A mobile phone or other mobile device is configured to compute a location code based on Wi-Fi or other wireless networking configuration parameters. The location code is computed as a cryptographic hash of the configuration parameters and is provided to a telecommunications system that supports Wi-Fi or other WLAN voice services. The telecommunications system maintains one or more location tables, each of which indicates multiple location codes and corresponding street addresses. When processing an emergency 9-1-1 call to an emergency response service, the system looks up the street address of the calling mobile device based on the most recently provided location code, and provides the street address to the emergency response service.