tailieunhanh - cwts certified wireless technology specialist official study guide exam pw0 070 phần 6

Một ví dụ về diplex là kết hợp các tín hiệu từ hai tần số khác nhau vào một máy phát / thu. A. DSSS thiết bị hoạt động trong băng tần 2,4 đến 2,5 GHz ISM. OFDM thiết bị hoạt động trong các băng UNII 5GHz. B. hoạt động ở băng tần 2,4 GHz ISM. | Wireless LAN Modes of Operation 207 Basic service set BSS Extended service set ESS Each of these configurations will be discussed in more detail in this chapter. The application deployment scenario for a wireless LAN is the determining factor for the best mode to use. The IBSS configuration does not require the use of an access point and unless specifically justified is not commonly used in enterprise wireless LAN deployments. In addition the IBSS can introduce security vulnerabilities if not properly implemented. The most common configuration for wireless LANs is infrastructure mode which uses at least one access point. Infrastructure mode requires a minimum of one access point but can consist of up to thousands of access points. The access points are connected by a common medium known as the distribution system. This chapter will look at each of these modes and the details of how they are configured. Independent Basic Service Set IBSS It is important to understand what the independent basic service set IBSS is how it works and potential uses advantages and disadvantages. This operation mode uses no access points and consists of only wireless LAN devices or client computers. Communication occurs only among devices that are part of the same IBSS. Unlike an access point this mode has no centralized control or managed security features. Figure shows devices in IBSS. FIGURE Example of an independent basic service set 208 Chapter 7 WLAN Terminology and Technology Certain parameters must be set on the devices that wish to participate in an IBSS. These parameters must be the same on all the devices in order for them to effectively communicate with one another. Three common parameters set on devices that belong to the same IBSS are Service set identifier SSID Radio frequency channel Security configuration Service Set Identifier SSID The service set identifier SSID is a common parameter used in all WLAN operation configurations. Although it is discussed here