WO2017055186A1

WO2017055186A1 - Transmission of uplink control information in unlicensed spectrum

Info

Publication number: WO2017055186A1
Application number: PCT/EP2016/072700
Authority: WO
Inventors: Timo Erkki Lunttila; Esa Tapani Tiirola; Kari Juhani Hooli
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2015-10-01
Filing date: 2016-09-23
Publication date: 2017-04-06

Abstract

There is provided a method comprising transmission of feedback information associated with received data packets in an uplink transmission opportunity subject to regulations on the execution of a clear channel assessment procedure, wherein the timing for transmission of the feedback information is determined in relation to the downlink transmission opportunity in which the data packets have been received.

Description

Title

TRANSMISSION OF UPLINK CONTROL INFORMATION IN UNLICENSED SPECTRUM Field

The present invention relates to the field of wireless communications. More specifically, the present invention relates to methods, apparatus, systems and computer programs for transmission of uplink control information in unlicensed spectrum.

Background

A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and/or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can typically be divided into cells, and are therefore often referred to as cellular systems.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (UE). A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and/or receive communications on the carrier. The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. An example of attempts to solve the problems associated with the increased demands for capacity is an architecture that is known as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The LTE is being standardized by the 3rd Generation Partnership Project (3GPP). The various development stages of the 3GPP LTE specifications are referred to as releases. Certain releases of 3GPP LTE (e.g., LTE Rel-1 1 , LTE Rel-12, LTE Rel-13) are targeted towards LTE-Advanced (LTE- A). LTE-A is directed towards extending and optimizing the 3GPP LTE radio access technologies.

Wireless communication systems may be licensed to operate in particular spectrum bands. A technology, for example LTE, may operate, in addition to a licensed band, in an unlicensed band. LTE operation in the unlicensed spectrum may be based on the LTE Carrier Aggregation (CA) framework where one or more low power secondary cells (SCells) operate in the unlicensed spectrum and may be either downlink-only or contain both uplink (UL) and downlink (DL), and where the primary cell (PCell) operates in the licensed spectrum and can be either LTE Frequency Division Duplex (FDD) or LTE Time Division Duplex (TDD).

Two proposals for operating in unlicensed spectrum are LTE Licensed-Assisted Access (LAA) and LTE in Unlicensed Spectrum (LTE-U). LTE-LAA and LTE-U may imply that a connection to a licensed band is maintained while using the unlicensed band. Moreover, the licensed and unlicensed bands may be operated together using, e.g., carrier aggregation or dual connectivity. For example, carrier aggregation between a primary cell (PCell) on a licensed band and one or more secondary cells (SCells) on unlicensed band may be applied, and uplink control information of the SCells is communicated in the PCell on licensed spectrum.

In an alternative proposal stand-alone operation using carrier in unlicensed spectrum only may be used. In stand-alone operation at least some of the functions for access to cells on unlicensed spectrum and data transmission in these cells are performed without or with only minimum assistance or signaling support from license-based spectrum. Dual connectivity can be seen as an example of the scenario with minimum assistance or signaling from license-based spectrum. Unlicensed technologies may need to abide by certain rules, e.g. a clear channel assessment procedure, such as Listen-Before-Talk (LBT), in order to provide fair coexistence between LTE and other technologies such as Wi-Fi as well as between LTE operators. In some jurisdictions respective rules may be specified in regulations.

In LTE-LAA, before being permitted to transmit, a user or an access point (such as eNodeB) may, depending on regulatory requirements, need to monitor a given radio frequency, i.e. carrier, for a short period of time to ensure the spectrum is not already occupied by some other transmission. This requirement is referred to as Listen-Before-Talk (LBT). The requirements for LBT vary depending on the geographic region: e.g. in the US such requirements do not exist, whereas in e.g. Europe and Japan the network elements operating on unlicensed bands need to comply with LBT requirements. Moreover, LBT may be needed in order to guarantee co-existence with other unlicensed band usage in order to enable e.g. fair co-existence with Wi-Fi also operating on the same spectrum and/or carriers.

The following relates to stand-alone operation on unlicensed spectrum. Specifically, it relates to the transmission of uplink control information, such as Hybrid Automatic Repeat Request acknowledgement (HARQ-ACK) messages on a carrier in unlicensed spectrum.

In operation on unlicensed carriers, depending on the regulatory rules, a communication device may need to perform a clear channel assessment procedure, such as LBT, prior to UL transmission. However, LBT operation may be omitted in LTE under certain conditions according to specific regulations. The transmission of uplink control information, such as HARQ-ACK messages, may not be subject to LBT (similar to WiFi operation) if the time between a DL transmission and a subsequent UL transmission is less than or equal to a predetermined value. Further, certain signaling rules, such as Short Control Signaling (SCS) rules defined for Europe by ETSI, may allow for the transmission of control or management information without LBT operation, if the duty cycle of the related signaling does not exceed a certain threshold, e.g. 5%, within a specified period of time, for example 50 ms. The aforementioned SCS rules, for example, can be used by compliant communication devices, operating in adaptive mode for respective SCS transmission of management and control frames without sensing the channel for the presence of other signals. The term "adaptive mode" is defined in ETSI as a mechanism by which equipment can adapt to its environment by identifying other transmissions present in a band, and addresses a general requirement for efficient operation of communications systems on unlicensed bands. Further, scheduled UL transmissions may in general be allowed without LBT, if the time between a DL transmission from an access node and a subsequent UL transmission is less than or equal to a predetermined value, and the access node has performed a clear channel assessment procedure, such as LBT, prior to the DL transmission. The total transmission time covering both DL transmission and subsequent UL transmission may be limited to a maximum burst or channel occupancy time. The maximum burst or occupancy time may be specified by a regulator.

A communication system may employ a retransmission mechanism, such as Automatic Repeat Request (ARQ), for handling transmission errors. A receiver in such a system may use an error-detection code, such as a Cyclic Redundancy Check (CRC), to verify whether a data packet was received in error. The receiver may notify the transmitter on a feedback channel of the outcome of the verification by sending an acknowledgement (ACK) if the data packet was correctly received or a non-acknowledgement (NACK) if an error was detected. The transmitter may subsequently transmit a new data packet related to other information bits, in case of an ACK, or retransmit the data packet received in error, in case of a NACK. The retransmission mechanism may be combined with forward error-correction coding (FEC), in which redundancy information is included in the data packet prior to transmission. This redundancy information can be used at the receiver for correcting at least some of the transmission errors, and retransmission of a data packet is only requested in case of uncorrectable errors. Such a combination of FEC and ARQ is referred to as Hybrid Automatic Repeat Request (HARQ). In a HARQ scheme the receiver may not simply discard a data packet with uncorrectable errors, but may combine obtained information with information from one or more retransmissions related to the same information bits. These retransmissions may contain identical copies of the first transmission. In more advanced schemes, such as Incremental Redundancy (IR) HARQ, the first transmission and related retransmissions are not identical. Rather, the various transmissions related to the same information bits may comprise different redundancy versions (RV), and each retransmission makes additional redundancy information available at the receiver. The number of transmissions related to the same information bits may be limited in a communication system by a maximum number of not successful transmissions, and a data packet related to new information bits may be transmitted once the maximum number of not successful transmissions has been reached. A scheduling grant may comprise a New Data Indicator (NDI) notifying a communication device whether the scheduled transmission is destined for a data packet related to new information bits. Further or alternatively, the scheduling grant may comprise an indication of the redundancy version (RV) used or to be used in the transmission. Each data packet, often referred to as transport block, may be transmitted in a communication system within a Transmission Time Interval (TTI), such as a subframe in LTE. At least two transport blocks may be transmitted in parallel in a TTI when spatial multiplexing is employed. Processing of a transport block, its transmission and the processing and transmission of the corresponding HARQ-ACK feedback may take several TTIs. For example, in LTE-FDD such a complete HARQ loop takes eight subframes. Accordingly, eight HARQ processes are needed in a data stream in LTE-FDD for continuous transmission between an access node and a communication device, The HARQ processes are handled in the access nodes and the communication devices in parallel, and each HARQ process controls the transmission of transport blocks and ACK/NACK feedback related to a set of information bits in the data stream.

