S/I: Signal-to-interference ratio
Signal-to-interference ratio (S/I) is the ratio of power in a signal to the interference power in the channel. The term is usually applied to lower frequency signals, such as voice waveforms, but can also be used to describe the carrier wave. See also carrier-to-interference ratio.
S/N: Signal-To-Noise Ratio
Signal-To-Noise Ratio (S/N) is a measure of the power of a signal versus noise. A higher ratio means that there is more signal relative to noise.
SABP: Service Area Broadcast Protocol
Service Area Broadcast Protocol (SABP) is a 3G UMTS protocol for information broadcasting services, which allows cellular operators to deliver information such as stock prices, traffic information, weather reports and emergency alerts to mobile users within selected cells of the network.
SACCH: Slow Associated Control Channel
Slow Associated Control Channel (SACCH) is a GSM signalling channel that provides a relatively slow signalling connection. The SACCH is associated with either a traffic or dedicated channel. The SACCH can also be used to transfer Short Message Service (SMS) messages if associated with a traffic channel.
SALT: Speech Application Language Tags
The Speech Application Language Tags (SALT) specification largely overlaps the VoiceXML specification and both are under review by the same W3C working group. Both specifications share some common functionality, but SALT includes multi-modal capabilities for inputting and outputting data, making speech and traditional data I/O more interchangeable.
Sampling is the process performed in the conversion of analog waveforms to a digital format. It converts a continuous time signal into a discrete time signal or sequence of numbers.
SAT: Set-up Audio Tone
Set-up Audio Tone (SAT) is an audio tone in the 6 kHz range added to the downlink or forward channel in analog cellular systems. The mobile detects and returns the tone. The SAT tone is used to determine channel continuity, and only one SAT tone is usually assigned to a base station or sector.
A satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth. They are used for such diverse purposes as weather forecasting, television broadcast, amateur radio communications, Internet communications, and the Global Positioning System.
Satellite Communication refers to the use of orbiting satellites to relay data between multiple earth-based stations. Satellite communications offer high bandwidth and a cost that is not related to distance between earth stations, long propagation delays, or broadcast capability.
Satellite Internet refers to utilize telecommunications satellites in Earth orbit to provide Internet access to consumers. Satellite Internet service covers areas where DSL and cable access is unavailable. Satellite offers less network bandwidth compared to DSL or cable, however. In addition, the long delays required to transmit data between the satellite and the ground stations tend to create high network latency, causing a sluggish performance experience in some cases. Network applications like VOIP, VPN and online gaming may not function properly over satellite Internet connections due to these latency issues.
Satellite phone is a type of wireless mobile telecommunications system using satellites as base stations. Such systems have the ability of providing service to the oceans and other remote areas of the globe.
Scattering is a phenomenon that occurs when the medium through which a radio wave travels consists of objects with dimensions small compared to the wavelength and diffuses the wave as it propagates through it.
SCCH: Signaling Control Channel
Signaling Control Channel (SCCH) is a logical channel used in the PDC system to convey signalling information between the mobile and the network.
SCH: Synchronization Channel
Synchronization Channel (SCH) is a logical channel used by mobile stations to achieve time synchronization with the network. SCH is used in GSM, cdma2000, and W-CDMA systems.
SDCCH: Stand-alone Dedicated Control Channel
Stand-alone Dedicated Control Channel (SDCCH) is used in the GSM system to provide a reliable connection for signalling and Short Message Service (SMS) messages. The Slow Associated Control Channel(SACCH) is used to support this channel.
SDMA: Space Division Multiple Access
Space Division (or Diversity) Multiple Access (SDMA), also known as multiple beam frequency reuse, employs spot beam antennas to reuse frequencies by pointing the antenna beams using the same frequency in different directions.
SDP: Service Discovery Protocol
In the Bluetooth protocol stack, the Service Discovery Protocol (SDP), also known as Bluetooth SDP, provides special means for applications in the Bluetooth environment to discover which services are available and to
determine the characteristics of those available services. The SDP defines how a Bluetooth client's application shell acts to discover available Bluetooth servers' services and their characteristics. The protocol defines how client can search for a service based on specific attributes without the client knowing anything of the available services. The SDP provides means for discovery of new services becoming available when the client enters an area where a Bluetooth server is operating. The SDP also provides functionality for detecting when a service is no longer available.
Sector is a coverage area associated with a base station having its own antennas, radio ports and control channels. The concept of sectors was developed to improve co-channel interference in cellular systems, and most wireless systems use three sector cells.
Sector Antenna is an antenna type that radiates in only a specific direction. Multiple sector antennas are commonly used in point-to-multipoint situations.
Service area is the specified area over which the operator of a wireless communications network or system provides services.