835  Wi-Fi: Comprehensive Review - Wi-Fi 6 Features

import {InlineKnowledgeCheck} from "/assets/js/iotclass-inline-kc.js"

ImportantWi-Fi 6 Game-Changing Features for IoT

Note: The magnitude of power and efficiency gains depends on chipset, PHY rate, beacon interval, and traffic patterns; treat the numeric examples below as illustrative.

Target Wake Time (TWT): - Schedules exact device wake times → eliminates beacon listening - Battery life improvement: 98× longer (16.6 years vs 61.8 days) - Example: Sensor sleeps deeply, wakes at 10:00:00, transmits, returns to sleep

OFDMA (Orthogonal Frequency Division Multiple Access): - Divides channel into Resource Units for simultaneous multi-device transmission - Efficiency improvement: 4× more devices per AP vs Wi-Fi 5 - Example: 8 IoT sensors transmit concurrently instead of queuing

BSS Coloring: - Differentiates overlapping networks → reduces co-channel interference - Spatial reuse improvement: 30% more concurrent transmissions - Example: Adjacent APs reuse channels without causing collisions

835.0.1 Wi-Fi 6 OFDMA Resource Unit Allocation

Wi-Fi 6 revolutionizes multi-device efficiency by dividing channels into Resource Units:

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graph TB
    subgraph WIFI5["Wi-Fi 5 (802.11ac) - Sequential OFDM"]
        AP5[Access Point]
        T1[Time Slot 1: Camera 2Mbps]
        T2[Time Slot 2: Sensor 100 bytes]
        T3[Time Slot 3: Vibration 200 kbps]
        T4[Time Slot 4: AGV 400 kbps]

        AP5 --> T1
        T1 --> T2
        T2 --> T3
        T3 --> T4
    end

    subgraph WIFI6["Wi-Fi 6 (802.11ax) - Parallel OFDMA"]
        AP6[Access Point]

        subgraph RU["Single Transmission - Multiple RUs"]
            RU1[RU1: 242-tone<br/>Camera 2Mbps]
            RU2[RU2: 106-tone<br/>AGV 400 kbps]
            RU3[RU3: 52-tone<br/>Vibration 200 kbps]
            RU4[RU4: 26-tone<br/>Sensor 100 bytes]
        end

        AP6 -.->|Parallel TX| RU1
        AP6 -.->|Parallel TX| RU2
        AP6 -.->|Parallel TX| RU3
        AP6 -.->|Parallel TX| RU4
    end

    style WIFI5 fill:#fdeaa8,stroke:#E67E22,stroke-width:3px
    style WIFI6 fill:#d5f4e6,stroke:#16A085,stroke-width:3px
    style AP5 fill:#E67E22,stroke:#2C3E50,stroke-width:2px
    style AP6 fill:#16A085,stroke:#2C3E50,stroke-width:2px
    style T1 fill:#7F8C8D,stroke:#2C3E50,stroke-width:1px
    style T2 fill:#7F8C8D,stroke:#2C3E50,stroke-width:1px
    style T3 fill:#7F8C8D,stroke:#2C3E50,stroke-width:1px
    style T4 fill:#7F8C8D,stroke:#2C3E50,stroke-width:1px
    style RU fill:#ecf0f1,stroke:#16A085,stroke-width:2px
    style RU1 fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style RU2 fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style RU3 fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style RU4 fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff

Figure 835.1: Wi-Fi 6 OFDMA enables simultaneous multi-device transmission by dividing the channel into Resource Units (RUs). Wi-Fi 5 forces sequential transmission with one device at a time, while Wi-Fi 6 allocates different-sized RUs to 4+ devices transmitting in parallel, reducing latency and improving airtime efficiency by 2.77×.

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  if (typeof InlineKnowledgeCheck !== 'undefined') {
    container.appendChild(InlineKnowledgeCheck.create({
      question: "A logistics company operates a warehouse with 80 battery-powered Wi-Fi asset tracking tags and 20 always-on IP cameras on the same access point. The tags report location every 5 seconds, while cameras stream 2 Mbps video continuously. After upgrading to Wi-Fi 6, which feature combination would provide the greatest benefit for this mixed workload?",
      options: [
        {text: "1024-QAM for higher data rates and BSS Coloring for interference reduction", correct: false, feedback: "Incorrect. 1024-QAM provides 25% more throughput per symbol but isn't the main benefit here - the cameras only need 40 Mbps total. BSS Coloring helps with neighboring AP interference but doesn't address the core challenge of efficiently serving 100 devices with very different traffic patterns."},
        {text: "OFDMA for efficient multi-device scheduling combined with TWT for tag battery life", correct: true, feedback: "Correct! OFDMA allows the AP to allocate small Resource Units to tags while dedicating larger RUs to cameras - all in the same transmission. TWT schedules tag wake times to eliminate contention and beacon listening, dramatically extending battery life. This combination addresses both the density challenge (80 tags + 20 cameras) and power efficiency for battery devices."},
        {text: "MU-MIMO for parallel transmission to cameras and standard OFDM for tags", correct: false, feedback: "Incorrect. MU-MIMO helps when transmitting to multiple high-throughput devices simultaneously, but tags only need tiny packets. OFDMA is specifically designed for mixing small IoT packets with larger streams. MU-MIMO alone doesn't address the tag battery life issue that TWT solves."},
        {text: "Wider 160 MHz channels for maximum throughput to serve all devices faster", correct: false, feedback: "Incorrect. Wider channels reduce the number of available non-overlapping channels and can increase interference. The bottleneck isn't throughput (20 cameras × 2 Mbps = 40 Mbps, well under Wi-Fi 6 capacity). OFDMA and TWT provide targeted benefits for the mixed high-density, battery-powered workload."}
      ],
      difficulty: "hard",
      topic: "wifi-standards"
    }));
  }
  return container;
}

