CONTROL METHOD OF WIRELESS COMMUNICATION MODULE FOR PPDU END TIME ALIGNMENT

The present invention provides a control method of a wireless communication module, wherein the control method includes the steps of: receiving target end time information of a PPDU, and estimating a symbol count of the PPDU according to the target end time information; determining a duration of a packet extension of the PPDU; refining at least one of a padding factor, the duration of packet extension, and the symbol count of the PPDU, wherein the padding factor indicates invalid data information of the PPDU; generating an alignment setting comprising a final symbol count of the PPDU, the duration of packet extension, and the padding factor of the PPDU; and aggregating a plurality of MPDUs to generate the PPDU according to the alignment setting.

BACKGROUND

IEEE 802.11be defines multiple link operations that allow an access point (AP) and a station to communicate with each other by using two or more links. Due to a hardware limitation such as the capability of radio frequency (RF) filters between RF bands within the station, the AP/station can be operated in a synchronous mode or an asynchronous mode. The synchronous mode is also named as a non-simultaneous transmit and receive (NSTR) mode, that is the AP/station cannot transmit and receive data at the same time via multiple links. The asynchronous mode is also named as a simultaneous transmit and receive (STR) mode, that is the AP/station can transmit and receive data at the same time via multiple links, but the AP/station does not need to transmit data by using the multiple links simultaneously.

Regarding the NSTR mode, IEEE 802.11be also defines physical layer protocol data unit (PPDU) end time alignment requirements, that is when multiple PPDUs are simultaneously transmitted via multiple links, respectively, their end times should be aligned, and all differences between each pair of multiple links between the end times of the simultaneously transmitted PPDUs is required to be less than or equal to a specific time, to avoid the interference between pairs of multiple links. However, because the given length (in time as a unit) of a PPDU to be transmitted may not be the same as the actual transmission time of the PPDU, the multiple PPDUs may not be accurately aligned.

SUMMARY

It is therefore an objective of the present invention to provide a wireless communication method, which can determine a suitable symbol count and a duration of packet extension (PE) within a PPDU for the PPDU end time alignment mechanism, to solve the above-mentioned problems.

According to one embodiment of the present invention, a control method of a wireless communication module comprises the steps of: receiving target end time information of a PPDU, and estimating a symbol count of the PPDU according to the target end time information; determining a duration of a packet extension of the PPDU; refining an alignment setting comprising at least one of a padding factor, the duration of the packet extension, and the symbol count of the PPDU, wherein the padding factor indicates invalid data information of the PPDU; generating the alignment setting comprising a final symbol count of the PPDU, the duration of the packet extension, and the padding factor of the PPDU; and aggregating a plurality of media access control protocol data units (MPDUs) to generate the PPDU according to the alignment setting.

According to one embodiment of the present invention, a circuitry of a wireless communication module is configured to perform the steps of: receiving target end time information of a PPDU, and estimating a symbol count of the PPDU according to the target end time information; determining a duration of a packet extension of the PPDU; refining an alignment setting comprising at least one of a padding factor, the duration of the packet extension, and the symbol count of the PPDU, wherein the padding factor indicates invalid data information of the PPDU; generating the alignment setting comprising a final symbol count of the PPDU, the duration of the packet extension, and the padding factor of the PPDU; and aggregating a plurality of MPDUs to generate the PPDU according to the alignment setting.

DETAILED DESCRIPTION

FIG.1is a diagram illustrating a wireless communication system according to one embodiment of the present invention. As shown inFIG.1, the wireless communication system comprises an access point (AP)110and at least one station such as120. The AP110is a Wi-Fi access point that allows other wireless devices such as the station120to connect to a wired network, and the AP110mainly comprises a processing circuit112and a wireless communication module114. The station120is a Wi-Fi station comprising a processing circuit122and a wireless communication module124, and the station120can be a cell phone, a tablet, a notebook, or any other electronic device capable of wirelessly communicating with the AP110. In addition, the wireless communication module114/124comprises at least a media address control (MAC) layer circuitry and physical layer circuitry.

