Patent Description:
Example embodiments, although not limited to this, relate to V2X communications, and in more general to communications which may be carried out directly between UEs.

In particular in situations with fast moving UEs (such as in case of vehicles), the distance, i.e., the range between the UEs plays a factor. It is however difficult to correctly determine a relative range between a transmitting UE and a receiving UE with high precision.

Document <CIT>, discloses a distance based retransmission protocol.

This may lead to situations in which in a HARQ procedure acknowledgements (ACK) or negative acknowledgments (NACK) are not correctly sent.

These and other objects, features, details and advantages will become more fully apparent from the following detailed description of example embodiments of the present invention which is to be taken in conjunction with the appended drawings, in which:.

In the following, description will be made to example embodiments of the present invention. It is to be understood, however, that the description is given by way of example only, and that the described example embodiments are by no means to be understood as limiting the present invention thereto.

Before describing example embodiments in detail, the problem underlying the present application is described in some more detail.

As mentioned above, some example embodiments relate to V2X, i.e., vehicle to everything transmission. A direct transmission from one UE to another UE is also referred to as sidelink (SL). Currently, the WI for Rel16 V2X sidelink (SL) discussion includes QoS application and measurements application.

In respect to SL groupcast, and potentially broadcast, it is currently discussed whether/how there will be any form of HARQ procedures, with the agreement that it at least HARQ NACK will be supported in SL groupcast.

Another topic is whether/how to define and measure the QoS over SL groupcast or broadcast. When analysing QoS one of the measures may be the packet loss, for which statistics may be collected based on i.e. the HARQ feedback of the devices.

One of the issues is how to define which devices should respond with e.g. a HARQ NACK, and a proposal is to provide a range parameter between devices as to decide whether to e.g. respond with a NACK to a current data reception. If the device is within the range provide through e.g. the QoS parameter, but the receiving UE cannot decode, then a NACK should be sent. However, if the UE is not able to decode, but is outside the maximum communication range, then the NACK should not be sent. It is also still under discussion whether the maximum range is static by configuration, or dynamic by signaling. Several concepts have been suggested on how to calculate this range, each with different precision.

Relative range between the transmitting and receiving entity may be difficult to determine to a high precision, based on the methods used. If the range is calculated i.e. based on zones, the range parameter precision varies based on zone design, but in general will deviate more than i.e. a GPS based solution. However, using the GPS signal to determine a NACK, requires the device to have prior knowledge of the transmitters position and extrapolate the current position based on that, as the current data packet, and its location content, could not be decoded. This means that in SL group and broadcast scenarios, it is not trivial for the receiving, or transmitting UE to determine whether data packets are eligible for retransmission given the range. This may either lead to increased load on the network, as the receiving UE may send a NACK without being in the range, or a wrong QoS measurement due to a too high packet error rate.

Example embodiments aim to solve this problem.

In the following, a general overview of some example embodiments is described by referring to <FIG>.

<FIG> shows a first user equipment (UE) <NUM> as an example for a first apparatus according to the present example embodiment. The apparatus may be a first radio device such as the UE <NUM>, or may be a part thereof. A procedure carried out by the UE <NUM> is illustrated in <FIG>.

The UE <NUM> comprises at least one processor <NUM> and at least one memory <NUM> including computer program code. The at least one processor <NUM>, with the at least one memory <NUM> and the computer program code, is configured to cause the apparatus to perform: transmitting data to at least one second radio device (e.g., UE <NUM> shown in <FIG>), wherein transmission of the data is controlled by (according to) an automatic retransmission procedure (as shown in S31 of <FIG>), receiving a response from the at least one second radio device, the response indicating the result of an attempt to decode the data and including range estimation information of the second radio device (as shown in S32 of <FIG>), and deciding on retransmitting the data based on the response and on the range estimation information of the second radio device (as shown in S33 of <FIG>).

<FIG> shows a second user equipment (UE) <NUM> as an example for a second apparatus according to the present example embodiment. The apparatus may be second radio device such as the UE, or may be a part thereof. A procedure carried out by the UE <NUM> is illustrated in <FIG>.

The UE <NUM> comprises at least one processor <NUM> and at least one memory <NUM> including computer program code. The at least one processor <NUM>, with the at least one memory <NUM> and the computer program code, is configured to cause the apparatus to perform: receiving data from a first radio device (e.g., UE <NUM> shown in <FIG>), wherein transmission of the data is controlled by (according to) an automatic retransmission procedure (as shown in S41 of <FIG>), attempting to decode the received data (as shown in S42 of <FIG>), providing range estimation information concerning a range between the first radio device and the second radio device (as shown in S43 of <FIG>), and transmitting a response to the first radio device indicating the result of the attempt to decode the received data based on the estimated range between the first radio device and the second radio device, the response including the range estimation information (as shown in S44 of <FIG>).

The UE <NUM> may further comprise an I/O unit <NUM>, which is capable of transmitting to and receiving from other radio devices such as the UE <NUM>, and, likewise, the UE <NUM> may further comprise an I/O unit <NUM>, which is cable of transmitting to and receiving from other radio devices such as the UE <NUM>, for example.

