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Module D3

Module D3. More on Cellular Networks Femtocells Frequency Management Mobility Management Wireless Ad Hoc Networking Routing Examples m obnet.epfl.ch. Femtocells. Home base stations for mobile networks Licensed spectrum Low-power, low-range At user’s premises

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Module D3

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  1. Module D3 • More on Cellular Networks • Femtocells • Frequency Management • Mobility Management • Wireless Ad Hoc Networking • Routing • Examples mobnet.epfl.ch

  2. Femtocells • Home base stations for mobile networks • Licensed spectrum • Low-power, low-range • At user’s premises • Operated by cell. provider • Cellular access throughfixed broadband connection (ADSL,…) • Why femtocells? • Better throughput, coverage, lower prices for users • Unload wide area cellular networks, reduce op. costs

  3. Femtocell Deployment

  4. Network Architectures UMTS LTE

  5. Security and Privacy Challenges • New threats • Attacks on femtocells • Attacks on backhaul and core network (IPsec tunnel) FGW:Femtocell Gateway Source: www.SafeNet-Inc.com

  6. Femtocells : Radio Measurements Measurements carried out by Carl Hedari and Charles-Edmond Renouard with the contribution from Igor Bilogrevic

  7. Femtocells – Radio Measurements • Radiation pattern shows the performance of the antenna • The signal does not propagate equally all around the femtocell • W-CDMA Femtocell, ~5 MHz channelbandwidth

  8. How to Test a Femtocell in a Femtocell-less Country • The femtocell should only work in its originating country, mainly because of • frequency allocation issues • Often, the femtocell uses only the IP verification and customer • address to be localized • Idea: fool the verification process using a VPN located in • country X

  9. AnechoicChamberat EPFL Designed to stop reflections of RF • Simulates a quiet space of infinite dimension • Removes all source of exterior RF Avoids jamming Swiss carriers and allows isolating the femtocell

  10. Spectrum Analyzer – One Femtocell Femtocell : • Frequency : 2.137 GHz (UMTS) • Power : -60.25 dBm • Channel : 2.1351 GHz to 2.1396 GHz Spectrum Analyzer

  11. Spectrum Analyzer – Two Femtocells • Another femtocell brought into the anechoic chamber The femtocell listens to stations emitting on the same frequency and adapts its power output.

  12. Spectrum Analyzer – TwoFemtocells One femtocell operating normally Power : -60.25 dBm The same femtocell and another femtocell nearby. Power : -54.18 dBm With two active femtocells, the received power was increased by 6 dB (4 times more power)

  13. Radio Traces : Measures • 1 Femtocell • 1 Mobile from Operator X • 1 Mobile from Orange CH • An antenna was plugged into a 6 GHz capable Oscilloscope, and put inside the chamber to “listen” • The radio traces are displayed on the screen Inside the anechoic chamber

  14. Experiment 1 : Call established from Orange CH to X ∞ 50cm 50cm Orange CH Mobile X Femtocell Oscilloscope(not spectrumanalyzeranymore) Fs = 5 GHz Femtocell & Mobile X

  15. Experiment 2 : Call established between two Orange mobiles 2m 2.5m Orange CH Orange CH Oscilloscope Fs = 2.5 MHz Note: The sampling theorem was not respected for practical issues

  16. Experiment 3 : Initialization of the femto-cell ∞ 50cm 50cm Orange CH Mobile X Femtocell Oscilloscope Fs = 2.5 MHz Note: The sampling theorem was not respected for practical issues

  17. Frequency Management

  18. Frequency Management • In all countries of the world, the licensedspectrumismanaged by the governmentand (usually) leasedto privateoperators • Regulationauthority • In Switzerland: Federal Commission for Communications, or ComCom; assisted by BAKOM • In the US: FCC • In the EU: each country still has itsnationalregulationauthority • Somepoliticalwillingness (especially in the US) to reduce the role of the FCC  Dynamic Spectrum Allocation (cognitive radios)See the IEEE DySpanconference (ieee-dyspan.org)

  19. Procedure for Frequency Allocation • 2 main options • Auction • Beauty contest • Usuallyfixedprice • Basedon verydetailed dossiers + : pricepre-determined • : temptation/suspicion of bribery; no pricediscovery

