1. Low Power Wireless Personal Area Network (LP-WPAN)
IEEE (Zigbee)
Low Power Wireless Personal Area Network (LP-WPAN)
9/20/2018
Chao GAO, VAMK

2. IEEE 802.15.4 General Description
16 channels in the 2.4GHz band, 10 channels in the 915 MHz band, and 1 channel in the 868 MHz band; Over-the-air data rates of 250kb/s @2.4G, and respectively.
Star or peer-to-peer topology
Allocated 16-bit short or 64-bit extended addresses
Allocation of guaranteed time slots (GTSs)
CSMA-CA channel access with synchronized sleep mode (low power consumption)
Energy detection (ED)
Link quality indication (LQI)
Aimed to a Low-Rate Wireless Personal Area Network (LR-WPAN) Standard.
9/20/2018
Chao GAO, VAMK

3. IEEE 802.15.4 Channels At 2.4GHz shared with WiFi 1 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 10
868.3MHz
902MHz
928MHz
Channel spacing:
2MHz 26 25
2400MHz
2412MHz
ch1
2417MHz
ch2
2422MHz
ch3
channel
Spacing: 5MHz
2462MHz
ch11
Tx power 11 16 17 12 18 20 13 21 23 14 19 22 15
bandwidth: 22MHz 24
2405
2410
channel
2470
Freq. (MHz)
9/20/2018
Chao GAO, VAMK

4. IEEE Topology
Two basic topologies are supported: star and peer-to-peer
Two types of nodes: FFD (Full-Function Device), and RFD (Reduced- Function Device)
Thus two MAC protocols are used: CSMA/CA (for p2p) and CSMA/CA with superframe synchronization (for star)
Star topology
Peer-to-peer topology
Communication flow
PAN coordinator
Reduced function device (RFD)
PAN coordinator
Full function device (FFD)
9/20/2018
Chao GAO, VAMK

5. IEEE802.15.4 standard and ZigBee Stack Architecture
Application Profile
Application
ZDO
SSP
App Support (APS)
ZigBee Stack
NWK
Physical Radio (PHY)
Medium Access (MAC)
IEEE
9/20/2018
Chao GAO, VAMK

6. Need of MAC Collision may happen ???
Tonight I am free. Can you give me a hand?
If you have a watch, tell me what the time is now?
9/20/2018
Chao GAO, VAMK

7. I have ordered some pizza. Do you want to eat?
Need of Address
In a network, address is critical.
I have ordered some pizza. Do you want to eat?
Is she talking to me?
Is she talking to me?
9/20/2018
Chao GAO, VAMK

8. Need of Error Checking and ACK
Verify data is error free and acknowledge it.
Lets meet at 8pm tonight in front of cinema. (DATA)
Ok, 8pm cinema. (ACK)
9/20/2018
Chao GAO, VAMK

9. PHY Service Data Unit (PSDU)
IEEE Physical Layer
Power:
Transmitter power: 0dBm
Receiver Sensitivity: ~-85dBm
PHY Packet Fields
Preamble (4 octets) – synchronization
Start of Packet Delimiter (SPD, 1 octet)
PHY Header (1 octet) – PSDU length
PSDU (0 to 127 octets) – Data field 4 1 1
Pramble
SPD
PSDU
LEN
PHY Service Data Unit (PSDU)
6 octets
0-127 octets
9/20/2018
Chao GAO, VAMK

10. PHY Service Data Unit (PSDU)
IEEE Frames
4 types: DATA, BEACON, ACK, CONTROL
In a P2P network, we only see DATA and ACK
PHY Header
Pramble (4)
SPD (1)
PSDU
LEN (1)
PHY Service Data Unit (PSDU)
MHR: MAC Header
MSDU: MAC Service Data Unit
MFR: MAC Footer
MHR
MSDU
MFR
Frame
control
Seq.
No.
Addresses
Data payload
Frame
Chksum
DATA frame 2 1
4-20 2
Frame
control
Seq.
No.
Frame
Chksum
ACK frame
9/20/2018
Chao GAO, VAMK

11. Sequence Number in MHR
Monotonically incrementing (00 – 01 – … – FF – 00)
CSMA/CA supports retransmission. SN helps the receiver to avoid
Run 20km
Ok. Run 20km
collision
???
Run 20km
9/20/2018
Chao GAO, VAMK

12. Frame Control & Address
Depends on settings, address fields may contain 3 addresses:
PAN address: 2 octets, indicating the specific PAN (multi-PAN co-existence)
Destination and Source addresses: 2/6 octets (depends on settings)
Frame control is 2 octets (first 2 bytes in MAC header)
Frame TYPE: 001-DATA, 000-BEACON, 010-ACK, 011-Control, others-Reserved
SE: 0 if no encryption is applied
FP: 0 if no further frames are waiting for transmission
AR: ACK required, usually set in a DATA frame
PANID Compression: 1 if destination and source nodes are in the same PAN
Address Mode: 00-no address, 01-reserved, bit short addr, bit extended addr
9/20/2018
Chao GAO, VAMK

13. IEEE Frame Examples
A sniffer capture (from out laboratory facility) 2 1 2 2 2 5 2
DATA 2 1 2
ACK
DATA
ACK
What is the temperature? (DATA 01H)
OK wait (ACK)
Temperature is 0x16 (DATA 16H)
OK thanks (ACK)
PAN coordinator
Sensor
9/20/2018
Chao GAO, VAMK

14. Power Consumption of Sensor Node
It is desirable to put a sensor node into sleep mode.
The question is: when it can sleep?
From [Tsiatis et al, 2002]
Can you come here?
9/20/2018
Chao GAO, VAMK
Chao Gao, VAMK

15. Zigbee Programming XBee is a very popular 802.15.4-compatible module.
The module requires 3.3V DC power. An regulator is needed if you want to work with Arduino or RPi.
Working with PC, you can also use a USB adaptor.
Arduino example: Modules-As-Transmitter-Receiver-Ar/.
Raspberry Pi example: hacks.com/documentation/tutorials/xbee-arduino-raspberry-pi-tutorial/.
Xbee with whip and chip antenna
Xbee on a regulator
Xbee USB adapter
9/20/2018
Chao GAO, VAMK