Patent Description:
Radio communications involving at least one vehicle, also referred to as vehicle-to-everything (V2X) communications, carry both non-safety and safety information. Corresponding applications and services using the V2X communications are associated with a specific set of requirements, e.g., in terms of latency, reliability, capacity, etc. for transmitting messages known as Common Awareness Messages (CAM) and Decentralized Notification Messages (DENM) or Basic Safety Messages (BSM). The data volume of these messages is very low compared to mobile broadband (MBB) communications. Rather, safety-related V2X communications usually require high reliability, low latency and instant communication.

At least in certain situations, these requirements can be fulfilled only if the transmission is self-contained, that is by including control information and data in one transmission time interval (TTI). By blindly decoding the control information scrambled with an identifier, the identified radio device can receive the control information, e.g., a scheduling assignment, for instant data reception.

The Third Generation Partnership Project (3GPP) has specified V2X communications in the context of Long Term Evolution (LTE). <FIG> schematically illustrates a mapping of resources in time (on the horizontal axis) and frequency (on the vertical axis) for a physical sidelink control channel (PSCCH) and a physical sidelink shared channel (PSSCH) in LTE V2X. The two channels, PSCCH and PSSCH, are encoded and modulated separately.

As two radio devices move relative to each other and/or move within an environment that scatters and blocks radio propagation, the signal power received at a receiving radio device from a transmitting radio device varies irregularly. Hence, it may be unpredictable whether a receiver gain applied successfully for data reception in the last transmission time interval (TTI) is suitable for the current TTI, or renders data reception impossible in the current TTI. Therefore, each receiving radio device has to perform a mechanism for controlling its receiver gain, which is known as automatic gain control (AGC). For example, V2X communications according to LTE and New Radio (NR), as specified by 3GPP, largely include broadcast transmissions without power control.

In a conventional LTE V2X communication, the PSCCH and its associated PSSCH are multiplexed in frequency. More specifically, each of the channels is allocated a different group of resource blocks (RBs) contiguous in the frequency domain, which is illustrated in <FIG>. Such a signal structure provides for a self-contained TTI. In this way of multiplexing, however, both channels have their first symbol as an AGC settling symbol. The remaining symbols include either demodulation reference signals (DMRSs) and sidelink control information (SCI) in case of PSCCH, or DMRSs and data in case of PSSCH. The demodulation of the two channels is performed separately using their respective DMRSs. For each channel, if the first symbol is not lost while performing AGC, i.e., the first symbol is not lost due to AGC settling, the DMRSs included in the first symbol may be used for the demodulation of the corresponding channel.

The 3GPP draft contribution R1-<NUM> describes a NR SL numerology and frame structure comprising an AGC settling symbol as the first symbol followed by symbols comprising SCI on a PSCCH before the start of data payload transmission on a PSSCH with optionally another PSCCH time-multiplexed after the PSSCH before a guard period (GP) at the end of a slot. DMRS may be mapped in a comb-like manner in the PSSCH frequency-multiplexed with data on every other subcarrier.

The document <CIT> describes a method for configuring RS for V2V communication, wherein the RS configuration is defined for frequency correction according to a hop sync of a center frequency for dedicated short range communication. The first half of the first symbol of a TTI or a sTTI may be used for AGC, and the remaining half of the first symbol may be used for DMRS. Likewise, the last symbol of the TTI may be divided into an empty half reserved for timing advance (TA), with the preceding half of the last symbol used for DMRS.

The 3GPP draft contribution_R1-<NUM> describes the L1 design for V2V transmissions using, wherein DMRS is transmitted in every OFDM symbol in every <NUM>th subcarrier and data is rate matched accordingly. The AGC settling time may be reduced to the second half of the first symbol, and the GP may be reduced to the second half of the last symbol. A receiver may duplicate the second half of the first symbol and/or the first half of the last symbol. sTTls of <NUM> may be introduced.

The 3GPP draft contribution R1-<NUM> raises open questions when using 64QAM in eV2X services or PC5 (i.e. SL) functionalities necessitated for platooning, advanced driving, sensor sharing and report driving. The indication of <NUM> QAM is possible when extending an existing limitation in the SCI format <NUM>. The TBS in SL conventionally comprises an overhead of up to four DM-RS symbols, one AGC settling symbol and one TX/RX switching symbol, which may need to be adjusted for higher MCS indices, in particular 64QAM. Further, the modulation symbol mapping in the first and last symbols may require changes due to performance differences between "puncturing" and "rate-matching".

The 3GPP draft contribution R1-<NUM> proposes a seamless coexistence of SL unicast, SL groupcast and SL broadcast modes for eV2X. In SL broadcast, resources may be reserved by a transmitter using some pre-emption mechanism still requiring development. For SL groupcast, intra-group resource coordination/alignment in a distributed resource allocation mode remains to be studied, with slot level radio-resource management disfavored and common channel access principles favored. For SL unicast, a feedback mechanism between transmitter and receiver involving a SL scheduling request, SL scheduling grant and scheduling assignment with associated data may be used to improve performance.

If the latest AGC setting is unsuitable for the current TTI, at least some symbols of the SCI in the TTI are lost, so that the control information and, as a consequence, the data is rendered undecodable. Transmitting the SCI beforehand in another TTI could solve this problem in some situation at the price of increasing latency and violating the principle of self-contained TTIs.

Accordingly, there is a need for a radio communication technique that enables a sidelink between mobile devices. An alternative or further object is a technique for resource-efficient and/or low-latency radio communication on a sidelink between mobile devices. An alternative or more specific object is a radio communication technique that enables self-contained TTls on a sidelink between mobile devices.

As to a first method aspect, a method of receiving a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI) is provided according to appended claim <NUM>.

By transmitting in the at least one first symbol reference signals and/or data, the radio resources of a sidelink can be used more efficiently by at least some embodiments. For example, a receiving mobile device can opportunistically improve coherent demodulation using the reference signals in the at least one first symbol. Alternatively or in addition, the receiving mobile device can opportunistically decode further data or improve the reliability of data reception based on the data (e.g., further data or redundant data) encoded in the at least one first symbol.

In same or further embodiments, the AGC symbol in the TTI can enable a self-contained transmission, so that the receiving mobile device is able to adjust its reception gain for the particular TTI and the particular SL from the transmitting mobile device.

Same or further embodiments enable using the at least one first symbol as an AGC settling symbol that opportunistically carries useful information for a control channel and/or a data channel of the SL, e.g., in case the AGC settling symbol is not completely lost due to the AGC process at a receiver.

Each of the symbols of the SL in the TTI may be an orthogonal frequency-division multiplexing (OFDM) symbol.

The method may be performed by a receiving mobile device. The SL may be a direct radio link between a transmitting mobile device and the receiving mobile device. Any of the transmitting and/or receiving mobile devices may be a user equipment (UE), e.g., according to the Third Generation Partnership Project (3GPP).

The TTI may be a slot or a subframe, e.g., in a radio frame structure of the SL.

The sequence of symbols may be transmitted on the SL from a transmitting mobile device to a receiving mobile device within the TTI.

A gain resulting from the AGC may be applied to both the control channel and the shared channel.

The AGC may be based on received power of the at least one first symbol on the SL. The received power may be a reference signal received power (RSRP).

The at least one first symbol of the SL may be received prior to the reception of the at least one second symbol of the SL in the TTI. Alternatively or in addition, the at least one second symbol of the SL may be received prior to the reception of the at least one third symbol of the SL in the TTI.

