WO2019095320A1

WO2019095320A1 - Machine type communication physical downlink control channel order

Info

Publication number: WO2019095320A1
Application number: PCT/CN2017/111735
Authority: WO
Inventors: Chunhai Yao; Rapeepat Ratasuk
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2017-11-17
Filing date: 2017-11-17
Publication date: 2019-05-23
Also published as: EP3711428A4; EP3711428A1; CN111357376B; CN111357376A

Abstract

Various communication systems may benefit from improved random access related communications. For example, certain embodiments may benefit from improved physical downlink control channel order in enhanced machine type communications. A method, in certain embodiments, may include receiving at a user equipment a command to start random access from a network entity. The method may also include determining at the user equipment, after receiving the command, timing for transmitting a random access preamble based on a repetition value of a physical downlink control channel. The repetition value may be used by the user equipment while another repetition value is used for the command to start the random access. In addition, the method may include transmitting the random access preamble from the user equipment to the network entity on a physical random access channel using the determined timing.

Description

MACHINE TYPE COMMUNICATION PHYSICAL DOWNLINK CONTROL CHANNEL ORDER

BACKGROUND: Field:

Various communication systems may benefit from improved random access related communications. For example, certain embodiments may benefit from improved physical downlink control channel order in enhanced machine type communications.

Description of the Related Art:

In Third Generation Partnership Project (3GPP) technology, such as Long Term Evolution (LTE) and LTE Advanced (LTE-A) , random access procedures are generally used to connect a user equipment to a network via a physical random access channel (PRACH) or a narrowband physical random access channel (NPRACH) . While the random access procedures are generally triggered or initiated by auser equipment, in some cases the random access procedures may be triggered or initiated by the network. The initiation of random access procedures at the network occurs when the user equipment is not synchronized with the network, and when there is a downlink data transmission that the network needs to transmit to the user equipment.

The PDCCH order is a procedure used to by the network initiate random access procedures at the user equipment, thereby synchronizing the uplink and/or downlink transmissions of the user equipment with a network entity located within the network. The initiated random access procedures may be contention-less random access procedures. The user equipment receiving the PDCCH order may send a random access preamble to the network entity using the preamble index included in the PDCCH order. The network entity then responds to the random access preamble with a random access response message that include a new timing advance value, which is used by the user equipment to synchronize uplink and/or downlink transmissions.

Enhanced machine type communications are communications between user equipment that require little to no human interventions. Machine type communication devices are capable of receiving the PDCCH order from the network entity by MTC Physical Downlink Control Channel (MPDCCH) or the narrowband Physical Downlink Control Channel (NPDCCH) . Specifically, the machine type communication devices may use the PDCCH order to synchronize their uplink transmissions with the network.

SUMMARY

According to certain embodiments, an apparatus may include at least one memory including computer program code, and at least one processor. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to receive a command to start random access from a network entity. The at least one memory and the computer program code may also be configured, with the at least one processor, to cause the apparatus at least to determining, after receiving the command, timing for transmitting a random access preamble based on a repetition value of a physical downlink control channel. The repetition value may be used by the user equipment while another repetition value is used for the command to start the random access. In addition, the at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to transmit the random access preamble from the user equipment to the network entity on a physical random access channel using the determined timing.

A method, in certain embodiments, may include receiving at a user equipment a command to start random access from a network entity. The method may also include determining at the user equipment, after receiving the command, timing for transmitting a random access preamble based on a repetition value of a physical downlink control channel. The repetition value may be used by the user equipment while another repetition value is used for the command to start the random access. In addition, the method may include transmitting the random access preamble from the user equipment to the network entity on a physical random access channel using the determined timing.

An apparatus, in certain embodiments, may include means for receiving at a user equipment a command to start random access from a network entity. The apparatus may also include means for determining at the user equipment, after receiving the command, timing for transmitting a random access preamble based on a repetition value of a physical downlink control channel. The repetition value may be used by the user equipment while another repetition value is used for the command to start the random access. In addition, the apparatus may include means for transmitting the random access preamble from the user equipment to the network entity on a physical random access channel using the determined timing.

