Industrial Wireless LAN I-Features, Applications, Examples

Transcription

1 Industrial Wireless LAN I-Features, Applications, Examples

2 Aims: This White Paper explains the technology of Industrial Wireless LAN and its special features compared with Wireless LAN according to IEEE It also outlines applications and provides examples of use in industry. The White Paper is completed by a description of the products available today and the products and technologies of the future. Note: Wireless LAN based on the IEEE standard and further wireless technologies will be dealt with in a separate White Paper The information in this White Paper is as of Autumn 2004 This symbol highlights references to SIMATIC NET products or special SIMATIC NET solutions Published by Siemens AG Automation and Drives Group SIMATIC NET Industrial Communication Subdivision P.O. Box Nuernberg, Germany Further Support: If you have additional questions, please contact your local Siemens representative. You will also find SIMATIC NET on the Internet at

3 Aims:... 1 Aims:... 2 Introduction... 4 Reliable... 4 Robust Construction... 5 Data Security... 5 Industrial Wireless LAN... 7 I-Features (Industry Features)... 7 Robust Construction and Connectors Influence of Other Wireless Technologies Safety-related Signals in Industrial Wireless LAN Applications of an Industrial Wireless LAN in Automation Engineering Applications Examples SIMATIC NET Products for Industrial Wireless LAN Access Point SCALANCE W788-1PRO Dual Access Point SCALANCE W788-2PRO Ethernet Client Module SCALANCE W744-1PRO PC Card CP PCMCIA Card CP Power Supply PS791-1PRO FC Modular Outlet Power Insert...40 Accessories Future Products from SIMATIC NET Industrial Wireless LAN RR Applications for Industrial Wireless LAN RR SCALANCE W788-1RR SCALANCE W788-2RR Ethernet Client Module SCALANCE W747-1RR IWLAN/PB Link PN IO IWLAN RCoax Cable Antennas Glossary... 50

4 Introduction Wireless networks are becoming more and more popular. They allow a high degree of flexibility reducing costs during installation and operation of a plant. They are therefore used in many areas such as Manufacturing and process automation Foodstuffs and beverages Storage/logistics Transport (railway/road) Crane erection Without with a wireless link to the communication network, many applications with moving equipment are impossible or can only be implemented much less efficiently. Drag chains and slip rings that are liable to wear and tear are no longer necessary. Moving vehicles involved in data communication are no longer restricted to fixed tracks that require considerable effort to modify. In a wireless network, production and service data is available practically everywhere within the company. It can be acquired and modified simultaneously. During commissioning, engineers can observe actions affecting the entire plant directly on-site. Reliable In industrial applications, operating reliability is of particular importance. It demands the use of extremely reliable products providing mechanisms for real-time support (guaranteed transmission times) and deterministic characteristics (predictable data traffic). This means that devices such as programmable controllers (PLCs) can transfer their data reliably even in critical situations. The wireless standards from the IEEE working group (to which the Wi-Fi seal relates) provide only limited options. The methods of the IEEE standard can be taken as a good basis that can then be optimized for industrial application. This is achieved with the I-features of Industrial Wireless LAN in the products of SIMATIC NET. These features represent an expansion of IEEE and are fully compatible; in other words, devices complying with IEEE (and having, for example, the Wi-Fi seal) can be used in an Industrial Wireless LAN radio cell. Apart from the use of reliable products, operating reliability is also achieved by optimum planning and installation of the wireless link. With a measurement report of the field strength

5 values of the intended wireless network, the customer is confident even in the face of dynamic disturbances. There must be an adequate budget reserve even when a moving fork lift truck carrying large metal containers causes reflections and shadows that change the wireless link. Robust Construction Apart from being "reliable", a robust construction is an important requirement of the industrial customer. This is reflected in housings, that are dust- and waterproof. As a result, devices can be set up centrally without a switching cabinet and therefore allow maximum flexibility. This installation flexibility, however, has a further important aspect. Often, the simplest location for installation (for example in a switching cabinet) is not the ideal location from a wireless transmission perspective. As a simple illustration of this, a switching cabinet functions like a Faraday cage and traps radio waves. It would be possible to install a distant antenna on the roof of the switching cabinet but it must be remembered that the coaxial cable connecting the antenna and device attenuates valuable output power. This is not the case when this coaxial cable is not required for additional antennas because the ideal location in terms of wireless transmission can be selected and the antennas supplied with the product can be used. Data Security The question as to the degree of security often depends on the security policy of the company that prescribes clear rules. In this case, encryption of the data transmitted is important since the data traffic on a wireless link can be tracked using directional antennas. However, it is not enough simply to encrypt the data. Even before any data traffic takes place, it is necessary to establish that the correct partners are taking part in the communication. The question "Who are you?" is handled in suitable authentication protocols. At the same time when this question is clarified, the question "What am I allowed to do?" (authorization) can also be decided. Whatever shape the security solution takes, it is important that the products used are standardized and do not include proprietary procedures. The more publicity given to a security solution, the faster hackers will find possible loopholes. An open standard provides protection for investment (interoperability between different providers) and a high degree of data security. In contrast to other providers (for example Cisco's LEAP protocol), Industrial Wireless LAN uses only mechanisms that

6 are precisely defined in the standard of the IEEE and the specifications of the WECA (for example, PA). For this reason, this White Paper does include information on this topic and the reader is referred to the separate White Paper on the IEEE standard.

7 Industrial Wireless LAN Industrial Wireless LAN from SIMATIC NET provides not only data communication according to the IEEE standard but also numerous expansions (I-features) that are extremely useful for industrial customers. I-Features (Industry Features) If wireless communication is used in industry in production and manufacture, the reliability of the wireless channel becomes an important issue. In contrast to a consumer environment, machine downtimes involve high costs. To increase operating reliability, Industrial Wireless LAN from SIMATIC NET provides additional functions. Antenna Diversity Operation with 2 Antennas If radio is used in the productive sector of a plant, diversity antennas should be used. With this technique, it is possible to achieve a significantly more reliable wireless link in a "difficult" environment in which reflections and multipath reception interfere with wave propagation. The use of antenna diversity is easy to recognize because two antennas are available for one wireless card. The recipient can then evaluate the information from two different antennas and select the better antenna dynamically during reception. When transmitting, the diversity function automatically selects the other antenna after a set number of failed attempts. Monitoring the Wireless Channel In the IEEE standard, monitoring of the quality of the wireless link is required. This factor, however, has a considerable effect on reliability. If a mobile device is used for diagnostics or monitoring of a machine (in a comparatively slow process), is important that the management level knows whether or not the device is still capable of performing the task.

