RF Receiving Device (RRD) receives over the air data and forwards it to the mobile computer.

Reverse Rate Indicator (RRI) is a parameter in a 3G wireless network provided by the reverse link, which aids the Access Point in determining the rate at which the reverse link is sending data. The RRI is included as the preamble for reverse link frames, indicating the rate at which the data was sent.

Relay Station (RS), a concept defined in the IEEE 802.16j for the WiMAX network, is a station with the following functions: (1) to relay user data and possibly control information between other stations, and (2) to execute processes that indirectly support mobile multihop relay. All RSs are managed by an MMR-BS, but they may have some control of relay functions within their neighborhood.

Rural Service Area (RSA) is a geographic area in the US over which a cellular operator is licensed to provide service. RSAs are a group of rural counties having common financial, commercial and economic ties and were used to license cellular services together in the latter 1980s. RSAs cross state lines in some instances and were developed during a public rule making process at the FCC in 1987 and 1988..

Relative Signal Strength Indicator (RSSI) is a measurement of radia signals at the point in which they are received and measured.

Receive/transmit Transition Gap (RTG), a concept in the mobile wireless network, is a gap between the last sample of the uplink burst and the first sample of the subsequent downlink burst at the antenna port of the BS in a time division duplex (TDD) transceiver. This gap allows time for the base station (BS) to switch from receive to transmit mode. During this gap, the BS is not transmitting modulated data but simply allowing the BS transmitter carrier to ramp up, and the transmit/receive (Tx/Rx) antenna switch to actuate.

Real-Time Polling Service (rtPS) is one of the five QOS service types defined in the IEEE 802.16 WiMAX. The 802.16 protocol supports five types of QoS: UGS (Unsolicited grant service), rtPS (Real time polling Service), ertPS (Extended Real-time POLLING SERVICE), nrtPS (Non-real-time polling service and BE (Best effort service). The Real-Time Polling Service (rtPS) is designed to support real-time service flows that generate variable size data packets on a periodic basis, such as MPEG video. The service offers real-time, periodic, unicast request opportunities, which meet the flow’s real-time needs and allow the SS to specify the size of the desired grant. This service requires more request overhead than UGS, but supports variable grant sizes for optimum data transport efficiency.

Removable User Identity Module (R-UIM), also known as UIM, is similar to a Subscriber Identity Module (SIM), but is designed for networks other than GSM such as CDMA. R-UIM cards support roaming between CDMA and GSM networks.

Redundant Arrays of Independent Disks (RAID) is a type of disk drives with two or more drives in combination for increasing data integrity, fault tolerance, throughput or capacity and performance. RAID provides seceral methods of writing data across/to multiple disks at once. RAID is one of many ways to combine multiple hard drives into one single logical unit. Thus, instead of seeing several different hard drives, the operating system sees only one. RAID is typically used on server computers, and is usually implemented with identically-sized disk drives. With decreases in hard drive prices and wider availability of RAID options built into motherboard chipsets, RAID is also being found and offered as an option in higher-end end user computers, especially computers dedicated to storage-intensive tasks, such as video and audio editing.

RAM cache, also known as Level 2 (L2) cache, is the cache memory external to the CPU. RAM cache memory resides on a separate chip from the microprocessor chip. RAM cache contains a subset of the contents of main memory. The design of the memory and L2 cache is a significant way designers differentiate their systems.