Method and apparatus for random access

Methods and apparatuses for random access. A method performed by a terminal device comprises determining a random access procedure to be performed, the random access procedure being one of a two-step random access procedure and a four-step random access procedure, and transmitting a request message for random access in the determined random access procedure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National stage of International Application No. PCT/CN2020/073858, filed Jan. 22, 2020, which claims priority to International Application No. PCT/CN2019/073983, filed Jan. 30, 2019, which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure generally relates to wireless communications, and more specifically, to methods and apparatuses for random access.

BACKGROUND

In a new radio (NR) system, a four-step approach may be used for a random access procedure, as shown inFIG.1. In this approach, a user equipment (UE) detects a synchronization signal (SS) which comprises NR-primary synchronization signal (NR-PSS), NR-secondary synchronization signal (NR-SSS) and NR-physical broadcast channel (PBCH), and decodes broadcasted system information, e.g. remaining minimum system information (RMSI). Then the UE may transmit a physical random access channel (PRACH) preamble (message1) in uplink (UL). In response to receiving the message1, a base station (e.g. next generation node B (gNB)) replies with a random access response (RAR, message2). The RAR message is octet aligned and may comprise a timing advance (TA) command, a UL grant, and a temporary cell-radio network temporary identifier (TC-RNTI).

After receiving the RAR message, the UE may transmit a message3including a UE identification and a transport block on a physical uplink shared channel (PUSCH). The gNB then replies with a contention resolution message (message4). The timing advance command in the RAR message allows the message3PUSCH to be received with a timing accuracy within a cyclic prefix (CP). Without this timing advance, a very large CP would be needed in order to be able to demodulate and detect the PUSCH, unless the system is applied in a cell with a very small distance between the UE and the gNB. Since NR will also support larger cells with a need for providing a timing advance to the UE, the four-step approach is needed for the random access procedure.

A two-step random access procedure has been approved as a work item for NR release16. As illustrated inFIG.2, an initial access is completed in only two steps. At the first step, the UE sends a message, which may be called message A, including a random access preamble together with higher layer data such as radio resource control (RRC) connection request possibly with some small payload on PUSCH. At the second step, the gNB sends to the UE a response message, which may be called message B, including e.g. UE identifier assignment, TA information, and contention resolution message, etc.

SUMMARY

The present disclosure proposes an improved solution for random access.

According to a first aspect of the present disclosure, there is provided a method performed by a terminal device. The method comprises determining a random access procedure to be performed. The random access procedure is one of a two-step random access procedure and a four-step random access procedure. The method further comprises transmitting a request message for random access in/with the determined random access procedure. With the method, the terminal device can select an appropriate random access procedure to perform random access.

In accordance with an exemplary embodiment, the random access procedure to be performed may be determined according to a random access type indication received from a network node, the random access type indication indicating a random access procedure that the terminal device can use.

In accordance with an exemplary embodiment, the random access type indication may be received in downlink control information.

In accordance with an exemplary embodiment, the random access type indication may be received via radio resource control, RRC, signaling.

In accordance with an exemplary embodiment, the random access procedure to be performed may be determined based on at least one of followings: a measurement on a downlink signal or channel, a type of service for which the terminal device is in operation, a frequency band on which the terminal device is operating, a number of random access failures, a coverage of the network node, an availability of a physical uplink shared channel, PUSCH, resource to be used for a two-step random access procedure, and a moving speed of the terminal device.

In accordance with an exemplary embodiment, the random access type indication may indicate that both two-step random access procedure and four-step random access procedure can be used by the terminal device. In the embodiment, the random access procedure to be performed may be determined further based on at least one of followings: a measurement on a downlink signal or channel, a type of service for which the terminal device is in operation, a frequency band on which the terminal device is operating, a number of random access failures, a coverage of the network node, an availability of a physical uplink shared channel, PUSCH, resource to be used for a two-step random access procedure, and a moving speed of the terminal device.

In accordance with an exemplary embodiment, the method may further comprise receiving, in response to transmitting the request message, a response message from the network node, the response message indicating a random access procedure to be used by the terminal device for a subsequent random access.

