Basic theory of CDMA capacity

Outline

Basic theory of calculating

reverse capacity

Basic theory of calculating

forward capacity

Net model (19cell)

Theoretical equation of calculating reverse capacity

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Voice Activity factorfv

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Theoretical equation of calculating reverse capacity

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Interference factoru

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Tabl e StandardDevi ati on

Nc=1 Nc=2 Nc=3 Nc=4

0 0. 44 0. 44 0. 44 0. 442 0. 48 0. 43 0. 43 0. 434 0. 67 0. 47 0. 45 0. 456 1. 13 0. 56 0. 49 0. 498 2. 38 0. 77 0. 57 0. 5510 6. 17 1. 28 0. 75 0. 6612 19. 8 2. 62 1. 17 0. 91

Theoretical equation of calculating reverse capacity

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Loading factor

Reverse real capacity vs. reverse pole capacity

Theoretical equation of calculating reverse capacity

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sectorization factor sSectorization factor is one parameter

induced by influence of interference between sectors on capacity.

Theoretical equation of calculating reverse capacity

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Theoretical equation of calculating reverse capacity

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An example

processi ng gai n 128 l oadi ng factor 0. 7S/ N 7 sectori zati on factor 2. 55Voi ce Act i vi ty f actor 0. 4 non-accurate power control0. 8i nterference from other cel l s 0. 55 capaci ty 20

Outline

Basic theory of calculating

reverse capacity

Basic theory of calculating

forward capacity

Theoretical equation of calculating forward capacity

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Derivation process

Theoretical calculating result of the forward capacity

Type of handoff Area i n Handoff (%) ξ co

Sof t 25 0. 25Sof ter 20 0. 20

Sof t- sof t 10 0. 20Sof t- sof ter 10 0. 20

Total ξ co =0. 85

Channel Overhead Facor for Vari ous Types of Sof t Handdff s

Soft handoff payload

Forward capacity supported by

each sector: 38

Equivalent occupied channel

number： 1.85

Forward link capacity： 20

Example

Some discussion about the capacity

Is the system capacity limited to forward or reverse link?How to consider the capacity of mixed traffic system?

Senior subscriber action (to solve data Erl)

Information on demand WWW/WAP E-MAIL FTP VOD/AOD E-COMMERCE OTHER

1 average monthly use times n1 60 60 60 60 5 20 15

2 busy day concentrated coefficient M1 5% 5% 5% 5% 5% 5% 5%

3 average daily use times n2=n1*M1 3 3 3 3 0.25 1 0.75

4 busy concentrated coefficient M2 10% 10% 10% 10% 10% 10% 10%

5 busy use times n3=n2*M2 0.3 0.3 0.3 0.3 0.025 0.1 0.075

6 average time for each use T1(s) 120 300 15 30 300 120 60

7 duty cycle M3 0.1 0.1 0.75 0.8 0.8 0.1 0.1

8 average real time for each use T2(s)=T1*M3 12 30 11.25 24 240 12 6

9 average data traffic rate R 26210 26210 26210 26210 26210 26210 26210

10 data throughput of busy data subscriber S(bps)=R*T2*n3/3600 26.21 65.53 24.57 52.42 43.68 8.74 3.28

data throughput of busy data subscriber(add up all traffics) (bps) 224.42 250

Traffic(mErl) 10.00 25.00 1.25 2.50 2.08 3.33 1.25

From upper table, we can calculate busy use times and traffic, and then calculate use time by the traffic equation.

busy use times 1.4

Traffic(mErl) 45.42

average time for each use(s) 117

Some discussion about the capacity

Is the system capacity limited to forward or reverse link?How to consider the capacity of mixed traffic system?

low-grade subscriber action (to solve data Erl)

Information on demand WWW/WAP E-MAIL FTP VOD/AOD E-COMMERCE OTHER

1 average monthly use times n1 30 30 20 30 0 10 10

2 busy day concentrated coefficient M1 5% 5% 5% 5% 5% 5%

3 average daily use times n2=n1*M1 1.5 1.5 1 1.5 0 0.5 0.5

4 busy concentrated coefficient M2 10% 12% 10% 10% 10% 10%

5 busy use times n3=n2*M2 0.15 0.18 0.1 0.15 0 0.05 0.05

6 average time for each use T1(s) 120 300 15 30 0 120 60

7 duty cycle M3 0.1 0.1 0.75 0.8 0 0.1 0.1

8 average real time for each use T2(s)=T1*M3 12 30 11.25 24 0 12 6

9 average data traffic rate R 9600 9600 9600 9600 9600 9600

10 data throughput of busy data subscriber S(bps)=R*T2*n3/3600 4.80 14.40 3.00 9.60 1.60 0.80

data throughput of busy data subscriber(add up all traffics) (bps) 34.20 35

Traffic(mErl) 5.00 15.00 0.42 1.25 0.00 1.67 0.83

From upper table, we can calculate busy use times and traffic, and then calculate use time by the traffic equation.

busy use times 0.68

Traffic(mErl) 24.17

average time for each use(s) 128

Some discussion about the capacity

Is the system capacity limited to forward or reverse link?

How to consider the capacity of mixed traffic system?

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Capacity analysis and network optimization

Limited capacityIncreasing

dropped call rate

Difficult access

Degressive voice quality