The wireless-capable customer laptops communicate with a WLAN device called an access point (AP). Unfortunately, Most 802.11n equipment available today use only tape 2.4 GHz (and are therefore not compatible with the 802.11a). The fact that WiFi is originally designed to perform WLAN does not prevent not also be used in other contexts. immovable or move only inside a BSS. The 802.11b reached a speed of 11 Mb / s and 802.11g rises to 54 Mb / s. The 802.11a is not compatible with 802.11b and 802.11g, because it works with the waves a radio frequency of 5 GHz. Security Units: These units take care of the network security. • The basic services set contain stationary or mobile wireless stations and a central base station called access point (AP). Connection-oriented and connectionless services . The following list describes some of the many applications made possible through the power and flexibility of wireless LANs: • Doctors and nurses in hospitals can be more productive because wireless hand-held terminals or notebook computers with wireless LAN capability can deliver patient information instantly. 5 IEEE 802.11 (WiFi) Overview Adopted in 1997 … Complete Wireless LAN - PowerPoint Presentation, Computer Network, Engineering Notes | EduRev chapter (including extra questions, long questions, short questions, mcq) can be found on EduRev, you can check out lecture & lessons summary in the same course for Syllabus. There are three different types of frames: 1. Unit VIII Orthogonal Frequency Division Multiplexing: Basic Principles of Orthogonality. Anna University EC6802 Wireless Networks Syllabus Notes 2 marks with answer is provided below. Palmtops or Personal Digital Assistants (PDA) with communication capability. The frame is going from a station to an AP. There are 4 address fields of 6 bytes length. In this case, the WLAN is used to achieve a WPAN. HYPER LAN, HYPER LAN – 2. The following list describes some of the many applications made possible through the power and flexibility of wireless LANs: • Doctors and nurses in hospitals can be more productive because wireless hand-held terminals or notebook computers with wireless LAN capability can deliver patient information instantly. If the channel is not free the station waits for back off time. To extract data, a radio receiver tunes in one radio frequency while rejecting all other frequencies. • It supports four data rates: 1,2,5.5 and 11 Mbps. h�dP�KBQ=O��T�Ȃ�����j)� � • Each flag can be 0 or 1, resulting in 4 different situations. 3. •  Type networks Ad Hoc, where stations communicate directly; • Infrastructure type networks where stations communicate through access points. • The distribution system can be any IEET LAN. • Consulting or accounting audit teams or small workgroups can increase the productivity with quick wireless network setup. This note explains the following topics: Introduction To Mobile Computing, Applications Of Mobile Computing, GSM Protocols, CDMA, Spread Aloha Multiple Acces, Mobile Network Layer, Traditional TCP, Database, Data Dissemination, Mobile Ad Hoc Networks. Section 4.3, 4.4, and 4.8 in the textbook W12-1: 11/12 LAN Switching Topics: Concept … %PDF-1.5 %���� It is called as bridge. (ii) Stationary stations: These are AP stations that are part of a wired LAN. 1. On hearing this short frame, all stations other than the receiving station, avoid transmission, thereby allowing the communication to take place without interference. A wireless local area network (WLAN) is a wireless distribution method for two or more devices that use high-frequency radio waves and often include an access point to the Internet. Each bit is transmitted as 11 chips using a Barker sequence. WLANs and the 802.11 Standard, March 31, 2001 5 P. Nedeltchev WLAN Components 802.11 defines two pieces of equipment, a wirelessstation, which is usually a PC equipped with a wireless network interface card (NIC), and anaccess point (AP) , which acts as a bridge between the wireless and wired networks. • Training sites at corporations and students at universities use wireless connectivity to ease access to information, information exchanges, and learning. This can be called Wireless MAN (WMAN). 1. These four addresses represent source, destination, source base station and destination base station. WAN . Ethernet: 802.3 • Dominant wired LAN technology - 10BASE5 (vampire taps) - 10BASE-T, 100BASE-TX, 1000BASE-T • The AP performs polling for stations that wants to transmit data. Reassociation: • Consulting or accounting audit teams or small workgroups can increase the productivity with quick wireless network setup. Why Wireless is Insecure and What can we do about it? Introduction to Wireless Networks 15 Wireless Data Networks Each type of wireless data network operates on a specific set of radio fre-quencies. Le nom Wi-Fi (contraction de Wireless … Data frame. Mobility Users on a wireless LAN systems can access to real-time information from anywhere within their organization. The second modification was to apply the binary exponential back off algorithm to source-destination pair. • To give priority to PCF over DCF, another interframe space called PIFS is defined. FCS. It can reach 54 Mb / s. The 802.11n allows to achieve a real flow rate greater than 100 Mb / s. It is capable of operating at 2.4 GHz or 5 GHz and is compatible with the 802.11b / g and 802.11a. In this