Cellular/Mobile Implementations
Mobile broadband refers to wireless Internet access delivered through mobile phone towers to computers, mobile phones, and other digital devices using portable modems. Figure 1 shows a cell tower used in a mobile broadband network.
Mobile phones use radio waves to communicate through a nearby mobile phone tower. The mobile phone has a small radio antenna. The provider has a much larger antenna that sits at the top of a tower, as shown in the figure.
Cellular/mobile broadband access consists of various standards supporting speeds of up to 5 Mb/s. Variations include 2G using GSM, CDMA, or TDMA; 3G using UMTS, CDMA2000, EDGE, or HSPA+; and 4G, using WiMAX or LTE. A mobile phone subscription does not necessarily include a mobile broadband subscription.
Three common terms that are used when discussing cellular/mobile networks include:
- Wireless Internet - A general term for Internet services from a mobile phone or from any device that uses the same technology.
- 2G/3G/4G Wireless - Major changes to the mobile phone companies’ wireless networks through the evolution of the second, third, and fourth generations of wireless mobile technologies.
- Long-Term Evolution (LTE) - A newer and faster technology considered to be part of 4G technology.
Satellite Implementations
Satellite Internet services are used in locations where land-based Internet access is not available, or for temporary installations that are mobile. Internet access using satellites is available worldwide, including for providing Internet access to vessels at sea, airplanes in flight, and vehicles moving on land.
There are three ways to connect to the Internet using satellites:
- One-way multicast - Satellite Internet systems are used for IP multicast-based data, audio, and video distribution. Even though most IP protocols require two-way communication for Internet content including web pages, one-way satellite-based Internet services can be used to push pages to local storage at end-user sites. Two-way interactivity is impossible.
- One-way terrestrial return - Satellite Internet systems use traditional dialup access to send outbound data through a modem and receive downloads from the satellite.
- Two-way satellite Internet - Sends data from remote sites via satellite to a hub, which then sends the data to the Internet. The satellite dish at each location needs precise positioning to avoid interference with other satellites.
Figure 2 illustrates a two-way satellite Internet system. Upload speeds are about one-tenth of the download speed, which is in the range of 500 kb/s.
The primary installation requirement is for the antenna to have a clear view toward the equator, where most orbiting satellites are stationed. Trees and heavy rains can affect reception of the signals.
Two-way satellite Internet uses IP multicasting technology that allows one satellite to serve up to 5,000 communication channels simultaneously. IP multicast sends data from one point to many points at the same time by sending data in a compressed format. Compression reduces the size of the data and the bandwidth requirements.
A company can create a private WAN using satellite communications and Very Small Aperture Terminals (VSAT). A VSAT is a type of satellite dish similar to the ones used for satellite TV from the home and is usually about 1 meter in width. The VSAT dish sits outside, pointed at a specific satellite, and is cabled to a special router interface, with the router inside the building. Using VSATs creates a private WAN.