In accordance with an exemplary embodiment, the response message may further comprise at least one of the preamble in the request message, TA information, and a random access failure cause.

In accordance with an exemplary embodiment, the TA information may be used for a subsequent two-step random access procedure.

In accordance with an exemplary embodiment, the response message may be received on a physical downlink shared channel, PDSCH, or a physical downlink control channel, PDCCH.

In accordance with an exemplary embodiment, when the random access procedure to be performed is determined as the two-step random access procedure, the request message may comprise a preamble and a PUSCH.

In accordance with an exemplary embodiment, when the random access procedure to be performed is determined as the two-step random access procedure, the request message may comprise a PUSCH with a demodulation reference signal, DMRS.

In accordance with an exemplary embodiment, the PUSCH may be of a channel structure carrying information with or without a demodulation reference signal, DMRS.

According to a second aspect of the present disclosure, there is provided a method performed by a network node. The method comprises receiving, from a terminal device, a request message for random access in a random access procedure, and determining whether the random access procedure is a two-step random access procedure or a four-step random access procedure based on the request message. The method further comprises transmitting, to the terminal device, a response message according to the determination.

In accordance with an exemplary embodiment, determining whether the random access procedure is a two-step random access procedure or a four-step random access procedure based on the request message may comprise: determining whether a PUSCH is received in a PUSCH resource for a two-step random access procedure; determining, in response to the determination that the PUSCH is received in the PUSCH resource for the two-step random access procedure, that the random access procedure is the two-step random access procedure; and determining, otherwise, that the random access procedure is the four-step random access procedure.

In accordance with an exemplary embodiment, the method may further comprise determining, in response to successfully detecting a preamble in the request message and failing to decode a PUSCH in the request message, a random access procedure to be used by the terminal device for a subsequent random access, and transmitting the response message indicating the determined random access procedure.

In accordance with an exemplary embodiment, the random access procedure may be determined based on at least one of followings: a measurement on an uplink signal, a frequency band on which the terminal device is operating, a number of random access failures, a coverage of the network node, an availability of a PUSCH time-frequency resource to be used for a two-step random access procedure, and a PUSCH decoding status.

In accordance with an exemplary embodiment, the response message may further comprise at least one of the preamble in the request message, TA information, and a random access failure cause.

In accordance with an exemplary embodiment, the response message may be transmitted on a PDSCH or a PDCCH.

In accordance with an exemplary embodiment, the method may further comprise transmitting a random access type indication to the terminal device, the random access type indication indicating a random access procedure that the terminal device can use.

In accordance with an exemplary embodiment, the random access type indication may be transmitted in downlink control information.

In accordance with an exemplary embodiment, the random access type indication may be transmitted via RRC signaling.

According to a third aspect of the present disclosure, there is provided a terminal device. The terminal device may comprise one or more processors and one or more memories comprising computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the terminal device at least to perform any step of the method according to the first aspect of the present disclosure.

According to a fourth aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the first aspect of the present disclosure.

According to a fifth aspect of the present disclosure, there is provided a network node. The network node may comprise one or more processors and one or more memories comprising computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the network node at least to perform any step of the method according to the second aspect of the present disclosure.

According to a sixth aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the second aspect of the present disclosure.

According to some embodiments of the present disclosure, a terminal device and a network node can determine to perform which random access procedure for random access. Moreover, according to some embodiments, the terminal device and the network node can switch the random access from the two-step random access procedure to the four-step random access procedure or vice versa.

DETAILED DESCRIPTION

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as new radio (NR), long term evolution (LTE), LTE-Advanced, wideband code division multiple access (WCDMA), high-speed packet access (HSPA), and so on. Furthermore, the communications between a terminal device and a network node in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), 4G, 4.5G, 5G communication protocols, and/or any other protocols either currently known or to be developed in the future.

The term “network node” refers to a network device in a communication network via which a terminal device accesses to the network and receives services therefrom. The network node or network device may refer to a base station (BS), an access point (AP), a multi-cell/multicast coordination entity (MCE), a controller or any other suitable device in a wireless communication network. The BS may be, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a next generation NodeB (gNodeB or gNB), an IAB node, a remote radio unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth.