In a conventional LTE system HARQ-ACK feedback is communicated in UL according to a predefined timing in relation to the transmission time interval in which a transport block has been transmitted in DL. Specifically, HARQ-ACK feedback is transmitted by a communication device in subframe n for a DL transport block intended for the communication device and transmitted/detected on PDSCH (Physical Downlink Shared Channel) in subframe n-k. The minimum value for the HARQ-ACK delay k is four subframes in a conventional LTE system, which allows for sufficient time to receive and decode the DL transport block by a communication device, and for preparing the corresponding HARQ-ACK transmission in UL. In FDD mode, HARQ-ACK delay is fixed in 3GPP specification TS 36.213 to the minimum value of four subframes. In other words, when a transport block intended for a communication device is detected on PDSCH by the communication device in subframe n-4, the corresponding HARQ-ACK message is transmitted in subframe n by the communication device. In TDD mode, the HARQ-ACK delay k depends on the selected UL/DL configuration as well as the subframe number in which the transport block is transmitted on PDSCH. The relationship is given by means of the DL association set index K, shown in Table 1 and specified in 3GPP specification TS 36.213. In other words, when one or more transport blocks on PDSCH intended for a communication device are detected by the communication device within subframe(s) ^{n ~ k} (where ^{k e K} and ^K as specified in Table 1 ), the corresponding HARQ-ACK message is transmitted in subframe n by the communication device.

Table 1 : Downlink association set

Κ : {k₀, k , - - - k_M_ } for LTE-TDD UL-DL Subframe n

Configuration 0 1 2 3 4 5 6 7 8 9

0 - - 6 - 4 - - 6 - 4

1 - - 7, 6 4 - - - 7, 6 4 -

2 - - 8, 7, 4, 6 - - - - 8, 7, 4, 6 - -

3 - - 7, 6, 1 1 6, 5 5, 4 - - - - -

4 - - 12, 8, 7, 1 1 6, 5, 4, 7 - - - - - -

5 - - 13, 12, 9, 8, 7, 5, 4, 1 1 , 6 - - - - - - -

6 - - 7 7 5 - - 7 7 -

As discussed above, HARQ-ACK feedback is transmitted in a conventional LTE system by a communication device in subframe n for a DL transport block intended for the communication device and transmitted on PDSCH in subframe n-k. However, such a predetermined association between DL data transmissions and HARQ-ACK messages is not longer applicable, due to LBT requirements and/or channel availability problems, when HARQ-ACK messages are communicated on unlicensed bands. Therefore, there is a need to provide a new scheme for scheduling UL HACK-ACK messages on unlicensed bands.

Summary

This invention discusses the arrangement of DL data transmissions and corresponding UL HARQ-ACK messages on unlicensed bands under consideration of channel availability problems on unlicensed bands and HARQ-ACK processing delays.

In a first aspect, there is provided a method comprising receiving one or more first data packets wirelessly in a downlink transmission on a frequency band, and causing wireless transmission of first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure, wherein the timing for transmission of the first uplink control information is determined in relation to the downlink transmission. The method may comprise causing wireless transmission of second uplink control information comprising feedback information associated with one or more second received data packets in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure, wherein the timing for transmission of the second uplink control information is determined according to a preconfigured transmission pattern.

The one or more second received data packets may comprise one or more of the first data packets.

The method may comprise causing wireless transmission of user data on an uplink data channel in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure.

The uplink transmission opportunity may be subdivided into one or more transmission time intervals.

The first uplink control information may be transmitted on resources of a first uplink control channel.

The first uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel. The second uplink control information may be transmitted on resources of a second uplink control channel.

Signaling related to the second uplink control channel may stay below a duty cycle threshold for which the rules allow transmission without execution of the clear channel assessment procedure.

The second uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel. Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure.

Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure, if the clear channel assessment procedure was executed prior to downlink transmission. Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure, if the clear channel assessment procedure was executed prior to a downlink transmission, and the time interval covering the downlink transmission and the transmission in the uplink transmission opportunity does not exceed a threshold specified in the rules.

The first uplink control information may be transmitted in the first of the one or more transmission time intervals of the uplink transmission opportunity.

The first uplink control information may be transmitted when feedback information associated with the last of the one or more first data packets gets available for transmission. The first uplink control information may be transmitted in the transmission time interval when feedback information associated with the last of the one or more first data packets gets available for transmission, or in the first transmission time interval after the transmission of user data on the uplink data channel in the uplink transmission opportunity, whichever occurs first,

The second uplink control information may comprise feedback information associated with data packets received in one or more downlink transmission opportunities within a preconfigured time window. The second uplink control information may comprise feedback information for all the data packets in the time window.

The second uplink control information may comprise only feedback information associated with data packets in the time window which has not yet been transmitted.

The method may be carried out by a communication device, wherein the second uplink control information may comprise feedback information for hybrid automatic repeat request and the preconfigured time window may be selected such that it comprises feedback for all hybrid automatic repeat request processes of the communication device.

The first uplink control information and the second uplink control information may be transmitted in the same transmission time interval. The method may comprise receiving an indication of use of first uplink control channel resources in a cell in a transmission time interval. The method may comprise rate matching and/or puncturing and/or resource mapping in processing of the user data for transmission in the transmission time interval according to the received indication for avoiding on the uplink data channel use of resources related to the first uplink control channel. In a second aspect, there is provided an apparatus, said apparatus comprising at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus to receive one or more first data packets wirelessly in a downlink transmission on a frequency band, and cause wireless transmission of first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure, wherein the timing for transmission of the first uplink control information is determined in relation to the downlink transmission. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus to cause wireless transmission of second uplink control information comprising feedback information associated with one or more second received data packets in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure, wherein the timing for transmission of the second uplink control information may be determined according to a preconfigured transmission pattern.

The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus to cause wireless transmission of user data on an uplink data channel in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure.

The uplink transmission opportunity may be subdivided into one or more transmission time intervals. The first uplink control information may be transmitted on resources of a first uplink control channel. The first uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel.

The second uplink control information may be transmitted on resources of a second uplink control channel.

Signaling related to the second uplink control channel may stay below a duty cycle threshold for which the rules allow transmission without execution of the clear channel assessment procedure. The second uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel.

Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure.

Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure, if the clear channel assessment procedure was executed prior to downlink transmission.

Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure, if the clear channel assessment procedure was executed prior to a downlink transmission, and the time interval covering the downlink transmission and the transmission in the uplink transmission opportunity does not exceed a threshold specified in the rules.

The first uplink control information may be transmitted in the first of the one or more transmission time intervals of the uplink transmission opportunity. The first uplink control information may be transmitted when feedback information associated with the last of the one or more first data packets gets available for transmission.

