Transmission and reception of physical layer packets with intermediate codes

Abstract

A method of a transmitter configured to transmit a physical layer packet having a plurality of intermediate codes is disclosed. The method includes applying a respective phase shift for each intermediate code of the physical layer packet, and transmitting the physical layer packet. A corresponding phase shift is applied to at least a portion of the symbols of the intermediate code. A method of a receiver configured to receive a physical layer packet having a plurality of intermediate codes is also disclosed. The method includes receiving a physical layer packet and cancelling a respective phase shift for each intermediate code of the physical layer packet. Cancellating the respective phase shift includes applying an opposite phase shift of the respective phase shift to at least a portion of the symbols of the intermediate code, or compensating for the respective phase shift of the at least a portion of the symbols of the intermediate code. The corresponding phase shifts are from a sequence of phase shifts having random or pseudo-random characteristics. In some embodiments, the plurality of intermediate codes may include a plurality of periodically occurring intermediate codes. Corresponding apparatus, transmitter, receiver, communication device, vehicle and computer program product are also disclosed.

Description

[0001] This application is a divisional application of the Chinese patent application “Transmission and Reception of Physical Layer Packets with Intermediate Codes” with application number 202080098694.0 (filing date March 18, 2020). Technical Field

[0002] The present disclosure generally relates to the field of wireless communications and more particularly to the transmission and reception of physical layer packets including midambles. Background Art

[0003] A midamble may be defined as a block of non-data carrying symbols inserted in the data carrying portion of a physical layer packet.

[0004] For example, in scenarios where the channel varies substantially over the duration of a physical layer packet (i.e., when a single channel estimation instance (such as a preamble) in each physical layer packet is insufficient for adequate channel estimation), a midamble may be used to support channel estimation.

[0005] Therefore, a method for transmitting and receiving a physical layer packet including a midamble is needed. Summary of the invention

[0006] It should be emphasized that when used in this specification, the term "includes / comprising" (replaceable with "includes / comprising") is used to specify the presence of stated features, integers, steps, or components, but does not exclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0007] Generally, when an arrangement is mentioned herein, it is to be understood as a physical product; for example, a device. A physical product may include one or more components, such as a control circuit in the form of one or more controllers, one or more processors, and the like.

[0008] It is an object of some embodiments to solve or mitigate, alleviate, or eliminate at least some of the disadvantages associated with sending and / or receiving physical layer packets including midambles.

[0009] A first aspect is a method of a transmitter configured to transmit a physical layer packet having a plurality of midambles. The method includes: applying a corresponding phase shift for each midamble of the physical layer packet, and transmitting the physical layer packet. The corresponding phase shift is from a phase shift sequence having a random or pseudo-random property, and the corresponding phase shift is applied to at least a portion of the symbols of the midamble.

[0010] In some embodiments, the portion of symbols includes: all symbols of the midamble, or all non-pilot symbols of the midamble, or all symbols of the midamble used for channel estimation purposes.

[0011] In some embodiments, the phase shift sequence has a zero phase average value.

[0012] In some embodiments, the sequence of phase shifts includes phase shifts of 0 radians and π radians represented by scaling values ​​of 1 and -1, respectively.

[0013] In some embodiments, applying the phase shift to the symbol comprises multiplying the symbol value by a scaling value representing the phase shift.

[0014] In some embodiments, the phase shift sequence is predefined or generated using a predefined algorithm.

[0015] In some embodiments, the physical layer packet is used for multiple-input multiple-output (MIMO) transmission via multiple two or more spatial streams, each midamble includes at least a corresponding plurality of training parts, and the same corresponding phase shift is applied to all training parts of the midamble.

[0016] In some embodiments, the plurality of midambles may include a plurality of midambles that appear periodically.

[0017] In some embodiments, applying the corresponding phase shift is in response to a period of occurrence of the midamble being shorter than a threshold.

[0018] A second aspect is a method of a receiver configured to receive a physical layer packet having a plurality of midambles. The method comprises: receiving the physical layer packet, and cancelling a corresponding phase shift for each midamble of the physical layer packet. The corresponding phase shift is from a phase shift sequence having a random or pseudo-random characteristic, and cancelling the corresponding phase shift comprises: applying an opposite phase shift of the corresponding phase shift to at least a portion of the symbols of the midamble, or compensating for the corresponding phase shift of at least a portion of the symbols of the midamble.

[0019] In some embodiments, the portion of symbols includes symbols of a midamble to which a corresponding phase shift is applied by a transmitter of the physical layer packet.

[0020] In some embodiments, the sequence of phase shifts includes phase shifts of 0 radians and π radians represented by scaling values ​​of 1 and -1, respectively.

[0021] In some embodiments, applying the inverse of the phase shift to the symbol comprises multiplying the symbol value by a scaling value representing the phase shift.

[0022] In some embodiments, the phase shift sequence is predefined or generated using a predefined algorithm.

[0023] In some embodiments, the method further comprises acquiring a phase shift sequence.

[0024] In some embodiments, acquiring the phase shift sequence includes one or more of: receiving a signal indicating the phase shift sequence, reading the phase shift sequence from a memory of the receiver, generating the phase shift sequence using a predefined algorithm, and detecting the phase shift sequence based on a received physical layer packet.

[0025] In some embodiments, the plurality of midambles may include a plurality of midambles that appear periodically.

[0026] A third aspect is a computer program product comprising a non-transitory computer readable medium having thereon a computer program comprising program instructions. The computer program is loadable into a data processing unit and is configured to cause the performance of the method according to the first and second aspects when the computer program is run by the data processing unit.

