JP4881194B2 - Wireless communication system, wireless communication apparatus, and wireless communication method - Google Patents

Description

  The present invention relates to a radio communication system, a radio communication apparatus, and a radio communication method, and more particularly to a radio communication system for a radio ad hoc network, a radio communication apparatus constituting the radio ad hoc network, and a radio communication method applied to the radio ad hoc network.

  Currently, an ad hoc network in which a plurality of wireless communication devices are connected by a wireless link has been put into practical use. Since an ad hot network connects wireless communication apparatuses without interposing an access point, it is possible to flexibly and easily expand the coverage area of the system.

In wireless ad hoc networks, communication signal quality (referred to as signal error rate, noise, transmission rate, etc., hereinafter also referred to as wireless link quality) varies due to radio wave propagation distance, interference, and the like. For this reason, in a wireless ad hoc network, an optimum communication path is generally selected in consideration of the quality of a wireless link.
For example, Patent Document 1 is cited as a conventional technique for selecting a communication path in consideration of the quality of a radio link.
JP 2005-33557 A

By the way, a wireless ad hoc network has a function called carrier sense. Carrier sense refers to detecting in advance whether another wireless communication device is transmitting a signal before the wireless communication device transmits a signal on the network. According to the carrier sense, it is possible to avoid a signal collision by transmitting a signal to a wireless communication device from which another wireless communication device is transmitting a signal.
However, in a wireless ad hoc network, there is a problem that a state of a wireless communication apparatus that cannot transmit / receive communication signals may occur because carrier sense does not function mutually due to the influence of a radio wave propagation distance, an obstacle, and the like. Such a problem is called a hidden terminal problem (Hidden Termina1 Problem), and the relationship between wireless communication devices that cause the hidden terminal problem is called a hidden terminal relationship.

In the two wireless communication devices in the hidden terminal relationship, since carrier sense does not function effectively, it is possible that signals (packets) are transmitted simultaneously. If the wireless communication devices that are the transmission destinations of the signals of the two wireless communication devices are the same, a packet collision occurs in the wireless communication devices of the transmission destinations, and the link quality decreases due to a decrease in transmission speed. .
In Patent Document 1 described above, the communication path is selected in consideration of the transmission rate of the radio link using a metric indicating the quality of the radio link. The quality metric is a value indicating a traffic state such as a usable communication band or the signal quality of communication described above.

Such selection of a communication path using the quality metric of Patent Document 1 cannot sufficiently cope with the hidden terminal problem. Therefore, there is a possibility that packet collision due to the hidden terminal problem frequently occurs in the selected route, the delay time increases, and the data transmission speed decreases. Therefore, it can be said that the technique of Patent Document 1 still cannot sufficiently solve the hidden terminal problem.
The present invention has been made in view of these points, and an object of the present invention is to provide a wireless communication device system, a wireless communication device, and a wireless communication method that can select a route that is less affected by the hidden terminal problem in a wireless ad hoc network. And

  The communication system according to claim 1 described above is a wireless communication system in which a plurality of wireless communication devices establish a link with each other and communicate with each other through the link, and the wireless communication device includes a plurality of wireless communication devices. Of these, adjacent information receiving means for periodically receiving information related to adjacent wireless communication devices capable of direct communication, adjacent information storage means for storing information related to adjacent wireless communication devices received by the adjacent information receiving means, and the adjacent information storage A hidden terminal determining means for determining a wireless communication device in a hidden terminal relationship based on information stored by the means and information received by the adjacent information receiving means, and a hidden terminal by the hidden terminal determining means. A collision estimating means for estimating a probability of occurrence of a collision by a wireless communication device determined to be present; An adjacent station information processing unit that obtains an index of the communication characteristic of the link based on the determined collision occurrence probability, and a communication path based on the index of the communication characteristic of the link obtained by the adjacent station information processing unit It is characterized by controlling. According to such an invention, it is possible to compare the information on the adjacent wireless communication device received in the current cycle with the stored information on the adjacent wireless communication device. Further, based on the stored information and the received information, it can be determined whether or not both transmission sources are in a hidden terminal relationship. Furthermore, it is possible to estimate the probability of occurrence of a collision by the wireless communication apparatus determined to be a hidden terminal, and to determine the link quality based on the estimated collision rate. By selecting a link with good determined quality, it is possible to provide a wireless communication apparatus system that can select a path that is less affected by the hidden terminal problem in a wireless ad hoc network.

