Patent Application
20240179771
The present invention relates to an access point apparatus, a station apparatus, and a communication method.
This application claims priority to JP 2021-62886 filed on Apr. 1, 2021, the contents of which are incorporated herein by reference.
The Institute of Electrical and Electronics Engineers Inc. (IEEE) has been continuously working to update the IEEE 802.11 specification that is a wireless Local Area Network (LAN) standard in order to achieve a higher speed and frequency efficiency of wireless LAN communication. In a wireless LAN, radio communication can be performed using unlicensed bands that can be used without permission (license) by nations or regions. For applications for individuals including an application for domestic use, Internet accesses from residences are wirelessly established by, for example, including wireless LAN access point functions in line termination apparatuses for connection to a Wide Area Network (WAN) line such as the Internet or connecting wireless LAN access point apparatuses to the line termination apparatuses. In other words, wireless LAN station apparatuses such as smartphones and PCs can connect to the wireless LAN access point apparatuses to access the Internet.
The standardization of a specification of IEEE 802.11ax is expected to be completed in 2020, and wireless LAN devices compliant with the draft specification and smartphones and Personal Computers (PCs) with the wireless LAN devices equipped therein are already on the market as products compliant with Wi-Fi 6 (trade name, a name for IEEE 802.11ax compliant products certified by the Wi-Fi Alliance). Also, activities for standardizing IEEE 802.11be as a standard to succeed IEEE 802.11ax has been started. As the wireless LAN devices have been widely used, in the standardization of IEEE 802.11be, further improvement has been studied that allows throughput per user to be improved in environments where wireless LAN devices are densely installed.
Meanwhile, the European Telecommunications Standards Institute (ETSI) in Europe and the Federal Communications Commission (FCC) in the United States are studying the use of 6 GHz band (5.935 to 7.125 GHz) as an unlicensed band, and the similar study is also being performed in other countries in the world. This means that in the wireless LANs 6 GHz band is expected to be available in addition to 2.4 GHz band and 5 GHz. In order to support the expansion of frequencies to be supported, the Wi-Fi Alliance is to standardize Wi-Fi 6E (trade name), which is an extended version of Wi-Fi 6, to use 6 GHz band.
To be precise, 6 GHz band corresponds to frequencies of 5.935 to 7.125 GHz, and a bandwidth of about 1.2 GHz in total becomes newly available, that is, there is increase by 14 channels each having a bandwidth of 80 MHz or 7 channels each having a bandwidth of 160 MHz. This makes a sufficient number of frequency resources available, and a study has been performed to increase the maximum channel bandwidth usable by a single wireless LAN communication system (equivalent to a BSS to be described below) from the 160 MHz in IEEE 802.11ax to double, 320 MHz, in IEEE 802.11be (see NPL 1).
The decrease of latency has been studied in IEEE 802.11 be (see NPL 2). In this study, a low latency of 1 millisecond or less is under study.
In the wireless LAN in the related art, CSMA/CA based access control is performed and the latency is largely affected by a congestion state of a channel. Specifically, in a case that carrier sense is successful and a transmission occasion is not acquired, it is necessary to further wait for a prescribed random time (perform random backoff) in order to perform transmission. In a case that the channel is congested, a situation in which a transmission occasion is not acquired continues, and as a result, there is a problem in that communication latency increases. An application that requires low latency has high frequency of transmission of data and causes increase in radio channel occupancy time, and as a result, further encourages congestion of radio channels, and this thus leads to a problem of making acquisition of a transmission occasion difficult.
An access point apparatus, a station apparatus, and a communication method according to an aspect of the present invention for solving the aforementioned problems are as follows.
(1) Specifically, an access point apparatus according to an aspect of the present invention uses multiple radio links, and includes: a radio communication circuitry configured to perform communication in each of the multiple radio links; and a radio control circuitry configured to control transmission and/or reception of data to and/or from each of the multiple radio links. The radio control circuitry performs configuration of multi-link communication with a first station apparatus communicating with the access point apparatus. The radio control circuitry performs configuration of low-latency communication with the first station apparatus. In a case that the configuration of the low-latency communication includes information indicating configuration of communication in a direction from the first station apparatus to the access point apparatus, and further includes information indicating order of use of a first radio link and a second radio link, after carrier sense is performed in the first radio link, a first trigger frame is transmitted to the first station apparatus, and after the first trigger frame is transmitted, and after carrier sense is performed in the second radio link based on the information indicating the order of the use of the first radio link and the second radio link, a second trigger frame is transmitted to the first station apparatus.
(2) The access point apparatus according to an aspect of the present invention is described in (1) above. The radio control circuitry may perform the configuration of the multi-link communication with a second station apparatus other than the first station apparatus. The radio control circuitry may perform configuration of second low-latency communication with the second station apparatus. In a case that the configuration of the second low-latency communication includes configuration of communication in a direction from the second station apparatus to the access point apparatus, after carrier sense is performed in the first radio link, the first trigger frame may be transmitted to the first station apparatus and the second station apparatus, and after the first trigger frame is transmitted, and after carrier sense is performed in the first radio link, the second trigger frame may be transmitted to the first station apparatus and the second station apparatus in the first radio link.
(3) The access point apparatus according to an aspect of the present invention is described in (2) above. The configuration of the first low-latency communication may include information related to a first transmission period, and the configuration of the second low-latency communication may include information related to a second transmission period. In a case that the first transmission period indicated by the information related to the first transmission period is shorter than the second transmission period indicated by the information related to the second transmission period, after the first trigger frame is transmitted to the first station apparatus and the second station apparatus in the first radio link, and after carrier sense is performed in the second radio link, the second trigger frame may be transmitted to the first station apparatus in the second radio link.
(4) The access point apparatus according to an aspect of the present invention is described in (1) above. The configuration of the first low-latency communication may include information of the multiple radio links used for low-latency communication.
(5) In a communication apparatus according to an aspect of the present invention, configuration of the low-latency communication may include information of transmission frequency. In a case that carrier sense is performed in the first radio link, and a period in which it is determined that the first radio link is busy is longer than a prescribed period based on the information of the transmission frequency, a trigger frame may not be transmitted in the first radio link, and after carrier sense is performed in the second radio link, the second trigger frame may be transmitted to the first station apparatus and a second station apparatus.
(6) A station apparatus according to an aspect of the present invention uses multiple radio links, and includes: a radio communication circuitry configured to perform communication in each of the multiple radio links; and a radio control circuitry configured to control transmission and/or reception of data to and/or from each of the multiple radio links. The radio control circuitry performs configuration of multi-link communication with an access point apparatus. The radio control circuitry performs configuration of low-latency communication with the access point apparatus. In a case that the configuration of the low-latency communication includes information indicating a first radio link and a second radio link and information indicating order of the first radio link and the second radio link, after a trigger frame is received in the first radio link, low-latency communication data is transmitted using the first radio link, and after the trigger frame is received in the second radio link after the first low-latency communication data is transmitted, the low-latency communication data is transmitted using the second radio link.
