Patent Description:
Mobile communication by means of cellular networks is an integral part of modem life. Examples of cellular networks include the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE; sometimes also referred to as <NUM>) and 3GPP New Radio (NR; sometimes also referred to as <NUM>) technology. Here, multiple nodes are connected to form the network. The network may comprise a plurality of cells.

Such communication systems can be combined with communication on an open spectrum including unlicensed bands. For example, see <NPL>) and <NPL>).

A particular use case for communication on unlicensed bands relates to Internet of Things (IoT) solutions. For communication on unlicensed bands, the transmission resources are shared among multiple networks, operators, or, generally, any node that wants to access the unlicensed band. Typically, this involves listen before talk (LBT) techniques to ensure that resources for transmission are available on the unlicensed band. Alternatively or additionally to LBT techniques, back-off techniques can be applied. According to back-off techniques, a transmission attempt resulting in a collision with one or more further nodes attempting to transmit on the unlicensed band can result in a further retransmission attempt, e.g., after a random timeout time duration.

A set of features where a comparably large coverage is achieved is referred to as Coverage Enhancement (CE). CE technology is envisioned to be applied for Machine Type Communication (MTC) and the Narrowband loT (NB-IOT), sometimes also referred to as NB-LTE. For example, such techniques may be based on the 3GPP LTE technology to some extent and may reuse some of the LTE concepts.

A key feature of the CE is to implement multiple transmission repetitions of encoded data. Here, each repetition may include the same redundancy version of the encoded data. The repetitions may be "blind", i.e., may not in response to a respective retransmission request that may be defined with respect to a Hybrid Acknowledgement Repeat Request protocol (HARQ protocol). Rather, repetitions according to CE may be preemptive. Examples are provided by the 3GPP Technical Report (TR) <NUM> version <NUM>. <NUM> (<NUM>- <NUM>), section <NUM>. By employing CE, a likelihood of successful transmission can be increased even in scenarios of poor conditions of communicating on a corresponding wireless link. Thereby, the coverage of networks can be significantly enhanced - even for no transmission powers as envisioned for the MTC and MB-IOT domain.

However, techniques of CE may face certain restrictions and drawbacks in combination with transmission on an unlicensed band. In particular, the count of repetitions according to the CE may be larger than <NUM>, sometimes larger than <NUM>, sometimes even larger than <NUM>. Then, a combination of CE implementing large counts of repetitions and a highly utilized unlicensed band can result in a significantly increased likelihood of collisions. This may be due to the increased transmission time required for the large count of repetitions according to the CE. Transmission collisions result typically in back-off and, consequently, further retransmissions. This can increase the latency and may result in increased energy consumption for the transmitting node.

Some related prior art is provided below:
<CIT> discloses a receiving node that makes an early estimate of the outcome of a decoding attempt and sends a corresponding early feedback to the sending node. This has an effect of enabling a fast retransmission of the data by the sending node in case the decoding by the receiving node is likely to fail. An advantage of this is that any delays due to data retransmission may be minimized, resulting in a higher average throughput of the data transmission between the nodes.

<CIT> anticipates systems and methods relating to preemptive retransmission of a transport block in successive subframes on, e.g., a Listen-Before-Talk cell. Implementations of a method of operation of a radio node of a cellular communications network are also disclosed. The radio node serves an Listen-Before-Talk cell. In some implementations, the method of operation of the radio node comprises transmitting a transport block in a first subframe on the Listen-Before-Talk cell and retransmitting the transport block in a second subframe (e.g., on the Listen-Before-Talk cell), where the second subframe is adjacent, in time, to the first subframe. In implementations in which the retransmission of the transport block is on the Listen-Before-Talk cell (or another Listen-Before-Talk cell), the time span of a transmission burst can be extended to a maximum allowed burst duration.

Therefore, a need exists for advanced techniques of transmission of data. In particular, a need exists for advanced techniques of transmission of data employing CE.

A method according to claim <NUM> is provided.

Hereinafter, techniques of transmitting and/or receiving (communicating) encoded data between a first node in the second node of a network are disclosed.

For example, the data may correspond to payload data of applications implemented by the first node and/or the second node. Alternatively or additionally, the data may correspond to control data, e.g., Layer <NUM> or Layer <NUM> control data according to the Open Systems Interface (OSI) model.

According to various examples, the data may be uplink (UL) data or downlink (DL) data. For example, the data may be UL data transmitted from a mobile device (user equipment; UE) implementing the first node to a base station (BS) implementing the second node of a network. It would also be possible that the data is DL data transmitted from the base station to the UE. In other examples, device-to-device (D2D) communication on a sidelink of the wireless link of the network between two UEs could be employed.

