RF Technology - The Key to Next-Generation WLAN[Copy link]
Author: techupdate.zdnet.com 2004-04-23 02:19 PM
As one of the most exciting communication technologies, wireless local area network technology (WLAN) is now available for implementation in enterprises. It is a technology based on the 802.11 series of standards. As business needs develop further, more and more enterprises require the use of fewer resources to achieve higher efficiency and productivity. In order to achieve this goal, IT organizations are now turning to these emerging technologies and trying to use these new technologies as tools to achieve this goal. However, current WLAN solutions cannot fully solve enterprise-level reliability, scalability, security and manageability issues. By comprehensively examining the existing problems in the wired and wireless fields, the next-generation system provides IT organizations with solutions to solve the shortcomings of current systems.
According to META Trend research: In 2003, the focus of campus local area network (LAN) initiators was mainly on increasing network availability. In their view, network availability has a higher priority than other applications that are about to emerge (such as VoIP). However, network intelligence will bring voice, video and data together, making WLAN configuration easier. By the end of 2003, WLAN standards will focus on dual-band, and enterprises will rely more on wireless technology to reduce costs and improve productivity. By mid-2004, WLAN security standards will be in place and interoperable, and the market's attention will shift to management and services that are ubiquitous on both wired and wireless networks.
The emergence of WLAN solutions based on a single, interoperable Wi-Fi standard at a relatively low cost paves the way for the development of the WLAN market. Although the first generation of WLAN products is important, enterprises are more concerned about the future and whether the use of such products can meet enterprise-level needs and solve practical problems for enterprises.
The biggest flaw of the first generation of access points is that they cannot detect and collect information about what is happening in the radio frequency (RF) environment around them. This detection capability is very important for a variety of reasons. This capability allows the access point to act as the eyes and ears of the broadband wireless system - using it, the system can interpret what is happening in the RF environment around it and can direct the access point to make necessary changes. As the emergence of a large number of unlicensed frequencies leads to an increase in wireless signal interference, ITOs must improve their ability to view and control the RF domain to mitigate interference and ensure optimal network connectivity and performance.
First-generation products have only some basic management frameworks that are extended from traditional wired management systems. Therefore, to some extent, the wireless environment itself has no real management system. Many providers rely on existing system management providers to tie these access points into the management framework of the broadband infrastructure. However, this implementation approach largely retains the central management approach of wired and does not provide management methods for the RF domain. Furthermore, the basic functions of wired SNMP-based management systems are limited to basic information because the 802.11 management information base (MIB) is often a proprietary protocol. Existing WLAN solutions are not optimal for supporting real-time applications such as mobile access between multiple access points or multiple IP subnets. For
an enterprise, security continues to be a key issue that needs to be considered when configuring a WLAN. In fact, our users continue to cite security as the biggest barrier to wireless LAN adoption in most enterprises. Although many standards have been proposed to address security issues, implementing a highly secure wireless network with first-generation products will require the integration of many cutting-edge products. Here, security will be largely focused on the central access point and lack the broader system-level insights that are necessary to more effectively manage security specifications.
Much like Ethernet, the 802.11RF environment is also a shared medium. However, unlike Ethernet, the 802.11RF environment is a constrained network that currently cannot divide bandwidth based on individual users, nor can it be effectively expanded. Therefore, its scalability is still questionable. Although additional standards such as 802.11b, which supports data rates exceeding 11Mbps, have been approved, first-generation products neither provide support for these standards nor consider the RF domain from a holistic system level, making it difficult for the entire system to control transmission standards and reflect better adaptability.
Exploring the Application of RF Domain Compared with existing Ethernet local area networks (LANs), WLANs are very different in that they use RF to send and receive data packets. Although this is easy to understand in the wired Ethernet environment, predicting RF characteristics is currently an art at best. To ensure the performance levels required to support critical applications, WLAN systems must evolve to provide more deterministic features. Due to the nature of wireless, unlicensed frequencies also share the environment because there is no single entity implementing spectrum control. Therefore, WLANs must be able to detect and adapt to changes in the RF environment to mitigate interference between access points, which may be temporary (for example, from elevators moving up and down) or permanent (for example, from newly installed access points nearby).
Unlike wired networks, the physical layer of WLANs extends from access points in an unpredictable manner. Therefore, enterprises must be aware of the fact that wireless signals penetrate walls and can often break through the limitations of buildings. Existing solutions use directional antennas to control the propagation of RF signals.
Due to the fixed nature of the 2.4GHz and 5GHz frequencies, WLANs are very limited in capacity and scalability. Unlike wired Ethernet, which can be continuously segmented through the use of switches, WLANs provide an inverse relationship between the number of users supported and the bandwidth available to each user. First-generation WLAN solutions have limited ability to respond to changes in user density and are not able to effectively optimize bandwidth resources. As WLAN load increases, existing products are often unable to determine whether the load and user volume of adjacent access points are similar, nor can they determine whether it is necessary to share the load with adjacent access points. User load balancing requires the use of more centralized software control, which can be used to evaluate network efficiency based on the system level to optimize the ratio of users to access points.
