1 / 25

Location management

Location management. Prof. Malathi Veeraraghavan Elec. & Comp. Engg. Dept/CATT Polytechnic University mv@poly.edu. EL604: Wireless & Mobile Networking. What is the problem?.

evers
Download Presentation

Location management

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Location management Prof. Malathi Veeraraghavan Elec. & Comp. Engg. Dept/CATT Polytechnic University mv@poly.edu EL604: Wireless & Mobile Networking

  2. What is the problem? • How does a network deliver a packet or a call to a destination that may not be located at the physical location indicated by its address? • e.g., a 212 telephone user located in SF

  3. Location management • Solutions to the problem combine mobile location with limited mobile tracking in order to decrease the “find” operation cost • Thus, location management is the set of procedures to • track a mobile user • find a mobile user to deliver it calls or packets

  4. Extreme solution: an overlay approach • Don’t track the mobile user at all • When a call/packet is to be delivered, page at all base stations in all networks • Cost • huge “find” cost • zero “move” cost

  5. Another extreme solution an integrated approach • Every time a mobile moves, send a routing update with its reachability to all switches in all networks • When a call/packet arrives at a switch, it immediately knows where mobile is • Cost • huge “move” cost • zero “find” cost

  6. Routing tables Dest. Next hop IV III-5 Local Routing protocol Routing protocol Dest. Next hop III-* II Dest. Next hop III-5 Mobile III-5 IV III-* III III-5 Local Routing protocol + routing table precomputation + “move” update II Mobile III-5 III I Host A IV • Routing protocols exchange topology/loading/reachability information • Summarized routes precomputed • Mobile III-5’s move causes a route update

  7. Two approaches • Integrated • Overlay

  8. Completely integrated approach • Move operation • Send updates via routing protocol as mobile user moves • Find operation • Route packets or calls trusting routing information • Second “extreme” case solution

  9. Overlay approach • Move operation • Send updates via a separate registration message to one “home” server • Find operation • Send a query message to find location of mobile before routing calls/packets • Solution somewhere between extremes

  10. Hybrid integrated/overlay • Move • Limit region to which routing updates sent (integrated) • Say just CA if NY mobile is visiting in SF • Create a “neighborhood” around mobile • Register current neighborhood with home switch (overlay) • Cancel information at old neighborhood • Find (integrated) • If calls/packets originate at some other switch within CA, call/packet will be routed directly • If calls/packets originate in other neighborhoods, they will be routed to home switch and will then be forwarded to mobile’s current neighborhood • may need route optimization

  11. e.g. Location management in cellular networks • Move operation • a mobile’s location is registered at a Home Location Register (HLR) or a Visitor Location Register (VLR) – 2-level database hierarchy • Find operation • location query message is sent to HLR to find mobile’s location when a call arrives

  12. Cellular network architecture • MSC: Mobile Switching Center • SS7: Signaling System No. 7

  13. Signaling associated with location management • On air interface: • Registration: a mobile sends a registration (called association in 802.11) to the network when it changes location area • Group of cells form a registration area or location area; BSs send ID of location area in their beacons allowing a mobile to recognize an area change as it moves • Page: to find mobile to deliver it a call • Between base-stations and MSCs: A interface • Between network elements: IS-41

  14. IS41 MAP • MAP: Mobile Application Part • Used on the interfaces between MSCs, HLRs and VLRs

  15. IS41 location management messages • RegistrationNotification • RegistrationCancellation • ServiceProfileRequest • QualificationRequest • LocationRequest • RouteRequest

  16. RegistrationCancellation RegistrationNotification VLR1 VLR2 HLR air-interface/ A interface registration 718-555-1234 IS41 move operation MSC2 415-555 MSC1 718-555

  17. RouteRequest RouteRequest Reply (TLDN = 415-555-5643) Page LocationQuery Setup (415-555-5643) 718-555-1234 Setup (718-555-1234) IS41 find operation HLR VLR2 VLR1 MSC2 415-555 MSC1 718-555 PSTN Switch PSTN Switch PSTN Switch TLDN: Temporary Local Directory Number

  18. RouteRequest VLR1 RouteRequest LocationQuery Reply (TLDN = 415-555-5643) Setup(415-555-5643) Page Setup (718-555-1234) Setup (718-555-1234) IS41 find operation – if originating switch does not support mobility HLR VLR2 PSTN Switch MSC2 415-555 MSC1 718-555 PSTN Switch PSTN Switch PSTN Switch TLDN: Temporary Local Directory Number 718-555-1234

  19. IS41 location management • Overlay or integrated?

  20. IS41 questions • How are the IS41 signaling messages transported? • How does the originating switch know the address HLR of the called party? • Type of address: point codes (SS7 network)

  21. Transport of IS41 signaling messages in cellular networks • Telephony networks are circuit switched • Signaling messages to set up circuits could potentially be sent on direct links between switches • Mobility management related signaling messages (i.e., IS41 messages) are sent between “non-neighboring” nodes (location registers, switches)

  22. Best choice: CL network • Best choice for such messaging: CL network • Don’t want to waste time setting up a connection from VLR to HLR before sending a Register message • The network used for this purpose: SS7

  23. GTT – Global Title Translation • Solution for the second problem: • How does the originating switch know the address HLR of the called party? • GTT is used to determine point code address of HLR corresponding to a mobile’s MIN • Mappings are stored in STPs • Analogy: STP is comparable to a combined IP router/DNS server

  24. Analogous to DNS for email service • DNS typically used to translate domain name to IP address of host • Also used to find the server of a specific host for applications such as the Simple Mail Transfer Protocol (SMTP) • DNS type field: MX • MX DNS queries ask for IP address of SMTP server that serves a given email user given the user’s email address (e.g., xxx@yahoo.com)

  25. Summary • Location management • Move and find operations • Integrated and overlay methods • Examples • IS41 • Mobile IP • GSM

More Related