Wireless 101
M12 · L03
Module 12 · Lesson 3
Five Roles, One Radio
Forty-five lessons of arithmetic, and this is where a course usually goes soft. So: no advice. Each role gets its artefacts, its maths, how it fails, and the modules it uses on an ordinary Tuesday.
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Wireless 101
M12 · L03
The ground rule
Judge a Role by What It Makes
- RF: a measured board and a test report
- Systems: a link budget and a trade study
- Protocol: specification text, state machines, test cases
- Signal processing: an algorithm and an error-rate curve
- Planning: a cell plan, a parameter change, a KPI report
Standards → systems → RF → planning. The seams between them are where projects fail — slide 9.
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Wireless 101
M12 · L03
RF engineer — M7, M9-L1
Move It 30 mm, Change the Budget
The formula this role lives inside (M9-L1)
F_{sys} = F_1 + \frac{F_2 - 1}{G_1} + \frac{F_3 - 1}{G_1 G_2} + \cdots
- Stage one enters undivided — so order and placement are design
- Artefacts: layout, S-parameter files, a calibrated test report
- Tools: network analyser, spectrum analyser, EM solver
- Fails late: the fix is a new board, so schedule is the pain
Not taught here: S-parameters, Smith charts, compression, EVM. That is the honest gap.
03 / 11
Wireless 101
M12 · L03
Systems engineer — M6, M8, M9, M10
Margin Is the Currency
M9-L4, one line
P_{rx} = P_{tx} + G_{tx} + G_{rx} - L_{path} - L_{misc},\quad M = P_{rx} - S_{rx}
- Owns the numbers everyone else is constrained by
- Decides band, bandwidth, waveform, numerology, power, antennas
- Uses more of this course than any other role here
- Fails quietly: 2 dB conceded here, 1 dB there, then everywhere at once
The discipline, from M9-L4: let a drive test replace a guess, then shrink the margin honestly.
04 / 11
Wireless 101
M12 · L03
Protocol and standards — M10, M11
You Can Add to It, Never Fix It
- Owns agreement between radios that have never met
- Discrete maths: states, timers, sequence numbers, overhead
- Reads specifications; the third answer is “the spec is ambiguous”
- NB-IoT = one 180 kHz LTE resource block so it fits what exists
- Bluetooth 5 added two PHYs to the same 40 channels
Backward compatibility is a hard constraint, and it is why standards grow options instead of redesigns.
05 / 11
Wireless 101
M12 · L03
Try it — rate the work, not the job title
Which Role, and Which Modules?
best fit: systems engineer
reread: M9-L4, M6, M8, M10-L2
next: build a link budget, then measure it
06 / 11
Wireless 101
M12 · L03
Signal processing — M5, M6, M9-L2
The Gap Is the Job
M6-L1 — the bound you are measured against
C = B\log_2\!\left(1 + \frac{S}{N}\right)
- Two questions all day: what was the channel, which symbol was sent
- M5-L3’s decision regions are detection theory in plain dress
- Every curve is plotted against the bound, or it says nothing
- Dies on hardware the model omitted — phase noise, AGC, quantisation
- 0.2 dB gained for 3× the silicon area: correct result, rejected proposal
07 / 11
Wireless 101
M12 · L03
Planning and optimisation — M8, M9-L3, M11
Power Is Not a Lever
Owns
1000s of links
Answer
measured
Watches
5th pct
- M9-L3: co-channel interference cannot be filtered — no frequency gap
- So raise power and you raise your neighbour’s interference equally
- The levers are geometry, tilt, azimuth, reuse — not watts
- Every fix trades with a neighbour: cure overshoot, open a hole
- Fits a path-loss exponent to real data (M8-L4), not to a textbook
08 / 11
Wireless 101
M12 · L03
The seams
Projects Fail on the Arrows
- Standards → systems: a legal corner nobody deploys still fails
- Systems → RF: 4.0 dB budgeted, 4.6 delivered, nobody owned the 0.6
- RF → planning: peak gain is directional (M7-L2), not a scalar
- Field → systems: the missing return path — σ = 9 dB measured, 5.1 dB margin assumed
Not “communicate better”. Every quantity crossing an interface needs an owner, a tolerance and a source.
10 / 11
Wireless 101
M12 · L03
Course complete
M1 to M12, all 46 lessons
- You began with a wave and a spectrum to divide up
- You can now read a link budget and defend a modulation choice
- And say why a range claim needs a path-loss exponent attached
- Certifications matter less than one specification read properly
- Still unbuilt: 11 module labs and the capstone project
Wireless 101 — complete
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