Learning tool · from bits to shared airtime

Wi-Fi, generation
by generation.

A radio has two jobs: turn bits into a waveform, then find a chance to send it. Each Wi-Fi generation changes some part of those jobs. Change one ingredient at a time and see which number moves, which stays fixed, and what the receiver can learn about a room.

In plain words A radio turns bits into a waveform and waits for a chance to send it. Change the signal, the available spectrum or the sharing rules and see which part of the result changes.

Three bands, one room Signals, up close

Reviewed 2026-09-20. Standards facts and worked teaching models; no live measurements. Begin with the explanations, then open “A closer look” for the qualifications. All examples remain readable without JavaScript.

Three names, three different things

IEEE 802.11 specifies wireless LAN operation. Amendments such as 802.11ax extend it and later revisions consolidate amendments. Wi-Fi 6 is the Wi-Fi Alliance generation and certification name based on ax. 6 GHz is a frequency band. A generation, a radio band and a certification are not interchangeable.

The PHY is the physical layer: tones, modulation, coding, antennas and training signals. The MAC is medium access control: contention, scheduling, acknowledgments and link coordination. An AP is an access point; a STA is a station, including a client. New PHY and MAC mechanisms often work together.

The foundations before numbered Wi-Fi generations
Amendment	Band	Mechanism	Peak PHY
802.11b	2.4 GHz	DSSS / CCK, not OFDM	11 Mbit/s
802.11a / g	5 / 2.4 GHz	OFDM: many orthogonal tones in one channel	54 Mbit/s

Historical foundation: Bensky, Short-range Wireless Communication, chapter 11 (vault: bensky2019_6c00). “Orthogonal” means tones can overlap in frequency while an ideal synchronized receiver still separates them.

Fig. 1 · what each generation changesDeclared / illustrative

Modern families: capability ceilings
Name / amendment	Bands (GHz)	Maximum width	QAM	Streams	What changes
Wi-Fi 4 / 802.11n	2.4 / 5	40 MHz	64	4	Send parallel spatial streams and aggregate frames. More antenna paths can add information. Antennas, spatial streams and independent observations are different quantities.
Wi-Fi 5 / 802.11ac	5	160 MHz	256	8	Widen the channel; serve multiple users with downlink MU-MIMO. Wider frequency coverage changes the delay aperture. It does not remove hardware phase errors or environmental drift.
Wi-Fi 6 / 6E / 802.11ax	2.4 / 5 / 6	160 MHz	1024	8	Share frequency with OFDMA; add uplink MU-MIMO, BSS coloring and target wake time. 6E names 6 GHz capability. The finer tone grid samples frequency more densely. Scheduling and power saving also change when measurements arrive.
Wi-Fi 7 / 802.11be	2.4 / 5 / 6	320 MHz	4096	8	Coordinate links with MLO, allow multiple RUs per user, and extend bandwidth to 320 MHz in 6 GHz. Track the link and its frequency mask. A Wi-Fi 7 badge is not a CSI export interface or a sensing accuracy guarantee.

Select a generation to connect its mechanism with the measurement it changes. These are upper capabilities of the family, not requirements for every product.Sources: MathWorks: HT configuration and MCS · MathWorks: VHT configuration, data tones and restrictions · MathWorks: HE single-user configuration · MathWorks: EHT MCS and eight-stream limit

A closer look: 6E, sensing, and the next generation

Wi-Fi 6E extends Wi-Fi 6 into 6 GHz; it is still 802.11ax. Local spectrum rules and device capabilities decide which channels are usable. The controls below show PHY-family possibilities, not a regulatory channel plan.

802.11be received IEEE approval in September 2024. 802.11bf-2025 is a separate WLAN sensing amendment, published in September 2025. It does not mean “Wi-Fi 7 with a people counter.” 802.11bn, associated with Wi-Fi 8, remains a draft project: the TGbn page records D2.0 balloting in July 2026 and projects final approval in 2028. Future features and dates may change.

The family also has branches: 802.11ah targets sub-1 GHz operation; 802.11ad/ay target directional 60 GHz operation. They are not steps in the 2.4/5/6 GHz speed ladder.

Sources: IEEE TGbe: approval in September 2024 · IEEE: 802.11bf-2025 publication announcement · IEEE TGbn: Ultra High Reliability, draft timeline · Du et al. (2025): An Overview on IEEE 802.11bf

More choices in the same signal

Quadrature amplitude modulation (QAM) chooses a point with two coordinates: in-phase I and quadrature Q. Together they set amplitude and phase. A receiver estimates the point and decides which was sent. With M possible points, one symbol carries log₂(M) coded bits on a data tone.