The at least one first symbol may define the beginning of the TTI. Alternatively or in addition, the at least one third symbol may define the end of the TTI.

The at least one first symbol of the SL and the at least one second symbol of the SL may be consecutive in the TTI. Alternatively or in addition, the at least one second symbol of the SL and the at least one third symbol of the SL are consecutive in the TTI.

The at least one first symbol may comprise at least one reference signal. This may be particularly implemented in any embodiment referred to as the second or fourth embodiment herein. The reference signal or each of more than one reference signal may be a demodulation reference signal (DMRS), e.g., for coherently demodulating one or more spatial streams, respectively.

Receiving the SCI may comprise or initiate a step of demodulating the at least one second symbol using the at least one reference signal in the at least one first symbol. This may be particularly implemented in an embodiment referred to as the fourth embodiment herein.

The at least one reference signal in the at least one first symbol may be used in addition to further reference signals included in the at least one second symbol for demodulating the at least one second symbol. The at least one reference signal in the at least one first symbol may be used opportunistically. For example, the at least one first symbol may be used for either AGC setting (if the AGC setting has to be changed) or for additional reference signals.

The at least one reference signal in the at least one first symbol may support demodulating the at least one second symbol. The at least one second symbol may be coherently demodulated based on the at least one reference signal in the at least one first symbol and further reference signals in the TTI.

The step of performing the AGC may comprise and/or may be based on measuring a received power of the at least one first symbol at a mobile device receiving the SL. This may be particularly implemented in an embodiment referred to as the fourth embodiment herein. The received power may be the RSRP.

Data may be encoded in the at least one first symbol. This may be particularly implemented in any embodiment referred to as the first, second or third embodiment herein. The method may further comprise or initiate the step of demodulating and/or decoding the data encoded in the at least one first symbol.

The data and the at least one reference signal in the at least one first symbol may be frequency-multiplexed in the at least one first symbol. Preferably, each of the data and the reference signal may be arranged according to a comb-like allocation of subcarriers in the at least one first symbol.

The comb-like allocation of subcarriers in the at least one first symbol may leave every second subcarrier empty. Alternatively or in addition, the at least one reference signal, e.g. a DMRS, may be fed into every n active subcarriers, wherein n is a positive integer larger than or equal to <NUM>. For example, DMRS may be fed into every second or every third active subcarrier of the at least one first symbol.

Receiving the data encoded in the at least one first symbol may comprise or initiate demodulating the at least one first symbol based on the at least one reference signal included in the at least one first symbol. This may be particularly implemented in any embodiment referred to as the second embodiment herein.

Optionally, the at least one first symbol may be transmitted on the same antenna port as the at least one second symbol and/or the at least one third symbol. For example, the data encoded in the at least one first symbol and the SCI encoded in the at least one second symbol and/or the data encoded in the at least one third symbol may be coherently demodulated based on reference signals included in the at least one first symbol and the second and/or third symbols.

Receiving the data encoded in the at least one first symbol may comprise or initiate a step of demodulating the at least one first symbol based on reference signals included in the at least one second symbol. This may be particularly implemented in any embodiment referred to as the first embodiment herein. The at least one first symbol and the at least one second symbol may be transmitted on the same antenna port.

The reference signals included in the at least one second symbol may comprise one or more DMRS.

Receiving the data encoded in the at least one first symbol may comprise or initiate a step of demodulating the at least one first symbol based on reference signals included in the at least one third symbol, if a coherence condition for the TTI is fulfilled. This may be particularly implemented in any embodiment referred to as the third embodiment herein. The coherence condition may be fulfilled if a velocity of a mobile device receiving the SL is less than an absolute velocity threshold, if a relative velocity between the receiving mobile device and a mobile device transmitting the SL is less than a relative velocity threshold, and/or if a rate of change of a channel state or channel estimate is less than a rate threshold.

The at least one first symbol and the at least one third symbol may be transmitted on the same antenna port. The demodulation of the at least one first symbol may be selectively based on reference signals included in the at least one third symbol, if the coherence condition is fulfilled.

The channel state may be measured at the receiving mobile device and/or reported to the transmitting mobile device. For example, the receiving mobile terminal may estimate the channel state based on reference signals included in the at least one third symbol. Alternatively or in addition, the transmitting mobile device may measure the channel state (e.g., based on channel reciprocity). For example, the transmitting mobile device may estimate the channel state based on reference signals transmitted from the receiving mobile terminal, if the channel underlying the SL is reciprocal.

Any of the steps of demodulating based on any of the at least one reference signal may comprise performing a channel estimation based on the respective at least one reference signal and demodulating using the channel estimation.

The at least one first symbol of the SL in the TTI may be encoded redundantly to the data encoded in the at least one third symbol of the SL in the TTI. This may be particularly implemented in any embodiment referred to as the first, second or third embodiment herein.

The at least one first symbol may be encoded with data that is redundant to the data encoded in at least one third symbol of the SL in the TTI. The data encoded in the at least one first symbol may provide for a forward error correction (FEC). The at least one first symbol and the at least one third symbol may be encoded according to a codeword resulting from a redundant code, e.g., an error-correcting code (ECC).

Based on the SCI, the receiving mobile device may determine (e.g., on the physical layer) whether or not the data on the SL in the TTI (or a corresponding data packet) is addressed to the receiving mobile device. Alternatively or in addition, the receiving mobile device may deduce the information necessary to demodulate the data.

The SCI may be indicative of whether or not the at least one first symbol comprises data. The receiving mobile device may be configured to selectively perform any one of the first, second and third embodiments in response to the SCI indicating that the at least one first symbol comprises data.

In addition, the SCI is indicative of whether the data encoded in the at least one first symbol is transmitted on an antenna port corresponding to reference signals included in the first, second or third symbols. The receiving mobile device may be configured to selectively perform the first, second or third embodiment according to the indication.

The reference signals included in the first, second or third symbols may comprise one or more DMRS.

Alternatively or in addition, the SCI may be indicative of a modulation scheme and/or a coding scheme. The method may further comprise or initiate a step of decoding at least one of the data encoded in the at least one first symbol and the data encoded in the at least one third symbol according to the modulation scheme and/or the coding scheme. The step of decoding may start after receiving the SCI and/or before the end of the TTI.

The SCI may provide at least one of the following pieces of information. The SCI may comprise a frequency hopping flag. The SCI may be indicative of whether frequency hopping is applied for the at least one first symbol and/or third symbol. The SCI may be indicative of a resource block assignment. The SCI may provide information about a number of allocated resource blocks (RBs) and/or their location (e.g., in time and/or frequency). The SCI may be indicative of a number of the at least one first symbol and/or a number of the at least one third symbol. The SCI may be indicative of a modulation and coding scheme (MCS). The SCI may be indicative of a timing advance, i.e., a timing adjustment value for the receiving mobile device.

The SL may comprise a radio channel from the transmitting mobile device to the receiving mobile device. The first method aspect may be performed by or at the receiving mobile device.

The at least one second symbol may be allocated to a physical SL control channel (PSCCH). The at least one third symbol may be allocated to a physical SL shared channel (PSSCH).

The at least one first symbol may be allocated to a physical SL broadcast channel (PSBCH).

As to a second method aspect, a method of transmitting a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI) is provided according to appended claim <NUM>. The method comprises or initiates a step of transmitting at least one first symbol of the SL in the TTI as a basis for performing an automatic gain control (AGC) for the SL. The method further comprises or initiates a step of transmitting, after the transmission of the at least one first symbol, SL control information (SCI) encoded in at least one second symbol of the SL in the TTI. The method further comprises or initiates a step of transmitting, according to the SCI, data encoded in at least one third symbol of the SL in the TTI.

