Conrad L. Young’s Wired Broadband and Related Industry Glossary of Terms with Acronyms As of 15 February 2012 Open Access This document is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial
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Rectangular QAM, also known as “square” constellations have evenly divisible by two (2) symbols per rectangular quadrant and are, in general, sub-optimal in the sense that they do not maximally space the constellation points for a given energy. However, they have the considerable advantage that they may be easily transmitted as two pulse amplitude modulation (PAM) signals on quadrature carriers, and can be easily demodulated. The non-square constellations achieve marginally better bit-error rate (BER) but are harder to modulate and demodulate. The first rectangular QAM constellation usually encountered is 16-QAM, the constellation diagram for which is shown here. 
Constellation diagram for rectangular 16-QAM A Gray coded bit-assignment is also given. The reason that 16-QAM is usually the first is that a brief consideration reveals that 2-QAM and 4-QAM are in fact binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK), respectively. Also, the error-rate performance of 8-QAM is close to that of 16-QAM (only about 0.5 dB better, but its data rate is only three-quarters that of 16-QAM). (Wikipedia) Redundancy The part of a system that duplicates the essential tasks in order to take over should the original fail. (Arris Glossary of Terms) Reflectance The negative of return loss. In many instances, reflectance and return loss are used synonymously. Minimum directivity and return loss are the lower limits which apply over the entire wavelength range specified in the bandpass. (AOFR) Reflection 1. Reflected energy which substantially covers the spectrum occupied by the originating signal. 2. The abrupt change in direction of a light beam at an interface between two dissimilar media so that the light beam returns into the medium from which it originated. (Arris Glossary of Terms) Reflection Coefficient Ratio of reflected wave to incident wave. Reflections or Echoes In video transmission this may refer either to a signal or to the picture produced. In a signal it is either waves reflected from structures or other objects or waves which are the result of impedance or other irregularities in the transmission medium. In a picture, “Echoes” observed in the picture produced by the reflected waves. Refraction The abrupt change in direction of light as it travels from one material to a dissimilar material. Some of the reflected power in a fiber gets transmitted back to the source. (Arris Glossary of Terms) Also, the changing of direction of a lightwave in passing through a boundary between two dissimilar media in a graded-index medium where refractive index is a continuous function of position. (FiberOpticsInfo) Refractive Index A number that indicates the ratio of the speed of light in a vacuum to the speed of light in a specified. material; abbreviated as n. The higher the number, the slower the speed of light. (Arris Glossary of Terms) Refractive Index Gradient The description of the value of the refractive index as a function of distance from the optical axis along an optical fiber diameter. Also called refractive index profile. (FiberOpticsInfo) Regenerative Repeater A repeater, designed for digital transmission, in which digital signals are amplified, reshaped, retimed, and retransmitted. (FiberOpticsInfo) 
Regenerative Repeater Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/r Regenerator Synonym for regenerative repeater. (FiberOpticsInfo) Regional Bell Operating Company (RBOC) RBOC comprises the U.S. local carriers created in the 1982 Consent Decree to break up AT&T. Seven were formed to serve as parent companies for the 22 then-existing Bell Operating Companies. Registration, Admission, and Status (RAS) RAS Channel is an unreliable channel used to convey the RAS messages and bandwidth changes between two H.323 entities. Remote Access Dial-In User Service (RADIUS) An internet protocol (IETF RFC 2138 and RVC 2139) originally designed for allowing users dial-in access to the internet through remote servers. Its flexible design has allowed it to be extended well beyond its original intended use. Remote Method Invocation (RMI) A Java programming feature that allows a program running on one computer to access the objects and methods of another Java program running on a separate computer. Repeater A network device that repeats signals from one cable onto one or more other cables, while restoring signal timing and waveforms. Also, a receiver and transmitter set designed to regenerate attenuated signals. Used to extend operating range. (FiberOpticsInfo) 
