JP2004289373A - Wireless communication system, wireless terminal device, and method for switching communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To seamlessly and flexibly switch the communication system of a wireless terminal device to the optimum communication system in the communication systems of a plurality of standards corresponding to the communication states. <P>SOLUTION: A control unit 82 monitors the communication states during wireless communication with an access point device 1 by a wireless part 81 of the wireless terminal device 2. And, it determines whether the communication system is switched. When it determines that the communication system is switchable to another communication system, it searches a communication target station for the wireless communication with the communication system different from the communication system in current use. When there is the communication target station for the wireless communication, for example, a 11b standard communication part 811 in current use is switched to another 11a standard communication part 812 so as not to interrupt the communication. By this, the wireless terminal device seamlessly and flexibly changes to the optimum communication system corresponding to the communication states. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless communication system such as a wireless LAN and a wireless terminal device thereof, and particularly to a communication method switching method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a wireless LAN system for performing wireless communication between an access point device (hereinafter referred to as an AP) connected to a wired LAN and a plurality of wireless terminal devices such as a portable personal computer having a wireless communication function has been developed. I have.
[0003]
In such a wireless LAN system, IEEE 802.11b (hereinafter referred to as 11b) and IEEE 802.11a (hereinafter referred to as 11b) as shown in the upper and middle parts of the table of FIG. These standards are generally used not only in different frequency bands, but also in transmission systems and communication speeds (transfer rates).
[0004]
In general, the 11b standard has a long radio wave range but a low communication speed, and the 11a standard has a high communication speed but a short radio wave range. In the near future, in addition to the above standards, a standard called IEEE802.11g (hereinafter referred to as 11g) shown in the lower part of the table in FIG. 8 will be established.
[0005]
The 11g standard has a property that is located between the 11b standard and the 11a standard, and aims at achieving both the reach of radio waves of the 11b standard and the communication speed of the 11a standard, and the communication speed is relatively high. In addition, the reach of radio waves is relatively long. Moreover, since the 11g standard is based on the 11b standard, it has a property of being highly interchangeable with the 11b standard, but it is generally considered that the effective speed is not as high as the 11a standard.
[0006]
Recently, as a wireless terminal device, a dual-mode compatible device capable of performing wireless communication in both the communication systems of the 11a standard and the 11b standard has begun to appear, and if this device is used, the user can switch the communication system and use it. In addition, 11g standard-compliant devices are dual mode compatible with the 11b standard and 11g standard from the beginning, and there is a strong opinion that 11b standard, 11g standard, and 11a standard multimode compatible devices will appear in the future.
[0007]
By the way, in a conventional wireless terminal device compatible with the dual mode, each of the communication systems of the 11b standard and the 11a standard operates independently, and to switch between these communication systems, a user manually switches or an AP of a communication partner. Has only to match the communication method on the wireless terminal side with the communication method specified by. However, a wireless terminal device capable of automatically selecting a communication speed and a channel according to a communication state among communication systems currently in use and capable of improving throughput has been already known (for example, Patent Document 1). 1).
[0008]
[Patent Document 1]
JP-A-2000-101596 (page 3-4, FIG. 1)
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional wireless terminal device, depending on the communication situation, the communication speed is changed over from the maximum communication speed of 54 Mbps of the 11a standard to the minimum communication speed of the It was not possible to automatically and seamlessly and flexibly change up to 1 Mbps to maintain an optimal communication state. Further, in the above-described conventional wireless terminal device, the communication condition becomes favorable during communication at the communication speed of, for example, 11 Mbps of the communication method of the 11b standard, and a situation may occur in which the communication method may be switched to 18 Mbps of the communication method of the 11a standard. However, the communication system was not automatically switched, and dynamic operation of the communication system could not be performed.
[0010]
The present invention has been made in order to solve the conventional problems as described above, and an object of the present invention is to seamlessly and flexibly switch to an optimal communication method among communication methods of a plurality of standards according to a communication situation. Wireless communication system, a wireless terminal device, and a communication system switching method capable of dynamically performing efficient communication with high throughput or stable communication with low throughput across multiple communication systems. Is to provide a way.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, according to a preferred embodiment of the present invention, a wireless station that performs wireless communication using one of a plurality of communication schemes between a communication target station and the communication target station. A wireless communication system having a terminal device, wherein the wireless terminal device monitors a communication status of a plurality of communication means corresponding to each of the plurality of communication methods, and a communication state currently being used, and Determination means for determining whether or not to switch, a search means for searching for a communication target station capable of wireless communication with a communication method different from the communication method of the communication means currently being used, and a communication method by the determination means If it is determined to switch, and if there is the communication target station capable of performing wireless communication by another search method by the search means, the communication means currently used is changed to correspond to the another communication method. And a switching means for switching the communication means.