The second method aspect may further comprise or initiate any of the steps and/or any of the features disclosed in the context of the first method aspect, or steps and/or features corresponding thereto.

As to a signal aspect, a signal structure comprising a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI) is provided. The signal structure comprises at least one first symbol of the SL in the TTI as a basis for performing an automatic gain control (AGC) for the SL. The signal structure further comprises, in the TTI after the at least one first symbol, at least one second symbol encoded with sidelink control information (SCI). The signal structure further comprises, in the TTI after the at least one second symbol, at least one third symbol encoded with data according to the SCI.

The signal structure may be transmitted on the SL from the transmitting mobile device to the receiving mobile device within the TTI. The at least one first symbol may enable performing the AGC at the receiving mobile device of the SL. Based on the AGC, the receiving mobile device may receive the SCI and, furthermore, the data according to the SCI.

Each of the symbols may be defined by a set of Fourier components respectively corresponding to resource elements (REs) or subcarriers. The signal structure may be implemented as an arrangement of REs carrying the symbols in at least one of frequency and time. Alternatively or in addition, the signal structure may be implemented as an arrangement of (e.g., coherent) photons in at least one of space and time.

Further data and/or redundant data may be encoded in the at least one first symbol. This may be particularly implemented in any embodiment referred to as the first, second or third embodiment herein. The further data may be encoded in addition to the data encoded in the at least one third symbol. Alternatively or in addition, the data encoded in the at least one first symbol may be redundant to the data encoded in the at least one third symbol.

The at least one first symbol may comprise at least one reference signal. This may be particularly implemented in any embodiment referred to as the second or fourth embodiment herein.

The symbols in the sequence may be at least one of consecutive and not overlapping in time. The symbols in the sequence may be contiguous in the TTI.

The signal structure may further comprise any feature disclosed in the context of the first or second method aspect, or a feature corresponding thereto.

The TTI may be a subframe or slot of a radio frame structure. The SL may comprise or serve, e.g., according to 3GPP, at least one of vehicle-to-vehicle (V2V) communication, vehicle-to-infrastructure (V2I) communication, vehicle-to-pedestrian (V2P) communication, vehicle-to-everything (V2X) communication (which may comprise at least one of V2V, V2I and V2P communication), and device-to-device communication (D2D).

Different reference signals may be received from different antenna ports of the transmitting mobile device, e.g., for a multiple-input or beamforming SL. Alternatively or in addition, each reference signal may be received at multiple antenna ports of the receiving mobile device, e.g., for a multiple-input multiple-output (MIMO) SL.

The technique may be implemented at one or more mobile devices, e.g., connectable to a radio access network (RAN) configured to serve the one or more mobile devices.

Any of the mobile devices may be configured for peer-to-peer communication on the SL) and/or for accessing the RAN (e.g. on an uplink and/or a downlink). The radio device may be a user equipment (UE, e.g., a 3GPP UE), a mobile or portable station (STA, e.g. a Wi-Fi STA), a device for machine-type communication (MTC), a device for narrowband Internet of Things (NB-IoT) or a combination thereof. Examples for the UE and the mobile station include a mobile phone and a tablet computer. Examples for the portable station include a laptop computer and a television set. Examples for the MTC device or the NB-IoT device include robots, sensors and/or actuators, e.g., in manufacturing, automotive communication and home automation. The MTC device or the NB-IoT device may be implemented in household appliances and consumer electronics. Examples for the combination include a self-driving vehicle, a door intercommunication system and an automated teller machine.

Examples for the base station may include a <NUM> base station or Node B, <NUM> base station or eNodeB, a <NUM> base station or gNodeB, an access point (e.g., a Wi-Fi access point) and a network controller (e.g., according to Bluetooth, ZigBee or Z-Wave).

The RAN may be implemented according to the Global System for Mobile Communications (GSM), the Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE) and/or New Radio (NR).

The technique may be implemented on a Physical Layer (PHY), a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer and/or a Radio Resource Control (RRC) layer of a protocol stack for the radio communication.

As to another aspect, a computer program product is provided. The computer program product comprises program code portions or instructions for performing any one of the steps of the first method aspect and/or the second method aspect disclosed herein when the computer program product is executed by one or more computing devices. The computer program product may be stored on a computer-readable recording medium. The computer program product may also be provided for download via a data network, e.g., via the ad hoc network, the RAN, the Internet and/or by the base station. Alternatively or in addition, the method may be encoded in a Field-Programmable Gate Array (FPGA) and/or an Application-Specific Integrated Circuit (ASIC), or the functionality may be provided for download by means of a hardware description language.

As to a first device aspect, a device for receiving a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI) is provided according to appended claim <NUM>. The device comprises an AGC unit configured to perform an automatic gain control (AGC) for the SL based on at least one first symbol of the SL in the TTI. The device further comprises a control information receiving unit configured to receive, based on the AGC, SL control information (SCI) encoded in at least one second symbol of the SL in the TTI. The device further comprises a data receiving unit configured to receive, based on the SCI, data encoded in at least one third symbol of the SL in the TTI.

The device, e.g., any one of the units or a dedicated unit, may be further configured to perform any of the steps disclosed in the context of another aspect, particularly the first method aspect, or may comprise any feature disclosed in the context of another aspect, particularly the first method aspect.

As to a second device aspect, a device for transmitting a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI) is provided according to appended claim <NUM>. The device comprises an AGC transmitting unit configured to transmit at least one first symbol of the SL in the TTI as a basis for performing an automatic gain control (AGC) for the SL. The device further comprises a control information transmitting unit configured to transmit, after the transmission of the at least one first symbol, SL control information (SCI) encoded in at least one second symbol of the SL in the TTI. The device further comprises a data transmitting unit configured to transmit, according to the SCI, data encoded in at least one third symbol of the SL in the TTI.

The device, e.g., any one of the units or a dedicated unit, may be further configured to perform any of the steps disclosed in the context of another aspect, particularly the second method aspect, or may comprise any feature disclosed in the context of another aspect, particularly the second method aspect.

Further aspects of the invention are provided in accordance with the appended dependent claims.

Further details of embodiments of the technique are described with reference to the enclosed drawings, wherein:.

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as a specific network environment in order to provide a thorough understanding of the technique disclosed herein. It will be apparent to one skilled in the art that the technique may be practiced in other embodiments that depart from these specific details. Moreover, while the following embodiments are primarily described for a New Radio (NR) or <NUM> implementation, it is readily apparent that the technique described herein may also be implemented in any other radio network, including 3GPP LTE or a successor thereof, Wireless Local Area Network (WLAN) according to the standard family IEEE <NUM>, Bluetooth according to the Bluetooth Special Interest Group (SIG), particularly Bluetooth Low Energy and Bluetooth broadcasting, and/or ZigBee based on IEEE <NUM>.

Moreover, those skilled in the art will appreciate that the functions, steps, units and modules explained herein may be implemented using software functioning in conjunction with a programmed microprocessor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP) or a general purpose computer, e.g., including an Advanced RISC Machine (ARM). It will also be appreciated that, while the following embodiments are primarily described in context with methods and devices, the invention may also be embodied in a computer program product as well as in a system comprising at least one computer processor and memory coupled to the at least one processor, wherein the memory is encoded with one or more programs that may perform the functions and steps or implement the units and modules disclosed herein.

