Dual-Layer Beam Forming in Cellular Networks

• US 20100303034A1
• Filed: 05/25/2010
• Published: 12/02/2010
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Chen, Runhua, Onggosanusi, Eko Nugroho
• Granted Patent: US 8,797,950 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/023 with extension to other symbols
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/003 Arrangements for allocating sub-channels of the transmission path
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/0089 due to addition or removal of users or terminals
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal

Abstract

Single user and multiuser MIMO transmission in a cellular network may be performed by selecting by a base station (eNB) to transmit either one or two transmission layers. When one transmission layer is selected, a first transmission layer is precoded with a first precoder. A first demodulation reference signal (DMRS) sequence or a second DMRS sequence is selected by the eNB and precoded using the first precoder. The first transmission layer is transmitted with the selected precoded DMRS from the eNB to a user equipment (UE), and an indicator is transmitted to the UE to indicate which DMRS sequence is selected and transmitted.

Claims

1. A method for transmitting in a downlink channel of a cellular network, the method comprising:

selecting by a base station (eNB) to transmit either one or two transmission layers;

when one transmission layer is selected;

precoding a first transmission layer with a first precoder;

selecting a first demodulation reference signal (DMRS) sequence or a second DMRS sequence and precoding the selected DMRS sequence using the first precoder;

transmitting the first transmission layer with the selected precoded DMRS from the eNB to a user equipment (UE); and

transmitting an indicator to the UE to indicate which DMRS sequence is selected and transmitted.

2. The method of claim 1, wherein when two transmission layers are selected, comprising:

precoding a first transmission layer with a first precoder, and precoding a first DMRS sequence using the first precoder;

precoding a second transmission layer with a second precoder, and precoding a second DMRS sequence using the second precoder;

transmitting the first transmission layer and the first DMRS sequence to the UE; and

transmitting the second transmission layer and the second DMRS sequence to the UE.

3. The method of claim 1, wherein the indicator is a one-bit indicator comprised in a downlink grant.

4. Method for receiving in a downlink channel of a cellular network, the method comprising:

receiving at a user equipment (UE) a rank indicator from a base station (eNB) indicating one transmission layer or two transmission layers;

when one transmission layer is indicated;

receiving an indicator from the eNB to indicate which demodulation reference signal (DMRS) sequence was selected by the eNB from a first DMRS sequence or a second DMRS sequence;

receiving a first transmission layer from the eNB with the selected DMRS; and

demodulating the selected DMRS and the first transmission layer, wherein the first transmission layer and the selected DMRS have a same precoding.

5. The method of claim 4, wherein the indicator is a one-bit indicator comprised in a downlink grant.

6. The method of claim 4, wherein when two transmission layers are indicated, comprising:

receiving at the UE from the eNB a first transmission layer and a first DMRS having a first sequence;

receiving at the UE from the eNB a second transmission layer and a second DMRS having a second sequence;

demodulating the first DMRS and the first transmission layer, wherein the first transmission layer and the selected DMRS have the same precoding; and

demodulating the second DMRS and the second transmission layer, wherein the second transmission layer and the selected DMRS have the same precoding.

7. A base station for a cellular network, the device comprising:

a transceiver configured to couple to a plurality of antenna, wherein the transceiver is configured to transmit to and receiver from user equipment via the plurality of antenna in the cellular network;

a processor coupled to a memory configured to execute a control program in the memory for controlling the transceiver;

wherein the transceiver is configured to select to transmit either one or two transmission layers;

when one transmission layer is selected, the transceiver is configured to;

precode a first transmission layer with a first precoder;

select a first demodulation reference signal (DMRS) sequence or a second DMRS sequence and precode the selected DMRS sequence using the first precoder;

transmit the first transmission layer with the selected precoded DMRS from the base station to a user equipment (UE); and

transmit an indicator to the UE to indicate which DMRS sequence is selected and transmitted.

8. The base station of claim 7, wherein when two transmission layers are selected the transceiver is configured to:

precode a first transmission layer with a first precoder, and precode a first DMRS sequence using the first precoder;

precode a second transmission layer with a second precoder, and precode a second DMRS sequence using the second precoder;

transmit the first transmission layer and the first DMRS sequence to the UE; and

transmit the second transmission layer and the second DMRS sequence to the UE.