  The wireless communication device according to claim 2 is a wireless communication device that establishes a link with each other and communicates through the link, and from the adjacent wireless communication device that can directly communicate among the plurality of wireless communication devices, Neighboring information receiving means for periodically receiving information about the communication apparatus; neighboring information storing means for storing the information received by the neighboring information receiving means in association with the neighboring wireless communication apparatus that is the information transmission source; A hidden terminal determination unit that determines a wireless communication device in a hidden terminal relationship based on information stored by the adjacent information storage unit and information received by the adjacent information reception unit, and the hidden terminal determination unit A collision rate estimation means for estimating the probability of occurrence of a collision by a wireless communication device determined to be a hidden terminal by the collision rate estimation means, An adjacent station information processing unit that obtains an index of the communication characteristic of the link based on the determined collision occurrence probability, and a communication path based on the index of the communication characteristic of the link obtained by the adjacent station information processing unit It is characterized by controlling. According to such an invention, it is possible to compare the information on the adjacent wireless communication device received in the current cycle with the stored information on the adjacent wireless communication device. Further, based on the stored information and the received information, it can be determined whether or not both transmission sources are in a hidden terminal relationship. Furthermore, it is possible to estimate the probability of occurrence of a collision by the wireless communication apparatus determined to be a hidden terminal, and to determine the link quality based on the estimated collision rate. By selecting a link with good determined quality, it is possible to provide a wireless communication apparatus that can select a path that is less affected by the hidden terminal problem in a wireless ad hoc network.

  According to a third aspect of the present invention, in the wireless communication apparatus according to the second aspect of the present invention, the information received by the adjacent information receiving unit is the adjacent wireless communication of the first adjacent wireless communication apparatus that is the information transmission source. A second adjacent wireless communication device that is a transmission source of information stored in the adjacent information storage unit, including information on another adjacent wireless communication device that is a device and is not its own device. The first adjacent wireless communication device and the second adjacent wireless communication device are in a hidden terminal relationship if they do not match the first adjacent wireless communication device and do not match the other adjacent wireless communication device. It is characterized by determining. According to such an invention, it is possible to easily determine a hidden terminal by receiving information including another adjacent wireless communication device from the adjacent wireless communication device.

  According to a fourth aspect of the present invention, there is provided the wireless communication device according to the third aspect, wherein the collision rate estimator is configured by the data transmitted by the first adjacent wireless communication device and the second adjacent wireless communication device. The collision probability with the transmitted data is estimated based on at least the amount of data transmitted per unit time by the second adjacent wireless communication device. According to such an invention, it is possible to estimate the collision occurrence rate using the degree of reduction in the amount of transmitted data.

  According to a fifth aspect of the present invention, there is provided the wireless communication device according to the fourth aspect of the invention, wherein the information received by the adjacent information receiving means is a rate at which the link with the first adjacent wireless communication device transmits data. Including the error occurrence rate of the transmitted data, and the adjacent station information processing means determines the collision probability estimated by the collision rate estimation means, the speed at which the link transmits data, and the error occurrence rate of the transmitted data. Based on this, an index of the communication characteristic of the link is calculated. According to such an invention, it is possible to obtain an index of link communication characteristics such as a quality metric in consideration of a collision occurrence rate by a hidden terminal.

  According to a sixth aspect of the present invention, in the invention of the fifth aspect, the adjacent station information processing unit is configured to detect the collision probability estimated by the collision rate estimating unit, from the first adjacent wireless communication device. The communication of the link based on the speed at which the transmitted link transmits data, the error occurrence rate of the transmitted data, the speed at which the link transmits data in its own device, and the error occurrence rate of the transmitted data A characteristic index is calculated. According to such an invention, the bidirectional communication characteristics of the link can be evaluated, and the link quality can be more accurately evaluated.

The wireless communication method according to claim 7 is a communication method applied to a wireless communication device that establishes a link with each other and communicates through the link, and is adjacent wireless communication that can directly communicate among a plurality of wireless communication devices. An adjacent information receiving step for periodically receiving information related to the adjacent wireless communication device from the device; information received in the adjacent information receiving step; and an adjacent wireless communication device received and stored in a previous cycle. A hidden terminal determination step for determining a wireless communication device in a hidden terminal relationship based on information, and a collision rate estimation for estimating a probability of occurrence of a collision by the wireless communication device determined to be a hidden terminal in the hidden terminal determination step a method, based on the estimated collision probability in the collision rate estimation step, to give an indication of the communication characteristics of the link Characterized in that it comprises an adjacent station information processing step. According to such an invention, it is possible to compare the information on the adjacent wireless communication device received in the current cycle with the stored information on the adjacent wireless communication device. Further, based on the stored information and the received information, it can be determined whether or not both transmission sources are in a hidden terminal relationship. Furthermore, it is possible to estimate the probability of occurrence of a collision by the wireless communication apparatus determined to be a hidden terminal, and to determine the link quality based on the estimated collision rate. By selecting a link with good determined quality, it is possible to provide a wireless communication method capable of selecting a route that is less affected by the hidden terminal problem in a wireless ad hoc network.

