Transcript
XE37KTR Communication Technology – Radio Systems
Radio Systems - Communication Systems 2
CTU Prague, FEE, Dept. of Radioelectronics
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XE37KTR Communication Technology – Radio Systems
Communication Systems • Terrestrial – Fixed • Microwave, Optical data links • HF – UHF commercial communications • Amateur licensed radio
– Mobile • cellular systems (GSM, GPRS,UMTS,...) • License-free radio – CB – Civilian Band Radio – FRS, PMR466
Communication Systems
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XE37KTR Communication Technology – Radio Systems
Fixed communication links • VHF/UHF – over-the-horizon communication – effect of atmosferical refraction and scattering Diffraction
Refraction
Communication Systems
Scatter
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XE37KTR Communication Technology – Radio Systems
Fixed communication links • MW and optical links • Direct visibility, attenuation by rain, fog – dispersion, troposphere scatter – over the horizon • Microwave radio relay – post office, governmental links, leased links
Communication Systems
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XE37KTR Communication Technology – Radio Systems
MW and optical links • • • • • •
WLAN core connections 2, 5, 10, 14 GHz Bands, up to 10 Mbps Typical output power ~ 10W Digital modulations – PSK, QAM, FSK Point-to-point connection Ronja (Reasonable Optical Near Joint Access) – community project for two-directional optical link Communication Systems
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XE37KTR Communication Technology – Radio Systems
Amateur radio – Ham Radio • • • • •
Ham radio Amateur license – associated callsign FM, SSB HF, VHF, UHF bands Long distance connections (reflection from Moon surface) – HF
Communication Systems
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XE37KTR Communication Technology – Radio Systems
Amateur radio – Ham Radio • Preferable voice communication • Morse code, Q-codes • International Amateur Radio Union (IARU)
Communication Systems
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XE37KTR Communication Technology – Radio Systems
Terrestrial Mobile Systems
Communication Systems
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XE37KTR Communication Technology – Radio Systems
Applications •
Vehicles – transmission of news, road condition, weather, music via DAB – personal communication using GSM – position via GPS – local ad-hoc network with vehicles close-by to prevent accidents, guidance system, redundancy – vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance
•
Emergencies – early transmission of patient data to the hospital, current status, first diagnosis – replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc. – crisis, war, ... Communication Systems
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XE37KTR Communication Technology – Radio Systems
Applications 2 •
Traveling salesmen – direct access to customer files stored in a central location – consistent databases for all agents – mobile office
•
Replacement of fixed networks – remote sensors, e.g., weather, earth activities – flexibility for trade shows – LANs in historic buildings
•
• Entertainment, education, ... – outdoor Internet access – intelligent travel guide with up-to-date location dependent information – ad-hoc networks for multi user games Communication Systems
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Mobile Systems Overview XE37KTR Communication Technology – Radio Systems
Generation
Name
Comment
NMT (Nordic Mobile Telephone); 450 MHz, 900 MHz AMPS (Advance Mobile Telephone System); USA 1 (1980 - 1995) TACS (Total Access Communication System); UK, I, SP, Radiocom 2000; FR GSM (Global System for Mobile communications) - GSM 900 - GSM 1800 (DCS, Digital Communication System) DAMPS (Digital AMPS, or IS136) 2 PCS 1900 (Personal Communication systém) (1992 - 2000) USA GSM variant IS95 (Interim Standard) based on CDMA - IS95a,b dsignated also as cdmaOne PDC (Personal Digital Communication) GPRS/ (General Packet Radio Service) 2,5 EGPRS/EDGE (Enhanced GPRS/Enhanced Data rates (1999 - 2010) for Global Evolution) cdma2000 - cdma2000 1xEV-DO (cdma2000 Evolution-Data 3 Only/Optimazi) (2004 - ) - cdma2000 1xEV-DV (cdma2000 Evolution-Data/Voice) UMTS (Universal Mobile Telecommunication System) Communication Systems
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Analogue Systems National Systems Voice Digital Systems Voice+Data
Digital Systems Voice+Data Digital Systems Multimedia Content
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XE37KTR Communication Technology – Radio Systems
