Interference cancellation in wireless networks

Patent metadata

Field	Value
Publication number	US-9813202-B2
Application number	US-201214405706-A
Country	US
Kind code	B2
Filing date	Sep 28, 2012
Priority date	Jun 14, 2012
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

The present application relates to a method of a wireless device for interference cancellation (IC) in a cellular radio network system comprising a serving network node serving said wireless device. The method comprises using a first IC method for at least partly removing a time aligned symbol of an interfering radio signal from at least a first symbol of a time slot received from the serving network node. The method also comprises using a second IC method, different from the first IC method, for at least partly removing a non-time aligned symbol of an interfering radio signal from at least a second symbol of said time slot received from the serving network node.

First claim

The invention claimed is:

1. A method in a wireless device for interference cancellation (IC) in a cellular radio network system comprising a serving network node serving said wireless device, the method comprising:
determining whether an interfering symbol of an interfering radio signal present in a time slot of a signal received from the serving network node is a time aligned symbol or whether the interfering symbol is a non-time aligned symbol;
when the interfering symbol is the time aligned symbol, using a first IC method for at least partly removing the time aligned symbol from at least a first symbol in the time slot of the signal received from the serving network node; and
when the interfering symbol is the non-time aligned symbol, using a second IC method, different from the first IC method, for at least partly removing the non-time aligned symbol from at least the first symbol in the time slot of the signal received from the serving network node,
wherein the second IC method comprises estimating a portion of the interfering radio signal that is present in the time slot using an estimation method that utilizes information about slot timing in the interfering radio signal; and
subtracting the estimated portion of the interfering radio signal from the received signal.

2. The method of claim 1 , wherein the first symbol received from the serving network node, as well as the time aligned and non-time aligned symbols of the interfering radio signal, are Orthogonal Frequency Division Multiplexing (OFDM) symbols.

3. The method of claim 1 , wherein the interfering radio signal of the time aligned symbol and the interfering signal of the non-time aligned signal are known by the wireless device.

4. The method of claim 3 , wherein at least one of the interfering radio signal of the time aligned symbol and the interfering signal of the non-time aligned symbol is a Common Reference Signal (CRS), a pilot signal or a synchronization signal.

5. The method of claim 1 , wherein the interfering radio signal of the non-time aligned symbol comprises a cyclic prefix (CP) which has a length that is different from a length of a CP used in the time slot of the first symbol received from the serving network node.

6. The method of claim 1 , wherein the first IC method, for the time aligned symbol, comprises:
performing a discrete Fourier transform (DFT) operation on a time window of the time slot, the time window corresponding to said at least the first symbol;
estimating the interfering signal within said time window; and
subtracting the estimated interfering signal from said at least the first symbol within said time window.

7. The method of claim 1 , wherein the second IC method, for the non-time aligned symbol, comprises:
performing a first DFT operation on a first time window of the time slot, the first time window corresponding to said non-time aligned symbol of the interfering signal, whereby a frequency domain representation of the interfering signal in the first time window is obtained;
estimating the interfering signal within said first time window;
performing a second DFT operation on a second time window of the time slot, the second time window corresponding to said at least the first symbol, whereby a frequency domain representation of said at least the first symbol in the second time window is obtained;
distributing the estimated interfering signal over the frequency domain representation of said at least the first symbol; and
subtracting the estimated interfering signal from said at least the first symbol in frequency domain.

8. The method of claim 1 , wherein the second IC method, for the non-time aligned symbol, comprises:
performing a first DFT operation on a time window of the time slot, the time window corresponding to said non-time aligned symbol of the interfering signal, whereby a frequency domain representation of the interfering signal in the time window is obtained;
estimating a channel for the interfering signal in a frequency domain representation within said time window;
performing an inverse DFT (IDFT) on the frequency domain representation of the interfering signal, whereby a time domain representation of the interfering signal in the time window is obtained; and
subtracting the estimated interfering signal from said at least the first symbol in time domain.

9. The method of claim 1 , wherein the second IC method, for the non-time aligned symbol, comprises:
performing a DFT operation on a time window of the time slot, the time window corresponding to said at least the first symbol, whereby a frequency domain representation of said at least the first symbol in the time window is obtained;
determining said at least the first symbol which are affected by the interfering signal of the non-aligned symbol;
estimating the interfering signal in frequency domain based on a known difference in timing between the non-aligned symbol and the at least the first symbol; and
subtracting the estimated interfering signal from said at least the first symbol in frequency domain.

10. The method of claim 1 , further comprising:
choosing one or both of the first IC method and the second IC method from a plurality of different methods based on one or both of hardware and software resources available for IC in the wireless device.

11. A wireless device comprising:
processor circuitry; and
radio receiver circuitry;
wherein the processor circuitry is configured for, in cooperation with the receiver circuitry:
determining whether an interfering symbol of an interfering radio signal present in a time slot of a signal received from a serving network node is a time aligned symbol or whether the interfering symbol is a non-time aligned symbol;
when the interfering symbol is the time aligned symbol, using a first IC method for at least partly removing the time aligned symbol from at least a first symbol in the time slot of the signal received from the serving network node; and
when the interfering symbol is the non-time aligned symbol, using a second IC method, different from the first IC method, for at least partly removing the non-time aligned symbol from at least the first symbol in the time slot of the signal received from the serving network node,
wherein the second IC method comprises estimating a portion of the interfering radio signal that is present in the time slot using an estimation method that utilizes information about slot timing in the interfering radio signal; and
subtracting the estimated portion of the interfering radio signal from the received signal.

12. The wireless device of claim 11 , wherein the processor circuitry is configured for, when using the first IC method, in cooperation with the receiver circuitry:
performing a discrete Fourier transform (DFT) operation on a time window of the time slot, the time window corresponding to said at least the first symbol;
estimating the interfering signal within said time window; and
subtracting the estimated interfering signal from said at least the first symbol within said time window.

13. The wireless device of claim 11 , wherein the processor circuitry is configured for, when using the second IC method, in cooperation with the receiver circuitry:
performing a first DFT operation on a first time window of the time slot, the first time window corresponding to said non-time aligned symbol of the interfering signal, whereby a frequency domain representation of the interfering signal in the first time window is obtained;
estimating the interfering signal within said first time window;
performing a second DFT operation on a second time window of the time slot, the secon

Assignees

• Lindoff Bengt
• Andgart Niklas
• Nordstrom Fredrik
• ERICSSON TELEFON AB L M (publ)

Inventors

• Lindoff Bengt
• Andgart Niklas
• Nordstrom Fredrik

Classifications

• H04L5/0032 Primary

  Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation · CPC title

• H04L5/0007

  the frequencies being orthogonal, e.g. OFDM(A) or DMT · CPC title

• H04B2201/70707

  Efficiency-related aspects · CPC title

• H04B1/7103 Primary

  the interference being multiple access interference · CPC title

• H04B2201/70702

  Intercell-related aspects · CPC title