Searching space and operation for enhanced PDCCH in LTE systems
A method is provided for operating an eNB in a wireless communication network. The method comprises allocating, by the eNB, one or more resource units within one or more physical resource block pairs to a user equipment for transmitting enhanced control information.
1. A method of operating an enhanced node B (eNB) in a wireless communication network, the method comprising:
partitioning a physical resource block (PRB) pair comprising a plurality of resource elements into at least a first resource unit partition and a second resource unit partition, wherein the first and second resource unit partitions are used to convey respective first and second portions of information for an enhanced physical downlink control channel (E-PDCCH), and wherein the first and second resource unit partitions exclude resource elements used for transmission of channel state information reference signals (CSI-RS) within the PRB pair;
transmitting, within the first resource unit partition, the first portion of E-PDCCH information and an associated demodulation reference signals (DMRS) using a first antenna port; and
transmitting, within the second resource unit partition, the second portion of E-PDCCH information and an associated DMRS using a second antenna port.
2. The method of claim 1 , wherein each resource unit partition is associated with one or more reference signals.
3. The method of claim 1 , wherein the PRB pair is partitioned based on frequency to create three resource units of equal size in frequency.
4. The method of claim 1 , further comprising assigning, by the eNB, an index to each of the resource unit partitions, and assigning a starting index of the resource unit partitions to a user equipment (UE) according to at least one of:
a user ID;
a subframe number;
E-PDCCH candidates; or
a number of resource units required.
5. A method of operating a network element in a wireless communication network, the method comprising:
semi-statically providing, by the network element, a configuration of at least one resource region usable for transmission of an enhanced physical downlink control channel (E-PDCCH) to a user equipment (UE);
dynamically allocating, by the network element, one or more enhanced control channel elements (eCCEs) in the at least one E-PDCCH resource region for transmitting the E-PDCCH to the UE;
transmitting, by the network element, the E-PDCCH to the UE over the allocated eCCEs , and
assigning, by the network element, two or more demodulation reference signal (DMRS) ports to each of the one or more eCCEs for E-PDCCH demodulation by the UE.
6. The method of claim 5 , wherein semi-statically providing the configuration comprises transmitting, by the network element, one or more information elements to the UE via higher layer signaling.
7. The method of claim 6 , wherein at least one of the information elements comprises information on the at least one E-PDCCH resource region.
8. The method of claim 5 , wherein the at least one E-PDCCH resource region is configured to transmit UE-specific control information.
9. The method of claim 5 , wherein the at least one E-PDCCH resource region is configured to transmit non-UE-specific control information.
10. The method of claim 7 , wherein the information on the at least one E-PDCCH resource region comprises at least one of resource allocation types and a corresponding bit string describing resource allocation.
11. The method of claim 10 , wherein the resource allocation is in terms of virtual resource blocks (VRBs).
12. The method of claim 5 , further comprising:
allocating, by the network element, a number of mutually orthogonal eCCEs in each of allocated resource blocks (RBs) in the at least one E-PDCCH resource region.
13. The method of claim 5 , wherein the network element is configured to use a number of mutually orthogonal eCCEs predefined in each of a plurality of allocated resource blocks.
14. The method of claim 5 , further comprising:
associating implicitly, by the network element, the two or more demodulation reference signal (DMRS) ports to each of the one or more eCCEs for E-PDCCH demodulation.
15. The method of claim 5 , wherein the network element is configured to use a plurality of demodulation reference signals (DMRS) predefined in a resource block for E-PDCCH transmission in each eCCE.
16. The method of claim 15 , wherein each of the two or more DMRS ports is associated with a respective one of the eCCEs in a physical resource block (PRB) for E-PDCCH demodulation over the eCCE.
17. The method of claim 16 , wherein the network element is configured to use the same one or more DMRS ports for all eCCEs in a PRB, and wherein DMRS resource elements of the DMRS ports within an eCCE are used for the E-PDCCH demodulation over the eCCE.
18. The method of claim 12 , wherein the number of mutually orthogonal eCCEs is based on at least one of:
time divisional multiplexing;
frequency divisional multiplexing; and
code divisional multiplexing.