According to certain embodiments, a non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform a process. The process may include receiving at a user equipment a command to start random access from a network entity. The process may also include determining at the user equipment, after receiving the command, timing for transmitting a random access preamble based on a repetition value of a physical downlink control channel. The repetition value may be used by the user equipment while another repetition value is used for the cormnand to start the random access. In addition, the process may include transmitting the random access preamble from the user equipment to the network entity on a physical random access channel using the determined timing.

According to certain other embodiments, a computer program product may encode instructions for performing a process. The process may include receiving at a user equipment a command to start random access from a network entity. The process may also include determining at the user equipment, after receiving the command, timing for transmitting a random access preamble based on a repetition value of a physical downlink control channel. The repetition value may be used by the user equipment while another repetition value is used for the command to start the random access. In addition, the process may include transmitting the random access preamble from the user equipment to the network entity on a physical random access channel using the determined timing.

According to certain embodiments, an apparatus may include at least one memory including computer program code, and at least one processor. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to transmit a command to start random access to a user equipment using another repetition number other than a repetition value. The at least one memory and the computer program code may also be configured, with the at least one processor, to cause the apparatus at least to receive a random access preamble from the user equipment via a physical random access channel according to a timing for transmitting the random access preamble that is based on the repetition value.

A method, in certain embodiments, may include transmitting from a network entity a command to start random access to a user equipment using another repetition number other than a repetition value. The method may also include receiving a random access preamble at the network entity from the user equipment via a physical random access channel according to a timing for transmitting the random access preamble that is based on the repetition value.

An apparatus, in certain embodiments, may include means for transmitting from a network entity a command to start random access to a user equipment using another repetition number other than a repetition value. The apparatus may also include means for receiving a random access preamble at the network entity from the user equipment via a physical random access channel according to a timing for transmitting the random access preamble that is based on the repetition value.

According to certain embodiments, a non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform a process. The process may include transmitting from a network entity a command to start random access to a user equipment using another repetition number other than a repetition value. The process may also include receiving a random access preamble at the network entity from the user equipment via a physical random access channel according to a timing for transmitting the random access preamble that is based on the repetition value.

According to certain other embodiments, a computer program product may encode instructions for performing a process. The process may include transmitting from a network entity a command to start random access to a user equipment using another repetition number other than a repetition value. The process may also include receiving a random access preamble at the network entity from the user equipment via a physical random access channel according to a timing for transmitting the random access preamble that is based on the repetition value.

BRIEF DESCRIPTION OF THE DRAWINGS:

For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

Figure 1 illustrates an example of a timing relationship between PDCCH order and PRACH according to certain embodiments.

Figure 2 illustrates an example of a flow diagram according to certain embodiments.

Figure 3 illustrates an example of a flow diagram according to certain embodiments.

Figure 4 illustrates an example of a system according to certain embodiments.

DETAILED DESCRIPTION:

Certain embodiments may relate to a relationship between a command to start random access, such as the MPDCCH/NPDCCH/PDCCH order, and a timing for transmitting a random access preamble, such as the PRACH/NPRACH transmission. MPDCCH, NPDCCH, and/or PDCCH may generally be referred to a PDCCH below, while NPRACH and/or PRACH may generally be referred to as PRACH below. Although certain embodiments refer to MPDCCH, NPDCCH, PDCCH, NPRACH, and PRACH, certain other embodiments may use any other type of channel provided for by 3GPP or any other standard setting body. In addition, while some embodiments described below related to 3GPP LTE and LTE-A, other embodiments may apply to 3GPP 5^th generation (5G) or New Radio (NR) technology.

Section 6.1.1 of 3GPP TS 36.213 describes that when a random access procedure is initiated by a PDCCH order in subframe n and/or the reception of the PDCCH order ends in subframe n, the UE transmits a random access preamble in the first subframe n+k₂, k₂ ≥ 6, where a PRACH resource is available. In other words, 3GPP TS 36.213 describes that the PRACH resource is available 6 or more subframes after subframe n. The UE described in 3GPP TS 36.213 is a non-bandwidth limited (BL) or non-coverage enhanced (CE) user equipment (UE) . A BL/CE UE may be a machine type communication device. Section 16.3.2 of 3GPP TS 36.213 describes a similar procedure for a Narrowband Internet of Things (NB-IoT) . 3GPP TS 36.213 is hereby incorporated by reference in its entirety.

