APPARATUS AND METHOD FOR ALLOCATING CODE RESOURCES TO UPLINK ACK/NACK CHANNELS IN A CELLULAR WIRELESS COMMUNICATION SYSTEM

• US 20090046646A1
• Filed: 08/11/2008
• Published: 02/19/2009
• Est. Priority Date: 08/10/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: CHO, Joon-Young, Pi, Zhouyue, Papasakellariou, Aris, Zhang, Jianzhong, Lee, Ju-Ho
• Granted Patent: US 8,295,155 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 11/005 of intercell interference
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04J 13/0062 Zadoff-Chu
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04L 1/1861 Physical mapping arrangements for ACK signaling see also H04L5/0053
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0019 in which one code is applied, as a temporal sequence, to all frequencies
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/0055 Physical resource allocation for ACK/NACK for physical mapping arrangements in ARQ protocols H04L1/1861
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 72/0466 the resource being a scrambling code
• CPC Class Codes: H04W 72/20 Control channels or signalling for resource management
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems

Abstract

A method and apparatus are provided for allocating code resources to ACK/NACK channel indexes, when UEs need ACK/NACK transmission in a wireless communication system in which a predetermined number of orthogonal cover Walsh codes is selected from among available orthogonal cover Walsh codes, at least one subset is formed, having the selected orthogonal cover Walsh codes arranged in an ascending order of cross interference, subsets are selected for use in first and second slots of a subframe, and the orthogonal cover Walsh codes of the subset selected for each slot and ZC sequence cyclic shift values are allocated to the ACK/NACK channel indexes.

Claims

1. A method for allocating code resources to ACKnowledgment/Negative ACKnowledgment (ACK/NACK) channel indexes, when User Equipments (UEs) need ACK/NACK transmission in a wireless communication system, the method comprising:

selecting a predetermined number of orthogonal cover Walsh codes from among available orthogonal cover Walsh codes

forming at least one subset in which the selected orthogonal cover Walsh codes are arranged in an ascending order of cross interference;

selecting subsets from the at least one formed subset for use in first and second slots of a subframe; and

allocating the orthogonal cover Walsh codes of the selected subset for each slot and Zadoff-Chu (ZC) sequence cyclic shift values to the ACK/NACK channel indexes.

2. The method of claim 1, wherein the subset forming comprises forming the at least one subset based on

when the UE moves so fast such that a channel experiences fading, an interference level R(0,3) between Walsh functions W₀ and W₃ is 10% of a maximum interference level of 1,

when the CDF is 90%, R(0, 2) representing the cross interference between Walsh codes, W₀ and W₂ is near 0.75, higher than R(0, 3) at the CDF of 90%,

then, when three Walsh codes are used for ACK/NACK channel transmission in one slot, the following subsets of Walsh codes are made:

TABLE 1 Best 2^nd Best Worst Code A Code B Code C Subset 0 W1 W2 W0 W0, W1, W2 Subset 1 W0 W3 W1 W0, W1, W3 Subset 2 W3 W0 W2 W0, W2, W3 Subset 3 W2 W1 W3 W1, W2, W3

3. The method of claim 1, wherein the allocating further comprises allocating an orthogonal cover Walsh code causing less cross interference among the orthogonal cover Walsh codes of a subset to ACK/NACK channel indexes using a ZC sequence cyclic shift value to which more ACK/NACK channel indexes are allocated.

4. The method of claim 3, wherein the allocating further comprises, in the second slot, allocating a second orthogonal cover Walsh code to ACK/NACK channel indexes that have used a first orthogonal cover Walsh code in the first slot.

5. The method of claim 4, wherein the allocating further comprises allocating ZC sequence cyclic shift values mapped to the second orthogonal cover Walsh code to the ACK/NACK channel indexes in the second slot, in a randomly changed order.

6. The method of claim 3, wherein the allocating further comprises, in the second slot, randomly changing the sequence of ZC sequence cyclic shift values allocated to ACK/NACK channel indexes using the same orthogonal cover Walsh code in the first slot.

