Brief Review on Wireless Communications and Networks

1. Brief Review on Wireless Communications and Networks Dr. Frank Lee Computer Science Department California Lutheran University 10/26/2005

2. Outline • Cellular Wireless Networks • Wireless Local (Subscriber) Loop • Mobile Internet Protocol (IP) • Wireless Application Protocol (WAP) • Wireless Local Area Networks (LAN)

4. Cellular Systems Terms • Base Station (BS) – includes an antenna, a controller, and a number of receivers • Mobile telecommunications switching office (MTSO) – connects calls between mobile units

7. Steps for a Mobile Cellular Call (Fig. 10.6) 1. Mobile unit initialization: selects the strongest setup control channel 2. Mobile-originated call: sends the number of the called unit on the pre-selected setup channel 3. Paging: The MTSO sends a paging message to certain BSs depending on the called mobile unit number

8. Steps for a Mobile Cellular Call (Fig. 10.6) 4. Call accepted: The called mobile unit recognizes its number on the setup channel being monitored and responds to that BS, which send the response to the MTSO 5. Ongoing call: The two mobile units exchange voice or data signals, going through their respective BSs and the MTSO 6. Handoff: If a mobile unit moves out of range of one cell and into the range of another during a connection, the traffic channel has to change (without either interrupting the call or alerting the user) to one assigned to the BS in the new cell

9. Cellular Phone Networks – First Generation • Provided analog traffic channels • Advanced Mobile Phone Service (AMPS) • A popular system developed by AT&T • In North America, two 25-MHz bands allocated to AMPS • One for transmission from base to mobile unit • One for transmission from mobile unit to base

10. Second-Generation • GSM: Global System for Mobile Communications (Europe, 1990) • Advantages over first-generation • Higher quality signals • Higher data rates for supporting digital services • Greater channel capacity • Better security system • Multiple channels per cell • Each channel is dynamically shared by a number of users by using CDMA (Code-Division Multiple Access) technology

12. Third-Generation • Using WCDMA (wide-band CDMA) technology • Good voice quality • Provide high-speed data rate for motor vehicles over large areas • Available to pedestrians standing or moving slowly over small areas • Support for 2.048 Mbps for office use • Support for both packet switched and circuit switched data services

14. Outline • Cellular Wireless Networks • Wireless Local (Subscriber) Loop • Mobile Internet Protocol (IP) • Wireless Application Protocol (WAP) • Wireless Local Area Networks (LAN)

15. Wireless Local Loop (WLL) • Fixed wireless access • Narrowband – offers a replacement for existing telephony services • Broadband – provides high-speed two-way voice and data service • Cost – wireless systems are less expensive due to cost of cable installation that’s avoided • Installation time – WLL systems can be installed in a small fraction of the time required for a new wired system • Selective installation – radio units installed for subscribers who want service at a given time • With a wired system, cable is laid out in anticipation of serving every subscriber in a given area

17. Outline • Cellular Wireless Networks • Wireless Local (Subscriber) Loop • Mobile Internet Protocol (IP) • Wireless Application Protocol (WAP) • Wireless Local Area Networks (LAN)

19. Operations of Mobile IP (Fig. 12.1) 1. Server X transmits an IP datagram destined for mobile node A. 2. The home agent encapsulates the entire datagram inside a new IP datagram that has the A’s care-of address (foreign agent’s location) in the header, and retransmits the datagram to foreign agent. The use of an outer IP datagram with a different destination IP address is known as tunneling.

20. Operations of Mobile IP (Fig. 12.1) 3. The foreign agent strips off the outer IP header, encapsulates the original IP datagram in a network-level PDU (protocol data unit, such as a LAN logic link control frame), and delivers the original datagram to node A across the foreign network. 4. Each IP datagram is sent from A to a router (the foreign agent) on the foreign network for routing to X. 5. The IP datagram from A to X travels directly across the Internet to X, using X’s IP address.

22. Mobile IP Applications • Enable computers to maintain Internet connectivity while moving from one Internet attachment point to another • Mobile – user's point of attachment changes dynamically and all connections are automatically maintained despite the change • Nomadic - user's Internet connection is terminated each time the user moves and a new connection is initiated when the user dials back in • A new temporary IP address is assigned

23. Outline • Cellular Wireless Networks • Wireless Local (Subscriber) Loop • Mobile Internet Protocol (IP) • Wireless Application Protocol (WAP) • Wireless Local Area Networks (LAN)

24. Wireless Application Protocol (WAP) • Open standard providing mobile users of wireless terminals access to telephony and information services • Wireless terminals include wireless phones, pagers and personal digital assistants (PDAs) • Designed to work with all wireless network technologies such as GSM, CDMA, and TDMA • Based on existing Internet standards such as IP, WML (wireless markup language), XML, HTML, and HTTP • Includes security facilities

26. Operations of WAP (Fig. 12.10) • Using WAP, a mobile user can browse Web content on an ordinary Web server • The Web server provides content in the form of HTML-coded pages that are transmitted using the standard Web protocol stack (HTTP/TCP/IP) • The HTML content must go through an HTML filter, which may either be co-located with the WAP proxy or in a separate physical module • The filter translates the HTML content into WML content

27. Operations of WAP (Fig. 12.10) 5. If the filter is separate from the proxy, HTTP/TCP/IP is used to deliver the WML to the proxy 6. The proxy converts the WML to a more compact form known as binary WML and delivers it to the mobile user over a wireless network using the WAP protocol stack 7. If the Web server is capable of directly generating WML content, then the WML is delivered using HTTP/TCP/IP to the proxy, which converts the WML to binary WML and then delivers it to the mobile node using WAP protocols

28. Outline • Cellular Wireless Networks • Wireless Local (Subscriber) Loop • Mobile Internet Protocol (IP) • Wireless Application Protocol (WAP) • Wireless Local Area Networks (LAN)

31. Wireless LAN Applications • LAN extension • Cross-building interconnect • Nomadic access • Ad hoc networking

32. LAN Extension • Wireless LAN linked into a wired LAN on same location • Wired LAN • Backbone • Support servers and stationary workstations • Wireless LAN • Stations in large open areas • Manufacturing plants, stock exchange trading floors, and warehouses

33. Cross-Building Interconnect • Connect LANs in nearby buildings • Wired or wireless LANs • Point-to-point wireless link is used • Devices connected are typically bridges or routers

34. Nomadic Access • Wireless link between LAN hub and mobile data terminal equipped with antenna • Laptop computer or notepad computer • Uses: • Transfer data from portable computer to office server • Extended environment such as campus

35. Ad Hoc Networking • Temporary peer-to-peer network set up to meet immediate need • Example: • Group of employees with laptops convene for a meeting; employees link computers in a temporary network for duration of meeting

37. Wireless LAN Requirements • Throughput • Number of nodes • Connection to backbone LAN • Service area • Battery power consumption • Transmission robustness and security • Collocated network operation • License-free operation • Handoff/roaming • Dynamic configuration

38. Wireless LAN Categories • Infrared (IR) LANs • Spread spectrum LANs • Narrowband microwave

40. Thank You!