Power Control Technology
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Transcript of Power Control Technology
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CDMA Key Technology
ZTE Corporation
CDMA Division
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CDMA Key Technology
Spread Spectrum Communication
Code Division Multiple Access
Power Control
Diversity
Soft Handoff
Rake Receiver
Variable Rate Vocoder
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Power Control (1)
The Need for Power Control
CDMA is an Interference-limited system (not frequency-limited)Same frequency transmission: system internal interference critical tosystem capacity and voice qualityTransmit power of each mobile should be controlled to limitinterferenceChanges of RF environment: fast and slow fading, shadowing,external interference.
Near and Far effect: mobile closer to the base station transmit less power than those far away
Objective: Reducing interference by limiting transmitted power onthe forward and reverse links while maintaining link quality
Meet user-defined performance objectives: BER, FER, capacity,dropped-call rate, coverage
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Power Control (2)
Reverse Link Power Control: on the basis of E/I ratioOpen Loop Power Control :
No involvement of BS, MS determines initial power transmittedon the access and traffic channels, adjustment for path lossClosed loop control :inner loop control/outer loop control:MS seizes a forward traffic channel and receives control bits, MSand BS engage in closed-loop power control
Inner loop control: Keeps the mobile as close to its target E/Iratio as possibleOuter loop control: Adjust the base station target E/I ratio fora given mobile
Forward Link Power Control : on the basis of FERReducing both in-cell interference and other cell/sectorinterferenceFERs are measured instead of E/I
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Power Control (3)
Target Power controlalgorithm
Adjustment instructionMS
Transmitting Power
o b I/E
o b I/E
Information packet
Error rate algorithmAdjustment of Target E/I
Inner loop
Outer loop
BS
o b I/E
(Constant) Transmitting Power Control range: ± 32 dB
Receiving Power
MS
Reverse Open Loop Power Control
Reverse Closed Loop Power Control
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Power Control (Continued)
Reverse Open Loop
Mobile BTS
Reverse Open LoopPower Control
Reverse Link Open Loop Power ControlAn initial estimation of required transmission power by the mobileCoarse measure of path loss based upon total receive power at mobileReceive Power+Transmitted Power=-73(dbm)+Parameter
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Power Control (Continued)
Reverse Closed Loop
Reverse Link Closed Loop Power ControlUsed to compensate for asymmetries in forward/reverse linksUp/down commands sent to mobile based upon SNR measured at BaseStation compared to a specified thresholdTransmitted 800 times per second at 1dB increments
Mobile BTS
Signal StrengthMeasurement
Setpoint
orReverse Closed Loop
Power Control
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Power Control (Continued)
Reverse Outer Loop
Reverse Outer Loop Power Control Setpoint is varied according to FER on reverse link (measured at theBase Station Controller)Sampled at 50 frames per second rate (20msec)Setpoint adjusted every 1-2 seconds
FER
Mobile BTS BSC
Reverse OuterLoop Power
Control
Signal StrengthMeasurement
Setpoint
or
Reverse Closed LoopPower Control
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BS
MS
BS
measurement Nt
Stat. Backward link
FER
Outer loop adjustment
algorithm, new
Power control(bit) 0
TransmitPower control
(bit) 1
Transmit poweradjustment
Power control
command detection
=1% ?
> ?
1%
Outer-loop adjustment
Closed-loop control
Power Control (Continued)
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Power Control (Continued)
Forward Link
Forward Link Power ControlBase station slowly decreases power to each mobile
As FER (measured at the mobile) increases, the mobile requests a raisein forward link power
FER
Mobile BTS BSC
Adjust Fwd.power
Forward Link Power Control
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Diversity
Three types of diversity in CDMA.
Time Diversity
Frequency DiversitySpace Diversity
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Diversity Reception (1)
Definition:Simultaneous reception of multiple input signals. Combining andcorrelation of the signals help reduce multi-path fading
Types of Diversity: compensation for fading factors of
frequency, space and timeFrequency diversity reception: spread spectrumtransmission
Space diversity receptionTwo or more separate antennas for reception and tr ansmission toguarantee separate propagation fading/loss
Two BTS: in case of soft handoff
ReceptionReception
BS 1 BS 2
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Diversity Reception (2)
Time Diversity ReceptionRAKE receivers of both BS and MS. When thedelay of the signals is larger than 1μs RAKE
receiver extract them without confusion
Reception window 1
Reception window 2
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Rake Receiver
The rake receiver is a CDMAfeature that turns what is aproblem in other technologies intoan advantage for CDMA.Signals sent over the air can takemulti-paths to the receiver. It canresult in the receiving gettingserveral versions of the same signalbut at slightly different times.Multi-paths can cause a loss ofsignal through cancellation in othertechnologies.CDMA rake receiver is multiplereceivers in one. The rake receiveridentifies the three strongest multi-path signals and combines them toproduce one very strong signal.
