Simple Reference Model MOBILE COMMUNICATION Simple Reference Model

Simple Reference Model PDA Computer BTS Inter working unit

Simple Reference Model PDA Computer BTS Inter working unit Application Application Transport Transport Network Network Network Network Data Link Data Link Data Link Data Link Physical Physical Physical Physical Medium Radio Protocol Stacks

Physical Layer Converts bits into signals at transmitter side and vice-versa at receiver side. Responsible for frequency selection Generates carrier frequency Signal detection Encryption and decryption of data Combating Interference, attenuation Modulation of data into carrier frequency

Data Link Layer Media access/control Authentication, Multiplexing of different data streams Correction of transmission errors Synchronizations (detection of data frames Reliable point to point connection between two devices or point – to – multipoint connection between sender and several receivers.

Network Layer Responsible for routing packets through a network or establishing a connection between two entities over many other intermediate systems. Addressing Device location, Hand-over between different networks

Transport Layer Used for end to end connection Flow and congestion control Quality of service

Application layer Service location Support for multimedia applications, new/adaptive applications that can handle the large variations in transmission characteristics Wireless access to the www using a portable device. Video (high data rate) and interactive gaming (low jitter, low latency) are very demanding applications.

Function of Layers in a Mobile Communication Environment Service location, multimedia, new/adaptive applications End to end connection, congestion/flow control quality of service addressing, routing, device location, hand-over between different networks Media access/control, authentication, multiplexing, error correction, point to point connection, Synchronizations, Converts signals in to bits and vice-versa, Encryption, modulation, Frequency selection, Interference, attenuation Application layer Transport layer Network layer Data link layer Physical layer

Overlay Networks - the global goal integration of heterogeneous fixed and mobile networks with varying transmission characteristics regional vertical handover metropolitan area campus-based horizontal handover in-house

FREQUENCIES FOR RADIO TRANSMISSION

Electromagnetic Spectrum

Frequencies for communication 300 Hz 10 km 30 kHz 100 m 3 MHz 1 m 300 MHz 10 mm 30 GHz 100 m 3 THz 1 m 300 THz visible light VLF LF MF HF VHF UHF SHF EHF infrared UV optical transmission coax cable twisted pair Divided into bands which exhibit certain advantages and disadvantages. VLF = Very Low Frequency UHF = Ultra High Frequency LF = Low Frequency SHF = Super High Frequency MF = Medium Frequency EHF = Extra High Frequency HF = High Frequency UV = Ultraviolet Light VHF = Very High Frequency Frequency and wave length  = c/f  =wave length, c = speed of light  3x108m/s, and f = frequency

Frequencies for mobile communication VHF-/UHF-ranges for mobile radio simple, small antenna for cars deterministic propagation characteristics, reliable connections SHF and higher for directed radio links, satellite communication small antenna, beam forming large bandwidth available Wireless LANs use frequencies in UHF to SHF range some systems planned up to EHF limitations due to absorption by water and oxygen molecules (resonance frequencies) weather dependent fading, signal loss caused by heavy rainfall etc.

VLF LF 30-300 KHz) Submarine Comn, Radio (1.48.5 & 283.5 KHz in Germany) MF , HF, VHF Radio stations. AM (520-1605 KHz & SW 5.9 -26.1 MHz) FM 87.5-108 MHz VHF(30-300 MHz) TV (174-230 MHz) , DAB (223-230 MHz) UHF (300-3000 MHz) TV (470-790 MHz), DAB (1452-1472 MHz) Mobile phones (450-465 MHz, GSM (890-960 MHz, 1710-1880 MHz), DECT(1880-1900 MHz), 3G/UMTS (1900-1980 MHZ, 2020-2025 MHz, 2110-2190 MHz) SHF(3 GHZ-30 GHZ) Microwaves( 2-40 GHZ), FSS in C, Ku,Ka Bands EHF(30 GHz-300GHz) Close to IR. Note : All radio frequencies are regulated to avoid interference

