Wireless communication device, network node and methods for handling data transmissions

Embodiments herein relate to a method implemented by a wireless communication device (10). The wireless communication device (10) transmits data to a radio node (12) of a wireless communication network (1). The wireless communication device (10) monitors for a positive acknowledgement or a negative acknowledgement of the data from the radio node (12). The wireless communication device (10) retransmits the data to the radio node (12) when said monitoring indicates reception of a negative acknowledgement of the data. The wireless communication device (10) refrains from retransmitting the data to the radio node (12) when said monitoring indicates reception of a positive acknowledgement of the data. The wireless communication device (10) also refrains from retransmitting the data to the radio node (12) when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data.

TECHNICAL FIELD

Embodiments herein relate to a wireless communication device, a network node and methods performed by the wireless communication device and the network node in a wireless communication network. In particular, embodiments herein relate to handling data transmissions from wireless communication device to a radio node in the wireless communication network.

BACKGROUND

In a typical communication network, wireless communication devices, also known as wireless devices, mobile stations, stations (STA) and/or user equipments (UE), communicate via a Radio Access Network (RAN) to one or more core networks. The RAN covers a geographical area which is divided into service areas or cell areas, with each service area or cell area being served by a radio node such as a radio access node e.g., a Wi-Fi access point (AP) or a base station (BS), which in some networks may also be denoted, for example, a “NodeB” or “eNodeB”. The area or cell area is a geographical area where radio coverage is provided by the radio node. The radio node communicates over an air interface operating on radio frequencies with wireless communication devices within range of the radio node.

Specifications for the Evolved Packet System (EPS), also known as Fourth Generation (4G) network, have been completed within the 3GPP and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as a radio access network of a Long Term Evolution (LTE) network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a 3GPP radio access network wherein the radio nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of an RNC are distributed between the radio nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio nodes, this interface being denoted the X2 interface.

The ongoing 3GPP Rel-13 study item “Licensed-Assisted Access” (LAA) intends to allow LTE equipment to also operate in the unlicensed 5 GHz radio spectrum. The unlicensed 5 GHz spectrum is used as a complement to the licensed spectrum. Accordingly, wireless communication devices connect in the licensed spectrum, via a primary cell or PCell, and use carrier aggregation to benefit from additional transmission capacity in the unlicensed spectrum, via a secondary cell or SCell. To reduce the changes required for aggregating licensed and unlicensed spectrum, the LTE frame timing in the primary cell is simultaneously used in the secondary cell.

Regulatory requirements, however, may not permit transmissions in the unlicensed spectrum without prior channel sensing. Since the unlicensed spectrum must be shared with other radios of similar or dissimilar wireless technologies, a so called listen-before-talk (LBT) method needs to be applied. LBT involves sensing the medium for a pre-defined minimum amount of time and backing off if the channel is busy. Today, the unlicensed 5 GHz spectrum is mainly used by equipment implementing the IEEE 802.11 Wireless Local Area Network (WLAN) standard. This standard is known under its marketing brand “Wi-Fi.”

Due to the LBT procedure, the first slot in which the LAA SCell or LAA UE is permitted to transmit cannot be predicted in advance. This makes it difficult to pre-compute the data payload since several parameters are currently dependent on the slot number in which data is transmitted.

Long Term Evolution (LTE)

LTE uses Orthogonal Frequency-Division Multiplexing (OFDM) in the downlink and Discrete Fourier Transform (DFT)-spread OFDM, also referred to as single-carrier (SC)—Frequency Division Multiple Access (FDMA), in the uplink. The basic LTE downlink physical resource can thus be seen as a time-frequency grid as illustrated inFIG. 1, where each resource element corresponds to one OFDM subcarrier during one OFDM symbol interval. The uplink subframe has the same subcarrier spacing as the downlink subframe and the same number of SC-FDMA symbols in the time domain as number of OFDM symbols in the downlink subframe.

In the time domain, LTE downlink transmissions are organized into radio frames of 10 ms, each radio frame consisting of ten equally-sized subframes of length Tsubframe=1 ms as shown inFIG. 2. Each subframe comprises two slots of duration 0.5 ms each, and the slot numbering within a frame ranges from 0 to 19. For normal cyclic prefix, one subframe consists of 14 OFDM symbols. The duration of each symbol is approximately 71.4 ρs.

Furthermore, the resource allocation in LTE is typically described in terms of resource blocks, where a resource block corresponds to one slot (0.5 ms) in the time domain and 12 contiguous subcarriers in the frequency domain. A pair of two adjacent resource blocks in time direction (1.0 ms) is known as a resource block pair. Resource blocks are numbered in the frequency domain, starting with 0 from one end of the system bandwidth.

Downlink transmissions are dynamically scheduled, i.e., in each subframe the base station transmits control information about which terminals data is transmitted to and upon which resource blocks the data is transmitted, in the current downlink subframe. This control signalling is typically transmitted in the first 1, 2, 3 or 4 OFDM symbols in each subframe and the number n=1, 2, 3 or 4 is known as the Control Format Indicator (CFI). The downlink subframe also contains common reference symbols, which are known to the receiver and used for coherent demodulation of e.g. the control information. A downlink system with CFI=3 OFDM symbols as control is illustrated inFIG. 3.

