Fundamentals. Antennas Mobility Management. Frequencies Modulation. Mobile Communication Fundamentals 1

Transcription

1 Mbile Cmmunicatins Fundamentals Frequencies Mdulatin Antennas Mbility Management Mbile Cmmunicatin Fundamentals 1

2 Frequency Spectrum fr Cmmunicatin Frequencies, Examples: Audi TV VLF LF HF VHF UHF IR UV XR Walkie-Talkie 27 MHz Cellular GSM Paging g Cellular GSM Crdless DECT UMTS 900 MHz 930 MHz 1800 MHz 1880 MHz 2000 MHz Mbile Cmmunicatin Fundamentals 2

3 Frequency Spectrum fr Cmmunicatin Different applicatins use different frequency spectrum (carrier frequencies) e.g. FM-Radi 88,5 MHz 107,9 MHz e.g. crdless telephne DECT 1880 MHz 1990 MHz ITU-R regularly rganizes cnferences in rder t crdinate the frequency spectrum wrldwide e.g. FM-Radi (UKW) is apprximately the same in Germany and Cratia Hwever, there is n exact harmnizatin f spectrum ver the wrld, because spectrum is a natinal issue e.g. GSM Eurpe 900 and 1800 MHz e.g. GSM USA 1900 MHz Mbile Cmmunicatin Fundamentals 3

4 Frequency spectrum fr cellular mbile systems Mbile Cmmunicatin Fundamentals 4

5 Frequency spectrum fr wireless LAN (WLAN) max. pwer [mw] Mbile Cmmunicatin Fundamentals 5

6 Mdulatin Digital Infrmatin is mdulated n a carrier frequency e.g. Amplitude mdulatin ASK (Amplitude Shift Keying) Frequency mdulatin FSK (Frequency Shift Keying) Phase mdulatin Phasen shift at binery 0 Phasenmdulatin PSK (Phase Shift Keying) 180 phase shift Mbile Cmmunicatin Fundamentals 6

7 Mdulatin: several bits per signal state There are variants f the mdulatin techniques which can transmit serveral bits at ne signal state change, e.g. amplitude with 4 levels Mbile Cmmunicatin Fundamentals 7

8 I/Q-Mdulatin diagram Example: Oscillatin with stable amplitude (Magnitude) Plar diagram: Phase and Amplitude are spcified by a Q and I value Mbile Cmmunicatin Fundamentals 8

9 Mdulatin: several bits per signal state The signal changes fr every pair f bits between 4 states (10) (11) (00) -45 (01) A cmbinatin f 4 phases and tw amplitudes results in 8 different signal states, i.e. 3 bits can be transmitted in parallel Mbile Cmmunicatin Fundamentals 9

10 Amplitude and Phase mdulatin cmbined Mbile Cmmunicatin Fundamentals 10

11 Mdulatin schemes fr mbile cmmunicatin fr the efficient use f spectrum frequency, amplitude and phase mdulatin are cmbined, e.g. 8-PSK (Phase Shift Keying), e.g. EDGE 16-QAM (Quadrature Amplitude Mdulatin), e.g. High Speed Dwnlink Packet Access (HSDPA), 10Mbps UMTS 8-PSK 16-QAM Q I 1000 Mbile Cmmunicatin Fundamentals 11

12 Mdulatin schemes fr mbile cmmunicatin 8-PSK cmbines 8 phases, at each phase change 3 bits can be transmitted Theretically, there can be any number f signal states (phases) Hwever, in reality it is difficult fr the receiver t distinguish tw states which are clse t each ther Mbile Cmmunicatin Fundamentals 12

13 Mdulatin schemes fr mbile cmmunicatin Examples: BPSK ( = 2-PSK) pwer line cmmunicatin mdem QPSK ( = 4-PSK) UMTS/CDMA 8-PSK GSM/EDGE 16-QAM HSDPA 64-QAM HSPA (cat15/16), LTE, a GMSK GSM 256QAM Digital Vide Bradcast 1024QAM cabel mdem Mbile Cmmunicatin Fundamentals 13

14 Mdulatin schemes fr mbile cmmunicatin GSM uses GMSK (Gaussian Minimum Shift Keying) GMSK is a frequency ptimized FSK scheme GMSK is a mdulatin scheme that is rbust against radi disturbance uses the spectrum in a very efficient way (bandwidth per transmissin rate) facilitates highly effective signal amplificatin s that mbile statins with battery have lnger peratin Mre n mdulatin can be fund here, fr example: df/ e.pdf Mbile Cmmunicatin Fundamentals 14

15 Ultra Wide Band (UWB) Candidate fr future high bit rate Wireless Persnal Area Netwrks (WPANs). Ranges f <10m In rder t increase wireless capacity, it is necessary t be able t transmit mre kbps/m² (kil bit per secnd per square meter) Example capacity f transmissin systems: Mbile Cmmunicatin Fundamentals 15