(7) The station apparatus according to an aspect of the present invention is described in (6) above. The configuration of the low-latency communication may include information of frequency of the low-latency communication. In a case that the trigger frame is not received for a prescribed period based on the frequency of the low-latency communication in the first radio link, the trigger frame may be received in the second radio link, and the low-latency communication data may be subsequently transmitted using the second radio link.
(8) A communication method according to an aspect of the present invention uses multiple radio links, and includes the steps of: performing configuration of multi-link communication with an access point apparatus; performing configuration of low-latency communication with the access point apparatus; and in a case that the configuration of the low-latency communication includes information indicating a first radio link and a second radio link and information indicating order of the first radio link and the second radio link, after a trigger frame is received in the first radio link, transmitting low-latency communication data using the first radio link, and after the trigger frame is received in the second radio link after the first low-latency communication data is transmitted, transmitting the low-latency communication data using the second radio link.
According to an aspect of the present invention, in a wireless LAN communication system, efficiency of low-latency communication can be enhanced by averaging channel occupancy time of radio channels used for low-latency communication.
A communication system according to the present embodiment includes a radio transmission apparatus (an access point apparatus or a base station apparatus that is an access point or a base station apparatus) and multiple radio terminal apparatuses (station apparatuses or terminal apparatuses that are stations or terminal apparatuses). A network including the base station apparatus and terminal apparatuses is called a basic service set (BSS or a control range). In addition, the station apparatus according to the present embodiment can have functions of the access point apparatus. Similarly, the access point apparatus according to the present embodiment can have functions of the station apparatus. Therefore, in a case that a communication apparatus is simply mentioned below, the communication apparatus can indicate both the station apparatus and the access point apparatus.
The base station apparatus and the terminal apparatuses in the BSS are assumed to perform communication based on Carrier sense multiple access with collision avoidance (CSMA/CA). Although the present embodiment is intended for an infrastructure mode in which a base station apparatus performs communication with multiple terminal apparatuses, the method of the present embodiment can also be performed in an ad hoc mode in which terminal apparatuses perform communication directly with each other. In the ad hoc mode, a terminal apparatus substitutes for a base station apparatus to form a BSS. The BSS in the ad hoc mode may also be referred to as an independent basic service set (IBSS). In the following description, a terminal apparatus that forms an IBSS in the ad hoc mode can also be considered to be a base station apparatus. The method of the present embodiment can also be implemented in Wi-Fi Direct (trade name) in which terminal apparatuses directly communicate with each other. In the Wi-Fi Direct, a terminal apparatus substitutes for a base station apparatus to form a Group. In the following description, a Group owner terminal apparatus that forms a Group in the Wi-Fi Direct can also be regarded as a base station apparatus.
In an IEEE 802.11 system, each apparatus can transmit transmission frames of multiple frame types in a common frame format. Each of the transmission frames is defined as a physical (PHY) layer, a medium access control (MAC) layer, or a logical link control (LLC) layer.
A transmission frame of the PHY layer may be referred to as a physical protocol data unit (PPDU, PHY protocol data unit, or physical layer frame). The PPDU includes a physical layer header (PHY header) including header information and the like for performing signal processing in the physical layer, a physical service data unit (PSDU, PHY service data unit, or MAC layer frame) that is a data unit processed in the physical layer, and the like. The PSDU can include an aggregated MAC protocol data unit (MPDU) (A-MPDU) in which multiple MPDUs serving as retransmission units in a wireless section are aggregated.
A PHY header includes a reference signal such as a short training field (STF) used for detection, synchronization, and the like of signals, a long training field (LTF) used for obtaining channel information for demodulating data, and the like and a control signal such as a signal (SIG) including control information for demodulating data. In addition, STFs are classified into a legacy-STF (L-STF), a high throughput-STF (HT-STF), a very high throughput-STF (VHT-STF), a high efficiency-STF (HE-STF), an extremely high throughput-STF (EHT-STF), and the like in accordance with corresponding standards, and LTFs and SIGs are also similarly classified into an L-LTF, an HT-LTF, a VHT-LTF, an HE-LTF, an L-SIG, an HT-SIG, a VHT-SIG, an HE-SIG, and an EHT-SIG depending on the corresponding standards. The VHT-SIG is further classified into VHT-SIG-A1, VHT-SIG-A2, and VHT-SIG-B. Similarly, the HE-SIG is classified into HE-SIG-A1 to 4 and HE-SIG-B. In addition, on the assumption of technology update in the same standard, a universal SIGNAL (U-SIG) field including additional control information can be included.
Furthermore, the PHY header can include information for identifying a BSS of a transmission source of the transmission frame (hereinafter, also referred to as BSS identification information). The information for identifying a BSS can be, for example, a service set identifier (SSID) of the BSS or a MAC address of a base station apparatus of the BSS. In addition, the information for identifying a BSS can be a value unique to the BSS (e.g., a BSS color, etc.) other than an SSID or a MAC address.
The PPDU is modulated in accordance with the corresponding standard. In the IEEE 802.11n standard, for example, the PPDU is modulated into an orthogonal frequency division multiplexing (OFDM) signal.
An MPDU includes a MAC layer header (MAC header) including header information and the like for performing signal processing in the MAC layer, a MAC service data unit (MSDU) or a frame body that is a data unit processed in the MAC layer, and a frame check sequence (FCS) for checking whether there is an error in a frame. In addition, multiple MSDUs can be aggregated as an Aggregated MSDU (A-MSDU).
The frame types of transmission frames of the MAC layer are roughly classified into three frame types, namely a management frame for managing a connection state and the like between apparatuses, a control frame for managing a communication state between apparatuses, and a data frame including actual transmission data. Each frame type is further classified into multiple kinds of subframe types. The control frame includes a reception completion notification (Acknowledge or Ack) frame, a transmission request (Request to send or RTS) frame, a reception preparation completion (Clear to send or CTS) frame, and the like. The management frame includes a Beacon frame, a Probe request frame, a Probe response frame, an Authentication frame, an Association request frame, an Association response frame, and the like. The data frame includes a data frame, a polling (CF-poll) frame, and the like. Each apparatus can recognize the frame type and the subframe type of a received frame by interpreting contents of the frame control field included in the MAC header.
Note that an Ack may include a Block Ack. A Block Ack can give a reception completion notification with respect to multiple MPDUs.
The beacon frame includes a field in which a periodicity at which a beacon is transmitted (beacon interval) and an SSID are described. The base station apparatus can periodically broadcast a beacon frame within a BSS, and each terminal apparatus can recognize the base station apparatus in the surroundings of the terminal apparatus by receiving the beacon frame. The action of the terminal apparatus recognizing the base station apparatus based on the beacon frame broadcast from the base station apparatus may be referred to as passive scanning. On the other hand, the action of the terminal apparatus searching for the base station apparatus by broadcasting a probe request frame in the BSS may be referred to as active scanning. The base station apparatus can transmit a probe response frame in response to the probe request frame, and details described in the probe response frame are equivalent to those in the beacon frame.
