line coding techniques in DCS
EE4512 Analog and Digital Communications
Chapter 7
Multiplexing Techniques
Chapter 7
EE4512 Analog and Digital Communications
Chapter 7
Multiplexing Techniques
• Time Division Multiplexing
• Pages 364-368
Chapter 7
EE4512 Analog and Digital Communications
Chapter 7
• Time division multiplexing (TDM) combines several low, fixed and predefined bit rate sources into a single high speed bit stream for transmission over a single digital communication channel:
Time slots
Multiplexer
Demultiplexer
EE4512 Analog and Digital Communications
Chapter 7
• The TDM time slots have to be chosen properly. If the time slots are too small (for example, 1 bit) then the multiplexer and demultiplexer must switch rapidly. If the time slots are too large (for example, 64 Kb) then the data must be buffered and delay would be produced. TDM is used for baseband (not bandpass) data transmission.
Time slots
Multiplexer
Demultiplexer
EE4512 Analog and Digital Communications
Chapter 7
• The T1 TDM system for telephone networks uses a 193 bit frame where each frame has 24 8-bit slots and 1-bit in each frame for signaling. The T1 bit rate rb = 1.544 Mb/sec.
S&M Figure 7-3
The duration of each frame Tf = 193 b / 1.544 Mb/sec =
125 µsec or 8 k samples/sec. Here all the data sources have the same data rate.
EE4512 Analog and Digital Communications
Chapter 7
• If the data sources have different rates a multiplexer scheme must reconcile the disparate rates.
S&M Figure 7-4
The data rates are in the lowest possible ratio of 8:16:24 or
1:2:3 for a total of 1 + 2 + 3 = 6 slots. The slots are apportioned to the channels as: a b b c c c and the channel data rate is 48 kb/sec.
Another example is data rates of 10, 15, 20, and 30 Kb/sec which reduces to 2:3:4:6 (the LCD is 5) for 2 + 3 + 4 + 6 =
15 slots and the channel data rate is 45 kb/sec.
EE4512 Analog and Digital Communications
Chapter 7
• If
Chapter 7
Multiplexing Techniques
Chapter 7
EE4512 Analog and Digital Communications
Chapter 7
Multiplexing Techniques
• Time Division Multiplexing
• Pages 364-368
Chapter 7
EE4512 Analog and Digital Communications
Chapter 7
• Time division multiplexing (TDM) combines several low, fixed and predefined bit rate sources into a single high speed bit stream for transmission over a single digital communication channel:
Time slots
Multiplexer
Demultiplexer
EE4512 Analog and Digital Communications
Chapter 7
• The TDM time slots have to be chosen properly. If the time slots are too small (for example, 1 bit) then the multiplexer and demultiplexer must switch rapidly. If the time slots are too large (for example, 64 Kb) then the data must be buffered and delay would be produced. TDM is used for baseband (not bandpass) data transmission.
Time slots
Multiplexer
Demultiplexer
EE4512 Analog and Digital Communications
Chapter 7
• The T1 TDM system for telephone networks uses a 193 bit frame where each frame has 24 8-bit slots and 1-bit in each frame for signaling. The T1 bit rate rb = 1.544 Mb/sec.
S&M Figure 7-3
The duration of each frame Tf = 193 b / 1.544 Mb/sec =
125 µsec or 8 k samples/sec. Here all the data sources have the same data rate.
EE4512 Analog and Digital Communications
Chapter 7
• If the data sources have different rates a multiplexer scheme must reconcile the disparate rates.
S&M Figure 7-4
The data rates are in the lowest possible ratio of 8:16:24 or
1:2:3 for a total of 1 + 2 + 3 = 6 slots. The slots are apportioned to the channels as: a b b c c c and the channel data rate is 48 kb/sec.
Another example is data rates of 10, 15, 20, and 30 Kb/sec which reduces to 2:3:4:6 (the LCD is 5) for 2 + 3 + 4 + 6 =
15 slots and the channel data rate is 45 kb/sec.
EE4512 Analog and Digital Communications
Chapter 7
• If