19. The method of claim 5 , further comprising selecting one eCCE aggregation level and a set of eCCEs corresponding to an E-PDCCH candidate in a search space at a selected aggregation level for the UE.
20. The method of claim 19 , wherein the search space is determined by at least one of:
a value of the UE's radio network temporary identifier;
a subframe index; and
a total number eCCEs in the E-PDCCH resource region.
21. The method of claim 20 , wherein the set of eCCEs is interleaved before being mapped to the virtual resource blocks configured for the E-PDCCH resource region.
22. The method of claim 5 , wherein the transmitting comprises transmitting an E-PDCCH using transmit diversity.
23. A method of operating a user equipment (UE) in a wireless communication network, the method comprising:
receiving, by the UE, a configuration of at least one resource region usable for transmission of an enhanced physical downlink control channel (E-PDCCH); and
detecting, by the UE, in each of a plurality of subframes, one or more E-PDCCHs for the UE over the configured at least one E-PDCCH resource region, wherein at least one of the E-PDCCHs is transmitted to the UE from a plurality of demodulation reference signal (DMRS) ports,
wherein symbols of the at least one E-PDCCH are mapped to resource elements in the at least one E-PDCCH resource region that are not used for transmission of channel state information reference signals (CSI-RS) within a resource block over which E-PDCCH detection is performed by the UE.
24. The method of claim 23 , wherein receiving the configuration comprises receiving, by the UE, one or more information elements via radio resource control signaling.
25. The method of claim 24 , wherein the information element comprises information on at least one of resource allocation types and a corresponding bit string, wherein the bit string describes one or more of:
resource allocation;
an E-PDCCH multiplexing method;
one or more reference signals; or
a transmission mode.
26. The method of claim 25 , wherein the resource allocation is in terms of virtual resource blocks.
27. The method of claim 25 , wherein the transmission mode is one of transmit diversity and beamforming.
28. The method of claim 23 , wherein the detecting comprises identifying a plurality of E-PDCCH candidates in the at least one E-PDCCH resource region, and wherein an E-PDCCH candidate comprises one or more enhanced control channel elements (eCCEs) in the at least one E-PDCCH resource region usable for transmitting the E-PDCCH to the UE.
29. The method of claim 28 , wherein the detecting further comprises identifying a demodulation reference signal associated with each eCCE of at least one of the E-PDCCH candidates.
30. The method of claim 29 , wherein the detecting further comprises demodulating each of the E-PDCCH candidates using the corresponding demodulation reference signal.
31. The method of claim 30 , wherein the detecting further comprises E-PDCCH decoding after E-PDCCH demodulation for each of the E-PDCCH candidates.
32. A method of operating an enhanced node B (eNB) in a wireless communication network, the method comprising:
partitioning a plurality of resource elements within a physical resource block (PRB) pair into a first resource unit partition associated with a first antenna port and a second resource unit partition associated with a second antenna port
mapping symbols of an encoded Enhanced Physical Downlink Control Channel (E-PDCCH) to resource elements within either the first resource unit partition or the second resource unit partition, wherein the resource elements to which the E-PDCCH symbols are mapped exclude resource elements used for transmission of channel state information reference signals (CSI-RS) within the PRB pair;
transmitting symbols associated with the first resource unit partition and a first demodulation reference signal (DMRS) on the first antenna port; and
transmitting symbols associated with the second resource unit partition and a second DMRS on the second antenna port.
33. A method of receiving an Enhanced Physical Downlink Control Channel (E-PDCCH), the method comprising:
partitioning a plurality of resource elements within a received physical resource block (PRB) pair into a first resource unit partition associated with a first received demodulation reference signal (DMRS) and a second resource unit partition associated with a second received DMRS, wherein the first and the second resource unit partition exclude resource elements used for transmission of channel state reference signals (CSI-RS) within the PRB pair;
performing first and second channel estimations based on the respective first and second received DMRS within the first and second resource unit partitions;
demodulating symbols associated with the first and second resource unit partitions using the respective first and second channel estimations; and
decoding the E-PDCCH using the demodulated symbols.