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Istumbler 103 2 Find Local Wireless Networks Phone Number Lookup Introduction
Community Wireless Networks can be designed in many ways. To help you understand these different methods for designing networks, this document covers the basics of what different devices do in wireless networks, and how they can be used in different configurations. Using the knowledge and activities in this document, you can work with others to design the wireless network that works best for your community.
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Reading and working through Learn Wireless Basics before this document will help you with some of the concepts used in designing wireless networks. It provides some necessary background information for this document.
Reading through this material should take about 30 to 45 minutes. Working through the activities, or diving deeper into the subject with a group may take longer. Wireless Device Roles
There are three major modes a Wi-Fi device can use. These modes define the role a Wi-Fi device has in the network, and networks must be built out of combinations of devices operating in these different modes. How the devices are configured depends on the types of connections you want to use between parts of the network.
In discussing these modes and the examples below, several types of devices are used. In addition to the phones, tablets, and laptops you use in accessing a network, routers make up the hardware that runs the network. These routers are defined in Learn Networking Basics, but for the sake of this document the quick definition of a router is a network device that can connect one network to another, determine what traffic can pass between them, and perform other functions on a network, such as assigning IP addresses. The three wireless roles are:
Wireless Clients (Station)
Devices such as computers, tablets, and phones are common Clients on a network. When you are accessing a wireless hotspot, or the router in your home or office, your device is the client. This client mode is also known as station mode as well.
Some routers can operate as Clients as well, which allows them to act like the wireless card in a computer, and connect to other Access Points. This can bridge two Ethernet networks, or connect to more distant APs.
A Wireless Client is similar to a person in the audience of a play or movie. They are one of several or many people accessing information through the same conduit - someone speaking.
Access Points (Master)
Most wireless networks are made using Access Points - devices that host and control the wireless connection for laptops, tablets, or smart phones. If you use Wi-Fi in your home or office, it is most likely through an Access Point. When a router is set up as an AP, it is said to be in Master or Infrastructure mode.
An AP is sometimes a stand-alone device that bridges between a wireless and wired (Ethernet) network, or is part of a router. APs can cover a range of areas with a wireless signal, depending on the power of the device and the type of antenna. There are also some APs that are weatherproof, designed to be mounted outdoors.
An Access Point is similar to a person on stage, addressing an audience or crowd - they are providing the information for everyone else. Those audience members can ask questions of the person on the stage, and receive a response.
Ad-Hoc Node (Mesh)
Some wireless devices (laptops, smart phones, or wireless routers) support a mode called Ad-Hoc. This allows those devices to connect together directly, without an Access Point in-between controlling the connection. This forms a different type of network - in Ad-Hoc mode, all devices are responsible for sending and receiving messages to the other devices - without anything else in between. In an Ad-Hoc network, every device must be in this role, and using the same configuration to participate. Not all devices use this mode, and some have it as a hidden feature.
Ad-Hoc devices are used to create a Mesh network, so when they are in this mode, they are called Mesh Nodes.
An Ad-Hoc or Mesh node is similar to an individual in a group or roundtable discussion. They can take equal part in the conversation, raising their hand when they want to speak so the others will listen. If someone at the end of the table cannot hear, one of the individuals in-between can repeat the original message for the listener.
Quick Activity: Describe the differences in the two example networks below. What are the roles and relationships between the different colored nodes in the networks? Example 1
Example 2
Role of the Pink Nodes:
__________________________________
Relationship between nodes:
__________________________________ Role of the Yellow nodes:
__________________________________
Role of the Blue nodes:
__________________________________
Relationship between nodes:
__________________________________
The two networks above are Ad-Hoc and Infrastructure (Access Point) networks. Are there places or times in a social situation where you are in an Access Point or Client situation? Are there places or times when you are in an Ad-Hoc situation? What connects to what?
From the roles above, you can see that Clients always need to connect to an Access Point, and Mesh nodes all connect to each other. It should also be noted that due to how Wi-Fi is designed, this also prevents different roles from connecting to each other as well.
Access Points cannot connect to each other wirelessly:
Clients cannot connect to each other wirelessly:
Clients cannot connect to Ad-Hoc (Mesh) devices wirelessly:
Access Points cannot connect to Ad-Hoc (Mesh) devices wirelessly: Wireless devices in networks
Treat the three types of roles above - Clients, Access Points, and Ad-Hoc nodes - as the building blocks for large networks. Below are several examples that demonstrate how devices configured for different roles can be used. Access Point - Home or Office network
Wireless networks used in your home or office are generally a combination of a router and a wireless Access Point (AP).
In the diagram above:
1 represents the connection to the Internet (Optional - networks can function without the Internet).
2 represents the router that assigns IP addresses and provides a firewall between your network and the Internet.
3 represents the Access Point, providing a wireless bridge between the router and the users devices.
4 represent user devices, such as laptops, tablets, and smartphones.
In many home networks, or small office networks, the router and AP may be combined into a single device. This is usually just called a wireless router. It may also have a DSL, Cable, 3G, or 4G port to provide the connection to the Internet. In large office scenarios, there may be several AP devices spread throughout the building to provide more even wireless coverage, connected back to the router through long Ethernet cables. Point to Point link - Long Distance Connections
Wireless networks can be used to connect distant buildings or areas. It usually requires very focused antennas - such as a dish antenna - that can send a narrow beam in a specific direction. This is discussed in Learn Wireless Basics - so go there for more details on how that works.
A long-distance connection is often called a point-to-point, or PtP link. The name describes the concept: two points are connected together, and nothing else. This requires two wireless devices: one configured as an Access Point; the other configured as a Client. In the example below, two wireless devices are configured to create a point-to-point link. Omnidirectional Access Point and Client Link
1 represents computers connected with Ethernet cables to the wireless devices. These computers are connected to each other over the Point-to-Point link.
2 represents the wireless device setup as an Access Point.
3 represents the wireless device setup as a Client, connected to the Access Point.
This could look like the building-to-building connection, as shown below: Long-distance directional Access Point and Client Link
Here we have another example of a point-to-point link, but where the routers have dish antennas for greater link distance.
In the diagram above:
1 represents computers connected with Ethernet cables to the wireless devices. These computers are connected to each other over the Point-to-Point link.
2 represents the wireless device setup as an Access Point.
3 represents dish antennas that focus the wireless signal, allowing connections over long distances.
4 represents the wireless device setup as a Client, connected to the Access Point.
This could look like the network below, where an AP mounted on a tower is able to connect with a Client device in a home very far away, since the dishes are facing one another.
In both of these examples, there are just two wireless devices linked together - and the antennas determine the range at which they can connect. The more focused the signal, the further the point-to-point link can reach. As the distance between the devices grow, it is more an more important to focus the signal with antennas - at both ends of the connection. Otherwise one end may hear the other, but not be loud enough to be heard! Point to MultiPoint - Wireless Internet Service Provider model
If we combine the two principles used in the networks above - many client devices connecting to an Access Point, and more powerful antennas used for outdoor devices to create longer links - we can create Point to Multipoint networks. These are larger-scale Access Point networks, where there is a single device in the center, controlling all of the Clients connected to it and bridging those connections to the Internet.
