A method and system for uplink-downlink transmission of data packets in a wireless cellular network, during idle state of User Equipment (UE) using connectionless transmission is disclosed. The method establishes S1 common bearer between a Radio Access Network (RAN) node and Serving Gateway (SGW) and S5 common bearer between the SGW and Packet Data Network Gateway (PGW). The method defines a modified Uu interface between the UE and the RAN node. The method appends data packets with UE Identifier (ID) and routing information as packet header information to independently route data packets through wireless cellular network in a self-sustainable manner using the established common bearers and the modified Uu interface. The method secures data packets by providing integrity and ciphering protection. The method eliminates cost of dedicated bearer set up and reduces signaling overhead on the Uu interface thereby improving network efficiency and battery life of the UE.