Glossary of Metropolitan Broadband Terms: P-T

P2MP - P2MP stands for point-to-multipoint. The term is used to describe wireless broadband technology that sends a signal from one point to many. This technology is currently used as a substitute for DSL or cable. P2MP technology is sometimes referred to as WiMAX, a standard that is not yet in production (should be referenced as "pre-WiMAX.")

Packet - In network communications, a packet is the fundamental bundle of data that is organized in a group for transmission. A packet typically contains three elements: control information, data to be transferred, and error detection and correction bits.

Packet Switching - In computer networking and telecommunications, packet switching is a communications paradigm in which packets (messages or fragments of messages) are individually routed between nodes, with no previously established communication path. In 2.5G or 3G, a phone call is broken into packets and sent across the network where it is reassembled into an audio stream on the other side. With packet switching, a communications channel is only tied up for the time it takes to transmit a single packet, making it generally more efficient than circuit switching, which ties up an entire channel for the duration of the transmission. If a network is analogous to a freeway, with circuit switching, a lane can only be used by one car at a time, whereas packet switching allows a lane to be used by many cars at once.

Physical Layer - In network communications, the physical layer is level one in the seven level OSI model of computer networking. The physical layer performs services requested by the data link layer. The physical layer is the segment of the ISP industry comprised of those companies that build and operate physical network infrastructure, such as Regional Bell Operating Companies (RBOCs), long distance carriers and cable companies, and those who sell wholesale access to network layer companies such as UUNET, who in turn operate nationwide TCP/IP networks. Physical layer companies include SBC, Verizon and AT&T.

PLC - PLC stands for Power Line Communications, the use of the existing utility power grid as the medium to send broadband data communications. In theory, plugging a computer device into an existing power outlet would connect the user to the Internet by tapping into already established national and global power grid networks. PLC is not a wireless technology. See BPL.

Podcasting - Put iPod together with broadcasting and what do you get? I'll give you a hint - it's not a Reese's peanut butter cup. No, this is a new way to experience radio - by the drink. When a producer or distributor of audio content makes the content available for individual, personalized downloads, she is "podcasting," presumably to people's iPods. This is a new way to experience audio content, and it has even been applied recently to video content. We've come a long way from the radio fireside chats of FDR (linked for our younger readers), which were so popular on the "wireless" of 60 years ago. See Convergence of Paris Hilton and G.M. - New York Times for more.

POP - A POP is a Point of Presence, which is a network router that allows a user in one place to connect to their ISP in another. In a broader sense, a POP is also an artificial demarcation or interface point between communications entities. In the US, this term became important during the court-ordered breakup of the Bell Telephone system in the 1980s. Back then, a point of presence was a location where a long-distance carrier could terminate services and provide connections into a local telephone network.

Reverse 911 - The idea behind reverse 9-1-1 is to store resident's telephone numbers in a confidential database, so that in the case of a public emergency, emergency workers or police would be able to send a telephone or cellular message to alert citizens of the situation and provide any necessary warning or evacuation information.

Roaming - Roaming is a general term in wireless telecommunications that refers to the extending of connectivity service in a network that is different than the network with which a station is registered. The canonical example of "roaming" is for cell phones, when you take your phone to an area where your service provider does not have coverage (eg, another country).

Roaming Layer - The roaming layer is the segment of the Wi-Fi industry that serves as clearing house and technology provider between the network layer and the brand layer.

RSS - Really Simple Syndication is a standard for publishing regular updates to web-based content. Using this standard, Web publishers provide updates, such as the latest news headlines or weblog postings. Meanwhile, consumers use RSS reader applications (or one of a growing number of online services) to collect and monitor their favorite feeds in one place (RSS content from a publisher, viewed in one of these readers, is often called a "feed"). Consumer Bottom Line: RSS makes reviewing a large number of sites in a very short time possible. Publisher Bottom Line: RSS permits instant distribution of content updates to consumers. Use this tool on this site to get email updates when I put new content on.

SCADA - SCADA is an acronym for Supervisory Control And Data Acquisition. As the name indicates, it is not a full control system, but rather focuses on the supervisory level. Utilities use SCADA systems to monitor and control their distributed infrastructures. For instance, electric utilities rely on SCADA to know what the voltage levels are at different points out on the grid.

System Integrator or SI - A system integrator brings together multiple pieces of a complex system like a municpal broadband network, in much the same way that a general contractor takes responsibillity to get a house built. The SI serves a vital role as a single point of contact responsible for the creation of the system. Examples of an SI include IBM Global Services, which works with several vendors on a custom solution, and WFI, which started off building cellular networks and migrated to building municipal networks.

T-1 - Also known as DS1 and T1, a T-1 is a dedicated digital communication link provided by a telephone company that offers 1.5 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers.

TCP/IP - TCP/IP stands for Transmission Control Protocol / Internet Protocol, the set of standards for how computers and other devices communicate with each other over networks. Developed in the 1970's, TCP/IP allowed computers from different manufacturers to talk to each other in a common way for the first time, and TCP/IP became the foundation for communication on the Internet.

Telecommunication - Any transmission, emission, or reception of signs, signals, writings, images, sounds, or information of any nature by wire, radio, visual, or other electromagnetic systems.

Terreestrial Trunked Radio (TETRA) - TETRA is a specialist professional mobile radio and walkie talkie standard used by emergency responders such as police, ambulance, and by the military.