Dr. Dóra Maros. Korszerű mobil rendszerek Evolution of Communication.
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Transcript of Dr. Dóra Maros. Korszerű mobil rendszerek Evolution of Communication.
![Page 1: Dr. Dóra Maros. Korszerű mobil rendszerek Evolution of Communication.](https://reader035.fdocuments.net/reader035/viewer/2022062322/5697bfc01a28abf838ca3fe4/html5/thumbnails/1.jpg)
Modern mobile networks
Dr. Dóra Maros
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Korszerű mobil rendszerek
Evolution of Communication
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Korszerű mobil rendszerek
…..mobile phones….are also developed
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Korszerű mobil rendszerek
…the beginnings….
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Korszerű mobil rendszerek
Comité Européen de Normalisation Électrotechnique;
European Telecommunications Standards Institute
International Telecommunication Union
International Electrotechnical
CommissionInternational Organization
for Standardization
Regulatory Organizations
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Korszerű mobil rendszerek
Institute of Electrical and Electronics
Engineers Internet Engineering
Task Force
International
International Federation for Information Processing
Hungarian
Independent Organizations
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Korszerű mobil rendszerek
Generations of Mobile Networks (2G - 3G+)
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Korszerű mobil rendszerek
After 3G
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Korszerű mobil rendszerek
900 MHz-2,6 GHz
Electromagnetic Wave Spectrum
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Korszerű mobil rendszerek
FDMA (Frequency Division Multiple Access)
Frequency
ITime
TDMA (Time Division Multiple Access)
CDMA (Code Division Multiple Access)
Frequency
ITime
Frequency
Time
The users share the available frequency bands in the cell
NMT 450 GSM UMTS
Multiple Division Access Technologies
OFDMA (Orthogonal Frequency Division Multiple Access)
ITime
Frequency
LTE
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Korszerű mobil rendszerek
Same frequency band butTDMA:
Different time
CDMA: Different
codes
FDMA: different
frequency bands
OFDMA: multiple
frequency bands in the same time
Single Carrier and Multi Carrier Systems
Single carrier
Multi carrier
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Korszerű mobil rendszerek
FDD (Frequency Division Multiplex) Different frequency bands for downlink and uplink Jelenleg preferált megoldás Benefits: speech, videophone, real time connection Disadvantage: if assymetric load , unsufficient band usage
TDD (Time Division Multiplex) Same frequency band for downlink and uplink Future applications Benefits: sufficient band usage Disadvantage: correct timing
Types of Duplexing
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Korszerű mobil rendszerek
Downlink
Uplink
FDD: Frequency Duplexing
One channel bandwidth:
GSM :200 KHz UMTS: 5 MHzLTE: 20 MHz
TDD: Time DuplexingUL and DL on the same bandwidth, but in different times (UMTS és LTE)
B(dl): bandwidth
B(ul)
B(dl)=B(ul)
fk(dl)
fk(ul): center frequency
fk(dl)-fk(ul)= duplex distance
Downlink
Uplink
idő
Duplexing on Radio Interface
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Korszerű mobil rendszerek
GSM 900, 1800, 1900 bands (2G)
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Korszerű mobil rendszerek
Duplexing Uplink Downlink Bandwidth
UMTS-FDD 1920 - 1980 MHz 2110 - 2170 MHz 60 + 60 MHz
UMTS-TDD 1900 - 1920 MHz UL/DL2010 - 2025 MHz
UL/DL20 + 15 MHz
Satelite 1980 - 2010 MHz 2170 - 2200 MHz 30 + 30 MHz
in 2000, new frequency bands 806 - 960 MHz, 1710 - 1885 MHz (GSM
bands!) 2500 - 2690 MHz
DEC
TGSM1800
1800 1900 2000 2100 2200 2500 2600 2700
UMTSFDD
Mű
hold
UM
TS
TD
D
UM
TS
TD
D
UMTSFDD
Mű
hold
UMTS
[MHz]
Paired fr. bands
Unpaired fr. bands
Channel bandwidth: 5,10, or 20 MHz
UMTS Frequency Bands
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Korszerű mobil rendszerek
30 bands:21 FDD9 TDD
LTE Bands
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Korszerű mobil rendszerek
