TECHNICAL FIELD

The present application relates to a method and devices for communicating payload data in a random access procedure.

BACKGROUND

A terminal, also known as terminal device or user equipment (UE), configured to wirelessly communicate with a base station (BS) of a network may be in a disconnected state or idle state or initial state. Then, for connecting to the network, the UE may transition into a connected state by performing a random access (RA) procedure. Triggers for performing the random access procedure may include uplink (UL) data scheduled or queued for transmission and/or receipt of a downlink paging indicative of downlink (DL) data scheduled for transmission and/or a schedule for a downlink data transmission. Typically, the RA procedure includes multiple messages, e.g., four messages; RA message 1 in UL direction, RA message 2 in DL direction, RA message 3 in UL direction and RA message 4 in DL direction. Details of such a RA procedure in the 3GPP Long Term Evolution (LTE) framework are described in 3GPP Technical Specifications (TSs) 36.211, 36.231, 36.321, and 36.331.

For many Internet of Things (IoT) applications the amount of data to be transmitted on the user plane (also called payload data or application layer data) in each connection occasion is relatively small and therefore there is a concept to be defined in 3GPP denoted as Early Data Transmission (EDT) for Rel-15 eMTC and NB-IoT. With EDT the UE can reduce the amount of signaling for small data transmissions by including UL payload data into the RA message 3 transmission. Also, the network can transmit DL payload data in the RA message 4 transmission, in order to enable application/payload data in both directions with the EDT concept.

At a point in time when the RA message 3 is transmitted from the UE to the network or BS, there is no user plane transport bearer for application data set up. Hence, EDT is a method to include a container of payload data, even before the user plane transport bearer has been configured.

However, such techniques of EDT face certain restrictions and drawbacks. One major limitation is the amount of data that is possible to be transmitted. The data to be transmitted needs to fit into the RA message 3 for UL EDT and RA message 4 for DL EDT, essentially limiting the data size to tens or a few hundred bytes, e.g., 125 bytes.

Another limitation is that the EDT function within the single RA procedure is not very suitable for a transmit and response action from a UE to an application server and back. If, for example, the UE connects to the network and transmits UL payload data via EDT to an application server, the server may respond to the UE based on the transmitted UL payload data within a few seconds. However, such response cannot fit into the same RA procedure, since RA message 4 is expected to be transmitted immediately (within a few milliseconds or within a few frames) after RA message 3. Hence, the application response may be sent in another connection, which could be initiated via a downlink initiated paging or possibly via another UE-initiated RA procedure. However, this may introduce additional communication overhead and power consumption.

SUMMARY

Therefore, a need exists for advanced RA procedures. In particular, a need exists for techniques, which overcome or mitigate at least some of the above-identified restrictions and drawbacks.

This need is met by the features of the independent claims. The features of the dependent claims define embodiments.

A method includes communicating, between a UE and a BS, an UL control message of a RA procedure. The UL control message includes an indicator indicative of UL payload data queued for transmission during the RA procedure. Furthermore, according to the method, the RA procedure is configured depending on the indicator.

In the RA procedure configured in accordance with the indicator, the UL payload data is communicated.

The UL payload data may include for example UL application layer data communicated to a server in an application layer. The UL payload data may include any kind of upper layer data in a layer above Layer 3 of the OSI layer model, e.g., originating from layer 7. The UL payload data may include user plane data, i.e. the UL payload may include application or user data that conventionally would be transmitted via user plane, for example, when a radio resource connection (RRC) has been established and a dedicated radio bearer (DRB) is setup

For example, a timing of messages of the RA procedure may be configured depending on the indicator. For example, a point in time at which certain messages of the RA procedure are communicated may be set accordingly. For example, a repetition rate or count of repetitions of one or more messages of the RA procedure may be configured depending on the indicator.

Multiple repetitions of a message, as used herein, may refer to a scenario where a given message—e.g., defined by a certain header or message type—is repeated more than once. From repetition to repetition, the payload included in the message may vary. Multiple repetitions of a message may enable to transmit larger amounts of payload. For example, to deliver in total 3000 bits of payload information, the payload may be communicated by three repetitions of the message, each repetition including 1000 bits. Further, in IoT context, repetitions may comprise the transmission of the same information repeatedly to obtain time diversity.