A terminal apparatus recognizes a base station apparatus and performs connection processing with respect to the base station apparatus. The connection processing is classified into an authentication procedure and an association procedure. A terminal apparatus transmits an authentication frame (authentication request) to a base station apparatus that the terminal apparatus desires to connect with. Once the base station apparatus receives the authentication frame, then the base station apparatus transmits, to the terminal apparatus, an authentication frame (authentication response) including a status code indicating whether authentication can be made for the terminal apparatus. The terminal apparatus can determine whether the terminal apparatus has been authenticated by the base station apparatus by interpreting the status code described in the authentication frame. Note that the base station apparatus and the terminal apparatus can exchange the authentication frame multiple times.
After the authentication procedure, the terminal apparatus transmits an association request frame to the base station apparatus in order to perform the association procedure. Once the base station apparatus receives the association request frame, the base station apparatus determines whether to allow the connection to the terminal apparatus and transmits an association response frame to notify the terminal apparatus of the intent. In the connection response frame, an association identifier (AID) for identifying the terminal apparatus is described in addition to the status code indicating whether to perform the connection processing. The base station apparatus can manage multiple terminal apparatuses by configuring different AIDs for the terminal apparatuses for which the base station apparatus has allowed connection.
After the connection processing is performed, the base station apparatus and the terminal apparatus perform actual data transmission. In the IEEE 802.11 system, a distributed coordination function (DCF), a point coordination function (PCF), and mechanisms in which the aforementioned mechanisms are enhanced (an enhanced distributed channel access (EDCA) or a hybrid control mechanism (hybrid coordination function (HCF)), and the like) are defined. A case that the base station apparatus transmits signals to the terminal apparatus using the DCF will be described below as an example.
In the DCF, the base station apparatus and the terminal apparatus perform carrier sense (CS) for checking usage of a radio channel in the surroundings of the apparatuses prior to communication. For example, in a case that the base station apparatus serving as a transmitting station receives a signal of a higher level than a predefined clear channel assessment level (CCA level) on a radio channel, transmission of transmission frames on the radio channel is postponed. Hereinafter, a state in which a signal of a level that is equal to or higher than the CCA level is detected on the radio channel will be referred to as a busy (Busy) state, and a state in which a signal of a level that is equal to or higher than the CCA level is not detected will be referred to as an idle (Idle) state. In this manner, CS performed based on power of a signal actually received by each apparatus (reception power level) is called physical carrier sense (physical CS). Note that the CCA level is also called a carrier sense level (CS level) or a CCA threshold (CCAT). Note that, in a case that a signal of a level that is equal to or higher than the CCA level has been detected, the base station apparatus and the terminal apparatus start to perform an operation of demodulating at least a signal of the PHY layer.
The base station apparatus performs carrier sense in an inter-frame space (IFS) in accordance with the type of transmission frame to be transmitted and determines whether the radio channel is in a busy state or idle state. A period in which the base station apparatus performs carrier sense varies depending on the frame type and the subframe type of a transmission frame to be transmitted by the base station apparatus. In the IEEE 802.11 system, multiple IFSs with different periods are defined, and there are a short frame interval (Short IFS or SIFS) used for a transmission frame with the highest priority given, a polling frame interval (PCF IFS or PIFS) used for a transmission frame with a relatively high priority, a distribution control frame interval (DCF IFS or DIFS) used for a transmission frame with the lowest priority, and the like. In a case that the base station apparatus transmits a data frame with the DCF, the base station apparatus uses the DIFS.
The base station apparatus waits by DLFS and then further waits for a random backoff time to prevent frame collision. In the IEEE 802.11 system, a random backoff time called a contention window (CW) is used. CSMA/CA works with the assumption that a transmission frame transmitted by a certain transmitting station is received by a receiving station in a state in which there is no interference from other transmitting stations. Therefore, in a case that transmitting stations transmit transmission frames at the same timing, the frames collide against each other, and the receiving station cannot receive them properly. Thus, each transmitting station waits for a randomly configured time before starting transmission, and thus collision of frames can be avoided. In a case that the base station apparatus determines, through carrier sense, that a radio channel is in the idle state, the base station apparatus starts to count down a CW, acquires a transmission right for the first time after the CW becomes zero, and can transmit a transmission frame to the terminal apparatus. Note that, in a case that the base station apparatus determines through the carrier sense that the radio channel is in the busy state during the count-down of the CW, the base station apparatus stops the count-down of the CW. Thereafter, in a case that the radio channel becomes in the idle state, then the base station apparatus restarts the count-down of the remaining CW after the previous IFS.
Next, details of frame reception will be described. A terminal apparatus that is a receiving station receives a transmission frame, interprets the PHY header of the transmission frame, and demodulates the received transmission frame. Then, the terminal apparatus interprets the MAC header of the demodulated signal and thus can recognize whether the transmission frame is addressed to the terminal apparatus itself. Note that the terminal apparatus can also determine the destination of the transmission frame based on information described in the PHY header (for example, a group identifier (Group ID or GID) described in VHT-SIG-A).
In a case that the terminal apparatus determines that the received transmission frame is addressed to the terminal apparatus and successfully demodulates the transmission frame without any error, the terminal apparatus is to transmit an ACK frame indicating the proper reception of the frame to the base station apparatus that is the transmitting station. The ACK frame is one of transmission frames with the highest priority transmitted only after a wait for the SIFS period (with no random backoff time). The base station apparatus ends the series of communication with the reception of the ACK frame transmitted from the terminal apparatus. Note that, in a case that the terminal apparatus is not able to receive the frame properly, the terminal apparatus does not transmit ACK. Thus, in a case that the ACK frame has not been received from the receiving station for a certain period (a length of SIFS+ACK frame) after the transmission of the frame, the base station apparatus considers the communication to be failed and ends the communication. In this manner, an end of a single communication operation (also called a burst) in the IEEE 802.11 system is to be determined based on whether an ACK frame is received, except for special cases such as a case of transmission of a broadcast signal such as a beacon frame, a case that fragmentation for splitting transmission data is used, or the like.
In a case that the terminal apparatus determines that the received transmission frame is not addressed to the terminal apparatus itself, the terminal apparatus configures a network allocation vector (NAV) based on the length of the transmission frame described in the PHY header or the like. The terminal apparatus does not attempt communication during the period configured in the NAV. In other words, because the terminal apparatus performs the same operation as in the case that the terminal apparatus determines the radio channel is in the busy state through physical CS for the period configured in the NAV, the communication control based on the NAV is also called virtual carrier sense (virtual CS). The NAV is also configured by a transmission request (Request to send or RTS) frame or a reception preparation completion (Clear to send or CTS) frame, which are introduced to solve a hidden terminal problem in addition to the case that the NAV is configured based on the information described in the PHY header.
Unlike the DCF in which each apparatus performs carrier sense and autonomously acquires the transmission right, with respect to the PCF, a control station called a point coordinator (PC) controls the transmission right of each apparatus within a BSS. In general, a base station apparatus serves as a PC and acquires the transmission right of a terminal apparatus within a BSS.
