JP3762872B2 - Wireless communication system and wireless communication method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio communication system and a radio communication method including a control station and a plurality of radio terminals, and more particularly to a radio communication system and a radio communication method for performing direct communication between a plurality of radio terminals.
[0002]
[Prior art]
In wireless communication, the positional relationship and communication environment between wireless terminals change dynamically, and the communication quality changes greatly. In order to perform stable communication in such an unstable situation, it is necessary to appropriately control settings related to transmission power (transmission power setting) and settings related to reception power (reception sensitivity setting) according to changes in the communication environment. is there.
[0003]
Communication quality is information that specifically represents the quality of communication when communication is performed between a wireless terminal and a wireless terminal. For example:
(1) Error rate
It represents the ratio of data packet transmission failure when data transmission is performed from one wireless terminal to the other wireless terminal.
(2) Maximum received power
This is the reception power at the reception-side wireless terminal when the transmission-side wireless terminal transmits at the maximum transmission power.
[0004]
In Japanese Patent Application Laid-Open No. 11-266256, each wireless terminal transmits an inspection signal in the frame head region, and the other wireless terminals receive this and measure its strength or error rate, etc. A method for knowing the communication quality is disclosed.
Based on this, it is possible to perform data transmission with high communication quality between wireless terminals with high communication quality but low reliability, and with wireless terminals with low communication quality, transmission with high reliability can be performed with low communication speed.
In this way, it is possible to dynamically determine the communication quality by using the inspection signal that is periodically transmitted, and to determine the optimum modulation scheme according to the communication quality.
[0005]
[Problems to be solved by the invention]
However, the apparatus described in the above publication has the following problems.
There are three types of information to be transmitted: control data, a temporally continuous data stream, and asynchronous data such as commands. From now on, when it is simply described as data, it means asynchronous data.
A data communication procedure will be described.
[0006]
FIG. 16 is a schematic diagram showing a flow of a data communication procedure.
As shown in FIG. 16, the data communication procedure can be divided into data transmission (request transmission) and data transmission confirmation (response transmission). In request transmission, request data is transmitted to the responding wireless terminal. In response transmission, the responding wireless terminal transmits response data to the requesting wireless terminal. The requesting wireless terminal requests the responding wireless terminal to operate the content of the request data as a request transmission by transmitting the request data. After receiving the request data, the responding wireless terminal performs an operation based on the content of the data, and transmits the response data using the reception result of the request data as a response transmission to the requesting wireless terminal. The requesting wireless terminal knows that the request data has been received by receiving the response data, and the communication ends.
[0007]
FIG. 17 is a schematic diagram of a request data packet, and FIG. 18 is a schematic diagram of a response data packet.
As shown in these figures, the sequence number in the request data is assigned to each request data. The sequence number in the response data stores the sequence number of the request data to which the responding wireless terminal responds. The requesting wireless terminal determines which request data the response is based on the sequence number in the response data.
[0008]
When the requesting wireless terminal detects the sequence number in the response data, it determines that the request data transmission of the sequence number is successful. If a transmission timeout occurs without confirming the successful transmission after transmitting the request data, it is determined that the transmission of the request data has failed. If the requesting wireless terminal determines that the data transmission has failed, it retransmits the requested data.
[0009]
When the response-side wireless terminal receives again the sequence number of the transmitted response data from the request-side wireless terminal, it determines that the response data transmission has failed. If the request data of the transmitted sequence number is not retransmitted before the response data transmission times out, it is determined that the transmission is successful. However, the time taken to determine that the transmission is successful is much longer than the request transmission because it waits until timeout.
[0010]
In data transmission, there is a polling system in order to give each wireless terminal equal opportunities for transmission. The polling method is a method in which one wireless terminal in a wireless communication system gives a right to transmit data by transmitting a polling packet to another wireless terminal in the wireless communication system. The wireless terminal given the transmission right starts data transmission if there is data to be transmitted.
[0011]
In polling communication, any wireless terminal transmits a polling packet to give a data transmission right to a destination wireless terminal. Here, the control station gives a data transmission right to the wireless terminal by transmitting a polling packet. The control station, after giving a data transmission right to the wireless terminal by transmitting a polling packet addressed to the wireless terminal, determines that the wireless terminal data transmission is completed or no data transmission is performed, and then the next wireless terminal Is given the right to send data.
Here, the device described in the above publication is such that the optimum modulation scheme is appropriately selected according to the transmission path, and does not consider power control in data transmission.
[0012]
When data transmission is performed in polling communication, not only the communication quality between the transmitting wireless terminal and the receiving wireless terminal but also the communication quality with the control station of the transmitting wireless terminal must be considered. The transmission power and reception power must be controlled appropriately according to the communication quality. For example, even when the communication quality between the transmission side wireless terminal and the reception side wireless terminal is very good, if the communication quality between the control station and the transmission side wireless terminal is poor, the transmission side wireless terminal can transmit data at the maximum output. If transmission is not performed, data transmission may not be successful.
[0013]
Here, with reference to FIG. 19 to FIG. 21, consider a case where the distance between the transmitting wireless terminal and the receiving wireless terminal is very close and the distance from the control station is very long.
