TWI487397B - Channel selection method, channel selector and network connecting apparatus - Google Patents

Description

Channel selection method, channel selector and network connection device

The invention relates to a channel selection method, in particular to a channel selection method, a channel selector and a network connection device, which are suitable for wireless local area network connection and can dynamically and automatically find the best working channel and avoid mutual interference. .

Direct Sequence Spread Spectrum (DSSS) is a method for radio frequency modulation in the unlicensed 2.4 GHz ISM (Industrial Scientific Medical, Industrial, Scientific, Medical) band, which can be used for wireless USB, 802.11b/g /a (commonly known as Wi-Fi, Wireless Fidelity, Wireless Fidelity) and 802.15.4 (called ZigBee, Group Bee). The Wi-Fi network defines 11 channels in the 2.412 GHz to 2.462 GHz band, and the ZigBee network divides the 2.405 GHz to 2.48 GHz into 16 channels, wherein each network has a channel with a low channel frequency. Max provides an incremental channel number.

ZigBee technology is a short-range, low-complexity, low-power, low-data-rate, low-cost, high-capacity wireless sensor network technology. It is mainly suitable for services with small data flow, such as automatic control and remote control. In the field of monitoring and other fields, the purpose is to meet the wireless networking and control of small and inexpensive devices. Compared to existing wireless communication technologies, ZigBee technology is the lowest power and cost technology.

In contrast to ZigBee technology, WiFi is a long-distance, high-complexity, high-power, high-data rate (up to 54Mbps), high-cost wireless network. Road technology. Currently, it is widely used in wireless local area networks, and is very convenient for accessing the Internet, and is suitable for the market of schools, commercial buildings or home networks.

Since ZigBee and WiFi each have distinct features, and many features are complementary. Therefore, as the market demand for low-rate applications continues to grow, the possibility of Zigbee and Wi-Fi systems coexisting is growing. However, since both of them mainly work in the 2.4 GHz ISM band, mutual interference will inevitably occur. If the communication quality is poor, the network connection device is often required to retransmit and cannot transmit the data efficiently. If the command/receive response information cannot be transmitted immediately, the operation performance will be degraded and the power of the network connection device will be wasted. Therefore, how to dynamically and automatically find the best working channel and avoid mutual interference to improve the operation efficiency of the network connection device and avoid the waste of electric energy is the biggest problem at present.

Therefore, one of the objects of the present invention is to provide a channel selection method and a channel selector that use a software to memorize the number of error retransmissions of each channel and a frequency hopping judgment mechanism to switch channels according to transmission efficiency, so that interference can be selected. The smallest working channel.

Another object of the present invention is to provide a network connection device that can select a working channel with better communication quality to avoid waste of power caused by erroneous retransmission.

Therefore, the present invention provides a channel selection method, which is suitable for determining a working channel for communication by the network from a plurality of candidate channels of a network, comprising the following steps: (A) reading another network for communication One channel, and According to the channel that the other network communicates, the channel that overlaps the other network for communication is marked in a channel list of the candidate channels on which the network is recorded to determine the network. a candidate channel, and the candidate channels do not overlap the channel in which the other network communicates, wherein the highest data transmission rate of the other network is greater than the highest data transmission rate of the network; (B) the network Each candidate channel of the road evaluates the communication quality of the channel, and selects the candidate channel corresponding to the communication quality of the preferred channel as the working channel; (C) switches to the working channel for communication by the network; Transmitting a packet to monitor the number of times the packet is retransmitted; (E) deciding whether to update the working channel based on the number of retransmissions of the packet; and (F) deciding to update the working channel to be outside the current working channel The candidate channel evaluates the communication quality of the channel, and selects the candidate channel corresponding to the communication quality of the preferred channel as the updated working channel; wherein the number of the candidate channels of the network is less than the supportable transmission of the network The total number of channels.