TDD Spectrum Allocation
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Korszerű mobil rendszerek
ClassesConversation
alStreaming Interactive Background
Delay
Response time
between the users
Response time of demand
Response time of server
Not relevant
<< 1 s ~ 1s < 10 s > 10 s
Error Tolerance? Yes Yes No No
Switching Mode
Typical: Circuit
Switched
Packet Switched
Packet Switched
Packet Switched
ServiceSpeech
Videophone
Streaming
multimedia
Web browsing
Databases
Email, SMS,
MMS…
QoS Classes
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Korszerű mobil rendszerek
Conversational Cl Speech
▪ Symmetric load▪ Round Trip Time < 400 ms ▪ AMR (Adaptive Multi-rate) codec▪ AMR-WB (AMR Wideband) codec (Release 5)
▪ Sampling: 16 kHz (instead 8 kHz)▪ Good quality ▪ Adative Multirate (AMR) codecs: 24 ÷ 6,6 kbps
Videophone▪ Circuit Switched: H. 324▪ Packet Switched: SIP (Session Initiation Protocol)
Conversational Class
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Korszerű mobil rendszerek
Streaming Assymetric load Services:
▪ Web broadcast (a lot of users connect to mediaserver) ▪ Video on Demand
Interactive Tranzaction-oriented services
▪ Applications: databases, web browsing▪ Protocolls: HTTP, DNS stb▪ Assymetric, short switching time
Background Lowest priority, messages• MMS, SMS, E-mail
Other QoS Classes
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Korszerű mobil rendszerek
For each 3G (UMTS) service classes different (SW and PW): Delay Bit error rate (BER) Data rate
Near future: Services are based on packet switching solutions (IP) instead circuit switched networks 4 QoS (Quality of Service) Class using IP Delay time Packet Loss Ratio Packet jitter Buffer size CODEC rate
Features of 3G Services
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Korszerű mobil rendszerek
ME:Mobile Equipment radio terminal: voice, audio, video, internet, navigation, etc.
services
USIM (UMTS SIM) Similar to GSM SIM, but more features, capacity
USIM
ME
UE
Mobile Equipment
UMTS Subsciber Identity Modul
User Equipment (UE)
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Korszerű mobil rendszerek
Cells and Datarates (Release 99)
HSDPA (from Release 5) High Speed Downlink Packet Access: >10Mbit/s
Earth Cell(satelite)
MacrocellSize: 350m-20 kmDatarate: 384 kbit/sOutdoor, rural, roads
MicrocellSize: 50m-300 mDatarate: 384 kbit/sOutdoor, city
PicocellSize: some 10 mDatarate: 2 Mbit/sIndoor
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Korszerű mobil rendszerek
MSBTS
BSC
MSC/VLR
SGSN
BTS
HLR
GMSC
Internet
PLMN, ISDN
GERANCN:Core Network
Other networks
GGSN
MS= ME+SIM
Circuit Switched (CS)
Packet Switched (PS)
MS: Mobile Station BTS: Base Transceiver Station BSC: Base Station Controller PCU: Packet Contol Unit MSC: Mobile Switching (Serving) Center GMSC: Gateway MSC VLR: Visitor Location Register HLR: Home Location Register AUC: Authentication Center SGSN: Serving GPRS Support Node GGSN: Serving GPRS Support Node EIR: Equipment Identiy Register
AUC
PCU
PCU
EIR
GSM network (2.5 G)
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Korszerű mobil rendszerek
UE Node B
RNC
MSC/VLR
SGSN
Node B
HLR
GMSC
Internet
PLMN, ISDN
UTRAN CN:Core Network
Other Networks
GGSN
UE
Circuit Switched (CS)
Packet Switched
UE: User Equipment UTRAN: UMTS Terrestrial Radio Access Network
Node B: Base Station RNC: Radio Network Controller
AUCEIR
UMTS network (Release 99)
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Korszerű mobil rendszerek
MGW: Media Gateway HSS: Home Subscriber Server MRF: Media Resource Function CSCF: Call Session Control Function MGCF: Media Gateway Control Function IMS: IP Multimedia Subsystem
MGW
SGSN
MGW
GGSN
UTRAN
MSCserver
GMSCserver
PSHSS
PSTN
IP networ
k
MRF
CSCF
MGCF
IMS
Data & Control
Control
Instead MSC (MSS)
Instead GMSC
Instead HLR
AUC
GERAN
EIR
IMSMGW
CS
Evolution of UMTS Core (Release 4-)
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Korszerű mobil rendszerek
Node B (Base Station) Channel coding and interleaving,
spreading/despreading) modulation/demodulation, rate adaption, radio measurements, etc.)