FIG. 19 is a schematic diagram illustrating an example of arrangement of wireless terminals. FIG. 20 is a schematic diagram in the case of the wireless terminal arrangement (FIG. 16), and shows communication quality between the control station and each wireless terminal. FIG. 21 is a schematic diagram in the case of the wireless terminal arrangement (FIG. 16), and shows the communication quality between the terminals.
[0014]
As shown in FIG. 20, the transmitting wireless terminal does not reach the control station, assuming that the transmitting wireless terminal transmits at an appropriate intensity that the receiving wireless terminal can receive without attenuating the received radio wave. The control station determines that the transmitting wireless terminal has not performed data transmission and starts transmitting a polling packet to give a transmission right to the next wireless terminal. It will collide. On the other hand, if the transmitting wireless terminal transmits at a strength at which radio waves reach the control station, as shown in FIG. 21, the receiving strength of the radio waves at the receiving wireless terminal becomes very strong. Received data is too strong to receive data.
[0015]
As in this example, even if the communication environment between the transmitting-side wireless terminal and the receiving-side wireless terminal is extremely good, the transmitting-side wireless terminal may not be able to communicate normally without transmitting at the maximum transmission strength. Come out.
For this reason, in order to perform normal communication between wireless terminals, the communication quality between the transmitting wireless terminal and the receiving wireless terminal and the communication quality between the transmitting wireless terminal and the control station are determined and appropriate transmission is performed. The power setting must be derived.
As a transmission power control method, there is also a method in which a control station performs transmission control by managing control of transmission power of all terminals in the system. However, this method increases communication overhead.
[0016]
The present invention has been made in view of such problems, and the control station does not manage the control of transmission power, and the radio terminals of the non-control stations determine the communication quality and set the appropriate transmission power. An object of the present invention is to provide a wireless communication system and a wireless communication method capable of appropriately setting the above.
[0017]
[Means for Solving the Problems]
The wireless communication system of the present invention includes a control station and a plurality of wireless terminals wirelessly connected to the control station, and in the wireless communication system capable of direct communication between the wireless terminals, the wireless terminal transmits Switching means for switching power levels, communication quality A with the control station, and storage means for storing n communication qualities b1, b2,..., Bn with other wireless terminals, and the storage Control means for determining a transmission power level based on the communication quality A and communication quality b1, b2,..., Bn stored in the means, and switching the switching means so that the determined transmission power level is obtained; And a transmission means for transmitting data to another wireless terminal at the determined transmission power level.
[0018]
Further, the communication quality A or the communication quality b1, b2,..., Bn may include communication quality information based on a reception result when transmitting with a known transmission power, and the communication quality A or communication quality. b1, b2,..., bn include information indicating a margin value up to the lower limit of receivable power of each wireless terminal calculated by the control station based on a reception result when transmission is performed with a known transmission power. May be.
[0019]
Further, the communication quality A or the communication quality b1, b2,..., Bn may include communication quality information based on a reception result when each wireless terminal performs transmission power control. The communication quality for the reception result when performing transmission power control may include sufficient / insufficient binary information.
[0020]
More preferably, the margin value is included in the communication quality A, the binary information is included in the communication quality A and communication quality b1, b2,..., Bn, and each radio terminal When transmitting with a transmission power larger than the transmission power indicated by the value, the transmission power is controlled by the binary information included in the communication quality b1, b2,..., Bn, and smaller than the transmission power indicated by the margin value. When transmitting with transmission power, transmission power may be controlled by the binary information included in the communication quality A and the communication qualities b1, b2,..., Bn.
[0021]
Further, the wireless communication method of the present invention includes a control station and a plurality of wireless terminals wirelessly connected to the control station, and the wireless communication method of the wireless communication system capable of direct communication between the wireless terminals, Each wireless terminal stores communication quality A between the control station and its own wireless terminal and n communication qualities b1, b2,..., Bn between its own wireless terminal and each of the other wireless terminals. And, based on the communication quality A and the communication qualities b1, b2,..., Bn, transmission power control of its own wireless terminal is performed.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a wireless communication system and a wireless communication method of the present invention will be described in detail with reference to the accompanying drawings.
First, the basic concept of the present invention will be described.
The wireless communication system to which the present invention is applied is divided into a region for transmitting a frame with a known transmission power (known transmission power region) and a transmission region (a variable transmission power region) with variable transmission power.
[0023]
Each wireless terminal determines communication quality between its own wireless terminal and control station, and between its own wireless terminal and other wireless terminals. Depending on the communication quality, the own wireless terminal determines a transmission power setting when transmitting to another wireless terminal in the variable transmission power region, and transmits to the other wireless terminal with the determined transmission power setting. To.
[0024]
Each wireless terminal determines the communication quality related to reception from the reception results in the known transmission power region and the variable transmission power region, and broadcasts the result to all wireless terminals. Each wireless terminal stores the received communication quality, and determines the quality of communication between its own wireless terminal and control station, and between its own wireless terminal and other wireless terminals.
Each wireless terminal stores a margin value up to the lower limit of the receivable power of the wireless terminal and binary information indicating that the transmission power of the wireless terminal in the variable transmission power region is sufficient / insufficient.
