What does a wireless physical-layer standard actually specify?

It specifies how data is encoded into the radio signal, the transmission frequency and power, how the receiver detects and decodes the signal, and the antenna design.

Wireless standards from the IEEE and the telecom industry cover both the data link and physical layers. The physical-layer portion dictates:

• Data-to-radio-signal encoding methods
• Frequency and power of transmission
• Signal reception and decoding requirements
• Antenna design and construction

Why it matters: these specs are what make interoperability possible — two devices built by different vendors can communicate only because they agree on the same frequencies, modulation, and decoding rules. It also explains why you must match equipment to a standard (e.g. 802.11) when buying WLAN gear.

Go deeper:

• IEEE 802.11 — Wikipedia — the MAC and PHY protocols a Wi-Fi standard defines, including frequencies and modulation.

• Wireless standards (CompTIA Network+) — Professor Messer — how each 802.11 standard pins down frequency and speed.