Patent Description:
The Internet usage has recently increased year by year along with the development of information communication technologies, and various communication techniques have been developed to cope with an increase in demand. In particular, wireless local area network (wireless LAN) techniques implement throughput improvement in Internet communications for packet data, audio, video, and the like by wireless LAN terminals, and various technological developments have still been conducted actively.

In the development of wireless LAN techniques, a lot of standardization works by the IEEE (Institute of Electrical and Electronics Engineers) <NUM>, which is a standardization organization for wireless LAN techniques, play an important role. As one of the wireless LAN communication standards, the IEEE802. <NUM> standards are known, including standards such as IEEE802.11n/a/b/g/ac and IEEE802.11ax. For example, IEEE802.11ax implements a high peak throughput of up to <NUM> gigabits per second (Gbps) and additionally improves the communication speed under a congestion situation using OFDMA (Orthogonal frequency-division multiple access) (PTL <NUM>).

Recently, in order to further improve throughput, a study group called IEEE802.11EHT (Extremely High Throughput) has been formed as a successor standard of IEEE802.11ax. One of measures for throughput improvement that is a target for the IEEE802.11EHT is increasing the number of spatial streams of the MIMO (Multi-Input Multi-Output) method. The MIMO is a method of improving a channel resource use efficiency in a wireless communication network formed by an access point (AP) and a station (STA) that is a wireless LAN terminal by forming a plurality of spatial streams using a plurality of antennas and performing communication. If there is a single STA, the method is called SU-MIMO (Single-User MIMO). If a plurality of STAs exist, the method is called MU-MIMO (Multi-User MIMO). The MIMO has proliferated as a technique for a next-generation communication system in recent years, and is employed in the IEEE802. <NUM> standards as well. For example, in IEEE802.11ax, the method is adaptable to eight spatial streams (SS) at maximum. In IEEE802.11EHT, increasing the maximum number of spatial streams to <NUM> has been examined. When the number of spatial streams is increased, the space use efficiency further improves, and throughput improvement can be implemented.

<NPL>, contains a proposal for the TGax draft amendment. It captures the feature requirements outlined in the TGax specification framework document (<NUM>-<NUM>/<NUM>) in detailed draft text.

An IEEE document, Eunsung Park (<NPL>, discusses PHY features to be considered for enabling potential EHT candidates. The following candidates had been proposed as the potential technologies for EHT: wider bandwidth, i.e. <NUM>, increased spatial streams, i.e. <NUM> SS, Multi-AP coordination, HARQ, <NUM> operation/Multi-band operation. The contribution focuses on the first four candidates.

As described above, in the IEEE802.11EHT, the maximum number of spatial streams is assumed to be set to <NUM>. However, in the conventional standards for a wireless LAN, a mechanism that notifies each STA of information concerning allocation of the number of spatial streams in a case in which the total number of spatial streams allocated to one or more STAs (wireless LAN terminals) becomes larger than <NUM> has not been defined.

In consideration of the above-described problem, the present invention provides a mechanism configured to notify one or more wireless LAN terminals of allocation of the number of spatial streams, which is larger than <NUM> in total.

According to one aspect of the present invention there is provided a communication device as recited in claim <NUM> of the accompanying claims.

According to another aspect of the present invention there is provided a communication device as recited in claim <NUM> of the accompanying claims.

According to another aspect of the present invention there is provided a control method of a communication device as recited in claim <NUM> of the accompanying claims.

According to the present invention, there is provided a mechanism configured to notify one or more wireless LAN terminals of allocation of the number of spatial streams, which is larger than <NUM> in total.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain principles of the invention.

<FIG> shows an example of the configuration of a wireless communication network according to this embodiment. This wireless communication network is configured to include one access point (AP <NUM>) and three STAs (STA <NUM>, STA <NUM>, and STA <NUM>) as devices (EHT devices) complying with the IEEE802.11EHT (Extremely High Throughput) standard. Note that it may be understood that EHT is an acronym of Extremely High Throughput. The AP <NUM> can be considered as one form of an STA because it has the same functions as the STAs <NUM> to <NUM> except that it has a relay function. STAs located in a circle <NUM> representing the area where a signal transmitted from the AP <NUM> reaches can communicate with the AP <NUM>. The AP <NUM> communicates with the STAs <NUM> to <NUM> in accordance with the wireless communication method of the IEEE802.11EHT standard. The AP <NUM> can establish a radio link with each of the STAs <NUM> to <NUM> via connection processing such as an association process complying with a standard of the IEEE802. <NUM> series.