  The present invention described above detects that the wireless communication device that has received the state announcement is a wireless communication device that is in a hidden terminal relationship with the adjacent wireless communication device, and easily identifies the wireless communication device that is a hidden terminal. be able to. In addition, it is possible to estimate the probability of occurrence of a collision by a hidden terminal and obtain an indicator of the communication characteristics of the radio link based on the probability of occurrence. Therefore, in a wireless ad hoc network where a hidden terminal exists, it is possible to select a wireless link that is not easily affected by the hidden terminal.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(System configuration)
FIG. 1 is a diagram for explaining a communication system according to an embodiment of the present invention. The illustrated communication system is a system that communicates via a wireless ad hoc network, and includes a plurality of wireless communication devices 101a to 101f that establish a link with each other and communicate with each other via wireless links 111 to 117. Yes. In the figure, the wireless communication device is shown as a personal computer (PC). However, the present embodiment is not limited to using a PC as the wireless communication device, and any device that functions as a wireless communication terminal device can be used. Any wireless communication device may be used.
In the illustrated wireless ad hoc network, wireless communication devices that communicate directly are referred to as adjacent wireless communication devices. A wireless link used by one wireless communication device for communication with an adjacent wireless communication device is referred to as an adjacent wireless link.

(Configuration of wireless communication device)
FIG. 2 is a functional block diagram for explaining the configuration of the wireless communication apparatus 101a. In the present embodiment, it is assumed that the plurality of wireless communication devices 101a to 101f have the same configuration. For this reason, in this embodiment, the illustration and description of the communication device 101a are replaced with the configurations of the other communication devices 101b to 101f.
However, the present embodiment is not limited to a configuration in which a wireless ad hoc network is configured by only the wireless communication device 101 having a similar configuration, and wireless communication devices having different configurations may be mixed.

In the present embodiment, the configuration mainly related to the present embodiment is illustrated and described. Therefore, the wireless communication devices 101a to 101f have a functional configuration (such as a power supply unit) that is not shown in the drawing, which is essential for the communication devices that form the wireless ad hoc network.
The wireless communication device 101a illustrated in FIG. 2 includes a wireless communication unit 201 that establishes a wireless link for the wireless communication devices 101a to 101f to communicate with each other. The wireless communication unit 201 periodically receives information related to the adjacent wireless communication device from the adjacent wireless communication device that can directly communicate among the plurality of wireless communication devices 101a to 101f.

In addition, the wireless communication device 101 a is hidden based on the storage unit 205 that stores the received information related to the adjacent wireless communication device, the information stored in the storage unit 205, and the information received by the wireless communication unit 201. A wireless communication device that is in a terminal relationship is determined, a probability of occurrence of a collision by the wireless communication device determined to be a hidden terminal is estimated, and an index (quality metric) of communication characteristics of the link is calculated based on the probability of occurrence of the collision. An adjacent station information processing unit 204 is provided.
In the present embodiment, communication characteristics refer to communication signal quality (signal error rate, noise, transmission speed, etc.). Further, the quality metric refers to an index of traffic state including signal quality and communication usable bandwidth.

  In addition, the wireless communication apparatus 101a includes a path control unit 203 that determines a communication path using a wireless link. The path control unit 203 selects a radio link having a good quality metric calculated by the adjacent station information processing unit 204 and determines a communication path. The packet transfer unit 202 transfers communication data as a packet according to the route (transfer route) determined by the route control unit 203.

  That is, the wireless communication device 101a receives a state announcement from the wireless communication unit 201 of another wireless communication device (for example, the wireless communication device 101b). The state announcement is information including information related to the wireless communication device 101b and the adjacent wireless link 111 that are adjacent wireless communication devices. The state announcement is received by the wireless communication unit 201 of the wireless communication apparatus 101a. The state announcement will be described in detail later.

  When the wireless communication device 101a receives the state announcement of the wireless communication device 101b, the adjacent station information processing unit 204 determines that the packet transmitted from the wireless communication device 101b is a hidden terminal problem based on the received state announcement. Is used to estimate the probability of collision with a packet transmitted by the wireless communication apparatus 101a. The estimation of the probability is performed based on the transmission rate per unit time of the wireless communication device 10b described in the state announcement and adjacent station information.

The adjacent station information processing unit 204 also determines the quality metric of the adjacent radio link based on the collision rate obtained by the estimation and the transmission rate and packet error rate of the adjacent radio link 111 described in the state announcement. Is calculated.
The storage unit 205 stores the collision probability with the adjacent wireless communication apparatus estimated by the adjacent station information processing unit 204 and the calculated quality metric of the wireless link, together with information included in the state announcement. In the present embodiment, the storage unit 205 stores the collision probability estimated by the adjacent station information processing unit 204 and the calculated quality metric as a table. This table is referred to as an adjacent station information table.