Yet further examples of the network device comprise multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, positioning nodes and/or the like. More generally, however, the network node may represent any suitable device (or group of devices) capable, configured, arranged, and/or operable to enable and/or provide a terminal device access to a wireless communication network or to provide some service to a terminal device that has accessed to the wireless communication network.

The term “terminal device” refers to any end device that can access a communication network and receive services therefrom. By way of example and not limitation, the terminal device may refer to a user equipment (UE), or other suitable devices. The UE may be, for example, a subscriber station, a portable subscriber station, a mobile station (MS) or an access terminal (AT). The terminal device may include, but not limited to, portable computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable device, a personal digital assistant (PDA), a vehicle, and the like.

As yet another specific example, in an Internet of things (IoT) scenario, a terminal device may also be called an IoT device and represent a machine or other device that performs monitoring, sensing and/or measurements etc., and transmits the results of such monitoring, sensing and/or measurements etc. to another terminal device and/or a network equipment. The terminal device may in this case be a machine-to-machine (M2M) device, which may in a 3rd generation partnership project (3GPP) context be referred to as a machine-type communication (MTC) device.

As one particular example, the terminal device may be a UE implementing the 3GPP narrow band Internet of things (NB-IoT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, e.g. refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment, for example, a medical instrument that is capable of monitoring, sensing and/or reporting etc. on its operational status or other functions associated with its operation.

As used herein, the terms “first”, “second” and so forth refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “has”, “having”, “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on”. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment”. The term “another embodiment” is to be read as “at least one other embodiment”. Other definitions, explicit and implicit, may be included below.

As described above, in the two-step random access procedure as shown inFIG.2, the preamble and the PUSCH will be transmitted by the UE in one message called message A. In the four-step random access procedure, the message3PUSCH is transmitted only when a preamble is correctly detected and the message2is correctly received by the UE. Moreover, the two-step random access procedure may be preferred for time-critical services, and the four-step random access procedure may be preferred for services requiring reliable reception. In NR, both the two-step random access procedure and the four-step random access procedure can be supported. Therefore, it would be desirable to provide a solution for the UE and gNB to determine what random access procedure is used.

In accordance with some exemplary embodiments, the present disclosure provides an improved solution for random access. The solution may be applied to a wireless communication system including a terminal device and a base station. Prior to performing a random access, the terminal device may determine a random access procedure to be performed, and the random access procedure determined can be one of a two-step random access procedure and a four-step random access procedure. Then the terminal device may transmit a request message for random access in/with the determined random access procedure. Also, the base station can determine the random access procedure upon receipt of the request message for random access. With the improved solution, the terminal device and the base station can determine the random access procedure used for the random access.

It is noted that some embodiments of the present disclosure are mainly described in relation to 5G specifications being used as non-limiting examples for certain exemplary network configurations and system deployments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples and embodiments, and does not limit the present disclosure naturally in any way. Rather, any other system configuration or radio technologies may equally be utilized as long as exemplary embodiments described herein are applicable.

FIG.3is a flowchart illustrating a method300according to some embodiments of the present disclosure. The method300illustrated inFIG.3may be performed by an apparatus implemented in/as a terminal device or communicatively coupled to a terminal device. In accordance with an exemplary embodiment, the terminal device may be a UE.

According to the exemplary method300illustrated inFIG.3, the terminal device determines a random access procedure to be performed, as shown in block302. The determined random access procedure is one of a two-step random access procedure or a four-step random access procedure. In some embodiments, the random access procedure may be determined according to a random access type indication. The random access type indication indicates a random access procedure that the terminal device can use.

In some embodiments, the random access type indication may be one bit. For example, if the bit is set to 0, the random access type indication indicates that only two-step random access procedure can be used. If the bit is set to 1, the random access type indication indicates that only four-step random access procedure can be used.

Alternatively, in some embodiments, the random access type indication may be two bits. In this case, for example, if the bits are set to 00, the random access type indication indicates that only two-step random access procedure can be used. If the bits are set to 01, the random access type indication indicates that only four-step random access procedure can be used. If the bits are set to 10, the random access type indication indicates that both two-step random access procedure and four-step random access procedure can be used.