Repeater Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/r Reprovision
Reserve Gain An amplifier has a maximum amount of available gain. When designing a network, amplifiers are specified to supply this maximum amount of gain, less some amount of reserve gain. This reserve can be used to accommodate signal level variations that can occur during installations. (Arris Glossary of Terms) Resident Application A resident application is an application that is saved on the host device and may be run at any time. Resident applications, such as the monitor application or EPG, are typically responsible for host device control. Residential Gateway A part of the Access Network which adds network functionality and multiplexes different services. The gateway must perform the basic functions of media translation and address translation. Residual Loss The loss of the attenuator at the minimum setting of the attenuator. (FiberOpticsInfo) Resistance The opposition that a substance offers to the flow of electric current. In DC circuits, the opposition a material offers to current measured in ohms; in AC circuits, resistance is the real component of impedance and may be higher than the value measured at DC. (Arris Glossary of Terms) Resistor An electronic component that is deliberately designed to have a specific amount of resistance. Resolution A measure of picture resolving capabilities of a television system determined primarily by bandwidth, scan rates and aspect ratio. Relates to fineness and details perceived. Resolution (Horizontal) The amount of resolvable detail in the horizontal direction in a picture. It is usually expressed as the number of distinct vertical lines, alternately black and white, which can be seen in three-quarters of the width of the picture. This information usually is derived by observation of the vertical wedge of a test pattern. A picture which is sharp and clear and shows small details has good, or high, resolution. If the picture is soft and blurred and small details are indistinct it has poor, or low, resolution. Horizontal resolution depends upon the high-frequency amplitude and phase response of the pickup equipment, the transmission medium and the picture monitor, as well as the size of the scanning spots. Resolution (Vertical) The amount of resolvable detail in the vertical direction of a picture. It is usually expressed as the number of distinct horizontal lines, alternately black and white, which can be seen in a test pattern. Vertical resolution is primarily fixed by the number of horizontal scanning lines per frame. Beyond this, vertical resolution depends on the size and shape of the scanning spots of the pickup equipment and picture monitor and does not depend upon the high-frequency response or bandwidth of the transmission medium or picture monitor. Resource reSerVation Protocol (RSVP) An Internet protocol used for negotiating end-to-end IP quality of service (QoS) within the network. In a PacketCable-based network, RSVP can be used to negotiate QoS on the cable access network. Or IETF resource reservation setup protocol for IP networks. Response The fidelity with which the output of a system, device, or network corresponds to its input. (Arris Glossary of Terms) Responsivity The ratio of generated photocurrent to incident light power, typically expressed in Amperes per Watt (A/W) when used in photoconductive mode. The responsivity may also be expressed as a Quantum efficiency, or the ratio of the number of photogenerated carriers to incident photons and thus a unitless quantity. (Wikipedia) 
Graph of Responsivity of a Silicon Die Based Photodiode versus Optical Wavelength courtesy of Wikipedia, http://en.wikipedia.org/wiki/Photodiode Response Time The length of time between the occurrence of an event and the response of an instrument or circuit to that event. Return Channel A return channel refers to the communications mechanism that provides connection between OpenCable and a remote server. Return Loss The parameter describing the attenuation of a guided wave signal (e.g., via a coaxial cable) returned to a source by a device or medium resulting from reflections of the signal generated by the source. Also, the ratio of optical power launched into an input port to the optical power returning to the same input port. Both directivity and return loss are expressed as positive dB and are measured with all output ports optically terminated. (AOFR) Return Path The term used to describe traffic and paths that go from the subscriber to the headend. Also known as Upstream, or Reverse Path. Return Path Optical Receiver (RPOR) Converts optical wavelengths to RF for distribution of quad-play HFC network content (voice, video, data, cellular) within a cable or telco network headend, hub, or central office (CO). 
