Methods, Network Nodes and User Equipments in a Wireless Network for Communicating an EPDCCH

Abstract

A network node in a wireless communication network communicates an enhanced Physical Downlink Control Channel (ePDCCH) to a user equipment (UE). This begins with the transmission, to the UE, of a configuration message that indicates the mappings of ePDCCH onto resource elements for both a first ePDCCH set and a second ePDCCH set. The mapping for the first ePDCCH set avoids the use of resource elements already in use by a first type of signal (e.g., a Cell-Specific Reference Signal or CRS), whereas the mapping for the second ePDCCH set avoids the use of resource elements in use by a second type of signal. The choice of an ePDCCH set for transmitting data to a UE may then be dynamically made in order to avoid interference caused by the first or second types of signal.

What is claimed is: 
     
         1 . A method, performed by a user equipment (UE) in a wireless communication network, for communicating an enhanced Physical Downlink Control Channel (ePDCCH) with a network node providing coverage to a serving cell, the method comprising:
 receiving a configuration message from the network node, the configuration message comprising:
 an indication of a first mapping of the ePDCCH for the serving cell to resource elements belonging to a first ePDCCH set, where the ePDCCH is mapped around resource elements of the first ePDCCH set used for a first Cell-Specific Reference Signal (CRS), the indication of the first mapping comprising an indication of at least one of (a) the number of CRS ports for the first CRS and (b) the CRS frequency shift for the first CRS, and 
 an indication of a second mapping of the ePDCCH for the serving cell to resource elements belonging to a second ePDCCH set, where the ePDCCH is mapped around resource elements of the second ePDCCH set used for a second CRS, the indication of the second mapping comprising an indication of at least one of (c) the number of CRS ports for the second CRS and (d) the CRS frequency shift for the second CRS; and 
   monitoring ePDCCH candidates in the first ePDCCH set according to the first mapping and monitoring ePDCCH candidates in the second ePDCCH set according to the second mapping.   
     
     
         2 . The method of  claim 1 , wherein the configuration message comprises an indication of an ePDCCH start symbol for the first ePDCCH set and an indication of an ePDCCH start symbol for the second ePDCCH set. 
     
     
         3 . The method of  claim 2 , wherein the indicated ePDCCH start symbol for the first ePDCCH set is the same start symbol as scheduled for a Packet Data Shared Channel (PDSCH) to be transmitted by the network node. 
     
     
         4 . The method of  claim 1 , wherein one or more of the following configuration parameters are shared between the ePDCCH and a Packet Data Shared Channel (PDSCH):
 a number of CRS antenna ports;   a CRS frequency shift;   a start position;   a Multicast/Broadcast Single Frequency Network (MBSFN) subframe configuration; and   a Zero Power Channel State Information Reference Signal (CSI-RS) resource configuration.   
     
     
         5 . The method of  claim 1 , further comprising:
 receiving a message from the network node comprising the ePDCCH allocated to a selected one of the first ePDCCH set and the second ePDCCH set;   decoding ePDCCH candidates according to the first mapping and decoding ePDCCH candidates according to the second mapping;   detecting whether the ePDCCH was allocated to the first ePDCCH set or the second ePDCCH set.   
     
     
         6 . The method of  claim 1 , wherein the first ePDCCH set consists of N Physical Resource Block, (PRB) pairs, where N is 2, 4 or 8, and the second ePDCCH set consists of N Physical Resource Block (PRB) pairs, where N is 2, 4 or 8. 
     
     
         7 . The method of  claim 1 , wherein the configuration message is received in a Radio Resource Control (RRC) message. 
     
     
         8 . A user equipment (UE) for use in a wireless communication network, the UE being configured for communicating an enhanced Physical Downlink Control Channel (ePDCCH) with a network node providing coverage to a serving cell, the UE comprising:
 a receiving circuit configured to:
 receive a configuration message from the network node, the configuration message comprising
 an indication of a first mapping of the ePDCCH for the serving cell to resource elements belonging to a first ePDCCH set, where the ePDCCH is mapped around resource elements of the first ePDCCH set used for a first Cell-Specific Reference Signal (CRS), the indication of the first mapping comprising an indication of at least one of (a) the number of CRS ports for the first CRS and (b) the CRS frequency shift for the first CRS, and 
 an indication of a second mapping of the ePDCCH for the serving cell to resource elements belonging to a second ePDCCH set, where the ePDCCH is mapped around resource elements of the second ePDCCH set used for a second CRS, the indication of the second mapping comprising an indication of at least one of (c) the number of CRS ports for the second CRS and (d) the CRS frequency shift for the second CRS; and 
 
   a monitoring circuit configured to monitor ePDCCH candidates in the first ePDCCH set according to the first mapping and monitoring ePDCCH candidates in the second ePDCCH set according to the second mapping.   
     
     
         9 . The UE of  claim 8 , wherein the configuration message comprises an indication of an ePDCCH start symbol for the first ePDCCH set and an indication of an ePDCCH start symbol for the second ePDCCH set. 
     
     
         10 . The UE of  claim 9 , wherein the indicated ePDCCH start symbol for the first ePDCCH set is the same start symbol as scheduled for a Packet Data Shared Channel (PDSCH) to be transmitted by the network node or another network node. 
     
     
         11 . The UE of  claim 8 , wherein the receiving circuit is further configured to receive a message from the network node comprising the ePDCCH allocated to a selected one of the first ePDCCH set and the second ePDCCH set, the UE further comprising:
 a decoding circuit configured to decode ePDCCH candidates according to the first mapping and decode ePDCCH candidates according to the second mapping;   a detecting circuit configured to detect whether the ePDCCH was allocated to the first ePDCCH set or to the second ePDCCH set.   
     