REGULATIONS RF are scarce resource Nations find it difficult for common word wide regulation due to their national / economic interest ITU , sub org of UN, at Geneva; is responsible for world wide coordination of telecommunication activities (wired & wireless) ITU-R (formerly CCIR) handles (a) Standardisation in the wireless (b) Freq planning Three regions – for world wide coordination and to reflect national interest Region 1 – Europe, Africa , Middle East and Countries of erstwhile Soviet Union Region 2 – North and South America and Green Land Region 3 – Far East, India, Australia and New Zealand

- Systems are operating at different frequencies REGULATIONS National agencies are responsible within these regions e.g. FCC in USA, CEPT in Europe, WPC in India Harmonisation. ITU-R holds the world wide conference (WRC) to discuss and decide freq allocation for the three regions – a difficult task - Systems are operating at different frequencies - Satl Freq – generally cross national boundaries - ISM band - 2.4, 5, 17.2, 24 & 61 GHz 433 & 686 MHz – for car locks, wireless hand sets, RFIDs

Frequencies and regulations Universität Karlsruhe Institut für Telematik Frequencies and regulations Mobilkommunikation SS 1998 ITU-R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences) Examples Europe USA Japan Cellular phones GSM 880-915, 925-960, 1710-1785, 1805-1880 UMTS 1920-1980, 2110-2170 AMPS, TDMA, CDMA, GSM 824-849, 869-894 TDMA, CDMA, GSM, UMTS 1850-1910, 1930-1990 PDC, FOMA 810-888, 893-958 PDC 1429-1453, 1477-1501 FOMA 1920-1980, 2110-2170 Cordless phones CT1+ 885-887, 930-932 CT2 864-868 DECT 1880-1900 PACS 1850-1910, 1930-1990 PACS-UB 1910-1930 PHS 1895-1918 JCT 245-380 Wireless LANs 802.11b/g 2412-2472 802.11b/g 2412-2462 802.11b 2412-2484 802.11g 2412-2472 Other RF systems 27, 128, 418, 433, 868 315, 915 426, 868 Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller 18

ASSIGNMENT NO 1 Q1. Differentiate between user mobility and device portability. Q2. Write short history of mobile communication. Q3. What are the two different approaches in regulation regarding mobile phone systems ? What are its consequences? Q4. Draw the simplified reference model and explain the functions of each layer. Q5. Differentiate between mobile and wireless.

Assignment No. 1 Q1. Differentiate between user mobility and device portability. (PP 21) Q2. Differentiate between mobile and wireless. (PP 21-22) Q3.). Write short history of mobile communication. (pp 29-34). Q4. Draw the simplified reference model and explain the functions of each layer. (pp 39)

Q3. What are the two different approaches in regulation regarding mobile phone systems ? What are its consequences? Ans. 1. The classical European approach was based on standardisation and regulation before any products were available. The EU governments founded ETSI to harmonize all national regulations. ETSI created the standards, all countries had to follow. 2.In the US companies develop systems and try to standardize them or the market forces decide upon success. The FCC, e.g., only regulates the fairness among different systems but does not stipulate a certain system. The effects of the two different approaches are different. Many “governmental” standards in Europe failed completely, e.g., HIPERLAN 1, some succeeded only in Europe, e.g., ISDN, and however, some soon became a worldwide success story, e.g., GSM. For most systems the US approach worked better, first some initial products, then standards. One good example is the wireless LAN family 802.11, a good counter example is the mobile phone market: several different, incompatible systems try to succeed, many features, well established in Europe since many years, are not even known in the US (free roaming, MMS, GPRS roaming, no charges for being called etc.).

