Advantech ADAM-4561 Instrukcja Użytkownika Pobierz pdf (Strona 7)

IEEE 802.15.4

IEEE 802.15.4 is defined and maintained by the IEEE organization. The standard intends to offer fundamental lower

network layers of low-rate wireless personal area networks (WPANs) which focuses on low-data rate, low-power

consumption ubiquitous wireless communication between devices. IEEE 802.15.4 conforming devices may use one of

three possible unlicensed frequency bands for operation:

Network Topologies

Wireless Sensor Networks (WSN) can be built using a few or a lot of “nodes”. Each node can be connected to one or

several sensors; the network topology is composed of three typical components, PAN Coordinator/Gateway, Router

and End Device (or called End Node), which can be built to Star, Tree and Mesh network topologies.

Three components of a wireless sensor network

PAN Coordinator/Gateway

A coordinator is the data collection

center and also exists as a gateway to

transfer and translate wireless data to

other interfaces.

ADAM-2000 Introduction

Router

A router enhances the wireless

signal and a wireless router is

used to select the optimal path for

wireless communication between the

coordinator and the end nodes.

End Node/Device

An end node is a wireless remote I/O

for data acquisition. Data is acquired

from sensors or devices which are then

transmitted through it. The end node

communicates with the coordinator

directly or via a router to a coordinator.

868.0-868.6 MHz: Europe, allows one

communication channel.

902-928 MHz: North America, up to ten

channels, extended to thirty.

2400-2483.5 MHz: worldwide use, up to

sixteen channels.

IEEE 802.15.4 defines the Wireless

Medium Access Control (MAC) and

Physical Layer (PHY) for WPANs

only, upper layer stacks can be

implemented by users for variety of

applications. One example of the

known protocols is ZigBee.

Comparison of Topologies

Topology

Star Tre e Mesh

Power Consumption

Low Medium High

Installation Fee

Low Medium High

Network Coverage

Small Large Large

Network Capability

Small Large Large

Reliability

Low Low High

1 2 3 4 5 6 7 8 9 10 11 12 ... 35 36

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