Wireless Glossary – R

Random Access (sometimes called direct access) is the ability to access an element at an arbitrary position in a sequence in equal time, independent of sequence size. The position is arbitrary in the sense that it is unpredictable, thus the use of the term “random” in “random access”. The opposite is sequential access, where a remote element takes longer time to access.

Resource Allocation is used to assign the available resources in an economic way. It is part of resource management. In project management, resource allocation is the scheduling of activities and the resources required by those activities while taking into consideration both the resource availability and the project time.

Routing Area is an area in which a mobile station, in specific operation modes, may move without updating the Serving GPRS Support Node (SGSN).

The Radiation (Antenna) Pattern is a graphical representation in three dimensions of the radiation of the antenna as a function of angular direction. Antenna radiation performance is usually measured and recorded in two orthogonal principal planes (such as E-Plane and H-plane or vertical and horizontal planes). The pattern is usually plotted either in polar or rectangular coordinates. The pattern of most WLAN antennas contains a main lobe and several minor lobes, termed side lobes. A side lobe occurring in space in the direction opposite to the main lobe is called back lobe.

Radio Frequency (RF) is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. RF usually refers to electrical rather than mechanical oscillations, although mechanical RF systems do exist.

A generic term for radio-based technology.

Relative measure of the strength of a received signal. An acceptable link displays an Radio Signal Strength Indicator (RSSI) value of greater than 700.

RADIUS (Remote Authentication Dial In User Service) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. It is intended to work in both local and roaming situations.

When you connect to an ISP using a modem, DSL, cable or wireless connection, you must enter your username and password. This information is passed to a Network Access Server (NAS) device over the Point-to-Point Protocol (PPP), then to a RADIUS server over the RADIUS protocol. The RADIUS server checks that the information is correct using authentication schemes like PAP, CHAP or EAP. If accepted, the server will then authorize access to the ISP system and select an IP address, L2TP parameters, etc.

The RADIUS server will also be notified when the session starts and stops, so that the user can be billed accordingly; or the data can be used for statistical purposes.

Random-Access Memory is a form of computer data storage. A random-access device allows stored data to be accessed in very nearly the same amount of time for any storage location, so data can be accessed quickly in any random order.

Radio Access Network is part of a mobile telecommunication system. It implements a radio access technology. Conceptually, it resides between a device such as a mobile phone, a computer, or any remotely controlled machine and provides connection with its core network (CN).

Number that the Bandwidth and Authentication Manager (BAM) generates, invisible to both the SM and the network operator, to send to the SM as a challenge against an authentication attempt.

A linear measure of the distance that a transmitter can send a signal.

This protocol maps a recognized MAC address to an IP address.

Radio Access Technology is the type of radio technology used in a Radio Access Network to access the Core Network.

Routing Area Update is a change from routing area to routing area, and is done in an almost identical way to a change from location area to location area.

A measurement of the weakest signal a receiver can receive and still correctly translate it into data.

Resumed accumulation of data in available data space (buckets). See Buckets.

A technique of configuring routing protocols so that they advertise networks from other routing protocols.

Reflectance is the ratio of power reflected to the incident power at a connector junction or other component or device, usually measured in decibels or dB. Reflectance is stated as a negative value, e.g., -30 dB. A connector that has a better reflectance performance would be a -40 dB connector or a value less than -30 dB. The terms return loss, back reflection and reflectivity are also used synonymously in the industry to describe device reflections, but stated as positive values.

Change of direction and reduction of amplitude of a signal that encounters an object larger than the wavelength. Reflection may cause an additional copy of the wavelength to arrive at after the original, unobstructed wavelength arrives. This causes partial cancellation of the signal and may render the link unacceptable. However, in some instances where the direct signal cannot be received, the reflected copy may be received and render an otherwise unacceptable link acceptable.

Change in the direction of propagation of a ray (wave) at the interface between two media with different refractive index (see refractive index).

Factor by which the velocity of light in an optical medium (e.g. glass) is lower than it is in a vacuum.

An EXEC command which enacts a reboot of the router or switch.

A remote is a base or a subscriber interface. For a base interface, the number of remotes is the number of SUs registered. For a subscriber interface, there is only one remote, which is the base.

A VPN connection that enables telecommuting employees to connect to the corporate network from their remotely located computers.

A device that is both a transmitter and receiver. After receiving a signal, the repeater amplifies that signal and then retransmits. This process permits the signal to travel over greater distances.

Repeater is a radio transceiver used to extend the transmission of a base station beyond its normal range.

A connector type unique to Aironet radios and antennas. Part 15.203 of the FCC rules covering spread-spectrum devices limits the types of antennas that may be used with transmission equipment. In compliance with this rule, Aironet, like all other wireless LAN providers, equips its radios and antennas with a unique connector to prevent attachment of non-approved antennas to radios.

Commonly used in 802.11 wireless networks, RF is method of broadcasting that uses alternating current to produce radio waves.

Cable with fiber ribbons (see fiber ribbons).

Reduced Interframe Spacing

A network topology which creates a ring or loop by directly connecting one device to two other devices on the same network. When a device transmits a data signal, it is sent in one direction to the next connected device. This transmission passes along to each device successively until it arrives back to the original device of transmission.

