Fill in some examples below each type:. Do you use more transmitters, receivers, or transceivers throughout the day? What is different about the way you use each of these? When building a network, you will be using Wi-Fi technology, which has some unique characteristics you will need to know. Each frequency band used in Wi-Fi is divided up into multiple "channels". Each channel is similar to rooms at a party - if one room is crowded it is hard to carry on a conversation.
You can move to the next room, but that might get crowded as well. As soon as the building is full, it becomes difficult to carry on a conversation at the party. If you are setting up a mesh network -- all of the mesh links will need to be on the same channel. The available channels vary depending on where you are in the world.
For example, in the United States channels 12, 13 and 14 are not allowed for Wi-Fi, as those frequencies are used by TV and satellite services. If you are building networks in the United States, you can only use channels 1 through In the rest of the world, channels 1 through 13 are generally usable, and in a few places channel 14 is available.
Despite that, the best channels in the United States and most of the world to use for 2. This will minimize interference caused by partially overlapping Wi-Fi signals:. You could use other sets of Wi-Fi channels, as long as they are 5 channels apart - for instance 3, 8 and This may not be optimal though, as channels 1 and 2 would be unused, and in many places in the world channel 13 is not available.
Wherever you are, try and check what channels are most in use, and plan your network to use a channel that doesn't overlap. This may not always be true -- more and more wireless equipment is starting to use the 5GHz. In the United States, only channels available for building mesh networks are 36, 40, 44, 48, , , , , and The best place to check what is allowed in your area is online. Links are provided in External Resources at the end of this document.
When setting up your wireless network, you will need to think about what frequency band to use, and what channel to use. Many people want to know how far wireless signals will go.
Knowing this is important for planning a network, as the power of the routers will affect the design of the network, and how much equipment is needed. Different Wi-Fi routers can have very different power levels. Some are much stronger: they have more speaking or transmitting power than others. Some are very good listeners: they have what is called a better receive sensitivity.
These two elements define how well wireless devices will connect, and how far away a receiving Wi-Fi router can be. In some cases, usually with more business or professional oriented equipment you can find the information for transmit power and receive sensitivity. For instance, a light bulb might be 40 watts.
A router will have an output power of mW, which is times less! A dBm is a relative measurement using logarithms. One milliwatt is 0 dBm. This is the scale that many network designers use to calculate if longer wireless links will work. About 25 to 50 meters. About 50 to meters. About 5 to 10 kilometers.
About 10 to 20 kilometers or more. Wireless transmitter power is only one half of the connection. This is also known as the receive sensitivity. The receive sensitivity values are generally rated in dBm, and are usually in the range of dBm to dBm.
The negative number indicates a very small signal -- tiny fractions of a milliwatt. Below we have an example of two routers in relatively close range.
They have a good connection because the signal strength between them is strong. Below, we can see the same routers, but with more distance between them. In this case, the routers have a weaker connection because the signal is near the limit of what the routers can hear.
The speed between the routers will be less. The optimal signal range for outdoor wireless equipment is between dBm and dBm. This will ensure the connection can maintain the highest bandwidth possible. Wireless routers have different types of antennas. Some routers will have antennas built in, and sometimes the routers will have a choice of antenna you can attach to the router. There are many specific types of antennas, but three basic types are used most of the time, and will be useful in building a wireless network.
The first type of antenna is also the most common--omnidirectional. Using omnidirectional antennas has the benefit of creating connections in any direction. If there is enough signal between nodes, they should connect. The all-direction strength of these antennas comes with the drawback of transmitting a weaker signal. Since the signal is going in all directions, it spreads out and gets weaker with distance very fast. If nodes or clients are far away, they may not connect well.
Also, if there are only nodes or clients in one direction of the router, then the signals going in the opposite direction are wasted:. The next type of antenna is known as directional--it sends out a signal in a more focused way. Sign up for our Newsletter! Mobile Newsletter banner close.
Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. How WiFi Works. Wireless networks make it easy to connect to the internet wherever you go. Contents What Is WiFi? What Is WiFi? Here's what happens: A computer's wireless adapter translates data into a radio signal and transmits it using an antenna.
A wireless router receives the signal and decodes it. The router sends the information to the internet using a physical, wired ethernet connection. They transmit at frequencies of 2. This frequency is considerably higher than the frequencies used for cell phones, walkie-talkies and televisions.
The higher frequency allows the signal to carry more data. The 2. In ideal conditions, the 5 GHz band has a max range of about feet 61 meters , but in the real world, it is much more prone to interference from walls, doors and other objects. For a while, its cost made it popular, but now it's less common as faster standards become less expensive.
It can handle up to 11 megabits of data per second, and it uses complementary code keying CCK modulation to improve speeds. It uses orthogonal frequency-division multiplexing OFDM , a more efficient coding technique that splits that radio signal into several sub-signals before they reach a receiver. This greatly reduces interference. It significantly improved speed and range over its predecessors. For instance, although It is less prone to interference and far faster than its predecessors, pushing a maximum of megabits per second on a single stream, although real-world speeds may be lower.
Like It is sometimes called 5G because of its frequency band, sometimes Gigabit WiFi because of its potential to exceed a gigabit per second on multiple streams and sometimes Very High Throughput VHT for the same reason.
This standard extends the capabilities of First of all, the new routers allow an even higher data flow rate, up to 9. WiFi 6 also lets manufacturers install many more antennas on one router, accepting multiple connections at once without any worry of interference and slowdown. Some new devices also connect on a higher 6 GHz band, which is about 20 percent faster than 5GHz in ideal conditions. WiFi Hot Spots " ". WiFi has enabled people to work anywhere they can get a signal, like at this coffee shop.
Building a Wireless Network " ". Smartphones, tablets, smart TVs and laptops all access the internet with the help of a router the device pictured with two antennas. The name of the network, known as its service set identifier SSID.
The default setting is usually the manufacturer's name. The channel that the router uses. Most routers use channel 6 by default. If you live in an apartment and your neighbors are also using channel 6, you may experience interference. Switching to a different channel should eliminate the problem.
Your router's security options. Many routers use a standard, publicly available sign-on, so it's a good idea to set your own username and password. AES is considered the most secure. Public hot spots are either open or use any of the available security protocols, including WEP, so use caution when connecting away from home.
WiFi Protected Setup WPS , a feature that ties a hard-coded PIN to the router and makes setup easier, apparently creates a vulnerability that can be exploited by hackers, so you may want to turn off WPS if possible, or look into routers that do not have the feature. WPA3 was released in and became the security standard as of It aims to solve some of the vulnerabilities in WPA2 by putting much more complex encryption on both the router side and client side of the connection.
This encryption also changes over time, meaning if a hacker had managed to access an unauthorized connection at one point in time, they would be locked out again the next time they try to connect.
WPA3-enabled devices can also add some client-side encryption while using open public networks. It's worth noting that no matter how secure, a wireless network will surely have some method of exploit that can be used by hackers.
And to receive the information found in these waves, your radio receiver needs to be set to receive waves of a certain frequency. For WiFi this frequency happens to be 2. These waves are very similar to the frequency found in your microwave!
Your microwave uses 2. This is why some people with old or faulty microwaves experience a problem with their WiFi signal when they try to make popcorn. Just to clear up a popular misconception: These microwaves are non-ionizing radiation. That means that they do not cause cancer. Already a subscriber?
Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options.
0コメント