[0025]
When the wireless terminal transmits with a transmission power larger than the transmission power indicated by the margin value between the wireless terminal and the control station, the binary information between the wireless terminal and the receiving wireless terminal Control transmission power more. When transmitting with a transmission power smaller than the transmission power indicated by the margin value between the own wireless terminal and the control station, between the own wireless terminal and the control station, the own wireless terminal and the receiving wireless terminal Transmission power is controlled by binary information.
In this way, each wireless terminal determines communication quality between its own wireless terminal and control station, and between its own wireless terminal and other wireless terminals, and performs transmission power control of its own wireless terminal according to the communication quality. Do.
[0026]
FIG. 1 is a block diagram showing a configuration of a transmission / reception unit of a wireless terminal in the wireless communication system according to the embodiment of the present invention based on the above basic concept, and shows an example of the flow of transmission power control and reception power control. In the figure, thick arrows indicate control signals.
In FIG. 1, a transceiver 10 of a wireless terminal includes an antenna 11, a transmission amplifier 12 (switching means), a modulator 13, an attenuator 14, an AGC (Automatic Gain Control) circuit 15, and a demodulator 16. Based on the inputs from the reception level indicating circuit (RSSI circuit) 17, the demodulator 16 and the RSSI circuit 17, which detects the received signal level from the intermediate frequency signal (IF signal), performs logarithmic conversion and outputs the RSSI output signal, A controller 18 (control means) that controls the transmission amplifier 12, the attenuator 14, and the AGC circuit 15 is provided. The controller 18 stores a communication quality (communication quality A) between the control station and its own wireless terminal. A circuit 19 (storage means) and a memory for storing n communication qualities b1, b2,..., Bn between the own wireless terminal and each of the other wireless terminals as communication quality B It has a memory 2 circuit 20 (storage means).
[0027]
The antenna 11, the transmission amplifier 12, and the modulation unit 13 constitute a transmission unit that transmits data to other wireless terminals at the determined transmission power level as a whole.
The operation of the radio communication system configured as described above will be described below. First, the operation of the transmission / reception device 10 will be described.
[0028]
When transmitting, the transmission signal is modulated by the modulation unit 13, the signal is amplified by the transmission amplifier 12, transmitted to the antenna 11, and transmitted. The controller 18 controls the transmission amplifier 12 to adjust the transmission power.
When receiving, the signal is first attenuated from the antenna 11 to the attenuator 14 and attenuated. The attenuation rate of the attenuator 14 is adjusted by the controller 18. When the controller 18 demodulates the received signal, the controller 18 determines that the received signal is too strong and saturates when demodulating the received radio wave. Is adjusted so as not to be saturated at the time of demodulation. Information about whether or not the demodulator 16 is saturated is sent from the demodulator 16 to the controller 18.
[0029]
The received signal that has passed through the attenuator 14 is sent to the AGC circuit 15 and the RSSI circuit 17. The AGC circuit 15 performs variable gain control and amplifies the IF signal to an appropriate input level in the demodulator 16. Next, the demodulator 16 demodulates the received signal to restore the baseband signal.
The other IF signal is converted into a DC signal by the RSSI circuit 17, and then the input power is logarithmically converted by an internal current-voltage conversion amplifier and the output is sent to the controller 18.
[0030]
The wireless terminal including the transmission / reception device 10 performs transmission power setting / reception sensitivity setting in accordance with transmission / reception. Specifically, the controller 18 adjusts the transmission amplifier 12, the attenuator 14, and the AGC circuit 15 to set the transmission power setting and the reception sensitivity setting in accordance with transmission / reception. Information about the received power is obtained from the output from the RSSI circuit 17 and the setting of the attenuator 14. The received power at the end of the antenna 11 is obtained by correcting the amount of attenuation in the attenuator 14 to the reception result from the RSSI circuit 17.
[0031]
Next, reception sensitivity setting processing will be described.
The reception power is controlled by the attenuator 14 and the AGC circuit 15. The attenuator 14 performs an attenuating operation with the setting designated by the controller 18. With respect to the AGC circuit 15, the controller 18 only sets an initial value for the setting of the AGC circuit 15, and the subsequent operation is performed by the AGC circuit 15 based on an input signal to the AGC circuit 15, regardless of an instruction from the controller 18. Perform the action.
[0032]
The control value used for the control of the AGC circuit 15 can be read by the controller 18. The controller 18 changes the setting of the attenuator 14 according to the control value read from the AGC circuit 15 so that the power passing through the attenuator 14 falls within the controllable range of the AGC circuit 15.
[0033]
Further, when setting the transmission power setting and the reception sensitivity setting, the controller 18 derives a setting value based on the communication quality of the wireless communication system. The controller 18 includes a storage 1 circuit 19 and a storage 2 circuit 20. The communication quality between the control station and each wireless terminal is stored in the storage 1 circuit 19, and the communication quality between each wireless terminal is stored in the storage 2 circuit 20. To remember. The controller 18 can extract the communication quality from the storage circuits 19 and 20 when the communication quality is required.
[0034]
Next, operations of the control station of the wireless communication system and each wireless terminal will be described with reference to FIGS. In the following description, the wireless terminal 0 is a control station, and the wireless terminals 1 to 3 are wireless terminals of controlled stations.
