A simple radio link can be constructed from a single Access Point (infrastructure mode). The Access Point provides an Industrial Ethernet interface for connection to the wireline network. Stations, such as mobile controllers or a Field PG can move freely within the radio link and exchange data with other stations through this Access Point.

If the radio link of a single Access Point (radio cell) is insufficient, it can be expanded by further Access Points. The individual radio cells must overlap so that moving stations can be passed seamlessly from one Access Point to the next (roaming). This is performed invisibly to the application. The Access Points must be able to exchange data over Industrial Ethernet if a wireless distribution system (WDS) is not used.

If the Access Points are not connected to Industrial Ethernet using a wired connection (e.g. no cable route available for data line), the operating mode "Wireless Distribution System" must be selected. In this case an Access Point from the SCALANCE W-780 product line can communicate with up to eight other Access Points which are not connected to the data network by a direct wired connection. Directional additional antennas can be used to achieve ranges of several thousand meters outdoors.

Apart from a reliable radio link, the SCALANCE W-780 Access Points are characterized by excellent support from IT mechanisms:

• IEEE 802.11b/ g/ a/ h for different frequency ranges
• IEEE 802.11e for multimedia, wireless multimedia (WMM)
• IEEE 802.11i for security
• Construction of redundant networks with the Rapid Spanning Tree Protocol (RSTP)
• Virtual networks (VLAN) to logically separate, for example, different user groups
• Sending the log entries of the SCALANCE W devices to a Syslog server
• In client mode:
  Network and Port Address Translation (NAT/PAT) (mapping of private IP addresses and ports onto public addresses)
• Modern security mechanisms (e.g. network security such as IEEE 802.1x, RADIUS, EAP mechanisms)

Security

A high degree of data security is achieved by means of the WPA2/IEEE 802.11i mechanisms. These define modern procedures that control a regular exchange of the complete 128-bit code as well as performing the access check (authentication) of a station. The Advanced Encryption Standard (AES) is available for data encryption. All encryption mechanisms are integrated in the products and do not incur any additional costs.

Access to the devices (HTTPS) is encrypted and secure logon (SSH) is possible. If a security concept with Virtual Private Networks (VPN) or the SCALANCE S range is required, the products can be integrated without any difficulty.

iFeatures (only for RR versions of the Access Points)

iPCF (industrial Point Coordination Function)

The iPCF mode is recommended for applications with a requirement for real-time and predictable response times (deterministic response), even during roaming of moving stations from one access point to the next. This ensures that wireless PROFINET IO is supported and that safety-related signals, e.g. Emergency Stop, can be integrated into the radio link. This means that even video signals from moving stations can be transmitted with a high level of quality.

The iPCF mechanism expands the IEEE 802.11 standard and must be available on both the station and the Access Point (e.g. SCALANCE W788-1RR). In a radio link in which iPCF is used, no IEEE 802.11-compliant stations can be operated.

iPCF is recommended for applications where radio network nodes move along predefined paths (e.g. suspended monorail). RCoax leaky wave cables or directional antennas must be used for this purpose.

Note:
The IWLAN/PB Link PN IO network transition also supports iPCF

iPCF-MC (iPCF Management Channel)

iPCF-MC is available as further development of iPCF. This mode should be used if IWLAN stations that also support iPCF-MC (e.g. Client Modules SCALANCE W747-1RR, Mobile Panel 277F IWLAN) move freely about in the coverage area (especially when using omni-directional antennas) and are to exchange data deterministically. This functionality can only be implemented in combination with RR Access Point versions with at least two radio interfaces.

Note:
Due to the lower bandwidth when using iPCF-MC, we recommend the iPCF mode for transmitting video signals.

Roaming of a mobile panel between two access points while maintaining error-free communication with iPCF-MC

iHOP

With the supplementary function iHOP, the Access Point changes the channel in coordination with its clients. If it detects interferences which are caused, for example, by sporadically active WLANs on a channel, it avoids the affected channel temporarily. Hopping to the other channel is carried out so rapidly that usually the application is not impaired by the channel change. If the interferences occur throughout the complete frequency band, it is even possible to change to another frequency band (e.g. from 2.4 to 5 GHz). This guarantees reliable communication even with interferences in the radio field.

Note:
These iFeatures cannot be used in parallel.

Coordinated changing of channels by means of a channel hopping procedure (iHOP) to avoid disrupters

SCALANCE W-788 product variants

SCALANCE W788-1PRO
with an integrated radio card

SCALANCE W788-1RR
with an integrated radio card and additional functions

SCALANCE W788-2PRO
with two integrated radio cards

SCALANCE W788-2RR
with two integrated radio cards and additional functions

The SCALANCE W-788 Access Points are ideally suited to industrial applications and cabinet-free installation. The devices can be installed at the location that is most favorable for the radio link. The housing and the connectors resist high levels of shock and vibration loading because all the connections are screwed or latched. To achieve optimal illumination for special applications, the supplied antennas can be replaced. SCALANCE W-788 Access Points can also be operated as stations (clients). As an alternative, the SCALANCE W-740 client modules can be used for this mode.

The devices with two interfaces have two separate radio modules and behave like two separate devices in the radio network. This feature can be used to implement cost-effective solutions, e.g. when a radio interface is used for wireless connection of a distant production site and the second radio interface provides a radio link at the Access Point. Local stations can log in here and move around freely. Two separate radio modules also offer many different possibilities for providing redundant radio links, so that a high level of operational reliability can be achieved.