The RA procedure, by means of the indicator, is configured on-the-fly, i.e. within the RA procedure itself: the indicator for configuration of the RA procedure is communicated in the RA procedure itself, for example in RA message 1. Hence, configuring the RA procedure depending on the indicator may in particular include configuring a remaining part (for example RA message 2, RA message 3 and/or RA message 4) of the RA procedure depending on the indicator. In detail, a part subsequent of the RA access procedure following the UL control message including the indicator may be configured. For example, the above described RA message 2, RA message 3 and RA message 4 may be configured depending on the indicator. Further, configuring the remaining part of the RA procedure may include configuring a message flow, for example a number of messages and/or a timing of messages of the RA procedure. This may enable to communicate more payload data within the RA procedure and may enable to include responses from an application layer within a single RA procedure.

Communicating as used herein may relate to transmitting and/or receiving. For example within the RA procedure, the UE may send multiple RA message 3 each including payload data to the BS. The BS may concatenate this payload and may send it to a server. The server may respond and the response payload may be split up by the BS in multiple RA message 4 each including payload data.

The indicator may be a 1-bit flag. For example, the indicator may indicate whether or whether not there is UL payload data queued for transmission. In other examples, the indicator may be a multi-bit indicator. Here, the indicator may be indicative of additional information such as the size of the data, a quality of service associated with a service of the data, a type of the data, the service of the data, a round-trip time associated with the data, etc.

The method may be implemented in a UE. The UE may be a mobile telephone, for example a smart phone, or an Internet of Things (IoT) device. According to the method, an UL control message of a RA procedure may be transmitted from the UE to a BS. The UL control message includes an indicator indicative of UL payload data queued for transmission during the RA procedure. Depending on the indicator, the RA procedure performed by the UE is configured, and in the RA procedure configured in accordance with the indicator, the UL payload data is transmitted from the UE to the BS.

The method may, alternatively or additionally, be implemented in BS or by devices providing radio access functionality of a communication network. The BS may receive, from a UE, UL control message of a RA procedure. The UL control message includes an indicator indicative of UL payload data queued for transmission during the RA procedure. Depending on the indicator, the BS configures the RA procedure, and receives, in the RA procedure configured in accordance with the indicator, the UL payload data from the UE.

The UL control message may include a RA message of the RA procedure, which includes a RA preamble sequence (hereinafter simply referred to as RA preamble) of the UE. For example, the UL control message may be implemented by the so-called “RA message 1” of the RA procedure in 3GPP network environments.

As a general rule, various options are available for implementing the indicator. The RA preamble may implement the indicator. For example, a specifically predefined subset of RA preambles from a pool of predefined RA preambles may be used to indicate certain information as indicator for configuring the RA procedure. Then, by selecting the appropriate RA preamble from the pool of preambles inside or outside the predefined subset, it is possible to provide the indication of the queued UL payload data. In other words, the RA preamble can implement the indicator. As an alternative, the RA message may include the RA preamble and the indicator as separate information field. The separate information field for the indicator may be added to the RA message—beyond the RA preamble. The indicator may be placed in currently unused fields of the RA message. As will be appreciated, the indicator may be an implicit indicator or an explicit indicator.

Optionally or as an alternative, the UL control message may include a Layer 3 connection request message of the RA procedure. For example, the UL control message may be implemented by the RA message 3 of the RA procedure in 3GPP networks.

Here, the indicator may be included in a specific information field of the RA message 3. For example, the indicator may be included in a RRC information field.

The indicator may be indicative of a size of the UL payload data. The indicator may be indicative of the size of the UL payload data in terms of a byte count or symbol count, or in terms of a block count of blocks of UL payload data of a predefined size. Furthermore, the indicator may be indicative the size of the UL payload data by a selector value indicating the size of the UL payload data by selecting one predefined size of a plurality of predefined sizes.

Depending on the indicator, configuring the RA procedure may include setting a count of repetitions of a Layer 3 connection request message—e.g., the RA message 3—of the RA procedure, each Layer 3 connection request message including UL payload data. Thus, the RA procedure may be configured such that a plurality of repetitions of the Layer 3 connection request messages are communicated for delivering the UL payload data.

In some scenarios, it would be possible to communicate a plurality of repetitions of a Layer 3 connection response message. Thereby, it may be possible to acknowledge receipt of each of a plurality of repetitions of the Layer 3 connection request message. For this, the multiple repetitions of the Layer 3 connection request message and the multiple repetitions of the Layer 3 connection response message be communicated interleaved in time domain, i.e., in an alternating sequence.

Optionally, multiple repetitions of the Layer 3 connection response message may be used to communicate larger sizes of DL payload data. Then, it may not be required to communicate the multiple repetitions of the Layer 3 connection request message and the multiple repetitions of the Layer 3 connection response message interleaved in time domain.