From LTE Rel-11 onwards, above described resource assignments can also be scheduled on the enhanced Physical Downlink Control Channel (EPDCCH). For Rel-8 to Rel-10 only Physical Downlink Control Channel (PDCCH) is available.

The reference symbols shown inFIG. 3are the cell specific reference symbols (CRS) that are used to support multiple functions including fine time and frequency synchronization and channel estimation for certain transmission modes.

The generation of the baseband transmit signal on the physical shared channels for either the downlink (DL) or uplink (UL) generally involve scrambling, modulation mapping, layer mapping, precoding, and RE mapping. The specific baseband chain for the UL Physical Uplink Shared Channel (PUSCH) is shown inFIG. 4as an example. For PUSCH scrambling, the initialization of the scrambling sequence generator at the start of each subframe is a function of the current slot number ns. This is also true for Physical Downlink Shared Channel (PDSCH) scrambling on the DL.

Carrier Aggregation

The LTE Rel-10 standard supports bandwidths larger than 20 MHz. One important requirement on LTE Rel-10 is to assure backward compatibility with LTE Rel-8. This should also include spectrum compatibility. That would imply that an LTE Rel-10 carrier, wider than 20 MHz, should appear as a number of LTE carriers to an LTE Rel-8 wireless communication device. Each such carrier can be referred to as a Component Carrier (CC). In particular for early LTE Rel-10 deployments it can be expected that there will be a smaller number of LTE Rel-10-capable wireless communication devices compared to many LTE legacy wireless communication devices. Therefore, it is necessary to assure an efficient use of a wide carrier also for legacy wireless communication devices, i.e. that it is possible to implement carriers where legacy wireless communication devices can be scheduled in all parts of the wideband LTE Rel-10 carrier. The straightforward way to obtain this would be by means of Carrier Aggregation (CA). CA implies that an LTE Rel-10 wireless communication device can receive multiple CC, where the CC have, or at least have the possibility to have, the same structure as a Rel-8 carrier. CA is illustrated inFIG. 5. A CA-capable wireless communication device is assigned a primary cell (PCell) which is always activated, and one or more secondary cells (SCells) which may be activated or deactivated dynamically.

The number of aggregated CC as well as the bandwidth of the individual CC may be different for uplink and downlink. A symmetric configuration refers to the case where the number of CCs in downlink and uplink is the same whereas an asymmetric configuration refers to the case when the number of CCs in downlink and uplink is different. It is important to note that the number of CCs configured in a cell may be different from the number of CCs seen by a wireless communication device: A wireless communication device may for example support more downlink CCs than uplink CCs, even though the cell is configured with the same number of uplink and downlink CCs.

In addition, a key feature of carrier aggregation is the ability to perform cross-carrier scheduling. This mechanism allows a (E)PDCCH on one CC to schedule data transmissions on another CC by means of a 3-bit Carrier Indicator Field (CIF) inserted at the beginning of the (E)PDCCH messages. For data transmissions on a given CC, a wireless communication device expects to receive scheduling messages on the (E)PDCCH on just one CC—either the same CC, or a different CC via cross-carrier scheduling; this mapping from (E)PDCCH to PDSCH is also configured semi-statically. Licensed-assisted access (LAA) to unlicensed spectrum using LTE

Up to now, the spectrum used by LTE is dedicated to LTE. This has the advantage that LTE system does not need to care about the coexistence issue and the spectrum efficiency can be maximized. However, the spectrum allocated to LTE is limited and cannot meet the ever increasing demand for larger throughput from applications/services. Therefore, a new study item has been initiated in 3GPP on extending LTE to exploit unlicensed spectrum in addition to licensed spectrum. Unlicensed spectrum can, by definition, be simultaneously used by multiple different technologies. Therefore, LTE needs to consider the coexistence issue with other systems such as IEEE 802.11 (Wi-Fi). Operating LTE in the same manner in unlicensed spectrum as in licensed spectrum can seriously degrade the performance of Wi-Fi as Wi-Fi will not transmit once it detects that the channel is occupied.

Furthermore, one way to utilize the unlicensed spectrum reliably is to transmit essential control signals and channels on a licensed carrier. That is, as shown inFIG. 6, a UE is connected to a PCell in the licensed band and one or more SCells in the unlicensed band. A secondary cell in the unlicensed spectrum is herein denoted as licensed-assisted access secondary cell (LAA SCell).

Hybrid Automatic Repeat Request (HARQ) is a mechanism used in LTE to handle retransmission of missing or erroneous transmitted packets. The HARQ procedure consists in providing feedback, such as Acknowledgement (ACK) and Non-Acknowledgement (NACK), to the transmitter on a transport block basis, thereby offering the possibility to successfully decode a transport block very quickly. The probability to eventually decode with success a given packet is enforced by the soft combining technique that enforces the HARQ operation. In particular, a receiver implementing the soft combining scheme stores the erroneously received packet and later combines it with the retransmitted replicas of that packet requested by the HARQ feedback. Such replicas contain the same data as the original transport block but a different set of coded bits obtained with different redundancy versions, i.e. by using a different puncturing pattern of the code.

In legacy LTE, the uplink HARQ feedback, such as ACK and NACK, is conveyed by a Physical Hybrid-ARQ Indicator Channel (PHICH) that is transmitted by the radio node upon detection of an uplink transmission on the Physical Uplink Shared Channel (PUSCH) from the wireless communication device.

