GSM 网络中的小区（cell-id）、BTS 和 BSS
BTS和小区有什么关系？我认为一个BTS硬件可以覆盖几个小区，而且有些小区可以被多个BTS覆盖，不是吗？
移动设备从具体 BTS 或移动电话的 GSM 网络标识接收的信息的一部分是否只知道小区 ID？
移动设备从BSC的GSM网络标识接收的信息的一部分吗？
what is the relation between BTS and cell? I think one BTS hardware can cover few cells and also some cells could be covered by more than one BTS isn't it?
Is part of information, that mobile receives from GSM network identification of concrete BTS or mobile phone knows only cell-id?
Is part of information, that mobile receives from GSM network identification of BSC?
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Ad 1：通常一个 BTS 可以处理多个小区。常见的模式是一个 BTS，用一根圆形辐射天线覆盖一个圆形区域，或者一个三扇区 BTS，用扇区辐射天线覆盖三个小区。一个小区一次只能由一个 BTS 处理。两个或多个 BTS 是不可能的，因为无线电通信会相互干扰。请注意，这在 WCDMA/UMTS 中完全不同，因为没有小区的概念。
Ad 2：由于一个小区恰好被一个BTS覆盖，因此小区id唯一地标识了具体的BTS。
Ad 3：由于BTS不包含任何控制逻辑，因此移动设备直接与BSC进行通信，例如关于无线电资源的通信。
评论后编辑：
1/简单地说，BTS 很“愚蠢”。它只执行 BSC 指示的操作。例如，BSC 告诉 BTS 以及移动设备使用哪些频率进行无线电通信。 BTS 不会路由流量，因为它只连接到一个 BSC。它甚至不会将流量路由到连接到 BTS 的多个移动设备之一，因为这是由 BSC 完成的。将 BTS 视为 Um-to-Abis 物理层和协议转码器。
2/ 实际上，我之前关于 UMTS 没有小区概念的说法并不完全正确，只是有所不同。
GSM 是 FTDMA（频分和时分多址）。通过使用不同的频率（每个小区）和时隙（每个移动设备）来共享无线电信道。由于无线电频率用于区分参与者，因此必须非常小心，不能有两个 GSM 参与者在同一时间、同一位置使用同一频率。解决方案是小区，其中地理区域分配有不同的频率。网络规划必须确保没有两个相邻小区使用相同的频率，因为这可能会导致干扰，因为您无法精确控制小区的大小（例如由于吸收和反射）。在GSM中，BTS具有固定数量的无线传输信道，该数量取决于BTS的硬件配置。如果所有信道都在使用中，则小区已满，这与移动设备在小区中的位置无关。
UMTS 是CDMA（码分多址）。通过以允许稍后解码的方式对有效负载进行编码来共享无线电信道，即使多个发送器使用相同的频率范围也是如此。这需要无冲突的编码方案（所有代码彼此不同，以避免发送者使用过于相似的代码）和大量的信号处理。打个比方：在聚会上，即使十个人在说话，你也能听懂房间另一边的人的声音。小区内通信的发送者越多，小区就越小，以便 BTS/Node-B 能够区分发送者。因此，在UMTS中，小区大小在地理上不是固定的。细胞根据其负载进行“呼吸”。
Ad 1: Typically one BTS can handle several cells. Common patterns are a one BTS covering a circular area with one round-radiating antenna or a three-sector BTS which covers three cells with sector-radiating antennas. One cell can only be handed by one BTS at a time. Two or more BTSes are not possible since the radio communication would interfere with each other. Note that this is completely different in WCDMA/UMTS since there is no concept of cells.
Ad 2: Since one cell is covered by exactly one BTS, the cell id uniquely identified the concrete BTS.
Ad 3: Since the BTS does not contain any control logic, the mobile communicates directly with the BSC, e.g. about radio resources.
Edit after comment:
1/ The BTS is "dumb" to say it simply. It does only what the BSC instructs it to do. E.g. The BSC tells the BTS as well as the mobile which frequencies to use for the radio communication. A BTS does not route traffic as it is hooked to exactly one BSC. It even does not route traffic to one of several mobiles attached to the BTS as this is done by the BSC. Think of the BTS as a Um-to-Abis physical layer and protocol transcoder.
2/ Actually my earlier statement that UMTS has no cell concept is not exactly true, it's just different.
GSM is FTDMA (frequency and time division multiple access). The radio channel is shared by using different frequecies (per cell) and timeslots (per mobile). Since radio frequency is used to distinguish participants, great care must be taken that not two GSM participants use the same frequency at the same time at the same location. The solution to this is cells, where geographic areas have different frequencies assigned. Network planning must ensure that no two neighbouring cells use the same frequencies as this may lead to interference since you cannot control exactly the size of a cell (e.g. due to absorption and reflection). In GSM, a BTS has a fixed number of radio transmission channels, the number depends on the BTS hardware configuration. If all channels are in use, the cell is full, this is indpendent of the location of a mobile in the cell.
