PowWow

Key takeaways

PowWow belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PowWow to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PowWow from memory before moving on to harder problems.

Reference excerpt

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.

Hardware Source: 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.

Processing motherboard TI MSP430 low-power microcontroller MSP430F1612 version, 8 MHz clock 55 KB of flash memory, 5 KB of on-chip RAM 330uA at 1 MHz and 2.2 V in active mode, 1.1uA in standby mode P1, P2 connectors for extension JTAG, RS232 and I2C interfaces

Radio Board TI CC2420 RF transceiver Digital direct sequence spread spectrum baseband modem Single-chip 2.4 GHz IEEE 802.15.4 compliant Spreading gain of 9 dB, data rate of 250 kbit/s Hardware support for packet handling, data buffering, burst transmissions, data encryption, data authentication, clear channel assessment, link quality indication and packet timing information

Co-processing Board A 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 period MAX6370, 8uA Dynamic Voltage and Frequency Scaling (DFVS) Programmable Clock LTC6930, 490uA 8 MHz divided by 1 to 128 Programmable DC/DC converter TPS62402/TPS61030 FPGA co-processing Low-power Igloo FPGA from Actel AGL125: 130 nm, 125 kgates, 32 kbits on-chip RAM, 1 kbits Flash, PLL for clock management. Supply voltages 0 to 1.65V Power consumption: 2.2 uW, 16 uW, 1 to 30 mW in sleep, freeze, run modes e.g. Viterbi decoder for link layer implemented on the FPGA consumes 5 mW

Networking MAC layer: preamble sampling protocol PowWow 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 routing Geographical routing PowWow uses a simple geographical routing protocol.

Each node has (x,y) coordinates Next node for hop transmission is chosen in the neighbors as the nearest to the destination in the sense of Euclidean distance

Neighbor table management A neighbor is a node in the radio range of a node Neighbors are discovered at power-up and on regular time period Transmission modes Broadcast Direct transmission to {neighbors}, no ACK Flooding Broadcast a packet to all network nodes, no ACK Direct Hop with/without ACK Direct transmission to a specific neighbors with/without ACK Robust Multi-Hop Multi-hop transmission to a specific node in the network Each hop is with ACK Uses node address

Software PowWow 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)

Development Tools Currently based on IAR Embedded Workbench Compiling with gcc for MSP430 is also possible Energy estimation methodology

Availability The 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.

External links Official website

Sources

Illustrations

Worked examples

Example 1 — a first encounter with PowWow

Start with the simplest possible case. Write down what PowWow claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to PowWow before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about PowWow ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of PowWow

In research: PowWow appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses PowWow in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: PowWow is common in secondary-school and first-year university syllabi. It links to neighbouring topics Sensors, Wireless sensor network, so understanding it makes those chapters shorter.
In everyday life: Look for PowWow outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study PowWow in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PowWow means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain PowWow out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PowWow in simple terms?

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.

Why does PowWow matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study PowWow?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on PowWow.