Description

The present invention relates to the field of mobile communication systems, more specifically to techniques checking or verifying if information sent by a transmitter has been correctly received at a receiver so as to initiate a retransmission in case of a non successful transmission of the information. Embodiments relate to simultaneous synchronous and asynchronous HARQ, hybrid automatic repeat request, operations in a network entity of the wireless communication system, like a base station or a user equipment, UE.

Fig. 1 is a schematic representation of an example of a terrestrial wireless network 100 including a core network 102 and a radio access network 104. The radio access network 104 may include a plurality of base stations gNEh to gNBs, each serving a specific area surrounding the base station schematically represented by respective cells 106i to 106s. The base stations are provided to serve users within a cell. The term base station, BS, refers to a gNB in 5G networks, an eNB in U TS/LTE/LTE-A/ LTE-A Pro, or just a BS in other mobile communication standards. A user may be a stationary device or a mobile device. The wireless communication system may also be accessed by mobile or stationary loT devices which connect to a base station or to a user. The mobile devices or the loT devices may include physical devices, ground based vehicles, such as robots or cars, aerial vehicles, such as manned or unmanned aerial vehicles (UAVs), the latter also referred to as drones, buildings and other items or devices having embedded therein electronics, software, sensors, actuators, or the like as well as network connectivity that enable these devices to collect and exchange data across an existing network infrastructure. Fig. 1 shows an exemplary view of only five cells, however, the wireless communication system may include more such cells. Fig. 1 shows two users UEi and UE2, also referred to as user equipment, UE, that are in cell I O62 and that are served by base station gNB2. Another user UE3 is shown in cell I O64 which is served by base station gNB4. The arrows I O81 , 1082 and I O83 schematically represent uplink/downlink connections for transmitting data from a user UE1, UE2 and UE3 to the base stations gNB2, gNB4 or for transmitting data from the base stations gNB2, gNB4 to the users UE1, UE2, UE3. Further, Fig. 1 shows two loT devices 1 10i and 1 102 in cell 1064, which may be stationary or mobile devices. The loT device 1 10i accesses the wireless communication system via the base station gNB4 to receive and transmit data as schematically represented by arrow 112i. The loT device 1 102 accesses the wireless communication system via the user UE3 as is schematically represented by arrow 1122. The respective base station gNBi to gNBs may be connected to the core network 102, e.g. via the S1 interface, via respective backhaul links 1 14i to 1 14s, which are schematically represented in Fig. 1 by the arrows pointing to“core”. The core network 102 may be connected to one or more external networks. Further, some or all of the respective base station gNBi to gNBs may connected, e.g. via the S1 or X2 interface or XN interface in NR, with each other via respective backhaul links 1 1 61 to 1 1 65, which are schematically represented in Fig. 1 by the arrows pointing to "gNBs”.

For data transmission a physical resource grid may be used. The physical resource grid may comprise a set of resource elements to which various physical channels and physical signals are mapped. For example, the physical channels may include the physical downlink and uplink shared channels (PDSCH, PUSCH) carrying user specific data, also referred to as downlink and uplink payload data, the physical broadcast channel (PBCH) carrying for example a master information block (MIB) and a system information block (SIB), the physical downlink and uplink control channels (PDCCH, PUCCH) carrying for example the downlink control information (DCI). For the uplink, the physical channels may further include the physical random access channel (PRACH or RACH) used by UEs for accessing the network once a UE synchronized and obtained the MIB and SIB. The physical signals may comprise reference signals or symbols (RS), synchronization signals and the like. The resource grid may comprise a frame or radio frame having a certain duration in the time domain and having a given bandwidth in the frequency domain. The frame may have a certain number of subframes of a predefined length. Each subframe may include one or more slots of 14 OFDM symbols depending on the cyclic prefix (CP) length and subcarrier spacing (SCS). A frame may also consist of a smaller number of OFDM symbols, e.g. when utilizing shortened transmission time intervals (sTTI) or a mini slot/non-slot-based frame structure comprising just a few OFDM symbols.

The wireless communication system may be any single-tone or multicarrier system using frequency-division multiplexing, like the orthogonal frequency-division multiplexing (OFDM) system, the orthogonal frequency-division multiple access (OFDMA) system, or any other IFFT-based signal with or without CP, e.g. DFT-s-OFDM. Other waveforms, like non-orthogonal waveforms for multiple access, e.g. filter-bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM) or universal filtered multi carrier (UFMC), may be used. The wireless communication system may operate, e.g., in accordance with the LTE-Advanced pro standard or the 5G or NR, New Radio, standard.

