Extended guard interval for outdoor wlan

Method and device for generating data unit with selected guard interval

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present disclosure requires that the United States Provisional Patent Application No. 61/875,968 filed on September 10, 2013 under the title "Longer GI for Outdoor" and the filed on December 3, 2013 under the title "Longer GI for Outdoor Of the United States Provisional Patent Application No. 61/911,232, the disclosures of which are incorporated herein by reference in their entirety.

Technical field

[0003] The present disclosure relates generally to communication networks, and more particularly, to wireless local area networks that utilize Orthogonal Frequency Division Multiplexing (OFDM).

Background technique

[0004] When operating in infrastructure mode, a wireless local area network (WLAN) typically includes an access point (AP) and one or more client sites. WLAN has evolved rapidly over the past decade. WLAN standards such as electrical and electronic The development of the Institute of Engineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n standards) has improved the single-user peak data throughput. For example, the IEEE 802.11b standard specifies a peak throughput of a single user of 11 megabits per second (Mbps), the IEEE 802.11a and 802.11g standards specify a peak throughput of a single user of 54 Mbps, and the IEEE 802.11n standard specifies a single user of 600 Mbps. Peak throughput, and the IEEE 802.11ac standard specifies a single user peak throughput in the gigabit per second (Gbps) range. Future standards promise to provide even greater throughput, such as throughput in the tens of Gbps range.

Summary of the invention

[0005] In one embodiment, a method for generating a data unit for transmission via a communication channel includes: generating a data portion of the data unit, including using (i) normal guard interval, (ii) short protection One of the interval and (iii) the long guard interval is used to generate Orthogonal Frequency Division Multiplexing (OFDM) symbols of the data part. The method further includes: generating a preamble of the data unit, including generating the preamble to indicate at least whether the OFDM symbol of the data part is generated using a normal guard interval, a short guard interval, or a long guard interval. The method additionally includes: generating the data unit to include the preamble and the data portion.

[0006] In another embodiment, an apparatus includes a network interface configured to generate a data portion of a data unit, including using (i) a normal guard interval, (ii) a short guard interval, and (iii) a long guard interval. One of the guard intervals is used to generate Orthogonal Frequency Division Multiplexing (OFDM) symbols for the data portion. The network interface is further configured to generate the preamble of the data unit, including generating the preamble to indicate whether at least the OFDM symbol of the data part is generated using a normal guard interval, a short guard interval, or a long guard interval. The network interface is additionally configured to generate the data unit to include the preamble and the data portion.

Description of the drawings

[0007] FIG. 1 is a block diagram of an example wireless local area network (WLAN) 10 according to an embodiment.

[0008] FIGS. 2A and 2B are diagrams of a data unit format of the prior art.

[0009] FIG. 3 is a diagram of another prior art data unit format.

[0010] FIG. 4 is a diagram of another prior art data unit format.

[0011] FIG. 5 is a diagram of another prior art data unit format.

[0012] FIG. 6A is a diagram of modulation used to modulate symbols in a data unit of the related art.

[0013] FIG. 6B is a diagram of modulation used to modulate symbols in an example data unit, according to an embodiment.

[0014] FIG. 7A is a diagram of an orthogonal frequency division multiplexing (OFDM) data unit according to an embodiment.

[0015] FIG. 7B is a diagram of modulation used to modulate symbols in the data unit depicted in FIG. 7A, according to an embodiment.

[0016] FIG. 8 is a block diagram of an OFDM symbol according to an embodiment.

[0017] FIG. 9A is a diagram illustrating an example data unit in which a normal guard interval is used for a preamble of the data unit according to an embodiment.

[0018] FIG. 9B is a diagram illustrating an example data unit in which a normal guard interval is used for only a part of the preamble of the data unit according to an embodiment.

[0019] FIG. 10A is a diagram illustrating an example data unit in which the OFDM tone spacing is used to effectively increase the guard interval duration according to an embodiment.

[0020] FIG. 10B is a diagram illustrating an example data unit in which the OFDM tone spacing is used to effectively increase the guard interval duration according to another embodiment.

[0021] FIG. 11A is a diagram illustrating a conventional guard interval pattern data unit according to an embodiment.

[0022] FIG. 11B is a diagram illustrating an extended guard interval mode data unit according to an embodiment.

[0023] FIGS. 12A-12B are diagrams illustrating two possible formats of a long training field according to two example embodiments.

[0024] FIG. 13A is a diagram illustrating a non-traditional signal field of the conventional guard interval pattern data unit of FIG. 11A according to an embodiment.

[0025] FIG. 13B is a diagram illustrating a non-traditional signal field of the extended guard interval mode data unit of FIG. 11B according to an embodiment.

[0026] FIG. 14A is a block diagram illustrating an extended guard interval mode data unit according to an embodiment.

[0027] FIG. 14B is a diagram illustrating a conventional signal field of the extended guard interval data unit of FIG. 14A according to an embodiment;

[0028] FIG. 14C is a diagram illustrating a fast Fourier transform (FFT) window for the conventional signal field of FIG. 14B at a conventional receiving device according to an embodiment.

[0029] FIG. 15 is a block diagram illustrating the format of a non-traditional signal field according to an embodiment.

[0030] FIG. 16 is a flowchart of a method for generating a data unit according to an embodiment.

Detailed ways

[0031] In the embodiments described below, a wireless network device, such as an access point (AP) of a wireless local area network (WLAN), transmits a data stream to one or more client stations. The AP is configured to operate with the client station according to at least a first communication protocol. The first communication protocol is sometimes referred to herein as the "High Efficiency WiFi" or "HEW" communication protocol. In some embodiments, different client sites near the AP are configured to operate according to one or more other communication protocols. These other communication protocols define operations in the same frequency band as the HEW communication protocol, but generally With lower

Data throughput. These lower data throughput communication protocols (for example, IEEE 802.11a, IEEE 802.11n, and/or IEEE 802.11ac) are collectively referred to herein as "traditional" communication protocols. In at least some embodiments, these traditional communication protocols are generally deployed in indoor communication channels, while HEW communication protocols are at least sometimes deployed for outdoor communication.

[0032] According to an embodiment, the symbols transmitted by the AP include a guard interval to prevent or minimize inter-symbol interference caused by multipath propagation in the communication channel at the receiver. The length of the guard interval required to mitigate interference generally depends on the delay spread of the specific channel being utilized. For example, in at least some embodiments and/or scenarios, outdoor communication channels are generally characterized by a larger channel delay spread compared to indoor communication channels. In one embodiment, the HEW communication protocol defines a regular guard interval mode and an extended guard interval mode. In one embodiment, the conventional guard interval mode is generally used with a communication channel characterized by shorter channel delay spread (for example, an indoor communication channel), and the extended guard interval mode is generally used with a relatively long Communication channels (for example, outdoor communication channels) characterized by channel delay spread are used together. In one embodiment, a normal guard interval (NGI) or a short guard interval (SGI) is used in the regular guard interval mode, and a long guard interval (LGI) is used in the extended guard interval mode.

[0033] In an embodiment, the data unit transmitted by the AP includes a preamble and a data part, wherein the preamble is used at least in part to signal various parameters for the transmission of the data part to the receiving device. In various embodiments, the preamble of the data unit is used to signal to the receiving device at least the specific guard interval utilized in the data portion of the data unit. In some embodiments, the same preamble format is used in the regular guard interval mode and the extended guard interval mode. In one such embodiment, the preamble includes an indication that is set to indicate whether NGI, SGI, or LG I is used at least for the data portion of the data unit. In some embodiments, in addition to the data portion of the data unit, the indicated NGI, SG I, or LG I is also used for at least a part of the preamble of the data unit. In one embodiment, the receiving device determines the specific guard interval utilized based on the indication in the preamble of the data unit, and then uses the specific guard interval to decode the appropriate remaining part of the data unit (for example, the data part). , Or part of the preamble and data part).