Note that the configuration of the wireless communication network shown in <FIG> is merely an example for the description and, for example, a network including many EHT devices and legacy devices (communication devices complying with the IEEE802.11a/b/g/n/ax standards) in a wider area may be formed. Also, the arrangement of the communication devices is not limited to that shown in <FIG>, and the following argument is applicable to various positional relationships of the communication devices as well.

<FIG> is a block diagram showing the functional configuration of the AP <NUM>. The AP <NUM> includes, as an example of its functional configuration, a wireless LAN control unit <NUM>, a frame generation unit <NUM>, a signal analysis unit <NUM>, and a UI (User Interface) control unit <NUM>.

The wireless LAN control unit <NUM> can be configured to include one or more antennas <NUM> and circuits configured to transmit/receive a radio signal (radio frame) to/from another wireless LAN device, and a program configured to control these. The wireless LAN control unit <NUM> executes communication control of the wireless LAN based on a frame generated by the frame generation unit <NUM> in accordance with the standard of the IEEE802. <NUM> series.

The frame generation unit <NUM> generates a frame to be transmitted by the wireless LAN control unit <NUM> based on the result of analysis performed by the signal analysis unit <NUM> for a signal received by the wireless LAN control unit <NUM>. The frame generation unit <NUM> may create a frame without depending on the analysis result of the signal analysis unit <NUM>. The signal analysis unit <NUM> analyzes a signal received by the wireless LAN control unit <NUM>. The UI control unit <NUM> accepts an operation by the user (not shown) of the AP <NUM> on an input unit <NUM> (<FIG>), and performs control of transmitting a control signal corresponding to the operation to each constituent element or controls output (including display and the like) for an output unit <NUM> (<FIG>).

<FIG> shows the hardware configuration of the AP <NUM> according to this embodiment. The AP <NUM> includes, as an example of its hardware configuration, a storage unit <NUM>, a control unit <NUM>, a function unit <NUM>, the input unit <NUM>, the output unit <NUM>, a communication unit <NUM>, and the one or more antennas <NUM>.

The storage unit <NUM> is formed by both of a ROM and a RAM or one of them, and stores programs for performing various kinds of operations to be described later and various kinds of information such as communication parameters for wireless communication. Note that other than the memories such as a ROM and a RAM, a storage medium such as a flexible disk, a hard disk, an optical disk, a magnetooptical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, or a DVD may be used as the storage unit <NUM>.

The control unit <NUM> is formed by, for example, a processor such as a CPU or an MPU, an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like. Here, CPU is an acronym of Central Processing Unit, and MPU is an acronym of Micro Processing Unit. The control unit <NUM> executes the programs stored in the storage unit <NUM>, thereby controlling the entire AP <NUM>. Note that the control unit <NUM> may control the entire AP <NUM> by cooperation of the programs stored in the storage unit <NUM> and an OS (Operating System).

In addition, the control unit <NUM> controls the function unit <NUM> to execute predetermined processing such as image capturing, printing, or projection. The function unit <NUM> is hardware used by the AP <NUM> to execute predetermined processing. For example, if the AP <NUM> is a camera, the function unit <NUM> is an image capturing unit and performs image capturing processing. For example, if the AP <NUM> is a printer, the function unit <NUM> is a printing unit and performs print processing. For example, if the AP <NUM> is a projector, the function unit <NUM> is a projection unit and performs projection processing. Data to be processed by the function unit <NUM> may be data stored in the storage unit <NUM>, or may be data communicated with an STA or another AP via the communication unit <NUM> to be described later.

The input unit <NUM> accepts various kinds of operations from a user. The output unit <NUM> performs various kinds of outputs for the user. Here, the output by the output unit <NUM> includes at least one of display on a screen, audio output by a loudspeaker, vibration output, and the like. Note that both the input unit <NUM> and the output unit <NUM> may be implemented by one module, like a touch panel.

