Introduction to Mobile Computing - Wireless Local Area Networks - Part 1

1. Introduction to Mobile Computing - Wireless Local Area Networks - Part 1

2. Overview • History of WLANs • Benefits of WLANs • The 802.11 Standards • WLAN Components • WLAN Architectures • WLAN Applications

3. History of WLANs • LANs first developed in the last 1970s and early 1980s to allow interconnection of users through wires or cables to facilitate sharing of data and resources • the benefits of this new technology soon led to the standardisation by the IEEE committee which is summarised by the IEEE 802 standard • Since the early days LANs further developments have resulted in a whole family of standards that are all known as IEEE 802

4. History of WLANs • WLANs evolved through the change in requirements and technology advances to overcome the limitations of wired LANs • WLANs are defined as part of the 802 family of standards as 802.11 that was defined in 1997 • This standard defines wireless communication for fixed, portable and moving stations within a restricted area allowing for communication to take place without the need for cables • the 802.11 standard comprises different standards that are constantly evolving

5. Benefits of WLANs • Compared to traditional LANs WLANs offer many benefits to networking such as mobility, flexibility and scalability • they are capable of providing transmission speeds close to wired LANs • they are easy to install and cost-efficient • provide access for several machines

6. WLANs – The 802.11 Standard • The 802.11 standard is a group of standards known as 802.11a, 802.11b and the latest addition 802.11g • The standards have been agreed and defined by the IEEE committee • the individual standards define the parameters such as transmission speed and frequency range as well as how access to the air interface is facilitated and services that can be used • standards are backwards compatible

7. WLANs – The 802.11 Standard • Summary of WLAN Standards • There is a variety of hardware components available to implement WLANs depending on the type of application it is used for such as user equipment, Access points and bridges

8. WLANs – The 802.11 Standard

9. WLANs – The 802.11 Standard • 802.11 is often referred to as Wi-Fi although this is strictly speaking not accurate • Despite the agreed and defined 802.11 standards companies are allowed to modify these standards to their requirements • This can result in two devices that seemingly follow the same standard being unable to communicate • The Wi-Fi certified logo indicates that devices have been certified and will be able to communicate with other Wi-Fi certified devices that follow the same agreed standard • Further details regarding Wi-Fi can be found under: http://wi-fi.org

10. WLAN Components User Equipment (UE): • Any device that provides access to a WLAN through a wireless LAN air interface • Most frequently used device on WLAN • E.g. Laptop, PDA, bar code reader, etc. • Devices can be upgraded to provide WLAN capabilities

11. WLAN Components Access Points (AP): • Acts as a point of access for WLAN user equipment • Provides access between the wireless and wired part of the network • Usually requires an antenna • Multiple access points can be used to provide roaming for larger networks

12. WLAN Components Wireless Bridges (WB): • WLAN component that allows linking up two or more LANs in different buildings through a high speed data link between them • used to connect sites that are hard to link up in a traditional way • requires the use of an antenna – various options available depending on requirements • in order to establish a link using a wireless bridge at least two bridges are required

13. WLAN Architectures • Although WLANs are considered to be wireless networks they are not completely wireless • in most cases WLANs are part of a traditional wired LAN as they rely on wired network to provide full access to other wired networks such as the Internet • Hence WLANs can be seen as an extension or add-on to normal local area networks to provide support for wireless nodes such as laptops • Wireless local area networks can be established in two basic system architectures: infrastructure based or ad hoc

14. Ad Hoc Architectures • In ad hoc configuration mode mobile stations communicate directly with each other without the help of other WLAN infrastructure • Ad hoc networks are the most basic type of WLAN that consists of a minimum of two stations • as machines are directly connected they are also referred to as a peer-to-peer network • to allow machines to communicate they have to be within range of their transmitters/receivers • this mode requires no planning

15. Ad Hoc Architectures Example architecture:

16. Infrastructure Based Architectures • An infrastructure based system architecture relies on the attached infrastructure to provide full access for the mobile stations • The connection to the wired networks is provided through wireless access points • access points form part of the wired network but at the same time provide a wireless interface and can hence be considered to link the wired and wireless parts of the network • this mode requires planning in order to provide optimal coverage

17. Infrastructure Based Architectures Example architecture – Basic Service Set (BSS):

18. Infrastructure Based Architectures Example architecture – Extended Service Set (ESS):

19. Infrastructure Based Architectures • Another implementation of WLANs is for the purpose of linking two networks in different buildings through the use of wireless bridges • This involves the involvement of antennaes on both sides for the wireless transmission • a requirement for the WLAN implementation is the line of sight • There is a limit regarding the maximum distance of the two sites allowed in order to allow for wireless data transfer

20. Infrastructure Based Architectures Example architecture:

21. WLAN Applications T-Mobile HotSpot: • WLAN network provided by T-Mobile in a variety of places such as hotels, coffee shops, airports etc. all over the United Kingdom • Allows users to wirelessly access the Internet with a WiFi enabled device that is within the HotSpot range • Users needs to be registered with the network in order to gain access • HotSpot Network compatible with 802.11b standard

22. WLAN Applications Skype WiFi Phone: • Mobile WiFi enabled phone that allows users to make free Internet calls through to other skype users • Skype software is already pre-installed on phone and ready to be used with a wireless network – no configuration required • Example on the left is 802.11g compatible and backwards compatible with the 802.11b standard

23. WLAN Applications WiFi enabled camera: • Allows user to transmit photos wirelessly to either a computer or printer • In the case of wireless printing printer needs to be equipped with special software and hardware • Nikon P1/P2 are 802.11g compatible and backwards compatible with the 802.11b standard

24. WLAN Applications Playstation 3 PS3 - WiFi enabled: • Game Console with WiFi built in • Can be integrated into a network through WiFi capabilities • Further wireless feature provided through wireless controller that uses Bluetooth standard to connect to playstation

25. WLAN Applications WiFi enabled printers: • Allows adding a printer to the network without running cables through the room • Printer receives transmissions wirelessly • Further option: connect a Wi-Fi enabled camera and print directly without having to transfer pictures onto your PC first

26. WLAN Applications Eye-Fi – WiFi enabled memory card: • Memory card to automatically upload pictures without having to plug it into a card reader • Pictures can be uploaded to any WiFi enabled device such as PCs, printers, etc. • http://www.eye.fi/

27. IMWT – WLANs Part 1 Questions ...?