[0034] In another embodiment, the preamble used in the extended guard interval mode is formatted differently from the preamble used in the regular guard interval mode. For example, the preamble used in the extended guard interval mode is formatted so that the receiving device can automatically (eg, before decoding) detect that the data unit corresponds to the extended guard interval mode. In one embodiment, when the receiving device detects that the data unit corresponds to the extended guard interval mode, the receiving device uses LG I to decode the data portion of the data unit, and in at least some embodiments, decode the data unit At least part of the preamble and the data part. On the other hand, in an embodiment, when the receiving device detects that the data unit does not correspond to the extended guard interval mode, the receiving device assumes that the data unit corresponds to the regular guard interval mode. In one embodiment, the receiving device then determines whether NGI or SGI is used in the data unit, for example based on the indication in the preamble, and uses NGI or SGI to decode at least the data part of the data unit according to the determination .

[0035] In addition, in at least some embodiments, the preamble of the data unit in the regular guard interval mode and/or the extended guard interval mode is formatted so that the client station operating according to the traditional protocol instead of the HEW communication protocol It is possible to determine certain information about the data unit, such as the duration of the data unit, and/or determine that the data unit does not conform to traditional protocols. In addition, in an embodiment, the preamble of the data unit is formatted so that a client station operating according to the HEW protocol can determine that the data unit complies with the HEW communication protocol. Similarly, in one embodiment, the client station configured to operate according to the HEW communication protocol also transmits data units such as those described above.

[0036] In at least some embodiments, a formatted data unit such as described above is for example for the following AP

And/or is useful for WLANs where the AP is configured to operate with client stations according to multiple different communication protocols, and in these WLANs, multiple client stations operate according to multiple different communication protocols . Continuing with the above example, a communication device configured to operate according to both the HEW communication protocol and the conventional communication protocol can determine that the data unit is formatted according to the HEW communication protocol instead of the conventional communication protocol. Similarly, a communication device configured to operate according to a conventional communication protocol instead of the HEW communication protocol can determine that the data unit is not formatted according to the conventional communication protocol, and/or determine the duration of the data unit.

[0037] FIG. 1 is a block diagram of an example wireless local area network (WLAN) 10 according to an embodiment. The AP 14 includes a host processor 15 coupled to a network interface 16. The network interface 16 includes a medium access control (MAC) processing unit 18 and a physical layer (PHY) processing unit 20. The PH Y processing unit 20 includes a plurality of transceivers 21, and these transceivers 21 are coupled to a plurality of antennas 24. Although three transceivers 21 and three antennas 24 are illustrated in FIG. 1, in other embodiments, the AP 14 includes other suitable numbers (for example, 1, 2, 4, 5, etc.) of transceivers 21 and antennas. twenty four. In one embodiment, the MAC processing unit 18 and the PHY processing unit 20 are configured to operate according to a first communication protocol (for example, the HEW communication protocol). In another embodiment, the MAC processing unit 18 and the PHY processing unit 20 are also configured to operate according to a second communication protocol (for example, the IEEE 802.11ac standard). In yet another embodiment, the MAC processing unit 18 and the PHY processing unit 20 are additionally configured according to the second communication protocol, the third communication protocol and/or the fourth communication protocol (for example, the IEEE 802.11a standard and/or IEEE 802.11n standard) to operate.

[0038] The WLAN 10 includes a plurality of client stations 25. Although four client sites 25 are illustrated in FIG. 1, in various scenarios and embodiments, the WLAN 10 includes other suitable numbers (for example, 1, 2, 3, 5, 6, etc.) of client sites 25. At least one client site 25 (eg, client site 25-1) is configured to operate according to at least the first communication protocol. In some embodiments, at least one client station 25 is not configured to operate according to the first communication protocol but is configured to communicate according to at least one of the second communication protocol, the third communication protocol, and/or the fourth communication protocol Protocol (referred to as "traditional client site" in this article).

[0039] The client site 25-1 includes a host processor 26 coupled to a network interface 27. The network interface 27 includes a MAC processing unit 28 and a PHY processing unit 29° The PHY processing unit 29 includes a plurality of transceivers 30, and these transceivers 30 are coupled to a plurality of antennas 34. Although three transceivers 30 and three antennas 34 are illustrated in FIG. 1, in other embodiments, the client site 25-1 includes other suitable numbers (eg, 1, 2, 4, 5, etc.) of transceivers 30 and antenna 34.

[0040] According to one embodiment, the client station 25-4 is a traditional client station, that is, the client station 25-4 is not enabled to receive and completely decode the first communication by the AP 14 or another client station 25 according to the first communication The data unit transmitted by the protocol. Similarly, according to one embodiment, the legacy client station 25-4 is not enabled to transmit data units according to the first communication protocol. On the other hand, the conventional client station 25-4 is enabled to receive and completely decode and transmit data units according to the second communication protocol, the third communication protocol, and/or the fourth communication protocol.

[0041] In an embodiment, one or both of the client sites 25-2 and 25-3 have the same or similar structure as the client site 25-1. In one embodiment, the client site 25-4 has a similar structure to the client site 25-1. In these embodiments, the client station 25, which is constructed the same or similar to the client station 25-1, has the same or a different number of transceivers and antennas. For example, according to one embodiment, the client station 25-2 has only two transceivers and two antennas.

[0042] In various embodiments, the PHY processing unit 20 of the AP 14 is configured to generate a data unit conforming to the first communication protocol and having the format described herein. The transceiver(s) 21 is configured to transmit the generated data unit via the antenna(s) 24. Similarly, the transceiver(s) 24 is configured to receive these data units via the antenna(s) 24. According to various embodiments, the PHY processing unit 20 of the AP 14 is configured to process received data conforming to the first communication protocol

And it has a data unit in the format described later, and it is determined that such a data unit complies with the first communication protocol. [0043] In various embodiments, the PHY processing unit 29 of the client device 25-1 is configured to generate a data unit conforming to the first communication protocol and having the format described herein. The transceiver(s) 30 is configured to transmit the generated data unit via the antenna(s) 34. Similarly, the transceiver(s) 30 is configured to receive these data units via the antenna(s) 34. According to various embodiments, the PHY processing unit 29 of the client device 25-1 is configured to process the received data unit conforming to the first communication protocol and having the format described later, and to determine that such data unit conforms to The first communication protocol.

[0044] FIG. 2A is a diagram of a prior art OFDM data unit 200 in which the AP 14 is configured to transmit to a client station 25-4 via orthogonal frequency division multiplexing (OFDM) modulation, according to an embodiment. In one embodiment, the client station 25-4 is also configured to transmit the data unit 200 to the AP 14. The data unit 200 complies with the IEEE 802.11a standard and occupies a frequency band of 20 megahertz (MHz). The data unit 200 includes a preamble. The preamble has a traditional short training field (L-STF) 202 and a traditional long training field (L-LTF) 204, The traditional short training field (L-STF) 202 is generally used for packet detection, initial synchronization, automatic gain control, etc., and the traditional long training field (L-LTF) 204 is generally used for channel estimation and fine synchronization. The data unit 200 also includes a legacy signal field (L-SIG) 206. The legacy signal field (L-SIG) 206 is, for example, used to carry certain physical layer (PHY) parameters of the data unit 200, such as those used to transmit the data unit. Modulation type and coding rate. The data unit 200 also includes a data portion 208. Figure 2B is a diagram of an example data portion 208 (not encoded by low-density parity check) that includes a service field, a scrambled physical layer service data unit (PSDU), tail bits, and if necessary padding bits. The data unit 200 is designed for transmission on a spatial stream or a space-time stream in a single input single output (SISO) channel configuration.

