1. Cellular Networks 1

2. 6-2 What is mobility? Spectrum of mobility, from the network perspective: no mobility high mobility mobile wireless user, using same access point mobile user, passing through multiple access point while maintaining ongoing connections ( like cell phone) mobile user, connecting/ disconnecting from wired network.

3. Cellular Network Basics There are many types of cellular services. Cellular network/telephony is a radio-based technology; Radio waves are electromagnetic waves that antennas propagate Most signals are in the 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz frequency bands Cell phones operate in this frequency range (logarithmic scale) 3

4. Mobile Switching Center Public telephone network, and Internet Mobile Switching Center Components of cellular network architecture  connects cells to wide area net  manages call setup  handles mobility MSC  covers geographical region  base station (BS)  mobile users attach to network through BS  air-interface: physical and link layer protocol between mobile and BS cell wired network

5. In a cellular network, a geographical region is divided into service areas called “cells.” A cell is represented as a hexagon. At the center of a cell, is a Base Transceiver Station (BTS or BS) that serves users within the cell. Each cell is allocated a certain number of channels operating at a certain frequency.

6. Base Station: It is a BS consisting of a transceiver that receives or transmits signals over the radio interface. It serves one cell only. BS controller (BSC): controls one or more BSs.

7. Mobile switching center (MSC) sets up and maintains calls made in the network. An MSC connects the cellular network to the fixed telephone network infrastructure (i.e., the Public Switched Telephone Network [PSTN]). It performs all switching and signaling functions for MSs located in its area.

8. When you subscribe to a mobile telephony service, your information is stored in a database called: a Home Location Register (HLR). The HLR plays an important role in providing you with the services offered by your Service Provider. Databases

9. Home Location Register (HLR), stores data of participants, which are reported in an HLR-area –Semi-permanent data: Call number identity (International Mobile Subscriber Identity) - IMSI: MCC = Mobile Country Code (262 for.de) + MNC = Mobile Network Code Personal data (name, address, mode of payment) Service profile ( call transfer, Roaming-limits etc.) –Temporary data: MSRN (Mobile Subscriber Roaming Number) (country, net, MSC) VLR-address, MSC-address Authentication Sets of AuC Charge data

10. VLR is a database in a mobile communications network associated to a Mobile Switching Centre (MSC). The VLR contains the exact location of all mobile subscribers currently present in the service area of the MSC. This information is necessary to route a call to the right base station. Deleted when the subscriber leaves the service area. The Visitor Location Register (VLR)

11. Databases Visitor Location Register (VLR) local database of each MSC with following data: –IMSI, MSISDN –service profile –Accounting information –TMSI (Temporary Mobile Subscriber Identity) - pseudonym for data security –MSRN –LAI (Location Area Identity) –MSC-address, HLR-address

12. Mobile Communication Networks

13. UMTS (Universal Mobile Telecommunications System): European Standard for future digital Mobile Radio Networks GSM (Global System for Mobile Communications): worldwide standard for digital, cellular Mobile Radio Networks 802.11: International standard for Wireless Local Networks Bluetooth, Zigbee. Mobile Communication Networks

14. Mobile Communication Tied to electro-magnetic radio transmission radio transmission terrestrial orbital (satellite) beam radio broadcast radio equatorial orbit non-equatorial orbit cellularnon-cellular Principles: – Propagation and reception of electro-magnetic waves – Multiplex – Satellite orbits/Sight- and overlap areas

15. GSM: Properties Cellular radio network (2nd Generation) Digital transmission, data communication up to 9600 Bit/s Roaming (mobility between different net operators, international) good transmission quality (error detection and -correction) Scalable (large number of participants possible) Security mechanisms (authentication, authorization, encryption) Good resource use (frequency and time division multiplexing) Integration within ISDN and fixed network

16. Wireless Local Networks, WLAN

17. Why do we need Wireless LANs? Advantages No cables Flexibility Ad-hoc-networks Disadvantages High error vulnerability on the transmission link in comparison to Standard-LANs National restrictions, no international standards at used frequency bands (Industrial Scientific Medical (ISM)- Band) Security, costs

18. Basic WLAN- structure Ad-hoc-network: AP STA4STA5 3 connected infrastructure networks: AP - Access Point

19. Mobile IP (Internet Protocol)

20. Internet Protocol (IP) IP is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. The first major version of IP, Internet Protocol Version 4 (IPv4), is the dominant protocol of the Internet (IPv6).