A communication period using the PCF includes a Non-period (Contention free period (CFP)) and a Contention period (CP). Communication is performed based on the aforementioned DCF during a CP, and a PC controls the transmission right during a CFP. The base station apparatus serving as a PC broadcasts a beacon frame with description of a CFP period (CFP max duration) and the like in a BSS prior to communication with a PCF. Note that the PIFS is used for transmission of the beacon frame broadcast at the time of a start of transmission by the PCF, and the beacon frame is transmitted without waiting for the CW. The terminal apparatus that has received the beacon frame configures the CFP period described in the beacon frame in a NAV. Hereinafter, the terminal apparatus can acquire the transmission right only in a case that a signal (e.g., a data frame including CF-poll) for signalling the acquisition of the transmission right transmitted by the PC is received, until the NAV elapses or a signal (e.g., a data frame including CF-end) broadcasting the end of the CFP in the BSS is received. Note that, because no packet collision occurs in the same BSS during the CFP period, each terminal apparatus does not take a random backoff time used for the DCF.
A radio medium can be split into multiple resource units (RUs).
Multiple terminal apparatuses (e.g., multiple STAs) can transmit frames at the same time by mapping and transmitting the frames to and in the respective RUs allocated to themselves. The multiple STAs can perform frame transmission after waiting for a prescribed period after receiving the frame including trigger information transmitted from the AP (trigger frame or TF). Each STA can recognize the RU allocated to the STA itself based on the information described in the TF. Each STA can acquire the RU through random access with reference to the TF.
The AP can allocate multiple RUs to one STA at the same time. The multiple RUs can include continuous subcarriers or can include discontinuous subcarriers. The AP can transmit one frame using multiple RUs allocated to one STA or can transmit multiple frames after allocating them to different RUs. At least one of the multiple frames can be a frame including common control information for multiple terminal apparatuses that transmit resource allocation information.
One STA can be allocated multiple RUs by the AP. The STA can transmit one frame using the multiple allocated RUs. Also, the STA can use the multiple allocated RUs to transmit multiple frames allocated to different RUs. The multiple frames each can be a frame of a different frame type.
The AP can allocate multiple AIDs to one STA. The AP can allocate an RU to each of the multiple AIDs allocated to the one STA. The AP can transmit different frames using the respective RUs allocated to the multiple AIDs allocated to the one STA. The different frames each can be a frame of a different frame type.
One STA can be allocated multiple AIDs by the AP. The one STA can be allocated an RU with respect to each of the multiple allocated AIDs. The one STA recognizes all of the RUs allocated to the respective multiple AIDs allocated to the STA itself as RUs allocated to the STA and can transmit one frame using the multiple allocated RUs. In addition, the one STA can transmit multiple frames using the multiple allocated RUs. At this time, the multiple frames can be transmitted with information indicating the AIDs associated with the respective allocated RUs described therein. The AP can transmit different frames using the respective RUs allocated to the multiple AIDs allocated to the one STA. The different frames can be frames of different frame types.
Hereinafter, the base station apparatus and the terminal apparatuses may be collectively referred to as radio communication apparatuses or communication apparatuses. Information exchanged in a case that a certain radio communication apparatus performs communication with another radio communication apparatus may also be referred to as data. In other words, radio communication apparatuses include a base station apparatus and a terminal apparatus.
A radio communication apparatus includes any one of or both the function of transmitting a PPDU and a function of receiving a PPDU.
L-STF, L-LTF, and L-SIG surrounded by the dotted line in
However, because the radio communication apparatus that is compliant with the IEEE 802.11a/b/g standard cannot demodulate the PPDU that is compliant with the IEEE 802.11n/ac standard following the L-header, it is not possible to demodulate information about a transmitter address (TA), a receiver address (RA), and a Duration/ID field used for configuring a NAV.
As a method for the radio communication apparatus that is compliant with the IEEE 802.11a/b/g standard to appropriately configure a NAV (or to perform a receiving operation for a prescribed period), IEEE 802.11 defines a method of inserting Duration information to the L-SIG. Information about a transmission speed in the L-SIG (a RATE field, an L-RATE field, an L-RATE, an L_DATARATE, and an L_DATARATE field) and information about a transmission period (a LENGTH field, an L-LENGTH field, and an L-LENGTH) are used by the radio communication apparatus that is compliant with the IEEE 802.11a/b/g standard to appropriately configure a NAV.
Next, a method of identifying a BSS from a frame received by a radio communication apparatus will be described. In order for a radio communication apparatus to identify a BSS from a received frame, the radio communication apparatus that transmits a PPDU preferably inserts information for identifying the BSS (BSS color, BSS identification information, or a value unique to the BSS) into the PPDU. The information indicating the BSS color can be described in HE-SIG-A.
The radio communication apparatus can transmit L-SIG multiple times (L-SIG Repetition). For example, demodulation accuracy of L-SIG is improved by the radio communication apparatus on the reception side receiving L-SIG transmitted multiple times by using Maximum Ratio Combining (MRC). Moreover, in a case that reception of L-SIG is properly completed using MRC, the radio communication apparatus can interpret the PPDU including the L-SIG as a PPDU that is compliant with the IEEE 802.11ax standard.
Even during the operation of receiving the PPDU, the radio communication apparatus can perform an operation of receiving part of a PPDU other than the corresponding PPDU (e.g., the preamble, L-STF, L-LTF, and the PLCP header prescribed by IEEE 802.11) (also referred to as a double-reception operation). In a case that a part of a PPDU other than the PPDU is detected during the operation of receiving the PPDU, the radio communication apparatus can update a part or an entirety of information about a destination address, a transmission source address, a PPDU, or a DATA period.
An Ack and a BA can also be referred to as a response (response frame). A probe response, an authentication response, and a connection response can also be referred to as a response.
In
An example of a frame transmission procedure in a case that the station apparatus 2-1 transmits a frame to the access point apparatus 1-1 on the assumption that the primary channel is configured as the CH 1 will be described. The station apparatus 2-1, in a case of performing carrier sense in the CH 1 after waiting for the random backoff time to determine that the radio channel is in the idle state, transmits an RTS frame 11-11 onto the CH 1 and transmits equivalent frames as RTS frames 11-12 to 11-14 to the CH 2 to the CH 4 at the same timing. The access point apparatus 1-1 receiving the RTS frame checks the radio channel conditions of the CH 1 to the CH 4. In a case of determining that the radio channel conditions are the idle states, the access point apparatus 1-1 transmits CTS frames 11-21 to 11-24 indicating the idle states to the CH 1 to the CH 4, respectively, and the station apparatus 2-1 receives the CTS frames 11-21 to 11-24. The station apparatus determines that the radio channels of the CH 1 to the CH 4 are available, and transmits data frames 11-31 to 11-34. Specifically, the entire channel bandwidth 80 MHz can be used for data frame transmission.
On the other hand, even in a case that the station apparatus 2-1 transmits the RTS frame, there may be a case that the CTS frame cannot be received on all of the CH 1 to the CH 4. For example, that is a case that the access point apparatus 1-1 receiving the RTS frames 11-41 to 11-44 on the CH 1 to the CH 4, respectively, checks the radio channel conditions to determine that only the CH 3 and the CH 4 are in the idle states, and transmits the CTS frames (11-53 and 11-54) only to the CH 3 and the CH 4. The station apparatus 2-1, in a case of being incapable of receiving the CTS frame on the CH 1 which is the primary channel, cannot transmit the data frames on any of the CH 1 to the CH 4. Specifically, the determination on whether to transmit the data frame depends on the condition of the primary channel.
