Allocating a control channel for carrier aggregation

1. A method for determining physical downlink control channel (PDCCH) assignments in a long term evolution (LTE) communication system, comprising:

monitoring by a user equipment (UE) a set of PDCCH candidates, the set of PDCCH candidates to monitor defined in a search space S k (L) at an aggregation level Lε{1,2,4,8} for a sub frame k;

wherein if the UE is configured with a carrier indicator field (CIF), the UE monitors one or more UE-specific search spaces at each of aggregation levels 1, 2, 4, 8, and wherein if the UE is not configured with the CIF, the UE monitors a common search space;

wherein if the UE is configured to monitor PDCCH candidates with a given downlink control information (DCI) format size with the CIF and if the PDCCH candidates may have one or more possible values of CIF for a given DCI format size, the UE monitors PDCCH candidates with the given DCI format size in UE-specific search spaces corresponding to possible values of the CIF for the given DCI format size; and

wherein the given DCI format that the UE is configured to monitor uses a configured transmission mode.

2. The method of claim 1 , wherein the search space S k (L) uses a carrier index CI to monitor the set of PDCCH candidates, wherein the carrier index CI includes a CIF value or an index of a sorted CIF value.

3. The method of claim 1 , wherein the search space S k (L) is represented by S k (L) =L·{(Y k +m)mod└N CCE,k /L┘}+i; where the search space S k (L) uses the configured transmission mode to monitor the set of PDCCH candidates; Y k is a variable; m=0, . . ., M (L) −1, and M (L) is the number of PDCCH candidates to monitor in the search space; N CCE,k is the total number of control channel elements (CCEs) in a kth subframe where Kε{0,1,2,3,4,5,6,7,8,9}; and i=0, . . ., L−1 is an increment integer.

4. The method of claim 3 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(T c,m ))]mod D ; where A=39827,Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(T c,m ) is a function using the configured transmission mode T c,m for a carrier c.

5. The method of claim 3 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m )) is a function using the configured transmission mode T c,m for a carrier c and a carrier index CI in a DCI format.

6. The method of claim 3 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ,S))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ,S) is a function using the configured transmission mode T c,m for a carrier c, a carrier index CI in a DCI format, and the DCI format size S.

7. The method of claim 1 , wherein monitoring the set of PDCCH candidates further comprises:

receiving the PDCCH at the UE;

searching for a selected component carrier's (CC's) downlink control information (DCI) in the search space S k (L) by identifying a starting control channel elements (CCE) location based on a selected CC's carrier index and the aggregation level L for the UE receiving the selected CC, wherein the carrier index includes a CIF value or an index of a sorted CIF value;

decoding each PDCCH candidate in the search space S k (L) beginning at the starting CCE location until a validly decoded PDCCH candidate is decoded; and

obtaining the selected CC's DCI from the validly decoded PDCCH candidate.

8. The method of claim 1 , wherein monitoring the set of PDCCH candidates further comprises recursively searching the search space S k (L) at a different aggregation level L until a validly decoded PDCCH candidate is decoded.

9. An apparatus, comprising:

a communications processor for a user equipment (UE) operative to determine physical downlink control channel (PDCCH) assignments in a long term evolution (LTE) communication system by monitoring by a user equipment (UE) a set of PDCCH candidates, the set of PDCCH candidates to monitor defined in a search space S k (L) at an aggregation level Lε{1,2,4,8} for a subframe k;

wherein if the UE is configured with a carrier indicator field (CIF), the UE monitors one or more UE-specific search spaces at each of aggregation levels 1, 2, 4, 8; and

wherein the UE monitors the set of PDCCH candidates using a configured transmission mode for the UE.

10. The apparatus of claim 9 , wherein if the UE is not configured with the CIF, the UE monitors a common search space;

wherein if the UE is configured to monitor PDCCH candidates with a given downlink control information (DCI) format size with the CIF and if the PDCCH candidates may have one or more possible values of CIF for a given DCI format size, the UE monitors PDCCH candidates with the given DCI format size in UE-specific search spaces corresponding to possible values of the CIF for the given DCI format size; and

wherein the given DCI format that the UE is configured to monitor uses a configured transmission mode.

