WiFi 与蓝牙

WiFi (802.11)

世代演进

关键概念

频段

2.4 GHz: 拥挤 (微波炉/BT/Zigbee 都在这), 穿墙好
  信道 1~13 (中国), 仅 3 个不重叠信道 (1/6/11)

5 GHz: 干净、信道多、带宽大, 穿墙差
  信道多, 可捆绑 80/160 MHz

6 GHz (WiFi 6E/7): 全新频谱, 几乎没有干扰
  但穿墙更差, 目前仅室内用

OFDM / OFDMA

OFDM (WiFi 4/5): 每次传输占用整个信道
  → 小包也占满, 效率低

OFDMA (WiFi 6+): 把信道切分为 RU (资源单元)
  → 多个设备同时传输, 类似 LTE
  → 大幅降低延迟, 提高多设备效率

类比: OFDM = 单车道, OFDMA = 多车道

MIMO / MU-MIMO

MIMO: 多天线同时收发
  2×2: 2 发 2 收 (常见手机/笔记本)
  4×4: 4 发 4 收 (高端路由器)

MU-MIMO: 同时向多个客户端发送数据
  WiFi 5: 仅下行, WiFi 6: 上下行都支持

MLO (Multi-Link Operation) — WiFi 7

同时使用 2.4G + 5G + 6G 多频段传输
→ 更高吞吐 + 更低延迟 + 更好的可靠性
→ 一个频段被干扰可无缝切到另一个

蓝牙 (Bluetooth)

Classic vs BLE

BLE 版本

4.0: 基础 BLE
4.2: 安全增强, 包长扩展
5.0: 2M PHY, 长距离编码, 广播扩展
5.1: 寻向 (AoA/AoD → 厘米级定位)
5.2: LE Audio, 等时通道 (给 TWS 耳机)
5.3: 信道分类, 连接子事件
5.4: 周期性广播响应 (电子价签)

其实 BLE 4.2 就够大部分场景了
5.0+ 主要带来: 更快、更远、更省电

BLE 连接流程

① 广播 (Advertising)

② 扫描请求 (Scan Request)

③ 扫描响应 (Scan Response)

④ 连接请求 (Connection Request)

持续音频 → Classic (A2DP)
偶尔数据 + 低功耗 → BLE
需要 iOS 后台通信 → BLE (Apple 对 BLE 友好)
HID 键盘/鼠标 → BLE (HID over GATT)
文件传输 → Classic (或 WiFi Direct)
TWS 耳机 → BLE 5.2+ (LE Audio)

2.4GHz 是 WiFi + BT + Zigbee + Thread + 微波炉 的战场

WiFi 和 BT 都在同一设备中:
  → 时分复用 (TDM): 交替使用天线
  → 共存接口: 蓝牙告诉 WiFi "我要发包了", WiFi 暂停

实现: 大多数 WiFi/BT 组合芯片内部有共存机制
     (MTK/Realtek/Broadcom/Qualcomm 各有实现)
驱动侧问题常导致共存失效 (如你的 MT7927)

消费电子中 WiFi 和 BT 几乎总是同一芯片
  MT7921/7925/7927 (MTK)
  AX200/AX210 (Intel)
  BCM 系列 (Broadcom)

走 PCIe/USB/SDIO 接 Host
蓝牙部分通常通过 USB 暴露 HCI 接口