EP4652690A1

EP4652690A1 - Preamble adaptation for enhanced transmission parameter estimation

Info

Publication number: EP4652690A1
Application number: EP23701408.9A
Authority: EP
Inventors: Rocco Di Taranto; Abhishek AMBEDE; Leif Wilhelmsson; Dennis SUNDMAN; Charlie PETTERSSON
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-01-19
Filing date: 2023-01-19
Publication date: 2025-11-26
Also published as: WO2024153338A1

Abstract

A wireless communication device (10, 20) sends a first wireless transmission to a further wireless communication device (10, 20). The first wireless transmission includes a first preamble portion, which enables estimation of at least one transmission parameter by the further wireless communication device (10, 20), and a first data portion. Further, the wireless communication device (10, 20) sends a second wireless transmission to the further wireless communication device (10, 20). The second wireless transmission comprises a second preamble portion, which enables estimation of the at least one transmission parameter by the further wireless communication device (10, 20), and a second data portion. The second preamble portion is adapted with respect to the first preamble portion.

Description

Preamble adaptation for enhanced transmission parameter estimation

Technical Field

The present invention relates to methods for controlling wireless transmissions and to corresponding devices, systems, and computer programs.

Background

Wireless communication technologies may use licensed frequency bands and/or licenseexempt frequency bands. A typical example of a wireless communication technology operating in license-exempt frequency bands is the WLAN (Wireless Local Area Network) technology, according to "IEEE Standard for Information Technology-Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks-Specific Requirements - Part 11 : Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications," in IEEE Std 802.11-2020 (Revision of IEEE Std 802.11-2016), pp.1- 4379, 26 Feb. 2021 , in the following denoted as “IEEE 802.11 standard”. The WLAN technology based on the IEEE 802.11 Standard is also referred to as “Wi-Fi”.

Wireless transmissions according to the IEEE 802.11 standard are based on a frame structure which includes a preamble portion, also denoted as “preamble”, followed by a data portion. The preamble portion typically has the purpose of enabling the receiving station (STA) to estimate certain parameters. Such parameters may in turn be needed to demodulate and decode the data portion. Upon receiving a wireless transmission, the receiving STA uses the preamble to estimate the necessary transmission parameters and can then typically decode the data portion without requiring any additional input. The wireless transmissions according to the IEEE 802.11 standard may thus be regarded as self-contained. The data portion could be modulated and coded using a modulation and coding scheme (MCS) that is different from the MCS used for transmitting the preamble. The preamble is typically the same for all wireless transmissions on a wireless link between a given pair of STAs.

Extensions of the IEEE 802.11 standard also define additional preamble formats. For example, the 802.11 n amendment is based on using a High Throughput (HT) preamble. Further, the 802.11ac amendment is based on using a Very High Throughput (VHT) preamble. Still further, the 802.11 ax amendment is based on using a High Efficiency (HE) preamble. Similarly, the EHT (Extremely High Throughput) amendment, see “IEEE Standard for Information technology-Telecommunications and information exchange between systems Local and metropolitan area networks-Specific requirements - Part 11 : Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment: Enhancements for Extremely High Throughput (EHT)”, in the following denoted as “802.11be amendment”, is based on using a specific EHT preamble. For backward compatibility, all wireless transmissions frames in the HT technology, the VHT technology, the HE technology and the EHT technology start with the same legacy preamble. The legacy preamble starts with a short training field (L-STF) and a long training field (L-LTF), which are used for frame detection, receiver synchronization, and channel estimation. The next OFDM (Orthogonal Frequency Division Multiplexing) symbol carries a Legacy Signal (L-SIG) field that indicates which MCS is used for the subsequent signal of the wireless transmission and the frame length. Further, an RL-SIG (Repeated L-SIG) field is provided in 802.11 ax preambles for purposes of packet autodetection.

Irrespective of the above different variants of frame types, the frame type used on a certain wireless link between two STAs is static and defined by the technology (or flavor of technology) on which the link is based. Accordingly, also the preambles and the estimation algorithms which are utilized are the same for every wireless transmission from the sending STA to the receiving STA. For each wireless transmission, the preamble(s) of the wireless transmission itself allow for performing all estimations needed to decode the data portion of the wireless transmission. This may however result in significant signaling overhead due to the included preamble(s).

Accordingly, there is a need for techniques which allow for efficiently performing parameter estimation based on preambles of wireless transmissions.

Summary

According to an embodiment, a method of controlling wireless transmissions in a wireless communication system is provided. According to the method, a wireless communication device sends a first wireless transmission to a further wireless communication device. The first wireless transmission comprises a first preamble portion, which enables estimation of at least one transmission parameter by the further wireless communication device, and a first data portion. Further, the wireless communication device sends a second wireless transmission to the further wireless communication device. The second wireless transmission comprises a second preamble portion, which enables estimation of the at least one transmission parameter by the further wireless communication device, and a second data portion. The second preamble portion is adapted with respect to the first preamble portion. According to a further embodiment, a method of controlling wireless transmissions in a wireless communication system is provided. According to the method, a wireless communication device receives a first wireless transmission from a further wireless communication device. The first wireless transmission comprises a first preamble portion and a first data portion. Further, the wireless communication device receives a second wireless transmission from the further wireless communication device. The second wireless transmission comprises a second preamble portion and a second data portion. The second preamble portion is adapted with respect to the first preamble portion. Based on the first preamble portion and the second preamble portion, the wireless communication device estimates at least one transmission parameter.

According to a further embodiment, a wireless communication device for a wireless communication system is provided. The wireless communication device is configured to send a first wireless transmission to a further wireless communication device. The first wireless transmission comprises a first preamble portion, which enables estimation of at least one transmission parameter by the further wireless communication device, and a first data portion. Further, the wireless communication device is configured to send a second wireless transmission to the further wireless communication device. The second wireless transmission comprises a second preamble portion, which enables estimation of the at least one transmission parameter by the further wireless communication device, and a second data portion. The second preamble portion is adapted with respect to the first preamble portion.

According to a further embodiment, a wireless communication device for a wireless communication system is provided. The wireless communication device comprises at least one processor and a memory. The memory contains instructions executable by said at least one processor, whereby the wireless communication device is operative to send a first wireless transmission to a further wireless communication device. The first wireless transmission comprises a first preamble portion, which enables estimation of at least one transmission parameter by the further wireless communication device, and a first data portion. Further, the memory contains instructions executable by said at least one processor, whereby the wireless communication device is operative to send a second wireless transmission to the further wireless communication device. The second wireless transmission comprises a second preamble portion, which enables estimation of the at least one transmission parameter by the further wireless communication device, and a second data portion. The second preamble portion is adapted with respect to the first preamble portion. According to a further embodiment, a wireless communication device for a wireless communication system is provided. The wireless communication device is configured to receive a first wireless transmission from a further wireless communication device. The first wireless transmission comprises a first preamble portion and a first data portion. Further, the wireless communication device is configured to receive a second wireless transmission from the further wireless communication device. The second wireless transmission comprises a second preamble portion and a second data portion. The second preamble portion is adapted with respect to the first preamble portion. Further, the wireless communication device is configured to, based on the first preamble portion and the second preamble portion, estimate at least one transmission parameter.