The first uplink control information may be transmitted in the transmission time interval when feedback information associated with the last of the one or more first data packets gets available for transmission, or in the first transmission time interval after the transmission of user data on the uplink data channel in the uplink transmission opportunity, whichever occurs first, The second uplink control information may comprise feedback information associated with data packets received in one or more downlink transmission opportunities within a preconfigured time window.

The second uplink control information may comprise feedback information for all the data packets in the time window.

The second uplink control information may comprise only feedback information associated with data packets in the time window which has not yet been transmitted. The apparatus may be a communication device, wherein the second uplink control information may comprise feedback information for hybrid automatic repeat request and the preconfigured time window may be selected such that it comprises feedback for all hybrid automatic repeat request processes of the communication device. The first uplink control information and the second uplink control information may be transmitted in the same transmission time interval.

The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus to receive an indication of use of first uplink control channel resources in a cell in a transmission time interval.

The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus to perform rate matching and/or puncturing and/or resource mapping in processing of the user data for transmission in the transmission time interval according to the received indication for avoiding on the uplink data channel use of resources related to the first uplink control channel. In a third aspect, there is provided a method comprising causing wireless transmission of one or more first data packets in a downlink transmission on a frequency band, receiving wirelessly from a transmitter first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure at the transmitter, wherein the timing for receiving the first uplink control information is determined in relation to the downlink transmission.

The method may comprise receiving second uplink control information from the transmitter comprising feedback information associated with one or more second received data packets in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure at the transmitter, wherein the timing for receiving of the second uplink control information is determined according to a preconfigured transmission pattern.

The method may comprise receiving user data from the transmitter on an uplink data channel in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure at the transmitter.

The first uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel.

The second uplink control information may be transmitted on resources of a second uplink control channel. Signaling related to the second uplink control channel may stay below a duty cycle threshold for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter. The second uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel. Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter.

Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter, if the clear channel assessment procedure was executed prior to downlink transmission.

The uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter, if the clear channel assessment procedure was executed prior to a downlink transmission, and the time interval covering the downlink transmission and the transmission in the uplink transmission opportunity does not exceed a threshold specified in the rules.

The first uplink control information may be transmitted when feedback information associated with the last of the one or more first data packets gets available for transmission.

The first uplink control information may be transmitted in the transmission time interval when feedback information associated with the last of the one or more first data packets gets available for transmission, or in the first transmission time interval after the transmission of user data on the uplink data channel in the uplink transmission opportunity, whichever occurs first,

The second uplink control information may comprise feedback information associated with data packets transmitted in one or more downlink transmission opportunities within a preconfigured time window. The second uplink control information may comprise feedback information for all the data packets in the time window.

The second uplink control information may comprise only feedback information associated with data packets in the time window which has not yet been transmitted by the transmitter.

The transmitter may be a communication device, wherein the second uplink control information may comprise feedback information for hybrid automatic repeat request and the preconfigured time window may be selected such that it comprises feedback for all hybrid automatic repeat request processes of the communication device.

The first uplink control information and the second uplink control information may be transmitted in the same transmission time interval. The method may comprise causing transmission of an indication of use of first uplink control channel resources in a cell in a transmission time interval.

In a forth aspect, there is provided an apparatus, said apparatus comprising at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus to perform at least to cause wireless transmission of one or more first data packets in a downlink transmission on a frequency band, and receive wirelessly from a transmitter first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure at the transmitter, wherein the timing for receiving the first uplink control information is determined in relation to the downlink transmission.

The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus to receive second uplink control information from the transmitter comprising feedback information associated with one or more second received data packets in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure at the transmitter, wherein the timing for receiving of the second uplink control information may be determined according to a preconfigured transmission pattern. The one or more second received data packets may comprise one or more of the first data packets.

The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus to receive user data from the transmitter on an uplink data channel in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure at the transmitter.

The first uplink control information may be transmitted on resources of a first uplink control channel. The first uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel.

Signaling related to the second uplink control channel may stay below a duty cycle threshold for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter. The second uplink control information may be multiplexed with the user data and transmitted on resources of the uplink data channel.

Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter.

Transmission in the uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter, if the clear channel assessment procedure was executed prior to downlink transmission. The uplink transmission opportunity may be started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter, if the clear channel assessment procedure was executed prior to a downlink transmission, and the time interval covering the downlink transmission and the transmission in the uplink transmission opportunity does not exceed a threshold specified in the rules.

The first uplink control information may be transmitted in the transmission time interval when feedback information associated with the last of the one or more first data packets gets available for transmission, or in the first transmission time interval after the transmission of user data on the uplink data channel in the uplink transmission opportunity, whichever occurs first, The second uplink control information may comprise feedback information associated with data packets transmitted in one or more downlink transmission opportunities within a preconfigured time window.

The second uplink control information may comprise only feedback information associated with data packets in the time window which has not yet been transmitted by the transmitter. The transmitter may be a communication device, wherein the second uplink control information may comprise feedback information for hybrid automatic repeat request and the preconfigured time window may be selected such that it comprises feedback for all hybrid automatic repeat request processes of the communication device. The first uplink control information and the second uplink control information may be transmitted in the same transmission time interval. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus to cause transmission of an indication of use of first uplink control channel resources in a cell in a transmission time interval.

In a fifth aspect, there is provided a computer program embodied on a non-transitory computer-readable storage medium, the computer program comprising program code for controlling a process to execute a process, the process comprising receiving one or more first data packets wirelessly in a downlink transmission on a frequency band, and causing wireless transmission of first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure, wherein the timing for transmission of the first uplink control information is determined in relation to the downlink transmission.

In a sixth aspect, there is provided a computer program embodied on a non-transitory computer-readable storage medium, the computer program comprising program code for controlling a process to execute a process, the process comprising causing wireless transmission of one or more first data packets in a downlink transmission on a frequency band, receiving wirelessly from a transmitter first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure at the transmitter, wherein the timing for receiving the first uplink control information is determined in relation to the downlink transmission.

In a seventh aspect there is provided a computer program product for a computer, comprising software code portions for performing the steps of the method of the first aspect and/or third aspect when said product is run on the computer. In a eighth aspect there is provided a mobile communications system comprising at least one apparatus according to an embodiment of the second aspect and at least one apparatus according to an embodiment of the forth aspect.

In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above. Description of Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system comprising a base station and a plurality of communication devices; Figure 2 shows a schematic diagram of an example mobile communication device;

Figure 3 shows an example method of a mobile communication device for communicating uplink control information; Figure 4 shows an example method of an access node for communicating uplink control information;

Figure 5 shows a schematic diagram illustrating aperiodic transmission of uplink control information;

Figure 6 shows a schematic diagram illustrating periodic transmission of uplink control information;

Figure 7 shows a schematic diagram of an example control apparatus;

Detailed description

Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 2 to assist in understanding the technology underlying the described examples.

In a wireless communication system 100, such as that shown in figure 1 , mobile communication devices or user equipment (UE) 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. Base stations are typically controlled by at least one appropriate controller apparatus, so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The controller apparatus may be located in a radio access network (e.g. wireless communication system 100) or in a core network (CN) (not shown) and may be implemented as one central apparatus or its functionality may be distributed over several apparatus. The controller apparatus may be part of the base station and/or provided by a separate entity such as a Radio Network Controller. In Figure 1 control apparatus 108 and 109 are shown to control the respective macro level base stations 106 and 107. The control apparatus of a base station can be interconnected with other control entities. The control apparatus is typically provided with memory capacity and at least one data processor. The control apparatus and functions may be distributed between a plurality of control units. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller.

