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multiplexing


 Multiplexing
Multiplexing .
   By multiplexing refers transmission of several streams (channels) with a lower data rate (bandwidth) for one channel of a higher speed .
Multiplexing is subdivided into:
- Frequency division (FDM)
- Time-division (TDM)
- A wavelength division (WDM)
 
Frequency division multiplexing (FDM):

Technology .
  Frequency division multiplexing involves placing within the band multiple channels with a smaller width.
 
Application .
  A good example is the radio, where within a single channel ( radio broadcast ) a plurality of radio channels at different frequencies (in different frequency bands ) .
 
Time-division multiplexing (TDM):

Technology .
  Time-division multiplexed data transmission is a method for combining various digital signals onto a single transmission with higher transmission rate. Each channel in that metod placed (multiplexed) in frame, multiple frames.
  Figure 2 : A, B and C - the multiplexed channels with bandwidth (width) N and the frame length Δt; E - multiplexed channel with the same durations Δt but with a width of M * N, where one frame (superframe) carries all 3 frames multiplexed input signals sequentially assigned to each channel of the time superframe - timeslot length ΔtM = Δt / M
  Thus, the channel with bandwidth M * N can pass M channels with N bandwidth, the subject channel rate (frames per second) equal to the result of demultiplexing the initial flow channel ( A, B or C in the figure) and in phase, and speed , ie, goes unnoticed to the final destination.
 
Application .
  TDMA- wireless networks , Wi-Fi, WiMAX;
  Channel switching in PDH and SONET / SDH;
  packet switching in ATM, Frame Relay, Ethernet, FDDI;
  switching in telephone networks ;
  Serial Bus : PCIe, USB.
 
Wavelength division multiplexing (WDM):

Technology .
  Wavelength division multiplexing involves transmission over a single optical fiber channels at different wavelengths. Technology is based on the fact that the waves with different wavelengths propagate independently. There are three main types of WDM : WDM, CWDM and DWDM.
Application .
  urban data network
  backbone data network
 
  Flexible Multiplexer - network device provides an integrated, switching and distribution (cross connection) different information flows , interfaces, protocols. It can work with both wired (copper) and optical transmission lines. Functionality, a wide range of protocols and interfaces, ease of use/configure make this kind of multiplexers " flexible."

 Key interfaces and protocols used :
• digital streams STM-(SDH)
• digital streams E1 (PDH)
• GbE
• 10/100 Ethernet
• RS- 232
• RS- 485
• X.21
• V.35
• FXO / FXS
• E & M 2- 4-wire voice-frequency channels (PM)
Main tasks:
• organization of digital channels (both for " copper " and optical fiber );
• business telephony (eg connection of "ordinary" phones, pay phones , PBX );
• the organization of local area networks (such as connecting routers);
• organization of radio lines and lines to mobile phone base stations.
• Organization of overhead transmission (eg telemetry, relay protection and automation).

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