Patent Description:
WLAN, as defined in IEEE <NUM>-<NUM>, implements packet-based data transmission. When one or more input data packets or MSDUs (MAC layer service data unit) are present and the wireless channel is free, these MSDUs are processed by the MAC layer to one or more MPDUs (MAC layer protocol data unit) and by the PHY layer, before they are transmitted to one or more peer WLAN communication device as PPDUs (physical layer protocol data unit).

Certain restrictions apply to the length of such a PPDU, measured on the wireless channel. This restriction limits the maximum length or transmit time to a range from <NUM> to <NUM> (sometimes <NUM>) depending on the considered standard. The transmit time is determined and fixed at the beginning of a PPDU transmission. A long transmit time is favorable for high efficiency in communications as the overhead for gaining channel access, preamble transmission, and/or control frame transmission gets negligible.

In the context of low-latency communications, an access point (AP) or a station (STA) may want to transmit both non-latency sensitive and latency sensitive data packets. Often, the arrival of a latency sensitive packet is random, unknown, and unpredictable. Thus, it may happen that a transmission of one or more non-latency sensitive MSDUs has just started when one or more latency sensitive MSDUs arrive. According to the current WLAN behavior, the ongoing PPDU transmission is required to finish before a new PPDU transmission that conveys the latency sensitive MSDUs can be initiated. Thus, the latency sensitive MSDUs may need to wait unacceptably long for their transmission.

Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure. <CIT> discloses establishing a radio connection for the wireless communication, determining a configuration for whether to segment one or more packets for the wireless communication using the established radio connection, and communicating the one or more packets based on the determined configuration. Some aspects provide for assembling a first frame comprising one or more packets, transmitting the first frame, determining whether a portion of one or more packets was truncated during the assembling of the first frame, and transmitting a second frame comprising at least the truncated portion of the one or more packets of the first frame. Some aspects provide for receiving a first frame comprising one or more packets, determining that a portion of one or more packets is truncated, and determining whether to ignore as padding at least the truncated portion of the one or more packets of the first frame. <CIT> discloses systems and techniques relating to wireless communications. A described technique includes obtaining data for a transmission to a wireless communication device. The wireless communication device can be configured to process incoming transmissions based on an aggregate data unit format that specifies signaling for aggregating multiple medium access control (MAC) data units. The technique includes, in a physical (PHY) frame, an aggregate data unit that is based on the data and the aggregate data unit format, the aggregate data unit including a single MAC data unit. The technique includes, in the PHY frame, an indication to signal that the MAC data unit in the aggregate data unit is singular and to cause the wireless communication device to accept the aggregate data unit without a corresponding block acknowledgement agreement.

It is an object to enable dealing with situations where a data transmission is ongoing when e.g. a latency sensitive data unit arrives in an improved manner.

According to an aspect there is provided a communication device for transmitting data to another communication device as defined in claim <NUM>.

According to a further aspect there is provided another communication device for receiving data from another communication device as defined in claim <NUM>.

According to still further aspects, corresponding methods and a computer program comprising program means for causing a computer to carry out the steps of any one of the methods disclosed herein, when said computer program is carried out on a computer are provided.

It shall be understood that the disclosed communication methods, the disclosed computer program and the disclosed computer-readable recording medium have similar and/or identical further embodiments as the claimed communication devices and as defined in the dependent claims and/or disclosed herein.

One of the aspects of the disclosure is to truncate or interrupt an ongoing transmission of one or more data units, particularly if a more urgent or latency sensitive data unit arrives for transmission, in a manner that the receiver is still able to process a received data unit, even if it is not complete. For this purpose, a number of modulation padding bits is determined and added to the unprocessed modulation input bits to obtain a complete modulation input block for subsequent modulation. This enables that other data units having e.g. a higher priority or urgency can be transmitted without a large delay.

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, <FIG> shows the generally known relation and construction of data units in WLAN, in particular of MSDUs or A-MSDUs (aggregated MSDUs), MPDUs, PSDUs (physical layer service data units) and PPDUs.

