CONTROL CHANNEL FORMULATION IN OFDM SYSTEMS

• US 20100260036A1
• Filed: 10/28/2008
• Published: 10/14/2010
• Est. Priority Date: 10/29/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Cheng, Jung-Fu, Molnar, Karl, Parkvall, Stefan
• Granted Patent: US 8,385,360 B2
• Time in Patent Office: Days
• US Class Current: 370/203
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals

Abstract

Control channel information is formulated for transmission in orthogonal frequency division multiplexing (OFDM) systems. In an example embodiment, a method entails formulating control channel information for a transmitting device operating in an OFDM system in which a control channel spans n OFDM symbols, with n being an integer. The method includes acts of allocating, creating, and mapping. Control channel data is allocated to at least one set of resource element groups. At least one order for the set of resource element groups is created in accordance with one or more permutation mechanisms that involve at least one interleaving sequence having a low cross-correlation property. The set of resource element groups is mapped to resource elements of the n OFDM symbols of the control channel responsive to the order that is created using the permutation mechanism(s). The permutation mechanisms may include interleaving sequence(s) and/or cyclic shift(s).

Claims

1. A method of formulating control channel information for a transmitting device operating in an orthogonal frequency division multiplexing (OFDM) system in which a control channel spans n OFDM symbols, with n being an integer;

the method comprising acts of;

allocating control channel data to at least one set of resource element groups;

creating at least one order for the at least one set of the resource element groups in accordance with one or more permutation mechanisms that involve at least one interleaving sequence having a low cross-correlation property; and

mapping the at least one set of the resource element groups to resource elements of the n OFDM symbols of the control channel responsive to the at least one order that is created using the one or more permutation mechanisms.

2. The method as recited in claim 1, wherein n is an integer greater than one, the at least one set of the resource element groups comprises n sets of the resource element groups, and the one or more permutation mechanisms comprise n permutation mechanisms;

and wherein;

the act of allocating comprises allocating the control channel data to the n sets of the resource element groups;

the act of creating comprises creating n respective orders along an OFDM frequency dimension for the n sets of the resource element groups for respective ones of the n OFDM symbols in accordance with the n permutation mechanisms, the n permutation mechanisms differing from one another; and

the act of mapping comprises mapping the n sets of the resource element groups to the resource elements of the respective ones of the n OFDM symbols responsive to the n respective orders that are created using the n permutation mechanisms.

3. The method as recited in claim 2, wherein the n permutation mechanisms entail n interleaving sequences that are selected from a family of F sequences having low auto-correlation and low cross-correlation properties;

wherein the n interleaving sequences are employed in common across multiple cells of the OFDM system; and

wherein the act of creating further comprises creating the n respective orders along the OFDM frequency dimension for the n sets of the resource element groups using a different respective interleaving sequence of the n interleaving sequences for each respective one of the n OFDM symbols.

4. The method as recited in claim 3, wherein the n permutation mechanisms further entail a single cyclic shift for the n OFDM symbols;

and

wherein the act of creating further comprises creating the n respective orders along the OFDM frequency dimension for the n sets of the resource element groups using the single cyclic shift for the n OFDM symbols.

5. The method as recited in claim 4, wherein the OFDM system comprises a cell-based wireless system;

wherein each cell of the cell-based wireless system has a different single cyclic shift that is used across its n OFDM symbols; and

wherein the single cyclic shift for each cell is based on an identifier of the cell.

6. The method as recited in claim 2, wherein the n permutation mechanisms entail a single interleaving sequence that is selected from a family of F sequences having low auto-correlation and low cross-correlation properties;

wherein each cell of the OFDM system employs a different interleaving sequence derived from the family of F sequences;

wherein the n permutation mechanisms entail at least n−

1 cyclic shifts; and

wherein the act of creating further comprises creating the n respective orders along the OFDM frequency dimension for the n sets of the resource element groups using the single interleaving sequence and a different respective cyclic shift of the at least n−

1 cyclic shifts for each respective one of the n OFDM symbols.

7. The method as recited in claim 6, further comprising an act of:

hashing an identifier of a cell to one of F numbers to select from the family of F sequences an interleaving sequence as the single interleaving sequence.