[0012]
According to the present invention, during wireless communication with a communication target station, the wireless terminal device monitors the communication status of the currently used communication method and determines whether to switch the communication method, and as a result, for example, If it becomes disadvantageous for the communication system being used, it is determined that the communication system can be switched to another communication system. Further, the communication target station capable of performing wireless communication by a communication method different from the communication method of the communication means currently in use is searched, for example, in the background. As a result, when it is determined that switching is to be performed by another communication method, and the communication target station capable of performing wireless communication by another communication method exists, the communication unit currently in use corresponds to the another communication method. The communication means is switched so that the communication is not interrupted. Accordingly, the wireless terminal device can seamlessly and flexibly change to the optimal communication method according to the communication situation, and can operate the wireless communication system efficiently.
[0013]
In a preferred embodiment of the present invention, there is provided a wireless terminal device for performing wireless communication with a communication target station using any one of a plurality of communication systems, wherein each of the plurality of communication systems A plurality of communication means corresponding to, a communication state of the communication means currently being used, a determination means for determining whether to switch the communication method, and a communication method different from the communication method of the currently used communication means A search means for searching for the communication target station capable of wireless communication by the communication method; and the communication target station which is determined by the determination means to switch the communication method, and is capable of wireless communication by another communication method by the search means. Switching means for switching the communication means currently in use to the communication means corresponding to the other communication method.
[0014]
According to the present invention, during wireless communication with a communication target station, the wireless terminal device monitors the communication status of the currently used communication method and determines whether to switch the communication method, and as a result, for example, If it becomes disadvantageous for the communication system being used, it is determined that the communication system can be switched to another communication system. Further, the communication target station capable of performing wireless communication by a communication method different from the communication method of the communication means currently in use is searched, for example, in the background. As a result, when it is determined that the communication method is to be switched and the communication target station capable of performing wireless communication by another communication method is present, the communication means currently used is changed to the communication means corresponding to the another communication method. Switch so that communication is not interrupted. As a result, the wireless terminal device can further improve the communication throughput, or can seamlessly and flexibly change to an optimal communication method capable of performing more stable communication operation although the throughput is reduced.
[0015]
Further, in a preferred aspect of the present invention, it is preferable that the determination unit monitors a current communication rate and determines whether or not to switch to another communication method by comparing the communication rate with a predetermined rate reference value.
[0016]
According to the present invention, the wireless terminal device monitors the communication status by comparing the communication rate of the currently used communication method with a predetermined rate reference value, and according to the comparison result, It is determined whether to switch the communication method to another communication method. As a result, it is possible to switch to a higher-rate communication scheme or to switch to a lower-rate but stable communication scheme.
[0017]
In a preferred embodiment of the present invention, the determining means has an upper limit rate reference value as the rate reference value, and determines the current error rate if the current communication rate has reached the upper limit rate reference value, If the current error rate is equal to or less than the first error reference value, it is determined that the communication method is to be switched to a communication method capable of communicating at a high communication rate, and the search means is more than the communication method of the communication means currently in use. It is desirable to search for a communication target station that can communicate with a high communication rate communication method.
[0018]
According to the present invention, the wireless terminal device determines the current error rate if the current communication rate has reached the upper limit rate reference value, and determines whether the current error rate is equal to or less than the first error reference value. For example, even if communication is performed at the upper limit rate of the wireless communication system in use, the error rate is not so bad and there is a margin, so that it is determined that the communication method is switched to a communication method capable of communication at a high communication rate, and the communication means currently in use is determined. A communication target station that can communicate with a communication system having a higher communication rate than that of the communication system is searched. As a result, if there is a communicable communication target station, the communication system can be switched to a communication system with a high communication rate, and the communication throughput can be further improved.
[0019]
Further, in a preferred embodiment of the present invention, the determination means has a lower limit rate reference value as the rate reference value, and determines the current error rate if the current communication rate has reached the lower limit rate reference value. If the error rate is equal to or greater than the second error reference value, it is determined that the communication method is to be switched to a communication method capable of communicating at a low communication rate, and the search means is lower than the communication method of the communication means currently in use. It is desirable to search for a communication target station that can communicate with the communication system at the communication rate.