RRM (Radio Resource Functions): softer handover, closed loop power regulation
RNC (Radio Network Controller) Contols the interface functions between UMTS
radio interface and Core Network Controls RRM-Radio Resource Management, like
soft and hard handover, outer loop power regulation
Controls protokolls between: UE-RNC, RNC-RNC and RNC-MSC/SGSN
Load Management, Admission Control
Tasks of UTRAN Elements
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Korszerű mobil rendszerek
CBC: Text Message Service for all users in the cell (without addressing)
SMLC : Handles and Contols Location Based Services
RNCCell Broadcast Centre (CBC)
Iu-BC
Serving Mobile Location
Centre(SMLC)
Iu-PC
New Network Elements in UMTS
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Korszerű mobil rendszerek
MSC, GMSC server Controls signalling functions One MSC, GMCS server controls several MGWs
MGW (Media Gateway) Controls and Swithes Circuit switched connectionsHSS (Home Subsciber Server) Instead HLR (mobility management, security functions,
authentication, etc.)MRF (Media Resource Function) Handles and contols multimedia connections and resources
CSCF (Call Session Control Function) Sets up and controls voice connections (Voice over IP)
MGCF (Media Gateway Control Function) Controls gateway functions between IP Multimedia
Subsystem (IMS) and other networks (eg. Internet)
Network Elements in 3G Core Network
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Korszerű mobil rendszerek
RRM features Dimanic channel allocation, spectrum
capacity handling Guaranteed QoS parameters for users Channel optimization for cell Capacity optimization for channels
RRM control functions Power control Handover Admission control Load control
Radio Recource Management (RRM)
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Korszerű mobil rendszerek
GSM antennas
Adjustable antennas
Directional Antennas
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Korszerű mobil rendszerek
Omni antenna mounted on mobile tower
„Handy” omni antenna
Omni antennas
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Korszerű mobil rendszerek
Micro antennas: connections towards the core network (some ten GHz)
Microwave Antennas
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Korszerű mobil rendszerek
MIMO antennas (LTE)
Multiple sector
antennas in the same cell
3G/4G Antennas
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Korszerű mobil rendszerek
Indoor Antennas (examples)
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Korszerű mobil rendszerek
Channel Capacity
C - channel capacity [bit/s]B - channel bandwidth [Hz]S - signal power [W]N - noise power [W] (Caused by the interferences)
- If we want to keep the same S/N for a channel, and we want to increase the datarate, we must to increase the bandwith.
- If the interference (Noise) is high, S/N is decreasing, channel capacity is also decreasing.