In some embodiments, the PDCCH may be an enhanced machine type communication (eMTC) PDCCH (MPDCCH) or NPDCCH. MPDCCH may simply be referred to as PDCCH hereinafter. Because the PRACH/NPRACH transmission is triggered by the PDCCH order, the timing of the MPDCCH/NPDCCH reception determines when the PRACH/NPRACH transmission may occur. As discussed above, the PDCCH order ends in subframe n, which means that the timing of the PRACH transmission may be determined based on when the PDCCH order ends. However, because a repetition number of MPDCCH is not known to the UE, but only known by the network, the UE does not know when the PDCCH order ends, and when PRACH transmissions begin.

The PDCCH order may be transmitted to the UE in a variety of different formats. For example, one such format may be a downlink control information (DCI) format 6-lA. Another example may be a DCI format 6-1B or N1, where N1 may be the NB-IoT DCI format. The DCI corresponding to a PDCCH order may be carried by MPDCCH. As described in section 5.3.3.1.12 of 3GPP TS 36.212, format 6-1A may be used for a random access procedure initiated by a PDCCH order only when format 6-1A cyclic redundancy check (CRC) is scrambled with a cell radio network temporary identity (C-RNTI) . 3GPP TS 36.212 is hereby incorporated by reference in its entirety. The remaining fields in the 6-1A format may include a resource block assignment determined by the following equation:

bits, with

representing the downlink bandwidth configuration, expressed in a number of resource blocks. In addition, the 6-1A format may include 6 bits of a preamble index, 4 bits of a PRACH mask index, 2 bits for a starting coverage enhancement level. All of the remaining bits in the DCI format 6-1A used for compact scheduling assignment of a physical downlink shared channel may be set to zero.

Section 5.7.1 of 3GPP TS 36.211 further describes that for BL/CE UEs, such as MTC devices, only a subset of the subframes are allowed for preamble transmissions, while also being allowed to serve as starting subframes for

repetitions.

may be a subframe in which the UE may start to transmit data via the PRACH. 3GPP TS 36.211 is hereby incorporated by reference in its entirety.

In certain embodiments, therefore, the starting subframe for a PRACH transmission may be determined by the end of the repetitions of the PDCCH order and the starting subframe periodicity of the PRACH. However, neither DCI format 6-1A nor 6-1B include a DCI subframe repetition number field. This means that the UE may not be informed of the ending subframe of the PDCCH order, and therefore may not know the starting subframe of the PRACH transmissions. This lack of awareness by the UE may lead to erroneous and conflicting operations being conducted by both the UE and the network entity transmitting the PDCCH order.

Certain embodiments described below may be used in any communication system in which the DCI subframe repetition number or the PDCCH order repetition number is unknown. The embodiments help to ensure proper operation for eMTC PDCCH order, since it is not clear when the UE should send the PRACH in response to the reception of the order. This may help to achieve a common understanding between the UE and the network entity of the timing of the PRACH transmissions.

Figure 1 illustrates an example of a timing relationship between PDCCH order and PRACH transmission according to certain embodiments. In particular, Figure 1 illustrates an example of a PDCCH order reception and corresponding PRACH transmissions. In the example shown in Figure 1, a network entity, such as an enhanced NodeB (eNB) , may configure MPDCCH 110 for PDCCH order with 256 repetitions. The UE may assume that the PDCCH order is capable of 256 repetitions. If the decoding of the PRACH order by the UE does not reveal that the PDCCH order is capable of 256 repetitions, the UE may not transmit on the PRACH.

The eNB may expect the UE to transmit the PRACH between subframes number 128 to 255 of the second search space. Despite this expectation by the eNB, the UE may be capable of decoding the MPDCCH correctly in the first MPDCCH candidate with 64 repetitions. When the UE decodes the MPDCCH correctly in the first MPDCCH with 64 repetitions, the UE may transmit the PRACH between subframes number 128 to 255 of the first MPDCCH search space. In another example, the UE may transmit PRACH from subframes number 0 to 127 of the second MPDCCH search space, and/or from subframes number 128 to 255 of the second MPDCCH search space. In other words, the user equipment may have two different options for transmitting on the PRACH that the eNB may not expect.