[0020]
According to the present invention, the wireless terminal device determines the current error rate if the current communication rate has reached the lower limit rate reference value, and determines whether the current error rate is equal to or greater than the second error reference value. For example, even if communication is performed at the lower limit rate of the wireless communication system in use, the error rate is poor and the communication quality is not sufficient, so that it is determined that the communication method is switched to a communication system capable of performing communication at a low communication rate, and the communication means currently in use is determined. Search for a communication target station that can communicate with a communication system with a lower communication rate than the communication system. As a result, if there is a communication target station capable of communication, the communication system can be switched to a communication system with a low communication rate, and communication throughput is reduced, but stable communication with good communication quality can be performed.
[0021]
In a preferred embodiment of the present invention, the switching means, when switching to the communication means of another communication method, if the received electric field strength obtained via the communication means of the other communication method is at a sufficient level, It is desirable to switch to communication means of another communication method.
[0022]
According to the present invention, in the case where the currently used communication means is switched to another communication means, there is a communication target station capable of performing wireless communication by this other communication method, and the communication means of this another communication method is used. Only when the received electric field strength obtained through the communication is at a sufficient level, in order to switch to the communication means of this another communication method, switching to another communication method is performed, but the electric field strength is low and communication becomes unstable. It is possible to prevent the communication situation from deteriorating or, in the worst case, from being unable to maintain the communication.
[0023]
Further, according to a preferred embodiment of the present invention, there is provided a method for switching the communication method when performing wireless communication with a communication target station using any one of a plurality of communication methods, A communication step of monitoring a communication status and determining whether or not to switch the communication method; a search step of searching for the communication target station capable of wireless communication by a communication method different from the current communication method; A switching step of switching a current communication method to another communication method when it is determined that the method is to be switched and the communication target station capable of performing wireless communication by another communication method is present in the search step.
[0024]
According to the present invention, during wireless communication with a communication target station, the communication status of the currently used communication method is monitored to determine whether or not to switch the communication method, and the communication that can perform wireless communication in another communication method is performed. Search for the target station. As a result, when there is the communication target station capable of performing wireless communication by another communication method, the current communication method is switched to this another communication method. As a result, the communication scheme with the communication target station can be changed seamlessly and flexibly according to the communication status.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a configuration of the wireless communication system according to the first embodiment of the present invention.
[0026]
In this embodiment, the wireless communication system is a wireless LAN, so-called multi-mode access point device (base station) 1 corresponding to three communication systems of 11b, 11a and 11g standards, and this access point device 1 It is assumed that the AP 1 is connected to a wired LAN (not shown) with the wireless terminal device 2 that supports the multi-mode of the 11b, 11a, and 11g standards and performs wireless communication with the AP.
[0027]
Although only one wireless terminal device 2 is shown in FIG. 1 for convenience of explanation, the access point device 1 normally performs wireless communication with a plurality of wireless terminal devices 2 and establishes a wireless LAN. Building. Although a plurality of access point devices are usually installed, only one access point device is shown here.
[0028]
FIG. 2 is a block diagram showing a schematic configuration of the access point device 1 shown in FIG. The access point device 1 includes an 11b standard wireless transmission / reception unit 3b that performs wireless communication with the wireless terminal device 2 using the 11b standard communication method, and an 11a standard wireless transmission / reception unit 3a that performs wireless communication with the wireless terminal device 2 using the 11a standard communication method. And an 11g standard wireless transmission / reception unit 3g for performing wireless communication with the wireless terminal device 2 using the 11g standard communication system, and control for controlling these 11b, 11a, 11g standard wireless transmission / reception units 3b, 3a, 3g and the wired LAN transmission / reception unit 3. Unit 4, a wired LAN transmitting and receiving unit 5 for transmitting and receiving signals to and from the wired LAN 30 via the interface 6, an interface 6 for connecting the wired LAN 30 and the wired LAN transmitting and receiving unit 5, and an antenna for transmitting and receiving radio waves of the 11b standard communication system. 7b, an antenna 7a for transmitting and receiving radio waves of the 11a standard communication system, and an antenna 7a for transmitting and receiving radio waves of the 11g standard communication system. And it has a container 7g.
[0029]
The above-described access point device 1 is configured to be able to perform wireless communication with the wireless terminal device 2 by using three types of communication systems using one of the three types of communication systems. A configuration may be employed in which three access point devices capable of wireless communication with the wireless terminal device 2 only by the communication method are separately installed, and the communication methods conform to the above three types of communication methods.