B
C
N
S
N
SBC
N
SBC
2ln
2ln1log2
Hartlay-Shannon law:
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Korszerű mobil rendszerek
In CDMA networks:
1. If the number of UEs the level of interference is also ▪ Each UE causes interference:
▪ For other UEs in the cell▪ For other UEs in adjacent cells
…………means the capacity of cell is
2. If the output power of UE the interference is also
…………means the capacity of cell is
Importance and Necessity of Power Control
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Korszerű mobil rendszerek
Power control:minimalizálni kell az interferenciát hogy a kapacitást növelni lehessen
UE2UE1
Node B• The accurate and fast
power control is one of the main factors of the capacity efficiency of WCDMA networks
• If the output power of UE is too high, it can block the traffic of other UE in the given cell and adjacent cells too
Near-far problem
Power Control (near-far problem)
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Korszerű mobil rendszerek
UMTS-ben alkalmazott háromféle teljesítmény-szabályozás megoldás:
Open loop Fast inner closed loop Slow outer closed loop
Types of Power Control
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Korszerű mobil rendszerek
Used, when UE wants to attach to a cell (uplink)Tolerance: ± 9-12 dB (path loss, slow fading)
When uplink connection starts, the closed loop power control begins
Node BUE
Downlink power measurement (BCH)
Tx power
Open-loop Power Control
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Korszerű mobil rendszerek
Uplink Node B measures BER and calculates SIR (Signal to
Interference Ratio) If SIRmeasured> SIRtarget Node B regulates UE to decrease the
output power Ha SIRmeasured< SIRtarget Node B regulates UE to increase the
output power
Speed of regulation = 1500/s at each UE (accuracy: average 1dB)▪ In GSM-ben slow power contol is used (2 Hz)▪ The process is very fast, ensures good channel quality
The high output power of UE causes interference in the cell
Downlink No near-far problem Node B power depends on the traffic and required QoS in
the cell
UE2
UE1
Node B
Tx telj. Tx telj.
Fast Closed-loop Power Control (UE-Node B)
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Korszerű mobil rendszerek
SIRtarget depends on channel FER and traffic in the cell and adjacent cellsSIRtarget depends on speed of UE (BER is changing in UL).
Outer loop between NodeB and RNC SIRtarget is changing, its value is increasing or decreasing
continuously depending on the traffic (number of Ues and QoS)
RNC(Outer loop control)
Node B(Inner loop control)
UE
FER
SIRtarget
SIRtarget
Time
Outer Loop Power Control
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Korszerű mobil rendszerek
Handover: Channel or cell reselection procedure during a connection (speech or data)
Types: Hard handover
Frequency change in the same system: used in WCDMA system between different carrier bands (FDD1-FDD2 or FDD-TDD)Frequency band change because of system is changed (intersystem handover): UMTS-GSM , UMTS-LTE
Soft handover: Between two Node Bs
Softer handover: Between two sectors of one Node B
Types of Handover
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Korszerű mobil rendszerek
MS or UE connects only one BTS/Node B at the same time
MS/UE changes carrier frequency during handover! BTS 1
(f1,TS5)
BTS 2 BTS 1
(f2,TS3)
BTS 2
MSa
MSa
GSM
UMTS
f2
f1 f1
f2
UMTS
GSM
Hard Handover in GSM and UMTS
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Korszerű mobil rendszerek
Used in WCDMA systems
Soft handover One UE is connected to more Node Bs at the same time
UE communicates with NodeB2 and NodeB1 parallely „Seamless” handover between cells (no frequency
reallocation)
Multiple connection to NodeBs is called→ Macro-diverzity
Soft Handover
Node B1Node B2
1
UEa Node B1
Node B2
2
UEa
Node B1
Node B2
UEa
Node B3
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Korszerű mobil rendszerek
UE communicates at the border of the sectors of two Node Bs
UE-Node Bs communicaton on different radio channels in parallel, channel combination is required
Two power control loops are active
Szektor 1
Szektor 2
RNCNode B1
UEa
Node B2
Soft Handover
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Korszerű mobil rendszerek
UE communicates on the border of two sectors of one Node B
UE-Node B communicaton on two different radio channels Channel combination (uplink) by Node B
One power contol loop is active
Sector 1
Sector 2
RNCNode B
UEa
Softer Handover
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Korszerű mobil rendszerek
Hard HandoverBTS1 – BTS1
BTS1 - BTS2
- GSM/GPRS-Discontinuity in the connection