According to examples, the encoded data is redundantly communicated using a plurality of repetitions. Hence, the same encoded version of the data may be redundantly communicated a number of times according to various examples. Each repetition of the plurality of repetitions can include the data encoded according to the same redundancy version, e.g., redundancy version <NUM> or redundancy version <NUM>, etc.. Then, it is possible to combine the plurality of repetitions of the encoded data. Such combination may be implemented in in analog domain, e.g., in the baseband. The combination yields a combined signal. Then, the decoding of the encoded data can be based on the combined signal. Thus, by aggregating the received information across the multiple repetitions, the probability of successfully decoding of the encoded data increases. This facilitates CE. Such techniques of CE may find particular application in the framework of the loT technology, e.g., according to 3GPP MTC or NB-IOT. Here, typically, the transmitting UE implements a comparably low transmit power. Due to the multiple repetitions of the encoded data, nonetheless, a sufficiently high likelihood of successfully receiving and decoding the encoded data is provided for.

According to various examples, a first plurality of repetitions of encoded data and a second plurality of repetitions of the encoded data are subsequently communicated, e.g., offset by a time gap. Again, all repetitions of the first plurality of repetitions, as well as all repetitions of the second plurality of repetitions may include the data encoded according to the same redundancy version such that combination of the first plurality of repetitions and the second plurality of repetitions of the encoded data to yield the combined signal is facilitated. In-between communication of the first plurality of repetitions and the second plurality of repetitions, an acknowledgement signal can be communicated in a direction opposing the direction of communication of the encoded data. For sake of simplicity, this acknowledgement signal is, hereinafter, referred to as fast acknowledgement (FastACK).

By means of the FastACK, the following effect can be achieved. Prior to completing the full set of retransmissions of the encoded data - i.e., prior to completing transmission of, both, the first plurality of repetitions of the encoded data, as well as the second plurality of the encoded data - the likelihood of successful completion of the transmission of the data, e.g., including the likelihood of successfully decoding the encoded data, is implicitly or explicitly indicated by means of the FastACK. Such indication is even possible prior to commencing decoding of the encoded data, e.g., based on secondary indicators such as a receive signal level of the corresponding signals including the multiple repetitions of the encoded data and/or a comparison between one or more reference symbols included in the corresponding signals and predefined symbols at the receiver. Thereby, in other words, it is possible to predict the likelihood with which the transmission of the encoded data will be successfully completed, i.e., the likelihood with which decoding yields the uncorrupted data. For example, if the likelihood with which the transmission of the encoded data will be successfully completed is comparably low, the transmitting node decides to abort transmission of the repetitions of the encoded data, i.e., abort transmitting the second plurality of repetitions of the encoded data. Rather, the transmitting node decides to implement a back-off.

The various techniques described herein may find particular application for transmission on unlicensed bands. An unlicensed band may reside in an open spectrum. Multiple operators or networks may share access to the open spectrum. In other words, access to the open spectrum may not be restricted to a single operator or network. Typically, the communication on the open spectrum may involve LBT procedures and/or back-off procedures. Such techniques are sometimes also referred to as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). In particular, in the context of the open spectrum, the FastACK may be helpful to implement early identification of collision between multiple nodes attempting to access the spectrum. In particular, such collision may be detected prior to completion of the full set of retransmissions of the encoded data, i.e., prior to completing, both, transmission of the first plurality of repetitions of the encoded data, as well as the second plurality of repetitions of the encoded data. Then, a back-off can commence comparably early. This reduces the overall latency required for transmission of the encoded data, as well as the energy consumption of the transmitting node.

<FIG> illustrates the architecture of a cellular network <NUM> according to some examples implementations. In particular, the cellular network <NUM> according to the example of <FIG> implements the 3GPP LTE architecture, sometimes referred to as evolved packet system (EPS). This, however, is for exemplary purposes only. In particular, various scenarios will be explained in the context of a wireless link <NUM> between a UE <NUM> and the cellular network <NUM> operating according to the 3GPP LTE radio access technology (RAT) for illustrative purposes only. Similar techniques can be readily applied to various kinds of 3GPP-specified RATs, such as Global Systems for Mobile Communications (GSM), Wideband Code Division Multiplex (WCDMA), General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), Universal Mobile Telecommunications System (UMTS), and High Speed Packet Access (HSPA), and corresponding architectures of associated cellular networks.

A further particular example is the 3GPP NB-loT RAT. The 3GPP NB-loT RAT may be based on the 3GPP LTE RAT, i.e., the Evolved UMTS Terrestrial Radio Access (E-UTRA). Further, the NB-loT RAT may be combined with the EPS as illustrated in <FIG>. The various examples disclosed herein may be readily implemented for the 3GPP NB-loT RAT, alternatively or additionally.

Other examples include other types of networks, e.g., Institute of Electrical and Electronics Engineers (IEEE) <NUM>. 11X Wireless Local Area Network, Bluetooth or Zigbee.

The 3GPP LTE RAT implements a HARQ protocol. The HARQ protects data communicated via the wireless link <NUM>. FEC and retransmission are employed in this respect.

The UE <NUM> is connected via the wireless link <NUM> to a BS <NUM> of the cellular network <NUM>. The BS <NUM> and the UE <NUM> implement the evolved UMTS terrestrial radio access technology (E-UTRAN); therefore, the BS <NUM> is labeled evolved node B (eNB) in <FIG>.

For example, the UE <NUM> may be selected from the group including: a smartphone; a cellular phone; a table; a notebook; a computer; a smart TV; a MTC device, an loT device; etc..

