Transcript Designing a ZigBee-ready IEEE 802.15.4

Class Presentation of Custom DSP Implementation Course on:
ECE Department – University of Tehran
ZigBee/IEEE 802.15.4
Presented by:
Elaheh Rahmani
May 2005
Outline:
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Introduction to ZigBee
Application
PHY Layer
MAC Layer
Comparison between Bluetooth & ZigBee
Designing a ZigBee-ready IEEE 802.15.4- compliant radio
transceiver
Physical Layer for the Specknet – Design and Implementation
Conclusion
Refrences
What is ZigBee/IEEE 802.15.4?
ZigBee:
- Technology that addresses the market needs for costeffective ,standards-based wireless network that supports
low data rates, low power consumption, security, and
reliability, based on IEEE 802.15.4 standard.
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 IEEE 802.15.4:
- The IEEE 802.15.4 standard defines the PHY and MAC
layers, for low-rate wireless personal area networks (LRWPANs), which are used by Zigbee.
- The IEEE 802.15.4 standard and the ZigBee technology
address easy, low-cost deployment of power-friendly and
flexible implementations of a virtually unlimited number of
wireless low data rate monitoring and control applications.
What is ZigBee/802.15.4 ?
Ref. [7]
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ZigBee Alliance:
The Zigbee alliance is responsible for the Zigbee wireless
technology, which defines the network, security, and application
layers upon the IEEE 802.15.4 PHY and MAC layers, and also
provides interoperability and conformance testing specifications.
Why ZigBee?
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Reliable and self healing
Supports large number of nodes
Easy to deploy
Very long battery life
Secure
Low cost
Can be used globally
Application:
 The application sphere of this wireless personal area
network (WPAN) technology ranges from :
- industrial monitoring and
control
- home automation
- sensor networks
- personal health care
- PC & peripherals
- gaming, and automotive
solutions.
Ref. [2]
ZigBee/IEEE 802.15.4
General Characteristics:
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Dual PHY (2.4GHz and 868/915 MHz)
Data rates of 250 kbps (@2.4 GHz), 40 kbps (@ 915
MHz), and 20 kbps (@868 MHz)
Optimized for low duty-cycle applications (<0.1%)
CSMA-CA channel access Yields high throughput
and low latency for low duty cycle devices like
sensors and controls
ZigBee/IEEE 802.15.4
General Characteristics:
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Low power (battery life multi-month to years)
Multiple topologies: star, peer-to-peer, mesh
Addressing space of up to:
- 18,450,000,000,000,000,000 devices (64-bit IEEE
and 16-bit short addresses )
- 65,535 networks
Range: 50m typical (5-500m based on environment)
IEEE 802.15.4 and ZigBee working model.
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The IEEE 802.15.4 standard specifies the PHYsical (PHY) and Media Access
Control (MAC) layers at the 868 MHz, 915 MHz and 2.4 GHz ISM bands.
Ref. [1]
Physical (PHY) Layer[11]:
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The 802.15.4 physical layer specifies:
- Transmit power of at least .5 milliwatt
- Receiver sensitivity of less than or equal to
85 dbm in the 2.4 GHz band
- Receiver energy detection (ED)
- Link quality indication (LQI)
- The air interface is direct sequence spread
spectrum (DSSS) using BPSK for 868 MHz
and 915 MHz and O-QPSK for 2.4 GHz.
IEEE 802.15.4 PHY Parameters:
Ref. [10]
Media Access Control (MAC) layer[6]:
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The 802.15.4 MAC layer envisions two classes of
devices: one is the Full Function Device (FFD), which
works with any topology (star, mesh and cluster tree), can
function as a network coordinator, and can talk to any
other device in the network. The other is the Reduced
Function Device (RFD), which is limited to start network
topology, can't be a network coordinator.
The access method in IEEE 802.15.4-enabled networks is
carrier sense multiple access with collision avoidance
(CSMA-CA).
The MAC layer also specifies three security levels
including access control lists, data freshness timer and
128-bit encryption.
Topology Models:
Ref. [2]
Bluetooth (IEEE 802.15.1) &
ZigBeeIEEE (IEEE 802.15.4)
Their similarities and differences[8]:
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Bluetooth and ZigBee have much in common.
ZigBee aims more for grand-scale automation and
remote control.
Bluetooth eliminates cabling between electronic
products and accessories, such as between computers
and printers.
Both are types of IEEE 802.15 "wireless personalarea networks," or WPANs.
Both run in the 2.4-GHz unlicensed frequency band .
Both use small form factors and low power.
Technical differences between Bluetooth
and ZigBee [8]:
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Modulation technique
Bluetooth: Frequency Hopping Spread Spectrum
(FHSS)
ZigBee: Direct Sequence Spread Spectrum (DSSS)
Protocol stack size
Bluetooth: 250K bytes
ZigBee: 28K bytes
Battery
Bluetooth: Intended for frequent recharging
ZigBee: Not rechargeable (one reason batteries will
last for up to 10 years)
Technical differences between Bluetooth
and ZigBee [8]:
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Maximum network speed:
Bluetooth: 1M bit/sec
ZigBee: 250K bit/sec
Network range:
Bluetooth: 1 or 100 meters, depending on radio class
ZigBee: Up to 70 meters
Typical network join time
Bluetooth: 3 seconds
ZigBee: 30 milliseconds
Comparison of Key Features of
Complementary Protocol:
Ref. [2]
Designing a ZigBee-ready IEEE
802.15.4- compliant radio transceiver[1]:
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An efficient implementation of IEEE 802.15.4compliant radio-on-a-chip by identifying potential
low-power features in the standard, suitable
transceiver architectures and considering standard
CMOS design issues.
