smart grid communicationssite.iugaza.edu.ps/mtastal/files/sg_comm_2021-introzigbee.pdf · child...
TRANSCRIPT
Acknowledgment
This presentation is prepared based on :
1. PPT of Course: Fundamentals of Smart Grid Design andAnalysis, that was prepared by eSCO: www.eAcademy.ps
2. Smart Grid Course, Topic 3, of Department of Electrical &Computer Engineering Texas Tech University
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CONTENT
CONTENT
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NIST Conceptual Reference Model for Smart Grid
Smart Grid Technologies
• Overview, applications, & products
• Wireless channels & Packet structure • Device classes & addressing
• Routing (assignment)
2 ZigBee
• Collocation problem & Z-wave alternative
• Each domain involves its own actors and applications.
• Interactions across 7 Smart Grid Domains:
Texas Tech University
Composition of the Smart Grid
NIST Conceptual Reference Model for Smart Grid
• Each domain involves its own actors and applications.
• Interactions across 7 Smart Grid Domains:
Composition of the Smart Grid
NIST Conceptual Reference Model for Smart Grid
• Consumers:
• The end users of electricity.
• May also generate/store electricity.
• Traditionally: Residential, Commercial, and Industrial.
• Market:
• Participants in wholesale market: day‐ahead, hour‐ahead,...
• Involves prediction, bidding, auctions, …
• Service Providers:
• Organizations providing service to:
• Both utilities and consumers.
• ISPs, Cell Phone Companies, Aggregators,…
• Operations:
• Independent System Operators (ISOs)
• Regional Transmission Organization (RTOs)
• Bulk Generation:
• Major Power Plants.
• Transmission:
• Carriers of bulk electricity over long distances.
• Distribution:
• Distribution of electricity to (and from!)
consumers.
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Composition of the Smart Grid
NIST Model for Smart Grid Information Network
•There are two questions to answer:
✓ How can different smart grid entities exchange
messages?
✓ What kind of messages (and why) should they
exchange?
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➢ Our focus in Topic 3 is on the first question.
•We want to learn which communication technologies may help.
Smart Grid communications?
Smart Grid Communications
• In particular, we cover these communications technologies:
Smart Meter
Aggregator
PLC IP WMN
ZigBee (Home Area Network)
Substations
Operation
Sensors
PLC IP/IEC
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Smart Grid communications?
Smart Grid Communications
ZigBee
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ZigBee
• ZigBee is a working group to promote IEEE 802.15.4 standard.
Texas Tech University
ZigBee
ZigBee Overview
• EEE 802.15 is for Wireless Personal Area Networking (WPAN)✓ 802.15.1: Bluetooth✓ 802.15.2: Co‐existence (e.g., with WLAN)✓ 802.15.3: High Rate WPAN via Ultra wideband (UWB)✓ 802.15.4: Low Rate
Low Power Consumption / Long Battery Life
Inexpensive!
802.16
WiMAX
802.11
WiFi
802.15
WPAN
Freq 2 – 11GHz 2.4GHz Varies
Range 31 miles 100 Meters 10 Meters
R 70 Mbps 11 - 110Mbps 20k – 55Mbps
Nodes Thousands Dozens Dozens
•WPAN vs WLAN/WiFi and WMAN/WiMax
* Data for 802.16a and 802.11a
ZigBee
ZigBee Overview
•Simpler and Less Expensive than Bluetooth
✓ Cost: One fourth of Bluetooth
✓ Complexity:▪ Complex ZigBee Nodes: 10% Code of a Bluetooth node
▪ Simple ZigBee Nodes: 2% Code of a Bluetooth node
ZigBee
ZigBee Application
• Automatic Notification: Call the owner if problem occurs.
• Door Control: When the door is locked, lights are turned off.
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ZigBee
ZigBee Building Solution
•Smart appliances can also communicate with smart meters.
• Example: They can obtain prices and adjust their load. (Demand Response topic)
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ZigBee
ZigBee Building Solution
•ZigBee solutions by Texas Instrument (TI) at different layers:
• Refer to TI’s ZigBee pages for more detail.