An MTC or loT device is typically a device with a low to moderate requirement on data traffic volumes and loose latency requirements. Additionally, communication employing MTC or IoT devices should achieve low complexity and low costs. Further, energy consumption of an MTC or an loT device should be comparably low in order to allow battery-powered devices to function for a comparably long duration: The battery life should be sufficiently long. For example, the loT device may be connected to the EPS via the NB-loT RAT.

Communication on the wireless link <NUM> can be in UL and / or DL direction. Details of the wireless link <NUM> are illustrated in <FIG>.

<FIG> illustrates aspects with respect to channels implemented on the wireless link. The wireless link <NUM> implements a plurality of communication channels <NUM>-<NUM>. Transmission frames <NUM> - e.g., implemented by subframes - of the channels <NUM>-<NUM> occupy a certain time duration. Each channel <NUM> - <NUM> includes a plurality of resources which are defined in time domain and frequency domain. For example, the resources may be defined with respect to symbols encoded and modulated according to Orthogonal Frequency Division Multiplexing (OFDM).

For example, a first channel <NUM> may carry synchronization signals which enable the BS <NUM> and the UE <NUM> to synchronize communication on the wireless link <NUM> in time domain.

A second channel <NUM> may be associated with control messages (control channel <NUM>). The control messages may configure operation of the UE <NUM>, the BS <NUM>, and/or the wireless link <NUM>. For example, radio resource control (RRC) messages and / or HARQ ACKs and NACKs can be exchanged via the control channel. According to the E-UTRAN RAT, the control channel <NUM> may thus correspond to a Physical DL Control Channel (PDCCH) and / or a Physical UL Control Channel (PUCCH) and / or a Physical Hybrid ARQ indicator Channel (PHICH).

Further, a third channel <NUM> is associated with a payload messages carrying higherlayer user-plane data packets associated with a given service implemented by the UE <NUM> and the BS <NUM> (payload channel <NUM>). According to the E-UTRAN RAT, the payload channel <NUM> may be a Physical DL Shared Channel (PDSCH) or a Physical UL Shared Channel (PUSCH).

In some examples, it is possible that at least some of the resources reside - at least partly or fully - in an open spectrum. Then, it is possible that the UE <NUM> and/or the BS <NUM> performs a LBT procedure and/or a back-off procedure when transmitting data on the respective channels <NUM> - <NUM>.

Turning again to <FIG>, the BS <NUM> is connected with a gateway node implemented by a serving Gateway (SGW) <NUM>. The SGW <NUM> may route and forward payload data and may act as a mobility anchor during handovers of the UE <NUM>.

The SGW <NUM> is connected with a gateway node implemented by a packet data network Gateway (PGW) <NUM>. The PGW <NUM> serves as a point of exit and point of entry of the cellular network <NUM> for data towards a packet data network (PDN; not shown in <FIG>): for this purpose, the PGW <NUM> is connected with an access point node <NUM> of the packet data network. The access point node <NUM> is uniquely identified by an access point name (APN). The APN is used by the UE <NUM> to seek access to the packet data network.

The PGW <NUM> can be an endpoint of an end-to-end connection <NUM> for packetized payload data of the UE <NUM>. The end-to-end connection <NUM> may be used for communicating data of a particular service. Different services may use different end-to-end connections <NUM> or may share, at least partly, a certain end-to-end connection.

The end-to-end connection <NUM> may be implemented by one or more bearers which are used to communicate service-specific data. An EPS bearer which is characterized by a certain set of quality of service parameters indicated by the QoS class identifier (QCI).

<FIG> illustrates aspects with respect to CE. In particular, <FIG> illustrates aspects with respect to a burst <NUM> including multiple repetitions <NUM> of data encoded according to a redundancy version <NUM>. As can be seen from <FIG>, the plurality of repetitions <NUM> are communicated in subsequent subframes <NUM> of the channel <NUM>. The transmission burst <NUM> of the repetitions <NUM> has a certain duration <NUM>.

While in the scenario of <FIG> the transmission burst <NUM> includes subsequent repetitions <NUM> of the encoded data in subsequent subframes <NUM>, in other examples, it is also possible that subsequent repetitions are not arranged contiguously with respect to the subframes <NUM>, i.e., there may be intermittent subframes not occupied by a repetition of the encoded data of the transmission burst (not shown in <FIG>). In other examples it would be possible that subsequent repetitions <NUM> are arranged within a single subframe <NUM> (not shown in <FIG>).

The specific time-frequency arrangement of the repetitions <NUM> is illustrated in the example of <FIG> is an example only. Other examples are possible.

While in the scenario of <FIG> encoded data is communicated on the payload channel <NUM>, similar techniques may be readily applied to other kinds and type of data, e.g., control data.

<FIG> illustrates aspects of encoding data <NUM>-<NUM> according to different redundancy versions <NUM> - <NUM>. As can be seen from <FIG>, the raw data <NUM> includes a sequence of bits. For example, the data <NUM> can be a data packet, e.g., a MAC layer Service Data Unit (SDU). It would also be possible that the data <NUM> corresponds to a RRC command or other control data such as a ACK, NACK, UL grant, or DL assignment.