FIG. 2 is a table showing an example of storage of reception results in the control station stored in each wireless terminal. FIG. 3 is a table showing a storage example of a data unreceivable power flag stored in each wireless terminal.
[0035]
The control station broadcasts reception results in the known transmission power region and the variable transmission power region in the known transmission power region for each frame (for example, one frame is 4 ms). The information shown in FIG. 2 is transmitted to all wireless terminals by the broadcast of the control station.
The expected surplus received power is information on a margin value from the received power at the control station when each wireless terminal transmits in the known transmission power region to the lower limit of the received power that can be received by the control station derived by the control station.
[0036]
The control station data unreceivable power flag is a reception result at the control station when each wireless terminal transmits to another wireless terminal in the variable transmission power region. When the received power is not enough, this flag is set to report that the received power is not enough.
In addition, each wireless terminal broadcasts a reception result when another wireless terminal has transmitted to its own wireless terminal in the variable transmission power area in the past as a data unreceivable power flag in the known transmission power area for each frame. As a result of the broadcast of each wireless terminal, each terminal transmits one column, and therefore the data unreceivable power flag in FIG. 3 is transmitted to all wireless terminals.
[0037]
The data unreceivable power flag is a reception result in the other wireless terminal when the upper wireless terminal transmits in the variable transmission power region. When the received power is not enough, this flag is set to report that the received power is not enough.
Also, the lower limit transmission power setting is derived from the expected surplus received power shown in FIG.
[0038]
Each wireless terminal controls transmission power with the data unreceivable power flag in FIG. 3 until the lower limit transmission power is set. When performing transmission power control below the power guaranteed to be received at the control station, the transmission power is controlled by the control station data unreceivable power flag shown in FIG. 2 and the data unreceivable power flag shown in FIG.
In this way, each wireless terminal determines communication quality between its own wireless terminal and control station, and between its own wireless terminal and other wireless terminals, and performs transmission power control of its own wireless terminal according to the communication quality. Do.
[0039]
FIG. 4 is a schematic diagram illustrating a schematic configuration of the wireless communication system in the present embodiment. In FIG. 4, a portion surrounded by an ellipse indicates a cover area in which communication can be performed in each wireless terminal.
As a configuration form of the network, a star-type topology structure is formed around a control station in which only one control station exists in one wireless communication system. Therefore, an active wireless terminal on the wireless communication system is always in a state in which bidirectional communication with the control station is possible. Also, wireless terminals communicate directly with each other if the communication environment between the wireless terminals is good. However, communication may not be possible between wireless terminals due to the distance between wireless terminals or due to obstacles. In that case, communication is performed by relaying other wireless terminals.
[0040]
FIG. 5 is a schematic diagram illustrating a configuration of a radio frame used by the radio communication system. As shown in FIG. 5, the radio frame is divided into a known transmission power region and a variable transmission power region. The known transmission power area is a management area, and the variable transmission power area is a user data area.
[0041]
The management area is an area for performing communication between the control station and the wireless terminal in order to perform maintenance and management of frames, confirmation of communication quality between the wireless terminals, and the like. Communication in this management area uses a common modulation method and coding rate, and transmission power is performed at the maximum output. Also, polling packets use a common modulation method and coding rate, and transmit power at the maximum output so that it reaches all terminals.
[0042]
<Management area>
(1) Frame start area 21
In order to notify the start of the frame to all the wireless terminals in the wireless communication network, the control station transmits to all the wireless terminals. It is also used as an area for maintaining and managing a wireless communication system.
(2) Operation status report area 22
This is an area in which each wireless terminal participating in the wireless communication system reports its own operation state as an operation state report packet. The position information where the wireless terminal transmits the operation state report packet is indicated in the frame management area, and each wireless terminal transmits the operation state report packet based on the management information.
[0043]
<User data area>
(1) User data area 23
Data communication is performed as appropriate without securing a bandwidth in advance. Within one frame, data is sequentially transmitted in an empty area from the end of the management area to the start of the next frame. The control station transmits a polling packet including the identification value, and the wireless terminal that has obtained the transmission right starts transmitting data.
[0044]
<Frame start area>
FIG. 6 is a schematic diagram showing the configuration of the frame start area 21.
(1) Frame management area 24
The control station transmits information for maintaining and managing the wireless communication system.
[0045]
The location information when the wireless terminal transmits the operation status report packet in the operation status report area is also transmitted here.
(2) Wireless terminal information area 25
This is an area for the control station to transmit information on the wireless terminal. Information about each wireless terminal is stored as wireless terminal information. The broadcast shown in FIG. 2 is performed in this area.
[0046]
<Wireless terminal information>
FIG. 7 is a schematic diagram illustrating a configuration of wireless terminal information.
(1) Wireless terminal number 26
It is a number for recognizing a wireless terminal. The wireless terminal information is information regarding the wireless terminal recognized by the wireless terminal number.
(2) Wireless terminal state 27
This status indicates what state the wireless terminal is currently in. Indicates whether it is in operation or power saving.
(3) Expected surplus received power information 28
In the control station, whether or not the operation state report packet transmitted by the wireless terminal of the non-control station has been successfully received, or the expected surplus power is stored when the reception is successful.