Keep average energy fixed and add points: the gaps shrink. The same disturbance can now move the received point closer to the wrong choice. That is the trade behind higher-order modulation.

Open Signals, up close → Pick a QAM point and build its waveform, add noise and channel rotation, combine OFDM tones, and move a receiver through an illustrative room.

Fig. 2 · the constellationDeclared / illustrative

Square constellations at unit mean symbol energy; adjacent-point distance = √(6/(M−1))
Modulation	Bits / tone-symbol	Point distance
4 points	2	1.414
16 points	4	0.632
64 points	6	0.309
256 points	8	0.153
1024 points	10	0.077
4096 points	12	0.038

Increase QAM order while holding the disturbance fixed. 4096-QAM carries 12 rather than 10 bits per tone-symbol: 20% more than 1024-QAM at equal coding, tone count and symbol duration.Sources: MathWorks: EHT MCS and eight-stream limit

A closer look: coding, MCS and channel estimation

Forward error correction adds redundancy. A coding rate of 5/6 means five information bits for six coded bits. The modulation and coding scheme (MCS) selects both. Higher QAM does not make the wave travel faster, increase bandwidth, or by itself improve CSI. A receiver estimates the channel using known training signals before decoding the unknown payload.

Sources: MathWorks: EHT MCS and eight-stream limit · Cominelli et al. (2023): Exposing the CSI

Build the rate from its ingredients

OFDM sends symbols on many data tones at once. Spatial multiplexing adds independent streams over suitable antenna paths. A guard interval copies the end of a symbol to its beginning, helping the receiver tolerate delayed echoes; that time carries no new data.

PHY rate = data tones × bits/tone × coding rate × spatial streams ÷ (useful symbol + guard interval)

Fig. 3 · one link, one calculationDeclared / illustrative

Full-band maximum examples at the shortest guard interval, one link
PHY	Width / tones	Bits / coding	Streams	Symbol + GI	Rate
HT	40 MHz / 108	6 / 5:6	4	3.2 + 0.4 µs	600.0 Mbit/s
VHT	160 MHz / 468	8 / 5:6	8	3.2 + 0.4 µs	6933.3 Mbit/s
HE	160 MHz / 1960	10 / 5:6	8	12.8 + 0.8 µs	9607.8 Mbit/s
EHT	320 MHz / 3920	12 / 5:6	8	12.8 + 0.8 µs	23058.8 Mbit/s

Change width, MCS, guard interval or stream count independently. Bits per microsecond are Mbit/s. The selected family and band constrain the offered widths; devices may support a smaller subset.Sources: MathWorks: HT configuration and MCS · MathWorks: VHT configuration, data tones and restrictions · MathWorks: bandwidth/stream-dependent VHT MCS restrictions · MathWorks: HE single-user configuration · MathWorks: EHT configuration, puncturing and MRU · MathWorks: EHT MCS and eight-stream limit

A rate is not a download speed. Preambles, contention, headers, acknowledgments, retries, transport behavior and the wired path consume time or limit delivery. A two-stream EHT link at 320 MHz, MCS 13 and 0.8 µs GI computes to about 5.76 Gbit/s PHY; that is a specified operating point, not a throughput promise.

A closer look: why “46 Gbit/s Wi-Fi 7” needs checking

Early EHT discussions included 16 streams. The current EHT configuration reference limits the total to eight streams per RU, and this tool uses eight: about 23.06 Gbit/s at the full 320 MHz operating point. Adding separately usable links is a different calculation. The older 802.11ac family ceiling is about 6.93 Gbit/s at eight streams, 160 MHz and short GI; 3.5 Gbit/s describes fewer streams, not its full ceiling.

HE/EHT tone spacing is 78.125 kHz, versus 312.5 kHz for HT/VHT. Four times as many FFT bins accompany a four-times-longer useful symbol. Count data tones, not FFT bins, pilots, or the number of CSI values a driver exports.

Sources: MathWorks: VHT configuration, data tones and restrictions · MathWorks: EHT MCS and eight-stream limit · Cominelli et al. (2023): Exposing the CSI

Faster bits still have to wait their turn

Wi-Fi shares a medium. A station listens, waits through the required idle interval and counts down a random backoff while the channel is idle. Another transmission freezes the countdown. Collisions and retransmissions remain possible. Carrier-sense multiple access with collision avoidance (CSMA/CA) does not disappear when OFDMA arrives.

