The disclosure of Japanese Patent Application No. 2010-138874, filed on Jun. 18, 2010, is incorporated herein by reference.
1. Field of the Invention
The present invention relates to multiple-channel wireless communications capable wireless communications systems including wireless relay devices and wireless terminal devices, to the wireless terminal devices included in the wireless communications systems, and to communications-channel switching methods executed by the wireless communications systems.
2. Description of the Background Art
In wireless communications systems that include wireless relay devices and wireless terminal devices carrying out multiple-channel wireless communications, technology in which the wireless relay devices switch the channel used for communications with the wireless terminal devices according to the occurrence rate of received-signal noise has been known to date (cf., for example, Japanese Laid-Open Patent Publication No. 2004-180106 and Japanese Laid-Open Patent Publication No. 10-42353).
However, the process of switching channels used for communications between the wireless relay devices and the wireless terminal devices as performed in the conventional technology is not necessarily satisfactory in terms of accuracy and efficiency. A need is therefore felt to improve over the present situation the channel switching process in order to minimize decline in the speed of communications between the wireless relay devices and the wireless terminal devices.
An object of the present invention is to make available a wireless communications system including a wireless relay device and a wireless terminal device that perform multiple-channel wireless communications, the wireless terminal device itself, and a communications-channel switching method executed by the wireless communications system, capable of efficiently minimizing, with a high level of accuracy, decline in the speed of communications between the wireless relay device and the wireless terminal device.
The present invention is directed to: a wireless communications system including a wireless relay device and a wireless terminal device capable of multiple-channel wireless communications; and the wireless terminal device thereof. In order to attain the aforementioned objects, the wireless terminal device of the wireless communications system according to the present invention includes: a throughput measurement section for measuring a throughput of communications with the wireless relay device through a first channel used for communications with the wireless relay device; a determination section for determining whether the throughput measured by the throughput measurement section is greater than or equal to a predetermined level; a terminal-device-side channel switching section for switching the first channel used for communications with the wireless relay device, to a second channel different from the first channel if the determination section determines that the throughput is not greater than or equal to the predetermined level; and a terminal-device-side communications section for transmitting to the wireless relay device switching destination channel information indicating the second channel to which the first channel is switched by the terminal-device-side channel switching section. Further, the wireless relay device of the wireless communications system according to the present invention includes: a relay-device-side communications section for receiving the switching destination channel information from the wireless terminal device; and a relay-device-side channel switching section for switching, to the second channel, the first channel used for communications with the wireless terminal device, according to the switching destination channel information received by the relay-device-side communications section.
The throughput measurement section further measures throughput of communications with the wireless relay device through the second channel in response to the switching from the first channel to the second channel by the terminal-device-side channel switching section. The terminal-device-side channel switching section switches the second channel used for communications with the wireless relay device to a third channel different from the first and the second channels if the determination section determines that the throughput of the second channel is not greater than or equal to the predetermined level. In the present invention, these process steps are repeatedly performed until the throughput becomes greater than or equal to the predetermined level.
Preferably, in a case where the relay-device-side communications section transmits response data to the wireless terminal device through the second or the third channel, in response to the switching from the first channel to the second channel or the third channel by the relay-device-side channel switching section, if the terminal-device-side communications section does not receive the response data through the second or the third channel within a predetermined time period, the terminal-device-side channel switching section switches, to the first channel, the second or the third channel used for communications with the wireless relay device.
Further, it is preferable that the determination section determines that the throughput measured by the throughput measurement section is not greater than or equal to the predetermined level if the ratio of the throughput measured by the throughput measurement section, relative to a throughput upper limit preestablished between the wireless terminal device and the wireless relay device, is less than a predetermined threshold value
The process steps performed by the wireless communications system can be implemented as a channel switching method for switching channels used for wireless communications between a wireless relay device and a wireless terminal device. In the channel switching method, the wireless terminal device carries out steps of: measuring throughput of communications between the wireless relay device and the wireless terminal device through a first channel used for communications with the wireless relay device; determining whether the throughput measured is greater than or equal to a predetermined level; and switching the first channel used for communications between the wireless relay device and the wireless terminal device to a second channel different from the first channel if the throughput is determined to be not greater than or equal to the predetermined level; and transmitting to the wireless relay device switching destination channel information indicating the second channel to which the first channel is switched in the switching step. The wireless relay device carries out steps of: receiving switching destination channel information from the wireless terminal device; and switching to the second channel the first channel used for communications with the wireless terminal device, according to the switching destination channel information.
