CROSS REFERENCES

The present 371 application for patent claims priority to International Patent Application No. PCT/CN2018/107321 to RICO ALVARINO et. al., titled “INCREASING PHYSICAL RANDOM ACCESS CAPACITY USING ORTHOGONAL COVER CODES”, filed Sep. 25, 2018; and to International Patent Application No. PCT/CN2017/104266 to RICO ALVARINO et. al., titled “INCREASING PHYSICAL RANDOM ACCESS CAPACITY USING ORTHOGONAL COVER CODES”, filed Sep. 29, 2017, each of which is assigned to the assignee hereof.

BACKGROUND

The following relates generally to wireless communication, and more specifically to increasing physical random access channel (PRACH) capacity using orthogonal cover codes (OCCs).

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as a Long Term Evolution (LTE) systems or LTE-Advanced (LTE-A) systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform-spread-OFDM (DFT-S-OFDM). A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).

In some wireless communications systems, a UE may initialize a system access procedure by transmitting a PRACH or random access (RACH) preamble message in the PRACH. However, as the UE has yet to gain access to the base station, these PRACH resources may be shared with any other UEs attempting to access the system. In such a contention-based system, large numbers of UEs attempting to access the system simultaneously using the limited resources of the PRACH may result in collisions, unreliable system access procedures, and increased latency in the wireless communications system.

SUMMARY

The described techniques relate to improved methods, systems, devices, or apparatuses that support increasing physical random access channel (PRACH) capacity using orthogonal cover codes (OCCs). Generally, the described techniques provide for a base station transmitting an indication of a PRACH configuration in a system information block (SIB) or in downlink control information (DCI). A user equipment (UE) may receive the indicated PRACH configuration, and may identify PRACH resources corresponding to the PRACH configurations. In some cases, these PRACH resources may support using OCCs, while in other cases, a subset of these resources may support using OCCs. The UE may determine whether to transmit a random access (RACH) preamble message—or repetitions of the RACH preamble message—in PRACH resources supporting OCCs. In some cases, the UE may instead determine to transmit the RACH preamble message in PRACH resources not configured for OCCs. The UE may transmit the RACH preamble message to the base station in the determined resources to initiate a system access procedure, and in some cases may receive a RACH response message in return. The response message may be based on the whether the RACH preamble message was transmitted using an OCC or not, or based on the specific cover code used by the UE. The use of OCCs may increase the capacity of the PRACH, improving reliability and reducing the latency of system access procedures.

A method of wireless communication is described. The method may include receiving a PRACH resource configuration indicating a set of PRACH resources for a cell, identifying, from the set of PRACH resources, a subset of PRACH resources for performing system access using OCCs, determining whether to perform system access on the cell using the subset of the set of PRACH resources, and transmitting a random access preamble message for the system access based at least in part on the determining.

An apparatus for wireless communication is described. The apparatus may include means for receiving a PRACH resource configuration indicating a set of PRACH resources for a cell, means for identifying, from the set of PRACH resources, a subset of PRACH resources for performing system access using OCCs, means for determining whether to perform system access on the cell using the subset of the set of PRACH resources, and means for transmitting a random access preamble message for the system access based at least in part on the determining.

Another apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a PRACH resource configuration indicating a set of PRACH resources for a cell, identify, from the set of PRACH resources, a subset of PRACH resources for performing system access using OCCs, determine whether to perform system access on the cell using the subset of the set of PRACH resources, and transmit a random access preamble message for the system access based at least in part on the determining.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions executable by a processor to receive a PRACH resource configuration indicating a set of PRACH resources for a cell, identify, from the set of PRACH resources, a subset of PRACH resources for performing system access using OCCs, determine whether to perform system access on the cell using the subset of the set of PRACH resources, and transmit a random access preamble message for the system access based at least in part on the determining.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, identifying the subset of PRACH resources supporting OCCs comprises identifying an OCC applicability criteria associated with supporting OCCs for the set of PRACH resources. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining that the PRACH resource configuration supports OCCs based on the set of PRACH resources and the OCC applicability criteria.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the PRACH resource configuration comprises a number of contiguous PRACH transmission opportunities greater than or equal to an OCC length.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the OCC applicability criteria comprises a repetition separation time threshold, wherein the PRACH resource configuration comprises PRACH transmission opportunities separated in a time domain by a length of time less than the repetition separation time threshold.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions, from the set of PRACH resources, a second subset of PRACH resources not configured for supporting OCCs.