Mobile Systems Development
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM System • Global System for Mobile communications (Groupe Spécial Mobile)
• Mobile cellular Telephony System • History: Specification started 1982 (CEPT) – 1989 (ETS), First network 1991 (Radiolinja, FIN / Ericsson) • Regulatory and standardization body: 3GPP • Four operational bands across the world Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM System Frequencies System
Band
Uplink (MHz)
Downlink (MHz)
Channel Number
T-GSM-380
380
380.2–389.8
390.2–399.8
Dynamic
T-GSM-410
410
410.2–419.8
420.2–429.8
Dynamic
GSM-450
450
450.4–457.6
460.4–467.6
259–293
GSM-480
480
478.8–486.0
488.8–496.0
306–340
GSM-710
710
698.0–716.0
728.0–746.0
Dynamic
GSM-750
750
747.0–762.0
777.0–792.0
438–511
T-GSM-810
810
806.0–821.0
851.0–866.0
Dynamic
GSM-850
850
824.0–849.0
869.0–894.0
128–251
P-GSM-900
900
890.0–915.0
935.0–960.0
1–124
E-GSM-900
900
880.0–915.0
925.0–960.0
975–1023, 0-124
R-GSM-900
900
876.0–915.0
921.0–960.0
955–1023, 0-124
T-GSM-900
900
870.4–876.0
915.4–921.0
Dynamic
DCS-1800
1800
1710.0–1785.0
1805.0–1880.0
512–885
PCS-1900
1900
1850.0–1910.0
1930.0–1990.0
512–810
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM 900 Specification • • • • • • •
Carrier Separation Duplex Distance No. of RF Carriers Access Method Modulation Transmission Rate Speech Coding
200 kHz 45 MHz 124 TDMA/FDMA GMSK 270.833 kbps
– 13 kbps (full rate) – 6 kbps (half rate) Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM 1800 • GSM-1800 uses two 75 MHz bands with a • Maximum of 375 carriers at 200 kHz spacing. • Each carrier is divided into 8 TDMA channels. • GMSK modulation
Communication Systems
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XE37KTR Communication Technology – Radio Systems
Fixed Terminal – Mobile Terminal Communication Subscriber Line (2W)
MS
Inter-Exchange Junction
Telephone Exchange
Mobile Switching Centre (MSC)
Communication Systems
BSC
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BTS 17
XE37KTR Communication Technology – Radio Systems
Mobile Communication Frequency Constraints Wired System Network Tel. Exchange
BW for Telephony speech: 3KHz, increases to 25 KHz with FM for Radio transmission
Wireless system with dedicated radio channel for each link:
100,000 users x 50 kHz BW = 5 Ghz !!
Individual RF Link is not established Channels are distributed in common band Communication Systems
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Transmission Link Sharing by Multiplexing • Multiplexing (MA) in 4 possible dimensions – frequency – time – space – code
Communication Systems
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Transmission Link Sharing by Multiplexing • Multiplexing (MA) in 4 possible dimensions – frequency
Insufficient number of channels for system capacity requirements Communication Systems
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Transmission Link Sharing by Multiplexing • Multiplexing (MA) in 4 possible dimensions – – time
Lags in transmission due to queue of connections, no simultaneous transfer Communication Systems
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XE37KTR Communication Technology – Radio Systems
Transmission Link Sharing by Multiplexing • Multiplexing (MA) in 4 possible dimensions • frequency • time • Better protection against tapping • Protection against frequency selective interference • Higher data rates as compared to code multiplex Communication Systems
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XE37KTR Communication Technology – Radio Systems
Transmission Link Sharing by Multiplexing • Multiplexing (MA) in 4 possible dimensions – – – space • Implementation in cellular systems: base station covers a certain transmission area (cell) • Mobile stations communicate only via the base station Communication Systems
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XE37KTR Communication Technology – Radio Systems
Cellular Mobile Concepts • A fixed base station (transmitter) having a number of RF channels is called a cell • Each cell covers a limited number of mobile subscribers within the cell boundaries (Coverage area) • Cell Radius can vary from tens of Km (open country) to 100 m – picocells (urban)
Communication Systems
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Voice or Control Channels Co ve are rage a
r
k) in nl ow (d k) th in pa pl d (u ar h at rw Fo ep rs ve Re
XE37KTR Communication Technology – Radio Systems
A Radio Cell
Lines to BSC Mobile Subsystem
Communication Systems
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Frequency Planning
f1
f3 f2
