RF Communication in TinyOS2X

㈜한백전자

Background

IEEE 802 LAN/MAN Standards Committee802.1Higher

802.1Higher Layer LAN Protocols Working Group

802.11Wireless Local Area Network Working Group

802.15Wireless Personal Area Network Working Group

802.20MBWA Working Group

TG1 WPAN/Bluetooth Task Group

TG2 Coexistence Task Group

TG3 WPAN High Rate Task Group

TG4 WPAN Low Rate Task Group

… … … …

+ ZigBee

IEEE 802.15.4 TG4

Low Rate Wireless Personal Area Networks

LR-WPAN A LR-WPAN is a simple, low-cost communication network that allows

wireless connectivity in applications with limited power

Main objectives of an LR-WPAN Easy installation

Reliable data transfer

Short-range operation

Low cost

Reasonable battery life,

Simple protocol.

Table1 cited in 29 of standard

BAND COVERAGE DATARATE CHANNELS

2.4 GHz ISM Worldwide 250 kbps 16

915 MHz ISM Americas 40 kbps 10

868 MHz Europe 20 kbps 1

The IEEE Standard 802.15.4 A low-rate wireless personal area network

low-cost, very low-power short-range wireless communication LR-WPAN’s important goal

“cost” “power consumption”

Applications Industry controlling Home automation, networking Personal healthcare Vehicle communication

IEEE 802.15.4a

Scope Detecting distance (<1m) / low power / low-cost

Alternative PHY UWB

CSS: Chirp Spread Spectrum

IEEE 802.15.4b

Scope Extension previous IEEE 802.15.4-2003

Beacon mode, beacon schedule

Security

Remove unnecessary descriptions

Current Beacon IEEE 802.15.4-2006 (publish)

6LoWPAN (IPv6 over Low Power Wireless PAN)

Implement IPv6 technology on USN

Issue 15.4 PDU -> 102 byte, IPv6 MTU -> 1280byte

Shim layer for fragmenting and assembling MTU

802.15.4 and Zigbee

802.15.4 Define PHY and MAC

ZigBee Define Network, Security

and Applications

PHY868MHz / 915MHz / 2.4GHz

MAC

NetworkStar / Mesh / Cluster-Tree

Security32- / 64- / 128-bit encryption

Application

API

ZigBeeAlliance

IEEE 802.15.4

Customer

Silicon Stack App

CC2420

About Chipcon CC2420

CC2420 Features Support 2.4 GHZ IEEE 802.15.4

DSSS modem, 250 kbps, 50 registers, 368 byte RAM

Low power consumption (RX: 19.7mA, TX:17.4mA)

Separate transmit and receive FIFOs (each 128 byte)

Easy configuration interface (4-wire SPI interface)

802.15.4 MAC hardware support: Automatic preamble generator, Synchronization word insertion/detection

CRC-16 computation and checking over the MAC payload

Clear Channel Assessment

Energy detection / digital RSSI

Link Quality Indication

Full automatic MAC security

About Chipcon CC2420

CC2420 power consumption and switch delay

State Consumption

Voltage Off 1 uA

Power Down 20 uA

IDLE Mode 426 uA

Receive Mode 19.7 mA

Transmit Mode

P = -25 dBm

P = -15 dBm

P = -10 dBm

P = −5 dBm

P = 0 dBm

8.5 mA

9.9 mA

11 mA

14 mA

17.4 mA

states Delay

Startup time 300 ~ 500 uS

Startup time (V on) 100 uS

Setting time 2 uS

CC2420 Receive Mode 1

Receive Mode Set SRXON register

RX check by SFD, FIFO, FIFOP pin In TinyOS, use FIFOP pin

SFLUSHRX command flush RX RAM

CC2420 Receive Mode 2

Data in RXFIFO Data in RXFIFO includes MPDU as well as RSSI and QLI

RSSI and QLI are inserted instead of CRC filed

CC2420 Transmit Mode

Transmit Mode Set STXON register

TX check by SFD pin In TinyOS, do not use interrupt pin

SFLUSHTX command flush TX RAM

CC2420 Radio Chip

RSSI, LQI, CCA

RSSI (Received Signal Strength Indicator) 8 bit values in RSSI_VAL register (need 8 symbol)

P = RSSI_VAL – RSSI_OFFSET (-45) [dBm]

LQI (Link Quality indication) LQI is limited from 0 to 255, however CC2420 support 0~110 correlation

base on the incoming packets LQI = (CORR – a) x b

CCA (Clear Channel Assessment) CS threshold level is programmed by CCA_THR register

CCA 3 modes are assigned CCA_POLARITY register

RF Communication

RF functions in TinyOS2X

Flooding Protocol

Flooding

Flooding is that all nodes participate with data forwarding without fixed

routing path.

Firstly, source node broadcasts its data packet including destination

address, and other neighbor nodes forward it.

Finally, destination node can receive the data packet

Drawback of Flooding

Flooding’s limitations Nodes can receive same packets because of broadcast

All nodes should participate flooding for transmitting one data packet

Even if the destination node received data packet, the flooding protocol is

not finished

It has serious collision problem because all nodes participate flooding

Other approach for overcoming flooding

LAR By using location information, flooding

region is limited

Gossiping By using probability, data forwarding decision is changed

Hierarchical Routing Select coordinator

Only coordinator participate flooding

p.23

Gradient-Based or Tree-Based Routing

GBR (Gradient-Based Routing) or Tree Routing The interest packet is required to record the number of hops from the sink.

Each node calculates the minimum number of hops, called height.

A gradient is defined as the difference between a node's height and that of its

neighbor.

Data packet is forwarded on the link

with the largest gradient.

Homework

Ubi-HomeNet Exercise Hanback_TestTree. Read 15 chapter (ZigbeX’s textbook)

Understand 15 chapter example

Experiment 15 chapter tests

Report Searching some special codes to force multihop in Hanback TestTree

Changing the example not to work forced multihop in Hanback TestTree

Draw function diagram of tree routing components

Q & A