[0045] FIG. 3 is a diagram of a prior art OFDM data unit 300 in which the AP 14 is configured to transmit to the client station 25-4 via orthogonal frequency domain multiplexing (OFDM) modulation, according to an embodiment. In one embodiment, the client station 25-4 is also configured to transmit the data unit 300 to the AP 14. The data unit 300 conforms to the IEEE 802.11n standard, occupies a frequency band of 20 MHz, and is designed for mixed mode situations, that is, when the WLAN includes one or more clients that conform to the IEEE 802.11a standard but do not conform to the IEEE 802.11n standard Site time. The data unit 300 includes a preamble, the preamble has L-STF 302, L-LTF 304, L-SIG 306, high throughput signal field (HT-SIG) 308, high throughput short training field (HT-STF) 310 , And M data high-throughput long training fields (HT-LTF) 312, where M is an integer, generally determined by the number of spatial streams used to transmit the data unit 300 in a multiple-input multiple-output (MIMO) channel configuration. In particular, according to the IEEE 802.11n standard, if two spatial streams are used to transmit the data unit 300, the data unit 300 includes two HT-LTFs 312, and if three or four spatial streams are used to transmit the data unit 300, then Data unit 300 Includes four HT-LTF 312. An indication of the specific number of spatial streams utilized is included in the HT-SIG field 308. The data unit 300 also includes a data portion 314.

[0046] FIG. 4 is a diagram of a prior art OFDM data unit 400 in which the AP 14 is configured to transmit to the client station 25-4 via orthogonal frequency domain multiplexing (OFDM) modulation, according to an embodiment. In one embodiment, the client station 25-4 is also configured to transmit the data unit 400 to the AP 14. The data unit 400 conforms to the IEEE 802.11n standard, occupies a 20MHz frequency band, and is designed for the "Greenfield" situation, that is, when the WLAN does not include any that conforms to the IEEE 802.11a standard but does not conform to the IEEE 802.11n standard When the client site. The data unit 400 includes a preamble, and the preamble has a high-throughput green field short training field (HT-GF-STF) 402, a first high-throughput long training field (HT-LTF1) 404, an HT-SIG 406, and M The data HT-LTF 408, where M is an integer, generally corresponds to the number of spatial streams used to transmit the data unit 400 in a multiple-input multiple-output (MIMO) channel configuration. The data unit 400 also includes

Data section 410.

[0047] FIG. 5 is a prior art OFDM data unit 500 in which the client station AP 14 is configured to transmit to the client station 25-4 via orthogonal frequency domain multiplexing (OFDM) modulation according to an embodiment. Diagram. In one embodiment, the client station 25-4 is also configured to transmit the data unit 500 to the AP 14. The data unit 500 complies with the IEEE802.11ac standard and is designed for "Mixed field" situations. The data unit 500 occupies a 20 MHz bandwidth. In other embodiments or scenarios, data units similar to data unit 500 occupy different bandwidths, such as 40MHz, 80MHz, or 160MHz bandwidth. The data unit 500 includes a preamble. The preamble has: L-STF 502; L-LTF 504; L-SIG 506; two first very high throughput signal fields (VHT-SIGA) 508, which include the first very high throughput Volume signal field (VHT-SIGA1) 508-1 and the second very high throughput signal field (VHT-SIGA2) 508-2; Very high throughput short training field (VHT-STF) 510; M very high throughput long Training field (VHT-LTF) 512, where M is an integer; and the second very high throughput signal field (VHT-SIG-B) 514. The data unit 500 also includes a data portion 516.

[0048] FIG. 6A is a set of diagrams illustrating the modulation of the L-SIG field, the HTSIG1 field, and the HT-SIG2 field of the data unit 300 of FIG. 3 defined by the IEEE 802.11n standard. The L-SIG field is based on two Phase shift keying (BPSK) is modulated, while the HT-SIG1 field and HT-SIG2 field are modulated (Q-BPSK) according to BPSK but on the quadrature axis. In other words, the modulation of the HTSIG1 field and the HT-SIG2 field is rotated by 90 degrees compared to the modulation of the L-SIG field.

[0049] FIG. 6B is a set of diagrams illustrating the modulation of the L-SIG field, the VHT-SIGA1 field, and the VHT-SIGA2 field of the data unit 500 of FIG. 5 defined by the IEEE 802.11ac standard. Different from the HT-SIG1 field in FIG. 6A, the VHTSIGA1 field is modulated according to BPSK, which is the same as the modulation of the L-SIG field. On the other hand, the VHT-SIGA2 field is rotated by 90 degrees compared with the modulation of the L-SIG field.

[0050] FIG. 7A is a diagram of an OFDM data unit 700 that the client station AP 14 is configured to transmit to the client station 25-1 via orthogonal frequency domain multiplexing (OFDM) modulation, according to an embodiment. In one embodiment, the client station 25-1 is also configured to transmit the data unit 700 to the AP 14. The data unit 700 conforms to the first communication protocol and occupies a 20 MHz bandwidth. In other embodiments, a data unit similar to the data unit 700 occupies other suitable bandwidths, such as, for example, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, or other suitable bandwidths. The data unit 700 is suitable for use in a "mixed mode" situation, that is, when the WLAN 10 includes a client station that conforms to the conventional communication protocol but does not conform to the first communication protocol (for example, the conventional client station 24-4). In some embodiments, the data unit 700 is also utilized in other situations.

[0051] The data unit 700 includes a preamble 701. The preamble 701 has: L-STF 702; L-LTF 704; L-SIG 706; two first HEW signal fields (HEW-SIGA) 708, which include the first HEW Signal field (HEW-SIGA1) 708-1 and second HEW signal field (HEW-SIGA2) 708-2; HEW short training field (HEW-STF) 710; M HEW long training fields (HEWLTF) 712, where M is Integer; and the third HEW signal field (HEW-SIGB) 714°L-STF 702, L-LTF 704, LSIG 706, HEW-SIGA 708, HEW-STF 710, M HEW-LTF 712 and HEW-SIGB 714 Each includes an integer number of one or more OFDM symbols. For example, in one embodiment, HEW-SIGA 708 includes two OFDM symbols, where the HEW-SIGA1 708-1 field includes the first OFDM symbol, and HEW-SIGA 2 includes the second OFDM symbol. In at least some examples, HEW-SIGA 708 is collectively referred to as a single HEW signal field (HEW-SIGA) 708. In some embodiments, the number The data unit 700 also includes a data part 716. In other embodiments, the data unit 700 omits the data portion 716.

[0052] In the embodiment of FIG. 7A, the data unit 700 includes one for each of the L-STF 702, L-LTF 704, L-SIG 706, and HEW-SIGA1 708. In other embodiments where the OFDM data unit similar to the data unit 700 occupies a cumulative bandwidth different from 20 MHz, each of the L-STF 702, L-LTF 704, L-SIG 706, and HEW-SIGA1 708 is in one type.

In the embodiment, it is repeated on a corresponding number of 20 MHz subbands in the entire bandwidth of the data unit. For example, in one embodiment, the OFDM data unit occupies a bandwidth of 80MHz, and therefore in one embodiment, each of L-STF 702. L-LTF 704, LSIG 706, HEW-SIGA1 708 includes four . In some embodiments, the modulation of different 20 MHz subband signals is rotated at different angles. For example, in one embodiment, the first sub-band is rotated by 0 degrees, the second sub-band is rotated by 90 degrees, the third sub-band is rotated by 180 degrees, and the fourth sub-band is rotated by 270 degrees. In other embodiments, different suitable rotations are utilized. In at least some embodiments, the different phases of the 20 MHz subband signals result in a reduced peak-to-average power ratio (PAPR) of the OFDM symbols in the data unit 700. In an embodiment, if the data unit conforming to the first communication protocol is an OFDM data unit occupying a cumulative bandwidth such as 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, etc., HEW-STF, HEW-LTF, The HEW-SIGB and HEW data part occupy the corresponding entire bandwidth of the data unit.

[0053] FIG. 7B is a set of diagrams illustrating the modulation of L-SIG 706, HEW-SIGA1 708-1, and HEW-SIGA2 708-2 of the data unit 700 of FIG. 7A according to an embodiment. In this embodiment, the L-SIG field 706, the HEW-SIGA1 field 708-1, and the HEW-SIGA2 field 708-2 have the same modulation as the corresponding fields as defined in the IEEE 802.11ac standard and depicted in FIG. 6B. The same modulation. Therefore, the HEW-SIGA 1 field is modulated the same as the L-SIG field. On the other hand, the HEW-SIGA2 field is rotated by 90 degrees compared with the modulation of the L-SIG field.