In the configuration described above, the wireless communication unit 201 functions as an adjacent information receiving unit, the storage unit 205 functions as an adjacent information storage unit, the adjacent station information processing unit 204 functions as a hidden terminal determination unit, a collision rate estimation unit, and an adjacent station information processing unit. To do.
FIG. 3 is a diagram for explaining a hardware configuration of the wireless communication apparatus 101 according to the present embodiment. The wireless communication apparatus 101 includes a wireless communication module 301 used for wireless communication, a CPU (Central Processing Unit) 302, a ROM (Read Only Memory) 303, and a RAM (Random Access Memory) 304. The wireless communication unit 201, the packet transfer unit 202, the route control unit 203, and the adjacent station information processing unit 204 illustrated in FIG. 2 function in the CPU 302 and the wireless communication module 301. The storage unit 205 functions in the ROM 303 and the RAM 304.

Next, each configuration described above will be described in more detail.
1 State Announcement FIG. 4 is a diagram for explaining a state announcement transmitted / received by the wireless communication unit 201, and shows a frame format of a packet transmitted as a state announcement.

In the frame format shown in the figure, ID information (ID = State Announcement) indicating that the packet is a state announcement, Length indicating the length of the packet, transmission speed of the adjacent wireless link, and wireless link performing packet communication Packet error rate, the amount of data transmitted by the wireless communication apparatus 101a per unit time (transmission rate per unit time), and address information of the adjacent wireless communication apparatus of the wireless communication apparatus 101a.
The state announcement is periodically unicast from each wireless communication device to the adjacent wireless communication device of the wireless communication device.

2 Adjacent Station Information Table FIG. 5 is a diagram illustrating an adjacent station information table of the wireless communication apparatus 101a. The illustrated adjacent station information table stores n adjacent wireless communication apparatuses and information on wireless links for connecting to the wireless communication apparatuses. Specifically, the transmission rate of the radio link, the packet error rate, the transmission rate, the collision rate due to the hidden terminal problem, and the quality metric of the radio link are stored in association with the ID (station ID) of each adjacent radio communication device. Yes.
In the present embodiment, a plurality of adjacent wireless communication devices recorded in the adjacent station information table are also referred to as members of the adjacent station information table.

3. Adjacent Station Information Processing Unit Next, processing performed by the adjacent station information processing unit 204 will be described. The adjacent station information processing unit 204 of the present embodiment detects a wireless communication device that is in a hidden terminal relationship with its own device. Moreover, the collision rate by the detected hidden terminal is estimated, and the quality metric of the adjacent radio link is calculated based on the estimated collision rate.

i. Determination of presence / absence of hidden terminal As shown in FIG. 1, the wireless ad hoc network includes a plurality of wireless communication devices. In the wireless ad hoc network illustrated in FIG. 1, the wireless communication device 101a receives state announcement packets from the wireless communication device 101b and the wireless communication device 101d. The storage unit 205 of the wireless communication apparatus 101a stores the received packet data in the adjacent station table in association with the wireless communication apparatuses 101b and 101d. FIG. 6 shows an adjacent station table of the wireless communication apparatus 101a.

In the present embodiment, the adjacent station information processing unit 204 of the wireless communication apparatus 101a will be described as estimating the packet collision rate.
FIG. 7 is a diagram showing a state announcement transmitted from the wireless communication apparatus 101a to the adjacent wireless communication apparatus. FIG. 7A shows a state announcement transmitted from the wireless communication apparatus 101a to the wireless communication apparatus 101b by unicast. Further, (b) shows a state announcement transmitted from the wireless communication apparatus 101a to the wireless communication apparatus 101d by unicast.

In any of the state announcements shown in FIGS. 7A and 7B, the speed at which the wireless link with the wireless communication apparatus 101a transmits data (transmission speed R), and the error occurrence rate of transmitted data ( Packet error rate PER), and the data transmission rate Tx per unit time of the wireless communication apparatus 101a.
Furthermore, the state announcement transmitted from the wireless communication apparatus 101a (first adjacent wireless communication apparatus) to the wireless communication apparatus 101b includes the adjacent wireless communication apparatus of the wireless communication apparatus 101a that is the transmission source of information, In addition, ID information of another adjacent wireless communication device 101d that is not the wireless communication device 101b (self device) is included. The state announcement transmitted from the wireless communication apparatus 101a to the wireless communication apparatus 101d includes a wireless communication apparatus 101d (self apparatus) that is an adjacent wireless communication apparatus of the wireless communication apparatus 101a that is the information transmission source. ID information of other adjacent wireless communication device 101b that is not) is included.