[0030]
FIG. 3 is a block diagram showing a schematic configuration of the wireless terminal device 2 shown in FIG. The wireless terminal device 2 is configured by mounting a wireless communication card 8 on a personal computer 9. The wireless communication card 8 transmits and receives information to and from the wireless unit 81 that performs wireless communication with the access point device 1. The control unit 82 controls the wireless unit 81 to perform wireless communication control, a memory 83 storing programs and various data necessary for operating the control unit 82, An electric field intensity measuring unit 84 for measuring the electric field intensity, a packet error measuring unit 85 for measuring the packet error rate during wireless communication of the wireless unit 81, and the wireless communication card 8 via the PCI interface 91 on the personal computer 9 side. It has a PCI interface 86 connected to the personal computer 9 and an antenna 87 for transmitting and receiving wireless signals. There.
[0031]
Here, the wireless unit 81 includes an 11b standard communication unit 811 that performs wireless communication using the 11b standard communication system, an 11a standard communication unit 812 that performs wireless communication using the 11a standard communication system, and 11g that performs wireless communication using the 11g standard communication system. It has a standard communication unit 813, and these communication units 811, 812, and 813 are switched by the control unit 82, and perform wireless communication with the access point device 1 by any one communication method.
[0032]
Next, the operation of the present embodiment will be described. For example, a wireless terminal device 2 in which a wireless communication card 8 is attached to a mobile personal computer 9 performs wireless data communication with the access point device 1 to configure a wireless LAN. The access point device 1 is connected to the wired LAN 30 and relays data transmission and reception between the wired LAN 30 and the wireless terminal device 2.
[0033]
During wireless communication with the access point device 1, the wireless terminal device 2 may move to, for example, positions L1, L2, and L3 from the access point device 1, as shown in FIG. As described above, when the distance between the wireless terminal device 2 and the access point device 1 is different, the communication status changes according to the distance. Therefore, the wireless terminal device 2 monitors the current communication status, and automatically performs control for optimally switching the communication speed and the communication method based on the result.
[0034]
FIGS. 4 and 5 are flowcharts showing a control procedure for switching the communication speed and communication method of the wireless terminal device 2. However, the flowcharts of FIGS. 4 and 5 are connected by (A) and (B) in the drawings.
[0035]
In FIG. 4, the control unit 82 of the wireless terminal device 2 monitors the current communication rate, and when the communication rate reaches the upper limit, performs a switching process (S2 to S8) to a communication method capable of high-rate communication. Conversely, if the current communication rate has reached the lower limit, switching processing (S10 to S17) to a communication method capable of stable communication at a low rate is executed; otherwise, the current communication is performed. The communication rate is appropriately changed in the system while maintaining the system (S18).
[0036]
Specifically, the control unit 82 of the wireless terminal device 2 sets the current communication rate to the upper limit value of the communication rate, that is, the maximum rate or the switching rate specified from the personal computer 9 during wireless communication with the access point apparatus 1. Is determined (step S1). If so, the process proceeds to step S2 and subsequent steps, that is, the high-rate communication system switching process, and if not, the process proceeds to step S9 in FIG.
[0037]
If the current communication rate is the maximum rate or the specified switching rate, the control unit 82 determines whether the packet error rate of the current communication method measured by the packet error measurement unit 85 is equal to or less than a threshold (predetermined communication quality). Is determined) (step S2). Here, the determination of the packet error rate is based on the fact that the communication state is poor in the current communication method, and in a situation where high-rate communication cannot be expected, the communication rate is changed in the method while maintaining the current communication method. It is more desirable. By performing the determination based on the packet error rate in this manner, it is possible to prevent the communication system from being unnecessarily changed.
[0038]
If the packet error rate is equal to or less than the threshold in step S2, a background scan is performed (step S3) to determine what kind of communication type access point device (network) exists around the wireless terminal device 2. Explore. In this case, as the background scan, communication units corresponding to communication systems other than the current communication system are sequentially activated to check whether beacon signals of each communication system can be received. When the beacon signal is successfully received, it is determined that an access point device of the communication method exists. Further, when the beacon signal can be received, the received electric field strength at that time is measured using the electric field strength measuring unit 84, and the search is performed by associating the access point of each communication method found by the search with the received electric field strength. A list is created and stored in the memory 83.
[0039]
Then, based on the search list, it is determined whether or not there is another access point device of another communication system that can expect a higher throughput than the currently used communication system among the searched access point devices. (Step S4).