[0027] A fourth aspect is an apparatus of a transmitter configured to send a physical layer packet having a plurality of midambles. The apparatus includes a control circuit configured to: apply a corresponding phase shift to each midamble of the physical layer packet, and send the physical layer packet. The corresponding phase shift is from a phase shift sequence having a random or pseudo-random characteristic, and the corresponding phase shift is applied to at least a portion of the symbols of the midamble.

[0028] A fifth aspect is an apparatus of a receiver configured to receive a physical layer packet having a plurality of midambles. The apparatus includes a control circuit configured to: receive the physical layer packet, and cancel a corresponding phase shift for each midamble of the physical layer packet. The corresponding phase shift is from a phase shift sequence having a random or pseudo-random characteristic, and canceling the corresponding phase shift includes applying an opposite phase shift of the corresponding phase shift to at least a portion of the symbols of the midamble or compensating for the corresponding phase shift of at least a portion of the symbols of the midamble.

[0029] A sixth aspect is a communication transmitter comprising the apparatus of the fourth aspect.

[0030] The seventh aspect is a communication receiver including the apparatus of the fifth aspect.

[0031] The eighth aspect is a communication device, which includes one or more of the following: the device of the fourth aspect, the device of the fifth aspect, the transmitter of the sixth aspect, and the receiver of the seventh aspect.

[0032] A ninth aspect is a vehicle including the communication device of the eighth aspect.

[0033] In some embodiments, any of the above aspects may additionally have features that are the same as or correspond to any of the various features as explained for any of the other aspects above.

[0034] An advantage of some embodiments is that spectral lines associated with a midamble of a physical layer packet are mitigated (eg, suppressed).

[0035] An advantage of some embodiments is that higher output power can be achieved compared to prior art methods while meeting spectrum requirements.

[0036] An advantage of some embodiments is that less interference may be caused to other users.

[0037] An advantage of some embodiments is that more relaxed requirements on the transmission filter may be applied compared to prior art methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further objects, features and advantages will appear from the following detailed description of embodiments with reference to the accompanying drawings.The drawings are not necessarily drawn to scale, emphasis instead being placed upon illustrating example embodiments.

[0039] Figure 1 is a flow chart illustrating example method steps according to some embodiments;

[0040] Figure 2 is a flow chart illustrating example method steps according to some embodiments;

[0041] Figure 3 is a schematic diagram illustrating example physical layer grouping according to some embodiments;

[0042] Figure 4 is a schematic diagram illustrating example phase shifts for physical layer packets according to some embodiments;

[0043] Figure 5 is a collection of simulation graphs illustrating example power spectral densities associated with some embodiments;

[0044] Figure 6 is a collection of simulation graphs illustrating example power spectral densities associated with some embodiments;

[0045] Figure 7 is a collection of simulation graphs illustrating example power spectral densities associated with some embodiments;

[0046] Figure 8 is a schematic block diagram illustrating an example apparatus according to some embodiments; and

[0047] Fig. 9 is a schematic block diagram illustrating an example apparatus according to some embodiments; and

[0048] Fig.10 is a schematic diagram illustrating an example computer-readable medium in accordance with some embodiments. DETAILED DESCRIPTION

[0049] As already mentioned above, it should be emphasized that when used in the specification, the term "comprises / comprising" (alternatively "includes / comprising") is understood to specify the presence of the stated features, integers, steps, or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof. As used in this document, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0050] Embodiments of the present disclosure will be more fully described and illustrated below with reference to the accompanying drawings. However, the solutions disclosed herein may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein.

[0051] In some communication applications, multiple midambles are inserted into a physical layer packet so that when some midamble symbols coincide for different midambles (e.g., when the midambles include the same training sequence), spectral lines appear in the power spectrum of the physical layer packet. In the following, the case of a periodically occurring midamble will be considered as an example. However, it should be noted that for a non-periodically occurring midamble, similar problems of spectral lines appearing in the power spectrum of the physical layer packet may be experienced.

[0052] Generally, the plurality of midambles may include a plurality of midambles that appear periodically, or a plurality of midambles that appear non-periodically, or a first plurality of midambles that appear periodically and a second plurality of midambles that appear non-periodically.

[0053] In some communication applications, multiple midambles are inserted into a physical layer packet at equal distances from each other (e.g., separated by the same number of data-bearing symbols). This approach may result in spectral lines appearing in the power spectrum of the physical layer packet when at least some of the midamble symbols overlap for different midambles (due to periodic symbol repetition).

[0054] Such spectral lines may be undesirable. For example, they may present problems in meeting a spectral mask and / or other frequency requirements (e.g., regarding power spectral density (PSD) and / or out-of-band emissions). Therefore, a method for sending and receiving physical layer packets including a midamble is needed in which the spectral lines are mitigated (e.g., suppressed).

[0055] In the following, an embodiment of processing a physical layer packet including a midamble by applying a corresponding phase shift to each midamble of the physical layer packet will be described, wherein the corresponding phase shift comes from a phase shift sequence having a random or pseudo-random property. This results in the spectral lines associated with the midamble of the physical layer packet being mitigated.

[0056] In certain applications, the physical layer packet is a physical layer protocol data unit (PPDU) of the IEEE 802.11 standard (eg, for vehicle-to-everything V2X communications), including a component in the form of a long training field (LTF). However, it should be understood that the embodiments are not limited thereto.

[0057] Figure 1 An example method 100 according to some embodiments is shown. The method is for a transmitter configured to send a physical layer packet with multiple (eg, periodically occurring) midambles. Typically, at least some symbol values ​​are the same for different midambles, which results in undesirable spectral lines.