According to a further embodiment, a wireless communication device for a wireless communication system is provided. The wireless communication device comprises at least one processor and a memory. The memory contains instructions executable by said at least one processor, whereby the wireless communication device is operative to receive a first wireless transmission from a further wireless communication device. The first wireless transmission comprises a first preamble portion and a first data portion. Further, memory contains instructions executable by said at least one processor, whereby the wireless communication device is operative to receive a second wireless transmission from the further wireless communication device. The second wireless transmission comprises a second preamble portion and a second data portion. The second preamble portion is adapted with respect to the first preamble portion. Further, the memory contains instructions executable by said at least one processor, whereby the wireless communication device is operative to, based on the first preamble portion and the second preamble portion, estimate at least one transmission parameter.

According to a further embodiment, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a wireless communication device for a wireless communication system. Execution of the program code causes the wireless communication device to send a first wireless transmission to a further wireless communication device. The first wireless transmission comprises a first preamble portion, which enables estimation of at least one transmission parameter by the further wireless communication device, and a first data portion. Further, execution of the program code causes the wireless communication device to send a second wireless transmission to the further wireless communication device. The second wireless transmission comprises a second preamble portion, which enables estimation of the at least one transmission parameter by the further wireless communication device, and a second data portion. The second preamble portion is adapted with respect to the first preamble portion

According to a further embodiment, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a wireless communication device for a wireless communication system. Execution of the program code causes the wireless communication device to receive a first wireless transmission from a further wireless communication device. The first wireless transmission comprises a first preamble portion and a first data portion. Further, execution of the program code causes the wireless communication device to receive a second wireless transmission from the further wireless communication device. The second wireless transmission comprises a second preamble portion and a second data portion. The second preamble portion is adapted with respect to the first preamble portion. Further, execution of the program code causes the wireless communication device to, based on the first preamble portion and the second preamble portion, estimate at least one transmission parameter.

Details of such embodiments and further embodiments will be apparent from the following detailed description.

Brief Description of the Drawings

Fig. 1 schematically illustrates a wireless communication system according to an embodiment.

Figs. 2A and 2B schematically illustrate examples of wireless transmissions consisting of a preamble portion and a data portion as used in embodiments of the present disclosure.

Figs. 3A and 3B schematically illustrate an example of preamble adaptation in accordance with an embodiment of the present disclosure.

Figs. 3C and 3D schematically illustrate a further example of preamble adaptation in accordance with an embodiment of the present disclosure.

Figs. 4A schematically illustrates an example of a scenario involving preamble adaptation for data traffic in a TXOP, in accordance with an embodiment of the present disclosure. Fig. 4B schematically illustrates an example of a scenario involving preamble adaptation for data traffic in a scheduled service period, in accordance with an embodiment of the present disclosure.

Figs. 5A and 5B schematically illustrate comparative examples of spatial sounding for data traffic in a scheduled service period.

Fig. 6 schematically illustrates a further example of a scenario involving preamble adaptation for data traffic in a scheduled service period, in accordance with an embodiment of the present disclosure.

Fig. 7 shows a flowchart for schematically illustrating a method according to an embodiment of the present disclosure.

Fig. 8 shows a flowchart for schematically illustrating a further method according to an embodiment of the present disclosure.

Fig. 9 schematically illustrates structures of a wireless communication device according to an embodiment of the present disclosure.

Detailed Description

In the following, concepts in accordance with exemplary embodiments of the invention will be explained in more detail and with reference to the accompanying drawings. The illustrated embodiments relate to controlling of wireless transmissions in a wireless communication system. The wireless communication system may be a WLAN system based on an IEEE 802.11 technology. However, it is noted that the illustrated concepts could also be applied to other wireless communication technologies, e.g., to contention-based modes of the LTE (Long Term Evolution) or NR (New Radio) technology specified by 3GPP (3^rd Generation Partnership Project) or to the Bluetooth technology.

In the illustrated concepts, an adaptive preamble portion of wireless transmissions is used for estimation of one or more transmission parameters, such as frequency offset or time offset. The preamble portion may be used as a basis for decoding a data portion of the respective wireless transmission. The preamble portion being adaptive may involve that, in a sequence of two or more wireless transmissions between a pair of transmitting wireless communication device and receiving wireless communication device, the preamble portion differs between at least two of the wireless transmissions. For example, on a wireless link established between a first wireless communication device and a second wireless communication device, a first wireless transmission could include a first preamble portion and a first data portion, while a second wireless transmission includes a second preamble portion and a second data portion. In such case, the second preamble portion could be adapted, e.g., by making the second preamble portion shorter than the first preamble portion and/or by applying an MCS which is different from the MCS applied for the first preamble portion. In addition or as an alternative, the preamble portion being adaptive may involve that it is modified with respect to a certain baseline preamble, e.g., based on conditions. The baseline preamble could for example correspond to an existing standardized preamble, e.g., an HT preamble, an HE preamble, or a VHT preamble. For example, the preamble portion as applied for a specific MCS could be set depending on the conditions, by modifying the baseline preamble, without requiring that the baseline preamble itself is actually used in a wireless transmission. The adaptation of the preamble portion could for example be based on feedback provided from the receiving wireless communication device to the transmitting wireless communication device, e.g., in terms of acknowledgements (ACKs) for successful reception of data by the receiving wireless communication device. The wireless communication devices may correspond to stations (STAs) of a WLAN system. Here, it is noted that such STA may be an AP (Access Point) STA or a non-AP STA. For example, the transmitting wireless communication device could be an AP STA, while the receiving wireless communication device is a non-AP STA. Alternatively, the transmitting wireless communication device could be a non-AP STA, while the receiving wireless communication device is an AP STA. Still further, both the transmitting and the receiving wireless communication device could be non-AP STAs, e.g., in the case of ad-hoc communication modes. In the following, the transmitting wireless communication device is also shortly denoted as “transmitter” and the receiving wireless communication device is also shortly denoted as “receiver”.

Fig. 1 illustrates an exemplary wireless communication system according to an embodiment. In the illustrated example, the wireless communication system includes multiple APs 10, in the illustrated example referred to as AP1 , AP2, AP3, AP4, and multiple stations 20, in the illustrated example referred to as STA11 , STA21 , STA22, STA31 , and STA41. STA11 is served by AP1 , in a first BSS (Basic Service Set) denoted as BSS1. STA21 and STA22 are served by AP2, in a second BSS denoted as BSS2. STA31 is served by AP3, in a third BSS denoted as BSS3. STA41 is served by AP4, in a fourth BSS denoted as BSS4. The stations 20 may be non-AP STAs and correspond to various kinds of wireless devices, for example user terminals, such as mobile or stationary computing devices like smartphones, laptop computers, desktop computers, tablet computers, gaming devices, or the like. Further, the stations 20 could for example correspond to other kinds of equipment like smart home devices, printers, multimedia devices, data storage devices, or the like.