In addition, the present invention provides a channel selector, which is applicable to a network connection device for coupling a first network and a second network, where the first network corresponds to at least one first channel, the first The second network corresponds to the plurality of second channels, and the channel selector comprises: a marking unit, reading the at least one first channel that the first network communicates, and the communication according to the first network a first channel, in the second network candidate channel list of the second channels in which the second network is recorded, marking which second channels overlap the first network to communicate with the at least one first a channel to determine a plurality of candidate channels in the second channel, and the determined candidate channels do not overlap the at least one first channel in which the first network communicates, wherein The highest data transmission rate of the first network is greater than the highest data transmission rate of the second network; an evaluation unit estimates the channel communication quality for each of the candidate channels to select the candidate channel corresponding to the preferred channel communication quality. a working channel for the network connection device to communicate with the second network; and a monitoring unit, wherein the network connection device transmits a packet to the second network via the working channel, the monitoring unit monitors The number of times the network connection device retransmits the packet to determine whether to enable the evaluation unit to update the working channel; wherein, when the monitoring unit causes the evaluation unit to update the working channel, the evaluation unit is other than the current working channel The candidate channel evaluates the communication quality of the channel, and selects the candidate channel corresponding to the communication quality of the preferred channel as the updated working channel; wherein the number of the candidate channels is less than the total number of the second channels.

Furthermore, the present invention provides a network connection device, which is adapted to be coupled to a first network and a second network, the first network corresponding to a first channel, and the second network corresponding to a plurality of second channels The network connection device includes: a first transceiver unit for communicating with the first network via the first channel; and a second transceiver unit for communicating with the second network via a working channel And a processor electrically connected to the first transceiver unit and the second transceiver unit, further comprising: a channel selector, having: a marking unit, reading the first channel of the first network for communication, And marking, according to the first channel that is communicated by the first network, which second channel overlaps the first network candidate channel list of the second channels in which the second network is recorded a first channel that is communicated by a network to determine a plurality of candidate channels in the second channels, and the determined candidate channels do not overlap The first channel that communicates with the first network, wherein a highest data transmission rate of the first network is greater than a highest data transmission rate of the second network; an evaluation unit that evaluates channel communication for each of the candidate channels Quality, the candidate channel corresponding to the communication quality of the preferred channel is selected as the working channel; and a monitoring unit monitors the number of times the second transceiver unit retransmits a packet on the working channel to determine whether to make the evaluation unit Updating the working channel; wherein, when the monitoring unit causes the evaluation unit to update the working channel, the evaluation unit evaluates channel communication quality for the candidate channels other than the current working channel, and selects the candidate corresponding to the preferred channel communication quality The channel is treated as an updated working channel; wherein the number of candidate channels is less than the total number of the second channels.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention.

Before the present invention is described in detail, it is noted that in the following description, similar elements are denoted by the same reference numerals.

First preferred embodiment

Referring to FIG. 1, a first preferred embodiment of the network connection device 300 of the present invention is adapted to couple a first network 100 and a second network 200. The first network 100 corresponds to a plurality of first channels that can support transmission, and the plurality of first wireless devices c1 in the first network 100 can jointly use one of the first channels to wirelessly connect to the network connection device 300. Similarly, the second network 200 corresponds to a plurality of second channels that can support transmission, and the plurality of second wireless channels in the second network 200 The device c2 can use one of the second channels in common to wirelessly connect to the network connection device 300. Therefore, the first wireless device c1 and the second wireless device c2 are able to transfer data to each other.

