关于SFN ？

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我是靠谱客的博主缓慢石头，最近开发中收集的这篇文章主要介绍关于SFN ？，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

SFN翻译成系统桢号，CFN翻译成连接桢号。
SFN是在UE进行小区同步时从P-CCPCH中读取的信息，CFN是在进行二次交织后用来识别无线桢用的。
SFN
Cell System Frame Number counter. SFN is sent on BCH. SFN is used for paging groups and system information scheduling etc.
In FDD SFN = BFN adjusted with T_cell.
In TDD, if Inter Node B synchronisation port is used, SFN is locked to the BFN (i.e. SFN mod 256 = BFN mod 256).
Range: 0 to 4095 frames.
CFN
Connection Frame Number (counter). CFN is the frame counter used for the L2/transport channel synchronisation between UE and UTRAN. A CFN value is associated to each TBS and it is passed together with it through the MAC-L1 SAP. CFN provides a common frame reference (at L2) to be used e.g. for synchronised transport channel reconfiguration .
The duration of the CFN cycle is longer than the maximum allowed transport delay between MAC and L1 (in UTRAN side, between SRNC and Node B, because the L1 functions that handle the transport channel synchronisation are in the Node B).
Range: 0 to 255 frames. When used for PCH the range is 0 to 4095 frames
Frame Offset is a radio link specific L1 parameter used to map the CFN, used in the transport channel, into the SFN that defines the specific radio frame for the transmission on the air interface.
At the L1/L2 interaction, the mapping is performed as:
- SFN mod 256 = (CFN + Frame Offset) mod 256 (from L2 to L1) (5.1);
- CFN = (SFN - Frame Offset) mod 256 (from L1 to L2) (5.2).
The resolution of all three parameters is 1 frame. Frame Offset and CFN have the same range (0…255) and only the 8 least significant bits of the SFN are used. The operations above are modulo 256.
In the UTRAN, the Frame Offset parameter is calculated by the SRNC and provided to the node B.
The Transport Channel (or L2) synchronisation provides a L2 common frame numbering between UTRAN and UE (frame synchronisation between the L2 entities). This frame number is the Connection Frame Number (CFN) and it is associated at L2 to every TBS and passed to L1: the same CFN is received on the peer side associated with the same TBS.
The CFN is not transmitted in the air interface for each TBS, but is mapped by L1 to the SFN of the first radio frame used for the transmission of the TBS (the SFN is broadcast at L1 in the BCH). The mapping is performed via the Frame Offset parameters (see Figure 8).