In the example of Fig. 1 , each of the stations 20 may connect through a wireless link to one of the APs 10. For example, depending on location or channel conditions experienced by a given station 20, the station 20 may select an appropriate AP 10 and BSS for establishing the wireless link. The wireless link may be based on one or more OFDM carriers from a frequency spectrum which is shared on the basis of a contention-based mechanism, e.g., an unlicensed or license-exempt band like the 2.4 GHz ISM (Industrial, Scientific and Medical) band, the 5 GHz band, the 6 GHz band, or the 60 GHz band. The wireless links may be used for downlink (DL) transmissions of data from the AP 10 to station 20 and/or for uplink (UL) transmissions of data from the station 20 to the AP 10.

Each AP 10 may provide data connectivity of the stations 20 connected to the AP 10. As further illustrated, the APs 10 may be connected to a data network (DN) 110. In this way, the APs 10 may also provide data connectivity between stations 20 connected to different APs 10. Further, the APs 10 may also provide data connectivity of the stations 20 to other entities, e.g., to one or more servers, service providers, data sources, data sinks, user terminals, or the like. Accordingly, the wireless link established between a given station 20 and its serving AP 10 may be used for providing various kinds of services to the station 20, e.g., a voice service, a multimedia service, or other data service. Such services may be based on applications which are executed on the station 20 and/or on a device linked to the station 20. By way of example, Fig. 1 illustrates an application service platform 150 provided in the DN 110. The application(s) executed on the station 20 and/or on one or more other devices linked to the station 20 may use the wireless link for data communication with one or more other stations 20 and/or the application service platform 150, thereby enabling utilization of the corresponding service(s) at the station 20.

For at least some of the wireless links between the APs 10 and stations 20, a frame format with adaptive preamble may be utilized. The adaptation of the preamble may be used to optimize the size of the preamble, e.g., to take into account reception conditions, receiver hardware, and the fact that multiple wireless transmissions are being sent on the same wireless link, so that estimation results for earlier wireless transmissions on the same wireless link may be re-used to some extent in the receiver processing for later wireless transmissions, which may in turn allow for reducing the preamble size of the later wireless transmissions. Figs. 2A and 2B schematically illustrate frame structures which may be utilized in the wireless transmissions. As illustrated in Fig. 2A, the frame structure generally consists of a preamble (P) portion and a data portion. As further illustrated in Fig. 2B, the preamble portion may include a legacy preamble portion, e.g., as specified in the IEEE 802.11a standard, and a further preamble portion, such as the HT preamble portion, VHT preamble portion, or HE preamble portion of the IEEE 802.11 standard amendments or the EHT preamble portion of the IEEE 802.11 be amendment. Due to backward compatibility requirements, it is typically not possible to adapt or otherwise modify the legacy preamble. However, the further preamble portion could be changed in the course of the adaptation of the illustrated concepts, e.g., by omitting fields of the further preamble portion or by even omitting the entire further preamble portion. Further, it would be possible to extend the preamble portion by adding further fields, e.g., by repeating one or more fields of the legacy preamble and/or of the further preamble. As a result, the overall size (or length) of the preamble portion can be adapted from one wireless transmission to the next wireless transmission, depending on the expected requirements of the parameter estimation process. In the sequence of wireless transmissions, this allows for relaxing requirements of each packet being self-contained. Rather, the size or other configuration of the preamble may be adjusted depending on measured or expected conditions. The adaptation may be performed with respect to a certain baseline preamble. Such baseline preamble could for example correspond to the EHT preamble. Without adaptation, the wireless transmissions could thus include the complete EHT preamble, and when applying the adaptation, one or more fields of the EHT preamble can be omitted, one or more fields of the EHT preamble can be modified, and/or one or more fields can be added to the EHT preamble. The possible adapted preamble formats may be agreed in advance, so that the receiver is able to decode the adapted preamble portion even without being beforehand informed about its adaptation.

Figs. 3A and 3B schematically illustrate an example of implementing the preamble adaptation based on the HE frame structure of the IEEE 802.11 standard. Fig. 3A illustrates the regular HE frame structure, including the legacy preamble and the HE preamble. The frame structure of Fig. 3A corresponds to a full preamble PPDll (Physical Packet Data Unit). The legacy preamble includes the L-STF, the L-LTF, and the L-SIG. The HE preamble includes the RL- SIG, the HE-SIG-A, the HE-STF, and a number of N_SS HE-LTFs. The HE preamble is followed by a data field, which carries the actual data payload of the PPDU, and a packet extension (PE). Fig. 3B shows a PPDU with applied preamble adaptation. The frame structure of Fig. 3B corresponds to a reduced preamble PPDU, in which some of the preamble fields of Fig. 3A are omitted. Specifically, in the frame structure of Fig. 3B, the HE-SIG-A, the HE-STF, and the HE-LTFs are omitted, thereby significantly reducing the overall size of the preamble portion. Specifically, when considering that the number of HE-LTFs typically corresponds to the number of spatial streams on the wireless link, and when for example assuming that the number of spatial streams N_SS is eight, the length of the preamble is reduced from possibly 36 + 16 N_SS ps = 164 ps down to 24 us, i.e., by 140 ps. If the reduced preamble PPDll would still include the HE-STF, the reduction would still be 128 ps.

Figs. 3C and 3D schematically illustrate an example of implementing the preamble adaptation based on the EHT frame structure of the 802.11 be amendment. Fig. 3C illustrates the regular EHT frame structure, including the legacy preamble and the EHT preamble. The frame structure of Fig. 3C corresponds to a full preamble PPDll. The legacy preamble includes the L-STF, the L-LTF, and the L-SIG. The EHT preamble includes the RL-SIG, the ll-SIG, the EHT-SIG, the EHT-STF, and a number of EHT-LTFs. The EHT preamble is followed by a data field, which carries the actual data payload of the PPDll, and a PE. Fig. 3D shows a PPDU with applied preamble adaptation. The frame structure of Fig. 3D corresponds to a reduced preamble PPDU, in which some of the preamble fields of Fig. 30 are omitted. Specifically, in the frame structure of Fig. 3D, the U-SIG, the EHT-SIG, the EHT-STF, and the EHT-LTFs are omitted, thereby significantly reducing the overall size of the preamble portion.

Reducing the size of the preamble portion or using a different MOS may preclude the respective wireless transmission being self-contained, but such preclusion is not a necessary consequence. For example, under favorable conditions, such as high SNR (Signal-to-Noise Ratio), low or no interference, and/or receiver hardware with higher performance, it may still be possible for the receiver to perform the required estimation and decode the data portion. In such a case, the adaptation could be beneficial even for a single wireless transmission. As an example, a scenario could be considered where under favorable conditions 4096-level Quadrature Amplitude Modulation (4096-QAM) is supported for the data portion. As such high- level MCS typically only works at a very high SNR, e.g., of 40 dB, it can be expected that it is not needed to apply the most robust MCS to the preamble portion. Rather, a more powerful MCS, such as 256-QAM or even higher, could also be applied to the preamble portion.