These types of networks are used by Wireless Internet Service Providers (WISPs) to connect homes and businesses to the Internet. Instead of running cables around a neighborhood or town, they put up one or more powerful Access Points on a tall building or tower. By installing directional wireless devices in a Client role on other rooftops, and pointing them back at the tall building or tower, those buildings can be connected to the WISPs networks, and thereby the Internet.
The diagram below demonstrates one model for how this works. There is a powerful Access Point mounted on a high building, and several nearby buildings with rooftop wireless Client devices: this forms the Point-to-Multipoint network. Connected to each of the Client devices is an indoor router or Access Point, which allows users to connect their computers, laptops, tablets, or smartphones to the WISP network.
In the diagram above:
1 represents the connection to the Internet.
2 represents an Access Point providing the signal for Client devices to connect to.
3 represents a powerful omnidirectional (all directions) antenna, sending the wireless signal to a large area around the building.
4 represent Client wireless devices on the roof of other buildings, linking to the powerful Access Point, and able to connect to the Internet through that AP.
5 represents small Access Points distributing wireless service inside the building. Mesh - Neighbor-to-neighbor Networks
A mesh network takes the principle of Point-to-Multipoint, and extends it to the idea of every node connecting to every other node in range. In effect, this creates a Multipoint-to-Multipoint network. This requires that all the devices are in the Ad-Hoc mode - wireless devices all in AP mode or Client mode cant perform the same function. For more information on how this principle works, see the Introduction to Mesh document.
The diagram below demonstrates one model for how this works. Wireless mesh nodes are installed on the rooftops of various buildings, and those nodes that are in range and dont have anything blocking the signals will connect. These nodes will share all resources connected to them such as local servers hosting applications and connections to the Internet. They can also be connected to computers, Access Points, or routers inside the buildings so users can access the resources anywhere on the network.
In the diagram above:
1 represents the connection to the Internet.
2 represents a Mesh Node with a connection to the Internet, with an omnidirectional (all directions) antenna.
3 represents Mesh Nodes with omnidirectional (all directions) antennas. These nodes are receiving Internet access from Mesh Node B . They may be connected to different devices inside the building.
4 represents small Access Points distributing wireless service inside the building. Hybrid Networks
When designing and building town or community-sized networks, it may be difficult or impossible to use a single method to connect everyone. For instance, a single Point-to-Multipoint network may not cover an entire community. Mesh nodes can be used to extend client sites to nearby buildings. Point-to-point connections can bridge longer distances and join several disconnected networks together.
In the diagram below, we can see an example of a hybrid network. There is no single example that can cover all of the possible uses for a network! In the activity that follows, you will explore the different ways to build a network by working through scenarios.
One last note before we move on to the activity - in the examples above, and in the activity that follows, the diagrams focus on building networks across rooftops or from building to building. This is generally the best way to build networks that cover neighborhoods, towns, or communities. In the diagrams, the way people connect to this network isnt always shown.
Keep in mind that these rooftop routers may not provide connections to users on the ground, or in buildings. A good way to provide these connections is by attaching Access Points to an Ethernet port on the rooftop router. This indoor Access Point can be set up to use the rooftop network as the source of connections to the Internet, or to provide access to applications and servers on the network. A detailed look at this is below:
In the diagram:
1 represents the rooftop wireless device. It could be a Mesh Node, or Client router.
2 represents the Ethernet cable running out to the rooftop from the Power over Ethernet adapter.
3 represents a Power over Ethernet (PoE) adapter - a common way to power outdoor wireless devices.
4 represents an Access Point, connected to the neighborhood or community network through the rooftop router. Group Activity
Since there are so many ways to build wireless networks to cover your town or community, we recommend working through these pen-and-paper activities. Download the network worksheets and example solutions and try your hand at designing wireless networks.
If you are working through the activity on your own, try printing out the worksheets first and draw in a possible solution to each of the scenarios. You can then review the example solutions and see how your networks compare with some others.
We recommend you work through this activity with a group of your community members, especially when planning and designing a network. First print out a few sets of the network worksheets, and break into groups of two or three people (depending on how many people are gathered). Draw solutions to each scenario, then meet back up and compare all of your solutions to the scenarios. You can also look through the example solutions and compare them to what your groups came up with. Discuss what solutions might be best for your community.
There are a few basic rules to follow when working through the activity. Istumbler 103 2 Find Local Wireless Networks Phone Number 1-800
1. There are three types of routers you will use:
Omnidirectional. These can send and receive wireless signals in every direction.
Sector. These send and receive wireless signals in a limited arc. Limit the connections these routers make to a wedge-shaped area.
Focused. These send and receive wireless signals in a narrow beam. Limit the connections to a single thin line.
2. You have a limited amount of equipment available for each network. Each worksheet has icons of the types and number of pieces of equipment. The example below provides three omnidirectional, one sector, and one focused router:
3. You can configure the wireless equipment in your network to serve any of the wireless roles - AP, client, or ad-hoc node (mesh). The equipment can be any combination of roles, they dont have to all be the same role. Label each router with an A, C, or M depending on the role.
4. You can assume that all of the wireless equipment in the examples are within range of each other - the signals will reach.
5. Remember that Clients can only connect to Access Points. APs cannot connect to each other wirelessly, Clients cannot connect to each other wirelessly, and Mesh nodes cannot connect to APs or Clients wirelessly.
6. Many Clients can connect to a single Access Point. Ad-hoc (mesh) devices can have connections to multiple other mesh devices at once.
7. If you want to connect different combinations of devices together, you can wire them together, as if you plugged an Ethernet cable in between the devices. This way devices that normally cannot connect wirelessly can still be networked. For example, an Access Point or Client can be connected to a Mesh node with an Ethernet cable.
Now download and print out the worksheets and example solutions, and try out some designs! /section Definitions Ad-hoc Network / Device Network On some devices (e.g. laptops) some available network connections are shown as computer to computer networks. These are networks that may be ad-hoc mesh networks or point to point links between computers for small file sharing. The term ad-hoc can also refer to unplanned, decentralized network connections. Antenna Converts electrical signals to radio waves. It is normally connected to a radio transmitter or radio receiver, and is the interface between the electrical signals in the radio, and the movement of the signals through the air. AP (Access Point) A device that allows wireless devices to connect to a wired network using Wi-Fi or related standards Client Device : The device with a wifi radio that you use to connect to a wireless access point, e.g. a computer, cell phone or tablet device. Ethernet A type of networking protocol - it defines the types of cables and connections that are used to wire computers, switches, and routers together. Most often Ethernet cabling is Category 5 or 6, made up of twisted pair wiring similar to phone cables. PoE (Power over Ethernet) describes systems which pass electrical power along with data on Ethernet cabling. Node An individual device in a mesh network. Related Information
This document is intended to be used after you have worked through Every Network Tells a Story, and Learn Wireless Basics. It is a partner document to Wireless Challenges, and can be done before or after that activity. Documentation
Commotion Construction Kit
Wireless + Networking Download PDF Introduction
This document covers the basics of how wireless technology works, and how it is used to create networks. Wireless technology is used in many types of communication. We use it for networking because it is cheaper and more flexible than running cables. While wireless networks can be just as fast and powerful as wired networks, they do have some drawbacks.