16 Ultra Wide Band (UWB) UWB desn t need it s wn frequency band, it c-exists as an verlay system with ther services can be perated license free and uses unused r used spectrum can be perated very inexpensively and energy efficient transmits at very high transmissin rate, multi channel and is rbust against interference because f lw PSD (Pwer Spectral Density), UWB cannt easily be detected by ther systems Mbile Cmmunicatin Fundamentals 16

17 Ultra Wide Band (UWB) Hw des it wrk? Traditinal systems use carrier frequencies and mdulate digital infrmatin n them UWB des nt use a carrier. The 0s and 1s are cded by very shrt bursts, by use f ne f the fllwing methds: Mbile Cmmunicatin Fundamentals 17

18 Ultra Wide Band (UWB) Biplar mdulatin: a 1 is represented by a psitive (increasing) pulse, while a 0 is represented by the inverse (decreasing) Amplitude mdulatin: a 1 is represented by the full amplitude, while the 0 is represented by half f it Pulse psitin mdulatin: the time slt between tw signals varies, a delayed pulse represents a 0 Mbile Cmmunicatin Fundamentals 18

19 Ultra Wide Band (UWB) Hw des it wrk? emitted transmissin signal pwer vs. used spectrum Mbile Cmmunicatin Fundamentals 19

20 Ultra Wide Band (UWB) Why d the bursts ccupy wide frequency band? Furier transfrmatin says that every pulse frm can be apprximated by the weighted sum f sine curves e.g., a rectangular pulse can be generated by the sum f a Fundamental sine curve plus s called Harmnics Mbile Cmmunicatin Fundamentals 20

21 Ultra Wide Band (UWB) The shrter the pulse, the higher the frequency f the sine curve must be t reach apprximatin In the example belw the 4 Harmnics ccupy a higher bandwidth fr a shrt pulse cmpared t a lnger pulse Mbile Cmmunicatin Fundamentals 21

22 Ultra Wide Band (UWB) Cmparisn between the spectrum ccupied by a 600 psec pulse cmpared by a that f a 300 psec pulse. Mbile Cmmunicatin Fundamentals 22

23 Ultra Wide Band (UWB) Example f a wireless HDMI device with UWB "Wireless HDMI Extender f Gefen range is 10m line f sight transmitter receiver Mbile Cmmunicatin Fundamentals 23

24 Ultra Wide Band (UWB) T date systems: transmit 480 Mbit/s ver 3m transmit 110 Mbit/s ver 10m Mbile Cmmunicatin Fundamentals 24

25 Example usage scenari fr UWB Mbile Cmmunicatin Fundamentals 25

26 Ultra Wide Band (UWB) Surces: tecchannel B4A8809EC588EEDF&pageNumber=1&catID=2 B4A8809EC588EEDF Mbile Cmmunicatin Fundamentals 26

27 Antennas: istrpic radiatr Radiatin and receptin f electrmagnetic waves Istrpic radiatr: equal radiatin in all directins (three dimensinal) - nly a theretical reference antenna Real antennas always have directive effects (vertically and/r hrizntally) Radiatin pattern: measurement f radiatin arund an antenna Gain: maximum pwer in the directin f the main lbe cmpared t the pwer f an istrpic radiatr (with the same average pwer) Antenna Mbile Cmmunicatin Fundamentals 27

28 Antennas: directed and sectrized Antennas fr mbile cmmunicatin are ften cntructed in a way that they preferably transmit r receive in certain directins, e.g. transmissin and receptin alng a rail track y y z x z x directed antenna side view (xy plane) side view (yz plane) tp view (xz plane) z z x x sectred antenna tp view, 3 sectrs tp view, 6 sectrs Mbile Cmmunicatin Fundamentals 28

29 Antennas: samples L-band satellite receiver statin (DFD, Oberpfaffenhfen) L- and S-band receiver antenna Mbile Cmmunicatin Fundamentals 29

30 Antennas The received pwer P r decreases with the distance between receiver and transmitter. It depends n the transmitted pwer P, the gain and the distance. P t G t P r G r P r G r d kilmeter d kilmeter P r P = energy (t/r = transmit/receive) P 2 t Gt Gr d = wave length (c/frequency) G = gain c = speed f light Mbile Cmmunicatin Fundamentals 30

31 Antennas because f the frmula abve the higher frequency is used fr dwnlink and the lwer frequency fr uplink Example GSM Mhz (uplink) Mhz (dwnlink) Mbile Cmmunicatin Fundamentals 31

32 Antennas example 500 W 0,8 W 2 W 10 kilmeter 20 kilmeter influenced by curvature f the earth relief features (muntains, etc.) buildings, trees, etc. atmsphere (in particular fr high frequencies, e.g. 60 GHz) Mbile Cmmunicatin Fundamentals 32

