Mobile Communication and Mobile Computing

Transcription

1 Department of Computer Science Institute for System Architecture, Chair for Computer Networks Mobile Communication and Mobile Computing Prof. Dr. Alexander Schill

2 Structure of the Lecture Part I: Mobile Communication - Introduction and Principles - GSM and Extensions - 4G Networks - 5G Evolution - WiFi - Satellite and Broadcast Systems Part II: Mobile Computing - Mobile Internet Protocols - Web-based Mobile Applications - Mobile Platforms and Middleware - Context Awareness and Adaptation - Industry Presentations and Practice Reference: - Jochen Schiller: Mobile Communications, Addison-Wesley 2

3 Introduction and Principles 3

4 Application Example: Civil Engineering, Field Service Large archives, Videoconferences Drafts, urgent modification Enterprise A (main office) Gigabit Ethernet Enterprise A (branch office) Fast Ethernet Architect Gigabit Ethernet Selected drafts, Videoconferences UMTS, LTE Construction supervisor GSM, UMTS Enterprise B Material data, status data, dates Building site 4

5 Mobile Multimedia Local Resources, Test Protocols Product Data Main office Caching Maintenance technician Mobile Access Client LAN-Access Very different performances and costs: radio networks versus fixed networks Software-controlled, automatic adaptation to concrete system environments Example: Access to picture data / compressed picture data / graphics / text 5

6 Example: End-User Application 6

7 Traffic Telematics Systems Main Office Content Provider Content Provider Gigabit Ethernet GSM, TMC, DAB... Internet Point-to-Point Radio, Internet GSM GSM GSM Radio/Infrared DAB: Digital Audio Broadcasting TMC: Traffic Message Channel Infrastructure 7

8 Mobile Communication: Development Mobile Phone Networks C D (GSM900) E (GSM1800) HSCSD EDGE Packet Networks Modacom GPRS Circuit Switched Networks Satellite Networks Mobitex Inmarsat Tetra Iridium/ Globalstar 3G/UMTS 4G/LTE advanced 5G (beyond LTE) Cordless Telephony CT DECT Local Networks Radio-LAN IR-LAN IEEE Bluetooth n, ac WiMAX

9 Used Acronyms C: C: Analog C Network (1st Generation) CT: CT: Cordless Telephone DECT: Digital Enhanced Cordless Telecommunications EDGE: Enhanced Data Rates for GSM Evolution GSM: Global System for Mobile Communications (2nd Generation) GPRS: General Packet Radio Service HSDPA+: HSCSD:High Speed Downlink Packet Access (advanced) HSUPA+: HSCSD: High Speed Uplink Packet Access (advanced) High Speed Circuit Switched Data EDGE: LTE: Long Term Evolution (4th Generation) TETRA: Terrestrial Trunked Radio (Multicast Communication System) UMTS: Universal Mobile Telecommunications System (3rd Generation) WiMAX: 4G: W Worldwide Interoperability for Microwave Access 9

10 Correspondent data rates 1 Gbit/s LTE (downlink) 300 Mbit/s 5G 200 Mbit/s 100 Mbit/s LTE (uplink) / HSDPA+ 50 Mbit/s HSUPA+ 10 Mbit/s UMTS (pico cell) WiFi 1 Mbit/s DECT 100 kbit/s EDGE HSCSD/ GPRS UMTS (macro cell) 10kbit/s GSM Satellites

11 Frequency Assignment Circuit Switched Radio Mobile Phones Cordless Phones Wireless LANs TETRA NMT TETRA LTE 800 CT2 CT1+ GSM900 CT1+ GSM Mhz GHz (nationally different) TFTS (Pager, aircraft phones) GSM1800 TFTS GSM1800 DECT UMTS WLAN IEEE b/g/n Bluetooth LTE 2600 WIMAX ( ) IEEE a/n Future 5G Beyond 5 GHz up to 100 GHz ,4 GHz and higher: often license free, nationally different -> interesting for high data rates TFTS - Terrestrial Flight Telephone System NMT Nordic Mobile Telephone 11 MHz

12 Principles of Mobile Communication Based on electro-magnetic radio transmission radio transmission terrestrial orbital (satellite) point-to-point Broadcast radio equatorial orbit non-equatorial orbit cellular non-cellular Principles: Propagation and reception of electro-magnetic waves Modulation and multiplex methods; focusing on cellular networks 12

13 Cellular networks well known from mobile networks (GSM, UMTS) base station (BS) covers at least one cell; a combination of multiple cells is also called a cellular structure provides different kinds of handovers between the cells higher capacity and better coverage than non-cellular networks bidirectional* antennas instead of omni-directional** can better serve the selected sectors along highways or train lines for covering of larger areas * ** 13

