Channel capacity
Multiple Access, SCPC and TDMA Planner
Allocate limited satellite spectrum, time and transmit power.
Enter the design inputs, then calculate to inspect the results.
Swipe the diagram sideways to see the full view. With a keyboard, focus the diagram and use the arrow keys.
Understand the system
Three access domains
FDMA separates simultaneous carriers in frequency and uses guard bands. TDMA separates bursts in time and requires timing, synchronization and guard intervals. CDMA distinguishes overlapping transmissions using codes and correlation; code separation does not eliminate multiuser interference or power-control requirements. The aim is efficient use of limited power and spectrum.
Source: week 3/reference.pdf · PDF page 289
Common mistakes
- Bits are not bytes.
- Capacity counts must be floored, not rounded upward.
- State whether reference burst guards are included.
- FDMA nonlinear multicarrier amplification may need backoff.
Formula reference and symbol definitions
SCPC capacity
B_T,B_C: same frequency unit
Channel spacing includes guards; sufficient power.
Example: For 54 MHz and 60 kHz spacing, N = floor(54000/60) = 900 channels.
Open related tool →TDMA efficiency
Counts: integers; b: bits; R_T: bit/s; T_f: s
Lecture convention includes reference guards.
Example: For 10000 frame bits, 2 reference bursts of 100 bits, 3 traffic preambles of 50 bits and 10-bit guards, lecture overhead = 200 + 150 + 50 = 400 bits; efficiency = 96%.
Open related tool →PCM voice capacity
Rates: bit/s; η: actual frame efficiency
Whole channels; PCM rate per channel.
Example: For 6.4 Mbit/s net payload and 64 kbit/s PCM, N = floor(6400000/64000) = 100 voice channels.
Open related tool →