The wireless network or communication system depicted in Fig. 1 may by an heterogeneous network having distinct overlaid networks, e.g., a network of macro cells with each macro cell including a macro base station, like base station gNBi to gNB5, and a network of small cell base stations (not shown in Fig. 1 ), like femto or pico base stations.

In addition to the above described terrestrial wireless network also non-terrestrial wireless communication networks exist including spaceborne transceivers, like satellites, and/or airborne transceivers, like unmanned aircraft systems. The non-terrestrial wireless communication network or system may operate in a similar way as the terrestrial system described above with reference to Fig. 1 , for example in accordance with the LTE-advanced pro standard or the 5G or NR, new radio, standard.

In mobile communication networks, for example in a network like that described above with reference to Fig. 1 , like a LTE or 5G/NR network, there may be UEs that communicate directly with each other over one or more sidelink (SL) channels, e.g., using the PC5 interface. UEs that communicate directly with each other over the sidelink may include vehicles communicating directly with other vehicles (V2V communication), vehicles communicating with other entities of the wireless communication network (V2X communication), for example roadside entities, like traffic lights, traffic signs, or pedestrians. Other UEs may not be vehicular related UEs and may comprise any of the above mentioned devices. Such devices may also communicate directly with each other (D2D communication) using the SL channels.

When considering two UEs directly communicating with each other over the sidelink, both UEs may be served by the same base station, i.e. , both UEs may be within the coverage area of a base station, like one of the base stations depicted in Fig. 1. This is referred to as a “in coverage" scenario. In accordance with other examples, both UEs that communicate over the sidelink may not be served by a base station which is referred to as an“out-of-coverage” scenario. It is noted that“out-of-coverage” does not mean that the two UEs are not within one of the cells depicted in Fig. 1 , rather, it means that these UEs are not connected to a base station, for example, they are not in a RRC connected state. Yet another scenario is called a“partial coverage” scenario, in accordance with which one of the two UEs which communicate with each other over the sidelink, is served by a base station, while the other UE is not served by the base station.

Fig. 2 is a schematic representation of a situation in which two UEs directly communicating with each other are both in coverage of a base station. The base station gNB has a coverage area that is schematically represented by the circle 200 which, basically, corresponds to the cell schematically represented in Fig. 1. The UEs directly communicating with each other include a first vehicle 202 and a second vehicle 204 both in the coverage area 200 of the base station gNB. Both vehicles 202, 204 are connected to the base station gNB and, in addition, they are connected directly with each other over the PC5 interface. The scheduling and/or interference management of the V2V traffic is assisted by the gNB via control signaling over the Uu interface, which is the radio interface between the base station and the UEs. The gNB assigns the resources to be used for the V2V communication over the sidelink. This configuration is also referred to as a mode 3 configuration.

Fig. 3 is a schematic representation of a situation in which the UEs are not in coverage of a base station, i.e., the respective UEs directly communicating with each other are not connected to a base station, although they may be physically within a cell of a wireless communication network. Three vehicles 206, 208 and 210 are shown directly communicating with each other over a sidelink, e.g., using the PCS interface. The scheduling and/or interference management of the V2V traffic is based on algorithms implemented between the vehicles. This configuration is also referred to as a mode 4 configuration. As mentioned above, the scenario in Fig. 3 which is an out-of-coverage scenario does not mean that the respective mode 4 UEs are outside of the coverage 200 of a base station, rather, it means that the respective mode 4 UEs are not served by a base station or are not connected to the base station of the coverage area. Thus, there may be situations in which, within the coverage area 200 shown in Fig. 2, in addition to the mode 3 UEs 202, 204 also mode 4 UEs 206, 208, 210 are present.