Thus, according to example embodiments, a second radio device (a receiving UE, e.g., UE2 shown in <FIG>) checks, upon receiving a message from a first radio device (a transmitting UE, e.g., UE <NUM> shown in <FIG>), which it is unable to decode, the precision (reliability) of a range estimation (e.g. a range parameter described later) and the range itself (i.e., whether the UE2 is close to a maximum range or far way therefrom), and indicates a result of this check in a response (e.g., a soft NACK) to the transmitting UE (UE1), which then decides whether and how to transmit or retransmit based on this result.

In the automatic retransmission procedure described above the response may be an acknowledgement (e.g., ACK) in case of a successful attempt to decode the data, and the response may be a non-acknowledgement (NACK) in case of a non-successful attempt to decode the received data. In this way, the response can indicate the result of the attempt to decode the data. Moreover, upon deciding on retransmitting the data, the UE <NUM> may retransmit the data, based on the decision on retransmitting the data, in case a non-acknowledgement (NACK) is received, or stop retransmitting the data in case an acknowledgement (ACK) is received or in case neither an acknowledgement (ACK) nor a non-acknowledgement (NACK) is received.

For the decision as to whether the data (the data to be transmitted from the first radio device (transmitting UE <NUM>) to the second radio device (receiving UE <NUM>) controlled by the automatic retransmission procedure) should be retransmitted or not, an estimated precision of a range estimation included in the range estimation information may be used.

The automatic retransmission procedure described above, by which the transmission of the data from the first radio device to the second radio device is controlled, may be a HARQ procedure, for example.

In the following, some example embodiments are described in more detail.

According to some example embodiments, a soft-HARQ response for at least SL group and broadcast is provided which will help control the number of retransmissions. This may also enable a more reliable measure of QoS. The soft-HARQ will indicate the receiving UEs perceived eligibility to request a retransmission, based on i.e. the range.

The eligibility to request a retransmission of the receiving UE is in the following also referred to as NACK eligibility. A low eligibility NACK indicates that the UE perceives or considers that the eligibility to request a retransmission is low (for example due to a low precision of the range parameter, as described in the following), whereas low a high eligibility NACK indicates that the UE perceives or considers that the eligibility to request a retransmission is high (for example due to a high precision of the range parameter or since the distance or the range to the transmitting UE is short). The eligibility can be represented in different levels, which may be indicated by eligibility figures. For example, in case there only two levels, these can be indicated as a high or low eligibility NACK, as will be described in the following. When there are three levels, these could be indicated as high, middle or low eligibility NACK. Otherwise, they could also be indicated by eligibility figures (numbers). Thus, the eligibility indicates a confidence of the receiving UE concerning its range.

The soft HARQ can be L1 based, using i.e. extended orthogonal HARQ sequence feedbacks, mapped to different NACK eligibility.

Alternatively, the soft HARQ can be MAC based, by extending the HARQ procedure through RRC, using the HARQ ID as a reference. The below description assumes a HARQ NACK response only, but the concept could also be applied to HARQ ACK.

According to some example embodiments, when a transmitting UE transmits data, which should be received by peer UEs within a certain range, the receiving UE will reply with a soft-NACK, reflecting the devices perceived reliability of the range estimate that triggered the NACK. The soft-HARQ response may then be used by the network, or device, to decide whether to i.e. retransmit the data packet, or even calculate a weighted mean of the experienced packet error, as exemplified in the following.

In the following, some use cases with the soft-NACK are described.

In general, the triggering procedure would be:
At first, a transmitting UE (which is referred to as UE1 in the following) sends a group (or broadcast) message.

A receiving UE (which is referred to as UE2 in the following) UE2 receives the data packet but is unable to decode.

Then, the UE2 checks the range requirement for the data packet, i.e. through the QoS, PFI, QFI, or other measures, for the given bearer, and compares to the internal range estimation between the transmitting UE1 and the receiving UE2.

Hereafter, the following novel procedures could be followed:
First, a first example with a low eligibility NACK is described.

In this first example, it is assumed that the UE2 estimates that the range parameter is of low precision and/or that it is close to the maximum range. In this case, the UE2 sends a soft-NACK with a value indicating that the NACK might be wrong (low eligibility NACK).

The UE1 receives this soft-NACK. Based therein, the UE1 either:.

Next, a second example with a high eligibility NACK is described.

In this second example, it is assumed that UE2 estimates that the range parameter is of low precision and indicates that the maximum range is well exceeded (i.e., that the range between UE1 and UE2 is larger than the maximum range). In this case, the UE2 sends a soft-NACK with a value indicating that the NACK is of high precision.

The UE1 does not retransmit the data packet due to received NACK.

Next, a third example with a high eligibility NACK is described.

In this third example, it is assumed that the UE2 estimates that the range parameter is of low precision but that it does not exceed the maximum range. In this case, the UE2 sends a soft-NACK with a value indicating that the NACK is most likely correct.

The UE1 retransmits the data packet due to received NACK status, as the uncertainty does not justify a high enough probability for the UE2 to be out of range.

Next a fourth example with a high eligibility NACK is described.