Integrating Wireless into Wired Networks From a historical perspective, although WLAN has been separated from the existing wired Ethernet LAN, it still retains the physical and logical characteristics of the wired network. As wireless network configurations increase, more and more traditional applications, including common business applications, are also being implemented in wireless networks. It is important to provide a range of network services covering both wired and wireless fields. Since WLAN will become an enterprise-level application, the technology of wireless network must conform to existing network policies and services, rather than changing the existing network design.
Integrating wireless network into the existing wired network is a key step to maximize network availability. Because the first-generation access points operate as independent entities, the redundancy provided by first-generation solutions is very limited. Next generation systems will drive system-wide monitoring capabilities so that the transmit power settings of access points can be adjusted if a neighboring access point fails. This will give users the option to configure access points within a certain range so that they can maintain coverage of the entire work area in the event of an access point failure. While this approach was also possible with first generation solutions, first generation solutions did not have comprehensive monitoring and control capabilities for moving users, re-adjusting channels, and setting capabilities.
Moving towards dynamic, adaptive RF: Viewing wireless network intelligence from a system perspective Over the past year, a topic of debate has centered around where intelligence should reside in a WLAN system. Most vendors advocate lightweight access points, preferring centralized intelligence in switches or appliances that lack advanced intelligence. Other vendors believe that access points should be feature-rich to support all current and emerging services that enterprise users require. We are not here to advocate one implementation approach over another. However, we believe that control and management of wireless systems should be centralized to operate the system more efficiently. The key question is what features can be provided through the overall software framework, rather than specifying where to place the processing (e.g., in the access point or in a switch or other appliance). The goal of any WLAN solution should be to provide stable network coverage within a predictable range and that the wireless network should be easy to manage. To achieve this goal, the system must improve its ability to control the RF medium. Controlling the
RF Domain To improve control over the wired infrastructure, most enterprises have now begun to invest in network management systems. Typically, the level of expertise of the network team is quite high. However, the principles of managing the wireless environment are poorly understood. There are many similarities between managing wireless and wired network systems. However, users should not underestimate the rather unique characteristics that wireless networks bring to the management framework.
Leading-edge WLAN solutions will provide the necessary tools to collect information about the RF domain and apply policies and rules to the entire system to improve overall system stability. As the number of devices and systems operating in unlicensed frequency ranges increases, the ability of the wireless infrastructure to detect and interpret irregular signals in the RF environment will become increasingly important. This is especially important for wireless networks deployed in adjacent enterprises or for ITOs that have limited control over the RF domain. It is easy to adjust the settings of access points relative to individual access points, but any system-level decision to adjust access point settings due to changes in the RF environment is very important to the enterprise. This is because any change to any access point will have a small impact on adjacent access points, which can be better managed at a macro level.
Real-time monitoring of the wireless domain is an important step in ensuring high availability of the wireless network. Whether the system can intelligently react to changes in the RF environment is a key consideration in the next generation of solutions and should be given as much attention as monitoring capabilities. The degree of automatic fault tolerance of the system over other solutions will largely determine the user's choice. Furthermore, different enterprises will require different levels of automatic reconfiguration of access points, and they will also require different timings for changing policies. Leading-edge systems must be flexible and versatile, providing network administrators with the ability to manually modify configurations or fully automatic self-healing when the network fails or the RF environment changes.
Enterprises should now focus on the ability of wireless systems to communicate with internal access points so that each access point can know what its neighbors are doing. This will allow the system to optimize frequency, power, and bandwidth allocation. As more WLANs and other wireless systems are deployed, the 2.4 GHz and 5 GHz frequencies will become increasingly crowded. While ensuring network uptime for current business applications, ITO will also require wireless systems to monitor, detect, and react to changes in the surrounding RF environment. Practical Applications of RF Control We have
already established that control of the RF domain is very important in the deployment of next-generation enterprise WLANs. We should now turn our attention to the extent to which improved RF domain control can improve the management and configuration of the entire WLAN.
Perhaps the biggest benefit of improved RF control is improved wireless network availability. As enterprises deploy more and more critical applications in their networks, they will also require greater network resiliency. First-generation wireless networks offer only limited availability. Each access point has little, if any, knowledge of whether nearby access points are functioning properly, limiting its ability to react to failures. Next-generation systems will leverage the entire software framework to detect access point failures and automatically adjust based on the performance of nearby access points.
By controlling the output transmit power and operating frequency of each access point, the system can allow specific access points to fill in gaps in coverage by increasing power or changing channels, or to mitigate interference between access points, thereby increasing network stability. Further, if an access point fails, the system can direct specific access points to offload certain clients to optimize communication routing and network load. Finally, access points can learn what is happening around them and detect gaps in range. Because RF coverage patterns cannot be predicted, system availability can be greatly affected by seemingly innocuous behavior, such as the movement of an elevator. Although many companies shy away from systems that are too adaptive, increasing output power can enable systems to detect and fix gaps in range, with other benefits such as increased network uptime.