In this embodiment, the AP110and the station120are multi-link devices (MLD), that is the AP110and the station120are communicated with each other by using two or more links such as Link-1and Link-2shown inFIG.1. In this embodiment, the Link-1may use a channel corresponding to a 2.4 GHz band (e.g., 2.412 GHz-2.484 GHz), a 5 GHz band (e.g., 4.915 GHz-5.825 GHz) or a 6 GHz band (e.g., 5.925 GHz-7.125 GHz); and the Link-2may also use a channel corresponding to the 2.4 GHz band, the 5 GHz band or the 6 GHz band.

In this embodiment, the AP110and the station120operate in the NSTR mode, that is the AP110cannot transmit and receive data at the same time via multiple links. As described in the background of the present invention, IEEE 802.11be defines PPDU end time alignment requirements, that is when multiple PPDUs are simultaneously transmitted via multiple links, respectively, their end times should be aligned with a specific tolerance requirement. Therefore, the following embodiments provide control methods that can generate the PPDU with suitable length.

FIG.2is a control method of one of the wireless communication modules114and124according to one embodiment of the present invention. In the following description, the wireless communication module114serves as an example to perform the following steps, but the present invention is not limited thereto. In Step200, the flow starts, and the AP110and the station120have established two or more links. In Step202, the wireless communication module114obtains a plurality of MAC service data units (MSDUs), and the wireless communication module114aggregates the MSDUs to generate MPDUs, wherein one MPDU may comprise one or more MSDUs. In Step204, the wireless communication module114performs sequence number (SN) and packet number (PN) assignment for each MPDU. In Step206, an encryption operation is performed on the MPDUs. In Step208, a MAC layer circuit within the wireless communication module114performs a PPDU end time alignment operation to determine a symbol count and related setting of the PPDU. In Step208, the MAC layer circuit within the wireless communication module114aggregates a plurality of MPDUs to generate a PPDU, and the PPDU is transmitted to the station120via a physical layer circuit of the wireless communication module114. It is noted that Steps202-206and Step210are known by a person skilled in the art, and the present invention focuses on the PPDU end time alignment operation of Step208, so the detailed operations of Steps202-206and Step210are omitted here.

FIG.3shows a flowchart of the PPDU end time alignment operation according to one embodiment of the present invention. In Step302, the MAC layer circuit of the wireless communication module114receives target end time information of the PPDU, and estimates a symbol count of the PPDU according to the target end time information, wherein the symbol count of the PPDU may comprise data symbol count in the physical layer service data unit (PSDU) and/or SIG/LTF (Signal/Long Training Field) symbol in the preamble. In one embodiment, the target end time information comprises a target length of a PPDU, and this information can be derived based on multi-link operation (MLO) or dual band dual concurrent (DBDC) links, or “TXVECTOR” parameter defined in IEEE 802.11 specification. It is noted that the determination of target end time information or the target length of PPDU is known by a person skilled in the art, further descriptions are omitted here. In this embodiment, the symbol count of the PPDU can be estimated by the target length of a PPDU, a length of each symbol (orthogonal frequency division multiplexing (OFDM) symbol), a length of a preamble of the PPDU and other parameter(s) such as packet extension disambiguity information. For example, without a limitation of the present invention, the data symbol count of the PPDU can be estimated by the following formula:

In the formula (1), “Nsym” is the data symbol count of the PPDU, “L_LENGTH” is the target length of a PPDU, “Tsym” is the length of each data symbol, “TEHT-PREAMBLE” is length of a preamble, “b PE-Disambiguity” is the packet extension disambiguity information, and “[ ]” is a truncation operator. It is noted that the formula (1) is provided in the IEEE 802.11be specification, so a person skilled in the art should understand the operation corresponding to this formula.

In Step304, the MAC layer circuit determines a length of a packet extension (PE) according to the symbol count of the PPDU, the target length of the PPDU, a length of each symbol and a length of a preamble of the PPDU. For example, without a limitation of the present invention, the duration of the PE (TpE) can be estimated by the following formula:

It is noted that the formula (2) is provided in the IEEE 802.11be specification, so a person skilled in the art should understand the operation corresponding to this formula.