Reading and working through Learn Networking Basics before this document will help you with some of the concepts used in wireless networks.
In addition to some background information, this document covers six basic concepts:
Wireless signals - what they are and how signals can differ.
Wireless devices - the differences and uses for receivers and transmitters.
Wi-Fi Modes - how networks are made up of clients, access points, or ad-hoc devices.
Wi-Fi Signals - the unique characteristics of Wi-Fi, and how signals are organized.
Power and Receiver sensitivity - how far each wireless device can go, and how well a router can listen and filter out interference and noise.
Antennas - how the type of antenna changes the way the router broadcasts.
Reading through this material should take about an hour. Working through the activities, or diving deeper into the subject with a group may take longer. What is a wireless signal?
Wireless signals are important because they can transfer information -- audio, video, our voices, data -- without the use of wires, and that makes them very useful.
Wireless signals are electromagnetic waves travelling through the air. These are formed when electric energy travels through a piece of metal -- for example a wire or antenna -- and waves are formed around that piece of metal. These waves can travel some distance depending on the strength of that energy.
For more on how electromagnetic signals work, check the External Resources section at the end of this document. Types of Wireless Signals
There are many, many types of wireless technologies. You may be familiar with AM and FM radio, Television, Cellular phones, Wi-Fi, Satellite signals such as GPS and television, two-way radio, and Bluetooth. These are some of the most common signals, but what makes them different? Frequency
First of all, wireless signals occupy a spectrum, or wide range, of frequencies: the rate at which a signal vibrates. If the signal vibrates very slowly, it has a low frequency. If the signal vibrates very quickly, it has a high frequency. Frequency is measured in Hertz, which is the count of how quickly a signal changes every second. As an example, FM radio signals vibrate around 100 million times every second! Since communications signals are often very high in frequency, we abbreviate the measurements for the frequencies - millions of vibrations a second is Megahertz (MHz), and billions of vibrations a second is Gigahertz (GHz). One thousand Megahertz is one Gigahertz. Example Frequency Ranges
Below we can see the span of frequencies that are commonly used in communications. Broadcast transmitters for AM, FM and Television use frequencies below 1000 MHz, Wi-Fi uses two bands at higher frequencies - 2.4 and 5GHz. Cellular phones use many different frequencies.
The frequencies from left to right:
AM Radio: Around 10MHz
FM Radio: Around 100MHz
Television: Many frequencies from 470MHz to 800MHz, and others.
Cellular phones: 850MHz, 1900MHz, and others
Wi-Fi: 2.4GHz
Satellite: 3.5GHz
Wi-Fi: 5GHz Modulation
In addition to having different frequencies, wireless signals can be different in the way they convey information. A wireless signal needs to be modulated--or changed--to send information. There are many types of modulation, and different technologies can use one or more types to send and receive information. In the two examples below -- AM and FM radio -- the M stands for modulation. The type of modulation is what makes them different.
Example one: AM radio. The A in AM comes from Amplitude - the energy or strength of the signal, operating at a single frequency. An un-modulated AM wave might look like:
And a modulated AM radio wave has higher and lower energy (amplitude) waves indicating higher and lower audio frequencies in the signal:
From left to right, we have the normal, un-modulated wave, then the lower amplitude wave (representing low points in audio waves), then the higher amplitude wave (representing crests or high points in audio waves).
A more detailed version of an AM signal is below:
The audio signal is the wave on the top, with the corresponding Amplitude Modulated wave below it.
Example two: FM radio. The F in FM comes from Frequency - defined by how quickly the wave vibrates every second. An un-modulated FM wave might look like:
And a modulated FM radio wave has higher and lower frequencies indicating higher and lower audio frequencies in the signal:
From left to right, we have the normal, un-modulated wave, then the lower frequency wave (representing lower audio amplitudes), then the higher frequency wave (representing higher audio amplitudes).
The type of modulation various technologies use to communicate can be very different, and are often not compatible. Satellite equipment cannot speak directly to your laptop or smartphone, which uses Wi-Fi to send and receive information. This is because the radios in different devices can listen only to certain types of modulations and frequencies.
As an example, some broadcast radio receivers have a switch to select between AM and FM signals, for two reasons: they use different frequencies to transmit, and they use different modulation types. If you try and listen to an AM signal with a radio in FM mode, it wont work. The opposite is also true - in AM mode, an FM signal doesnt make sense to the receiver. It is important that transmitters and receivers use the same frequencies and modulation types to communicate.
Devices in your daily life use many types of wireless signals. Look at the table below to see the various frequencies and types of modulation each uses: Technology or device Type of wireless signal
Analog video - Amplitude modulated from 50MHz to 800MHz
Digital video - complex modulation from 200MHz to 800MHz
Voice - analog or digital modulation from 800MHz to 900MHz
3G, 4G or LTE - digital modulation from 1700MHz to 1900MHz and others
Bluetooth - digital modulation at 2400MHz
Walkie-talkie / two-way radio - analog AM, FM or digital modulation over many frequencies
Many types of signals - voice, audio, video, data
Many modulation types - analog and digital
Many, many frequencies - 3400MHz, 5900MHz, 10.7GHz, 14.5GHz, 23GHz, and many others.
Wi-Fi - digital modulation at 2400MHz or 5000 to 5800MHz.
Bluetooth - digital modulation at 2400MHz
AM Radio - AM modulation from 0.6MHz to 1.6MHz
FM Radio - FM modulation from 88MHz to 108MHz
Nearly every device or technology uses a different wireless frequency and modulation. This means most devices can only understand a very specific kind of wireless signal. Receivers and Transmitters
When a device sends out a wireless signal, it is called a transmitter. When another device picks up that wireless signal and understands the information, it is called a receiver. In the case of FM radio, there is one transmitter--owned and operated by the radio station--and many receivers that people listen to the station with. When a device has both a transmitter and a receiver, it is sometimes called a transceiver. Devices such as routers can both transmit and receive, which is what makes them useful for building networks--you probably want to be able to send messages to your neighbors and out to the world, as well as receive messages!
Quick Activity: What devices do you own or use frequently that are transmitters, receivers or transceivers? Fill in some examples below each type: Transmitter Receiver Transceiver Examples:
Examples:
Examples:
Do you use more transmitters, receivers, or transceivers throughout the day? What is different about the way you use each of these? Backgrounds 6 2 dynamic desktop wallpapers. Wi-Fi Signals
When building a network, you will be using Wi-Fi technology, which has some unique characteristics you will need to know.
There are two types of Wi-Fi signal, based on the frequencies they use:
2.4GHz - A lower frequency, this is the more common Wi-Fi technology in use today. Many devices use it, so the signals can become more crowded and interfere with each other. It can pass through walls and windows fairly well.