f4 f1 f7
f5 f6
f1 f3
f3 f2 f1 f3
f2 f1 f3 f2
f1 f3 f2 f1 f3
f2 f1
f2
f3 f2 d
K=7
K=3
repeat-distance d is larger than twice the maximum radius r covered by each transmitter. Communication Systems
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Cell Reuse • Frequency can’t be reused in the same pattern • Larger K – More channels in a pattern – Higher subscriber number – Worse frequency reusability • Smaller K – Less channels in a pattern, high channel distortion – Smaller subscriber number – Better frequency reusability Communication Systems
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XE37KTR Communication Technology – Radio Systems
Cell Breathing • CDM systems: cell size depends on current load • Additional traffic appears as noise to other users • If the noise level is too high users drop out of cells
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM 900 FDMA
890
915
935
960
25 MHz
1
0
25 MHz
2
Mobile to Base 890.2
890.4 890.6
200 kHz 45MHz
1
0
2
Base to Mobile (MHz)
935.2
935.4
935.6
200 kHz
Channel layout and frequency bands of operation
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM TDMA Amplitude
45 MHz
1
F1 (Cell Rx)
2
3
4
5 6
7 8
1
F2
2
3
4
5 6
7 8
Frequency
F2’ F1’ (Cell transmit)
Typical TDMA/ FDMA frame structure Communication Systems
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FDMA/TDMA Scheme XE37KTR Communication Technology – Radio Systems
TIME
BP1 BP0 BP8 BP7 BP6 BP5
BURST
F R
BP4
A
BP3
M
BP2
E
BP1
FREQ
890.2 890.6 891.0 890. 890.4 890.8 891.2 0 Communication Systems
915.8 MHz 27th April 2010
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Network Architecture XE37KTR Communication Technology – Radio Systems
1 MSC=16 BSC 1 BSC=1024 TRU
OSS
HLR
B T S
PSTN ISDN B T S
BSC BSC
MSC VLR
A Interface B T S
Data Networks
A-bis interface MSC VLR
Air interface
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XE37KTR Communication Technology – Radio Systems
Network Parts • Mobile Station Subsystem (MSS) Mobile Termination (MT) and SIM card (SIM)
• Base Station Subsystem (BSS) BSC and BTS
• Network and Switching Subsystem (NSS) MSC, HLR, VLR, EIR and AuC
• Operation and Support Subsystem (OSS) OMC and NMC
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM Functions of Mobile Station • Voice and data transmission • Frequency and time synchronization • Monitoring of power and signal quality of the surrounding cells • Provision of location updates even during inactive state • Equalization of multi path distortions Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM Mobile Station • Portable, vehicle mounted, hand held • MS works together with SIM (Subscriber Identity Module) • MS identified by unique IMEI (International Mobile Equipment Identity) – IEEE Defined 48 bit number • All MSS belong to Class 1 commercial telecom equipment (Class 2 are restricted equipments) – (subclass 9) :Other radio equipment, which transmits only under the control of a network
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM Mobile Station Power Classes • Equipment Classes and Their Max. Power – Vehicle mounted (class 2), portables (class 4) Class
GSM-900
I II III iV V
20 8 5 2 0.8
GSM-1800 GSM-1900 1 0.25 4 -
1 0.25 2 -
Power in Watts
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM IMSI • International Mobile Subscriber’s Identity • The IMSI is an unique identity which is used internationally and used within the network to identify the mobile subscribers. • The IMSI is stored on the subscriber identity module (SIM), the HLR, VLR and AC database. • 15 digit = 3 for country code, 3 for mobile network code and 9 for mobile ID number. • Often replaced by TMSI (Temporary MSI) Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM MSISDN • Mobile Station International Subscriber Directory Number – de facto mobile phone number including country code
• • • •
CC - Country Code NDC - National Destination Code SN - Subscriber Number (user number) ITU-T recommendation E.164 CC NDC SN
420 Czech Republic 603 O2 776453 Jan Novak Communication Systems
MSISDN = CC + NDC + SN MSISDN = 420 + 603 + 776453 27th April 2010
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BTS – Base Transceiver Station • • • •
Encodes, encrypts, multiplexes, modulates and feeds the RF signals to the antenna Transcoding and rate adaption Functionality Time and frequency synchronization signals transmission. 11 power classes from 10 mW to 320 W
Communication Systems
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Function of BTS • • • •
Frequency hopping Random access detection Uplink radio channel measurements BTS mainly consists of a set of transceivers (TRX).