As another example, there is a case that the CTS frame is received on the CH 1 which is the primary channel but the CTS frame cannot be received on all of the CH 1 to the CH 4. For example, that is a case that the access point apparatus receiving the RTS frames 11-61 to 11-64 on the CH 1 to the CH 4, respectively, checks the radio channel conditions to determine that only the CH 1 and the CH 2 are in the idle states, and transmits the CTS frames (11-71 and 11-72) to only the CH 1 and the CH 2. The station apparatus 2-1 is capable of data frame transmission because of having received the CTS frame on the CH 1 which is the primary channel, but recognizes that only the CH 1 and the CH 2 are in the idle states and transmits data frames 11-81 and 11-82. Specifically, only the 40 MHz bandwidth can be used in the 80 MHz bandwidth.
In
The higher layer circuitry 10001-1 is connected to another network and can notify the autonomous distributed controller 10002-1 of information about traffic. The information about traffic may be, for example, information addressed to another radio communication apparatus, or may be control information included in a management frame or a control frame.
The CCA circuitry 10002a-1 can use either of or both of information about reception signal power received via radio resources and information about the reception signal (including information after decoding), the notification of which are provided from the receiver, to determine a state of the radio resources (including determining whether the state is busy or idle). The CCA circuitry 10002a-1 can notify the backoff circuitry 10002b-1 and the transmission determination circuitry 10002c-1 of the state determination information of the radio resources.
The backoff circuitry 10002b-1 can perform backoff using the state determination information of the radio resources. The backoff circuitry 10002b-1 has a function of generating a CW and counting down the CW. For example, the count-down of the CW is performed in a case that the state determination information of the radio resources indicates idle, and the count-down of the CW can be stopped in a case that the state determination information of the radio resources indicates busy. The backoff circuitry 10002b-1 can notify the transmission determination circuitry 10002c-1 of the value of the CW.
The transmission determination circuitry 10002c-1 performs transmission determination using either of or both the state determination information of the radio resources or/and the value of the CW. For example, the notification of transmission determination information can be provided to the transmitter 10003-1 in a case that the state determination information of the radio resources indicates idle and the value of the CW is zero. The notification of the transmission determination information can be provided to the transmitter 10003-1 in a case that the state determination information of the radio resources indicates idle.
The transmitter 10003-1 includes a physical layer frame generator (physical layer frame generation step) 10003a-1 and a radio transmitter (radio transmission step) 10003b-1. The physical layer frame generator 10003a-1 has a function of generating a physical layer frame (PPDU) based on the transmission determination information, the notification of which is provided from the transmission determination circuitry 10002c-1. The physical layer frame generator 10003a-1 performs error correction coding, modulation, precoding filter multiplication, and the like on transmission frames sent from the higher layer. The physical layer frame generator 10003a-1 notifies the radio transmitter 10003b-1 of the generated physical layer frame.
Although the physical layer frame generator performs error correction coding on the information bits transferred from the MAC layer, a circuitry in which the error correction coding (coding block length) is performed is not limited. For example, the physical layer frame generator can divide the information bit sequence transferred from the MAC layer into information bit sequences having a prescribed length to perform error correction coding on each of the sequences, and thus can make the sequences into multiple coding blocks. Note that dummy bits can be inserted into the information bit sequence transferred from the MAC layer in a case that coding blocks are configured.
The frame generated by the physical layer frame generator 10003a-1 includes control information. The control information includes information indicating to which RU the data addressed to each radio communication apparatus is mapped (here, the RU including both frequency resources and spatial resources). The frame generated by the physical layer frame generator 10003a-1 includes a trigger frame for indicating, to the radio communication apparatus that is a destination terminal, frame transmission. The trigger frame includes information indicating the RU to be used by the radio communication apparatus that has received the indication for the frame transmission to transmit the frame.
The radio transmitter 10003b-1 converts the physical layer frame generated by the physical layer frame generator 10003a-1 into a signal in a radio frequency (RF) band to generate a radio frequency signal. Processing performed by the radio transmitter 10003b-1 includes digital-to-analog conversion, filtering, frequency conversion from a baseband to an RF band, and the like.
The receiver 10004-1 includes a radio receiver (radio reception step) 10004a-1 and a signal demodulator (signal demodulation step) 10004b-1. The receiver 10004-1 generates information about reception signal power from a signal in the RF band received by the antenna unit 10005-1. The receiver 10004-1 can notify the CCA circuitry 10002a-1 of the information about the reception signal power and the information about the reception signal.
The radio receiver 10004a-1 has a function of converting a signal in the RF band received by the antenna unit 10005-1 into a baseband signal and generating a physical layer signal (e.g., a physical layer frame). Processing performed by the radio receiver 10004a-1 includes frequency conversion processing from the RF band to the baseband, filtering, and analog-to-digital conversion.
The signal demodulator 10004b-1 has a function of demodulating a physical layer signal generated by the radio receiver 10004a-1. Processing performed by the signal demodulator 10004b-1 includes channel equalization, demapping, error correction decoding, and the like. The signal demodulator 10004b-1 can extract, from the physical layer signal, information included in the physical layer header, information included in the MAC header, and information included in the transmission frame, for example. The signal demodulator 10004b-1 can notify the higher layer circuitry 10001-1 of the extracted information. Note that the signal demodulator 10004b-1 can extract any one or all of the information included in the physical layer header, the information included in the MAC header, and the information included in the transmission frame.
The antenna unit 10005-1 has a function of transmitting a radio frequency signal generated by the radio transmitter 10003b-1 into the radio space toward another radio apparatus. The antenna unit 10005-1 has a function of receiving a radio frequency signal transmitted by the radio apparatus 0-1.
The radio communication apparatus 10000-1 can describe, in the PHY header or the MAC header of the frame to be transmitted, information indicating a period in which the radio communication apparatus 10000-1 uses the radio medium, to cause a radio communication apparatus around the radio communication apparatus 10000-1 to configure a NAV for the period. For example, the radio communication apparatus 10000-1 can describe the information indicating the period in the Duration/ID field or a Length field of the frame to be transmitted. The NAV period configured for the radio communication apparatuses around the radio communication apparatus 10000-1 is referred to as a TXOP period (or simply TXOP) acquired by the radio communication apparatus 10000-1. The radio communication apparatus 10000-1 that has acquired the TXOP is referred to as a TXOP holder. The type of frame to be transmitted by the radio communication apparatus 10000-1 to acquire TXOP is not limited to any frame type, and the frame may be a control frame (e.g., an RTS frame or a CTS-to-self frame) or may be a data frame.