[0054] In an embodiment, because the modulation of the L-SIG field 706, the HEW-SIGA 1 field 708-1, and the HEWSIGA2 field 708-2 of the data unit 70 0 corresponds to a data unit compliant with the IEEE 802.11ac standard (for example, , The modulation of the corresponding field in the data unit 500) in FIG. 5, so a traditional client station configured to operate in accordance with the IEEE 802.11a standard and/or IEEE 802.11n standard will assume that the data unit 700 conforms to the The IEEE 802.11ac standard and will handle the data unit 700 accordingly. For example, a client station compliant with the IEEE 802.11a standard will recognize the traditional IEEE 802.11a standard part in the preamble of the data unit 700, and will set the data unit duration according to the duration indicated in the L-SIG 706. For example, according to one embodiment, a traditional client station will calculate the duration based on the rate and length (e.g., in the number of bytes) indicated in the LSIG field 706. In one embodiment, the rate and length in the L-SIG field 706 are set so that a client station configured to operate according to the traditional communication protocol will calculate the packet duration (T) based on the rate and the length , Which corresponds to or at least receives Close to the actual duration of the data unit 700. For example, in one embodiment, the rate is set to indicate the lowest rate defined by the IEEE 802.11a standard (ie, 6 Mbps), and the length is set to the following value, which is calculated so that the lowest rate is used The calculated packet duration is at least close to the actual duration of the data unit 700.

[0055] In one embodiment, when a traditional client station conforming to the IEEE 802.11a standard receives the data unit 700, it will, for example, use the rate field and the length field in the L-SIG field 706 to calculate the data unit 700 And in one embodiment, it will wait until the end of the calculated packet duration before performing a clear channel assessment (CCA). Therefore, in this embodiment, the communication medium is protected at least for the duration of the data unit 700 to prevent access by traditional client sites. In one embodiment, the traditional client station will continue to decode the data unit 700, but will fail the error check at the end of the data unit 700 (for example, using a frame check sequence (FCS)).

[0056] Similarly, in one embodiment, a traditional client station configured to operate in accordance with the IEEE 802.11n standard, when receiving the data unit 700, will be based on the data indicated in the L-SIG 706 of the data unit 700 Rate and length are used to calculate the packet duration of the data unit 700 (1). The traditional client station will detect the modulation (BPSK) of the first HEW signal field (HEWSIGA1) 708-1, and will assume that the data unit 700 is a traditional data unit compliant with the IEEE 802.11a standard. In one embodiment, the traditional client station will continue to decode the data unit 700, but will fail the error check at the end of the data unit (for example, using a frame check sequence (FCS)). In one embodiment, in any case,

According to the IEEE 802.11n standard, the traditional client station will wait until the end of the calculated packet duration (T) before performing clear channel assessment (CCA). Therefore, in one embodiment, the communication medium will be protected from being accessed by traditional client sites for the duration of the data unit 700.

[0057] In one embodiment, a traditional client station configured to operate according to the IEEE 802.11ac standard instead of the first communication protocol, when receiving the data unit 700, will be based on the data unit 700 in the L-SIG 706 The indicated rate and length are used to calculate the packet duration (T) of the data unit 700. However, in one embodiment, the traditional client station will not be able to detect that the data unit 700 does not comply with the IEEE 802.11ac standard based on the modulation of the data unit 700. In some embodiments, one or more HEW signal fields (eg, HEW-SIGA1 and/or HEWSIGA2) of the data unit 700 are formatted to intentionally cause the traditional client station to detect an error when decoding the data unit 700, And therefore stop decoding (or "discard") the data unit 700. For example, in one embodiment, the HEW-SIGA 708 of the data unit 700 is formatted to intentionally cause an error when the SIGA field is decoded by legacy equipment according to the IEEE 802.11ac standard. Further, in one embodiment, according to the IEEE 802.11ac standard, when an error is detected in the decoded VHT-SIGA field, the client station will discard the data unit 700 and will wait before performing a clear channel assessment (CCA) Until for example based on data unit 70 The end of the calculated packet duration (1) calculated based on the rate and length indicated in the L-SIG706 of 0. Therefore, in one embodiment, the communication medium will be protected from being accessed by traditional client sites for the duration of the data unit 700.

[0058] FIG. 8 is a diagram of an OFDM symbol 800 according to an embodiment. In one embodiment, the data unit 700 of FIG. 7 includes OFDM symbols such as OFDM symbols 800. The OFDM symbol 800 includes a guard interval part 802 and an information part 804. In one embodiment, the guard interval includes a cyclic prefix that repeats the end part of the OFDM symbol. In one embodiment, the guard interval section 802 is used to ensure the orthogonality of the OFDM tones at the receiving device (eg, the client station 25-1), and to minimize or eliminate inter-symbol interference, which is due to The OFDM symbol 800 is caused by multipath propagation in the communication channel through which the transmitting device (for example, AP 14) is transmitted to the receiving device. In one embodiment, the length of the guard interval portion 802 is selected based on the expected worst-case channel delay spread in the communication channel between the transmitting device and the receiving device. For example, in one embodiment, a longer guard interval is selected for outdoor communication channels that are typically characterized by longer channel delay spread, and in contrast, a shorter guard interval is selected for An indoor communication channel characterized by channel delay spread.

[0059] According to an embodiment, depending on the transmission mode utilized, the guard interval portion 802 corresponds to a short guard interval, a normal guard interval, or a long guard interval. In one embodiment, a short guard interval or a normal guard interval is used for indoor communication channels or a communication channel with relatively short channel delay spread, and a long guard interval is used for outdoor communication channels or a communication channel with relatively long delay spread. Communication channel. In an embodiment, when the HEW data unit (for example, the HEW data unit 700) is transmitted in the regular guard interval mode, the normal guard interval or the short guard interval is used for some or all of the OFDM symbols of the HEW data unit, and When the HEW data unit is transmitted in the extended guard interval mode, a long guard interval is used for at least some OFDM symbols of the HEW data unit.

[0060] In an embodiment, the short guard interval (SGI) has a length of 0,4 us, the normal guard interval is 0.8 us, and the long guard interval (LGI) has a length of 1.2 us or 1.8 us. In one embodiment, the information portion 804 has a length of 3.2 us. In other embodiments, other suitable lengths for SGI, NGI, LGI, and/or information portion 804 are utilized. In some embodiments, SGI has a length of 50% of the length of NG I, and NG I has a length of 50% of the length of LGI. In other embodiments, the SGI has a length of 75% or less of the length of the NGI, and the NGI has a length of 75% or less of the length of the LGI. In other embodiments, SGI has a length of 50% or less of the length of NGI, and NGI has a length of 50% or less of LGI

length.

[0061] In some embodiments, the extended guard interval mode uses the normal guard interval duration of the regular guard interval mode, but uses a different OFDM modulation that effectively extends the guard interval duration in the extended guard interval mode. For example, in one embodiment, OFDM modulation with reduced pitch spacing is used in the extended guard interval mode. For example, the conventional guard interval mode uses a 64-point discrete Fourier transform (DFT) for a 20MHz bandwidth OFDM data unit to generate 64 OFDM tones, while the extended guard interval mode uses a 128-point DFT for a 20MHz OFDM data unit. , 128 in the same bandwidth. FDM tone. In this case, the pitch spacing in the extended guard interval mode OFDM symbol is reduced by a factor of 2 (1/2) compared with the regular guard interval mode OFDM symbol. As another example, the conventional guard interval mode uses a 64-point discrete Fourier transform (DFT) for a 20MHz bandwidth OFDM data unit to generate 64 OFDM tones, while the extended guard interval mode uses a 256-point discrete Fourier transform (DFT) for a 20MHz OFDM data unit. The point DFT produces 256 OFDM tones in the same bandwidth. In this case, the pitch spacing in the extended guard interval mode OFDM symbol is the same as the regular guard interval mode. The OFDM symbol is reduced by a factor of 4 (1/4) compared to that. In such an embodiment, a long GI duration of, for example, 1.6 us is used. However, in one embodiment, the duration of the information part of the extended guard interval mode OFDM symbol is increased (for example, from 3.2 us to 6.4 us), and the GI part duration remains the same as the percentage of the total OFDM symbol duration . Therefore, in this case, in at least some embodiments, the efficiency loss due to longer GI symbols is avoided. In various embodiments, the term "long guard interval" as used herein encompasses an increased guard interval duration as well as a reduced OFDM tone pitch that effectively increases the duration of the guard interval.

