Long-range Wi-Fi

Long-range Wi-Fi is used for low-cost, unregulated point-to-point computer network connections, as an alternative to other fixed wireless, cellular networks or satellite Internet access.

Wi-Fi networks have a range that's limited by the transmission power, antenna type, the location they're used in, and the environment.

A typical wireless router in an indoor point-to-multipoint arrangement using 802.11b or 802.11g and a stock antenna might have a range of 32 metres (105 ft).

Outdoor point-to-point arrangements, through use of directional antennas, can be extended with many kilometers between stations.
Long range Wi-Fi especially in the 2.4 GHz band (as the shorter range higher bit rate 5.8 GHz bands become popular alternatives to wired LAN connections) have proliferated with specialist devices from many vendors including Premiertek CPE, Ubiquiti, EnGenius, Luxul and the Cisco AiroNet line.

While Wi-Fi hotspots are ubiquitous in urban areas, some rural areas use more powerful longer range transceivers as alternatives to cell (GSM, CDMA) or fixed wireless (Motorola Canopy and other 900 MHz) applications.

The main drawbacks of 2.4 GHz vs. these lower-frequency options are: Despite a lack of commercial service providers, applications for long range Wi-Fi have cropped up around the world.
Some benefits of using long range Wi-Fi for these applications include: Nonprofit organizations operating widespread installations, such as forest services, also make extensive use of long-range Wi-Fi to augment or replace older communications technologies such as shortwave or microwave transceivers in licensed bands.

The Technology and Infrastructure for Emerging Regions (TIER) project at University of California at Berkeley in collaboration with Intel, uses a modified Wi-Fi setup to create long-distance point-to-point links for several of its projects in the developing world.

This technique, dubbed Wi-Fi over Long Distance (WiLD), is used to connect the Aravind Eye Hospital with several outlying clinics in Tamil Nadu state, India.
In most standard Wi-Fi routers, the three standards, a, b and g, are enough.

But in long-range Wi-Fi, special technologies are used to get the most out of a Wi-Fi connection.

On the other hand, using dual antennas with orthogonal polarities along with a 2x2 MIMO chipset effectively enable two independent carrier signals to be sent and received along the same long distance path.

Specially shaped directional antennas can increase the range of a Wi-Fi transmission without a drastic increase in transmission power.
High gain antenna may be of many designs, but all allow transmitting a narrow signal beam over greater distance than a non-directional antenna, often nulling out nearby interference sources.

The standard IEEE 802.11 protocol implementations can be modified to make them more suitable for long distance, point-to-point usage, at the risk of breaking interoperability with other Wi-Fi devices and suffering interference from transmitters located near the antenna.

Methods that stretch the range of a Wi-Fi connection may also make it fragile and volatile, due to mundane problems including: Obstacles are among the biggest problems when setting up a long-range Wi-Fi.
Sheet metal in walls or roofs, may efficiently reflect Wi-Fi signals, causing signal loss or multipath problems.

By its very nature, "long range" connotes an antenna system which can see many of these devices, which when added together produce a very high noise floor, whereby no single signal is usable, but nonetheless are still received.

The aim of a long range system is to produce a system which over-powers these signals and/or uses directional antennas to prevent the receiver "seeing" these devices, thereby reducing the noise floor.

Cellular repeater

A cellular repeater, cell phone repeater, or wireless cellular signal booster, a type of bi-directional amplifier (BDA) as commonly named in the wireless telecommunications industry, is a device used for boosting the cell phone reception to the local area by the usage of a reception antenna, a signal amplifier and an internal rebroadcast antenna.

Modern cellular repeater amplifiers rebroadcast cellular signals inside the building.

The systems usually use an external, directional antenna to collect the best cellular signal, which is then transmitted to an amplifier unit which amplifies the signal, and retransmits it locally, providing significantly improved signal strength.
One advantage of cellular repeaters is an increase in the cell phone's battery life due to the lower power required to broadcast the signal to the local bi-directional amplifier, due to its proximity to the phone.

This is because the antenna can be oriented and located outside to provide the best possible signal, usually aligned with the nearest cell tower.

Generally speaking the larger the external antenna the better the signal - although even a small, correctly oriented external antenna should provide better signal than the internal antenna on any cell phone.
The better systems will generally include an internal monopole antenna (although the type of antenna is far from standardised) for rebroadcasting the signal internally - the advantage of using a monopole antenna is that the signal will be equally distributed in all directions (subject, of course, to attenuation from obstacles).

Because all radio antennas are intrinsically polarized, cell phones perform best when their antennas are oriented parallel to the booster's antenna - although within reasonable proximity the booster's signal will be strong enough that the orientation of the cell phone's antenna will not make a significant difference in usability.
Excellent high-power models (not home usage - smart and expensive technology of the operators) offering gain around 100dBm (ICE function is welcomed as an improvement of the radio isolation between donor and service antenna).

