Chain three sandboxes into one wireless link — choose a modulation and read its error rate, size an antenna and read its beam, then assemble the budget and read whether the link closes and how fast it can run. Predict each number before the screen shows it, and record your design at the end.
A working link is never one number. The modulation sets how many bits ride each symbol and how fragile they are to noise; the antenna sets how tightly the power is aimed; the budget adds them up against the noise floor to say whether the signal even arrives — and only then does Shannon's C = B log2(1 + SNR) set the ceiling on rate. This project is the interaction: change the modulation and the required SNR moves; narrow the beam and the received power rises; and the capacity follows both.
Open each of the three sandboxes in a tab. Each step below names the one sandbox to read and the single choice to make in it; leave every other knob at its default so your numbers match these.
1 Constellation & BER -> 16-QAM, Eb/N0 = 12 dB, Gray, AWGN
2 Antenna array -> N = 16, d = lambda/2, broadside 3 Link budget -> Office WiFi 2.4 GHz
Read four numbers across the three tabs: the BER on the curve, the half-power beamwidth under the polar plot, and the link margin and Shannon capacity in the budget's readouts.
In the constellation sandbox pick 16-QAM (4 bits per symbol) and set Eb/N0 = 12 dB, Gray labelling, an AWGN channel. Predict roughly where the BER point lands, then read it off the curve.
The theory BER is about 0.000139 (≈ 1.4 × 10^-4) — roughly one bit error in every seven thousand. This is the demo's own exact expression for 16-QAM, not a typed number.
In the antenna sandbox set N = 16 elements at d = λ/2, steered to broadside (θ0 = 0°). Predict whether the beam is wider or narrower than the 8-element default, then read the half-power beamwidth (HPBW) under the plot.
The HPBW is about 6.36° — half the width of the 8-element beam, because doubling the aperture halves the beamwidth. This is the demo's own pattern integrator, measured off the −3 dB points, not the small-angle formula.
In the link-budget sandbox choose the Office WiFi 2.4 GHz preset. The budget adds every gain and loss to a received power, then subtracts the sensitivity. Predict the sign of the margin M = Prx - S, then read it.
The margin is about +18.13 dB — comfortably positive, so the link closes with 18 dB to spare against fades. This is the demo's own received power minus its own sensitivity.
Same Office WiFi 2.4 GHz preset. The link margin only says the signal arrives; the Shannon capacity C = B log2(1 + SNR) says the most it can carry. With a 20 MHz channel and this link's SNR, predict the order of magnitude, then read the capacity.
The capacity is about 293.2 Mbit/s — the ceiling this channel and SNR allow. Your 16-QAM choice runs well below it, which is exactly the headroom a real link keeps for coding and fades. This is B log2(1 + SNR) from the demo's own bandwidth and SNR.
Open all three sandboxes and run the round trip yourself: change the modulation and watch the required SNR move, narrow the beam and watch the received power rise, then watch the margin and the capacity follow both.
A link design is a set of choices and the numbers they produce. Write yours down — fill in each blank from the sandboxes, then add one sentence of reasoning. This is the deliverable; there is no number to read off the screen here.
Modulation ....... 16-QAM (4 bits/symbol) BER @ Eb/N0 = 12 dB ... ______
Antenna .......... N = 16, d = lambda/2 HPBW at broadside .... ______ deg
Link (WiFi 2.4) .. margin ............ ______ dB closes? Y / N
Throughput ....... Shannon capacity ... ______ Mbit/s
Design note ...... which knob would you change first, and why? __________
Then change one thing — a denser modulation, a bigger array, a wider channel — and note which of the four numbers moved and by how much. That coupling is the whole lesson of the project.