[0062] FIG. 9A is a diagram illustrating an example data unit 900 in which a normal guard interval is used for the preamble of the data unit according to an embodiment. The data unit 900 is generally the same as the data unit 700 of FIG. 7A and includes elements that are numbered similarly to the data unit 700 of FIG. 7A. The HEW-SIGA field 708 (for example, HEW-SIGA1 708-1 or HEW-SIGA2 708-2) of the data unit 900 includes a GI indication 902. According to an embodiment, the GI indication 902 is set to indicate one of the following: (1) normal guard interval, (ii) short guard interval, or (iii) long guard interval. In one embodiment, the guard interval (GI) indicator 902 includes two bits, where the first combination of bit values indicates a normal guard interval, the second combination of bit values indicates a short guard interval, and the third combination of bit values This combination indicates long protection. As illustrated in FIG. 9A, in the illustrated embodiment, the normal guard interval is used for all OFDM symbols of the preamble of the data unit 700, and the normal guard interval, short guard interval as indicated by the GI indication 902 are used. One of the interval and the long guard interval is used for the OFDM symbol of the data part 716.

[0063] FIG. 9B is a diagram illustrating an example data unit 950 in which a normal guard interval is used for a portion of the preamble of the data unit, according to an embodiment. The data unit 950 is generally the same as the data unit 900 of FIG. 9A, except that the data unit 750 includes a preamble 751, and the guard interval indicated by the GI indication 902 is applied to the OFDM symbols of a part of the preamble 751 and the data part 716. OFDM symbol. In particular, in the illustrated embodiment, a normal guard interval is used for the first part 751-1 of the preamble 701, and in addition to the OFDM symbol of the data part 716, the normal protection as indicated by the GI indication 902 One of the interval, the short guard interval, and the long guard interval is also used for the OFDM symbol of the second part 751-2 of the preamble 751. Therefore, in the illustrated embodiment, the guard interval indicated by the GI indication 902 skips the OFDM symbol corresponding to HEW-STF 710, and is applied starting with the OFDM symbol corresponding to HEW-STF 712-1 . In at least some embodiments, skipping the HEW-STF 710 allows the device receiving the data unit 950 to have sufficient time to decode the GI indication 902 before receiving such an OFDM symbol, and use the guard interval indicated by the GI indication 902 To properly set up the receiver to start decoding OFDM symbols.

[0064] FIG. 10A illustrates a method in which the OFDM tone spacing is used to effectively increase the guard interval according to an embodiment;

An illustration of an example data unit 1000 of duration. The data unit 1000 is generally the same as the data unit 900 of FIG. 7A, except that in the data unit 1000, when the GI indication 902 indicates that the long GI is being used, the tone having the FDM symbol with the normal guard interval 0 for the data unit 1000 is used. The OFDM symbol of the data part 716 is generated by OFDM modulation with a pitch pitch smaller than the pitch pitch.

[0065] FIG. 10B is a diagram illustrating an example data unit 1050 in which the OFDM tone spacing is used to effectively increase the guard interval duration according to another embodiment. The data unit 1050 is generally the same as the data unit 950 of FIG. 9B, except that in the data unit 1000, when the GI indication 902 indicates that the long GI is being used, the FDM symbol with the normal guard interval of the data unit 105 0 is used. The OFDM modulation with a pitch pitch smaller than that of the pitch pitch generates the OFDM symbols of the second part 751-2 and the OFDM symbols of the data part 716.

[0066] In some embodiments, a different preamble format is used for the extended guard interval mode data unit compared to the preamble used for the regular guard interval mode data unit. In such an embodiment, the device receiving the data unit can automatically detect whether the data unit is a regular guard interval mode data unit or an extended guard interval mode data unit based on the format of the preamble of the data unit. FIG. 11A is a diagram illustrating a conventional guard interval mode data unit 1100 according to an embodiment. The regular guard interval mode data unit 1100 includes a regular guard interval mode preamble 1101. The regular guard interval mode preamble 1101 is generally the same as the preamble 701 of the data unit 700 of FIG. 7A. In an embodiment, the preamble 1101 includes the HEW-SIGA field 1108, and the HEW-SIGA field 1108 includes the first HEW-SIGA1 field 1108-1 and the second first HEW-SIGA 2 field 1108-1. In an embodiment, the HEW-SIGA field 1108 of the preamble 1101 (for example, HEW-SIGA1 1108-1 or HEW-SIGA2 1108-2) includes a GI indication 1102. In one embodiment, the GI indication 1102 is set to indicate whether a normal guard interval or a short guard interval is used for the data of the data unit 1100 Part 716 of OFDM symbols. In one embodiment, the GI indication 1102 includes one bit, where the first value of the bit indicates the normal guard interval and the second value of the bit indicates the short GI. As will be explained in more detail below, in one embodiment, the device receiving the data unit 1100 can detect that the preamble 1101 is a regular guard interval mode preamble based on the format of the preamble 1101 instead of an extended guard interval mode preamble. In one embodiment, upon detecting that the preamble 1101 is a regular guard interval mode preamble, the receiving device determines whether the normal guard interval or the short guard interval is used for the OFDM symbol of the data part 716 based on the GI indication 1101, and correspondingly The data portion 716 is decoded ground.

[0067] FIG. 11B is a diagram illustrating an extended guard interval mode data unit 115 0 according to an embodiment. The extended guard interval mode data unit 1150 includes an extended guard interval mode preamble 1151. The data unit 1150 is generally similar to the data unit 1100 of FIG. 11A, except that the preamble 1151 of the data unit 1150 and the preamble 1101 of the data unit 1100 are formatted differently. In one embodiment, the preamble 1151 is formatted so that a receiving device operating according to the HEW communication protocol can determine that the preamble 1151 is an extended guard interval mode preamble instead of a regular guard interval mode preamble. In an embodiment, the extended guard interval mode preamble 1151 includes L-STF 702, L-LTF 704, and L-SIG 706, and one or more first HEW signal fields (HEW-SIGA) 1152. In one embodiment, the preamble 1150 further includes one or more secondary L-SIG 1154 following the L-SIG field 706. In some embodiments, the second L-SIG 1154 is followed by the second L-LTF field (L-LTF2) 1156. In other embodiments, the preamble 1151 omits L-SIG 1154 and/or L-LTF2 1156. In some embodiments, the preamble 1151 also includes HEW-STF 1158, one or more HEW-LTF fields 1160, and a second HEW signal field (HEW-SIGB) 1162. In other embodiments, the preamble 1151 omits HEW-STF 1156, HEW-LTF 1158, and/or HEW-SIGB 1162. In an embodiment, the data unit 1150 further includes a data part 716 (not shown in FIG. 11B).

[0068] In an embodiment where the preamble 1151 includes one or more secondary L-LSIGs 1154, the L-LSIG(s)

The content and data unit 115 of each of 1154. The content of L-LSIG 706 is the same. In an embodiment, the receiving device receiving the data unit 1150 determines that the preamble 1151 corresponds to the extended guard interval mode preamble by detecting (multiple) repetitions of the L-SIG field 706.1154. Further, in one embodiment, both the rate subfield and the length subfield of the L-SIG 706, and therefore the rate subfield(s) and the length subfield(s) of the secondary L-SIG 1154(s) The length subfield is set to a fixed (for example, predetermined) value. In this case, in one embodiment, once the (multiple) repetitions of the L-SIG field 706, 1154 are detected, the receiving device uses these fixed values in the repeated L-SIG field as additional training information. Improve channel estimation. However, in some embodiments, at least the length subfield of L-SIG 706, and therefore at least the length subfield of secondary L-SIG 1154(s) are not set to a fixed value. For example, in one embodiment, the length field is instead set to a value determined based on the actual length of the data unit 1150. In one such embodiment, the receiving device first decodes L-SIG 706, and then uses the value of the length subfield in L-SIG 706 to detect the L-SIG field The (multiple) repetitions of 706.1154. In another embodiment, the receiving device first detects (multiple) repetitions of the L-SIG field 706.1154, and then combines the detected multiple L-SIG fields 706.1154 to improve the decoding reliability of the L-SIG field 706.1154, And/or use the redundant information in the multiple L-SIG fields 706.1154 to improve channel estimation.

