TD系统中,在的空口消息中，我们可以看到如下的cell id IE:
在系统消息3中出现：

2012-12-18 09:12:08 上传
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也在某些厂家的rrcConnectionSetup等消息中出现，如鼎桥/中兴的设备，如下为上海鼎桥网络下：

2012-12-18 09:15:08 上传
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那么这个cell id 协议中定义的概念是怎样的？
通过研究，了解到：
TD中cell id分三个层次：全球cell id/PLMN下cell id/RNC下cell id, 其中：
全球cell id = PLMN id + PLMN下cell id;
PLMN下cell id = RNC id +RNC下cell id
我们在系统消息3中及如下rrcConnectionSetup消息中看到的cell id 是PLMN下cell idLMN下cell-id 由28bit组成，其中12bit表示RNC id, 16bit表示RNC下cell id,所以RNCid的表示范围是0-4095，RNC下cell id的表示范围是0-65535。

如下是在规范中以上信息的检索过程：
1） 既然在系统消息3中出现，查25.331 中有：
10.3.2.2
Cell identityThis information element identifies a cell unambiguously within a PLMN.
NOTE:
This information element may carry any implementation dependent identity that unambiguously identifies a cell within a PLMN. For GAN to UTRAN HO the Cell id is encoded as required in [9].

Information Element/Group name	Need	Multi	Type and reference	Semantics description
Cell identity	MP		bit string(28)

如上信息表明，在空口信令中出现的cell id是在一个PLMN下唯一标识cell 的标志，所以是PLMN下cell id ; 这个层次的cell id由28bit来表示。按照如上协议中的说明该PLMN下cell id的编码可以查看：
[9]
3GPP TS 25.401: "UTRAN overall description".

2）查看25.401 , 其中有：

6.1.5
Cell IdentifierThe Cell identifier (C-Id) is used to uniquely identify a cell within an RNS/BSS. The Cell-Id together with the identifier of the controlling RNC/BSS (CRNC-Id) constitutes the UTRAN/GERAN Cell Identity (UC-Id) and is used to identify the cell uniquely within UTRAN/GERAN Iu mode. UC-Id or C-Id is used to identify a cell in UTRAN Iub and Iur interfaces or Iur-g interface.
-
UC-Id = RNC-Id + C-Id.
The C-Id is defined by the operator, and set in the RNC/BSS via O&M. The C-Id is set in a Node B by its C-RNC or in the GERAN Iu mode cell.
按照如上的信息，UC-Id 在接入网中是唯一的，可以理解为在PLMN下是唯一的；C-Id在RNC下是唯一的。
对于RNC-Id 在25.401中也有定义：
6.1.3
RNC IdentifierAn RNC node is uniquely identified by its RNC Identifier among the nodes in UTRAN and GERAN Iu mode as defined in [6] sub-clause 12.3. A BSS node in GERAN Iu mode is uniquely identified by its RNC Identifier among the nodes in GERAN Iu mode and UTRAN.
从中可以看到，关于RNC identifier的更多信息可以查看：

[6]
3GPP TS 23.003: "Numbering, Addressing and Identification".
3）查看23.003 , 在12.4而不是上面提到的12.3章节中，有：
12.4
RNC Identifier
An RNC node is uniquely identified within UTRAN by its RNC Identifier (RNC-Id). RNC-Id together with the PLMN identifier is used to globally identify the RNC. RNC-Id or the RNC-Id together with the PLMN-Id is used as RNC identifier in UTRAN Iub, Iur and Iu interfaces. SRNC-Id is the RNC-Id of the SRNC. C-RNC-Id is the RNC-Id of the controlling RNC. D-RNC-Id is the RNC Id of the drift RNC.
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Global RNC-Id = PLMN-Id + RNC-Id
The RNC-Id is defined by the operator, and set in the RNC via O&M
For syntax description and the usage of this identifier in RANAP signalling, see 3GPP TS 25.413.
从中可以看到关于RNC-Id的更多信息可以查看： RANAP signalling, see 3GPP TS 25.413.

4）查看25.413 中有：

9.2.1.39
Global RNC-IDGlobal RNC-ID is used to globally identify an RNC.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
Global RNC-ID
>LMN identity	M		OCTET STRING (SIZE (3))	- digits 0 to 9, encoded 0000 to 1001, - 1111 used as filler digit, two digits per octet, - bits 4 to 1 of octet n encoding digit 2n-1 - bits 8 to 5 of octet n encoding digit 2n -The PLMN identity consists of 3 digits from MCC followed by either -a filler digit plus 2 digits from MNC (in case of 2 digit MNC) or -3 digits from MNC (in case of a 3 digit MNC).
>RNC-ID	M		INTEGER (0..4095)

这样就得到RNC-ID的取值范围是INTEGER (0..4095) ，也就是12 bit 。
另外在25.413 中也可以查到如下的描述信息：

Target Cell ID

C - ifUEinvolved

INTEGER (0..268435455)

This information element identifies a cell uniquely within UTRAN and consists of RNC-ID (12 bits) and C-ID (16 bits) as defined in TS 25.401 [3].

-

-

综上，就可以明确：
PLMN下cell-id 由28bit组成，其中12bit表示RNC id, 16bit表示RNC下cell id,所以RNCid的表示范围是0-4095，RNC下cell id的表示范围是0-65535。

TD下全球cell id 的结构是：
全球cell id = PLMN id + RNC id + cell id

GSM下全球cell id的结构是：
GSM 全球cell id = PLMN id + LAC + cell id

TD下与GSM下的标识是有区别的。
GSM下全球cell id的定义见：3GPP TS 23.003: "Numbering, Addressing and Identification".

4.3.1
Cell Identity (CI) and Cell Global Identification (CGI)The BSS and cell within the BSS is identified within a location or routing area by adding a Cell Identity (CI) to the location or routing area identification, as shown in figure 5. The CI is of fixed length with 2 octets and it can be coded using a full hexadecimal representation.
The Cell Global Identification is the concatenation of the Location Area Identification and the Cell Identity. Cell Identity must be unique within a location area.

2012-12-18 10:46:28 上传
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Figure 5: Structure of Cell Global Identification

TD及GSM下cell identifier(CID)的概念.doc (70.5 KB)