In a wireless communication system as described above with reference to Fig. 1 , like a LTE system or a 5G/NR system, approaches for checking or verifying if a transmission sent by a transmitter, like a BS, is correctly arrived at a receiver, like a UE, are implemented which request, in case of a non-successful transmission, a retransmission of the information or a retransmission of one or more redundancy versions of the information. Naturally, such a process may also be implemented when transmitting from

the UE to the BS. In other words, for handling error packets received at a UE or a gNB, a mechanism is applied to rectify the error. In accordance with LTE or NR, a HARQ mechanism is implemented to correct error packets in the physical layer. In case a receive packet has an error, the receiver may buffer the packet and request a retransmission from the transmitter or sender. Once the receiver received the re-transmitted packet, it may combine with the buffered data prior to channel decoding and error detection, for example, by applying a chase combination approach or an incremental redundancy approach.

Fig. 4 describes briefly an example for a conventional HARQ mechanism as it may also be derived from TS 38.321 , section 5.3.2 and 5.4.2 which describes the HARQ operation and entity. Fig. 4 illustrates a transmitter, e.g., a gNB, which sends a data packet 1 to a receiver, e.g., a UE. The data packet 1 (1 ) is initially transmitted, and the receiver attempts to decode the received data packet. If the data packet was successfully decoded the receiver delivers the data packet from the MAC/PHY layer to an upper layer. If the data packet was not successfully decoded the receiver buffers the data packet in a soft buffer as is indicate at ® in Fig. 4. Further, the receiver send the NACK message to the transmitter, and, responsive to the NACK message, the transmitter sends a retransmission 1 (2) of the data packet. The buffered initial transmission is combined with the retransmission as is indicated at ©. The combining may use chase combination or incremental redundancy. In case the combined data can be decoded, as is indicated at CD, the ACK message is send to the transmitter to indicate the successful transmission.

The HARQ mechanism may include a synchronous HARQ process or an asynchronous HARQ process.

When applying the asynchronous HARQ process, the gNB may use any of the available HARQ processes, for example a process out of the 8 SAW, Stop&Wait, processes for the downlink. Fig. 5 illustrates an 8-channel Stop-and-Wait HARQ protocol according to which during a time period, which may be the minimum time until a retransmission may be send due to a missing ACK/NACK or due to received NACK, further data packets are transmitted. In the latter case (receipt of a NACK) the time period is defined by the processing time for decoding at the receiver a data packet and the processing time at the transmitter for decoding the ACK/NACK message related to the data packet. The gNB provides instructions to the UE regarding which HARQ process will be used during each sub-frame for which resources are allocated, and the respective identity or HARQ process ID may be included within a PDCCH transmission. The asynchronous HARQ process

come together with an increase in the signaling overhead as it needs to include the HARQ process ID within the DCI message, but increases flexibility as retransmissions do not have to be scheduled during every sub-frame. Fig. 6 illustrates an adaptive asynchronous HARQ at is may be used in NR. Fig. 6 shows the minimum time until a retransmission may be send due to a missing ACK/NACK so that a retransmission for HARQ process #0 may be made at a time after this minimum time. When scheduling the retransmission, the HARQ process number #0 - #7 and the location of the retransmission in frequency and transport format are signaled. Thus, the process is adaptive with regard to the location and the transport format.

When applying the synchronous HARQ process retransmissions are scheduled at fixed time intervals, thereby generating a reduced overhead signaling as it is not needed to include an information about the process to be used, for example the HARQ process identifier, into the outgoing data. The process is cyclic, so that even if no resources are allocated during a specific subframe, the first process will repeat at the initially scheduled intervals, for example, after every 8ms.

Fig. 1 illustrates schematically a synchronous HARQ process in a LTE wireless communication system using adaptive or non-adaptive transmissions/operations. Fig. 7 illustrates a sub-frame n, a sub-frame n+8 and a sub-frame n+16. At sub-frame n, the synchronous ARQ process is scheduled using the PDCCH, causing the retransmissions to be scheduled in multiples of the HARQ roundtrip time, RTT, which may be 8 sub-frames. In a non-adaptive operation, the HARQ feedback on the physical hybrid ARQ indicator channel, PHICH, is used to determine, if a retransmission is needed or not. In Fig. 7, it is assumed that the received information in sub-frame n included an error, i.e., the transmission to a receiver, like a UE, was not successful so that, on the PHICH the non-acknowledgement message NACK is transmitted. Dependent on the scheduled initial uplink resource, there is a unique PHICH resource corresponding to the non-successful transmission, and the retransmission will be provided with the same MCS on the same frequency resource using the corresponding retransmission slot, which, in the example of Fig. 7 is at sub-frame n+8. In other words, in a non-adaptive HARQ operation, the retransmission is triggered at the sender or transmitter once a NACK message is received on the PHICH, and, at the next time for doing a transmission, the same resources as in the previous transmission are used, i.e., MCS and resource blocks, RBs, remain unchanged. Fig. 8 illustrates non-adaptive synchronous HARQ at is may be used for ULLRC services. The operation is synchronous in time meaning that the HARQ processes

#0 - #7 are served one after the other, and a retransmission occurs exactly N slots/symbols after last transmission so that there is no need to signal the process number. This limited scheduling freedom comes together with a minimum uplink signaling overhead and a minimum delay.