8 Figure 1: Monitoring the wireless channel between an Internet Pad moving from location A to location B that leaves the area covered by the access point If, for example, as shown in Figure 1, the Internet Pad MOBIC loses radio contact, it is important that the controller at the management level is informed of this and can take over control of the process. This situation can occur when the wireless channel is badly degraded or when the client simply moves out of the cell (in Figure 1, this is location B) and no longer has radio contact. The access point must then, for example, send an SNMP trap to the network management system or an E- mail. As an option, a software block can also be used in the controller to query the status of the client cyclically. In Industrial Wireless LAN, two methods are available with which monitoring of the wireless channel can be implemented. Link Check When the link check is used, if there is no communication taking place, frames are sent to the node at selectable cyclic intervals to check its presence in the wireless network. This

9 method somewhat reduces performance but provides a high degree of operating reliability. IP-Alive IP-alive monitors the cyclic communication connections that are extremely common in automation engineering environments. On selected IP connections, the monitoring function checks whether packets are actually exchanged at the times prescribed by the cycle time. If packets are missing, errors can be reported in various ways just as with the link check mechanism (error LED, log file, , SNMP trap). The user can configure the method of reporting to suit the situation. Deterministic, Real-Time Wireless LAN implemented according to IEEE provides a powerful wireless connection that can be used as it stands for many applications in the office and home environment. Unfortunately, the standard does not support applications with real-time and deterministic requirements. Wireless LAN according to the IEEE standard is a "shared medium" in which all stations must share access to the common medium. While this access is controlled, it is not fully predictable. Reservation of the Data Rate With this method, Industrial Wireless LAN provides the option of guaranteeing both a minimum data rate and a "worst-case" transmission time for selected clients (Quality of Service, QoS). These parameters are negotiated prior to communication. Example 1: Cyclic data traffic If the configuration engineer of an automation application wants to be sure that a node is capable of sending a 64-byte long packet every 50 ms over the Industrial Wireless LAN link to the central controller, the following parameters must be configured: 1. Transmission time (response time) Less than 50 ms, so that data does not "pile up" at the node. After 50 ms, the last bit of the previous packet must have been transmitted so that the next 64-byte packet can be transmitted. 2. Data rate (bandwidth) If 64 bytes are to be transmitted in 50 ms, a data rate of at least (64 bytes x 8 bits) / 50 ms = Kbps must be set. These two settings guarantee that the wireless channel is not a bottleneck in the system and that the cyclic data traffic of the node can be forwarded smoothly to the central controller.

10 Example 2: Transfer of files If the node has a file with a size of 1 Mbyte for transmission, a predictable transmission duration can be achieved with the following settings: 1. Transmission time (response time) Since a time in the seconds range can be expected, the latency of the wireless channel is not a major factor. A time of 500 ms can be selected here. 2. Data rate (bandwidth) If a data rate of 500 Kbps is set, the entire file will be transmitted in (1 Mbyte x 8 bits) / 500 Kbps = 16 s. That individual packets could theoretically have a latency of up to 500 ms does not play a major role. The following constraints should be taken into account when reserving the data rate: 1. The data rate setting is based on the net data rate of the Ethernet connection. The protocol overhead due to wireless transmission does not need to be taken into account. 2. When a wireless station is handed over to a different cell, a station only takes the transmission time and data rate attributes with it when it is also configured as "critical client" on the new AP. However, at the precise moment of the handover from one cell to the next, delays occur because the station is extremely busy logging on at the next access point. This phase can take up to several hundreds of milliseconds. During this time, there is no productive data traffic. In a future further development of Industrial Wireless LAN, this property will be improved making handover times less than 20 ms possible. 3. If a critical wireless station is assigned a transmission time and data rate, this does not mean that its performance will not be better in a cell that is not being fully utilized. Example: A single station in a 2.4 GHz, 54 Mbps cell has the attributes 100 ms and 500 Kbps. This station naturally has the entire bandwidth of the wireless channel available when there are no other stations in the cell. 4. Cyclic data exchange is possible in both communication directions: Both from the station to the access point (upstream) and from the access point to the station (downstream). 5. Comparable methods of other manufacturers simply provide prioritization of data streams of one category. This means,

11 for example, that the entire voice traffic has priority. Priority assigned on a device basis is then not possible. In many cases, these methods also provide prioritization of downstream data. Figure 2: By reserving time slots for stations with timecritical data, productive communication presents no problem To illustrate the mechanism described above, let us assume an access point at which 6 stations are logged on (Figure 2, client 1 through 6). If an application requires that clients 1, 2, and 3 (for example mobile controllers) interface with the factory network over the Industrial Wireless LAN, it must be guaranteed that these controllers can send a status message at fixed, cyclic points in time. This is possible only if an additional mechanism is available to assign the right to transmit. By reserving the data rate in SIMATIC NET, in the example above, clients 1 and 3 have the opportunity to access the access point in the first phase although clients 4 and 5 obviously have large files to transmit. This is followed by a period in which all other stations have their turn according to the normal rules. In Figure 2, this is first client 5 and then client 6. This is once again followed by the phase in which the stations with a reserved data rate can access the access point. In the schematic in Figure 2, it is also clear that client 4 is a "victim" of the IEEE access method. Since it is not a client with previously configured assured performance (QoS), it must wait until clients 5 and 6 have transmitted their data. Figure 2 also makes it clear that within an Industrial Wireless LAN, there is both standard-compliant Wireless LAN traffic as well as prioritized wireless traffic. It must be emphasized that any IEEE compliant device can be included in the prioritized wireless traffic and that it is not necessary to use only client products of SIMATIC NET. If there is both IEEE traffic as well as prioritized traffic in the cell of an access point, remember that the performance of the standard traffic deteriorates disproportionately since the prioritized data traffic also requires bandwidth for its administration. This response was tested in an analysis performed by ComConsult.