Again, there are various options available of implementing the respective indicator: The number of Layer 3 connection request messages may be configured in the RA message 1 by including the indicator as explained above. In a further scenario, the respective indicator may be included in the first RA message 3. Further, each RA message 3 may provide the indicator indicating if a further RA message 3 including UL payload data will follow within the same RA procedure, i.e., an incremental indicator. For example, the indicator may be implemented as a dedicated information, i.e. bits in the RA message 1 carrying this information. Hence, the indicator may be implemented as an explicit indicator. In another scenario, the indicator may be implemented as an implicit indicator. For example, the indicator may be implemented by defining a set of preambles for various message sizes or defining a set of RACH resources for various message sizes. For example, preambles #1to #15may be used for normal size, #16to #31may be used for RA message 3 including one transmission with data, #32to #47may be used for RA message 3 including two transmissions with data, etc.

The method may further include communicating a RA response message of the RA procedure. The RA response message may include a scheduling grant for the UL payload data. The scheduling grant may depend on the indicator. For example, a size of the scheduled resources and/or a timing of the scheduled resources may be selected by the BS in accordance with the indicator. The RA response message may be implemented by the RA message 2.

The scheduling grant may be indicative of repetitively re-occurring resources for communicating multiple repetitions of a RA message 3. This may corresponds to semi-persistent scheduling.

Furthermore, the method may include selectively aborting the RA procedure in response to communicating the payload UL data and depending on the scheduling grant. Aborting the RA procedure may be communicated from the BS to the UE in the RA message 2 or in the RA message 4 of the RA procedure in 3GPP network environments. For example, if the scheduling grant allocates sufficient resources for completing communication of the UL payload data, then the RA procedure may be aborted; otherwise, a user plane transport bearer may be set up. Not having to set up the user plane transport bearer saves resources, e.g., in terms of energy consumption at the UE and in terms of control signaling overhead on wireless link.

Furthermore, the method may include communicating a first Layer 3 connection response message including a further indicator indicative of a count of at least one second Layer 3 connection response message, and communicating the at least one second Layer 3 connection response message in accordance with the further indicator. The first and second Layer 3 connection response messages may each be implemented by a RA message 4 of the RA procedure in a 3GPP LTE 4G framework or 3GPP New Radio (NR) 5G framework.

In each repetition of the connection response message, DL payload data may be included. Thereby, larger amounts of payload data may be communicated within the RA procedure in the DL direction also by increasing the count of the Layer 3 connection response message. By indicating in the first Layer 3 connection response message a count of at least one second Layer 3 connection response message, the amount of DL payload data communicated during the RA procedure may be flexibly varied and correspondingly configured.

Configuring the RA procedure depending on the indicator may include setting a size of an UL payload data field of a Layer 3 connection request message of the RA procedure depending on the indicator. For example, the Layer 3 connection request message may be implemented by the RA message 3 of the RA procedure in 3GPP networks. Depending on the indicator, a size information for the UL payload data field of the Layer 3 connection request message may be included in at least one of RA message 1 or RA message 3 of the RA procedure.

Configuring the RA procedure depending on the indicator may include setting a delay of a Layer 3 connection response message of the RA procedure with respect to a Layer 3 connection request message of the RA procedure depending on the indicator. The delay may not be smaller than 200 ms, or may be at least 1 second. The delay may have a value in the range of 200 ms to 5 seconds. The delay may be communicated between the BS and the UE in any message of the RA procedure and may be determined in the UE or in the BS or negotiated between the UE and the BS. Additionally or as an alternative, the delay may be preconfigured, provided at an initial attachment or registering of the UE at the BS, or by a dedicated signaling at e.g. RRC Connection Release or Suspend. The delay may specify the time delay in an absolute manner as a number of ms or seconds. Alternatively, the delay may be indicated as a counter of multiple radio frames, DRX intervals or other system specific units, which correspond to a time delay value.

In this regard, the indicator may be indicative of a type of the UL payload data. For example, the indicator could be indicative of a specific service/application associated with the UL payload data. Then, based on knowledge of typical higher-layer round-trip times (RTTs) for this type of UL payload data, the delay may be set appropriately. In other examples, the indicator may be directly indicative of the RTT or the delay. This may be based on respective historical data accumulated at the UE. This helps to facilitate transmission of DL payload data being a response to the UL payload data in the RA procedure.