[0047]
FIG. 8 is a diagram illustrating an example of information stored in the expected surplus received power information 28. In FIG. 8, from reception failure classification “0” to reception success, the lower limit value from the maximum reception power is 0 dB, to classification “1”, and further, reception is successful and the lower limit value is −60 dB to classification “7”. There are 8 classifications. The control station derives the expected surplus received power regarding the wireless terminal from the maximum received power of the packet of the wireless terminal indicated by the wireless terminal number in the control station.
[0048]
Here, the expected surplus power is information indicating that the control station can receive a packet of power up to minus how much dB from the maximum received power in the control station. This information is derived by the control station.
The control station can receive packets from the expected surplus received power to the power of (maximum received power)-(expected surplus received power), and the radio terminal indicated by the radio terminal number is (maximum transmit power)-(expected surplus It can be determined that the transmission power can be reduced to the reception power).
[0049]
(4) Control station data unreceivable power flag 29
Returning to FIG. 7, the control station receives the data transmitted from the wireless terminal to other wireless terminals, and the received power of the received data is too small in the received power of the received data, resulting in a failure in reception. When there is data determined to be possible, it is determined that the received power is insufficient, and the control station data unreceivable power flag is set.
FIG. 9 is a diagram showing an example of information stored in the control station data unreceivable power flag 29. As shown in FIG.
[0050]
<Operation status report packet>
The use operation state report packet used in the operation state report region 22 is a packet for the wireless terminal to report its own wireless terminal information and communication quality with other wireless terminals.
[0051]
FIG. 10 is a schematic diagram illustrating a configuration of an operation state report packet. The operation status report packet includes self-terminal information 30 and each terminal information area 31.
(1) Self-terminal information 30
Used to report the status of its own wireless terminal.
(2) Each terminal information area 31
Broadcasting for each column shown in FIG. 3 is performed here.
[0052]
It is used to report the communication status between its own wireless terminal and each terminal. Information on all wireless terminals is stored in the operation status report packet, and the number of pieces of terminal information is the same as the number of all wireless terminals. Each terminal information is stored side by side in the order of wireless terminal numbers in each terminal information area.
[0053]
If all the information related to the communication status of the wireless communication system is stored in each terminal information, each terminal can reliably and accurately determine the communication quality. However, the packet length of the operation status report packet becomes long, and the bandwidth is compressed. For this reason, the information stored in each terminal information is simplified.
Among each terminal information, only the data unreceivable power flag is related to transmission power control, and has a 1-bit configuration.
[0054]
<Each terminal information>
FIG. 11 is a schematic diagram of each terminal information. It comprises an operation state report packet reception result 32 and a data unreceivable power flag 33.
(1) Operation status report packet reception result 32
Stores information about whether the reception of the operation status report packet has succeeded or failed, and the received power when the reception has succeeded.
(2) Data reception impossible power flag 33
In the wireless terminal, when it is determined that the reception power in the data area is too small and there is a possibility of reception failure, it is determined that the reception power is insufficient and the data unreceivable power flag 33 is set. Conversely, if the data unreceivable power flag 33 is not set, it is determined that the received power is sufficiently large.
FIG. 12 is a diagram illustrating an example of information stored in the data unreceivable power flag.
[0055]
Next, communication quality will be described. The communication quality between the wireless terminals is derived based on the reception result of the operation state report packet received by its own wireless terminal and the communication result in the user area. The communication quality refers to information indicating the quality of communication held in the wireless terminal, and is derived from past communication records. The communication quality includes the following.
[0056]
(1) Maximum received power
This is the reception power at the reception-side wireless terminal when the transmission-side wireless terminal transmits at the maximum transmission power. The operation status report packet is transmitted at the maximum power. The reception power of the operation state report packet is set as the maximum reception power in the own wireless terminal from another wireless terminal.
(2) Lower limit transmission power setting
This is the lower limit of the transmission power setting at which the control station can receive data when its own wireless terminal transmits data to other wireless terminals. When its own wireless terminal transmits to another wireless terminal with a transmission power setting larger than the lower limit transmission power setting, it determines that the received power at the control station is the power at which packets can be received.
The lower limit transmission power setting is derived from (maximum transmission power) − (expected surplus reception power). Here, the expected surplus received power is information indicating how much minus minus dB the packet can be received, stored in the expected surplus received power information.
[0057]
Here, determination of the success of data transmission will be described. As shown in FIG. 16, the data communication procedure can be divided into data transmission (request transmission) and data transmission confirmation (response transmission).
In request transmission, request data is transmitted to the response side wireless terminal. In response transmission, the response side wireless terminal transmits response data to the request side wireless terminal. The requesting wireless terminal requests the responding wireless terminal to operate the content of the request data as a request transmission by transmitting the request data. After receiving the request data, the responding wireless terminal performs an operation based on the content of the data, and transmits the response data using the reception result of the request data as a response transmission to the requesting wireless terminal. The requesting wireless terminal knows that the request data has been received by receiving the response data, and the communication ends.
[0058]
FIG. 17 is a schematic diagram of a request data packet, and FIG. 18 is a schematic diagram of a response data packet. As shown in FIGS. 17 and 18, the sequence number in the request data is assigned to each request data. The sequence number in the response data stores the sequence number of the request data to which the responding wireless terminal responds. The requesting wireless terminal determines which request data the response is based on the sequence number in the response data.