As mentioned above, in the illustrated concepts a requirement of all wireless transmissions being self-contained can be relaxed, because in some situations the receiver may perform the receiver processing by relying on preambles of multiple wireless transmissions of a sequence of consecutive wireless transmissions. For example, the first wireless transmission of the sequence could include a longer preamble and/or use a more robust MCS for the preamble than subsequent wireless transmissions of the sequence. In this way, it could for example be taken into account that it may be sufficient to estimate and correct the frequency and timing offsets only relying on the first wireless transmission, and to continue using this initial frequency and time synchronization for the subsequent wireless transmissions of the sequence.

In some scenarios, the adaptation may be performed depending on communication conditions, such as distance between the transmitter and the receiver, interference, noise, hardware capabilities of transmitter, and/or hardware capabilities of the receiver. Depending on the conditions, one or more fields of the preamble portion could be omitted and/or a less robust MCS could be applied to some or all fields in the preamble portion. In some cases, estimation of one or more transmission parameters could be performed based on the legacy preamble instead of the omitted preamble field(s). For example, if the wireless channel has a flat frequency characteristic, i.e. , if the channel characteristics does not vary much as a function of frequency, the estimation of the channel characteristics could be performed based on the L- LTF of the legacy preamble. In the case of very unfavorable conditions, additional fields could be added to the preamble portion, and/or or a more robust MCS could be applied to one or more fields of the preamble portion.

In some scenarios, the receiver may provide feedback to the transmitter, and the transmitter may accomplish the adaptation of the preamble portion based on the feedback from the receiver. The feedback could for example be based on ACKs for successful reception of data at the receiver. Further, the feedback could indicate a suggested preamble format or frame format and/or a suggested MCS for at least some fields of the preamble portion. In some scenarios, the ACK may include an indication, e.g., in the form of a field or flag, that not only the data portion was decoded correctly, but also that the estimation of parameters, such as frequency and time synchronization, were performed with desired accuracy. In some cases, the ACK could also indicate an accuracy level of the performed estimation. Based on such indication, the transmitter may then decide that it is enough to send a shorter preamble portion. The shorter preamble portion could for example have a length which allows for maintaining the initially obtained synchronization. If one or more expected ACKs are not received by the transmitter, the transmitter may react by adapting not only the MCS of the data portion of the next wireless transmission but could also adapt the preamble portion. For example, the transmitter could decide to re-introduce one or more previously omitted fields of the preamble portion and/or to apply a more robust MCS to one or more fields of the preamble portion.

As mentioned above, in some scenarios full preamble portions may be used in an initial phase of a sequence of wireless transmissions, e.g., to enable frequency and time synchronization. Such approach may be effective at least for DL wireless transmission. For example, an AP 10 could broadcast a single wireless transmissions with a full preamble portion to all associated STAs 20 in its BSS, thereby enabling reliable initial synchronization by the STAs 20. Subsequent wireless transmissions to at least some of the associated STAs 20 may then use an adapted preamble, from which one or more fields are omitted and/or in which a less robust MCS is applied to one or more fields.

In some scenarios, the receiver could also inform the transmitter of certain hardware capabilities or other capabilities of the receiver, and the transmitter may consider such capabilities when adapting the preamble portion. For example, the requirements on estimation of the frequency offset between the transmitter and the receiver may depends on how much total difference in frequency can be accommodated. If the uncertainty of the frequency is ±100 kHz at both the receiver and the transmitter, the uncertainty that needs to be handled by the receiver is 200 kHz. The preamble portion sent by the transmitter should thus enable estimating a frequency offset in the range of up to 200 kHz. On the other hand, if the transmitter is aware that the receiver only has a frequency uncertainty of 20 kHz, it would be sufficient that the preamble portion enables estimating a frequency offset in the range of up to 120 kHz, and the transmitter could select a correspondingly adapted preamble portion.

As mentioned above, in some scenarios the adaptation of the preamble portion may have the effect that at least some of the wireless transmissions of a sequence are no longer self- contained. In such cases, estimation of the transmission parameters and decoding of the data portions of each data packet can however still be accomplished by considering the preamble portions of other wireless transmissions, e.g., the preamble portions of one or more preceding wireless transmissions of the sequence. For example, such sequence of wireless transmissions could occur within a TXOP (transmit opportunity) reserved on the wireless channel. In such cases, an AP may gain access to the wireless channel, reserve a TXOP and then control wireless transmissions within the TXOP, e.g., by allocating channel resources to one or more STAs. During the TXOP, the AP can schedule both DL and UL wireless transmissions, e.g., using OFDMA or TDMA. Within such TXOP, it can be expected that channel conditions are rather static, so that parameters estimated of the first wireless transmission(s) within the TXOP can be reused for one or more later wireless transmissions within the TXOP. This allows for reducing the preamble size of the later wireless transmissions.

In some scenarios, the AP could adapt the preamble portion for multiple wireless transmissions to be performed with a given STA, taking into account the knowledge that the receiver will receive multiple consecutive wireless transmissions from the same transmitter, so that the preamble portions of the multiple wireless transmissions may be used jointly for estimating the transmission parameter(s). For example, the first wireless transmission could include a full preamble portion which enables the receiver to reliably and accurately perform frequency and time synchronization. Subsequent wireless transmissions could in turn include only a reduced preamble portion which is only long enough for the receiver to maintain the previously acquired synchronization. Fig. 4A illustrates a corresponding example, in which a TXOP is used for sending a sequence of PPDlls between the same transmitter and receiver. In this sequence, the first PPDll includes a full preamble portion, without any adaptation, i.e. , corresponds to a full preamble PPDll. The subsequent PPDlls of the sequence correspond to reduced preamble PPDlls and include an adapted preamble portion, e.g., adapted by omission of one or more preamble fields and/or or by selection of a less robust MCS for one or more of the preamble fields.

In some scenarios, all wireless transmissions of the sequence may carry data. In other cases, data could be omitted from one or more of the wireless transmissions. For example, at the beginning of the TXOP the AP could broadcast a full preamble PPDU without data. This broadcasted full preamble PPDU could be used by all STAs in the AP’s BSS to perform frequency and time synchronization. The STAs may then confirm that the synchronization was successful. For the remaining time of the TXOP, the AP can then send reduced preamble PPDUs with data to the STAs which successfully acquired synchronization. Similar procedures could also be used for UL wireless transmissions from the STAs to the AP, however based on sending an individual initial full preamble PPDU by each of the STAs, instead of broadcasting the full preamble PPDU to all intended receivers.

In some scenarios, a sequence of wireless transmissions may also occur in a service period (SP) scheduled on the wireless channel. Specifically, such SP may be based on the TWT (Target Wake Time) functionality introduced by the 802.11ax amendment or based on the r- TWT (restricted TWT) functionality specified by the 802.11be amendment. In each case, an AP can schedule activity in its BSS based on a TWT agreement. The TWT agreement allows for bundling the wireless transmissions of STAs in predefined SPs, thereby also reducing contention between STAs, as the number of simultaneously active STAs can be lowered by separating them into different SPs of different TWT agreements. In the case of an r-TWT, protection of the SPs is further increased, and it is possible that an AP prioritizes certain latency sensitive traffic flows only during the r-TWT SP. To protect the r-TWT SP from other devices (without critical traffic) trying to access the medium, a scheduling AP may signal a quiet interval with the same start time as the SP. Such quiet interval typically has a duration of 1 TU (Time Unit) (= 1024 ps). Further, r-TWT capable non-AP STAs shall ensure that their ongoing TXOP ends before any upcoming SP advertised by the associated AP. Similarly, if they are not a member of an upcoming SP, they cannot start new data transmissions that will not finish before the SP starts.

