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In telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
, point-to-multipoint communication (P2MP, PTMP or PMP) is communication
Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...
which is accomplished via a distinct type of one-to-many connection, providing multiple paths from a single location to multiple locations.
Point-to-multipoint telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
is typically used in wireless Internet
Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
and IP telephony
Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...
via gigahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is sā1, meaning that one h ...
radio frequencies
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upper ...
. P2MP systems have been designed with and without a return channel In communications systems, the return channel (also reverse channel or return link) is the transmission link from a user terminal to the central hub. Return links are often, but not always, slower than the corresponding forward links. Examples where ...
from the multiple receivers. A central antenna or antenna array
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves. The individual antennas (called ''elements'') are usually connected to a single receiver ...
broadcasts to several receiving antennas and the system uses a form of time-division multiplexing
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fracti ...
to allow for the return channel traffic.
Modern point-to-multipoint links
In contemporary usage, the term point-to-multipoint wireless communications relates to fixedwireless data communication
Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
s for Internet or voice over IP via radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...
or microwave
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...
frequencies in the gigahertz range.
Point-to-multipoint is the most popular approach for wireless communications that have a large number of nodes, end destinations or end users. Point to Multipoint generally assumes there is a central base station
Base station (or base radio station) is ā according to the International Telecommunication Union's (ITU) Radio Regulations (RR) ā a "land station in the land mobile service."
The term is used in the context of mobile telephony, wireless com ...
to which remote ''subscriber units'' or customer premises equipment (CPE) (a term that was originally used in the wired telephone industry) are connected over the wireless medium. Connections between the ''base station'' and ''subscriber units'' can be either line-of-sight or, for lower-frequency radio systems, non-line-of-sight where link budgets permit. Generally, lower frequencies can offer non-line-of-sight connections. Various software planning tools can be used to determine feasibility of potential connections using topographic data as well as link budget simulation. Often the point to multipoint links are installed to reduce the cost of infrastructure and increase the number of CPE's and connectivity.
Point-to-multipoint wireless networks employing directional antennas are affected by the hidden node problem
In wireless networking, the hidden node problem or hidden terminal problem occurs when a node can communicate with a wireless access point (AP), but cannot directly communicate with other nodes that are communicating with that AP. This leads to d ...
(also called hidden terminal) in case they employ a CSMA/CA
Carrier-sense multiple access with collision avoidance (CSMA/CA) in computer networking, is a network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by beginning transmission only after the channel i ...
medium access control protocol. The negative impact of the hidden node problem can be mitigated using a time-division multiple access (TDMA) based protocol or a polling protocol rather than the CSMA/CA protocol.
The telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
s signal in a point-to-multipoint system is typically bi-directional, TDMA or channelized. Systems using frequency-division duplexing (FDD) offer full-duplex connections between base station and remote sites, and time-division duplex (TDD) systems offer half-duplex connections.
Point-to-multipoint systems can be implemented in licensed, semi-licensed or unlicensed frequency bands depending on the specific application. 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.
The base station may have a single omnidirectional antenna or multiple sector antennas, the latter of which allowing greater range and capacity.
See also
*Backhaul (telecommunications)
In a hierarchical telecommunications network, the backhaul portion of the network comprises the intermediate links between the core network, or backbone network, and the small subnetworks at the ''edge'' of the network.
The most common network t ...
*Broadcasting (networking)
In computer networking, telecommunication and information theory, broadcasting is a method of transferring a message to all recipients simultaneously. Broadcasting can be performed as a high-level operation in a program, for example, broadcas ...
* Local Multipoint Distribution Service
* Multichannel Multipoint Distribution Service
*Wireless access point
In computer networking, a wireless access point (WAP), or more generally just access point (AP), is a networking hardware device that allows other Wi-Fi devices to connect to a wired network. As a standalone device, the AP may have a wired co ...
References