Patent Description:
Base stations and terminal apparatuses in a wireless LAN access channels using carrier sense multiple access with collision avoidance (CSMA/CA) and transmit wireless signals. In CSMA/CA, the base stations and the terminal apparatuses wait for periods of time defined by access parameters, confirm that channels are not being used by other terminal appratuses or the like through carrier sensing, and then transmit wireless signals.

As one priority control scheme in a wireless LAN, enhanced distribution channel access (EDCA) has been defined. In EDCA, traffic from upper layers is categorized into any of four access categories (AC), that is AC_VO (voice), AC_VI (video), AC_BE (best effort), and AC_BK (background). Also, in EDCA, CSMA/CA is carried out for each access category. In EDCA, access parameters are allocated such that transmission of wireless signals is relatively prioritized in order of AC_VO, AC_VI, AC_BE, and AC_BK.

<CIT> discloses measuring system latency and latency jitter on a near real-time basis regarding packets of information moving from sources to destination. The method for measuring system latency and latency jitter includes time-stamping packets of information as they pass through a plurality of locations between the source and destination of these packets, with the time-stamping being performed by real-time clocks set to a universal standard. The time-stamped packets are analyzed to determine latency and latency jitter.

<CIT> discloses a game management program, a game management method and a game management system for playing a game with synchronization at a plurality of computer terminals in different communication states.

EDCA assigns relative priority among traffic. Here, a real-time application (RTA) such as control of a network game and an industrial robot, for example, may have requirements such as an absolute latency and a jitter for each application. The relative prioritization alone does not indicate whether the RTA is available, or whether control is available to make the RTA available.

A terminal apparatus according to claim <NUM> includes: a measurement unit, a data processing unit, and a wireless signal processing unit. The measurement unit measures at least one of a latency when a wireless signal is transmitted to a base station and a jitter of the wireless signal. The data processing unit generates information including a result of the measurement. The wireless signal processing unit transmits the information to the base station.

According to the embodiment, information for determining whether requirements are satisfied can be provided even with absolute requirements for a latency or jitter.

Hereinafter, embodiments will be described based on the drawings. <FIG> is a diagram illustrating a configuration of an example of a communication system according to an embodiment. A communication system <NUM> includes a base station <NUM> and terminals <NUM>. The base station <NUM> performs wireless LAN communication with terminals inside a predefined service area. Although not illustrated in <FIG>, communication may be performed between the terminals <NUM>.

<FIG> is a diagram illustrating an exemplary hardware configuration of the base station <NUM>. The base station <NUM> is an access point (AP) for the terminals <NUM>. The base station <NUM> is not necessarily fixed, and may be mounted in a mobile body.

The base station <NUM> includes a processor <NUM>, a read only memory (ROM) <NUM>, a random access memory (RAM) <NUM>, a wireless module <NUM>, and a router module <NUM>.

The processor <NUM> is a processing device that performs overall control for the base station <NUM>. The processor <NUM> is, for example, a central processing unit (CPU). The processor <NUM> is not limited to a CPU. Also, an application specific IC (ASIC) or the like may be used instead of a CPU. In addition, the number of processors <NUM> may not be one, and it may be two or more.

The ROM <NUM> is a storage device dedicated to reading. The ROM <NUM> stores firmware and various programs required for operations of the base station <NUM>.

The RAM <NUM> is a storage device in which writing can be arbitrary performed. The RAM <NUM> is used as a work area for the processor <NUM> and temporarily stores the firmware and the like stored in the ROM <NUM>.

The wireless module <NUM> is a module configured to perform processing required for wireless LAN communication. The wireless module <NUM> forms a MAC frame from data transferred from the processor <NUM>, for example, converts the formed MAC frame into a wireless signal, and transmits the wireless signal to the terminal <NUM>. Also, the wireless module <NUM> receives a wireless signal from the terminal <NUM>, extracts data from the received wireless signal, and transfers the data to the processor <NUM>, for example.

The router module <NUM> is provided for the base station <NUM> to communicate with a server, which is not illustrated, for example, via a network. Note that the base station <NUM> may not necessarily include the router module <NUM>. The base station <NUM> may be configured to access a router provided outside the base station <NUM> through wireless communication or wired communication and connect to the network via the router.

