sensors network and environment. Mobility and instability in and consumed by users will affect the way data is wireless links preclude the use of many existing edge- compressed, routed, and aggregated. Because of the network gateway protocols for internetworking IP and peer-to-peer connectivity and the lack of a global sensor networks. Table 3.7-1 Comparison of the four sensor platforms shown in Figure 3.7-2. WINS NG 2.0 Node iPAQ with 802.11 and Berkeley MICA Smart Dust** A/D Cards in Sleeve Mote* Parts cost (quantity $100s $100s 1000+) Size (cm³ Weight (g) (including battery) Battery capacity (kJ) (Less) Sensors Off-board Microphone & light Integrated on PCB: MEMS sensors to be sensors integrated, Acceleration, integrated others off-board temperature, light, sound Memory 32 MB RAM, 32 MB flash 64 MB RAM, 32 MB flash 4 KB RAM, 128 KB flash (Less) Hitachi SH4 StrongARM or XScale ATmega 103L (Less powerful) Operating system Linux WinCE or Linux TinyOS (smaller) Processing capability 400 MIPS/1.4 GFLOPS 240 MIPS 4 MIPS (Less) Radio range 100 m 100 m (Shorter) The MICA mote is slightly larger than the WeC mote shown in Figure 3.7-2(c), and is more widely used. Smart Dust is not yet fully operational, but the size goal and power sources are known, and cost and weight are estimated. Note that the parts cost is based on large-quantity production. CHAPTER 3.7 Wireless sensor networks Psend(Nr) Psend(Nr) Preceive Figure 3.7-3 The power advantage of using a multihop RF communication over a distance of Nr. To summarize, the challenges we face in designing energy efficiency in communications is enabled by the sensor network systems and applications include: multihop topology of the network. Moreover, additional Limited hardware: Each node has limited processing, relevant information from other sensors can be aggre- storage, and communication capabilities, and limited gated during this multihop transmission through in- energy supply and bandwidth. network processing. But perhaps the greatest advantages Limited support for ne