The communication unit <NUM> controls wireless communication complying with the IEEE802.11EHT standard, or controls wireless communication complying with Wi-Fi or IP (Internet Protocol) communication. Also, the communication unit <NUM> controls the one or more antennas <NUM> to transmit/receive radio signals for wireless communication. The AP <NUM> communicates contents such as image data, document data, and video data with another communication device via the communication unit <NUM>.

The functional configuration and the hardware configuration of the STAs <NUM> to <NUM> are the same as the functional configuration (<FIG>) and the hardware configuration (<FIG>) of the AP <NUM> described above, respectively. That is, each of the STAs <NUM> to <NUM> can be configured to include, as its functional configuration, the wireless LAN control unit <NUM>, the frame generation unit <NUM>, the signal analysis unit <NUM>, and the UI control unit <NUM> and include, as its hardware configuration, the storage unit <NUM>, the control unit <NUM>, the function unit <NUM>, the input unit <NUM>, the output unit <NUM>, the communication unit <NUM>, and the one or more antennas <NUM>.

Next, the procedure of processing executed by the AP <NUM> configured as described above and the sequence of processing executed by the wireless communication system shown in <FIG> will be described with reference to <FIG> is a flowchart showing processing executed by the AP <NUM>. The flowchart shown in <FIG> can be implemented when the control unit <NUM> of the AP <NUM> executes a control program stored in the storage unit <NUM> and executes calculation and processing of information and control of each hardware. <FIG> shows a sequence chart of processing executed by the wireless communication system.

The AP <NUM> performs connection processing complying with the standard of the IEEE802. <NUM> series for each of the STAs <NUM> to <NUM> (step S401, F501). That is, frames such as Probe Request/Response, Association Request/Response, and Auth (authentication) are transmitted/received between the AP <NUM> and each of the STAs <NUM> to <NUM>, thereby establishing a radio link. Next, the AP <NUM> decides the number of spatial streams for each of the STAs <NUM> to <NUM>. The number of spatial streams for each STA can be decided by the signal analysis unit <NUM> based on information concerning the reception state such as CSI (Channel State Information) received from each STA. Also, the number of spatial streams for each STA may be decided in advance in the wireless communication network or may be decided by an operation of the user (not shown) of the AP <NUM> on the input unit <NUM>. Next, the AP <NUM> decides communication parameters including the information concerning the numbers of spatial streams decided in step S402 or F502 and other parameters (information/values), which are included in a radio frame to be transmitted (step S403, F503). Next, the AP <NUM> transmits data in a form of a radio frame including the decided communication parameters and data to the STAs <NUM> to <NUM> (step S404, F504).

<FIG> shows an example of the PHY (physical) frame structure of a PPDU defined by the IEEE802.11EHT standard and transmitted in step S404 or F504. Note that PPDU is an abbreviation of Physical Layer Protocol Data Unit. The head portion of the PPDU shown in <FIG> includes an L (Legacy)-STF (Short Training Field) <NUM>, an L-LTF (Long Training Field) <NUM>, and an L-SIG (Signal Field) <NUM> having backward compatibility with the IEEE802.11a/b/g/n/ax standards. The L-STF <NUM> is used for detection of a PHY frame signal, automatic gain control (AGC), timing detection, or the like. The L-LTF <NUM> arranged immediately after the L-STF <NUM> is used for highly accurate frequency/time synchronization, obtainment of propagation channel information (CSI), or the like. The L-SIG <NUM> arranged immediately after the L-LTF <NUM> is used for transmitting control information including information such as a data transmission rate and a PHY frame length. A legacy device complying with the IEEE802.11a/b/g/n/ax standards can decode data of the above-described various kinds of legacy fields (the L-STF <NUM>, the L-LTF <NUM>, and the L-SIG <NUM>).