Further, the channel switching method may be realized in a form of a program for executing each step described above. Furthermore, the program may be stored in a non-transitory computer-readable storage medium.
The present invention is applicable to, for example, a communications device for performing communications including wireless communications over a communications network. These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The wireless device 110 is connected to the terminal PC 120 such as a personal computer which is a client device of the wireless LAN. The access point 200 is connected to the Internet INT. The terminal PC 120 can be connected to the Internet INT by wireless communications between the access point 200 and the wireless device 110.
Further, the wireless device 110 includes: an indicator section 13 for indicating predetermined information to a user; and a button section 15 which may be pressed by a user. The indicator section 13 is implemented as, for example, a colored light-emitting element such as a LED (light emitting diode). Functions of the indicator section 13 and the button section 15 will be described below.
The wireless device 110 may be any device which has a function of relaying communications between the terminal PC 120 and the access point 200. Therefore, examples of the wireless device 110 include, in addition to a dedicated communications relay device, a mobile telephone, a tablet terminal, a game machine, a printer, and a digital camera each having a wireless LAN function. Further, the wireless communications system 1000 may include a plurality of the access points 200, and a plurality of the wireless devices 110. Moreover, the configuration of the wireless communications system 1000 is not limited to a configuration in which the access point 200 is connected to the Internet INT. The configuration of the wireless communications system 1000 may be a configuration in which the access point 200 is connected to a WAN (Wide Area Network), another access point, or a switching hub.
Next, configurations of the wireless device 110 and the terminal PC 120 according to the present embodiment will be described in detail with further reference to
The wireless device 110 includes: a wireless device control section 130; two wireless communications circuits 111 and 112; a USB (Universal Serial Bus) controller 115; and a USB port 103. The wireless device control section 130 is connected to each of the wireless communications circuits 111 and 112, the USB controller 115, the indicator section 13, and the button section 15.
The wireless device control section 130 is configured as a CPU (Central Processing Unit) and/or a memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory), which are not shown. The wireless device control section 130 controls the entirety of the wireless device 110. The wireless device control section 130 functions as a communications control section 131, a throughput measurement section 132, a determination section 133, and a channel switching section 134, by the CPU executing firmware and/or a computer program stored in the memory.
The communications control section 131 controls the wireless communications circuits 111 and 112, and the USB controller 115, to perform data transfer between the wireless device 110, and a communications device such as the terminal PC 120 and the access point 200 which are connected to the wireless device 110. In the present embodiment, the communications control section 131 communicates by using the LLD2 (link layer discovery and diagnostics) protocol which is a Layer 2 protocol. The wireless device 110 exchanges messages with the communications device, and obtains information about the communications device such as a MAC address (media access control address), according to the LLD2 protocol.
The throughput measurement section 132 measures a throughput of communications between the wireless device 110 and the access point 200. The determination section 133 determines whether a channel used for wireless communications between the wireless device 110 and the access point 200 is to be switched, based on the throughput measured by the throughput measurement section 132. The channel switching section 134 switches a channel used for the wireless communications with the access point 200, according to the result of the determination made by the determination section 133. Specific operations of the throughput measurement section 132, the determination section 133, and the channel switching section 134 will be described below in description for a channel switching process.
The wireless communications circuits 111 and 112 are wireless LAN interfaces including the antennas 11 and 12, respectively, and amplifiers (not shown). The wireless communications circuits 111 and 112 each modulate radio wave to be transmitted and demodulate received radio wave, according to an instruction from the wireless device control section 130. For example, the wireless communications circuits 111 and 112 each generate a transmission signal based on transmission data to be transmitted to the access point 200. Specifically, the wireless communications circuits 111 and 112 divides transmission data received from the wireless device control section 130, and generate two sequences of transmission signals corresponding to the two antennas 11 and 12, respectively. The radio waves to be transmitted, which represent two sequences of transmission signals generated, are simultaneously outputted in the same frequency band from the two antennas 11 and 12. Furthermore, the wireless communications circuits 111 and 112 generate reception data based on reception signals which are received through the antennas 11 and 12 from the access point 200. Specifically, the wireless communications circuits 111 and 112 each estimate a transmission matrix for a transmission path between the access point 200 and the wireless device 110, based on distortion between direct wave and reflected wave which are received through the two antennas 11 and 12. The wireless communications circuits 111 and 112 separate and reproduce, from the received radio wave, the two sequences of original transmission signals transmitted from the access point 200 by using the transmission matrix, and combines the two sequences of the reproduced signals, to generate reception data.
