PowWow (Power Optimized Hardware and Software FrameWork for Wireless Motes) is a wireless sensor network (WSN) mote developed by the Cairn team of IRISA/INRIA. The platform is currently based on IEEE 802.15.4 standard radio transceiver and on an MSP430 microprocessor. Unlike other available mote systems, PowWow offers specific features for a very-high energy efficiency:
the MAC layer is based on an asynchronous rendezvous scheme initiated by the receiver,architectural and circuit level optimizations were performed such as power management, frequency and voltage scaling and FPGA co-processing for low power,the software stack is very light (5 kbytes) uses event-driven programming and is currently derived from the Protothread library of Contiki.PowWow hardware platform is composed of a motherboard including an MSP430 microcontroller and of other daughter boards such as the radio transceiver board, the coprocessing board and some sensor and energy harvester boards.
TI MSP430 low-power microcontrollerMSP430F1612 version, 8 MHz clock55KB of flash memory, 5KB of on-chip RAM330uA at 1 MHz and 2.2 V in active mode, 1.1uA in standby modeP1, P2 connectors for extensionJTAG, RS232 and I2C interfacesTI CC2420 RF transceiverDigital direct sequence spread spectrum baseband modemSingle-chip 2.4 GHz IEEE 802.15.4 compliantSpreading gain of 9 dB, data rate of 250 kbit/sHardware support for packet handling, data buffering, burst transmissions, data encryption, data authentication, clear channel assessment, link quality indication and packet timing informationA co-processing board can be added to the motherboard on P1, P2 connectors. This board provides dynamic voltage scaling and hardware acceleration to increase the energy efficiency of the network.
Power Mode Management (PMM)Low-Power Programmable Timer for Wake-up periodMAX6370, 8uADynamic Voltage and Frequency Scaling (DFVS)Programmable ClockLTC6930, 490uA8 MHz divided by 1 to 128Programmable DC/DC converterTPS62402/TPS61030FPGA co-processingLow-power Igloo FPGA from ActelAGL125: 130 nm, 125 kgates, 32kbits on-chip RAM, 1 kbits Flash, PLL for clock management.Supply voltages 0 to 1.65VPower consumption: 2.2 uW, 16 uW, 1 to 30 mW in sleep, freeze, run modese.g. Viterbi decoder for link layer implemented on the FPGA consumes 5 mWMAC layer: preamble sampling protocolPowWow uses RICER protocol proposed by UC Berkeley to reduce the time spent in radio reception (RX) mode. This protocol consists in cycled rendez-vous initiated by a wake-up beacon from potential receivers. Thanks to this method, nodes are sleeping most of the time, hence saving energy.
Multi-hop routingGeographical routingPowWow uses a simple geographical routing protocol.
Each node has (x,y) coordinatesNext node for hop transmission is chosen in the neighbors as the nearest to the destinationin the sense of Euclidean distance
Neighbor table managementA neighbor is a node in the radio range of a nodeNeighbors are discovered at power-up and on regular time periodTransmission modesBroadcastDirect transmission to {neighbors}, no ACKFloodingBroadcast a packet to all network nodes, no ACKDirect Hop with/without ACKDirect transmission to a specific neighbors with/without ACKRobust Multi-HopMulti-hop transmission to a specific node in the networkEach hop is with ACKUses node addressPowWow software distribution provides an API organized into protocol layers (PHY, MAC, LINK, NET and APP). The software is based on the protothread library of Contiki, which provides a sequential control flow without complex state machines or full multi-threading.
Memory efficiency: 6 Kbytes (protocol layers) + 5 Kbytes (application)Over-the-air re-programmation (and soon reconfiguration)Currently based on IAR Embedded WorkbenchCompiling with gcc for MSP430 is also possibleEnergy estimation methodologyThe first version of PowWow were released July, 2009. PowWow V1 includes the motherboard, the radio board and the software. A first prototype of the coprocessing board is currently available but not yet distributed. PowWow V2 is under development.
PowWow is delivered as an open source hardware and open source software under the GPL license.