Preferably, the first network 100 of the embodiment is a Wi-Fi wireless area network, the second network 200 is a ZigBee wireless area network, and the network connection device 300 is a Wi-Fi ZigBee network connection device. The first wireless device c1 is, for example, a wireless access point (WAP) equipped with a Wi-Fi transceiver function, a mobile phone, a computer, or other electronic device having similar functions, and the second wireless device c2 is configured with a ZigBee transceiver function, for example. Wireless speakers, light switches, air conditioners or other electronic devices with similar functions. The Wi-Fi ZigBee network connection device can convert Wi-Fi and ZigBee with Wi-Fi and ZigBee format, and the transmission rate (quantity/frequency) of Wi-Fi is much higher than that of ZigBee and Wi-Fi. The power is also much higher than ZigBee. Referring to FIG. 2, as known to those skilled in the art, the Wi-Fi wireless local area network can support the first channel including 11 channels in the frequency band of 2.412 GHz to 2.462 GHz, and the ZigBee wireless network can support the second channel including 16 channels in the 2.405 GHz to 2.48 GHz band. Please note that the supported channels of the two networks overlap each other, so the ZigBee transmission will be moved to Wi-Fi, using other working channels with better signal strength.

Through these channels, for example, mobile phones can transmit data to, for example, a lighting switch via a Wi-Fi ZigBee network connection device, to achieve remote control and management effects.

Referring to FIG. 1 and FIG. 3, the network connection device 300 includes a first transceiver unit 4, a first interface 3, a processor 2, and a first The second interface 5 and the second transceiver unit 6. In addition, the network connection device 300 further includes a storage 1 electrically connected to the processor 2. Moreover, the processor 2 includes a filtering unit 21, a format converter 22, and a channel selector 23. The memory 1 stores an address table, which records the address of the first wireless device c1 and the address of the second wireless device c2.

In this embodiment, for example, the processor 2 is a Micro-control Unit (MCU), and the first interface 3 is a SDIO (Secure Digital Input/Output) for the Wi-Fi wireless network. The digital input/output interface, the first transceiver unit 4 is a Wi-Fi network interface device, and the second interface 5 is a UART (Universal Asynchronous Receiver/Transmitter) interface for the ZigBee wireless network. The two transceiver unit 6 is a ZigBee network interface device.

The Wi-Fi ZigBee network connection device 300 has a Wi-Fi network interface device, a microcontroller, and a ZigBee network interface device, and can communicate commands and data through the SDIO interface and the UART interface. The microcontroller is responsible for receiving commands from the first network through the Wi-Fi network interface device and the SDIO interface, interpreting it as a ZigBee command (ZCL command), and transmitting it to the ZigBee network interface device through the UART interface and the ZigBee network interface device. The second network, after which the ZigBee network interface device transmits the result or state of the second network back to the microcontroller, and then converts it into a Wi-Fi format reply to the first network. Similarly, the Wi-Fi ZigBee network connection device 300 can also receive commands from the second network and interpret the Wi-Fi commands to the first network, and then reply the results or status of the first network. Give the second network.

Using one of the first network 100 and the network connection device 300 In the case where a channel is accessed, the channel selector 23 marks in the second network candidate channel list which second channel overlaps the first channel used by the first network 100, and the remaining second channel is Candidate channel. The second network candidate channel list is a list in which the second network candidate channel is recorded.

The channel selector 23 picks out one of the candidate second channels as a working channel for communication with the second network 200, and the selected second channel does not overlap the first network 100 and the network connection device 300. The first channel used between. The first channel used in the foregoing may be determined by the first wireless device c1 or specified by the user. The first transceiver unit 4 receives a first packet sent by the first network 100 via the first channel for receiving, and sends the first packet to the filtering unit 21 through the first interface 3. The filtering unit 21 analyzes a source address and a destination address carried by the first packet, and compares the records of the address table to determine which first wireless device c1 of the first network 100 is to be transmitted. Which wireless device is given to which network.

When the filtering unit 21 determines that the first packet is one of the first wireless devices c1 of the first network 100 to transmit the second wireless device c2 of the second network 200, the format converter 22 will conform to the first network. The first packet of the 100 transmission format is interpreted as a second packet conforming to the transmission format of the second network 200, and then transmitted through the second interface 5 and the second transceiver unit 6. The second transceiver unit 6 transmits the second packet to the second wireless device c2 pointed to by the destination address in the second network 200 via the second channel selected in the candidate channel list.