However, since the decibel scale is measured on a logarithmic scale a 30dB gain represents a one thousandfold signal power increase - meaning the total amplification of a repeater with greater than around 50dB is likely to be useless without a good, well aligned antenna.

The power gain is calculated by the following equation: For repeater is needed to secure sufficient isolation between donor and service antenna.
The isolation is possible to improve by antenna type selection, in macro environment by angle between donor and service antenna (ideally 180°), space separation (typically vertical distance in case of the tower installation between donor and service antenna is several meters), inserting of the attenuating environment (smart placement of the donor and service antenna, e.g., between donor and service antenna is wall, placement of the metal mesh), reduction of reflections - in front of the donor antenna no near obstacle (like tree, metal-sheet building, glasshouse, or house)).

Because of the cellular network has form principle reduced cell size (depends on the technology and activated features typically X*10 km (for standard GSM 35 km), urban FDD/TDD network 20 km) usage of repeater virtually moving user to bigger distance: radio distance = real distance + (repeater delay in us) *0.3 km (delay of RF signal in air is 3.3us/km).
As a result, the only way to obtain strong cell phone signal in these areas is usually to install a home cellular repeater.

In these cases the installation of a cellular repeater will generally massively increase signal strength just due to the amplifier, even a great distance from the broadcast towers.

Some construction materials very rapidly attenuate cell phone signal strength.

Even in urban areas which usually have strong cellular signals throughout, there are often dead zones caused by destructive interference of waves which have taken different paths (caused by the signal bouncing off buildings etc.)

Because the frequencies which cell phones use are too high to reflect off the ionosphere as shortwave radio waves do, cell phone waves cannot travel via the ionosphere.
Repeaters are available for all the different GSM frequency bands, some repeaters will handle different types of network such as multi-mode GSM and UMTS repeaters however dual- and tri-band systems cost significantly more.

The use of a mobile signal booster in the UK is only permitted by the mobile networks who hold the licences in the cellular bands.

However, in cities and areas where many cells exist from each operator, the use of devices ranging from small mobile signal boosters to high power repeaters can cause loss of coverage through interference and desensitisation of the cells.

Firewall (computing)

A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass.

Many routers that pass data between networks contain firewall components and, conversely, many firewalls can perform basic routing functions.

The predecessors to firewalls for network security were the routers used in the late 1980s: The first paper published on firewall technology was in 1988, when engineers from Digital Equipment Corporation (DEC) developed filter systems known as packet filter firewalls.


TCP and UDP protocols constitute most communication over the Internet, and because TCP and UDP traffic by convention uses well known ports for particular types of traffic, a "stateless" packet filter can distinguish between, and thus control, those types of traffic (such as web browsing, remote printing, email transmission, file transfer), unless the machines on each side of the packet filter are both using the same non-standard ports.

Packet filtering firewalls work mainly on the first three layers of the OSI reference model, which means most of the work is done between the network and physical layers, with a little bit of peeking into the transport layer to figure out source and destination port numbers.


When a packet originates from the sender and filters through a firewall, the device checks for matches to any of the packet filtering rules that are configured in the firewall and drops or rejects the packet accordingly.

For example, if a rule in the firewall exists to block telnet access, then the firewall will block the TCP protocol for port number 23.

The NuFW firewall provides real identity-based firewalling, by requesting the user's signature for each connection.

Network layer firewalls, also called packet filters, operate at a relatively low level of the TCP/IP protocol stack, not allowing packets to pass through the firewall unless they match the established rule set.


If a packet matches an existing connection based on comparison with the firewall's state table, it will be allowed to pass without further processing.

Modern firewalls can filter traffic based on many packet attributes like source IP address, source port, destination IP address or port, destination service like WWW or FTP.

Application firewalls accomplish their function by hooking into socket calls to filter the connections between the application layer and the lower layers of the OSI model.

Application firewalls work much like a packet filter but application filters apply filtering rules (allow/block) on a per process basis instead of filtering connections on a per port basis.


It is rare to find application firewalls not combined or used in conjunction with a packet filter.

Also, application firewalls further filter connections by examining the process ID of data packets against a ruleset for the local process involved in the data transmission.

Because of these limitations, application firewalls are beginning to be supplanted by a new generation of application firewalls that rely on mandatory access control (MAC), also referred to as sandboxing, to protect vulnerable services.

Firewalls often have network address translation (NAT) functionality, and the hosts protected behind a firewall commonly have addresses in the "private address range", as defined in RFC 1918.

Home network

A home network or home area network (HAN) is a residential local area network (LAN) for communication between digital devices typically deployed in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices.

Home networks may use wired or wireless technologies.

One of the most common ways of creating a home network is by using wireless radio signal technology; the 802.11

Some home networking devices operate in both radio-band signals and fall within the standard 802.11n.

A wireless network can be used for communication between many electronic devices, to connect to the Internet or to wired networks that use Ethernet technology.


With the installation of a home networking device, the network can be accessed by simply plugging the Computer into a wall socket.

