11

Wireless Sensor Networks (WSN)

CPU GroupProgress Presentation Almir DavisYong Zhang

Halligan Hall 03/17/2005

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Agenda

Sensor Card Diagram

Choosing Power Supply

CPU Design Progress

CPU New Features

Questions from the Proposal Presentation

Current Questions

33

WSN Block Diagram

TRANCEIVERCPU

BASE STATIONFIXED LINE NETWORK

WIRELESS SENSOR

NETWORK

SENSOR CARD

TRANCEIVERCPU

SENSOR CARD

TR

AN

CE

IVE

RC

PUS

EN

SO

R C

AR

D

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Sensor Card

CPU

TIO SIO

I/O to WSN

A/D

Display and debug

interfaceTranceiver Controller

Sensor Controller

MEMCore logic

Power Control

TRANCEIVER

BATTERY

DC-DC

RADIO SENSOR

55

Types of Chemical Weapons

Nerve Agents– Nerve agents attack the bodies nervous system. Nerve agents causse

breathing difficulties, convulsions, paralysis, and death. Nerve agents can be inhaled or absorbed through the skin. Symptoms of nerve agent poisoning include runny nose, tightness of chest, difficulty breathing, excessive sweating, nausea, vomiting dimness of vision, pinpointing of the pupils, convulsion, and death.

Blister Agents– Blister agents attack the lungs, eyes, and skin. They blister both skin and

mucous membranes. Blood Agents

– Blood agents interfere with the bodies ability to absorb oxygen. The victim dies because the body tissues are starved of oxygen. Blood agents cause headaches, vertigo, and nausea before death.

Choking Agents– Choking agents attack the lungs, causing them to fill with fluid. Choking

agents are detected by their smell and their irritancy. The victim suffocates by drowning in his own body fluid. Choking agents cause coughing, choking, tightness of the chest, nasea, headache, and watering of the eyes.

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Common Chemical Weapons

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Choosing power supplies

AA Batteries– Capacity: 650mAh ~ 3135mAh

Button Cells– Capacity: 45mAh ~ 500mAh

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AA Batteries

Alkaline AA batteries – most common AA battery type. – Pre-charged to 1.5 Volt.– Unsteady voltage. – Capacity: 2,700 to 3,135 mAh. Most AA Alkaline cells offer a

capacity of 2,850 mAh. The expensive Energizer e2 alkaline offer 3,135 mAh and the cheapest cells offer 2,700 mAh, all pretty much alike at low drains. (That's why Consumer Report's testing suggested to get whatever's cheapest).

– Shelf life: some current premium brands exceed 6 years.

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AA Batteries

Lithium AA batteries– Premium AA battery type. – Pre-charged to 1.5 Volt. – Constant 1.5 Volt over their life. – Capacity: premium brand Lithium AA cells offer around 3,000

mAh, the same as Alkaline.– Shelf life up to ten years, and a longer lifetime than an alkaline

battery. Also retain much better capacity in low temperature (less than 25 °C) than alkaline batteries

– Disadvantage: expensive compared to Alkaline. 

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Rechargeable AA batteries – Ni-Cd, Nickel-Cadmium: Capacity: 650 to 1,000 mAh – Ni-MH, Nickel-Metal Hydride: Capacity: 1,350 to 2,500

mAh

AA Batteries

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Low Battery Warning Circuit

What would be required is a circuit that constantly monitors the battery voltage, and if it reaches a magic low-point, it gives a signal to CPU. Then the CPU will command the transceiver to send a low battery warning to the base station.

Such a circuit would have to be micro-powered; that is, it draws next to nothing from the battery itself, so it may be left in the circuit continuously without adversely affecting battery reserve.

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CPU Block Diagram

CPU

SENSOR 2

SENSOR 1

TRANSCEIVER

READY1

DATA1

READY2

DATA2

CLOCK RESET

RX_CTRL[1:0]

DATA_IN

TX_CTRL[1:0]

DATA_OUT

ADDR[2:0] RCV_DATA[8:0]

9

DV

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CPU Features Cut-through data path Aggregation of Sensors’ packets Selection of Sensors’ packets “Sleep” cycles, RX “Active cycles”, TX “Active cycles” In-Band Hot reset Support for downstream traffic

– CPU configuration registers programmable wirelessly– Operating system instruction set support– “Send to” node selection capability– “Receive from” node selection capability

Node ID wireless reprogram option Event-Based Queries and Lifetime-Based Queries support

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Transmit Cut-Through Data Path

SENSORTRANSCEIVER

NID[2:0](ADDR[2:0]) RCV_DATA[8:0]

9

DV

Data[5:0]Sync

bit

CPU

Data[5:0]SIDNID[2:0]

Data[5:0]SIDNID[2:0]

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Receive Cut-Through Data Path