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ZigBee
ZigBee Products
ZigBee Protocol Stack
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• There are four layers in ZigBee Protocol Stack:
User Defined
ZigBee Alliance
Texas Tech University
IEEE 802.15.4
[DE: Data Entity, ME: Management Entity, SAP: Service Access Point]
• ZigBee devices may use different frequency bands:
PHYFrequency
Band
Channel
NumberingBit Rate
868 MHz 868 – 870 MHz 0 20 kb/s
915 MHz 902 – 928 MHz 1 - 10 40 kb/s
2.4 GHz 2.4 – 2.4835 GHz 11 - 26 250 kb/s
ZigBee
ZigBee Wireless Channel
• Frequency channels used by ZigBee devices:
868.3 MHz
Channel 0
Channels 1‐10
Channels 11‐26928 MHz902 MHz 5 MHz
2 MHz
2.4835 GHz
2.4 GHz
ZigBee
ZigBee Wireless Channel
868.3 MHz
Channel 0
Channels 1‐10
Channels 11‐26
928 MHz902 MHz
5 MHz
2 MHz
2.4835 GHz
2.4 GHz
• Some of the features for co‐existence at certain bands:
• Carrier Sense Multiple Access (CSMA)
• End‐to‐end ACK and Retransmission
• Built‐in Channel Scanning / Find Available Channels
ZigBee
ZigBee Packet Structure
• Packet Fields [specified by IEEE 802.15.4]:• Preamble: 32 bits for synchronization• Start of Packet Delimiter: 8 bits• PHY Header: 8 bits / indicates PSDU length, etc.• PSDU: 0 to 127 bytes of data
PreambleStart of
PacketDelimiter
PHYHeader
PHY Service Data Unit (PSDU)
6 Bytes 0‐127 Bytes
•Inside PSDU:
CRCLink Layer PDUPC ADDR DSN PC: Addressing Mode FlagsADDR: AddressDSN: Data Sequence NumberCRC: Cyclic Redundancy Check
•All Devices Have Address:
•Two‐bytes: We can have up to 65,536 nodes (Q: Why?)
•Addressing Modes:
•Star
• Peer‐to‐Peer
• Cluster Tree
Addressing Modes Depend on the Network Topology.
[We will see more on topologies…]
Texas Tech University
ZigBee
ZigBee Device Addressing
• ZigBee has two main Device Classes (in term of capabilities) :
1. Full Function Device (FFD)
✓ Available in any topology
✓ Can become a network coordinator
✓ Talks to any other device
2. Reduced Function Device (RFD)
✓ Limited to star topology
✓ Cannot become a network coordinator
✓ Talks to only a network coordinator
✓ Simpler Implementation & less power consumption
ZigBee
ZigBee Device Classes
• Each ZigBee network has one network coordinator.• It initiates network formation.• We need at least one Full Function Device. (Q: Why?)
• Other devices can be either FFD or RFD.
• FFDs that are not network coordinator act as routers.• Recall that RFDs only talk to the network coordinator.
in term of functionality
Q: Can we build a mesh topology with RFDs only?
ZigBee
ZigBee Network Topologies
ZigBee
ZigBee Network Topologies
Network Coordinator initiatesthe network formation.
ZigBee routers help expanding the network
We can form Tree Clusters.
ZigBee
ZigBee Network Topologies
• Each cluster has one FFD as its root.
• The root for the overall tree is the
network coordinator.
• They allow routing with minimum
overhead.
• The tree may span physically large
areas.
• In total, we can have 255 clusters of 254
nodes = 64,770 nodes.
ZigBee
ZigBee Addressing
• For each new node (i.e., associated device):
•A unique address is allocated by parent (router/coordinator)
•Recall that the parent can only be a FFD.
• The max number of devices that a parent can support = 32.
• Two types of addresses:
•Network Address: 16‐bit, only unique in this network
•Extended Address: 64‐bit, unique in all networks
ZigBee
ZigBee Addressing
•The following network attributes are important:
✓ nwkcMaxDepth:
•The maximum absolute depth allowed in this
network.
✓ nwkMaxDepth (Lm):
•The maximum absolute depth a particular device
can have.
✓ nwkMaxChildren (Cm):
•The maximum number of children a device is
allowed to have.
✓ nwkMaxRouters (Rm):
•The maximum number of routers a device can
have as children, and it set by the coordinator The network attributes for a
node/router with absolute depth d:
•These attributes let us compute:
✓ the function Cskip(d): Size of address block allocated by each parent at
depth d. A FFD parent withCskip(d) > 0 may accept
child devices.
• A parent assigns addresses to children based on whether the child is router
capable or not.
• Let Aparent denote the address of a parent at depth d.
ZigBee
ZigBee Addressing
Router Capable Child: [nth such child at depth d+1] • End‐Device Child: [mth suchchild at depth d+1]
• Note that each child needs an address.