21. Problem definition of classical IP Computer mobility in heterogenic networks Relocation between different IP-subnets Goal: transparent migration and localization, compatibility to IP, no changes of existing routers Idea: introduction of temporary/ actual IP-addresses Mapping of permanent to temporary IP-addresses using localization technique

22. Requirements to MobileIP Transparency: – mobile computer is permanently reachable via its previous “home-address” – can change its network access point freely – can also communicate after coupling/uncoupling Compatibility: – mobile computer can also communicate with each “non- mobileIP”-computer – no changes to existing computer/routers Security: – all registering messages must be authenticated

23. Sridhar IyerIIT Bombay23 3G Network Architecture Mobile Access Router Wireless Access Network IP Base Stations Gateway Telephone Network Core Network User Profiles & Authentication (HLR) 3G Air Interface Wired Access 802.11 IP Intranet Programmable Softswitch Application Server 802.11 Access Point Internet

24. What is 802.11? A family of wireless LAN (WLAN) specifications developed by a working group at the Institute of Electrical and Electronic Engineers (IEEE) Defines standard for WLANs using the following four technologies – Frequency Hopping Spread Spectrum (FHSS) – Direct Sequence Spread Spectrum (DSSS) – Infrared (IR) – Orthogonal Frequency Division Multiplexing (OFDM) Versions: 802.11a, 802.11b, 802.11g, 802.11e, 802.11f, 802.11i

25. Performance 802.11a maximum rate of 54Mbps in the 5 GHz band 802.11b maximum rate of 11Mbps at in the 2.4 GHz spectrum band 802.11g is a new standard for data ratesup to 54 Mbps at 2.4 GHz.

26. Mobile Ad Hoc Networks

27. 27 Introduction Two types of wireless networks: – Infrastructured network: Base stations are the bridges A mobile host will communicate with the nearest base station Handoff is taken when a host roams from one base to another

28. 28 – Ad hoc network: infrastructureless: no fixed base stations without the assistance of base stations for communication Due to transmission range constraint, – two units need multi-hop routing for communication quickly and unpredictably changing topology

29. 29 MANET = Mobile Ad Hoc Networks – a set of mobile hosts, each with a transceiver – no base stations; no fixed network infrastructure – multi-hop communication – needs a routing protocol which can handle changing topology

30. 30 Single-Hop Ad Hoc

31. 31 Multi-hop Ad Hoc

32. 32 Typical Ad-Hoc applications Personal area networking – cell phone, laptop, ear phone, wrist watch Military environments – soldiers, tanks, planes Civilian environments – car network meeting rooms – sports stadiums – boats, small aircraft Emergency operations – search-and-rescue – policing and fire fighting

33. The Dynamic Host Configuration Protocol (DHCP) is a standardized network protocol used on Internet Protocol (IP) networks for dynamically distributing network configuration parameters, such as IP addresses for interfaces and services. With DHCP, computers request IP addresses and networking parameters automatically from a DHCP server, reducing the need for a network administrator or a user to configure these settings manually.

34. 6-34 How do you contact a mobile friend: search all phone books? call her parents? expect her to let you know where he/she is? I wonder where Alice moved to? Consider a friend frequently changing addresses, how do you find her?

35. 6-35 Mobility: approaches Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. – routing tables indicate where each mobile located – no changes to end-systems Let end-systems handle it: – indirect routing: communication from correspondent to mobile goes through home agent, then forwarded to remote – direct routing: correspondent gets foreign address of mobile, sends directly to mobile

36. 6-36 Mobility: approaches Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. – routing tables indicate where each mobile located – no changes to end-systems Let end-systems handle it: – indirect routing: communication from correspondent to mobile goes through home agent, then forwarded to remote – direct routing: correspondent gets foreign address of mobile, sends directly to mobile not scalable to millions of mobiles

37. Mobile Switching Center VLR old BSS new BSS old routing new routing GSM: handoff with common MSC Handoff goal: route call via new base station (without interruption) reasons for handoff: – stronger signal to/from new BS (continuing connectivity, less battery drain) – load balance: free up channel in current BS

38. 6-38 Mobile Switching Center VLR old BSS 1 3 2 4 5 6 7 8 GSM: handoff with common MSC new BSS 1. Old BS informs MSC of impending handoff, provides list of 1 + new BSs 2. MSC sets up path (allocates resources) to new BS 3. new BS allocates radio channel for use by mobile 4. new BS signals MSC, old BS: ready 5. old BS tells mobile: perform handoff to new BS 6. mobile, new BS signal to activate new channel 7. mobile signals via new BS to MSC: handoff complete. MSC reroutes call 8 MSC-old-BS resources released

39. 6-39 home network Home MSC PSTN correspondent MSC anchor MSC MSC (a) before handoff GSM: handoff between MSCs anchor MSC: first MSC visited during call – call remains routed through anchor MSC new MSCs add on to end of MSC chain as mobile moves to new MSC IS-41 allows optional path minimization step to shorten multi-MSC chain

40. 6-40 home network Home MSC PSTN correspondent MSC anchor MSC MSC (b) after handoff GSM: handoff between MSCs r anchor MSC: first MSC visited during cal m call remains routed through anchor MSC r new MSCs add on to end of MSC chain as mobile moves to new MSC r IS-41 allows optional path minimization step to shorten multi-MSC chain