Communication Systems
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BSC - Base Station Controller • • • • • •
It is connected to BTS and offloads MSC Radio resource management Inter-cell handover Reallocation of frequencies Power control Time delay measurement of the received signals from MS with respect to BTS clock. • Performs traffic concentration to reduce the number of lines from BSC to MSC. Communication Systems
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MSC - Mobile Switching Center • Manages communication between GSM & other network • Call setup functions, basic switching are done • Paging, specifically call handling • Location update • Handover management • Billing for all subscribers based in its area • Reallocation of frequencies to BTSs in its area to meet heavy demands Communication Systems
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XE37KTR Communication Technology – Radio Systems
Visitor Location Register (VLR) ●
It controls those mobiles roaming in its area.
●
VLR reduces the number of queries to HLR
●
One VLR may be incharge of one or more LA.
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VLR is updated by HLR on entry of MS its area.
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VLR assigns TMSI which keeps on changing.
●
IMSI detach and attach operation Communication Systems
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XE37KTR Communication Technology – Radio Systems
Data in VLR IMSI & TMSI ● MSISDN ● MSRN. ● Location Area ● Supplementary service parameters ● MS category ● Authentication Key ●
Communication Systems
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Home Location Register (HLR) Reference store for subscriber’s parameters, numbers, authentication & Encryption values. ● Current subscriber status and associated VLR. ● Both VLR and HLR can be implemented in the same equipment in an MSC. ● One PLMN may contain one or several HLR. ●
Communication Systems
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Home Location Register(HLR) Permanent Data • Data stored is changed only by manmachine. • IMSI, MS-ISDN number. • Category of MS ( whether pay phone or not ) • Roaming restriction ( allowed or not ). • Supplementary services like call forwarding Communication Systems
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XE37KTR Communication Technology – Radio Systems
Home Location Register(HLR) Temporary Data The data changes from call to call & is dynamic ● MSRN ● RAND /SRES and Kc ● VLR address, MSC address. ● Messages waiting data used for SMS ●
Communication Systems
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XE37KTR Communication Technology – Radio Systems
Signal Processing
Communication Systems
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Signal Processing • The voice input is sampled at 8 kHz and coded at 13 bits/sample. • The resulting 104 kbits/s is reduced to 13 kb/s using Regular Pulse Excitation-LongTerm Prediction Linear Prediction Coding (RPE-LTP-LPC) • FEC and interleaver • GMSK modulation
Communication Systems
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Signal Processing • • • • • • • • • •
Take 20 ms speech or 160 samples. Represent it by 260 bits divided as follows – 36 bits for LPC coefficients – 36 bits for long-term prediction – 188 bits for excitations The coding rate is (260 bit)/(0.02 seconds) = 13 kb/s. Bits are classified as – Class 1a: 50 bits are essential. – Class 1b: 132 bits are important. – Class 2: 78 bits are less important. Communication Systems
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Signal Processing • 3 parity bits are added to the Class 1a bits to give 53 bits. • These 53 bits are added to the132 bits Class 1b bits and appended by “0000” to give 189 bits. After rate ½ convolutional encoding gives 378 bits. • Adding the 78 Class 2 bits gives 456 bits in 20 ms, or 456/0.02=22.8 kb/s. • Two 456 bit blocks are interleaved and transmitted over 8 frames, i.e. spread out to 114 bits per frame. Communication Systems