• A router child also needs an address block for its future children.
• Overall Idea: Assure having unique addresses for all nodes.
ZigBee
ZigBee Addressing
• Example: Rm = 1, Cm = 2, and Lm = 3.
• Cskip(0) = 1 + 2 x (3 – 0 – 1) = 5• Cskip(1) = 1 + 2 x (3 – 1 – 1) = 3• Cskip(2) = 1 + 2 x (3 – 2 – 1) = 1
Block with 5 Addresses
Block with 3 Addresses
ZigBee
ZigBee Addressing
• Consider addressing at the network coordinator with ANC = 0.
• Router Child:
Addr = 0 + 5 x 1 + 1 = 6• End‐device Child:
Block: 1…5
Block with 3 Addresses
0
1 6
ZigBee
ZigBee Addressing
• At the router node at depth 1 with Aparent = 1.
• Router Child: Addr = 1 + 3 x (1 – 1) + 1 = 2Addr Block = 2 … 1 + 3 x 1 = 2 … 4
• End‐device Child:
Block: 1…5
Block: 2…4
0
1 6
2 5
Addr = 0 + 5 x (1 – 1) + 1 = 1Addr Block = 1 … 5 x 1 = 1 … 5
Addr = 1 + 3 x 1 + 1 = 5
• Example: Rm = 2, Cm = 4, and Lm = 3.
• Cskip(0) = (1 + 4 – 2 – 4 x 23‐0‐1) / (1‐2) = 13
• Cskip(1) =
• Cskip(2) =
ZigBee
ZigBee Addressing
Your Job: Choose the addresses and address blocks!
• Q: What if the topology is not complete?
• Q: What if the topology is not star? Does it affect addresses?
ZigBee
ZigBee Addressing
• This routing mechanism is particularly good for tree topologies.
• Although it works for other topologies as well.
• However, for more complex networks, ZigBeeuses:
• AODV: Ad‐hoc On‐demand DistanceVector
• Uses Bellman‐Ford (BF) Equation as a DV algorithm…
• But first it requires route discoveryon‐demand
ZigBee
ZigBee Addressing
• Based on initial slides of given in Moodle, explain the ZigBee
routing mechanism (deliverables : 15 minutes video)
ZigBee
ZigBee Routing
• In addition to medium access control:
• They should automatically avoid common channels.
Ref
:P. Y
iet
al.
• ZigBee and WiFi collocate at 2.4 GHz Frequency Band
ZigBee
ZigBee Collocation with WiFi
• ZigBee (or WiFi or both) should search for unused channels.
Ref
:P. Y
iet
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• ZigBee and WiFi collocate at 2.4 GHz Frequency Band
WiFi:
ZigBee:
(3 Orthogonal Channels)
ZigBee
ZigBee Collocation with WiFi
• An Algorithm for ZigBee Channel Switching:
• PER: Packet Error Rate
• To be checked by End‐Device
• LQI: Link Quality Indicator
• To be checked by Router / Coordinator
• Strength of Received Packets
• From 0 to 255 [Strongest]
• ED: Energy Detection
• RSSI: Received Signal Strength Indicator
Ref
:P. Y
iet
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ZigBee
ZigBee Collocation with WiFi
• Experimental Results by P. Yi et al. to obtain:
• Safe Distance
• Safe Offset Frequency
• WiFI Uplink and Downlink as source of interference on ZigBee:
Ref
:P. Y
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PER vs Distance (Meter)
ZigBee
ZigBee Collocation with WiFi
• At 7 MHz Frequency Offset, “Safe Distance” is 5 Meter.
PER vs Distance (Meter)
Ref
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ZigBee
ZigBee Collocation with WiFi
• 8 MHz is “Safe Frequency Offset” regardless of Distance.
• We can do similar experiments for other technologies.
• One can also study ZigBee interference on WiFi [the reverse!].
Ref
:P. Y
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PER vs Distance (Meter)
ZigBee
ZigBee Collocation with WiFi
• An alternative home area networking technology for ZigBee:
• To resolve ZigBee/WiFi collocation problem.
• Z‐Wave operates at around 900 MHz band
• It does not collocate with WiFi
• It may compete with some cordless telephones
ZigBee
Z-Wave
• Similar to ZigBee, Z‐Wave aims to build a “smart home”:
• A wireless HAN “ecosystem”
Z‐Wave appliances can participate in AMI, AMR, and Demand Response
ZigBee
Z-Wave