The ITU-T G.hn and IEEE Powerline standard, which provide high-speed (up to 1 Gbit/s) local area networking over existing home wiring, are examples of home networking technology designed specifically for IPTV delivery.

A home network may consist of the following components: Older devices may not have the appropriate connector to the network.

As networking technology evolves, more electronic devices and home appliances are becoming Internet ready and accessible through the home network.

Computer network

A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information.

Networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, scale, topology, and organizational scope.

Communications protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming.


Well-known communications protocols are Ethernet, a hardware and link layer standard that is ubiquitous in local area networks, and the internet protocol suite, which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, as well as host-to-host data transfer, and application-specific data transmission formats.

Before the advent of computer networks that were based upon some type of telecommunications system, communication between calculation machines and early computers was performed by human users by carrying instructions between them.

Today, computer networks are the core of modern communication.


The scope of communication has increased significantly in the past decade, and this boom in communications would not have been possible without the progressively advancing computer network.

Computer networks can be classified according to the hardware and associated software technology that is used to interconnect the individual devices in the network, such as electrical cable (HomePNA, power line communication, G.hn), optical fiber, and radio waves (wireless LAN).

A communications protocol is a set of rules for exchanging information over a network.


An important example of a protocol stack is HTTP running over TCP over IP over IEEE 802.11 (TCP and IP are members of the Internet Protocol Suite, and IEEE 802.11 is a member of the Ethernet protocol suite).

Ethernet is a family of connectionless protocols used in LANs, described by a set of standards together called IEEE 802 published by the Institute of Electrical and Electronics Engineers.

MAC bridging (IEEE 802.1D) deals with the routing of Ethernet packets using a Spanning Tree Protocol, IEEE 802.1Q describes VLANs, and IEEE 802.1X defines a port-based Network Access Control protocol, which forms the basis for the authentication mechanisms used in VLANs, but it is also found in WLANs – it is what the home user sees when the user has to enter a "wireless access key".


Synchronous Optical NETworking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers.

Computer network programming involves writing computer programs that communicate with each other across a computer network.

A personal area network (PAN) is a computer network used for communication among computer and different information technological devices close to one person.

A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings.


Current wired LANs are most likely to be based on Ethernet technology, although new standards like ITU-T G.hn also provide a way to create a wired LAN using existing home wires (coaxial cables, phone lines and power lines).

Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP.

LANs can be connected to Wide area network by using routers.

A home area network (HAN) is a residential LAN which is used for communication between digital devices typically deployed in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices.


A campus area network (CAN) is a computer network made up of an interconnection of LANs within a limited geographical area.

A backbone network is part of a computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks.

A specific case of a backbone network is the Internet backbone, which is the set of wide-area network connections and core routers that interconnect all networks connected to the Internet.

A Metropolitan area network (MAN) is a large computer network that usually spans a city or a large campus.

A wide area network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances, using a communications channel that combines many types of media such as telephone lines, cables, and air waves.

A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires.

An internetwork is the connection of multiple computer networks via a common routing technology using routers.

Intranets and extranets are parts or extensions of a computer network, usually a LAN.

Telecommunications network

A telecommunications network is a collection of terminals, links and nodes which connect to enable telecommunication between users of the terminals.

Each terminal in the network must have a unique address so messages or connections can be routed to the correct recipients.

A large number of protocols have been developed over the years to specify how each different type of telecommunication network should handle the control and bearer messages to achieve this efficiently.

In general, every telecommunications network conceptually consists of three parts, or planes (so called because they can be thought of as being, and often are, separate overlay networks): The data network is used extensively throughout the world to connect individuals and organizations.


TCP/IP are the fundamental protocols that provide the control and routing of messages across the data network.

Wireless mesh network

A wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology.

Wireless mesh networks often consist of mesh clients, mesh routers and gateways.

The coverage area of the radio nodes working as a single network is sometimes called a mesh cloud.

The animation below illustrates how wireless mesh networks can self form and self heal.

A wireless mesh network often has a more planned configuration, and may be deployed to provide dynamic and cost effective connectivity over a certain geographic area.


In this way, the wireless mesh network differs from an ad-hoc network, since these nodes are often constrained by resources.

Wireless mesh architecture is a first step towards providing cost effective and dynamic high-bandwidth networks over a specific coverage area.

Wireless mesh architectures infrastructure is, in effect, a router network minus the cabling between nodes.

Wireless mesh networks have a relatively stable topology except for the occasional failure of nodes or addition of new nodes.


Practically all the traffic in an infrastructure mesh network is either forwarded to or from a gateway, while in ad hoc networks or client mesh networks the traffic flows between arbitrary pairs of nodes.

An important possible application for wireless mesh networks is VoIP.

One of the more often cited papers on Wireless Mesh Networks identified the following areas as open research problems in 2005 - There are more than 70 competing schemes for routing packets across mesh networks.