12 ( rodukte/2004_07_comconsult_siemens_iwlan.pdf) Forced Roaming The IEEE standard in no way specifies that an access point must be connected to the wired network over Ethernet. Moreover, it is not even specified that a wired network must be available at all. This means that a station in the cell does not immediately recognize whether or not the wired interface is impaired or interrupted. Such a fault has far-reaching consequences if the station is a mobile controller that sends important process data to the control room. Figure 3: Forced roaming of a station if the wired interface to the logged-on access point is interrupted If the wired interface to access point 1 is interrupted in Figure 3, the access point detects the fault and automatically turns off its

13 cell (prerequisite: the user has selected this option in the Web interface of access point 1). If the cell is designed redundantly (overlapping cells), the station roams to the next available access point (AP 2). Without this mechanism, there is no way that the mobile controller can keep up the connection to the controlling computer. Note: This mechanism must not be confused with the redundancy mode. Difference in this case: Point-to-point link Dual access point Switchover from one wireless card to another within a dual access point Storm Threshold In communication networks, a not insignificant amount of traffic is generated by multicasts and broadcasts. If such messages get the upper hand, there is a danger that productive data traffic will be restricted. This problem in a communication network is not countered by the Industrial Wireless LAN cell, but must be handled in the devices themselves. To achieve this, the SCALANCE W products provide the "storm threshold to prevent overload and to restrict multicast/broadcast traffic to a maximum value. Events A significant cost factor in industrial plants is the effort required for service and maintenance. Here, there is a considerable potential for saving when device malfunctions and their causes can be recognized in good time. Apart from errors, it is also helpful if important steps during configuration are logged and are available for later scrutiny. Restart/hot restart Connection to Ethernet Error in authentication (Who am I? - Who is logging on?) Power supply Monitoring of the wireless link Reservation of the data rate possible/not possible Redundancy mode Figure 4: List of error states and the events detected by SCALANCE W products From our perspective, it is not adequate to simply detect the error and status; suitable reactions must also be triggered. To allow this, SCALANCE W products provide mechanisms such as

14 Error display (LED) on the device Sending of s SNMP traps Logging in a buffer that can be read out later All the methods of indicating problems can be activated or deactivated apart from a few serious errors that are always logged and signaled by the fault/error LEDs. Wizards A system can only be as reliable as allowed by the configuration created by the commissioning personnel. The best mechanisms will not help if the parameter assignment and configuration is complicated and can only be undertaken by experts. This applies, in particular, to settings relating to data security. Unfortunately, standardization has moved very quickly in this respect so that the current mechanisms are not adequately known by everyone. In such situations, it is important that the customer be supported with online help and wizards. If users make the proposed settings of the basic wizard and security wizards with SCALANCE W products in the specified in order, they can be sure that the Industrial Wireless LAN cell has a suitable quality and that no necessary parameters have been forgotten. Wireless Distribution System, WDS If an Industrial Wireless LAN needs to be upgraded in a plant, it is sometimes not possible to connect the access points over Ethernet to make communication beyond cells possible. Possible reasons: Temporary equipment required for commissioning Cable channels cannot be expanded or do not exist Installation difficult (for example in a sandpit) In such situations, the access points can be used in the Wireless Distribution System mode without being wired.

15 Figure 5: Although the access points are not wired, it is possible for the two stations (laptop and controller) to communicate with each other In WDS mode, it is important that an access point can "see" its neighbors (otherwise the chain would be interrupted!). This can make it necessary to use special, distant antennas instead of the supplied antennas. As shown in Figure 5, stations are perfectly capable of taking part in wireless operations in this mode. One important property emerges from its; namely, that stations and access points must share the entire data rate available. This situation can be made more critical because in WDS mode, ALL access points and stations work on the same wireless channel (for example g and channel 1, 2,4 GHz at 54 Mbps). This restriction does, of course, have consequences for applications. Applications in which a high data rate is necessary for large numbers of stations (for example a hot spot on a trade fair site) should be avoided. In applications, on the other hand, in which controllers (several 100 Kbps) or HMI (several Mbps) access the wireless network, and seldom download large files for configuration, a bottleneck is not normally to be expected. The performance of the wireless infrastructure in Figure 5 can be improved if dual access points (SCALANCE W788-2PRO) are used (see Figure 6). One wireless card can then be used to set up the wireless infrastructure (backbone) and the other wireless card provides the stations with a cell at the location of the dual access point with which they can access this wireless infrastructure. Once again, it is possible that special distant antennas may be required.

16 Figure 6: Wireless distribution system with dual access points to improve the performance of the cell Another useful application of WDS is when several outlying plant sections need to be interconnected. This could, for example, be several docks on the premises of a shipyard that need to be connected over wireless since cables are unwanted. Figure 7: WDS in the wireless networking of four plant sections A central access point and one wireless card in each of the four dual access points implement a WDS. The central access point is used at the same time as an interface to the wired network. As shown in Figure 6, the dual access points implement a "local" wireless network at the location where they are installed, and this is used as a wireless interface by the stations. WDS therefore once again provides the backbone of the wireless infrastructure.

17 Bridge Operation, Redundancy Mode In industrial environments, it is often the case that an outlying part of the plant is connected to the communication network over a point-to-point link. For this situation, the products of SCALANCE W provide the option of a bridge mode - a special wireless distribution system application. Here, directional antennas are often used so that the wave propagation is optimized for the point-to-point link. To interface the outlying part of the plant, the full bandwidth of the Wireless LAN is available if only the directional wireless link is used. Figure 8: Bridge operation between two plant sections. To increase reliability, the redundancy mode is used In Figure 8, the two communication networks must be connected (Note: In this situation, communication network means a large network with lots of stations. To keep the situation clear, only one controller is shown in the network). Two SCALANCE W access points are used. For a directional wireless link, no further stations can be included in their cells. Redundancy Mode The wireless link in Figure 8 connects two important parts of a plant. This means that vital data is transported over this backbone. Interference of the wireless link would have serious consequences for the entire plant. The I-feature of SCALANCE W used here ensures that the data communication is handled not over one wireless card but also over a second card that handles the same data stream. In this mode, a dual access point must, of course, be used (SCALANCE W788-2PRO). The reliability of the data transmission becomes clear when one card operates in the 2.4 GHz band and the other in the 5 GHz band (taking into account transmit power permitted in specific countries). However, it is not even necessary to change to a different frequency band. Even using channel 1 and channel 11 at 2.4 GHz, means that the data streams are so far from each other that there is hardly a disturbance that would cause problems in both channels. It must be stressed that this technique is fully transparent for the application and that the

