Um interface
≈ 3 min read
Names in other languages
No names in other languages are held for this entry yet.
Article bodies are English and are not machine-translated. A name in another language is not a translation of the article.
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.
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. === Network Layer (L3)=== The Um network layer is defined in GSM 04.07 and 04.08 and has three sublayers. A subscriber terminal must establish a connection in each sublayer before accessing the next higher sublayer. Radio Resource (RR). This sublayer manages the assignment and release of logical channels on the radio link. It is normally terminated in the base station controller (BSC). Mobility Management (MM). This sublayer authenticates users and tracks their movements from cell to cell. It is normally terminated in the Visitor Location Register (VLR) or Home Location Register (HLR). Call Control (CC). This sublayer connects telephone calls and is taken directly from ITU-T Q.931. GSM 04.08 Annex E provides a table of corresponding paragraphs in GSM 04.08 and ITU-T Q.931 along with a summary of differences between the two. The CC sublayer is terminated in the MSC. The access order is RR, MM, CC. The release order is the reverse of that. Note that none of these sublayers terminate in the BTS itself. The standard GSM BTS operates only in layers 1 and 2. Combination V: FCCH + SCH + BCCH + CCCH + 4 SDCCH + 2 SACCH. [(5x1)+(5x1)+(1x4)+(3x4)+(4x4)+(2x4)+1idle=51frame multiframe] This is the typical C0T0 combination for small cells, which allows the BTS to trade unnecessary CCCH capacity for a pool of 4 SDCCHs. It can be used only on C0T0. Combination VI: BCCH + CCCH. This combination is used to provide additional CCCH capacity in large cells. It can be used on C0T2, C0T4 or C0T6. Combination VII: 8 SDCCH + 4 SACCH.[(8x4)+(4x4)+3idle=51frame multiframe] This combination is used to provide additional SDCCH capacity in medium and large cells. It can be used anywhere but C0T0. ==See also== OpenBTS GSM 03.40 ==Further reading== ==External links== 3GPP - The current standardization body for GSM with free standards available. General Packet Radio Service GPRS: Architecture, Protocols, and Air Interface.
Text derived from https://en.wikipedia.org/w/index.php?oldid=1318167645 under CC BY-SA 4.0; modifications have been made.