Encoding the data <NUM> can correspond to adding a checksum <NUM> to the data <NUM> to yield the encoded data <NUM>-<NUM>.

Different techniques of encoding can be employed such as, e.g., Reed Solomon encoding, turbo convolutional encoding, convolutional coding, etc. Provisioning the checksum <NUM> can facilitate reconstruction of corrupted bits of the corresponding message <NUM> - <NUM> according to the coding scheme. Typically, the longer (shorter) the checksum <NUM>, the more (less) robust the communication of the corresponding message <NUM> - <NUM> against noise and channel imperfections; thus, a probability for successful transmission of the data <NUM> can be tailored by the length of the checksum. Alternatively or additionally, encoding the data can correspond to applying interleaving where the bits of the data <NUM> are shuffled (not shown in <FIG>).

Typically, different redundancy versions <NUM> - <NUM> correspond to checksums <NUM> of different length (as illustrated in <FIG>). In other examples, it would also be possible that different redundancy version <NUM> - <NUM> employ checksums <NUM> of the same length, but encoded according to the different coding scheme. Alternatively or additionally, different redundancy versions may employ different interleaving schemes. Alternatively or additionally, different redundancy versions may employ different puncturing schemes.

Hereinafter, an example implementation of constructing different redundancy versions is given.

STEP <NUM> of constructing different redundancy versions: A block of information bits, i.e., the raw data <NUM> to be transmitted, is encoded. Here, additional redundancy bits are generated, i.e., in addition to the data <NUM>. Let N denote the number of information bits; then - e.g., for E-UTRA RAT - the total number of the encoded bits (i.e., the sum of information bits and redundancy bits) may amount to 3N. A decoder that receives all 3N bits typically is able to decode the information bits, even if a large number of bit errors is present in the received bits due to a high BER.

STEP <NUM> of constructing different redundancy versions: Thus, in order to avoid excessive overhead of transmission, only a fraction of the redundancy bits is selected. The information bits and the selected redundancy bits form the first redundancy version <NUM>. The amount of encoded bits according to the first redundancy version is <NUM> therefore, using the above example, somewhere between N and 3N. The process of removing redundancy bits by selecting the fraction is sometimes referred to as puncturing. This first redundancy version <NUM> may then be sent to the receiver.

STEP <NUM> of constructing different redundancy versions: In case a retransmission is required according to the HARQ protocol, a new redundancy version <NUM>, <NUM> is sent. The higher order redundancy version <NUM>, <NUM> includes additional redundancy bits from the ones that were previously punctured in step <NUM>, and typically the same information bits again. In this way, after a couple of repetitions the whole 3N bits have been sent at least once.

According to examples, each transmission burst <NUM> includes a plurality of repetitions <NUM> of the encoded data <NUM>-<NUM> being encoded according to the same redundancy version <NUM> - <NUM>.

<FIG> illustrates aspects of the HARQ protocol implemented by the MAC layer (generally, Layer <NUM>) of the transmission protocol stack of the UE <NUM> and the BS <NUM>, respectively. The HARQ protocol according to the example of <FIG> employs transmission bursts <NUM> including multiple repetitions <NUM> of encoded data <NUM>-<NUM>. For example, <FIG> may relate to a scenario of transmission on an open spectrum shared between multiple networks. Central scheduling between the multiple networks may not be available such that collisions may occur. LBT and back-off procedures may be employed when transmitting.

At <NUM>, the raw data <NUM> is received, e.g., from a higher layer at the transmit buffer implemented by the UE <NUM>. The data <NUM> is encoded to yield the encoded data <NUM>-<NUM>.

Then, a signal <NUM> including multiple repetitions <NUM> of the data <NUM> are transmitted by the UE <NUM> to the BS <NUM>. This defines a transmission burst <NUM> according to CE. All repetitions <NUM> of the data <NUM> are encoded according to the redundancy version <NUM>.

Generally, when operating with CE in an open spectrum, there may be different aspects limiting the amount of repetitions <NUM> of the encoded data <NUM>. For example, the UE <NUM> may operate in half duplex and may therefore require a so-called measurement gap during which the UE switches from transmission mode to reception mode in order to listen for the synchronization channel to maintain its timing synchronization with the network. Furthermore, when operating in an open spectrum, there will also be typically a maximum channel occupancy time restriction which limits the time that a single node may use the resources on the open spectrum after a successful LBT. The UE <NUM> may use a CE level defining a number of repetitions of the encoded data <NUM> that can fit into the maximum channel occupancy time for the open spectrum. The number of repetitions <NUM> expected at <NUM> can, therefore, be defined with respect to a CE level. Typically, a count of repetitions <NUM> is in the range of <NUM> - <NUM>.

Once communication of the signal <NUM> including the multiple repetitions <NUM> of the data <NUM> encoded according to the redundancy version <NUM> has ended, i.e., at the end of the transmission burst <NUM>, the BS <NUM> attempts to decode the encoded data <NUM>, <NUM>. Decoding at <NUM> is based on a combination of the multiple repetitions <NUM> of the data <NUM> encoded according to the redundancy version <NUM>. This helps to increase the probability of successfully decoding the data <NUM>. In the example of <FIG>, decoding fails at <NUM> and, consequently, the BS <NUM> sends a negative acknowledgement message <NUM> to the UE <NUM> at <NUM>.