The foremost benefits of CMOS are low cost and
single-chip integration capability. CMOS enables the
integration of digital baseband processing, RF/analog
circuits and system memory in the same physical
silicon.
[1] Khanh Tuan Le ,”Designing a ZigBee-ready IEEE 802.15.4- compliant radio transceiver”,
Next Generation Wireless,November 2004.
Receiver Architecture :
 Traditional heterodyne receiver architectures are not optimal
solutions for achieving the low-cost, low-power targets of the IEEE
802.15.4 PHY specification.
The zero-IF (also often
referred to as directconversion) and low-IF
receiver architectures
are excellent candidates
for completely integrated
receivers with good
performance at low power
and small silicon area.
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Ref. [1]
Transmitter Architecture :
 Similar to their heterodyne receiver counterparts, transmitters
based on multiple upconversion and filtering stages do not
comply with the low-cost and low-power philosophy of the
IEEE 802.15.4 standard.
 Efficient generation of
the transmit signal
according to the IEEE
802.15.4 PHY can be
achieved by using singlestep I/Q upconversion or
VCO modulation
transmitter topologies.
Ref. [1]
IEEE 802.15.4-compliant and ZigBee-ready
CC2420 radio transceiver:
Ref. [1]
Physical Layer for the Specknet –
Design and Implementation:
(Zigbee chosen as demonstration platform)
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Physical Layer
Transmitter
Design Flow
Simulation, Implementation and Testing
Conclusions
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Physical Layer:
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Network
Physical Layer
RF
Layers
DSP
Section
Zigbee chosen as demonstration platform
Development of prototype
- Gained design experience
- Resolved some practical problems
Ultimate Physical Layer design may be simpler than Zigbee
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Context of Physical Layer:
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Digital signal processing of
data for transmission, and data
received
Simple protocol chosen for
initial implementation
- 802.15.4 (Zigbee)
Zigbee specifies:
- Maximum data rate 250kb/s
Higher Layers
Physical Layer
RF transmit / receive
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Development system aims
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To design and implement a prototype physical layer on FPGA
To interface with RF section
To test performance and hardware requirements, and improve and
optimise where possible
To aid in creating a channel model for further development
To create IP blocks which can be integrated with MAC and network
layers onto a single FPGA
Air interface
DAC
RF
RF
DAC
FPGA
FPGA
Transmit side
Receive side
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Transmitter detail:
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Data rates shown are for Zigbee – may be reduced in
proportion
Binary data
250 kb/s
Transmit
Filter I Phase
Bit to symbol
mapping
b3
b2
b1
1 Mchip/s
b0
I phase
Transmit
Filter Q Phase
62.5 kbaud
Symbol to chip
mapping
Offset QPSK
mapping
2 Mchip/s
Q phase
1 Mchip/s
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Design Flow:
High level simulation
Test vectors
User Constraints File
VHDL design entry
Simulation
Synthesis
RTL Netlist
Place and Route
Download to FPGA
Reports, Floorplan etc.
Oscilloscope probe
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Simulation results:
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Active HDL simulator used to verify output
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Synthesis:
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Synplify Pro was used as the synthesis tool
A netlist is created from the VHDL source
This is the main input to the Place and Route stage
It can also be used to visualise the design
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
Implementation:
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Xilinx ISE was used to
target the Spartan II FPGA
on board the Nallatech
“Strathnuey” development
board
- 150,000 gates on User FPGA
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A User Constraints File was
created
- Maps output signals to pins
- Applies timing constraints
[4]Luise Crockett, University of Strathclyde, Speckled Computing.
On-board Testing:
 For testing, a “wrapper” had to be created around the
transmitter entity. Included:
- Test vectors,
- Formatting of I and Q outputs for DAC
- SNDACINF entity to interface with on-board DAC
- Mapping of selected outputs to on-board LEDs
[4] Luise Crockett, University of Strathclyde, Speckled Computing.
Conclusion:
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ZigBee and the underlying IEEE 802.15.4
standard promise a low-cost, low-power
and reliable wireless network technology
for a wide range of control and monitoring
applications within the private sphere and
industrial environment.
References:
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[1] Khanh Tuan Le ,”Designing a ZigBee-ready IEEE
802.15.4- compliant radio transceiver”, Next Generation
Wireless,November 2004.
[2] Bob HeileChairman, ZigBee Alliance,”Emerging
Standards:Where does ZigBee
fit”,Presentation,[email protected]
[3] ZigBee Alliance Website ,http://www.ZigBee.org
[4] Luise Crockett,” Physical Layer for the Specknet –
Design and Implementation”, University of Strathclyde,
Speckled Computing
[5] HTML Page.”I've heard a little about ZigBee and IEEE
802.15.4. What's the difference?”, Retired Expert - Robert
_Poor.
[6] Larry Leob,([email protected]. “Roaming charges
ZigBee goes to work.htm”,18 Nov 2004,IBM.
References:
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[7] Ed Callaway,” Low Power Consumption Features of the
IEEE 802.15.4/ZigBee LR-WPAN Standard”, Florida
Communication Research Lab, Motorola Labs,
[email protected]
[8] Joanie Wexler,” Bluetooth and ZigBee: Their similarities
and differences, ZigBee challenges Bluetooth for
mindshare,Network World, 02/28/05.
[9] ZigBee vendor group to wireless-enable facilities
monitoring, Network World on Wireless in the Enterprise,
08/25/03.
[10] Bryon Gloden, Murat Senel, and Waseem Sheikh
,”Wireless sensor networks looking to Zigbee Alliance”.
[11] Steve Montgomery,” Wi.232DTS vs. Zigbee
Comparing proprietary and standards based solutions”,
October, 2004