During an r-TWT SP, a subset of EHT-STAs with critical traffic exclusively use the wireless medium. The intended use for r-TWT is when there is latency critical data traffic to be sent by either the AP or the STA. One example may be traffic of a virtual reality (VR) service or application, e.g., involving transmission of a latency sensitive video stream in the DL direction and transmission of latency-sensitive pose data in the UL direction. In such scenario, it can be assumed that reserving the medium for a single STA is resource expensive. Minimization of the required duration of the r-TWT SP is thus desirable.

In the illustrated concepts, the AP and the STAs with critical traffic may perform estimation of transmission parameters, e.g., frequency synchronization and/or time synchronization, before the SP starts. This may for example be accomplished before any data to be exchanged becomes available, e.g., in an initial setup phase. Accordingly, before the SP the AP may send a full preamble PPDll to the STA, and/or the STA may send a full preamble PPDll to the AP. Fig. 4B schematically illustrates an example of a corresponding scenario. In the example of Fig. 4B, full preamble PPDll is sent some time before the SP. Based on the preamble of the full preamble PPDU, the receiving STA may estimate the transmission parameters, e.g., perform frequency synchronization and/or time synchronization. Subsequently, during the SP, the data is exchanged using a reduced preamble PPDU, e.g., adapted by omission of one or more preamble fields and/or or by selection of a less robust MCS for one or more of the preamble fields. If operations within the SP are not scheduled, the preambles of the reduced preamble PPDUs may for example be used to keep the STAs synchronized to the AP. By using the reduced preamble PPDU, signaling overhead in the SP can be reduced which in turn may allow for shortening the SP. In some scenarios, a specific type of preamble may be provided for the purpose of being used in the SP. Accordingly, at least two preamble types could be available: a regular preamble, e.g., as illustrated in Fig. 3C, which is used in PPDUs transmitted outside a SP, and a reduced preamble, e.g., as illustrated in Fig. 3D, which is used in PPDUs transmitted within an SP.

In some scenarios, wireless transmissions within an SP may be based on spatial multiplexing, using a sounding procedure for estimating channel parameters. In such scenarios, the sounding procedure could be performed outside the SPs. Alternatively, the sounding procedure could be performed in only some of the SPs. In the case of spatial multiplexing, the HE preamble has an extended duration, due to the need for including one HE-LTF per spatial stream, as illustrated in Fig. 3A. Similarly, the EHT preamble has an extended duration, due to including one HE-LTF per spatial stream, as illustrated for example in Fig. 3C. Fig. 5A schematically illustrates how the sounding procedure could be implemented based on the known functionalities of HE technology. The sounding procedure involves transmission of a HE NDP (Null-Data-PPDU) Announcement by the AP, followed by transmission of an HE Sounding NDP by the AP. Based on the HE Sounding NDP, the STA provides compressed beamforming and CQI (Channel Quality Indicator) feedback to the AP. In the example of Fig. 5A, the sounding procedure is implemented within the SP. Alternatively, the sounding procedure could also be performed before each SP, as illustrated in Fig. 5B.

Fig. 6 schematically illustrates an example how the sounding procedure may be efficiently implemented together with the preamble adaptation of the illustrated concepts. As illustrated, the sounding procedure is performed outside the SPs, e.g., in an initial setup phase. In a first SP following the sounding procedure, a full preamble PPDll is transmitted which includes a full preamble to enable channel estimation for reception of multiple spatial streams by the receiver, e.g., as illustrated in Fig. 3A. In one or more subsequent SPs, a reduced preamble PPDll is transmitted. In the reduced preamble PPDll, the preamble is adapted, e.g., by omission of one or more preamble fields and/or or by selection of a less robust MCS for one or more of the preamble fields, such as illustrated in Fig. 3B. In some scenarios, the sequence of SPs may from time to time include an SP with a full preamble PPDll. Further, from time to time an SP could be preceded by a sounding procedure. For example, every 10th SP could be preceded by a sounding procedure, and every 5th SP could involve transmission of a full preamble PPDU. Due to jitter of the data being transmitted, the SP typically needs to be scheduled with a longer duration than the net time required for transmission of the data. This may be efficiently taken into account by sending the full preamble PPDU in cases where the data arrives in time or early, while sending the reduced preamble PPDU when the data arrives late. In this way, it can be avoided that the SP needs to be extended to allow for transmission of a delayed full preamble PPDU.

In some scenarios, the adaptation of the preamble portion could also depend on the type of the intended wireless transmission. For example, different preambles could be selected for different types of wireless transmission. Such types of wireless transmission could for example be trigger-based transmissions and non-trigger based transmissions, e.g., multi-user (MU) or single user (SU) trigger-based transmissions and non-trigger-based SU transmissions. For example, a first type of preamble could be selected if the wireless transmission intended by the transmitter is a non-trigger-based SU transmission, and a second type of preamble could be selected if the wireless transmission intended by the transmitter is a trigger-based MU transmission or trigger-based SU transmission. Here, an MU transmission may involve that an AP transmits a PPDll to multiple non-AP STAs or that the AP receives a PPDll from multiple non-AP STAs.

For DL MU transmissions, the non-AP STAs may use the preamble to estimate time and frequency to process the remaining part of the PPDU. Both the timing uncertainty and the frequency error may in this case be rather large. For UL MU transmissions, the non-AP STAs may send their respective PPDUs in response to a trigger frame from the AP. Such triggered UL wireless transmission typically needs to happen at a specific time relative to the end of the trigger frame. As a result, the timing uncertainty in the UL direction may be considerably smaller than in the DL direction. Further, the non-AP STAs are typically required to adjust their frequency based on the frequency estimated from received DL wireless transmissions, so that it can be ensured that the non-AP STAs transmitting in the UL direction are reasonably aligned in frequency. This may have the effect that frequency estimation is less demanding for the UL direction than for the DL direction. In some cases, the AP may assume that there is no frequency error in the UL direction and may therefore decide not to perform frequency estimation at all. In such case, the preamble used in the UL direction may be adapted to be shorter than the preamble used in the DL direction. Similar methods can be applied also for trigger-based SU transmissions, e.g., as introduced in the 802.11be amendment.

In the case of UL wireless transmissions, it may also occur that the non-AP STA needs to transmit at a specific time relative to a DL wireless transmission and to adjust its frequency based on the frequency estimated from the DL wireless transmission. In such case, the preamble in the UL wireless transmission may be adapted to be rather short. On the other hand, if the non-AP STA sends a UL wireless transmission packet that is not in response to a DL wireless transmission, the timing uncertainty may become rather large, and the frequency error may be significant as the frequency is not adjusted based on a DL wireless transmission. In such case, the preamble in the UL wireless transmission may be adapted to be rather long.