On the contrary, the network connection device 300 receives the second network 200 In the case of two packets, the second packet can also be interpreted into a first packet conforming to the first network 100 transmission format in a similar manner as described above, and then provided to the first network 100.

More specifically, both the first network 100 and the second network 200 mainly operate in the 2.4 GHz band, and the communication quality of each channel is not uniform, so the channel selector 23 specifically performs the preferred embodiment of the channel selection method of the present invention. Optimize packet transmission efficiency. The channel selector 23 has an evaluation unit 24, a monitoring unit 25, and a marking unit 26, and the channel selection method includes the following steps of FIG.

Step 70: The marking unit 26 reads the first channel currently used to access the first network.

Step 71: When the marking unit 26 reads the first channel currently used for receiving, in the second network candidate channel list, which second channel is overlapped with the first channel currently used for receiving, and according to other The second channel is a candidate channel for evaluation. If the first channel currently used for access is not read, all the second channels are regarded as candidate channels, and all candidate channels are not marked at this time. In this embodiment, the channel occupied by Wi-Fi is marked on the ZigBee channel list, and other unmarked channels are candidate channels available for ZigBee.

Step 72: The evaluation unit 24 evaluates a quality signal for each unmarked candidate channel. Preferably, the quality signal of this embodiment is a Link Quality Indicator (LQI). However, for example, the Receive Signal Strength Indicator (RSSI) or other quality signals that can indicate the channel communication quality can also be used as the quality of the evaluation packet. Standard.

The evaluation process of each unmarked candidate channel is: first, the second transceiver unit 6 transmits a quality detection packet to the second wireless device c2 via the candidate channel, and receives the return of the second wireless device c2. After the quality response packet, the corresponding quality signal is calculated based on the strength and quality of the quality response packet.

Of course, in another aspect, the second transceiver unit 6 can also broadcast the quality detection packet to all the second wireless devices c2, and the evaluation unit 24 evaluates the quality response packets returned by all the second wireless devices c2 to calculate. Quality signal.

Step 73: The evaluation unit 24 picks out the candidate channel with the best quality signal (the channel with the least interference) as a working channel, and causes the second transceiver unit 6 to broadcast a frequency change indication packet to notify all the second wireless devices c2 that it is going to Switch to the working channel to pick up the packet. In particular, the frequency change here refers to changing to another second channel, that is, frequency hopping.

Step 74: The evaluation unit 24 causes the second transceiving unit 6 to switch to the working channel as a basis for transmitting the second packet.

Step 75: As time passes, the second transceiver unit 6 sequentially sends a plurality of second packets. The monitoring unit 25 updates the highest number of retransmissions according to the number of times the second transceiver unit 6 retransmits the same second packet at intervals, until the highest number of retransmissions exceeds one retransmission threshold, and then jumps to step 76.

In other words, when the number of retransmissions of the packet on the working channel is not higher than the preset retransmission threshold, the monitoring unit 25 continues to monitor the maximum number of retransmissions of each packet; when the packet is retransmitted on the working channel Higher than the retransmission gate When the value is depreciated, the flow jumps to step 76.

The number of retransmissions refers to the number of times the second wireless device c2 pointed by the destination address requests to retransmit the second packet after the second transceiver unit 6 sends a second packet. The poorer the communication quality of the working channel, the easier it is to be retransmitted.

The monitoring unit 25 mainly updates the maximum number of retransmissions with the current number of retransmissions when the current number of retransmissions > the maximum number of retransmissions. In this embodiment, preferably, when the second transceiver unit 6 sends a second packet every 1 second, the retransmission threshold is 10, but not limited thereto, the retransmission threshold may be along with the desired transmission efficiency. And change.

Step 76: When the number of times the packet is retransmitted on the working channel is higher than the retransmission threshold, the marking unit 26 marks the working channel in the second network candidate channel list.