In some embodiments, the random access type indication may be signaled from a network node such as a base station (e.g. a gNB). In an embodiment, the random access type indication may be included in downlink control information, DCI, and signaled in PDCCH. When the terminal device needs to initiate random access, the terminal device can determine what random access procedure to be used from the DCI. In another embodiment, the random access type indication may be signaled via RRC signaling. For example, the random access type indication may be included in system information and broadcasted in a RRC message.

In some embodiments, the terminal device may determine the random access procedure based on other one or more factors than the random access type indication.

In an embodiment, the terminal device may determine the random access procedure based on a measurement on a downlink (DL) signal or channel. In particular, the terminal device may measure a Reference Signal Receiving Power (RSRP) or Reference Signal Receiving Quality (RSRQ) in downlink. If the RSRP or RSRQ is lower than a threshold, the terminal device may determine to perform the two-step random access procedure. Otherwise, the four-step random access procedure is determined to be performed. The threshold may be predefined or may be configured via a signaling message.

In another embodiment, the terminal device may determine the random access procedure based on a type of service for which the terminal device is in operation. As described above, the two-step random access procedure may be preferred for time-critical services, for example, Ultra Reliable Low Latency Communications (URLLC) services, New Radio Unlicensed (NRU) services, etc. Therefore, when the terminal service is in a time-critical service, the terminal device may determine to perform the two-step random access procedure. When the terminal device is in a non-time critical service, the terminal device may determine to perform the four-step random access procedure.

In yet another embodiment, the terminal device may determine the random access procedure based on a frequency band on which the terminal device is operating. For example, it may be defined that the two-step random access procedure can be performed in an unlicensed band and the four-step random access procedure can be performed in a licensed band. Thus, when the terminal device is operating in the unlicensed band, the terminal device may determine to perform the two-step random access procedure, thereby reducing the number of Listen Before Talk (LBT) procedures to complete the random access. When the terminal device is operating in the licensed band, the terminal device may determine to perform the four-step random access procedure.

In yet another embodiment, the terminal device may determine the random access procedure based on a number of random access failures. Herein, the random access failure means that the random access is not completed. For example, the terminal device may count a number of random access failures for the two-step random access procedure. When the number of random access failures reaches a threshold value, (i.e. the random access procedure is not successfully completed even after transmitting msgA for ‘N’ times, N is a natural number), the terminal device may determine to perform the four-step random access procedure, i.e. only transmitting a PRACH preamble. Alternatively or additionally, the terminal device may count a number of random access failures for the four-step random access procedure. When the number reaches a threshold value, the terminal device may determine to perform the two-step random access procedure. The above threshold values (e.g. N) may be predefined or may be configured via a signaling message by the network node.

In yet another embodiment, the terminal device may determine the random access procedure based on coverage of the network node, such as the base station (e.g. gNB) serving the terminal device. For example, when the coverage of the network node is smaller than a threshold, the terminal device may determine to perform the two-step random access procedure. Otherwise, the four-step random access procedure is determined.

In yet another embodiment, the terminal device may determine the random access procedure based on an availability of a PUSCH resource to be used for the two-step random access procedure. For example, dedicated PUSCH resources may be allocated to the two-step random access procedure. When performing the two-step random access procedure, the terminal device may use an instance of the dedicated PUSCH resources to transmit the PUSCH. If the instance of the dedicated PUSCH resources is determined as being unavailable, e.g. the PUSCH resource is occupied by a higher priority UL transmission or the PUSCH resource is not for a UL subframe, the terminal device may determine to perform the four-step random access procedure. If the instance of the dedicated PUSCH resources is determined as available, the terminal device may determine to perform the two-step random access procedure.

In yet another embodiment, the terminal device may determine the random access procedure based on a moving speed of the terminal device. For example, when the moving speed of the terminal device is lower than a predetermined threshold, the terminal device may determine to perform the two-step random access procedure. Otherwise, the terminal device may determine to perform the four-step random access procedure.

In some embodiments, if the received random access type indication indicates that both two-step random access procedure and four-step random access procedure can be used by the terminal device, the terminal device may further determine the actual random access procedure based on at least one of the factors as described above.

