Outline. Wireless System Integration WLAN. WAN Technologies ดร. อน นต ผลเพ ม LAN. WAN Server LAN. Wireless System Architecture Protocols

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1 Wireless LANs 1 st semester 2002 (June September) Wireless System Integration ดร. อน นต ผลเพ ม Anan Phonphoem, Ph.D. [email protected] Intelligent Wireless Network Group (IWING Lab) Computer Engineering Department Kasetsart University, Bangkok, Thailand 1 Roaming Protocol Connectivity Software 2 Wireless System Architecture WLAN Distributed system WAN Server Wireless Access Point Wireless NIC Adapter (PCMCIA/PCI adapter) LAN Department Store Chain Example 3 4 LAN LAN Technologies Ethernet Token Ring FDDI Speed 10 / 100 / 1000 Mbps Media UTP / Coax / Fiber Network devices Hub / Switch / Bridge / Repeater WAN Technologies Frame Relay Packet SW, less overhead X Kbps 2 Mbps Switched Multimegabit Data Sevice (SMDS) Packet Sw, connectionless datagram Mbps ATM Circuit Sw 155 Mbps 5 6 1

2 WAN Technologies Private WAN High cost /Dedicate links / Fixed BW Leased T1 and 56 Kbps Public WAN Low cost / variable BW / reliability Leased connections shared among companies Roaming Protocol Protocol Connectivity Software 7 8 Roaming Protocols Multiple-Cell WLAN Wireless station moves from cell to cell Seamlessly connectivity maintain No roaming specified in IEEE Roaming Concept station checks its signal strength (Communication Quality:CQ) from Access Point CQ decreases when station move away from an Access Point If too low, looking for a new Access Point Reassociate to the new strong signal strength Access Point 9 10 Proprietary Roaming Protocol Proprietary Roaming Protocol Lucents WaveAROUND All linked cells are called Domain Each wireless station can move among cells Cells need not to be overlapped Cell-1 Cell-2 Cell-3 11 regularly broadcast beacon Beacon contain DomainID NetworkID of Communications-quality info Cell-Search threshold value Wireless Station uses beacon for monitoring and switch 12 2

3 Responsiveness 3 Modes Relaxed mode: low beacon rate Normal mode: moderate beacon rate Fast mode: High beacon rate Quality VS. overhead Cell Search Thresholds Sensitivity Time used to search and switch Level of Communication Quality 3 thresholds Regular cell search: Start searching, switch only quality > Stop cell search Threshold Stop cell search: Stop searching quality level [Low, Normal, High] Fast cell search: start searching, switch if quality is better Inter-Access Point Protocol (IP) Roaming through multiple-vendor s Use Distribution system interface of IEEE Operate between by using UDP & IP 2 basic protocols: Announce Protocol Handover Protocol Roaming note Depend on the product Choose the one that support IP Choose common vendor/product Roaming Protocol Communications Protocol Connectivity Software Communication Protocols TCP/IP Static / Dynamic IP address (DHCP) TCP/IP issues for WLAN High overhead (TCP) Marginal condition Mobile node address Mobile IP

4 Mobile IP Enhancement of standard IP protocol Enable station to roam among different IP network (subnetwork) Use Address forwarding mechanism (post mail delivery) No change in the DNS or router Mobile IP Entities Mobile Node Home Agent (a host / a router) Foreign Agent (a host / a router) Care-of-Address (Foreign Agent IP) Correspondent Node (a server) Mobile IP Server Mobile IP Home Agent Server Foreign Agent Mobile Node Mobile Node Mobile IP Protocol Agent Discovery Assignment of Care-of-Address Registration Tunneling & Encapsulation Agent Discovery Goal Bind mobile host to foreign/home agent Foreign Agent & Home agent periodically broadcast beacon Mobile listens and initiate registration request Determine its location If it is located on home network not use mobility function If it is located on foreign network obtain a Care-of-Address

5 Assignment of Care-of-Add Home network uses Care-of-Address to forward packet to the mobile node To assign a Care-of-Address 1. Foreign agent maintain a single care-of-add for all mobiles (IP of FA) 2. Mobile node acquires the care-of-address through a protocol (DHCP) Care-of-Address Home Address Care-of-Address LifeTime (ms) Home Agent Table (mobility binding table) Home Address Home Agent Address Mobile Address F F LifeTime (ms) 300 Foreign Agent Table (visitor list) Registration Registration After receiving a care-of-add, Mobile node (Foreign agent) registers to Home agent Establish a link between the foreign and Home network Mobile node & Home Agent communicate with encryption (like a tunnel) Source: CS640 - WISC Tunneling & Encapsulation The tunnel end point Home agent IP Care-of-Address Home agent intercepts datagram of mobile node Then encapsulate and send to the care-of-address destination Foreign agent decapsulates Then passes the datagram to mobile node Mobile node can send data using regular IP packet to the destination 29 Tunneling & Encapsulation Source: CS640 - WISC 30 5

6 Mobile IP in action Encapsulation Source: 31 Source: 32 Mobile IP Problems? Sub-Optimal Triangle Routing Reliability problem Home agent down? Security Fake connection Etc. Roaming Protocol Connectivity Software Software Connectivity Software Deal with the application software (presentation layer) Terminal Emulation Direct Database Connectivity Internet-Based Connectivity Software Middleware Terminal Emulation Make the appliance appear as a terminal on hostbased OS No programming needed Centralize Low cost Inflexible Limited application support Significantly effect on wireless network (TCP)

7 Direct DB Connectivity Interface directly to database on the server Communicate via I or ODBC (Open Database Connectivity) Flexible / Low cost Good support for client/server Good data transfer Distributed software control TCP overhead Internet-Based Web client / server Using HTTP No programming needed Centralize Low cost Strong support of client/server TCP overhead Middleware Increase performance of application running across wireless network BW & disruption connection Data compression Intelligent restart (from disruption) Picky-back ACK Store-and-forward packet Support Mobile IP High cost (long term cost saving) 39 7