Delay compensation
AssigneeAT&T Wireless Services, Inc.
InventorElliott Hoole
Life of this patent
Estimating the term…
Abstract
In a discrete tone system, a base station receives a transmission burst from a remote unit being installed that includes delay compensation pilot tones that are uniformly spread throughout the transmission bandwidth. The arrival time transmission burst is not synchronized with the other remote units transmitting to the base station. The base station measures the phase delay of each tone and calculates the delay of the remote unit from the slope of the line of phase angle versus tone frequency. The base station transmits a signal to the remote unit that includes the magnitude and direction of the delay, which allows the remote unit to adapt the timing of its transmission to be synchronized with the other remote units.
Claims11
In a communication system, a method for calculating a delay in transmitting a signal between multiple remote units and a base station, the method comprising:
- transmitting multiple delay compensation pilot (DCP) tones from a remote unit to the base station wherein the DCP tones comprise frequencies that are uniformly spaced through an upper sub-band frequency range and a lower sub-band frequency range;
- at the base station, digitizing the multiple received DCP tones, including passing the multiple received DCP tones through a Fast Fourier Transform (FFT) processor;
- storing the digitized DCP tones in incremental frequency bins as complex numbers, wherein the complex numbers represent a number of points in a Quadrature Amplitude Modulation (QAM) constellation, and wherein the complex numbers are related to an amount of energy of a received DCP tone in a frequency increment;
- and
- calculating a phase difference between an expected phase angle and a received phase angle for each of the multiple digitized DCP tones, wherein calculating the phase angle difference includes multiplying a first digitized DCP tone by complex conjugates of all other digitized DCP tones to determine one phase-angle measurement for each of the digitized DCP tones.
In a communication system, a method for calculating a delay in transmitting a signal between multiple remote units and a base station, the method comprising:
- the base station receiving multiple delay compensation pilot (DCP) tones from a remote unit, wherein the DCP tones comprise frequencies that are uniformly spaced through an upper sub-band frequency range and a lower sub-band frequency range;
- the base station digitizing the multiple received DCP tones, including passing the multiple received DCP tones through a Fast Fourier Transform (FFT) processor;
- storing the digitized DCP tones in incremental frequency bins as complex numbers, wherein the complex numbers represent a number of points in a Quadrature Amplitude Modulation (QAM) constellation, and wherein the complex numbers are related to an amount of energy of a received DCP tone in a frequency increment;
- and
- calculating a phase difference between an expected phase angle and a received phase angle for each of the multiple digitized DCP tones, wherein the calculating the phase difference comprises,
- correlating each symbol sequence from a DCP tone in a frequency sub-band selected from a group comprising the upper sub-band and the lower sub-band with a symbol sequence corresponding to one of the elements of the QAM constellation;
- acquiring a correlation coefficient for each of the correlations;
- and
- determining a phase-angle measurement for each of the correlation coefficients.
In a communication system, a method for calculating a delay in transmitting a signal between multiple remote units and a base station, the method comprising:
- a base station receiving multiple delay compensation pilot (DCP) tones from a remote unit, wherein the DCP tones comprise frequencies that are uniformly spaced through an upper sub-band frequency range and a lower sub-band frequency range;
- the base station digitizing the multiple received DCP tones, including passing the multiple received DCP tones through a Fast Fourier Transform (FFT) processor;
- storing the digitized DCP tones in incremental frequency bins as complex numbers, wherein the complex numbers represent a number of points in a Quadrature Amplitude Modulation (QAM) constellation, and wherein the complex numbers are related to an amount of energy of a received DCP tone in a frequency increment;
- and
- calculating a phase difference between an expected phase angle and a received phase angle for each of the multiple digitized DCP tones, wherein calculating the phase difference comprises,
- for each DCP tone in the upper sub-band, creating a symbol sequence;
- for each DCP tone in the lower sub-band, creating a symbol sequence;
- adding corresponding symbol sequences from the upper sub-band and the lower sub-band to each other to create one set of symbol sequences
- correlating each symbol sequence from the one set of symbol sequences with a symbol sequence corresponding to one of the elements of the QAM constellation;
- acquiring a correlation coefficient for each of the correlations;
- and
- determining a phase-angle measurement for each of the correlation coefficients.
In a communication system, a method for calculating a delay in transmitting a signal between multiple remote units and a base station, the method comprising:
- a base station receiving multiple delay compensation pilot (DCP) tones from a remote unit, wherein the DCP tones comprise frequencies that are uniformly spaced through an upper sub-band frequency range and a lower sub-band frequency range, wherein eight antenna elements are used, and wherein sixteen symbol sequences are received from each of the upper sub-band and lower sub-band for each antenna element;
- the base station digitizing the multiple received DCP tones, including passing the multiple received DCP tones through a Fast Fourier Transform (FFT) processor;
- storing the digitized DCP tones in incremental frequency bins as complex numbers, wherein the complex numbers each represent one of sixteen points in a Quadrature Amplitude Modulation (QAM) constellation, and wherein each of the complex numbers is related to an amount of energy of a received DCP tone in a frequency increment;
- and
- calculating a phase difference between an expected phase angle and a received phase angle for each of the multiple digitized DCP tones, wherein calculating the phase difference includes,
- creating sixteen symbol sequences, including summing symbol sequences of each of the upper and lower sub-bands for each antenna element in groups of thirty-two symbol sequences per group;
- normalizing each summed sequence;
- and
- correlating each normalized, summed sequence with a symbol sequence corresponding to one of the elements of the QAM constellation.
Dependencies are inferred from the claim text.