case following procedure is used for collision avoidance: 1. Wireless LANs provides dual advantage of connectivity and mobility. All other stations that are affected by the transmission creates a timer caned network allocation vector (NAV). Lecture Notes . Apart from the components needed by the conventional wired LAN, a wireless LAN needs additional components. MAN-Wireless- Home Networks . Radio waves at lower frequencies can travel through walls whereas higher RF can travel in straight line and bounce back.The power of low frequency waves decreases sharply as t… Lectures 6: Security for Mobile and Wireless Computing Ing-Ray Chen CS 6204 Mobile Computing Virginia Tech Courtesy of G.G. The wired LAN provides reliable service to users, working in a fixed environment. Lecture Notes: Wireless Networking, Spring 2007. WLAN security - Lecture 2 14 • Wireless LAN uses radio signal • Attacker needs equipment capable of: – monitoring (passive attacks) and transmitting (active attacks) encrypted traffic passive attacks can be carried out using off-the-shelf equipment by modifying driver settings active attacks are more difficult but not beyond reach and easy when firmware (e.g., Orinocco) … Hubs, bridges, network operating system, servers, and other components are functioning exactly as they were, on a wired LAN. Lecture Notes On Wireless Networks And Mobile Computing. • Network managers in dynamic environments minimize the overhead caused by moves, extensions to networks, and other changes with wireless LANs. • This method is capable of delivering data upto 18 or 54 Mbps. • For a 2-Mbps data rate, a 2 bit code is encoded into 4 bit code. • The 5.5. The access point receives, buffers, and retransmits data between the wireless LAN and the wired network infrastructure. When two or more stations send RTS to a station at same time, their control frames collide. 802.11 Wireless Networks: The Definitive Guide, M. Gast, O’Reilly, 2002* ANSI/IEEE Std 802.11, 1999 Edition ANSI/IEEE Std 802.11b-1999 ANSI/IEEE Std 802.11a-1999 *Most drawings used in the lectures are from this book TOC – 802.11 – References. • In OFDM all the subbands are used by one source at a given time. These three banks are unlicensed and their ranges are. • The procedure used in NAV is explained below: 1. Prof. Dr.-Ing. Laptop computers: Laptop PCs with two-way communication facility (Transceiver) 2. change networks by changing access points scanning, i.e. %%EOF During 1990, Kam developed the MACA (Multiple Access with Collision Avoidance) protocol for wireless transmission. The 802.11architecture defines two types of services and three different types of stations. Evolution of the WLAN industry, Wireless home networking. Wireless transmission is a form of unguided media. 3. Radio frequencies are sub-divided into six bands. Control frame. UNIT 1: Network Hardware: LAN . View DCF255 Lecture 11 - Notes - Wireless Trouble Shooting.pdf from DCF 255 at Seneca College. • If at the same time, a station is using DCF and AP is using PCF, then AP is given priority over the station. • 802.11 standard uses Network Allocation Vector (NAV) for collision avoidance. • Due to this priority of PCF over DCF, stations that only use DCF may not gain access to the channel. • A mobile station can belong to more than one BSS at the same time. Today the WiFi version of the most used is far 802.11g. Single Versus Multi channel Systems. This note explains the following topics: Introduction To Mobile Computing, Applications Of Mobile Computing, GSM Protocols, CDMA, Spread Aloha Multiple Acces, Mobile Network Layer, Traditional TCP, Database, Data Dissemination, Mobile Ad Hoc Networks. 802.11 support two different modes of operations. Portable FAX 4. Enables transfer of data between a station on an IEEE 802.11 LAN and a station on an integrated IEEE 802.x LAN (through a portal).! • Here, 4 or 8 bits are encoded into a special symbol called complementary code key (CCK). • To overcome this problem, a repetition interval is defined that is repeated continuously. This 4 bit code contains three Os and a single 1. IEEE 802.11 is commonly referred to as wireless Ethernet because of its close similarity with the IEEE 802.3. If To DS = 1 and From DS = 0, it indicates that the frame is going to a distribution system. • It supports the data rates of 22 or 54 Mbps. Hubs, bridges, network, 2. If To DS = 1 and From DS = 1,it indicates that frame is going from one AP to another AP in a wireless distributed system. Evolution of the WLAN industry, Wireless home networking. 5. 2. The wired LAN provides reliable service to users, working in a fixed environment. The frame is coming from an AP and is going to a station. Installation Flexibility: Wireless network is suitable for any kind of geographical conditions. The data being transmitted is superimposed on the radio carrier so that it can be accurately extracted at the receiving end. A station can be of two types − 1.1. Lecture Series on Computer Networks by Prof. S. Ghosh,Department of Computer Science & Engineering, I.I.T.,Kharagpur. If the station finds a channel to be idle, the station waits for a period of time called distributed interframe space (DIFS). Two wireless LANs can communicate with each other using a bridge. 4. So one sees now what might be called WWAN (Wireless Wide Area Networks) based on WiFi technology (WiFi technology itself, however, carries data over short distances). Frame Control (FC). 