Multi-path Propagation
A
t
10-15 dB
Rayleigh Fading
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Diversity (Continued)
Time Diversityg0
g1
C0
C1
Input
C 2g2
Output
1 33 65 97 12 9 16 1 19 3 22 5 25 7 28 9 32 1 35 3 38 5 41 7 44 9 48 1 51 3 54 5
2 34 66 98 13 0 16 2 19 4 22 6 25 8 29 0 32 2 35 4 38 6 41 8 45 0 48 2 51 4 54 6
3 35 67 99 13 1 16 3 19 5 22 7 25 9 29 1 32 3 35 5 38 7 41 9 45 1 48 3 51 5 54 7
4 36 68 10 0 1 3 2 16 4 1 9 6 22 8 2 6 0 29 2 3 2 4 35 6 3 8 8 42 0 4 5 2 48 4 5 1 6 54 8
5 37 69 10 1 1 3 3 16 5 1 9 7 22 9 2 6 1 29 3 3 2 5 35 7 3 8 9 42 1 4 5 3 48 5 5 1 7 54 9
6 38 70 10 2 1 3 4 16 6 1 9 8 23 0 2 6 2 29 4 3 2 6 35 8 3 9 0 42 2 4 5 4 48 6 5 1 8 55 0
7 39 71 10 3 1 3 5 16 7 1 9 9 23 1 2 6 3 29 5 3 2 7 35 9 3 9 1 42 3 4 5 5 48 7 5 1 9 55 1
8 40 72 10 4 1 3 6 16 8 2 0 0 23 2 2 6 4 29 6 3 2 8 36 0 3 9 2 42 4 4 5 6 48 8 5 2 0 55 2
9 41 73 10 5 1 3 7 16 9 2 0 1 23 3 2 6 5 29 7 3 2 9 36 1 3 9 3 42 5 4 5 7 48 9 5 2 1 55 3
10 42 74 10 6 1 3 8 17 0 2 0 2 23 4 2 6 6 29 8 3 3 0 36 2 3 9 4 42 6 4 5 8 49 0 5 2 2 55 411 43 75 10 7 1 3 9 17 1 2 0 3 23 5 2 6 7 29 9 3 3 1 36 3 3 9 5 42 7 4 5 9 49 1 5 2 3 55 5
12 44 76 10 8 1 4 0 17 2 2 0 4 23 6 2 6 8 30 0 3 3 2 36 4 3 9 6 42 8 4 6 0 49 2 5 2 4 55 6
13 45 77 10 9 1 4 1 17 3 2 0 5 23 7 2 6 9 30 1 3 3 3 36 5 3 9 7 42 9 4 6 1 49 3 5 2 5 55 7
14 46 78 11 0 1 4 2 17 4 2 0 6 23 8 2 7 0 30 2 3 3 4 36 6 3 9 8 43 0 4 6 2 49 4 5 2 6 55 8
15 47 79 11 1 1 4 3 17 5 2 0 7 23 9 2 7 1 30 3 3 3 5 36 7 3 9 9 43 1 4 6 3 49 5 5 2 7 55 9
16 48 80 11 2 1 4 4 17 6 2 0 8 24 0 2 7 2 30 4 3 3 6 36 8 4 0 0 43 2 4 6 4 49 6 5 2 8 56 0
17 49 81 11 3 1 4 5 17 7 2 0 9 24 1 2 7 3 30 5 3 3 7 36 9 4 0 1 43 3 4 6 5 49 7 5 2 9 56 1
18 50 82 11 4 1 4 6 17 8 2 1 0 24 2 2 7 4 30 6 3 3 8 37 0 4 0 2 43 4 4 6 6 49 8 5 3 0 56 2
19 51 83 11 5 1 4 7 17 9 2 1 1 24 3 2 7 5 30 7 3 3 9 37 1 4 0 3 43 5 4 6 7 49 9 5 3 1 56 3
20 52 84 11 6 1 4 8 18 0 2 1 2 24 4 2 7 6 30 8 3 4 0 37 2 4 0 4 43 6 4 6 8 50 0 5 3 2 56 4
21 53 85 11 7 1 4 9 18 1 2 1 3 24 5 2 7 7 30 9 3 4 1 37 3 4 0 5 43 7 4 6 9 50 1 5 3 3 56 5
22 54 86 11 8 1 5 0 18 2 2 1 4 24 6 2 7 8 31 0 3 4 2 37 4 4 0 6 43 8 4 7 0 50 2 5 3 4 56 6
23 55 87 11 9 1 5 1 18 3 2 1 5 24 7 2 7 9 31 1 3 4 3 37 5 4 0 7 43 9 4 7 1 50 3 5 3 5 56 7
24 56 88 12 0 1 5 2 18 4 2 1 6 24 8 2 8 0 31 2 3 4 4 37 6 4 0 8 44 0 4 7 2 50 4 5 3 6 56 8
25 57 89 12 1 1 5 3 18 5 2 1 7 24 9 2 8 1 31 3 3 4 5 37 7 4 0 9 44 1 4 7 3 50 5 5 3 7 56 9
26 58 90 12 2 1 5 4 18 6 2 1 8 25 0 2 8 2 31 4 3 4 6 37 8 4 1 0 44 2 4 7 4 50 6 5 3 8 57 0
27 59 91 12 3 1 5 5 18 7 2 1 9 25 1 2 8 3 31 5 3 4 7 37 9 4 1 1 44 3 4 7 5 50 7 5 3 9 57 1
28 60 92 12 4 1 5 6 18 8 2 2 0 25 2 2 8 4 31 6 3 4 8 38 0 4 1 2 44 4 4 7 6 50 8 5 4 0 57 2
29 61 93 12 5 1 5 7 18 9 2 2 1 25 3 2 8 5 31 7 3 4 9 38 1 4 1 3 44 5 4 7 7 50 9 5 4 1 57 3
