In general, a Wireless Local Area Network (WLAN), which may be referred to as Wireless Fidelity (Wi-Fi), is a technology referring to a Local Area Network (LAN) through which access to the wireless internet can be made within a distance from a place where an Access Point (AP) is installed, by using an electric wave, such as a Radio Frequency (RF) signal, an infrared transmission, or any other similar and/or suitable method based on an Institute of Electrical and Electronics Engineers (IEEE) 802.11 technology. The Wi-Fi changes a wired LAN transmission method to be suitable for a wireless environment and provides the same to a wireless network environment, thereby providing mobility to a user of a mobile station and reducing an installation cost of the LAN.
Meanwhile, ZigBee, one of technologies supporting a Wireless Personal Area Network (WPAN), is a sensor network technology based on IEEE 802.15.4. The ZigBee has been optimized for networking having a small amount of data transmission, a small amount of power consumption, and security. Home automation, ZigBee smart energy, building automation, and health care are fields to which the ZigBee is applied. Further, as a small scale network system, such as a home network, or a ubiquitous environment develops, the ZigBee optimized for the small scale network using small power is increasingly used.
Usable frequency bands for Wi-Fi communication and ZigBee communication, respectively, are differentiated into a plurality of usable frequency bands. Among the plurality of usable frequency bands, a usable frequency band of 2.4 GHz is an Industrial, Scientific, and Medical (ISM) band commonly used around the world, and may be commonly used for the Wi-Fi communication and the ZigBee communication.
FIG. 1A illustrates an example of a general channel structure for Wi-Fi communication in a usable frequency band of 2.4 GHz according to related art.
Referring to FIG. 1A, an entire usable frequency band of the Wi-Fi is from 2400 MHz to 2483.5 MHZ, a channel bandwidth of the Wi-Fi is 22 MHz, and an interval between Wi-Fi channels may be set to 5 MHz. In this case, a total of three channels, including channels 1, 6, and 11, may be used for the Wi-Fi communication in the entire usable frequency band.
FIG. 1B illustrates an example of a general channel structure for ZigBee communication in a usable frequency band of 2.4 GHz according to related art.
Referring to FIG. 1B, an entire usable frequency band for the ZigBee communication is from 2400 MHz to 2483.5 MHZ, which is the same as the entire usable frequency band for the Wi-Fi communication. A channel bandwidth for the ZigBee communication may be 2 MHz, which is smaller than the channel bandwidth for the Wi-Fi communication. In this case, a total of sixteen channels, including channels 11 to 26, may be used for the ZigBee communication in the entire usable frequency band.
When the same usable frequency band is used for the Wi-Fi communication and the ZigBee communication, as described above, the Wi-Fi channels and the ZigBee channels overlap each other. Thus, a collision within the channels may occur between devices using the Wi-Fi communication and devices using the ZigBee communication. A Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) technology is used to prevent such a collision problem.
FIG. 2 illustrates a process of using a CSMA/CA technology when Wi-Fi communication and ZigBee communication are simultaneously used in a same frequency band according to related art.
Referring to FIG. 2, when a ZigBee coordinator 200 and a Wi-Fi AP 210 respectively detect a device to perform ZigBee communication and a device to perform Wi-Fi communication, they perform a coordination operation for making the corresponding communication.
Specifically, the ZigBee coordinator 200 detects, at a time point of t0, that ZigBee communication from a first device is initiated. Then, the ZigBee coordinator 200 performs a Channel Clear Assessment (CCA) operation for determining whether there is another device using a channel at the time point of t0. When the other device is not detected as a result of the CCA operation, then the ZigBee coordinator 200 performs packet transmission and/or reception with the first device.
Meanwhile, Wi-Fi communication may be initiated by a second device at a time point of t1, which is within a time interval in which the packet transmission and/or reception is performed between the ZigBee coordinator 200 and the first device. At this time, the Wi-Fi AP 210 also performs the CCA operation for identifying whether there is another device using the channel.
However, since a transmission output of the ZigBee communication is generally very small relative to a transmission output of the Wi-Fi communication, the Wi-Fi AP 210 does not recognize that the packet transmission and/or reception of the ZigBee communication is performed at the time point of t1. Thus, the Wi-Fi AP 210 determines that the channel is to be used, and starts communication with the second device. Accordingly, a collision 202, according to simultaneous performance of the ZigBee communication and the Wi-Fi communication, occurs in the packet transmission and/or reception interval of the ZigBee communication. The packet transmission and/or reception of the ZigBee communication fails due to the collision so that a first delay of the ZigBee communication occurs.
When a predetermined period of time elapses after the first delay, the ZigBee coordinator 200 performs a second CCA operation at a time point of t2 in order to perform transmission and/or reception of the packet again. In this case, when the ZigBee coordinator 200 recognizes that the channel is being used for the Wi-Fi communication, the ZigBee communication may not be performed, and thus, a second delay of the ZigBee communication occurs. On the other hand, a normal operation 204 is performed for the Wi-Fi communication.
The ZigBee coordinator 200 periodically repeats the CCA operation. When it is determined, as a result of a CCA operation performed at a time point of tn, that the channel is to be used, then the ZigBee coordinator 200 performs the packet transmission and/or reception operation through the ZigBee communication so that success of transmission 206, according to the ZigBee communication, may be achieved.
When the ZigBee communication and the Wi-Fi communication are performed in the same frequency band as described above, the Zig-Bee communication having a relatively low transmission output is generally delayed.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.
USPTO Backgrounds
USPTO Backgrounds