Interference Based Power Control in Local Area Environment

1. Interference Based Power Control in Local Area Environment Bilal Rasheed Chaudhry AALTO UNIVERSITY SCHOOL OF SCIENCE AND TECHNOLOGY Faculty of Electronics, Communications and Automation Department of Communications and Networking Espoo, Finland, June 2010

2. This work was carried out at Nokia Research Center, Helsinki, Finland. Supervisor: Professor Olav Tirkkonen Instructor: M.Sc. Chia-Hao Yu Methods • Literature studies, Simulations

3. SEQUENCE OF PRESENTATION • Thesis Objectives • Power Control • Fractional Power Control • Interference Based Power Control • Envelope Modeling • Future Work

4. THESIS OBJECTIVES • Study the FPC technique present in the current standardized formula, in a local area scenario, to obtain a reference performance and analysis framework. • Examine the influence of power control parameters on system performance by introducing new and finer values of the path loss compensation factor. • Study IPC by exploring different combinations of the PC parameters and find out the combination that gives good operating points for the system. • Find out the envelope of the system throughput performance points.

5. KEY PERFORMANCE INDICATORS • User Throughput at Cell Edge (ηedge): The cell edge user throughput is defined as the 5th percentile point of the Cumulative Distribution Function of user throughput. It is an indicator of the coverage performance. • Average User Throughput (ηavg): Sum of the user throughput of each drop in the system divided by the total number of drops. • Uplink Received Signal-to-Interference and Noise Ratio: The ratio of the desired signal power received, at the Access Point (AP), to the received noise and interference power corrupting the signal. It is a measure of transmission quality. The ratio is expressed in decibels (dB).

6. WHY POWER CONTROL • Maintains the link quality in uplink and/or in downlink by controlling the transmission powers. • Prevents near-far effect. • Minimizes effects of fast and slow fading. • Minimizes interference in network. • Reduces power consumption (important especially for handheld terminals

7. TYPES OF POWER CONTROL • Open Loop Power Control

8. TYPES OF POWER CONTROL • Closed Loop Power Control

9. PHYSICAL RESOURCE BLOCK

10. POWER CONTROL IN LTE • Open loop power control. • Provision for closed loop power control • Channel sensitive scheduling • Hybrid ARQ

11. FRACTIONAL POWER CONTROL • Why? • LTE supports diversified data services which require different SINR target. • UEs located near the interior of the cell do not contribute to the interference for other cells as much as the UEs near cell edge

12. FRACTIONAL POWER CONTROL • is the maximum allowed transmit power. • is the number of allocated physical resource blocks valid for subframe i. • is a cell specific parameter provided by the higher layers. From here onwards will simply be referred to as • is a 3-bit cell specific parameter provided by higher layers. • PL is the downlink path loss estimate calculated in UE in dB based on the transmit power of the reference signal. • is an UE specific offset used to consider different SINR requirements against various Modulation and Coding Schemes (MCS). • is a function that represents power correction value provided by CLPC.

13. FRACTIONAL POWER CONTROL Simplified formula M=1 =0 =0

14. FRACTIONAL POWER CONTROL

15. I U2 S S U1 I 2-CELL SCENARIO

16. 2-CELL SCENARIO-(Simulation Parameters)

17. 2-CELL SCENARIO-(TP CALCULATION) [mW/PRB] • Where: • PL11 is the path loss from user 1 to AP1 [mW/PRB] Similarly interference signal I ca be written as : [mW/PRB]

18. 2-CELL SCENARIO-(TP CALCULATION) Throughput can be calculated using Shanon’s formula

19. 2-CELL SCENARIO Every combination of Po and α generates a point on the figure

20. INTERFERENCE BASED POWER CONTROL Signal Interference AP 1 UE AP 2 Cell boundary

21. INTERFERENCE BASED POWER CONTROL

22. INTERFERENCE BASED POWER CONTROL Every combination of Po, α and β generates a point on the figure

23. INTERFERENCE BASED POWER CONTROL Values of Po that maximize cell edge throughput

24. INTERFERENCE BASED POWER CONTROL Simulation Parameters

25. INTERFERENCE BASED POWER CONTROL

26. SIMULATION IN AN INDOOR OFFICE ENVIRONMENT • Simulation consists of 200 independent drops. • WINNER A1 indoor path loss model. • 3 users per Access point and 4 access points in one floor. • 200 snapshots for each drop. • Random scheduler. • Ideal link adaptation. • No wrap around. • Street Width = 20m. • Height of a floor = 3m. • Dimensions of a floor = 50m × 100m. • Maximum transmit power = 21dBm. • Range of α = from 0 to 1 with a step size of 0.1 • Range of β = from 0 to 1 with a step size of 0.1 • BW = 20MHz. • Po values = from -190 to 21dBm with a step size of 1dBm. • Noise Figure = 6dB. • Noise Floor/Hz = (-174 + Noise Figure) dBm/Hz. • Thermal Noise =

27. 16 BUILDINGS 1 FLOOR

28. 16 BUILDINGS 1 FLOOR

29. 16 BUILDINGS 1 FLOOR

30. 16 BUILDINGS 1 FLOOR

31. 9 BUILDINGS 3 FLOORS

32. 9 BUILDINGS 3 FLOORS

33. 9 BUILDINGS 3 FLOORS

34. ENVELOPE MODELING

35. ENVELOPE MODELING

36. ENVELOPE MODELING

37. ENVELOPE MODELING

38. CONCLUSIONS • It was shown that FPC gives better cell edge throughput compared to conventional OLPC. • Significant improvement in when using IPC compared to FPC. • Two cell model has a small trade-off region. • In a scenario with nine, 3-floor buildings we found about 8% improvement in (ηedge) and 5% improvement in (ηavg) with IPC when compared with FPC. • β≥0.3 & α≤0.6 and give a range of possible values for good system performance.

39. FUTURE WORK • Studies to measure increased signaling overhead with reduced step size. • Interesting to find out a linear or complex combination of α,β and Po that describes the envelope. • Automatic adjustment of path loss compensation factors.

40. Thank You