A TVWS ZigBee Prototype Cognitive Plane Control Plane Application Protocol Plane Customer API James “Jody” Neel Security Propagation benefits ZigBee james.neel@crtwireless.com 32- / 64- / 128-bit encryption Alliance might enable more Network amenable deployments SDR 11 Star / M esh / Cluster-Tree M AC Nov 29-Dec 2, 2011 IEEE PHY 802.15.4 868M Hz / 915M Hz / 2.4GHz Silicon Stack App Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Presentation Material • Objective : Design a ZigBee-based solution suitable for operation in the TV White Space without modifying PHY / MAC (802.15.4) – 802.15.4m PAR was approved this month • Why ZigBee in the TV White Space (TVWS)? • Design approaches for addressing issues posed by putting ZigBee in TVWS Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Trends and Motivating Insights • Limited spectrum with large population presence • Rural broadband demand is not that high From M. Gibson, “TV White Space Geolocation Database Issues & Opportunities”, CommSearch, TVWS Workshop Sep 16, 2010 • Long history of automating agricultural applications • Much greater range http://www.ers.usda.gov/publications/eib3/charts.htm#fig1 possible implied by Frijs (100 mW) Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
TV White Space for Rural Sensor Applications Precision Agriculture • Agricultural Applications – Soil Moisture, pH – Cattle Monitoring – Paddy field monitoring – Equipment tracking – Farm automation • Environmental Applications – Water quality • Oil contamination Propagation benefits – Weather Sensing Grid might enable more – Flood monitoring amenable deployments – Air quality – Forest health • Fires, disease – Seismic activity – Energy source management Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Why not modify 802.15.4? • Preserving existing chipsets and protocols: – Simplifies integration with existing applications – Reduces costs – Reduces time to market Cognitive Plane • Wanted to beat 802.15.4m Control Plane • 802.15.4m PAR approved Nov 2011 Application Protocol Plane Customer – IEEE 802.22-11/0136r1 API • In theory, geo-location DSA does not Security require modifications to PHY or MAC if ZigBee 32- / 64- / 128-bit encryption you can already control transmit Alliance Network frequency reasonably quickly Star / M esh / Cluster-Tree – Not as true for sensing-based DSA or M AC IEEE many other cognitive radio applications PHY 802.15.4 – A. Mody, “Making Current Military Radios 868M Hz / 915M Hz / 2.4GHz Cognitive without Hardware or Firmware Silicon Stack App Modifications,” AIE CONFERENCE on Spectrum Management and Dynamic Spectrum Access for Government and Defense , Sep 27-28, 2011. Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
• Available Channels By Class TVWS Rules • Geolocation + Database – Sensing kinda allowed – 9 Database providers – Regs (kinda) finalized Sep 23, 2010 –Above: no TVBD devices in 608-614 • FCC 10-174 (adjacent to chan 37) in 13 metros (LMR conflict) – Channels 36,38 reserved for wireless mics •Protected users: –TV (including low power), TV translators, TV boosters, licensed mics, registered mics for major events, PLMRS/CMRS, MVPD receive sites, radio astronomy Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com Diagram from: Marvell, WinnForum TVWS Workshop Dec 2010
Available channels Fixed More TVWS Device Location (< 50m) Identifiers Either can provide • Fixed Location (< 50m) channel list – HAAT restricted to 76 m, 30 FCC ID Geolocation m above ground Database – Not achievable in hilly terrain Portable AP • Less power when adjacent Mode II to incumbent + TPC Available Channels • Identifications to geolocation FCC ID database Available Channels – Fixed devices provide long list of identifying information. Portable Stored in registration Laptop Mode I database (maintained with geolocation database) – Portables provide FCC ID • Fixed / Mode II can pass Database along each others’ information for channel availability • Mode I must receive “enabling signal” every 60s • Secure and authenticate Cognitive Radio Technologies Web: www.crtwireless.com channel lists 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lower Diagram from: Marvell, WinnForum TVWS Workshop Dec 2010 Lynchburg, VA 24502 Email: info@crtwireless.com
High Level System Considerations • Mode II devices implemented as 802.15.4 Full Function Devices (FFD) – Sends beacon frames – Offer network join services – Augment with GPS • Mode I devices implemented as 802.15.4 Reduced Function Devices – Only interface with single FFD • Network manager – Assumed co-located with • Routing implemented in tree coordinator (doesn’t have to be) mode – Internet connection to database – FFD act as RFD until given – Mesh mode does not implement channel assignment by NM beaconing – Send position initial Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Communications • Should operate in beacon- enabled mode • Mesh mode does not implement beaconing • Not strictly necessary, but non-beacon mode will greatly limit ability to sleep as active messaging every minute is required • 60s enabling beacon – Superframe configured to satisfy 60 second interval – 802.15.4 allows 15 ms to 245 s • Some performance issues in allowing FFD / Mode II devices to sleep as aggressively, but not unique to geo-location DSA Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Channel Considerations • Coordinator uses 802.15.4 energy • 5 MHz BW < 6 MHz TV channel scan to select least congested – 2.4 GHz PHY channel (after getting list from – Narrower version available but bad database / other Mode II) for PSD limits – Has to consider available channels • Network uses same channel for all routers in network • Private ZigBee profiles used for – Can get information from other devices custom channel restrictions • More restrictive channel mask – Remap channel #s in BSP – More of a HW issue • Most chipsets have APIs for channel selection that can be leveraged • 802.15.4 similarly has SAPs for configuring which channels to look at in a scan and transmit on • Zigbee supports frequency agility – Network Manager can switch entire network over to a new frequency – Required in ZigBee Pro – Use when channel availability changes Cognitive Radio Technologies Web: www.crtwireless.com Marvell, WinnForum TVWS Workshop Dec 2010 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Network Formation and Rendezvous • If Mode I • If orphaned (e.g., channel switch while sleeping) – Use passive scan mode to find channel with appropriate beacons – Mode I can’t directly use for association 802.15.4 orphan scan due to transmission of orphan – MLME-SCAN primitive notification commands – Receive available channel list as – Mode II is not similarly limited if part of DSA “application” channel list is not out of date • If Mode II • Mode I waking from sleep – If directly connected to internet mode • Report location (and other info) and get channels – Start passive scan on only • Enter active scan to check for previous channel existing coordinator / network – If fails go change scan channel manager list to previously received – Must prohibit active scan mode if channel scan list channel list is not available – If not connected to Internet – If that fails, scan over entire channel list • Enter passive scan mode to find FFD that does have a connection • After connected, report type location and act as non-coordinator FFD Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Other Considerations • ZigBee has potential issue • TPC already supported by with regenerating PAN IDs 802.15.4 when evacuating a channel – Step sizes of -25, -15, -10, -7, and entering a channel with -5, -3, -1, 0 dBm an existing PAN with the • TVWS requires encryption same ID and authentication of channel – Not true for ZigBee Pro info which enforces unique IDs – All devices at least implement even across different AES-CCM-64 channels – MAC level authentication from CBC-MAC – Network and application layer authentication and from ZigBee • Application authentication more appropriate Cognitive Radio Technologies Web: www.crtwireless.com 147 Mill Ridge Rd, Ste 119 Ph: (540) 230-6012 Lynchburg, VA 24502 Email: info@crtwireless.com
Recommend
More recommend