<FIG> schematically illustrates a block diagram of a device for receiving a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI). Reference sign <NUM> generically refers to such a device.

The device <NUM> comprises an automatic gain control (AGC) module <NUM> that performs or initiates an AGC for the SL based on at least one first symbol of the SL in the TTI. The device <NUM> further comprises a sidelink control information (SCI) reception module <NUM> that receives SCI encoded in at least one second symbol of the SL in the TTI based on the AGC. The device <NUM> further comprises a data reception module <NUM> that receives, based on the SCI, data encoded in at least one third symbol of the SL in the TTI.

Any of the modules of the device <NUM> may be implemented by units configured to provide the corresponding functionality.

<FIG> schematically illustrates a block diagram of a device for transmitting a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI). Reference sign <NUM> generically refers to such a device.

The device <NUM> comprises an automatic gain control symbol transmission module <NUM> that transmits at least one first symbol of the SL in the TTI as a basis for performing an automatic gain control (AGC) for the SL. The device <NUM> further comprises a sidelink control information transmission module <NUM> that transmits, after the transmission of the at least one first symbol, sidelink control information (SCI) encoded in at least one second symbol of the SL in the TTI. The device <NUM> further comprises a data transmission module <NUM> that transmits, according to the SCI, data encoded in at least one third symbol of the SL in the TTI.

The device <NUM> may be implemented by a receiving mobile device, e.g., a receiving terminal of the SL. Alternatively or in addition, the device <NUM> may be implemented by a transmitting mobile device, e.g., a transmitting terminal of the SL.

In any aspect, the device <NUM> may be wirelessly connected or connectable to the device <NUM>, and/or vice versa, for example for vehicle-to-vehicle (V2V) communications or any vehicular (V2X) communications. V2X communications are also referred to as vehicle-to-everything communications. Any of the devices <NUM> and <NUM> may be embodied by or at a radio device configured for wireless ad hoc connections via the SL.

Optionally, any of the devices <NUM> and <NUM> may be wirelessly connected or connectable to a radio access network (RAN), e.g., to a base station of the RAN. Any of the devices <NUM> and <NUM> may be embodied by or at a radio device configured for accessing the RAN, for example in a vehicle configured for radio-connected driving. The base station may encompass a network controller (e.g., a Wi-Fi access point) or a radio access node (e.g. a <NUM> Node B, a <NUM> eNodeB or a <NUM> gNodeB) of the RAN. The base station may be configured to provide radio access.

Alternatively or in addition, any of the devices <NUM> and <NUM> may include a mobile or portable station or a radio device connectable to the RAN. Any of the devices <NUM> and <NUM> may be a user equipment (UE), particularly a device for machine-type communication (MTC) and/or a device for (e.g., narrowband) Internet of Things (IoT).

<FIG> schematically illustrates an embodiment of a signal structure comprising a sequence of symbols on a sidelink (SL) in a transmission time interval (TTI). The signal structure is generically referred to by reference sign <NUM>.

The signal structure <NUM> comprises at least one first symbol <NUM> of the SL in the TTI as a basis for performing an automatic gain control (AGC) for the SL. The at least one first symbol <NUM> may also be referred to as AGC symbol <NUM> or AGC settling symbol <NUM>.

The signal structure <NUM> further comprises, in the TTI after the at least one first symbol <NUM>, at least one second symbol <NUM> encoded with sidelink control information (SCI). The at least one second symbol <NUM> may also be referred to as SCI symbol <NUM>.

In the TTI after the at least one second symbol <NUM>, the signal structure <NUM> comprises at least one third symbol <NUM> encoded with data according to the SCI. The at least one third symbol <NUM> may also be referred to as data symbol <NUM>.

The at least one second (or SCI) symbol may be allocated to a physical sidelink control channel (PSCCH) of the SL. The at least one second symbol may also be referred to as PSCCH symbol <NUM> or, briefly, PSCCH <NUM>.

The at least one third (or data) symbol may be allocated to a physical sidelink shared channel (PSSCH) of the SL. The at least one third symbol may also be referred to as PSSCH symbol <NUM> or, briefly, PSSCH <NUM>.

Optionally, the at least one first (or AGC) symbol <NUM> is a further symbol allocated to the PSSCH of the SL. In this case, the at least one first symbol may also be referred to as opportunistic PSSCH symbol <NUM>.

A complete transmission of a data packet on the SL may comprise the transmissions of two physical channels, namely the PSCCH and the PSSCH. The PSCCH carries SCI to enable the decoding of the PSSCH, which carries the actual data. Specifically, the SCI in the PSCCH comprises information about the radio resources (e.g., in terms of time or symbols, frequency or subcarriers, and/or spatial streams or filtering) in which the PSSCH <NUM> is transmitted and/or information of how the PSSCH <NUM> is encoded (e.g., the modulation and coding scheme, MCS).

The receiving device <NUM> may first decode the PSCCH <NUM>, which may be encoded using a pre-defined format. Based on the control information received in the PSCCH <NUM>, the receiving device <NUM> then decodes the associated PSSCH <NUM>.

The signal structure <NUM> may be transmitted from the device <NUM>, e.g., a transmitting mobile device of the SL. Alternatively or in addition, the signal structure <NUM> may be received at the device <NUM>, e.g., a receiving mobile device of the SL.

<FIG> shows a flowchart for a method <NUM> of receiving a sequence of symbols on a SL in a TTI. The method <NUM> comprises or initiates a step <NUM> of performing an AGC for the SL based on at least one first symbol of the SL in the TTI. Based on the AGC, SCI encoded in at least one second symbol of the SL in the TTI is received in a step <NUM> of the method <NUM>. Based on the SCI, data encoded in at least one third symbol of the SL in the TTI is received in a step <NUM> of the method <NUM>.

The method <NUM> may be performed by the device <NUM>, e.g., at or using a receiving mobile device for accessing another radio device, e.g., the device <NUM>. Particularly, the modules <NUM>, <NUM> and <NUM> may perform the steps <NUM>, <NUM> and <NUM>, respectively.

<FIG> shows a flowchart for a method <NUM> of transmitting a sequence of symbols on a SL in a TTI. The method <NUM> comprises or initiates a step <NUM> of transmitting at least one first symbol of the SL in the TTI as a basis for performing an AGC for the SL. After the transmission of the at least one first symbol, SCI encoded in at least one second symbol of the SL in the TTI is transmitted in a step <NUM>. In a step <NUM>, data encoded in at least one third symbol of the SL in the TTI is transmitted according to the SCI.

The step <NUM> may enable and/or trigger AGC settling for the SL (e.g., D2D or V2X) transmissions in the step <NUM> and/or <NUM>.

The method <NUM> may be performed by the device <NUM>, e.g., at or using a transmitting mobile device for accessing another radio device, e.g., the device <NUM>. Particularly, the modules <NUM>, <NUM> and <NUM> may perform the steps <NUM>, <NUM> and <NUM>, respectively.

Furthermore, a signal resulting from the method <NUM> and/or a signal processed by the method <NUM> may be structured according to the signal structure <NUM>. Particularly, the modules <NUM>, <NUM> and <NUM> may generate and/or transmit the symbols <NUM>, <NUM> and <NUM>, respectively. The modules <NUM>, <NUM> and <NUM> may receive and/or process the symbols <NUM>, <NUM> and <NUM>, respectively.

Embodiments of the device <NUM> and/or the device <NUM> may be configured for standalone radio communication, ad hoc radio networks and/or vehicular radio communications (V2X communications), particularly according to technical standard documents of the Third Generation Partnership Project (3GPP). In Release <NUM>, the 3GPP standard for Long Term Evolution (LTE) had been extended with support of device-to-device (D2D) communications (also referred to as "sidelink" communications). D2D features (also referred to as Proximity Services, ProSe) are targeting both commercial and Public Safety applications. ProSe features enabled since 3GPP LTE Release <NUM> include device discovery, i.e., one radio device is able to sense the proximity of another radio device and associated application by broadcasting and detecting discovery messages that carry device and application identities. Further ProSe features are an example for features that enable direct communication based on physical channels terminated directly between devices <NUM> and <NUM>. Such features are defined, inter alia, in the documents 3GPP TS <NUM>, Version <NUM>. <NUM>, and 3GPP TS <NUM>, Version <NUM>.

In 3GPP LTE Release <NUM>, the D2D communications were further extended to support of V2X communications, which include any combination of direct communication between vehicles, pedestrians and infrastructure. While V2X communications may take advantage of a network infrastructure (e.g., a RAN) if available, at least basic V2X connectivity is possible even in case of lacking RAN coverage. Implementing V2X communications based on a 3GPP radio interface (e.g., according to LTE and/or NR) can be economically advantageous due to economies of scale. Furthermore, using or extending a 3GPP radio interface may enable a tighter integration between communications with the network infrastructure (V2) communications) and vehicular D2D communications (such as vehicle-to-pedestrian, V2P, and vehicle-to-vehicle, V2V, communications) as compared to using a dedicated communication technology.

The at least one first symbol <NUM> may also be referred to as the at least one AGC settling symbol. The at least one first symbol may be one symbol in the TTI, particularly the first symbol in the TTI. Any or each of the first, second and third symbols may be an orthogonal frequency-division multiplexing (OFDM) symbol.

The technique may be implemented for efficient use of the at least one first symbol <NUM>, i.e., for efficient use of the at least one AGC settling symbol <NUM> (e.g., the first OFDM symbol in the TTI). The efficient use may be implemented according to one or more of the following four embodiments.

In a first embodiment, the AGC settling symbol <NUM> carries data for the PSSCH, e.g., further data or data that is encoded redundantly to the data encoded in the data symbols <NUM>. The AGC settling symbol <NUM> is transmitted using the same antenna port as the PSCCH, i.e., the antenna port used for transmitting the SCI symbols <NUM> from the device <NUM>. Hence, the DMRSs of the SCI symbols <NUM> (i.e., the DMRSs in the PSCCH) are used for the demodulation of the AGC settling symbol <NUM>. Since the SCI symbols <NUM> are closer to the AGC settling symbol <NUM> in the time domain, as compared to the data symbols <NUM>, the DMRSs of the PSCCH improves the demodulation as compared to a demodulation based on the DMRSs of the PSSCH.

In a second embodiment, the AGC settling symbol <NUM> carries data for the PSSCH and has its own one or more DMRSs. For example, the AGC settling symbol <NUM> may comprise a code word or a portion of a code word encoding the data that is also encoded in the data symbols <NUM>. In the AGC settling symbol <NUM>, the data (i.e., the encoded data) and the one or more DMRSs are in the same symbol at different subcarriers.

In a third embodiment, the AGC settling symbol <NUM> carries data for the PSSCH and is transmitted using the same antenna port as the PSSCH, if or when the transmitter (e.g., the device <NUM>) measures or expects slow changes in the channel condition for the SL. Herein, "slow" may relate to changes that allow the receiver (e.g., the device <NUM>) to use the same AGC setting over one or more TTIs. The DMRSs of the PSSCH (i.e., the DMRSs in the data symbols <NUM>) are used for the demodulation of the AGC settling symbol <NUM>. Preferably, the DMRSs in the data symbols <NUM> are also used for the demodulation of the PSCCH, i.e., of the SCI symbols <NUM>, if the same antenna port is used.

In a fourth embodiment, the AGC settling symbol <NUM> carries one or more DMRSs only. The one or more DMRSs in the AGC settling symbol <NUM> is opportunistically used for the demodulation of the PSCCH, i.e., for demodulating the SCI symbols <NUM>. Optionally, the one or more DMRSs in the AGC settling symbol <NUM> is opportunistically used also for the demodulation of the PSSCH, i.e., for demodulating the data symbols <NUM>.

Any of the embodiments may be realized by the receiving device <NUM>, the transmitting device <NUM>, the signal structure <NUM>, the receiving method <NUM> and/or the transmitting method <NUM>. Furthermore, the technique may be implemented as a method of signaling in an AGC settling symbol for SL communications.

<FIG> schematically illustrates an exemplary radio environment <NUM> for implementing the technique. Optionally, the radio environment <NUM> comprises a network infrastructure, e.g., a RAN, including at least one base station <NUM> providing radio access within a cell <NUM>. Thus, the radio environment <NUM> optionally comprises vehicle-to-everything (V2X) communications <NUM> with the network infrastructure and/or scheduled by the network infrastructure.

Alternatively or in combination, the radio environment <NUM> includes direct V2X communications <NUM>, e.g., without the need for or without the involvement of a network infrastructure, particularly direct V2V communications and/or direct V2P communications. These direct communication functionalities are built upon LTE D2D (device-to-device), also known as ProSe (Proximity Services), as first specified in the Release <NUM> of LTE, and include many important enhancements targeting the specific characteristics of vehicular communications. For example, LTE V2X operation is possible with and without network coverage and with varying degrees of interaction between the UEs and the RAN, including support for standalone (i.e., network-less) operation.

Any radio communication, e.g., any of the V2X communications <NUM> or <NUM>, may be associated with specific sets of requirements, e.g., in terms of latency, reliability, capacity and/or Quality of Service. By way of example, the European Telecommunications Standards Institute (ETSI) has defined two types of messages for road safety, including a Co-operative Awareness Message (CAM) and a Decentralized Environmental Notification Message (DENM).

The CAM message enables vehicles, including emergency vehicles, to notify their presence and other relevant parameters in a broadcast fashion. Such messages target other vehicles, pedestrians and infrastructure, and are handled by their applications. CAM message also serves as an active assistance to safety driving for normal traffic. Conventionally, the availability of a CAM message is indicatively checked for every <NUM>, yielding a maximum detection latency requirement of on the order of (e.g., a maximum latency of) <NUM> for most messages.

A latency requirement for a warning message triggered by or for pre-crash sensing may be <NUM>, which can be fulfilled by embodiments of the technique, e.g., by a self-contained transmission. The self-contained transmission may include in the TTI a widebeam reception of the AGC settling symbol <NUM> (optionally including reference signals) and the SCI symbols <NUM> (including reference signals) followed by a transmission and/or a reception of data encoded in the data symbols <NUM> in accordance with the SCI received in the SCI symbols <NUM>.

The DENM message may be triggered by an event, e.g., by braking the vehicle hosting an embodiment of the device <NUM> and/or <NUM>. An embodiment of the device <NUM> may check the availability of a DENM message for every <NUM> or less.

CAM messages and DENM messages are supposed to be detected by all vehicles in proximity, which can be achieved by implementing an embodiment of the device <NUM> in vehicles, e.g., for a broadcast transmission and/or a widebeam transmission in the steps <NUM>, <NUM> and/or <NUM>.

Alternatively or in addition, embodiments of the device <NUM> and the device <NUM> may be configured for multi-antenna radio reception and transmission, respectively, using multiple-input multiple-output (MIMO) radio channels and/or performing beamforming or spatial filtering in radio receptions and transmissions, respectively.