In case of an adaptive synchronous HARQ operation, the PHICH is ignored if a DC! message is received via the PDCCH indicating an adaptive retransmission, as is indicated between sub-frame n+8 and sub-frame n+16 in Fig. 7. Although in the adaptive operation the MCS and frequency resource may be changed using the DC! signaling the adaptive transmission operation, still, since it is a synchronous HARQ process, the retransmission sub-frame is already predetermined by the initial transmission at sub-frame n and will be carried out at the next retransmission time, which, in the example of Fig. 7 is sub-frame n+16.

In accordance with the LIE Rel.8, synchronous HARQ processes are only used in the uplink, and the synchronous HARQ process may be operated either in the adaptive or non-adaptive mode, as described above.

NR Rel.15 introduces an asynchronous HARQ process to be used also in the uplink direction so that the retransmission is always preschedule by the gNB. However, this results in additional latency needed for scheduling, and since there is no explicit acknowledgement message, ACK, anymore, the UE needs to store relevant information in its HARQ processes until a new transmission is started on the same HARQ process.

It is noted that the information in the above section is only for enhancing the understanding of the background of the invention and therefore it may contain information that does not form prior art that is already known to a person of ordinary skill in the art.

It is an object of the present invention to provide an approach for reliably handling retransmissions in a wireless communication system for data or information associated with different services types.

This object is achieved by the subject-matter as defined in the independent claims, and further, advantageous embodiments are defined in the dependent claims.

Embodiments of the present invention are now described in further detail with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic representation of an example of a wireless communication system;

Fig. 2 shows a schematic representation of a situation in which UEs directly communicating with each other are in coverage of a base station;

Fig. 3 shows a scenario in which UEs directly communicating with each other are not are not in coverage of a base station, i.e., are not connected to a base station;

Fig. 4 describes briefly an example for a conventional HARQ mechanism as it may also be derived from TS 38.321 , section 5.3.2 and 5.4.2 which describes the HARQ operation and entity;

Fig. 5 illustrates an 8-channel Stop-and-Wait HARQ protocol;

Fig. 6 illustrates an adaptive asynchronous HARQ at is may be used in NR;

Fig. 7 illustrates schematically a synchronous HARQ process in a LTE wireless communication system using adaptive or non-adaptive transmissions/operations;

Fig. 8 illustrates non-adaptive synchronous HARQ at is may be used for ULLRC services;

Fig. 9 is a schematic representation of a wireless communication system for communicating information between a transmitter and one or more receivers in accordance with embodiments of the present invention;

Fig. 10 illustrates an embodiment of a layer structure for implementing synchronous and asynchronous HARQ operation at the base station or the user equipment using a common MAC entity in the MAY layer;

Fig. 11 illustrates a further embodiment of a layer structure for implementing synchronous and asynchronous HARQ operation at the base station or the user equipment using separate MAC entities in the MAY layer;

Fig. 12 illustrates details of a UE, like a UE as described above with reference to

Fig. 9 including the antennas ANTR, the signal processor 302a and the transceiver 302b;

Fig. 13 illustrates the above concept of using for the feedback LL-PUCCHs in case of synchronous HARQ, and multiplexing the feedback into the regular PUCCH in case of asynchronous HARQ; and

Fig. 14 illustrates an example of a computer system on which units or modules as well as the steps of the methods described in accordance with the inventive approach may execute.

Embodiments of the present invention is now described in more detail with reference to the accompanying drawings in which the same or similar elements have the same reference signs assigned.