After the L-SIG <NUM>, the PPDU further includes an RL-SIG <NUM>, an EHT-SIG-A <NUM>, an EHT-SIG-B <NUM>, an EHT-STF <NUM>, an EHT-LTF <NUM>, a data field <NUM>, and a Packet extension <NUM>. The RL-SIG <NUM> may be absent. The EHT-SIG-A <NUM> is arranged after the L-SIG <NUM>, the EHT-SIG-B <NUM> is arranged immediately after the EHT-SIG-A <NUM>, the EHT-STF <NUM> is arranged immediately after the EHT-SIG-B <NUM>, the EHT-LTF <NUM> is arranged immediately after the EHT-STF <NUM>. Note that the field including the L-STF <NUM>, the L-LTF <NUM>, the L-SIG <NUM>, the RL-SIG <NUM>, the EHT-SIG-A <NUM>, the EHT-SIG-B <NUM>, the EHT-STF <NUM>, and the EHT-LTF <NUM> is called a preamble. Note that <FIG> shows a frame structure having backward compatibility with the IEEE802.11a/b/g/n/ax standards. If backward compatibility need not be ensured, the fields of the L-STF and the L-LTF may be omitted. Instead, the EHT-STF and the EHT-LTF may be inserted.

<FIG> shows fields that form the EHT-SIG-B <NUM>. The EHT-SIG-B <NUM> is formed by a Common field <NUM> and a User specific field <NUM>. The User specific field <NUM> is formed by connecting User Block fields <NUM>, <NUM>, and <NUM> corresponding to sub-bands each having a bandwidth of <NUM>. Subfields that form the User Block field and a description thereof are shown in Table <NUM>.

In Table <NUM>, the bit count of the User field is expressed, using an integer N, as N × <NUM> bits. If the User Block field is the final user block field in the User specific field, and if it holds information of only one user, N = <NUM>. Otherwise, N = <NUM>.

In the User Block field shown in Table <NUM>, the User field uses a format shown in Table <NUM> when transmitting data to a plurality of users (STAs) by MU-MIMO. Table <NUM> shows a description of the subfields of the User field when transmitting data by MU-MIMO. Spatial Configuration indicates the number of spatial streams (the array of spatial streams) allocated to each STA, and <NUM> bits are ensured for this subfield.

In this embodiment, the maximum number of spatial streams of MU-MIMO is set to <NUM>, and the upper limit of the number of spatial streams (the number of antennas) held by each STA is set to <NUM>. The bit string of the Spatial Configuration subfield indicates the list of the numbers of spatial streams allocated to STAs in a specific number. As an example, <FIG> shows the correspondence between the bit string of the Spatial Configuration subfield and the number of streams of each STA in a case in which the number of STAs is <NUM>.

In <FIG>, the bits of the Spatial Configuration subfield (<NUM> bits) are represented by B5,. , B0 for the description. In addition, Nsi indicates the number of antennas of the ith (i = an ID added to an STA) STA, and the spatial streams are allocated such that concerning i > j, "Nsi is always not less than Nsj" holds. Note that each STA that has received the frame including the subfield grasps the correspondence shown in <FIG> and the ID of the STA in the correspondence, thereby detecting, from the frame, the number of spatial streams allocated to the self-STA. <FIG> lists all arrays of spatial streams in a case in which the sum of all Nsi (i = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) is <NUM> or less. For example, if the Spatial Configuration subfield is "<NUM>", the number of spatial streams is <NUM> in all the six STAs. If the Spatial Configuration subfield is "<NUM>", the numbers of spatial streams of the six STAs are <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. There are a total of <NUM> patterns of spatial stream arrays. If the number of STAs is less than <NUM>, the number of patterns is less than <NUM>. That is, all patterns of spatial stream arrays can be expressed by <NUM> bits independently of the number of STAs. Although a detailed correspondence will be omitted, a similar correspondence can be created even if the number of STAs is other than <NUM>.

As described above, according to this embodiment, when <NUM> or more bits are ensured for the subfield indicating the number of spatial streams allocated to each STA in the EHT-SIG-B, even if the total number of spatial streams is larger than <NUM>, it is possible to notify each STA of the number of allocated spatial streams. Also, there is provided a mechanism configured to include, in the PPDU, the information of the spatial stream array in a case in which the number of users (STAs) is <NUM>, the maximum number of spatial streams of MU-MIMO is <NUM>, and the upper limit of the number of spatial streams (the number of antennas) held by each STA is <NUM>. This makes it possible to communicate the information of the spatial stream array between the AP and each STA.

In this example, a case in which the number of users (STAs) is <NUM>, the maximum number of spatial streams of MU-MIMO is <NUM>, and the upper limit of the number of spatial streams (the number of antennas) held by each STA is <NUM> will be described. Differences from the first embodiment will be described below.

