Robust PBCH-IC method in LTE advanced

Patent metadata

Field	Value
Publication number	US-10015696-B2
Application number	US-201415313655-A
Country	US
Kind code	B2
Filing date	Jun 11, 2014
Priority date	Jun 11, 2014
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A Physical Broadcast Channel (PBCH) Interference Cancellation (PBCH-IC) solution is presented herein. The PBCH-IC provides accurate and efficient techniques for cancelling interference from a serving cell PBCH. In one embodiment, PBCH symbols previously determined for an aggressor cell are canceled from a PBCH sequence currently received by the wireless device to produce a serving cell PBCH free of interference. In another embodiment, the PBCH symbols of the aggressor cell are reconstructed in the frequency domain and converted to the time domain to generate an aggressor PBCH sequence. The aggressor PBCH sequence is then subtracted from the received PBCH sequence to cancel the aggressor cell interference.

First claim

The invention claimed is:

1. A method of cancelling aggressor cell interference, in a wireless device using a joint frequency domain and time domain process, the method comprising;
receiving a physical broadcast channel (PBCH) sequence at the wireless device from a serving cell and an aggressor cell, wherein the serving cell comprises a serving network node that serves the wireless device;
applying a denoise process to channel estimates associated with the aggressor cell in the time domain to remove noise from the channel estimates and to determine denoised channel estimates;
converting the denoised channel estimates from the time domain to the frequency domain to determine denoised frequency domain channel estimates;
determining PBCH symbols generated by the aggressor cell based on a master information block corresponding to the aggressor cell in the received PBCH sequence;
reconstructing aggressor PBCH symbols for the aggressor cell in the frequency domain based on the denoised frequency domain channel estimates and the determined PBCH symbols;
converting the reconstructed aggressor PBCH symbols from the frequency domain to the time domain to generate a reconstructed PBCH sequence; and
subtracting the reconstructed PBCH sequence from the received PBCH sequence in the time domain to cancel the aggressor cell interference.

2. The method of claim 1 , wherein reconstructing the aggressor PBCH symbols comprises applying the denoised frequency domain channel estimates to the generated PBCH symbols to generate the reconstructed aggressor PBCH symbols.

3. The method of claim 1 , further comprising determining a weight for each generated PBCH symbol based on the denoised frequency domain channel estimates, wherein reconstructing the aggressor PBCH symbols comprises multiplying each of the generated PBCH symbols with the corresponding weight to generate the reconstructed aggressor PBCH symbols.

4. The method of claim 1 , further comprising:
determining a weight for each generated PBCH symbol based on the denoised frequency domain channel estimates; and
scaling the weights according to a scaling factor inversely proportional to a signal quality estimate associated with the generated PBCH symbols to generate scaled weights;
wherein reconstructing the aggressor PBCH symbols comprises multiplying the generated PBCH symbols with the scaled weights to generate the reconstructed aggressor PBCH symbols.

5. The method of claim 1 , wherein reconstructing the aggressor PBCH symbols in the frequency domain comprises reconstructing the aggressor PBCH symbols in the frequency domain based on the denoised frequency domain channel estimates, the generated PBCH symbols, and a resource element of the aggressor cell shifted with respect to the serving cell according to a cell-specific reference signal shift.

6. A wireless device served in a wireless network by a serving network node in a serving cell, the wireless device comprising:
a transceiver circuit configured to
receive a physical broadcast channel (PBCH) sequence from the serving cell and an aggressor cell;

a denoising circuit configured to:
apply a denoise process to channel estimates in the time domain to remove noise from the channel estimates and to determine denoised channel estimates; and
convert the denoised channel estimates to the frequency domain to determine denoised frequency domain channel estimates;

a reconstruction circuit configured to:
determine PBCH symbols generated by the aggressor cell based on a master information block corresponding to the aggressor cell in the received PBCH sequence; and
reconstruct aggressor PBCH symbols for the aggressor cell in the frequency domain based on the denoised frequency domain channel estimates and the determined PBCH symbols;

a conversion circuit configured to
convert the reconstructed aggressor PBCH symbols from the frequency domain to the time domain to generate a reconstructed PBCH sequence; and

a cancellation circuit configured to
subtract the reconstructed PBCH sequence from the received PBCH sequence in the time domain to cancel the aggressor cell interference.

7. The wireless device of claim 6 , wherein the reconstruction circuit reconstructs the aggressor PBCH symbols by applying the denoised frequency domain channel estimates to the generated PBCH symbols to generate the reconstructed aggressor PBCH symbols.

8. The wireless device of claim 6 , further comprising a weight circuit configured to determine a weight for each generated PBCH symbol based on the denoised frequency domain channel estimates, wherein the reconstruction circuit reconstructs the aggressor PBCH symbols by multiplying each of the generated PBCH symbols with the corresponding weight to generate the reconstructed aggressor PBCH symbols.

9. The wireless device of claim 6 , further comprising:
a weight circuit configured to determine a weight for each generated PBCH symbol based on the denoised frequency domain channel estimates; and
a scale circuit configured to scale the weights according to a scaling factor inversely proportional to a signal quality estimate associated with the generated PBCH symbols to generate scaled weights;
wherein the reconstruction circuit reconstructs the aggressor PBCH symbols by multiplying the generated PBCH symbols with the scaled weights to generate the reconstructed aggressor PBCH symbols.

10. The wireless device of claim 6 , wherein the reconstruction circuit reconstructs the aggressor PBCH symbols in the frequency domain by reconstructing the aggressor PBCH symbols in the frequency domain based on the denoised frequency domain channel estimates, the generated PBCH symbols, and a resource element of the aggressor cell shifted with respect to a resource element of the serving cell according to a cell-specific reference signal shift.

11. A method of cancelling interference, in a wireless device using a joint frequency domain and time domain process, the method comprising;
receiving a current physical broadcast channel (PBCH) sequence at the wireless device from a serving cell and an aggressor cell, wherein a serving network node in the serving cell serves the wireless device;
converting the received current PBCH sequence from the time domain to the frequency domain to generate current PBCH symbols;
reconstructing PBCH symbols generated by the aggressor cell before receipt of the current PBCH sequence by the wireless device;
storing the reconstructed PBCH symbols in a memory in the wireless device;
retrieving the reconstructed PBCH symbols associated with the aggressor cell for each subcarrier of the PBCH in the frequency domain from the memory in the wireless device;
correlating each of the reconstructed PBCH symbols with the current PBCH symbols to determine a correlation factor for each of the subcarriers;
determining a peak-to-average ratio (PAR) of a power of the correlation factors based on the correlation factors; and
if the PAR exceeds a threshold, cancelling aggressor cell interference from the current PBCH symbols based on the reconstructed PBCH symbols.

12. The method of claim 11 , wherein determining the PAR comprises:
determining, for each of the subcarriers, a power of at least one correlation factor based on the corresponding correlation factor;
averaging the determined powers to determining an average power;
identifying a maximum of the determined powers as a maximum power; and
dividing the maximum power by the average power to determine the PAR.

13. The method of claim 11 , wherein determining the PAR comprises:
determining, for each of the subcarriers, an amplitude based on the corresponding correla

Assignees

• Ericsson Telefon Ab L M

Inventors

• Liu Peng
• Ma Jing

Classifications

• H04W28/04 Primary

  Error control · CPC title

• H04L5/0048

  Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091) · CPC title

• H04W24/02

  Arrangements for optimising operational condition · CPC title

• H04J11/005

  of intercell interference · CPC title

• H04W52/225

  Calculation of statistics, e.g. average or variance · CPC title