The UE <NUM> receives the negative acknowledgement message <NUM> and transmits a signal <NUM> including multiple repetitions <NUM> of the data <NUM> now encoded according to the redundancy version <NUM> in the respective transmission burst <NUM>.

Then, at <NUM>, decoding - which is based on a combination of the multiple repetitions <NUM> of the signal <NUM> - again fails and the BS <NUM>, at <NUM>, transmits another negative acknowledgement message <NUM>.

The negative acknowledgement message <NUM> is received by the UE <NUM> which, in response to reception of the negative acknowledgement message <NUM>, transmits a signal <NUM> including multiple repetitions <NUM> of the data <NUM> encoded according to the redundancy version <NUM>.

Then, at <NUM>, decoding - which is based on the combination of the multiple repetitions <NUM> of the data <NUM> included in the signal <NUM> - is successful and, consequently, the BS <NUM> transmits a positive acknowledgement message <NUM> at <NUM> to the UE <NUM>. Then, the decoded data <NUM> can be passed to higher layers at <NUM>, e.g., from a receive buffer of the BS <NUM>.

<FIG> is an example of communication of the data <NUM> in UL direction. Similar techniques may be readily applied for communication and DL direction.

<FIG> illustrates aspects of transmission of a FastACK <NUM> during a transmission burst <NUM> including multiple repetitions <NUM> of data <NUM> encoded according to the same redundancy version, i.e., in the example of <FIG>, the redundancy version <NUM>. For example, <FIG> may relate to a scenario of transmission on an open spectrum shared between multiple networks. Central scheduling between the multiple networks may not be available such that collisions may occur. LBT and back-off procedures may be employed when transmitting.

A <NUM> corresponds to <NUM> (cf.

Then, a signal <NUM> including multiple repetitions <NUM> of the data <NUM> encoded according to the redundancy version <NUM> is transmitted. This corresponds to a part of the retransmission burst <NUM>. However, in the scenario of <FIG>, the retransmission burst <NUM> is not completed upon completion of transmission of the signal <NUM>.

In response to receiving a signal <NUM>, the BS <NUM> transmits a FastACK <NUM> to the UE <NUM>, <NUM>. After transmitting the FastACK <NUM>, the BS <NUM> then receives, from the UE <NUM>, a second signal <NUM> including a second plurality of repetitions <NUM> of the data <NUM> encoded according to the redundancy version <NUM>. Both signals <NUM> and <NUM> include the data <NUM> encoded according to the redundancy version <NUM>; thus, both signals <NUM>, <NUM> contribute to the burst <NUM>.

For example, the time gap <NUM> between transmission of the signal <NUM> and transmission of the signal <NUM> may be less than ten subframes <NUM>, optionally less than four subframes <NUM>, further optionally less than three subframes <NUM>. A short time gap <NUM> facilitates low latencies for transmission of the data <NUM>. The short time gap <NUM> may be enabled by the low-layer implementation of the FastACK <NUM> which may be, e.g., native to the physical Layer <NUM>.

Then, at <NUM>, the BS <NUM> attempts to decode the data <NUM> encoded according to the redundancy version <NUM> based on a combination of the repetitions <NUM> of the data <NUM> transmitted at <NUM> and the repetitions <NUM> of the data <NUM> transmitted at <NUM>. In the example of <FIG>, decoding at <NUM> fails and, therefore, the BS <NUM> - in response to decoding at <NUM> - transmits a negative acknowledgement message <NUM>, <NUM>. Generally, the acknowledgement message <NUM> may be indicative of a decoding result of the decoding. The acknowledgement message <NUM> may be a negative or positive ACK of the HARQ. Thus, the acknowledgement message <NUM> may be native to Layer <NUM> or Layer <NUM> of the transmission protocol stack.

The FastACK <NUM> may be indicative of the likelihood of successfully decoding at <NUM>. Because the FastACK <NUM> is transmitted prior to executing said decoding at <NUM>, the FastACK <NUM> may be indicative of a prospective likelihood of successfully decoding at <NUM>. In particular, as is apparent from <FIG>, decoding of the repetitions <NUM> of the data <NUM> encoded according to the redundancy version <NUM> does not commence prior to transmitting the FastACK <NUM>.

Various examples are conceivable to determine the likelihood of successfully decoding at <NUM>. In the example of <FIG>, a reception check is implemented at <NUM>. The reception check at <NUM> serves as a trigger criterion for transmitting the FastACK <NUM> at <NUM>. In the various examples described herein, different trigger criteria for transmitting the FastACK <NUM> are conceivable.

For example, it would be possible to perform, at <NUM>, a symbol comparison between at least one repetition of at least one reference symbol included in the signal <NUM>. The at least one reference symbol may be predefined and a-priori known to the UE <NUM> and the BS <NUM>: the comparison can be with respect to at least one predefined symbol. Then, depending on the symbol comparison, it is possible to selectively transmit the acknowledgement signal <NUM>.