The duration of the PE calculated in Step304is used for a nominal packet padding requested by the receiver (e.g., the station120) defined in IEEE 802.11 specification, for the receiver to have additional processing time to decode the received symbols. It is noted that TPEcalculated in Step304may not enough for the nominal packet padding requirement.

The duration of the packet extension (TpE) obtained in Step304is for the mode supporting a packet padding by PE mechanism, such as High Efficiency (HE) defined in IEEE 8002.11ax and Extreme High Throughput (EHT) modes defined in IEEE 802.11be. If the operation mode of the wireless communication module114does not support the packet padding by PE mechanism (e.g., Very High Throughput (VTH)), the duration of the packet extension can be directly set to zero.

In Step306, the MAC layer circuit refines an alignment setting based on an alignment mechanism, wherein the alignment mechanism may be a force-extra-symbol(-segment) mechanism, an avoid-extra-symbol mechanism or a best-effort mechanism; and the alignment setting comprises at least one of a padding factor, a duration of packet extension and a final symbol count of the PPDU.

Regarding the force-extra-symbol(-segment) mechanism, the MAC layer directly subtracts one symbol or one symbol segment from “NsyM” calculated by formula (1) to obtain an alignment setting. In one embodiment, referring toFIG.4, the wireless communication module114does not have the mode of packet padding by PE mechanism, and if the data symbol count of the PPDU calculated by using formula (1) is “NsyM”, the MAC layer determines that the new data symbol count Nsym′ is equal to (Nsym-1). That is, when the PPDU is generated, the content contained more invalid data across all OFDM symbols.

In another embodiment, the wireless communication module114has the mode of packet padding by PE mechanism, and the MAC layer circuit intentionally reduce a pre-FEC (forward error correction) padding factor (hereinafter, a-factor) to make the PPDU has more invalid data. In the IEEE 802.11 specification, the pre-FEC padding factor has four different value, the last orthogonal frequency-division multiple access (OFDMA) symbol has four segments, and the pre-FEC padding factor having the value “1” indicates that only the first segment of the last OFDMA symbol has valid data, the pre-FEC padding factor having the value “2” indicates that only the first two segments of the last OFDMA symbol have valid data, the pre-FEC padding factor having the value “3” indicates that only the first three segments of the last OFDMA symbol have valid data, and the pre-FEC padding factor having the value “4” indicates that all the four segments of the last OFDMA symbol have valid data. In detail, referring toFIG.5, assuming that the duration of PE (i.e., TpEshown inFIG.5) calculated by formula (2) is 8 microseconds (us), and the nominal packet padding required by the receiver is 16 us, the last OFDMA symbol has four segments, a length of each segment is 4 us, the MAC layer circuit can initially determine that that the last OFDMA symbol has the a-factor equal to “2” so that only the first two segments of the last OFDMA symbol have valid data, and the last two segments only have invalid data, to make the length of the overall invalid data is equal to or greater than nominal packet padding (i.e., a summation of 8 us invalid symbol segment and 8 us packet extension is equal to 16 us nominal packet padding). Then, the MAC layer circuit adjusts the initial a-factor to be “1” to increase invalid data of a segment, and the final a-factor serves as the alignment setting that will be provided to the following module.

In the above force-extra-symbol(-segment) mechanism, by intentionally increase invalid data of one symbol or one symbol segment, the PPDU length (PPDU time) will not change much due to subsequent encoding operations. Specifically, if a low density parity check (LDPC) FEC is used in the subsequent encoding operations, the encoder may temporarily need to use one more symbol or symbol segment during the encoding process to improve the encoding quality, wherein this one more symbol or symbol segment is also called “LDPC extra symbol or symbol segment” in the IEEE 802.11 specification. At this time, the increased invalid data of one symbol or symbol segment can be used for this one more symbol or symbol segment, and the invalid data within the PPDU still satisfies nominal packet padding requirement (i.e., the a-factor becomes “2” from “1” in the encoding operations).