[0069] In an embodiment where the preamble 1151 includes the L-LTF 704, a long guard interval (eg, a guard interval that increases the duration or a guard interval that decreases the OFDM tone spacing) is used to generate the L-LTF 704(s) OFDM symbol. In another embodiment where the preamble 1151 includes L-LTF2 1156, the normal guard interval is used to generate the OFDM symbol(s) of L-LTF2 1156. For example, if the double guard interval (DGI) used in L-LTF 704 is long enough for the communication channel that the data unit 1150 travels from the transmitting device to the receiving device, the normal guard interval is used to generate the OFDM symbol of L-LTF2 1156, Or alternatively, in one embodiment, the preamble 1151 omits L-LTF2 1156.

[0070] In another embodiment, the preamble 1151 omits the secondary L-SIG 1154(s), but includes L-LTF2 1156. In this embodiment, the receiving device detects that the preamble 1151 is an extended range preamble by detecting the presence of L-LTF2 1156. 12A-12B are diagrams illustrating two possible formats suitable for LTF used as L-LTF2 1156 according to two example embodiments. Turning first to FIG. 12A, in the first exemplary embodiment, L-LTF2 1200 is formatted in the same manner as L-LTF 704, that is, defined in accordance with the traditional communication protocol (for example, IEEE 802.11a/n/ac standard). In particular, in the illustrated embodiment, L-LTF2 1200 includes a double guard interval (DGI) 1202, followed by two repetitions 1204, 1206 of a long training sequence. Turning now to FIG. 12B, in another example embodiment, L-LTF2 1202 is formatted differently than L-LTF 704. In particular, in the illustrated embodiment, L-LTF2 1202 includes a first normal guard interval 1210, a first repetition of the long training sequence 1212, a second normal guard interval 1214, and a second repetition of the long training sequence 1216. [0071] Referring back to FIG. 11B, in one embodiment, a long guard interval (eg, a guard interval that increases the duration or a guard interval that decreases the OFDM tone spacing) is used to generate the HEW-SGA 1152(s). In one embodiment, the number of HEWSGA 1152 is the same as the number of HEW-SGA 1108 of the regular guard interval mode preamble 1101. Similarly, in one embodiment, the content of HEW-SIGA 1152 is the same as the content of HEWSGA 1108 of the regular guard interval mode preamble 1101(s). In other embodiments, the number and/or content of HEW-SIGA 1152 is different from the number and/or content of HEW-SGA 1108 of the conventional guard interval mode preamble 1101. In one embodiment, the device receiving the data unit 115 0 uses the long guard interval to decode the HEW-SIGA 1152(s) based on detecting that the preamble 1151 corresponds to the extended guard interval mode preamble, and appropriately according to the extended guard interval The guard interval mode is defined to explain (multiple) HEW-SIGA 1152.

[0072] In an embodiment in which the L-SIG 1154 and/or L-LTF2 1156 are omitted from the preamble 1151, the receiving device performs autocorrelation based on the HEW-SIGA field using the long guard interval and the normal guard interval. Detect in the preamble

The HEW-SIGA field is generated using a long guard interval or a normal guard interval to determine whether the preamble corresponds to the extended guard interval mode preamble 1151 or the normal guard interval preamble 1101. 13A-13B are diagrams of the HEW-SIGA 1108 of the conventional guard interval mode preamble 1101 and the HEW-SIGA 1152 of the extended guard interval mode preamble 1151, respectively, according to an embodiment. In the illustrated embodiment, the HEW-SIGA 1108 of the regular guard interval mode preamble 1101 includes a first NGI 1302, a first HEW-SIGA field 1304, a second NGI 1306, and a second HEW-SIGA field 1308. On the other hand, the HEW-SIGA 1152 of the extended guard interval mode preamble 1151 includes a first LGI 1310, a first HEWSIGA field 1312, a second LGI 1314, and a second HEW-SIGA field 1316. In one embodiment, the receiving device uses a normal guard interval structure (such as the structure illustrated in FIG. 13A) to perform the first autocorrelation of the HEW-SIGA field, and uses a long guard interval structure (such as the structure illustrated in FIG. 13B). Structure) to perform the second autocorrelation, and in one embodiment Comparison of autocorrelation results. In one embodiment, if the autocorrelation of the HEW-SIGA field using the long guard interval produces a result that is larger than the result of the autocorrelation of the HEW-SIGA field using the normal guard interval, the receiving device determines the preamble Corresponds to the extended guard interval mode preamble 1151. On the other hand, in an embodiment, if the autocorrelation of the HEW-SIGA field using the normal guard interval produces a larger result than the result of the autocorrelation of the HEW-SIGA field using the long guard interval, the receiving device It is determined that the preamble corresponds to the regular guard interval mode preamble 1151.

[0073] Referring again to FIG. 11B, in one embodiment, the preamble 1151 is formatted so that the traditional client site can determine the duration of the data unit 1150 and/or the data unit does not conform to the traditional communication protocol. In addition, in one embodiment, the preamble 1151 is formatted so that a client station operating according to the HEW protocol can determine that the data unit complies with the HEW communication protocol. For example, using BPSK modulation to modulate at least two OFDM symbols of the L-SIG 706 immediately following the preamble 1151, such as L-LSIG1154(s) and/or L-LTF2 1156 and/or HEW-SIGA(s) 1152 . In this case, in one embodiment, the traditional client site will treat the data unit 1150 as a traditional data unit, will determine the duration of the data unit based on the L-SIG 706, and will determine the duration of the data unit based on the L-SIG 706. Access to the medium is prohibited for the duration. Further, in one embodiment, Q-BPSK modulation is used to modulate one or more other OFDM symbols of the preamble 1151, such as one or more HEW-SIG 1152, which allows clients operating in accordance with the HEW communication protocol The end station detects that the data unit 115 0 conforms to the HEW communication protocol.

[0074] In some embodiments, the HEW communication protocol allows beamforming and/or multi-user MIMO (MU-MIMO) transmission in an extended guard interval mode. In other embodiments, the HEW communication protocol allows the transmission of only a single stream and/or only a single user in the extended guard interval mode. Continuing to refer to FIG. 11B, in an embodiment where the preamble 1151 includes HEW-STF 1158 and HEW-LTF 1160(s), AP 14 applies beamforming and/or multi-user transmission starting with HEW-STF 1158. In other words, in one embodiment, the field of the preamble 1151 before the HEW-STF 1158 is omnidirectional, and in the multi-user mode, is intended to be received by all intended recipients of the data unit 1150, and The HEW-STF field 1158, and the preamble field following the HEW-STF field 1158 and the data portion following the preamble 1151, are beamformed and/or included are intended to be performed by different intended recipients of the data unit 1150 The different parts of the reception. In one embodiment, the HEW-SIGB field 1162 includes user-specific information for the intended recipient of the data unit 1150 in the MU-MIMO mode. Depending on the embodiment, NGI or LGI is used to generate the HEW-SIGB field 1162. Similarly, depending on the embodiment, use NGI or LG I to generate HEW-STF 1158. In one embodiment, the training sequence used on the HEW-STF 1158 is a sequence defined in a traditional communication protocol (such as in the IEEE 802.11ac protocol).