In legacy LTE, the downlink HARQ feedbacks, such as ACK and NACK, are conveyed by the Physical Uplink Control Channel (PUCCH). It is transmitted by the wireless communication device upon detection of a downlink transmission on the Physical Downlink Shared Channel (PDSCH) by the radio node. The wireless communication device determines to retransmit previous data when NACK is received or if no feedback is received.

SUMMARY

An object of embodiments herein is to provide a mechanism that improves the performance of the wireless communication network in a more efficient manner. One or more embodiments herein include methods, apparatus, systems, and computer programs as described in the accompanying claims.

According to an aspect the object is achieved by a method implemented by a wireless communication device. The wireless communication device transmits data to a radio node of a wireless communication network. The wireless communication device also monitors for a positive acknowledgement or a negative acknowledgement of the data from the radio node. When said monitoring indicates reception of a negative acknowledgement of the data, the wireless communication device retransmits the data to the radio node. When said monitoring indicates reception of a positive acknowledgement of the data, the wireless communication device refrains from retransmitting the data to the radio node. When said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, the wireless communication device also refrains from retransmitting the data to the radio node.

According to another aspect the object is achieved by a method implemented by a network node in a wireless communication network. The network node transmits signalling to a wireless communication device, which signalling indicates that the wireless communication device is to refrain from retransmitting data when the wireless communication device receives neither positive acknowledgement nor negative acknowledgement for that data from a radio node.

According to yet another aspect the object is achieved by providing a wireless communication device configured to transmit data to a radio node of a wireless communication network. The wireless communication device is configured to monitor for a positive acknowledgement or a negative acknowledgement of the data from the radio node. When reception of a negative acknowledgement of the data is indicated in the monitoring, the wireless communication device is configured to retransmit the data to the radio node. When reception of a positive acknowledgement of the data is indicated in the monitoring, the wireless communication device is configured to refrain from retransmitting the data to the radio node. When neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data is indicated in the monitoring, the wireless communication device is configured to also refrain from retransmitting the data to the radio node.

According to still another aspect the object is achieved by providing a network node for a wireless communication network. The network node is configured to transmit signalling to a wireless communication device, which signalling indicates that the wireless communication device is to refrain from retransmitting data when the wireless communication device receives neither positive acknowledgement nor negative acknowledgement for that data from a radio node.

It is furthermore provided herein a computer program comprising instructions, which, when executed on at least one processor, cause the at least one processor to carry out any of the methods above, as performed by the network node or the wireless communication device. It is additionally provided herein a carrier containing the computer program, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

Thus, according to embodiments herein, the wireless communication device assumes that absence of feedback, e.g. HARQ feedback, is the same thing as that an ACK, e.g. HARQ ACK, has been received. Either all the time or only, according to some embodiments, given that one or more conditions are fulfilled such as only on LAA carriers, given that the network has configured the wireless communication device to do so, etc.

An advantage of this solution is that a wireless communication device will not perform retransmissions which the network has not ordered, hence it is avoided that the wireless communication device performs transmissions which will collide with other transmissions and create interference whereby the performance of the wireless communication network may be improved in a more efficient manner.

DETAILED DESCRIPTION

Embodiments herein are related to communication in licensed and unlicensed bands, such as LTE, Wireless Local Area Network (WLAN) or similar. In typical deployments of WLANs, carrier sense multiple access with collision avoidance (CSMA/CA) is used for medium access. This means that the channel is sensed to perform a clear channel assessment (CCA), and a transmission is initiated only if the channel is declared as Idle. In case the channel is declared as Busy, the transmission is essentially deferred until a later time when the channel is deemed to be Idle. When the range of several Access Points (AP) using the same frequency overlap, this means that all transmissions related to one AP might be deferred in case a transmission on the same frequency to or from another AP which is within range can be detected. Effectively, this means that if several APs are within range, they will have to share the channel in time, and the throughput for the individual APs may be severely degraded. A general illustration of the listen before talk (LBT) mechanism is shown inFIG. 7. Action1. The transmitter performs a CCA using energy detection. The transmitter detects no traffic on the channel. Action2. The transmitter occupies the channel and starts data transmission. Furthermore, the transmitter may send Control (Ctrl) signals without (w/o) CCA check denoted as action5. Action3. The transmitter remains idle and starts a CCA in the end of the idle period. Traffic is detected on the channel and the channel is busy. Action4. Thus, no transmission is allowed on the channel as the channel is busy and in the end of the prohibited time the transmitter starts a CCA using energy detection. The transmitter detects no traffic on the channel and the transmitter occupies the channel and starts data transmission.

To operate in e.g. unlicensed bands one needs to obey certain rules. One such rule is that a transmitter, such as a radio node or a wireless communication device, needs to listen on the carrier before starting to transmit. If the medium is free the transmitter can transmit while if the medium is busy, e.g. some other node is transmitting, the transmitter needs to suppress the transmission and the transmitter can try again at a later time. This is referred to as Listen Before Talk (LBT).

Due to LBT a transmission in an unlicensed band may be delayed until a later time when the medium is free. And in case there is no coordination between the transmitting nodes, which often is the case, the delay may appear random.