The present invention addresses the way the HARQ processes are currently implemented, which is disadvantageous because in certain scenarios, like mobile communication scenarios, a single UE may support different service types simultaneously. The different service types may have different latency requirements, for example, a delay non-critical service, like a eMBB service, and a delay critical service like a URLLC service, may be supported simultaneously by a single UE. In such a situation, the radio transmission technology, RAT, needs to handle each service type, for example in terms of data rate, latency and reliability. However, in current releases, like LTE Rel.8 and NR Rel.15, the HARQ design is limited. For example, NR uses a synchronous HARQ in uplink and downlink transmissions, and the retransmissions are explicitly scheduled using the PDCCH resource allocation for providing high flexibility. The gNB spends time to execute scheduling before sending the resource allocation, and the HARQ feedback channel may send immediately the ACK/NACK message. However, for delay critical traffic, like URLLC traffic, the burden on scheduling HARQ retransmissions is substantial and causes additional delays in the transmission. Additionally, also for massive Machine-Type

Communication (mMTC) this demands a higher receiver complexity and reduces the battery lifetime.

This is addressed by the present invention as described hereinbelow in more detail, and embodiments of the present invention may be implemented in a wireless communication system as depicted in Fig. 1 , Fig. 2 and Fig. 3 including base stations and users, like mobile terminals or loT devices. Fig. 9 is a schematic representation of a wireless communication system for communicating information between a transmitter 300 and one or more receivers 302i to 302n. The transmitter 300 and the receivers 302 may communicate via a wireless communication links or channels 304a, 304b, 304c, like a radio link. The transmitter 300 may include one or more antennas ANTT or an antenna array having a plurality of antenna elements, a signal processor 300a and a transceiver 300b, coupled with each other. The receivers 302 include one or more antennas ANTR or an antenna array having a plurality of antennas, a signal processor 302ai, 302an, and a transceiver 302bi, 302bn coupled with each other.

In accordance with an embodiment, as for example also depicted in Fig. 2, the transmitter 300 may be a base station and the receivers may be UEs. The base station 300 and the UEs 302 may communicate via respective first wireless communication links 304a and 304b, like a radio link using the Uu interface, while the UEs 302 may communicate with each other via a second wireless communication link 304c, like a radio link using the PCS interface.

In accordance with an embodiment, as for example also depicted in Fig. 3, the transmitter 300 may be a first UE and the receivers may be further UEs. The first UE 300 and the further UEs 302 may communicate via respective wireless communication links 304a to 304c, like a radio link using the PCS interface.

The transmitter 300 and the one or more receivers 302 may operate in accordance with the inventive teachings described herein.
CLAIMS

1 An apparatus, wherein

the apparatus is configured to

receive one or more data packets from a transmitter in a wireless communication system, the data packets transmitted over a radio channel of the wireless communication system, and

request from the transmitter a retransmission for a data packet in case of a non successful transmission of the data packet, and

the apparatus comprises

a plurality of Hybrid ARQ, HARQ, entities, the plurality of HARQ, entities including at least a first HARQ entity and a second HARQ entity, the first HARQ entity to perform a first HARQ operation, and the second HARQ entity to perform a second HARQ operation, the first and second HARQ operations being different, or a Hybrid ARQ, HARQ, entity performing a first HARQ operation and a second HARQ operation, the first and second HARQ operations being different.

2. An apparatus,

wherein the apparatus is configured to

transmit one or more data packets to a receiver in a wireless communication system, the data packets transmitted over a radio channel of the wireless communication system, and

receive from the receiver a request for a retransmission for a data packet in case of a non-successfui transmission of the data packet, and

the apparatus comprises

a plurality of Hybrid ARQ, HARQ, entities, the plurality of HARQ, entities including at least a first HARQ entity and a second HARQ entity, the first HARQ entity to perform a first HARQ operation, and the second HARQ entity to perform a second HARQ operation, the first and second HARQ operations being different, or a Hybrid ARQ, HARQ, entity performing a first HARQ operation and a second HARQ operation, the first and second HARQ operations being different.

3. The apparatus of claim 1 or 2, wherein, responsive to a signaling or based on an association between a logical channel the data packet belongs to and the HARQ entity, the apparatus applies for the one or more data packets

the first HARQ operation, or

the second HARQ operation, or

the first and second HARQ operations simultaneously.

4. The apparatus of claim 3, wherein the first and second HARQ operations comprise one or more of

a Stop-and-Wait ARQ protocol,

a window based ARQ protocol,

a synchronous protocol, the synchronous protocol scheduling the one or more retransmissions and/or the one or more HARQ ACK/NACKs at pre-defined time instances after the initial transmission,

an asynchronous protocol, the asynchronous protocol scheduling the one or more retransmissions and/or the one or more HARQ ACK/NACKs dynamically in time.