Step 77: The monitoring unit 25 checks if the number of unmarked candidate channels is below an unmarked threshold. If so, the flag of the second network candidate channel list is cleared, and then jump back to step 72. If not, jump back directly to step 72.

Therefore, as long as the maximum number of retransmissions of the current working channel is too large, the channel selector 23 judges that the transmission efficiency is not good and further selects another candidate channel with better communication quality to update the working channel to effectively maintain high-efficiency transmission performance.

The channel selector 23 can be a software or a hardware. Preferably, in this embodiment, a software that records the channel selection method is written in the processor 2, and the software uses the software to memorize the frequency hopping judgment mechanism of each channel, and records the number of error retransmissions in the storage. 1 in.

Moreover, the preferred unmarked threshold of the embodiment is not less than a quarter of the total number of second channels (total = 16), for example, the unmarked threshold may be selected as 5. When the number of unlabeled candidate channels is lower than the unmarked threshold, the working channel can only be selected from a few channels, and it is not easy to maintain high transmission efficiency. Moreover, the channel quality changes with time, and the previously marked channel may have improved communication quality at this time. Therefore, in this embodiment, when the number of unmarked candidate channels is too small, the flag of the second network candidate channel list is cleared, and then Re-evaluate all candidate channel communication qualities.

It should be reminded that if there is a change in the first channel of communication, the flow of the channel selection method will jump back to step 71 to redefine the candidate channel. This is because the highest data transmission rate of the first network 100 is higher than that of the second network 200, and the transmission power is also high, and a channel of better quality is required to maintain high transmission efficiency, so that the first network 100 is preferentially selected. Channel.

In this embodiment, the first channel used by Wi-Fi is known through the microcontroller (MCU) of the network connection device 300, so that the channel selector 23 knows which of the remaining available second channels, and the ZigBee network interface device is correct. These candidate second channels transmit signals, perform LQI value (Link Quality) measurement, and preset the channel with the LQI maximum value that can be found as the working channel with the least interference (the new channel to be used).

In summary, since the Wi-Fi ZigBee network connection device plays the role of a Coordinator in the ZigBee network, the broadcast packet can be sent before the frequency hopping to notify the associated second wireless device c2 (for example, a router and a terminal). The device (End device) is switched to the new channel.

Memory and statistical errors are heavy when transmitting/receiving packets during operation The number of transmissions, if the number is higher than the set maximum value, marking the channel is very disturbing, and then sending signals to other available channels, performing LQI value (Link Quality) measurement, and finding the channel with the highest LQI value is The next available working channel and notify other devices to switch to the new channel.

As the number of available channels is reduced by continuously increasing the mark on the ZigBee channel list, the "available channel minimum (ie, unmarked threshold)" will be set. If the number of available channels is lower than this value, Wi will be canceled. The mark other than the -Fi channel, the LQI value is measured again to determine the new working channel.

Moreover, the present invention is applicable to wireless transmission between two different transmission rate devices. Although the foregoing first network 100 is a Wi-Fi wireless local area network, and the second network 200 is a ZigBee wireless local area network, this embodiment can also be applied to other network types as long as the first network 100 is satisfied. The highest data transmission rate is greater than the highest data transmission rate of the second network 200. Of course, when the types of the first network 100 and the second network 200 are changed, the types of the first interface 3 and the second interface 5 are also adjusted correspondingly. The network that normally operates in the 2.4 GHz band using DSSS (Direct Sequence Spread Spectrum) technology includes wireless USB (universal serial bus), 2.4 GHz radiotelephone, and CDMA (Code Division Multiple Access, The code division multiplexing access system) can be selected as the first network 100 or the second network 200 of the present embodiment.

It should be noted that the channel selector 23 can also be independent of the network connection device 300, and the implementation of the network connection device 300 is not limited to a bridge, but can also be a gateway, a router or the like. In addition, the storage 1 can also It is built into the processor 2' as shown in FIG.