For example, the Layer 3 connection response message may include a RTT indicator indicative of a RTT of communication between the BS and the destination of the UL payload data—e.g., a server in a data network such as the Internet and accessed by the network via a gateway node. The destination of the UL payload data may include for example a server or a network application. Based on the provided RTT, the UE and/or the BS may determine the delay for setting the delay in the RA procedure. Respective historical data may be accumulated.

The UL payload data may be included in a Layer 3 connection request message of the RA procedure, for example in RA message 3 of the RA procedure in 3GPP network environments. The method may further include communicating a Layer 3 connection response message including DL payload data from an application server to which the UL payload data is directed. For example, the Layer 3 connection response message may be implemented by a RA message 4 of the RA procedure in 3GPP network environments. The DL payload data may be a response to the UL payload data. The DL payload data may be triggered by the UL payload data. The application server may include any device to which the UL payload data is directed, for example any device which terminates UL data in a layer above the Layer 3.

A delay between the Layer 3 connection request message and the Layer 3 connection response message may be set in the RA procedure as described above. Therefore, the method enables data exchange between the UE and an application server during the RA procedure even before a user plane transmission bearer has been set up. For example, in response to communicating UL and/or DL payload data, the RA procedure may be aborted and the UE may transition to an idle mode. It is not required to fully set up the user plane transmission bearer. The data exchange provided within the RA procedure may be sufficient in MTC or IoT applications for notifying messages or measurement values such that a user plane communication may be avoided and communication resources as well as electrical energy may be saved.

The method may further include communicating a Layer 3 connection response message—e.g., implemented by the RA message 4—including a positive or negative acknowledgement of reception of the UL payload data. Thus, a reliable communication of the UL payload data between the UE and the BS may be accomplished.

A delay between the Layer 3 connection request message including the UL payload data and the Layer 3 connection response message including the acknowledgement may be smaller than 500 ms, optionally smaller than 50 ms, further optionally smaller than 10 ms. Thereby, an Automatic Repeat Request (ARQ) protocol may be implemented on Layer 2 or Layer 3.

A computer program product or a computer program includes program code that may be executed by a control circuitry of a device, for example a BS or a UE. Executing the program code may cause the control circuitry to perform a method, which includes communicating, between a UE and a BS, an UL control message of a RA procedure. The UL control message includes an indicator indicative of UL payload data queued for transmission during the RA procedure. The method includes furthermore configuring the RA procedure depending on the indicator, and communicating, in the RA procedure configured in accordance with the indicator, the UL payload data.

For example, a computer program product or a computer program may include program code that may be executed by a control circuitry of a UE, for example a user equipment like a mobile telephone or smart phone. Executing the program code may cause the control circuitry to perform a method, which includes transmitting, to a BS of a wireless network, an UL control message of a RA procedure, wherein the control message includes an indicator indicative of UL payload data queued for transmission during the RA procedure. The method includes furthermore configuring the RA procedure depending on the indicator, and transmitting, in the RA procedure configured in accordance with the indicator, the UL payload data.

In another example, a computer program product or a computer program may include program code that may be executed by a control circuitry of a BS, for example a BS of a wireless communication network. Executing the program code may cause the control circuitry to perform a method, which includes receiving, from a UE, an UL control message of a RA procedure, wherein the UL control message includes an indicator indicative of UL payload data queued for transmission during the RA procedure. The method includes additionally configuring the RA procedure depending on the indicator, and receiving, in the RA procedure configured in accordance with the indicator, the UL payload data.

A UE of a network, for example a wireless communication network, in particular a wireless cellular communication network, includes control circuitry configured to perform: transmitting, to a BS of the wireless network, an UL control message of a RA procedure, wherein the UL control message includes an indicator indicative of UL payload data queued for transmission during the RA procedure. The control circuitry is also configured to perform: configuring the RA procedure depending on the indicator, and transmitting, in the RA procedure configured in accordance with the indicator, the UL payload data.

The control circuitry of the UE is furthermore configured to perform the above-described method and the embodiments thereof.

A BS of a network, for example a wireless communication network or a wireless cellular communication network, includes control circuitry configured to perform: receiving, from a UE, an UL control message of a RA procedure, the UL control message including an indicator indicative of UL payload data queued for transmission during the RA procedure. The control circuitry is furthermore configured to perform: configuring the RA procedure depending on the indicator, and receiving, in the RA procedure configured in accordance with the indicator, the UL payload data.

The control circuitry of the BS is furthermore configured to perform the above described methods and the embodiments thereof.

It is to be understood that the features mentioned above and those yet to be explained below may be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the invention.

