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Understanding Practical Ethernet Commissioning

When choosing which type of industrial wireless Ethernet to commission for

your application, several aspects should be considered...

Which Wireless Ethernet Is Right For My Application?

Several factors should be considered when choosing which

industrial wireless Ethernet is right for your application: country

regulatory dependent.

Reliable Communications Distance

Reliable wireless Ethernet communications is fundamentally

determined by a few key factors: the amount of Radio

Frequency (RF) power emitted from the antenna (government

regulated), the lowest level that the receiving module can

reliably demodulate (ie receiver sensitivity) and the frequency

waveform properties relative to the terrain over the distance

required of the application.

Frequency and Terrain

Radio signals are transmitted between the sending and

receiving units. The radiated radio signals form an elliptical

path of concentric circles known as a Fresnel zone. The radio

path may be described as either obstructed or line of sight.

It is the level of obstruction relative to the frequency waveform

and its Fresnel zone that determines the success level of

communications. Higher frequencies such as 2.4/5GHz have

smaller waveforms and can be susceptible to obstructed paths

and congestion. 900MHz waveforms are more reliable in non-

line of sight distance applications due to greater diffraction

(bending), reﬂection (bouncing) and susceptibility to multipath

fading of the waveform (relative to higher frequencies).

RF Power

Receiver

Sensitivity

Fresnel Zone

Terrain

Distance

Image demonstrates the Fresnel zone between two antennas over the

distance required of the application. It is the amount of obstruction relative to

the waveform Fresnel zone (and other factors) that determines success.

The 900MHz Radio Spectrum

The 900MHz radio spectrum is regulated by government

communications regulatory authorities. These bodies stipulate

both bandwidth size and the number of channels available for

use. As such the 945U-E supports up to 4 channels depending

on regulations within the country of use. This has an impact on

the potential data throughput available to the end user (eg USA

up to 54Mbps and Australia up to 13.5Mbps).

902 907 912 915 917 922 928

10 MHz Ch 12 10 MHz Ch 32

10 MHz Ch 22 10 MHz Ch 42

USA/Canada (902 - 928MHz)

Australia (915 - 928 MHz)

5 MHz Ch 11

5 MHz Ch 21 5 MHz Ch 41

5 MHz Ch 31

20 MHz Ch 24

20 MHz Ch 34

900 MHz Channels

Image depicts bandwidth and channel size as per country regulations.

Understanding the 945U-E Advantage

The majority of 900MHz Ethernet products use Frequency

Hopping Spread Spectrum (FHSS) as the modulation method

in their design. FHSS products hop throughout the channels

in the radio spectrum, hopping to the next available channel

when communicating and/or experiencing interference.

Due to the size and the use of a small number of channels,

FHSS products are limited in their data throughput capabilities.

RF Amplitude

Frequency band

Time

Ch1

Ch2

Ch n

Channels

T 1

T n

Ch f

T f

FHSS devices scan the channels within the band hopping channels in

communicating and/or when experiencing interference.

ELPRO’s 945U-E’s innovative design uses Direct Sequence

Spread Spectrum (DSSS) modulation allowing signiﬁcant gains

in data throughput compared to traditional FHSS devices.

This allows end users to beneﬁt from 900MHz transmission/

propagation and high data throughputs in distance

applications.

Coding schemes

(eg CCK, OFDM)

prepare the data

helping to combine

multiple bits for

DSSS transmission.

802.11 2007 for Wireless LANs

Wireless modulation transmission technique (ie DSSS with chipping key).

All DSSS require good SNR’s to be effective.

Chipping key helps

spread the data for

DSSS transmission

(multiple channel

simultaneous data

transmission).

Chipping keys and

coding schemes

help to reformulate

the data.

DSSS devices use both coding schemes and chipping keys to spread the data

and reform the same data allowing greater data communications throughput.

Summary

ELPRO’s 945U-E innovative design allows distance

communications with greater data throughput, providing

end users with an alternative option where higher frequency

Ethernet products may not be suitable (eg IP/PTZ cameras).

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