<FIG> is a diagram illustrating an exemplary hardware configuration of the terminal <NUM>. The terminal <NUM> is a terminal apparatus (station) such as a smartphone. The terminal <NUM> may be a mobile terminal, a terminal mounted in a mobile object, or a fixed terminal.

The terminal <NUM> includes a processor <NUM>, a ROM <NUM>, a RAM <NUM>, a wireless module <NUM>, a display <NUM>, and a storage <NUM>.

The processor <NUM> is a processing device that controls the entire terminal <NUM>. The processor <NUM> is, for example, a CPU. The processor <NUM> is not limited to a CPU. Also, an ASIC or the like may be used instead of a CPU. In addition, the number of processors <NUM> may not be one and it may be two or more.

The ROM <NUM> is a storage device dedicated to reading. The ROM <NUM> stores firmware and various programs required for operations of the terminal <NUM>.

The wireless module <NUM> is a module configured to perform processing required for wireless LAN communication. The wireless module <NUM> forms a MAC frame for wireless communication from data transferred from the processor <NUM>, for example, converts the formed MAC frame into a wireless signal, and transmits the wireless signal to the base station <NUM>. Also, the wireless module <NUM> receives a wireless signal from the base station <NUM>, extracts data from the received wireless signal, and transfers the data to the processor <NUM>, for example.

The display <NUM> is a display device that displays various screens. The display <NUM> may be a liquid crystal display, an organic EL display, or the like. Also, the display <NUM> may include a touch panel.

The storage <NUM> is a storage device such as a hard disk. The storage <NUM> stores various applications executed by the processor <NUM>, for example.

<FIG> is a diagram illustrating processing of a media access control (MAC) layer during communication between the base station <NUM> and the terminal <NUM>. <FIG> illustrates both processing on a transmission side and processing on a reception side. When a wireless module of one of the base station <NUM> and the terminal <NUM> performs the processing on the transmission side, a wireless module of the other of the basestation <NUM> and terminal <NUM> performs the processing on the reception side. In the following example, the wireless modules on the transmission side and the reception side will be described without any distinction.

First, the processing on the transmission side will be described. In Step S10, the wireless module performs A-MSDU aggregation. Specifically, the wireless module unifies a plurality of items of data input from an upper layer such as an application layer to generate an aggregate-MAC service data unit (A-MSDU).

In Step S11, the wireless module assigns a sequence number (SN) to the A-MSDU. The sequence number is a unique number for identifying the A-MSDU.

In Step S12, the wireless module fragments (splits) the A-MSDU into a plurality of MAC protocol data units (MPDUs).

In Step S13, the wireless module encrypts each MPDU to generate an encrypted MPDU.

In Step S14, the wireless module adds a MAC header and an error detection code (FCS) to each encrypted MPDU. The error detection code is, for example, a cyclic redundancy check (CRC) code.

In Step S15, the wireless module performs A-MPDU aggregation. Specifically, the wireless module unifies the plurality of MPDUs to generate an aggregate-MAC protocol data unit (A-MPDU) as a MAC frame.

After Step S15, the wireless module performs processing of a physical layer on the MAC frame. In other words, the wireless module performs modulation processing or the like on the MAC frame to generate a wireless signal and transmits the wireless signal to the base station <NUM>.

Next, the processing on the reception side will be described. When a wireless signal is received, the wireless module performs processing of the physical layer to restore a MAC frame from a wireless signal. Thereafter, the wireless module performs processing of the MAC layer illustrated in <FIG>.

In Step S20, the wireless module performs A-MPDU deaggregation. Specifically, the wireless module splits A-MPDU in units of MPDUs.

In Step S21, the wireless module performs error detection. For example, the wireless module determines whether the wireless signal has successfully been received through CRC. When the reception of the wireless signal has failed, the wireless module may provide a retransmission request. At this time, the wireless module may request retransmission in units of MPDUs. On the other hand, when the wireless signal has successfully been received, the wireless module performs the following processing.

In Step S22, the wireless module performs address detection. At this time, the wireless module determines whether the transmitted MPDU is directed to the wireless module itself based on an address recorded in the MAC header of each MPDU. When the MPDU is not directed to the wireless module itself, the wireless module does not perform the following processing. When the MPDU is directed to the wireless module itself, the wireless module performs the following processing.

In Step S23, the wireless module dycripts encrypted MPDUs.