[0059]
When the requesting wireless terminal detects the sequence number in the response data, it determines that the request data transmission of the sequence number is successful. If a transmission timeout occurs without confirming the successful transmission after transmitting the request data, it is determined that the transmission of the request data has failed. When the requesting wireless terminal determines that the data transmission has failed, it retransmits the request data.
[0060]
When the response-side wireless terminal receives again the sequence number of the transmitted response data from the request-side wireless terminal, it determines that the response data transmission has failed. If the request data of the transmitted sequence number is not retransmitted before the response data transmission times out, it is determined that the transmission is successful. However, the time taken to determine that the transmission was successful is much longer than that of the requested academic because it waits until timeout.
[0061]
Next, transmission process will be described.
FIG. 13 is a flowchart showing the process of the transmission process. In the figure, S indicates each step of the flow. The transmission process is performed according to the following procedure.
First, the operation when performing fine control of transmission power will be described. When the transmission power is slightly increased, the transmission power setting is increased by one step. When the transmission power is slightly reduced, the transmission power setting is lowered by one step. When the transmission power setting is increased by one step, for example, an operation of increasing the transmission power by 0.5 dBm is performed. When lowering the transmission power setting, for example, an operation of lowering the 0.5 dBm transmission power is performed.
[0062]
(1) It is determined whether or not the transmission power is small (step S1).
When the data unreceivable power flag of each terminal information in the operation status report packet is set, it is determined that the transmission power is small. In other cases, it is determined that the communication quality is stable.
(2) If the transmission power is not small, it is determined that the communication quality is stable, a transmission power setting is derived in step S2, data transmission is performed in step S4, and the transmission process is terminated.
(3) When the transmission power is small, it is determined that the communication quality is unstable, the transmission power setting is increased by one step (for example, 0.5 dBm) in step S3, and data transmission is performed in step S4 to perform transmission process processing. Exit.
[0063]
FIG. 14 is a flowchart showing the transmission power setting derivation process when the communication quality is stable, and corresponds to the process of step S13 of FIG.
First, in step S11, it is determined whether or not the transmission power setting is larger than the lower limit transmission power setting. If the transmission power setting is equal to or lower than the lower limit transmission power setting, the control station data unreceivable power flag in the wireless terminal information is set in step S12. It is determined whether or not it has been. When the transmission power setting is larger than the lower limit transmission power setting in step S11 or when the control station data reception impossible power flag of the wireless terminal information is not set in step S12, the transmission power setting is changed in step S13. Determine whether the data transmission was successful.
[0064]
If the data transmission is successful after changing the transmission power setting, the transmission power setting is lowered by one step in step S14 to end this flow. If the data transmission is not successful after changing the transmission power setting, In step S15, the transmission power setting is maintained as it is, and this flow is finished. On the other hand, when the control station data unreceivable power flag of the wireless terminal information is set in step S12, the transmission power setting is increased by one step in step S16, and this flow is ended.
[0065]
In this way, if the transmission power setting is larger than the lower limit transmission power setting addressed to the control station of its own wireless terminal, if the data transmission is successful after changing the transmission power setting, the transmission power setting is lowered by one step. If the data transmission is not successful after changing the power setting, the transmission power setting is maintained as it is.
[0066]
Also, if the transmission power setting is smaller than the lower limit transmission power setting addressed to the control station of its own wireless terminal, if the control station data reception impossible power flag of the wireless terminal information is set, the transmission power setting is increased by one step, If the transmission power setting is not set and the data transmission is successful after changing the transmission power setting, the transmission power setting is lowered by one step. If data transmission is not successful after changing the transmission power setting, the transmission power setting is maintained as it is.
[0067]
Next, the process of the reception process will be described.
FIG. 15 is a flowchart showing the process of the reception process. The reception process is performed according to the following procedure.
(1) It is determined whether or not the maximum received power has been updated between the previous reception process and the current reception process (step S21).
(2) When the maximum received power is updated, the setting of the attenuator 14 is derived (step S22).
[0068]
The wireless terminal controls the AGC circuit 15 even when the transmitting wireless terminal suddenly starts transmission with the transmission intensity of the maximum transmission power from the situation in which the wireless terminal of the wireless terminal receives the low power packet. The attenuator 14 is designed so that the reception power control can be handled only by the above.
The wireless terminal compares the maximum received power with the control range of the AGC circuit 15. When it is determined that the maximum received power is outside the control range of the AGC circuit 15, the setting of the attenuator 14 is derived so that the control range of the AGC circuit 15 is obtained when the received power is the maximum received power.
[0069]
(3) The setting of the AGC circuit 15 is derived in accordance with the setting of the attenuator 14 (step S23).
The wireless terminal derives the setting of the AGC circuit 15 when the previous received power data is received with the current setting of the attenuator 14.
When the setting of the attenuator 14 is changed, the wireless terminal corrects the setting of the AGC circuit 15 by the amount of change in the setting of the attenuator 14.
[0070]
(4) Automatic control by the AGC circuit 15 is performed (step S25).