UMTS is CDMA (code division multiple access). The radio channel is shared by encoding the payload in a way that allows to decode it later even if several senders use the same frequency range. That requires coding schemes which are collision free (all codes are different from each other to avoid senders using too similar codes) and a great deal of signal processing. As an analogy: on a party you can understand someone accross the room, even if ten people are talking. The more senders communicate within the cell, the smaller the cell gets in order to allow the BTS/Node-B distinguishing between senders. Therefore, in UMTS a cell size is not geographically fixed. The cell "breathes" depending on its load.
好吧，这个帖子已经很老了，但需要为下一代做一些进一步的澄清。
当谈论 GSM 物理网络架构时，术语 BTS（基站收发器系统）指的是物理站点本身 - “带塔的小房子”（尽管现代小型 BTS 只是挂在墙上或墙上的盒子）放置在屋顶上）。
每个这样的物理站点可以托管一个全向小区或多个扇区小区。
在GSM逻辑网络架构中，存在一些混乱。
术语“小区”和“基站”实际上指的是同一物理实体（一组收发器单元，每个单元用于接收和发送配对的 UL/ BA频率集中分配的DL载波频率）。为了澄清起见，我们将这个实体称为“物理细胞”。
术语基站用于无线电资源管理。 BSIC（BS Id 代码，或 BTS Id 代码）被分配给“物理小区”，并用于 MS（移动站）和 BSS（BTS 和 BSC）之间的无线电相关对话，例如用于测量报告。
BSIC 由“本地”参数组成 - 网络颜色代码 (NCC) 和 BS 颜色代码 (BCC)，因此在网络外部是未知的。
这就是术语“单元”的由来：
术语单元用于移动管理。 小区标识 (CI) 被定义为路由区域的细化 - 一个 RA 将在其中包含多个小区。
全局小区标识符（GCI）由网络、RA和CI组成，用于网络内外的切换。
由BSC将BSIC转换为Cell Identity（BSC可以直接将BSIC转换为GCI，或者BSC转换为CI，MSC将其转换为GCI）。
希望能有所帮助。
OK, this thread is quite old, but requires some further clarifications for next generations.
When talking about GSM physical network architecture, the term BTS (Base Transceiver System) refers to the physical site itself - the 'small house with the tower' (although modern small BTSs are just boxes hanged on walls or placed on roof tops).
Each such physical site can host one omni-directional cell, or several sector cells.
In GSM logical network architecture, there is some confusion.
The terms 'Cell' and 'Base Station' actually refer to the same physical entity (a set of transceiver units, each used to receive and transmit one of the paired UL/DL carrier frequencies allocated in the BA frequency set). Let's call this entity 'physical cell' just for clarification.
The term Base Station is used for radio resource management. A BSIC (BS Id Code, or BTS Id Code) is allocated for the 'physical cell' and is used in the radio-related conversations between the MS (Mobile Station) and the BSS (BTS and BSC), e.g. for measurement reports.
The BSIC is composed of 'local' parameters - Network Color Code (NCC) and BS Color Code (BCC), and is therefore unknown outside the network.
This is where the term Cell comes in:
The term Cell is used for Mobility Management. A Cell Identity (CI) is defined as a refinement of the Routing Area - one RA will include several cells in it.
The Global Cell Identifier (GCI) is composed of network, RA and CI, and is used for handovers inside and outside the network.
It is up to the BSC to convert the BSIC to the Cell Identity (the BSC may convert the BSIC directly to GCI, or the BSC converts to CI, and the MSC will convert it to GCI).
Hope that helps a bit.
BTS在不同的地方意思不同！
MS、BTS、BSC，当这些词一起出现时，BTS意味着你的手机和MSC之间的东西。
有时我们将一个站点（一座小房子和一座塔）称为 BTS。
在NOKIA gsm设备中，cell被称为segment。每个小区至少有一个BTS，不同的BTS具有不同的功能，例如：BTS1提供语音服务，BTS2提供EDGE服务。
电话通过BCCH(freq)/NCC/BCC来识别不同的小区。解码BCCH中的信息，得到CI、LAC...等。
BTS means different at different place！
MS, BTS, BSC, when these words appear together, BTS means something between your phone and the MSC.
Sometimes we call a site (a small house and a tower) as a BTS.
In NOKIA gsm equipment，cell is called segment. Every cell has at least one BTS，different BTS has different functions，Eg：BTS1 provide voice service，BTS2 provide EDGE service。
Phone get BCCH(freq)/NCC/BCC to identificate different cells. Decode the information from BCCH to get CI, LAC...etc.