835.0.2 Wi-Fi 6 Target Wake Time (TWT) Operation

TWT schedules device wake times to eliminate power-hungry beacon listening:

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gantt
    title Wi-Fi 6 TWT Power Savings (10-second reporting cycle)
    dateFormat X
    axisFormat %L ms

    section Wi-Fi 5 (No TWT)
    Beacon Listen (100ms @ 100mA)     :active, 0, 100
    Deep Sleep (9.9s @ 10µA)          :crit, 100, 9900

    section Wi-Fi 6 (With TWT)
    Scheduled Wake (0.028ms)          :active, 0, 1
    Deep Sleep (10s @ 10µA)           :crit, 1, 10000

Figure 835.2: Wi-Fi 6 Target Wake Time (TWT) comparison showing power consumption over 10-second reporting cycle. Wi-Fi 5 requires 100ms beacon listening at 100mA consuming 24.28 mAh/day (61.8 days battery life). Wi-Fi 6 TWT eliminates beacon listening, waking only 0.028ms for scheduled transmission consuming 0.248 mAh/day (16.6 years battery life) - a 98× improvement.

kc_wifi_8 = {
  const container = document.createElement('div');
  container.className = 'inline-kc-container';

  if (typeof InlineKnowledgeCheck !== 'undefined') {
    container.appendChild(InlineKnowledgeCheck.create({
      question: "A smart building has 500 occupancy sensors reporting every 60 seconds via Wi-Fi 6. The building automation system requires that sensor data arrive within 2 seconds of transmission to maintain accurate occupancy counts. The network administrator is configuring TWT (Target Wake Time). What TWT interval should they configure?",
      options: [
        {text: "TWT interval of 60 seconds to match the sensor reporting interval exactly", correct: false, feedback: "Incorrect. While matching the reporting interval seems logical, a 60-second TWT interval means sensors can only wake at their scheduled time. If a sensor misses its window (clock drift, RF interference), it must wait another 60 seconds - violating the 2-second latency requirement."},
        {text: "TWT interval of 500ms with wake duration of 10ms to ensure sensors can transmit promptly", correct: true, feedback: "Correct! A short TWT interval (500ms) ensures sensors have frequent transmission opportunities while still providing significant power savings over continuous beacon listening. With 500ms intervals, worst-case latency is 500ms (well under 2s requirement). The 10ms wake window is sufficient for small sensor packets while maintaining 98% sleep time for battery efficiency."},
        {text: "Disable TWT entirely since latency requirements prevent using scheduled wake times", correct: false, feedback: "Incorrect. TWT can absolutely meet 2-second latency with appropriate configuration. Disabling TWT would dramatically reduce battery life (beacon listening every 100ms vs scheduled wake). The key is configuring TWT with sufficiently short intervals - not disabling it entirely."},
        {text: "TWT interval of 10 seconds with immediate transmission capability", correct: false, feedback: "Incorrect. A 10-second TWT interval creates up to 10-second latency in worst case, violating the 2-second requirement. Immediate transmission capability would require the sensor to wake outside its TWT window, negating the power savings. A 500ms interval provides both low latency and power efficiency."}
      ],
      difficulty: "hard",
      topic: "wifi-power-saving"
    }));
  }
  return container;
}

835.0.3 Wi-Fi Channel Planning for Dense Deployments

Proper channel allocation is critical for avoiding co-channel interference:

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graph TB
    subgraph BAND24["2.4 GHz Band - Limited Channels"]
        CH1[Channel 1<br/>2412 MHz]
        CH6[Channel 6<br/>2437 MHz]
        CH11[Channel 11<br/>2462 MHz]
        OVL[Overlapping Channels<br/>2-5, 7-10, 12-14<br/>Avoid unless crowded]