According to the present disclosure, a PPDU transmission, i.e. a transmission of a data unit, is to be truncated (i.e., shall be truncated or interrupted) without losing data that has already been transmitted. It can thus be considered as a receiver friendly truncation of an ongoing PPDU transmission.

<FIG> show diagrams illustrating the benefit of PPDU truncation with respect to low latency communications. According to <FIG>, showing conventional WLAN behavior, PPDU truncation is not used; according to <FIG> PPDU truncation is used. It shall be noted that the MSDU arrival times are equal in both figures.

According to <FIG>, the PPDU <NUM> holding the non-latency sensitive MSDUs is required to be finished before the latency sensitive MSDUs held in the PPDU <NUM> can be transmitted. This causes an unwanted queuing delay for the latency sensitive MSDUs because the latency sensitive MSDUs need to be buffered in a queue or memory until they can be transmitted. According to <FIG>, however, the truncation of the PPDU <NUM> holding non-latency sensitive data into two PPDU parts <NUM> and <NUM> allows for a speedy transmission of the PPDU <NUM> holding the latency sensitive data. Thus, the queuing delay of the latency sensitive MSDUs is smaller compared to <FIG>. The queuing delay of the non-latency sensitive data increases in <FIG> compared to <FIG>. Thus, PPDU truncation can provide a trade-off of queuing delay of different traffic types but not a reduction. It should be noted that non-latency sensitive and latency-sensitive MSDUs may target different STAs.

Within WLAN, PHY and MAC layer signal processing may in an embodiment be done block-wise. Several processing steps have different block lengths. The block lengths that may be respected for the envisioned PPDU truncation operation are LDPC code word length, OFDM symbol length, and MPDU data unit.

The MPDU data unit consists of (i) header information, (ii) (encrypted) user data, often MSDU, and (iii) frame check sequence (FCS). The FCS is used to detect transmission errors within the user data and/or header information. In case an error is detected, the MPDU is discarded and a retransmission may be requested from the transmitter of that MDPU. One or more MPDUs may be aggregated to an A-MPDU for transmission in a single PPDU (<FIG>). Once the PSDU, i.e. MPDU or A-MPDU, is readily available in the MAC layer, or at least the amount of data to be transmitted is known, the PHY layer is triggered for transmission.

<FIG> shows the interaction between PHY and MAC for a transmission, i.e. initiation of a PPDU transmission and data transfer between MAC and PHY. The MAC triggers the PHY to start transmission by PHY-TXSTART. request (TXVECTOR) function (or primitive). This request includes the TXVECTOR which holds one or more configuration parameters for the PHY such as length information of PHY input data unit (PSDU), modulation coding scheme (MCS), i.e. code rate and constellation diagram size, number of spatial streams, MIMO mode, bandwidth and RU size, etc..

Based on this information, the PHY determines block sizes for LDPC and OFDM modulation and their respective structure. This process holds various steps and is omitted here because this is not part of the disclosed solution. The different block sizes are determined such that at least at the end (and preferably at the beginning as well) of the PSDU the borders of all blocks coincide. These block sizes and related block structures are kept fixed during the entire encoding and modulation process for the respective PPDU. <FIG> visualizes the block-wise operation and coincidence of block borders at the beginning and end of a PSDU.

In <FIG>, following the PHY-TXSTART. request and block size computation, the PHY starts transmitting channel estimation sequences (STF, LTF) and training symbols as well as signaling information (SIG). The signaling information is used by the receiver to configure its PHY for reception of that PPDU. Once the SIG field data is compiled, the PHY reports to the MAC its readiness for data exchange by issuing the PHY-TXSTART. confirm (TXSTATUS) primitive. Following that, the MAC sends data to the PHY by using the PHY-DATA. request (DATA, USER_INDEX) primitive. Thereby, DATA holds the actual data to be transmitted for the user identified by USER_INDEX. Often, the DATA is of size <NUM> octet. The PHY confirms successful data transfer by issuing the PHY-DATA. confirm primitive. The data exchange continues until the MAC issues the PHY-TXEND. request indicating to the PHY to terminate transmission. After that the PHY notifies the MAC that transmission ended by PHY-TXEND. confirm once it does not transmit on the wireless medium anymore.