In Step S24, the wireless module performs defragmenting on the MPDUs. In other words, the wireless module restores the A-MSDU from the plurality of MPDUs.

In Step S25, the wireless module performs A-MSDU deaggregation. Specifically, the wireless module restores the A-MSDU to data in units of MSDUs.

After Step S25, the wireless module outputs the data to the upper layer of the MAC layer. The upper layer is, for example, an application layer.

<FIG> is a functional block diagram of the base station <NUM>. The base station <NUM> includes a data processing unit <NUM>, a wireless signal processing unit <NUM>, and a management unit <NUM>. The data processing unit <NUM>, the wireless signal processing unit <NUM>, and the management unit <NUM> are realized by the processor <NUM> and the wireless module <NUM>, for example.

The data processing unit <NUM> forms a MAC frame from data transferred from the server in the network, for example. Also, the data processing unit <NUM> restores data from the MAC frame transferred from the wireless signal processing unit <NUM>. The data includes a report transmitted from the terminal <NUM>.

The wireless signal processing unit <NUM> performs processing for transmitting or receiving a wireless signal. For example, the wireless signal processing unit <NUM> converts the MAC frame formed by the data processing unit <NUM> into a wireless signal and transmits the wireless signal to the terminal <NUM>. Also, the wireless signal processing unit <NUM> receives a wireless signal from the terminal <NUM>, extracts a MAC frame from the received wireless signal, and transfers the MAC frame to the data processing unit <NUM>.

The management unit <NUM> manages a report transmitted from the terminal <NUM>. For example, the management unit <NUM> holds the report and uses information held in the report at a necessary timing. The report includes information regarding a latency or a jitter of transmission of the wireless signal in the terminal <NUM>. Details of the report will be described below.

Here, the wireless signal processing unit <NUM> may be configured to transmit a wireless signal by EDCA, for example. In this case, the wireless signal processing unit <NUM> includes transmission queues AC_VO, AC_VI, AC_BE, and AC_BK for access categories (AC). The transmission queue AC_VO is a queue for holding a MAC frame categorized into VO (voice). The transmission queue AC_VI is a queue for holding a MAC frame categorized into VI (video). The transmission queue AC_BE is a queue for holding a MAC frame categorized into BE (best effort). The transmission queue AC_BK is a queue for holding a MAC frame categorized into BK (background).

The wireless signal processing unit <NUM> maps the MAC frame transferred from the data processing unit <NUM> to any of the four access categories in accordance with a category of data recorded in the MAC frame. The wireless signal processing unit <NUM> inputs the MAC frame to a corresponding transmission queue in accordance with a result of the mapping.

The wireless signal processing unit <NUM> confirms, through carrier sense for each access category, that there has been no transmission of any wireless signal by another terminal or the like and waits a period of time defined by an access parameter set for each access category for transmission. If there has been no transmission of any wireless signal by another terminal or the like when the wireless signal processing unit <NUM> is waiting, the wireless signal processing unit <NUM> extracts a MAC frame from a corresponding transmission queue, converts the MAC frame into a wireless signal, and transmits the wireless signal.

Here, the access parameter may be allocated such that relative priority is placed on transmission of wireless signals in an order of VO, VI, BE, and BK. The access parameter may include CWmin, CWmax, AIFS, and TXOP Limit. CWmin and CWmax are the maximum value and the minimum value, respectively, of a contention window (CW) which is a time for waiting for transmission. A transmission queue can more easily obtain a transmission right as CWmin and CWmax are shorter. An arbitration inter frame space (AIFS) is a transmission interval of a wireless signal. Priority of the transmission queue increases as the AIFS decreases. TXOP Limit is an upper limit value of a transmission opportunity (TXOP), which is a channel occupation time. It is possible to transmit more wireless signals with one transmission right as the value of TXOP Limit increases.

<FIG> is a functional block diagram of the terminal <NUM>. The terminal <NUM> includes a data processing unit <NUM>, a wireless signal processing unit <NUM>, and a measurement unit <NUM>. The data processing unit <NUM>, the wireless signal processing unit <NUM>, and the measurement unit <NUM> are realized by the processor <NUM> and the wireless module <NUM>, for example.