[0058] For example, in scenarios where the channel varies substantially over the duration of a physical layer packet (eg, in scenarios with substantial Doppler effects, such as high-speed scenarios), midambles may be used for channel estimation.

[0059] In step 130, a corresponding phase shift is applied for each midamble of the physical layer packet, and in step 140, the physical layer packet is transmitted.

[0060] In step 130, the corresponding phase shift is applied to at least a portion of the symbols of the midamble. In some embodiments, the portion of symbols includes (e.g., consists of) all symbols of the midamble. In some embodiments, the portion of symbols includes (e.g., consists of) all symbols that are part of the midamble. In some embodiments, the portion of symbols includes (e.g., consists of) all non-pilot symbols of the midamble. In some embodiments, the portion of symbols includes (e.g., consists of) all symbols of the midamble used for channel estimation purposes (e.g., training symbols or other reference symbols).

[0061] According to some embodiments, the phase shift sequence may be predefined. For example, a sequence or a set of indexed sequences may be predefined (eg, according to a standard).

[0062] Alternatively or additionally, the phase shift sequence may be generated using a predefined algorithm.For example, the algorithm and / or one or more seed values ​​may be predefined (eg, according to a standard).

[0063] In optional step 110, a phase shift sequence is acquired.

[0064] Acquisition of the phase shift sequence may, for example, include receiving a signal indicating the phase shift sequence; for example, from another communication node, such as a network node or a receiver of a physical layer packet. The signal indicating the phase shift sequence may, for example, include one or more of the following: a sequence, a sequence index, an algorithm identifier, an algorithm seed value, or an algorithm seed value index.

[0065] Alternatively or additionally, acquiring the phase shift sequence may include reading the phase shift sequence from a memory of the transmitter; for example, based on a sequence index when two or more phase shift sequences exist in the memory.

[0066] Still alternatively or additionally, obtaining the phase shift sequence may include generating the phase shift sequence using a predefined algorithm; for example, based on an algorithm seed value.

[0067] In optional step 120, a signal indicating the phase shift sequence is sent to a receiver of the physical layer packet. For example, the signal indicating the phase shift sequence may include one or more of: a sequence, a sequence index, an algorithm identifier, an algorithm seed value, or an algorithm seed value index.

[0068] Optional step 105 shows that applying the corresponding phase shift may be in response to the occurrence period (per) of the midamble being shorter than a threshold value (thr). Therefore, if it is determined that the occurrence period of the midamble is shorter than the threshold value (the "yes" path in step 105), the method is performed as described above. Otherwise (the "no" path in step 105), the method proceeds directly to step 140, where the physical layer packet is sent without applying the phase shift.

[0069] Figure 2 An example method 200 according to some embodiments is shown. The method is for a receiver configured to receive a physical layer packet with multiple (e.g., periodically occurring) midambles. Typically, at least some symbol values ​​are the same for different midambles, which (using prior art methods) results in undesirable spectral lines.

[0070] For example, in scenarios where the channel varies substantially over the duration of a physical layer packet (eg, in scenarios with substantial Doppler effects, such as high-speed scenarios), midambles may be used for channel estimation.

[0071] In step 210, a physical layer packet is received, and in step 230, a corresponding phase shift is canceled for each midamble of the physical layer packet.

[0072] Typically, cancelling the corresponding phase shift may be defined as applying an opposite phase shift of the corresponding phase shift (restoring the corresponding phase shift). Thus, cancelling the corresponding phase shift in step 230 may include applying an opposite phase shift of the corresponding phase shift (e.g., a phase shift having the same phase amplitude as the corresponding phase shift but an opposite phase direction (i.e., sign) as the corresponding phase shift) to at least a portion of the symbols of the midamble. Alternatively or additionally, cancelling the corresponding phase shift may be defined as compensating for the corresponding phase shift of at least a portion of the symbols of the midamble without explicitly restoring the corresponding phase shift. For example, a receiver processing step (e.g., channel estimation) may take into account the corresponding phase shift without explicitly restoring the corresponding phase shift.

[0073] In some embodiments, a portion of symbols includes (e.g., consists of) all symbols of a midamble. In some embodiments, a portion of symbols includes (e.g., consists of) all symbols that are part of a midamble. In some embodiments, a portion of symbols includes (e.g., consists of) all non-pilot symbols of a midamble. In some embodiments, a portion of symbols includes (e.g., consists of) all symbols of a midamble used for channel estimation purposes (e.g., training symbols, or other reference symbols).

[0074] A portion of symbols may typically include symbols of a midamble to which the transmitter of the physical layer packet has applied a corresponding phase shift. Information about which symbols have the phase shift applied may, for example, be predefined or indicated (implicitly or explicitly) in a preamble of the physical layer packet.

[0075] However, it should be noted that other methods are also possible. For example, when the corresponding phase shift is applied by the transmitter to all symbols of the midamble, the receiver may apply the opposite phase shift of the corresponding phase shift only to the symbols of the midamble used for channel estimation purposes and / or non-pilot symbols of the midamble. Accordingly, when the corresponding phase shift is applied by the transmitter to only the symbols of the midamble used for channel estimation purposes and / or non-pilot symbols of the midamble, the receiver may apply the opposite phase shift of the corresponding phase shift to all symbols of the midamble.

[0076] According to some embodiments, the phase shift sequence may be predefined. For example, a sequence or a set of indexed sequences may be predefined (eg, according to a standard).

[0077] Alternatively or additionally, the phase shift sequence may be generated using a predefined algorithm.For example, the algorithm and / or one or more seed values ​​may be predefined (eg, according to a standard).

[0078] In optional step 220, a phase shift sequence is acquired.