The radio communication apparatus 10000-1 that is a TXOP holder can transmit the frame to a radio communication apparatus other than the radio communication apparatus 10000-1 itself during the TXOP. In a case that the radio communication apparatus 1-1 is a TXOP holder, the radio communication apparatus 1-1 can transmit a frame to the radio communication apparatus 2A during the TXOP period. The radio communication apparatus 1-1 can indicate, to the radio communication apparatus 2A, a frame transmission addressed to the radio communication apparatus 1-1 during the TXOP period. The radio communication apparatus 1-1 can transmit, to the radio communication apparatus 2A, a trigger frame including information for indicating a frame transmission addressed to the radio communication apparatus 1-1 during the TXOP period.
The radio communication apparatus 1-1 may acquire a TXOP for the entire communication band (e.g., operation bandwidth) in which frame transmission is likely to be performed, or may acquire a TXOP for a specific communication band (Band) such as a communication band in which frames are actually transmitted (e.g., transmission bandwidth).
The radio communication apparatus, to which the radio communication apparatus 1-1 indicates a frame transmission in the TXOP period acquired by the radio communication apparatus 1-1, is not necessarily limited to a radio communication apparatus connected to the radio communication apparatus 1-1. For example, the radio communication apparatus can indicate, to radio communication apparatuses that are not connected to the radio communication apparatus itself, a frame transmission in order to cause a radio communication apparatus around the radio communication apparatus itself to transmit a management frame such as a Reassociation frame or a control frame such as an RTS/CTS frame.
Furthermore, TXOP in EDCA that is a data transmission method different from DCF will also be described. The IEEE 802.11e standard relates to the EDCA, and defines the TXOP from the perspective of QoS (Quality of Service) assurance for various services such as video transmission or VoIP. The services are roughly classified into four access categories, namely VOice (VO), VIdeo (VI), Best Effort (BE), and BacK ground (BK). In general, the services include VO, VI, BE, and BK, starting with the highest priority in this order. Each of the access categories has parameters including CWmin as a minimum value of CW, CWmax as a maximum value, AIFS (Arbitration IFS) as a type of IFS, and TXOP limit as an upper limit value of the transmission occasion, which are configured to give a difference in the priority. For example, it is possible to perform data transmission prioritized over the other access categories by setting CWmin, CWmax, and AIFS of VO with the highest priority for the purpose of voice transmission equal to a relatively small value as compared with the other access categories. For example, for the VI, where the amount of transmission data is relatively large due to video transmission, the TXOP limit can be configured to be larger, so that the transmission occasion can be longer than the other access categories. In this manner, four parameter values of each of the access categories are adjusted for the purpose of QoS assurance in accordance with various services. Access categories other than these four access categories may be provided. As an example, an access category, such as an access category Low Latency (LL) for low-latency, may be provided.
In the present embodiment, the signal demodulator of the station apparatus can perform a decoding processing for the received signal in the physical layer, and perform error detection. Here, the decoding processing includes decoding of error correction codes applied to the received signal. Here, the error detection includes error detection using an error detection code (e.g., a cyclic redundancy check (CRC) code) that has been given to the received signal in advance, and error detection using an error correction code (e.g., low-density parity-check code (LDPC)) having an error detection function from the first. The decoding processing in the physical layer can be applied for each coding block.
The higher layer circuitry transfers the result of decoding of the physical layer by the signal demodulator to the MAC layer. In the MAC layer, the signal of the MAC layer is restored from the transferred decoding result of the physical layer. Then, error detection is performed in the MAC layer, and it is determined that whether the signal of the MAC layer transmitted by the station apparatus as a transmission source of the reception frame has been properly restored.
An example of an embodiment in a radio network illustrated in
The base station apparatus 1-1 configures two or more radio channels among the multiple radio channels to be used for low-latency communication. As an example, in the present embodiment, four channels, i.e., the radio channel 1 to the radio channel 4, are configured for low-latency communication. The base station apparatus 1-1 transmits a beacon including an information element indicating radio channels used for low-latency communication, that is, the radio channels 1, 2, 3, and 4 used for low-latency communication in the present embodiment, through the multiple radio channels to be used. At this time, the same beacon as that transmitted on the primary channel may be transmitted on one or more radio channels other than the primary channel. In the present embodiment, the beacon including the information element indicating that the radio channels 1, 2, 3, and 4 are for low-latency communication is transmitted to the radio channels 1 to 4. In a case that it is determined that the low-latency communication cannot be performed for some reason, for example, a case that a usage rate of the radio channel configured for low-latency communication exceeds a certain threshold or a case that a signal of a level at which interference is received from a channel adjacent to the radio channel configured for low-latency communication is detected in the adjacent channel, the base station apparatus 1-1 may transmit a beacon including an information element indicating that the low-latency communication cannot be performed regarding a radio channel that has become unavailable or an information element indicating that the low-latency communication cannot be performed temporarily.
Note that, in the present embodiment, the description is given for the low-latency communication, but embodiments are not limited to usage of the low-latency communication. For example, the communication for low-latency communication described in the present embodiment may be used for frequent communication, or may be applied to communication for connecting a large number of terminals or the like. The low-latency communication may be referred to as a low-latency communication method or a method (communication method) for decreasing latency, to be distinguished from a communication method using the DCF.
In the present embodiment, it is assumed that the terminal apparatus 2-1 performs low-latency communication. The terminal apparatus 2-1, after receiving the beacon including the information element indicating the radio channel used for low-latency communication, transmits a request for starting low-latency communication to the base station apparatus 1-1. The low-latency communication is communication (uplink communication) in a direction from the terminal apparatus 2-1 to the base station apparatus 1-1. In a case that capability information received from the base station apparatus 1-1 at the time of initial connection (at the time of association) includes an information element indicating that the base station apparatus 1-1 supports the low latency information, the terminal apparatus 2-1 may transmit the request for starting low-latency communication to the base station apparatus 1-1 based on the information element. At this time, the request for starting low-latency communication may be transmitted without specifying the radio channel to be used, or the terminal apparatus 2-1 may transmit the request for starting low-latency communication specifying two or more radio channels that can be used by the terminal apparatus 2-1, for example. The terminal apparatus 2-1 may include information indicating a requested latency in the request for starting low-latency communication to be transmitted to the base station apparatus 1-1. A format of the information indicating the latency is not limited, and may be, for example, a numerical value in milliseconds, or may be numerical information corresponding to a class obtained by classifying the requested latency. The terminal apparatus 2-1 may include information indicating how frequently the low-latency communication is to be performed in the request for starting low-latency communication to be transmitted to the base station apparatus 1-1. A format of the information indicating how frequently the low-latency communication is to be performed is not limited, and may be, for example, a numerical value in milliseconds, or may be numerical information corresponding to a class obtained by classifying how frequently performed the low-latency communication.