In addition, in the force-extra-symbol(-segment) mechanism, “LDPC extra symbol” or “LDPC extra symbol segment” is always set to be true (e.g., the parameter “bextra” shown inFIG.5is always set “1”), even if the encoder will not use one more symbol or symbol segment during the subsequent encoding process. Furthermore, the preamble of the PPDU generated later will always indicate the presence of the LDPC extra symbol or symbol segment.

Regarding the avoid-extra-symbol mechanism, the MAC layer circuit refers to the nominal packet padding requirement to determine the a-factor, and intentionally increase invalid data of one or more segment(s) to avoid introducing extra data symbol by the encoder. TakingFIG.5as an example, after the MAC layer circuit initially determines that the last OFDMA symbol has the a-factor equal to “1” or “2”, which depends on the results of encoding process, to make the length of the overall invalid data is equal to or greater than nominal packet padding, this a-factor can directly serve as an alignment setting that will be provided to the following module. In one embodiment, if the encoder temporarily needs to use one more symbol or symbol segment during the encoding process to improve the encoding quality, the duration of packet extension may be increased to satisfy the nominal packet padding requirement.

Regarding the best-effort mechanism, the MAC layer circuit does not intentionally adjust the a-factor according to the nominal packet padding requirement, that is the a-factor is determined by using a look-up table defined in the IEEE 802.11 specification.

In Step308, the alignment setting is provided to the following module for the encoding processing and MPDU aggregation. In this embodiment, the alignment setting comprises the symbol count and the a-factor mentioned above, and by using the symbol count and the a-factor, the byte count of one PPDU can be obtained for the MPDU aggregation.

FIG.6is a diagram of a circuitry600within the wireless communication module114according to one embodiment of the present invention, wherein the circuitry600is configured to perform the Step200-Step210and Step302-Step308. As shown inFIG.6, the circuitry600comprises an aggregation module610, a PPDU end time alignment module620and two transmission modules630and640. The aggregation module610is configured to receive MPDUs corresponding to Link-1and Link-2, and the aggregation module610transmits target end time information of two PPDUs respectively corresponding to Link-1and Link-2to the PPDU end time alignment module620. Then, the PPDU end time alignment module620uses the above embodiments to generate the alignment settings to the aggregation module610, for the byte count determination and MPDU aggregation. Then, the aggregation module610generates a first PPDU and a second PPDU, wherein the first PPDU is wirelessly transmitted by the transmission module630via Link-1, and the second PPDU is wirelessly transmitted by the transmission module640via Link-2.

FIG.7is a diagram of a circuitry700within the wireless communication module114according to one embodiment of the present invention, wherein the circuitry700is configured to perform the Step200-Step210and Step302-Step308. As shown inFIG.7, the circuitry700comprises two aggregation modules710and720, at least one PPDU end time alignment module730and two transmission modules740and750, wherein the aggregation module710and the transmission module740correspond to Link-1, and the aggregation module720and the transmission module750correspond to Link-2. The aggregation module710is configured to receive MPDUs corresponding to Link-1, and the aggregation module710transmits target end time information of a PPDU to the PPDU end time alignment module730. Then, the PPDU end time alignment module730uses the above embodiments to generate the alignment setting to the aggregation module710, for the byte count determination and MPDU aggregation. Then, the aggregation module710generates a first PPDU, wherein the first PPDU is wirelessly transmitted by the transmission module740via Link-1. Similarly, the aggregation module720is configured to receive MPDUs corresponding to Link-2, and the aggregation module720transmits target end time information of a PPDU to the PPDU end time alignment module730. Then, the PPDU end time alignment module730uses the above embodiments to generate the alignment setting to the aggregation module720, for the byte count determination and MPDU aggregation. Then, the aggregation module720generates a second PPDU, wherein the second PPDU is wirelessly transmitted by the transmission module750via Link-2.