The USB controller 115 controls communications between the wireless device control section 130 and a USB device which is connected to the USB port 103 in compliance with the USB standard. In the present embodiment, the terminal PC 120 is connected to the USB port 103 via the USB cable 102.
The terminal PC 120 includes: a CPU 121; a RAM (Random Access Memory) 122; a ROM (Read Only Memory) 123; a display unit 125; an operation section 127; a USB controller 129; and a USB port 104. The CPU 121, the RAM 122, the ROM 123, the display unit 125, the operation section 127, and the USB controller 129 are connected to each other via a bus 101.
The CPU 121 loads a computer program stored in the ROM 123 or an external storage unit (not shown) such as a hard disk drive, into the RAM 122 which is a main storage unit, and executes the computer program to control each component of the terminal PC 120.
The display unit 125 is implemented as an output interface such as a liquid crystal display. The operation section 127 is implemented as an input interface such as a mouse and a keyboard. The USB controller 129 controls communications between the terminal PC 120 and a USB device connected to the USB port 104. In the present embodiment, the wireless device 110 is connected to the USB port 104 via the USB cable 102.
The wireless device 110 and the terminal PC 120 may be connected to each other via a LAN such as a wired LAN or a wireless LAN, or via a bus using a bus cable, as well as via a USB using the USB cable 102 describe above.
Next, a configuration of the access point 200 according to the present embodiment will be described in detail with further reference to
The AP control section 210 is configured as a CPU and/or a memory such as an EEPROM, which are not shown, and controls the entirety of the access point 200. The AP control section 210 functions as an AP-side communications control section 211 and an AP-side channel switching section 214, by the CPU executing firmware and/or a computer program stored in the memory.
The AP-side communications control section 211 controls the wireless communications circuits 221 and 222, to perform data transfer between the access point 200 and the wireless device 110. Further, the AP-side communications control section 211 performs data transfer to and from a router (not shown) connected to the communications port 231, in order to allow exchange of information between the access point 200 and a communications device (not shown) through the Internet INT. In the present embodiment, the AP-side communications control section 211 uses the LLD2 protocol, similarly to the wireless device 110. Therefore, the access point 200 exchanges messages with the wireless device 110 in compliance with the LLD2 protocol. When the access point 200 receives a CH switching request described below from the wireless device 110, the AP-side channel switching section 214 switches a channel used for wireless communications with the wireless device 110 to a channel designated in the CH switching request.
The wireless communications circuits 221 and 222 are wireless LAN interfaces which include antennas 21 and 22, respectively, and amplifiers (not shown). The wireless communications circuits 221 and 222 each modulate radio wave to be transmitted, and demodulate received radio wave, according to an instruction from the AP control section 210. The wireless communications circuits 221 and 222 have the same functions and configurations as the wireless communications circuits 111 and 112, respectively, of the wireless device 110, and each generate transmission signal and reception data for wireless communications according to the MIMO system.
In the communications according to the MIMO system, a transmission matrix for a transmission path is estimated based on distortion between direct wave and reflected wave of a transmission signal. Therefore, influence of an obstacle in the transmission path can be reduced in the wireless communications. However, even in the communications according to the MIMO system, when, for example, a device which generates noise in a frequency band used for wireless communications is provided, a sufficient communications speed for communications between the wireless device 110 and the access point 200 may not be obtained in some cases. In this case, it is preferable that the frequency band used for the wireless communications is changed to a band in which influence of noise is small, to perform communications. Therefore, the wireless device 110 according to one embodiment of the present invention performs a channel switching process described below.