Note that the letters “ab” attached to the transmission speed and the like shown in the figure indicate that the wireless link is between the wireless communication apparatuses 101a and 101b. The letters “ad” indicate that the wireless link is between the wireless communication apparatuses 101a and 101d.
By receiving such a state announcement, the wireless communication device 101b and the wireless communication device 101d can communicate with the wireless communication device 101a that is the adjacent wireless communication device to an adjacent wireless communication device other than its own device (other adjacent wireless communication devices). ) Can be detected.

  Further, the wireless communication device 101b and the wireless communication device 101d receive the ID information of each adjacent wireless communication device as a state announcement from the adjacent wireless communication device including the wireless communication device 101a, and store it in the adjacent station table of the own device. ing. The adjacent station information processing unit 204 of the wireless communication device 101b and the wireless communication device 101d compares the detected ID information of the other adjacent wireless communication device with the ID information of the adjacent wireless communication device stored in the adjacent station table. . By this comparison, for example, the wireless communication device 101a (second adjacent wireless communication device) that is the transmission source of the information stored in the adjacent station table does not match the wireless communication device 101a (first adjacent wireless communication device), And when it does not correspond with the said other adjacent radio | wireless communication apparatus, it determines with both having a hidden terminal relationship.

That is, as described above, the wireless communication device 101a transmits the state announcement shown in FIGS. 7A and 7B to the wireless communication device 101b and the wireless communication device 101d. The wireless communication device 101b that has received the state announcement records the received state announcement along with the ID information of the wireless communication device 101a in the adjacent station information table of its own device.
As shown in FIG. 1, the wireless communication device 101b and the wireless communication device 101c are in the relationship of adjacent wireless communication devices. The wireless communication device 101b also receives the state announcement from the wireless communication device 101c. The received state announcement is stored in the adjacent station information table of the wireless communication apparatus 101b.

FIG. 8 shows an adjacent station information table of the wireless communication apparatus 101b. The members of the illustrated adjacent station information table are the wireless communication device 101a and the wireless communication device 101c. The adjacent station information processing unit 204 of the wireless communication apparatus 101b performs adjacent station information based on a state announcement periodically transmitted from the wireless communication apparatus 101a (not shown, but attached with ID information of the wireless communication apparatus 101a). The wireless communication device 101a is checked among the members of the table.
As a result of the check, since the wireless communication device 101a is a wireless communication device that has transmitted the state announcement, it is determined that it is not related to the hidden terminal.

Next, the adjacent station information processing unit 204 checks the wireless communication device 101c among the members by a state announcement periodically transmitted from the wireless communication device 101a. As a result of the check, it is determined that the wireless communication device 101c is not the wireless communication device that transmitted the state announcement.
The adjacent station information processing unit 204 further determines whether or not the wireless communication device 101c is another adjacent wireless communication device of the wireless communication device 101a. This determination can be made by determining whether or not the ID information of another adjacent wireless communication device included in the state announcement of the wireless communication device 101a matches the ID information of the wireless communication device 101c.

As a result of the determination, the adjacent wireless communication device 101c is not an adjacent wireless communication device of the adjacent wireless communication device 101a. In such a case, the wireless communication device 101b determines that the wireless communication device 101c has a hidden terminal relationship with the wireless communication device 101a.
Similarly, the wireless communication device 101d records the received state announcement in the adjacent station information table of the own device together with the ID information of the wireless communication device 101a. The wireless communication device 101d is adjacent to the wireless communication devices 101c, 101e, and 101f in addition to the wireless communication device 101a. Therefore, the members of the adjacent station information table of the wireless communication device 101d are the wireless communication devices 101a, 101c, 101e, and 101f. FIG. 9 shows an adjacent station information table of the wireless communication apparatus 101d.

  The adjacent station information processing unit 204 of the wireless communication apparatus 101d sequentially checks the members of the adjacent station information table according to the state announcement of the wireless communication apparatus 101a that is periodically transmitted. That is, first, the wireless communication device 101a among the members is checked, and it is determined that the wireless communication device 101a is not a hidden terminal because it is the wireless communication device that has transmitted the state announcement.

  Next, the wireless communication device 101c among the members is not the wireless communication device 101a that has transmitted the state announcement, and is not another adjacent wireless communication device of the wireless communication device 101a. It is determined that it is a hidden terminal. Similarly, the wireless communication devices 101e and 101f are also determined to be hidden terminals for the wireless communication device 101a.

ii Estimation of packet collision rate When the hidden terminal of the wireless communication apparatus 101a is detected, the adjacent station information processing unit 204 estimates the probability of collision caused by the presence of the hidden terminal (due to the hidden terminal problem or due to the hidden terminal). To do. Note that the collision due to the hidden terminal problem means that a packet transmitted by the wireless communication apparatus 101a and a packet transmitted by the wireless communication apparatus 101c serving as a hidden terminal collide in a common adjacent wireless communication apparatus.