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XE37KTR Communication Technology – Radio Systems
Signal Processing
Communication Systems
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Radio Channels • After deducting 100 kHz as guard band at both ends of the spectrum, only 124 carriers are used. • Radio frequency channel number N∈ {1, 2, …, 124} is defined and corresponds to center frequency in MHz as follows for GSM-900 fup = 0.2 N + 890 fdown = 0.2 N + 935 • For GSM-1800, N∈{512, 513, …, 855} fup = 0.2 N + 1607.8 fdown = 0.2 N + 1702.8 Communication Systems
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XE37KTR Communication Technology – Radio Systems
Frame Structure 1 hyperframe = 3h 28 m 53.76 s
0
0
1
1
---
h
1 superframe = 6.12 s
---
s
---
2048
---
51/26
1 multiframe = 120 ms or 235.4 ms
0
1
---
---
m
26/51
1 frame = 4.615 ms
0
1
---
1 slot = 156.25
f
---
7
bits = 577us
1bit = 3.69us Communication Systems
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XE37KTR Communication Technology – Radio Systems
Frame Structure • A frame has duration 4.615 ms. Consists of 8 slots. Each slot can accommodate one burst of duration 577 micro-second. • Two kinds of multiframe: • – traffic MF = 26 frames(120ms), • – control MF = 51 frames. • Superframe --- same structure as multiframe. • 2048 superframes form a hyperframe of duration 3 h 28 m 53.76 s.
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM Burst Structure
Communication Systems
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XE37KTR Communication Technology – Radio Systems
GSM Bursts • For carrying traffic, network control data, frequency correction, synchronization and random access data. • Flag - indicate the type of information, traffic or network control. • Training - for channel adaptive equalization. • Tail - all-zero bits to indicate the start and the end of the burst. • Guard - ramping time for transmitter ON/OFF, to avoid overlapping between adjacent time slots. Necessarily much longer for Access Burst. • Synchronization - a known sequence for time synchronization. Communication Systems
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GSM Logical Channels XE37KTR Communication Technology – Radio Systems
•
Traffic Channels (TCH) – TCH/F and TCH/H for full and half rate speech channels. – TCH/9.6, TCH/4.8 and TCH/2.4 for 9.6, 4.8 and 2.4 kb/s data channels.
•
Broadcast Channels (BCH) – frequency correction channel (FCCH), – synchronization channel (SCH), – broadcast control channel (BCCH).
•
Common control channels – paging channel (PCH), – access grant channel (AGCH), – random access channel (RACH).
•
Dedicated control channels – stand-alone dedicated control channel (SDCCH), – slow associated control channel (SACCH), – fast associated control channel (FACCH). Communication Systems
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XE37KTR Communication Technology – Radio Systems
Other Mobile Terrestrial Systems • License-free – Citizen Band Radio (CB Radio) – 27MHz – Family Radio Service (FRS) – 462, 467 MHz – Private Mobile Radio (PMR446) – 446 MHz – Other (baby monitors, toys) • 49 MHz, 902 MHz or 2.4 GHz (U.S.) • 433 MHz, 868 MHz (Europe) Communication Systems
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XE37KTR Communication Technology – Radio Systems
Other Mobile Terrestrial Systems • Cordless Telephone – UPCS (Unlicensed Personal Communications Services) – 1.9 GHz – DECT (Digital Enhanced Cordless Telecommunications) – 1880 MHz–1900 MHz – 10 FDMA channels – 12 TDMA in one FDMA channel – ADPCM voice coding – 250mW peak power, 10 mW mean power Communication Systems
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XE37KTR Communication Technology – Radio Systems
Thank you for your attention!
20th April 2010
Communication Systems
CTU Prague, FEE, Dept. of Radioelectronics
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