30 62 94 12 6 1 5 8 19 0 2 2 2 25 4 2 8 6 31 8 3 5 0 38 2 4 1 4 44 6 4 7 8 51 0 5 4 2 57 4
31 63 95 12 7 1 5 9 19 1 2 2 3 25 5 2 8 7 31 9 3 5 1 38 3 4 1 5 44 7 4 7 9 51 1 5 4 3 57 5
32 64 96 12 8 1 6 0 19 2 2 2 4 25 6 2 8 8 32 0 3 5 2 38 4 4 1 6 44 8 4 8 0 51 2 5 4 4 57 6
Convolutional
Interleaving
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Diversity (Continued)
Frequency Diversity
Bandwidth of Traditional Signal :200~300 KHz
Bandwidth of CDMA Signal :1.25MHz
200 - 300 KHz
1.25 MHz
50 times
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Diversity (Continued)
Space Diversity
Correlator
Correlator
Correlator
Rake Receiver Soft Handoff
MS
RX1
RX0
Diversity Antenna
Diversity receiver is useful in reducing multipath fading
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Soft Handoff
A soft handoff establishes aconnection with the new BTS prior tobreaking the connection with the oldone. This is possible because CDMAcells use the same frequency and themobile uses a rake receiver.The CDMA mobile assists thenetwork in the handoff. The mobiledetects a new pilot as it travels to thenext coverage area. The new BTSthen establishes a connection with the
mobile. This new communication linkis established while the mobilemaintains the link with the old BTS.Soft handoffs are also called “make -before- break”. It reduces call drop.
Soft Handoff
Softer Handoff
Soft/Softer Handoff
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Soft Handoff (1)
Features:
First establish target connection, then cut off the originalconnection
Seamless communication, less call dropping, high voicequality
Types of soft handoff:
Inter sector: softer handoff, performed by BTS
Inter BS : soft handoff, performed by BSC
Inter BSC/MSC Soft Handoff
CDMA system with High-speed packet switchingfunctions
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Soft Handoff (2)
BTS BTS BTS
BSC
HIRS
SVBS
BSC
HIRS
SVBS
MSC MSC MSC
BSC
HIRS
SVBS
BTS1
BSC
HIRS
SVBS
MSC
BTS2 BTS1
BSC
HIRS
SVBS
MSC
BTS2 BTS1
BSC
HIRS
SVBS
MSC
BTS2
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Voice Coding
64kPCM
13kGSM
8kCDMA
13kCDMA
Q-CELP Voice Coder with variable rate Voice quality of CDMA 8K Vocoder equals that of GSM 13KVocoderCDMA13K Vocoder has good Voice quality close to that ofwire telephone with strong background noise reductionCDMA EVRC very close to CDMA 13K Vocoder
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Sampling
8KHz
160Sampled
Value
Tone parameterSub-frame
Code tablePara Sub-frame
Para Frame
20 ms
Refresh20 msFixed
Refresh
Refresh
Data rate
Data rate
NoiseSelf-adaptive
Threshold
LPCFilter parameter
Sub-frameVoice
Q-CELP Coding
M ul t i pl e x
C h a nn e l
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Thank you