In this fourth example, it is assumed that the UE2 estimates that the range parameter is of high precision but that it is close to the maximum range. In this case, the UE2 sends a soft-NACK with a value indicating that the NACK is most likely correct.

The UE1 retransmits the data packet due to received NACK status.

Additionally in all cases, the UE1 may use the eligibility figure (e.g., whether it is a high eligibility NACK or a low eligibility NACK) to estimate the packet error rate. If the eligibility is low, the weighting of the NACK should be lower than if it were high, when calculating e.g. QoS parameters such as packet error ratio.

Thus, according to example embodiments, an increased reliability is achieved, as the transmitting UE may now have an indication of the range at which the receiving UE is at.

Moreover, a decreased network load is achieved as the transmitting UE does not need to retransmit packets with low QoS and a low eligibility of the NACK.

Furthermore, an increased precision of QoS parameter calculations such as packet error ratio is achieved, as the transmitting UE may now know whether/how the NACK should be incorporated in the calculation.

For example, the range parameter as described above can be determined in different ways. For example, the UE may have an indication of the vehicles around it. For example, all vehicles in proximity will have broadcasted the position, speed, direction, and other factors, at a point in time, wherein the receiving vehicle then is able to map them all approximately. It is noted that, as it is assumed the message to be NACK'ed is not able to be decoded, the range estimate may come from this exact message based on i.e. RSRP measurements, or other low layer signal measurements (potentially, it may also be by using the synchronisation bursts). Otherwise, the range estimation may come from prior decodable messages from the transmitting vehicle, such that the receiving vehicle has been able to track it.

The range requirement described above may assume comes from at least the given QoS requirement which is determined for the given logical channel. This may be indicated in i.e. the 5QI, PQI, or whatever QoS profile is chosen to be denoted as the applied one.

The above-described example embodiments are only examples and may be modified.

In some of the example embodiments, the UEs are provided in vehicles. However, the embodiments are not limited to vehicles, and the UE may be any kind of terminal devices.

Furthermore, in some of the example embodiments, a direct transmission between UEs is described. However, the embodiments are not limited to this, and the transmitting UE may be any kind of base station (gNB, eNB), for example.

Moreover, according to some example embodiments, an estimation of the range is included in the NACK. However, the estimation of the range may also be included into the ACK. In this way, the estimation of the range may be used for sending different data in another message to the corresponding UE.

The decision for providing different NACK eligibilities (eligibility figures or levels) may also be based on other factors like the QoS, speed, and other factors. For example, the low eligibility NACK could also be an indication of a way forward for the transmitter.

There are several potential ways of implementing a decision at the transmitting UE (Tx UE) using various criteria:
If one, or more, high eligibility NACKs are received by the transmitting UE, the transmitting UE may retransmit.

Else if one, or more medium eligibility NACKs are received, and the QoS states a high reliability, the transmitting UE may retransmit.

Else if one, or more, low eligibility NACKs are received, and the network load is lower than a certain threshold, and QoS states a low reliability, then, if the transmitting UE perceives the message content to change within a timeframe at which the vehicle sent the low eligibility NACK vehicle will most likely not need the information right now, the transmitting UE may omit a retransmission. Else, the transmitting UE may retransmit.

Several potential implementation specific criteria for the transmitting UE may be defined, whereas some may be informed to the receiving UE(s) beforehand, as for them to be able to calculate the eligibility.

Names of network elements, protocols, and methods are based on current standards. In other versions or other technologies, the names of these network elements and/or protocols and/or methods may be different, as long as they provide a corresponding functionality.

In general, the example embodiments may be implemented by computer software stored in the memory (memory resources, memory circuitry) <NUM>, <NUM> and executable by the processor (processing resources, processing circuitry) <NUM>, <NUM> or by hardware, or by a combination of software and/or firmware and hardware.

As used in this application, the term "circuitry" refers to all of the following:.

The terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as non-limiting examples.

The memory (memory resources, memory circuitry) <NUM>, <NUM> may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, and non-transitory computer-readable media. The processor (processing resources, processing circuitry) <NUM>, <NUM> may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi core processor architecture, as non-limiting examples.

Claim 1:
An apparatus, for a first radio device (UE1), comprising:
at least one processor (<NUM>) and at least one memory (<NUM>) including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:
transmitting data to at least one second radio device (UE2), wherein transmission of the data is controlled by an automatic retransmission procedure,
receiving a response from the at least one second radio device (UE2), the response indicating the result of an attempt to decode the data and including range estimation information of the second radio device (UE2), the range estimation information comprising a range estimation indicating an estimated range between the first radio device (UE1) and the second radio device (UE2) and/or an estimated precision of the range estimation, wherein the response is an acknowledgement in case of a successful attempt to decode the data, and the response is a non-acknowledgement in case of a non-successful attempt to decode the received data, and
deciding on retransmitting the data based on the response and on the range estimation information of the second radio device (UE2) by
deciding to retransmit the data in case the estimated precision of the range estimation is higher than a certain precision threshold, and
deciding to not retransmit the data in case the estimated precision of the range estimation is lower than the precision threshold.