An AP that gains access can schedule users inside an exchange. OFDMA assigns resource units (RUs), groups of tones, to users. MU-MIMO separates users spatially, using the same frequency resource. Aggregation packs frames together to amortize overhead; block acknowledgments acknowledge groups of frames. These mechanisms can coexist.

Fig. 4 · four clients, equal workDeclared / illustrative

Four clients; 1500-byte packets; 600 Mbit/s total PHY budget; assumed exchange overheads of 100 / 160 µs
Packets per client	Sequential time	OFDMA time	Sequential payload rate	OFDMA payload rate
1	480 µs	240 µs	100.0 Mbit/s	200.0 Mbit/s
4	720 µs	480 µs	266.7 Mbit/s	400.0 Mbit/s
16	1680 µs	1440 µs	457.1 Mbit/s	533.3 Mbit/s
64	5520 µs	5280 µs	556.5 Mbit/s	581.8 Mbit/s

A frequency slice carries fewer bits per unit time than the full channel. In this equal-work model, OFDMA saves repeated exchange overhead; the gain shrinks as each queue grows. The numbers are classroom assumptions.Sources: MathWorks: HE single-user configuration

A closer look: efficiency, power and latency

BSS coloring helps distinguish overlapping basic service sets; spatial reuse decisions still depend on thresholds and interference. Target wake time (TWT) coordinates waking and sleeping. Restricted TWT in EHT protects designated service periods more tightly. None supplies an unconditional millisecond latency guarantee. For sensing, useful questions include how many frames arrive, how irregularly, and whether the transmitters or scheduling policy changed.

Block ACK is an efficiency mechanism, not a security feature. Security and certification requirements belong alongside, rather than inside, the PHY-rate formula.

Sources: MathWorks: HE single-user configuration · HPE Aruba: Wi-Fi 7 features and MLO device types

A wide channel can contain a hole

Channel bonding uses a wider frequency span. Puncturing omits permitted portions inside that span when they cannot be used. An allocation can therefore span a wide channel without occupying every segment. EHT extends the available mechanisms; puncturing already had a more limited form in HE.

Fig. 5 · span versus occupied segmentsDeclared / illustrative

Illustrative four-segment channel
Segment	Without puncturing	With puncturing
Primary 20 MHz	Available	Retained
Secondary 20 MHz	Available	Retained
Busy secondary 20 MHz	Interference	Omitted
Secondary 20 MHz	Available	Retained

This sketch is not a legal-pattern validator. Three retained nominal 20 MHz segments occupy 60 MHz within an 80 MHz span.

Toggle one secondary segment in an 80 MHz example. A missing segment changes the frequency sampling mask. Do not fill it with an invented measurement.Sources: MathWorks: EHT configuration, puncturing and MRU

Multi-RU allocation answers a related question: can one user receive more than one RU? EHT permits defined combinations. The RUs are not arbitrary slices; their tone plans and combinations are specified. A wide channel, a puncturing mask, an RU allocation and multiple links describe four different things.

Toy schedule: four 200 µs packets, A busy until 400 µs, B clear, EMLSR starts on A and takes 80 µs to switch
Mode	Schedule	Completion
One link	A: 400–1200 µs	1200 µs
EMLSR	B: 80–880 µs, one packet at a time	880 µs
STR multi-radio	B: 0–600 µs; A: 400–600 µs	600 µs

What changes for our thesis?

A communication receiver estimates how a known training signal changed on its way through the room. Channel state information (CSI) is that channel estimate, indexed by frequency and antenna paths. People can change it, but so can hardware, link selection and the environment. The communication generation describes the signal and protocol; it does not establish a crowd-counting accuracy.

Fig. 7 · aperture is different from grid densityDeclared / illustrative

Ideal contiguous aperture: approximate delay and propagation path-length scales
Bandwidth B	1/B	c/B
20 MHz	50.000 ns	14.990 m
40 MHz	25.000 ns	7.495 m
80 MHz	12.500 ns	3.747 m
160 MHz	6.250 ns	1.874 m
320 MHz	3.125 ns	0.937 m

312.5 kHz spacing gives 3.2 µs periodicity; 78.125 kHz gives 12.8 µs. These are not positioning errors. Monostatic range uses c/(2B); our bistatic paths do not have that simple range interpretation.

