TDMA FDMA SDMA Online Simulation

Interactive exploration of TDMA, FDMA, and SDMA modulation logic.

TDMA: Time Division Multiple Access

Users share the entire frequency band, but only for a specific time slot.

The Mathematics:

Frame Duration: $T_f = N \times (T_s + T_g)$
Throughput per User: $R_u = \frac{R_{total}}{N} \times \frac{T_s}{T_s + T_g}$

• N = Number of Users
• T_s = Slot Duration | T_g = Guard Time (prevents overlap)

Guard Time Intensity:

Time-Domain Buffer

Start of Frame End of Frame

Awaiting signal...

FDMA: Frequency Division Multiple Access

Users transmit simultaneously, but each is assigned a specific frequency sub-band.

The Mathematics:

Total Bandwidth: $BW_{total} = \sum_{i=1}^{N} BW_i + (N-1)BW_{guard}$
Channel Efficiency: $\eta = \frac{N \times BW_u}{BW_{total}}$

Bandwidth per User: Guard Band Size:

Power Spectral Density (PSD)

0 Hz Frequency Axis Max BW

SDMA: Spatial Division Multiple Access

Users use the same time and frequency, but are separated by directional antenna beams.

The Mathematics:

Radiation Pattern: $P(\theta) = | \sum_{n=0}^{M-1} w_n e^{j n \psi} |^2$
Spatial Correlation: $\rho = \frac{\mathbf{h}_1^H \mathbf{h}_2}{\|\mathbf{h}_1\| \|\mathbf{h}_2\|}$

If $\rho \to 1$, users interfere. If $\rho \to 0$, users are perfectly separated.

Interaction: Drag the User dots on the map. If two users get too close in angle, their signals interfere (the beams turn red).

Simulated Base Station with Beamforming