SIGNALS

SIGNALS Physical representation of data Layer 1 of OSI model is for conversion of data into signals & vice versa Signals are functions of time and location g(t) = At sin(2πft +φt) Classification continuous time/discrete time signals continuous values/discrete values signals analog signal = continuous time and continuous values digital signal = discrete time and discrete values signal parameters of periodic signals: period T, frequency f=1/T, amplitude A, phase shift  signal parameters: parameters representing the value of data

Signals Parameters of signal may change with time. Universität Karlsruhe Institut für Telematik Signals Mobilkommunikation SS 1998 Parameters of signal may change with time. Phase shift determines the shift of the signal relative to the same signal without shift. See fig below (a) (b) (c) Different representations of signals (a) amplitude (Time domain) (b) frequency spectrum (frequency domain) (c) phase state diagram (amplitude M and phase  in polar coordinates) A [V] Q = M sin  A [V] t[s]  I= M cos   f [Hz] Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller 24

Fourier representation of periodic signals Universität Karlsruhe Institut für Telematik Signals Mobilkommunikation SS 1998 sine wave is a special periodic signal for a carrier: g(t) = At sin(2  ft t + t) Fourier representation of periodic signals 1 1 t Ideal periodic signal t real composition (based on harmonics) Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller 25

Composed signals transferred into frequency domain using Fourier transformation Digital signals need - infinite frequencies for perfect transmission - modulation with a carrier frequency for transmission (analog signal!)

ANTENNA

ANTENNA Couples the EM energy to and from space from and to a wire or coaxial cable Isotropic antenna-- a reference antenna – a point radiating equal power in all directions. The radiation pattern is symmetric in all directions Radiation pattern- measurement of radiation around an antenna Y Z X Fig. Radiation pattern of an isotropic antenna However such antenna does not exist in reality

ANTENNA Real Antennas are not isotropic radiators but exhibit directive effects. Simplest real antenna is a thin, centre-fed dipole also called Hertzian dipole dipole with length /4 on car roof  shape of antenna proportional to wavelength λ/2 Dipole is made of two collinear conductors of equal length, separated by a small gap Dipole λ/4 Marconi antenna

Antennas: Simple Dipoles Example: Radiation pattern of a simple Hertzian dipole side view (xy-plane) x y side view (yz-plane) z top view (xz-plane) simple dipole Gain: maximum power in the direction of the main lobe compared to the power of an isotropic radiator (with the same average power) This type of antenna can only overcome environmental challenges by boosting power level of the signals. Challenges could be mountains, valleys, buildings, etc.

Directional Antennas Sectorized Antennas Multi element antenna arrays. Smart Antennas

Directed Antennas : Radiation Pattern Often used for microwave connections or base stations for mobile phones (e.g., radio coverage of a valley) y y z Directed antenna x z x side view (xy-plane) side view (yz-plane) top view (xz-plane) z Sectorized antenna – several antennas combined on single pole - Enables freq reuse z x x top view, 3 sector top view, 6 sector

Antennas: diversity Diversity combining Grouping of 2 or more antennas to improve reception Also called multi-element antenna arrays Antenna diversity switched diversity or selection diversity receiver chooses antenna with largest output Diversity combining combine output power to produce gain Co-phasing needed to avoid cancellation + /4 /2 ground plane

Smart Antennas : Salient Features Combine multiple antenna elements( also called antenna array) with signal processing to optimise the radiation / reception pattern. Can adapt to changes in received power, transmission conditions and many signal propagation effects. Can be used for beam forming. This would be an extreme case of directed antenna which can follow a single user thus using SDM. Today's hand set antenna are omni directional as integration of smart antenna into mobile is difficult.

ASSIGNMENT NO 1 Q1. Is it possible to transmit a digital signal, e.g., coded as square wave as used inside a computer, using radio transmission without any loss? Why? Q2. Is a directional antenna useful for mobile phones? Why? How can the gain of an antenna be improved? Q3. What are the main problems of signal propagation? Why do radio waves not always follow a straight line? Why is reflection both useful and harmful? Q4. Why, typically, is digital modulation not enough for radio transmission? What are general goals for digital modulation? What are typical schemes?

Q.5 Discuss various types of antennas briefly? (MDU May 09)