Upon the determination of the random access procedure to be performed, in block304, the terminal device transmits a request message for random access in/with the determined random access procedure. In some embodiments, if the four-step random access procedure is determined to be used, the terminal device may transmit the request message comprising a preamble, i.e. message1. If the two-step random access procedure is determined to be used, the terminal device may transmit the request message comprising a preamble and a PUSCH, i.e. message A. In some embodiments, the PUSCH may be of an existing channel structure carrying control and/or data information with DMRS. Alternatively, if the preamble is enough for PUSCH channel estimation, the PUSCH may be of a channel structure carrying control and/or data information without DMRS. In some embodiments, if DMRSs are enough to separate different terminal devices and timing can be estimated accurately, the request message in the two-step random access procedure may not comprise the preamble, that is, the request message may comprise only the PUSCH with the DMRS.

Additionally, in some embodiments, in response to transmitting the request message, the terminal device may receive a response message from the network node, as shown in block306. In some embodiments, when the request message is message1in the four-step random access procedure, the response message will be a RAR (message2). When the request message is transmitted for the two-step random access procedure, the response message may be message B if the network node determines to perform the two-step random access procedure, or may be message2if the network node determines to perform the four-step random access procedure. In the case of receiving message2, the terminal device may proceed with the four-step random access procedure by transmitting message3. In some embodiments, when the request message is message A in the two-step random access procedure, the response message may be a message indicating a random access procedure to be used for a subsequent random access. If the network node fails to decode the PUSCH message while successfully detecting the preamble in the request message, the network node may determine a random access procedure for a subsequent random access, and transmit a response message indicating the determined random access procedure. After receiving the response message, the terminal device may know what random access procedure will be used, and use it for the subsequent random access. The determined random access procedure may be indicated by a fallback indication. The fallback indication may be one bit. For example, if the bit is set to 0, it means that the two-step random access procedure is used for the subsequent random access. If the bit is set to 1, it means that the four-step random access procedure is used for the subsequent random access.

In some embodiments, in addition to the fallback indication, the response message may further comprise at least one of the detected preamble, TA information, and a random access failure cause. In an embodiment, the random access failure cause may comprise either of cyclic redundancy check (CRC) failure and low signal quality.

In the two-step random access procedure, the PUSCH transmission is not necessarily with poor UL time alignment even if a timing alignment timer has expired. The terminal device may use the last valid timing alignment timer value to transmit the PUSCH. When the terminal device receives the TA information in the response message, the TA information can be used for the subsequent two-step random access procedure.

In some embodiments, the response message may be received on a physical downlink shared channel, PDSCH. Alternatively, the response message may be received as control information on a physical downlink control channel, PDCCH.

FIG.4is a flowchart illustrating a method400according to some embodiments of the present disclosure. The method400illustrated inFIG.4may be performed by an apparatus implemented in/as a network node or communicatively coupled to a network node. In accordance with an exemplary embodiment, the network node may be a base station, e.g. a gNB. In the following description with respect toFIG.4, for the same or similar parts as those in the previous exemplary embodiments, the detailed description will be properly omitted.

According to the exemplary method400illustrated inFIG.4, the network node receives a request message for random access in a random access procedure, as shown in block402. In the four-step random access procedure, the request message may comprise a preamble without PUSCH. In the two-step random access procedure, the request message may comprise a preamble and a PUSCH with or without DMRS, or the request message may comprise a PUSCH with DMRS.

Then in block404, the network node determines whether the random access procedure is the two-step random access procedure or the four-step random access procedure based on the received request message. That is, the network node determines to perform what random access procedure.

In some embodiments, the network node may determine whether a PUSCH is received in a PUSCH resource for a two-step random access procedure. As described above, the two-step random access procedure may be allocated with the dedicated PUSCH resources. The terminal device may transmit the PUSCH in an instance of the dedicated PUSCH resources. If the network node determines that the PUSCH is received in the dedicated PUSCH resource, the network node determines that the random access procedure is the two-step random access procedure. Otherwise, if the network node determines that no PUSCH is received in the dedicated PUSCH resource, the network node determines that the random access procedure is the four-step random access procedure.

In some embodiments, the determination of the random access procedure may be based on other one or more factors than the PUSCH resources dedicated for the two-step random access procedure.