The data processing unit <NUM> forms a MAC frame from data input from an upper application, or the like. Also, the data processing unit <NUM> restores data from a MAC frame transferred from the wireless signal processing unit <NUM>. The data is used by the upper application, for example. Moreover, the data processing unit <NUM> generates a report including a result of the measurement performed by the measurement unit <NUM>. Then, the data processing unit <NUM> forms a MAC frame from the report. Here, the application is not limited to a specific application. For example, the application may be an RTA such as a control application for a network game or an industrial robot.

The wireless signal processing unit <NUM> performs processing for transmitting or receiving a wireless signal. For example, the wireless signal processing unit <NUM> converts the MAC frame formed by the data processing unit <NUM> into a wireless signal and transmits the wireless signal to the base station <NUM>, for example. Also, the wireless signal processing unit <NUM> receives a wireless signal from the base station <NUM>, extracts a MAC frame from the received wireless signal, and transfers the MAC frame to the data processing unit <NUM>. Here, the wireless signal processing unit <NUM> may be configured to transmit the wireless signal by EDCA, for example, similarly to the base station <NUM>.

The measurement unit <NUM> measures at least one of a latency of transmission of a wireless signal and a jitter of the wireless signal in the terminal <NUM>. The latency is measured from a time required until acknowledge (ACK) from the base station <NUM> is received after the wireless signal processing unit <NUM> transmits the wireless signal, for example. Also, the latency may be measured from a queue waiting time until the MAC frame reaches a head of a transmission queue after the MAC frame is input to an end of the transmission queue. In addition, the latency may be measured from a transmission waiting time until transmission is performed after the MAC frame reaches the head of the transmission queue. Also, the latency may be measured from a required retransmission time until retransmission is performed after retransmission is requested. A plurality of latencies among these may be measured. The jitter is measured from dispersion with respect to an average value of the latencies, for example. A method for measuring the latency and a method for measuring the jitter are not limited to specific methods. Note that time information used for the measurement may be provided by a common clock (not illustrated) included in the terminal to each functional unit.

<FIG> is a diagram illustrating a first example of a format of a MAC payload of the report. The payload of the report includes a data field for a result of measurement for each access category. The measurement result is at least one of a latency measurement result and a jitter measurement result. The measurement result may be a measurement value of the latency or the jitter obtained in individual events of measurement or may be a statistical value calculated by performing statistical processing on measurement values obtained in measurement performed a plurality of times. The statistical value includes, for example, an average value, a median value, a maximum value, and a minimum value. The payload of the report may store any one of these statistical values for each access category or may store a plurality of statistical values for each access category. Here, it is desirable to exclude outliers that significantly deviate from other measurement results from among results of measurement performed a plurality of times when the statistical values such as an average value, a median value, a maximum value, and a minimum value are calculated. Also, in a case in which both the latency and the jitter are measured, the number of measurement values used to calculate the average value may be reduced, for example, because outliers are likely to occur when the jitter is large.

For example, the report illustrated in <FIG> can be transmitted using an Action frame in the IEEE <NUM> standard. In a case in which the base station requests a report from each terminal, for example, the report may be requested with an Action frame to which a new field including a status notification request for requesting a report has been added. The terminal replies with the report through reception of the Action frame. When the report is replied with, the terminal may use an Action frame to which a new field storing the result of measuring the latency and the like has been added. In this case, the terminal may reply with the report through an ordinary CSMA/CA procedure after reception of a request from the base station as illustrated in <FIG>. Also, as illustrated in <FIG>, the terminal may reply with the report immediately after the request from the base station is received, without performing the CSMA/CA procedure, for example, after elapse of a short inter frame space (SIFS) or a PCF inter frame space (PIPS). Also, the base station may periodically provide a notification of a management frame or a control frame for requesting a report, and each terminal may transmit a report. For example, the base station may include a request for a report in a periodically transmitted frame, such as a beacon. The terminal may reply with the report in the Action frame in response to the request for the report as illustrated in <FIG>. Also, the terminal may add the report to the data frame as illustrated in <FIG>. In a case in which the terminal transmits data with a restriction of a latency, for example, the terminal can notify the base station of a latency status in relatively real time by adding information regarding a latency and the like measured when the same type (access category or the like) of data is previously transmitted. In a case in which the report is added to the data frame, the terminal may add a new field storing information regarding a latency and the like to a header of the data frame, for example.