  20. Auctioning of Frequencies • Goal of auction: best possible allocation of frequencies to operators • Auctions are notmeant to maximize the revenue for the government • Splitting of the frequency bands in blocks (e.g., of 2*5Mhz) • Issue: how to combine the auctioned blocks • Caps in high-value bands to avoidunfairbehavior • Typical duration of allocation: 10 to 20 years • Minimal (or starting) price: xxx CHFrs/MHz*Year (defined by law in the case of CH)

  21. The case of Switzerland • 3 main cellular operators (cellcos) • Swisscom (state-controlled) has 60% of the mobile market • Failedattempt of merger of Orange and Sunrise (in 2010) • Good quality of service, but high prices • Swisspecularities: topography, super-tightemissionregulations, site acquisitions (to set up base stations) oftenproblematic, expensivemanpower, high-revenue and change-averse population • All licencies (800, 900, 1800, 2100 and 2600MHz) to be (re-)allocated as of 2013 or 2016 until 2028 (auctionrun in February 2012; generated 996 MCHFrs)

  22. non-ionizing radiation

  23. Sunrise (50%) Swisscom (40%) Orange (10%) Previous frequency allocation in CH GSM900 Low frequencies • GSM 900 Frequencies • Allocation until 31.12.2013 • No free frequencies • GSM 1800 Frequencies • Allocation until 31.12.2013 • Some frequencies available (ex. Tele2) • UMTS Core Band • Allocation until 31.12.2016 • Some frequencies available 68MHz GSM1800 Sunrise (19%) Swisscom (21%) 146MHz Orange (40%) In&Phone (8%) ex. Tele2 (12%) UMTS core band (2100 MHz) Sunrise (25%) Swisscom (25%) Location of base stations: http://map.funksender.admin.ch/webgis/bakom.php Frequency allocation plan: www.bakom.admin.ch/themen/frequenzen/00652/00654/index.html?lang=en 140MHz Orange (25%) Not allocated (25%) High frequencies Courtesy: BAKOM

  24. Previous frequency allocation in CH

  25. Why an invitation to bid? • All mobile radio frequencies auctioned together • Bidders can purchase a new, future-proof spectrum package • A world first • Expiring licences: • GSM licences (900 + 1800 MHz): End of 2013 • UMTS licences (2100 MHz): End of 2016 • Many new mobile radio frequencies are available: • "Digital dividend" (in the 800 MHz band) ð Good propagation properties (even inside houses)ð Switzerland one of the first countries in Europe • UMTS extension band (2600 MHz) ð Suitable for LTE technology with high bandwidths • Goals: - more frequencies for more bandwidth in mobile communications - efficient use of spectrum with new technologies (LTE) Note: This slide and some of the following adapted from a slideshow kindly provided by Urs von Arx and Martin Dummermuth (BAKOM)

  26. Rapidly growing data traffic in mobile radio • Rapidly increasing amounts of data on mobile radio networksðDoubling every 9-12 months • More and more smartphones (iPhone, Android devices, etc):ð > 350 000 apps (incl. social networks such as Facebook and Twitter)ð mobile internet, mobile TV, YouTube...ð "Cloud computing" also mobile: same content present everywhere • Business Mobility:ðOffice applications and content on all devicesðnew, flexible forms of working • All internet applications and content anywhere, anytime on a mobile phone • Increase in network capacity essential

  27. New mobile radio technologies are coming • HSPA+ (Evolved High Speed Packet Access "plus") • Considerable increase in transfer rates (compared with UMTS) • Market-ready devices are already available • LTE(Long Term Evolution of UMTS; 4G) • 3 to 4 times higher spectrum efficiency than UMTS/HSPA • Increase in data rates to up to 100 Mbit/s in the downstream • Greater capacity in the network at a relatively low cost • New generation of mobile communications e.g. mobile HDTV, video streaming, on-line gaming…

  28. Why an auction? • A transparent procedure • The market determines the value of frequencies • The market decides on the scope of the licences(not the regulator): ð therefore: auction of small frequency blocksð Operators can acquire a new spectrum package which corresponds to their business models for the future • Equal treatment of all candidates:ðAll were able to take part on equal termsð No unilateral preference for any new entrants • Network operators purchase spectrum corresponding to their needs • No new market entry of an other network operator

  29. Result of the auction: CHFrs996'268'000

  30. Goals of the frequency allocation achieved • Consumers benefit: ü Technological innovation continues; new broadband services.ü High quality and good coverage • Technological progress supported:üfree choice of technology ü Operators can use LTE (high-speed broadband even in peripheral regions) • A frequency allocation with a promising future:ü All network operators acquire good spectrum + more spectrum • Long-term planning and investment security:ü Network operators can plan up to 2028 • Appropriate proceeds from the auction:ü A scarce public resource allocated appropriately üBenefits the community