        CH1 -.->|25 MHz spacing| CH6
        CH6 -.->|25 MHz spacing| CH11
    end

    subgraph BAND5["5 GHz Band - Many Channels"]
        UNII1[UNII-1: Ch 36,40,44,48<br/>5.15-5.25 GHz]
        UNII2[UNII-2: Ch 52,56,60,64<br/>5.25-5.35 GHz<br/>DFS Required]
        UNII3[UNII-3: Ch 100-144<br/>5.47-5.725 GHz<br/>DFS Required]
        UNII4[UNII-4: Ch 149-165<br/>5.725-5.850 GHz]

        UNII1 --> UNII2
        UNII2 --> UNII3
        UNII3 --> UNII4
    end

    subgraph PLAN["Optimal Channel Assignment"]
        GRID[28 APs in 4×7 Grid]
        P1[Pattern: Ch 42, 58, 106, 122, 138]
        P2[Reuse Factor: 2-channel spacing]
        P3[Reduced Co-Channel Interference]

        GRID --> P1
        P1 --> P2
        P2 --> P3
    end

    style BAND24 fill:#fdeaa8,stroke:#E67E22,stroke-width:3px
    style BAND5 fill:#d5f4e6,stroke:#16A085,stroke-width:3px
    style PLAN fill:#ecf0f1,stroke:#2C3E50,stroke-width:3px
    style CH1 fill:#E67E22,stroke:#2C3E50,stroke-width:2px
    style CH6 fill:#E67E22,stroke:#2C3E50,stroke-width:2px
    style CH11 fill:#E67E22,stroke:#2C3E50,stroke-width:2px
    style OVL fill:#7F8C8D,stroke:#2C3E50,stroke-width:1px
    style UNII1 fill:#16A085,stroke:#2C3E50,stroke-width:2px
    style UNII2 fill:#16A085,stroke:#2C3E50,stroke-width:2px
    style UNII3 fill:#16A085,stroke:#2C3E50,stroke-width:2px
    style UNII4 fill:#16A085,stroke:#2C3E50,stroke-width:2px
    style GRID fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style P1 fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style P2 fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style P3 fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff

Figure 835.3: Wi-Fi channel planning showing 2.4 GHz constraints (only 3 non-overlapping channels: 1, 6, 11) versus 5 GHz abundance (many non-overlapping 20 MHz channels across UNII-1/2/3/4 bands). For dense deployments, 5 GHz provides more channel options and enables reuse patterns that reduce co-channel interference.

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    container.appendChild(InlineKnowledgeCheck.create({
      question: "A retail chain is deploying 15 Wi-Fi access points in a 50,000 sq ft store using only the 2.4 GHz band (customer requirement for legacy device support). The RF engineer needs to assign channels to minimize co-channel interference. Which channel assignment strategy is correct?",
      options: [
        {text: "Assign channels 1-15 sequentially to maximize separation between adjacent APs", correct: false, feedback: "Incorrect. In 2.4 GHz, there are only 3 non-overlapping channels (1, 6, 11). Channels 2-5, 7-10, and 12+ overlap with adjacent channels. Using channels like 2, 3, 4, 5 causes ADJACENT channel interference which is often WORSE than co-channel interference because devices don't defer properly."},
        {text: "Use only channels 1, 6, and 11 in a repeating pattern with maximum physical separation between same-channel APs", correct: true, feedback: "Correct! In 2.4 GHz, only channels 1, 6, and 11 are non-overlapping (25 MHz spacing covers the 22 MHz channel width). With 15 APs, use a honeycomb pattern: assign 1, 6, 11 such that same-channel APs are maximally separated. Adjacent APs on different non-overlapping channels won't interfere. This is the only viable approach for 2.4 GHz deployments."},
        {text: "Use automatic channel selection (ACS) on all APs to dynamically optimize", correct: false, feedback: "Incorrect. While ACS can help, it typically causes channel hopping chaos when all 15 APs independently optimize. Coordinated manual planning using channels 1, 6, 11 in a fixed pattern provides stable, predictable performance. ACS is better suited for dynamic home environments, not planned enterprise deployments."},
        {text: "Reduce AP transmit power and use all channels 1-11 with wider spacing between APs", correct: false, feedback: "Incorrect. Lower power doesn't change the fundamental problem: channels 2-5 and 7-10 overlap with adjacent channels. Using channel 3 still interferes with channels 1 and 6. Only channels 1, 6, and 11 are truly non-overlapping in 2.4 GHz. Power reduction helps cell sizing but doesn't create more non-overlapping channels."}
      ],
      difficulty: "medium",
      topic: "wifi-channel-interference"
    }));
  }
  return container;
}

835.1 What’s Next

Continue to Summary and Visual Gallery to review key Wi-Fi concepts, explore visual references for Wi-Fi 6 features and channel planning, and test your comprehensive understanding with final assessment questions.