Power Control Technology

8/12/2019 Power Control Technology

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CDMA Key Technology

ZTE Corporation

CDMA Division



CDMA Key Technology

Spread Spectrum Communication

Code Division Multiple Access

Power Control

Diversity

Soft Handoff

Rake Receiver

Variable Rate Vocoder





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



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



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





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




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




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



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





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





Diversity

Three types of diversity in CDMA.

Time Diversity

Frequency DiversitySpace Diversity



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



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



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



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




Frequency Diversity

Bandwidth of Traditional Signal :200~300 KHz

Bandwidth of CDMA Signal :1.25MHz

200 - 300 KHz

1.25 MHz

50 times




Space Diversity

Correlator

Correlator

Correlator

Rake Receiver Soft Handoff

MS

RX1

RX0

Diversity Antenna

Diversity receiver is useful in reducing multipath fading



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



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



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







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



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



Thank you

Documents

Power Control Technology