For example, if the symbol comparison yields a low correlation between the at least one reference symbol included in the signal <NUM> and the at least one predefined symbol, it can be concluded that collision with a further node attempting to access the wireless link <NUM> is likely to have occurred during <NUM>. Then, it is possible to not transmit the FastACK <NUM>, thereby implicitly indicating to the UE <NUM> that collision is likely to have occurred and that, therefore, the likelihood of successfully decoding at <NUM> is reduced. The UE then implements a back-off. Alternatively it would also be possible to transmit the FastACK <NUM> at <NUM>, the FastACK <NUM> including an indicator indicative of the collision. This helps to explicitly indicate the collision.

A further example of a trigger criterion for transmitting the FastACK <NUM> that could be checked at <NUM> - alternatively or additionally to further trigger criteria such as the above-identified symbol comparison - includes a threshold comparison between a value indicative of a receive signal level of the signal <NUM> and a predefined threshold. For example, a power spectral density (PSD) could be considered. Alternatively or additionally, a maximum amplitude could be considered.

Then, it is possible that the FastACK <NUM> may be selectively transmitted depending on the threshold comparison. For example, if the value indicative of the received signal level exceeds the predefined threshold, it may be concluded that collision is likely to have occurred during <NUM> with a further node accessing the wireless link <NUM>. Then, it may be possible to not transmit the FastACK <NUM> at <NUM>, thereby implicitly indicating to the UE <NUM> that collision might have occurred. Alternatively or additionally, it would also be possible to implement the FastACK <NUM> including an indicator indicative of the collision that has likely occurred during <NUM>. This helps to explicitly indicate the collision.

<FIG> illustrates aspects with respect to the signal transmitted at <NUM>. The signal <NUM> includes the data <NUM> and a checksum <NUM>, i.e., the encoded data <NUM>. In particular, the signal <NUM> includes multiple repetitions <NUM> of the encoded data <NUM> (while in the example of <FIG> a count of two repetitions <NUM> is illustrated, generally, a larger count of repetitions <NUM> is possible; for example, the signal <NUM> may include at least <NUM> repetitions of the encoded data <NUM>, optionally at least <NUM> repetitions <NUM>, further optionally at least <NUM> repetitions <NUM>). The signal <NUM> also includes at least one reference symbol <NUM>. In the example of <FIG>, the signal <NUM> includes a single repetition <NUM> of the at least one reference symbol <NUM>; however, in other examples, the signal <NUM> may include multiple repetitions <NUM> of the at least one reference symbol <NUM>.

In particular, in the example of <FIG>, the single repetition <NUM> of the at least one reference symbol <NUM> is arranged adjacent to the repetitions <NUM> of the encoded data <NUM> within the signal <NUM>. This ensures that the reception characteristics of the at least one reference symbol <NUM> are indicative of the reception characteristics of the encoded data <NUM>.

<FIG> illustrates aspects with respect to the signal <NUM>. The example of <FIG> generally corresponds to the example of <FIG>. However, in the example of <FIG>, the signal <NUM> includes multiple repetitions <NUM> of the at least one reference symbol <NUM>. Furthermore, in the example of <FIG>, the plurality of repetitions <NUM> of the at least one reference symbol <NUM> are arranged interleaved with the plurality of repetitions <NUM> of the encoded data <NUM> within the signal <NUM>. In the example of <FIG>, a repetition <NUM> of the at least one reference symbol <NUM> is arranged in-between two neighboring repetitions <NUM> of the encoded data <NUM>.

<FIG> illustrates aspects with respect to the signal <NUM>. The example of <FIG> generally corresponds to the example of <FIG>. Also in the example of <FIG>, the signal <NUM> includes multiple repetitions <NUM> of the at least one reference symbol <NUM>. Furthermore, also in the example of <FIG>, the multiple repetitions <NUM> of the at least one reference symbol <NUM> are arranged interleaved with the repetitions <NUM> of the encoded data <NUM> within the signal <NUM>. In the example of <FIG>, an additional repetition <NUM> of the at least one reference symbol <NUM> is arranged in between the data <NUM> and the checksum <NUM> of each repetition <NUM> of the encoded data <NUM>.

Generally, there may be more repetitions <NUM> of the at least one reference symbol <NUM> than repetitions <NUM> of the encoded data <NUM>-<NUM> (cf. In other examples, however, there may be fewer repetitions <NUM> of the at least one reference symbol <NUM> than repetitions <NUM> of the encoded data <NUM>-<NUM> (cf. Hence, the count of repetitions <NUM> may be smaller than the count of repetitions <NUM>. This may facilitate low overhead. Furthermore, it may not be required to decode the reference symbols <NUM> so that typically a smaller count of repetitions <NUM> is sufficient to determine the likelihood of successfully decoding the data <NUM> at significant accuracy.

While in the example of <FIG> scenarios have been discussed with respect to the signal <NUM>, similar concepts may be readily applied with respect to the signal <NUM> including additional repetitions <NUM> of the encoded data <NUM>.