As can be seen in Figure 1, the eNB and UE could have a different understanding on the starting subframe of the PRACH transmission. This may cause the network entity, for example, to try to decode the PRACH while the PDCCH order is still transmitting. This is because subframe n , which is the subframe that marks the ending of the PDCCH order reception, may not be known by the UE. The implementation of the network entity, such as the eNB, may therefore become complicated, and possible errors may occur depending on UE implementation.

In order to prevent the above complications and errors, certain embodiments may improve the PDCCH order. Specifically, certain embodiments may configure a repetition value to the UE in order determine the PRACH timing. The repetition value, for example, may be a configured maximum repetition value (Rmax) . In some embodiments, the MPDCCH repetition number or value may be 1, 2, 4, 8, 16, 32, 64, 128, or 256. Rmax may be the maximum number of repetitions configured for a UE specific search space for the MPDCCH.

In certain embodiments, the UE may be informed of the Rmax via an RRC parameter mPDCCH-NumRepetition or nPDCCH-NumRepetitions, which may be configured by a network entity, such as an eNB. nPDCCH-NumRepetitions may be the parameter used in NB-IoT. Using the Rmax, certain embodiments may solve or help to prevent the ambiguity between the PRACH timing perceived by the eNB and the UE, such as an eMTC UE. Certain embodiments allow the UE to use a repetition value, such as Rmax, regardless of the repetition used by the network entity. In other words, the network entity may use a fraction of the repetition value for the PDCCH order, but then PRACH timing may be determined according to the repetition value, such as a Rmax. Therefore, the another repetition number used for the PDCCH order, which may be different than the Rmax assumed for PRACH timing. The above embodiments allow for solving the problem at hand, without having to extend the DCI.

Certain other embodiments may improve the PDCCH order format. Specifically, certain embodiments may introduce a field to indicate the number of repetitions in the downlink control information. The field may be a DCI subframe repetition number field, and may be included in DCI formats 6-1A, 6-1B, or N1. With the addition of this DCI subframe repetition number field, the ambiguity between the PRACH or NPRACH timing perceived by the eNB and the UE may be resolved.

Figure 2 illustrates an example of a flow diagram according to certain embodiments. In particular, Figure 2 illustrates a method or process performed by a UE, such as an eMTC or NB-IoT UE or an enhanced coverage user equipment. In step 210, the UE may receive a command to start random access from a network entity. For example, the command to start random access may take the form of a PDCCH order. In some embodiments, the UE may decode the PDCCH in order to determine the command to start random access, as shown in step 220. When decoding the PDCCH to determine the command to start random access, such as the PDCCH order, the UE may use the repetition value as the reference timing for random access. The repetition value, for example, may define a UE specific search space for the PDCCH. In some embodiments, the repetition value may be a configured maximum repetition value. The PDCCH order may be formatted according to a DCI format 6-1A, 6-1B, or N1. In certain embodiments, the actual repetition value may be indicated in a downlink control information (DCI) subframe repetition number field included in a format 6-1A, 6-1B, or N1 downlink control information.

In certain embodiments, the repetition value assumed or used by the UE may be different than the another repetition number used by the network entity to determine the repetition for the commend to start random access, such as a PDCCH order. The number used by the network, for example, may be a fraction of the repetition value assumed or used by the UE. In other words, the UE and the network entity may use a different or another repetition number for the command to start random access, such as a PDCCH order, than the repetition value used by the UE to determine timing for transmitting a random access preamble, such as the PRACH timing.

In some embodiments, the UE may determine the repetition value. For example, the repetition value may be determined based on a received message at the UE from a network entity, such as a eNB. In another example, the repetition value may be determined based on a standard set by a network operator or a standard setting body. Both the UE and the network entity may be configured with or have access to the repetition value. In certain embodiments, a fraction of the repetition value may be used by the network entity. For example, in embodiments in which the repetition value is Rmax, the another repetition value used by the network entity may be Rmax/8, Rmax/4, Rmax/2, or Rmax, while the UE may use Rmax. For example, ifthe Rmax is 256 repetition, the repetition value used by the network entity may be 128, 64, or 32.