18 access points negotiate which card is currently active and which is in "hot standby mode. If a problem occurs, switchover times from 20 ms to 25 ms can be achieved. This response was tested in an analysis performed by ComConsult. ( rodukte/2004_07_comconsult_siemens_iwlan.pdf) Redundant Wireless Infrastructure, Spanning Tree (ST) To provide protection against the failure of a wireless infrastructure, and to improve the reliability of a wireless network even further, it is also possible to use a ring topology instead of the normal star topology. Such a structure can also be used to back up a wired network with a wireless network in risky areas. Figure 9: Setting up a ring structure with WDS to increase protection against failure of the wireless network using the Spanning Tree algorithm Figure 9 represents a further development of the structure from Figure 6. The difference is that in Figure 9, the ring is closed at the last dual access point. To avoid loops in such a wireless infrastructure, the Spanning Tree algorithm is used. As a result, in Figure 9, it is possible to select the path for the data from the wired network in cell 2 over the dual access point in cell 1. If, however, there is a serious disturbance on the WDS link between the dual access points of cell 1 and cell 2, the ST

19 mechanism ensures that the wireless network automatically looks for a new path. In the figure above, this is the path over the dual access points of cell 3 and cell 4 a redundant wireless network is implemented. A precise analysis of the time response of such a system can be found in an analysis by ComConsult. ( rodukte/2004_07_comconsult_siemens_iwlan.pdf) Robust Construction and Connectors The major characteristics of wireless devices for use in industry are not only high-quality and reliability of the wireless channel but also their rugged construction and the choice of connectors. Metal Housing For wireless products, the robustness provided by a metal housing and a high degree of protection (for example IP65) are particularly important. Generally, the simplest location for installation is not the optimum location for wireless transmission. A switching cabinet is a Faraday cage that "traps" radio waves. The only remedy here is to use a distant antenna installed, for example, on the roof of the switching cabinet. Unfortunately, the coaxial cable connecting the antenna and the device attenuates the sensitive radio signals and valuable output power is lost along with a certain degree of reliability. It is better if the cable to the distant antenna is unnecessary because the device itself is installed at an ideal location for radio transmission and the antenna supplied with the device can be used. This also saves money. The robust construction is required not only to allow an optimum location for the wireless channel, but also keeps the device functionally in a hard everyday industrial environment. This is reflected in housings that are dust and waterproof up to degree of protection IP65. As a result, devices can be set up centrally without a switching cabinet and therefore allow maximum flexibility. Expanded Temperature Range If additional thermal resistance is added to this defined protection against dust and water and the permitted temperature range extended, the products can also be used outdoors. An expanded temperature range is not only significant for outdoor use; installation under the roof of the factory or in unheated logistics areas can lead to considerable thermal stress.

20 Condensation Protection against dampness is particularly important when devices are operated in sub-zero temperatures (Celsius). If the device provides protection "only" against sub-zero temperatures, this by no means guarantees protection against condensation. If the temperature falls below zero in the building, for example, when the gates to the workshop are opened, the humidity in the workshop condenses immediately on and in the device. If the device, however, is encapsulated so that humidity cannot enter, this risk is avoided. Summing up, we can say that in such situations, only products can be used that are fully operable in negative temperatures and that also have a high degree of protection (for example IP65). Vibration and Shock Apart from the construction, resistance to vibration and shock is necessary and must be proven in tests. This is particularly important because wireless is often used with moving devices. This cannot, of course, cope with every mechanical load, but such tests mean far greater operating reliability than is available with office and home products where the price often plays a significant role. SCALANCE W products are subjected to special SIMATIC environmental tests. The mechanical load caused by turning or moving machine parts not only affects the device itself. It is also important that the cable connectors used are secured by screws or clamps to avoid the high costs that can result from a loose connector. In the SCALANCE W products, special measures have been taken in this respect. Figure 10: Locking mechanism of the hybrid connector

21 Industrial Approvals The Industrial Wireless LAN product line from SIMATIC NET is characterized not only by its robust construction. Naturally, industrial approvals such as EMC (electromagnetic compatibility), FM (Factory Mutual), UL (Underwriters Laboratories) and ATEX approvals for use in the petrochemicals industry and in hazardous areas are a matter of course. When used in paint shops, devices must be free of silicone. To avoid toxic vapors in the event of fire, there must be no halogens either in the device or cable. If the products already have these properties and approvals, this is an important factor for the customer and helps to avoid additional costs. Power over Ethernet Apart from the power supply, Ethernet data cables must also be laid to an access point. To be able to use only one cable and to reduce effort during installation, the IEEE 802.3af working group has defined the Power-over-Ethernet standard af allows two options: Power is modulated onto the data cable. In this case, 4 wires are adequate (phantom power) In one cable, four wires carry data and four wires carry power. In this case an 8-wire cable is required. Unfortunately, the IEEE 802.3af standard (that originated in the office environment) does not include voltages under 30 V DC. This is a disadvantage for the automation user because here, a power network of 24 V DC is common along with devices requiring 24 V DC power supplies.

22 Figure 11: Power and data over one cable for the simplified installation of an access point, even at 24 V DC SIMATIC NET provides a complete solution (incl. cables) so that customers with a 24 V DC supply voltage can also benefit from simple installation over one cable. In this case, we take advantage of the 802.3af option allowing power and data over 8 wires. This is made possible by the FC modular outlet power insert that brings power and data together on one cable. Apart from this mode, SCALANCE W, of course, supports the IEEE 802.3af standard with both options. Influence of Other Wireless Technologies When looking at the influence of other wireless technologies, we will pay particular attention to the three most successful technologies on the market (according to sales): GSM, Wireless LAN, and Bluetooth. GSM does not pose problems since the licensed frequency band cannot be expected to cause regular problems (GSM900: MHz and MHz, GSM1800: MHz and MHz). Moreover, in the frequency bands being used, no other services apart from GSM are permitted. (Note:

23 Wireless LAN uses the 2.4 GHz and 5 GHz frequency bands). The situation with wireless LAN and Bluetooth is different since both use the license-free ISM band at 2.4 GHz. The first point to make is that both the frequency hopping mechanism (FHSS) of Bluetooth and the Direct Sequence Spread Spectrum (DSSS) modulation technique are both resilient when it comes to interference. Frequency hopping involves a very fast change in transmission frequency and therefore "escapes possible interference on a specific frequency. In DSSS, there is powerful redundancy due to the spreading of the frequency spectrum and it is hoped that this spread will compensate narrow-band interference. (Note: Broad band interference affecting an entire frequency range is seldom with microwaves). During frequency hopping in Bluetooth, it is perfectly possible that one of the frequencies used is in the range of the wireless LAN band. Interference occurs, however, only when the power of the Bluetooth device is great enough and the redundancy mechanisms of wireless LAN can no longer correct the error. The decisive factor here is the physical distance between the Bluetooth transmitter and the WLAN receiver. It should be noted that the normal Bluetooth class 2/3 transmitter with a power of 1 mw only causes real performance problems in the immediate vicinity of the wireless LAN station. As explained below, a plant in which a Bluetooth network and a Wireless LAN are both used tends to be the exception. Users have hardly any benefits from the double investment since many applications of one technology can also be solved by the other. The solution may not be quite as good but adequate to make the high costs of a second wireless network unnecessary. This reduces the question of interference to unwanted radiation, for example caused by mobile telephones with an active Bluetooth interface. Here, system operators themselves must take measures to avoid problems occurring. Just as today in factories, there must be clear rules for the layout of the manufacturing area and the routing of cables or IP address assignment, it will also be necessary in future to control the active wireless systems used so that certain combinations of systems are not installed alongside each other. The responsibility for peaceful coexistence of the two technologies is, however, not simply pushed onto the user. There are, for example, positive approaches in the new specifications of Bluetooth. Here, methods are implemented that avoid frequencies already in use thus preventing interference of Wireless LAN. Bluetooth does not lose anything in performance because the frequency hopping mechanism simply omits these frequencies and concentrates on those not being used.

24 In Wireless LAN, similar mechanisms are implemented in the IEEE h standard. This specifies that a wireless network must first scan the entire frequency band for existing transmitters before starting to transmit (Dynamic Frequency Selection, DFS). A transmitter must also control its power output (Transmit Power Control, TPC) to avoid a "quiet" station being "shouted down" by the strong signal. The simplest way for Wireless LAN to avoid a collision with Bluetooth is to use the 5 GHz band. Here, there are no Bluetooth devices. Safety-related Signals in Industrial Wireless LAN The transmission of safety-related signals in Industrial Wireless LAN deals with products such as emergency stop buttons whose integration in a wireless network involves special requirements of the wireless channel. Products of this quality must also be certified by national safety organizations. Separation or integration If safety-related signals are transmitted over a wireless network, the basic question is whether or not these signals need to use a reserved network or whether they can be transmitted along with the operational data traffic. The implementation of a separate infrastructure is one traditional approach and has the following advantages: Reduced bus load System of less complexity Simplified troubleshooting Availability of the system Simplified certification

25 Figure 12: Separation of safety-related data (broken line) and operational communication (continuous line) Although the advantages of a separate network are its reduced complexity, these signals can also be implemented in an integrated concept. If a wireless network is designed so that it can transmit safety-related signals alongside operational data, this opens a new dimension in customer benefits: Reduction of planning and configuration effort Reduction of the installation and commissioning costs Uniform operation Reduced effort for infrastructure Higher flexibility

26 Figure 13: Safety-oriented data (broken line) and operational communication (continuous line) in one network An integrated wireless network is, of course, a great challenge in terms of technical implementation and also requires modification of Industrial Ethernet (Safety on Industrial Ethernet). The major benefits are in the uniform handling of communication. This significantly reduces life-cycle costs. Safety Standards The risk potential of a system is analyzed in the EN 1050 and EN 292 standards. Taking into account the specified risk, EN then describes the general guidelines for implementing safety-related parts of control systems and divides these into various categories. This division ranges from the lowest category B to the highest category 4. DIN V 19250, on the other hand, considers the fundamental safety aspects of measurement and control equipment. Once again taking into account the specified risk, these are divided into different classes from AK1 through AK8. On the other hand, DIN provides requirements and measures for safeguarded functions according to class. DIN V VDE 0801 and modification A1 must also be taken into consideration. They define fundamental aspects for computers in systems with

27 safety functions. Since the term computer is to be understood generally, this standard also applies to micro controller systems. IEC IEC is a relatively new standard. It deals with the functional safety of electrical, electronic, and programmable electronic safety systems and classifies them in safety integrity levels from SIL 1 through SIL 4. The still valid standards DIN V and DIN V VDE 0801 are included in this standard. Naturally, the generally valid standards for electrical safety such as EN or DIN VDE 0110 and the European directive on machines (98/37/EEC) as well as the EMC standards must not be forgotten. Safe Wireless with Industrial Wireless LAN The development of wireless transmission mechanisms for safety-related signals provides additional benefits for customers, for example in hand-held programming devices for CNC machines or robots. If safety-related communication is changed by a protocol at the application level of both transmitter and receiver, the actual wireless transmission medium and its interfacing to the transmitter and receiver are of secondary importance in the engineering of safety-related functions. (This is known as a "gray channel ). Such a protocol will be available for PROFINET in If it is used, it is "only" necessary to make sure that the communication channel has the required degree of reliability. From a safety perspective, it is acceptable that a fail-safe application regularly switches to the safe state simply because the wireless channel is erratic. From a customer perspective, however, such a system is unusable. The I-features of Industrial Wireless LAN provide a wide range of mechanisms that allow reliable wireless systems to be set up. Along with a safety protocol for PROFINET, it will then also be possible to implement fail-safe wireless links.

28 Applications of an Industrial Wireless LAN in Automation Engineering Applications Applications can be found wherever mobility and flexibility are at a premium. This is the case in all processes in which movement is involved. This mobility makes it possible to reshape work processes and develop innovative solutions. Simply substituting hard-wired cables does not normally mean enough benefit except for temporary installations or new installations that would involve considerable effort setting up cable ducts and racks. Typical applications requiring mobility and flexibility: Driverless transport systems Monorail systems Moving tables Moving and rotating machines: Substitute for drag chains, slip contacts and slip rings Cranes Conveyor systems Mobile service/diagnostics with handheld and laptop Mobile operation and monitoring Fast networking of individual manufacturing areas / isolated groups of machines during commissioning Mobile data acquisition in stores and logistics. There are also many applications in the field of automation in which wireless communication between individual stations is an additional advantage for the user. Communication with mobile stations, mobile data acquisition The user can acquire data from all manufacturing and storage areas with mobile, industrial Internet pads such as the MOBIC (Mobile Industrial Communicator) from SIMATIC NET and pass it on for central data processing. The mobile handhelds used are not assigned to a specific machine or process but to a user. The requirements in terms of numbers of devices are reduced considerably. Time-consuming transfer of data from paper to the central database and the potential errors involved are eliminated. With a fully integrated concept for data acquisition, significant costs

