The document summarizes routing protocols for wireless sensor networks. It first defines wireless sensor networks and describes their key characteristics. It then surveys traditional routing techniques like flooding and gossiping, as well as current techniques including flat routing protocols like SPIN and directed diffusion, hierarchical routing protocols like LEACH and PEGASIS, and location-based routing protocols like GEAR. For each protocol, it provides a brief overview of how it works and compares their advantages and disadvantages. In conclusion, it states that hierarchical routing protocols generally outperform flat routing protocols, and references several papers on sensor network routing.