[0079] Acquiring the phase shift sequence may, for example, include receiving a signal indicative of the phase shift sequence; for example, from another communication node, such as a network node or a transmitter of a physical layer packet (with Figure 1 The signal indicative of the phase shift sequence may, for example, include one or more of: a sequence, a sequence index, an algorithm identifier, an algorithm seed value, or an algorithm seed value index.

[0080] Alternatively or additionally, acquiring the phase shift sequence may include reading the phase shift sequence from a memory of the receiver; for example, based on a sequence index when two or more phase shift sequences exist in the memory.

[0081] Still alternatively or additionally, obtaining the phase shift sequence may include generating the phase shift sequence using a predefined algorithm; for example, based on an algorithm seed value.

[0082] Further alternatively or additionally, obtaining the phase shift sequence may include detecting the phase shift sequence based on the received physical layer packet.For example, when a previous channel estimate is known (e.g., from a preamble or a previous midamble), this knowledge can be used to estimate the phase shift for subsequent (one or more) midambles.

[0083] For example, the phase of each subcarrier used for the LTF(s) in the preamble may be compared to the phase of the corresponding subcarrier in the first LTF in the midamble. The phase difference for each subcarrier may be determined, and the phase shift of the first midamble relative to the LTF(s) in the preamble may be estimated by averaging the subcarriers. The process may continue by comparing the phase of each subcarrier used for the first midamble with the phase of the corresponding subcarrier in the second midamble in the same manner to estimate the phase shift of the second midamble relative to the first midamble; and so on.

[0084] Optional step 215 shows that the corresponding phase shift can be offset in response to the occurrence period (per) of the midamble being shorter than a threshold value (thr). Therefore, if it is determined that the occurrence period of the midamble is shorter than the threshold value (the "yes" path in step 215), the method is performed as described above. Otherwise (the "no" path in step 215), the received physical layer packet is processed without phase shift offset.

[0085] In any case, processing of the received physical layer packet may include performing channel estimation based on the midamble, as shown in optional step 240. Step 230 may be considered a sub-step of step 240 when canceling the corresponding phase shift includes compensating for the corresponding phase shift during channel estimation.

[0086] It should be noted that Figure 1 and Figure 2 Some steps of may be performed in another order than the order shown according to some embodiments. Some examples include: performing steps 110 and / or 120 only once for multiple physical layer packets, performing step 220 before step 215 and / or before step 210, and performing step 220 only once for multiple physical layer packets.

[0087] Typically, the corresponding phase shifts are derived from a sequence of phase shifts having a random or pseudo-random nature.

[0088] For example, the respective phase shifts for the midamble sequence may be selected in the order of appearance in the (pseudo)random phase shift sequence; ie two consecutive midas are associated with two consecutive phase shifts in the (pseudo)random phase shift sequence.

[0089] In some embodiments, scrambling may be applied to the sequence of phase shifts and / or the corresponding phase shifts of the physical layer packet; to prevent a large number of consecutive phase shifts of the same value from being applied to the physical layer packet.

[0090] The phase shift sequence having random or pseudo-random characteristics may be defined according to any suitable definition of randomness.In addition, any suitable algorithm or other method may be used to provide the sequence.

[0091] For example, the phase shift sequence may have a zero phase average. Alternatively, the phase shift sequence may have a phase average close to zero; for example, within an absolute phase difference from zero phase below a phase threshold. Alternatively still, the phase shift sequence may have any suitable phase average.

[0092] The phase average of the phase shift sequence may be in the context of a phase shift space defined as [-π,π] radians. For example, a phase shift sequence having a zero phase average may be in the context of a phase shift space defined as [-π,π] radians, where half of the instances having a π radian value are counted as instances having a -π radian value, and vice versa.

[0093] In general, a respective phase shift applied for a single physical layer packet may have the same or a different phase average value as the sequence of phase shifts from which the respective phase shift was taken.

[0094] In some embodiments, the phase shift sequence consists of a phase shift of 0 radians (0°) and π radians (180°). Such phase shifts may be represented by scaling values ​​of 1 and -1, respectively. The latter is particularly suitable when the modulation scheme used for communication is such that a multiplication with -1 corresponds to a phase shift of π radians (e.g., phase shift keying PSK, in particular binary phase shift keying BPSK; quadrature amplitude modulation QAM, etc.). Applying the phase shift to the symbol may then include multiplying the symbol value by a scaling value representing the phase shift, and applying the opposite phase shift to the symbol may also include multiplying the symbol value by a scaling value representing the phase shift (because two products with -1 cancel each other, and a multiplication with 1 is an identity operation).

[0095] In some embodiments, the phase shift sequence consists of phase shifts of 0 radians (0°), π / 2 radians (90°), π radians (180°), and 3π / 2 radians (270°). Such phase shifts may be represented by complex scaling values ​​1, i, -1, and -i, respectively. The latter is particularly suitable when the modulation scheme used for communication is such that a multiplication with i corresponds to a phase shift of π / 2 radians, a multiplication with -1 corresponds to a phase shift of π radians, and so on (e.g., phase shift keying, PSK; quadrature amplitude modulation, QAM; etc.). Applying the phase shift to the symbol may then include multiplying the symbol value by a scaling value representing the phase shift, and applying the opposite phase shift to the symbol may include multiplying the symbol value by the complex conjugate of the complex scaling value representing the phase shift.

[0096] In some embodiments, the sequence of phase shifts consists of selecting from another set of phase shifts. For example, the set of phase shifts may be equally spaced in the interval [0, 2π] radians.