The base station apparatus 1-1, after receiving the request for starting low-latency communication from the terminal apparatus 2-1, transmits a response for starting low-latency communication to the terminal apparatus 2-1. At this time, an information element indicating radio channels for performing low-latency communication, that is, the radio channels 1, 2, 3, and 4 used for low-latency communication in the present embodiment and an information element indicating that each of the radio channels 1, 2, 3, and 4 is a physical frequency channel may be included and transmitted in the base station apparatus 1-1. At this time, as the physical frequency channel, an index indicating a frequency of a primary channel used in each radio channel may be used. The radio channels used for the low-latency communication may be notified in a table format. Examples of the tables are illustrated in
The base station apparatus 1-1, in the case of changing the radio channel for low-latency communication and that there is a terminal apparatus already performing low-latency communication, may notify the terminal already performing low-latency communication that the radio channel for low-latency communication is to be changed and then change the radio channel for low-latency communication. The base station apparatus 1-1, in the case of changing the radio channel for low-latency communication, may, prior to the change, transmit information including an information element indicating that the radio channel for low-latency communication is to be changed by using broadcast communication such as a beacon or using individually unicast communication with respect to the terminal apparatus. After changing the radio channel for low-latency communication, the base station apparatus 1-1 may transmit information including an information element indicating the changed radio channel for low-latency communication by using broadcast communication such as a beacon or using individually unicast communication with respect to the terminal apparatus. The base station apparatus 1-1 may configure a minimum period during which the radio channel allocated for low-latency communication is changed and transmit a beacon including information indicating the minimum period.
The base station apparatus 1-1, after transmitting the response for starting low-latency communication to the terminal apparatus 2-1, performs transmission for causing the terminal apparatus 2-1 to perform low-latency communication transmission by using the first radio channel for performing low-latency communication. Various methods can be used for the transmission for causing the terminal apparatus to perform low latency. For example, transmission of a trigger frame, transmission of a CTS frame, transmission of a CF-POLL, and the like can be used, and in the present embodiment, an example in which a trigger frame is used will be mainly described. The base station apparatus 1-1 periodically transmits a trigger frame to the terminal apparatus 2-1. Prior to the transmission of the trigger frame, the base station apparatus 1-1 may perform carrier sense in the radio channel for performing low-latency communication. As a result of the carrier sense, in a case that it is determined that the radio channel for performing low-latency communication is busy, the base station apparatus 1-1 may stop or postpone the transmission of the trigger frame. A threshold used for the carrier sense may be the same as or different from a threshold used for performing carrier sense in the radio channel on which low-latency communication is not performed. With a threshold for the carrier sense small, the terminal apparatus performs low-latency communication on a radio channel in a cleaner state. With a threshold for the carrier sense large, low-latency communication can be started even in a certain level of noise environment in which a weak interference signal arrives from an adjacent BSS or the like. A transmission period of the trigger frame may be configured based on the information of the latency or the information of the periodicity transmitted from the terminal apparatus 2-1. For example, in a case that the latency is specified, the trigger frame may be transmitted at a periodicity of a prescribed multiple of the specified latency. For example, in a case that 1 millisecond is specified as the latency, the trigger frame may be transmitted every 2 milliseconds that is twice the specified latency. This multiple does not need to be fixed, and may be changed based on other factors, for example, the number of terminal apparatuses that simultaneously perform low-latency communication, or other information such as information indicating how frequently the low-latency communication indicated from the terminal apparatus is to be performed. In a case that the information of a periodicity of low-latency communication is indicated from the terminal apparatus 2-1, a transmission frequency of how often the trigger frame is to be transmitted may be configured based on the information of the periodicity. As an example, in a case that 10 milliseconds, that is a prescribed multiple of the frequency of how often the low-latency communication is performed, is configured, the transmission frequency may be configured to be every 5 milliseconds, that is one-half times the configured 10 milliseconds. The transmission frequency of how often the trigger frame is to be transmitted may not consist of one interval. For example, in a case that a latency of 1 millisecond and a periodicity of 10 milliseconds are specified from the terminal apparatus 2-1, the transmission intervals of the trigger frame may be configured as 1 millisecond, 9 milliseconds, 1 millisecond, 9 milliseconds, . . . (hereinafter, repeated) to provide multiple transmission occasions in the period.
The base station apparatus 1-1 may include information indicating that a trigger frame to be transmitted is a trigger frame for low-latency communication in the trigger frame to be transmitted. The base station apparatus 1-1 may include information indicating that a trigger frame to be transmitted is addressed to the terminal apparatus 2-1 in the trigger frame to be transmitted. The base station apparatus 1-1 may include information specifying a radio resource to be used by the terminal apparatus 2-1 for low-latency communication in the trigger frame. At this time, information may be included indicating that, as the resource to be used, the entire radio channel is used or a resource unit of a part of the radio channel is specified. The base station apparatus 1-1 may include information indicating a time used for low-latency communication in the trigger frame to be transmitted.
After transmitting the trigger frame in the first radio channel used for low-latency communication, at timing of transmitting the trigger frame next, the base station apparatus 1-1 performs carrier sense in a second radio channel used for low-latency communication, and in a case that the radio channel is not busy, transmits the trigger frame to the terminal apparatus 2-1 in the second radio channel. As a result of the carrier sense, in a case that it is determined that the radio channel for performing low-latency communication is busy, the base station apparatus 1-1 may stop or postpone the transmission of the trigger frame. Thereafter, the base station apparatus 1-1 transmits the trigger frame in accordance with the radio channels used for low-latency communication and order of the radio channels to be used, and causes the terminal apparatus 2-1 to perform transmission of low-latency communication.
The terminal apparatus 2-1, after receiving the response for starting low-latency communication from the base station apparatus 1-1, waits for the trigger frame to be transmitted on the radio channels used for the low-latency communication from the base station apparatus 1-1. After receiving the trigger frame, the terminal apparatus 2-1 checks whether the trigger frame includes the information addressed to the terminal apparatus 2-1. In a case that the trigger frame includes the information addressed to the terminal apparatus 2-1, the terminal apparatus 2-1 transmits data for low-latency communication. In a case that the received trigger frame includes the information addressed to the terminal apparatus 2-1 and the received trigger frame further includes the information indicating that the received trigger frame is for low-latency communication, the terminal apparatus 2-1 may transmit data for low-latency communication. In a case that the received trigger frame includes the information specifying a radio resource to be used for low-latency communication, the terminal apparatus 2-1 may transmit the data for low-latency communication by using the specified radio resource, for example, the specified resource unit. As data for low-latency communication, the terminal apparatus 2-1 may transmit data of a specific access category, one example of which is data of an access category of VO or LL.
After a prescribed time elapses after the terminal apparatus 2-1 receives the trigger frame for low-latency communication addressed to the terminal apparatus 2-1 from the base station apparatus 1-1, the terminal apparatus 2-1 transmits the data for low-latency communication. In the present embodiment, the transmission is performed after a Short InterFrame Space (SIFS) used in communication other than low-latency communication, but embodiments are not limited to this. As an example, at the time of low-latency communication, the terminal apparatus 2-1 may be configured to perform the transmission in a time shorter than the SIFS in order to decrease the latency after receiving the trigger frame.