Firstly, when the wireless device 110 detects a predetermined operation, the wireless device 110 performs a MAC address obtaining process for obtaining MAC addresses from all the communications devices connected to the wireless device 110 (
In the MAC address obtaining process, the communications control section 131 of the wireless device control section 130 transmits a message, Discovery message, to all the devices connected to the wireless device 110 (
When the MAC address obtaining process is completed, and the MAC address of the access point 200 is obtained, the wireless device 110 performs a throughput calculation process for calculating a throughput of communications between the wireless device 110 and the access point 200 (
In the throughput calculation process, the communications control section 131 of the wireless device control section 130 transmits a message, Echo message, to the access point 200 (
With every exchange of Echo message, the throughput measurement section 132 of the wireless device control section 130 measures the communications time t required for transmitting and returning Echo message one time, and stores the communications times t1, t2, . . . , tn for n times. Communications time in the present embodiment is the period from when the communications control section 131 starts dividing data representing Echo message so as to generate a transmission signal, to when a process of reproducing, from the received radio wave, the returned Echo message is completed.
In a case where the communications control section 131 does not receive a returned Echo message from the access point 200 when a predetermined time has elapsed after transmission of Echo message to the access point 200, it is determined that Echo message has been lost in the transmission path. The communications control section 131 transmits Echo message anew (
When Echo message exchanges have been performed n times, the throughput measurement section 132 calculates, as Echo-message response rate, a ratio (=m/n×100) of the number m of times (m represents a natural number) the returned Echo message from the access point 200 has been received, relative to the number n of times Echo message has been transmitted. The throughput measurement section 132 determines (
On the other hand, when Echo message response rate is determined to be greater than or equal to the predetermined value (
In the present embodiment, an exemplary case in which the throughput measurement section 132 calculates the throughputs in a MAC layer. However, the throughput measurement section 132 may calculate the throughputs in a layer different from the MAC layer, such as an IP (Internet Protocol) layer, a TCP (Transmission Control Protocol) layer, or a PHY (physical) layer. When the process steps as described above have been performed, the throughput calculation process is completed.
When the effective throughput Ve is obtained, and the throughput calculation process is completed, the determination section 133 determines whether a channel used for communications between the wireless device 110 and the access point 200 is to be switched, based on the effective throughput Ve (
The determination section 133 may determine whether a channel is to be switched, in various manners as well as a manner in which the effective rate R is used. For example, the determination section 133 may compare the effective throughput Ve with a threshold value which is preestablished for each settable linking speed, and determines whether a channel is to be switched, according to whether the effective throughput Ve is greater than the threshold value. Alternatively, the determination section 133 may compare the effective throughput Ve with a fixed threshold value regardless of the linking speed, and determines whether a channel is to be switched.
When the effective rate R is determined to be greater than or equal to the threshold value Th (
The wireless device 110 may have a function of indicating, on the indicator section 13, that the effective rate R is less than the threshold value Th. Further, the wireless device 110 may perform the channel setting process when pressing of the button section 15 by a user is detected after it is indicated on the indicator section 13 that the effective rate R is less than the threshold value Th.
In the channel setting process, the channel switching section 134 of the wireless device control section 130 determines a switching destination of the channel used for the communications with the access point 200 (
When the switching destination channel is determined, the communications control section 131 firstly transmits, to the access point 200, a CH switching request which contains information about the switching destination channel (
On the other hand, when the access point 200 receives the CH switching request from the wireless device 110, the AP-side channel switching section 214 of the access point 200 controls the wireless communications circuits 221 and 222, to switch from the original channel, to the switching destination channel designated in the CH switching request (
When the wireless device control section 130 receives the CH switching response from the access point 200 (
When the wireless device control section 130 does not receive the CH switching response from the access point 200 even if the wireless device control section 130 waits for the predetermined time period (
For example, the following causes may be assumed when the wireless device 110 cannot receive the CH switching response from the access point 200. Specifically, the CH switching request may not reach the access point 200 due to, for example, the switching destination channel including a noise source. Although the CH switching request reaches the access point 200, a channel is not switched in the access point 200 due to, for example, weather radar being detected in the switching destination channel. Even if the wireless device 110 has difficulty in communications with the access point 200 through the switching destination channel due to these causes, the switching destination channel can be automatically restored to the original channel. Thus, the communications with the access point 200 can be continued again through the original channel. When the process steps as described above have been performed, the channel setting process is completed.