V2X communications support one transmitting (Tx) antenna and two receiving (Rx) antennas since 3GPP LTE Release <NUM>. The number of antennas can be increased to enhance reliability and data rate, e.g., according to 3GPP LTE V2X Release <NUM>.

The technique is applicable for any number of antenna ports per device <NUM> and <NUM>.

Most of the transmissions in LTE sidelink (including D2D or ProSe and V2X) may be broadcast transmissions, at least from the point of view of the physical layer (PHY). This means that all embodiments of the receiving device <NUM> in the proximity of an embodiment of the transmitting device <NUM> pick up the signal structure <NUM>. Each of the embodiments of the receiving device <NUM> in the proximity of the transmitting device <NUM> may perform an individual AGC.

In contrast to the signal structure <NUM>, due to this broadcast nature, there has been no power control mechanism in the conventional LTE SL. As a result, the signal strength at a receiver can vary significantly from one TTI to another TTI. The reason is that the devices are moving, creating rapid changes in the signal and interference condition. Therefore, there is a need to adjust the dynamic range of the receiver before receiving a transmission. D2D according to 3GPP Releases <NUM> and/or <NUM> as well as V2X according to Releases <NUM> and/or <NUM> assume that a receiver will use the first symbol in a <NUM>-symbol subframe to adjust its AGC. This symbol is commonly referred to as the AGC settling symbol. In conventional LTE SL, this symbol contains information bits (i.e., it is part of PSCCH or PSSCH, depending on the case, e.g., as illustrated in <FIG>). However, the decoding requirements are defined under the assumption that the AGC settling symbol may not be available for decoding purposes.

If the received signal strength does not vary a lot from one TTI to another TTI, the receiving device <NUM> effectively does not need to re-adjust its AGC setting and, therefore, can start decoding the at least one first symbol <NUM> in the TTI. As a result, at least some embodiments can opportunistically use the AGC settling symbol <NUM> (which may carry data and/or reference signals) whenever the AGC settling symbol <NUM> is not lost due to performing the AGC in the step <NUM>. For example, the receiving device <NUM> demodulates and/or decodes the AGC settling symbol <NUM>, which may be used as any other data symbol <NUM> later in the TTI. Soft-bits resulting from demodulating the AGC settling symbol <NUM> and soft-bits resulting from demodulating the data symbols <NUM> may be decoded as a single code block, e.g., to improve forward error correction and, thus, reduce a block error rate.

<FIG> shows a schematic time-frequency grid for an embodiment of the signal structure <NUM>. The first symbol <NUM> of the signal structure <NUM> is used for AGC settling.

The AGC settling symbol <NUM> comprises opportunistic information, e.g., reference signals and/or data. Reception of the opportunistic information is facultative and/or advantageous for the receiving device <NUM>. For example, the data encoded in the AGC settling symbol <NUM> may be redundant to the data encoded in the data symbols <NUM>.

The number of AGC settling symbols <NUM> may be less than the number of SCI symbols <NUM>. The number of SCI symbols <NUM> may be less than the number of data symbols <NUM>.

Optionally, DMRS symbols <NUM> are arranged between the symbols <NUM> and <NUM> and/or between the symbols <NUM> and <NUM> in the signal structure <NUM>. Alternatively or in addition, DMRS symbols <NUM> are arranged between at least some of the SCI symbols <NUM> and/or between at least some of the data symbols <NUM> in the signal structure <NUM>.

In a variant, the SCI symbols <NUM> and/or the data symbols <NUM> comprise DMRSs distributed in both time and frequency (e.g., without symbols dedicated to DMRS). In other words, the DMRS <NUM> may be (e.g., exclusively) included in symbols <NUM> and/or <NUM> carrying SCI and data, respectively.

Optionally, the signal structure <NUM> comprises at the end of the TTI a guard period symbol <NUM>, e.g., contiguous after the data symbols <NUM>.

The embodiment of the signal structure <NUM> according to <FIG> may be an extension of a physical format of the PSCCH and/or the PSSCH of the LTE V2X (e.g., according to 3GPP Release <NUM> or Release <NUM>), in which the first symbol in each channel is assumed to be used for AGC settling at the receiver. In contrast to a conventional signal structure, the SCI symbols <NUM> of the PSCCH are arranged before the data symbols <NUM> of the PSSCH in the (or each) TTI.

<FIG> shows a schematic time-frequency grid for an embodiment of the signal structure <NUM>. The signal structure <NUM> may correspond to a resource mapping of PSCCH and PSSCH on a SL according to 3GPP NR, e.g., for V2X communications.

The AGC settling symbol <NUM> defines the beginning of the TTI. The SCI symbols <NUM> for the PSCCH follow (e.g., contiguously) the AGC settling symbol <NUM>. The SCI symbols <NUM> optionally comprise DMRSs <NUM>. The data symbols <NUM> for the PSSCH follow (e.g., contiguously) the SCI settling symbols <NUM>. The symbols <NUM> for the PSSCH optionally comprise DMRSs.

Any embodiment of the signal structure <NUM> may be implemented according to 3GPP NR for V2X communication (i.e., on a SL). The multiplexing of the PSCCH and its PSSCH may be identical or similar to that of a 3GPP NR for cellular communication (i.e., on an uplink or downlink). In contrast to a conventional V2X communication according to 3GPP LTE, the PSCCH may precede the associated PSSCH in the same TTI (e.g., subframe) in the signal structure <NUM>, examples of which are illustrated in each of <FIG>, <FIG> and <FIG>.

The temporal multiplexing of SCI symbols <NUM> (i.e., PSCCH) and data symbols <NUM> (i.e., PSSCH) has several advantages compared to the conventional frequency multiplexing illustrated in <FIG>. For example, the signal structure <NUM> enables fast decoding of the PSSCH, since the receiving device <NUM> does not need to wait until the end of the TTI to start decoding the PSSCH (e.g., as opposed to what happens in LTE V2X).

Consequently, the AGC settling symbol <NUM> is followed by several symbols <NUM> for SCI (i.e., the control channel, PSCCH), and then by the symbols <NUM> of the data channel (e.g., the PSSCH). The PSCCH and the PSSCH may comprise independent DMRSs, so that each of the channels can use a different (e.g., spatial) transmission scheme.

The AGC settling symbol <NUM> may comprise at least one of the following examples, preferably opportunistic information. As a first illustrative example, the AGC settling symbol <NUM> comprises a training sequence that allows for setting the AGC. In terms of demodulation performance, this approach is not desirable, because it prevents the opportunistic use of the AGC settling symbol <NUM> for decoding one or more of the channels. As a second illustrative example, the AGC settling symbol <NUM> carries SCI, i.e., is allocated to the PSCCH. From a robustness point of view, this approach is not desirable, because the impact of losing PSCCH would be high. As a preferred example, the at least one AGC settling symbol <NUM> may comprise at least one data symbol carrying or allocated to the PSSCH. From a channel estimation point of view, a naïve implementation may not be desirable, e.g., since the ACG symbol and the PSSCH are not adjacent in time, so that the DMRSs of the data channel may not be useful for the demodulation of the AGC symbol anymore, especially when the channel changes very fast, which is typical for V2X communication at high vehicle velocities.

