Lecture 4

IEEE standard for wireless sensor

network – IEEE 802.15.4 MAC layer

Jingcheng Zhang

Linköping University

2013-01-22

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Content

General description: wireless sensor network architecture,

topology and function overview

IEEE 802.15.4 Specification: service, message and

command frame, function description

Example: How is IEEE 802.15.4 utilized in ZigBee protocol

MAC association

Orphan request

Data polling

Data Request

Lab 1 introduction

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How much information is contained in

IEEE 802.15.4?

323 pages in version 2006

202 pages amendment released in 2007

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How can we read this document?

Do not try to remember everything, use it as a reference

Clearly know the structure of the document so you know

where to find it

Fully understand the general description part

Get the general idea of each function presented in the

document

What else can we get by reading standard?

The standard

shows the best way of description in technical language

shows the best pattern to draw the message flow

shows the best way to organize the document when

describing the system

show the most logical way to design the system

shows you the optimized way to communicate with

people by using document. (It is so difficult!)

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Flash back: Which layers are we talking

about this time?

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• MLDE-SAP

• MLME-SAP

• PD-SAP

• PLME-SAP

Goal of IEEE802.15.4 standard

IEEE Std 802.15.4 defined the protocol and compatible

interconnection for data communication devices using

low-data-rate, low-power, and low-complexity short-range

radio frequency (RF) transmissions in a wireless personal

area network (WPAN).

low-data-rate

low-power

low-complexity

short-range

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Introduction

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The main objectives of an LR-WPAN are ease of installation, reliable data

transfer, short-range operation, extremely low cost, and a reasonable battery

life, while maintaining a simple and flexible protocol.

Some of the characteristics of an LR-WPAN are as follows:

— Over-the-air data rates of 250 kb/s, 100kb/s, 40 kb/s, and 20 kb/s

— Star or peer-to-peer operation

— Allocated 16-bit short or 64-bit extended addresses

— Optional allocation of guaranteed time slots (GTSs)

— Carrier sense multiple access with collision avoidance (CSMA-CA)

channel access

— Fully acknowledged protocol for transfer reliability

— Low power consumption

— Energy detection (ED)

— Link quality indication (LQI)

— 16 channels in the 2450 MHz band, 30 channels in the 915 MHz band,

and 3 channels in the868 MHz band

Topology

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• Two kinds of devices:

• FFD: Full function device

• RFD: Reduced function device

Special example - Cluster Tree network (not the same cluster tree definition in ZigBee)

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IEEE 802.15.4 device architecture

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Function description of PHY

The PHY provides two services: the PHY data service

and the PHY management service interfacing to the

physical layer management entity (PLME) service access

point (SAP) (known as the PLME-SAP). The PHY data

service enables the transmission and reception of PHY

protocol data units (PPDUs) across the physical radio

channel.

The features of the PHY are activation and deactivation

of the radio transceiver, energy detection, link quality

identification, channel selection, clear channel assess-

ment and transmitting as well as receiving packets

across the physical medium.

The radio operates at one or more of the following

unlicensed bands:

868–868.6 MHz (e.g., Europe)

902–928 MHz (e.g., North America)

2400–2483.5 MHz (worldwide) 11

Function description of MAC

The MAC sublayer provides two services: the MAC data

service and the MAC management service interfacing to

the MAC sublayer management entity (MLME) service

access point (SAP) (known as MLME-SAP). The MAC

data service enables the transmission and reception of

MAC protocol data units (MPDUs) across the PHY data

service.

The features of the MAC sublayer are beacon

management, channel access, GTS management, frame

validation, acknowledged frame delivery, association,

and disassociation. In addition, the MAC sub-layer

provides interfaces which can be used to implement

application-appropriate security mechanisms.

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Functional overview – Beacon (not utilized in ZigBee)

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Data transfer model

- Data transfer to a coordinator

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Data transfer model - Data transfer from a coordinator

Frame structure

The frame structures have been designed to keep the

complexity to a minimum while at the same time making them

sufficiently robust for transmission on a noisy channel. Each

successive protocol layer adds to the structure with layer-

specific headers and footers. This standard defines four frame

structures:

A beacon frame, used by a coordinator to transmit beacons

A data frame, used for all transfers of data

An acknowledgment frame, used for confirming successful frame

reception

A MAC command frame, used for handling all MAC peer entity

control transfers

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Frame field definition

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Frame field definition

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Improving probability of successful

delivery

CSMA-CA mechanism

Synchronized: Wait random slot

Un-synchronized: Wait random time

Frame acknowledgment

Data verification

FCS :16 bit of CRC

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Concept of primitives

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•Request: The request primitive is passed from the N-user to the N-layer to request

that a service is initiated.

•Indication: The indication primitive is passed from the N-layer to the N-user to

indicate an internal N-layer event that is significant to the N-user. This event may be

logically related to a remote service request, or it may be caused by an N-layer

internal event.

•Response: The response primitive is passed from the N-user to the N-layer to

complete a procedure previously invoked by an indication primitive.

•Confirm: The confirm primitive is passed from the N-layer to the N-user to convey

the results of one or more associated previous service requests.

PHY service specifications

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MAC sub-layer specification

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This clause specifies the MAC sublayer of this standard. The MAC sublayer

handles all access to the physical radio channel and is responsible for the

following tasks:

Generating network beacons if the device is a coordinator (not utilized in

ZigBee)

Synchronizing to network beacons (not utilized in ZigBee)

Supporting PAN association and disassociation

Supporting device security

Employing the CSMA-CA mechanism for channel access

Handling and maintaining the GTS mechanism (Not utilized in ZigBee)

Providing a reliable link between two peer MAC entities

MAC primitives

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MLME-ASSOCIATE.request

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The MLME-ASSOCIATE.request primitive allows a device to request an

association with a coordinator.

Why there is no Logical Channel information in the frame?

MLME-ASSOCIATE.response

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MLME-ORPHAN.Indication

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MLME-ORPHAN.Response

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MLME-POLL.request

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MCPD-Data.Request

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Lab 1 introduction

First Half

Introduction of IDE: IAR WB 810 for 8051

Introduction of the sniffer software

Introduction of Z-Stack from TI

File structure

Configuration

Implement your first application

Second Half

Understanding MAC frames within the ZigBee message flow

Beacon Request

Association Request

Orphan Response

Data Polling

Try to transmit message using ZigBee even before you

know it.

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Tack så mycket!

www.liu.se

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