Unlike current LTE procedures, in LAA both uplink and downlink scheduled transmissions in any physical channels can be aborted before the scheduled transmission actually occurs. For example, the Listen Before Talk (LBT) entails the sensing of the wireless medium by the transmitter in order to detect the presence of other nodes in the surroundings that are currently transmitting and that can potentially disturb. If the medium was identified as busy by the LBT procedure, the transmission is aborted.

In current LTE systems, if an HARQ feedback on PHICH is aborted by the radio node due to busy channel, detected in e.g. an LBT procedure, the wireless communication device will interpret the expected feedback as absent or “discontinuous transmission (DTX)” since no transmission was actually detected over the air. According to current LTE operation if ACK is not detected, the wireless communication device will consider that a NACK has been received and act accordingly. This means that in case of DTX, i.e. no ACK detected, the wireless communication device considers that it has received an NACK. Thus, the wireless communication device will proceed with retransmitting the transport block at subframe12, as shown inFIG. 8.

As part of developing embodiments herein a problem has been identified. The problem with the aforementioned behaviour is that if the radio node intended to send an ACK, it is likely that physical resources (PRB) which the wireless communication device will use for the retransmission has been reallocated by the radio node to some other wireless communication device that will also transmit at subframe12, thus creating interference in the subframe.

While the wireless communication device may already today, without LAA, miss to receive HARQ feedback, the frequency in missing HARQ feedback would be much higher in case of LAA due to the LBT mechanism, seeFIG. 8. Hence it is even more harmful in unlicensed bands, i.e. on LAA carriers. In fact, PHICH in LTE undergoes relatively robust channel coding, e.g. Binary Phase Shift Keying (BPSK) modulation is used, that should prevent from frequent DTX, and also ACK/NACK misinterpretation, at the wireless communication device side. Instead, when the PHICH is transmitted over the unlicensed spectrum, the probability that LBT identifies the transmission medium as busy, thus inducing the PHICH transmission to be aborted, can be relatively high especially in case many (or highly loaded) systems and nodes are using the same spectrum.

Embodiments herein relate to communication networks in general.FIG. 9ais a schematic overview depicting a wireless communication network1. The wireless communication network1comprises one or more RANs and one or more CNs. The communication network1may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced. 5G, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations.

In the wireless communication network1, wireless devices e.g. a wireless communication device10such as a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and/or a wireless terminal, communicate via one or more Access Networks (AN), e.g. RAN, to one or more core networks (CN). It should be understood by those skilled in the art that “wireless communication device” is a non-limiting term which means any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablet or even a base station communicating with wireless communication devices within a cell.

The wireless communication network1comprises a radio node12providing radio coverage over a geographical area, a first service area11, according to a first radio access technology (RAT), such as LTE, WI-Fi or similar. The radio node12may be a radio access network node such as an access point e.g. a WLAN access point or an Access Point Station (AP STA), a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNodeB), a base transceiver station, Access Point Base Station, base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of serving a wireless communication device within the service area served by the radio node12depending e.g. on the first radio access technology and terminology used. The wireless communication network1further comprises a controller node16such as an access controller or radio network controller, base station controller or similar. The radio node12and the controller node16are defined as a network node15herein. Embodiments herein relate to behavior of the wireless communication device10in case absence of feedback, e.g. HARQ feedback.

In embodiments herein the wireless communication device10will consider absence of HARQ feedback as ACK, i.e. if the wireless communication device10does not detect any HARQ feedback the wireless communication device10interprets this situation as if the wireless communication device10has received an ACK for that HARQ procedure or data transmission. This is exemplified inFIG. 9b. In subframe0, the radio node12transmits an initial grant. The wireless communication device10receives the grant and transmits an UL transmission (TX) e.g. Radio Link Control Protocol Data Unit (RLC PDU) in subframe4as granted. The radio node12receives the UL transmission but the channel is busy, sensed by e.g. a LBT procedure, and the radio node12is not allowed to transmit on the channel, i.e. the HARQ feedback is blocked. In this situation, the wireless communication device10is according to embodiments herein configured to assume that absence of HARQ feedback is considered as an ACK.

When the wireless communication device10considers that it has received an ACK, the wireless communication device10may suspend the associated HARQ procedure and refrain from sending any retransmissions. This can be seen when comparingFIG. 9bwithFIG. 8; inFIG. 9bthe wireless communication device10will not perform a retransmission while inFIG. 8the wireless communication device10performs retransmission. The wireless communication device10will not resume the HARQ process until that it has received an NACK from the network or received a grant for uplink transmissions.

If the wireless communication device10considers the absence of HARQ feedback as ACK, the following two scenarios may occur:The radio node12intended to send an ACK but the transmission with the ACK was aborted due to busy medium. In this case, the wireless communication device will wait for further instruction from network, NACK or a new transmission grant.The radio node12intended to send a NACK but the transmission with the NACK was aborted due to busy medium. In this case, the radio node12wanted the wireless communication device10to perform a retransmission, but since the radio node12aborted the NACK transmission, the radio node12will at a later time send the NACK and/or a PDCCH command with a new data indicator (NDI) not toggled and redundancy version indicator (RVI) stepped to indicate to the wireless communication device10a different puncturing pattern.

The method actions performed by the wireless communication device10according to some embodiments will now be described with reference to a flowchart depicted inFIG. 10. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments, but not necessarily in all embodiments, are marked with dashed boxes.

