Long-range Wi-Fi

Long-range Wi-Fi is a way to connect computers and other devices over long distances without using expensive equipment or special permissions. It is often used instead of fixed wireless, cellular networks, or satellite Internet access.

Regular Wi-Fi networks usually work only over short distances, like inside a house. A typical wireless router might only reach about 50 meters, especially indoors. However, when used outdoors with special directional antennas, Wi-Fi can connect stations that are many kilometers apart. This makes it a useful option for places that are hard to reach with other types of Internet service.

Introduction

Since the creation of the IEEE 802.11 standard, known as Wi-Fi, the technology has become cheaper and faster. Long-range Wi-Fi, especially at 2.4 GHz, has grown popular with special devices. While Wi-Fi hotspots are common in cities, some rural areas use stronger, longer-range devices instead of cell or fixed wireless networks.

Long-range Wi-Fi has some disadvantages compared to other options, like not working well through walls and having a shorter distance. However, it has been useful in connecting communities in difficult areas where other options are limited. Benefits include not needing permission from telecom companies, using smaller and simpler antennas, and having free software that works on older routers. Some organizations also use long-range Wi-Fi to improve their communication systems.

Applications

Business

Long-range Wi-Fi can help connect big offices, business areas, or whole campuses. It can link tall buildings, airports, or even construction sites and research labs that are far away from regular internet services. It’s useful for homes that can’t get regular cable or DSL, like vacation homes in remote places, or even yachts on the water. It can also let neighbors share a neighborhood Wi-Fi network.

Nonprofit and Government

This kind of Wi-Fi helps connect far apart guard posts, like those used by foresters, without needing new wires. In areas where cell service is weak, it can fill in gaps so tourists and local businesses stay connected. It also saves money and keeps information safe by using modern security methods.

Military

Long-range Wi-Fi can link important places like schools and police stations, even in difficult areas. It uses simpler, cheaper equipment that can work well even where resources are limited. This helps save money and energy, making it easier to keep networks running.

Scientific research

See also: Wireless sensor network

Scientists have used long-range Wi-Fi for projects like the Andean Seismic Project in Peru. They set up a network stretching over 320 kilometres (200 miles) to send seismic data in real time from distant stations to UCLA.

Large-scale deployments

The EHAS-@LIS project, funded by the European Commission between 2003 and 2006, helped create the CuzcoSur network in Peru. This network linked rural health centers with the Cuzco Hospital, allowing them to use telemedicine, phone calls, and internet. The entire network used long-range Wi-Fi, with connections stretching over 40 kilometers in some places. Researchers from University Rey Juan Carlos in Spain studied how Wi-Fi works over long distances.

The Technology and Infrastructure for Emerging Regions (TIER) project at the University of California at Berkeley, working with Intel, uses a special Wi-Fi setup to create long-distance connections for projects in developing countries. This method, called Wi-Fi over Long Distance (WiLD), connects the Aravind Eye Hospital with clinics in Tamil Nadu, India. Distances range from five to over fifteen kilometers, with stations in direct sight of each other. These connections let hospital experts talk with nurses and patients at clinics using video calls. If a patient needs more care, an appointment can be set up. Another network in Ghana links the University of Ghana Legon campus to its campuses at Korle bu Medical School and the City campus, with plans for connections up to 80 kilometers apart.

The Tegola project from the University of Edinburgh is creating new technologies to bring fast, affordable internet to rural areas far from fiber cables. A ring of five connections links Knoydart, the north shore of Loch Hourne, and a remote community at Kilbeg to the Gaelic College on Skye. All connections cross tidal waters, ranging from about 2.4 to 19.3 kilometers long.

Increasing range in other ways

Further information: 802.11 non-standard equipment and Radio propagation

To make Wi‑Fi work over longer distances, special methods are used. Some Wi‑Fi standards, like the 802.11-2007 version, add new ways to send signals that help them travel farther. This includes changing how signals are protected and using special settings that can double the distance a signal can go.

