Promote Wi-Fi certification worldwide by encouraging manufacturers to follow standardized 802.11 processes in the development of wireless LAN products. It was standardized in IEEE 802.3 in 1980. The Wireless World: An Introduction to Concepts, Chapter 2. A major difference with HiperLAN/2 is the use of a connection-oriented protocol with time division multiplexing as the basis for supporting data transfer between users. FHSS transmits a wideband signal that spans the entire 2.4-GHz band. Wireless MANs: Networks for Connecting Buildings and Remote Areas, Chapter 7. These will … The following sections provide a brief overview of these specifications and standards. Ethernet, Token Ring and Wireless LAN using IEEE 802.11 are examples of standard LAN technologies. If high performance is an important requirement, lean toward the 5-GHz band. As a result, there's no guarantee of when a particular station will be able to send a packet. If the text is equivalent, the access point assumes that the radio NIC has the correct key. The IEEE 802.11 group of standards defines the technologies for wireless LANs. The Institute of Electrical and Electronics Engineers (IEEE) has s… A potential issue of 802.11a is limited range, mainly because of operation in the higher frequency 5-GHz band. The problem to date, however, is that these enhanced security mechanisms are proprietary, making it difficult to support multivendor client devices. This requires a greater number of access points to fully cover a facility, as compared to an 802.11b system. The access point then responds with a CTS frame, indicating that the radio NIC can send the data frame. The combination of these two mechanisms provides dynamic key encryption and mutual authentication, something much needed in wireless LANs. (See Figure 5-9.) A wireless network or Wireless Local Area Network (WLAN) serves the same purpose as a wired one to link a group of computers. When assessing the pros and cons of 2.4-GHz and 5-GHz systems, be sure to first define requirements. A unique feature of HiperLAN/2 technology is the ability to interface with other high-speed networks, including 3G cellular, asynchronous transfer mode (ATM), and other Internet protocol-based networks. The following sections summarize primary 802.11 MAC functions. A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier. 2.4-GHz products are certainly inexpensive and capable of supporting most application requirements. Keep in mind, however, that 5-GHz systems might have equal or even better range in some situations. Microwave ovens and other devices operating in the 2.4-GHz band can also cause interference. Association is necessary to synchronize the radio NIC and access point with important information, such as supported data rates. The NAV must be 0 before a station can attempt to send a frame. “Wireless local area Network (WLANS)” IPT201_14_ODD_34 2. Because of this, carefully consider interoperability issues that might result if you choose to deploy 802.11a networks. In order to qualify for obtaining Wi-Fi certification for products, a company must become a member of the Wi-Fi Alliance. As a result, 5-GHz systems can provide enhanced security over 2.4-GHz systems because of less range. The initial 802.11 standard ratified in 1997 includes frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) physical layers operating in the 2.4-GHz band with data rates of up to 2 Mbps. Boggs in the year 1970. RF Interference? This can be a real advantage when integrating wireless LANs with cellular systems and WANs. The last common LAN technology is wireless, using infrared light or radio waves instead of wires or fiber optics to transport the network signals. If the radio NIC activates RTS/CTS, it first sends an RTS frame to an access point before sending a data frame. The textbook definition of a WAN is a computer network spanning regions, countries, or even the world. The random delay causes stations to wait different periods of time and avoids all of them sensing the medium at exactly the same time, finding the channel idle, transmitting, and colliding with each other. With most radio NICs, users can set a maximum frame-length threshold for when the radio NIC activates RTS/CTS. The beacons contain information about the access point, including SSID and supported data rates. Stations set to ad hoc mode form are what the 802.11 standard refers to as an independent basic service set. Many hackers know how to break through shared key authentication, however, so it's not a good idea to depend on it for a high level of security. 