It is possible for the MAC to truncate PPDU transmission at any time by the PHY-TXEND. request primitive. In this case, the last OFDM symbol is stuffed. This type of truncation is lossy as it comes with data loss or partially damages PPDU, which cannot be demodulated by the receiver. Furthermore, it is not clear to the receiver what caused the PPDU truncation. It could be carrier loss, interference as well as an intentional truncation.

The envisioned behavior is as follows: The MAC may notify the PHY to truncate the transmission at next suitable point in time. Several steps may be performed by MAC and PHY such that the truncation is (almost) loss less. First, processing on the transmitter side will be described before processing on the receiver side will be outlined.

<FIG> shows a diagram illustrating a communication device <NUM> according to an aspect of the present disclosure for transmitting data to another communication device <NUM>, wherein each of the communication devices comprises circuitry <NUM>, <NUM> configured to perform particular operations. The circuitries may be implemented by a respective processor or computer, i.e. as hardware and/or software, or by dedicated units or elements. For instance, respectively programmed processors may represent the respective circuitries <NUM>, <NUM>.

<FIG> shows a flow chart of a communication method <NUM> according an embodiment of the present disclosure, which may be performed by the circuitry <NUM> of the communication device <NUM> on the transmission side. In a first step <NUM> a truncation notification indicating that an ongoing transmission of a data unit (e.g. physical layer protocol data unit - PPDU) shall be truncated is obtained, e.g. from the MAC layer or another layer or an external control unit (e.g. a station management entity (SME)). In response to the truncation notification, based on the number of unprocessed modulation input bits of the data unit, a remaining bit length of a modulation input block is determined (step <NUM>). A number of modulation padding bits corresponding to the determined remaining bit length of a modulation input block is added (step <NUM>) to the unprocessed modulation input bits to obtain a complete modulation input block. Subsequently, the complete modulation input block is modulated (step <NUM>) to obtain a modulation output block. Finally, a transmit data stream containing the obtained modulation output block is transmitted (step <NUM>) to the other communication device <NUM>.

<FIG> shows a flow chart of another embodiment of a communication method <NUM>, which may be performed by the circuitry <NUM> of the communication device <NUM>. According to this embodiment, not only modulation padding bits are added, but also encoding padding bits. In particular, in response to the truncation notification (i.e. after step <NUM>), based on a current bit length of encoding input bits, a remaining bit length of an encoding input block is determined (step <NUM>). Padding to add a number of encoding padding bits corresponding to the determined remaining bit length of an encoding input block to the current bit length of encoding input bits is then performed (step <NUM>) to obtain a complete encoding input block. The complete encoding input block is then encoded (step <NUM>) to obtain an encoding output block for subsequent modulation. Subsequently, steps <NUM> to <NUM>, as described above with reference to <FIG>, are carried out.

<FIG> shows a schematic (simplified) diagram of an embodiment of a communication device <NUM> on the transmission side according to the present disclosure, in particular of the PHY layer. A (more detailed) diagram of another embodiment of a communication device <NUM> on the transmission side according to the present disclosure is shown in <FIG>. The communication device <NUM> comprises a pre-padding circuitry <NUM>, an encoding circuitry <NUM>, a post-padding circuitry <NUM> and a modulation circuitry <NUM>. The pre-padding circuitry <NUM> may perform steps <NUM>, <NUM> and <NUM> (see <FIG>), the encoding circuitry <NUM> may perform step <NUM>, the post-padding circuitry <NUM> may perform steps <NUM> and <NUM>, and the encoding circuitry <NUM> may perform step <NUM> (and optionally step <NUM>, which may alternatively be performed by (not shown) transmission circuitry). Alternatively, step <NUM> may be performed by the MAC layer <NUM> or the SME.

