary oscillator enters a holdover state and transmits a notification of the holdover state to the primary communications unit. The primary communication unit then transmits time insensitive synchronization data based upon the virtual model through the packet switched network to the secondary communications unit to maintain synchronization.

Enhanced holdover for synchronous networks employing packet switched network backhaul

A reference timing signal apparatus with a phase-locked loop has a computer algorithm which adaptively models the multiple frequencies of an oscillator following a training period. The oscillation frequency of the oscillator is controlled in response to a phase detector output. The computer algorithm processes the control signal applied to the oscillator. The computer algorithm updates the characteristics of the model relating to the aging and temperature of the oscillator, using for example, a Kalman filter as an adaptive filter. By the algorithm, the subsequent model predicts the future frequency state of the oscillator on which it was trained. The predicted frequency of the model functions as a reference to correct the frequency of the oscillator in the event that no input reference timing signal is available. In a case of using pre-processing infinite impulse response filters (IIRFs) before the adaptive processor, the time delay caused by the filters are compensated after the adaptive processor. Without pre-processing IIRFs, aging and temperature update rates are adaptively controlled by dynamically changing the rates depending upon the loop condition to achieve a wider tracking bandwidth. With the model updating algorithm, oscillators of low stability performance may be used as cellular base station reference oscillator.

Reference timing signal apparatus and method

A communications tower, or other structure is provided with at least one waveguide defined in a structural support. The waveguide can be used to transmit signals up and down the communications tower thereby eliminating at least some cabling.

Structural waveguide formed in a leg of an antenna tower and method of use

Narrowband interference in a wideband RF signal is reduced by a notch filter operating at IF between down- and up-converters supplied by a local oscillator (LO) at a frequency controlled by a control circuit. The control circuit detects interference by determining power in each of a plurality of narrowband channels, also at IF via another down-converter with a controlled LO frequency, relative to power of the wideband RF signal and scaled in accordance with the wideband and narrowband bandwidths. The control circuit controls the LOs for scanning the narrowband channels to determine a channel with greatest interference and to filter out this narrowband channel with the notch filter. In the absence of interference, the notch is tuned outside the signal bandwidth.

Reducing narrowband interference in a wideband signal

A reference timing signal apparatus with a phase-locked loop (PLL) has a computer algorithm which adaptively models the multiple frequencies of an oscillator following a training period. The oscillator is part of a PLL and the oscillation frequency thereof is controlled in response to the phase detector output. The computer algorithm processes the control signal applied to the oscillator. The computer algorithm updates the characteristics of the model relating to the aging and temperature of the oscillator, using for example, a Kalman filter as an adaptive filter, in accordance with a cumulative phase error in the PLL calculated during a given time interval. By the algorithm, the subsequent model predicts the future frequency state of the oscillator on which it was trained. The predicted frequency of the model functions as a reference to correct the frequency of the oscillator in the event that no input reference timing signal is available. Also, the calculated phase error is stored and is used while no input reference timing signal or accurate predicted frequency value is available. With the model updating algorithm, oscillators of low stability performance may be used as cellular base station reference oscillator, which is based on satellite systems, for example, GPS, GLONASS or Galileo systems.

Systems and methods are provided for identifying frequency offsets which may for example have been introduced after a signal has been transmitted over a wireless channel. The method involves sampling a received signal having an input bandwidth to generate a respective set of samples for each of a plurality of symbol periods; filtering the sets of samples using DWPT (discrete wavelet packet transform) filters to produce a plurality of sub-sampled outputs, the sub-sampled outputs each having a respective fraction of the input bandwidth; for each of the sub-sampled outputs, performing a narrowband FFT on the sub-sampled output produced over a plurality of symbol periods to generate a respective set of frequency domain samples; processing each set of frequency domain samples to determine at least one respective frequency offset.

Apparatus and method for measuring sub-carrier frequencies and sub-carrier frequency offsets

An input reference timing signal oscillator of a phase-locked loop has a computer algorithm which adaptively models the multiple frequencies of an oscillator following a training period. The oscillator is part of a phase-locked loop and the oscillation frequency thereof is controlled in response to the phase detector output. The computer algorithm processes the control signal applied to the oscillator. The computer algorithm updates the characteristics of the model relating to the aging and temperature of the oscillator, using for example, a Kalman filter as an adaptive filter. By the algorithm, the subsequent model predicts the future frequency state of the oscillator on which it was trained. The predicted frequency of the model functions as a reference to correct the frequency of the oscillator in the event that no input reference timing signal is available. With the model updating algorithm, oscillators of low stability performance may be used as cellular base station reference oscillator.

Reference timing signal oscillator with frequency stability

A method and apparatus for determining the state, at any time in the past, relative to a present state, of a linear feedback shift register comprises determining a an inverse transition matrix which, if multiplied by the current state in modulo-2 arithmetic, yields the state one step into the past; and multiplying in modulo-2 arithmetic the present state of the linear feedback shift register by the inverse transition matrix N times to obtain the state N steps into the past.

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Ottawa, Canada

Gregory Carleton