Patent Application
20050148298
1. Field of Invention
The invention is related to a channel quality evaluation method for wireless network, especially a channel quality evaluation method applicable to Bluetooth wireless network.
2. Related Art
In a co-exist environment having Bluetooth wireless network and other standard wireless network, interferences between different wireless devices can visibly reduce transmission speed. Since Bluetooth system uses spread spectrum modulation and frequency hopping is its frequency spreading method, interferences can be avoided by using a Bluetooth device to skip channels that are used by other wireless devices. However, to effectively omit the used channels, channel usages need to be identified beforehand. The current Bluetooth standard does not specify the method for evaluating channel quality; they are determined by the manufacturers. It should reference to Bluetooth specification 1.1 and 1.2 (the specifications can be found in www.bluetooth.com). The usual convention uses the following methods for channel quality evaluation:
1. received signal strength (RSS);
2. carrier sensing (CS); and
3. error rate (ER).
The first method, RSS, has the advantage of simple structure, and its disadvantage is its difficulty to identify the strength threshold of the receiving signal between the usable and unusable channels. The second method, CS, has the advantage of high accuracy and the disadvantage of being expensive due to the additional packet detector inserted into the Bluetooth receiver for detecting other wireless devices. Therefore, if interferences come from packets generated by a wireless device undetectable by the extra packet detector (such as noise), it is still undetectable. The advantage of the third method, ER, is its high accuracy; yet, its disadvantages include having an error rate calculation that cannot be clearly defined, and a compatibility problem between different manufacturers. Therefore, to effectively retrieve channel quality without disturbing the Bluetooth operation is an important issue.
To solve the described technical problem, this invention reveals a channel quality evaluation method applicable to Bluetooth wireless network, providing a more accurate channel quality evaluation and simultaneously solving the compatibility problem between Bluetooth devices produced by different manufacturers.
To achieve the described goal, this invention provides a channel evaluation method applicable to Bluetooth wireless network. First, the Bluetooth master device transmits a first channel detecting format packet to the Bluetooth slave device. According to the response from the Bluetooth slave, it can be determined if the slave recognizes the first channel detecting format packet. If the Bluetooth slave cannot recognize the first channel detecting format packet, the Bluetooth master device will transmit a second channel detecting format packet. Finally, the master executes error rate calculation and obtains the channel quality evaluation according to the response from the Bluetooth slave device.
This invention uses the three channel evaluating methods from known technology. By using the special design of first channel detecting format packet, it obtains a more accurate channel quality evaluation. Also, the design of second channel detecting format packet solves the compatibility problem between Bluetooth devices made by different manufacturers.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow for illustration only, and thus are not limitative of the present invention, and wherein:
As shown in
According to the response from the Bluetooth slave, it will determine if the slave recognizes the first channel detecting format packet (step 102). If the Bluetooth slave cannot recognize the first channel detecting format packet, the Bluetooth master device transmits a second channel detecting format packet (step 103). The master executes error rate calculation and obtains the channel quality evaluation according to the response from the Bluetooth slave device (step 104).
In the Bluetooth system, when a Bluetooth slave device receives a POLL packet, it returns a NULL packet to the Bluetooth master device. This characteristic can be used to calculate the bit error rate (BER) or packet error rate (PER) for evaluating channel quality. The advantage of this method is that there exists no compatibility problem so that all Bluetooth devices can be operated under this protocol. The disadvantage is the fact that its short packet size will result in a less accurate error rate calculation. The packet combination of POLL and NULL packets is called the second channel detecting packet format.
In a Bluetooth packet, the header error checking (HEC) is used to verify the accuracy of the packet header. If the error checking result is true, the decoding operations will be engaged. However, if the error checking result is false, the decoding operation will be halted. Using this characteristic, by modifying the HEC to a specified value and placing a consistent data as the payload, a special channel detecting packet can be generated. This invention called such packet format as the first channel detecting packet format. Bluetooth devices that can recognize this packet format is called device A, and the ones that cannot recognize it is called B. There is no limitation for choosing the special HEC; any special HEC value can be used. As shown in
When applying the two aformentioned channel detecting packet formats into the actual operation, they solve the following possible situations. As shown in
As shown in
As shown in
The invention being thus described will become obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