Further, some wireless transmissions may correspond to control frames, e.g., ACK frames. Such control frames are typically sent with a robust MCS, even if the conditions would allow for using a higher-level MCS. In view of this situation, the preamble in the control frames may be adapted to be rather short, e.g., shorter that in wireless transmissions carrying data.

Fig. 7 shows a flowchart for illustrating a method of controlling wireless transmissions in a wireless communication system, which may be utilized for implementing the illustrated concepts. The method of Fig. 7 may be used for implementing the illustrated concepts in a wireless communication device operating in a wireless communication system, e.g., in an AP of the wireless communication system, e.g., one of the above-mentioned APs 10, or in a STA, such as one of the above-mentioned STAs. The wireless communication system may be based on a wireless local area network, WLAN, technology, e.g., according to the IEEE 802.11 standards family.

If a processor-based implementation of the wireless communication device is used, at least some of the steps of the method of Fig. 7 may be performed and/or controlled by one or more processors of the wireless communication device. Such wireless communication device may also include a memory storing program code for implementing at least some of the below described functionalities or steps of the method of Fig. 7.

At step 710, the wireless communication device sends wireless transmissions. In particular, the wireless communication device sends at least a first wireless transmission and a second wireless transmission to a further wireless communication device. The first wireless transmission includes a first preamble portion and a first data portion. The second wireless transmission includes a second preamble portion and a second data portion. The preamble portions enable estimation of the at least one transmission parameter by the further wireless communication device. The at least one transmission parameter may include a frequency offset and/or a time offset. The second preamble portion is adapted with respect to the first preamble portion.

In some scenarios, step 710 may involve that the wireless communication device sends a sequence of wireless transmissions to the further wireless communication device. The first wireless transmission and the second wireless transmission could then be consecutive wireless transmissions of the sequence. Each wireless transmission of the sequence may include a preamble portion, and due to the adaptation, the preamble portions of at least some of the wireless transmissions of the sequence may differ from each other.

In some scenarios, the second preamble portion may be adapted to be shorter than the first preamble portion. In some scenarios, the first preamble portion is based on a first MCS and the second preamble portion is based on a second MCS, which is adapted to be different from the first MCS.

In some scenarios, the wireless communication device may send the first wireless transmission and the second wireless transmission within a single TXOP reserved on a wireless channel. In some scenarios, the wireless communication device may send the first wireless transmission and the second wireless transmission within a single SP scheduled on a wireless channel. Alternatively, the wireless communication device may send the first wireless transmission before an SP scheduled on a wireless channel and subsequently send the second wireless transmission within the SP. In each case, the SP may be scheduled by a TWT agreement or by an r-TWT agreement.

In some scenarios, the second data portion may be decodable based on the first preamble portion and the second preamble portion, i.e., the preamble portions of multiple received wireless transmissions may be used in the decoding process.

In some scenarios, the first preamble portion and the second preamble portion each include a common set of preamble elements, The first preamble portion may then include a further set of preamble elements, which is not part of the second preamble portion. The common set of preamble elements could for example correspond to a legacy preamble, e.g., as illustrated in Fig. 2B. If the wireless communication system is based on a WLAN technology according to the IEEE 802.11 standards family, the common set of preamble elements could include an L- STF, an L-LTF, and an L-SIG. The further set of preamble elements could include an HE-STF and at least one HE-LTF. Alternatively, the further set of preamble elements could include an EHT-STF and at least one EHT-LTF.

At step 720, the wireless communication device may receive feedback information from the further wireless communication device. The feedback information may be based on acknowledgements of successful data reception at the further wireless communication device, e.g., ACKs. In some scenarios, the feedback information may also include an indication whether estimation of the at least one transmissions parameter was successfully performed by the further wireless communication device.

At step 730, the wireless communication device may adapt the second preamble portion. This may be accomplished based on the feedback information received at step 720. Alternatively or in addition, the wireless communication device could adapt the second preamble portion based on a type of the second wireless transmission, e.g., depending on whether the second wireless transmission is a multi-user transmission or a single-user transmission, depending on whether the second wireless transmission is a UL wireless transmission or a DL wireless transmission, depending on whether the second wireless transmission is a UL wireless transmission in response to a DL wireless transmission, and/or depending on whether the second wireless transmission corresponds to a control frame. Fig. 8 shows a flowchart for illustrating a method of controlling wireless transmissions in a wireless communication system, which may be utilized for implementing the illustrated concepts. The method of Fig. 8 may be used for implementing the illustrated concepts in a wireless communication device operating in a wireless communication system, e.g., in an AP of the wireless communication system, e.g., one of the above-mentioned APs 10, or in a STA, such as one of the above-mentioned STAs 20. The wireless communication system may be based on a wireless local area network, WLAN, technology, e.g., according to the IEEE 802.11 standards family.

If a processor-based implementation of the wireless communication device is used, at least some of the steps of the method of Fig. 8 may be performed and/or controlled by one or more processors of the wireless communication device. Such wireless communication device may also include a memory storing program code for implementing at least some of the below described functionalities or steps of the method of Fig. 8.

At step 810, the wireless communication device receives wireless transmissions. In particular, the wireless communication device receives at least a first wireless transmission and a second wireless transmission from a further wireless communication device. The first wireless transmission includes a first preamble portion and a first data portion. The second wireless transmission includes a second preamble portion and a second data portion. The second preamble portion is adapted with respect to the first preamble portion.

In some scenarios, step 810 may involve that the wireless communication device receives a sequence of wireless transmissions from the further wireless communication device. The first wireless transmission and the second wireless transmission could then be consecutive wireless transmissions of the sequence. Each wireless transmission of the sequence may include a preamble portion, and due to the adaptation, the preamble portions of at least some of the wireless transmissions of the sequence may differ from each other.

In some scenarios, the wireless communication device may receive the first wireless transmission and the second wireless transmission within a single TXOP reserved on a wireless channel. In some scenarios, the wireless communication device may receive the first wireless transmission and the second wireless transmission within a single SP scheduled on a wireless channel. Alternatively, the wireless communication device may receive the first wireless transmission before an SP scheduled on a wireless channel and subsequently receive the second wireless transmission within the SP. In each case, the SP may be scheduled by a TWT agreement or by an r-TWT agreement.

In some scenarios, the first preamble portion and the second preamble portion each include a common set of preamble elements, The first preamble portion may then include a further set of preamble elements, which is not part of the second preamble portion. The common set of preamble elements could for example correspond to a legacy preamble, e.g., as illustrated in Fig. 2B. If the wireless communication system is based on a WLAN technology according to the IEEE 802.11 standards family, wherein the common set of preamble elements could include an L-STF, an L-LTF, and L-SIG. The further set of preamble elements could include an HE-STF and at least one HE-LTF. Alternatively, the further set of preamble elements could include an EHT-STF and at least one EHT-LTF.

At step 820, the wireless communication device estimates at least one transmission parameter based on the first preamble portion and the second preamble portion. The at least one transmission parameter may include a frequency offset and/or time offset.

At step 830, the wireless communication device may send feedback information to the further wireless communication device. The feedback information may be based on acknowledgements of successful data reception at the wireless communication device, e.g., ACKs. Alternatively or in addition, the feedback information could be based on success of preamble detection or on accuracy of the estimation performed based on the preamble portion. In some scenarios, the feedback information may also include an indication whether estimation of the at least one transmissions parameter was successfully performed by the wireless communication device.