In an embodiment, the operation of the pre- and post-padding circuitry in the proposed setup is determined occasionally subsequent to a truncation notification. Once a truncation notification has been received (e.g. from the MAC layer <NUM>), the following steps may be performed in the dashed blocks. The other blocks continue to operate in the normal manner, i.e. they use the same settings as before. These settings have been determined at the point in time when the MAC has requested the PHY layer to start a transmission with the parameters signaled in TXVECTOR, i.e. based on information contained in PHY-TXSTART. request primitive.

<FIG> shows a diagram that visualizes the operation of the communication device <NUM> with block encoding (e.g. LDPC encoding). All parameters labeled with L are determined at the beginning of transmission and are unchanged during operation, whereas all parameters labeled with R are computed instantly when a truncation notification is received.

The encoding circuitry <NUM> operates with an input block size of LC,i bits and an output block size of LC,e bits. LC,r = LC,e - LC,i bits of redundancy data are added which consist of (punctured or non-punctured) code parity bits and/or repetition of data bits. This relation is illustrated in more detail in <FIG>. In contrast, the modulation circuitry <NUM> has an input block size of LM bits. At the point in time a truncation notification is received, RC,p unprocessed bits reside in the encoder circuitry <NUM> and RM,p unprocessed bits reside in the modulation circuitry <NUM>.

In an embodiment the pre-padding circuitry <NUM> may perform the following steps:.

The post-padding circuitry <NUM> may perform the following steps:.

After the last modulation output block has been transmitted the transmission is stopped and an indication to the MAC layer that transmission has been truncated may be issued.

Equation (<NUM>) assumes that LM ≤ LC,· If this condition is not met, more than two modulation output blocks may be generated before transmission is truncated. In this case RM = NLM - RM,p - LC,e with <MAT> holds ( <MAT> denotes rounding up operation) and N - <NUM> modulation input blocks may be processed before padding is performed in the Nth modulation input block.

It should be noted that the remaining lengths RC and RM can also be computed at the same time when the truncation notification arrives as RM after the padding and encoding step can be predicted.

The scheme described above with reference to <FIG> is particularly used by encoders that employ block-wise encoding such as LDPC codes. For encoders that operate continuously such as BCC encoder, the operation is somewhat different as will be explained in the following.

The pre-padding circuitry <NUM> appends RM bits in total but at least the last LC,e bits of the RM bits are set to zero. This is because the last LC,e bits are used to return the BCC encoder, which may comprise a shift register, in zero state. In an exemplary implementation, LC,e is either <NUM> or <NUM> bits for WLAN BCC case. The post-padding circuitry <NUM> is not present.

<FIG> shows a diagram illustrating the padding procedure for a continuous encoder, e.g. a BCC encoder. Fig. 13A shows a first embodiment of a modulation input block <NUM>. It is assumed that LC,e is smaller than or equal to RM. If this is not the case a new modulation block of size LM is added to the transmit signal and padding is done as shown in Fig. 13B showing another embodiment of two modulation input blocks <NUM>. In Fig. 13A, <NUM> are the encoded information bits (encoded by BCC) present in the unprocessed modulation input block at the point in time a truncation notification is received. <NUM> are the padding bits with arbitrary value. <NUM> are the padding bits with zero value (LC,e).

In Fig. 13B, <NUM> are two modulation input blocks because LC,e is larger than the remaining modulation input block length at the point in time of truncation notification. <NUM> (= <NUM>) are the encoded information bits (encoded by BCC) present in the unprocessed modulation input block at the point in time a truncation notification is received. <NUM> is the remaining modulation input block length at the point in time of truncation notification is less than LC,e. <NUM> are also the padding bits with arbitrary value in the first modulation input block. <NUM> are the padding bits with arbitrary value in the second modulation input block. <NUM> and <NUM> are thus the padding bits with arbitrary value. <NUM> (= <NUM>) are the padding bits with zero value (LC,e).

The number of padded bit in both cases is <MAT>.