[0097] For example, the non-pilot symbols of the mid-code can be understood in the context of the IEEE 802.11 standard. Then, in each orthogonal frequency division multiplexing (OFDM) symbol, some subcarriers can be dedicated to pilot signals so that coherent detection is robust to frequency offset and phase noise. The long training field (LTF) is used for channel estimation and improves the accuracy of frequency and time estimation. In very high throughput (802.11ac), high efficiency (802.11ax) and 802.11bd physical layers, LTF allows phase tracking by inserting pilot subcarriers in subcarriers dedicated to channel sounding. OFDM symbols that support channel sounding and include LTF contain both pilot subcarriers and non-pilot subcarriers. Then, the non-pilot symbol of the mid-code can refer to the (one or more) parts of the mid-code corresponding to the non-pilot subcarriers.

[0098] In general, non-pilot symbols of a midamble may refer to any (one or more) portions of the midamble whose function is not affected by phase randomization. For such (one or more) portions of the midamble, the corresponding phase shift may be applied for transmission and not cancelled for reception, or the corresponding phase shift may be applied for transmission and cancelled for reception, or the corresponding phase shift may not be applied for transmission and still cancelled for reception, or the corresponding phase shift may not be applied for transmission and not cancelled for reception.

[0099] Figure 3 An example physical layer packet 300 according to some embodiments is schematically shown. A plurality of midambles 301, 302 are inserted into the physical layer packet (e.g., at equal distances from each other - separated by the same number of data-carrying symbols, as indicated by 305). Each midamble 301, 302 may include one or more (usually identical) constituent parts 310, 320; for example, a sequence of training symbols or similar symbols.

[0100] When the physical layer packet is used for multiple-input multiple-output (MIMO) transmission via multiple two or more spatial streams, each midamble may include (at least) a corresponding plurality of components (e.g., a training portion). For example, in a MIMO application with two spatial streams, each midamble may include two components.

[0101] In particular applications, the physical layer packet is a physical layer protocol data unit (PPDU) of the IEEE 802.11 standard (e.g., for vehicle-to-everything V2X communications), a portion of the midamble is a long training field (LTF), and some embodiments are intended to mitigate (e.g., suppress) spectral lines in the power spectral density (PSD) of the PPDU signal caused by repetition of the LTF within the midamble and / or between midambles.

[0102] Figure 4 An example physical layer packet (e.g., PPDU) 400 according to some embodiments is schematically shown. A plurality of midambles 401, 402 are inserted into the physical layer packet (e.g., at equal distances from each other). Each midamble 401, 402 comprises two constituent parts 410, 420; 430, 440 (e.g., LTF).

[0103] Also shown is the application / cancellation of corresponding phase shifts 491, 492 by multiplication with the scaling value. In this example, the corresponding phase shift is applied to the entire midamble. Thus, the original phase difference between the components of the same midamble is preserved, which can be particularly beneficial in MIMO applications because different components of the midamble are used for channel estimation associated with corresponding spatial streams.

[0104] Specific example applications of some embodiments will be described.

[0105] The current IEEE 802.11 technology used for V2X applications is based on the IEEE 802.11p-2010 amendment, which in turn is derived from the IEEE 802.11a-1999 Orthogonal Frequency Division Multiplexing (OFDM) Physical Layer (PHY). There is ongoing activity in the IEEE 802.11bd task group to provide support for higher throughput and range in IEEE 802.11-based V2X applications by adopting more modern IEEE 802.11 technologies than IEEE 802.11a.

[0106] The IEEE 802.11ax amendment introduces so-called midambles to better support channel estimation in propagation environments with high Doppler. At least in this context, a midamble can be viewed as a set of one or more long training fields (LTFs) that are periodically inserted (e.g., by M MAData field symbol separated) in a physical layer protocol data unit (PPDU) to facilitate the update of the channel estimate (with Figure 3 and Figure 4 For example, for IEEE 802.11ax, each midamble may include multiple high-efficiency (HE) LTFs, each of which is the same as the HE-LTF of the PPDU preamble.

[0107] Since high Doppler is typical in V2X communications, IEEE 802.11bd is considering adopting midambles. Moreover, IEEE 802.11bd recommends shortening the midamble period relative to IEEE 802.11ax. It seems that the number of data symbols M between a pair of midambles is MA Can be as low as four (ie, M MA ≥4).

[0108] In addition, IEEE 802.11bd is considering adopting MIMO with up to two spatial streams to increase throughput.If both MIMO and midamble are adopted, each midamble usually includes (at least) two LTFs.

[0109] When the midamble period is short (for example, when M MA =4), a peak appears in the spectrum. The reason is that the LTF in the midamble is repeated, which produces strong periodic time correlations. These correlations produce spectral lines, which are peaks in the power spectral density (PSD) of the PPDU. Figure 5 and Figure 6 The PSD of an IEEE 802.11bd PPDU is shown.

[0110] Figure 5 The PSD of an IEEE 802.11bd PPDU with one spatial stream is shown.

[0111] In the above figure, the y-axis represents the PSD ranging from -40dB to 10dB, and the x-axis represents the frequency interval of about 12MHz. MA =4), and the figure on the right is the PSD 501 of the PPDU without the midamble.

[0112] In the lower figure (which represents an enlarged version of the upper figure), the y-axis represents the PSD ranging from -15dB to 10dB, and the x-axis represents the frequency interval of about 0.5MHz. The spectral lines generated from the midamble can be seen in the figure on the left, and some of them are indicated by 503.

[0113] Figure 6The PSD of an IEEE 802.11bd PPDU with two spatial streams is shown, where the PSD shown corresponds to the output signal from one of the transmit chains.

[0114] In the above figure, the y-axis represents the PSD ranging from -40dB to 10dB, and the x-axis represents the frequency interval of about 12MHz. MA =4), and the figure on the right is the PSD 601 of the PPDU without the midamble.