In step 230, the UE may determine a timing for transmitting a random access preamble, for example a PRACH timing, based on a repetition value of a PDCCH. The repetition value is used by the user equipment while another repetition value is used for the command to start the random access. In other words, the UE may use the assumed repetition value to determine the timing of the random access preamble, while a separate or different another repetition value may be used by the network for the command to start the random access. The another repetition value for the command to start the random access may be a fraction of the repetition value used for the timing for transmitting the random access preamble. In step 240, the UE may transmit the random access preamble from the UE to the network entity on the PRACH using the determined timing, such as a PRACH timing. The transmitting of the preamble from the UE to the network entity using the PRACH timing may act to synchronize uplink transmissions between the UE to the network entity. In other words, the transmitting of the preamble may be part of a random access operation.

In certain embodiments, the transmitting of the preamble may occur on a starting subframe of the PRACH. The starting subframe may be determined based on at least one of the repetition value of the PDCCH and/or a periodicity of the starting subframe. For example, in some embodiments the starting subframe of the physical random access channel is later than a pre-defined number of subframes after an end subframe of a user equipment specific search space of the physical downlink control channel. For example, the pre-defined number of subframes may be 6 for eMTC, while the pre-defined number of subframes may be 8 for NB-IoT. In other words, the starting subframe of the PRACH, for example, may be later than the subframe Rmax+6 or Rmax+8. The periodicity of the starting subframe may be configured by the network entity. In other embodiments, however, the periodicity may not be configured by the network.

Figure 3 illustrates an example of a flow diagram according to certain embodiments. In particular, Figure 3 illustrates a method or process performed by a network entity, such as an eNB or a 5^th generation or New Radio NodeB (gNB) . In step 310, the network entity may transmit a command to start random access to a UE using another repetition number other than a repetition value. The another repetition value for the command to start the random access may be a fraction of the repetition value used for the determined timing for the random access preamble. In other words, the UE may use the repetition value for transmitting the random access preamble regardless of the fact that the network entity may use a different repetition value, such as a fraction of the repetition value, for transmitting the command to start the random access.

The repetition number may be indicated in a downlink control information subframe repetition number field included in a downlink control information format 6-1A, 6-1B, or N1. In step 320, the network entity may receive a random access preamble from the UE via a physical random access channel according to a timing for transmitting the random access preamble that is based on the repetition value. In other words, the UE may assume the repetition value, regardless of the another repetition value used by the network entity to transmit the command for random access. The receiving of the preamble may occur on a starting subframe of the PRACH and/or the starting subframe may be determined based on the maximum repetition value of the PDCCH or a periodicity of the starting subframe.

In step 330, the network entity may decode the random access preamble transmitted from the UE via the PRACH with a specific number of repetitions according to a coverage enhancement level of the UE. The network entity may then transmit a random access response from the network entity to the UE based on the decoded preamble, as shown in step 340. The transmitting of the random access response from the network entity to the user equipment acts to synchronize uplink transmissions between the user equipment and the network entity.

Figure 4 illustrates a system according to certain embodiments. It should be understood that each block in Figures 1, 2, and 3 may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry. In one embodiment, a system may include several devices, such as, for example, a network entity 420 or a UE 410. The system may include more than one UE 410 and more one network entity 420, although only one network entity is shown for the purposes of illustration. The network entity may be a network node, an access node, a base station, a eNB, a gNB, a server, a host, or any of the other access or network node discussed herein.

Each of these devices may include at least one processor or control unit or module, respectively indicated as 411 and 421. At least one memory may be provided in each device, and indicated as 412 and 422, respectively. The memory may include computer program instructions or computer code contained therein. One or

more transceiver

413 and 423 may be provided, and each device may also include an antenna, respectively illustrated as 414 and 424. Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Higher category UEs generally include multiple antenna panels. Other configurations of these devices, for example, may be provided. For example, network entity 420 and UE 410 may be additionally configured for wired communication, in addition to wireless communication, and in such a

case antennas

414 and 424 may illustrate any form of communication hardware, without being limited to merely an antenna.

Transceivers

413 and 423 may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception. In other embodiments, the network entity may have at least one separate receiver or transmitter. The transmitter and/or receiver (as far as radio parts are concerned) may also be implemented as a remote radio head which is not located in the device itself, but in a mast, for example. The operations and functionalities may be performed in different entities, such as nodes, hosts or servers, in a flexible manner. In other words, division of labor may vary case by case. One possible use is to make a network node deliver local content. One or more functionalities may also be implemented as virtual application (s) in software that can run on a server.