Table <NUM> shows a description of the subfields of a User field in an EHT-SIG-B <NUM> when transmitting data by MU-MIMO. Spatial Configuration indicates the number of spatial streams (the array of spatial streams) allocated to each STA, and <NUM> bits are ensured for this subfield.

In this example, the maximum number of spatial streams of MU-MIMO is set to <NUM>, and the upper limit of the number of spatial streams (the number of antennas) held by each STA is set to <NUM>. The bit string of the Spatial Configuration subfield indicates the list of the numbers of spatial streams allocated to STAs in a specific number. <FIG> shows the correspondence between the bit string of the Spatial Configuration subfield and the number of streams of each STA in a case in which the number of STAs is <NUM>.

In <FIG>, the bits of the Spatial Configuration subfield (<NUM> bits) are represented by B7,. , B0 for the description. In addition, Nsi indicates the number of antennas of the ith STA, and the spatial streams are allocated such that concerning i > j, "Nsi is always not less than Nsj" holds. <FIG> lists all arrays of spatial streams in a case in which the sum of all Nsi (i = <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) is <NUM> or less. For example, if the Spatial Configuration subfield is "<NUM>", the number of streams is <NUM> in all the five STAs. If the Spatial Configuration subfield is "<NUM>", the numbers of streams of the five STAs are <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. There are a total of <NUM> patterns of spatial stream arrays. If the number of STAs is less than <NUM>, the number of patterns is less than <NUM>. That is, all patterns can be expressed by <NUM> bits independently of the number of STAs. Although a detailed correspondence will be omitted, a similar correspondence can be created even if the number of STAs is other than <NUM>.

As described above, according to this example, there is provided a mechanism configured to include, in the PPDU, the information of the spatial stream array in a case in which the number of users (STAs) is <NUM>, the maximum number of spatial streams of MU-MIMO is <NUM>, and the upper limit of the number of spatial streams (the number of antennas) held by each STA is <NUM>. This makes it possible to communicate the information of the spatial stream array between the AP and each STA.

It is noted that the independent claims recite the User field includes a subfield comprised of consecutive <NUM> bits for indicating numbers of spatial streams allocated to each of two or more devices with a value <NUM> as shown, for example, in <FIG>. The example as described above with reference to <FIG> is not part of the present invention but is useful for understanding aspects of the present invention.

The present invention can be implemented by processing of supplying a program for implementing one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and causing one or more processors in the computer of the system or apparatus to read out and execute the program. The present invention can also be implemented by a circuit (for example, an ASIC) for implementing one or more functions.

Claim 1:
A communication device comprising:
generation means (<NUM>) for generating an Extremely High Throughput, EHT, Physical layer Protocol Data Unit, PPDU, that is defined by IEEE802.<NUM> standard, including a preamble and a data field; and
transmission means (<NUM>) for transmitting the generated EHT PPDU,
wherein the preamble includes:
a Legacy Short Training Field, L-STF;
a Legacy Long Training Field, L-LTF, arranged immediately after the L-STF in the EHT PPDU;
a Legacy Signal Field, L-SIG, as a first Signal Field, arranged immediately after the L-LTF in the EHT PPDU;
a Repeated Legacy Signal Field, RL-SIG, as a second Signal Field, arranged immediately after the L-SIG in the EHT PPDU;
a third Signal Field arranged after the RL-SIG in the EHT PPDU;
a fourth Signal Field arranged immediately after the third Signal Field in the EHT PPDU;
a second Short Training Field arranged immediately after the fourth Signal Field in the EHT PPDU; and
a second Long Training Field arranged immediately after the second Short Training Field in the EHT PPDU, and
wherein the fourth Signal Field includes a User field, the User field includes at least a subfield indicating numbers of spatial streams allocated to each of two or more other communication devices that communicate with the communication device, the subfield is comprised of consecutive <NUM> bits, and the EHT PPDU, in which a value <NUM> is set in the subfield, is an EHT PPDU by which, in a case where the communication device communicates with six other communication devices, data is transmitted to a first other communication device using two spatial streams, data is transmitted to a second other communication device using two spatial streams, data is transmitted to a third other communication device using one spatial stream, data is transmitted to a fourth other communication device using one spatial stream, data is transmitted to a fifth other communication device using one spatial stream, and data is transmitted to a sixth other communication device using one spatial stream.