Wi-Fi: what it is, IEEE 802.11 standards, and how it works

What is Wi-Fi?

Wi-Fi is a trademark of the Wi-Fi Alliance for products certified to comply with IEEE 802.11 standards. The technology provides wireless device connectivity to a local network and the internet through an Access Point (AP). Unlike cellular communication, Wi-Fi operates in the unlicensed ISM band and is designed for local coverage — up to 50–100 meters indoors.

Wi-Fi architecture includes two operation modes: Infrastructure Mode (client-server via AP) and Ad-Hoc Mode (peer-to-peer between devices). Mobile applications use Infrastructure Mode: the smartphone connects to a router, and the router connects to the ISP. For direct device-to-device transfer (AirDrop, Nearby Share), Wi-Fi Direct is used — an extension that organizes a P2P connection without a router.

According to the Cisco Annual Internet Report (2023), Wi-Fi remains the primary connection type for mobile devices indoors: 59% of all mobile traffic is generated over Wi-Fi, and this share is growing by 3–5% per year due to the spread of mesh networks and Wi-Fi 6.

IEEE 802.11 Standards: from b to be

The evolution of Wi-Fi spans seven generations — from 802.11b (1999) to 802.11be (Wi-Fi 7, 2024). Each new standard increased throughput, connection density, and energy efficiency. Wi-Fi 6 (802.11ax) was the most significant update: OFDMA and MU-MIMO allow serving dozens of devices simultaneously without speed degradation.

Backward compatibility is a key Wi-Fi feature: a Wi-Fi 6 router can serve Wi-Fi 4 clients, but at their maximum speed. Mobile application developers do not directly control the standard selection — the driver and OS automatically choose the optimal PHY mode.

2.4, 5, and 6 GHz Bands: Comparative Analysis

Wi-Fi uses three frequency bands, each with its own physical limitations. 2.4 GHz is the most congested: Bluetooth, Zigbee, microwave ovens, and neighboring networks create interference. Only 3 non-overlapping channels (1, 6, 11 at 20 MHz width) are available.

The 5 GHz band offers 23 non-overlapping channels (at 20 MHz) and supports 80 and 160 MHz widths. The shorter wavelength means worse wall penetration — the range is 30–40% less than 2.4 GHz at the same transmitter power. However, low noise provides more stable speed.

The 6 GHz band — exclusive to Wi-Fi 6E and Wi-Fi 7 — has 59 additional 20 MHz channels. There is no interference from older devices — only certified clients are allowed. According to Qualcomm tests (2024), at a distance of 5 meters, Wi-Fi 6E in 6 GHz shows speeds 40% higher than Wi-Fi 6 in 5 GHz.

Band Steering and Band Selection

Modern routers use Band Steering — a mechanism where the access point offers the client the optimal band based on RSSI and load. Developers do not control Band Steering on the application side, but can influence preferences through Android's WifiNetworkSpecifier.Builder or iOS NEHotspotNetwork.

Wi-Fi Security: WEP, WPA2, WPA3

Wireless network protection has evolved from outdated WEP (1997) to modern WPA3 (2018). WPA2 (2004) with AES-CCMP remains the minimum secure standard but is vulnerable to the KRACK attack (2017) on the 4-way handshake. WPA3 eliminates this vulnerability through the SAE (Simultaneous Authentication of Equals) protocol.

WPA3 introduces three key improvements: individual encryption instead of a shared Pre-Shared Key (PSK), resistance to offline brute-force attacks, and Forward Secrecy — compromising the long-term key does not allow decrypting previously intercepted sessions. Mandatory WPA3 certification for Wi-Fi 6E and 7 devices ensures modern-level protection.

For mobile applications transmitting sensitive data over Wi-Fi, additional application-level encryption (TLS 1.3) is recommended. Even WPA3 only protects the channel between the device and the router — data travels to the server over the internet without additional protection.

Network security check example in Kotlin (Android)

fun isSecureNetwork(context: Context): Boolean {
    val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE)
        as ConnectivityManager
    val network = cm.activeNetwork ?: return false

    val caps = cm.getNetworkCapabilities(network) ?: return false
    return caps.hasCapability(
        NetworkCapabilities.NET_CAPABILITY_NOT_VPN
    )
}

The code checks whether the device is connected to an active network (not VPN). For a full Wi-Fi security check, additional analysis of the encryption type via WifiManager is required — the application can warn the user about connecting to an open network.

Wi-Fi in Mobile Devices: Scanning and Connection

Mobile OSes provide APIs for managing Wi-Fi connections. On Android, WifiManager and WifiNetworkSpecifier are available — the application can scan available networks, connect to them, and monitor connection status. Starting with Android 12, scanning requires the ACCESS_FINE_LOCATION permission to prevent user tracking via access point MAC addresses.

iOS restricts Wi-Fi management in third-party applications: NEHotspotNetwork allows connecting to known networks, while scanning is not available — only navigating to the system network list via Settings URL. For enterprise applications, iOS supports configuration profiles with certificates and auto-connection to corporate networks.

For applications working with Wi-Fi Direct (peer-to-peer), Android provides WifiP2pManager. iOS has no public API for Wi-Fi Direct — the Multipeer Connectivity Framework is used instead, operating over Bluetooth and Wi-Fi.

Wi-Fi network scanning example in Kotlin (Android)

val wifiManager = context.getSystemService(Context.WIFI_SERVICE) as WifiManager

val receiver = object BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        val results = wifiManager.scanResults
        results.filter { it.level > -70 }
            .sortedByDescending { it.level }
            .forEach { network ->
                Log.d("WiFi", "${network.SSID} — ${network.level} dBm")
            }
    }
}

context.registerReceiver(receiver, IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION))
wifiManager.startScan()

The BroadcastReceiver notifies the application when scanning completes. ScanResults contain SSID, BSSID, signal level (RSSI), and encryption type. Filtering by signal level > -70 dBm filters out networks too weak for a stable connection.

Wi-Fi 7 (802.11be): MLO, 4096-QAM, and 320 MHz Channel Width

Wi-Fi 7 is the newest standard, approved by the Wi-Fi Alliance in 2024. The key innovation is Multi-Link Operation (MLO): a device can simultaneously transmit data over two bands (e.g., 5 and 6 GHz) to increase throughput and reduce latency. In Broadcom tests (2024), MLO showed a 50% latency reduction when a client moves within the coverage area.

Other innovations: 4096-QAM instead of 1024-QAM (20% higher speed), 320 MHz channel width (double compared to Wi-Fi 6), and automatic band switching without session interruption. For mobile applications, Wi-Fi 7 means the ability to stream 8K video and AR scenes with latency under 5 ms.

According to Dell'Oro Group (2025), by the end of 2026, 15% of new smartphones will support Wi-Fi 7. Developers do not need to change application code — improvements work at the driver and OS level, but applications adapted for high bandwidth (video conferencing, cloud gaming) will benefit from lower latency.