5. The apparatus of any one of the preceding claims, wherein the apparatus is configured to process both data packets of a first logical channel and data packets of a second logical channel.

6. The apparatus of claim 5, wherein

the data packet of the first logical channel includes

a data packet provided by a delay critical service of the wireless communication system, like an URLLC service having, e.g., a low rate and/or a low latency, or a data packet having associated therewith a first Quality of Service, QoS, or a data packet having associated therewith a first guaranteed bit rate, GBR, and

wherein the data packet of the second logical channel includes

a data packet provided by a delay non-critical service of the wireless communication system, like an eMBB service having, e.g., a high rate and/or a medium latency requirement or a mMTC service having, e.g., a low rate and/or a low latency requirement, or

a data packet having associated therewith a second QoS, the first QoS being higher than the second QoS, or

a data packet having associated therewith a second GBR, the first GBR being higher than the second GBR.

7. The apparatus of any one of the preceding claims, wherein

the first HARQ entity is preconfigured with the first HARQ operation, and the second HARQ entity is preconfigured with the second HARQ operation, or

each of the first and second HARQ entities are preconfigured with a HARQ operation having different settings, the settings of the HARQ operation being configurable, responsive to the signaling or based on the association, to implement the first HARQ operation or the second HARQ operation.

8. The apparatus of claim 7, wherein the apparatus is configured to receive a configuration message or a reconfiguration message, e.g. using the RRC protocol, the configuration/reconfiguration message causing the apparatus to establish the first and second HARQ entity and/or to configure/reconfigure the settings of the first and second HARQ entities to perform the first and second HARQ operations.

9. The apparatus of claim 8, wherein the apparatus is to

receive the configuration message or the reconfiguration message from a base station, gNB,

decode the configuration message or the reconfiguration message and

configure the MAC Layer and/or Physical Layer so as to establish and/or to configure/reconfigure the first and second HARQ entities to provide HARQ retransmissions.

10. The apparatus of any one of claims 1 to 7, wherein the establishment and/or configuration of first and second HARQ entities is a predefined procedure and/or configuration specified in the standard.

1 1. The apparatus of any one of the preceding claims, wherein the first and second HARQ entities comprise and/or supports one or more of

different numbers of HARQ processes,

HARQ processes supporting a different number of data packets, e.g. Transport

Blocks, depending on the spatial multiplexing scheme being used

different redundancy versions,

different sequences of redundancy versions, RVs,

different channels for ACK/NACK reporting,

different ACK/NACK timings,

a different maximum number of HARQ retransmissions,

different aggregation factors for bundling transmissions of a data packet, like a Transport Block, in multiple transmission parts of the same bundle,

different target Block Error Rates, BLERs for all transmissions and/or specific retransmissions.

12. The apparatus of claim 11 , wherein

each HARQ entity maintains one or more parallel HARQ processes, each HARQ process being associated with a HARQ process identifier, wherein the HARQ process identifier may either be selected autonomously out of a pool of HARQ processes (e.g., by timing of the initial transmission and/or retransmissions) or predefined by a sequence number or dynamically selected by an apparatus (e.g. a gNB base station) and signaled to an apparatus (e.g. a User Equipment).

13. The apparatus of any one of the preceding claims, wherein the first and second HARQ entities are semi-staticaliy configured and/or associated to different logical channels, e.g., by RRC configuration/reconfiguration, and/or are dynamically scheduled, e.g., by the MAC scheduler.

14. The apparatus of any one of the preceding claims, wherein

a first and second HARQ entity are semi-statically configured and/or associated to different logical channel and

the apparatus is configured to determine for a received resource assignment on the PDCCH control channel which of the first and second HARQ entities to select and/or to apply either using

one or more specific Radio Network Temporary Identifiers, RNTIs, or

one or more DCI formats, or

a HARQ Entity Selector being part of HARQ information send with a DCI format, or a PDCCH resource assignment on configurable Control Resource Sets, CORESETs, on different physical resources, or

different Physical Channels, e.g., a low latency PDSCH or low latency PUSCH.