[0040]
Here, when the wireless terminal device 2 is currently performing wireless communication with the access point device 1 at the maximum rate of 11 Mbps in the 11b standard communication method using the 11b standard communication unit 811 of the wireless unit 81, the surroundings are It is assumed that an access point device that performs communication using the communication method and the 11g standard communication method is found. In this case, it is determined that there is another access point device (network) of the communication system that can expect high throughput by the process of step S4, and it is determined to switch to a higher-rate communication system, for example, communication of the 11a standard communication system. Is performed (step S5). In this example, it is determined that the wireless communication with the access point device 1 is performed by switching from the 11b standard communication system to the 11a standard communication system.
[0041]
When it is determined to switch to the new communication method as described above, it is determined whether or not the electric field strength of the communication method of the switching destination measured in step S3 is at a level at which there is no problem in communication (step S6). If the level is not a problem, the control unit 82 controls the wireless unit 81 to switch to the selected new communication method and continue wireless communication with the access point device 1 (step S8). That is, the control unit 82 turns off the communication unit currently used, activates the communication unit corresponding to the new communication system, and switches the communication system. By confirming the electric field strength of the switching destination in this way, it is possible to prevent beforehand switching to a communication method in which communication cannot be maintained.
[0042]
However, when adopting the new communication method, if the electric field strength of the switching destination is at a level where communication is problematic due to weakness, another high-rate communication method among the communication methods found by the above background scan is used. Is determined (step S7), and if there is a high-rate communication method, the process returns to step S5, and a decision is made to switch the high-rate communication method to a new communication method. The same is true.
[0043]
On the other hand, if it is determined in step S2 that the current packet error rate is not equal to or less than the threshold value, and if it is determined in step S4 that there is no other communication method that can expect a higher throughput than the present, as a result of the background scan, Further, when it is determined in step S7 that there is no other high-rate communication system network, the process proceeds to step S9 in FIG. In the process of step S9, the control unit 82 determines whether the current communication rate is the lower limit value of the communication rate, that is, the minimum rate or the specified switching rate. If not, the control unit 82 proceeds to step S18 and proceeds to step S18. After the communication method is maintained, the communication rate is changed in accordance with the communication state in the communication method, and the process returns to step S1.
[0044]
Here, at first, the 11a standard communication system was selected as the high-rate communication system. However, when it is determined in step S6 that the electric field strength is too weak to adopt the 11a standard communication system, another high-rate communication system is used. It is assumed that the 11g standard communication system is selected as the communication system. In this case, if it is determined in step S6 that the electric field strength in the 11g standard communication system is not a problem, the process proceeds to step S8 to change the communication system between the wireless terminal device 2 and the access point device 1 from the 11b standard communication system to the 11g standard communication system. It will switch to the method.
[0045]
Even if the communication between the wireless terminal device 2 and the access point device 1 is switched from, for example, the 11b standard communication system to the 11a standard communication system in the processes of steps S2 to S8, the control unit 82 of the wireless terminal device 2 naturally , The processing shown in FIG. At this time, the control unit 82 can increase the communication speed to, for example, 24 Mbps based on the packet error rate or the like in the 11a standard communication system in the above-described step S18, and perform communication using the 11b standard communication system. It is possible to improve the throughput as compared with the case where it has been performed.
[0046]
Next, when it is determined that the current communication rate is not the maximum rate or the specified switching rate (step S1), the control unit 82 determines that the current communication rate is the minimum rate that is the lower limit of the communication rate or the specified switching rate. It is determined whether or not the rate is a rate (step S9), and if so, the process proceeds to step S10 and subsequent steps; otherwise, the process proceeds to step S18.
[0047]
If the current communication rate is the minimum rate or the specified switching rate, the control unit 82 determines whether the packet error rate of the current communication method measured by the packet error measurement unit 85 is equal to or greater than a threshold (step S10). ). The reason for making the determination based on the packet error rate is that if the packet error rate of the current communication method is not bad, it is desirable to maintain the current communication method and change the communication rate in that method. By performing the determination based on the packet error rate in this manner, it is possible to prevent the communication system from being unnecessarily switched.
[0048]
If the packet error rate is equal to or higher than the threshold in step S10, it is determined whether the electric field intensity of the current communication method measured by the electric field intensity measuring unit 84 is equal to or lower than the threshold (step S11). As a result, when the electric field strength is equal to or less than the threshold value, a background scan is performed by the same method as in step S3 (step S12), and an access point device (network) of any communication method is provided around the wireless terminal device 2. Whether there is another access point device of another communication system that has a lower throughput than the currently used communication system but can expect strong stable operation for long-distance communication. Is determined (step S13).