Action1000. The wireless communication device10may receive signalling from the network node15, e.g. the radio node12or the core network node16, indicating that the wireless communication device10is to refrain from retransmitting data when neither positive acknowledgement nor negative acknowledgement is received for that data. The data may in one example be data transmitted by the wireless communication device10to the radio node12. The network node15may configure the wireless communication device10to apply one behaviour on non-LAA carriers or licensed carriers but another behaviour for LAA carriers or unlicensed carriers. The behavior on an LAA carrier may for example be to refrain from retransmitting the data when neither positive acknowledgement nor negative acknowledgement is received for the transmission of that data on the LAA carrier to the radio node12, whereas the behavior on a non-LAA carrier may in this example be to retransmit the data when neither positive acknowledgement nor negative acknowledgement is received for the transmission of that data on the non-LAA carrier to the radio node12.

Action1001. The wireless communication device10transmits data to the radio node12of the wireless communication network1. The wireless communication device10may transmit the data to the radio node over unlicensed spectrum or over an asynchronous protocol. The wireless communication device10may be configured to perform a Listen Before Talk procedure before transmitting data to the radio node12. Hence, the wireless communication device10may listen on a carrier to determine that the carrier is free for transmission before transmitting data on the carrier.

Action1002. The wireless communication device10monitors for a positive acknowledgement or a negative acknowledgement of the data from the radio node12. The positive acknowledgement may be an ACK or a PDCCH command with a new data indicator (NDI) toggled and the negative acknowledgement may be a NACK or a PDCCH command with a new data indicator (NDI) not toggled. The PDCCH command may comprise an UL grant. In this way whether the wireless device10should retransmit or not may be controlled by ACK/NACK or UL grant on PDCCH indicating positive acknowledgement or negative acknowledgement, i.e. if NDI flag is toggled in PDCCH new data will be transmitted, whereas if it is not toggled retransmission will happen. Toggle means that a “switch” indicates a new transmission. So if the network previously indicated 1 but then indicates 0, that means that the network has “toggled” the indicator and the wireless communication device shall perform a new transmission. If the network then indicates 0 again that means that the wireless communication device shall perform a retransmission. The wireless communication device will keep on retransmitting until that the network toggles to 1 upon which the wireless communication device will perform a new transmission. The positive or negative acknowledgement of the data may in some embodiments be conveyed on a Physical Hybrid Automatic Repeat reQuest Indicator Channel (PHICH). For example, the positive or negative acknowledgement of the data may in some embodiments be received by the wireless communication device10on the PHICH as a result of the monitoring. In other embodiments it may be conveyed on the Physical Downlink Control Channel (PDCCH), e.g. in form of a PDCCH command or an UL grant as explained above. For example, the positive or negative acknowledgement of the data may then be received by the wireless communication device10on the PDCCH as a result of the monitoring.

The radio node12may be configured to perform a Listen Before Talk (LBT) procedure when a carrier, upon which the positive acknowledgement or the negative acknowledgement is to be transmitted, must be occupied by the radio node12before transmitting said positive acknowledgement or said negative acknowledgement of the transmitted data to the wireless communication device10. When the LBT procedure identifies the transmission medium, i.e. a carrier upon which the positive acknowledgement or the negative acknowledgement is to be transmitted, as busy, the transmission of the positive acknowledgement or the negative acknowledgement may be aborted, as described above.

Action1003. The wireless communication device10retransmits the data to the radio node12when said monitoring indicates reception of a negative acknowledgement of the data. The wireless communication device10may in some embodiments retransmit the data a certain maximum number of retransmissions before the wireless communication device10considers it failed and hence would not perform any more retransmissions.

Action1004. The wireless communication device10refrains from retransmitting the data to the radio node12when said monitoring indicates reception of a positive acknowledgement of the data. As stated above the wireless communication device10may receive an ACK or a PDCCH with NDI toggled indicating that previous HARQ loop was successful and new data can be transmitted.

Action1005. In addition to the refraining of Action1004, the wireless communication device10secondly, further, additionally, refrains from retransmitting the data to the radio node12when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data. In this additional refraining action, the wireless communication device may additionally refrain from retransmitting the data to the radio node12when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data until reception of a negative acknowledgement of the data or reception of a grant for transmitting different data. In other words, the additional refraining from retransmitting the data said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data to the radio node12may be performed until a negative acknowledgement of the data or a grant for transmitting different data is received by the wireless communication device10. The negative acknowledgement may comprise a NACK or a grant for retransmission, i.e. an UL grant where the NDI-flag has not been toggled. The wireless communication device may additionally refrain from retransmitting the data to the radio node12when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data when one or more conditions are met. Stated differently, the additional refraining from retransmitting the data to the radio node12may be performed when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data and, in addition, one or more conditions are met.

For example, the one or more conditions may be one or more of the following: whether or not the data was transmitted over unlicensed spectrum e.g. whether or not LBT is applied on a specific carrier or on any carrier; whether or not the data was transmitted over a first type of radio access; whether the data was transmitted over a first type of radio access or over a second type of access, the second type of access being different from the first type of access; whether the data is of a first type or a second type, e.g. the first type of data may have a lower quality of service (QoS) classification or be less delay sensitive than the second type of data.