15. The apparatus of any one of claims 1 to 13, wherein the first and second HARQ entities are located at the MAC layer and being associates and/or linked and/or mapped to one or more Physical Layer procedures or Physical Layer channels such as one or more of

different downlink resource allocation methods e.g. scheduled on the PDCCH, different PDCCH monitoring periodicity.

different DCI formats for downlink, uplink and sidelink scheduling via the PDCCH on the PHY,

different RNTIs indicated in the DCIs for scheduling via the PDCCH on the PHY, different downlink control channels to request uplink retransmission e.g. a retransmission requested via a PDCCH resource allocation, a retransmission requested via a NACK transmission on a Physical HARQ ACK/NACK indicator channel, PHICH,

different physical channels for data transmission e.g. PDSCH, Low Latency PDSCH

different uplink grant methods e.g. scheduled on PDCCH, a response message to a uplink random access, pre-configured uplink grants and/or a semi-persistent scheduling,

different uplink control channels to request downlink retransmission e.g. a retransmission requested via and NACK part of the Uplink Control Information, UCI, send via a PUCCH control channel, or via a Low Latency PUCCH control channel, via PUCCHs with different formats (e.g. short and long PUCCH format), via a Compact PUCCH,

16. The apparatus of any one of the preceding claims, wherein the first and second HARQ entities are located at the MAC layer providing downlink control information or uplink control information to the physical layer (e.g. to support the transmission or reception of data packet or to request a retransmission) for transmission and/or to support Physical Layer operation such as

different control information bits in the Downlink Control Information e.g. different bits (incl. not bits) for HARQ process identifiers, for redundancy version number, for the new data indicator (NDl), for ACK/NACK timing/resource information, or different control information bits in the Uplink Control Information, UCI, send from the MAC layer to the PHY layer e.g. ACK/NACKs for Code Block Groups or ACK/NACKs for Transport Blocks, single ACK/NACK, multiple ACK/NACKs, bundled ACK/NACKs,

17. The apparatus of any one of claims 14 to 16, wherein, when using the RNTI, the apparatus is configured to receive a configuration and/or reconfiguration message, e.g. via RRC signaling, the configuration message causing the apparatus to be configured with a new RNTI which is associated with the first or second HARQ entity, so that the apparatus, upon a blind decoding process testing all RNTIs, determines which of the first or second HARQ entities to select and/or apply.

18. The apparatus of any one of claims 14 to 17, wherein

the DC! format comprises a first DCI format that explicitly signals associated HARQ control information and a second DCI format that does not explicitly signal all HARQ control information, the non-signaled HARQ control information being derived by the apparatus, wherein the first DCI may be used for the initial transmission, and the second DCI format may be used for the one or more retransmissions, and

the apparatus is configured to

test all PDCCH candidates against second DCI formats and against the first DCI format, and

evaluate the embedded checksum to identify which one of the first DCI format and the second DCI format has been received so as to determine which of the first or second HARQ entities to apply.

19. The apparatus of any one of the preceding claims, wherein each of the first and second receiving HARQ entities located at the MAC layer send ACK/NACK control information to the Physical Layer for transmission on a dedicated control channel for an HARQ ACK/NACK feedback to the transmitting HARQ entities, like a Physical Uplink Control Channel, PUCCH or a Physical Hybrid Indicator Channel, PHICH.

20. The apparatus of claim 19, wherein the control channel comprises the PHICH, the PHICH transmitting only ACK/NACK messages.

21 . The apparatus of claim 20, wherein the apparatus, responsive to a NACK on the PHICH, performs the retransmission with a fixed format on same resource used of the preceding transmission/retransmission, wherein a predefined sequence of RVs may be used.

22. The apparatus of any one of claims 19 to 21 , wherein the control channel comprises a low latency PUCCH including the ACK/NACK message, the low latency PUCCH being send more frequently than a regular PUCCH and/or the low latency PUCCH carrying a smaller payload than a regular PUCCH.

23. The apparatus of claim 22, wherein the apparatus is configured to

estimate the radio channel (e.g. based on Demodulation Reference Symbols, DM- RS) over which the data packet is transmitted and/or decodes the control channel (e.g. PDCCH) with the resource allocation of the data packet to provide a CSI, responsive to receiving the data packet and prior to processing the data packet, and

include the CSI into a low latency PUCCH or transmit the CSI once obtained using a first low latency PUCCH and ahead of the ACK/NACK message which is send in a second low latency PUCCH.