29 can be saved particularly at interfaces at which data must be transferred from one process step to the next. Mobile service and diagnostics If a fault occurs, service personnel can analyze the problem on site and can obtain information for the fast elimination of the problem over the MOBIC wireless Internet pad. The availability of spare parts in the warehouse can be immediately checked and parts ordered online if necessary. Diagnostics does not, however, only relate to fault situations. Operational data such as levels or the load on machines can also be assessed quickly and reliably by personnel. Figure 14: Industrial Wireless LAN in Automation Engineering

30 Communication with Mobile Stations and Mobile Commissioning Using mobile communication can greatly simplify and speed up the commissioning phase and lead to considerable cost savings. Maintenance engineers can monitor machine settings directly via their wireless service units and intervene immediately when problems occur. Personnel can use devices with which they are familiar such as the field PG because they can be included in the wireless network thanks to standardized interfaces (PCMCIA wireless adapter). Flexible manufacture in temporary configurations and communication with outlying units In today's world, assembly lines can no longer be rigid, inflexible units requiring considerable time and money before they can be modified for other uses. Particularly in automobile manufacturing plants, the factory layout is liable to fast modification. Flexible production means meeting customer requirements quickly and without long conversion times. By using wireless data networking, production units can be integrated in the data network quickly and with little effort. Test configurations can also be implemented quickly. An industrial wireless LAN also allows cost-effective integration of machines and controllers installed in otherwise inaccessible locations. Expensive and time-consuming cabling is avoided. Note: Wireless is preferable to cable only where an existing cable duct cannot be used (for example data and power cables must not laid together) a new cable duct must be installed data must be transmitted across public thoroughfares or over water Communication with moving stations The interfacing of moving devices to the data network involves considerable effort. A wireless connection saves the entire data

31 busbar installation for monorail systems and avoids systems with slip contacts for driverless transport systems that easily become polluted and require considerable maintenance effort. In both these applications, routes can also be changed simply, achieving considerable flexibility. The integration of rotating devices in a data network avoids wear and tear on the slip rings. The same advantage also applies to the substitution of drag chains. Examples Local Service and Diagnostics on the Company Premises Application Works sites are often extensive areas (tens of meters up to several hundreds of meters) predominantly with indoor areas but also outdoor units. The environmental conditions often mean an increased degree of protection for equipment unless it is installed in switching cabinets. The machines to be monitored are part of an extensive manufacturing or process plant and are interdependent so that the output of one machine strongly influences the operation of another. A communication network (for example Ethernet) is installed for data exchange between the control level and field level and ensures reliable data exchange. For local servicing (on-site troubleshooting, program uploads, data downloads, firmware updates, commissioning, configuring), access to the process must be monitored locally. This is achieved with a mobile device that has an effective range of a few meters from the machine. For diagnostics (process visualization, monitoring of operating data), it is not absolutely necessary that the process is observed locally so that the effective range of a mobile device can be between several meters up to several hundreds of meters.

32 Figure 15: Mobic used for service in manufacturing automation Solution To be of benefit to the customer, it is necessary that the wireless network allows not only for service work in the local (several meters) vicinity of the machine but that diagnostic functions are also possible over a much wider area. For diagnostic purposes or for visualization of process data, an adequate data rate is important since complex data is also visualized. For diagnostics, a device with a large display can therefore be assumed (laptop, Internet Pad). The data must be transferred with extremely reliable communication devices. This relates not only to the construction but to the communication technology. Since laptops or Internet Pads are mobile devices, there must be mechanisms that inform the process when they exit the cell so that the process can continue in automatic mode. For these reasons (transmission range, data rate, reliability), the use of an Industrial Wireless LAN must be recommended for this application. In addition, the roaming function supported in wireless LAN allows continuous use over large areas since it is possible to move from one access point to another without any interruption. The costs for the installation of a wireless network and for the purchase of mobile stations are spread over the numerous machines in the data network that can be included in diagnostics. Data Exchange between an Outlying Controller and a Data Network on the Works Site Application Information is exchanged between an outlying controller or machine and the wired data network (for example Ethernet) on

33 the works site over a maximum distance of several hundreds of meters. The attachment to the data network is not over cable either because no cable conduits are available or because the data cable must not be laid in the existing conduit. Regularly changing factory layouts or setup of test equipment increase the benefits of setting up a wireless network. Not only operational data but also alarm messages for maintenance requests are transmitted over the wireless network. Both the outlying unit and the wired data network require a wireless interface. Solution In this application, reliable data transfer over a distance that is normally significantly greater than 10 m but does not exceed several hundreds of meters on the works site. The wireless network must be resilient to disturbances and reflections in the industrial surroundings. The net data rate for shorter data packets as normally found in automation engineering must not be too low. Since the controller sends information about critical states in the equipment in the form of alarm messages, it must be able to access the communication infrastructure at any time. To achieve this, suitable technologies must be used. For these reasons (transmission range, data rate, guaranteed access to the wireless network), the use of an Industrial Wireless LAN is practical for this application. The comparatively high data rate means that mobile handhelds can also be used in this wireless network. This would reduce the share of infrastructure costs for the outlying controller. By reserving the data rate, the controller can send an alarm message at any time even when other mobile handhelds are communicating in the same wireless network. The infrastructure costs for a wireless network play a major role, in particular, when only one outlying controller needs to be connected. In this case, the solution should be compared with a wired solution to determine customer benefits. Conveyor Systems Application In logistics and materials management, vehicles without a driver are often used today. Travel is either along an induction loop in the floor or along a guide rail above the goods to be transported. The data is transferred either inductively, optically or with a slip contact and connects a mobile controller with a fixed central unit. Power is supplied either by batteries, over slip contacts, or inductively. The effective range of such a system is often over several hundreds of meters.