The one or more conditions may in example embodiments be met, such that the refraining of Action1005is performed, when the data was transmitted over unlicensed spectrum. Alternatively or additionally, the one or more conditions may be met, such that the refraining of Action1005is performed, when the data was transmitted over a first type of radio access, whereas the one or more conditions are not met when the data was transmitted over the second type of radio access, such that the refraining of Action1005is not performed, meaning that when the data was transmitted over the second type of radio access and the monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, retransmission of the data is made. Furthermore, in addition or alternatively, the one or more conditions may be met, such that the refraining of Action1005is performed, when the data is of the first type, whereas the one or more conditions are not met when the data is of the second type, such that the refraining from retransmitting the data to the radio node12of Action1005is not performed when the data is of the second type different than the first type. The second type of data may thus be retransmitted to the radio node12when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data. The data of the second type is different than data of the first type. Thus, the network node15may configure the wireless communication device10for which QoS classes the wireless communication device10should additionally refrain from retransmitting the data when neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data is indicated in said monitoring.

The wireless communication device10may perform the additional refraining from retransmitting the data to the radio node12of Action1005when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data in accordance with the received signalling in Action1000.

As stated above, in some embodiments, the wireless communication device10may interpret absence of HARQ feedback as ACK or NACK depending on whether one or more conditions are met. Some further illustrations on example conditions are provided below.

Condition on Carrier Type

In one embodiment the wireless communication device10may apply a condition on which carrier type the HARQ feedback was expected to be received on.

One possibility is that the wireless communication device10applies a first behavior with regards to how to handle absence of HARQ feedback when operating an LAA carrier, or other type of carrier carried on unlicensed spectrum, and applies a second behavior with regards to how to handle absence of HARQ feedback when operating other carriers, e.g. non-LAA carriers.

The first behavior with regards to how to handle absence of HARQ feedback can be that the wireless communication device10considers absence of HARQ feedback as ACK. The second behavior could be that the wireless communication device10considers absence of HARQ feedback as NACK and retransmits the data. It could also be so that the second wireless communication device behavior is undefined. The first behavior thus corresponds to the refraining described in Action1005above.

The benefit of this embodiment is that in legacy spectrum it might still be desired to interpret DTX, i.e. absence of HARQ feedback, as NACK since this procedure is more aggressive in terms of how quickly the wireless communication device10will retransmit the data and avoids the inherent delay induced by considering absence of HARQ feedback as ACK. In fact, if the radio node12had scheduled a NACK on PHICH, the wireless communication device10can retransmit without waiting for further commands via PDCCH by the network. This might be convenient especially for delay-sensitive traffic.

On the other hand, the unlicensed spectrum is already in its nature affected by unpredictable sources of interference thus it is important to prevent any additional disturbance/interference that the legacy approach, i.e. interpreting absence of HARQ feedback as NACK, would imply. Moreover, the unlicensed band is not typically configured by the operator to carry delay-sensitive information thus the suggested procedure is not expected to harm the unlicensed spectrum traffic.

Condition on Traffic Type

In yet another embodiment, the wireless communication device10considers the absence of HARQ feedback as ACK or NACK on the basis of the type of traffic that is setup. Such decision can be for instance taken on the basis of the Quality Class Indicator (QCI) associated with the traffic. If a traffic is delay-sensitive, e.g. real time gaming, Voice over IP (VoIP) calls etc. then NACK is assumed in case of absence of HARQ feedback. Otherwise, for other type of bearers, e.g. File Transfer Protocol (FTP) applications, ACK is assumed in case of absence of HARQ feedback.

The method actions implemented by the network node15, such as the radio node12or the core network node16, in the wireless communication network1according to some embodiments will now be described with reference to a flowchart depicted inFIG. 11. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments, but not necessarily in all embodiments, are marked with dashed boxes. The network node15, e.g when implemented as the radio node12, may be configured to perform an LBT procedure before transmitting data and/or feedback to the wireless communication device10.FIG. 11relates to the signalling mentioned above in Action1000above where the wireless communication device10receives the signalling from the network node15.

Action1101. The network node15may determine that the wireless communication device10is to refrain from retransmitting data when the wireless communication device receives neither positive acknowledgement nor negative acknowledgement for the transmission of that data. The data may be data transmitted by the wireless device10to the radio node12in the wireless communication network1. The determination may be performed by the network node15based on statistics accumulated within the wireless communication network1. e.g. by the network node15. The determination may be performed by the network node15based on interference conditions at the wireless communication device10, the network node15, and/or the radio node12to which the wireless communication device10transmits the data. The positive or negative acknowledgement of the data may in some embodiments be conveyed on a Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH). In other embodiments it may be conveyed on the Physical Downlink Control Channel (PDCCH), e.g. in form of a PDCCH command or an UL grant as explained above.

Action1102. The network node15may generate signalling that indicates that the wireless communication device10is to refrain from retransmitting data when the wireless communication device10receives neither positive acknowledgement nor negative acknowledgement for that data. The feedback, i.e. the positive acknowledgement or negative acknowledgement for the data may be expected by the wireless communication device10from the radio node12, to which the data was transmitted.

Action1103. The network node15transmits the signalling generated in Action1102to the wireless communication device10, which signalling indicates that the wireless communication device10is to refrain from retransmitting data when the wireless communication device10receives neither positive acknowledgement nor negative acknowledgement for that data. The feedback, i.e. the positive acknowledgement or negative acknowledgement for the data may be expected by the wireless communication device10from the radio node12.