802.11a access points and radio NICs just became available in late 2001; therefore, the installed base of 802.11a wireless LANs today is relatively small as compared to 802.11b. As a result, you might benefit by deploying 2.4-GHz systems in larger facilities unless high performance is critical. Wireless Network Security: Protecting Information Resources, Appendix A. The similarities between 802.11a and HiperLAN/2, however, stop at the MAC Layer. There are a number of different wireless technologies out there that can be implemented in hardware products for the Internet of Things (IoT) and Machine to Machine (M2M) communication. With WPA, an environment having many different types of 802.11 radio NICs?such as public hotspots?can benefit from enhanced forms of encryption. An access point polls stations according to a polling list, then switches to a contention period when stations use DCF. 802.11 and HiperLAN/2 are the most common standards for wireless LANs. This gives users the ability to move around within the area and remain connected to the network. Combined with the absence of HiperLAN/2 products, it's doubtful that HiperLAN/2 will catch up and become the dominant player in the wireless LAN market. This avoids collisions between hidden nodes. The 5-GHz bands have much greater spectrum available. Products, however, didn't become available until 2000, primarily because of the difficulties in developing circuitry in the 5-GHz band. Ethernet shares media. For supporting time-bounded delivery of data frames such as video, the 802.11 standard defines the optional PCF where the access point grants access to an individual station to the medium by polling the station during the contention-free period. In fact, exhaustive searches on the Internet reveal no HiperLAN/2 products available to consumers. Often viewed as the brains of the network, the 802.11 MAC Layer directs a particular 802.11 Physical layer, such as 802.11a, 802.11b, or 802.11g, to perform the tasks of sensing the medium, transmission, and receiving of 802.11 frames. With power save mode on, the radio NIC indicates its desire to enter a sleep state to the access point through a status bit located in the header of each frame. As a result, 5-GHz systems generally have less range than ones operating in the 2.4-GHz band. Other wireless technologies such as Bluetooth also exist, fulfilling specific networking functions. The interfering signals degrade the performance of an 802.11b wireless LAN by periodically blocking users and access points from accessing the shared air medium. It may serve 2 or 3 users to as many thousands of users. CableFree Wireless LAN Wireless Excellence is one of the UK’s leading WiFi wireless network design and implementation specialists. The second feature is Dynamic Frequency Selection (DFS), which allows the station to listen to the airspace before picking a channel. These beacons identify whether sleeping stations have frames buffered at the access point and are waiting for delivery to their respective destinations. HiperLAN/2 defines an efficient, high-speed wireless LAN technology that fully meets the requirements of Europe's spectrum regulations. With radio-based LANs, a transmitting station can't listen for collisions while sending data, mainly because the station can't have its receiver on while transmitting the frame. Some situations, how ever, benefit from the use of 5 GHz, such as densely populated environments and multimedia applications. The radio NIC starts by sending an authentication request frame to the access point. The 802.11 standard specifies a single MAC Layer, which provides a variety of functions that support the operation of 802.11-based wireless LANs. An issue with PCF is that not many vendors support it in their products. On the occurrence of collision in Ethernet, all its hosts roll back, wait for some random amount of time, … Copyright eTutorials.org 2008-2020. Interoperability? This can cause confusion when designing a wireless LAN, so take a look at what is necessary to consider when making this critical decision. Wi-Fi Alliance is also behind Wi-Fi Protected Access (WPA), the stepping stone between the much-criticized WEP and the 802.11i security standard. Wireless LAN, Uses, Benefits, Disadvantages. The superior range allows the deployment of wireless LANs with fewer access points to cover a facility as compared to 802.11a. A radio NIC initiates the process by sending an authentication request frame to the access point. The following are requirements for consideration when deciding between 2.4-GHz or 5-GHz solutions: Geographical Location? A wireless local area network (WLAN) links two or more devices over a short distance using a wireless distribution method, usually providing a connection through an access point for internet access. Wireless System Architecture: How Wireless Works, Flow of Information Through a Wireless Network, Chapter 3. With the CTS frame, the access point provides a value in the duration field of the frame header that holds off other stations from transmitting until after the radio NIC initiating the RTS can send its data frame. The access point responds by sending an association response frame containing an association ID along with other information regarding the access point. Optional active scanning is similar, except the radio NIC initiates the process by broadcasting a probe frame, and all access points within range respond with a probe response. 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