A user device or user equipment may be a mobile station (MS) such as a mobile phone or smart phone or multimedia device, a computer, such as a tablet, provided with wireless communication capabilities, personal data or digital assistant (PDA) provided with wireless communication capabilities, portable media player, digital camera, pocket video camera, navigation unit provided with wireless communication capabilities or any combinations thereof. In other embodiments, the UE may be a machine type communication (MTC) device, an eMTC UE, or an Internet of Things device, which may not require human interaction, such as a sensor, a meter, or an actuator.

In some embodiments, an apparatus, such as user equipment 410 or network entity 420, may include means for performing or carrying out embodiments described above in relation to Figures 1-3. In certain embodiments, the apparatus may include at least one memory including computer program code and at least one processor. The at least one memory including computer program code can be configured to, with the at least one processor, cause the apparatus at least to perform any of the processes described herein. The apparatus, for example, may be user equipment 410 or network entity 420.

Processors

411 and 421 may be embodied by any computational or data processing device, such as a central processing unit (CPU) , digital signal processor (DSP) , application specific integrated circuit (ASIC) , programmable logic devices (PLDs) , field programmable gate arrays (FPGAs) , digitally enhanced circuits, or comparable device or a combination thereof. The processors may be implemented as a single controller, or a plurality of controllers or processors.

For firmware or software, the implementation may include modules or unit of at least one chip set (for example, procedures, functions, and so on) .

Memories

412 and 422 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD) , random access memory (RAM) , flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate therefrom. Furthermore, the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal but may also be external or a combination thereof, such as in the case when additional memory capacity is obtained from a service provider. The memory may be fixed or removable.

The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as network entity 420 or UE 410, to perform any of the processes described above (see, for example, Figures 1-3) . Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions or one or more computer program (such as added or updated software routine, applet or macro) that, when executed in hardware, may perform a process such as one of the processes described herein. In other embodiments, a computer program product may encode instructions for performing any of the processes described above, or a computer program product embodied in a non-transitory computer-readable medium and encoding instructions that, when executed in hardware, perform any of the processes describes above. Computer programs may be coded by a programming language, which may be a high-level programming language, such as objective-C, C, C++, C#, Java, etc., or a low-level programming language, such as a machine language, or assembler. Alternatively, certain embodiments may be performed entirely in hardware.

Furthermore, although Figure 4 illustrates a system including a network entity 420 and UE 410, certain embodiments may be applicable to other configurations, and configurations involving additional elements, as illustrated and discussed herein. For example, multiple user equipment devices and multiple network entities may be present, or other nodes providing similar functionality, such as nodes that combine the functionality of a user equipment and an network entity, such as a relay node. The UE 410 may likewise be provided with a variety of configurations for communication other than communication network entity 420. For example, the UE 410 may be configured for device-to-device, machine-to-machine, and/or vehicle-to-vehicle transmission.

The above embodiments may provide for significant improvements to the functioning of a network and/or to the functioning of the user equipment and the network entities included within the network. Specifically, certain embodiments may help to prevent ambiguity between the network and the UE regarding the starting subframe of the PRACH. This may help to reduce the number of erroneous PRACH transmissions, while at the same time simplifying the PDCCH order. This network simplification and error reduction will help to reduce the number of resources used by the network, thereby significantly improving the functioning of the network as a whole, as well as the functioning of network entities included within the network and eMTC UEs communicating with the network. In addition, certain embodiments can help to improve the uplink synchronization process between the network and the UE, which may also help to reduce the amount of downtime experienced by the UE.

The features, structures, or characteristics of certain embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the usage of the phrases “certain embodiments, ” “some embodiments, ” “other embodiments, ” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. Thus, appearance of the phrases “in certain embodiments, ” “in some embodiments, ” “in other embodiments, ” or other similar language, throughout this specification does not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention. Although many of the above embodiments are directed to 3GPP LTE, LTE-A, and eMTC technology, other embodiments may apply to any other 3GPP technology, such as 5G or NR technology, 4^th generation (4G) , 3^rd generation (3G) , and/or Internet of Things.