When considering the scalability of a wireless network, it is also helpful to have a comprehensive understanding of the RF domain. The next generation of access points will be able to provide dual-band connectivity, including support for 802.11b, 802.11g, and 802.11a. With limited available spectrum such as the 2.4GHz and 5GHz frequencies, the goal of any network design should be to optimize the use of available channels to provide the maximum amount of bandwidth to each client.
ITOs should look for solutions that can share the load of client devices within a location. For example, if an access point is overloaded due to high user density in a physical location, the system should be able to recognize the fact that nearby access points with overlapping coverage can share some client devices with the access point, thereby sharing resources with a wider range of devices. As mentioned earlier, this type of feature requires that the access points must be aware of what is happening around them and know that certain types of inter-access point communications can drive more clients, so that traffic management can be implemented. This type of implementation also allows the system to collect statistics on normal bandwidth utilization and information on the load and ratio between access points and client devices. These statistics can ensure that the network is designed for optimal performance. The most advanced systems can use this information to adjust power and channel settings to improve the network's coverage area or make recommendations, such as how additional access points can improve network performance.
Traditionally, WLAN configuration involves a site survey, which identifies the physical constraints of the building and its surroundings to determine where to place access points for optimal performance. Much of this work is manual, using scanning tools to measure the amount of RF output power required at different locations. Next-generation systems will greatly simplify this process, reducing the total configuration time to just a few hours. In essence, the next-generation WLAN infrastructure will be self-correcting and provide an accurate simulation of how the network should be configured to achieve optimal performance by using floor plans. This feature will not only speed up the configuration of wireless networks, but also reduce the cost of implementation and increase the reusability of the network when it needs to be moved, new equipment is added, or changes occur.
Each access point will automatically be assigned a service set ID (SSID), a communication channel (or two), and a power setting. This automatic configuration will reduce the work of network administrators, who will not have to touch each access point to manage them, further reducing the cost of configuration. Finally, during the configuration process, each access point can collect RF information of interfering nature in its vicinity. The system can then recommend how to change the configuration position of the access point based on the interference information obtained. Leading providers will produce systems that can automatically determine the cause of interference (for example, interference from other access points or non-802.11 noise interference).
The RF medium plays a different role in the overall security of wireless networks. Although the physical layer is not responsible for device and user authentication, nor is it responsible for encrypting data packets transmitted over the air, it can provide important data about unauthorized access points or suspicious client device behavior. Although there are many detection solutions on the market, most of the products are configured to cover the entire network rather than integrating it into a single system. Wireless access points should be able to operate in detection mode to determine whether other wireless components are configured correctly. They should also be able to report which access points or client devices have not been approved by the ITO. Ideally, this RF implementation of wireless detection should be supplemented by a wired implementation with the ability to correlate suspicious behavior detected in the wireless network with information collected in the wired environment. Through this correlation capability, the system can determine whether the suspicious access point belongs to a host network or is simply part of the infrastructure of a neighboring enterprise. In addition, by continuously monitoring network behavior, the system can perform intrusion detection and prevention functions and report on rogue access points, ad hoc networks, denial of service attacks, and man-in-the-middle attacks.
Using triangulation techniques and RF diagnostic tools, the system should also be able to pinpoint the location and nature of potential, irregular interference, often referred to as "location tracking." For example, configuring a WLAN in a large enterprise should be able to determine that the cafeteria's microwave is a cause of channel interference. By pinpointing the location of the interference, the system will allow IT managers to confirm that the microwave is in fact causing the problem, allowing them to propose a remedy. This location capability can also be used to determine whether to allow or deny access to devices or users based on the location of the access point. For example, a network administrator can create a rule that denies network access to users who are physically outside a building.
Finally, the RF medium can serve as a management platform for wireless systems. Statistics, rules, and policies can be passed between different devices and access points, allowing them to maintain connectivity with established network policies. Although the access points that need to be managed are still distributed throughout the network infrastructure, management control is still centralized at a single user access point. This approach to RF management allows system components to communicate directly with each other for policy updates and configuration changes, without transmitting these updates over the wired network.
Although a large number of immature solutions continue to exist in the WLAN market, other system-level RF intelligence solutions have emerged and can effectively meet the needs of enterprises. By centrally managing the RF environment, security, and configuration, these systems reduce the cost of supporting WLAN networks. Enterprises should look for solutions that provide the greatest protection for their investments - that is, those that support all transmission standards and proposed security standards. A key part of the product and architecture selection criteria should focus on whether the WLAN system can better control the RF domain. While integrating WLAN into a wired LAN is important to ease overall network operations, the system's adaptability to changes in the RF environment will set it apart from other solutions and take it to a higher level.
META Group predicts that by 2005, 95% of corporate laptops will have embedded Wi-Fi directly on the platform. Therefore, wireless connectivity within the company will become a reality regardless of whether the business is ready or not. As companies consider WLAN as an optional network access technology, they will look for network systems that can match the reliability of existing wired LANs. The next generation of WLAN systems will not require changes to existing network strategies and will be able to well support the various business services provided by previous wired networks.
Wireless networks require systems with good manageability and security in order to support reliable and predictable business applications.
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