  In this embodiment, the probability of collision due to the hidden terminal problem is estimated based on the transmission rate R of the wireless communication device determined to be a hidden terminal. For example, when the wireless communication device i is in a hidden terminal relationship with the wireless communication device 101a, the collision probability CR by the wireless communication device i is estimated by the following equation. Note that Txi in equation (1) is the transmission rate of the wireless communication device i.

Hereinafter, estimation of the probability of occurrence of a collision due to the hidden terminal problem will be described in more detail.
When it is determined that the wireless communication device 101a and the wireless communication device 101c are in the hidden terminal relationship, the adjacent station information processing unit 204 of the wireless communication device 101b performs wireless communication between the wireless communication device 101a and the wireless communication device 101b. The collision probability CR_ab by the communication device 101c is estimated as follows.

That is, the collision probability CR_ab estimated by Expression (1) is expressed as follows using the transmission rate of the wireless communication apparatus 101c.
CR_ab = TX_c Formula (2)
The collision probability estimated in the wireless communication apparatus 101b is recorded in the adjacent station information table of the wireless communication apparatus 101b shown in FIG.

As described above, the wireless communication device 101d determines that the wireless communication device 101a and the wireless communication devices 101c, 101e, and 101f are in a hidden terminal relationship. The occurrence probability CR_ad of the collision between the wireless communication device 101a and the wireless communication device 101d by the wireless communication devices 101c, 101e, and 101f is estimated by the following equation.
CR_ad = 1- (1-TX_c). (1-TX_e). (1-TX_f) Formula (3)
The collision probability estimated in the wireless communication apparatus 101d is recorded in the adjacent station information table of the wireless communication apparatus 101d shown in FIG.

iii Calculation of Quality Metric In this embodiment, the adjacent station information processing unit 204 calculates the quality metric based on the collision probability estimated as described above and the speed at which the wireless link transmits data (transmission speed R). To do.
That is, in the present embodiment, the radio link quality metric RM is calculated based on the collision rate estimated by the equation (2) or the equation (3). The calculation of the quality metric RM is realized by the following equation (4).

In Equation (4), R is the link transmission rate, PER is the packet error rate, and Bt is the data packet length. Oca is the overhead time required for channel access, and Op is the protocol overhead time. Both Oca and Op can be set in the arithmetic expression as constants.
RM = (Oca + Op + (Bt / R)) * (1 / (1-PER)) * (1 / (1-CR))
Formula (4)

  The wireless communication apparatus 101b calculates the quality metric RM_ab of the wireless link with the wireless communication apparatus 101a by substituting the collision rate CR_ab into the equation (4). The calculated quality metric RM_ab is expressed by the following equation (5). Note that R_ab and PER_ab in the expression (5) are both included in the state announcement shown in FIG.

RM_ab = (Oca + Op + (Bt / R_ab))
× (1 / (1-PER_ab))
X (1 / (1-CR_ab)) Formula (5)
The quality metric calculated in the wireless communication apparatus 101b is recorded in the adjacent station information table of the wireless communication apparatus 101b shown in FIG.

  Similarly, the wireless communication device 101d calculates the quality RM_ad of the wireless link with the wireless communication device 101a by substituting the collision rate CR_ad into the equation (4). The calculated quality metric RM_ad is expressed by the following equation (6). Note that R_ad, PER_ad, and Bt in equation (6) are all included in the state announcement shown in FIG.

RM_ad = (Oca + Op + (Bt / R_ad))
× (1 / (1-PER_ad))
× (1 / (1-CR_ad)) Formula (6)
The quality metric calculated in the wireless communication apparatus 101d is recorded in the adjacent station information table of the wireless communication apparatus 101d shown in FIG.

(Wireless communication device communication method)
FIG. 10 is a flowchart for explaining the communication method executed in this embodiment described above. The illustrated flowchart is mainly executed by the adjacent station information processing unit 204.
The wireless communication device (for example, the wireless communication device 101b) receives a state announcement (SANN) from the adjacent wireless communication device (for example, the wireless communication device 101a) by the wireless communication unit 201 (S1). The adjacent station information processing unit 204 sequentially checks the members of the adjacent station information table based on the received state announcement. If it is determined that the check has been completed for all members (S2: Yes), the process is terminated.

Hereinafter, a check procedure by the adjacent station information processing unit 204 will be described. In this description, it is assumed that the adjacent station information processing unit 204 of the wireless communication apparatus 101b checks the adjacent station information table shown in FIG. 8 based on the state announcement transmitted by the wireless communication apparatus 101a.
The adjacent station information processing unit 204 first checks the wireless communication device 101a among the members (S3). The check is performed based on the information received in step 1 and the information related to the adjacent wireless communication device received and stored in the previous cycle.