In this embodiment, BCC encoding may reside in the same position as the encoding circuitry <NUM> shown in <FIG> and <FIG>. The BCC encoding has a continuous (in contrast to block wise) operation. Once a data bit goes in, a data bit and a parity bit goes out (for code rate ½). In the BCC case, there is only a pre-padding circuitry <NUM> that appends padding bits to fill a modulation block. The last LC,e bits of these padding bits are preferably zero. This is to return to BCC encoder in zero state at the end of transmission. There is no post-padding circuitry <NUM>. The parities are distributed over the output bit stream. BCC encoding is, hence, performed after pre-padding and before modulation.

The bits that are added in the padding circuitries may be either predefined (e.g. all zero, all one) or random (for the continuous encoder restrictions may apply). If the bits have a predefined value, they may be used in the receiver to improve demodulation and decoding. Simple receiver architectures require however that the number of bits padded in the pre- and post-padding circuitry is known. These data can be signaled by the transmitter before the truncation is done, as will be explained below.

In an embodiment (also called variant <NUM>), given that the output block size of the encoding LC,e and the input block size of the modulation LM unit are an integer multiple or an integer fraction of each other, the post-padding circuitry may be omitted. In this case the pre-padding circuitry may pad that many bits such that coding and modulation boundaries are simultaneously fulfilled.

In another embodiment (also called variant <NUM>), given that the MAC layer provides further data to be transmitted although it notified the PHY to truncate transmission, the encoder may continue encoding user data such that a coding input block of length LC,i is filled. The modulation circuitry either adds additional bits or removes bits to achieve the modulation block size. The truncation should only be done when no coding block that contains user data, which has been received before the truncation notification arrived, is affected.

The post-padding circuitry may partly be moved into the modulation circuitry. Thus, not only bit padding but also symbol padding may be performed. As can be seen from <FIG>, the transition from bit to symbol level includes the stream parser operation, which allocates the bit stream to each spatial stream in a round robin fashion. Thus, a symbol padding circuitry <NUM> operating on stream s (as provided in the embodiment of the communication device <NUM> on the transmission side illustrated in <FIG>) pads RM,sym(s) symbols as part of the post-padding procedure, wherein RM,sym(s) is given by equation (<NUM>): <MAT> wherein m(s) denotes the number of bits per symbol of the constellation diagram used for stream s (e.g. m = <NUM> for QPSK). The equation (<NUM>) uses a floor operation. Since symbols may combine more than one bit per symbol, limitations may apply to the symbol level padding because not any number of RM bits may be represented. Thus, a post-padding on bit level may still be required which pads <MAT> bits before symbol padding is performed.

It may be envisioned that the PHY transmits a truncation postamble after the padding process has ended. The truncation postamble is to inform the receiver PHY layer about the fact that transmission truncation was intentional. This information may be passed to the receiver MAC for further processing, because there may be a need to differentiate between an unintentional (e.g. signal loss) or an intentional PPDU truncation.

This signaling may comprise a unique symbol sequence or bit sequence such as an STF or LTF for example. Such a unique sequence may fit within one or more modulation blocks of size LM and may hold signaling information as well, for which a special (e.g. standardized) encoding may be applied. <FIG> shows a diagram of a modulation output block <NUM> including a truncation postamble <NUM>. After the PHY receives the request to truncate to ongoing PPDU, it may perform first padding as described above, followed by the addition of a unique sequence, which optionally includes signaling. After the transmission has ended, the transmitter PHY may inform the transmitter MAC of the transmission end.

Similar to a postamble as shown in <FIG>, a preamble may be suitable as well. In this case, the PHY transmits a truncation preamble after having received a truncation request and before the padding process begins. This signaling comprises a unique bit sequence. In contrast to the postamble, this unique sequence is a bit sequence that may or may not fit into one or more modulation output blocks of size LM. After the unique bit sequence and the (optional) signaling information has been added to the bit stream, the padding procedure as described above begins. <FIG> shows a diagram of a modulation output block <NUM> including a truncation preamble <NUM>.

Another signaling variant uses the padding itself. The padding bit pattern of variable length may be taken from a unique and standardized bit sequence. The receiving PHY may thus be able to detect if a truncation was made intentionally by comparing the received bits with the padding bit pattern. The longer the padding bit pattern is, the higher the likelihood of a correct detection.