Soft handover Node B1 - Node B2 - cdma2000, UMTS- No discontinuity in the connection
Softer handover Node B1 - Node B1 - UMTS
Frekvencia hard handover
Carrier f1 - Carrier f2 - UMTS
Rendszer hard handover
Network1 –Network2 - WCDMA FDD / GSM
Handover Review
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Korszerű mobil rendszerek
Frequency Hopping (fast, slow) Direct Sequence (DS)
- Simple implementation - Good channel and bandwidth efficiency - cdma2000, WCDMA
Time Hopping Multi Carrier systems (OFDM) Combined systems
Spead Spectrum Solutions
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A B AB
0 0 0
0 1 1
1 0 1
1 1 0
Spreading – one information bit is multiplied by a spreading code sequence Spreadind code bits = chips Number of bits/information bits = Spreading Factor (SF= 4,
8, 16, …512)
A B AB
+1 +1 +1
+1 -1 -1
-1 +1 -1
-1 -1 +1
XOR
100 kb/s (or kchip)
10 kb/s 100 kbpsInformation bits
Spreading code
sequence
Spreaded info
XOR logical function and its analog signals
Direct Sequence Spreading
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Information bits at the trasmitter
Spreading sequence (SF = 8)
Information on the channel
Spreading
Spreading sequenceDespreading
Information at the receiver
Information bit (0)
Chip
1-1
1-1
1-1
1-1
1-1
Synchronization is required
Theory of Spreading/Despreading (sample)
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Despreading causes a processing gain on the channel
The spectum power density is increasing at the receiver output
Processing gain: PG
PGSNRin SNRout(dB) = SNRin(dB) + PG(dB)
Despreading
Signal to Noise Ratio on the
receiver input
Signal to Noise Ratio after
despreading
Processing Gain
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][log10 10 dBR
RP
R
RP
Info
PNG
Info
PNG
RPN – chip rate RInfo – information bit rate
Example:RPN = 3,84 McpsRInfo = 12,2 kbps
PG = 10*log10(3,84*106/12,2*103) = 25 dB
After despeading, the signal power must be some dB more than the noise power, otherwise the channel information can be lost at the receiver.
Calculation of Processing Gain
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Two channels with different datarates:
Example:
1.) RPN = 3,84 Mcps 2.) RPN = 3,84 Mcps RInfo = 12,2 kbps (speech) RInfo = 2 Mbps (data) PG = 25 dB PG = 2,8 dB
Let we suppose: SNRout = 7 dB is requred
SNRout = SNRin + PG 1.) SNRIN = SNROUT - PG = -18 dB 2.) SNRIN = SNROUT - PG = 4,2 dB
Conclusion: Speech channel needs lower output power at the transmitter than fast rate data channelImportance of power regulation!
Processing Gain and Transmitter Output Power
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twAtctstctstctsS cnnTx cos)]()(...)()()()([ 2211
Channels are modulated on the same frequency band
Channels have different spreading codes (C1-Cn) Information bit rates are different (speech, data)
c1(t)
s1(t)
c2(t)
s2(t)
cn(t)
sn(t)
∑
Acos(ωct)
f(Hz)
Signal power
f(Hz)
f(Hz)
f(Hz)
f(Hz)
f(Hz)
f(Hz)
Power
STXPseudo-noise 1
Pseudo-noise 2
Pseudo-noise 3
Background noise
Signal power
Signal power
Modulator
Spreading
DS-CDMA Channel Multiplexing
Signal power
Signal power
Signal power
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1)()(,1)()(cos)()()(cos])()()([)()(
)(cos)]()(...)()()()([)()(
111'
111'
211
1'
22111
tctctctctwAtctctstwAtctctstctS
tctwAtctstctstctstctS
icc
n
iiiRx
cnnRx
f(Hz)
Signal at the receiver
fc = c/2
c1(t)
fc = c/2
Narrow band filter
The received signal is a sum of all channels on
radio inreface
Despreading means a XOR logical function between channel info and channel (Wlash) code
SRX
Unwanted signal (interference) Wanted signal
All channels on radio interface
Demodulator
DS-CDMA Despreading
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Natural and artificial objects cause reflections , diffractions, attenuation on the radio channels because of multipath propagation
The reflected signals arrive in different times to the receiver The changes of signal power density gives the profile of the
multipath propagation Delay:
1-2 µs in urban, suburban environment Some 10 µs in highways, roads, rural environment
Multipath components
Multipath Propagation
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Tchip = 0,26 µs (WCDMA, 3,84 Mc/s)
Két eset: Ha TMultiCom 0,26 µs, a vevő szét tudja választani és
kombinálni a többutas komponenseket hogy meghatározza a jel diverzitását ▪ TMultiCom ≥ 0,26 µs …ha az átviteli út ≥ 78 m
(kis mozgási/chip sebesség)▪ 1 Mc/s esetén, 300 m
Általában több egyforma hosszúságú terjedési út van adott idő alatt
Például a /2 (2GHz, =15 cm), késleltetéssel érkező jelek egy chipidő késleltetéssel érkeznek a vevőre
Ha az adó mozog jelvesztés vagy gyors fading jelentkezhet a kioltások miatt.