Also, the measurement result is assumed to be stored for each access category in <FIG>. However, the payload of the report may not necessarily be stored for each access category. For example, wireless LAN transmission control schemes include schemes that do not include priority control for each access category. In this case, the measurement result is not required to be stored for each access category. Also, the measurement result may be stored for each traffic type (TID) instead of each access category. The TID is applied in units of applications (sessions) handled by the terminal <NUM>. The mapping to the aforementioned access category may be performed based on the TID. It is possible to measure a latency and a jitter distinguished for each application by the measurement result being stored for each TID.

<FIG> is a diagram illustrating a second example of a format of a MAC payload of the report. The payload of the report includes attribute information of the measurement result in addition to the data field of the measurement result for each access category. The attribute information includes information related to the terminal, such as the position of the terminal <NUM> at the time of measuring a latency or a jitter, for example, the type of terminal <NUM>, and the type of application that is being executed by the terminal <NUM>.

Next, operations of the communication system <NUM> will be described. In the following description, it is assumed that the terminal <NUM> transmits a wireless signal while the base station <NUM> receives the wireless signal.

<FIG> is a flowchart illustrating exemplary transmission processing of the terminal <NUM>. In Step S31, the data processing unit <NUM> determines whether data to be transmitted has been input from the upper layer such as an application layer. When it is determined in Step S31 that no data has been input, the processing in <FIG> ends. When it is determined in Step S31 that data has been input, the processing proceeds to Step S32.

In Step S32, the data processing unit <NUM> performs the processing of the MAC layer illustrated in <FIG> on the input data to generate a MAC frame. The data processing unit <NUM> outputs the MAC frame to the wireless signal processing unit <NUM>.

In Step S33, the wireless signal processing unit <NUM> performs transmission processing using EDCA. In other words, the wireless signal processing unit <NUM> inputs the MAC frame to a transmission queue of the access category corresponding to the category of the data. Also, the wireless signal processing unit <NUM> determines a channel state through carrier sense and waits for transmission in accordance with a period of time defined by the access parameter for each access category. Also, the wireless signal processing unit <NUM> converts the MAC frame into a wireless signal and transmits the wireless signal if the channel is not being used by another terminal or the like.

In Step S34, the wireless signal processing unit <NUM> acquires, as a transmission start clock time, a clock time at which the wireless signal is transmitted. The wireless signal processing unit <NUM> outputs, to the measurement unit <NUM>, the transmission start clock time along with the sequence number allocated to the MAC frame and the access category to which the MAC frame is mapped.

In Step S35, the wireless signal processing unit <NUM> determines whether acknowledge (ACK) from the base station <NUM> has been received. In Step S35, the wireless signal processing unit <NUM> waits for processing until ACK is received. When it is determined that ACK has been received in Step S35, the processing proceeds to Step S36. Although not illustrated in <FIG>, the wireless signal processing unit <NUM> may retransmit the MAC frame when a retransmission request is received from the base station <NUM>. The retransmission may be performed in units of MPDUs.

In Step S36, the wireless signal processing unit <NUM> acquires, as a transmission completion clock time, a clock time at which ACK has been received. The wireless signal processing unit <NUM> outputs, to the measurement unit <NUM>, the transmission completion clock time, along with the sequence number assigned to the MAC frame and the access category to which the MAC frame is mapped.

In Step S37, the measurement unit <NUM> calculates a latency and a jitter for each access category. The latency is calculated from a time difference between the transmission completion clock time and the transmission start clock time, for example. On the other hand, the jitter can be calculated from dispersion with respect to an average value of the latency, for example. The measurement unit <NUM> outputs, to the data processing unit <NUM>, the measurement result along with the access category and the sequence number.

In Step S38, the data processing unit <NUM> stores the result of measuring the latency and the jitter. Thereafter, the processing returns to Step S31. The result of the measurement may be stored in the storage <NUM>, for example.

<FIG> is a flowchart illustrating report processing performed by the terminal <NUM>. The report processing is performed every specific period of time, such as every hour, every day, or every week. The specific period of time may be appropriately set. In addition, the report processing may be immediately performed in addition to the periodic processing in a case in which the measurement value or the statistical value exceeds a threshold value that is a requirement set by an application or the like.