33 Signal prpagatin Prpagatin in free space always like light (straight line) Receiving pwer prprtinal t 1/d² in vacuum much mre in real envirnments (d = distance between sender and receiver) Receiving pwer additinally influenced by fading (frequency dependent) d shadwing reflectin at large bstacles refractin depending n the density f a medium scattering at small bstacles diffractin at edges shadwing seflectin scattering diffractin Mbile Cmmunicatin Fundamentals 33

34 Multipath prpagatin Signals can take many different paths between sender and receiver due t reflectin, scattering, diffractin? results in additinal backgrund nise Is a particular prblem fr mdulatin schemes with high bitrate, e.g. 64-QAM Mbile Cmmunicatin Fundamentals 34

35 Multipath prpagatin effects The interference is lcatin and frequency dependent example f a measurement f received signal strength vs. distance t the sender surce: Mbile Cmmunicatin Fundamentals 35

36 Multipath prpagatin effects example f a measurement f received signal strength vs. Frequencs (lcatin is fixed) surce: Mbile Cmmunicatin Fundamentals 36

37 Multipath prpagatin effects example f a measurement f received signal strength by frequency and distance SNR (Signal t Nise Rati) is a measure f signal strength surce: sem/index htm Mbile Cmmunicatin Fundamentals 37

38 OFDM (Orthgnal Frequency Divisin Multiplexing) Separatin f a high speed bit tream int several lw speed nes verlap f frequency bands Frequency Frequency Mbile Cmmunicatin Fundamentals 38

39 OFDM (Orthgnal Frequency Divisin Multiplexing) Eliminatin f verlap interference by rthgnal frequencies sub channel frequencies are chsen in a way such that the maximum n an scillatin at ne frequency cincides with the zer lcatin f the neighburing frequencies Mbile Cmmunicatin Fundamentals 39

40 OFDM (Orthgnal Frequency Divisin Multiplexing) Each sub carrier can use its wn mdulatin scheme cmmn schemes: BPSK, QPSK, 16 QAM und 64 QAM OFDM is used in HSDPA, a and n adaptive wrt signal quality Time Signal quality SNR (Signal/Nise Rati) BPSK QPSK 16QAM Mbile Cmmunicatin Fundamentals 40

41 OFDMA (OFDM Access) Each sub carrier can be assigned t a different user fr multiplexing l i purpses OFDM tutrial e.g.: frequency frequency Mbile Cmmunicatin Fundamentals 41

42 Cellular netwrks the further transmitter and receiver are apart frm each ther, the higher h the energy necessary t transmit at the same data rate (assuming the envirnmental influences remain stable) because f limited battery capacity energy cnsumptin f mbile devices shuld be kept limited therefre the range is limited Hw can we build a wide area mbile netwrk? cellular netwrk Mbile Cmmunicatin Fundamentals 42

43 Mbility Management Questins: Wh is where? Hw can I reach him/her? May I access a freign netwrk? Hw? Hw can I be handed ver frm ne access pint t the next ne... the fundamentals f mbility management are very similar ver different netwrk types Mbile Cmmunicatin Fundamentals 43

44 Mbility Management: Registratin Hme (sub-)netwrk hme data base Freign (sub-)netwrk Mbile Cmmunicatin Fundamentals 44

45 Mbility Management: Cnnectin establishment hme data base Hme (sub-)netwrk 1 2 Freign (sub-)netwrk 4 3 Mbile Cmmunicatin Fundamentals 45

46 Mbility Management Fundamentals f mbility management are very similar ver different netwrk types. The hme data base has different names, and it can be several data bases: Hme Lcatin Register (HLR) in GSM/UMTS Hme Subscriber Server (HSS) in 3GPP-IMS Hme Agent (HA) bei MbileIP SIP-Prxy in Vice ver IP (VIP) services AAA-Server (Authenticatin, Authrizatin and Accunting) etc. The hme data base can be n ne s wn server (PC) at hme, such as in Mbile IP, r it can be a data base at a mbile netwrk peratr with whm ne has a cntract, such as in GSM. Mbile Cmmunicatin Fundamentals 46

47 Mbility Management: Challenges The challenges and the cmplexity f Mbility Management in real systems result, amng ther things, frm the fllwing: may the user access a freign netwrk? the user is mbile, i.e. he/she mves and therefre has t change access pint nce in a while (handver), hw can, at the same time the cnnectins be retained seamlessly? hw des the accunting take place, when users mve t freign netwrks? hw can it be insured that privacy is preserved, while the user is mving? n which rutes, ver which gateways, with which technlgy and resurces perates the cmmunicatin? Mbile Cmmunicatin Fundamentals 47