HFC Return Path System Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/r 
Return Path Optical Receiver, RPOR, Photograph courtesy of Aurora Networks Return To Zero (RZ) A class of encoding methods for physical circuits in which the carrier (current, voltage) returns to zero after each transmitted bit, i.e. the data is carried in pulse width or polarity, not in the level of the signal. (FreeDictionary dot com) Reuse/Frequency Reuse The utilization of frequency (channels) more than once in a wireless network; equated primarily with the basic cellular grid design, where each cell uses each channel once within its boundaries and is insulated from other cells using that frequency to allow for anticipated interference; due to the shortcomings of conventional transmission techniques, frequency reuse in adjacent cells has been largely implausible until the recent development of spatial processing technology, which can enable same-cell frequency reuse. Reverse Direction Indicates signal flow direction is toward the head-end. Low frequencies are amplified in this direction. (Arris Glossary of Terms) Revenue Generating Unit (RGU) Commonly referred to one additional cable subscription unit. For example, a customer who signs up for digital video and high-speed Internet access is counted as two RGUs, because the customer is signing up for two subscriptions. Reverse Channel The direction of signal flow toward the headend, away from the subscriber; equivalent to upstream. Reverse Path Forwarding A technique where a router receives a packet, then floods the packet out on all paths, except the path on which it received the packet. RF Radio Frequency RF4CE Radio Frequency for Consumer Electronics; a specification written and maintained by the Zigbee Alliance, http://www.zigbee.org/Specifications.aspx, and designed for simple, two-way device-to-device control applications that do not require the full-featured mesh networking capabilities offered by ZigBee 2007. The ZigBee RF4CE specification offers an immediate, low-cost, easy-to-implement solution for control of products and opportunity for a variety of standards including ZigBee Remote Control, ZigBee Input Device and the pending ZigBee 3D Sync. The ZigBee RF4CE specification is designed to control a wide range of products including home entertainment devices, garage door openers, keyless entry systems and many more. ZigBee RF4CE offers lower memory size requirements thereby enabling lower cost implementations. The simple device-to-device topology provides easy development and testing, resulting in faster time to market. ZigBee RF4CE provides a multi-vendor interoperable solution for consumer electronics featuring a simple, robust and low-cost communication network for two-way wireless connectivity. (Zigbee)
RFC Request For Comments RF Carrier An AM technique wherein a carrier, with a frequency much higher than the encoded information, varies according to the amplitude of the information being encoded. (FiberOpticsInfo) RFI Radio Frequency (RF) Interference RFI Request For Information RF Leakage Radiation of RF energy, either through a poor connection or a damaged cable. When leakage occurs, proper operation of the network may be hindered. (Arris Glossary of Terms) RFoG RF over Glass; SCTE 174 2010, “Radio Frequency over Glass Fiber-to-the-Home Specification “, defines a fiber-to-the-home system optimized for compatibility with hybrid fiber-coax (HFC) plant, using the same end equipment at both the home and at the headend or hub. The RFoG system is defined to begin where the plant becomes passive, extending from that point to the home. This interface is referred to as the Optical Hub. There are many possible variations on the structure of the optical hub, depending on the needs of the system. The RFoG system is defined to terminate at the subscriber-side interface of an RFoG Optical Network Unit (R-ONU) at the home. The specifications in SCTE 174 2010 apply to the RFoG Optical Network Unit (R-ONU) and are designed to allow interoperability between R-ONUs from various manufacturers. SCTE 174 2010 contains specifications for systems that use amplitude modulation (AM) in the upstream path and systems that use frequency modulation (FM) in the upstream path. SCTE 174 2010 details the requirements for AM systems. The sections that apply specifically to FM systems are so noted and do not apply to AM systems. Portions of the AM specifications that do not apply to FM systems are also noted. AM and FM systems cannot be mixed in the same optical distribution network (ODN). (SCTE)
PON Categories as of 01 March 2011 
RFoG Reference Architecture, excerpt from SCTE 174 2010
RG6 Cable A coaxial cable used for broadband video applications; RG6 has an 18 gauge center conductor, allowing a higher bandwidth than the RG59 cable, which has a smaller 20 gauge center conductor; RG6 uses standard “F” connectors for video equipment connections. (Linear LLC) RGB Red, Green, and Blue; the basic parallel component set in which a signal is used for each primary color, or the related equipment or interconnect formats or standards. (FiberOpticsInfo)
Revenue Generating Unit RG/U RG is the military designation for coaxial cable and U stands for general utility. (Arris Glossary of Terms) RIAA Recording Industry Association of America Ribbon Cable A cable whose conductors lie side by side in a single plane. Usually has a molded polyethylene insulation. (Arris Glossary of Terms) Right-Click Using the secondary mouse button (usually the right button) to open context menus. RIN Relative Intensity Noise; often used to quantify the noise characteristics of a laser. (FiberOpticsInfo) Ring A network topology in which the nodes are connected in a closed loop. Data is transmitted from node to node around the loop, always in the same direction. Ringing An oscillatory transient occurring in the output of a system as a result of a sudden change in input. Results in close-spaced multiple reflections, particularly noticeable when observing test patterns, equivalent square waves, sine-squared signal, or any fixed objects whose reproduction requires frequency components approximating the cutoff frequency of the system. Ring Network A network topology in which terminals are connected in a point-to-point serial fashion in an unbroken circular configuration. (FiberOpticsInfo) 
Ring Network Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/r RIP Routing Information Protocol Rise Time The time taken to make a transition from one state to another, usually measured between the 10% and 90% completion points of the transition. Alternatively the rise time may be specified at the 20% and 80% amplitudes. Shorter or faster rise times require more bandwidth in a transmission channel. (FiberOpticsInfo) Rise Time Download 2.22 Mb. Share with your friends:
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