SENSORTRANSCEIVER

NID[2:0](ADDR[2:0]) RCV_DATA[8:0]

9

DV

CPU

Data[5:0]NID[2:0]

Data[5:0]Sync NID[2:0]

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Aggregation of Sensors’ packets

SENSOR

TRANSCEIVER

NID[2:0](ADDR[2:0])

CPU

SENSOR

Data1[5:0]SIDNID[2:0] Data2[5:0]SIZE

Data1[5:0]SIDNID[2:0] Data2[5:0]SIZE

Data1[5:0]Sync

bit

Data2[5:0]Sync

bit

Sync

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Selection of Sensors’ packets

SENSOR 1

TRANSCEIVER

NID[2:0](ADDR[2:0])

CPU

SENSOR 2

SIDNID[2:0] Data2[5:0]SIZE

SIDNID[2:0] Data2[5:0]SIZE

Data1[5:0]Sync

bit

Data2[5:0]Sync

bit

Sync

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CPU Configuration Register Access

SIDNID[2:0] Data2[5:0]SIZESync REG

REG_NO[2:0] REG_DATA[2:0]

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CPU Register Map

ADDR Function DATA[2:0] Description

000 NODE ID Data signifies the NODE ID (default value selected using jumpers)

001 TX MODE 100 – TX Cut-through (default)

001 – TX Aggregation

010 – Select (parameter A relevant)

111 – Select (parameter B relevant)

010 RX DUTY 000 – X sec ACTIVE Y sec SLEEP

001 – Z sec ACTIVE N sec SLEEP

….

011 TX DUTY Same as RX DUTY except it applies to transmitter

100 RECEIVER NID Send packets only to the node specified by these 3 bits (111 – reserved for broadcast, 000 – default value for base station)

101 BATTERY LIFE RO register (packet aimed for this register will trigger a transmit packet with BATTERY LIFE information

110 Reserved

111 Reserved

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Duty Cycles

RX Duty Cycle (For example: wake up every 30 s for 1 sec)

TX Duty Cycle – Sensor TX side and Transmitter TX side can be decoupled– Transmitter might be turned on only if sensor detects an important

information– Sensor TX side and Transmitter TX side can be turned on at the

same time regardless what data is being sampled

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In-Band Hot Reset

The way to reset the node wirelessly

HOT = 1 signifies the hot reset insertion

The entire packet after the preamble should be all 1’s (packet includes only 1 DATA[5:0] word)

If HOT = 1 but the packet has some 0’s drop the packet - no reset

SIDNID[2:0] Data2[5:0]SIZESync REGHOT

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Support for downstream traffic

Capability to program the node from the base station or any other node

Capability to receive OS instructions and digest them

Node recognition capability– “Send to” node selection capability– “Receive from” node selection capability

SENSOR ID

SENDERNID[2:0]

Data1[5:0]SIZESync REGHOTRECEIVER

NID[2:0]Data2[5:0]

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Node ID wireless reprogram option

Node ID is programmed using jumpers (problem: cannot go into the bird’s nest to switch jumpers’ values) or using the default factory setting or using EPROM (EEPROM) etc…

Solution: Wireless ability to reprogram the default value

SENSOR ID

SENDERNID[2:0]

Data1[5:0]SIZESync REGHOTRECEIVER

NID[2:0]Data2[5:0]

Default value

Config reg

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Event-Based Queries support

Event-Based Query is the way to program the node to send the data acquired only if the programmed parameters are met

– ON EVENT bird-detect (loc)SELECT AVG (light), AVG (temp), event.locFROM sensors AS s WHERE dist (s.loc, event.loc)SAMPLE INTERVAL 2 s for 10 s

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Lifetime-Based Queries support

Lifetime-Based Query is the way for user to program the query duration in days, weeks or months.

– SELECT nodeid, accel– FROM sensors– LIFETIME 30 days

(Note: we do not plan to have day/month/year precision but rather permanent sampling, no sampling, even-based sampling, short-period sampling)

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Questions from the Proposal Presentation (1)

Internal tri-state buffer use?– Internal tri-state buffers is not planned to be used. We plan to

use simple multiplexers instead.

If receiver is asleep how are you going to get the data?– We will have to make sure that the receiver is awake at the

right point of time (synchronization needed, programmability support provided by our CPU)

How do you distinguish 2 sensors if you use the same 3-bit addr for both?

– Sensor ID field is used to distinguish among sensors.

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Questions from the Proposal Presentation (2)

How do you decide whether to send data or not?– Configuration registers provide the ability to decide the

operational mode. They will drive decisions when to sample/send data.

Run the CPU fast, sample quick, power down, go to sleep in between samples. Saves Power!

– We will research more on this one. At this point we are not sure that with the faster clock we will save power.

Is there a common power source between CPU/sensors/transceiver?

– Yes and most likely it will be 2 AA batteries.

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