Another way to increase range is by using more powerful devices that boost the signal. These can make the Wi‑Fi reach much farther than normal. Also, special antennas can focus the signal in one direction, helping it travel several kilometers if there are no obstacles.

Some people change the way Wi‑Fi works to make it better for long distances, though this might cause problems with other devices. Open source software often allows more control over these changes than regular router settings.

Further information: List of WLAN channels

In most regular Wi‑Fi routers, the basic settings are enough. But for long-range Wi‑Fi, special tools are used to improve the connection. The 802.11-2007 standard adds new ways to send signals, like using wider channels and better protection, which can help signals travel farther. Some routers made for this purpose can use these special settings, and some can even send signals at higher frequencies to reach even longer distances.

The 802.11n standard, which started appearing in routers in 2008, uses a technology called MIMO. MIMO uses multiple antennas to send and receive signals, which can make the connection faster. While it works best for short distances, using two antennas in a special way can help send two signals at once over long distances.

Further information: 802.11n

Using more powerful signal boosters can also help Wi‑Fi reach farther. These small devices can add extra power to the signal, sometimes making it reach more than five times farther. Even a small increase in power can make a big difference in how far the signal can go.

Special antennas shaped to focus the signal in one direction can also help Wi‑Fi travel farther without using more power. These antennas can send the signal like a beam, reaching many kilometers if there’s a clear path. This method can also reduce interference from nearby signals.

Changing the basic rules of how Wi‑Fi sends and receives signals can make it work better for long distances, though this might cause problems with other Wi‑Fi devices. This is often done with special software that lets users change more settings than regular routers allow. This can be very useful for older routers that have good hardware but not all features turned on by the factory settings. Using these changes can help improve how well Wi‑Fi works over long distances.

Breaking up data into smaller pieces can help Wi‑Fi work better when there’s a lot of traffic or noise. While this can sometimes slow things down, it can also make the connection more reliable. For example, sending smaller pieces of data can work much better than sending big pieces when there’s a lot of interference. However, breaking data into too many pieces can make things slower, so it’s important to find the right balance.

Obstacles to long-range Wi-Fi

Setting up long-range Wi-Fi can be tricky because of many things that can get in the way. Trees, hills, and rain can weaken the signal. In cities, buildings with metal or concrete can block or reflect the signal, making it harder to connect.

Other devices like microwave ovens, wireless phones, and Bluetooth gadgets also create interference, making it tough to keep a strong long-range connection. These devices can crowd the air with signals, making it hard for the Wi-Fi to work well over long distances.

Notable links

Italy

The longest unamplified Wi-Fi link is 304 km, achieved by CISAR (Italian Center for Radio Activities). It runs from Monte Amiata in Tuscany to Monte Limbara in Sardinia. This link uses a frequency of 5765 MHz and provides data rates of up to 5 Mbit/s. It uses Ubiquiti Networks AF-5X radios and Ubiquiti airFiber wireless routers. The antenna is 120 cm tall with a handmade waveguide, estimated at 35 dBi.

Venezuela

Another long unamplified Wi-Fi link is 279 km, created by the Latin American Networking School Foundation. It connects Pico del Águila to El Baúl. This link, established in 2006, uses a frequency of 2412 MHz and Linksys WRT54G routers with OpenWrt and DD-WRT firmware. Parabolic dish antennas were used at both ends, recycled from satellite service. The link improves on a previous U.S. record of 201 km.

Peru

Loreto, in the jungle region of Peru, hosts the world's longest Wi-Fi-based multihop network. This network, created by the Rural Telecommunications Research Group of the Pontificia Universidad Católica del Perú and the EHAS Foundation, stretches about 445 km. It connects Cabo Pantoja's Health Post to downtown Iquitos through seventeen hops across small villages. The network was set up in 2007 and uses frequency channels 1, 6, and 11. Doodle Labs wireless routers and L-com antennas were used. The network serves a flat, low-elevation area with towers averaging 80 meters in height.