RACH

Random Access Channel; uplink only, allows the MS to request an SDCCH in response to a page or for a call.

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RAN

The ground-based infrastructure required for delivery of third-generation (3G) wireless communications services, including high-speed mobile access to the Internet. The RAN must be able to manage a wide range of tasks for each 3G user, including access, roaming, transparent connection to the public switched telephone network and the Internet, and Quality of Service (QoS) management for data and Web connections.

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Rayleigh fading

A type of signal fading caused by independent multipath signals having a Rayleigh probability density function.

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Reuse

The assignment of frequencies or channels so that adjoining cells do not use the same frequencies and cause interference whereas more distant cells can use the same frequencies. Reuse expands the capacity of a cellular network by enabling the use of the same channels throughout the network.

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RF

Radio Frequency. The range of electromagnetic frequencies above the audio range and below visible light. All broadcast transmission, from AM radio to satellites, falls into this range, which is between 30 kHz and 300 GHz.

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RFP

Radio Fixed Part; equivalent to a base station in a DECT system.

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RNC

Radio Network Controller under the UMTS system. A complex network element of the RAN that connects to and co-ordinates as many as 150 base stations in W-CDMA systems. It is involved in managing activities such as hand-over of active calls between base stations.

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Roaming

A service unique to GSM that enables a subscriber to make and receive calls when outside the service area of his home network, e.g., when traveling abroad. Within your home network, this means that your mobile phone automatically sets up communication procedures with different radio base stations when on the move. International roaming means that you can use networks other than your own when traveling abroad.

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ROI

Return on investment. For a given use of money, ROI refers to how much profit or cost saving is realized. ROI calculations are often essential components for a given proposal or business case.

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Router

A data switch that handles connections between different networks. A router identifies the addresses on data passing through the switch, determines which route the transmission should take and collects data in so-called packets that are then sent to their destinations.

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Routing

The forwarding of data packets in packet-switched networks, to the intended address.

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RP

Radio Part.

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RRM

Radio Resource Management, part of the UMTS infrastructure.

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RT

Remote Terminal.

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