LTE systems may however be considered to have a so-called "flat" architecture, without the provision of RNCs; rather the (e)NB is in communication with a system architecture evolution gateway (SAE-GW) and a mobility management entity (MME), which entities may also be pooled meaning that a plurality of these nodes may serve a plurality (set) of (e)NBs. Each UE is served by only one MME and/or S-GW at a time and the (e)NB keeps track of current association. SAE-GW is a "high-level" user plane core network element in LTE, which may consist of the S-GW and the P-GW (serving gateway and packet data network gateway, respectively). The functionalities of the S-GW and P-GW are separated and they are not required to be co-located.

In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 1 13 via gateway 1 12. A further gateway function may be provided to connect to another network.

The smaller base stations 1 16, 1 18 and 120 may also be connected to the network 1 13, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 1 16, 1 18 and 120 may be pico or femto level base stations or the like. In the example, stations 1 16 and 118 are connected via a gateway 1 1 1 whilst station 120 connects via the controller apparatus 108. In some embodiments, the smaller stations may not be provided. Smaller base stations 1 16, 1 18 and 120 may be part of a second network, for example WLAN and may be WLAN APs. A possible mobile communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a 'smart phone', a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

The mobile device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

A mobile device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

The communication devices 102, 104, 105 may access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other non-limiting examples comprise time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on. Signaling mechanisms and procedures, which may enable a device to address in-device coexistence (IDC) issues caused by multiple transceivers, may be provided with help from the LTE network. The multiple transceivers may be configured for providing radio access to different radio technologies. An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The various development stages of the 3GPP specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE-A). The LTE employs a mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Base stations of such systems are known as evolved or enhanced Node Bs (eNBs) and provide E-UTRAN features such as user plane Packet Data Convergence/Radio Link Control/Medium Access Control/Physical layer protocol (PDCP/RLC/MAC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices. Other examples of radio access system comprise those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access). A base station can provide coverage for an entire cell or similar radio service area.

As discussed above, there is a need to provide a new scheme for transmitting/scheduling UL HACK-ACK messages on unlicensed bands under consideration of channel availability problems and HARQ-ACK processing delays. Such a scheme may arrange UL HARQ-ACK feedback for DL transport blocks using two complementary uplink control channels:

- A first uplink control channel (aperiodic PUCCH) may be used for transmitting uplink control information with severe latency requirements, such as HARQ-ACK messages. The timing of the first uplink control channel may be determined in relation to the timing of a preceding DL data burst. The first uplink control channel may be configured such that it can carry all or most of the uplink control information with severe latency requirements under usual operating and/or channel availability conditions on unlicensed spectrum.

- A second uplink control channel (periodic PUCCH) may be used as a fallback channel, if the first uplink control channel cannot carry all uplink control information with severe latency requirements, for example, when a LBT procedure prevents the transmission on the first uplink control channel, or due to processing delays. In particular, HARQ-ACK feedback information may not be available for transport blocks being received at the end of the preceding DL data burst, at the time uplink control information is transmitted on the first uplink control channel. The second uplink control channel may be transmitted according to a predetermined activity pattern. The second uplink control channel may in particular be transmitted at regular time intervals. The second uplink control channel may further carry control information with less severe latency requirements, such as scheduling requests, channel state information, sounding reference signals and random access information. The second uplink control channel may include predetermined reference signals that may be used for channel estimation supporting detection and coherent demodulation of symbols carrying control information. Predetermined reference signals may also be used as sequences modulated with symbols carrying control information and facilitate code division multiple access.

The scheme provides a robust framework for handling HARQ-ACK feedback for DL transmission blocks, in that it provides for different and complementary ways for transmitting HARQ-ACK feedback in a communication system. It may in particular resolve issues related to HARQ-ACK transmissions being blocked due to clear channel assessment procedures, such as LBT, in that, for example, the activity pattern of the second uplink control channel and its resources may be configured such that the transmission of the second uplink control channel may not be subject to the execution of a clear channel assessment procedure, for example, if the aforementioned SCS rules specified by ETSI or similar rules are applicable. It may in particular be possible to ensure favorable interference conditions at times when information on the second uplink control information is transmitted. Either by specifying suitable rules, for coordination of transmissions in a communication system, such as LTE, or by specifying certain rules governing the access to respective resources on unlicensed bands. Further, the transmission of HARQ-ACK feedback immediately after a DL data burst on the first uplink control channel may not be subject to the execution of a clear channel assessment procedure according to certain rules or regulations. The transmission of uplink control information immediately after a DL data burst or after or towards the end of the subsequent UL data burst may at least improve the interference conditions, in that other communication devices and access nodes may be squeezed out from the band being occupied by the preceding DL transmission and or the preceding or ongoing UL transmission. Moreover, the scheme allows for a more flexible adaption of uplink/downlink traffic in a cell due to a flexible timing relationship between the transport blocks associated with a DL data burst and the respective UL HARQ-ACK feedback in a communication system. More specifically, the scheme may allow for reducing or minimizing the HARQ-ACK feedback delay for at least the transport blocks associated with the first transmissions in a DL data burst. Accordingly, the next DL data transmissions (either retransmission of new data transmissions) will be available earlier, which in turn allows for configuring more DL data transmissions, that is more DL-heavy uplink/downlink traffic in a cell. The scheme further provides for a flexible adaption of uplink/downlink traffic in a cell, in that it allows for multiplexing between user data and uplink control data in a subframe of an UL data burst, for example through suitable time division multiplexing (TDM). In other words, HARQ-ACK feedback can flexibly transmitted within an UL data burst, so as to ensure that processing of the next DL data transmissions can be started early or when needed.

Data transmission on an unlicensed band or/and subject to a clear channel assessment procedure cannot occur pursuant to a predetermined schedule in a communication system. Rather, communication devices and access nodes need to determine suitable time windows for uplink transmission and/or downlink transmission. A respective time window may comprise one or more Transmission Time Intervals (TTI), such as subframes in LTE, and is in the following referred to as uplink transmission opportunity or downlink transmission opportunity. The determination of uplink transmission opportunities and/or downlink transmission opportunities may be based on parameters related to the communication system, such as a configured pattern governing the sequence of uplink and downlink transmissions in the system. The determination may further be based on rules or regulations specifying a minimum and/or maximum allowed length of uplink transmissions and/or downlink transmissions. Further rules or regulations may specify a maximum length of a time window covering a transmission in a first direction, for example in DL, and a subsequent transmission in the reverse direction, for example in UL, The determination of uplink and downlink opportunities may in particular be based on the outcome of a clear channel assessment procedure, and communication devices or access nodes will only start data transmission on a frequency band after having assessed that the frequency band is clear, that is not occupied by data transmissions from other communication devices or access nodes.

Figure 3 shows a flow diagram of a method for HARQ-ACK transmission on unlicensed bands carried out by a mobile communication device according to some embodiments. At step 310, the communication device monitors a DL control channel and determines whether a DL data burst contains at least one DL transport block intended for the communication device. If no such transport block is detected, the method proceeds to step 370. If at least one transport block is detected, the method proceeds to step 320. The communication device may start monitoring the DL control channel after detecting a DL data burst in a serving cell. The detection of the DL data burst may be based on the detection of a certain signal in the cell, for example a reference signal, such as a cell reference signal which the communication device may blindly detect, or explicit signaling indicative of the presence of the DL data burst. Monitoring the DL control channel may comprise blind detection of scheduling and resource allocation information destined to the communication device. The control channel may be a Physical Downlink Control Channel (PDCCH) or Enhanced Physical Downlink Control Channel (EPDCCH) as specified in LTE. The communication device may further detect a DL data transmission on a data channel, such as a Physical Downlink Shared Channel, based on the received scheduling and resource allocation information.

