An extended-range wireless sensor network (WSN) technology is presented in this paper. The proposed technology is based on a cross-layer optimization of the IEEE 802.15.4 standard. In the physical layer, the use of directive and adaptive phased arrays is proposed for the WSN gateways, increasing the communication range between sensors and their gateway. Next, a neighbor-cooperative channel access method is proposed to alleviate the hidden-terminal problem that is aggravated with the use of directive antennas on the one side of the communication links (asymmetric links). With the proposed technologies, a three-fold increase of the single-hop range is achieved, and the hidden terminal problem is addressed with minimal impact on the overall throughput, protocol complexity, overhead efficiency, and scalability.