11. The apparatus of claim 9 , wherein the search space S k (L) uses a carrier index CI to monitor the set of PDCCH candidates, wherein the carrier index CI includes a CIF value or an index of a sorted CIF value.

12. The apparatus of claim 9 , wherein the search space S k (L) is represented by S k (L) =L·{(Y k +m)mod└N CCE,k /L┘}+i; where the search space S k (L) uses the configured transmission mode to monitor the set of PDCCH candidates; Y k is a variable; m=0, . . ., M (L) −1, and M (L) is the number of PDCCH candidates to monitor in the search space; N CCE,k is the total number of control channel elements (CCEs) in a kth subframe where kε{0,1,2,3,4,5,6,7,8,9}; and i=0, . . ., L−1 is an increment integer.

13. The apparatus of claim 12 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(T c,m ))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(T c,m ) is a function using the configured transmission mode T c,m for a carrier c.

14. The apparatus of claim 12 , wherein variable Y k is represented by Y k =[A≠(Y k-1 +ƒ(CI,T c,m ))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ) is a function using the configured transmission mode T c,m for a carrier c and a carrier index CI in a DCI format.

15. The apparatus of claim 12 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ,S))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ,S) is a function using the configured transmission mode T c,m for a carrier c, a carrier index CI in a DCI format, and the DCI format size S.

16. The apparatus of claim 9 , wherein monitoring the set of PDCCH candidates further comprises:

receiving the PDCCH at the UE;

searching for a selected component carrier's (CC's) downlink control information (DCI) in the search space S k (L) by identifying a starting control channel elements (CCE) location based on a selected CC's carrier index and the aggregation level L for the UE receiving the selected CC, wherein the carrier index includes a CIF value or an index of a sorted CIF value;

decoding each PDCCH candidate in the search space S k (L) beginning at the starting CCE location until a validly decoded PDCCH candidate is decoded; and

obtaining the selected CC's DCI from the validly decoded PDCCH candidate.

17. A mobile device, comprising:

a user equipment (UE) operable in a long term evolution (LTE) communication system to monitor a set of PDCCH candidates, the set of PDCCH candidates to monitor defined in a search space S k (L) at an aggregation level Lε{1,2,4,8} for a subframe k;

wherein the search space S k (L) uses a carrier index CI to monitor the set of PDCCH candidates, wherein the carrier index CI includes a CIF value or an index of a sorted CIF value; and

wherein the UE monitors the set of PDCCH candidates using a configured transmission mode for the UE.

18. The mobile device of claim 17 , wherein if the UE is configured with a carrier indicator field (CIF), the UE monitors one or more UE-specific search spaces at each of aggregation levels 1, 2, 4, 8, and wherein if the UE is not configured with the CIF, the UE monitors a common search space;

wherein if the UE is configured to monitor PDCCH candidates with a given downlink control information (DCI) format size with the CIF and if the PDCCH candidates may have one or more possible values of CIF for a given DCI format size, the UE monitors PDCCH candidates with the given DCI format size in UE-specific search spaces corresponding to possible values of the CIF for the given DCI format size; and

wherein the given DCI format that the UE is configured to monitor uses a configured transmission mode.

19. The mobile device of claim 17 , wherein the search space S k (L) is represented by S k (L) =L·{(Y k +m)mod└N CCE,k /L┘}+i; where the search space S k (L) uses the configured transmission mode to monitor the set of PDCCH candidates; Y k is a variable; m=0, . . ., M (L) −1 ,and M (L) is the number of PDCCH candidates to monitor in the search space; N CCE,k is the total number of control channel elements (CCEs) in a kth subframe where kε{0,1,2,3,4,5,6,7,8,9}; and i=0, . . ., L−1 is an increment integer.

20. The mobile device of claim 19 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(T c,m ))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(T c,m ) is a function using the configured transmission mode T c,m for a carrier c.

21. The mobile device of claim 19 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ))]mod D ; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ) is a function using the configured transmission mode T c,m for a carrier c and a carrier index CI in a DCI format.