Another variant comprises the signaling as part of the MAC layer data stream. Thus, the MAC layer may add signaling to the A-MPDU that is being transmitted. It can be in the form of a special control or management frame or special delimiter. The MAC may then request the truncation after it has forwarded the MAC layer truncation signaling to the PHY layer. <FIG> shows a diagram a modulation output block <NUM> illustrates the truncation operation with MAC signaling <NUM> only. It should be noted that since the truncation signaling resides within the PSDU, it cannot be exploited by the PHY. In general, the MAC layer truncation signaling can be combined with PHY layer signaling variants, i.e. PHY layer pre- or postamble or fixed bit pattern padding.

Furthermore, the preamble of a PPDU may hold an indication that the PSDU part of the transmitted PPDU may be subjected to truncation. This information is provided for the receiver to expect intentional PPDU truncation for the particular PPDU.

The receiving PHY performs the following steps in case no truncation signaling is present. A PPDU is received as usual by synchronizing to the preamble, extracting preamble information, configuring demodulation and decoder unit according to preamble information, and performing demodulation and decoding. If a modulation output block (e.g. OFDM symbol) has been received completely and transmission stopped after that modulation block, the MAC is informed via a primitive that the unexpected PPDU truncation may be intentionally, and the potentially unfinished code word (e.g. LDPC code word; this option applies for variant <NUM>) is discarded before forwarding the received data to the MAC.

The receiving PHY performs the following steps in case a truncation signaling is present. A PPDU is received as usual by synchronizing to the preamble, extracting preamble information, configuring demodulation and decoder unit according to preamble information, and performing demodulation and decoding. Then, the received signal during reception process is correlated with the unique (bit or symbol) sequence in order to detect an intentional truncation. Once the unique sequence is detected, the signaling information may be extracted and the receiving communication device may act according to the signaling information provided. This includes that the receiving PHY may discard any padding bits before forwarding the data to the MAC. If signaling is present or not, the PHY may inform the MAC via a primitive that the unexpected PPDU truncation was made intentionally.

Any signaling that comes with the truncation preamble or postamble may signal one or more of the following data:.

The receive procedure according to an embodiment of the present disclosure is illustrated in <FIG>. Once the PHY detects an L-STF, it gives a carrier clear assessment (CCA) with a busy value to the MAC. Subsequently, the PHY receives signaling information and training symbols. This information is used to configure its receiver and to signal the start of data reception to the MAC including receive parameters, i.e. the RXVECTOR. Subsequently to receiver configuration, the PHY demodulates and decodes the received OFDM symbols. The information (user) data is forwarded to the MAC layer via one or more successive PHY-DATA. indication primitives. Often, one primitive conveys one octet of received PSDU data. When the reception ends, the PHY issues a PHY-RXEND indication holding the reason for the PPDU ending. Shortly thereafter, the CCA returns to idle.

The reason signaled in the PHY-RXEND indication can be the following: no error, format violation, carrier lost, unsupported rate, and/or filtered. According to the present disclosure, the receiver may differentiate another reason, which is 'intended truncation'. This reason may generated as follows.

If no PHY pre- or postamble or unique padding pattern is present (first variant), the PHY may issue the 'intended truncation' reason, if the received PPDU ended before intended end and if the ending of the received PPDU corresponds to the operations performed for intended PPDU truncation at the transmitter (as described above). For the most general case, this means that the last OFDM symbol has been completely received.

If a PHY pre- or postamble or unique padding pattern is present (second variant), the PHY may issue the 'intended truncation' reason, if the received PPDU holds any of the PHY signaling variants and the ending of the received PPDU corresponds to the operations performed for intended PPDU truncation at the transmitter.

As the second variant is much more reliable than the first variant with respect to a wrong detection, it should be preferably applied. Assuming OFDM symbol length of LM samples, the probability of a wrong detection, i.e. the PHY issues 'intended truncation' although it was a 'carrier lost', is <MAT>.

