CONTROL CHANNELS FOR WIRELESS COMMUNICATION

• US 20150181577A1
• Filed: 01/26/2015
• Published: 06/25/2015
• Est. Priority Date: 08/02/2012
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Moulsley, Timothy
• Granted Patent: US 9,924,505 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 which is received by a terminal, the method comprising,

on the network side:

configuring a respective search space in the frequency domain separately for each of a plurality of candidates for the control channel message;

making a selection of a location, using a pseudo-random function, within the respective search space so configured for at least one of the plurality of candidates;

determining one of the plurality of candidates to use for transmission of a control channel message, and

transmitting a control channel message at the selected location for the candidate so determined; and

on the terminal side;

decoding a control channel message corresponding to each of one or more of the plurality of candidates by making a selection of a set of one or more locations for blind decoding within each of the respective search spaces, using the same pseudo-random function used for the selection of the location for the corresponding candidate on the network side.

2. The method according to claim 1 wherein resources corresponding to the search spaces are different for each candidate.

3. The method according to claim 2 wherein the resources corresponding to the search spaces for the plurality of candidates are configured such that they are adjacently located in the frequency domain.

4. The method according to claim 1, wherein an amount of resource used for transmission of a control channel message has one of a plurality of sizes depending on an 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 the same cell.

7. The method according to claim 6 wherein the determining is performed in accordance with channel conditions between the network and the terminal or 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 representing a size of a resource used for transmission of a 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 localised ePDCCH and said configuring configures said search spaces such that the corresponding resources overlap with the 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 the frequency domain into pairs of Physical Resource Blocks, PRBs to which the eCCEs are mapped, the 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 a 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 the candidate, k is a subframe for transmission of the control channel message, N_eCCE,k is the total number of eCCEs available in subframe k, N′

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

_k,m,L is an offset within the subset of eCCEs defined for a given subframe, candidate and aggregation level, Y_k is a pseudo-random factor based on 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 a respective search space in the frequency domain separately for each of a plurality of candidates for the control channel message;

a selector for making a selection of a location using a pseudo-random function within the respective search space so configured for at least one of the plurality of candidates;

a scheduler for determining one of the plurality of candidates to use for transmission of a control channel message, and

a transmitter for transmitting a control channel message at the location selected by the selector for the candidate determined by the scheduler; and

the terminal comprising;

a receiver for receiving a 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 at least one of the plurality of candidates, the selector using the same pseudo-random function used by the selector of the base station; and

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

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 respective search space in the frequency domain separately for each of a plurality of candidates for the control channel message;

a selector for making a selection using a pseudo-random function of a location within the respective search space so configured for at least one of the plurality of candidates;

a scheduler for determining one of the plurality of candidates to use for transmission of a control channel message, and

a transmitter for transmitting a control channel message at the location selected by the selector for the candidate determined by the scheduler.

17. A terminal for use in a wireless communication network, the network arranged to transmit at least one control channel message to the terminal, the at least one each control channel message based on one of a plurality of candidates, a respective search space in the frequency domain being configured separately for each of the plurality of candidates, wherein the terminal comprises:

a receiver for receiving a search space configuration for each of the plurality of candidates from the network, 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 at least one of the plurality of candidates, 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 a candidate within the search space; and

a decoder for decoding a control channel message at the or each location selected by the selector.