In step S24, it is determined whether data is being received. If no data is being received, the process of the receiving process is terminated. If data is being received, automatic control by the AGC circuit 15 is repeated in step S25 until no data is received. .
During reception of data, the wireless terminal controls reception power by the AGC circuit 15 performing automatic control of reception power.
[0071]
As described above, in each wireless terminal of the wireless communication system of the present embodiment, the controller 18 stores the storage 1 circuit 19 in which the communication quality A between the control station and each wireless terminal is stored, and between the wireless terminals. And a storage 2 circuit 20 for storing the communication quality B between them, and determining the transmission power level of its own wireless terminal based on the communication quality A and the communication quality B, and the transmission amplifier 12 so as to become the determined transmission power level. Since the transmission power level is switched to perform transmission power control, each wireless terminal determines communication quality between its own wireless terminal and the other wireless terminal, and between its own wireless terminal and the control station, Transmission can be performed so that radio waves reach both the control station and the transmitting wireless terminal according to the communication quality.
[0072]
In other words, since the wireless terminal holds the communication quality up to the wireless terminal to be transmitted in advance, the wireless terminal can perform transmission with an appropriate transmission strength without establishing the communication path, and greatly shorten the communication establishment time. In addition, power saving can be achieved. In addition, since each wireless terminal performs the above transmission power control independently, the control station can reduce the burden of managing the transmission power control of all terminals in the system, and the communication overhead can be reduced. .
[0073]
In this way, when the communication environment fluctuates drastically as in wireless communication, transmission settings are set so that radio waves reach both the control station and the transmitting wireless terminal so that communication between the wireless terminal and the wireless terminal is possible. Therefore, transmission power can be appropriately controlled.
The above embodiment is an example applied to a wireless communication system including a control station and a wireless terminal wirelessly connected to the control station. However, an OFDM (Orthogonal Frequency Division Multiplex) method or a TDMA method is used. The present invention can be applied to any communication system device.
[0074]
Moreover, in the said embodiment, although the name of a control station and a radio | wireless terminal is used, this is for convenience of explanation, for example, a base station, a mobile station, etc. may be sufficient. Further, it may be incorporated in a part of a communication device or the like, and can also be applied to a PDA (Personal Digital Assistant) having a wireless communication function and a small notebook personal computer.
[0075]
In the present embodiment, the controller 18 stores a communication 1 circuit 19 for storing the communication quality A between the control station and each wireless terminal, and a storage 2 circuit 20 for storing the communication quality B between the wireless terminals. However, the type of storage means, the storage method, and the like are not limited to the above-described embodiments. For example, the memory circuits 19 and 20 need only be functionally separated and do not need to be separated into two hardware. Further, it may be provided outside the controller 18.
[0076]
Furthermore, the types and number of attenuators, amplifiers, AGC circuits, etc. constituting the receiving apparatus are not limited to the above-described embodiments. In the present embodiment, the high-frequency bandpass filter (RFBPF), the intermediate frequency bandpass filter (IFBPF), and the like are omitted, but it is needless to say that these may be provided.
[0077]
【The invention's effect】
As described above in detail, according to the present invention, the wireless terminal of the non-control station determines the communication quality and appropriately sets the appropriate transmission power setting without the control station managing the control of the transmission power. Each wireless terminal can perform appropriate transmission power control according to communication quality based on its own judgment. Therefore, even when the communication environment fluctuates drastically as in wireless communication, the transmission power is appropriately controlled and communication between the wireless terminal and the wireless terminal becomes possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a transmission / reception unit of a wireless terminal in a wireless communication system according to an embodiment of the present invention.
FIG. 2 is a table showing a storage example of reception results in a control station stored in each wireless terminal of the wireless communication system of the present embodiment.
FIG. 3 is a table showing a storage example of a data unreceivable power flag stored in each wireless terminal of the wireless communication system according to the present embodiment.
FIG. 4 is a schematic diagram showing a schematic configuration of a radio communication system according to the present embodiment.
FIG. 5 is a schematic diagram illustrating a configuration of a radio frame used by the radio communication system according to the present embodiment.
FIG. 6 is a schematic diagram showing a configuration of a frame start region of the radio communication system according to the present embodiment.
FIG. 7 is a schematic diagram illustrating a configuration of wireless terminal information of the wireless communication system according to the present embodiment.
FIG. 8 is a diagram illustrating an example of information stored in expected surplus received power information of the wireless communication system according to the present embodiment.
FIG. 9 is a diagram illustrating an example of information stored in a control station data unreceivable power flag of the wireless communication system according to the present embodiment.
FIG. 10 is a schematic diagram illustrating a configuration of an operation state report packet of the wireless communication system according to the present embodiment.
FIG. 11 is a schematic diagram of terminal information of the wireless communication system according to the present embodiment.
FIG. 12 is a diagram illustrating an example of information stored in a data unreceivable power flag of the wireless communication system according to the present embodiment.
FIG. 13 is a flowchart showing processing in a transmission process of the wireless communication system according to the present embodiment.
FIG. 14 is a flowchart showing transmission power setting derivation processing when the communication quality of the wireless communication system according to the present embodiment is stable.
FIG. 15 is a flowchart showing a reception process of the wireless communication system according to the present embodiment.