8. The method as recited in claim 7, wherein the at least n−

1 cyclic shifts are employed in common across multiple cells of the OFDM system, or the at least n−

1 cyclic shifts are predefined in dependence on the single interleaving sequence as selected from the family of F sequences.

9. The method as recited in claim 2, wherein the n permutation mechanisms entail n interleaving sequences that are selected from a family of F sequences having low cross-correlation properties;

and

wherein the act of creating further comprises creating the n respective orders along the OFDM frequency dimension for the n sets of the resource element groups using a different respective interleaving sequence of the n interleaving sequence for each respective one of the n OFDM symbols.

10. The method as recited in claim 9, wherein the n interleaving sequences that are employed in each cell of the OFDM system differ among different cells;

and wherein the method comprises a further act of;

using a respective function selected from n functions to hash an identifier of a cell to one of F numbers to select a respective interleaving sequence from the family of F sequences for each respective permutation mechanism of the n permutation mechanisms.

11. The method as recited in claim 9, wherein the n interleaving sequences that are employed in each cell of the OFDM system differ among different cells;

and wherein the method comprises further acts of;

using a function to hash an identifier of a cell to one of F numbers to select an interleaving sequence from the family of F sequences for one permutation mechanism of the n permutation mechanisms; and

using a respective sequence identification offset of n−

1 sequence identification offsets and the selected interleaving sequence to select a respective interleaving sequence from the family of F sequences for each other respective permutation mechanism of the n permutation mechanisms.

12. The method as recited in claim 11, wherein the n−

1 sequence identification offsets are employed in common across multiple cells of the OFDM system, or the n−

1 sequence identification offsets are predefined in dependence on the selected interleaving sequence from the family of F sequences.

13. The method as recited in claim 1, wherein the one or more permutation mechanisms entail a single interleaving sequence that is selected from a family of F sequences having low auto-correlation and low cross-correlation properties;

and

wherein the act of creating further comprises creating the at least one order for the at least one set of the resource element groups over the n OFDM symbols jointly.

14. The method as recited in claim 13, wherein a range of the single interleaving sequence covers both used and unused resource element groups of the control channel;

and

wherein the act of creating further comprises creating the at least one order for the at least one set of the resource element groups over both the used and the unused resource element groups.

15. The method as recited in claim 13, wherein each cell of the OFDM system employs a different single interleaving sequence;

and wherein the method further comprises an act of;

hashing an identifier of a cell to one of F numbers to select from the family of F sequences an interleaving sequence as the single interleaving sequence.

16. The method as recited in claim 15, wherein the one or more permutation mechanisms entails a cyclic shift that is dependent on the identifier of the cell;

and

wherein the act of creating further comprises creating the at least one order for the at least one set of the resource element groups over the n OFDM symbols jointly using the cyclic shift that is dependent on the identifier of the cell.

17. The method as recited in claim 13, wherein each cell of the OFDM system employs a common single interleaving sequence;

wherein the one or more permutation mechanisms entails a cyclic shift that is dependent on an identifier of a cell; and

wherein the act of creating further comprises creating the at least one order for the at least one set of the resource element groups over the n OFDM symbols jointly using the cyclic shift that is dependent on the identifier of the cell.

18. The method as recited in claim 1, wherein each resource element group of the set of resource element groups comprises a mini-control channel element, mini-CCE.

19. The method as recited in claim 1, wherein the at least one interleaving sequence having a low cross-correlation property comprises a sequence selected from hyperbolic congruence sequences, cubic congruence sequences, or extended quadratic congruence sequences.

20. A transmitting device for formulating control channel information in an orthogonal frequency division multiplexing (OFDM) system in which a control channel spans n OFDM symbols, with n being an integer;

the transmitting device comprising;

at least one processor; and

one or more memory including processor-executable instructions that are configured to be executed by the at least one processor, the processor-executable instructions adapted to direct the transmitting device to perform acts comprising;

allocating control channel data to at least one set of resource element groups;

creating at least one order for the at least one set of the resource element groups in accordance with one or more permutation mechanisms that involve at least one interleaving sequence having a low cross-correlation property; and

mapping the at least one set of the resource element groups to resource elements of the n OFDM symbols of the control channel responsive to the at least one order that is created using the one or more permutation mechanisms.