5GHz - This higher frequency technology is used by fewer devices, and can sometimes achieve higher speeds because the frequencies are less crowded. It cannot pass through walls and windows as well as the 2.4GHz band signals, so the range of 5GHz technology is often shorter.
These two types of Wi-Fi are called the Frequency Bands , or just Bands for short.
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.
2.4GHz Band
For the 2.4GHz band, there are 14 channels total. Unfortunately, these channels overlap, so they arent all usable at the same time. 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 11. 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 2.4GHz band equipment are channels 1, 6, and 11. 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 13. 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.
5GHz Band
The 5GHz frequency band is much wider and has more channels, so the diagram is a bit more extensive. Fortunately, these channels do not overlap, so you dont have to worry about picking non-standard channels like in the 2.4GHz band.
There are many more channels available in the 5GHz band, so it should be easier to select a channel in this band that doesnt cause interference. 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, 149, 153, 157, 161, and 165. There are other channels available for Access Points or other types of community networks, but those channels wont work with mesh wireless. 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. Power and Receiver Sensitivity
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.
Manufacturers do not usually publish information about their routers transmit power or receive sensitivity. Instead, the manufacturer will give a generic range rating to their routers, usually relative to each other. In some cases, usually with more business or professional oriented equipment you can find the information for transmit power and receive sensitivity.
A routers transmit power can be measured with two scales -- milliwatts (mW) or dBm:
A milliwatt is one thousandth (thats 1/1000) of a single watt - which is a generic measurement of power. For instance, a light bulb might be 40 watts. A router will have an output power of 100mW, which is 400 times less!
A dBm is a relative measurement using logarithms. One milliwatt is 0 dBm. 10 milliwatts is 10 dBm; 100 milliwatts is 20 dBm, and so on. This is the scale that many network designers use to calculate if longer wireless links will work.
A few examples of the transmit power levels in common Wi-Fi hardware is below:
10mW (10dBm): Laptop or smartphone, or very low cost Wi-Fi router.
About 25 to 50 meters
100mW (20dBm): Indoor home or office router.
About 50 to 100 meters
100mW (20dBm): Outdoor sector router.
About 5 to 10 kilometers
500mW (1/2 Watt or 27dBm): Outdoor, long distance focused routers.
About 10 to 20 kilometers or more
Wireless transmitter power is only one half of the connection. The Wi-Fi receiver has a range of power levels it can hear--the listen power in the diagram above. This is also known as the receive sensitivity . The receive sensitivity values are generally rated in dBm, and are usually in the range of -40dBm to -80dBm. 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.
As a receiver moves away from a wireless router, the signal it hears will get quieter -- in other words, the power it receives will go down. 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.
If the router moves too far away from the transmitter, it wont be able to receive any signal, either due to the signal being too weak or other signals interfering, and the routers will disconnect. Below we can see the two routers have disconnected, as there isnt enough signal.
The optimal signal range for outdoor wireless equipment is between -40dBm and -60dBm. This will ensure the connection can maintain the highest bandwidth possible. Antennas
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. Omnidirectional Antennas
An omnidirectional antenna sends a signal out equally in all directions around it.
Using omnidirectional antennas has the benefit of creating connections in any direction. You dont have to do as much planning to connect with multiple neighbors or buildings. 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: Istumbler 103 2 Find Local Wireless Networks Phone Number Customer Service Directional Antennas
The next type of antenna is known as directional--it sends out a signal in a more focused way. There are two main types of directional antennas: Sector Antenna
Focused Antenna
Sector antennas send out a pie-shaped wedge of signal - it can be anywhere between 30 degrees and 120 degrees wide. These are often long, rectangular antennas that are separate or integrated in to a router. A focused antenna sends out a narrow beam of signal - it is normally around 5 to 10 degrees wide, but it can be a little wider as well. These are often dishes or have a mesh bowl reflecting signal behind them.
Using directional antennas has the benefit of increasing the distance a signal will travel in one direction, while reducing it in all other directions. Since the signal is all going one way, the power that would be sent out in all directions with omnidirectional nodes is now focused, increasing the power in that direction.
It can also decrease the interference received at the node. There are fewer signals coming in to the antenna, since the node is only listening to signals from the direction it is pointing. It wont hear signals behind it or to the sides as well or at all. This reduces the signals it needs to sort out, and allows it to focus on other signals more, increasing the quality of those connections.
However, directional antennas also have the drawback of requiring more planning to create links in your neighborhood. Since you are defining and limiting the areas where wireless signals go, you need to think about how those signals cover your neighborhood. If there are areas that are then left out, how will those areas be included in the network?
Also, the node has a very powerful signal in a single direction. If omnidirectional units, or lower power units such as laptops, are connecting to the node, they may not connect properly. The laptop will hear the node very well, but the directional node may not hear the laptop. This will create the situation where it looks like there is a strong signal, but you cannot connect.
Quick Activity: What are the best uses for the different kinds of antennas? Antenna Type Best Uses Omnidirectional
Sector
Focused
______________________________ ______________________________
______________________________ ______________________________
______________________________ ______________________________
What would the best antennas to use for building a neighborhood network? Definitions Omnidirectional When a node has an omnidirectional antenna attached, it can send and receive wireless signals in all directions around it equally. The signal is actually strongest out to the sides of the antenna. Very little or no signal comes out of the ends of the antenna. Directional antenna When a node has a directional antenna attached, the wireless signal is very strong in one direction, and has a very weak or no signal in every other direction. This generally forms a cone or wedge shaped area from the front of the antenna. Receive sensitivity The minimum level of a received signal required for a device to understand the signal. Access point A device that allows wireless devices to connect to a wired network using Wi-Fi. Watt A unit of power, usually written W. The most common power levels for Wi-Fi devices are in the range of milliwatts - or thousandths of a watt. dBm An abbreviation for the power ratio in decibels (dB) of the power referenced to one milliwatt (mW). 0 dBm is equal to 1 milliwatt. Related Information
We recommend you work through Learn Networking Basics if you havent already. Networking concepts are important when dealing with wireless. External Resources
If you are interested in learning more about Wi-Fi and wireless technology, there is a lot of information out there. Good books to read for background and more information include How Radio Signals Work by Sinclair (ISBN 0070580588), and 802.11 Wireless Networks: The Definitive Guide by Gast (ISBN 0596100523). Istumbler 103 2 Find Local Wireless Networks Phone Number Technical Support
There are also excellent documents on Wikipedia about Wi-Fi and wireless signals. Similarly, an Internet search will most likely answer any questions you can think of, as wireless is a very popular technology.
For more information on what frequencies are available in your country or regulatory area, please see this article on Wikipedia on wireless channels. Documentation Istumbler 103 2 Find Local Wireless Networks Phone Number Lookup
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Istumbler 103 2 Find Local Wireless Networks Phone Number Lookup Introduction
Community Wireless Networks can be designed in many ways. To help you understand these different methods for designing networks, this document covers the basics of what different devices do in wireless networks, and how they can be used in different configurations. Using the knowledge and activities in this document, you can work with others to design the wireless network that works best for your community.
The WAP by the ISP or the ISP's WAP. Your WAP will be performing a network management task known as network address translation (NAT ). This converts the IP addresses on the 'inside' network (i.e., your local area network LAN and wireless connections) to address compatible with that of the 'outside' or wide area network (WAN). Araknis Networks routers, access points, and switches include OvrC (oh-ver-see), our exclusive, cloud management platform. Easily manage all OvrC-enabled devices by client or location from any mobile device using the ultra-intuitive user interface, and eliminate unnecessary service calls. In order to connect your computers wirelessly, all the gizmos on your wireless network must adhere to the 802.11 wireless networking standard. The standard has gone through released four (4) versions. Each version is indicated by a letter at the end of 802.11. With our reverse number lookup you can find number and landline phone number to unmask the name of the caller. We do our best to provide a good source of information concerning the service of Reverse Phone Lookup. You can take advantage of the service all over the world. Our company uses an extensive range of information resources and services. Lg Bridge Network Is Unavailable.
Reading and working through Learn Wireless Basics before this document will help you with some of the concepts used in designing wireless networks. It provides some necessary background information for this document.
Reading through this material should take about 30 to 45 minutes. Working through the activities, or diving deeper into the subject with a group may take longer. Wireless Device Roles
There are three major modes a Wi-Fi device can use. These modes define the role a Wi-Fi device has in the network, and networks must be built out of combinations of devices operating in these different modes. How the devices are configured depends on the types of connections you want to use between parts of the network.
In discussing these modes and the examples below, several types of devices are used. In addition to the phones, tablets, and laptops you use in accessing a network, routers make up the hardware that runs the network. These routers are defined in Learn Networking Basics, but for the sake of this document the quick definition of a router is a network device that can connect one network to another, determine what traffic can pass between them, and perform other functions on a network, such as assigning IP addresses. The three wireless roles are:
Wireless Clients (Station)
Devices such as computers, tablets, and phones are common Clients on a network. When you are accessing a wireless hotspot, or the router in your home or office, your device is the client. This client mode is also known as station mode as well.
Some routers can operate as Clients as well, which allows them to act like the wireless card in a computer, and connect to other Access Points. This can bridge two Ethernet networks, or connect to more distant APs.
A Wireless Client is similar to a person in the audience of a play or movie. They are one of several or many people accessing information through the same conduit - someone speaking.
Access Points (Master)
Most wireless networks are made using Access Points - devices that host and control the wireless connection for laptops, tablets, or smart phones. If you use Wi-Fi in your home or office, it is most likely through an Access Point. When a router is set up as an AP, it is said to be in Master or Infrastructure mode.
An AP is sometimes a stand-alone device that bridges between a wireless and wired (Ethernet) network, or is part of a router. APs can cover a range of areas with a wireless signal, depending on the power of the device and the type of antenna. There are also some APs that are weatherproof, designed to be mounted outdoors.
An Access Point is similar to a person on stage, addressing an audience or crowd - they are providing the information for everyone else. Those audience members can ask questions of the person on the stage, and receive a response.
Ad-Hoc Node (Mesh)
Some wireless devices (laptops, smart phones, or wireless routers) support a mode called Ad-Hoc. This allows those devices to connect together directly, without an Access Point in-between controlling the connection. This forms a different type of network - in Ad-Hoc mode, all devices are responsible for sending and receiving messages to the other devices - without anything else in between. In an Ad-Hoc network, every device must be in this role, and using the same configuration to participate. Not all devices use this mode, and some have it as a hidden feature.
Ad-Hoc devices are used to create a Mesh network, so when they are in this mode, they are called Mesh Nodes.
An Ad-Hoc or Mesh node is similar to an individual in a group or roundtable discussion. They can take equal part in the conversation, raising their hand when they want to speak so the others will listen. If someone at the end of the table cannot hear, one of the individuals in-between can repeat the original message for the listener.
Quick Activity: Describe the differences in the two example networks below. What are the roles and relationships between the different colored nodes in the networks? Example 1
Example 2
Role of the Pink Nodes:
__________________________________
Relationship between nodes:
__________________________________ Role of the Yellow nodes:
__________________________________
Role of the Blue nodes:
__________________________________
Relationship between nodes:
__________________________________
The two networks above are Ad-Hoc and Infrastructure (Access Point) networks. Are there places or times in a social situation where you are in an Access Point or Client situation? Are there places or times when you are in an Ad-Hoc situation? What connects to what?
From the roles above, you can see that Clients always need to connect to an Access Point, and Mesh nodes all connect to each other. It should also be noted that due to how Wi-Fi is designed, this also prevents different roles from connecting to each other as well.
Access Points cannot connect to each other wirelessly:
Clients cannot connect to each other wirelessly:
Clients cannot connect to Ad-Hoc (Mesh) devices wirelessly:
Access Points cannot connect to Ad-Hoc (Mesh) devices wirelessly: Wireless devices in networks
Treat the three types of roles above - Clients, Access Points, and Ad-Hoc nodes - as the building blocks for large networks. Below are several examples that demonstrate how devices configured for different roles can be used. Access Point - Home or Office network
Wireless networks used in your home or office are generally a combination of a router and a wireless Access Point (AP).
In the diagram above:
1 represents the connection to the Internet (Optional - networks can function without the Internet).
2 represents the router that assigns IP addresses and provides a firewall between your network and the Internet.
3 represents the Access Point, providing a wireless bridge between the router and the users devices.
4 represent user devices, such as laptops, tablets, and smartphones.
In many home networks, or small office networks, the router and AP may be combined into a single device. This is usually just called a wireless router. It may also have a DSL, Cable, 3G, or 4G port to provide the connection to the Internet. In large office scenarios, there may be several AP devices spread throughout the building to provide more even wireless coverage, connected back to the router through long Ethernet cables. Point to Point link - Long Distance Connections
Wireless networks can be used to connect distant buildings or areas. It usually requires very focused antennas - such as a dish antenna - that can send a narrow beam in a specific direction. This is discussed in Learn Wireless Basics - so go there for more details on how that works.
A long-distance connection is often called a point-to-point, or PtP link. The name describes the concept: two points are connected together, and nothing else. This requires two wireless devices: one configured as an Access Point; the other configured as a Client. In the example below, two wireless devices are configured to create a point-to-point link. Omnidirectional Access Point and Client Link
1 represents computers connected with Ethernet cables to the wireless devices. These computers are connected to each other over the Point-to-Point link.
2 represents the wireless device setup as an Access Point.
3 represents the wireless device setup as a Client, connected to the Access Point.
This could look like the building-to-building connection, as shown below: Long-distance directional Access Point and Client Link
Here we have another example of a point-to-point link, but where the routers have dish antennas for greater link distance.
In the diagram above:
1 represents computers connected with Ethernet cables to the wireless devices. These computers are connected to each other over the Point-to-Point link.
2 represents the wireless device setup as an Access Point.
3 represents dish antennas that focus the wireless signal, allowing connections over long distances.
4 represents the wireless device setup as a Client, connected to the Access Point.
This could look like the network below, where an AP mounted on a tower is able to connect with a Client device in a home very far away, since the dishes are facing one another.
In both of these examples, there are just two wireless devices linked together - and the antennas determine the range at which they can connect. The more focused the signal, the further the point-to-point link can reach. As the distance between the devices grow, it is more an more important to focus the signal with antennas - at both ends of the connection. Otherwise one end may hear the other, but not be loud enough to be heard! Point to MultiPoint - Wireless Internet Service Provider model
If we combine the two principles used in the networks above - many client devices connecting to an Access Point, and more powerful antennas used for outdoor devices to create longer links - we can create Point to Multipoint networks. These are larger-scale Access Point networks, where there is a single device in the center, controlling all of the Clients connected to it and bridging those connections to the Internet.
These types of networks are used by Wireless Internet Service Providers (WISPs) to connect homes and businesses to the Internet. Instead of running cables around a neighborhood or town, they put up one or more powerful Access Points on a tall building or tower. By installing directional wireless devices in a Client role on other rooftops, and pointing them back at the tall building or tower, those buildings can be connected to the WISPs networks, and thereby the Internet.
The diagram below demonstrates one model for how this works. There is a powerful Access Point mounted on a high building, and several nearby buildings with rooftop wireless Client devices: this forms the Point-to-Multipoint network. Connected to each of the Client devices is an indoor router or Access Point, which allows users to connect their computers, laptops, tablets, or smartphones to the WISP network.
In the diagram above:
1 represents the connection to the Internet.
2 represents an Access Point providing the signal for Client devices to connect to.
3 represents a powerful omnidirectional (all directions) antenna, sending the wireless signal to a large area around the building.
4 represent Client wireless devices on the roof of other buildings, linking to the powerful Access Point, and able to connect to the Internet through that AP.
5 represents small Access Points distributing wireless service inside the building. Mesh - Neighbor-to-neighbor Networks
A mesh network takes the principle of Point-to-Multipoint, and extends it to the idea of every node connecting to every other node in range. In effect, this creates a Multipoint-to-Multipoint network. This requires that all the devices are in the Ad-Hoc mode - wireless devices all in AP mode or Client mode cant perform the same function. For more information on how this principle works, see the Introduction to Mesh document.
The diagram below demonstrates one model for how this works. Wireless mesh nodes are installed on the rooftops of various buildings, and those nodes that are in range and dont have anything blocking the signals will connect. These nodes will share all resources connected to them such as local servers hosting applications and connections to the Internet. They can also be connected to computers, Access Points, or routers inside the buildings so users can access the resources anywhere on the network.
In the diagram above:
1 represents the connection to the Internet.
2 represents a Mesh Node with a connection to the Internet, with an omnidirectional (all directions) antenna.
3 represents Mesh Nodes with omnidirectional (all directions) antennas. These nodes are receiving Internet access from Mesh Node B . They may be connected to different devices inside the building.
4 represents small Access Points distributing wireless service inside the building. Hybrid Networks
When designing and building town or community-sized networks, it may be difficult or impossible to use a single method to connect everyone. For instance, a single Point-to-Multipoint network may not cover an entire community. Mesh nodes can be used to extend client sites to nearby buildings. Point-to-point connections can bridge longer distances and join several disconnected networks together.
In the diagram below, we can see an example of a hybrid network. There is no single example that can cover all of the possible uses for a network! In the activity that follows, you will explore the different ways to build a network by working through scenarios.
One last note before we move on to the activity - in the examples above, and in the activity that follows, the diagrams focus on building networks across rooftops or from building to building. This is generally the best way to build networks that cover neighborhoods, towns, or communities. In the diagrams, the way people connect to this network isnt always shown.
Keep in mind that these rooftop routers may not provide connections to users on the ground, or in buildings. A good way to provide these connections is by attaching Access Points to an Ethernet port on the rooftop router. This indoor Access Point can be set up to use the rooftop network as the source of connections to the Internet, or to provide access to applications and servers on the network. A detailed look at this is below:
In the diagram:
1 represents the rooftop wireless device. It could be a Mesh Node, or Client router.
2 represents the Ethernet cable running out to the rooftop from the Power over Ethernet adapter.
3 represents a Power over Ethernet (PoE) adapter - a common way to power outdoor wireless devices.
4 represents an Access Point, connected to the neighborhood or community network through the rooftop router. Group Activity
Since there are so many ways to build wireless networks to cover your town or community, we recommend working through these pen-and-paper activities. Download the network worksheets and example solutions and try your hand at designing wireless networks.
If you are working through the activity on your own, try printing out the worksheets first and draw in a possible solution to each of the scenarios. You can then review the example solutions and see how your networks compare with some others.
We recommend you work through this activity with a group of your community members, especially when planning and designing a network. First print out a few sets of the network worksheets, and break into groups of two or three people (depending on how many people are gathered). Draw solutions to each scenario, then meet back up and compare all of your solutions to the scenarios. You can also look through the example solutions and compare them to what your groups came up with. Discuss what solutions might be best for your community.
There are a few basic rules to follow when working through the activity. Istumbler 103 2 Find Local Wireless Networks Phone Number 1-800
1. There are three types of routers you will use:
Omnidirectional. These can send and receive wireless signals in every direction.
Sector. These send and receive wireless signals in a limited arc. Limit the connections these routers make to a wedge-shaped area.
Focused. These send and receive wireless signals in a narrow beam. Limit the connections to a single thin line.
2. You have a limited amount of equipment available for each network. Each worksheet has icons of the types and number of pieces of equipment. The example below provides three omnidirectional, one sector, and one focused router:
3. You can configure the wireless equipment in your network to serve any of the wireless roles - AP, client, or ad-hoc node (mesh). The equipment can be any combination of roles, they dont have to all be the same role. Label each router with an A, C, or M depending on the role.
4. You can assume that all of the wireless equipment in the examples are within range of each other - the signals will reach.
5. Remember that Clients can only connect to Access Points. APs cannot connect to each other wirelessly, Clients cannot connect to each other wirelessly, and Mesh nodes cannot connect to APs or Clients wirelessly.
6. Many Clients can connect to a single Access Point. Ad-hoc (mesh) devices can have connections to multiple other mesh devices at once.
7. If you want to connect different combinations of devices together, you can wire them together, as if you plugged an Ethernet cable in between the devices. This way devices that normally cannot connect wirelessly can still be networked. For example, an Access Point or Client can be connected to a Mesh node with an Ethernet cable.