Next, details with respect to the at least one reference symbol <NUM> are disclosed. In various examples, it is possible that the at least one reference symbol <NUM> includes a single symbol. In other examples, it would be possible that the at least one reference symbol <NUM> includes a sequence of reference symbols, e.g., including a count of not less than <NUM> reference symbols, optionally of not less than <NUM> reference symbols, further optionally of not less than <NUM> reference symbols. By employing a sequence of reference symbols <NUM>, a higher reliability can be achieved when performing a symbol comparison, e.g., at <NUM> (cf.

Next, details with respect to the FastACK <NUM> are disclosed. In the various examples described herein, it is possible to implement the FastACK <NUM> by one or more acknowledgement reference symbol. In particular, it would be possible to employ a sequence of acknowledgement reference symbols. The one or more acknowledgement reference symbols may have a predefined waveform and/or amplitude. In a manner which is comparable to the symbol comparison that has been described above with respect to the check at <NUM>, it is then possible that the receiver of the FastACK <NUM> performs a symbol comparison between the one or more acknowledgement reference symbols and predefined acknowledgement symbols. By transmitting such a FastACK <NUM> which is defined with respect to one or more acknowledgement reference symbols, i.e., which is native to the physical layer/Layer <NUM> according to the OSI model and does not encode control data, it becomes possible to transmit and analyze the FastACK <NUM> with low latency. In particular, it may be avoided that higher layers - e.g., Layer <NUM> or Layer <NUM> are involved when creating and/or analyzing the FastACK <NUM>. In particular, if compared to acknowledgement messages defined with respect to the HARQ protocol, such a lower-layer implementation of the FastACK <NUM> facilitates low latency in transmission. In some examples, the FastACK <NUM> may include one or more repetitions of a pilot signal. In such a scenario, the welldefined amplitude of the pilot signal can be reused to implement channel sounding of the wireless link <NUM>.

For example, the one or more acknowledgement reference symbols may be repeated a certain number of times. This helps to implement the symbol comparison at greater accuracy.

<FIG> schematically illustrates the UE <NUM>. The UE <NUM> includes control circuitry implemented by a processor <NUM>-<NUM>, e.g., a single core or multicore processor. Distributed processing may be employed. The processor <NUM>-<NUM> is coupled to a memory <NUM>-<NUM>, e.g., a non-volatile memory. The memory <NUM>-<NUM> may store program code that is executable by the processor <NUM>-<NUM>. Executing the program code may cause the processor <NUM>-<NUM> to perform techniques as disclosed herein, e.g., relating to: CE; transmitting and/or receiving a FastACK; communicating on an open spectrum; etc. Such functionality which is illustrated with respect to the processor <NUM>-<NUM> in the example of <FIG>, in other examples may also be implemented using hardware. The UE <NUM> also includes an interface <NUM>-<NUM> configured to communicate with the BS <NUM> on the wireless link <NUM>. The interface <NUM>-<NUM> may include an analog front end and/or a digital front end. The interface <NUM>-<NUM> may implement a transmission protocol stack, e.g., according to the 3GPP LTE technology. The transmission protocol stack may include a physical layer (Layer <NUM>), a MAC layer (Layer <NUM>), etc..

<FIG> schematically illustrates the BS <NUM>. The BS <NUM> includes control circuitry implemented by a processor <NUM>-<NUM>, e.g., a single core or multicore processor. Distributed processing may be employed. The processor <NUM>-<NUM> is coupled to a memory <NUM>-<NUM>, e.g., a non-volatile memory. The memory <NUM>-<NUM> may store program code that is executable by the processor <NUM>-<NUM>. Executing the program code can cause the processor <NUM>-<NUM> to perform techniques as disclosed herein, e.g., relating to: CE; transmitting and/or receiving a FastACK; and transmitting and/or receiving on an open spectrum. Such techniques as illustrated with respect to <FIG> for the processor <NUM>-<NUM> and the memory <NUM>-<NUM> may also be implemented partly or fully in hardware in other examples. The BS <NUM> also includes an interface <NUM>-<NUM> configured to communicate with the UE <NUM> on the wireless link <NUM>. The interface <NUM>-<NUM> may include an analog front end and/or a digital front end. The interface <NUM>-<NUM> may implement a transmission protocol stack, e.g., according to the 3GPP LTE technology. The transmission protocol stack may include a physical layer (Layer <NUM>), a MAC layer (Layer <NUM>), etc..

<FIG> is a flowchart of a method according to various examples. For example, the method according to <FIG> may be executed by the processor <NUM>-<NUM> of the BS <NUM> and/or the processor <NUM>-<NUM> of the UE <NUM>.

First, in <NUM>, a first signal is received. The first signal includes a first plurality of repetitions of encoded data. All repetitions may include the data encoded according to the same redundancy version.

The first signal may be received from a BS or a UE. For example, the first signal may be received on an open spectrum. The first signal may be received in UL, DL, or D2D.

The multiple repetitions included in the signal received at <NUM> may correspond to CE.

