Decoding the UMTS/UTRAN SpecificationsThe purpose of this wiki area is to provide a clear and concise presentation of the information given in the 3GPP UMTS/UTRAN specifications, specifically on the "Uu" interface. Because UMTS/UTRAN inherit many concepts and subprotocols from GSM and GPRS (" Um"), some understanding of those technologies is probably a prerequisite for understanding this wiki. General Comments on the WikiOne of the problem with UMTS complexity is that the standard supports a lot of deployment variations. For simplicity, this wiki should probably focus on the most commonly deployed style of UMTS/UTRAN worldwide: FDD radio interface and GSM-MAP core network. Please do not just copy-paste large sections of text from the specifications themselves into the wiki. First, it's a copyright violation. Second, it defeats the purpose of the wiki. So if you can't/won't rewrite something to make it more understandable, just make a reference to the specification document and section/paragraph, like this: "3GPP 25.331 10.5.1". Small quotations are good, but please put them in italics like this and note the document and paragraph from which the text was quoted. To edit this wiki, you can login as user "guest" with the password "guestpass". If you are a regular editor of this wiki, please request a personal account from Kurtis (log in to see contact info) so that your changes can be tracked. If you have a specific question about a specific part of the specification, please put the question into the wiki using italicized text like you see here. You can also subscribe to the UMTS discussion list here. Other Web Resources for Understanding UMTSGeneral Comments on UMTSLike GSM/GPRS, UMTS defines logical and physical channels, but there is a greater variety of physical channel types and there's is a new intermediate sublayer, the transport layer, between the logical and physical channel. The existence of transport channels permits the grouping of logical channels with similar bearer performance (e.g., error rate) requirements. UMTS ChannelsLogical Channels
Transport Channels
Physical ChannelsThe physical channels use different slot formats, documented in 3GPP 25.211 Section 5. The mapping of transport channels onto physical channels is defined in 3GPP 25.211 Section 6.
UMTS LayersLayer 1 - PHYThe UMTS PHY is based on WCDMA. Key features of CDMA:
Most UMTS deployments utilize frequency-division duplexing (FDD). Unlike GSM, in which transmit and receive bursts are separated in time, UMTS-FDD requires simultaneous transmission and reception. Thus, instead of a simple switch, the RF front-end in a UMTS handset utilizes a duplexer. Small duplexers are typically quite lossy, requiring the (already inefficient) PAs in handsets to produce even more power. UMTS Frequency BandsThe primary UMTS operating frequency band is the IMT-2000 band at 2100 MHz. This band is used for UMTS throughout most of the world including Asia, Europe, Australasia, Africa, and parts of South America. In the United States, the IMT-2000 band was not (entirely) available at the time UMTS was being rolled out. Therefore, the 1900 MHz "PCS" band and the 850 MHz "cellular" bands are used for UMTS in the U.S. and countries that typically follow U.S. frequency band planning in North America and parts of South America. The 3GPP technical specifications permit UMTS to be operated in numerous, often region-specific frequency bands - a total of 14 as of R8 of the specs. As traffic has grown, UMTS has been deployed in in more and more of these operating bands - a process colloquially referred to as spectrum "re-farming" - including 900 MHz (GSM), 1800 MHz (DCS), and 1700/2100 MHz (U.S. AWS). The 3GPP technical specifications support the use of virtually any downlink/uplink frequency pairing in FDD mode, though it is extremely rare for networks to utilize non-standard operating bands and duplex spacings. FDD RadiomodemThis is everything from the formatted radio frame data bits to the antenna, including:
Forward Error CorrectionFrom 3GPP 25.212 4.2. This is the encoding/transmission path between a transport block and a radio frame:
Special CasesLayer 2Layer 1-2 InterfaceData structures exchanged between L1 and L2 are called transport blocks. UMTS defines concatenation and rate-matching mechanisms in L1 that allows great flexibility in transport block size on most L1-L2 interfaces. However, there is a maximum code block size, defined in 3GPP 25.212 4.2.2.2 that determines the maximum available data rates for given channel types. See DecodingUMTS/FEC for more details. Medium Access Control (MAC)Radio Link Control (RLC)?Layer 3Layer 2-3 InterfaceRadio Resource Control (RRC)Layer 4Layer 3-4 (AS-NAS) InterfaceCall Control (CC)?Service Management (SM)?Mobility Management (MM)?GPRS Service Management (GSM)?GPRS Mobility Management (GMM)?Packet-Switched (PS) ServicesCircuit-Switched (CS) ServicesUser EquipmentSIM vs USIM注：Decoding the UMTS/UTRAN Specifications（原文出处，翻译整理仅供参考!） |
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