Low latency physical random access channel design

1. A User Equipment (UE) operable to communicate with a base station on a wireless network, comprising:

one or more processors to:

initiate a Listen-Before-Talk (LBT) procedure on a bandwidth of the wireless network, the bandwidth being unlicensed spectrum; and

generate a transmission if the LBT procedure indicates that the bandwidth is idle, the transmission comprising a Physical Random Access Channel (PRACH) preamble portion together with a message portion within the transmission, wherein the PRACH preamble portion is transmitted in a first part of an uplink (UL) subframe of the transmission, and the message portion is transmitted in second part of the UL subframe of the transmission;

process a Physical Downlink Control Channel (PDCCH) received from the base station containing a Cell Radio Network Temporary Identifier (C-RNTI) assigned to the UE; and

an interface to output the transmission.

2. The UE of claim 1 ,

wherein the message portion of the transmission comprises a Medium Access Control (MAC) part carrying at least one of: the C-RNTI assigned to the UE, a Buffer Status Report (BSR) indicator, a Layer I or MAC UE capability indicator, a UE identity for contention resolution, or a Radio Resource Control (RRC) part including an RRC message with the UE identity for contention resolution.

3. The UE of claim 2 , wherein the transmission is a first transmission, and wherein the one or more processors are to:

process a second transmission comprising at least one of: a Random Access Response (RAR), or a message portion.

4. The UE of claim 3 ,

wherein the second transmission comprises one of: the PDCCH containing the C-RNTI assigned to the UE or the UE identity, or an enhanced PDCCH (ePDCCH) containing the C-RNTI assigned to the UE or the UE identity.

5. The UE of claim 3 ,

wherein the second transmission comprises a MAC part carrying the C-RNTI assigned to the UE or the UE identity.

6. The UE of claim 3 ,

wherein the second transmission comprises an RRC part including an RRC message carrying at least one of: the C-RNTI assigned to the UE, or the UE identity for contention resolution.

7. Machine readable storage media having machine executable instructions that, when executed, cause one or more processors of a User Equipment (UE) operable to communicate with a base station on a wireless network to perform operations comprising:

initiating a Listen-Before-Talk (LBT) procedure on a bandwidth of the wireless network, the bandwidth being unlicensed spectrum;

generating a transmission if the LBT procedure indicates that the bandwidth is idle, the transmission comprising a Physical Random Access Channel (PRACH) preamble portion together with a message portion within the transmission, wherein the PRACH preamble portion is transmitted in a first part of an uplink (UL) subframe of the transmission, and the message portion is transmitted in a second part of the UL subframe of the transmission; and

processing a Physical Downlink Control Channel (PDCCH) received from the base station containing a Cell Radio Network Temporary Identifier (C-RNTI) assigned to the UE.

8. The machine readable storage media of claim 7 ,

wherein the message portion of the transmission comprises a Medium Access Control (MAC) part carrying at least one of: the C-RNTI assigned to the UE, a Buffer Status Report (BSR) indicator, a Layer 1 or MAC UE capability indicator, a UE identity for contention resolution, or a Radio Resource Control (RRC) part including an RRC message with the UE identity for contention resolution.

9. The machine readable storage media of claim 8 , wherein the transmission is a first transmission, and the operations further comprising:

processing a second transmission comprising at least one of: a Random Access Response (RAR), or a message portion.

10. The machine readable storage media of claim 9 ,

wherein the second transmission comprises one of: the PDCCH containing the C-RNTI assigned to the UE or the UE identity, or an enhanced PDCCH (ePDCCH) containing the C-RNTI assigned to the UE or the UE identity.

11. The machine readable storage media of claim 9 ,

wherein the second transmission comprises a MAC part carrying the C-RNTI assigned to the UE or the UE identity.

12. The machine readable storage media of claim 9 ,

wherein the second transmission comprises an RRC part including an RRC message carrying at least one of: the C-RNTI assigned to the UE, or the UE identity for contention resolution.

13. The UE of claim 1 , wherein the PRACH preamble portion is transmitted in one or more interlaces over the UL subframe, and the message portion is transmitted in one or more of remaining interlaces over the UL subframe.

14. The UE of claim 1 , wherein the UL subframe further includes a guard band between the PRACH preamble portion and the message portion in a frequency domain.

15. The UE of claim 1 , wherein the PRACH preamble portion is transmitted in a subset of OFDM symbols within the UL subframe, and the message portion is carried in remaining symbols within the UL subframe.

16. The UE of claim 15 , wherein the PRACH preamble portion is transmitted in consecutive OFDM symbols.

17. The machine readable storage media of claim 7 , wherein the PRACH preamble portion is transmitted in one or more interlaces over the UL subframe, and the message portion is transmitted in one or more of remaining interlaces over the UL subframe.

18. The machine readable storage media of claim 7 , wherein the UL subframe further includes a guard band between the PRACH preamble portion and the message portion in frequency domain.

19. The machine readable storage media of claim 7 , wherein the PRACH preamble portion is transmitted in a subset of OFDM symbols within the UL subframe, and the message portion is carried in remaining symbols within the UL subframe.

20. The machine readable storage media of claim 19 , wherein the PRACH preamble portion is transmitted in consecutive OFDM symbols.