34 Figure 16: Driverless Transport System Solution Since a central unit exists that implements the data exchange with the controllers on the mobile vehicles, a local wireless network is necessary to allow point-to-multipoint links. An adequate transmission range must be available. Since there are numerous stations in the wireless network, a suitable data rate is also necessary. The controllers on the moving vehicles often have an Ethernet interface. The provider of wireless products must therefore offer suitable products. An Industrial Wireless LAN provides not only the required transmission range and data rate but also the option of establishing point-to-multipoint. In such a network that allows seamless and uninterrupted operation over large areas, stations are passed on from one access point to the next (roaming). The conveyor system application is a typical application for wireless LAN. Substituting slip contacts that are liable to contamination problems and optical connections is of great benefit to the user and the comparatively low costs for a wireless infrastructure fade into insignificance. Linking Data Networks (Ethernet) of Remote Plants (many hundreds of meters up to several kilometers) Application Linking the data networks of two plants can be extremely difficult when, for example, public land, streets, rail tracks or

35 water have to be crossed. The customer even benefits from a wireless link when the link is only temporary or set up for test purposes. Solution In this application, the advantages of Industrial Wireless LAN in terms of transmission range and data rate come to the fore. To cover large distances, directional antennas are installed outdoors on masts or roofs. To avoid the need for unnecessarily long antenna cables, it makes sense to use devices that are resistant to the effects of weather (temperature, water). For such an application, Industrial Wireless LAN provides the redundancy mode with which data can be transmitted between the two plant sections with a particularly high degree of reliability. This is important since the wireless network is the only link between the two areas.

36 SIMATIC NET Products for Industrial Wireless LAN SIMATIC NET offers the following products for setting up an industrial wireless network: Access Point SCALANCE W788-1PRO An access point suitable for use in industry for setting up a wireless network (infrastructure) and for attaching to the wired data network (Ethernet) Figure 17: Access Point SCALANCE W788-1PRO Extremely reliable due to reservation of data rate and cyclic monitoring of the link (IWLAN) Wireless LAN b/g and a with up to 54 Mbps at 2.4 GHz and 5 GHz Forced roaming if wire break on the Ethernet cable (option) Wireless Distribution System (WDS) for point-to-point links Degree of protection IP65, robust metal housing Operating temperature 20 C C resistant to condensation Redundant power supply V DC and power-over- Ethernet, even at 24 V DC 10/100 Mbps Ethernet port for connection to the wired network Advanced data security with WPA and encryption with AES

37 C-PLUG (configuration plug) exchangeable memory medium for fast device replacement without programming device Integration in STEP 7/NCM PC Dual Access Point SCALANCE W788-2PRO Dual access point suitable for industrial use with two separate wireless adapters to establish a high-quality wireless network (infrastructure) and to connect to the wired data network (Ethernet) Figure 18: Dual Access Point SCALANCE W788-2PRO Identical to the SCALANCE W788-1PRO, plus: Second wireless adapter for wireless LAN b/g and a 2x R-SMA connectors for distant antennas Redundancy mode for extremely reliable point-to-point link between two separate wireless adapters Ethernet Client Module SCALANCE W744-1PRO Ethernet adapter suitable for industrial use to connect a node (with Ethernet attachment) to an Industrial Wireless LAN network

38 Figure 19: Ethernet Client Module SCALANCE W744-1PRO Extremely reliable due to reservation of data rate and cyclic monitoring of the link (IWLAN) Wireless LAN b/g and a with up to 54 Mbps at 2.4 GHz and 5 GHz Degree of protection IP65, robust metal housing Operating temperature 20 C C resistant to condensation Redundant power supply V DC and power-over- Ethernet, even at 24 V DC 10/100 Mbps Ethernet port for connection to terminals with an Ethernet port Advanced data security with WPA and encryption with AES C-PLUG (configuration plug) exchangeable memory medium for fast device replacement without programming device Integration in STEP 7/NCM PC PC Card CP 7515 PC card (32-bit cardbus) with integrated antennas to link a node (for example field PG) to an Industrial Wireless LAN network Figure 20: PC Card CP 7515

39 Extremely reliable due to reservation of data rate and cyclic monitoring of the link (IWLAN) Wireless LAN b/g and a with up to 54 Mbps at 2.4 GHz and 5 GHz PC Card with 32-bit Cardbus interface Degree of protection IP20 Operating temperature 0 C C Advanced data security with WPA and encryption with AES Installation and maintenance with management tool for Windows 2000, XP Integration in STEP 7/NCM PC PCMCIA Card CP 1515 PCMCIA card (16-bit) with integrated antennas to link MOBIC T8 to Industrial Wireless LAN Figure 21: PCMCIA Card CP 1515 Extremely reliable due to reservation of data rate and cyclic monitoring of the link (IWLAN) Wireless LAN b with up to 11 Mbps at 2.4 GHz PCMCIA card for installation in MOBIC T8 Degree of protection IP20 Operating temperature 0 C C Data security with WEP Integration in STEP 7/NCM PC Power Supply PS791-1PRO V AC power supply unit with degree of protection IP65 for free mounting or direct mounting on SCALANCE W-700

40 Figure 22: Power Supply PS791-1PRO 10 W AC/DC power supply unit ( V AC / 24 V DC (±7%)) Perfectly adapted to SCALANCE W-700 Degree of protection IP65, robust metal housing Operating temperature 20 C C with protection from condensation Connector that can be assembled on-site with a high degree of protection against shock and vibration Power M12 Plug pro for 24 V DC (output) AC Power 3+PE cable connector (input) FC Modular Outlet Power Insert Power insert for combining power (24 V DC) and Ethernet on an 8-wire cable Figure 23: FC Modular Outlet Power Insert

41 Power and data over one cable Input: V DC and 10/100 Mbps Ethernet port RJ- 45 Output : Power and Ethernet over 8-wire cable Perfectly adapted to SCALANCE W-700 Insulation displacement technique for 8-wire IE hybrid cable 2x Robust metal housing with dust protection Wall or standard rail mounting inside or outside the switching cabinet (IP40). Ideal EMI protection due to metal housing Accessories Figure 24: Accessories (antennas, lightning protection, cables, connectors) Omni-Directional Antenna ANT 795-4MR: 2.4 GHz and 5 GHz, 4 dbi, R-SMA, mounted directly on housing ANT 795-6MR: 2.4 GHz and 5 GHz, 3 dbi, R-SMA, 5 m antenna cable, mounted on mast or wall Directed Antenna ANT 793-8DR: 5.7 GHz, R-SMA, 15 dbi, 20, 5 m antenna cable, mounted on mast or wall, USA and Canada only Antenna extension cable FRNC, 5 m Lightning conductor element LP798-1PRO IP67 Hybrid cable connector Power M12 cable connector pro (IP65)

