RF Communication in TinyOS2X ㈜한백전자

Background

IEEE 802 LAN/MAN Standards Committee802.1Higher Higher Layer LAN Protocols Working Group Wireless Local A rea Network Wor king Group Wireless Personal A rea Network Wor king Group MBWA W orking Gr oup TG1 WPAN/Bluetooth Task Group TG2 Coexistence Task Group TG3 WPAN High Rate Task Group TG4 WPAN Low Rate Task Group ………… + ZigBee IEEE 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 MHz ISM Americas 40 kbps MHz Europe 20 kbps 1

The IEEE Standard  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 a  Scope Detecting distance (<1m) / low power / low-cost  Alternative PHY UWB CSS: Chirp Spread Spectrum

IEEE b  Scope Extension previous IEEE Beacon mode, beacon schedule Security Remove unnecessary descriptions Current Beacon IEEE (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

and Zigbee  Define PHY and MAC  ZigBee Define Network, Security and Applications PHY 868MHz / 915MHz / 2.4GHz MAC Network Star / Mesh / Cluster-Tree Security 32- / 64- / 128-bit encryption Application API ZigBee Alliance IEEE Customer Silicon Stack App

CC2420

About Chipcon CC2420  CC2420 Features Support 2.4 GHZ IEEE 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) 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 StateConsumption Voltage Off1 uA Power Down20 uA IDLE Mode426 uA Receive Mode19.7 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 statesDelay Startup time300 ~ 500 uS Startup time (V on)100 uS Setting time2 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.2323 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