Second preferred embodiment

Referring to FIG. 6, the network connection device 300" of the second preferred embodiment can connect a plurality of second wireless devices c2 by using a second network, wherein the network connection device 300" does not have a display device or an input device, and cannot directly Connect to an external network.

The network connection device 300", in order to connect the wireless service providing device c1' as the first wireless device with the first network, firstly connects to the network as the portable wireless device c1" of the other first wireless device. 300" establishes an ad-hoc wireless network, after which the portable wireless device c1" transmits information for logging in to the first network to the network connection device 300". Then, the network connection device 300" The first network is connected using the received login information to communicate with the wireless service providing device c1'.

Preferably, the first network in this embodiment is a Wi-Fi wireless area network, and the second network is a ZigBee wireless area network. The network connection device 300" is a Wi-Fi ZigBee network connection device; the wireless service providing device c1' is, for example, a wireless access point (WAP); and the portable wireless device c1" is configured to be equipped with Wi-Fi transceiver A functional mobile phone, a computer or other electronic device having similar functions; the second wireless device c2 is, for example, a wireless speaker configured with a ZigBee transceiver function, a lighting switch, an air conditioner or other electronic device having similar functions. In particular, the manner in which the portable wireless device c1" and the network connection device 300" of the present invention are connected is not limited to the foregoing description, as long as it is a reasonable network connection, such as an Ethernet network. Meanwhile, the above network connection device 300" is not limited to having no display device or losing Devices that are connected to the device and cannot be directly connected to the external network.

Thus, when the network connection device 300" and the wireless service providing device c1' communicate via a first channel, the network connection device 300" can select an optimal communication quality from the second channel that does not overlap the first channel. The working channel is connected to the second wireless device c2 (the details are as described in the first embodiment, and will not be described here), so that the portable wireless device c1" can remotely control and manage the second wireless. Device c2.

In summary, the channel selection method, the channel selector and the network connection device of the foregoing preferred embodiment have the following advantages:

(1) With a channel memory mechanism, the network connection device selects a suitable working channel from those second channels that do not overlap the first channel currently accessed by the first network, so as to avoid the effect of the channel with large interference.

(2) Reduce the frequency of incorrect retransmission of the network connection device and improve the performance of the network.

(3) Selecting a working channel with better communication quality, so that the network connection device avoids waste of power caused by incorrect retransmission.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

100‧‧‧First network

25‧‧‧Monitoring unit

200‧‧‧Second network

26‧‧‧Marking unit

300‧‧‧Network connection device

3‧‧‧ first interface

300’‧‧‧Network connection device

4‧‧‧First transceiver unit

300”‧‧‧Network connection device

5‧‧‧second interface

1‧‧‧Storage

6‧‧‧Second transceiver unit

2, 2'‧‧‧ processor

70~77‧‧‧Steps

21‧‧‧Filter unit

C1‧‧‧First wireless device

22‧‧‧ format converter

C1’‧‧‧Wireless service provider

23‧‧‧Channel selector

C1"‧‧‧ portable wireless device

24‧‧‧Evaluation unit

C2‧‧‧second wireless device

1 is a schematic diagram showing a first embodiment of a network connection device for coupling a first network and a second network; FIG. 2 is a schematic diagram showing the first channel and the second channel are located FIG. 3 is a block diagram illustrating a network connection apparatus of the first preferred embodiment; FIG. 4 is a flow chart illustrating a preferred embodiment of the channel selection method of the present invention; FIG. 5 is a block diagram. Another aspect of the network connection device is illustrated; and Figure 6 is a schematic diagram illustrating a second preferred embodiment of the network connection device.

