coexistence with wifi for a home automation zigbee product federico dominguez, abdellah touhafi,...
TRANSCRIPT
Coexistence with WiFi for a Home Automation ZigBee product
Federico Dominguez, Abdellah Touhafi, Jelmer Tiete and Kris Steenhaut ,Erasmus Hogeschool Brussel
Vrije Universiteit Brussel,Brussels, Belgium
Communications and Vehicular Technology in the Benelux (SCVT), 2012 IEEE 19th Symposium on, 6-16 Nov. 2012
Adviser: Presenter: Yu-Jhang ChenDate: 102/12/18
Outline
1. Introduction2. Materials and Methods3. Results4. Discussion5. Conclusion
Introduction(1)
• Home Automation(HA):
1. Heating Ventilation Air Conditioning (HVAC) 2. automatic garage doors3. intruder detection alarms4. smart sensors detect temperature
Introduction(2)
Introduction(3)
• Tradition HA: – Expensive
– Cabling difficulty
• Now HA:– Cheap– Smaller– Offer wireless connectivity
Introduction(4)
• HA products exploit frequencies bands :– 433MHz, 868MHz, 900MHz, 2.4GHz
• The 2.4GHz compared with 433MHz :– Higher data throughput– Worldwide availability as an Industrial Scientific
Medical (ISM) band
Introduction(5)
ZigBee:
• Advantage – low cost SoC platforms– High interoperability
• Defect– WiFi, Bluetooth, Microwaves, cordless phones interference
Materials and Methods(1)
Window Shutter HA system:• Content :
– Shutter motor and Remote Control (RC)
• Extra features :– Position and error feedback– Security– Scalability
Materials and Methods(2)
• The minimal Window Shutter HA system setup is just a Wall RC and a Window Shutter. The system can later be expanded with other RC models and more shutters
Materials and Methods(3)
ZigBee PRO:• Devices :– Texas Instruments(TI) CC253x SoC– 8051 8-bit microprocessor– AES coprocessor– USB controller– CC2591 RF
Materials and Methods(4)
Channel Allocation:• ZigBee defines 27 channels :–One in the 868 MHz band– Ten in the 915 MHz band– 16 in the 2.4 GHz band
• WiFi channels:– Range from 1 to 13
Materials and Methods(4)
• system uses ZigBee channel 26 and is vulnerable to interference from WiFi channel 13
Goals of tests :• Confirm or negate whether WiFi interference
poses a threat to the product• Find recommendations to avoid interference• Find a simple method to detect the presence
of disruptive interference during product installation
Materials and Methods(5)
• Packet Reception Rate (PRR)− Added a test function in the firmware− Counts all ZigBee packets flagged as test packets − RC have the capability to send test packets in
bursts of 1000 packets per second
Materials and Methods(6)
System Responsiveness (SR):• Assumed that a user expected− Response to UP, DOWN and STOP commands by
an RC , around 300ms − response of shutter position feedback in the
embedded LCD screen on the Multi RC while the shutter is moving
Materials and Methods(7)
• Cr is successfully executed commands • Cd is noticeable delay time• Ct is total number of commands • Fw is a weighted value for the quality of the
LCD visualization
Materials and Methods(8)
Materials and Methods(9)
WIFI interference:• Constructed a lab to test the affects:– Put in a metallic window frame to emulate– Used a Linksys WRT54GL and D-Link DIR-615– Used iperf to generate synthetic UDP test traffic
Materials and Methods(10)
• X: distance of interference source
• Y :WiFi traffic level • C:WiFi channel
Materials and Methods(11)
• Traffic rate Y equivalency in WiFi load
Materials and Methods(12)
• At distances below 5 meters from interfe-
rence source the sy- stem is practiuzally unreachable. The ef- fects of interference consistently dissipate after 15m in all chan- nels
Results(1)
• SR levels of 10% or less, where the sy-
stem is completely unresponsive,were observed at dista- nces of 5 meters or less from inter- ference source.
Results(2)
• Even at this rel- atively low traf- fic level a small but noticeable degradation (a- round 80%) of system respon- siveness was observed.
Results(3)
Confirm:• WiFi can create harmful interference to
ZigBee systems• Distance to interference source and WiFi
traffic level are key variables• Difficult to avoid the WiFi generate
interference with real traffic
Discussion(1)
• Distance from interference source– A distance of 5 meters can be tolerated– 15 meters seems to be a safe distance to avoid
harmful disruption
• PRR vs. SR– PRR can give a me accurate measure of the
expected performance– Measuring PRR is much simpler than measuring SR
Discussion(2)
• PRR vs. SR has a correlation value of 0.89. PRR% can the-
refore be used to predict the performance of the HA sys- tem.
Discussion(3)
• ZigBee can coexist with WiFi in a typical home environment
• Precautions are taken into account• New standards such as Wireless HD and
WiGig will not occupy the 2.4 GHz band
Conclusion(1)