In Step S41, the data processing unit <NUM> determines whether a report is to be generated. It is determined that the report is to be generated when a specific period of time has elapsed, when sufficient measurement results to calculate the statistical value have been obtained, or when a request is received from the base station <NUM>, for example. When it is determined that the report is not to be generated in Step S41, the processing proceeds to Step S45. When it is determined in Step S41 that the report is to be generated, the processing proceeds to Step S42. The data processing unit <NUM> may determine, using an Action frame, that the report is to be generated in a case in which a request for transmitting a report is received from the base station. In a case in which a latency and the like at the time of previous transmission of the data frame are added every time the data frame is transmitted, it may be used as a trigger for determining that a report of transmitting the data frame is generated.

In Step S42, the data processing unit <NUM> acquires the result of the measurement stored in the storage <NUM>, for example, for each access category.

In Step S43, the data processing unit <NUM> generates the report illustrated in <FIG> or <FIG>. The data processing unit <NUM> performs statistical processing of calculating an average value or the like of the acquired result of measurement for each access category as needed.

In Step S44, the data processing unit <NUM> stores the report. The report may be stored in the storage <NUM>, for example.

In Step S45, the data processing unit <NUM> determines whether the report is to be transmitted to the base station <NUM>. It is determined that the report is to be transmitted when a specific period has elapsed, when the measurement value or the statistical value has exceeded a threshold value that is a requirement set by the application or the like, or when a request is received from the base station <NUM>, for example. When it is determined in Step S45 that the report is to be transmitted, the processing proceeds to Step S46. When it is determined in Step S45 that the report is not to be transmitted, the processing in <FIG> ends.

In Step S46, the data processing unit <NUM> acquires data of the report from the storage <NUM>, for example. Then, the data processing unit <NUM> performs processing of the MAC layer illustrated in <FIG> on the acquired data to generate a MAC frame. The data processing unit <NUM> outputs the generated MAC frame to the wireless signal processing unit <NUM>.

In Step S47, the wireless signal processing unit <NUM> performs transmission processing using EDCA.

In Step S48, the wireless signal processing unit <NUM> determines whether ACK from the base station <NUM> has been received. In Step S48, the wireless signal processing unit <NUM> waits for processing until ACK is received. When it is determined in Step S48 that ACK has been received, the processing in <FIG> ends.

<FIG> is a flowchart illustrating reception processing performed by the base station <NUM>. In Step S51, the wireless signal processing unit <NUM> determines whether a wireless signal has been received. When it is determined in Step S51 that the wireless signal has not been received, the processing in <FIG> ends. When it is determined in Step S51 that the wireless signal has been received, the processing proceeds to Step S52.

In Step S52, the wireless signal processing unit <NUM> performs reception processing. In other words, the wireless signal processing unit <NUM> performs demodulation processing or the like on the wireless signal to extract an MAC frame. The wireless signal processing unit <NUM> outputs the MAC frame to the data processing unit <NUM>. The data processing unit <NUM> performs the processing of the MAC layer on the MAC frame to restore data.

In Step S53, the data processing unit <NUM> determines whether reception has successfully been made. Whether the reception has successfully been made can be determined by CRC, for example. When it is determined in Step S53 that the reception has successfully been made, the processing proceeds to Step S54. When it is determined in Step S53 that the reception has not successfully been made, the processing proceeds to Step S55.

In Step S54, the data processing unit <NUM> causes the wireless signal processing unit <NUM> to transmit ACK.

In Step S55, the data processing unit <NUM> causes the wireless signal processing unit <NUM> to request retransmission of the MAC frame. Retransmission may be requested in units of MPDUs.

In Step S56, the data processing unit <NUM> outputs data to the upper layer such as an application layer. Thereafter, the processing is returned to Step S51.

<FIG> is a flowchart illustrating report processing performed by the base station <NUM>. The report processing is performed every specific period of time, such as every hour, every day, or every week. The specific period of time may be appropriately set.

In Step S61, the management unit <NUM> determines whether to request a report. It is determined that the report is to be requested when a specific period has elapsed or when there is a need to request a report for latency control of the RTA, for example. When it is determined in Step S61 that the report is not to be requested, the processing in <FIG> ends. When it is determined in Step S61 that the report is to be requested, the processing proceeds to Step S62.

In Step S62, the management unit <NUM> causes the wireless signal processing unit <NUM> to request a report.