In other examples of the method, apparatus, and non-transitory computer-readable medium described above, determining whether to perform system access on the cell using the subset of PRACH resources comprises selecting between the subset of PRACH resources and the second subset of PRACH resources based at least in part on a random or pseudo-random function. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for performing system access on the cell based at least in part on the selection.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for identifying a weight value associated with selecting either the subset of PRACH resources or the second subset of PRACH resources, wherein selecting between the subset of PRACH resources and the second subset of PRACH resources may be based at least in part on the weight value.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, determining whether to perform system access on the cell using the subset of PRACH resources or the second subset of PRACH resources is based at least in part on a transmission type associated with the system access.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the transmission type comprises a first type of system access for radio resource control (RRC) connection or a second type of system access for connection-less data transmission.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the subset of PRACH resources and the second subset of PRACH resources overlap.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the PRACH resource configuration comprises an OCC PRACH resource configuration. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the subset of PRACH resources comprises a set of concentrated PRACH resources that may be contiguous or separated in a time domain by less than a repetition separation time threshold. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the subset of PRACH resources spans a length of time greater than or equal to an OCC length for the random access preamble message.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for identifying, from the set of PRACH resources, a second subset of PRACH resources not configured for supporting OCCs, wherein the second subset of PRACH resources comprises a set of distributed resources that may be separated in the time domain by an equal number of subframes or separated in the time domain by either a first number of subframes or a second number of subframes differing from the first number by one subframe.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for receiving a random access response message in response to the random access preamble message.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for identifying the random access response message based at least in part on a random access preamble identifier of the random access response message, a random access radio network temporary identifier (RNTI) of the random access response message, an OCC index included in the random access response message, or a combination thereof.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for receiving a DCI transmission comprising an OCC index, a random access preamble, or both, wherein determining whether to perform system access on the cell using the subset of PRACH resources may be based at least in part on the DCI transmission.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining an OCC length for the system access based at least in part on the PRACH resource configuration.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for performing frequency hopping for transmitting the random access preamble message, wherein the frequency hopping may be based at least in part on an OCC length for the system access.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for selecting, for the random access preamble message, a random preamble, a random OCC cover, or both.

A method of wireless communication is described. The method may include determining a set of PRACH resources, the set of PRACH resources comprising a subset of the set of PRACH resources for performing system access using OCCs, transmitting a PRACH resource configuration indicating the set of PRACH resources and the subset of the set of PRACH resources, and receiving a random access preamble message for the system access in the set of PRACH resources.

An apparatus for wireless communication is described. The apparatus may include means for determining a set of PRACH resources, the set of PRACH resources comprising a subset of the set of PRACH resources for performing system access using OCCs, means for transmitting a PRACH resource configuration indicating the set of PRACH resources and the subset of the set of PRACH resources, and means for receiving a random access preamble message for the system access in the set of PRACH resources.

Another apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to determine a set of PRACH resources, the set of PRACH resources comprising a subset of the set of PRACH resources for performing system access using OCCs, transmit a PRACH resource configuration indicating the set of PRACH resources and the subset of the set of PRACH resources, and receive a random access preamble message for the system access in the set of PRACH resources.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions executable by a processor to determine a set of PRACH resources, the set of PRACH resources comprising a subset of the set of PRACH resources for performing system access using OCCs, transmit a PRACH resource configuration indicating the set of PRACH resources and the subset of the set of PRACH resources, and receive a random access preamble message for the system access in the set of PRACH resources.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, receiving the random access preamble message comprises receiving the random access preamble message in the subset of the set of PRACH resources, wherein the random access preamble message comprises a random preamble, a random OCC cover, or both.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the PRACH resource configuration comprises a number of contiguous PRACH transmission opportunities greater than or equal to an OCC length. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the PRACH resource configuration comprises PRACH transmission opportunities separated in a time domain by a length of time less than a repetition separation time threshold.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the subset of the set of PRACH resources may be a first subset of the set of PRACH resources. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the set of PRACH resources comprises a second subset of the set of PRACH resources not configured for supporting OCCs.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, receiving the random access preamble message for the system access in the set of PRACH resources comprises receiving the random access preamble message in the first subset of the set of PRACH resources or in the second subset of the set of PRACH resources based at least in part on a configuration of a UE.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the PRACH resource configuration comprises an OCC PRACH resource configuration. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the subset of the set of PRACH resources comprises a set of concentrated PRACH resources that may be contiguous or separated in a time domain by less than a repetition separation time threshold. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the set of concentrated PRACH resources spans a length of time greater than or equal to an OCC length.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for transmitting a random access response message in response to the random access preamble message.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the random access response message comprises a random access preamble identifier, a random access RNTI, an OCC index, or a combination thereof.

