Method and system for assisting user devices in performing interference cancellation in OFDMA wireless communication networks

Patent metadata

Field	Value
Publication number	US-9781714-B2
Application number	US-201514871075-A
Country	US
Kind code	B2
Filing date	Sep 30, 2015
Priority date	Sep 30, 2014
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

A system and method are provided for assisting user devices in performing OFDMA downlink interference cancellation, in which an interfering base station transmits a downlink signal in a first slot and a second slot, both slots including cell reference signals (CRSs) for physical channel estimation, the CRS of the second slot is modified to indicate encoded values of parameters characterizing the physical channel according to an encoding procedure, the slots are received by a served user device that detects the physical channel parameters carried by dedicated control signalling and encodes them by the encoding procedure, an unchanged CRS is reconstructed, and the slots are received by an interfered user device obtaining the encoded values and comparing to parameter patterns indicating absence of modifications in the CRSs, wherein if the encoded values are different from the patterns, the interfered user device decodes them to perform interference cancellation of the downlink signal.

First claim

The invention claimed is:

1. A method for assisting user devices in performing downlink interference cancellation in Orthogonal Frequency-Division Multiple Access (OFDMA) wireless networks, comprising:
wherein an interfered user device is suffering from interference from an interfering base station to which a served user device is connected at a serving cell, and the interfered user device being at a neighbour cell which is neighbour of the serving cell;
transmitting by the interfering base station a downlink signal in a first slot and a second slot of a radio subframe, the first slot and the second slot including cell reference signals for physical channel estimation;
modifying phases of cell reference signals included in the second slot, the phase modifications indicating encoded values of parameters which establish the physical channel according to an encoding procedure,
receiving the first slot and the second slot of the radio subframe by the served user device, the served user device:
detecting the parameters which establish the physical channel as carried by dedicated control signalling applied to the physical channel,
encoding the detected parameters according to the encoding procedure,
reconstructing an unchanged cell reference signal for carrying the encoded detected parameters,
prior to physical channel estimation, removing the modified phases by comparing the modified cell reference signal received in the second slot with the reconstructed unchanged cell reference signal;

receiving the first slot and the second slot of the radio subframe by the interfered user device, the interfered user device:
obtaining the encoded values by comparing the phases of the cell reference signals included in the second slot and in the first slot,
for assisting in interference cancellation of the downlink signal from the interfering base station, comparing the encoded values with parameter patterns which indicate absence of modifications in the cell reference signals, and
if the encoded values are different from the parameter patterns which indicate absence of modifications in the cell reference signals, decoding the encoded values, and performing interference cancellation, by using the decoded values, of the downlink signal from the interfering base station.

2. The method according to claim 1 , wherein the parameters which establish the physical channel according to the encoding procedure are:
modulation and coding scheme,
redundancy version, and
radio network temporary identifier.

3. The method according to claim 2 , wherein the OFDMA wireless network is a Long-Term Evolution (LTE) wireless network.

4. The method according to claim 3 , further comprising determining whether the interfered user device is assisted to perform interference cancellation or not, by checking whether all the following three conditions are met for the physical channel in downlink:
LTE Transmission Mode 2 is used,
localized resource mapping is used, and
at least two resource blocks are reserved for the physical channel in downlink.

5. The method according to claim 4 , wherein, when all the three conditions are met, the modified cell reference signal for the physical channel is mapped on a first antenna port TX 0 of the interfering base station and mapped on a second antenna port TX 1 of the interfering base station, and r l,n s TX 0 being the component mapped on the first antenna port TX 0 and r l,n s TX 1 being the component mapped on antenna port TX 1 are given by the following expressions:

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Assignees

• Telefonica Sa

Inventors

• Lorca Hernando Javier

Classifications

• H04W72/23

  in the downlink direction of a wireless link, i.e. towards a terminal · CPC title

• H04W72/042 Primary

  Electricity · mapped topic

• H04L1/22

  using redundant apparatus to increase reliability · CPC title

• H04B7/0413

  MIMO systems · CPC title

• H04L27/2613 Primary

  Structure of the reference signals · CPC title