At step 320, the communication device determines whether it has received an UL grant for the subsequent UL data burst. If it has not received an UL grant, the method proceeds to step 330. If it has received an UL grant, the method proceeds to step 350.

At step 330, the communication device determines timing information of resources for aperiodic Physical Uplink Control Channel (PUCCH). The timing information may be determined in relation to the DL data burst. Resources for aperiodic PUCCH may be available after at least some DL data bursts, and HARQ-ACK may be transmitted by the device on aperiodic PUCCH after a certain time offset in relation to the end of the DL data burst. The device may determine suitable subframes from downlink control information (DCI) and/or other information indicative of the timing of DL data bursts and/or UL data bursts. The method may comprise receiving configuration information for aperiodic PUCCH, e.g. amongst others, frequency and/or code information, such as cover codes, sequences and cyclic shifts, of resources available or allocated to the communication device. Information indicative of the aperiodic PUCCH configuration may be signaled to the communication device by downlink control information (DCI) and/or may be preconfigured by dedicated and/or common control signaling. The method proceeds to step 340.

At step 340, the communication device transmits uplink control information on aperiodic PUCCH. This information may include all available HARQ-ACK feedback information for transport blocks transmitted in one or more preceding DL data bursts which has not yet been transmitted by the communication device. Alternatively, the information may only include available HARQ-ACK feedback information for transport blocks in the preceding DL data burst. Aperiodic PUCCH may be transmitted at the start of the subsequent UL data burst or UL transmission opportunity. Aperiodic PUCCH in subframe n may include HARQ-ACK feedback for transport blocks transmitted in DL up to subframe n-k, where k may denote a predetermined minimum HARQ-ACK processing delay. Transmission of aperiodic PUCCH at the start of the UL data burst or UL transmission opportunity minimizes the latency of HARQ- ACK feedback transmission for the oldest DL transport blocks, while a later transmission may include more complete HARQ-ACK feedback information. A later transmission may in particular be used, when the preceding DL data burst was rather short, i.e. in the range of the minimum HARQ-ACK processing delay. The method proceeds to step 370. At step 350, the communication device determines timing information for aperiodic PUCCH in accordance with the received UL grant. Aperiodic PUCCH may be located in the m-th subframe of a UL data burst or UL transmission opportunity. The m-th subframe may be determined in dependence on the HARQ-ACK delay of k subframes and the length of the UL data burst or UL transmission opportunity of M subframes. The value m may be set to m or M+1 , or to the minimum of k and M+1 . In an alternative embodiment, the communication device may transmit the HARQ-ACK information on the Physical Uplink Shared Channel (PUSCH) in the m-th subframe of the UL data burst or UL transmission opportunity multiplexed with the UL data. In the alternative embodiment the value m may be set to m ot M+1 , or to the minimum of k and M. The method may comprise receiving configuration information for aperiodic PUCCH, e.g. amongst others, frequency and/or code information as discussed in step 330. The method proceeds to step 360.

At step 360, the communication device transmits uplink control information either on aperiodic PUCCH or multiplexed with UL data on PUSCH resources. This information may include all available HARQ-ACK feedback information for transport blocks transmitted in the preceding DL data burst. Transmission of uplink control information in subframe n may include HARQ-ACK feedback for transport blocks transmitted in DL up to subframe n-k, where k may denote a predetermined HARQ-ACK delay. Early transmission of uplink control information in a UL data burst or UL transmission opportunity reduces the latency of HARQ- ACK feedback transmission for the oldest DL transport blocks, while a later transmission may include more complete HARQ-ACK feedback information. A later transmission may in particular be used, when the preceding DL data burst was rather short, i.e. in the range of the minimum HARQ-ACK processing delay. At step 370, the communication device determines whether UL control information is available. This information may include UL control information with rather severe latency requirements, for example HARQ-ACK feedback, which the device could not transmit in a preceding aperiodic transmission opportunity. The information may further include control information with less severe latency requirements, for example Channel State Information. If UL control information is available, the method proceeds to step 380. If there is no UL control information available, the method exits.

At step 380, the communication device determines whether the UL data burst or UL transmission opportunity comprises resources allocated to the second uplink control channel. The second uplink control channel may be configured as a periodic PUCCH, and may be transmitted at a predetermined periodicity PUCCH period of, for example, 10, 20, or 40 ms. Periodic PUCCH may be transmitted for a predetermined time duration, for example in 1 -3 symbols of a subframe. The periodicity and the duration may be defined such that the duty cycle of the periodic PUCCH does not exceed a certain threshold within a specified time period. This may allow for the transmission of periodic PUCCH without preceding LBT procedure. For example, a duty cycle threshold of 5% within a specified observation period of 50 ms. allows for the transmission of periodic PUCCH under the SCS rules, as specified for Europe by ETSI. The method may comprise receiving configuration information for periodic PUCCH, e.g. amongst others, frequency information, such as physical resource blocks, and/or code information, such as cover codes, sequences and cyclic shifts, of resources available or allocated to the communication device. Information indicative of the PUCCH configuration may be signaled to the communication device by downlink control information (DCI) and/or may be preconfigured by dedicated and/or common control signaling. If the UL data burst or UL transmission opportunity comprises resources allocated to the second uplink control channel, the method proceeds to step 390. If there are no resources allocated to the second uplink control channel, the method exits.

At step 390, the communication device transmits UL control information on periodic PUCCH. The UL control information in subframe n may comprise HARQ-ACK feedback for all DL transport blocks transmitted in a predefined time window. This time window may comprise all DL subframes between subframe (n-PUCCH_period-k) and subframe n-k, where k denotes the HARQ-ACK delay. Alternatively, the UL control information may comprise HARQ-ACK feedback only for those DL transport blocks in the time window, for which no HARQ-ACK feedback has been transmitted so far (for example on aperiodic PUCCH). Alternatively, the UL control information may comprise latest HARQ-ACK feedback for all DL HARQ processes. Periodic PUCCH may apply a specific HARQ-ACK bundling scheme, different to the bundling scheme applied on aperiodic PUCCH. Figure 4 shows a flow diagram of a method for HARQ-ACK transmission from a communication device on unlicensed bands carried out by an access node according to some embodiments. At step 410, the access node determines, for example based on scheduling and resource allocation information transmitted on a DL control channel, whether a DL data burst contains at least one DL transport block intended for the communication device (UE). The control channel may be a Physical Downlink Control Channel (PDCCH) or Enhanced Physical Downlink Control Channel (EPDCCH) as specified in LTE. If no transport block intended for the communication device is contained in the DL data burst, the method proceeds to step 480. If at least one transport block is detected, the method proceeds to step 420. The access node may transmit a certain signal in a cell indicative of the presence of a DL data burst in the cell. This signal may be a reference signal, such as a cell reference signal which a communication device in the cell may blindly detect, or explicit signaling indicative of the presence of the DL data burst. The DL data burst may be transmitted on a data channel, such as a Physical Downlink Shared Channel in LTE.

At step 420, the access node determines whether an UL grant has been provided for the communication device in the subsequent UL data burst. If no UL grant has been provided, the method proceeds to step 430. If an UL grant has been provided for the communication device, the method proceeds to step 450.