[0075] On the other hand, in an embodiment where the preamble 1151 omits the HEW-STF 1158 and the HEW-LTF 1160(s), beamforming and MUMIMO are not allowed in the extended guard interval mode. In this embodiment, only single-user single-stream transmission is allowed in the extended guard interval mode. In one embodiment, the receiving device obtains the single stream signal based on the L-LTF field 704.

Channel estimation, and demodulate the data portion of the data unit 1150 based on the channel estimation obtained based on the L-LTF field 704.

[0076] FIG. 14A is a block diagram illustrating an extended guard interval mode data unit 1400 according to an embodiment. The data unit 1400 includes an extended guard interval mode preamble 1401. The extended guard interval 1401 is generally similar to the extended guard interval mode 1151 of FIG. 11B, except that the L-SIG 706 and the secondary L-SIG 1154 of the preamble 1151 are combined into a single L-SIG field 1406 in the preamble 1401. FIG. 14B is a diagram illustrating the L-SIG field 1406 according to one embodiment. In the embodiment of FIG. 14B, the L-SIG field 1406 includes: a double guard interval 1410; a first L-SIG field 1412, which includes the content of the L-SIG field 706 of the preamble 1151; and a second L-SIG field 1414 , Which includes the content of the secondary LSIG2 field 1154 of the preamble 1151. In various embodiments, as discussed above with respect to the L-SIG field 706.1154 of FIG. 11B, the L-SIG field 1406 includes a length subfield that is set to a fixed value or is set to a variable value. In various embodiments, as discussed above with respect to the L-SIG field 706.1154 of FIG. 11B, the redundant (repetitive) bits in the L-SIG field 1406 are used for improved channel estimation.

[0077] In one embodiment, the traditional client station that receives the data unit 1400 assumes that the L-SIG field 1406 includes the normal guard interval. As illustrated in FIG. 14C, in this embodiment, the FFT window for L-SIG information bits assumed at the traditional client site is shifted compared to the actual L-SIG field 1412. In one embodiment, in order to ensure that the constellation points in the FFT window correspond to the BPSK modulation expected by the traditional client station, and in order to allow the traditional client station to properly decode the L-SIG field 1412, the L-SIG field 1412 The modulation is phase-shifted relative to conventional BPSK modulation. For example, in a 20MHz OFDM symbol, if the normal guard interval is 0.8ys and the double guard interval is 1.6ys, the modulation of the OFDM tone k of the L-SIG field 1412 is shifted with respect to the corresponding OFDM tone k of the original L-SIG, As can be seen from the following formula:

[0078] s = S delay G £ good "to become lame = LS, G · (i) Equation 1

[0079] Therefore, in one embodiment, the reverse Q-BPSK is used instead of regular BPSK to modulate the L-SIG field 1412. So, for example, in one embodiment, a bit of value 1 is modulated onto -j, while the value is. The bits of are modulated onto j, which produces modulation instead of regular {1,-1} BPSK modulation. In one embodiment, due to the reverse Q-BPSK modulation of the L-SIG field 1412, the traditional client station can properly decode the L-SIG field 1412, and in one embodiment based on the L-SIG field 1412 The duration of the data unit 1400 is determined. On the other hand, in an embodiment, a client station operating according to the HEW protocol can detect the repetition of the L-SIG field 1412, or detect the opposite of the L-SIG field in the FFT window of the traditional client station. Q-BPSK modulation, and the preamble 1401 is automatically detected as the preamble of the extended guard interval mode. Alternatively, in other embodiments, the client station operating according to the HEW protocol uses other detection methods discussed above, such as based on the modulation or format of the HEW-SIGA field(s) 1152, and the preamble 1401 is detected. It is the preamble of the extended guard interval mode.

[0080] Referring to FIGS. 11A-11B and 14A, in some embodiments, a long guard interval is used for a regular guard interval mode preamble (eg, preamble 1101) and a long guard interval preamble (eg, preamble 1151 or preamble Code 1401) The initial OFDM# number of the two. For example, referring to FIGS. 11A-11B, in one embodiment, the L-STF field 702, the L-LTF field 704, the L-SIG field 706.1154, and the HEW-SIGA field 1152 are each generated using a long guard interval. Similarly, referring to FIG. 14A, in one embodiment, a long guard interval is used to generate the L-STF field 702, the L-LTF field 704, the L-SIG field 1406, and the HEW-SIGA field(s) 1152. In an embodiment, in various embodiments, the receiving device can determine whether the preamble corresponds to the modulation (for example, Q-BPSK) of the HEW-SIGA field 1152 or based on the indication included in the HEW-SIGA field 1152. Whether it is the preamble of the regular guard interval mode or the extended guard interval mode. further

Specifically, similar to the preamble 1151 of FIG. 11B, depending on the embodiment and/or scenario, the preamble 1401 of FIG. 14A includes or omits the second L-LTF 2 field 1156.

[0081] FIG. 15 is a block diagram illustrating the format of the HEW-SIGA field 1500 according to an embodiment. In some embodiments, the HEW-SIGA field(s) 1152 of the data unit 1150 or the data unit 1400 are formatted according to the HEW-SIGA field 1500. In some embodiments, the HEW-SIGA field(s) 1108 is formatted according to the HEW-SIGA field 1500. The HEWSIGA field 1500 includes a double guard interval 1502, a first repetition 1504 of the HEW-SIGA field, and a second repetition 1506 of the HEW-SIGA field. In an exemplary embodiment, DGI is 1.8 us and each repetition of HEW-SIGA is 3.2 us. In one embodiment, the repeated bits in the HEW-SIGA field 1500 are used to increase the reliability of the decoding of the HEW-SIGA field 1500. In one embodiment, the format of the HEW-SIGA field 1500 is used based on the autocorrelation of the HEW-SIGA field using the preamble of the HEW-SIGA field 1500 and the regular HEW-SIGA field used in the regular guard interval mode. The format (such as the format illustrated in FIG. 13A) is compared between the autocorrelation of the HEW-SIGA field of the preamble, and the extended guard interval mode preamble is automatically detected.

[0082] FIG. 16 is a flowchart of an example method 1600 for generating a data unit according to an embodiment. Referring to FIG. 1, in one embodiment, the method 1600 is implemented by the network interface 16. For example, in one such embodiment, the PHY processing unit 20 is configured to implement the method 1600. According to another embodiment, the MAC processing 18 is also configured to implement at least a part of the method 1600. With continued reference to FIG. 1, in yet another embodiment, the method 1600 is implemented by the network interface 27 (for example, the PHY processing unit 29 and/or the MAC processing unit 28). In other embodiments, the method 1600 is implemented by other suitable network interfaces.

[0083] At block 1602, the data portion of the data unit is generated. Generating the data part at block 1602 includes: using one of (i) a normal guard interval, (ii) a short guard interval, or (iii) a long guard interval to generate an OFDM symbol of the data part.

[0084] At block 1604, the preamble of the data unit is generated. The preamble generated at block 1604 is generated to indicate whether at least the data part of the data unit generated at block 1602 is generated using (1) normal guard interval, (ii) short guard interval, or (iii) long guard interval. In various embodiments and/or scenarios, the preamble 701 (FIG. 9A, 10A), 751 (FIG. 9B, 10B), 1101 (FIG. 11A), 1151 (FIG. 11B), or 1401 (FIG. 14A) is generated at block 1604 )one. In other embodiments, other suitable preambles are generated at block 1604. In one embodiment, the preamble generated at block 1604 includes a GI indication, which is set to indicate whether at least the data part uses (i) a normal guard interval, (ii) a short guard interval, or (iii) a long guard interval. Interval to generate. In one embodiment, the GI indication includes two bits. In an embodiment, in addition to the data part, a part of the preamble is also generated using the guard interval indicated by the GI indication. In another embodiment, the preamble generated at block 1604 is formatted so that the receiving device can automatically detect (eg, without decoding) whether the preamble corresponds to a regular guard interval preamble or an extended guard interval mode preamble. In one embodiment, the extension The detection of the guard interval preamble signals the receiving device that at least the data part is generated using the long guard interval.

[0085] At block 1606, a data unit is generated to include the preamble generated at block 1604 and the data portion generated at block 1602.