FIG. 16 is a schematic diagram illustrating a flow of a data communication procedure of the wireless communication system.
FIG. 17 is a schematic diagram of a request data packet in a wireless communication system.
FIG. 18 is a schematic diagram of a response data packet in a wireless communication system.
FIG. 19 is a schematic diagram illustrating an example of arrangement of wireless terminals in a wireless communication system.
FIG. 20 is a schematic diagram in an example of arrangement of wireless terminals in a wireless communication system.
FIG. 21 is a schematic diagram of an example of arrangement of wireless terminals in a wireless communication system.
[Explanation of symbols]
10 Radio terminal transceiver
11 Antenna
12 Transmitting amplifier (switching means)
13 Modulator
14 Attenuator
15 AGC circuit
16 Demodulator
17 RSSI circuit
18 Controller (control means)
19 Memory 1 circuit (memory means)
20 memory 2 circuit (memory means)

Claims (12)

In a wireless communication system comprising a control station and a plurality of wireless terminals wirelessly connected to the control station, and capable of direct communication between the wireless terminals,
The control station predicts a margin value up to the lower limit of received power that can be received by the control station, and transmits this to the plurality of wireless terminals as expected surplus received power information by broadcast,
The wireless terminal includes switching means for switching a transmission power level;
Receiving means for receiving the expected surplus received power information transmitted from the control station;
Communication quality A between the control station calculated based on the expected surplus received power information and n (n is an arbitrary natural number) communication quality b1, b2,... , Bn for storing,
Based on the communication quality A and the communication qualities b1, b2,..., Bn stored in the storage means, when the own wireless terminal transmits data to other wireless terminals from the expected surplus received power information, the control A control means for determining a transmission power level by setting a lower limit transmission power that is a lower limit of a transmission power setting at which data can be received at a station , and for switching the switching means so as to be the determined transmission power level;
A wireless communication system comprising: transmission means for transmitting data to another wireless terminal at the determined transmission power level. The communication quality A or communication quality b1, b2,.
The wireless communication system according to claim 1, further comprising communication quality information based on a reception result when transmission is performed with a known transmission power. The communication quality A or communication quality b1, b2,.
The information according to claim 1 or 2, further comprising information indicating a margin value up to a lower limit of receivable power of each wireless terminal calculated by the control station based on a reception result when transmission is performed with a known transmission power. Wireless communication system. The communication quality A or communication quality b1, b2,.
4. The wireless communication system according to claim 1, further comprising communication quality information based on a reception result when each wireless terminal performs transmission power control. 5.   5. The wireless communication system according to claim 4, wherein communication quality with respect to a reception result when each wireless terminal performs transmission power control includes sufficient / insufficient binary information. The margin value is included in the communication quality A, and the binary information is included in the communication quality A and communication quality b1, b2,.
When each wireless terminal transmits at a transmission power larger than the transmission power indicated by the margin value, the transmission power is controlled by the binary information included in the communication quality b1, b2,..., Bn.
When transmitting with a transmission power smaller than the transmission power indicated by the margin value, the transmission power is controlled by the binary information included in the communication quality A and the communication quality b1, b2,..., Bn. The wireless communication system according to claim 3 or 5. In a wireless communication method of a wireless communication system comprising a control station and a plurality of wireless terminals wirelessly connected to the control station, and capable of direct communication between the wireless terminals,
The control station predicts a margin value up to the lower limit of the received power that can be received by the control station, and broadcasts it to the plurality of wireless terminals as expected surplus received power information,
Each wireless terminal receives the expected surplus received power information transmitted from the control station,
Communication quality A between the control station and its own wireless terminal calculated based on the expected surplus received power information, and n communication qualities b1, b1 between its own wireless terminal and each of the other wireless terminals memorize b2, ..., bn,
Based on the communication quality A and communication quality b1, b2,..., Bn, when the wireless terminal transmits data to other wireless terminals from the expected surplus received power information, the control station can receive the data. A wireless communication method comprising: setting a lower limit transmission power which is a lower limit of transmission power setting, and performing transmission power control of the own wireless terminal. The communication quality A or communication quality b1, b2,.
8. The wireless communication method according to claim 7, further comprising communication quality information based on a reception result when transmission is performed with a known transmission power. The communication quality A or communication quality b1, b2,.
The information indicating a margin value up to a lower limit of receivable power of each wireless terminal calculated by the control station based on a reception result when transmitting with a known transmission power is included. Wireless communication method. The communication quality A or communication quality b1, b2,.
The wireless communication method according to claim 7, further comprising communication quality information based on a reception result when each wireless terminal performs transmission power control.   The radio communication method according to claim 10, wherein the communication quality for the reception result when each radio terminal performs transmission power control includes binary information that is sufficient / insufficient. The margin value is included in the communication quality A, and the binary information is included in the communication quality A and communication quality b1, b2,.
In each wireless terminal, when transmitting with a transmission power larger than the transmission power indicated by the margin value, the transmission power is controlled by the binary information included in the communication quality b1, b2,.
When transmitting with a transmission power smaller than the transmission power indicated by the margin value, the transmission power is controlled by the binary information included in the communication quality A and the communication quality b1, b2,..., Bn. The wireless communication method according to claim 9 or 11.

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