[0049]
Here, when the wireless terminal device 2 is currently performing wireless communication with the access point device 1 at a minimum rate of 6 Mbps using the 11g standard communication system using the 11g standard communication unit 813 of the wireless unit 81, It is assumed that the access point device 1 that performs communication using the 11a standard communication system and the 11b standard communication system is found in the vicinity when the communication is about to be cut off when is less than or equal to the threshold. Since the 11b standard communication system is determined to be a communication system that can be expected to operate stably at a throughput lower than the above 6 Mbps, the control unit 82 replaces the current 11g standard communication system with the 11b standard communication system for lower-rate and long-distance communication. (Step S14).
[0050]
In adopting the new communication method as described above, it is determined whether the electric field strength of the switching destination measured at the time of the background scan in step S12 is at a level that does not cause a problem in communication (step S15), and there is no problem in communication. If the communication level is at the level, the control unit 82 controls the radio unit 81 to switch to the selected new communication method (that is, turns off the communication unit of the current communication method and turns on the communication unit of the new communication method). ), Wireless communication with the access point device 1 is continued (step S17).
[0051]
However, when adopting a new communication method, if the electric field strength is weak and the communication is at a problematic level, it is more suitable for long-distance communication at a lower rate than other communication methods found by the above background scan. It is determined whether or not there is a communication system (step S16). If there is a communication system that meets the conditions, the process returns to step S14 to determine that this low-rate communication system is a new communication system. The processing is the same as above.
[0052]
On the other hand, if it is determined in step S10 that the current packet error rate is not greater than or equal to the threshold, and if it is determined in step S11 that the current field strength is not less than or equal to the threshold, stable operation is expected at step S13 with a lower throughput than the current. If it is determined that there is no other available communication method, and if it is determined in step S16 that there is no other low-rate communication method network, the process proceeds to step S18. In step S18, the control unit 82 performs a normal communication rate change process in the current communication method, and returns to the process in step S1.
[0053]
Even if the communication between the wireless terminal device 2 and the access point device 1 is switched from, for example, the 11g standard communication system to the 11b standard communication system in the processing of steps S10 to S17, the control unit 82 of the wireless terminal device 2 naturally , The processing shown in FIG. At this time, the control unit 82 can appropriately reduce the communication speed in the 11b standard communication system to, for example, 2 Mbps in the above-described step S18, and can improve the throughput as compared with the case where the communication is performed in the 11g standard communication system. Can be performed, but a stable communication operation can be performed.
[0054]
According to the present embodiment, for example, when the wireless terminal device 2 moves away from the access point device 1 and the distance increases to L1, L2, and L3, the current processing is performed by the processing of step S18 described above. In the communication method, the transfer rate is reduced to keep the packet error below the threshold. However, when the packet rate is reduced to the minimum rate and the electric field strength is below the threshold and the so-called unstable state where communication is likely to be cut off, the transmission rate is longer at a lower rate. If there is an access point device that can communicate with a communication method suitable for distance communication, the communication with the access point device 1 is switched to this communication method and the communication operation with the access point device 1 is continued in a stable operation state by the processing of steps S10 to S17 described above. can do.
[0055]
Further, when the wireless terminal device 2 approaches the access point device 1 and the distance decreases to L3, L2, and L1, the packet error is reduced within a range equal to or less than the threshold value within the current communication method. If the transfer rate is maximized within the communication method, if there is an access point device that can communicate at a higher rate and a communication method suitable for short-range communication, the above-described steps S2 to S2 are performed. By the processing of S8, it is possible to continue the communication with the access point device 1 by maximizing the throughput by switching to this communication method, and depending on the communication state, the communication method of the plurality of standards is switched over. Optimal communication can be performed seamlessly and flexibly by automatically changing the communication method.
[0056]
Note that the communication status varies not only with the distance between the access point device 1 and the wireless terminal device 2 but also with various factors such as surrounding buildings. Therefore, it is needless to say that the communication can be optimally performed by automatically and seamlessly changing the communication method.
[0057]
(Embodiment 2)
FIGS. 6 and 7 are flowcharts showing a communication system switching process of the wireless terminal device according to the second embodiment of the present invention. However, the flowcharts of FIGS. 6 and 7 are connected by (A) and (B) in the drawings. Further, since the configuration of the present embodiment is the same as that of the above-described first embodiment, the description of the configuration and operation of each unit having the same configuration will be omitted, and the characteristic portions of the operation will be described below. explain.
[0058]
The difference between the switching process of the communication method of the wireless terminal device 2 of the present embodiment and the switching process of the first embodiment shown in FIGS. 4 and 5 is considered in the first embodiment (step S11 in FIG. 5). This is the point that the electric field strength is not considered. However, other processes are the same as those of the first embodiment.