Bandwidth controls an approximate delay-resolution scale; tone spacing controls delay periodicity. These independent mathematical controls explain two mechanisms and do not certify a Wi-Fi configuration.Sources: Cominelli et al. (2023): Exposing the CSI

The AX210 is a Wi-Fi 6E, two-stream, 160 MHz device. It cannot acquire an EHT 320 MHz CSI grid merely because the transmitter is a Wi-Fi 7 AP. The actual transmitted frame format, driver, firmware and export path determine what arrives in a capture. A newer AP may also transmit older-format frames. Inspect the record, not its product label. Sources: Intel: AX210 product specifications

Standards mechanisms translated into thesis questions, not claimed results
Change	What to record or control	Question for BLE-calibrated CSI sensing
Bandwidth / tone plan / puncturing	Actual tone frequencies, missing-tone mask, antenna paths	Does the calibrated feature survive a change of frequency aperture?
OFDMA / TWT / contention	Delivered timestamps, gaps and transmitter scope	Can a change in sampling mimic occupancy or drift?
MLO	Which link was heard; per-link coverage and calibration	Can we distinguish changed traffic allocation from a changed room?
802.11bf procedures	Supported sensing roles, sounding/report setup, accessible measurement format	Can standardized acquisition support the calibration–inference–drift cycle?

A closer look: 802.11bf is a procedure, not an inference model

The sensing procedure separates capability discovery, measurement setup, measurement instances and termination. An initiator coordinates responders; sounding produces observations and reporting conveys them when required. A sounding packet need not carry an application payload. Below 7 GHz the amendment chiefly changes MAC procedures; 60 GHz sensing also involves PHY changes. Which roles and measurements a product exposes remains an implementation question.

Our thesis connects periodic BLE calibration with CSI inference and drift detection. These standards support and constrain the measurement layer. They do not validate the calibration model, turn devices into people, or demonstrate transfer to a new room. The corpus describes acquisition and sensing limitations; this review found no final-EHT source in the returned corpus passages and no direct evidence that Wi-Fi 7 improves our crowd-counting model. Standards details were therefore checked against primary external references.

Sources: Cominelli et al. (2023): Exposing the CSI · Ropitault et al. (2024): IEEE 802.11bf WLAN Sensing Procedure · Du et al. (2025): An Overview on IEEE 802.11bf

Continue with carrier frequency and propagation, one real CSI record, its stored format, delivered sampling rates, and the sensing models.

Try it

Predict, change, explain

Make a prediction before moving a control. State what you held fixed and whether the output is a standard capability, a calculation, or a measurement.

At EHT, 160 MHz, two streams and 0.8 µs GI, change MCS 11 to 13.
Explain the result
Both use 5/6 coding. Bits per tone rise from 10 to 12, so the PHY rate rises by 20%, about 2402 to 2882 Mbit/s. This says nothing about whether the real link can sustain that modulation.
Keep the QAM disturbance at 0.06 and compare 64-QAM with 4096-QAM.
Explain the result
At equal energy, the adjacent-point gap shrinks from about 0.309 to 0.038. The same displacement crosses a decision boundary in the denser constellation. This single example is not a bit-error-rate estimate.
Give every client 64 packets instead of one in the airtime example.
Explain the result
The assumed overhead saving remains 240 µs. It is a much smaller share of the longer exchange. Four users in parallel do not create four times the spectral capacity.
Clear link A in the MLO example. Compare EMLSR and STR.
Explain the result
EMLSR still needs 800 µs for four serial data exchanges. STR can use two radios and finishes in 400 µs under these assumptions. With A busy, EMLSR may gain by moving to B, even without parallel payload transmission.
At 80 MHz, change tone spacing from 312.5 to 78.125 kHz.
Explain the result
The approximate delay scale stays 12.5 ns. Periodicity changes from 3.2 to 12.8 µs. More frequency samples do not by themselves widen the aperture.
A Wi-Fi 7 AP replaces the old AP. The CSI feature changes. Has occupancy changed?
Explain the result
The observation is ambiguous. Check the frame family, transmitter/link, tone mask, antenna mapping, gain/phase behavior and delivered sampling before interpreting a change as people. Revisit the BLE calibration and test transfer with an independent reference.

Sources and limits

The capture summary supplied the questions. Primary technical references and the indexed sensing literature supply the corrections. Early drafts and forecasts are not treated as current product guarantees. The interactive schedules are authored examples; no lesson output is a fleet measurement.

Wi-Fi, generationby generation.