Problem presentation: know Wi-Fi
In the basic part of Arduino, we have known Arduino to some extent. From this part, we will come to learn the knowledge on the combination of Arduino and wireless communication, which can promote us interact with Arduino. In the first chapter, we will simply get at the relevant concepts and basic knowledge about Wi-Fi (which is also written as wifi) to prepare the future work.
What is wifi
WIFI is the abbreviation of Wireless Fidelity, which is a technology working in the vicinity of the frequency 2.4/5GHz. Its velocity is relative high, and the distance is relative long. Moreover, it is compatible with the existing 802.11 DSSS devices. DSSS (Direct Sequence Spread Spectrum) is a wireless sequence transformation way with high security and anti-interference. DSSS can extend the signal spectrum at send end by utilizing the high velocity spread sequence. Naturally, at the receive end, by using the decoding with the same spread spectrum code sequence, the extended signal can restore to the original signal. This is the principle of direct sequence spread spectrum (DSSS). Wifi can be read as [waifai]. The wireless router shown in Figure 1-1 is already used the wireless communication technology, i.e., wifi.
Figure 1-1 Wi-Fi wireless router