This standard distance vector routing protocol utilizes only hop count as its metric.

An addition to RIP in order to support classless updates, router authentication, and multicast updates.

Standard cable that is typically used for telephone line or modem connection.

RJ-45 is a physical interface often used for terminating twisted pair type cables. It has eight “pins” or electrical connections per connector.

Radio Link is an association between single User Equipment and a single UTRAN access point.

Root Mean Square, also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids. RMS is used in various fields, including electrical engineering.

Radio Network Controller is a governing element in the UMTS radio access network (UTRAN) and is responsible for controlling the Node Bs that are connected to it. The RNC carries out radio resource management, some of the mobility management functions and is the point where encryption is done before user data is sent to and from the mobile. The RNC connects to the Circuit Switched Core Network through Media Gateway (MGW) and to the SGSN (Serving GPRS Support Node) in the Packet Switched Core Network.

Radio Network Subsystem is only the access part of the UTRAN or a full network offering the allocation and the release of specific radio resources to establish means of connection in between an User Equipment and the UTRAN.

Radio Network Temporary Identifier is used to identify an User Equipment within E-UTRAN.

A feature of some access points that allow users to move through a facility while maintaining unbroken connection to the LAN.

Roaming is a general term referring to the extension of connectivity service in a location that is different from the home location where the service was registered. Roaming ensures that the wireless device is kept connected to the network, without losing the connection.

A rogue access point is a wireless access point that has been installed on a secure company network without explicit authorization from a local network management. Rogue access points can pose a security threat to large organizations with many employees, because anyone with access to the premises can ignorantly or maliciously install an inexpensive wireless router that can potentially allow access to a secure network to unauthorized parties. To prevent the installation of rogue access points, large organizations sometimes even install wireless intrusion detection systems to monitor the radio spectrum for unauthorized access points.

RObust Header Compression (ROHC) is a standardized method to compress the IP, UDP, RTP, and TCP headers of Internet packets. This compression scheme differs from other compression schemes such as IETF RFC 1144 and RFC 2508 by the fact that it performs well over links where the packet loss rate is high, such as wireless links.

The Restriction of Hazardous Substances Directive (RoHS) 2002/95/EC was adopted in February 2003 by the European Union. The RoHS directive took effect on July 1, 2006, but is not a law; it is simply a directive. This directive restricts the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment. It is closely linked with the Waste Electrical and Electronic Equipment Directive (WEEE) 2002/96/EC which sets collection, recycling and recovery targets for electrical goods and is part of a legislative initiative to solve the problem of huge amounts of toxic e-waste.

Rise over Thermal indicates the ratio between the total power received from wireless sources at a base station and the thermal noise.

This process involves advertising multiple network IDs on a single route.

A packet sent to neighbor routers that provides updates concerning all networks connected to that particular internetwork. Route Update Packets are supported by routing protocols like RIP, EIGRP, and OSPF.

A protocol that can be routed using a router. One example is IP.

A router is a computer networking device that forwards data packets toward their destinations through a process known as routing. Routing occurs at layer 3 (Network layer) of the OSI seven-layer model.

An OSPF autonomous system recognizes a device through this IP address. It is established by the highest active loopback IP address that is configured when the OSPF process begins.

A protocol that exchanges network routes between routing devices to dynamically advertise networks. RIP, OSPF, and EIGRP are examples of routing protocols.

Stored in RAM, this is the routing logic where packet forwarding decisions are made.

A command that the Linux® operating system accepts to identify the version of Linux® software that operates on the Bandwidth and Authentication Manager (BAM) server.

Radio Resource Control protocol belongs to the UMTS WCDMA protocol stack and handles the control plane signalling of Layer 3 between the UEs (User Equipment) and the UTRAN.

Radio Resource Management is the system level control of co-channel interference and other radio transmission characteristics in wireless communication systems, for example cellular networks, wireless networks and broadcasting systems. RRM involves strategies and algorithms for controlling parameters such as transmit power, channel allocation, data rates, handover criteria, modulation scheme, error coding scheme, etc. The objective is to utilize the limited radio spectrum resources and radio network infrastructure as efficiently as possible.

Received Signal Code Power, in the UMTS cellular communication system, RSCP denotes the power measured by a receiver on a particular physical communication channel. It is used as an indication of signal strength, as a handover criterion, in downlink power control, and to calculate path loss. In CDMA systems, a physical channel corresponds to a particular spreading code, hence the name (RSCP).

Received Signal Strength Indication

Received Signal Strength Indicator is a measurement of the power present in a received radio signal. RSSI is a generic radio receiver technology metric, which is usually invisible to the user of the device containing the receiver, but is directly known to users of wireless networking of IEEE 802.11 protocol family.

Real-time Transport Control Protocol is a sister protocol of the Real-time Transport Protocol (RTP). Its basic functionality and packet structure is defined in the RTP specification RFC 3550, superseding its original standardization in 1996 (RFC 1889).

Round-Trip Delay or Round-Trip Time (RTT) is the length of time it takes for a signal to be sent plus the length of time it takes for an acknowledgment of that signal to be received. This time delay therefore consists of the transmission times between the two points of a signal.

Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and web-based push-to-talk features.

Request to Send

Receive.

Receive Diversity is the practice of two or more physically separated antennas for reception.