42 Antenna terminator TI795-1R, if only one antenna is connected (supplied with 795-6MR and 793-8DR) Future Products from SIMATIC NET Note on this section: All product and technology descriptions represent the current (provisional) range of functions and are subject to change. In particular, the names of products and technologies must be taken as provisional working names. The Industrial Wireless LAN products from SIMATIC NET provide the discerning industrial customer with the advantages of the wireless world for applications in which mobility and flexibility are demanded. At the same time, Industrial Wireless LAN is based on the standard mechanisms of IEEE This is particularly clear if we look at the Link Check I-feature. The access point uses compliant data packets to check whether or not the station is still within the cell. Another example is the reservation of data rate I-feature. Every compliant station can be included in this mechanism. Devices that are not included in the mechanism are handled as usual in an compliant cell. Figure 25: Positioning wireless LAN, Industrial Wireless LAN and IWLAN RR

43 When wireless LAN is used in industry, there are requirements that cannot be implemented if 100% compatibility (such as Industrial Wireless LAN) with IEEE is demanded. These requirements include, for example, extremely fast handover times when a station roams from one cell to another. This requirement is found particularly often in applications in which stations move at higher speeds. If a vehicle in a driverless transport system moves at 10 m/s and is involved with the handover to the next cell for 500 ms, it travels 5 m without access to the wireless communication. Another example, is PROFINET IO communication that acknowledges with an error message if a station cannot reply three times in succession because it is busy with the handover to the next cell. If such exacting requirements are to be met, the technology must be expanded but will no longer conform with the standard. Such a strategy has two important advantages: 1. Such closed systems provide a high degree of data security since standard stations no longer have access to the wireless channel without firmware exansion 2. By using standard wireless LAN chipsets, the customer has the benefit of standardized hardware that is also available from other vendors. Industrial Wireless LAN RR This technology is an expansion of Industrial Wireless LAN and provides customers with real-time wireless communication even when stations roam from cell to cell and when transmission times in the range 10 ms to 100 ms are required. As normal in Industrial Wireless LAN, even in this cell, communication is predictable (deterministic). It is important to be aware that no compliant stations can be operated in an Industrial Wireless LAN cell with the RR attribute. If such stations are required in wireless communication, this can be achieved with a "shadow cell" in which the SCALANCE W788-2PRO dual access point is extremely useful when one wireless card implements the Industrial Wireless LAN cell and the other works in RR mode.

44 Figure 26: Structure of a "shadow cell for operating wireless LAN stations in an Industrial Wireless LAN RR cell Applications for Industrial Wireless LAN RR With monorail systems, PROFINET IO 1 is being used more and more because the cyclic data traffic is well suited to support control of the suspended rail. To avoid the problems of wear and tear with slip contacts, these applications increasingly use contactless technology. To be able to transmit data cyclically with fixed response times, the wireless network must support this performance. In such situations, the performance of Industrial Wireless LAN RR can be put to optimum use. 1 Support of the PROFINET real-time property RT

45 Figure 27: Monorail system, today still using slip contacts to transfer the carriage control to the suspension rail, in future contactless with Industrial Wireless LAN RR Industrial Wireless LAN RR will basically be used wherever fast moving stations require close contact with the wireless network and fast handover times from cell to cell. SCALANCE W788-1RR An access point suitable for use in industry for setting up a wireless network (infrastructure) and for attaching to the wired data network (Ethernet). Optional support of rapid roaming. Figure 28: Access Point SCALANCE W788-1RR Very short handover times to support moving stations when roaming (IWLAN RR)

46 IEEE h for operation with higher power output in Europe at 5 GHz Extremely reliable due to reservation of data rate and cyclic monitoring of the link (IWLAN) Wireless LAN b/g and a with up to 54 Mbps at 2.4 GHz and 5 GHz Forced roaming if wire break on the Ethernet cable (option) Wireless Distribution System (WDS) for point-to-point links Degree of protection IP65, robust metal housing Operating temperature 20 C C resistant to condensation Redundant power supply V DC and power-over- Ethernet, even at 24 V DC 10/100 Mbps Ethernet port for connection to the wired network Advanced data security with WPA and encryption with AES C-PLUG (configuration plug) exchangeable memory medium for fast device replacement without programming device Integration in STEP 7/NCM PC SCALANCE W788-2RR Dual access point suitable for industrial use with two separate wireless adapters to establish a high-quality wireless network (infrastructure) and to connect to the wired data network (Ethernet).Optional support of rapid roaming separately for each individual wireless card. Figure 29: Dual Access Point SCALANCE W788-2RR Identical to the SCALANCE W788-1RR, plus: Second wireless adapter for wireless LAN b/g and a

47 2x R-SMA connectors for distant antennas Redundancy mode for extremely reliable point-to-point link between two separate wireless adapters Ethernet Client Module SCALANCE W747-1RR Ethernet adapter suitable for industrial use to connect a station (with Ethernet attachment) to an Industrial Wireless LAN RR network Optional support of rapid roaming. Figure 30: Ethernet Client Module SCALANCE W747-1RR Very short handover times to support moving stations when roaming (IWLAN RR) Logical support of up to 8 IP addresses IEEE h for operation with higher power output in Europe at 5 GHz Extremely reliable due to reservation of data rate and cyclic monitoring of the link (IWLAN) Wireless LAN b/g and a with up to 54 Mbps at 2.4 GHz and 5 GHz Degree of protection IP65, robust metal housing Operating temperature 20 C C resistant to condensation Redundant power supply V DC and power-over- Ethernet, even at 24 V DC 10/100 Mbps Ethernet port for connection to terminals with an Ethernet port Advanced data security with WPA and encryption with AES C-PLUG (configuration plug) exchangeable memory medium for fast device replacement without programming device Integration in STEP 7/NCM PC

48 IWLAN/PB Link PN IO Link between Industrial Wireless LAN and PROFIBUS with PROFINET IO functionality. Optional support of rapid roaming. Figure 31: IWLAN/PB Link PN IO Very short handover times to support moving stations when roaming (IWLAN RR) Extremely reliable due to reservation of data rate and cyclic monitoring of the link (IWLAN) PB master interface for flexible integration of field devices in an IWLAN wireless infrastructure Attachment of an IWLAN antenna or alternatively an antenna for operation with RCoax cable C-PLUG (configuration plug) exchangeable memory medium for project engineering data for fast device replacement without programming device PROFINET communication (IO proxy) Wireless LAN b/g and a with up to 54 Mbps at 2.4 GHz and 5 GHz IEEE h for operation with higher power output in Europe at 5 GHz Degree of protection IP20 for installation on a standard rail in the switching cabinet Advanced data security with WPA and encryption with AES Note: The device is not suitable for linking to PROFIBUS networks, but for linking traditional PROFIBUS DP slaves at the Ethernet control level. Customer benefits in the monorail system application: