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What types of Wi-Fi networks are there?

• Posted by sammu sri March 29, 2021 Filed in Arts & Culture 101 views
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  Wi-Fi networks play an important role in today's technological world, with billions of devices connected to Wi-Fi networks. Already today, most of the world's Internet connections take place over wireless networks. According to Juniper Research, 60% of mobile traffic will go through them by 2019. The global Wi-Fi market will grow from $ 14.8 billion in 2015 to $ 33.6 billion by 2020. With the spread of the Internet of Things and car hotspots, Wi-Fi networks will become the main link in the information space. For most users, Wi-Fi is synonymous with Internet connectivity. But in reality, Wi-Fi is the standard for wireless LAN connection. Simply put, Wi-Fi is a glue capable of connecting multiple devices with a router (router) that can be connected to the Internet.

  Different principles, common goal
  Wi-Fi networks can be built according to different principles, depending on the tasks that a particular wireless network solves. There are three basic principles behind most Wi-Fi networks of all sizes.

  An Access Point (AP) is the most common type of connection. Used at home or in offices as a combination of wireless access point and router. Typically, such Wi-Fi networks are designed to access the Internet, but they can also perform other tasks, such as organizing a local area network without access to the World Wide Web. An access point is like a theater: multiple viewers (client devices) receive information from a single actor (access point).

  The principle of building a Wi-Fi access point
  Photo 1: The principle of building a Wi-Fi access point

  The connection has the following structure:

  the router assigns IP addresses and provides a firewall between the network and the Internet;
  a wireless access point (AP) creates a wireless bridge between the router and user devices;
  user devices - tablets, smartphones, PCs.
  In smaller networks, the router and access point are often combined in the same device. Internet access is carried out via cable or 3G, 4G mobile networks. Large offices use multiple access points to evenly cover the entire office space with a wireless network. Also, access points can have a special design for installation on the street, transport.

  A Point to Point (P2P) connection is used for wirelessly connecting two routers when two LANs or two PCs need to be connected. Such a connection can be used, for example, to connect two houses at a distance of more than 100 m.

  Point-to-point connection
  Photo 2: Ground-level equipment for point-to-point networks can be used for distances of about 100 m in line of sight

  Typically, a point-to-point connection is used to link two computers or two access points over a long distance. For ranges over 500 m, sector, parabolic or panel directional antennas are used. At a cost of about $ 300, such antennas provide a wireless signal transmission range of 5-10 km at a frequency of 5 GHz (in FDD, TDM modes).

  Long distance point-to-point connection
  Photo 3:. Devices with directional antennas and powerful transmitters allow point-to-point connections over a distance of 1 km
  
  A point-to-point connection can consist of a chain of receivers and transmitters. Thus, you can transmit the Wi-Fi signal over a long distance in an environment where cabling is difficult. An example is the Napo Network Wi-Fi network in Peru. It is 445 km long and connects 15 healthcare facilities in a rural area surrounded by jungle. In such relay networks (radio bridges), due to long delays in data transmission, the usual network access method CSMA-CD is inapplicable, therefore, special modes of operation of the transmitter and receiver of the signal are used. So, the FDD mode has a frequency separation of the signal: the receiver and transmitter operate at different frequencies and do not interfere with each other. In TDM mode, the transmitter and receiver operate on the same frequency in half-duplex mode (transmission and reception are separated by time intervals).

  Napo Network, Peru
  Photo 4: Napo Network, Peru

  Rooftop radio bridges are only used to transmit signals to other buildings within line-of-sight. Usually they cannot provide a high-quality Wi-Fi signal inside buildings due to incompatibility of technologies and significant signal attenuation. A Point to Multipoint (P2MP) connection uses one powerful transmitter that broadcasts a Wi-Fi signal to multiple users. Typically, this connection scheme is used by providers to provide Internet access services. The point-to-multipoint connection has the following structure:

  modem with Internet access;
  an access point with a powerful omnidirectional antenna for broadcasting Wi-Fi signals;
  client receiving devices that transmit a signal to the user's wireless access point.
  Point-to-multipoint connection
  Photo 5: Point-to-multipoint connectivity allows multiple users to be connected to the network over a large area

  Point-to-multipoint connection is widely used in urban environments, for example, to organize a video surveillance network, in which video cameras can be miles away from the call center. The most common P2MP connection is used for wireless Internet access and IP telephony.

  The number of subscribers in a point-to-multipoint network depends on the characteristics of the equipment and the required connection speed for each of the end users. The number of subscribers is limited by the bandwidth of the base station connected to the main network resource (server, Internet). An increase in the number of subscribers leads to a decrease in the speed of access to the network for each of the subscribers connected to their access point. Also, the access speed decreases along with the drop in the signal level.

  Small access points are equipped with a low-performance chipset, therefore, they usually provide speeds of about 50 Mbps and serve 10-15 subscribers.

  When it is necessary to provide communication for a larger number of subscribers or to provide reliable communication in difficult terrain, productive access points with sector antennas are used. They direct all radiation of the access point towards subscribers within the sector from 30 to 180 degrees. This allows you to improve the quality of communication with the same or less transmitter power. For example, the Edimax EW-7303APn V2 access point with a built-in sector antenna provides speeds up to 150 Mbps (802.11n, 2.4 GHz). Antenna gain of 15 dBm ensures stable signal reception in the 90-degree sector at a distance of up to 500 m.

  Edimax EW-7303APn V2 access point with built-in sector antenna
  Photo 6: Edimax EW-7303APn V2 access point with built-in sector antenna

  Point-to-multipoint networks with sector antennas and multiple access points are capable of serving up to 1000 subscribers. Often, such networks are deployed to provide public Internet access in shopping centers, airports, train stations. To increase the throughput, the principle of "microcells" is used - the density of the points installation, operating at reduced power, is increased.

  The high bandwidth Wi-Fi can be used by mobile operators to offload networks (Wi-Fi-offload). Data transmission from smartphones is carried out via Wi-Fi network, and the entire GSM / 3G radio range is reserved for "voice". Registration of smartphones in the network is carried out using the SIM-EAP protocol (based on the SIM card number). This approach is common in Europe, however, when designing such a Wi-Fi network, one has to face the difficulties of organizing billing.

  The MESH network is a conceptually new approach to Wi-Fi. In essence, this is a multipoint-multipoint connection diagram. MESH does not require wires, access points are connected to each other via radio. Thus, you can quickly and inexpensively "cover" large areas with Wi-Fi. There are different approaches to designing such a network. The most popular is the use of Wi-Fi points with 2 or 3 independent radio interfaces. One of them (usually 2.4 GHz) is used to connect client devices. The second (5 GHz) - to maintain the transport network, communication with other MESH access points. The route to the Internet gateway can be hardcoded by the administrator, or dynamic routing protocols (802.11k, RIP, OSPF) can be used to select the optimal route taking into account the dynamic congestion of the channels.

  For more information about: what is wlan network