1. A User Equipment (UE) (112) arranged for packet-based device-to-device (D2D)
discovery operations, the UE (112) being enabled for proximity services, the UE
(112) comprising:
an antenna; and
a processor operably connected to the antenna, to cause the UE (112) to:
receive signalling from a base station indicating resources allocated for D2D discovery;
configure a discovery packet (300,320) in accordance with a predetermined configuration to have at least a discovery payload (304,324) and a cyclic-redundancy check (CRC) (306,326), the discovery payload (304,324) to include discovery-related content;
perform scrambling of the discovery packet (300,320) prior to quadrature phase-shift keying (QPSK) modulation, the scrambling based on a scrambling sequence initialized using a scrambling identity, wherein the scrambling identity is common for all discovery devices; and
transmit the discovery packet (300,320) on at least some of the indicated resources for receipt by a receiving UE (114).
2. The UE (112) as claimed in claim 1, wherein the UE (112) is to transmit the
discovery packet (300) in accordance with the predetermined configuration without
a header,
wherein the UE (112) is to transmit a demodulation reference signal (DMRS), and
wherein the DMRS is selected to indicate a payload size and/or modulation and coding scheme (MCS) of the discovery payload (304).
3. The UE (112) as claimed in claim 2, wherein the UE (112) is to transmit the
discovery packet (300) without a header,
wherein the discovery payload (304) is configurable to have one of a plurality of predetermined payload size and MCS combinations,

wherein each of the predetermined payload size and MCS combinations is mapped to one of a plurality of base sequences of the DMRS, and
wherein the UE (112) is arranged to select a DMRS having one of the base sequences based on the payload size and MCS combination of the discovery packet (300).
4. The UE (112) as claimed in claim 2, wherein the discovery payload (304) is
configurable to have one of a plurality of predetermined payload size and MCS
combinations,
wherein each of the predetermined payload size and MCS combinations is mapped to one of a plurality of cyclic shifts (CS) values and/or an orthogonal cover codes (OCCs) of the DMRS, and
wherein the UE is to select a DMRS that has a CS value and OCC based on the payload size and MCS combination of the discovery packet (300).
5. The UE (112) as claimed in claim 1, wherein the UE (112) is to transmit the
discovery packet (300) without a header, and
wherein the discovery payload (304) is configured to have a predetermined payload size and a predetermined modulation and coding scheme (MCS).
6. The UE (112) as claimed in claim 1, wherein the UE (112) is to transmit the
discovery packet (320) in accordance with the predetermined
configuration with a discovery header (322),
wherein the discovery header (322) is to indicate one of a plurality of predetermined payload size and modulation and coding scheme (MCS) combinations of the discovery payload (324).
7. The UE (112) as claimed in claim 6, wherein the discovery header (322) is
configured with a lower coding rate than the discovery payload (324), and
wherein the discovery header (322) has a predetermined MCS.
8. The UE (112) as claimed in claim 1, wherein a coding rate of the discovery
payload (324) corresponds to different levels of robustness, and

wherein the UE (112) is arranged to select the coding rate for the discovery payload (324) based on a desired level or robustness.
9. The UE (112) as claimed in claim 8, prior to configuring the discovery packet
(300/320), the UE is to perform a proximity sensing process to identify the
receiving UE (114), and
wherein the UE (112) is arranged to select one of the levels of robustness based on a range to the receiving UE (114).
10. The UE (112) as claimed in claim 6, wherein the discovery header (322) is mapped to one or more resource elements (REs) that are adjacent to an uplink DMRS symbol (210), and wherein the discovery payload (324) is mapped to REs (211) allocated for D2D discovery other than REs used for the discovery header and REs used for the uplink DMRS symbol.
11. The UE (112) as claimed in claim 1, wherein the UE (112) is to transmit the discovery packet (300,320) in accordance with a single-carrier frequency-division multiple access (SC-FDMA) technique on the indicated resources of a discovery zone (204), wherein the UE (112) is arranged to append the discovery packet (300,320) with parity check bits when turbo coding is employed for channel coding,
wherein after adding the CRC (306,326) to the discovery packet (300/320), the UE (112) is to encode the discovery packet (300,320) in accordance with a tail-biting convolutional coding (TBCC) technique when TBCC is used instead of turbo coding.
12. The UE (112) as claimed in claim 11, wherein after channel coding, the UE (112) is to perform rate matching based on an amount of resources to be used for transmission of the discovery packet (300/320).
13. The UE (112) as claimed in claim 1, wherein the scrambling identity is based on one or more of a cell identity (ID), a function of discovery resources used for transmission of the discovery packet (300/320), and a function of the cyclic shift value and/or orthogonal cover code (OCC) index of the DMRS that is transmitted by the UE (112).

14. The UE (112) as claimed in claim 1, wherein the signaling received from the
base station indicates that a discovery zone (204) is either semi-statically signaled
using radio-resource control (RRC) signaling or is provided in one or more system-
information blocks (SIBs),
wherein the UE (112) is configurable by the base station (104) for either Type 1 D2D discovery or Type 2 D2D discovery,
wherein when configured for Type 1 D2D discovery, resources for transmission of the discovery signal are allocated by the base station (104) on a non-UE specific basis, and
wherein when configured for Type 2 D2D discovery, specific resources for transmission of the discovery packet (300,320) are allocated by the base station (104) to the UE (112).
15. A method (600) for packet-based device-to-device (D2D) discovery operations
performed by user equipment (UE) (112) enabled for proximity services, the
method comprising:
receiving (602) signaling from a base station (104) indicating resources allocated for D2D discovery;
configuring (604) a discovery packet (300,320) in accordance with a predetermined configuration to have at least a discovery payload (304,324) and a cyclic-redundancy check (CRC) (306,326), the discovery payload (304,324) to include discovery-related content;
performing scrambling of the discovery packet (300,320) prior to quadrature
phase-shift keying (QPSK) modulation, the scrambling based on
a scrambling sequence initialized using a scrambling identity, wherein the scrambling identity is common for all discovery devices; and
transmitting (606) the configured discovery packet (300,320) on at least some of the indicated resources for receipt by a receiving UE (114).
16. The method (600) as claimed in claim 15, wherein the discovery packet (300)
is configured without a header and the UE (112) is to transmit a demodulation
reference signal (DMRS), and

wherein the method (600) includes selecting the DMRS to indicate a payload size and/or modulation and coding scheme (MCS) of the discovery payload (304).
17. The method (600) as claimed in claim 15, wherein the discovery packet (320) is configured with a discovery header (322), the method (600) includes configuring the discovery header (322) to indicate one of a plurality of predetermined payload size and modulation and coding scheme (MCS) combinations of the discovery payload (324).
18. The method (600) as claimed in claim 15, wherein a coding rate of the discovery payload (324) corresponds to different levels of robustness, and
wherein the method (600) includes selecting the coding rate for the discovery payload (324) based on a desired level or robustness.