300‧‧‧Network connection device

1‧‧‧Storage

2‧‧‧ Processor

21‧‧‧Filter unit

22‧‧‧ format converter

23‧‧‧Channel selector

24‧‧‧Evaluation unit

25‧‧‧Monitoring unit

26‧‧‧Marking unit

3‧‧‧ first interface

4‧‧‧First transceiver unit

5‧‧‧second interface

6‧‧‧Second transceiver unit

Claims (14)

A channel selection method is suitable for determining a working channel for communication from a plurality of candidate channels of a network, comprising the steps of: (A) reading a channel for communication by another network, and according to The channel communicated by the other network, the channel list of the candidate channels recording the network is marked with the channel overlapping the other network for communication to determine the network. a candidate channel, and the candidate channels do not overlap the channel in which the other network communicates, wherein the highest data transmission rate of the other network is greater than the highest data transmission rate of the network; (B) the network Each of the candidate channels evaluates the communication quality of the channel, and selects the candidate channel corresponding to the communication quality of the preferred channel as the working channel; (C) switches to the working channel for communication by the network; (D) Transmitting a packet to monitor the number of times the packet is retransmitted; (E) deciding whether to update the working channel based on the number of retransmissions of the packet; and (F) when deciding to update the working channel as a candidate other than the current working channel Total transmission channel can support wherein the number of candidate channels is less than those of the network of the network; communication channel quality of channel estimation, and the corresponding pick preferred communication channel quality of the channel as a candidate after the updating of the channel. According to the channel selection method described in item 1 of the patent application scope, a step (G) between steps (E) and (F): when it is decided to update the working channel, mark the candidate channel corresponding to the current working channel; and repeat the step (C) according to the updated working channel~ (E), (G), and (F), until the number of unmarked candidate channels is less than an unmarked threshold, the flags of all of the candidate channels are cleared. According to the channel selection method of claim 1, wherein the step (A) is based on the Wi-Fi (Wireless Fidelity) network, and the ZigBee network is determined. Candidate channel; and step (B) is to evaluate the channel communication quality for the candidate channels of the ZigBee network. A channel selector is applicable to a network connection device for coupling a first network and a second network, where the first network corresponds to at least one first channel, and the second network corresponds to multiple a second channel, and the channel selector includes: a marking unit, reading the at least one first channel that the first network communicates, and the at least one first channel that communicates according to the first network, Determining which of the second network candidate channel lists of the second channels of the second network are marked with the second channel overlapping the first network to communicate with the first network to determine the first channel a plurality of candidate channels in the second channel, and the determined candidate channels do not overlap the at least one first channel that the first network communicates, wherein the highest data transmission rate of the first network is greater than the first The highest data transmission rate of the second network; An evaluation unit that evaluates channel communication quality for each of the candidate channels to select the candidate channel corresponding to the preferred channel communication quality as a working channel used by the network connection device to communicate with the second network; a monitoring unit, when the network connection device transmits a packet to the second network via the working channel, the monitoring unit monitors the number of times the network connection device retransmits the packet to determine whether to enable the evaluation unit to update the work a channel; wherein, when the monitoring unit causes the evaluation unit to update the working channel, the evaluation unit evaluates channel communication quality for the candidate channels other than the current working channel, and selects the candidate channel corresponding to the preferred channel communication quality as The updated working channel; wherein the number of candidate channels is less than the total number of the second channels. The channel selector according to claim 4, wherein when the monitoring unit causes the evaluation unit to update the working channel, the marking unit marks the candidate channel corresponding to the current working channel; wherein the evaluation unit is Each unmarked candidate channel evaluates channel communication quality to select the candidate channel corresponding to the preferred channel communication quality as the updated working channel, and the marking unit monitors the updated working channel according to the monitoring unit. The candidate channel corresponding to the updated working channel is selectively marked; when the number of unmarked candidate channels is less than an unmarked threshold, the marking unit clears the markings of all of the candidate channels. According to the channel selector of claim 4, wherein the marking unit is determined from the second channels of the ZigBee network The candidate channels, and the candidate channels do not overlap the at least one first channel used by the network connection device to communicate with a Wi-Fi (Wireless Fidelity) network. A