Where there is no signal. Congestion does occur with cellular signals when many people are using the bandwidth at the same time. Causing a slow up in the signals reacting their destination. Cellular networks are expanding with more capacity now 3G, 4G and 5G networks are the norm. Cellphones are main device with this type of signal. 3) Bluetooth technology has a very small area of workability. Only meters wide for connections. Bluetooth can eliminate the need for wires in small areas. Bluetooth technology tends to be slow, but newer generations of Bluetooth is getting faster. Most likely you cant send large amounts of data on Bluetooth, because of the lack of capacity for speed. Cellphones, Laptops, IPad and MP3 players use this type of signal. 4) WIMAX is the newest wireless signal technology. WIMAX unlike Wi-Fi doesnt need a cabled line at all. It is a very fast signal, but WIMAX suppliers only offer a fraction of its speed.
In a network Wi-Fi can be used to connect office building without wires. Cellular can be used to transmit data and conversations among employees and other devices or employees. Bluetooth can transmit small files quickly in between devices. WIMAX could speed up the Internet signal and transfer data very quickly. A company may choose a satellite signal if they have very remote locations not accessible by other means. Satellite signals are effected greatly by weather conditions.