The adaptation of the second preamble portion may be based on the feedback information sent at step 830. Alternatively or in addition, the adaptation of the second preamble portion could be based on a type of the second wireless transmission, e.g., depending on whether the second wireless transmission is a multi-user transmission or a single-user transmission, depending on whether the second wireless transmission is a UL wireless transmission or a DL wireless transmission, depending on whether the second wireless transmission is a UL wireless transmission in response to a DL wireless transmission, and/or depending on whether the second wireless transmission corresponds to a control frame.

Fig. 9 illustrates a processor-based implementation of a wireless communication device 900. The structures as illustrated in Fig. 9 may be used for implementing the above-described concepts. The wireless communication device 900 may for example correspond to one of above-mentioned STAs 20 or to one of the above-mentioned APs 10.

As illustrated, the wireless communication device 900 includes a radio interface 910. The radio interface 910 may for example be based on a WLAN technology, e.g., according to an IEEE 802.11 family standard. However, other wireless technologies could be supported as well, e.g., the LTE technology or the NR technology. Further, the wireless communication device 900 may be provided with a network interface 920 for connecting to a data network, e.g., using a wire-based connection.

Further, the wireless communication device 900 may include one or more processors 950 coupled to the interfaces 910, 920, and a memory 960 coupled to the processor(s) 950. By way of example, the interfaces 910, 1020, the processor(s) 950, and the memory 960 could be coupled by one or more internal bus systems of the wireless communication device 900. The memory 960 may include a Read-Only-Memory (ROM), e.g., a flash ROM, a Random Access Memory (RAM), e.g., a Dynamic RAM (DRAM) or Static RAM (SRAM), a mass storage, e.g., a hard disk or solid state disk, or the like. As illustrated, the memory 960 may include software 970 and/or firmware 980. The memory 960 may include suitably configured program code to be executed by the processor(s) 950 so as to implement the above-described functionalities for controlling wireless transmissions, such as explained in connection with the method of Fig. 7 or the method of Fig. 8.

It is to be understood that the structures as illustrated in Fig. 9 are merely schematic and that the wireless communication device 900 may actually include further components which, for the sake of clarity, have not been illustrated, e.g., further interfaces or further processors. Also, it is to be understood that the memory 960 may include further program code for implementing known functionalities of an AP or non-AP STA in an IEEE 802.11 standard compliant technology. According to some embodiments, also a computer program may be provided for implementing functionalities of the wireless communication device 900, e.g., in the form of a physical medium storing the program code and/or other data to be stored in the memory 960 or by making the program code available for download or by streaming.

As can be seen, the concepts as described above may be used for enabling efficient and accurate transmission parameter estimation based on preambles of received wireless transmissions while at the same time avoiding excessive signaling overhead due to the preamble portions. Based on the illustrated concepts, a WLAN technology can be provided with a flexibly adjustable preamble. The preamble content and fields may be changed depending on the transmitter and receiver needs, which can allow for achieving a significant reduction of signaling overhead. Further, the illustrated concepts can be implemented with low complexity, e.g., by modifying existing preamble formats.

Moreover, by letting a receiver perform synchronization or other estimation tasks based on multiple received wireless transmissions, a further reduction of the preamble length can be obtained, because information learned from earlier received wireless transmissions can be reused when decoding the currently received wireless transmission.

When the transmissions are critical and are scheduled in dedicated periods of time, e.g., SPs based on a TWT or r-TWT agreement, the tasks to be performed based on the preambles can be performed before the dedicated period starts, such that the dedicated period can be predominantly used for critical data. By doing so, latency can be reduced and reliability further improved. Also, fairness for legacy devices or devices without critical traffic can be improved because exclusive periods of access to the wireless channel can be further minimized, thereby improving the chances of channel access for other devices.

In some scenarios, the receiver may provide enhanced feedback to the transmitter, for example also indicating the quality of the received preambles or the quality of parameter estimation. Such enhanced feedback may enable the transmitter to take more informed decisions when selecting the transmit parameters and adapting the preamble of subsequent wireless transmissions to the same receiver. Such enhanced feedback may also be used to adjust transmit parameters for the actual data transmission, e.g., by adapting MCS for the data portion of the subsequent wireless transmissions.

It is to be understood that the examples and embodiments as explained above are merely illustrative and susceptible to various modifications. For example, the illustrated concepts may be applied in connection with various kinds of wireless technologies, without limitation to WLAN technologies. Further, the illustrated concepts may be applied with respect to various enhancements of existing technologies utilizing preambles for parameter estimation. Moreover, it is to be understood that the above concepts may be implemented by using correspondingly designed software to be executed by one or more processors of an existing device or apparatus, or by using dedicated device hardware. Further, it should be noted that the illustrated apparatuses or devices may each be implemented as a single device or as a system of multiple interacting devices or modules.

Claims

1. A method of controlling wireless transmissions in a wireless communication system, the method comprising: a wireless communication device (10, 20; 900) sending a first wireless transmission to a further wireless communication device (10, 20; 900), the first wireless transmission comprising a first preamble portion, enabling estimation of at least one transmission parameter by the further wireless communication device (10, 20; 900), and a first data portion; and the wireless communication device (10, 20; 900) sending a second wireless transmission to the further wireless communication device (10, 20; 900), the second wireless transmission comprising a second preamble portion, enabling estimation of the at least one transmission parameter by the further wireless communication device (10, 20; 900), and a second data portion, wherein the second preamble portion is adapted with respect to the first preamble portion.

2. The method according to claim 1 , wherein the second preamble portion is adapted to be shorter than the first preamble portion.

3. The method according to claim 1 or 2, wherein the first preamble portion is based on a first modulation and coding scheme, MCS, and wherein the second preamble portion is based on a second MCS which is adapted to be different from the first MCS.

4. The method according to any one of the preceding claims, comprising: the wireless communication device (10, 20; 900) receiving feedback information from the further wireless communication device (10, 20; 900); and the wireless communication device (10, 20; 900) adapting the second preamble portion based on the received feedback information.

5. The method according to claim 4, wherein the feedback information is based on acknowledgements of successful data reception at the further wireless communication device.

6. The method according to any one of the preceding claims, comprising: the wireless communication device (10, 20; 900) adapting the second preamble portion based on a type of the second wireless transmission.

7. The method according to any one of the preceding claims, the wireless communication device (10, 20; 900) sending a sequence of wireless transmissions to the further wireless communication device (10, 20; 900), wherein the first wireless transmission and the second wireless transmission are consecutive wireless transmissions of the sequence.

8. The method according to any one of the preceding claims, wherein the wireless communication device (10, 20; 900) sends the first wireless transmission and the second wireless transmission within a single transmit opportunity, TXOP, reserved on a wireless channel.

9. The method according to any one of the preceding claims, wherein the wireless communication device (10, 20; 900) sends the first wireless transmission and the second wireless transmission within a single service period, SP, scheduled on a wireless channel.

