METHOD AND APPARATUS FOR TRANSMITTING/RECEIVING A REFERENCE SIGNAL IN A WIRELESS COMMUNICATION SYSTEM

• US 20120176885A1
• Filed: 09/07/2010
• Published: 07/12/2012
• Est. Priority Date: 09/07/2009
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Lee, Dae Won, Han, Seung Hee, Kim, Ki Jun, Ahn, Joon Kui
• Granted Patent: US 8,842,515 B2
• Time in Patent Office: Days
• US Class Current: 370/209
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

Disclosed are a method and apparatus for transmitting a reference signal. In a base station apparatus for transmitting a reference signal in a wireless communication system, a processor generates the same scrambling sequence for resource elements (REs) allocated to each layer for reference signal transmission, and spreads or covers Walsh codes such that scrambling sequences generated for the resource elements can be orthogonal to each other on a time axis, in order to generate a reference signal sequence. Here, the Walsh code spreading or covering by the processor is applied on a frequency axis on the basis of a plurality of resource blocks (RBs) or on the basis of a pair of resource blocks, such that mutually different sequences having mutually different sequence values can be mapped between resource blocks or between pairs of resource blocks. A transmission module transmits the reference signal, to which the thus-generated reference signal sequence is applied, to user equipment via each layer.

Claims

1. A method for transmitting a reference signal at an eNode B in a wireless communication system, the method comprising:

generating a pseudo-random sequence for each layer using a first m-sequence and a second m-sequence;

generating a reference signal sequence using the generated pseudo-random sequence and a Walsh code; and

transmitting a reference signal to which the reference signal sequence generated for the each layer is applied to a user equipment (UE) for the each layer,

wherein the pseudo-random sequence is generated using a sequence initialization value, the sequence initialization value being generated using a slot number in a radio frame, a physical layer cell ID value, and a value indicating a layer index group differentiated by a frequency.

2. The method according to claim 1, wherein the sequence initialization value is represented by the following Equation A:

c_init=2¹⁰·

(7·

(n_s+1)+l+1)·

(2·

N_ID^cell+1)+2¹·

N_ID^cellN_FO 

 

[Equation A]

where n_s denotes the slot number in a radio frame, N_ID^cell denotes the physical layer cell ID, and N_FO denotes the layer index group indication value.

3. The method according to claim 1, wherein the layer index group indicator value is 0 or 1.

4. The method according to claim 1, wherein the reference signal is used for demodulation of data and is determined UE-specifically.

5. The method according to claim 1, wherein the sequence initialization value is applied to at least one of the first m-sequence and the second m-sequence.

6. A method for transmitting a reference signal at an eNode B in a wireless communication system, comprising:

generating the same scrambling sequence for Resource Elements (REs) allocated to each layer for reference signal transmission;

generating a reference signal sequence by spreading or covering Walsh codes such that scrambling sequences generated for the REs are orthogonal to each other on a time axis; and

transmitting a reference signal to which the generated reference signal sequence is applied to a UE via each layer,

wherein the Walsh code spreading or covering is applied on a frequency axis on the basis of a plurality of resource blocks (RBs) or on the basis of a pair of resource blocks, such that mutually different sequences having mutually different sequence values are mapped between resource blocks or between pairs of resource blocks.

7. The method according to claim 6, wherein the scrambling sequence is a sequence corresponding to one or more resource blocks or resource block pairs allocated to the UE from among sequences generated over the entire bandwidth, or a sequence generated for one or more resource blocks or resource block pairs allocated to the UE.

8. The method according to claim 6, wherein in the generating of the reference signal sequence, in a first resource block of the plurality of resource block pairs, Walsh code elements are applied to a first Code Division Multiplexing (CDM) group such that the Walsh code elements are one-to-one mapped to REs of a first subcarrier allocated to the first resource block in the direction of the time axis, one-to-one mapped to REs of a second subcarrier in the opposite direction of the time axis, and one-to-one mapped to REs of a third subcarrier in the direction of the time axis,

wherein in a second resource block of the plurality of resource block pairs, the Walsh code elements are applied to the first CDM group such that the Walsh code elements are one-to-one mapped to REs of a first subcarrier allocated to the second resource block in the opposite direction of the time axis, one-to-one mapped to REs of a second subcarrier in the direction of the time axis, and one-to-one mapped to REs of a third subcarrier in the opposite direction of the time axis.

9. The method according to claim 8, wherein in the first and second resource block pairs, the Walsh code elements are applied to a second CDM group in an order different from the order of the Walsh code elements applied to the first CDM group.

