considerations on how to build your network infrastructure to support wireless applications


AbstractPlant-wide architectures increasingly use IEEE 802.11 wireless networks for critical Industrial Automation and Control System (IACS) applications. This technical session reviews the wireless LAN (WLAN) design and implementation considerations within the Cisco® and Rockwell Automation® CPwE architectures.Learn about the CPwE WLAN framework, wireless technology, Unified vs. autonomous WLAN, and Stratix 5100™ WLAN Access Point (AP) / Workgroup Bridge (WGB).Prior attendance of the Building Converged Plantwide Ethernet Architectures session is recommended.


Technology OverviewBenefits of industrial wireless network

Connection to hard-to-reach and restricted areas Integration of machines / skids

Remote diagnostics Intelligent assets

Lower installation and operational costs Cabling reduction, elimination of cable failures

Equipment mobility New and more efficient machine designs


Technology OverviewBenefits of industrial wireless network

Workforce mobility improves effectiveness Operators can trend/write back from a mobile

device when they step away from machine Engineering and Maintenance can see and

react to system alarming and production data from anywhere, anytime

Industrial IT provide secure infrastructure and multi-platform support


Technology OverviewChallenges of wireless communication

Half-duplex shared medium: Only one radio can transmit on a particular

wireless channel A radio cannot transmit and receive at the same

time on the same channel Higher latency, jitter and packet loss compared to

wired Ethernet Media contention, collisions and interference Can be minimized but not eliminated


Technology OverviewChallenges of wireless communication

Wireless coverage area cannot be precisely defined Site survey is required Spectrum sharing and security concerns

Signal quality may change over time Interference sources and obstructions Unauthorized transmissions

Wireless advantages > challenges when• WLAN is designed and maintained properly• Used for appropriate applications


Autonomous WLAN ArchitectureOverview

WGB

Autonomous AP

…

SSID15 GHz

Autonomous AP

…

SSID25 GHz

WGB

WGB

• Each autonomous AP is configured and managed independently

• Standalone IACS applications• Small number of APs and clients• Typically non-roaming clients• WGB mode is configured on the

autonomous AP only

WGB

Stratix 5100™ Wireless Access Point and Workgroup Bridge

http://ab.rockwellautomation.com/Networks-and-Communications/Stratix-5100-Wireless-Router


Identity Service Engine (ISE)

Cisco Prime® Infrastructure

Connected Mobile Experience (CompactLogix™)

Unified WLAN ArchitectureOverview

• Lightweight APs (LWAPs) are configured and managed by a Wireless LAN Controller (WLC)

• Plant-wide coverage and roaming• Plant-wide mobility and RF policies• Advanced security policies• Advanced spectrum analysis,

Location Based Services (LBS), wireless Intrusion Prevention

Note: Stratix 5100™ in WGB mode can join a Unified WLAN as a client to an LWAP

WGB

LWAP

…

SSID15 GHz

SSID25 GHz

WLC

LWAP

…WGB

LWAP LWAP

WGB (Roaming) WGB

SSID32.4 GHz


Selecting the WLAN Architecture

Large number of APs (>10) Plant-wide coverage for variety of applications

and clients Existing Unified WLAN in Enterprise Zone Applications require fast wireless roaming Managed jointly by IT and control engineers –

greater level of expertise Additional services: RF analysis, Location

Services, Wireless Intrusion Prevention

Small number of APs (<10) Standalone applications (machines),

mostly WGB clients Ad hoc WLAN installation Applications with no fast roaming Managed mostly by control engineers – lower

level of expertise May achieve better performance with real-time

EtherNet/IP traffic

Unified WLAN Autonomous WLAN


Application RecommendationsChoosing an Appropriate Application

IACS Traffic Type CIP Standard Use with Wireless Considerations

Supervisory information and diagnostics, peer-to-peer messaging

CIP Class 3 (HMI)CIP Class 3 (MSG)

Yes Need to control bandwidth if combined with CIP Class 1 Standard and Safety traffic

Peer-to-peer ControlI/O Control

CIP Class 1 Produced/Consumed Distributed I/O

Yes Application should tolerate occasional high latency, jitter and dropped packets;Packet rate restrictions

Safety Control CIP Safety Yes Fast safety reaction times may not be supported

Time synchronization CIP Sync Application Dependent

Accuracy and reliability can be optimized in specific configurations

Motion Control Integrated Motion on the EtherNet/IP™ network (direct drive control)

No Not feasible due to higher latency and jitter and limited CIP Sync accuracy


Conclusion Wireless communication brings many advantages to IACS applications Wireless advantages > challenges if WLAN is designed and maintained

properly Select appropriate wireless technology and WLAN architecture based on

requirements Following the application and WLAN recommendations is essential for

successful deployment and operation Security, spectrum management and site survey are critical

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