  Specifically, the adjacent station information processing unit 204 determines whether or not the member wireless communication apparatus 101a is the wireless communication apparatus 101a that has transmitted the state announcement. As a result, the wireless communication device 101a matches the wireless communication device that transmitted the state announcement (S3: Yes). Accordingly, the wireless communication device 101a determines that it is not a hidden terminal, and returns to determining whether the member check has been completed.

Next, the adjacent station information processing unit 204 checks the wireless communication device 101c among the members. The wireless communication device 101c is not the wireless communication device 101a (S2: No). Therefore, the adjacent station information processing unit 204 checks information on adjacent wireless communication devices other than the wireless communication device 101b included in the state announcement of the wireless communication device 101a.
The wireless communication device 101c determines whether it corresponds to another wireless communication device that is adjacent to the wireless communication device 101a and is not its own device (wireless communication device 101b) (S4). As shown in FIG. 7A, the other wireless communication device 101a is the wireless communication device 101d, not the wireless communication device 101c. Therefore, the adjacent station information processing unit 204 determines that the wireless communication device 101c does not correspond to another adjacent wireless communication device (S4: No), and the wireless communication device 101a and the wireless communication device 101c have a hidden terminal relationship. To do.

Then, the probability of collision caused by the hidden terminal is estimated (S5), and the quality metric of the radio link with the radio communication apparatus 101c is calculated using the estimated collision rate (S6). The estimated collision rate and the calculated quality metric are recorded in the adjacent station information table (S7). After the recording, it is determined again whether or not the check has been completed for all the members. If it is determined that the check has been completed (S2: Yes), it is prepared for the reception of the next state announcement.
In the above processing, Step 1 corresponds to an adjacent information reception step, Steps 3 and 4 correspond to hidden terminal determination steps, Step 5 corresponds to a collision rate estimation step, and Step 6 corresponds to an adjacent station information processing step.

In the present embodiment described above, the wireless communication device transmits, as a state announcement, ID information of another adjacent wireless communication device different from the transmission destination wireless communication device together with information such as the data transmission rate of the own device. Yes. Therefore, the wireless communication device that has received the state announcement can detect that there is a wireless communication device that is in a hidden terminal relationship with an adjacent wireless communication device, and can easily identify the wireless communication device that is a hidden terminal. .
And this embodiment can estimate the probability of occurrence of a collision based on the data transmission rate of the wireless communication device in the hidden terminal relationship, and can calculate the quality metric of the radio link based on the estimated rate of occurrence. . For this reason, in a wireless ad hoc network where a hidden terminal exists, it is possible to select a wireless link that is not easily affected by the hidden terminal.

(Modification)
The present embodiment is not limited to the configuration described above. That is, in the embodiment, the quality metric of the adjacent radio link is calculated in one communication control device. However, in this embodiment, for example, the quality metric of the wireless link between the wireless communication device 101a and the wireless communication device 101b is calculated with the value calculated with the wireless communication device 101a and the value calculated with the wireless communication device 101b. May be used to obtain a bidirectional quality metric of the wireless link 111.

  Note that the above-described bidirectional quality metric calculation may be executed by both the wireless communication apparatuses 101a and 101b. Moreover, you may perform either one of the radio | wireless communication apparatuses 101a and 101b. When the quality metric is performed by one of the wireless communication apparatuses 101a and 101b, the obtained quality metric is transmitted to the other, and the wireless communication apparatus that has received the transmitted quality metric stores it in the adjacent station information table of its own apparatus You may make it do.

Further, in the above-described embodiment, the quality metric of the adjacent radio link is calculated by substituting the transmission rate of the radio link, the packet error rate, and the estimated collision rate due to the hidden terminal problem into Equation (4). However, the present embodiment is not limited to such a configuration, and may be calculated using other physical quantities or other functions.
In addition to the transmission rate of the wireless link, the packet error rate, and the collision rate due to the hidden terminal problem, the present embodiment takes into account the time that the received packet is waiting in the queue of the wireless communication device. It may be calculated.

  The wireless communication system, the wireless communication apparatus, and the wireless communication method of the present invention described above are highly effective in increasing the data transmission efficiency by selecting a transmission path that is not easily affected by the hidden terminal in the wireless ad hoc network.

It is a figure for demonstrating the communication system of one Embodiment of this invention. It is a functional block diagram for demonstrating the structure of the radio | wireless communication apparatus of one Embodiment of this invention. It is a figure for demonstrating the hardware constitutions of the radio | wireless communication apparatus of one Embodiment of this invention. It is a figure for demonstrating the state announcement of one Embodiment of this invention. It is the figure which illustrated the adjacent station information table of one Embodiment of this invention. It is the figure which showed the adjacent station table of the radio | wireless communication apparatus 101a shown in FIG. It is the figure which showed the state announcement which the radio | wireless communication apparatus 101a shown in FIG. 1 transmits with respect to an adjacent radio | wireless communication apparatus. It is the figure which showed the adjacent station table of the radio | wireless communication apparatus 101b shown in FIG. It is the figure which showed the adjacent station table of the radio | wireless communication apparatus 101d shown in FIG. It is a flowchart for demonstrating the communication method performed in one Embodiment of this invention.