     
         12 . A method, performed by a network node providing coverage to a serving cell of a wireless communication network, for communicating an enhanced Physical Downlink Control Channel (ePDCCH) to a user equipment (UE), the method comprising
 transmitting a configuration message to the UE, the configuration message comprising:
 an indication of a first mapping of the ePDCCH in the serving cell to resource elements belonging to a first ePDCCH set, where the ePDCCH is mapped around resource elements of the first ePDCCH set used for a first Cell-specific Reference Signal (CRS), the indication of the first mapping comprising an indication of at least one of (a) the number of CRS ports for the first CRS and (b) the CRS frequency shift for the first CRS, and 
 an indication of a second mapping of the ePDCCH in the serving cell to resource elements belonging to a second ePDCCH set, where the ePDCCH is mapped around resource elements of the second ePDCCH set used for a second CRS, the indication of the second mapping comprising an indication of at least one of (c) the number of CRS ports for the second CRS and (d) the CRS frequency shift for the second CRS; 
   selecting, according to a selection criterion, one of the first ePDCCH set or the second ePDCCH set for transmission of the ePDCCH in the serving cell to the UE;   allocating the ePDCCH to resource elements according to the selected set; and   transmitting the allocated ePDCCH in the serving cell to the UE.   
     
     
         13 . The method of  claim 12 , further comprising:
 performing the first mapping of the ePDCCH to resource elements belonging to the first ePDCCH set; and   performing the second mapping of the ePDCCH to resource elements belonging to the second ePDCCH set.   
     
     
         14 . The method of  claim 12 , wherein the configuration message comprises an indication of an ePDCCH start symbol for the first ePDCCH set and an indication of an ePDCCH start symbol for the second ePDCCH set. 
     
     
         15 . The method of  claim 14 , wherein the indicated ePDCCH start symbol for the first ePDCCH set is the same start symbol as scheduled for a Packet Data Shared Channel (PDSCH) to be transmitted by the network node or another network node. 
     
     
         16 . The method of  claim 12 , wherein one or more of the following configuration parameters are shared between the ePDCCH and a Packet Data Shared Channel (PDSCH): a number of Cell-specific Reference Signal (CRS) antenna ports, a CRS frequency shift, a start position, a Multicast/Broadcast Single Frequency Network (MBSFN) subframe configuration, a Zero Power Channel State Information Reference Signal resource configuration, and a Channel State Information Reference Symbol (CSI-RS) resource configuration. 
     
     
         17 . The method of  claim 12 , wherein the first CRS is a CRS transmitted from a first network node, and the second CRS is a CRS transmitted from a second network node, and wherein the selection criterion is based upon whether the first CRS or the second CRS has the highest signal strength at the UE. 
     
     
         18 . The method of  claim 12 , wherein the configuration message is transmitted in a Radio Resource Control (RRC) message. 
     
     
         19 . A network node of a wireless communication network, configured for providing coverage to a serving cell and for communicating an enhanced Physical Downlink Control Channel (ePDCCH) to a user equipment (UE), the network node comprising
 a transmitting circuit configured to transmit a configuration message to the UE, the configuration message comprising:
 an indication of a first mapping of the ePDCCH in the serving cell to resource elements belonging to a first ePDCCH set, where the ePDCCH is mapped around resource elements of the first ePDCCH set used for a first Cell-specific Reference Signal (CRS), the indication of the first mapping comprising an indication of at least one of (a) the number of CRS ports for the first CRS and (b) the CRS frequency shift for the first CRS, and 
 an indication of a second mapping of the ePDCCH in the serving cell to resource elements belonging to a second ePDCCH set, where the ePDCCH is mapped around resource elements of the second ePDCCH set used for a second CRS, the indication of the second mapping comprising an indication of at least one of (c) the number of CRS ports for the second CRS and (d) the CRS frequency shift for the second CRS; 
   a selecting circuit configured to select one of the first ePDCCH set or the second ePDCCH set for transmission of the ePDCCH in the serving cell to the UE; and   an allocating circuit configured to allocate the ePDCCH to resource elements according to the selected set,   wherein the transmitting circuit is further configured to transmit the allocated ePDCCH to the UE.   
     
     
         20 . The network node of  claim 19 , further comprising a performing circuit adapted to perform the first mapping of the ePDCCH to resource elements belonging to the first ePDCCH set and to perform the second mapping of the ePDCCH to resource elements belonging to the second ePDCCH set. 
     
     
         21 . The network node of  claim 19 , wherein an indicated ePDCCH start symbol for the first ePDCCH set is the same start symbol as scheduled for a Packet Data Shared Channel (PDSCH) to be transmitted by the network node or another network node. 
     
     
         22 . The network node of  claim 19 , wherein one or more of the following configuration parameters are shared between the ePDCCH and a Packet Data Shared Channel (PDSCH): a number of Cell-specific Reference Signal (CRS) antenna ports, a CRS frequency shift, a start position, a Multicast/Broadcast Single Frequency Network (MBSFN) subframe configuration, a Zero Power Channel State Information Reference Signal resource configuration, and a Channel State Information Reference Symbol (CSI-RS) resource configuration. 
     
     
         23 . The network node of  claim 19 , wherein the first CRS is a CRS transmitted from a first network node, and the second CRS is a CRS transmitted from a second network node, and wherein the selecting of the first ePDCCH set or the second ePDCCH set is based upon whether the first CRS or the second CRS has the highest signal strength at the UE.