10. The method according to claim 8, wherein in the generating of the reference signal sequence, the different sequences having different sequence values are repeated on the basis of two resource block pairs on the frequency axis.

11. The method according to claim 8, wherein the Walsh code elements of the CDM groups is applied to layer 1 as (1, 1, 1, 1), applied to layer 2 as (1, −

1, 1, −

1), applied to layer 3 as (1, 1, −

1, −

1), and applied to layer 4 as (1, −

1, −

1,

     1).

12. The method according to claim 6, wherein the reference signal is used for demodulation of data and determined UE-specifically.

13. An eNode B apparatus for transmitting a reference signal in a wireless communication system, the eNode B apparatus comprising:

a processor generating a pseudo-random sequence for each layer using a first m-sequence and a second m-sequence, and generating a reference signal sequence using the generated pseudo-random sequence and a Walsh code; and

a transmission module transmitting a reference signal to which the reference signal sequence generated for the each layer has been applied to a UE for the each layer,

wherein the processor generates the pseudo-random sequence using a sequence initialization value, the sequence initialization value being generated using a slot number in a radio frame, a physical layer cell ID value, and a value indicating a layer index group differentiated by a frequency.

14. The eNode B apparatus according to claim 13, wherein the sequence initialization value is represented by the following Equation A:

c_init=2¹⁰·

(7·

(n_s+1)+l+1)·

(2·

N_ID^cell+1)+2¹·

N_ID^cellN_FO 

 

[Equation A]

where n_s denotes the slot number in a radio frame, N_ID^cell denotes the physical layer cell ID, and N_FO denotes the layer index group indication value.

15. The eNode B apparatus according to claim 13, wherein the layer index group indicator value is 0 or 1.

16. The eNode B apparatus according to claim 13, wherein the reference signal is used for demodulation of data and is determined UE-specifically.

17. The eNode B apparatus according to claim 13, wherein the sequence initialization value is applied to at least one of the first m-sequence and the second m-sequence.

18. An eNode B apparatus for transmitting a reference signal in a wireless communication system, the eNode B apparatus comprising:

a processor generating the same scrambling sequence for Resource Elements (REs) allocated to each layer for reference signal transmission, and generating a reference signal sequence by spreading or covering Walsh codes such that scrambling sequences generated for the REs are orthogonal to each other on a time axis; and

a transmission module transmitting a reference signal to which the generated reference signal sequence has been applied to a UE via each layer,

wherein the Walsh code spreading or covering of the processor is applied on a frequency axis on the basis of a plurality of resource blocks (RBs) or on the basis of a pair of resource blocks, such that mutually different sequences having mutually different sequence values are mapped between resource blocks or between pairs of resource blocks.

19. The eNode B apparatus according to claim 18, wherein the scrambling sequence is a sequence corresponding to one or more resource blocks or resource block pairs allocated to the UE from among sequences generated over the entire bandwidth, or a sequence generated for one or more resource blocks or resource block pairs allocated to the UE.

20. The eNode B apparatus according to claim 18, wherein the processor spreading or covering the Walsh code applies Walsh code elements to a first CDM group such that the Walsh code elements are one-to-one mapped to REs of a first subcarrier allocated to a first resource block of the plurality of resource block pairs in the direction of the time axis, one-to-one mapped to REs of a second subcarrier in the opposite direction of the time axis, and one-to-one mapped to REs of a third subcarrier in the direction of the time axis, in the first resource block of the plurality of resource block pairs,

wherein the processor applies the Walsh code elements to the first CDM group such that the Walsh code elements are one-to-one mapped to REs of a first subcarrier allocated to a second resource block of the plurality of resource block pairs in the opposite direction of the time axis, one-to-one mapped to REs of a second subcarrier in the direction of the time axis, and one-to-one mapped to REs of a third subcarrier in the opposite direction of the time axis, in the second resource block of the plurality of resource block pairs.

21. The eNode B apparatus according to claim 19, wherein in the first and second resource block pairs, the Walsh code elements are applied to a second CDM group in an order different from the order of the Walsh code elements applied to the first CDM group.

22. The eNode B apparatus according to claim 20, wherein the different sequences having different sequence values are repeated on the basis of two resource block pairs on the frequency axis.

23. The eNode B apparatus according to claim 20, wherein the Walsh code elements of the CDM groups is applied to layer 1 as (1, 1, 1, 1), applied to layer 2 as (1, −

1, 1, −

1), applied to layer 3 as (1, 1, −

1, −

1), and applied to layer 4 as (1, −

1, −

1,

     1).

24. The eNode B apparatus according to claim 18, wherein the reference signal is used for demodulation of data and determined UE-specifically.