22. The mobile device of claim 19 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ,S))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ,S) is a function using the configured transmission mode T c,m for a carrier c, a carrier index CI in a DCI format, and the DCI format size S.

23. The mobile device of claim 17 , wherein the UE monitors the set of PDCCH candidates by:

receiving the PDCCH at the UE;

searching for a selected component carrier's (CC's) downlink control information (DCI) in the search space S k (L) by identifying a starting control channel elements (CCE) location based on a selected CC's carrier index and the aggregation level L for the UE receiving the selected CC, wherein the carrier index includes a CIF value or an index of a sorted CIF value;

decoding each PDCCH candidate in the search space S k (L) beginning at the starting CCE location until a validly decoded PDCCH candidate is decoded; and

obtaining the selected CC's DCI from the validly decoded PDCCH candidate.

24. A base transceiver station (BTS), comprising:

an evolved Node B (eNB) operable in a long term evolution (LTE) communication system to assign a set of PDCCH candidates, the set of PDCCH candidates to assign defined in a search space S k (L) at an aggregation level Lε{1,2,4,8} for a subframe k;

wherein the eNB is operable to communicate with a radio network controller (RNC) and a user equipment (UE) in a universal terrestrial radio access network (UTRAN);

wherein the BTS configures the UE with a carrier indicator field (CIF) when the UE is to monitor one or more UE-specific search spaces; and

wherein the UE assigns the set of PDCCH candidates using a configured transmission mode for the UE.

25. The BTS of claim 24 , wherein the BTS does configure the UE with a carrier indicator field (CIF) when the UE is to monitor a common search space;

wherein if the UE is configured to monitor PDCCH candidates with a given downlink control information (DCI) format size with the CIF and if the PDCCH candidates may have one or more possible values of CIF for a given DCI format size, the BTS assigns a PDCCH with the given DCI format size in the UE-specific search space corresponding to the CIF for the given DCI format size; and

wherein the given DCI format that the UE is configured to monitor uses a configured transmission mode.

26. The BTS of claim 24 , wherein the search space S k (L) uses a carrier index CI to monitor the set of PDCCH candidates, wherein the carrier index CI includes a CIF value or an index of a sorted CIF value.

27. The BTS of claim 24 , wherein the search space S k (L) is represented by S k (L) =L·{(Y k +m)mod└N CCE,k /L┘}+i; where the search space S k (L) uses the configured transmission mode to monitor the set of PDCCH candidates; Y k is a variable; m=0, . . ., M (L) −1, and M (L) is the number of PDCCH candidates to monitor in the search space; N CCE,k is the total number of control channel elements (CCEs) in a kth subframe where kε{0,1,2,3,4,5,6,7,8,9}; and i=0, . . ., L−1 is an increment integer.

28. The BTS of claim 27 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(T c,m ))]mod D; where A=39827,Y −1 =n RNHTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s 2┘ where n s is a slot number within a radio frame; and ƒ(T c,m ) is a function using the configured transmission mode T c,m, for a carrier c.

29. The BTS of claim 27 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ))]mod D ; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ) is a function using the configured transmission mode T c,m for a carrier c and a carrier index CI in a DCI format.

30. The BTS of claim 27 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ,S))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ,S) is a function using the configured transmission mode T c,m for a carrier c, a carrier index CI in a DCI format, and the DCI format size S.

31. The BTS of claim 24 , wherein the BTS assigns the set of PDCCH candidates by:

selecting the aggregation level L for a PDCCH allocation for each of a plurality of user equipments (UEs);

identifying the carrier index for each of a plurality of component carriers (CCs) associated with the PDCCH, wherein the carrier index includes a CIF value or an index of a sorted CIF value; and

assigning each CC's downlink control information (DCI) into control channel elements (CCEs) in the search space S k (L) in the PDCCH at a control channel element (CCE) starting location that is selected based on the CC's carrier index and the aggregation level L for the UE receiving the CC.