When, in the channel setting process, the original channel is switched to the switching destination channel, or the original channel is determined to be continuously used, the wireless device 110 performs the throughput calculation process again (
When the channel setting process (
The original channel, the switching destination channel, and another unused switching destination channel of the present embodiment correspond to a first channel, a second channel, and a third channel, respectively, of claims. Further, the communications control section 131, the AP-side communications control section 211, the channel switching section 134, and the AP-side channel switching section 214 of the present embodiment correspond to a terminal device-side communications section, a relay device-side communications section, a terminal device-side channel switching section, and a relay device-side channel switching section, respectively, of claims.
As described above, in the wireless communications system 1000 according to one embodiment of the present invention, the wireless device 110 measures a throughput of communications with the access point 200, and when the throughput is less than a predetermined level, a channel used for communicating with the access point 200 is switched. Therefore, decline in the speed of communications between the wireless device 110 and the access point 200 can be prevented. For example, even when a channel used for communications with the access point 200 has its throughput reduced due to noise being received from a noise source such as a microwave oven, or due to the channel being used for a wireless terminal device belonging to another network, the channel to be used can be switched to another channel to make communications. Therefore, reduction in throughput can be prevented.
Conventionally, a wireless LAN system is known which switches a channel used for communications with a wireless terminal device according to strength (may be also referred to as received signal strength indicator: RSSI) of radio wave received from the wireless terminal device by a wireless relay device. However, even the conventional wireless LAN system cannot easily detect for noise according to the strength of the received radio wave, when radio wave received by the access point includes noise from a noise source. On the other hand, since the wireless device 110 switches a channel used for communications with the access point 200, according to a level of throughput measured by the wireless device 110, the wireless communications system 1000 according to one embodiment of the present invention can directly link reduction in throughput with switching of channel, thereby enabling reduction in throughput to be effectively prevented.
Modification 1
The configuration of the wireless terminal device according to the embodiment as shown in
Further, for example, as shown in
Modification 2
In the embodiment described above, an exemplary configuration in which the wireless terminal device includes the indicator section 13 and the button section 15 is described. The indicator section 13 and the button section 15 are not essential for performing the channel switching process. In particular, when the indicator section 13 and the button section 15 are eliminated from the configuration shown in
Modification 3
In the embodiment described above, as shown in
Modification 4
In the embodiment described above, as shown in
Modification 5
According to the embodiment described above, in the throughput calculation process shown in
Modification 6
According to the embodiment described above, in the channel setting process shown in
Modification 7
In the embodiment described above, the wireless device 110 and the access point 200 communicate with each other according to the LLD2 protocol. However, the wireless device 110 and the access point 200 may be configured to communicate with each other by using another layer 2 protocol, or may be configured to communicate with each other by using a Layer 3 or higher protocol such as the TCP/IP or the FTP (file transfer protocol). When the LLD2 protocol is used, obtaining of the MAC address of the connected device is relatively easy, so that communications for which a connected device is designated can be easily performed.
Modification 8
In the embodiment described above, the wireless device 110 is configured to automatically perform the channel setting process in the channel switching process when the effective rate R is less than the threshold value Th. However, the wireless device 110 may be configured to confirm with a user whether the channel setting process is to be performed. Specifically, the wireless device 110 may be configured such that, when the effective rate R is less than the threshold value Th, the wireless device 110 indicates, on the indicator section 13, that the effective rate R is less than the threshold value Th, and the channel setting process is performed when the wireless device 110 detects pressing of the button section 15 by a user. Further, the wireless device 110 may be configured to perform the channel setting process as necessary when pressing of the button section 15 by a user is detected, regardless of the effective rate R.
In the embodiment described above, the CPU loads, into the RAM, firmware or a computer program stored in the ROM or EEPROM, and executes the firmware or the computer program, to realize each component of the wireless terminal device. However, each component of the present invention may be realized by hardware or software as necessary. Further, when a portion or the entirety of the functions of the present invention is realized by software, the software (computer program) may be stored in a computer-readable storage medium, and provided. In the present invention, examples of the computer-readable storage medium include an internal storage device of a computer such as various types of RAMs and ROMs, and an external storage device, such as a hard disk, secured to the computer, as well as a portable storage medium such as a flexible disk and a CD-ROM.
While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It will be understood that numerous other modifications and variations can be devised without departing from the scope of the invention.
Number | Date | Country | Kind |
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2010-138874 | Jun 2010 | JP | national |