Control channels for wireless communication

• US 9,924,505 B2
• Filed: 01/26/2015
• Issued: 03/20/2018
• Est. Priority Date: 08/02/2012
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Moulsley, Timothy
• Primary Examiner(s): Lai, Andrew
• Assistant Examiner(s): Ganguly, Sumitra
• Application Number:
  US14/604,968
• Publication Number:
  US 20150181577A1
• Time in Patent Office: 1,149 Days
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/0096 Indication of changes in allocation
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal

Abstract

A method for configuring a search space within which a mobile terminal performs blind decoding attempts for potential control message candidates which may be transmitted by a base station. The frequency domain resource for which the terminal performs a blind decoding attempt for a given candidate message is determined by a pseudo-random selection (known by both terminal and network) from a pre-determined set of possible resources. A pre-determined set of resources can be different for each candidate. In one embodiment the set of resources is configured by the network for each terminal and each candidate. The method may be applied for example to ePDCCH of an LTE-A wireless communication system.

Claims

1. A wireless communication method in which a wireless network transmits a control channel message for receipt by a terminal, the method comprising,

at the wireless network side:

configuring resources from available resources to form a search space for each of one or more control channel elements for the control channel message;

making a pseudo-random selection of a location for the search space within a subframe using a pseudo-random function;

determining which of the one or more control channel elements to use for transmission of the control channel message, and

transmitting the control channel message at the selected location for the determined one or more control channel elements; and

at the terminal side;

decoding the control channel message corresponding to the one or more control channel elements by making a selection of locations for blind decoding each of the search space within the subframe, using the pseudo-random function,

wherein, the pseudo-random function is a function based on a sum of a first value and a second value, wherein the first value is a pseudo-random factor, and the second value is based on an aggregation level and a total of control channel elements in the subframe.

2. The method according to claim 1 wherein the resources corresponding to the search space are different for each of the one or more control channel elements.

3. The method according to claim 2 wherein the resources corresponding to the search space for each of the one or more control channel elements are configured such that the resources are adjacently located in adjacent frequency domain locations.

4. The method according to claim 1, wherein an amount of resources used for the transmission of the control channel message has one of a plurality of sizes depending on the aggregation level and the search space is different for each aggregation level.

5. The method according to claim 1, wherein the configuring comprises providing the terminal with a bit map defining the search spaces.

6. The method according to claim 1, wherein the configuring is performed independently for each terminal or group of terminals within a plurality of terminals served by a common cell.

7. The method according to claim 6 wherein the configuring is performed in accordance with channel conditions between the wireless network and the terminal or the group of terminals.

8. The method according to claim 1, wherein the configuring configures overlapping search spaces for a plurality of terminals and/or for a plurality of aggregation levels each of the plurality of aggregation levels representing a size of a resource used for transmission of the control channel message.

9. The method according to claim 1, applied to an enhanced Physical Downlink Control Channel, ePDCCH of an LTE-based wireless communication system wherein each of the control channel messages occupies one or more enhanced Control Channel Elements, eCCEs within a given subframe.

10. The method according to claim 9 wherein the ePDCCH is a localized ePDCCH and said configuring configures the search space such that corresponding resources overlap with resources corresponding to a search space configured for a distributed ePDCCH.

11. The method according to claim 9 wherein resources for the ePDCCH are divided in frequency domain into pairs of Physical Resource Blocks, (PRBs) to which the eCCEs are mapped, resources corresponding to each search space comprise a set of PRB pairs, and said selection comprises selecting a PRB pair from the set using said pseudo-random function.

12. The method according to claim 11 wherein the selection further selects an eCCE within the PRB pair.

13. The method according to claim 9 wherein each search space comprises a set of eCCEs and said selection selects one or more eCCEs from the set.

14. The method according to claim 9 wherein the selection is made based on the following pseudo-random function:

L{((Y_k+O′

_k,m,L,)mod|N′

_eCCE,k,m,L/L|+O_k,m,L)mod|N_eCCE,k/L/}+i

where L is the aggregation level, m is a ePDCCH candidate corresponding to eCCEs of the search space, k is the subframe for transmission of the control channel message, N_eCCE,k is a total number of eCCEs available in the subframe k, N′

_eCCE,k,m,L is a number of eCCEs within which the ePDCCH candidate may be located, O_k,m,L is an offset within the total number of eCCEs or a subset of eCCEs for the subframe, the ePDCCH candidate and the aggregation level, O′

_k,m,L is an offset within the subset of eCCEs defined for the subframe, the candidate and the aggregation level, Y_k is a pseudo-random factor based on the subframe k and a radio network temporary identifier, and i=0 . . . , L−

1.

15. A wireless communication system comprising a base station and a terminal, the base station arranged to transmit a control channel message which is received by the terminal, the base station comprising:

a configurer for configuring resources from available resources to form a search space for each of one or more control channel elements for the control channel message;

a selector for making a pseudo-random selection of a location for the search space within a subframe using a pseudo-random function;

a scheduler for determining which of the one or more control channel elements to use for transmission of the control channel message, and

a transmitter for transmitting the control channel message at the location selected by the selector for the one or more control channel elements determined by the scheduler; and

the terminal comprising;

a receiver for receiving the search space configuration from the base station and for receiving the control channel message;

a selector for making a selection of a set of one or more locations for blind decoding within the search space configured for the one or more control channel elements, the selector using the same pseudo-random function used by the selector of the base station; and

a decoder for decoding the control channel message at each location selected by the selector of the terminal,

wherein, the pseudo-random function is a function based on a sum of a first value and a second value, wherein the first value is a pseudo-random factor, and the second value is based on an aggregation level and a total of control channel elements in the subframe.

16. A base station for use in a wireless communication system and arranged to transmit a control channel message, the base station comprising:

a configurer for configuring a resource from available resources to form a search space for each of one or more control channel elements for the control channel message;

a selector for making a pseudo-random selection of a location for the search space within a subframe using a pseudo-random function;

a scheduler for determining at least one of the one or more control channel elements to use for transmission of the control channel message, and

a transmitter for transmitting the control channel message at the location selected by the selector for the at least one control channel element determined by the scheduler,

wherein, the pseudo-random function is a function based on a sum of a first value and a second value, wherein the first value is a pseudo-random factor, and the second value is based on an aggregation level and a total of control channel elements in the subframe.

17. A terminal for use in a wireless communication network, the wireless communication network arranged to transmit at least one control channel message to the terminal, the at least one control channel message based on at least one control channel element, a search space being configured from available resources for each of the at least one control channel element, wherein the terminal comprises:

a receiver for receiving the search space configured for the at least one control channel element from the network, and for receiving the at least one control channel message;

a selector for making a selection of locations for blind decoding the search space configured for the at least one control channel element, the selector using a pseudo-random function which is the same as a pseudo-random function used by the network for selecting a location of the at least one control channel element within the search space; and

a decoder for decoding the at least one control channel message at each location selected by the selector,

wherein, the pseudo-random function is a function based on a sum of a first value and a second value, wherein the first value is a pseudo-random factor, and the second value is based on an aggregation level and a total of control channel elements in a subframe.