10. The method according to any one of claims 1 to 8, wherein the wireless communication device (10, 20; 900) sends the first wireless transmission before an SP scheduled on a wireless channel and subsequently sends the second wireless transmission within the SP.

11. The method according to any one of the preceding claims, wherein the at least one transmission parameter comprises a frequency offset.

12. The method according to any one of the preceding claims, wherein the at least one transmission parameter comprises a time offset.

13. The method according to any one of the preceding claims, wherein the second data portion is decodable based on the first preamble portion and the second preamble portion.

14. The method according to any one of the preceding claims wherein the first preamble portion and the second preamble portion each comprise a common set of preamble elements, and wherein the first preamble portion comprises a further set of preamble elements, which is not part of the second preamble portion.

15. The method according to any one of the preceding claims, wherein the wireless communication system is based on a Wireless Local Area Network technology according to the IEEE 802.11 standards family.

16. The method according to claim 14 and 15, wherein the common set of preamble elements comprises a Legacy Short Training Field, L- STF and a Legacy Long Training Field, L-LTF.

17. The method according to claim 16, wherein the further set of preamble elements comprises a High Efficiency Short Training Field, HE-STF and at least one High Efficiency Long Training Field, HE-LTF.

18. The method according to claim 16, wherein the further set of preamble elements comprises an Extremely High Throughput Short Training Field, EHT-STF, and at least one Extremely High Throughput Long Training Field, EHT-LTF.

19. A method of controlling wireless transmissions in a wireless communication system, the method comprising: a wireless communication device (10, 20; 900) receiving a first wireless transmission from a further wireless communication device (10, 20; 900), the first wireless transmission comprising a first preamble portion, and a first data portion; the wireless communication device (10, 20; 900) receiving a second wireless transmission from the further wireless communication device (10, 20; 900), the second wireless transmission comprising a second preamble portion and a second data portion, wherein the second preamble portion is adapted with respect to the first preamble portion; and based on the first preamble portion and the second preamble portion, the wireless communication device (10, 20; 900) estimating at least one transmission parameter.

20. The method according to claim 19, wherein the second preamble portion is adapted to be shorter than the first preamble portion.

21. The method according to claim 19 or 20, wherein the first preamble portion is based on a first modulation and coding scheme, MCS, and wherein the second preamble portion is based on a second MCS which is adapted to be different from the first MCS.

22. The method according to any one of claims 19 to 21 , comprising: the wireless communication device (10, 20; 900) sending feedback information to the further wireless communication device (10, 20; 900), wherein the second preamble portion is adapted based on the received feedback information.

23. The method according to claim 22, wherein the feedback information is based on acknowledgements of successful data reception at the further wireless communication device.

24. The method according to any one of claims 19 to 23, wherein the second preamble portion is adapted based on a type of the second wireless transmission.

25. The method according to any one of claims 19 to 24, the wireless communication device (10, 20; 900) receiving a sequence of wireless transmissions from the further wireless communication device (10, 20; 900), wherein the first wireless transmission and the second wireless transmission are consecutive wireless transmissions of the sequence.

26. The method according to any one of claims 19 to 25, wherein the wireless communication device (10, 20; 900) receives the first wireless transmission and the second wireless transmission within a single transmit opportunity, TXOP, reserved on a wireless channel.

27. The method according to any one of claims 19 to 26, wherein the wireless communication device (10, 20; 900) receives the first wireless transmission and the second wireless transmission within a single service period, SP, scheduled on a wireless channel.

28. The method according to any one of claims 19 to 26, wherein the wireless communication device (10, 20; 900) receives the first wireless transmission before an SP scheduled on a wireless channel and subsequently receives the second wireless transmission within the SP.

29. The method according to any one of claims 19 to 28, wherein the at least one transmission parameter comprises a frequency offset.

30. The method according to any one of claims 19 to 29, wherein the at least one transmission parameter comprises a time offset.

31. The method according to any one of claims 19 to 30, wherein the wireless communication device decodes the second data portion based on the first preamble portion and the second preamble portion.

32. The method according to any one of claims 19 to 31 , wherein the first preamble portion and the second preamble portion each comprise a common set of preamble elements, and wherein the first preamble portion comprises a further set of preamble elements, which is not part of the second preamble portion.

33. The method according to any one of claims 19 to 32, wherein the wireless communication system is based on a Wireless Local Area Network technology according to the IEEE 802.11 standards family.

34. The method according to claim 32 and 33, wherein the common set of preamble elements comprises a Legacy Short Training Field, L- STF and a Legacy Long Training Field, L-LTF.

35. The method according to claim 34, wherein the further set of preamble elements comprises a High Efficiency Short Training Field, HE-STF and at least one High Efficiency Long Training Field, HE-LTF.

36. The method according to claim 34, wherein the further set of preamble elements comprises an Extremely High Throughput Short Training Field, EHT-STF, and at least one Extremely High Throughput Long Training Field, EHT-LTF.

37. A wireless communication device (10, 20; 900) for a wireless communication system, the wireless communication device (10, 20; 900) being configured to: send a first wireless transmission to a further wireless communication device (10, 20; 900), the first wireless transmission comprising a first preamble portion, enabling estimation of at least one transmission parameter by the further wireless communication device (10, 20; 900), and a first data portion; and send a second wireless transmission to the further wireless communication device (10, 20; 900), the second wireless transmission comprising a second preamble portion, enabling estimation of the at least one transmission parameter by the further wireless communication device (10, 20; 900), and a second data portion, wherein the second preamble portion is adapted with respect to the first preamble portion.

38. The wireless communication device (10, 20; 900) according to claim 37, wherein the wireless communication device (10, 20; 900) is configured to perform a method according to any one of claims 2 to 18.

39. The wireless communication device (10, 20; 900) according to claim 37 or 38, comprising: at least one processor (950), and a memory (960) containing program code executable by the at least one processor (950), whereby execution of the program code by the at least one processor (950) causes the wireless communication device (10, 20; 900) to perform a method according to any one of claims 1 to 18.

40. A wireless communication device (10, 20; 900) for a wireless communication system, the wireless communication device (10, 20; 900) being configured to: receive a first wireless transmission from a further wireless communication device (10, 20; 900), the first wireless transmission comprising a first preamble portion, and a first data portion; receive a second wireless transmission from the further wireless communication device (10, 20; 900), the second wireless transmission comprising a second preamble portion and a second data portion, wherein the second preamble portion is adapted with respect to the first preamble portion; and based on the first preamble portion and the second preamble portion, estimate at least one transmission parameter.

41. The wireless communication device (10, 20; 900) according to claim 40, wherein the wireless communication device (10, 20; 900) is configured to perform a method according to any one of claims 20 to 36.

42. The wireless communication device (10, 20; 900) according to claim 40 or 41 , comprising: at least one processor (950), and a memory (960) containing program code executable by the at least one processor (950), whereby execution of the program code by the at least one processor (950) causes the wireless communication device (10, 20; 900) to perform a method according to any one of claims 19 to 36.

43. A computer program or computer program product comprising program code to be executed by at least one processor (950) of a wireless communication device (10, 20; 900), whereby execution of the program code causes the wireless communication device (10, 20; 900) to perform a method according to any one of claims 1 to 36.