[0115] In the lower figure (which shows an enlarged version of the upper figure), the y-axis shows the PSD ranging from -40dB to -15dB, and the x-axis shows the frequency spacing of about 1 MHz. The spectral lines resulting from the midamble can be seen in the left figure, and some of them are indicated by 603.

[0116] like Figure 5 and Figure 6 As can be seen in Figure 1, the use of a midamble introduces undesirable spikes (spectral lines) in the PSD, which may make it more difficult to meet one or more of the spectrum mask requirements (e.g., requirements regarding leakage to adjacent channels) and the PSD requirements (e.g., requirements regarding power transmitted per frequency unit). As a result, the undesirable spikes may result in a forced reduction in the total transmit power well below the maximum allowed limit.

[0117] As illustrated in embodiments herein, applying a (pseudo) random phase shift to the LTFs in the midamble results in a randomization that mitigates or eliminates undesirable spikes in the PSD of an IEEE 802.11bd PPDU.

[0118] Randomization of the transmitted waveform results in mitigation of spectral lines, which can translate into one or more of higher output power, less interference to other users, and more relaxed requirements on transmit filters.

[0119] As exemplified above, some embodiments propose to impart (pseudo) random variations to the phases of the LTFs included in the midamble.

[0120] In the case of a MIMO PPDU, the transmitter typically applies orthogonal spreading codes to the LTFs to enable MIMO channel estimation at the receiver, and the changes in the phase of the LTFs included in one midamble should preferably be the same to preserve the phase differences between the LTFs. Specifically, the spreading code may impart 0° or 180° phase shifts to consecutive LTFs included in each midamble for MIMO, and these phase shifts may be important for obtaining orthogonality in the spreading code and enabling the receiver to estimate the channel. Therefore, randomization should preserve the relative phase shifts between different LTFs for MIMO.

[0121] As mentioned before, the phase shift sequence may be generated as a pseudo-random phase sequence.

[0122] An example sequence may be based on the IEEE 802.11-2016 Part 11 specification, which defines the pseudo-random sequence p in Section 17.3.5.10. n This sequence is a cyclic extension of 127 elements of the sequence defined in equations (17-25) of the specification and is typically used to control the polarity of the pilot subcarriers.

[0123] One example sequence may be based on the data scrambler defined in Section 17.3.5.5 of the IEEE 802.11-2016 Part 11 specification, which generates a scrambled sequence that may be mapped to logical bits of ±1.

[0124] Once the phase shift sequence is available, the LTF included in the nth midamble can be multiplied by the same phase factor p n ; For example, the nth entry of the phase shift sequence (with Figure 4 This approach preserves the relative phase between consecutive LTFs in the same midamble.

[0125] Figure 7 (It should be Figure 6 ) shows the PSD of an IEEE 802.11bd PPDU with two spatial streams, where the PSD shown corresponds to the output signal from one of the transmit chains.

[0126] The y-axis represents the PSD ranging from -40 dB to 10 dB, and the x-axis represents the frequency spacing of about 12 MHz. The left graph is a graph with a midamble (M) after applying the randomization as explained above. MA = 4) of the PPDU PSD 701 (see also Figure 4 ), the right figure is the PSD 702 of the PPDU without the midamble. Figure 7 Obviously, in Figure 6 The spectral lines resulting from the midamble seen in the left figure no longer exist; or at least they are not Figure 6 protrude.

[0127] If the periodicity is large enough, the effect of the repeated midamble on the PSD is not significant and can be ignored. MA The value of M is defined, for example MA =16), the midamble randomization as illustrated in this article can be applied.

[0128] Figure 8An example apparatus 810 according to some embodiments is schematically shown. The apparatus 810 is for a transmitter configured to send a physical layer packet with multiple (eg, periodically occurring) midambles. For example, the apparatus 810 may be configured such that (eg, performing) a combination of Figure 1 One or more of the described method steps.

[0129] The apparatus may be comprised (or may be comprised) in one or more of a (wireless) communication transmitter, a (wireless) communication device (eg a network node, an access point, a user equipment UE or a station STA), and a vehicle.

[0130] The apparatus includes a controller (CNTR; for example, a control circuit or a control module) 800 .

[0131] The controller 800 is configured to apply a corresponding phase shift (with respect to Figure 1 compared with step 130).

[0132] To this end, the controller 800 may include a phase shifter (PS; e.g., a phase shift circuit or a phase shift module) 801 or otherwise be associated with (e.g., connected or connectable to) the phase shifter 801. The phase shifter may be configured to apply a corresponding phase shift to each midamble of the physical layer packet. For example, the phase shifter may include one or more multipliers configured to multiply the symbol value by a scaling value representing the phase shift, as described in detail above.

[0133] The controller 800 is also configured to enable sending of physical layer packets (with Figure 1 compared with step 140).

[0134] To this end, the controller 800 may include or be otherwise associated with (eg, connected or connectable to) a transmitter (TX; eg, a transmit circuit or transmitter module) 830. The transmitter may be configured to transmit physical layer packets.

[0135] The controller 800 may also be configured to obtain a phase shift sequence (with Figure 1 compared with step 110).

[0136] To this end, the controller 800 may include an acquirer (ACQ; e.g., an acquisition circuit or acquisition module) 802 or otherwise be associated with (e.g., connected or connectable to) the acquirer 802. The acquirer may be configured to acquire the phase shift sequence (e.g., via reception, memory reading, and / or generation), as described in detail above.

