IEEE 802.15.4

Information Taken from IEEE 802.15.4-2011. Additional information can be found in the "Official" Wikipedia article linked below or the IEEE website (also linked below).

Wikipedia IEEE 802.15.4

IEEE Official Standards for 802.15

PDF 802.15.4 2011

Basics

• ~10m Range Devices
• Frequency Ranges
  • 868-868.6 MHz
  • 902-928 MHz
  • 2400-2483.5 MHz

Data Transfer

Beacon Enabled

Figures to be added soon.

Beacon Disabled

Figures to be added soon.

Device Types

• Full-Function Device
  • Personal Area Network Coordinator (PAN Coordinator)
  • Device
• Reduced-Function Device
  • Device

Frame Structures

• Beacon Frame
• Data Frame
• Acknowledgement Frame
• MAC Command Frame

Busy Channel Avoidance

CSMA-CA

Carrier Sense Multiple Access with Collision Avoidance.

Figure to be added soon.

ALOHA

Devices transmit without sensing the medium or waiting a specific amount of time. This protocol is best for a lightly loaded network.

MAC Layer

The MAC Layer is responsible for the following:

• Generating network beacons if the device is a coordinator
• Synchronizing to network beacons
• Supporting PAN association and disassociation
• Supporting device security
• Employing the CSMA-CA mechanism for channel access
• Handling and maintaining the GTS mechanism
• Providing a reliable link between two peer MAC entities

PHY Layer

The PHY Layer is responsible for the following:

• Activation and deactivation of the radio transceiver
• Energy detection (ED) within the current channel
• Link quality indicator (LQI) for received packets
• Clear channel assessment (CCA) for carrier sense multiple access with collision avoidance(CSMA-CA)
• Channel frequency selection
• Data transmission and reception
• Precision ranging for ultra-wide band (UWB) PHYs
• Minimum Transmit Power = -3dBm

Modulation Schemes

CSS Power Spectral Density Mask

• O-QPSK - Offset Quadrature Phase-Shift Keying, Direct Sequency Spread Spectrum (DSSS) employing O-QPSK
  • 868 MHz Band
  • 915 MHz Band
  • 2450 MHz Band

For 2450 MHz Band, the Power Spectral Density Mask is:

Frequency (from Carrier)	Relative Limit	Absolute Limit
<math>\pm</math>3.5 MHz	-20 dB	-30 dBm

• BPSK - Binary Phase Shift Keying, DSSS employing BPSK
  • 868 MHz Band
  • 915 MHz Band

• ASK - Amplitude Shift Keying, Parallel Sequence Spread Spectrum (PSSS) employing ASK and BPSK modulation
  • 868 MHz Band
  • 915 MHz Band

• CSS - Chirp Spread Spectrum, CSS employing differential quadrature phase-shift keying (DQPSK) modulation
  • 2450 MHz Band

• UWB - Ultra Wide Band, Combined Burst Position Modulation (BPM) and BPSK modulation
  • 3-10 GHz Bands

Data Rates

PHY (MHz)	Frequency Range (MHz)	Chip Rate (kchips/s)	Modulation	Bit Rate (kb/s)	Symbol Rate (ksymbol/s)	Symbols
868	868-868.6	300	BPSK	20	20	Binary
915	902-928	600	BPSK	40	40	Binary
2450 DSSS	2400-2483.5	2000	O-QPSK	250	62.5	16-ary Orthogonal

Channel Numbering

868, 915, 2450 MHz Bands

<math> F_c = 868.3 \, </math>

<math> F_c = 906 + 2(k-1) \, </math> for k = 1,2,...,10

<math> F_c = 2405 + 5(k-11) \, </math> for k = 11,12,...,26
k is the channel number

CSS PHY

Channel Number	Frequency (MHz)
0	2412
1	2417
2	2422
3	2427
4	2432
5	2437
6	2442
7	2447
8	2452
9	2457
10	2462
11	2467
12	2472
13	2484

Security

• Most security architectural elements can be implemented at higher layers
• Security relies on Symmetric-Key Cryptography
  • Uses either Link Keys (for two devices) or Group Keys (for multiple devices)
  • Is responsible for data confidentiality, authenticity, and replay protection