24. The apparatus of any one of the preceding claims, wherein the apparatus is configured to

detect a missing PUCCH for a HARQ ACK/NACK, which indicates that the receiver missed an initial scheduling of the transmission by the apparatus, and responsive to detecting the miss, reschedule the same transmission or the initial transmission or the next redundancy version, RV, explicitly with a PDCCH at the next opportunity.

25. The apparatus of claim 24, wherein

in case of a PUCCH format 0-1 , the apparatus is configured to perform a power thresholding to detect a missing PUCCH transmission, and

in case of a PUCCH format 2-41 , the apparatus is configured to perform a checksum detection, and a mismatch in the embedded checksum indicates the missing of the initial grant.

26. The apparatus of any one of the preceding claims, wherein the apparatus is configured to signal the capabilities (e.g. by means of a RRC UE Capability exchange message) for the first and second HARQ entities or for the apparatus one or more of

o the number of supported HARQ entities,

o the number of available HARQ processes,

o the available HARQ soft buffer,

o the supported DC! formats,

o the supported physical channels,

o if a low latency PUCCH is supported.

27. The apparatus of any one of the preceding claims, wherein

the wireless system comprises one or more base stations, BS, and one or more user equipments, UEs, a UE being served by one or more BSs or communication directly with one or more other UEs while being in connected mode or idle mode, and

the apparatus comprises a base station or a UE.

28. {system}

A wireless communication network, comprising:

one or more base stations, BS, and one or more user equipments, UEs, a UE being served by one or more BSs or communication directly with one or more other UEs while being in connected mode or idle mode,

wherein a base station and/or a UE comprises the apparatus of any one of claims 1 to 27

29. {What UE/BE may be}

The wireless communication network of claim 28, wherein

the UE comprise one or more of

a mobile terminal, or

stationary terminal, or

a vehicular terminal, or

cellular IoT-UE, or

an loT device, or

a ground based vehicle, or

an aerial vehicle, or

a drone, or

a moving base station, or

road side unit, or

a building, or

any other item or device provided with network connectivity enabling the item/device to communicate using the wireless communication network, e.g., a sensor or actuator, and

the BS comprise one or more of

a macro cell base station, or

a micro cell base station, or

a small cell base station, or

a central unit of a base station, or

a distributed unit of a base station, or

a road side unit, or

a UE, or

a remote radio head, or

an AMF, or

an SMF, or

a core network entity, or

a network slice as in the NR or 5G core context, or

any transmission/reception point (TRP) enabling an item or a device to communicate using the wireless communication network, the item or device being provided with network connectivity to communicate using the wireless communication network.

30. {method corresponding to claim 1 }

A method, comprising:

receiving one or more data packets from a transmitter in a wireless communication system, the data packets transmitted over a radio channel of the wireless communication system, and

requesting from the transmitter a retransmission for a data packet in case of a non successful transmission of the data packet,

wherein the retransmission comprises providing a first HARQ operation and/or a second HARQ operation, the first and second HARQ operations being different,

wherein

a plurality of Hybrid ARQ, HARQ, entities is provided, the plurality of HARQ, entities including at least a first HARQ entity and a second HARQ entity, the first HARQ entity performing the first HARQ operation, and the second HARQ entity performing the second HARQ operation, or

a Hybrid ARQ, HARQ, entity is provided performing the first HARQ operation and the second HARQ operation, the first and second HARQ operations being different.

31 A method, comprising:

transmitting one or more data packets to a receiver in a wireless communication system, the data packets transmitted over a radio channel of the wireless communication system,

receiving from the receiver a request for a retransmission for a data packet in case of a non-successful transmission of the data packet, and

wherein the retransmission comprises providing a first HARQ operation and/or a second HARQ operation, the first and second HARQ operations being different,

wherein

a plurality of Hybrid ARQ, HARQ, entities is provided, the plurality of HARQ, entities including at least a first HARQ entity and a second HARQ entity, the first HARQ entity performing the first HARQ operation, and the second HARQ entity performing the second HARQ operation, or

a Hybrid ARQ, HARQ, entity is provided performing the first HARQ operation and the second HARQ operation, the first and second HARQ operations being different..

32. A non-transitory computer program product comprising a computer readable medium storing instructions which, when executed on a computer, perform the method of any one of claims 30 to 31.