The technique may be implemented in the context of any direct communication between devices, which is referred to as SL (e.g., a PC5 communication in the terminology of 3GPP). While the technique is described for D2D and V2X communication, it is also applicable to any other similar types of communication. For conciseness and not limitation, the description of embodiments makes use of 3GPP terminology for the SL. Particularly the PSCCH is used as an example to denote any physical channel carrying control information. The PSSCH is used as an example to denote any physical channel carrying data. The PSCCH typically contains information needed to decode the associated PSSCH such as the time-frequency resources of the PSSCH and the modulation and coding scheme (MCS) for the PSSCH. Usually the PSCCH and the PSSCH have their own DMRSs needed by the receiving device <NUM> to estimate the propagation channel or channel state of the SL between the transmitting device <NUM> and the receiving device <NUM>. Thereby, the receiving device <NUM> is able to decode the control information and the data, respectively.

Moreover, the term "symbol" may denote an OFDM symbol.

Any embodiment of the receiving device <NUM>, the transmitting device <NUM>, the signal structure <NUM>, the receiving method <NUM>, and the transmitting method <NUM> may comprise at least the following three features. As a first feature, a part of the first symbol <NUM> or the whole first symbol <NUM> is used by the receiving device <NUM> for settling its AGC circuit, followed by one or more SCI symbols <NUM> for the PSCCH as a second feature, which is followed by one or more data symbols <NUM> for the associated PSSCH as a third feature.

Such a transmission <NUM> typically occurs within one TTI (e.g., one slot or one subframe) and comprises several symbols. Each of <FIG>, <FIG>, and <FIG> illustrates the above three features (optionally, further including a guard period at the end of the TTI).

In any embodiment described herein, the at least one first symbol <NUM> (i.e., the AGC settling symbol <NUM>) may be constructed to allow for an efficient (e.g., opportunistic) use of it. That is, the AGC settling symbol <NUM> may be constructed to allow performing the AGC whenever necessary. At the same time, the AGC settling symbol <NUM> may be constructed to allow for exploiting the contents of the AGC settling symbol <NUM> to decode a channel for the cases when the AGC is already configured.

In the first embodiment, the AGC settling symbol <NUM> may carry the PSSCH or may be allocated to the PSSCH, but the AGC settling symbol <NUM> may transmit the PSSCH using the antenna port of the PSCCH. In other words, the AGC settling symbol <NUM> may be a PSSCH symbol that is associated with or decoded using the DMRS of the PSCCH (e.g., as opposed to the rest of PSSCH symbols <NUM>, which use the DMRS of the PSSCH). The technical advantage of the first embodiment may be that no specific reference signal is needed for the data in the AGC settling symbol <NUM>. For example, all resource elements (REs) in the AGC settling symbol <NUM> may be used for the data. The first embodiment is practical because the AGC settling symbol <NUM> and the PSCCH are next to each other. Hence, the channel is likely to not have changed much.

In the second embodiment, the AGC settling symbol <NUM> may carry data and have its own one or more DMRSs, which is used for its demodulation at the receiving device <NUM>. The technical advantage of the second embodiment may be that it can give good channel estimate for the data resource elements in the AGC settling symbol <NUM>, thereby improving the demodulation quality.

In the third embodiment, the AGC settling symbol <NUM> may carry data, e.g., using the same antenna port as the PSSCH. The receiving device <NUM> may use one or more DMRSs of the PSSCH, e.g., included in the SCI symbols <NUM>, for demodulation of the AGC settling symbol <NUM>. This is applicable, for example, when the relative velocity between the TX device <NUM> and the RX device <NUM> is so low that the coherence time of the channel (i.e., of the SL) is larger than the time interval between the AGC settling symbol <NUM> and the first PSSCH symbol <NUM> carrying one or more DMRSs. Thus, the DMRSs of the PSSCH symbols <NUM> are usable for the demodulation of the AGC settling symbol <NUM>. The transmitting device <NUM> may determine when to perform the third embodiment based on its estimate of the rate of channel changes. The advantage of the third embodiment is that the whole AGC settling symbol <NUM> may be used to carry data.

In the fourth embodiment, the AGC settling symbol <NUM> may carry only one or more DMRSs. The DMRSs included in the AGC settling symbol <NUM> may be used for the demodulation of the PSCCH symbols <NUM>. The technical advantage of the fourth embodiment is that the AGC settling symbol <NUM> can contribute to improving the channel estimation for the PSCCH symbols <NUM>, which are the most important part in the transmission of the packet or self-contained TTI, because the PSCCH symbols <NUM> comprise details needed to decode the PSSCH symbols <NUM>. The fourth embodiment is also practical, because the AGC settling symbol <NUM> is next to the PSCCH symbols <NUM> in time. In a preferred implementation, the one or more DMRSs in the AGC settling symbol <NUM> are not a mandatory part of the demodulation of the PSCCH symbols <NUM>. The AGC settling symbol <NUM> may be rather an opportunistic part that can improve the quality of the demodulation.

Exemplary implementations of the four embodiments are described herein below.

According to the first embodiment, the AGC settling symbol <NUM> carries data and is transmitted using the same antenna port as the PSCCH <NUM>. As a result, the receiver uses the DMRS of the PSCCH <NUM> to estimate the channel for demodulating and/or decoding the data in the AGC settling symbol <NUM>.

In some implementations of the first embodiment, the transmitting device <NUM> places the one or more DMRS <NUM> of the PSCCH <NUM> as close as possible to the AGC settling symbol <NUM> to obtain good channel estimates for both the PSCCH <NUM> and the AGC settling symbol <NUM>, as is schematically illustrated in <FIG>. For example, if the PSCCH <NUM> consists of <NUM> consecutive OFDM symbols <NUM>, the one or more DMRSs <NUM> are placed in the first symbol of PSCCH <NUM>, so that the DMRSs <NUM> can result in a better estimate of the channel of the AGC settling symbol <NUM> (e.g., as compared to arranging the DMRSs in the second symbol of the PSCCH <NUM>). The density of the DMRSs illustrated in <FIG> is only illustrative.

According to the second embodiment, the AGC settling symbol <NUM> carries data, e.g., by being allocated to the PSSCH in addition to the PSSCH symbols <NUM>. The AGC settling symbol <NUM> comprises its own one or more DMRSs. The receiving device <NUM> uses the one or more DMRSs in the AGC settling symbol <NUM> to estimate the channel for demodulation of the data in the AGC settling symbol <NUM>.

In some implementations of the second embodiment, the AGC settling symbol <NUM> is transmitted in the step <NUM> using the same antenna port as the PSCCH <NUM>. In same or further implementations of the second embodiment, the AGC settling symbol <NUM> is transmitted using the same antenna port as the PSSCH <NUM>.

In some implementations, the AGC settling symbol <NUM> is transmitted using a different antenna port other than the antenna port of the PSCCH <NUM> and/or the antenna port of the PSSCH <NUM>.

In some implementations, the AGC settling symbol <NUM> is constructed in a comb-like manner. For example, every second subcarrier in the AGC settling symbol <NUM> is left empty (e.g., being fed with a value zero, being unloaded, or being left inactive). The remaining subcarriers (i.e., the active subcarriers) may carry either data or a DMRS.

For example, the one or more DMRSs <NUM> can be fed to every n active subcarriers, wherein n is a positive integer larger than or equal to <NUM>. <FIG> show examples for n = <NUM> in <FIG> and n = <NUM> in <FIG>.

According to the third embodiment, the ACG settling symbol <NUM> comprises PSSCH data. The AGC settling symbol <NUM> is transmitted using the same antenna port as the PSSCH <NUM>.