The transmitting of Action1103may in some embodiments be performed by one node, e.g. the radio node12, while the determination of Action1101is performed by another node in the wireless communication network1, e.g. core network node16or another radio node than the radio node12. For example, in e.g. Dual Connectivity and/or Carrier Aggregation the wireless communication device10may be connected to several radio nodes, i.e. there may be one radio node configuring the wireless communication device10and hence do the determining of Action1101and another radio node which makes the transmission of action1103and possibly performs an LBT procedure. It is also possible that the generating of Action1102is performed by another node than the node performing the transmission of Action1103. For example, the generating of Action1102may be performed by the core network node16while the transmission of Action1103is performed by the radio node12.

Condition on Network Indication

As stated above, whether the wireless communication device10interprets absence of HARQ feedback as NACK or ACK may be configured by the network node15. The network node15, such as a radio node12, may configure the wireless communication device10by using e.g. Radio Resource Control (RRC) signalling, Medium Access Control (MAC) signalling, or some other type of indication.

This may allow the network node15to adjust the wireless communication device behavior based on the preference of the network. For example, if the network wants that the wireless communication device10to quickly perform a retransmission the network node15may configure the wireless communication device10to interpret absence of HARQ feedback as NACK, which triggers a retransmission. And if the network wants the wireless communication device10to avoid performing unexpected retransmissions the network node15may configure the wireless communication device10to interpret absence of HARQ feedback as ACK.

Moreover, the decision by the network, e.g. by the network node15may also be taken on some statics accumulated by e.g. the radio node12over the time, e.g. in case of lack of stronger interferers in the surrounding, the radio node12may prefer to adopt the solution in which absence of HARQ feedbacks is interpreted by the wireless communication device10as ACK. However this solution would imply sending such decision via RRC signalling.

Apparatus

With the above modifications and variations in mind, a wireless communication device is configured, e.g., via functional means or units, to implement any processing described above.

FIG. 12is a block diagram depicting the wireless communication device10. The wireless communication device10may comprise processing circuit1201and communication Interface1202with a transmitter1203and a receiver1204.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to transmit data to the radio node12of the wireless communication network1.

The wireless communication device10, and/or the processing circuit1201, may be configured to monitor for a positive acknowledgement or a negative acknowledgement of the data from the radio node12.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when reception of a negative acknowledgement of the data is indicated in the monitoring, retransmit the data to the radio node12.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when reception of a positive acknowledgement of the data is indicated in the monitoring, refrain from retransmitting the data to the radio node12.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data is indicated in the monitoring, additionally refrain from retransmitting the data to the radio node12.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to transmit the data to the radio node12over unlicensed spectrum or over an asynchronous protocol.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when the monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, additionally refrain from retransmitting the data to the radio node12until reception of a negative acknowledgement of the data or reception of a grant for transmitting different data at the wireless communication device10. In other words, when neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data is indicated as a result of the monitoring, the wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to refrain from retransmitting the data to the radio node12until a negative acknowledgement of the data or a grant for transmitting different data is received at the wireless communication device10.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when the monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, additionally refrain from retransmitting the data to the radio node12when one or more conditions are met.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when the monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, additionally refrain from retransmitting the data to the radio node12when the data was transmitted over unlicensed spectrum.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when the monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, additionally refrain from retransmitting the data to the radio node12when the data was transmitted over a first type of radio access.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to, when the monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, additionally refrain from retransmitting the data to the radio node12when the data is of a first type. The first type of data may be of a lower quality of service classification or may be less delay sensitive than a second type of data and the wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured not to refrain from retransmitting the data to the radio node12when the data is of the second type different than the first type. In other words, the wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may when the data is of the second type be configured to retransmit the data to the radio node12.

The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may be configured to receive signalling from the network node15, which may in some embodiments be the radio node12, in other embodiments e.g. the core network node16or another radio node, indicating that the wireless communication device is to refrain from retransmitting data when neither positive acknowledgement nor negative acknowledgement is received for the transmission of that data to the radio node12. The wireless communication device10, the processing circuit1201, the communication interface1202and/or the transmitter1203may further be configured to, when the monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data, additionally refrain from retransmitting the data to the radio node12in accordance with the received signalling.

The radio node12may be configured to perform a Listen Before Talk procedure before transmitting data to the wireless communication device10. For example, the radio node12may be configured to perform the Listen Before Talk procedure when a carrier upon which the positive acknowledgement or the negative acknowledgement is to be transmitted must be occupied by the radio node12before transmitting said positive acknowledgement or said negative acknowledgement of the transmitted data to the wireless communication device10. The positive or negative acknowledgement of the data may in some embodiments be conveyed by the PHICH. In other embodiments it may be conveyed on the Physical Downlink Control Channel (PDCCH), e.g. in form of a PDCCH command or an UL grant as explained above.

In at least some embodiments, the wireless communication device10comprises one or more processing circuits configured to implement the above processing, such as by implementing functional means or units. In one embodiment, for example, the processing circuit(s) implement functional means or units as respective circuits. The circuits in this regard may comprise circuits dedicated to performing certain functional processing and/or one or more microprocessors in conjunction with a memory1205. In embodiments that employ memory, which may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., the memory stores program code that, when executed by the one or more processing circuits dedicated to performing certain functional processing and/or one or more microprocessors, carries out the techniques described herein.