In an embodiment, the network node may determine the random access procedure based on a measurement on an uplink signal. For example, the uplink signal may be the preamble in the physical random access channel (PRACH) occasion, or the PUSCH. The network node may measure a signal level or a time offset of the uplink signal. If the signal level or the time offset is lower than a threshold, the network node may determine to perform the two-step random access procedure. Otherwise, the four-step random access procedure is determined. The threshold may be predefined or may be configured via a signaling message.

In another embodiment, the network node may determine the random access procedure based on a frequency band on which the terminal device is operating. For example, as described above, it may be defined that the two-step random access procedure can be performed in an unlicensed band and the four-step random access procedure can be performed in a licensed band. Thus, when the terminal device is operating in the unlicensed band, the network node may determine to perform the two-step random access procedure. When the terminal device is operating in the licensed band, the network node may determine to perform the four-step random access procedure.

In yet another embodiment, the network node may determine the random access procedure based on a number of random access failures. For example, as described above, the network node may count the number of random access failures for the two-step random access procedure. When the number of random access failures reaches a threshold value, the network node may determine to perform the four-step random access procedure. Alternatively or additionally, the network node may count a number of random access failures for the four-step random access procedure. When the number reaches a threshold value, the network node may determine to perform the two-step random access procedure. The threshold value may be predefined or may be pre-configured.

In yet another embodiment, the network node may determine the random access procedure based on its coverage. For example, when the coverage of the network node is smaller than a threshold, the network node may determine to perform the two-step random access procedure. Otherwise, the four-step random access procedure is determined.

In yet another embodiment, the network node may determine the random access procedure based on an availability of a PUSCH resource to be used for the two-step random access procedure. For example, the dedicated PUSCH resources may be allocated to the two-step random access procedure. If the network node determines that the instance of the dedicated PUSCH resources corresponding to the detected preamble in the request message is unavailable, e.g. the PUSCH resource is occupied by a higher priority UL transmission or the PUSCH resource is not for a UL subframe, the network node may determine to perform the four-step random access procedure. If the instance of the dedicated PUSCH resources is determined as available, the network node may determine to perform the two-step random access procedure.

In yet another embodiment, the network node may determine the random access procedure based on a PUSCH decoding status. In particular, if the PUSCH decoding status indicates that the PUSCH decoding is failed, the network node may determine to perform the four-step random access procedure. If the PUSCH decoding status indicates that the PUSCH decoding is successful, the network node may determine to perform the four-step random access procedure. In an embodiment, the PUSCH decoding status may be a CRC status. Moreover, the PUSCH decoding status may be determined according to the number of error bits decoded.

Upon the determination of the random access procedure, in block406, the network node transmits a response message to the terminal device according to the determination. When the two-step random access procedure is determined, the response message is the RAR (message2). When the four-step random access procedure is determined, the response is the message B.

Additionally, in some embodiments, if the network node successfully detects the preamble in the request message and fails to decode the PUSCH message, the network node may determine a random access procedure to be used by the terminal device for a subsequent random access, as shown in block408. In some embodiments, the determination of the random access procedure may be based on at least one of the factors as described above. Then in block410, the network node may transmit the response message indicating the determined random access procedure to the terminal device. In some embodiments, the determined random access procedure may be indicated by a fallback indication. The fallback indication may be one bit. For example, if the bit is set to 0, it means that the two-step random access procedure is used for the subsequent random access. If the bit is set to 1, it means that the four-step random access procedure is used for the subsequent random access.

In some embodiments, in addition to the fallback indication, the response message may further comprise at least one of the detected preamble, TA information, and a random access failure cause. In an embodiment, the random access failure cause may comprise either of cyclic redundancy check (CRC) failure and low signal quality. In some embodiments, the response message may be transmitted on a PDCCH or a PDSCH.

Additionally, in some embodiments, the network node may transmit a random access type indication to the terminal device. The random access type indication indicates the random access procedure(s) that the terminal device can use. Accordingly, the terminal device can determine the random access procedure to be performed. The details of the random access type indication have been described above, and thus are omitted herein.