21. A memory storing processor-executable instructions for formulating control channel information for a transmitting device operating in an orthogonal frequency division multiplexing (OFDM) system in which a control channel spans n OFDM symbols, with n being an integer;

wherein the processor-executable instructions, when executed, direct the transmitting device to perform acts comprising;

allocating control channel data to at least one set of resource element groups;

creating at least one order for the at least one set of the resource element groups in accordance with one or more permutation mechanisms that involve at least one interleaving sequence having a low cross-correlation property; and

mapping the at least one set of the resource element groups to resource elements of the n OFDM symbols of the control channel responsive to the at least one order that is created using the one or more permutation mechanisms.

22. A transmitting device for formulating control channel information in an orthogonal frequency division multiplexing (OFDM) system in which a control channel spans n OFDM symbols, with n being an integer;

the transmitting device comprising;

one or more permutation mechanisms that include at least one interleaving sequence having a low cross-correlation property;

a data allocator to allocate control channel data to at least one set of resource element groups;

an order creator to create at least one order for the at least one set of the resource element groups in accordance with the one or more permutation mechanisms; and

a resource element group mapper to map the at least one set of the resource element groups to resource elements of the n OFDM symbols of the control channel responsive to the at least one order that is created using the one or more permutation mechanisms.

23. The transmitting device as recited in claim 22, wherein n is an integer greater than one, the at least one set of the resource element groups comprises n sets of the resource element groups, and the one or more permutation mechanisms comprise n permutation mechanisms;

and wherein;

the data allocator is to allocate the control channel data to the n sets of the resource element groups;

the order creator is to create n respective orders along an OFDM frequency dimension for the n sets of the resource element groups for respective ones of the n OFDM symbols in accordance with the n permutation mechanisms, the n permutation mechanisms differing from one another; and

the resource element group mapper is to map the n sets of the resource element groups to the resource elements of the respective ones of the n OFDM symbols responsive to the n respective orders that are created using the n permutation mechanisms.

24. The transmitting device as recited in claim 23, wherein the n permutation mechanisms include n interleaving sequences that are selected from a family of F sequences having low auto-correlation and low cross-correlation properties, and the n interleaving sequences are employed in common across multiple cells of the OFDM system;

and wherein the n permutation mechanisms further include a single cyclic shift for the n OFDM symbols, with the single cyclic shift being established differently per cell.

25. The transmitting device as recited in claim 23, wherein the n permutation mechanisms include a single interleaving sequence that is selected from a family of F sequences having low auto-correlation and low cross-correlation properties, and the single interleaving sequence is established differently per cell in each cell of multiple cells of the OFDM system;

and wherein the n permutation mechanisms further include at least n−

1 cyclic shifts that are respectively applied to n−

1 OFDM symbols, with the at least n−

1 cyclic shifts being employed in common across the multiple cells.

26. The transmitting device as recited in claim 23, wherein the n permutation mechanisms include n interleaving sequences that are selected from a family of F sequences having low cross-correlation properties, and the n interleaving sequences are established differently per cell in each cell of multiple cells of the OFDM system;

and wherein the order creator is to create the n respective orders along the OFDM frequency dimension for the n sets of the resource element groups using a different respective interleaving sequence of the n interleaving sequence for each respective one of the n OFDM symbols.

27. The transmitting device as recited in claim 22, wherein the n permutation mechanisms include a single interleaving sequence that is selected from a family of F sequences having low auto-correlation and low cross-correlation properties, and the single interleaving sequence is established differently per cell in each cell of multiple cells of the OFDM system;

and wherein the order creator is to create the at least one order for the at least one set of the resource element groups over the n OFDM symbols jointly.

28. The transmitting device as recited in claim 22, wherein the n permutation mechanisms include a single interleaving sequence that is selected from a family of F sequences having low auto-correlation and low cross-correlation properties, and the single interleaving sequence is employed in common across multiple cells of the OFDM system;

wherein the n permutation mechanisms further include a single cyclic shift for the n OFDM symbols, with the single cyclic shift being established differently per cell; and

wherein the order creator is to create the at least one order for the at least one set of the resource element groups over the n OFDM symbols jointly.