7. The method of claim 3, wherein the allocating comprises, in the second slot, randomly changing orthogonal cover Walsh codes and ZC sequence cyclic shift values allocated to ACK/NACK channel in the first slot.

8. The method of claim 3, wherein the subset selecting further comprises selecting different subsets for the first and second slots.

9. The method of claim 8, wherein the allocating further comprises, in the second slot, allocating a second orthogonal cover Walsh code to ACK/NACK channel indexes that have used a first orthogonal cover Walsh code in the first slot.

10. The method of claim 9, wherein the allocating further comprises allocating ZC sequence cyclic shift values mapped to the second orthogonal cover Walsh code to the ACK/NACK channel indexes in the second slot, in a randomly changed order.

11. The method of claim 8, wherein the allocating further comprises, in the second slot, randomly changing the sequence of ZC sequence cyclic shift values allocated to ACK/NACK channel indexes using the same orthogonal cover Walsh code in the first slot.

12. The method of claim 8, wherein the allocating further comprises, in the second slot, randomly changing orthogonal cover Walsh codes and ZC sequence cyclic shift values allocated to ACK/NACK channel in the first slot.

13. An apparatus for allocating resources to ACKnowledgment/Negative ACKnowledgment (ACK/NACK) channels to a User Equipment (UE) in a wireless communication system, comprising:

an ACK/NACK symbol generator for generation of an ACK/NACK symbol;

an orthogonal cover symbol generator for selection of subsets for use in a first and a second slot of a subframe from at least one subset formed by selection of a predetermined number of orthogonal cover Walsh codes from among available orthogonal cover Walsh codes and for arrangement of the selected predetermined number of orthogonal cover Walsh codes in an ascending order of cross interference, and generation of an orthogonal cover sequence symbol to be mapped to an ACK/NACK channel that will transmit ACK/NACK information;

a first multiplier for multiplication of the ACK/NACK symbol by the orthogonal cover sequence symbol;

a multiplexer for output of the multiplied ACK/NACK symbol and a generated Reference Signal (RS) symbol at least one predetermined symbol timing;

a second multiplier for multiplication of the multiplied ACK/NACK symbol output by the multiplexer, by a Zadoff-Chu (ZC) sequence; and

a subcarrier mapper for allocation of the output signal from the second multiplier to a band set for transmission of the ACK/NACK symbol.

14. The apparatus of claim 13, wherein the orthogonal cover symbol generator is further configured to allocate an orthogonal cover Walsh code that causes less cross interference among the orthogonal cover Walsh codes of a subset, to ACK/NACK channel indexes using a ZC sequence cyclic shift value to which more ACK/NACK channel indexes are allocated.

15. The apparatus of claim 14, wherein the orthogonal cover symbol generator is further configured to allocate in the second slot a second orthogonal cover Walsh code to ACK/NACK channel indexes that have used a first orthogonal cover Walsh code in the first slot.

16. The apparatus of claim 15, wherein the second multiplier is further configured to allocate in a randomly changed order ZC sequence cyclic shift values mapped to the second orthogonal cover Walsh code to the ACK/NACK channel indexes in the second slot.

17. The apparatus of claim 14, wherein in the second slot the second multiplier is further configured to randomly change the sequence of ZC sequence cyclic shift values allocated to ACK/NACK channel indexes using the same orthogonal cover Walsh code in the first slot.

18. The apparatus of claim 14, wherein selection of subsets by the orthogonal cover symbol generator further comprises selection of different subsets for the first and second slots.

19. The apparatus of claim 18, wherein the allocation in the second slot by the orthogonal cover symbol generator further comprises allocation of a second orthogonal cover Walsh code to ACK/NACK channel indexes that have used a first orthogonal cover Walsh code in the first slot.

20. The apparatus of claim 19, wherein the second multiplier is further configured to allocate ZC sequence cyclic shift values mapped to the second orthogonal cover Walsh code to the ACK/NACK channel indexes in the second slot, in a randomly changed order.

21. The apparatus of claim 18, wherein the second multiplier is further configured to randomly change in the second slot the sequence of ZC sequence cyclic shift values allocated to ACK/NACK channel indexes using the same orthogonal cover Walsh code in the first slot.