Roaming of moving units (e.g. Field PG and mobile controller) in a radio network with two Access Points

Stations, e.g. a Field PG M, can move freely in the radio field of the SCALANCE W788-1PRO access points for mobile HMI. In addition, SCALANCE W746-1PRO connects mobile HMI, controller and PC units wirelessly to the data network.

The IWLAN radio coverage of SCALANCE W788-1PRO permits S7 communication and open communication between the devices on the AGVs and stationary S7-400, as well as on the stationary SIMATIC HMI device.

Provided that a delay (several 100 ms) caused by roaming in accordance with IEEE 802.11 is tolerated by all communication stations when switching the radio cells, the communication continues uninterrupted.

If very fast update times are necessary, e.g. for PROFINET IO communication, access points and client modules that support the iPCF function for very fast roaming and deterministic data traffic are to be used, for example SCALANCE W788-1RR and W747-1RR.

When an extremely reliable radio link is essential, it is recommended that the RCoax Cable is used as an alternative to conventional antennas. This radiating cable is a special antenna along which a radio link propagates and which is therefore suitable for applications in which, for example, stations move along a rail but must be connected to the data network contact-less to prevent wear from trailing conductors.

The Field PG accesses a radio interface of SCALANCE W788-2RR for configuring, the other interface carries out communication with the RCoax cable using iPCF.

The dual Access Point, SCALANCE W788-2RR, can provide two separate radio links. In one a Field PG can log on for configuration for example. For clear separation of the applications an RCoax cable can be used to implement contactless PROFINET I/O data communication with the mobile suspension gear over an IWLAN/PB Link.

SCALANCE W-786 product variants

SCALANCE W786-1PRO
with an integrated radio card;
variants are available with:

• Two internal antennas
• Two external antenna connections
• RJ45 connection
• Fiber-optic cable connection

SCALANCE W786-2PRO
with two integrated radio cards;
variants are available with:

• Four internal antennas
• Four external antenna connections
• RJ45 connection
• Fiber-optic cable connection

SCALANCE W786-3PRO
with three integrated radio cards;
variants are available with:

• Six external antenna connections
• RJ45 connection
• Fiber-optic cable connection

SCALANCE W786-2RR
with two integrated radio cards;
variants are available with:

• Four internal antennas
• Four external antenna connections
• RJ45 connection

The devices of the SCALANCE W-786 product line are functionally identical to those of the SCALANCE W-788 product line, but they are particularly suited to applications with stringent climatic requirements for mounting outdoors and in public areas.

Where access points with three radio modules (e.g. W786-3PRO) are used, communication between the access points is implemented with two modules each. The radio field for the station, e.g. an automated guided vehicle, is established by the third radio module. This means that larger directional radio paths can be established and communication with the stations is also possible.

Programming of robots in the safety-related environment

In this configuration three effective ranges are defined, in which robots can be programmed using the Mobile Panel 277F IWLAN (teaching). If a fault occurs during the programming, e.g. on leaving the safety-related areas or in the case of unforeseen incidents, the plant is brought to the safe state with the aid of the integrated emergency-stop procedure using the IWLAN structure implemented with SCALANCE W786-2RR. The safety of the entire plant is achieved by means of PROFINET with the PROFIsafe protocol which is implemented not only on the PROFINET controller (CPU 317F-2 PN/DP ), but also on the PROFINET device (Mobile Panel 277F IWLAN ). The SCALANCE W786-2RR that has the iPCF mechanism ensures that the response times necessary for the functional safety are adhered to.

If the minimum length of standard Ethernet cables is insufficient due to the large distance of the access points from the wired network, SCALANCE W-786 can also be fitted with fiber-optic connections (multimode). This allows for distances up to 3000 m.

Implementation of the SCALANCE W-786 product line in sectors that are subject to high climatic requirements

In the case of SCALANCE W-786, this only concerns access points which can, however, be configured as client modules through Web-based management. Then, depending on the selected variant, a maximum of one radio module will be available as a client.

SCALANCE W-784 product variants

SCALANCE W784-1
with an integrated radio card

SCALANCE W784-1RR
with an integrated radio card and additional functions

The devices of the SCALANCE W-784 product line have the same functions as SCALANCE W-788PRO Access Points, but are very well suited to applications in which IWLAN must be applied in low-space cabinets or must be integrated in devices. These are an inexpensive alternative, especially for use indoors, i.e. under less harsh conditions. The rugged aluminum housing with degree of protection IP30 provides protection against mechanical and electromagnetic stress in industrial areas.

SCALANCE W-784 Access Points can also be operated as stations (clients). As an alternative, the SCALANCE W-740 client modules can be used for this mode.

In combination with the SCALANCE W-740 Client Modules with degree of protection IP30, an infrastructure can be set up in which great temperature differences and protection against dust and water play a somewhat less prominent role.

Implementing an automatic guided transport system in a radio link with SCALANCE W784-1RR and RCoax cable.

The mobile automated guided vehicles are integrated in the IWLAN radio link over the SCALANCE W747-1 Ethernet Client Modules. Both the Access Points and the Client Modules are in the control cabinet.

Diagnostics and management

• Web-based (HTTP/HTTPS) management tool for configuration and diagnostics using a standard browser
• Planning, configuration, simulation and measurement of the radio link on site (Site Survey) with SINEMA E
• LEDs for signaling operating states and fault conditions
• Signaling of faults by means of SNMP trap or e-mail to a network management tool
• Optional swap medium C-PLUG (Configuration Plug) for easy replacement of the module without a programming device in the event of a fault