  31. Reasons for the chosen form of the auction • The participants in the auction can bid on frequency packages. • The frequency packages correspond to their business model • Value, for which bidders are prepared to pay • Continuity for existing licensees: • Consistent with the existing frequency allocation

  32. Multi-phase sequence of the auction • Auction in two stages. The bidders were able: • to combine frequency ranges optimally; • bid in a second phase bid for the preferred frequencies within the individual ranges. • The auction took place over the internet from the bidders' company headquarters

  33. Example: CombinatorialClockAuction Increaseprice of band(s) withexcessdemand Yes Excessdemand in any band? Clock rounds No Supplementaryround (fine tune expression of wishes) Assignment of frequencies

  34. Bidding restrictions • Bidding restrictions (spectrum caps) • Maximum extent of frequencies per frequency band • Competition • Enabling competition during the auction • Increasing competition as much as possible after the auction by ensuring sufficient spectrum per bidder • No bidder may acquire the entire 900 MHz spectrum (GSM) • No market displacement of existing operators possible • Existing UMTS operators can purchase at least the current range of frequencies in the 2100 MHz band (UMTS) • No single bidder can dominate the major part of the GSM spectrum (900 MHz, 1800 MHz)

  35. Distribution of the frequency spectrum (I)

  36. Distribution of the frequency spectrum (II)

  37. Allocation of the frequency spectrum

  38. Licenses (1) • Term • Planning/investment security: early allocation and a term extending until 2028 • Utilization of free frequencies from award of license onwards • Neutrality with respect to technology • Flexible utilization of the spectrum for future developments • Conditions relating to utilization • Gradation: • - 50% population coverage for frequencies < 1 GHz • - 25% population coverage for frequencies > 1 GHz • No frequency hoarding • Freedom with respect to configuration (coverage, quality) • Supervisory procedures in the event of non-compliance

  39. Licenses (2) • Protection from immissions and spatial planning • Conditions as strict as those in existing licences • Provisions of Ordinance on Protection from Non-Ionising Radiation (OPNIR) • Shared use of sites outside the construction zone • Informing the cantons about network planning in good time

  40. References on Auctions • Cramton, Shohamand Steinberg (eds.): Combinatorial Auctions, MIT Press, 2006 • Ausubel, Lawrence M. and Paul Milgrom (2002), “Ascending Auctions with Package Bidding,” Frontiers of Theoretical Economics, 1, 1-45, http://www.bepress.com/bejte/frontiers/vol1/iss1/art1.

  41. Mobility Management

  42. User Tracking: Geographic-based Strategy Location area 1 (ID = 1) Location area 2 (ID = 2) 5. Inform the HLR of the new LA ID 1. Change LA 2. Receive the ID of the LA 3. Compare with stored ID 4. If different, update and ask for registration • Base stations periodically broadcast the ID of the LA • Users compare their last LA ID with the current ID, and transmits a registration message whenever the ID is different • When there is an incoming call directed to a user, all cells within its current LA are paged

  43. Location and Identity Privacy • Temporary Mobile Subscriber identifiers – TMSI – changed after crossing Location Area (LA) border or time-out trigger LA 0 Pseudo A LA 1 Pseudo B LA 3 Pseudo D LA 2 Pseudo C

  44. Handover Receivedsignal level Level at B Level at which handover is made(call transferred to BS2) t B A BS1 BS2

  45. MTSO: MobileTelecommunicationsSwitching Office (also called MSC: Mobile Switching Center)

  46. HandoverStrategies • The handover power level must becarefullychosen • Too small => risk of superfluous handovers • Too high => risk of losing the call due to weak signal • Mobile Assisted Handover (MAHO) • Mobiles measure power from surrounding base stations • Report to the serving base station • Handover if the power received from another station exceeds the serving station power by a certain threshold for a certain amount of time

  47. Hard/Soft Handover Hard: Communicate with one cell at a time Soft: Communicate with two cells simultaneously • TDMA & FDMA: Hard • Could technically use soft handover, but would be costly as it would require multiple parallel radio modules • CDMA: Soft • Needed to avoid near-far problem (i.e., Detect weaker signal amongst strong signals)

  48. Visited network Home network Subscriber database (IDs, keys, bills,…) Subscriber database (IDs, keys, bills,…) Roaming Principle Roaming agreement User

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