Point-to-point (telecommunications)

A 1 Gbit/s point-to-point millimeter-wave link installed in the UAE
A point-to-point wireless unit with a built-in antenna at Huntington Beach, California

In telecommunications, a point-to-point connection refers to a communications connection between two communication endpoints or nodes.

- Point-to-point (telecommunications)

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Microwave transmission

Transmission of information by electromagnetic waves with wavelengths in the microwave range of the electromagnetic spectrum.

The atmospheric attenuation of microwaves in dry air with a precipitable water vapor level of 0.001 mm. The downward spikes in the graph corresponds to frequencies at which microwaves are absorbed more strongly, such as by oxygen molecules.
A parabolic satellite antenna for Erdfunkstelle Raisting, based in Raisting, Bavaria, Germany
C-band horn-reflector antennas on the roof of a telephone switching center in Seattle, Washington, part of the U.S. AT&T Long Lines microwave relay network
Dozens of microwave dishes on the Heinrich-Hertz-Turm in Hamburg, Germany
Communications tower on Frazier Mountain, Southern California with microwave relay dishes
Danish military radio relay node
Production truck used for remote broadcasts by television news has a microwave dish on a retractible telescoping mast to transmit live video back to the studio.
Antennas of 1931 experimental 1.7 GHz microwave relay link across the English Channel. The receiving antenna (background, right) was located behind the transmitting antenna to avoid interference.
US Army Signal Corps portable microwave relay station, 1945. Microwave relay systems were first developed in World War II for secure military communication.
Richtfunkstelle Berlin-Frohnau
Microwave spying

Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna.

Duplex (telecommunications)

A simple illustration of a half-duplex communication system
A simple illustration of a full-duplex communication system. Full-duplex is not common in handheld radios as shown here due to the cost and complexity of common duplexing methods, but is used in telephones, cellphones and cordless phones.

A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions.

Parabolic antenna

Antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves to the receiver in its focal point.

Erdfunkstelle, a large parabolic satellite communications antenna in Raisting, Bavaria, Germany, the biggest facility for satellite communication in the world. It has a Cassegrain type feed.
Parabolic antennas are based on the geometrical property of the paraboloid that the paths FP1Q1, FP2Q2, FP3Q3 are all the same length. So a spherical wavefront emitted by a feed antenna at the dish's focus F will be reflected into an outgoing plane wave L travelling parallel to the dish's axis VF.
Wire grid-type parabolic antenna used for MMDS data link at a frequency of 2.5-2.7 GHz. It is fed by a vertical dipole under the small aluminum reflector on the boom. It radiates vertically polarized microwaves.
Main types of parabolic antenna feeds.
Array of multiple feed horns on a German airport surveillance radar antenna to control the elevation angle of the beam
Effect of the feed antenna radiation pattern (small pumpkin-shaped surface) on spillover. Left: With a low gain feed antenna, significant parts of its radiation fall outside the dish. Right: With a higher gain feed, almost all its radiation is emitted within the angle of the dish.
Radiation pattern of a German parabolic antenna. The main lobe (top) is only a few degrees wide. The sidelobes are all at least 20 dB below (1/100 the power density of) the main lobe, and most are 30 dB below. (If this pattern was drawn with linear power levels instead of logarithmic dB levels, all lobes other than the main lobe would be much too small to see.)
The angle theta is normal to the aperture.

Parabolic antennas are used as high-gain antennas for point-to-point communications, in applications such as microwave relay links that carry telephone and television signals between nearby cities, wireless WAN/LAN links for data communications, satellite communications and spacecraft communication antennas.

Broadcasting (networking)

Method of transferring a message to all recipients simultaneously.

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This is in contrast with the point-to-point method in which each sender communicates with one receiver.

Wireless network

Computer network that uses wireless data connections between network nodes.

Wireless icon
Computers are very often connected to networks using wireless links, e.g. WLANs
Wireless LANs are often used for connecting to local resources and to the Internet
Example of frequency reuse factor or pattern 1/4
In a hidden node problem Station A can communicate with Station B. Station C can also communicate with Station B. However, Stations A and C cannot communicate with each other, but their signals can interfere at B.
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Understanding of SISO, SIMO, MISO and MIMO. Using multiple antennas and transmitting in different frequency channels can reduce fading, and can greatly increase the system capacity.

