Multi-channel detailed data collection

In communication terms, multiplexing refers to channel multiplexing technology.

Multiplexing is a basic concept in communication technology. Various multiplexing technologies are widely used in the channels of computer networks.

Chinese Name: Multiplexing mbth: Definition of Multiplexing: The meaning of channel multiplexing technology, the classification of multiplexing technology, frequency division multiplexing, time division multiplexing, statistical time division multiplexing, wavelength division multiplexing, code division multiplexing, examples, the meaning of multiplexing is a basic concept in communication technology. Various multiplexing technologies are widely used in the channels of computer networks. The following figure shows that A 1, B 1 and C 1 use separate channels to communicate with A2, B2 and C2 respectively, and a total of three channels are required. However, if a multiplexer is used at the transmitting end, everyone can communicate using the shared channel. At the receiving end, a demultiplexer is used to send the combined information to the corresponding destinations. Classification of multiplexing technologies The classification of multiplexing technologies includes frequency division multiplexing (FDM) and time division multiplexing (TDM), statistical time division multiplexing (STDM), wavelength division multiplexing (WDM) and code division multiplexing CDM (code division multiplexing). Frequency division multiplexing Frequency division multiplexing is the simplest. After users are assigned to a certain frequency band, they occupy this frequency band from beginning to end in the communication process. It can be seen that all users of frequency division multiplexing occupy different bandwidth resources at the same time. When using frequency division multiplexing, if the bandwidth occupied by each user remains the same, the total bandwidth of the multiplexed channel will widen with the increase of the number of users. Time Division Multiplexing Time Division Multiplexing is a time division multiplexing frame (TDM frame), which divides time into equal-length segments. Each TDM user occupies a fixed number of time slots in each TDM frame. All users of time division multiplexing occupy the same frequency width at different times. When using time division multiplexing system to transmit computer data, due to the burst nature of computer data, the user's utilization rate of allocated subchannels is usually not high. When the user has no data transmission for a certain period of time, only the subchannels that have been allocated to him can be idle, and other users cannot use this temporarily idle line resource. Statistical Time Division Multiplexing Statistical Time Division Multiplexing STDM(Statistical TDM) is an improved time division multiplexing, which can obviously improve the channel utilization. Concentrators often use this statistical time division multiplexing. Wavelength division multiplexing (WDM) is the frequency division multiplexing of light. The application of optical fiber technology makes the data transmission rate increase unprecedentedly. Now people can borrow the traditional concept of carrier telephone frequency division multiplexing, and simultaneously transmit multiple optical carrier signals with very close frequencies with one optical fiber. In this way, the transmission capacity of optical fiber can be doubled. Because the frequency of optical carrier is very high, it is customary to use wavelength instead of frequency to represent the optical carrier used, so the term wavelength division multiplexing is used. Code division multiplexing code division multiplexing CDM (code division multiplexing) is another channel sharing method. In fact, the more commonly used term is code division multiple access (CDMA). Each user can use the same frequency band for communication at the same time. Because users use specially selected different codes, there will be no interference between users. Code division multiplexing was originally used in military communication, because the signal transmitted by this system has strong anti-interference ability, and its spectrum is similar to white noise, so it is not easy to be found by the enemy. Reuse refers to "using ready-made things", which scholars call "takenism" Reusable objects can be tangible objects or intangible achievements. Reuse is not a manifestation of human laziness, but a manifestation of wisdom, because human beings always inherit the achievements of predecessors and make progress after continuous use, improvement or innovation. The connotation of reuse includes both improving quality and productivity. Experience shows that in a new system, most of the contents are mature and only a few are innovative. Generally speaking, it can be believed that mature things are always reliable (that is, high quality), and a large number of mature jobs can be realized quickly through reuse (that is, high productivity). Hard-working and smart people should spend most of their time on a small proportion of innovative work and a small part of their time on a large proportion of mature work, so as to do their work quickly and well. Applying the idea of reuse to software development is called software reuse. According to statistics, there are more than 654.38 billion strokes in the world and countless functions have been rewritten thousands of times. What a waste. The mantra of object-oriented scholars is "Please don't invent the same wheel again". Examples refer to software components that have a certain degree of integration and can be reused as software components. Software reuse can be expressed as constructing a new software system, which can be directly assembled (or reasonably modified) into a new system by using existing software components without starting from scratch every time. Reuse method rationalizes and simplifies the software development process, reduces the total development workload and maintenance cost, reduces the software cost and improves the productivity. On the other hand, because the soft components are verified by repeated use, the quality is high. Therefore, the new system composed of soft components also has high quality. The process of making application software using soft components is shown in the figure. Software reuse should not only be convenient for yourself, but also for others to take it, that is, "take it away." The object-oriented method and COM specification of Microsoft [Rogerson 1999] can well realize large-scale software reuse.