---
title: WiFi and Bluetooth
url: https://doc.liz6.com/en/hardware/07-wireless-communications/01-wifi-and-bluetooth
locale: en
area: hardware
tags:
- hardware
- wireless-communications
date: 2026-06-30
modified: 2026-07-16
description: WiFi and Bluetooth WiFi (802.11) Generational Evolution | Generation | IEEE | Band | Max Rate | Key Technologies | Year | |------|------|------|----------|-----…
---

# WiFi and Bluetooth

## WiFi (802.11)

### Generational Evolution

| Generation | IEEE | Band | Max Rate | Key Technologies | Year |
|------|------|------|----------|----------|------|
| WiFi 4 | 802.11n | 2.4/5 GHz | 600 Mbps | MIMO, 40MHz | 2009 |
| WiFi 5 | 802.11ac | 5 GHz | 6.9 Gbps | MU-MIMO, 160MHz, 256QAM | 2013 |
| WiFi 6 | 802.11ax | 2.4/5 GHz | 9.6 Gbps | OFDMA, 1024QAM, TWT | 2019 |
| WiFi 6E | 802.11ax | +6 GHz | Same as 6 | Added 6GHz clean spectrum | 2021 |
| WiFi 7 | 802.11be | 2.4/5/6 GHz | 46 Gbps | 320MHz, 4096QAM, MLO | 2024 |

### Key Concepts

#### Frequency Bands
```
2.4 GHz: Crowded (microwaves/BT/Zigbee all operate here), good wall penetration
  Channels 1~13 (China), only 3 non-overlapping channels (1/6/11)

5 GHz: Clean, many channels, large bandwidth, poor wall penetration
  Many channels, can bond 80/160 MHz

6 GHz (WiFi 6E/7): New spectrum, almost no interference
  But worse wall penetration, currently only for indoor use
```

#### OFDM / OFDMA
```
OFDM (WiFi 4/5): Occupies the entire channel for each transmission
  → Small packets also occupy the full channel, low efficiency

OFDMA (WiFi 6+): Divides the channel into RUs (Resource Units)
  → Multiple devices transmit simultaneously, similar to LTE
  → Significantly reduces latency and improves multi-device efficiency

Analogy: OFDM = single lane, OFDMA = multi-lane highway
```

#### MIMO / MU-MIMO
```
MIMO: Multiple antennas transmit and receive simultaneously
  2×2: 2 transmit, 2 receive (common in phones/laptops)
  4×4: 4 transmit, 4 receive (high-end routers)

MU-MIMO: Simultaneously sends data to multiple clients
  WiFi 5: Downlink only, WiFi 6: Supports both uplink and downlink
```

#### MLO (Multi-Link Operation) — WiFi 7
```
Simultaneously uses multiple bands (2.4G + 5G + 6G) for transmission
→ Higher throughput + lower latency + better reliability
→ If one band is interfered with, seamlessly switch to another
```

---

## Bluetooth (Bluetooth)

### Classic vs BLE

| Feature | BR/EDR (Classic) | BLE (Low Energy) |
|------|-------------------|-------------------|
| Physical Channels | 79 x 1MHz | 40 x 2MHz |
| Rate | 1~3 Mbps | 125kbps~2Mbps |
| Power Consumption | ~1W (continuous) | ~0.01~0.5W |
| Latency | ~100ms | ~3ms |
| Topology | Piconet | Star/Broadcast/Mesh |
| Audio | A2DP/HFP | LE Audio (LC3) |
| Typical Applications | Speakers/Headphones/Car Infotainment | Wearables/IoT/Beacons |

### BLE Versions
```
4.0: Basic BLE
4.2: Security enhancements, packet length extension
5.0: 2M PHY, long-range coding, extended advertising
5.1: Direction finding (AoA/AoD → centimeter-level positioning)
5.2: LE Audio, Isochronous Channels (for TWS earbuds)
5.3: Channel classification, connection subevents
5.4: Periodic advertising sync (for electronic shelf labels)

Actually, BLE 4.2 is sufficient for most scenarios.
5.0+ mainly brings: faster, longer range, more power-efficient.
```

### BLE Connection Flow

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  <text x="360" y="28" text-anchor="middle" font-size="17" font-weight="700" fill="#1f2933">BLE Connection Establishment Flow: Advertising → Scan Request/Response → Connection Request</text>

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  <text x="150" y="77" text-anchor="middle" font-size="13" font-weight="700" fill="#3730a3">Peripheral</text>
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  <text x="360" y="118" text-anchor="middle" font-size="12" font-weight="700" fill="#3730a3">① Advertising</text>
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  <text x="360" y="158" text-anchor="middle" font-size="12" font-weight="700" fill="#334155">② Scan Request</text>
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  <text x="360" y="198" text-anchor="middle" font-size="12" font-weight="700" fill="#0f766e">③ Scan Response</text>
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  <text x="360" y="238" text-anchor="middle" font-size="12" font-weight="700" fill="#334155">④ Connection Request</text>
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  <rect x="150" y="270" width="420" height="26" rx="6" fill="#dcfce7" stroke="#4ade80"/>
  <text x="360" y="287" text-anchor="middle" font-size="12" font-weight="700" fill="#166534">⑤ Connection Established</text>

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  <text x="76" y="340" font-size="12.5" fill="#115e59">Connection parameters determine the trade-off between response speed and power consumption: Connection Interval 7.5ms~4s — shorter = lower latency/higher power consumption, longer = higher latency/lower power consumption.</text>
  <text x="76" y="360" font-size="12.5" fill="#115e59">Slave Latency = number of responses the slave can skip; Supervision Timeout = time without response before disconnection.</text>
</svg>


### Classic Bluetooth vs BLE Selection Guide
```
Continuous Audio → Classic (A2DP)
Occasional Data + Low Power → BLE
Need iOS Background Communication → BLE (Apple favors BLE)
HID Keyboards/Mice → BLE (HID over GATT)
File Transfer → Classic (or WiFi Direct)
TWS Earbuds → BLE 5.2+ (LE Audio)
```

---

## WiFi and Bluetooth Coexistence

### Co-frequency Interference
```
2.4GHz is the battlefield for WiFi + BT + Zigbee + Thread + Microwaves

WiFi and BT are in the same device:
  → Time Division Multiplexing (TDM): Alternating use of antennas
  → Coexistence Interface: Bluetooth tells WiFi "I'm about to send a packet", WiFi pauses

Implementation: Most WiFi/BT combo chips have internal coexistence mechanisms
     (MTK/Realtek/Broadcom/Qualcomm each have their own implementations)
Driver-side issues often cause coexistence failures (e.g., your MT7927)
```

### Combo Chips
```
In consumer electronics, WiFi and BT are almost always on the same chip
  MT7921/7925/7927 (MTK)
  AX200/AX210 (Intel)
  BCM series (Broadcom)

Connect to Host via PCIe/USB/SDIO
The Bluetooth part is usually exposed via a USB HCI interface
```

---
*Keywords: WiFi6, WiFi7, 802.11ax, OFDMA, MIMO, BLE, GATT, LE Audio, Coexistence*