[0137] Fig. 9An example apparatus 910 according to some embodiments is schematically shown. The apparatus 910 is for a receiver configured to receive a physical layer packet having a plurality of (eg, periodically occurring) midambles. For example, the apparatus 910 may be configured such that (eg, performing) a combination of Figure 2 One or more of the described method steps.

[0138] The apparatus may be comprised (or may be comprised) in one or more of a (wireless) communication receiver, a (wireless) communication device (eg a network node, an access point, a user equipment UE or a station STA), and a vehicle.

[0139] The apparatus includes a controller (CNTR; for example, a control circuit or a control module) 900 .

[0140] The controller 900 is configured to receive a physical layer packet (with Figure 2 compared with step 210).

[0141] To this end, the controller 900 may include or be otherwise associated with (eg, connected or connectable to) a receiver (RX; eg, a receive circuit or a receiver module) 930. The receiver may be configured to receive a physical layer packet.

[0142] The controller 900 is configured to cancel the corresponding phase shift (with respect to Figure 2 compared with step 230).

[0143] To this end, the controller 900 may include a phase shifter (PS; e.g., a phase shift circuit or a phase shift module) 901 or otherwise be associated with (e.g., connected or connectable to) the phase shifter 901. The phase shifter may be configured to restore the corresponding phase shift by applying the opposite phase shift of the corresponding phase shift for each midamble of the physical layer packet. For example, the phase shifter may include one or more multipliers configured to multiply the symbol value by a scaling value representing the opposite phase shift of the corresponding phase shift, as described in detail above.

[0144] The controller 900 may also be configured to acquire a phase shift sequence (with Figure 2 compared with step 220).

[0145] To this end, the controller 900 may include an acquirer (ACQ; e.g., an acquisition circuit or acquisition module) 902 or otherwise be associated with (e.g., connected or connectable to) the acquirer 902. The acquirer may be configured to acquire the phase shift sequence (e.g., via reception, memory reading, generation, and / or detection), as described in detail above.

[0146] The described embodiments and their equivalents may be implemented in software or hardware or a combination thereof. The embodiments may be performed by general purpose circuits. Examples of general purpose circuits include digital signal processors (DSPs), central processing units (CPUs), coprocessor units, field programmable gate arrays (FPGAs), and other programmable hardware. Alternatively or additionally, the embodiments may be performed by dedicated circuits, such as application specific integrated circuits (ASICs). General purpose circuits and / or dedicated circuits may, for example, be associated with or included in an apparatus such as a wireless communication device, a network node, or a vehicle.

[0147] Embodiments may occur within an electronic device (such as a wireless communication device, a network node, or a vehicle) that includes an arrangement, circuitry, and / or logic according to any of the embodiments described herein. Alternatively or additionally, an electronic device (such as a wireless communication device, a network node, or a vehicle) may be configured to perform a method according to any of the embodiments described herein.

[0148] According to some embodiments, the computer program product comprises a tangible or non-tangible computer readable medium, such as, for example, a Universal Serial Bus (USB) memory, a plug-in card, an embedded drive, or a Read Only Memory (ROM). Fig.10 An example computer readable medium in the form of a compact disc (CD) ROM 1000 is shown. A computer program including program instructions has been stored on the computer readable medium. The computer program may be loaded into a data processor (PROC; e.g., a data processing circuit or a data processing unit) 1020, which may, for example, be included in a device 1010 (e.g., a wireless communication device, a network node, or a vehicle). When loaded into the data processor, the computer program may be stored in a memory (MEM) 1030 associated with or included in the data processor. According to some embodiments, the computer program may, when loaded into and run by the data processor, cause execution according to, for example, Figure 1 and Figure 2 A method step of any of the methods shown or otherwise described herein.

[0149] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is explicitly given and / or a different meaning is implied from the context in which it is used.

[0150] Reference has been made to various embodiments herein. However, one skilled in the art will recognize many variations of the described embodiments that will still fall within the scope of the claims.

[0151] For example, the method embodiments described herein disclose example methods by steps performed in a specific order. However, it should be appreciated that these sequences of events may occur in another order without departing from the scope of the claims. In addition, some method steps may be performed in parallel, even if they have been described as being performed in sequence. Therefore, the steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless a step is explicitly described as being after or before another step and / or it is implied that a step must be after or before another step.

[0152] In the same manner, it should be noted that in the description of the embodiments, the division of the functional block into specific units is not intended to be restrictive. On the contrary, these divisions are only examples. The functional block described as a unit in this article can be divided into two or more units. In addition, the functional block described as being implemented as two or more units in this article can be merged into fewer (e.g., single) units.

[0153] Where appropriate, any feature of any embodiment disclosed herein may be applicable to any other embodiment. Likewise, any advantage of any embodiment may be applicable to any other embodiment, and vice versa.

[0154] Therefore, it should be understood that the details of the described embodiments are given as examples for illustrative purposes only and that all variations coming within the scope of the claims are intended to be embraced therein.

Claims

1. A method of a transmitter configured to send a physical layer packet having multiple midambles, the method comprising: applying a corresponding phase shift for each midamble of the physical layer packet, wherein the corresponding phase shift is from a phase shift sequence having a random or pseudo-random property, and wherein the corresponding phase shift is applied to at least a portion of symbols of the midamble, wherein the sequence is a cyclic extension of elements in a sequence for controlling polarity of pilot subcarriers of a training sequence provided by the transmitter; and The physical layer packet is sent.

2. The method according to claim 1, wherein: The phase shift sequence has a zero phase average value.

3. The method according to claim 1, wherein: The sequence of phase shifts includes phase shifts of 0 radians and π radians represented by scaling values ​​of 1 and -1, respectively.