Please note that the order for performing the steps as shown inFIG.4is illustrated just as an example. In some implementation, some steps may be performed in a reverse order or in parallel. In some other implementation, some steps may be omitted or combined.

It can be therefore seen that, with the proposed solutions for the random access according to the above embodiments, the terminal device and the network node can determine to perform what random access procedure for random access. Moreover, the terminal device and the network node can switch the random access from the two-step random access procedure to the four-step random access procedure or vice versa.

The various blocks shown inFIGS.3-4may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). The schematic flow chart diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of specific embodiments of the presented methods. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated methods. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.

FIG.5is a block diagram illustrating an apparatus500according to various embodiments of the present disclosure. As shown inFIG.5, the apparatus500may comprise one or more processors such as processor501and one or more memories such as memory502storing computer program codes503. The memory502may be non-transitory machine/processor/computer readable storage medium. In accordance with some exemplary embodiments, the apparatus500may be implemented as an integrated circuit chip or module that can be plugged or installed into a terminal device as described with respect toFIG.3, or a network node as described with respect toFIG.4.

In some implementations, the one or more memories502and the computer program codes503may be configured to, with the one or more processors501, cause the apparatus500at least to perform any operation of the method as described in connection withFIG.3. In such embodiments, the apparatus500may be implemented as at least part of or communicatively coupled to the terminal device as described above. As a particular example, the apparatus500may be implemented as a terminal device.

In other implementations, the one or more memories502and the computer program codes503may be configured to, with the one or more processors501, cause the apparatus500at least to perform any operation of the method as described in connection withFIG.4. In such embodiments, the apparatus500may be implemented as at least part of or communicatively coupled to the network node as described above. As a particular example, the apparatus500may be implemented as a network node.

Alternatively or additionally, the one or more memories502and the computer program codes503may be configured to, with the one or more processors501, cause the apparatus500at least to perform more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.

FIG.6is a block diagram illustrating an apparatus600according to some embodiments of the present disclosure. As shown inFIG.6, the apparatus600may comprise a determining unit601and a transmitting unit602. In an exemplary embodiment, the apparatus600may be implemented in a terminal device such as UE. The determining unit601may be operable to carry out the operation in block302. The transmitting unit602may be operable to carry out the operation in block304. Further, the apparatus600may also comprise a receiving unit603operable to carry out the operation in block306. Optionally, the determining unit601, the transmitting unit602and/or the receiving unit603may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.

FIG.7is a block diagram illustrating an apparatus700according to some embodiments of the present disclosure. As shown inFIG.7, the apparatus700may comprise a receiving unit701, a determining unit702, and a transmitting unit703. In an exemplary embodiment, the apparatus700may be implemented in a network node such as a base station (e.g. a gNB, or an eNB). The receiving unit701may be operable to carry out the operation in block402. The determining unit702may be operable to carry out the operation in blocks404,408, and the transmitting unit703may be operable to carry out the operation in blocks406,410. Optionally, the receiving unit701, the determining unit702and/or the transmitting unit703may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.

FIG.8is a block diagram illustrating a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments of the present disclosure.

With reference toFIG.8, in accordance with an embodiment, a communication system includes a telecommunication network810, such as a 3GPP-type cellular network, which comprises an access network811, such as a radio access network, and a core network814. The access network811comprises a plurality of base stations812a,812b,812c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area813a,813b,813c. Each base station812a,812b,812cis connectable to the core network814over a wired or wireless connection815. A first UE891located in a coverage area813cis configured to wirelessly connect to, or be paged by, the corresponding base station812c. A second UE892in a coverage area813ais wirelessly connectable to the corresponding base station812a. While a plurality of UEs891,892are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station812.

The telecommunication network810is itself connected to a host computer830, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer830may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. Connections821and822between the telecommunication network810and the host computer830may extend directly from the core network814to the host computer830or may go via an optional intermediate network820. An intermediate network820may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network820, if any, may be a backbone network or the Internet; in particular, the intermediate network820may comprise two or more sub-networks (not shown).