In one or more embodiments, the wireless communication device10also comprises one or more communication interfaces. The one or more communication interfaces include various components for sending and receiving data and control signals. More particularly, the interface(s) include the transmitter1203that is configured to use known signal processing techniques, typically according to one or more standards, and is configured to condition a signal for transmission (e.g., over the air via one or more antennas). Similarly, the interface(s) include the receiver1204that is configured to convert signals received (e.g., via the antenna(s)) into digital samples for processing by the one or more processing circuits.

Also, a network node is configured, e.g., via functional means or units, to implement any processing described above.

FIG. 13is a block diagram depicting the network node15in the wireless communication network1. The network node15may comprise processing circuit1301and a communication Interface1302with a transmitter1303and a receiver1304.

The network node15, the processing circuit1301, the communication interface1302and/or the transmitter1303may be configured to transmit signalling to the wireless communication device10, which signalling indicates that the wireless communication device is to refrain from retransmitting data when the wireless communication device10receives neither positive acknowledgement nor negative acknowledgement for that data from a radio node12.

The network node15and/or the processing circuit1301may be configured to generate the signalling that indicates that the wireless communication device10is to refrain from retransmitting data when the wireless communication device10receives neither positive acknowledgement nor negative acknowledgement for that data from the radio node12.

The network node15may be the radio node12and the radio node12may be configured to perform a Listen Before Talk procedure before transmitting data to the wireless communication device10. For example, the radio node12may be configured to perform the Listen Before Talk procedure when a carrier upon which the positive acknowledgement or the negative acknowledgement is to be transmitted must be occupied by the radio node12before transmitting said positive acknowledgement or said negative acknowledgement of the data to the wireless communication device10.

The network node15and/or the processing circuit1301may be configured to determine that the wireless communication device10is to refrain from retransmitting data when the wireless communication device receives neither positive acknowledgement nor negative acknowledgement for the transmission of that data to the radio node12.

The network node15and/or the processing circuit1301may be configured to perform said determination based on statistics accumulated within the wireless communication network1.

The network node15and/or the processing circuit1301may further be configured to perform said determination based on interference conditions at the wireless communication device, the network node, and/or the radio node to which the wireless communication device10transmits the data.

The positive or negative acknowledgement of the data may in some embodiments be conveyed on a Physical Hybrid Automatic Repeat Request Indicator Channel. In other embodiments it may be conveyed on the Physical Downlink Control Channel (PDCCH), e.g. in form of a PDCCH command or an UL grant as explained above.

In at least some embodiments, the network node15comprises one or more processing circuits configured to implement the above processing, such as by implementing functional means or units. In one embodiment, for example, the processing circuit(s) implement functional means or units as respective circuits. The circuits in this regard may comprise circuits dedicated to performing certain functional processing and/or one or more microprocessors in conjunction with a memory1305. In embodiments that employ memory, which may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., the memory stores program code that, when executed by the one or more processing circuits dedicated to performing certain functional processing and/or one or more microprocessors, carries out the techniques described herein.

In one or more embodiments, the network node15also comprises one or more communication interfaces. The one or more communication interfaces include various components (not shown) for sending and receiving data and control signals. More particularly, the interface(s) include the transmitter1303that is configured to use known signal processing techniques, typically according to one or more standards, and is configured to condition a signal for transmission (e.g., over the air via one or more antennas). Similarly, the interface(s) include the receiver1304that is configured to convert signals received (e.g., via the antenna(s)) into digital samples for processing by the one or more processing circuits.

Computer Program Embodiments

A computer program1206,1306comprises instructions which, when executed on at least one processor of the network node15or the wireless communication device10, cause node or device to carry out any of the respective processing described above. Embodiments further include a carrier containing such a computer program. This carrier may comprise one of an electronic signal, optical signal, radio signal, or computer readable storage medium1207,1307, such as a disc or similar.

A computer program in this regard may comprise one or more code modules corresponding to the means or units described above.

TERMINOLOGY

In some embodiments the non-limiting term user equipment (UE) is used and it refers to any type of wireless device communicating with a radio network node in a cellular or mobile communication system. Examples of wireless communication devices or UE are target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, PDA, iPAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles etc.

In some embodiments the non-limiting term radio network node or simply network node15is used and it refers to any type of network node serving UE and/or connected to other network node or network element or any radio node from where UE receives signal. Examples of radio network nodes are Node B, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNode B, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS) etc.

Alternatively, several of the functional elements of the processing means discussed may be provided through the use of dedicated hardware, while others are provided with hardware for executing software, in association with the appropriate software or firmware. Thus, the term “processor” or “controller” as used herein does not exclusively refer to hardware capable of executing software and may implicitly include, without limitation, digital signal processor (DSP) hardware, read-only memory (ROM) for storing software, random-access memory for storing software and/or program or application data, and non-volatile memory. Other hardware, conventional and/or custom, may also be included. Designers of communications receivers will appreciate the cost, performance, and maintenance trade-offs inherent in these design choices.

It will be appreciated that the foregoing description and the accompanying drawings represent non-limiting examples of the methods and apparatus taught herein. As such, the inventive apparatus and techniques taught herein are not limited by the foregoing description and accompanying drawings. Instead, the embodiments herein are limited only by the following claims and their legal equivalents.