[0059]
That is, when it is determined in step S29 that the current communication rate is the minimum rate or the specified switching rate, the control unit 82 of the wireless terminal device 2 determines whether the current packet error rate measured by the packet error measurement unit 85 is It is determined whether the packet error rate is equal to or higher than a threshold value (whether the communication quality is not a predetermined communication quality) (step S30). If the packet error rate is not equal to or higher than the threshold value (if the predetermined communication quality is maintained), the process proceeds to step S37. On the other hand, if the packet error rate is equal to or higher than the threshold (if the predetermined communication quality is not maintained), the process proceeds to step S31 for performing a background scan. The processing after this step S31 is the same as that of the first embodiment, and the throughput is lower than the current one. However, if there is an access point device of a communication scheme that can maintain a predetermined communication quality, the current communication scheme is changed to this communication. Processing for switching to the system is performed, but the detailed description is omitted because it is the same as that of the first embodiment.
[0060]
According to the present embodiment, when the packet error rate is equal to or higher than the threshold value in spite of the fact that the transfer rate has been reduced to the minimum rate in the current communication method, maintaining this communication method as it is, a predetermined communication quality is obtained. If an access point device that can communicate with a communication method that can lower the packet error rate at a lower rate than the current communication method is searched for by the background scan, the current communication method cannot be secured. Communication with the access point device 1 at a transfer rate even lower than the minimum rate of the communication method before the switching, so that the packet error rate is equal to or less than the threshold value and communication is performed in a state where predetermined communication quality is secured. You can continue. Other effects are the same as those of the first embodiment.
[0061]
In the above-described embodiment, the case where the communication method is switched between the access point connected to the wired LAN and the wireless terminal device has been described. However, the present invention is not limited to this. The present invention can be applied to a case where the communication method is switched. That is, the present invention can be applied to a case where it is desired to appropriately switch the communication system in an environment where there are communication target stations using different communication systems.
[0062]
In the above embodiment, the case where IEEE802.11a, IEEE802.11b, and IEEE802.11g are used as the communication method has been described. However, the present invention is not limited to this, and is applicable to the case where other communication methods are used. I can do it.
[0063]
Furthermore, in the above-described embodiment, the packet error rate is used as the error rate, but another error rate may be used as long as the communication quality can be determined.
[0064]
Furthermore, in the above-described embodiment, the current communication rate is monitored, and the process is switched to the communication method switching process based on the result. However, the present invention is not limited to this, and any one that can grasp the current communication status is used. If necessary, other parameters may be monitored.
[0065]
Further, in the above-described embodiment, a case has been described in which, after determining the communication rate and the packet error rate, a background scan is performed to search for a communicable base station. However, the present invention is not limited to this. Before determining the error rate, or in parallel with those processes, a search may be made for a base station with which communication is possible.
[0066]
Furthermore, the present invention is not limited to the above-described embodiment, and can be embodied in other various forms in specific configurations, functions, operations, and effects without departing from the gist thereof.
[0067]
【The invention's effect】
As described above in detail, according to the present invention, the wireless communication terminal monitors the communication status during wireless communication with the communication target station, and determines whether to switch to another communication method, Search for a communication target station that can communicate with another communication method, and if such a communication target station exists, switch the current communication method to another communication method, It is possible to seamlessly and flexibly switch to an optimal communication method among communication methods of a plurality of standards, thereby enabling efficient communication with a high throughput or wireless communication with a low throughput but a stable communication to a communication method of a plurality of standards. It can be performed dynamically across straddles.
Further, according to the present invention, the wireless terminal apparatus compares the communication rate of the currently adopted communication scheme with a predetermined rate reference value, and determines the communication scheme currently being used by another communication scheme according to the comparison result. By determining whether or not to switch to the system, it is possible to switch to a higher-rate communication system, or to seamlessly and flexibly switch to a lower-rate but stable communication system in which stable communication can be expected.
Further, according to the present invention, the wireless terminal device determines the current error rate if the current communication rate has reached the upper limit rate reference value, and determines that the current error rate is equal to or less than the first error reference value. Then, if there is a communication target station that can communicate, the communication system can be switched to a communication system with a high communication rate, and the communication throughput can be further improved.
Further, according to the present invention, the wireless terminal device determines the current error rate if the current communication rate has reached the upper limit rate reference value, and determines that the current error rate is equal to or greater than the second error reference value. Then, if there is a communication target station capable of communication, the communication system is switched to a communication system with a low communication rate, and communication throughput is reduced, but stable communication with good communication quality can be performed.