In a case that the terminal apparatus 2-1 receives the trigger frame for low-latency communication addressed to the terminal apparatus 2-1 from the base station apparatus 1-1 and that there is no data for low-latency communication to be transmitted, the terminal apparatus 2-1 need not transmit data. Alternatively, in the case that the terminal apparatus 2-1 receives the trigger frame for low-latency communication addressed to the terminal apparatus 2-1 from the base station apparatus 1-1 and that there is no data for low-latency communication to be transmitted, the terminal apparatus 2-1 may transmit only a confirmation packet (ACK packet) or may transmit a packet including dummy data. In a case that the trigger frame for low-latency communication addressed to the terminal apparatus 2-1 received from the base station apparatus 1-1 includes the information indicating a time to be used for low-latency communication, the terminal apparatus 2-1 may transmit to the base station apparatus 1-1 data including dummy data for setting a transmission time to a time equivalent to the indicated time. After receiving the trigger frame for low-latency communication addressed to the terminal apparatus 2-1 from the base station apparatus 1-1, the terminal apparatus 2-1 configures the radio channels used for low-latency communication and then the radio channels for receiving the trigger frame for low-latency communication in accordance with the order of the radio channels to be used.
In a case of carrier sense performed prior to transmission of the trigger frame for low-latency communication on a certain radio channel, in a case that the base station apparatus 1-1 determines that a busy period is longer than a certain period, the base station apparatus 1-1 may skip transmission of the trigger frame for low-latency communication on the current radio channel and may transmit the trigger frame for low-latency communication on the next radio channel. At this time, a period used for skipping the trigger frame for low-latency communication may be determined based on frequency of performing low-latency communication. An example of operation in a case that transmission of the trigger frame for low-latency communication is skipped based on the frequency of low-latency transmission will be described with reference to
Next, an example of operation in a case that a busy period of a radio channel is long in a case of carrier sense will be described with reference to
The base station apparatus 1-1, after transmitting the response for starting low-latency communication to the terminal apparatus, may transmit information indicating that the terminal apparatus has started low-latency communication on the radio channel for low-latency transmission in the information transmitted in the beacon. This information may include information such as the number of terminals performing low-latency communication, the frequency of how often the low-latency communication is to be performed, and the latency of low-latency communication.
The terminal apparatus 2-1, in a case of stopping low-latency communication, transmits a request for stopping low-latency communication to the base station apparatus 1-1. The request may be transmitted using a radio channel for performing low-latency communication or the primary channel. The base station apparatus 1-1, in a case of receiving the request for stopping low-latency communication from the terminal apparatus 2-1, transmits a response for stopping low-latency communication to the terminal apparatus 2-1. After that, the base station apparatus 1-1 may stop the transmission of the trigger frame for low-latency communication. In a case that there is a terminal apparatus performing low-latency communication other than the terminal apparatus 2-1, the base station apparatus 1-1 need not stop the transmission of the trigger frame for low-latency communication.
The above has described an example in which the counters of the base station apparatus 1-1 and the terminal apparatus 2-1 are synchronized using a beacon and low-latency communication is performed using time based on the counters; however, depending on implementation of the base station apparatus 1-1 and the terminal apparatus 2-1, there may be a large error between the value of the counters in a case of generating data to be transmitted as the beacon and time at which the beacon is actually transmitted, and synchronization accuracy of the counters of the base station apparatus 1-1 and the terminal apparatus 2-1 may not be sufficient. In order to prevent such a case, information related to management accuracy of the counters may be exchanged between the base station apparatus 1-1 and the terminal apparatus 2-1 in advance, and in a case that sufficient synchronization accuracy of the counters can be expected, low-latency communication may be performed. As an example, low-latency communication may be performed in a case of the base station apparatus 1-1 and the terminal apparatus 2-1 supporting Time Sensitive Network (TSN).
An example of the contents described above will be described with reference to
With operation as described above, the radio channels used for low-latency communication can be changed one after another, and usage rates of the radio channels used for low-latency communication can be averaged. This can prevent a specific radio channel from being occupied for low-latency communication, and can moderate reduction of latency in each radio channel.
Next, a modification of low-latency communication in which multiple terminal apparatuses perform multi-user transmission on one trigger frame for low-latency communication will be described with reference to
Although
With operation as described above, also in a case that low-latency communication is performed with multiple terminal apparatuses, the radio channels used for low-latency communication can be changed one after another, and usage rates of the radio channels used for low-latency communication can be averaged. This can prevent a specific radio channel from being occupied for low-latency communication, and can moderate reduction of latency in each radio channel.
Although the communication apparatuses according to an aspect of the present invention can perform communication in a frequency band (frequency spectrum) that is a so-called unlicensed band that does not require permission to use from a country or a region, available frequency bands are not limited thereto. Although permission to use a specific service is given from a country or a region, the communication apparatuses according to an aspect of the present invention can exhibit the effect that can be brought by the purpose of preventing interference between frequencies, and the like, in a frequency band called a white band that is not actually used (e.g., a frequency band that is allocated for television broadcasting but is not used depending on regions), or a shared spectrum (shared frequency band) that is expected to be shared by multiple service providers, for example.
A program operated in the wireless communication apparatuses according to an aspect of the present invention is a program (a program for causing a computer to function) for controlling a CPU or the like to implement the functions of the aforementioned embodiments according to an aspect of the present invention. In addition, information handled by these apparatuses is temporarily accumulated in a RAM at the time of processing, is then stored in various types of ROMs and HDDs, and is read by the CPU as necessary to be corrected and written. A semiconductor medium (e.g., a ROM, a non-volatile memory card, etc.), an optical recording medium (e.g., a DVD, an MO, an MD, a CD, a BD, etc.), a magnetic recording medium (e.g., a magnetic tape, a flexible disk, etc.), and the like can be examples of recording media for storing programs. In addition to implementing the functions of the aforementioned embodiments by performing loaded programs, the functions of the present invention may be implemented in processing performed in cooperation of an operating system, other application programs, and the like based on instructions of those programs.
In a case of delivering these programs to market, the programs can be stored and distributed in a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, storage apparatuses of the server computer are also included in an aspect of the present invention. A part or an entirety of the communication apparatuses in the aforementioned embodiments may be implemented as an LSI that is typically an integrated circuit. The functional blocks of the communication apparatuses may be individually implemented as chips or may be partially or completely integrated into a chip. In a case that the functional blocks are made as integrated circuits, an integrated circuit controller for controlling them is added.
The circuit integration technique is not limited to LSI but may be realized as dedicated circuits or a multi-purpose processor. Moreover, in a case that a circuit integration technology that substitutes an LSI appears with the advance of the semiconductor technology, it is also possible to use an integrated circuit based on the technology.
Note that, the invention of the present application is not limited to the above-described embodiments. The radio communication apparatus according to the invention of the present application is not limited to the application in the mobile station apparatus, and, needless to say, can be applied to a fixed-type electronic apparatus installed indoors or outdoors, or a stationary-type electronic apparatus, for example, an AV apparatus, a kitchen apparatus, a cleaning or washing machine, an air-conditioning apparatus, office equipment, a vending machine, and other household apparatuses.
Although the embodiments of the invention have been described in detail above with reference to the drawings, a specific configuration is not limited to the embodiments, and designs and the like that do not depart from the essential spirit of the invention also fall within the claims.
An aspect of the present invention can be preferably used in a communication apparatus and a communication method.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-062886 | Apr 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/013140 | 3/22/2022 | WO |