<FIG> shows a simplified diagram (in the form of a state machine) of a communication device <NUM> on the reception side according to conventional WLAN, in particular of the PHY layer. Once a preamble (step <NUM>) is detected, the receiver is configured (step <NUM>) according to the signaling and channel estimation sequences present in the PHY preamble. The receiver configuration holds length information of the PSDU part L. Following that, (OFDM) symbols are received (step <NUM>), decoded and descrambled (step <NUM>), and forwarded to the MAC until the PSDU ends (step <NUM>), i.e. L=<NUM>, and a NoError indication is given (step <NUM>) to the MAC. If a non-valid signal in received, a CarrierLost indication is issued (step <NUM>) to the MAC.

<FIG> shows a schematic diagram (in the form of a state machine) illustrating various embodiments of a communication device <NUM> on the reception side according to the present disclosure. The communication device <NUM> implements detection of an intentionally truncated PPDU. It shall be noted that not all blocks may actually be present in an implementation of such a communication device, e.g. in case a subset of signaling variants is to be supported. Steps <NUM> to <NUM> substantially correspond to steps <NUM> to <NUM> shown in <FIG> and are thus not explained again.

In case no signaling is present, the receiver checks if a modulation output block is partly received. If so, the PHY assumes (step <NUM>) CarrierLost as the reason of PPDU truncation, if not the PPDU truncation is potentially intentional (step <NUM>) with a certain likelihood (see above). A schematic diagram (in the form of a state machine) of such an embodiment of a communication device <NUM> is separately shown in <FIG>. A simplified schematic diagram of this communication device <NUM> comprising demodulation circuitry <NUM> and decoding circuitry <NUM> is shown in <FIG>.

In case a postamble is present, once a symbol is detected as a postamble, the receiver extracts (step <NUM>) the signaling (if present), receives (step <NUM>) more symbols (if present) and indicates (step <NUM>) to the MAC that PPDU truncation is intentional. A schematic diagram (in the form of a state machine) of such an embodiment of a communication device <NUM> is separately shown in <FIG>. A simplified schematic diagram of this communication device <NUM> comprising demodulation circuitry <NUM>, decoding circuitry <NUM>, (optional) post-padding removal circuitry <NUM> and (optional) pre-padding removal circuitry <NUM> is shown in <FIG>.

In case the postamble signaling indicates the padding size, it may truncate the padding part of the last received data. This means that this branch has an impact on the "valid and no postamble detected" branch of the previously received symbol. This is feasible, because of the delay inherent in the processing of the state machine, i.e. the assumption is that the "decode & descramble" processing takes longer than the reception of the postamble.

In case a preamble is present, once, after descrambling (step <NUM>), a preamble is detected (step <NUM>) within the data stream, the receiver extracts (step <NUM>) that preamble and applies related signaling. The signaling may reside in several OFDM symbols, which would be received (step <NUM>) until the end. As a last step (step <NUM>), the receiver forwards the last data part, which may be truncated according to the signaling information, to the MAC and issues a RXEND primitive that indicates intentional PPDU truncation. In case no preamble is detected in step <NUM>, steps <NUM> and <NUM> are carried out, which correspond to steps <NUM> and <NUM> shown in <FIG>. It shall be noted that steps <NUM>, <NUM>, <NUM> and <NUM> (for regular reception of a PPDU) may always be present, regardless if truncation signaling is present or not. A schematic diagram (in the form of a state machine) of such an embodiment of a communication device <NUM> is separately shown in <FIG>. A simplified schematic diagram of this communication device <NUM> comprising demodulation circuitry <NUM>, decoding circuitry <NUM>, (optional) post-padding removal circuitry <NUM> and (optional) pre-padding removal circuitry <NUM> is shown in <FIG>.