Now download and print out the worksheets and example solutions, and try out some designs! /section Definitions Ad-hoc Network / Device Network On some devices (e.g. laptops) some available network connections are shown as computer to computer networks. These are networks that may be ad-hoc mesh networks or point to point links between computers for small file sharing. The term ad-hoc can also refer to unplanned, decentralized network connections. Antenna Converts electrical signals to radio waves. It is normally connected to a radio transmitter or radio receiver, and is the interface between the electrical signals in the radio, and the movement of the signals through the air. AP (Access Point) A device that allows wireless devices to connect to a wired network using Wi-Fi or related standards Client Device : The device with a wifi radio that you use to connect to a wireless access point, e.g. a computer, cell phone or tablet device. Ethernet A type of networking protocol - it defines the types of cables and connections that are used to wire computers, switches, and routers together. Most often Ethernet cabling is Category 5 or 6, made up of twisted pair wiring similar to phone cables. PoE (Power over Ethernet) describes systems which pass electrical power along with data on Ethernet cabling. Node An individual device in a mesh network. Related Information
This document is intended to be used after you have worked through Every Network Tells a Story, and Learn Wireless Basics. It is a partner document to Wireless Challenges, and can be done before or after that activity. Documentation
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This document covers the basics of how wireless technology works, and how it is used to create networks. Wireless technology is used in many types of communication. We use it for networking because it is cheaper and more flexible than running cables. While wireless networks can be just as fast and powerful as wired networks, they do have some drawbacks.
Reading and working through Learn Networking Basics before this document will help you with some of the concepts used in wireless networks.
In addition to some background information, this document covers six basic concepts:
Wireless signals - what they are and how signals can differ.
Wireless devices - the differences and uses for receivers and transmitters.
Wi-Fi Modes - how networks are made up of clients, access points, or ad-hoc devices.
Wi-Fi Signals - the unique characteristics of Wi-Fi, and how signals are organized.
Power and Receiver sensitivity - how far each wireless device can go, and how well a router can listen and filter out interference and noise.
Antennas - how the type of antenna changes the way the router broadcasts.
Reading through this material should take about an hour. Working through the activities, or diving deeper into the subject with a group may take longer. What is a wireless signal?
Wireless signals are important because they can transfer information -- audio, video, our voices, data -- without the use of wires, and that makes them very useful.
Wireless signals are electromagnetic waves travelling through the air. These are formed when electric energy travels through a piece of metal -- for example a wire or antenna -- and waves are formed around that piece of metal. These waves can travel some distance depending on the strength of that energy.
For more on how electromagnetic signals work, check the External Resources section at the end of this document. Types of Wireless Signals
There are many, many types of wireless technologies. You may be familiar with AM and FM radio, Television, Cellular phones, Wi-Fi, Satellite signals such as GPS and television, two-way radio, and Bluetooth. These are some of the most common signals, but what makes them different? Frequency
First of all, wireless signals occupy a spectrum, or wide range, of frequencies: the rate at which a signal vibrates. If the signal vibrates very slowly, it has a low frequency. If the signal vibrates very quickly, it has a high frequency. Frequency is measured in Hertz, which is the count of how quickly a signal changes every second. As an example, FM radio signals vibrate around 100 million times every second! Since communications signals are often very high in frequency, we abbreviate the measurements for the frequencies - millions of vibrations a second is Megahertz (MHz), and billions of vibrations a second is Gigahertz (GHz). One thousand Megahertz is one Gigahertz. Example Frequency Ranges
Below we can see the span of frequencies that are commonly used in communications. Broadcast transmitters for AM, FM and Television use frequencies below 1000 MHz, Wi-Fi uses two bands at higher frequencies - 2.4 and 5GHz. Cellular phones use many different frequencies.
The frequencies from left to right:
AM Radio: Around 10MHz
FM Radio: Around 100MHz
Television: Many frequencies from 470MHz to 800MHz, and others.
Cellular phones: 850MHz, 1900MHz, and others
Wi-Fi: 2.4GHz
Satellite: 3.5GHz
Wi-Fi: 5GHz Modulation
In addition to having different frequencies, wireless signals can be different in the way they convey information. A wireless signal needs to be modulated--or changed--to send information. There are many types of modulation, and different technologies can use one or more types to send and receive information. In the two examples below -- AM and FM radio -- the M stands for modulation. The type of modulation is what makes them different.
Example one: AM radio. The A in AM comes from Amplitude - the energy or strength of the signal, operating at a single frequency. An un-modulated AM wave might look like:
And a modulated AM radio wave has higher and lower energy (amplitude) waves indicating higher and lower audio frequencies in the signal:
From left to right, we have the normal, un-modulated wave, then the lower amplitude wave (representing low points in audio waves), then the higher amplitude wave (representing crests or high points in audio waves).
A more detailed version of an AM signal is below:
The audio signal is the wave on the top, with the corresponding Amplitude Modulated wave below it.
Example two: FM radio. The F in FM comes from Frequency - defined by how quickly the wave vibrates every second. An un-modulated FM wave might look like:
And a modulated FM radio wave has higher and lower frequencies indicating higher and lower audio frequencies in the signal:
From left to right, we have the normal, un-modulated wave, then the lower frequency wave (representing lower audio amplitudes), then the higher frequency wave (representing higher audio amplitudes).
The type of modulation various technologies use to communicate can be very different, and are often not compatible. Satellite equipment cannot speak directly to your laptop or smartphone, which uses Wi-Fi to send and receive information. This is because the radios in different devices can listen only to certain types of modulations and frequencies.
As an example, some broadcast radio receivers have a switch to select between AM and FM signals, for two reasons: they use different frequencies to transmit, and they use different modulation types. If you try and listen to an AM signal with a radio in FM mode, it wont work. The opposite is also true - in AM mode, an FM signal doesnt make sense to the receiver. It is important that transmitters and receivers use the same frequencies and modulation types to communicate.
Devices in your daily life use many types of wireless signals. Look at the table below to see the various frequencies and types of modulation each uses: Technology or device Type of wireless signal
Analog video - Amplitude modulated from 50MHz to 800MHz
Digital video - complex modulation from 200MHz to 800MHz
Voice - analog or digital modulation from 800MHz to 900MHz
3G, 4G or LTE - digital modulation from 1700MHz to 1900MHz and others
Bluetooth - digital modulation at 2400MHz
Walkie-talkie / two-way radio - analog AM, FM or digital modulation over many frequencies
Many types of signals - voice, audio, video, data
Many modulation types - analog and digital
Many, many frequencies - 3400MHz, 5900MHz, 10.7GHz, 14.5GHz, 23GHz, and many others.
Wi-Fi - digital modulation at 2400MHz or 5000 to 5800MHz.
Bluetooth - digital modulation at 2400MHz
AM Radio - AM modulation from 0.6MHz to 1.6MHz
FM Radio - FM modulation from 88MHz to 108MHz
Nearly every device or technology uses a different wireless frequency and modulation. This means most devices can only understand a very specific kind of wireless signal. Receivers and Transmitters
When a device sends out a wireless signal, it is called a transmitter. When another device picks up that wireless signal and understands the information, it is called a receiver. In the case of FM radio, there is one transmitter--owned and operated by the radio station--and many receivers that people listen to the station with. When a device has both a transmitter and a receiver, it is sometimes called a transceiver. Devices such as routers can both transmit and receive, which is what makes them useful for building networks--you probably want to be able to send messages to your neighbors and out to the world, as well as receive messages!
Quick Activity: What devices do you own or use frequently that are transmitters, receivers or transceivers? Fill in some examples below each type: Transmitter Receiver Transceiver Examples:
Examples:
Examples:
Do you use more transmitters, receivers, or transceivers throughout the day? What is different about the way you use each of these? Backgrounds 6 2 dynamic desktop wallpapers. Wi-Fi Signals
When building a network, you will be using Wi-Fi technology, which has some unique characteristics you will need to know.
