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Synchronization Channel
Synchronization Channel is a downlink only control channel used in GSM cellular telephone systems. It is part of the Um air interface specification. The purpose of the SCH is to allow the mobile station (handset) to quickly identify a nearby cell (a BTS) and synchronize to that BTS's TDMA structures. Each radio burst on the SCH contains: * the current frame clock of the serving BTS, * the Base station identity code (or BSIC), a truncated form of cell identity, and * an extended Training Sequence that is easily detected with a matched filter. When mobile turns on after getting FCCH it waits for getting SCCH which is to synchronise mobile's oscillator frequency with the frequency of the Base channel. The burst structure of the SCH is defined in GSM specification 05.03 section 4.7. The encoding of the frame clock is defined in GSM specification 04.08 section 9.1.30. The TDMA multiplexing pattern of the SCH is defined in GSM specification 05.02 clause 7 table 3. The GSM Synchro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Um Air Interface
The Um interface is the air interface for the GSM mobile telephone standard. It is the interface between the mobile station (MS) and the Base transceiver station (BTS). It is called Um because it is the mobile analog to the U interface of ISDN. Um is defined in the GSM 04.xx and 05.xx series of specifications. Um can also support GPRS packet-oriented communication. Um layers The layers of GSM are initially defined in GSM 04.01 Section 7 and roughly follow the OSI model. Um is defined in the lower three layers of the model. Physical Layer (L1) The Um physical layer is defined in the GSM 05.xx series of specifications, with the introduction and overview in GSM 05.01. For most channels, Um L1 transmits and receives 184-bit control frames or 260-bit vocoder frames over the radio interface in 148-bit bursts with one burst per timeslot. There are three sublayers: # Radiomodem. This is the actual radio transceiver, defined largely in GSM 05.04 and 05.05. # Multiplexing and Timin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Transceiver Station
A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity, or antennas mounted on buildings or telecommunication towers. The network can be that of any of the wireless communication technologies like GSM, CDMA, wireless local loop, Wi-Fi, WiMAX or other wide area network (WAN) technology. BTS is also referred to as the '' node B'' (in 3G networks) or, simply, the ''base station'' (BS). For discussion of the LTE standard the abbreviation '' eNB'' for evolved node B is widely used, and GNodeB for 5G. Though the term BTS can be applicable to any of the wireless communication standards, it is generally associated with mobile communication technologies like GSM and CDMA. In this regard, a BTS forms part of the base station subsystem (BSS) developments for system management. It may also have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Division Multiple Access
Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity. Dynamic TDMA is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream. TDMA is used in the digital 2G cellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT) standard for portable phones. TDMA was first used in satellite communication systems by Western Union in its Westar 3 communications satelli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Station Identity Code
The base station identity code (BSIC), is a code used in GSM to uniquely identify a base station. The code is needed because it is possible that mobile stations receive the broadcast channel of more than one base station on the same frequency. This is due to frequency re-use in a cellular network. The BSIC is defined in GSM specification 03.03 section 4.3.2. Each base-station has its own BSIC, this code is at all times transmitted on the broadcast channel, so the mobile stations can distinguish between base stations. The BSIC is composed of a 3-bit network color code (NCC) and a 3-bit base station color code (BCC). The NCC is assigned to each network provider so the MS can sort out which base-stations it is allowed to camp on. The NCC of different providers must be different, also in national border-areas. The BCCHs (broadcast control channel) of each base stations are assigned frequencies by the network operator, and must be assigned such that no neighbor stations have equal BC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Training Sequence
In computer networks, a syncword, sync character, sync sequence or preamble is used to synchronize a data transmission by indicating the end of header information and the start of data. The syncword is a known sequence of data used to identify the start of a frame, and is also called ''reference signal'' or ''midamble'' in wireless communications. Prefix codes allow unambiguous identification of synchronization sequences and may serve as self-synchronizing code. Examples In an audio receiver receiving a bit stream of data, an example of a syncword is 0x0B77 for an AC-3 encoded stream. An Ethernet packet with the Ethernet preamble, 56 bits of alternating 1 and 0 bits, allowing the receiver to synchronize its clock to the transmitter, followed by a one-octet start frame delimiter byte and then the header. All USB packets begin with a sync field (8 bits long at low speed, 32 bits long at high speed) used to synchronize the receiver's clock to the transmitter's clock. A rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Station
A mobile station (MS) comprises all user equipment and software needed for communication with a mobile network. The term refers to the global system connected to the mobile network, i.e. a mobile phone or mobile computer connected using a mobile broadband adapter. This is the terminology of 2G systems like GSM. In 3G systems, a mobile station (MS) is now referred to as user equipment (UE). In GSM, a mobile station consists of four main components: *Mobile termination (MT) - offers common functions such as: radio transmission and handover, speech encoding and decoding, error detection and correction, signalling and access to the SIM. The IMEI code is attached to the MT. It is equivalent to the network termination of an ISDN access. *Terminal equipment (TE) - is any device connected to the MS offering services to the user. It does not contain any functions specific to GSM. *Terminal adapter (TA) - provides access to the MT as if it were an ISDN network termination with extended ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