At step 430, the access node determines timing information of resources for aperiodic Physical Uplink Control Channel (PUCCH). The timing information may be determined in relation to the DL data burst. PUCCH resources may be available after at least some DL data bursts, and HARQ-ACK may be transmitted from the communication device on aperiodic PUCCH after a certain time offset in relation to the end of the DL data burst. The access node may determine suitable subframes from downlink control information and/or other information indicative of the timing of DL data bursts and/or UL data bursts. The method may comprise transmitting configuration information for aperiodic PUCCH, e.g. amongst others, frequency and/or code information, such as cover codes, sequences and cyclic shifts, of resources available or allocated to the communication device. Information indicative of the periodic PUCCH configuration may be signaled from the access node by downlink control information (DCI) and/or may be preconfigured by dedicated control signaling. The method proceeds to step 440. At step 440, the access node receives uplink control information on aperiodic PUCCH. This information may include all available HARQ-ACK feedback information for transport blocks transmitted in one or more preceding DL data bursts which has not yet been transmitted by the communication device. Alternatively, the information may only include available HARQ- ACK feedback information for transport blocks in the preceding DL data burst. Aperiodic PUCCH may be transmitted at the start of the subsequent UL data burst or UL transmission opportunity. Aperiodic PUCCH in subframe n may include HARQ-ACK feedback for transport blocks transmitted in DL up to subframe n-k, where k may denote a predetermined HARQ- ACK delay. Transmission of aperiodic PUCCH at the start of the UL data burst or UL transmission opportunity minimizes the latency of HARQ-ACK feedback transmission for the oldest DL transport blocks, while a later transmission may include more complete HARQ- ACK feedback information. A later transmission may in particular be used, when the preceding DL data burst was rather short, i.e. in the range of the HARQ-ACK processing delay. The method proceeds to step 480.

At step 450, the access node determines timing information for aperiodic PUCCH in accordance with the UL grant transmitted to the communication device. Aperiodic PUCCH may be located in the m-th subframe of a UL data burst or UL transmission opportunity. The m-th subframe may be determined in dependence on the HARQ-ACK delay of k subframes and the length of the UL data burst or UL transmission opportunity of M subframes. The value m may be set to k or M+1 , or to the minimum of k and M+1 . In an alternative embodiment, the access node may receive the HARQ-ACK information on the Physical Uplink Shared Channel (PUSCH) in the m-th subframe of the UL data burst or UL transmission opportunity multiplexed with UL data. In the alternative embodiment the value m may be set to k or M, or to the minimum of k and M. The method may comprise transmitting configuration information for aperiodic PUCCH, e.g. amongst others, frequency and/or code information as discussed in step 430. The method proceeds to step 460.

At step 460, the access node receives uplink control information either on aperiodic PUCCH or multiplexed with UL data on PUSCH resources. This information may include all available HARQ-ACK feedback information for transport blocks transmitted in the preceding DL data burst. Transmission of uplink control information in subframe n may include HARQ-ACK feedback for transport blocks transmitted in DL up to subframe n-k, where k may denote a predetermined HARQ-ACK delay. Early transmission of uplink control information in a UL data burst or UL transmission opportunity reduces the latency of HARQ-ACK feedback transmission for the oldest DL transport blocks, while a later transmission may include more complete HARQ-ACK feedback information. A later transmission may in particular be used, when the preceding DL data burst was rather short, i.e. in the range of the HARQ-ACK processing delay. The method proceeds to step 480.

At step 480, the access nodes determines whether the UL data burst or UL transmission opportunity comprises resources allocated to the second uplink control channel. The second uplink control channel may be configured as a periodic PUCCH, and may be transmitted at a predetermined periodicity PUCCH period of, for example, 10, 20, or 40 ms. Periodic PUCCH may be transmitted for a predetermined time duration, for example in 1 -3 symbols of a subframe The periodicity and the duration may be defined such that the duty cycle of the periodic PUCCH does not exceed a certain threshold within a specified time period. This may allow for the transmission of periodic PUCCH without preceding LBT procedure. For example, a duty cycle threshold of 5% within a specified observation period of 50 ms allows for the transmission of periodic PUCCH under the SCS rules, as specified for Europe by ETSI. The method may comprise transmitting configuration information for periodic PUCCH, e.g. amongst others, frequency and/or code information, such as cover codes, sequences and cyclic shifts, of resources available or allocated to the communication device. Information indicative of the periodic PUCCH configuration may be signaled from the access node by downlink control information (DCI) and/or may be preconfigured by dedicated control signaling. If the UL data burst or UL transmission opportunity comprises resources allocated to the second uplink control channel, the method proceeds to step 490. If there are no resources allocated to the second uplink control channel, the method exits.

At step 490, the access node receives UL control information on the periodic PUCCH (second uplink control channel). The UL control information in subframe n may comprise HARQ-ACK feedback for all DL transport blocks transmitted in a predefined time window. This time window may comprise all DL subframes between subframe (n-PUCCH_period-k) and subframe n-k, where k denotes the HARQ-ACK delay. Alternatively, the UL control information may comprise HARQ-ACK feedback only for those DL transport blocks in the time window, for which no HARQ-ACK feedback has been transmitted prior to subframe n, for example on aperiodic PUCCH. Alternatively, the UL control information may comprise latest HARQ-ACK feedback for all DL HARQ processes. Periodic PUCCH may apply a specific HARQ-ACK bundling scheme, different to the bundling scheme applied on aperiodic PUCCH. Figure 5 shows a schematic diagram illustrating aperiodic transmission of uplink control information according to some embodiments. Figure 5 shows a first case (Case 1 ) in which the communication device did not receive an UL grant. The timing information of PUCCH resources for aperiodic transmission of uplink control information is determined in relation to the DL data burst ending in subframe n-4. Aperiodic PUCCH is transmitted at the start of the subsequent UL transmission opportunity at the beginning of subframe n-3. The aperiodic PUCCH in subframe n-3 includes HARQ-ACK feedback for transport blocks transmitted in DL up to and including subframe n-7, where a HARQ-ACK delay of k=4 subframes is assumed. In other words, aperiodic PUCCH transmission of HARQ-ACK feedback at the beginning of subframe n-3 minimizes the latency of HARQ-ACK feedback transmission for the DL transport blocks transmitted up to and including subframe n-7, but the aperiodic PUCCH in subframe n-3 does not include HARQ-ACK feedback for subframes n-6, n-5, and n-4. Therefore, a later transmission of aperiodic uplink control information may be preferred, as shown in Case 2 of Figure 5. In Case 2 it is assumed that the communication device received an UL grant and transmits uplink data in subframes n-3, n-2 and n-1 of an UL transmission opportunity. Aperiodic PUCCH is transmitted in subframe n, and includes HARQ-ACK feedback up to and including subframe n-4. Alternatively, the UL data burst can extend (at least) up to subframe n, and HARQ-ACK feedback information is multiplexed with the PUSCH transmission in subframe n. In another embodiment HARQ-ACK feedback information is multiplexed with PUSCH transmissions in subframes n-3 to n, as to reduce or minimize the latency of HARQ-ACK feedback transmissions. Specifically, HARQ-ACK feedback for transport blocks transmitted in DL up to and including subframe n-7 may be transmitted in subframe n-3, while transmissions in subframes n-2, n-1 and n may include HARQ-ACK feedback for transport blocks transmitted in subframes n-6, n-5 and n-4, respectively.