The communication system ofFIG.8as a whole enables connectivity between the connected UEs891,892and the host computer830. The connectivity may be described as an over-the-top (OTT) connection850. The host computer830and the connected UEs891,892are configured to communicate data and/or signaling via the OTT connection850, using the access network811, the core network814, any intermediate network820and possible further infrastructure (not shown) as intermediaries. The OTT connection850may be transparent in the sense that the participating communication devices through which the OTT connection850passes are unaware of routing of uplink and downlink communications. For example, the base station812may not or need not be informed about the past routing of an incoming downlink communication with data originating from the host computer830to be forwarded (e.g., handed over) to a connected UE891. Similarly, the base station812need not be aware of the future routing of an outgoing uplink communication originating from the UE891towards the host computer830.

FIG.9is a block diagram illustrating a host computer communicating via a base station with a UE over a partially wireless connection in accordance with some embodiments of the present disclosure.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference toFIG.9. In a communication system900, a host computer910comprises hardware915including a communication interface916configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system900. The host computer910further comprises a processing circuitry918, which may have storage and/or processing capabilities. In particular, the processing circuitry918may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer910further comprises software911, which is stored in or accessible by the host computer910and executable by the processing circuitry918. The software911includes a host application912. The host application912may be operable to provide a service to a remote user, such as UE930connecting via an OTT connection950terminating at the UE930and the host computer910. In providing the service to the remote user, the host application912may provide user data which is transmitted using the OTT connection950.

The communication system900further includes a base station920provided in a telecommunication system and comprising hardware925enabling it to communicate with the host computer910and with the UE930. The hardware925may include a communication interface926for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system900, as well as a radio interface927for setting up and maintaining at least a wireless connection970with the UE930located in a coverage area (not shown inFIG.9) served by the base station920. The communication interface926may be configured to facilitate a connection960to the host computer910. The connection960may be direct or it may pass through a core network (not shown inFIG.9) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware925of the base station920further includes a processing circuitry928, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station920further has software921stored internally or accessible via an external connection.

The communication system900further includes the UE930already referred to. Its hardware935may include a radio interface937configured to set up and maintain a wireless connection970with a base station serving a coverage area in which the UE930is currently located. The hardware935of the UE930further includes a processing circuitry938, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE930further comprises software931, which is stored in or accessible by the UE930and executable by the processing circuitry938. The software931includes a client application932. The client application932may be operable to provide a service to a human or non-human user via the UE930, with the support of the host computer910. In the host computer910, an executing host application912may communicate with the executing client application932via the OTT connection950terminating at the UE930and the host computer910. In providing the service to the user, the client application932may receive request data from the host application912and provide user data in response to the request data. The OTT connection950may transfer both the request data and the user data. The client application932may interact with the user to generate the user data that it provides.

It is noted that the host computer910, the base station920and the UE930illustrated inFIG.9may be similar or identical to the host computer830, one of base stations812a,812b,812cand one of UEs891,892ofFIG.8, respectively. This is to say, the inner workings of these entities may be as shown inFIG.9and independently, the surrounding network topology may be that ofFIG.8.

InFIG.9, the OTT connection950has been drawn abstractly to illustrate the communication between the host computer910and the UE930via the base station920, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE930or from the service provider operating the host computer910, or both. While the OTT connection950is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

Wireless connection970between the UE930and the base station920is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE930using the OTT connection950, in which the wireless connection970forms the last segment. More precisely, the teachings of these embodiments may improve the latency and the power consumption, and thereby provide benefits such as lower complexity, reduced time required to access a cell, better responsiveness, extended battery lifetime, etc.

A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection950between the host computer910and the UE930, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection950may be implemented in software911and hardware915of the host computer910or in software931and hardware935of the UE930, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection950passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which the software911,931may compute or estimate the monitored quantities. The reconfiguring of the OTT connection950may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station920, and it may be unknown or imperceptible to the base station920. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer910′s measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software911and931causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection950while it monitors propagation times, errors etc.

FIG.13is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference toFIG.8andFIG.9. For simplicity of the present disclosure, only drawing references toFIG.13will be included in this section. In step1310(which may be optional), in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In step1320(which may be optional), the base station initiates transmission of the received user data to the host computer. In step1330(which may be optional), the host computer receives the user data carried in the transmission initiated by the base station.