32. The BTS of claim 31 , wherein assigning each CC's DCI into CCEs further comprises:

assigning the CCEs of the CCs with a first carrier index CI 1 into a first carrier index search space S k (L) (CI 1 ) with a first carrier index CI 1 starting CCE location; and

assigning the CCEs of the CCs with a second carrier index CI 2 into a second carrier index search space S k (L) (CI 2 ) with a second carrier index CI 2 starting CCE location that differs from the first carrier index CI 1 starting CCE location, wherein first carrier index search space S k (L) (CI 1 ) and the second carrier index search space S k (L) (CI 2 ) are subsets of S k (L) .

33. A computer program product, comprising a non-transitory computer readable storage medium having a computer readable program code embodied therein, the computer readable program code adapted to be executed to implement a method for determining physical downlink control channel (PDCCH) assignments in a long term evolution (LTE) communication system, comprising:

monitoring by a user equipment (UE) a set of PDCCH candidates, the set of PDCCH candidates to monitor defined in a search space S k (L) at an aggregation level Lε{1,2,4,8} for a subframe k;

wherein if the UE is configured with a carrier indicator field (CIF), the UE monitors one or more UE-specific search spaces at each of aggregation levels 1, 2, 4, 8; and

wherein the UE monitors the set of PDCCH candidates using a configured transmission mode for the UE.

34. The computer program product of claim 33 , wherein if the UE is not configured with the CIF, the UE monitors a common search space;

wherein if the UE is configured to monitor PDCCH candidates with a given downlink control information (DCI) format size with the CIF and if the PDCCH candidates may have one or more possible values of CIF for a given DCI format size, the UE monitors PDCCH candidates with the given DCI format size in UE-specific search spaces corresponding to possible values of the CIF for the given DCI format size; and

wherein the given DCI format that the UE is configured to monitor uses a configured transmission mode.

35. The computer program product of claim 33 , wherein the search space S k (L) uses a carrier index CI to monitor the set of PDCCH candidates, wherein the carrier index CI includes a CIF value or an index of a sorted CIF value.

36. The computer program product of claim 33 , wherein the search space S k (L) is represented by S k (L) =L·{(Y k +m)mod└N CCE,k /L┘}+i; where the search space S k (L) uses the configured transmission mode to monitor the set of PDCCH candidates; Y k is a variable; m=0, . . ., M (L) −1 and M (L) is the number of PDCCH candidates to monitor in the search space; N CCE,k is the total number of control channel elements (CCEs) in a kth subframe where kε{0,1,2,3,4,5,6,7,8,9}; and i=0, . . ., L−1 is an increment integer.

37. The computer program product of claim 36 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(T c,m ))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(T c,m ) is a function using the configured transmission mode T c,m for a carrier c.

38. The computer program product of claim 36 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ))]mod D ; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ) is a function using the configured transmission mode T c,m for a carrier c and a carrier index CI in a DCI format.

39. The computer program product of claim 36 , wherein variable Y k is represented by Y k =[A·(Y k-1 +ƒ(CI,T c,m ,S))]mod D; where A=39827, Y −1 =n RNTI ≠0, and D=65537 are constant where n RNTI is a radio network temporary identifier (RNTI) assigned to the UE by an evolved Node B (eNB); k is an integer k=└n s /2┘ where n s is a slot number within a radio frame; and ƒ(CI,T c,m ,S) is a function using the configured transmission mode T c,m for a carrier c, a carrier index CI in a DCI format, and the DCI format size S.

40. The computer program product of claim 33 , wherein monitoring the set of PDCCH candidates further comprises:

receiving the PDCCH at the UE;

searching for a selected component carrier's (CC's) downlink control information (DCI) in the search space s k (L) by identifying a starting control channel elements (CCE) location based on a selected CC's carrier index and the aggregation level L for the UE receiving the selected CC, wherein the carrier index includes a CIF value or an index of a sorted CIF value;

decoding each PDCCH candidate in the search space S k (L) beginning at the starting CCE location until a validly decoded PDCCH candidate is decoded; and

obtaining the selected CC's DCI from the validly decoded PDCCH candidate.

41. The computer program product of claim 33 , wherein monitoring the set of PDCCH candidates further comprises recursively searching the search space S k (L) at a different aggregation level L until a validly decoded PDCCH candidate is decoded.