TMultiCom
Többutas terjedés problémája
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The received signal power is decreasing 20-30 dB suddenly
Rayleigh distribution fading
Solutions in WCDMA systemsRake receiverFast, closed loop power controlEfficient coding shames, interleaving, ARQ procedures
Fast Fading Problems
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Determination of received signals Determination of fingers on the same channel (peak power
density of the same signal) Same chips are received with different power density and in
different times because of multipath propagation
Characterization Fingers are characterized by vectors (phasors), with their
amplitudes and phase Changes ≤ 1 ms Signal Processing 3-4 consecutive fingers are processed in the receiver Rake receiver
CDMA Receiver
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Theory: Maximal Radio Combining (MRC) WCDMA systems use pilot signals, for channel estimation Compensation of delay is needed The fingers are added after compansation
Finger 1
Finger 2
Finger 3
Signal of transmitt
er
Fingers with
different delays
After delay compensation
Summed phasors
Σ
Phase compensation
Evaluation of Fingers
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Finger 3
Correlator and code generator: despreads de channel signalsChannel estimator: estimates the channel from pilot signalsPhase rotator: rotates the finger’s phase to the original (regarding the pilot)Phase equalizer: equalizes the different phases of fingersAdder: adds compensated signalsFilter: filters fingers from the channel
Incoming signal Ad
de
r
Finger 2
Finger 1
Correlator
Code generator
Channelestimation
Phase rotator
Phase compensation
Filter
De
co
de
r
Időzítés
CDMA Rake Receiver (with 3 fingers)
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Problems: Interference between channels Random cell load
Features: Auto-correlation Cross-correlation
Types of codes: PN (Pseudo random Noise) sequence
▪ MLS (Maximal Length Sequence) Gold code Walsh code
WCDMA Codes
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dttFtFACF
)()( ACF in the case of time dependent, continuous signal
NCCCCACF ACF for bit sequences (discrete signals): → Comparition of the bit sequence with its shifted version (shift: 1-L)
# Same bits
# Different bits
ACF: Auto-Correlation Function
Definition of Auto- Colleration
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-2
0
2
4
6
8
Shift (bits) Bit sequence CC NCC ACF
0 1011100 7 0 7
1 0111001 3 4 -1
2 1110010 3 4 -1
3 1100101 3 4 -1
4 1001011 3 4 -1
5 0010111 3 4 -1
6 0101110 3 4 -1
7 1011100 7 0 7
Kor
relá
ció
PN shift04 05 06 00 01 02 03 04 05 06 00 01 02 03
Calculation of Auto-correlation (example)
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dttGtFCCF
)()(
Time dependent F(t) és G(t) CCF
NCCCCCCF CCF for two different bit sequence → comparition of two sequence
# Same bits
# Different bits
Ortogonal codes: CCF = 0
CCF: Cross-Correlation Function
Definition of Cross-Correlation
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1... 1111 xaxaxaxP nnnn
123 xxxP
12 NL
7123 L
PN sequence – binary bit sequence with pszeudorandom features … PN sequence is not determinstic but fully random…
PN generator Linear Feedback Shift Regiszter (LFSR) Polinomal presentation:
Length of PN sequence:
x0 x1 x2 x3
clockPN sequence
[chipek] … N – number of D laches
Example: Shift register with 3 D laches
PN (Pseudo Noise) Sequence
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Gold code: Two PN sequnce are added by modulo 2 adder (XOR) (primitive expression)