Further, according to the present invention, when switching the communication means being used to another communication means, this switching is performed only when the reception electric field strength obtained through the communication means of the other communication method is at a sufficient level. By switching to the communication means of another communication method, the communication method is switched to another communication method, but the electric field strength is low, the communication becomes unstable, and the communication situation is deteriorated, or the communication is maintained in the worst case. Can be prevented.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a configuration of a wireless communication system according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a schematic configuration of the access point device shown in FIG.
FIG. 3 is a block diagram showing a schematic configuration of the wireless terminal device shown in FIG. 1;
FIG. 4 is a flowchart illustrating a control procedure for switching a communication method of the wireless terminal device.
FIG. 5 is a flowchart showing a control procedure for switching a communication method of the wireless terminal device.
FIG. 6 is a flowchart illustrating a communication system switching process of the wireless terminal device according to the second embodiment of the present invention.
FIG. 7 is a flowchart illustrating a communication system switching process of the wireless terminal device according to the second embodiment of the present invention.
FIG. 8 is a table listing wireless LAN communication schemes.
[Explanation of symbols]
1 access point device
2 Wireless terminal device
3b 11b standard wireless transceiver
3a 11a standard wireless transceiver
3g 11g standard wireless transceiver
4, 82 control unit
5 Wired LAN transceiver
6 Interface
7b, 7a, 7g, 87 antenna
8 Wireless communication card
9 Personal computer
30 Wired LAN
81 Radio section
83 memory
84 Electric field strength measurement section
85 Packet error measurement unit
86, 91 PCI interface

Claims (7)

A wireless communication system having a communication target station and a wireless terminal device that performs wireless communication using any one of a plurality of communication methods between the communication target station and the communication target station,
The wireless terminal device,
A plurality of communication means corresponding to each of the plurality of communication methods,
Monitoring means for monitoring the communication status of the communication means currently in use, and determining whether to switch the communication method,
Search means for searching for the communication target station capable of wireless communication in a communication method different from the communication method of the communication means currently in use,
When it is determined that the communication method is to be switched by the determination means, and the search target means that there is the communication target station capable of wireless communication in another communication method, the communication means currently used is changed to the another communication method. Switching means for switching to the corresponding communication means. A wireless terminal device that performs wireless communication with a communication target station using any one of a plurality of communication systems,
A plurality of communication means corresponding to each of the plurality of communication methods,
Monitoring means for monitoring the communication status of the communication means currently in use, and determining whether to switch the communication method,
Search means for searching for the communication target station capable of wireless communication in a communication method different from the communication method of the communication means currently in use,
When it is determined that the communication method is to be switched by the determination means, and the search target means that there is the communication target station capable of wireless communication in another communication method, the communication means currently used is changed to the another communication method. Switching means for switching to the corresponding communication means. The wireless terminal according to claim 2, wherein the determination unit monitors a current communication rate and determines whether to switch to another communication method by comparing the communication rate with a predetermined rate reference value. apparatus. The determining means has an upper limit rate reference value as the rate reference value, and determines a current error rate if the current communication rate has reached the upper limit rate reference value. If it is equal to or less than the error reference value, it is determined that the communication method is switched to a communication method capable of communicating at a high communication rate,
The search means,
The wireless terminal device according to claim 3, wherein a search is made for a communication target station that can communicate with a communication system having a higher communication rate than a communication system of the communication unit currently in use. The determination means has a lower limit rate reference value as the rate reference value, and determines a current error rate if the current communication rate has reached the lower limit rate reference value, and determines that the error rate is a second error rate. If the value is equal to or more than the reference value, it is determined that the communication method is switched to a communication method capable of communicating at a low communication rate,
The search means,
4. The wireless terminal device according to claim 3, wherein a search is made for a communication target station that can communicate with a communication system having a lower communication rate than the communication system of the communication unit currently in use. The switching means,
When switching to the communication means of another communication method, if the received electric field strength obtained through the communication means of the other communication method is at a sufficient level, switching to the communication means of the other communication method is characterized in that The wireless terminal device according to claim 2. A communication method switching method when performing wireless communication using any one of a plurality of communication methods with a communication target station,
A monitoring step of monitoring the current communication status and determining whether to switch the communication method, and a searching step of searching for the communication target station capable of wireless communication in a communication method different from the current communication method
A switching step of switching a current communication method to another communication method when it is determined that the communication method is to be switched by the determination step and the communication target station capable of performing wireless communication by another communication method is present by the search step; A switching method comprising:

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