Figure 6 shows a schematic diagram illustrating periodic transmission of uplink control information according to some embodiments. Figure 6 shows a recurring transmission of periodic PUCCH with a period PUCCH period of 10 subframes, and the UL control information in subframe n comprises HARQ-ACK feedback for all DL transport blocks transmitted in the time window which extends from subframe n-13 to subframe n-4, assuming a HARQ-ACK delay of k=4 subframes. Alternatively, the UL control information in subframe n can comprise HARQ-ACK feedback for only those DL transport blocks in the time window, for which no HARQ-ACK feedback has been transmitted prior to subframe n, for example on aperiodic PUCCH.

The aperiodic PUCCH may have a predefined time duration. The allowed time duration may be in the range of, for example, 1 to 3 symbols of an UL subframe, such as SC-FDMA symbols or OFDMA symbols. The configuration of the aperiodic PUCCH may be performed via higher layer signaling. In an example embodiment time-division multiplexing (TDM) is applied between PUCCH and PUSCH in subframes comprising aperiodic PUCCH. In an alternative embodiment frequency-division multiplexing (FDM) is applied between PUCCH and PUSCH in subframes comprising aperiodic PUCCH, and transmission of aperiodic PUCCH may extend over one or more subframes in the alternative embodiment.

Aperiodic and periodic PUCCH may coexist in the same subframe. Aperiodic and periodic PUCCH may apply a similar channelization structure for HARQ-ACK transmission. In other words, HARQ-ACK information may be transmitted on aperiodic and periodic PUCCH on the same or overlapping frequency resources, such as physical resource blocks and/or SC- FDMA symbols. Aperiodic and periodic PUCCH may share the same PUCCH resources for transmission of HARQ-ACK information. The PUCCH resources for aperiodic PUCCH may form a subset of the resources for periodic PUCCH. The PUCCH resources for periodic PUCCH may form a subset of the resources for aperiodic PUCCH. In another embodiment HARQ-ACK feedback may be transmitted only via aperiodic PUCCH or only via periodic PUCCH when both would occur in the same subframe or within a predefined time window. Aperiodic PUCCH may be prioritized for HARQ-ACK transmission, in this embodiment, whereas periodic PUCCH may preferably convey control information with less severe latency requirements, such as channel state information (CSI).

In an embodiment a clear channel assessment procedure, such as LBT, may not be applied for aperiodic PUCCH transmission, if the time between a DL transmission from an access node and the UL transmission comprising aperiodic PUCCH is less than or equal to a predetermined value, and the access node has performed a clear channel assessment procedure prior to the DL transmission. In this embodiment the total transmission time covering both DL transmission and subsequent UL transmission comprising aperiodic PUCCH may be limited to a maximum burst or channel occupancy time. The maximum burst or channel occupancy time may be specified by a regulator. In yet another embodiment a clear channel assessment procedure, such as LBT, may be performed at the beginning of an UL transmission comprising aperiodic transmission of uplink control information, such as HARQ-ACK feedback, on aperiodic PUCCH or multiplexed with UL data on PUSCH. In the case of negative clear channel assessment, a communication device may not transmit the UL transmission comprising aperiodic transmission of uplink control information, but may transmit HARQ-ACK feedback on periodic PUCCH. Alternatively, the communication device may transmit HARQ-ACK feedback on another transmission opportunity for aperiodic PUCCH. A communication device may determine the timing information for transmission of aperiodic PUCCH based on information indicating the occurrence of UL and DL transmission bursts/opportunities, and/or received UL grants. The communication device may further combine this information with predefined or preconfigured parameters, such as the minimum HARQ-ACK processing delay. The timing information for transmission of aperiodic PUCCH may individually be configured for communication devices in a cell. Respective information may be signaled to the communication device or may be derivable at the communication device. The communication device may receive information about the presence/allocation of PUSCH resources in a subframe via downlink assignment information on a downlink control channel, such as a Physical Downlink Control Channel (PDCCH). In case the communication device has missed UL grant information, it may not be able to use a respective transmission opportunity for aperiodic PUCCH, but may transmit HARQ-ACK feedback on periodic PUCCH. Alternatively, the communication device may transmit HARQ- ACK feedback on another transmission opportunity for aperiodic PUCCH.

Transmission of aperiodic PUCCH according to cases 1 and 2 of Figure 5 may occur within one UL transmission opportunity. In other words, some of the communication devices in a cell may transmit aperiodic PUCCH at the beginning of a UL transmission opportunity (Case 1 ), while other communication devices in a cell may transmit aperiodic PUCCH at the end of an UL burst or UL transmission opportunity (Case 2). The latter may in particular be applicable for communication devices which have received an UL grant for this UL transmission opportunity. Certain resources in a cell may be cell-specifically configured for aperiodic PUCCH transmission according to Case 1 . These resources may not be used by communication devices in the cell for transmitting data on PUSCH. In an embodiment these resources may not be used by communication devices for PUSCH in a cell, if communication devices are configured to transmit aperiodic PUCCH according to case 1 . The presence of such communication devices may be signaled in the cell, for example included in downlink assignment information. Communication devices in the cell may apply rate matching and/or puncturing to data transmissions on PUSCH as to avoid use of resources configured for aperiodic PUCCH transmission according to Case 1 .

A communication device may transmit aperiodic PUCCH and PUSCH separately in the same subframe. Alternatively, uplink control information may be multiplexed with PUSCH transmissions. The communication device may apply rate matching and/or puncturing to data transmission on PUSCH as to accommodate uplink control information. The HARQ-ACK codebook size, i.e. the number of HARQ-ACK bits assumed for feedback, for periodic PUCCH may be pre-configured semi-statically. Alternatively, the codebook size may be adapted according to the actual HARQ-ACK payload size. The codebook size may further be adapted to include information needed for a Cyclic Redundancy Check.

It should be understood that each block of the flowchart of the Figures and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry. The method may be implemented on a mobile device as described with respect to Figure 2 or control apparatus as shown in Figure 7. Figure 7 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a RAN node, e.g. a base station, (e) node B or 5G AP, a central unit of a cloud architecture or a node of a core network such as an MME or S-GW, a scheduling entity, or a server or host. The method may be implanted in a single control apparatus or across more than one control apparatus. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head. For example the control apparatus 300 can be configured to execute an appropriate software code to provide the control functions. Control functions may comprise providing configuration information for uplink control channels and uplink data channels.

It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and/or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities. It is noted that whilst embodiments have been described in relation to LTE networks, similar principles may be applied in relation to other networks and communication systems, for example, 5G networks. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer- executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

1 . A method comprising:

receiving one or more first data packets wirelessly in a downlink transmission on a frequency band; and

causing wireless transmission of first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure;

wherein the timing for transmission of the first uplink control information is determined in relation to the downlink transmission.

2. A method according to claim 1 , comprising causing wireless transmission of second uplink control information comprising feedback information associated with one or more second received data packets in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure;

wherein the timing for transmission of the second uplink control information is determined according to a preconfigured transmission pattern.

3. A method according to claim 2, wherein the one or more second received data packets comprise one or more of the first data packets.

4. A method according to any preceding claim, comprising causing wireless transmission of user data on an uplink data channel in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure.

5. A method according to any preceding claim, wherein the uplink transmission opportunity is subdivided into one or more transmission time intervals.

6. A method according to any preceding claim, wherein the first uplink control information is transmitted on resources of a first uplink control channel.

7. A method according to any one of claims 4 to 5, wherein the first uplink control information is multiplexed with the user data and transmitted on resources of the uplink data channel.