There are two types of Wi-Fi signal, based on the frequencies they use:
2.4GHz - A lower frequency, this is the more common Wi-Fi technology in use today. Many devices use it, so the signals can become more crowded and interfere with each other. It can pass through walls and windows fairly well.
5GHz - This higher frequency technology is used by fewer devices, and can sometimes achieve higher speeds because the frequencies are less crowded. It cannot pass through walls and windows as well as the 2.4GHz band signals, so the range of 5GHz technology is often shorter.
These two types of Wi-Fi are called the Frequency Bands , or just Bands for short.
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.
2.4GHz Band
For the 2.4GHz band, there are 14 channels total. Unfortunately, these channels overlap, so they arent all usable at the same time. 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 11. 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 2.4GHz band equipment are channels 1, 6, and 11. 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 13. 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.
5GHz Band
The 5GHz frequency band is much wider and has more channels, so the diagram is a bit more extensive. Fortunately, these channels do not overlap, so you dont have to worry about picking non-standard channels like in the 2.4GHz band.
There are many more channels available in the 5GHz band, so it should be easier to select a channel in this band that doesnt cause interference. 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, 149, 153, 157, 161, and 165. There are other channels available for Access Points or other types of community networks, but those channels wont work with mesh wireless. 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. Power and Receiver Sensitivity
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.
Manufacturers do not usually publish information about their routers transmit power or receive sensitivity. Instead, the manufacturer will give a generic range rating to their routers, usually relative to each other. In some cases, usually with more business or professional oriented equipment you can find the information for transmit power and receive sensitivity.
A routers transmit power can be measured with two scales -- milliwatts (mW) or dBm:
A milliwatt is one thousandth (thats 1/1000) of a single watt - which is a generic measurement of power. For instance, a light bulb might be 40 watts. A router will have an output power of 100mW, which is 400 times less!
A dBm is a relative measurement using logarithms. One milliwatt is 0 dBm. 10 milliwatts is 10 dBm; 100 milliwatts is 20 dBm, and so on. This is the scale that many network designers use to calculate if longer wireless links will work.
A few examples of the transmit power levels in common Wi-Fi hardware is below:
10mW (10dBm): Laptop or smartphone, or very low cost Wi-Fi router.
About 25 to 50 meters
100mW (20dBm): Indoor home or office router.
About 50 to 100 meters
100mW (20dBm): Outdoor sector router.
About 5 to 10 kilometers
500mW (1/2 Watt or 27dBm): Outdoor, long distance focused routers.
About 10 to 20 kilometers or more
Wireless transmitter power is only one half of the connection. The Wi-Fi receiver has a range of power levels it can hear--the listen power in the diagram above. This is also known as the receive sensitivity . The receive sensitivity values are generally rated in dBm, and are usually in the range of -40dBm to -80dBm. 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.
As a receiver moves away from a wireless router, the signal it hears will get quieter -- in other words, the power it receives will go down. 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.
If the router moves too far away from the transmitter, it wont be able to receive any signal, either due to the signal being too weak or other signals interfering, and the routers will disconnect. Below we can see the two routers have disconnected, as there isnt enough signal.
The optimal signal range for outdoor wireless equipment is between -40dBm and -60dBm. This will ensure the connection can maintain the highest bandwidth possible. Antennas
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. Omnidirectional Antennas
An omnidirectional antenna sends a signal out equally in all directions around it.
Using omnidirectional antennas has the benefit of creating connections in any direction. You dont have to do as much planning to connect with multiple neighbors or buildings. 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: Istumbler 103 2 Find Local Wireless Networks Phone Number Customer Service Directional Antennas
The next type of antenna is known as directional--it sends out a signal in a more focused way. There are two main types of directional antennas: Sector Antenna
Focused Antenna
Sector antennas send out a pie-shaped wedge of signal - it can be anywhere between 30 degrees and 120 degrees wide. These are often long, rectangular antennas that are separate or integrated in to a router. A focused antenna sends out a narrow beam of signal - it is normally around 5 to 10 degrees wide, but it can be a little wider as well. These are often dishes or have a mesh bowl reflecting signal behind them.
Using directional antennas has the benefit of increasing the distance a signal will travel in one direction, while reducing it in all other directions. Since the signal is all going one way, the power that would be sent out in all directions with omnidirectional nodes is now focused, increasing the power in that direction.
It can also decrease the interference received at the node. There are fewer signals coming in to the antenna, since the node is only listening to signals from the direction it is pointing. It wont hear signals behind it or to the sides as well or at all. This reduces the signals it needs to sort out, and allows it to focus on other signals more, increasing the quality of those connections.
However, directional antennas also have the drawback of requiring more planning to create links in your neighborhood. Since you are defining and limiting the areas where wireless signals go, you need to think about how those signals cover your neighborhood. If there are areas that are then left out, how will those areas be included in the network?
Also, the node has a very powerful signal in a single direction. If omnidirectional units, or lower power units such as laptops, are connecting to the node, they may not connect properly. The laptop will hear the node very well, but the directional node may not hear the laptop. This will create the situation where it looks like there is a strong signal, but you cannot connect.
Quick Activity: What are the best uses for the different kinds of antennas? Antenna Type Best Uses Omnidirectional
Sector
Focused
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What would the best antennas to use for building a neighborhood network? Definitions Omnidirectional When a node has an omnidirectional antenna attached, it can send and receive wireless signals in all directions around it equally. The signal is actually strongest out to the sides of the antenna. Very little or no signal comes out of the ends of the antenna. Directional antenna When a node has a directional antenna attached, the wireless signal is very strong in one direction, and has a very weak or no signal in every other direction. This generally forms a cone or wedge shaped area from the front of the antenna. Receive sensitivity The minimum level of a received signal required for a device to understand the signal. Access point A device that allows wireless devices to connect to a wired network using Wi-Fi. Watt A unit of power, usually written W. The most common power levels for Wi-Fi devices are in the range of milliwatts - or thousandths of a watt. dBm An abbreviation for the power ratio in decibels (dB) of the power referenced to one milliwatt (mW). 0 dBm is equal to 1 milliwatt. Related Information
We recommend you work through Learn Networking Basics if you havent already. Networking concepts are important when dealing with wireless. External Resources
If you are interested in learning more about Wi-Fi and wireless technology, there is a lot of information out there. Good books to read for background and more information include How Radio Signals Work by Sinclair (ISBN 0070580588), and 802.11 Wireless Networks: The Definitive Guide by Gast (ISBN 0596100523). Istumbler 103 2 Find Local Wireless Networks Phone Number Technical Support
There are also excellent documents on Wikipedia about Wi-Fi and wireless signals. Similarly, an Internet search will most likely answer any questions you can think of, as wireless is a very popular technology.
For more information on what frequencies are available in your country or regulatory area, please see this article on Wikipedia on wireless channels. Documentation Istumbler 103 2 Find Local Wireless Networks Phone Number Lookup
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