In Step S63, the wireless signal processing unit <NUM> performs reception processing. In other words, the wireless signal processing unit <NUM> performs demodulation processing or the like on the wireless signal to extract an MAC frame. The wireless signal processing unit <NUM> outputs the MAC frame to the data processing unit <NUM>. The data processing unit <NUM> performs processing of the MAC layer on the MAC frame to restore data of the report.

In Step S64, the data processing unit <NUM> determines whether reception has successfully been made. When it is determined in Step S64 that the reception has successfully been made, the processing proceeds to Step S65. When it is determined in Step S64 that the reception has not successfully been made, the processing proceeds to Step S66.

In Step S65, the data processing unit <NUM> causes the wireless signal processing unit <NUM> to transmit ACK. The data processing unit <NUM> outputs the data of the report to the management unit <NUM>.

In Step S66, the data processing unit <NUM> causes the wireless signal processing unit <NUM> to request retransmission of the MAC frame. Retransmission may be requested in units of MPDUs.

In Step S67, the management unit <NUM> stores the report. Thereafter, the processing is returned to Step S61. The result of the measurement may be stored in the ROM <NUM>, for example.

As described above, according to the embodiment, the terminal measures at least one of a latency and a jitter when a wireless signal is transmitted. Then, the terminal transmits a report including data of a result of measurement to the base station. Thus the base station can recognize a state of a wireless section with the corresponding terminal from the result of the measurement recorded in the report. In this manner, the base station can predict whether the requirement for a latency or a jitter is satisfied before an RTA traffic is actually input and can take a measure as needed. In a case in which the requirement cannot be satisfied, for example, the base station can determine that the RTA traffic is not handled and refuse a request for exchanging the RTA traffic when a request is received. Alternatively, the base station can also adjust the access parameter or the like to satisfy the requirement. In addition, when determining these, the base station can also evaluate reports of a plurality of terminals (such as calculation of the average and dispersion). As described above, according to the embodiment, it is possible to provide, to the base station, information that contributes to securing of the requirements even with an absolute requirements for latency and a jitter.

Hereinafter, modification examples of the embodiment will be described. The report may include information related to an interference status in the terminal in addition to the result of measuring the latency or the jitter for each access category of the terminal. A transmission opportunity (TXOP) may not be able to be obtained due to influences of other interference sources and the latency may increase depending on the location of the terminal even in the same service area of the base station. In a case in which there is such a terminal, deviation of latency properties occurs. The base station can distinguish a terminal with large interference from a terminal with small interference because information related to such interference as a report is transmitted to the base station, and it is thus possible to expect improvement in accuracy of the latency properties inside the service area.

The base station <NUM> periodically transmits a beacon as illustrated in <FIG> during communication between the base station and the terminal. The terminal <NUM> calculates a success rate of reception of a beacon from the base station <NUM> as information for evaluating the interference of the terminal <NUM>. In addition, the terminal <NUM> calculates a difference, as information for evaluating the interference of the terminal <NUM>, between a clock time (time stamp) at which the base station <NUM> stores the beacon at the time of creation of the beacon and a clock time when the beacon is received. The terminal <NUM> transmits, to the base station <NUM>, information for evaluating such interference included in the report. Note that the information for evaluating the interference of the terminal <NUM> is not limited to specific information.

Also, at least one of the latency and the jitter is measured by the terminal, and the result of the measurement is reported from the terminal to the base station in the aforementioned embodiment and the modification examples thereof. On the contrary, at least one of the latency and the jitter may be measured by the base station, and the result of the measurement may be reported from the base station to the terminal. In this case, the processing in <FIG> and <FIG> is performed by the base station, and the processing in <FIG> and <FIG> is performed by the terminal. In the case of the base station, the measurement result may be included in a beacon and transmitted to the terminal.

Claim 1:
A terminal apparatus comprising:
a measurement unit (<NUM>) configured to measure at least one of a latency when a wireless signal is transmitted to a base station and a jitter of the wireless signal;
a data processing unit (<NUM>) configured to generate information including a result of the measurement; and
a wireless signal processing unit (<NUM>) configured to transmit the information to the base station,
characterized in that
the wireless signal processing unit controls transmission of the wireless signal in accordance with an access category of the wireless signal classified in accordance with data included in the wireless signal, and
the measurement unit measures at least one of the latency and the jitter for the access category.