[0086] At least some of the various modules, operations, and techniques described above may be implemented using hardware, a processor that executes firmware instructions, a processor that executes software instructions, or any combination thereof. When implemented by a processor that executes software instructions or firmware instructions, these software instructions or firmware instructions can be stored in any computer-readable memory, such as on a magnetic disk, optical disk or other storage medium, and stored in RAM or ROM or flash memory. , Processors, hard drives, optical drives, tape drives, etc. Similarly, these software instructions or firmware instructions can be delivered to the user or the system via any known or desired delivery method. Any known or desired delivery method includes, for example,

On a computer-readable disk or other transportable computer storage mechanism, or via a communication medium. Communication media usually embodies computer-readable instructions, data structures, program modules, or other data in a modulated data signal (such as a carrier wave or other transportation mechanism). The term "modulated data signal" means a signal that causes one or more of its characteristics to be set or changed in a manner related to the encoded information in the signal. By way of example and not limitation, communication media include: wired media, such as a wired network or direct line connection; and wireless media, such as sound media, radio frequency media, infrared media, and other wireless media. Therefore, these software instructions or firmware instructions can be provided via communication channels such as telephone lines, DSL lines, cable TV lines, optical fiber lines, wireless communication channels, the Internet, etc. The software is the same or interchangeable) and delivered to the user or system. These software instructions or firmware instructions may include machine-readable instructions, which, when executed by the processor, cause the processor to perform various actions.

[0087] Further aspects of this disclosure relate to one or more of the following clauses.

[0088] In one embodiment, a method for generating a data unit for transmission via a communication channel includes: generating a data portion of the data unit, including using (i) normal guard interval, (ii) short protection One of the interval and (iii) the long guard interval is used to generate Orthogonal Frequency Division Multiplexing (OFDM) symbols of the data part. The method further includes: generating a preamble of the data unit, including generating the preamble to indicate at least whether the OFDM symbol of the data part is generated using a normal guard interval, a short guard interval, or a long guard interval. The method additionally includes: generating the data unit to include the preamble and the data portion.

[0089] In other embodiments, the method includes any suitable combination of one or more of the following features. [0090] Generating the preamble of the data unit includes: generating a signal field of the preamble, wherein the signal field includes a guard interval indication, the guard interval indication is set to indicate that at least the OFDM symbol of the data part uses a normal guard interval, Short guard interval or long guard interval is generated.

[0091] The guard interval indication includes two bits.

[0092] Generating the preamble includes: generating a first part of the preamble, where the first part of the preamble (i) is generated using a normal guard interval and (ii) includes a signal field, and uses the protection in the signal field The interval indicates the guard interval indicated to generate the second part of the preamble.

[0093] Generating the preamble of the data unit includes: generating one of (i) a regular guard interval mode preamble or (ii) an extended guard interval mode preamble.

[0094] Generating the preamble includes: formatting the preamble so that the receiving device can automatically detect whether the preamble corresponds to a regular guard interval preamble or an extended guard interval preamble, wherein when the preamble corresponds to an extended guard interval In the case of the preamble, the extended guard interval mode preamble is used as an indication that at least the OFDM symbol of the data part is generated using a long guard interval.

[0095] Generating the extended guard interval preamble includes: including two or more repetitions of the conventional signal field in the extended guard interval preamble, and wherein the receiving device can detect the two or more times of the conventional signal field based on More repetitions to automatically detect that the preamble corresponds to the extended guard interval mode preamble.

[0096] Generating the extended guard interval mode preamble includes: generating a non-legacy signal field to be included in the preamble, and the non-legacy signal field that is different from the corresponding non-legacy signal field in the conventional guard interval mode preamble The field is modulated.

[0097] The receiving device can automatically detect that the preamble corresponds to the extended guard interval mode preamble by detecting the modulation of the non-traditional signal field.

[0098] Generating the non-traditional signal field includes: using a long guard interval to generate the non-traditional signal field.

[0099] Generating the extended guard interval mode preamble includes: using a long guard interval to generate a non-legacy signal field to be included in the preamble, and wherein the receiving device can perform the non-legacy signal field by using the long guard interval The result of the autocorrelation is compared with the result of the autocorrelation of the non-traditional signal field performed using the normal guard interval to automatically detect that the preamble corresponds to the extended mode guard interval preamble.

[0100] The data unit complies with the first communication protocol, and generating the preamble further includes: generating the preamble so that (1) a conventional receiver configured to operate according to a conventional communication protocol instead of the first communication protocol can The duration of the data unit is determined, and (ii) a receiver configured to operate according to the first communication protocol can detect that the data unit conforms to the first communication protocol.

[0101] In another embodiment, an apparatus includes a network interface configured to generate a data portion of a data unit, including using (i) a normal guard interval, (ii) a short guard interval, and (iii) a long guard interval. One of the guard intervals is used to generate Orthogonal Frequency Division Multiplexing (OFDM) symbols for the data portion. The network interface is further configured to generate the preamble of the data unit, including generating the preamble to indicate whether at least the OFDM symbol of the data part is generated using a normal guard interval, a short guard interval, or a long guard interval. The network interface is additionally configured to generate the data unit to include the preamble and the data portion.

[0102] In other embodiments, the device includes any suitable combination of one or more of the following features.

[0103] The network interface is further configured to generate a signal field to be included in the preamble, wherein the signal field includes a guard interval indication, and the guard interval indication is set to indicate that at least the OFDM symbols of the data part are in normal use. Guard interval, short guard interval, or long guard interval are generated.

[0104] The guard interval indication includes two bits.

[0105] The network interface is further configured to generate the first part of the preamble, wherein the first part of the preamble (i) is generated using a normal guard interval and (ii) includes a signal field, and uses the The guard interval indicates the indicated guard interval to generate the second part of the preamble.

[0106] Generating the preamble of the data unit includes: generating one of (i) a regular guard interval mode preamble or (ii) an extended guard interval mode preamble, wherein generating the preamble includes: formatting the preamble so that the reception The device can automatically detect whether the preamble corresponds to a regular guard interval preamble or an extended guard interval preamble, wherein when the preamble corresponds to an extended guard interval preamble, the extended guard interval mode preamble is used as at least the data part The OFDM symbol is an indication that a long guard interval is used to generate.

[0107] Generating the extended guard interval preamble includes: including two or more repetitions of a conventional signal field in the extended guard interval preamble, and wherein the receiving device can detect the two or more times of the conventional signal field based on More repetitions to automatically detect that the preamble corresponds to the extended guard interval mode preamble.

[0108] Generating the extended guard interval mode preamble includes: generating a non-legacy signal field to be included in the preamble, and the non-legacy signal field that is different from the corresponding non-legacy signal field in the regular guard interval mode preamble. The field is modulated.

[0109] The receiving device can automatically detect that the preamble corresponds to the extended guard interval mode preamble by detecting the modulation of the non-traditional signal field.

[0110] Generating the non-traditional signal field includes: using a long guard interval to generate the non-traditional signal field.

[0111] Generating the extended guard interval mode preamble includes: using a long guard interval to generate a non-legacy signal field to be included in the preamble, and wherein the receiving device can perform the non-legacy signal by using the long guard interval

The autocorrelation result of the field is compared with the autocorrelation result of the non-traditional signal field performed using the normal guard interval to automatically detect that the preamble corresponds to the extended mode guard interval preamble.

[0112] The data unit conforms to the first communication protocol, and generating the preamble further includes: generating the preamble so that (1) a conventional receiver configured to operate according to a conventional communication protocol instead of the first communication protocol can The duration of the data unit is determined, and (ii) a receiver configured to operate according to the first communication protocol can detect that the data unit conforms to the first communication protocol.

[0113] When implemented in hardware, the hardware may include one or more of the following: discrete components, integrated circuits, application specific integrated circuits (ASICs), and so on.

[0114] Although the present invention has been described with reference to specific examples, it is intended to be illustrative only and not to limit the present invention. Without departing from the scope of the present invention, changes, additions, and/or changes may be made to the disclosed embodiments. Or delete.