4. This 2 byte field defines the sequence number of frame to be used in flow control. • Students or research scholars, attending a class inside an institute campus can instantly access the Internet to consult the catalog of the net digital library. These applications use. • The DCF is used in BSS having no access point. • There are four different addressing cases depending upon the value of To DS And from DS subfields of FC field. Lecture 4 Wireless LANs and PANs Reading: • “Wireless LANs and PANs,” in Ad Hoc Wireless Networks: Architectures and Protocols, Chapter 2. Also referred Radio LAN (WLAN) if the communication medium is the radio (not light infrared for example).The stations of the wireless network can communicate directly with each other, we called Ad Hoc network type, or via relay terminals called APs (Access Points, PA) then it is an infrastructure network. This NAV (created by other stations) specifies for how much time these stations must not check the channel. BK��(��O��GK�z��bA�54�59��� ��� ~�=�{��}�r/ #���HU�T�H����)/�8ϻ�y��V2'9��*T��S�t\u�k�-��Ƚ�r}��F��;!��&M�Ԅ IEEE 802.11b Wireless LANs Wireless Freedom at Ethernet Speeds With the recent adoption of new standards for high-rate wireless LANs, mobile users can realize levels of performance, … Introduction. Wireless LANs use management frames, control frames, and data frames. The nature of the wireless connection is transparent to the NOS. They often provide the final few meters of connectivity between a wired network and the mobile user. The fact that WiFi is originally designed to perform WLAN does not prevent not also be used in other contexts. These implementations, except the first one, operate in, • The modulation technique used is pulse position modulation (PPM), • This method uses frequency shift keying (two level or four level) for modulation, • There can also be a collision during handshaking, • There are four different addressing cases depending upon the value of. • IEEE 802.11 uses Frequency Hoping Spread Spectrum (FHSS) method for signal generation. The table below specifies the addresses of all four cases. • A pseudo random number generator selects the hopping sequence. No-transition .Mobility: These types of stations are either stationary i.e. If To DS = 0 and From DS = 1, it indicates that the frame is coming from a distribution system. A single access point can support a small group of users and can function within a range of less than one hundred to several hundred feet. Once data is superimposed (modulated) onto the radio carrier, the radio signal occupies more than a single frequency, since the frequency or bit rate of the modulating information adds to the carrier. Long-term cost benefits are greatest in dynamic environments, requiring frequent moves and changes. IEEE 802. Wireless LANs transmit and receive data over the atmosphere, using radio frequency (RF) or infrared optical technology, there by, eliminating the need for fixed wired connections. Lecture notes: Labs: Assignments: Project. • These are six different specifications of IEEE 802.11. Design Issues for the Layers . here EC6802 notes download link is provided and students can download the EC6802 Syllabus and Lecture Notes … • These extended networks are created by joining the access points of basic services sets through a wired LAN known as distribution system. This band is divided into 79 subbands of 1MHz with some guard bands. Richard III for providing some of the slides 1 . A special type of connectors which is used to establish connections between wired network devices such as Ethernet and different wireless networks such as wireless LAN. • In this method, at one moment data is sent by using one carrier frequency and then by some other carrier frequency at next moment. Data collecting units: These units collect data from other systems. This type of architecture is known as adhoc architecture. • Network managers installing networked computers in older buildings find that wireless LANs are a cost-effective network infrastructure solution. When a station is moved out of its range, it suffers from noise and error in the received data due to the poor signal strength. After this, an idle time is there in communication. • PCF uses centralized, contention free polling access method. Sending packets across shared networks ; Network wiring topologies; Details of Local Area Network (LAN) technologies; Previous: Next: Top of chapter: Lecture notes: Top of Telecom: Direct point-to-point communication. 6. 1.264 Lecture 36 Telecom: Wireless networks 1. The access point (or the antenna attached to the access point) is usually mounted high but may be mounted essentially anywhere that is practical as long as the desired radio coverage is obtained. The connection is very varied: there are WiFi USB adapters, PCMCIA, PCI, etc. the second type is by far the most common in business. These are used for accessing the channel and acknowledging frames. IEEE 802.11 defines several physical layers, with different data rates and modulating techniques. Design Issues for the Layers . 0 It acts as a point of control in wireless LAN architecture. A WLAN allows users to move around the coverage area, often a home or small office, while maintaining a network connection. 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