Flexible Allocation of Capacity in Multi-Cell CDMA Networks

Transcription

1 Flexble Allocaton of Capacty n Mult-Cell CDMA Networs Robert Al, Manu Hegde, Mort Naragh-Pour*, Paul Mn Washngton Unversty, St. Lous, MO *Lousana State Unversty, Baton Rouge, LA

2 Outlne Capacty and Probablty of Outage Calculaton of nter-cell nterference Capacty regon Power compensaton factor Effects of dfferent cell szes Optmzaton of capacty Flexble allocaton of capacty Results 2

3 Nne Cell Networ 3

4 Probablty of Outage For Each Cell 4

5 5 Probablty of Outage for Sngle Cell. users n cell the number of s factor, the voce actvty, 1 Pr 1, where 1 / ) )(1 / ( Pr 2 out n α ν η η N I K I E η R W ν P l o o n l ' o o b l

6 6 Probablty of Outage for Sngle Cell n l ' o l n l ' o l K ν K ν P 1 2 out Pr Pr 2,... 0,1,, Pr where Let 1 e! μ λ n ν Z μ λ n l l ' Pr out o K μ αλ ' o! μ αλ e K Z P

7 7 Gaussan Approxmaton We approxmate the Posson by a Gaussan varable wth the same mean and varance: y x ' o o dx e y Q μ α λ μ α λ K Q Z Z K Q P 2 ' out ) ( ) var( E

8 Probablty of Outage for Multple Cells I : Inter-cell nterference from cell to cell. P out M M n I 1 (W/R)( 1 Pr νl l1 Eb /I o s the total number of cells. η) 8

9 Shadow and Raylegh Fadng Assume power control overcomes both large scale path loss and shadow fadng, but not Raylegh fadng. The average of the Raylegh fadng s the shadow fadng on that path. 9

10 Inter-Cell Interference I m s the path loss exponent. ς E ρ E X 2 ς r n (x,y) m m r (x,y)/x Area of cell ς ς 2 s the decbel attenuaton ρ da(x,y) due to shadowng, and has zero mean and standard devaton cell σ s.

11 Soft Handoff User s permtted to be n soft handoff to ts two nearest cells. 11

12 12 Soft Handoff (c) regon 2 (c) regon 2 (b) regon 2 (a) regon 2 E E E E ρda(x,y) r r X r r I ρda(x,y) r r X r r I ρda(x,y) r r X r r I ρda(x,y) r r X r r I ς m ς m ς m m ς m ς m ς m m ς m ς m ς m m ς m ς m ς m m

13 Inter-Cell Interference Factor K : per user nter-cell nterference factor from cell to cell n users n cell produce an amount of nterference n cell equal to n K K are not necessarly zero because of soft handoff, users n cell can cause nter-cell nterference to cell. 13

14 Capacty Regon 14

15 Capacty Regon Capacty regon: set of all feasble user confguratons Unform capacty: n = c 1 for all Two level capacty: m 1 cells have capacty c 1 and m 2 cells have capacty c 2 where m 1 + m 2 = M 15

16 Example: 2 Cell Networ K BS-1 BS-2 BS BS

17 Capacty Regon

18 Power Compensaton Factor Fne tune the nomnal power of the users PCF defned for each cell PCF s a desgn tool to maxmze the capacty of the entre networ 18

19 Power Compensaton Factor Interference s lnear n PCF 19

20 Senstvty Analyss Dervatve of capacty functon wth respect to the PCF Capture effect of ncreases n PCF n one cell on the capacty of whole networ Tool to flexbly dstrbute capacty between cells 20

21 Senstvty Analyss For unform capacty case: 21

22 22 Senstvty Analyss * * f f κ β β κ β c κ β c dβ dc κ β β κ β c dβ dc M eff M eff M eff * * * *

23 Optmzaton Optmze the sum capacty: the sum of the capactes of the cells Constrant: PCF between a mn and a max Use the dervatves n steepest descent algorthm New PCF s the factor that the nomnal power needs to be ncreased by for every cell Each PCF s used by ts Base Staton n the Closed Loop Power Control 23

24 Optmzaton of Unform Capacty 24

25 Optmzaton of Two-Level Capacty 25

26 Capacty Regon

27 Hard Handoff vs. Soft Handoff HH BS-1 BS-2 BS-3 Cap Opt PCF BS BS BS SH BS-1 BS-2 BS-3 Cap Opt PCF BS BS BS

28 Seven Cell Networ 28

29 Probablty of Outage For Each Cell 29

30 Optmzaton Unform capacty C1: 11 (PCF=1) to 20 (PCF Optmzed) Sum capacty: 77 to 140 Two-level capacty Small cells: 14 (PCF=1) to 22 (PCF Optmzed) Large cells: 7 (PCF=1) to 11 (PCF Optmzed) Sum capacty: 77 to

31 Flexblty n Capacty Allocaton Case 1: Result: sum capacty of

32 Flexblty n Capacty Allocaton Case 2: Result: sum capacty of 152 but capacty of cell three drops from 20 to

33 Flexblty n Capacty Allocaton Case 3: Result: cell three has a capacty of 25 but sum capacty drops to

34 34

35 Conclusons Power Compensaton Factor s a desgn tool to: Flexbly dstrbute the capacty allocaton between cells Optmze the capacty of a networ Maxmze the capacty of a sngle cell Easy to mplement n an exstng networ Does not requre the relocaton or addton of Base Statons. 35

36 Future Wor Plot Power determnes the cell geometry whch determnes the nter-cell and ntra-cell nterference Determne the senstvty of capacty wth respect to Plot Power Determne the senstvty of capacty wth respect to Base Staton locaton Complete Desgn: Locaton, forward power, reverse power. 36