1. IEEE 802.15.4 Platforms, Progress, and TinyOS Joe Polastre

2. 2 IEEE 802.15.4 “Low Rate Wireless Personal Area Networks” IEEE Standard, 2003 Designed for low power, low data, high density rate wireless networks Services may interface with either 802.2 or directly with the MAC protocol Finally… a standard for interoperable radio communication And 802.15.4 is here… … but 802.15.4 is not Zigbee  Zigbee requires 15.4 as the link and physical protocols  The great “TinyOS vs Zigbee” debate 802.2 802.1 802.15.4 MAC 802.15.4 PHY “Upper Layers” Networking/Routing/Organization

3. 3 802.15.4 Physical Layer 2.4 GHz 250kbps / 2MChips O-QPSK DSSS 900 MHz 40kbps BPSK RSSI, LQI required for each packet CRC calculation and Address decoding Automatic Acknowledgements Encryption and Authentication

4. 4 802.15.4 MAC 802.15.4 Link Functionality  CSMA / Clear Channel Assessment  Beaconing / Coordinator  Slotting  Encryption / Authentication  Full Functionality Devices vs Reduced Functionality Device  Single hop organization and communication Integrated network/link protocol design 802.15.4 has lots of extra functionality that may never be used:  Enable the development of a “lightweight 802.15.4 MAC”  Use 15.4 hardware without using the 15.4 MAC protocol (eg: B-MAC, S-MAC, etc)

5. 5 The good, the bad, and the ugly Good  Standardized link protocol  Hardware support encryption/authentication CRC  Higher data rate  Packet link estimation (LQI and RSSI) Network link estimation speeds organization  Low duty cycle operation built in to design Reduces idle listening cost …but comes at the cost of synchronization and state The bad (and ugly)  Large protocol  Instance specific code  Couples single hop organization with communication Beaconing, PANs, etc  Power hungry 20x power of mcu  Hardware support vs flexibility Promiscuous mode Minimal Time Synchronization Support  Implicit heirarchy of networks Typically more powerful nodes act as a bridge to more powerful networks, not other 802.15.4 nodes

6. 6 What do routing/organization/network protocols actually want? What subset is actually necessary to support low power, low data rate, wireless sensor networks?  Factored link protocol using 802.15.4 hardware and primitives Network protocol optimization Minimal state, code, RAM Just get what each node (or the network) needs  More on this tomorrow (B-MAC)

7. 7 Interoperability and Platforms MicaZ  CC2420  AVR (8-bit, 4/128k)  MMCX  Maintains compatibility with previous mote generations/sensors  Get 15.4 to people quickly to start work with it Telos  CC2420  MSP430 (16-bit 2/60k)  Internal & SMA  New single board design with USB for ultra low power  New architecture = new low power mechanisms

8. 8 What is difficult about interoperability? Same radio doesn’t solve your problems  Different mcu = Different architecture Word Alignment Endian-ness RAM size, Flash size, MIPS Hardware interfaces AVR-centric Hardware abstractions  Over the air data format vs Local data format New area for TinyOS—Need marshalling/unmarshalling support  But don’t parse everything going out, just what needs to be parsed LibC for TinyOS?  Marshalling, byte order, qsort, etc…  Information hiding – Eliminate instance specific code

9. 9 Chipcon CC2420 Interoperability TinyOS Platform Independent Radio Stack One implementation, many platforms  Lower layers for communicating with the CC2420 part of each platform UCB wrote Telos drivers Xbow wrote MicaZ drivers  Link layer adjusts for: Byte ordering Alignment Proven MicaZ/Telos interoperability GenericComm AM CC2420Control SpiByte RandomLFSR Backoff Encoding Data Control (Freq,Power,etc) CC2420RadioM CC2420RadioC HPLCC2420M Read/Write CC2420 Registers/Commands Transfer to/from TXFIFO/RXFIFO Hardware Specific High Speed Timer GenericComm AM CC2420Control SpiByte RandomLFSR Backoff Encoding Data Control (Freq,Power,etc) CC2420RadioM CC2420RadioC HPLCC2420C Read/Write CC2420 Registers/Commands Transfer to/from TXFIFO/RXFIFO Hardware Specific High Speed Timer Telos (TI MSP430) MicaZ (AVR)

10. 10 TinyOS Tools Everything you’re used to still works  SerialForwarder with 802.15.4 Packets  TinyOS Mesh Networking “MintRoute” “Surge”  “make telos/micaz” ~60m

11. 11 Status and Questions TinyOS 802.15.4 RFD implementation in progress  Call for help from the community!  What do network protocols need? MicaZ and Telos available  Supported by next TinyOS release (1.1.7)  CC2420DBK initial support in CVS Demos this evening  Platforms  Security (David Wagner)