By shifting one PN sequence we get different GOLD codes
Simple auto-correlation is zero Helps asynchron transmission: A lot of codes can be generated with good
correlation
Gold Codes
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NN
NNN MM
MMM 2
Walsh codes:Differents codes in the same matrix are orthogal
(CCF = 0)Bad auto-correlation
Walsh matrix:▪ n x n matrix▪ Matrix description: (m = size of matrix, i = )
1001
0011
0101
1111
0110
1100
1010
00000110
1100
1010
0000
0110
1100
1010
0000
0110
1100
1010
0000
10
000 8421 MMMM
miW 8
1W
10101010
Walsh Codes
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01 W
0020 W
001142 W
0121 W
010141 W 01104
3 W
0000000080 W 000011118
4 W 0011001182 W 010101018
1 W 0011110086 W 010110108
5 W 0110011083 W 011010018
7 W
ismétlés& invertálás
ismétlés
000040 W
Walsh Code - Tree Presentation
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Codes Chips Analog signals
Walsh 0 0000
Walsh 1 0101
Walsh 2 0011
Walsh 3 0110
bit 0 ≈ +1bit 1 ≈ -1
Walsh code 3
bit 0 bit 1
User bits
Walsh 3
After spreading
A user (Walsh 0)
B user (Walsh 2)
C user (Walsh 3)
0
0
0
0
0
1
0
1
0
0
1
1
1
1
1
+3,+1,-1,+1
Walsh Codes- Spreading (example)
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14
4 1
4
4
1
4
4
A user (Walsh 0) 0 0 0 0 1
B user (Walsh 2) 0 0 1 1 1
C user (Walsh 3) 0 1 0 1 1
A (Walsh 0)
Walsh code * spreaded infoNumber of chips
14
4
Information bits (A user) 0 0 0 0 1
CCF=1*3+1*1+1*(-1)+1*1
14
4
Walsh Codes - Despreading
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Codes System Advantages Disadvantages
Walsh UMTS, cdmaOne • Codes are orthognal
• bad auto- and cross corretation
PN sorozat cdmaOne
• Good auto correlation
• Non orthogonal codes• Bad cross correlation • Small number of codes
Gold UMTS • Good cross correlation• Great number of codes•Auto correlation Walsh < Gold < PN sorozat
• non orthogonal codes
Correlation features determine the interference in the cells
WCDMA capacity depends on the level of interference
Codes - Review
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User dataSi
Chanellization kód(Walsh)
Signal rate (changing)
Chip rate (fix)
Spreading Codes= Walsh codes One channel one code Different channelization in UL and DL The length of code is changing (4-512)
Ci
Ci+1
Si+1
Ck
Sk
UMTS Codes –Transmitter (I.)
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Scrambling: the spreaded information is multiplied by a scrambling code
Used after speading The datarate does not change Scrambling codes: Identifies Node Bs (each Node B has different scrambling codes) Autocorrelation of a channel is better
Scrambling (Gold)
Chip rate
User infoSi
Channelization kód(Walsh)
Signal rate (changing)
Chip rate (fix)
Ci
Ci+1
Si+1
Ck
Sk
UMTS Codes in Downlink
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Chanellisation code Walsh code Separates data and control physical channels
Scrambling code Short (Gold code) vagy long (PN sequence) Separates Users (UE)
There is no synchronization between UE’s channels in Uplink!
UMTS Codes in Uplink
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Spreading/Chanellization codes Scrambling Codes
HasználatDownlink: separates Ues in the cellUplink: separates the control and data physical channels from UE
Downlink: Separates Node BsUplink: Separates Ues in the cell
Number of chips
Downlink: 4-512 chip
Uplink: 4-256 chip
Downlink: 10 ms = 38400 chips Uplink: 10 ms = 38400 chips or 66,7 µs = 256 chips
Number of codes
Given number in UL and DL applicationDownlink: 512Uplink: some billions
Bandwidth Megnöveli az átviteli sávszélességet Nincs hatása a sávszélességre
UMTS Codes Summary