Explanation of symbols

101a to 101f Wireless communication devices 111 to 117 Wireless link 201 Wireless communication unit 202 Packet transfer unit 203 Path control unit 204 Adjacent station information processing unit 205 Storage unit 301 Wireless communication module 302 CPU
303 ROM
304 RAM

Claims (7)

A wireless communication system in which a plurality of wireless communication devices establish a link with each other and communicate through the link,
The wireless communication device
An adjacent information receiving unit that periodically receives information related to the adjacent wireless communication device from an adjacent wireless communication device that can directly communicate among the plurality of wireless communication devices;
Adjacent information storage means for storing information related to the adjacent wireless communication device received by the adjacent information receiving means;
A hidden terminal determination unit that determines a wireless communication device in a hidden terminal relationship based on information stored by the adjacent information storage unit and information received by the adjacent information reception unit;
A collision rate estimation means for estimating a probability of occurrence of a collision by a wireless communication device determined to be a hidden terminal by the hidden terminal determination means;
Based on the collision occurrence probability estimated by the collision rate estimation means, the adjacent station information processing means for obtaining an index of the communication characteristics of the link,
A wireless communication system, wherein a communication path is controlled based on an index of communication characteristics of the link obtained by the adjacent station information processing means. A wireless communication device that establishes a link with each other and communicates through the link,
An adjacent information receiving unit that periodically receives information related to the adjacent wireless communication device from an adjacent wireless communication device that can directly communicate among the plurality of wireless communication devices;
Adjacent information storage means for storing information received by the adjacent information receiving means in association with an adjacent wireless communication device that is an information transmission source; and
A hidden terminal determination unit that determines a wireless communication device in a hidden terminal relationship based on information stored by the adjacent information storage unit and information received by the adjacent information reception unit;
A collision rate estimation means for estimating a probability of occurrence of a collision by a wireless communication device determined to be a hidden terminal by the hidden terminal determination means;
Based on the collision occurrence probability estimated by the collision rate estimation means, the adjacent station information processing means for obtaining an index of the communication characteristics of the link,
A wireless communication apparatus that controls a communication path based on an index of communication characteristics of the link obtained by the adjacent station information processing means. The information received by the adjacent information receiving means includes information of another adjacent wireless communication device that is the adjacent wireless communication device of the first adjacent wireless communication device that is the transmission source of information and that is not its own device,
The hidden terminal determination unit is configured such that a second adjacent wireless communication device that is a transmission source of information stored in the adjacent information storage unit does not match the first adjacent wireless communication device, and the other adjacent wireless communication device 3. The wireless communication device according to claim 2, wherein if the communication device does not match, the wireless communication device determines that the first adjacent wireless communication device and the second adjacent wireless communication device are in a hidden terminal relationship. The collision rate estimation means includes
The collision probability between the data transmitted by the first adjacent wireless communication device and the data transmitted by the second adjacent wireless communication device is set to at least the amount of data transmitted per unit time by the second adjacent wireless communication device. The wireless communication apparatus according to claim 3, wherein estimation is performed based on the estimation. The information received by the adjacent information receiving means includes a speed at which the link with the first adjacent wireless communication device transmits data, an error occurrence rate of the transmitted data,
The adjacent station information processing means includes
The communication characteristic index of the link is calculated based on a collision probability estimated by the collision rate estimation unit, a speed at which the link transmits data, and an error occurrence rate of transmitted data. 4. A wireless communication device according to 4. The adjacent station information processing means includes
The collision probability estimated by the collision rate estimation means, the speed at which the link transmitted from the first adjacent wireless communication device transmits data, the error occurrence rate of transmitted data, and the link at the own device transmits data. 6. The wireless communication apparatus according to claim 5, wherein an index of communication characteristics of the link is calculated based on a transmission speed and an error occurrence rate of transmitted data. A communication method that is applied to a wireless communication device that establishes a link with each other and communicates through the link,
An adjacent information receiving step for periodically receiving information on the adjacent wireless communication device from an adjacent wireless communication device capable of direct communication among the plurality of wireless communication devices;
A hidden terminal determination step of determining a wireless communication device in a hidden terminal relationship based on the information received in the adjacent information reception step and information on the adjacent wireless communication device received and stored in the previous cycle;
A collision rate estimation step for estimating a probability of occurrence of a collision by the wireless communication device determined to be a hidden terminal in the hidden terminal determination step;
Based on the estimated collision probability in the collision rate estimation step, the radio communication method characterized by comprising, a neighboring station information obtaining an indication of the communication characteristics of the link.

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