Wireless sensor networks (WSN) is a novel technology about acquiring and processing information. The designer of WSN must have a thorough understand about architecture, protocol and characteristics of WSN. This paper describes communication architecture, component of node and available building scheme for WSN in detail, analyzes the characteristics of all topologies, and presents a protocol stack based on layer theory. The popular wireless communication models are discussed, characteristics and features are also analyzed, which provide a guidance for designer.