Partial Glossary

3GPP 3rd Generation Partnership Project

LTE Long Term Evolution

eMTC Enhanced Machine Type Communication

NB-IoT Narrow Band Internet of Things

NPDCCH Narrowband Physical Downlink Control Channel

eNB Enhanced Node B

UE User Equipment

PUSCH Physical Uplink Sharing Channel

DCI Downlink Control Information

MPDCCH MTC Physical Downlink Control Channel

PRACH Physical Random Access channel

Claims

A method comprising:

receiving at a user equipment a command to start random access from a network entity;

determining at the user equipment, after receiving the command, timing for transmitting a random access preamble based on a repetition value of a physical downlink control channel, wherein the repetition value is used by the user equipment while another repetition value is used for the command to start the random access; and

transmitting the random access preamble from the user equipment to the network entity on a physical random access channel using the determined timing.
The method according to claim 1, wherein the repetition value is a configured maximum repetition value.
The method according to claims 1 or 2, wherein the another repetition value for the command to start the random access is a fraction of the repetition value used for the timing for transmitting the random access preamble.
The method according to claims 1-3, wherein the command to start the random access is a physical downlink control channel order.
The method according to any of claims 1-4, wherein the timing for the random access preamble is a physical random access channel timing.
The method according to any of claims 1-5, wherein the physical downlink control channel is a machine type communication physical downlink control channel or a narrowband physical downlink control channel.
The method according to any of claims 1-6, wherein the transmitting of the preamble occurs on a starting subframe of the physical random access channel.
The method according to claim 7, wherein the starting subframe is determined based on at least one of the repetition value of the physical downlink control channel, and physical random access channel repetition number or a periodicity of the starting subframe.
The method according to claim 8, wherein the periodicity of the starting subframe is configured by the network entity.
The method according to any of claims 6-9, wherein the starting subframe of the physical random access channel is later than a pre-defined number of subframes after an end subframe of a user equipment specific search space of the physical downlink control channel.
The method according to any of claims 1-10, further comprising:

decoding at the user equipment the physical downlink control channel to determine the command to start random access using the repetition value.
The method according to any of claims 1-11, wherein the repetition value defines the user equipment specific search space for the physical downlink control channel.
The method according to any of claims 1-12, further comprising:

determining the repetition value at the user equipment.
The method according to claim 13, wherein the repetition value is determined based on a message received from the network entity.
The method according to any of claims 1-7 and 10, wherein the repetition value is indicated in a downlink control information subframe repetition number field included in a downlink control information format 6-1A, 6-1B, or N1.
The method according to any of claims 1-15, wherein the transmitting of the preamble from the user equipment to the network entity using the determined timing acts to synchronize uplink transmissions between the user equipment to the network entity.
The method according to any of claims 1-16, wherein the user equipment is an enhanced machine type communication user equipment or an enhanced coverage user equipment, or narrowband internet of things user equipment.
A method comprising:

transmitting from a network entity a command to start random access to a user equipment using another repetition number other than a repetition value;

receiving a random access preamble at the network entity from the user equipment via a physical random access channel according to a timing for transmitting the random access preamble that is based on the repetition value.
The method according to claim 18, wherein the repetition value is a configured maximum repetition value.
The method according to claims 18 or 19, wherein the another repetition value for the command to start the random access is a fraction of the repetition value used for the determined timing for the random access preamble.
The method according to any of claims 18-20, further comprising:

decoding the random access preamble received from the user equipment via the physical random access channel using a specific number of repetitions according to a coverage enhancement level of the user equipment.
The method according to any of claims 18-21, further comprising:

transmitting a random access response from the network entity to the user equipment based on the decoded preamble.
The method according to any of claims 18-22, wherein the repetition value is indicated in a downlink control information subframe repetition number field included in a downlink control information format 6-1A, 6-1B, or N1.
The method according to any of claims 18-23, wherein the transmitting of the random access response from the network entity to the user equipment acts to synchronize uplink transmissions between the user equipment and the network entity.
The method according to any of claims 18-24, wherein the receiving of the random access preamble occurs on a starting subframe of the physical random access channel.
An apparatus comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform a process, the process including the method according to any of claims 1-25.
A non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform a process, the process including the method according to any of claims 1-25.
An apparatus comprising means for performing the method according to any of claims 1-25.
A computer program product encoding instructions for performing a process, the process including the method according to any of claims 1-25.
A computer program product embodied in a non-transitory computer-readable medium and encoding instructions that, when executed in hardware, perform a process, the process including the method according to any of claims 1-25.