The demodulation of the AGC settling symbol <NUM> is performed based on the one or more DMRSs <NUM> in the PSSCH <NUM>, e.g., as schematically illustrated in <FIG>. The DMRSs <NUM> in the PSSCH <NUM> are used for the demodulation of the AGC settling symbol <NUM>. For clarity, only DMRS resources <NUM> in the first DMRS symbol of the PSSCH <NUM> are shown in the <FIG>.

In some implementations of the third embodiment, the transmitting device <NUM> estimates how fast the channel (i.e., the SL) to the receiving device <NUM> will change, for example, based on measurements of channel state information reference signals or based on the absolute velocity of at least one of the transmitting device <NUM> and the receiving device <NUM>, or based on the transmitting device <NUM> estimating the relative velocity between the transmitting device <NUM> and the receiving device <NUM>. If the channel change is determined to be sufficiently slow that the DMRS in the PSSCH <NUM> can be used to estimate the channel for the AGC settling symbol <NUM>, the transmitting device <NUM> determines to transmit data symbols of the PSSCH in the AGC settling symbol <NUM>. For example, the channel change may be determined to be sufficiently slow when the relative velocity between the TX device <NUM> and the RX device <NUM> is so low that the coherence time of the channel (i.e., the SL) is larger than the time interval between the AGC settling symbol <NUM> and the first PSSCH symbol <NUM> carrying a DMRS.

In some implementations of the third embodiment, the PSCCH <NUM> carries information indicating that the AGC settling symbol <NUM> is carrying data for the PSSCH and that the AGC settling symbol <NUM> is transmitted using the same antenna port as the PSSCH symbols <NUM>.

According to the fourth embodiment, the AGC settling symbol <NUM> contains only one or more DMRSs, which can be used to support the channel estimate of the PSCCH <NUM>. This implies that the AGC settling symbol <NUM> is transmitted using the same antenna port as the PSCCH symbols <NUM>.

The PSCCH <NUM> has its own DMRSs, and the DMRSs in the AGC settling symbol <NUM> can be used to improve the channel estimate quality for the PSCCH <NUM> if the AGC settling symbol <NUM> is not lost due to the AGC settling in the step <NUM>.

In some implementations of the fourth embodiment, the DMRS in the ACG settling symbol <NUM> has the same frequency mapping (e.g., subcarrier allocation) as the DMRS in the PSCCH <NUM> (e.g., using the same subcarriers). This may facilitate an interpolation of the channel estimates in the time direction.

In some implementations of the fourth embodiment, the receiving device <NUM> applies a threshold after correlating the received AGC settling symbol <NUM> with a list of stored signal sequences for DMRSs to determine whether the AGC settling symbol <NUM> can be used in a channel estimation of the PSCCH <NUM>. For example, if the output of the correlator exceeds the threshold, the receiving device <NUM> may determine that the AGC settling symbol <NUM> contains a DMRS sequence and was not lost due to the AGC settling process <NUM>.

<FIG> shows a schematic block diagram for an embodiment of the device <NUM>. The device <NUM> comprises one or more processors <NUM> for performing the method <NUM> and memory <NUM> coupled to the processors <NUM>. For example, the memory <NUM> may be encoded with instructions that implement at least one of the modules <NUM> and <NUM>.

The one or more processors <NUM> may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and/or encoded logic operable to provide, either alone or in conjunction with other components of the device <NUM>, such as the memory <NUM>, data receiver functionality. For example, the one or more processors <NUM> may execute instructions stored in the memory <NUM>. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device <NUM> being configured to perform the action.

As schematically illustrated in <FIG>, the device <NUM> may be embodied by a radio device <NUM>, e.g., functioning as a data receiver. The radio device <NUM> comprises a radio interface <NUM> coupled to the device <NUM> for radio communication with one or more other radio devices and/or one or more base stations.

<FIG> shows a schematic block diagram for an embodiment of the device <NUM>. The device <NUM> comprises one or more processors <NUM> for performing the method <NUM> and memory <NUM> coupled to the processors <NUM>. For example, the memory <NUM> may be encoded with instructions that implement at least one of the modules <NUM>, <NUM> and <NUM>.

The one or more processors <NUM> may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and/or encoded logic operable to provide, either alone or in conjunction with other components of the device <NUM>, such as the memory <NUM>, data transmitter functionality. For example, the one or more processors <NUM> may execute instructions stored in the memory <NUM>. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device <NUM> being configured to perform the action.

As schematically illustrated in <FIG>, the device <NUM> may be embodied by a radio device <NUM>, e.g., functioning as a data transmitter. The radio device <NUM> comprises a radio interface <NUM> coupled to the device <NUM> for radio communication with one or more other radio devices and/or one or more base stations.

With reference to <FIG>, in accordance with an embodiment, a communication system <NUM> includes a telecommunication network <NUM>, such as a 3GPP-type cellular network, which comprises an access network <NUM>, such as a radio access network, and a core network <NUM>. The access network <NUM> comprises a plurality of base stations 1312a, 1312b, 1312c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 1313a, 1313b, 1313c. Each base station 1312a, 1312b, 1312c is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first user equipment (UE) <NUM> located in coverage area 1313c is configured to wirelessly connect to, or be paged by, the corresponding base station 1312c. A second UE <NUM> in coverage area 1313a is wirelessly connectable to the corresponding base station 1312a.

The communication system <NUM> of <FIG> as a whole enables connectivity between one of the connected UEs <NUM>, <NUM> and the host computer <NUM>.

In providing the service to the remote user, the host application <NUM> may provide user data that is transmitted using the OTT connection <NUM>.

It is noted that the host computer <NUM>, base station <NUM> and UE <NUM> illustrated in <FIG> may be identical to the host computer <NUM>, one of the base stations 1312a, 1312b, 1312c and one of the UEs <NUM>, <NUM> of <FIG>, respectively.

The wireless connection <NUM> between the UE <NUM> and the base station <NUM> is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE <NUM> using the OTT connection <NUM>, in which the wireless connection <NUM> forms the last segment. More precisely, the teachings of these embodiments may reduce the latency and improve the data rate and thereby provide benefits such as better responsiveness.

The measurements may be implemented in that the software <NUM>, <NUM> causes messages to be transmitted, in particular empty or "dummy" messages, using the OTT connection <NUM> while it monitors propagation times, errors etc..

As has become apparent from above description, embodiments of the technique achieves at least one of the following two goals, optionally simultaneously. A first goal allows receivers to dynamically adjust their dynamic reception according to the strength of the received signals. A second goal is efficient and/or self-contained use of radio resources. Embodiments make use of the AGC settling resources when they are usable for carrying data transmission or for demodulation of the control information or data transmission.

Claim 1:
A method (<NUM>) of receiving a sequence of symbols on a sidelink, SL, in a transmission time interval, TTI, the method comprising or initiating the steps:
performing (<NUM>) an automatic gain control, AGC, for the SL based on at least one first symbol (<NUM>) of the SL in the TTI;
receiving (<NUM>), based on the AGC, SL control information, SCI, encoded in at least one second symbol (<NUM>) of the SL in the TTI; and
receiving (<NUM>), based on the SCI, data encoded in at least one third symbol (<NUM>) of the SL in the TTI,
wherein
data is encoded in the at least one first symbol (<NUM>), and characterized in that the SCI is indicative of whether the data encoded in the at least one first symbol (<NUM>) is transmitted on an antenna port corresponding to reference signals included in the at least one first symbol (<NUM>), reference signals included in the at least one second symbol (<NUM>) or reference signals included in the at least one third symbol (<NUM>).