The Open Base Station Architecture Initiative (OBSAI) was a trade association created by Hyundai, LG Electronics, Nokia, Samsung and ZTE in September 2002 with the aim of creating an open market for cellular network base stations.

The hope was that an open market would reduce the development effort and costs traditionally associated with creating base station products.

The OBSAI specifications provided the architecture, function descriptions and minimum requirements for integration of a set of common modules into a base transceiver station (BTS).

The functions include encoding/decoding, ciphering/deciphering, frequency hopping (GSM), spreading and Rake receiver (WCDMA), MAC (WiMAX), protocol frame processing, MIMO etc.

RP1 specification also specifies UDPCP - a UDP based reliable communication protocol.

Examples are Uu or Um to the user equipment (UE) for 3GPP systems or R1 for WiMAX.