channel selector according to claim 4, wherein the channel selector is a software. A network connection device, configured to be coupled to a first network and a second network, where the first network corresponds to a first channel, and the second network corresponds to a plurality of second channels, the network connection device The method includes: a first transceiver unit configured to communicate with the first network via the first channel; a second transceiver unit configured to communicate with the second network via a working channel; and a processor, Electrically connecting with the first transceiver unit and the second transceiver unit, further comprising: a channel selector, having: a marking unit, reading the first channel for communication by the first network, and according to the first network The first channel for communicating, marking, in a second network candidate channel list of the second channels in which the second network is recorded, which second channel is overlapped with the first network for communication The first channel is configured to determine a plurality of candidate channels in the second channel, and the determined candidate channels do not overlap the first channel in which the first network communicates, wherein the first network The highest data transmission rate is greater than the second network High data transfer rate; An evaluation unit that evaluates channel communication quality for each of the candidate channels to select the candidate channel corresponding to the preferred channel communication quality as the working channel; and a monitoring unit that monitors the second transceiver unit to be heavy on the working channel The number of times a packet is transmitted to determine whether to cause the evaluation unit to update the working channel; wherein, when the monitoring unit causes the evaluation unit to update the working channel, the evaluation unit evaluates channel communication quality for the candidate channels other than the current working channel And selecting the candidate channel corresponding to the communication quality of the preferred channel as the updated working channel; wherein the number of the candidate channels is less than the total number of the second channels. The network connection device of claim 8, wherein when the monitoring unit causes the evaluation unit to update the working channel, the marking unit marks the candidate channel corresponding to the current working channel; wherein the evaluation unit Evaluating the channel communication quality for each unmarked candidate channel to select the candidate channel corresponding to the better channel communication quality as the updated working channel, and the marking unit monitors the updated working channel according to the monitoring unit. The candidate channel corresponding to the updated working channel is selectively marked; when the number of unmarked candidate channels is less than an unmarked threshold, the marking unit clears the markings of all of the candidate channels. The network connection device according to claim 8, wherein the evaluation unit calculates a link quality indicator (LQI) of each candidate channel, and connects Receive signal strength indicator (RSSI), or other quality signal that can show channel communication quality to evaluate channel communication quality. The network connection device of claim 8, further comprising: a storage device for recording the number of retransmissions of the packet monitored by the monitoring unit, and storing an address table and a candidate channel list, wherein the The address table records an address of a first wireless device in the first network and an address of a second wireless device in the second network, where the candidate channel list is for the marking unit to mark the current working channel The candidate channel. The network connection device of claim 11, wherein the processor further comprises: a filtering unit, according to the record of the address table, is contained in another packet sent to the first network a source address and a destination address; and a format converter, wherein the filtering unit compares the other packet to the first wireless device of the first network to be transmitted to the second network A second wireless device, the format converter interpreting the another packet from conforming to the first network transmission format to conform to the second network transmission format. The network connection device of claim 8, wherein the processor further comprises: a storage device for recording the number of retransmissions of the another packet monitored by the monitoring unit, and storing an address table and a a candidate channel list, wherein the address table records an address of a first wireless device in the first network and an address of a second wireless device in the second network, the candidate channel list Is for the marking unit to mark the candidate channel corresponding to the current working channel; a filtering unit, according to the record of the address table, than a source address and another source contained in the first network a destination address; and a format converter, when the filtering unit compares the other packet to be the first wireless device of the first network to be transmitted to the second wireless device of the second network, The format converter interprets the other packet from conforming to the first network transport format to conform to the second network transport format. The network connection device of claim 8, wherein the marking unit determines the candidate channels from the second channels of the ZigBee network, and the candidate channels do not overlap The network connection device is configured to communicate with the first channel of a Wi-Fi (Wireless Fidelity) network.