System and method for contention-free random access
A method for initiating a random access includes generating a first downlink control information (DCI) including random access parameters and selecting a control channel from a first downlink control channel in common search space of a first subframe and a second downlink control channel in a data region of the first subframe. The method also includes mapping the first DCI to the control channel and transmitting, by a communications controller to a UE, symbols of the first subframe including the first DCI in the control channel. Additionally, the method includes receiving, by the communications controller from the UE, a random access waveform in accordance with the random access parameters and transmitting, by the communications controller to the UE, after receiving the random access waveform, a second subframe including a second DCI in a control channel of the second subframe, where the second DCI includes scheduling information for a random access response.
1. A method for initiating random access, the method comprising:
receiving, by a user equipment (UE) from a communications controller, symbols of a first subframe comprising a first downlink control information (DCI), wherein the first DCI corresponds to a physical downlink control channel (PDCCH) order;
searching for the first DCI in a first downlink control channel in common search space of the first subframe and a second downlink control channel in a UE specific search space of an enhanced physical downlink control channel (ePDCCH) in a data region of the first subframe;
obtaining random access parameters from the first DCI, wherein the first DCI is in the data region of the first subframe;
transmitting, by the UE to the communications controller, a random access preamble in accordance with the random access parameters; and
receiving a second DCI in a control region of a second subframe, wherein the second DCI comprises scheduling information for a random access response.
2. The method of claim 1 , wherein a cyclic redundancy check (CRC) associated with the first DCI is scrambled with a cell radio network temporary (C-RNTI).
3. The method of claim 1 , wherein the first downlink control channel is an enhanced physical downlink control channel (ePDCCH).
4. The method of claim 1 , wherein the random access parameters comprise a preamble index.
5. The method of claim 1 , wherein the random access parameters comprise a physical random access channel (PRACH) mask index.
6. The method of claim 1 , wherein receiving the second subframe is performed in accordance with the random access parameters.
7. The method of claim 1 , wherein the common search space of the first subframe overlaps the UE specific search space of the ePDCCH.
8. A user equipment (UE) comprising:
a processor; and
a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
receive, from a communications controller, symbols of a first subframe comprising a first downlink control information (DCI), wherein the first DCI corresponds to a physical downlink control channel (PDCCH) order,
search for the first DCI in a first downlink control channel in common search space of the first subframe and a second downlink control channel in a UE specific search space of an enhanced physical downlink control channel (ePDCCH) in a data region of the first subframe,
obtain random access parameters from the first DCI, wherein the first DCI is in the data region of the first subframe,
transmit, to the communications controller, a random access preamble in accordance with the random access parameters, and
receive a second DCI in a control region of a second subframe, wherein the second DCI comprises scheduling information for a random access response.
9. A method for initiating random access, the method comprising:
generating a downlink control information (DCI) comprising random access parameters;
selecting a first control channel from a set including a physical downlink control channel (PDCCH) of a first subframe and an enhanced physical downlink control channel (ePDCCH) of the first subframe;
mapping the DCI to the first control channel; and
transmitting, by a communications controller to a user equipment (UE), symbols of the first subframe comprising the DCI in the first control channel, wherein the DCI corresponds to a PDCCH order, and wherein the DCI is in a data region of the first subframe.
10. The method of claim 9 , wherein the first control channel is in a control region of the first subframe.
11. The method of claim 9 , wherein the first control channel is in a UE specific search space of the PDCCH of the first subframe.
12. The method of claim 9 , wherein the first control channel is in a common search space of the PDCCH of the first subframe.
13. The method of claim 9 , wherein the first control channel is in a UE specific search space of the ePDCCH of the first subframe.
14. The method of claim 9 , wherein the first control channel is in a common search space of the ePDCCH of the first subframe.
15. The method of claim 9 , further comprising:
receiving, by the communications controller from the UE, a random access preamble in accordance with the random access parameters; and
transmitting, by the communications controller to the UE, after receiving the random access preamble, a second subframe comprising a second DCI in a second control channel of the second subframe, wherein the second DCI comprises scheduling information for a random access response.
16. The method of claim 9 , wherein the first subframe does not contain a control region.
17. The method of claim 9 , further comprising determining a length of the DCI in accordance with whether the first control channel is in the PDCCH of the first subframe or the ePDCCH of the first subframe.
18. The method of claim 9 , wherein the random access parameters comprise a preamble index.
19. The method of claim 9 , wherein common search space of the first subframe overlaps UE specific search space of the ePDCCH.
20. A communications controller comprising:
a processor; and
a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
generate a downlink control information (DCI) comprising random access parameters,
select a control channel from a set including a physical downlink control channel (PDCCH) of a subframe and an enhanced physical downlink control channel (ePDCCH) of the subframe,
map the DCI to the control channel, and
transmit, to a user equipment (UE), symbols of the subframe comprising the DCI in the control channel, wherein the DCI corresponds to a PDCCH order, and wherein the DCI is in a data region of the subframe.
21. A method for initiating random access, the method comprising:
generating a downlink control information (DCI) comprising random access parameters;
selecting a first control channel from an enhanced physical downlink control channel (ePDCCH) of a subframe;
mapping the DCI to the first control channel; and
transmitting, by a communications controller to a user equipment (UE), symbols of the subframe comprising the DCI in the first control channel, wherein the DCI corresponds to a PDCCH order, and wherein the DCI is in a data region of the subframe.
22. A communications controller comprising:
a processor; and
a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
generate a downlink control information (DCI) comprising random access parameters,
select a control channel from an enhanced physical downlink control channel (ePDCCH) of a subframe,
map the DCI to the control channel, and
transmit, to a user equipment (UE), symbols of the subframe comprising the DCI in the control channel, wherein the DCI corresponds to a PDCCH order, and wherein the DCI is in a data region of the subframe.