4. The method according to claim 3, wherein: Applying a phase shift to a symbol comprises multiplying the value of the symbol by the scaling value representing the phase shift.

5. The method according to claim 1, wherein: The plurality of midambles include a plurality of midambles that appear periodically.

6. A method of a receiver configured to receive a physical layer packet having a plurality of midambles, the method comprising: receiving the physical layer packet; as well as For each intermediate code of the physical layer grouping, a corresponding phase shift is offset, wherein the corresponding phase shift comes from a phase shift sequence having a random or pseudo-random characteristic, and wherein offsetting the corresponding phase shift comprises: applying an opposite phase shift of the corresponding phase shift to at least a portion of the symbols of the intermediate code or compensating for the corresponding phase shift of at least a portion of the symbols of the intermediate code, wherein the sequence is a cyclic extension of elements in a sequence for controlling the polarity of pilot subcarriers of a training sequence received by the receiver.

7. The method according to claim 6, wherein: The sequence of phase shifts includes phase shifts of 0 radians and π radians represented by scaling values ​​of 1 and -1, respectively.

8. The method according to claim 7, wherein: Applying the inverse of the phase shift to a symbol comprises multiplying the value of the symbol by the scaling value representing the phase shift.

9. The method according to claim 6, further comprising: The phase shift sequence is acquired.

10. The method according to claim 9, wherein: Acquiring the phase shift sequence includes one or more of the following: receiving a signal indicative of the phase shift sequence; reading the phase shift sequence from a memory of the receiver; generating the phase shift sequence using a predefined algorithm; and The phase shift sequence is detected based on the received physical layer packet.

11. The method according to claim 6, wherein: The plurality of midambles include a plurality of midambles that appear periodically.

12. An apparatus for a transmitter configured to send a physical layer packet having multiple midambles, the apparatus comprising a control circuit configured such that: A corresponding phase shift is applied to each midamble of the physical layer packet, wherein, The corresponding phase shifts are from a phase shift sequence having random or pseudo-random properties, and wherein the corresponding phase shifts are applied to at least a portion of the symbols of the midamble, wherein the sequence is a cyclic extension of elements in a sequence for controlling polarity of pilot subcarriers of a training sequence provided by the transmitter; and The physical layer packet is sent.

13. The device according to claim 12, wherein: The phase shift sequence has a zero phase average value.

14. The device according to claim 12, wherein: The sequence of phase shifts includes phase shifts of 0 radians and π radians represented by scaling values ​​of 1 and -1, respectively.

15. The device according to claim 14, wherein: Applying a phase shift to a symbol comprises multiplying the value of the symbol by the scaling value representing the phase shift.

16. The device according to claim 12, wherein: The plurality of midambles include a plurality of midambles that appear periodically.

17. An apparatus for a receiver configured to receive a physical layer packet having a plurality of midambles, the apparatus comprising a control circuit configured such that: receiving the physical layer packet; and For each midamble of the physical layer packet, a corresponding phase shift is offset, wherein, The corresponding phase shift comes from a phase shift sequence having random or pseudo-random characteristics, and wherein canceling the corresponding phase shift comprises applying an opposite phase shift of the corresponding phase shift to at least a portion of the symbols of the intermediate code or compensating for the corresponding phase shift of at least a portion of the symbols of the intermediate code, wherein the sequence is a cyclic extension of elements in a sequence for controlling the polarity of pilot subcarriers of a training sequence received by the receiver.

18. The device according to claim 17, wherein: The sequence of phase shifts includes phase shifts of 0 radians and π radians represented by scaling values ​​of 1 and -1, respectively.

19. The device according to claim 18, wherein: Applying the inverse of the phase shift to a symbol comprises multiplying the value of the symbol by the scaling value representing the phase shift.

20. The device according to claim 17, wherein: The control circuit is further configured to cause the phase shift sequence to be acquired.

21. The device according to claim 20, wherein: Acquiring the phase shift sequence includes one or more of the following: receiving a signal indicative of the phase shift sequence; reading the phase shift sequence from a memory of the receiver; generating the phase shift sequence using a predefined algorithm; and The phase shift sequence is detected based on the received physical layer packet.

22. The device according to claim 18, wherein The plurality of midambles include a plurality of midambles that appear periodically.

23. The device according to claim 12, wherein: The device is a component of a communication transmitter.

24. The device according to claim 17, wherein: The device is a component of a communication receiver.

25. A communication device comprising: A first device for a transmitter configured to send a first physical layer packet having a plurality of midambles, the first device comprising a control circuit, the control circuit being configured such that: a corresponding phase shift is applied for each midamble of the first physical layer packet, wherein the corresponding phase shift is from a phase shift sequence having a random or pseudo-random property, and wherein the corresponding phase shift is applied to at least a portion of symbols of the midamble, wherein the sequence is a cyclic extension of elements in a sequence for controlling polarity of pilot subcarriers of a training sequence provided by the transmitter; and sending the first physical layer packet; and A second device for a receiver configured to receive a second physical layer packet having a plurality of intermediate codes, the second device comprising a control circuit configured to: receive the second physical layer packet; and cancel a corresponding phase shift for each intermediate code of the second physical layer packet, wherein the corresponding phase shift comes from a phase shift sequence having a random or pseudo-random characteristic, and wherein canceling the corresponding phase shift comprises: applying an opposite phase shift of the corresponding phase shift to at least a portion of the symbols of the intermediate code or compensating for the corresponding phase shift of at least a portion of the symbols of the intermediate code, wherein the sequence is a cyclic extension of elements in a sequence for controlling the polarity of pilot subcarriers of a training sequence received by the receiver.

26. The communication device according to claim 25, wherein: The communication device is a component of a vehicle.

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