Next, in <NUM>, an acknowledgement signal - the FastACK - is transmitted. The reason for transmitting the acknowledgement signal <NUM> is to reduce the risk of the node transmitting the encoded data to waste a significant amount of the channel time and energy for transmission without the receiver of the encoded data being aware of the transmission and/or with a significantly reduced likelihood of successfully decoding the encoded data, e.g., due to collision on the open spectrum.

It is possible that the FastACK is transmitted in block <NUM> for any transmission of an ongoing data connection, possibly with the exception of the very first initialization message of a random access procedure.

After transmitting the FastACK at <NUM>, a second signal is received. The second signal includes a second plurality of repetitions of the encoded data. The data received in <NUM> may be encoded according to the same redundancy version as the data received in <NUM>. Hence, the first and second signals of <NUM>, <NUM> may be part of the same transmission burst of CE.

Next, in <NUM>, the first plurality of repetitions of the encoded data received in <NUM> and the second plurality of repetitions received in <NUM> are combined to yield a combined signal. This may be a combination of the signals in the digital baseband before decoding in the digital domain, such as the performing of channel decoding of the signals. This may be denoted a I-Q modulated combined signal. Then, the decoding and <NUM> is based on the combined signal.

Generally, the data may be UL data or DL data. In other words, it is possible that CE is applied for, both, UL and DL.

<FIG> is a flowchart of a method according to various examples. In particular, the method according to <FIG> is executed by the processor <NUM>-<NUM> of the BS <NUM> and/or the processor <NUM>-<NUM> of the UE <NUM>.

First, in <NUM>, a first signal is transmitted. The first signal includes a first plurality of repetitions of encoded data. <NUM> is inter-related with <NUM>.

Next, in <NUM>, an acknowledgement signal is received, i.e., the FastACK. <NUM> is inter-related with <NUM>.

Next, in <NUM>, a second signal is transmitted. The second signal includes a second plurality of repetitions of the encoded data. <NUM> is inter-related with <NUM>.

<FIG> is a flowchart of a method according to various examples. First, in <NUM>, transmission of data is initialized. This may be because the data arrives in a transmission buffer, e.g., of the UE or the BS.

Next, in <NUM>, a LBT channel sensing is performed. Based on the LBT channel sensing, in <NUM> it is judged whether resources are available on the respective channel on the wireless link <NUM>. If this is not the case, the LBT is repeated after a certain back-off time. Otherwise, the method commences with <NUM>.

In <NUM>, multiple repetitions of encoded data are transmitted. The number of repetitions may be defined by a CE level. All repetitions include the data encoded according to the same redundancy version.

In <NUM> it is checked whether further repetitions of the encoded data are required. If further repetitions of the encoded data are not required, the method commences with <NUM>. At <NUM>, waiting for a positive Layer <NUM> or Layer <NUM> acknowledgement message or a negative Layer <NUM> or Layer <NUM> acknowledgement message of a HARQ protocol is implemented (further details of HARQ re-transmissions are not illustrated in <FIG>).

If, at <NUM>, it is judged that further repetitions of the encoded data are required according to the CE level, the method commences with <NUM>. At <NUM>, waiting for a FastACK is implemented. The FastACK may correspond to one or more repetitions of a reference symbol sequence or even a single reference symbol. In other words, the FastACK may correspond to a Layer <NUM> control message.

The trigger criterion for transmission of the FastACK may be reception of a sequence of reference symbols transmitted along with the multiple repetitions of the encoded data in <NUM>. Such a sequence of reference symbols can be identified reliably. For example, the effective signal-to-noise ratio required to reliably detecting such a sequence of reference symbols may be lower than the signal-to-noise ratio required for successfully decoding a data transmission. Thus, generally, the number of repetitions of the at least one reference symbol can be smaller than the number of repetitions of the encoded data.

In <NUM> it is checked whether the FastACK has been detected, Here, it is again possible to implement a symbol comparison. Such a symbol comparison between one or more acknowledgement reference symbols and corresponding one or more predefined acknowledgement symbols can be performed with higher reliability even for comparably low signal-to-noise ratio.

If, in <NUM> it is judged that the FastACK has been detected, the method commences with re-executing <NUM>. Hence, multiple repetitions of the encoded data are retransmitted. If, at <NUM> it is judged that the FastACK has not been detected, the method commences with <NUM>. Here, a back-off is implemented and then a LBT and <NUM> is re-commenced.

Although the invention has been shown and described with respect to certain preferred embodiments, modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention is limited only by the scope of the appended claims.

Claim 1:
A method performed by a network node (<NUM>, <NUM>), the method comprising:
- transmitting, to a remote node (<NUM>, <NUM>), a first signal (<NUM>) comprising a first plurality of repetitions (<NUM>) of encoded data (<NUM>-<NUM>, <NUM>),
- in response to detecting an acknowledgement signal (<NUM>) indicating the likelihood of successfully completing the transmission of the encoded data:
transmitting, to the remote node (<NUM>, <NUM>), a second signal (<NUM>) comprising a second plurality of repetitions (<NUM>) of the encoded data (<NUM>-<NUM>, <NUM>), and
- if the acknowledgement signal is not detected: abort said transmitting of the second plurality of repetitions by implementing a back-off procedure.