<FIG> shows a flow chart of a communication method <NUM> according an embodiment of the present disclosure, which may be performed by the circuitry <NUM> of the communication device <NUM> on the reception side. In a first step <NUM> a receive data stream containing multiple modulation output blocks is received. It is then determined in step <NUM> if truncation has been applied by the other communication device (<NUM>) according to which an ongoing transmission of a data unit has been truncated. In case truncation has been applied by the other communication device, the received modulation output blocks are demodulated and decoded (step <NUM>) and it is indicated (step <NUM>) for subsequent processing by the communication device <NUM> (e.g. by the MAC layer) that an intended truncation was the reason for the truncation. In case truncation has not been applied, the received modulation output blocks are demodulated and decoded as usual (step <NUM>).

In order to minimize data loss in MAC layer, the MAC layer may choose the point in time of truncation wisely. A MAC layer (protocol) data unit (MPDU) is the smallest unit that can be independently processed by the MAC layer. It therefore holds a MAC header and a frame check sequence (FCS) to safeguard the header and/or data content. In case more than one MPDU is transmitted in form of an aggregated MPDU (A-MPDU), the MAC layer may preferably trigger the PHY layer to stop transmission at the point in time when an MPDU of an A-MPDU ended, i.e. the recently transmitted MPDU is finalized. Since each MPDU holds a FCS, no data is lost because of the transmission truncation and can be continued later. In case of more data is provided by the MAC although it triggered the PHY to truncate transmission, the MAC may provide successive delimiters as the data to be transmitted to the PHY. These delimiters may have additional information for the receiving MAC to detect an intentional transmission truncation.

<FIG> and <FIG> illustrate how minimal data loss can be achieved with the proposed PPDU truncation. <FIG> shows a diagram illustrating loss-less PPDU truncation (without truncation pre- or postamble). <FIG> shows a diagram illustrating loss-less PPDU truncation (with truncation postamble). <FIG> and <FIG> show the non-truncated PPDU structure, whereas the truncated PPDU is shown in <FIG> and <FIG>. It is assumed that after the first MPDU was transferred to the PHY, the MAC requests the PHY to truncate the PPDU. Following that the pre- and post-padding circuitry operates as described above in order to pad remaining data blocks. <FIG> assumes no further signaling, but <FIG> shows an example of the postamble which resides in a single OFDM symbol in the given example.

In case of multi-user PPDU (MU-PPDU), multiple MPDUs intended for different receiving STAs are multiplexed into one PPDU. In this case the padding is done similar as in the single user (SU) case, i.e. the pre-padding is done as above, whereas the post-padding is done to the longest remaining bit length. For MU-PPDU, the input block size of the modulation unit LM is same for all users u, but RM,p and LC,e are both a function of u, hence RM,p(u) and LC,e(u) holds. The number of post padding bits is given as follows <MAT> <MAT>.

The present disclosure enables interrupting a transmission of a data unit (e.g. of a PPDU) without losing data that has already been transmitted and thus provides a receiver-friendly truncation of an ongoing PPDU transmission. Truncation of a PPDU provides gains in queuing delay for latency sensitive traffic in cases where latency sensitive (or urgent or high-priority or otherwise preferred) and non-latency sensitive traffic share the same medium.

Thus, the foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. As will be understood by those skilled in the art, the present disclosure may be embodied in other specific forms without departing from the essential characteristics thereof. Accordingly, the disclosure of the present disclosure is intended to be illustrative, but not limiting of the scope of the disclosure, as well as other claims. The disclosure, including any readily discernible variants of the teachings herein, defines, in part, the scope of the foregoing claim terminology such that no inventive subject matter is dedicated to the public.

Further, such a software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claim 1:
Communication device (<NUM>) for transmitting data to another communication device (<NUM>), the communication device (<NUM>) comprising circuitry (<NUM>) configured to:
- obtain a truncation notification indicating that an ongoing transmission of a data unit is to be truncated;
- in response to the truncation notification,
- determine, based on the number of unprocessed modulation input bits of the data unit, a remaining bit length of a modulation input block, and
- perform padding to add a number of modulation padding bits corresponding to the determined remaining bit length of a modulation input block to the unprocessed modulation input bits to obtain a complete modulation input block;
- modulate the complete modulation input block to obtain a modulation output block; and
- transmit a transmit data stream containing the obtained modulation output block.