Fixed wireless technology implements point-to-point links between computers or networks at two distant locations, often using dedicated microwave or modulated laser light beams over line of sight paths.

Unicast

Unicast is data transmission from a single sender (red) to a single receiver (green). Other devices on the network (yellow) do not participate in the communication.

In computer networking, unicast is a one-to-one transmission from one point in the network to another point; that is, one sender and one receiver, each identified by a network address.

Point-to-multipoint communication

Communication which is accomplished via a distinct type of one-to-many connection, providing multiple paths from a single location to multiple locations.

A point-to-multipoint radio base station manufactured by CableFree installed for a wireless internet service provider in Rotterdam. The station has four radio interfaces each connected to a separate sector antenna, each providing 90 degrees coverage. Within 20 km of this base station, customer-premises equipment with high gain directional antennas are installed on sites which can then connect to the base station to receive broadband data connections of typically 10–200 Mbit/s capacity.

point-to-point and point-to-multipoint links are very popular in the wireless industry and when paired with other high-capacity wireless links or technologies such as free space optics (FSO) can be referred to as backhaul.

Physical layer

First and lowest layer; The layer most closely associated with the physical connection between devices.

RTL8201 Ethernet PHY chip
Texas Instruments DP83825 - 3mm x 3mm 3.3V PHY chip
Micrel KS8721CL - 3.3V Single Power Supply 10/100BASE-TX/FX MII Physical Layer Transceiver

Other topics associated with the physical layer include: bit rate; point-to-point, multipoint or point-to-multipoint line configuration; physical network topology, for example bus, ring, mesh or star network; serial or parallel communication; simplex, half duplex or full duplex transmission mode; and autonegotiation

Computer network

Set of computers sharing resources located on or provided by network nodes.

Network Packet
Common network topologies
A sample overlay network
Network links
Fiber optic cables are used to transmit light from one computer/network node to another
2007 map showing submarine optical fiber telecommunication cables around the world.
Computers are very often connected to networks using wireless links
An ATM network interface in the form of an accessory card. A lot of network interfaces are built-in.
A typical home or small office router showing the ADSL telephone line and Ethernet network cable connections
Firewalls
The TCP/IP model and its relation to common protocols used at different layers of the model.
Message flows between two devices (A-B) at the four layers of the TCP/IP model in the presence of a router (R). Red flows are effective communication paths, black paths are across the actual network links.
SONET & SDH
Asynchronous Transfer Mode
Routing calculates good paths through a network for information to take. For example, from node 1 to node 6 the best routes are likely to be 1-8-7-6, 1-8-10-6 or 1-9-10-6, as these are the shortest routes.
Partial map of the Internet, based on the January 15, 2005 data found on opte.org . Each line is drawn between two nodes, representing two IP addresses. The length of the lines is indicative of the delay between those two nodes. This graph represents less than 30% of the Class C networks reachable.

Bus network: all nodes are connected to a common medium along this medium. This was the layout used in the original Ethernet, called 10BASE5 and 10BASE2. This is still a common topology on the data link layer, although modern physical layer variants use point-to-point links instead, forming a star or a tree.

Teleprinter

Teletype teleprinters in use in England during World War II
Example of teleprinter art: a portrait of Dag Hammarskjöld, 1962
Hughes telegraph, an early (1855) teleprinter built by Siemens and Halske. The centrifugal governor to achieve synchronicity with the other end can be seen.
Siemens t37h (1933) without cover
Keyboard of a Baudot teleprinter, with 32 keys, including the space bar
International Telegraph Alphabet 2 development of the Baudot–Murray code
A Creed & Company Teleprinter No. 7 in 1930
Olivetti Teleprinter
Siemens Fernschreiber 100 teleprinter
A Teletype Model 33 ASR teleprinter, with punched tape reader and punch, usable as a computer terminal
A Teletype Model 32 ASR used for Telex service
A Teletype Model 33 ASR with paper tape reader and punch, as used for early modem-based computing

A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations.