用中文讲解一下时分复用是什么意思---**Title:** 统计时分复用 STDM (Statistic TDM)
**Diagram Description:**
* **Type:** Flowchart/Timing Diagram illustrating the concept of STDM.
* **Input Side:**
* Four horizontal lines representing users A, B, C, and D, each with a time axis labeled 't'.
* User A: Has two blocks labeled 'a' appearing at different times.
* User B: Has two blocks labeled 'b' appearing at different times.
* User C: Has two blocks labeled 'c' appearing at different times.
* User D: Has one block labeled 'd' appearing at a specific time.
* Lines labeled ①, ②, ③, ④ connect users A, B, C, D respectively to a central component.
* **Central Component:**
* A yellow triangle labeled "集中器" (Multiplexer).
* **Output Side:**
* A horizontal line representing the output line with a time axis labeled 't'.
* A sequence of colored blocks representing multiplexed data: a (pink), b (yellow), b (yellow), c (cyan), c (cyan), d (green), a (pink).
* Vertical dashed lines divide the output stream into three segments.
* Labels below the segments: #1, #2, #3.
* Arrows pointing from #1, #2, #3 to the text "3个 STDM 帧" (3 STDM frames).
* **Text Box:** Located above the output stream, containing the text: "STDM 帧不是固定分配时隙，而是按需动态地分配时隙，因此可以提高线路的利用率。" (STDM frames do not have fixed time slots; instead, time slots are allocated dynamically on demand, thus increasing line utilization.)
**Additional Text:**
* Below the diagram: "在输出线路上，某个用户所占用的时隙并不是周期地出现，统计时分复用又称为异步时分复用。普通的时分复用称为同步时分复用。" (On the output line, the time slots occupied by a certain user do not appear periodically. Statistic Time Division Multiplexing is also called Asynchronous Time Division Multiplexing. Ordinary Time Division Multiplexing is called Synchronous Time Division Multiplexing.)
**Page Number:** 11
**Image Content Extraction:**
**Diagram Description:**
The image is a timeline diagram illustrating the concept of Time-Division Multiplexing (TDM). It shows the data transmission timelines for four individual users (A, B, C, D) and how their data is combined into a shared timeline segmented into frames using TDM.
**Elements:**
1. **User Timelines:** Four parallel horizontal timelines on the left, each representing a user's data transmission over time (axis labeled 't').
* User A: Labeled "用户 A". Shows two instances of data block 'a' (pink rectangles).
* User B: Labeled "B". Shows two instances of data block 'b' (yellow rectangles).
* User C: Labeled "C". Shows two instances of data block 'c' (teal/green rectangles).
* User D: Labeled "D". Shows one instance of data block 'd' (green rectangle).
* Each user timeline has tick marks indicating time units and an arrow pointing right labeled 't'.
2. **Multiplexing Arrows:** Four curved arrows (labeled ①, ②, ③, ④) originate from the end of the respective user timelines (A to D) and converge towards a single timeline at the bottom. These arrows represent the process of multiplexing.
3. **Multiplexing Label:** The text "时分复用" (Time-division multiplexing) is placed near the converging arrows, indicating the method used.
4. **Shared Timeline (Multiplexed Output):** A single horizontal timeline at the bottom, representing the combined data stream over time (axis labeled 't').
* It is divided into four segments by dotted vertical lines.
* These segments are labeled "#1", "#2", "#3", and "#4" below the timeline.
* The text "4 个时分复用帧" (4 time-division multiplexing frames) points to these four segments, indicating they are TDM frames.
* Data blocks from the user timelines are placed within these frames:
* Frame #1: Contains data blocks 'a' (pink) and 'b' (yellow).
* Frame #2: Contains data blocks 'b' (yellow) and 'c' (teal/green).
* Frame #3: Contains data blocks 'c' (teal/green) and 'a' (pink).
* Frame #4: Contains data block 'd' (green).
5. **Rule/Annotation Text:** A text box in the top right corner contains the following sentence:
"当用户暂时无数据发送时，分配给该用户的时隙只能处于空闲状态。"
(Translation: When the user temporarily has no data to send, the time slot allocated to this user can only be in an idle state.)