8. A method according to any one of claims 2 to 7, wherein the second uplink control information is transmitted on resources of a second uplink control channel.

9. A method according to claim 8, wherein signaling related to the second uplink control channel stays below a duty cycle threshold for which the rules allow transmission without execution of the clear channel assessment procedure.

10. A method according to any one of claims 2 to 7, wherein the second uplink control information is multiplexed with the user data and transmitted on resources of the uplink data channel.

1 1 . A method according to any preceding claim, wherein transmission in the uplink transmission opportunity is started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure.

12. A method according to any one of claims 1 to 10, wherein transmission in the uplink transmission opportunity is started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure, if the clear channel assessment procedure was executed prior to downlink transmission.

13. A method according to any one of claims 1 to 10, wherein transmission in the uplink transmission opportunity is started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure, if the clear channel assessment procedure was executed prior to a downlink transmission, and the time interval covering the downlink transmission and the transmission in the uplink transmission opportunity does not exceed a threshold specified in the rules.

14. A method according to any one of claims 5 to 13, wherein the first uplink control information is transmitted in the first of the one or more transmission time intervals of the uplink transmission opportunity.

15. A method according to any one of claims 1 to 13, wherein the first uplink control information is transmitted when feedback information associated with the last of the one or more first data packets gets available for transmission.

16. A method according to claim 4 and any of claims 5 to 14, wherein the first uplink control information is transmitted in the transmission time interval when feedback information associated with the last of the one or more first data packets gets available for transmission, or in the first transmission time interval after the transmission of user data on the uplink data channel in the uplink transmission opportunity, whichever occurs first.

17. A method according to any one of claims 2 to 16, wherein the second uplink control information comprises feedback information associated with data packets received in one or more downlink transmission opportunities within a preconfigured time window.

18. A method according to any one of claims 2 to 17, wherein the second uplink control information comprises feedback information for all the data packets in the time window.

19. A method according to any one of claims 2 to 17, wherein the second uplink control information comprises only feedback information associated with data packets in the time window which has not yet been transmitted.

20. A method according to any one of claims 2 to 17 carried out by a communication device, wherein the second uplink control information comprises feedback information for hybrid automatic repeat request and the preconfigured time window is selected such that it comprises feedback for all hybrid automatic repeat request processes of the communication device.

21 . A method according to claim 2 and 5, wherein the first uplink control information and the second uplink control information is transmitted in the same transmission time interval.

22. A method according to any one of claims 4 and 6, comprising receiving an indication of use of first uplink control channel resources in a cell in a transmission time interval.

23. A method according to claim 22, comprising rate matching and/or puncturing and/or resource mapping in processing of the user data for transmission in the transmission time interval according to the received indication for avoiding on the uplink data channel use of resources related to the first uplink control channel.

24. An apparatus comprising:

at least one processor; and

at least one memory including computer program code, the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus to perform at least the following:

receive one or more first data packets wirelessly in a downlink transmission on a frequency band; and

cause wireless transmission of first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure;

25. A method comprising:

causing wireless transmission of one or more first data packets in a downlink transmission on a frequency band; and

receiving wirelessly from a transmitter first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure at the transmitter;

wherein the timing for receiving the first uplink control information is determined in relation to the downlink transmission.

26. A method according to claim 25, comprising receiving second uplink control information from the transmitter comprising feedback information associated with one or more second received data packets in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure at the transmitter;

wherein the timing for receiving of the second uplink control information is determined according to a preconfigured transmission pattern.

27. A method according to claim 26, wherein the one or more second received data packets comprise one or more of the first data packets.

28. A method according to any one of claims 25 to 27, comprising receiving user data from the transmitter on an uplink data channel in the uplink transmission opportunity on the frequency band subject to the rules on the execution of a clear channel assessment procedure at the transmitter.

29. A method according to any one of claims 25 to 28, wherein the uplink transmission opportunity is subdivided into one or more transmission time intervals.

30. A method according to any one of claims 25 to 29, wherein the first uplink control information is transmitted on resources of a first uplink control channel.

31 . A method according to any one of claims 28 to 29, wherein the first uplink control information is multiplexed with the user data and transmitted on resources of the uplink data channel.

32. A method according to any one of claims 26 to 31 , wherein the second uplink control information is transmitted on resources of a second uplink control channel.

33. A method according to claim 32, wherein signaling related to the second uplink control channel stays below a duty cycle threshold for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter.

34. A method according to any one of claims 26 to 31 , wherein the second uplink control information is multiplexed with the user data and transmitted on resources of the uplink data channel.

35. A method according to any one of claims 25 to 34, wherein transmission in the uplink transmission opportunity is started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter.

36. A method according to any one of claims 25 to 34, wherein transmission in the uplink transmission opportunity is started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter, if the clear channel assessment procedure was executed prior to downlink transmission.

37. A method according to any one of claims 25 to 34, wherein transmission in the uplink transmission opportunity is started with a time offset from the downlink transmission for which the rules allow transmission without execution of the clear channel assessment procedure at the transmitter, if the clear channel assessment procedure was executed prior to a downlink transmission, and the time interval covering the downlink transmission and the transmission in the uplink transmission opportunity does not exceed a threshold specified in the rules.

38. A method according to any one of claims 29 to 37, wherein the first uplink control information is transmitted in the first of the one or more transmission time intervals of the uplink transmission opportunity.

39. A method according to any one of claims 25 to 37, wherein the first uplink control information is transmitted when feedback information associated with the last of the one or more first data packets gets available for transmission.

40. A method according to claim 28 and any of claims 29 to 38, wherein the first uplink control information is transmitted in the transmission time interval when feedback information associated with the last of the one or more first data packets gets available for transmission, or in the first transmission time interval after the transmission of user data on the uplink data channel in the uplink transmission opportunity, whichever occurs first,

41 . A method according to any one of claims 26 to 40, wherein the second uplink control information comprises feedback information associated with data packets transmitted in one or more downlink transmission opportunities within a preconfigured time window.

42. A method according to any one of claims 26 to 41 , wherein the second uplink control information comprises feedback information for all the data packets in the time window.

43. A method according to any one of claims 26 to 41 , wherein the second uplink control information comprises only feedback information associated with data packets in the time window which has not yet been transmitted by the transmitter.

44. A method according to any one of claims 26 to 41 and the transmitter being a communication device, wherein the second uplink control information comprises feedback information for hybrid automatic repeat request and the preconfigured time window is selected such that it comprises feedback for all hybrid automatic repeat request processes of the communication device.

45. A method according to claim 26 and 29, wherein the first uplink control information and the second uplink control information is transmitted in the same transmission time interval.

46. A method according to any one of claims 28 and 30, comprising causing transmission of an indication of use of first uplink control channel resources in a cell in a transmission time interval.

47. An apparatus comprising:

at least one processor; and

cause wireless transmission of one or more first data packets in a downlink transmission on a frequency band; and

receive wirelessly from a transmitter first uplink control information comprising feedback information associated with one or more of the first data packets in an uplink transmission opportunity on the frequency band subject to rules on the execution of a clear channel assessment procedure at the transmitter;

48. An apparatus comprising means for performing a method according to any one of claims 1 to 23.

49. An apparatus comprising means for performing a method according to any one of claims

25 to 46.

50. A computer program product for a computer, comprising software code portions for performing the steps of any of claims 1 to 23 or any one of claim 25 to 46 when said product is run on the computer.

51 . A mobile communication system comprising at least one apparatus according to claim 24 and at least one apparatus according to claim 47.