14 Cellular networks: handover (1) A procedure inside a cellular network, which controls the switching process between the cells and end devices Reasons for handovers are: leaving the transmission range of a cell overloading or breakdown of the used cell loss of connection quality 14

15 Cellular networks: handover (2) Handover classes Intra-cell: switch-over inside the cell onto other frequency or other timeslot Inter-cell: switch-over to a neighboring cell Inter-system: switch-over between different technologies (e.g. UMTS, LTE or 5G); roaming Handover types Hard handover: active connection gets disconnected before the connection to a new cell is established Soft handover: active connection gets disconnected after the connection to a new cell is established (as usual in current networks) 15

16 Structure of a cellular network Major problems: limited frequency resources interference Therefore: reuse of frequency channels in remote cells Recommended reuse distance D: 1 D = 3N R where: N is the number of different cell types, and R is the cell radius 16

17 D/R Ratios versus Reuse Patterns D R D = 3N R D/R-Ratio Cluster size, N 3,46 4 4, , Cluster of N cells with R cell radius; D reuse distance with the use of sectored antennas 17

18 Frequency Distribution: Examples D/R=3 with N=3 Frequency distribution according to IEEE b/g/n D/R=4.6 with N=7 Frequency distribution according to IEEE a 18

19 Multiplex Methods: Principles Multiplex Concurrent usage of the medium without interference 4 multiplex methods: - Space - Time - Frequency - Code Medium Access controls user access to medium implemented by combining and exploiting multiplex methods 19

20 SDMA (Space Division Multiple Access) Communication channel relates to definite regional area or physical infrastructure Space Multiplex for instance in the Analog Phone Systems (for each participant one line), for Broadcasting Stations, and in Cellular Networks Problem: secure distance (interferences) between transmitting stations is required (using one frequency), and by pure Space Multiplex each communication channel would require an own transmitting station Therefore space Multiplex is only reasonable in combination with other multiplex methods 20

21 SDMA: Example k1 k2 k3 k4 k5 k6 f1 s SDMA selects cell s secure distance 21

22 FDMA (Frequency Division Multiple Access) frequencies are permanently assigned to transmission channels (known from broadcast radio) k1 k2 k3 k4 k5 k6 f k6 k5 f1 f2 f3 s FDMA selects frequency f4 f5 f6 k4 k3 k2 k1 t s secure distance 22

23 TDMA (Time Division Multiple Access) transmission medium is slot-assigned to channels for certain time, is often used in LANs Synchronization (timing, static or dynamic) between transmitting and receiving stations is required k1 k2 k3 k4 k5 k6 TDMA selects slot f1 f k1 k2 k3 k4 k5 k6 k1 t 23

24 Combination: FDMA and TDMA, (e.g. in GSM) GSM uses combination of FDMA and TDMA for better use of narrow resources the used bandwidth for each carrier is 200 khz => approx. 124 * 8 = 992 channels f in MHz 960 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 downlink 935,2 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 25 MHz khz TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 uplink 890,2 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 25 MHz 45 MHz t 24

25 CDMA (Code Division Multiple Access) k1 k2 k3 k4 k5 k6 CDMA decoded f1 definite Codes are assigned to transmission channels, these can be on the same Frequency for the same Time Implemented efficiently in hardware but: exact synchronization is required, code of transmitting station must be known to receiving station, complex receivers for signal separation are required; noise should not be very high 25

26 CDMA illustrated by example The principle of CDMA can be illustrated by the example of some party: communication partners stand close to each other, each transmission station (Sender) is only so loud that it does not interfere to neighbored groups transmission stations (Senders) use certain Codes (for instance, just different languages) receiving station (Listener) tunes to a specific language (Code) in order to decode the content if other receiving station (Listener) cannot understand this language (Code), then it can recognize the data (as a kind of background noise), but it cannot do anything with them if two communication partners would like to have some secure communication line, then they should simply use a secret language (Code) Potential Problems: security distance is sometimes too small: interferences (i.e. Polish und Russian) 26

27 CDMA example technically Sender A Sends A d =1, Key A k = (set: 0 = -1, 1 = +1) Transmit signal A s =A d *A k = (-1, +1, -1, -1, +1, +1) Sender B sends B d =0, Key B k = (set: 0 = -1, 1 = +1) Transmit signal B s =B d *B k = (-1, -1, +1, -1, +1, -1) Both signals overlay on the air Faults are ignored here (noises etc.) C = A s + B s =(-2,0,0,-2,+2,0) Receiver will listen to Sender A uses Key A k bitwise (internal product) - A e = C * A k = = 6 - Result is greater than 0, so sent bit was 1 likewise B - B e = C * B k = = -6, i.e. 0 27