1. Coexistence in heterogeneous networks Discuss the interference issue
Spectrum Co-existence of IEEE b and a Networks using the CSCC Etiquette Protocol
Coexistence in heterogeneous networks
Discuss the interference issue
Design a coordination protocol to improve the performance
Pilot channel
Power control mechanism

2. Coexistence Study in the 2500-2690 MHz Band between WiMAX and WCDMA Systems
Zheng Ruiming, Zhang Xin, Li Xi, Hai Yang, Yang Dacheng
Beijing University of Posts and Telecommunications
IEEE Vehicular Technology Conference, VTC2008
Presenter: Han-Tien Chang

3. Outline Introduction Interference Environment Analysis
Evaluation Methodology and Simulation Parameters
Simulation Results and Analysis
Mitigation Techniques
Conclusion
Comments

4. Introduction The bandwidth from 2500 to 2690 MHz
is assigned to IMT-2000 systems as the extension band, which is identified by the WRC-2000.
3G cellular systems (ex: WCDMA) in Europe
WiMAX (802.16e) as a member in IMT-2000 by WRC-07
makes it permitted to use 3G systems’ bandwidth, which also includes 2500 to 2690 MHz.
Analysis of coexistence issue between WiMAX and WCDMA systems in 2500 to 2690 MHz band is of great importance

5. Introduction (cont’d)
Related discussions and results on coexistence issue
[2] coexistence of FDD and TDD modes in UMTS
[3] coexistence of TD-SCDMA and WCDMA systems
[4] coexistence involving between two LTE systems
[5] coexistence of mobile WiMAX and GSM system
[6] interference analysis of d and WCDMA system
[7][8] techniques to mitigate the interference ,and hence to improve coexistence between TDD and FDD networks
[2] Impact of FDD/TDD coexistence on overall UMTS system performance
[3] Theoretical and Simulation Investigation on Coexistence between TD-SCDMA and WCDMA system
[4] Coexistence Analysis Involving 3GPP Long Term Evolution
[5] Co-Existence Study of Mobile WiMAX and GSM
[6] Interference Analysis between Macro WCDMA and Macro WIMAX Coexisted in Adjacent Frequency Band
[7] ITU-R M.2030, [8] ITU-R M.2045
FDD: Frequency Division Duplex
TDD: Time Division Duplex
[7] ITU-R M.2030, “Coexistence between IMT-2000 time division duplex
and frequency division duplex terrestrial radio interface technologies
around 2600 MHz operating in adjacent bands and in the same
geographical area,” 2003.
[8] ITU-R M.2045, “Mitigating techniques to address coexistence between
IMT-2000 time division duplex and frequency division duplex radio
interface technologies within the frequency range MHz
operating in adjacent bands and in the same geographical area,” 2004.

6. Introduction (cont’d)
The analysis on several interference paths with WiMAX and WCDMA system
Statistic Monte-Carlo simulation methods, assumptions and parameters in details.
Simulation from three different respects
Separation distances between two systems
Uplink power control mechanism of WiMAX system
Frequency reuse schemes

7. Interference Environment Analysis
The coexistence interference of mobile WiMAX (802.16e) and WCDNA systems in macro cellular network
WiMAX’s channel bandwidth: 10 MHz
WCDMA’s channel bandwidth: 5 MHz
Frequency Allocation and Interference Scenarios
Interference between WiMAX and WCDMA uplink (UL) as well as WiMAX and WCDMA downlink (DL)
From [10], WiMAX specification supports scalable channel bandwidths between 1.25 and 20MHz.

8. Interference Environment Analysis (cont’d)
The possible interference path
Interference between WiMAX system and WCDMA system uplink (MSBS)
1. Interference to WCDMA BS caused by WiMAX BS
2. Interference to WCDMA BS caused by WiMAX MS
3. Interference to WiMAX BS caused by WCDMA MS
4. Interference to WiMAX MS caused by WCDMA MS

9. Interference Environment Analysis (cont’d)
Interference between WiMAX system and WCDMA system downlink (BSMS)
1. Interference to WCDMA MS caused by WiMAX BS
2. Interference to WCDMA MS caused by WiMAX MS
3. Interference to WiMAX BS caused by WCDMA BS
4. Interference to WiMAX MS caused by WCDMA BS
Concentrate on several important interference scenarios in section IV

10. Interference Environment Analysis (cont’d)
Inter-system Interference
Adjacent Channel Interference (ACI)
Two main sources: one is out-of-band emission and the other one is spurious emission
The ACI can lead to significant reduction in its neighbor system capacity.
Adjacent Channel Interference Power Ratio (ACIR)
which is defined as the ratio of the total power transmitted from a source to the total interference power affecting a victim receiver
RF characteristics of transmitter and receiver are taken into account by weighting adjacent system signal

11. Evaluation Methodology and Simulation Parameters
Evaluation Methodology and Simulation Procedure
Certain number of users randomly distributed in service area after the deployment of system layout and setting simulation
Calculate each link’s path-loss, including antenna gain and shadow fading
Each MS chooses its BS based on the strongest signal it receives and then keeps the serving BS unchanged
The final statistics may be collected after SINR calculation and no more than 150-step power control iterations

12. Evaluation Methodology and Simulation Parameters (cont’d)
Network Deployment and Frequency Reuse
Service area deploy in simulation
a layout of 2-tier 19 hexagonal cells with 3 identical sectors in each cell
WiMAX Frequency reuse schemes
1*3*1: each cell uses the same 10 MHz
1*3*3: each sector only occupies 10/3 MHz
(Cell × Sector × Frequency Reuse Factor)
In WCDMA system, all the 5 MHz bandwidth is deployed in the whole service area.

13. Evaluation Methodology and Simulation Parameters (cont’d)

14. Evaluation Methodology and Simulation Parameters (cont’d)
Simulation Assumptions
and Parameters

15. Evaluation Methodology and Simulation Parameters (cont’d)

16. Evaluation Methodology and Simulation Parameters (cont’d)
Propagation Models
BS-to-MS propagation model [11][12]
Δhb: the difference between the base station antenna height and the average building height (6m)
R: the distance between BS and MS in kilometer
f: the frequency (2600 MHz)

17. Evaluation Methodology and Simulation Parameters (cont’d)
d: the distance in meters between the BS and MS
BS-to-BS propagation model
The Dual-Slope LOS propagation model is used in this transmitting environment with the breakpoint (dbreak) as the threshold to determine the appropriate model
htx and hrx are the heights over the reflecting surface of the transmitter and the receiver. λ is the wavelength.

18. Evaluation Methodology and Simulation Parameters (cont’d)
Where d is distance in meters
Minimum Coupling Loss (MCL)
Defined as the minimum distance loss including antenna gain measured between antenna connectors
The MCL values of base station to base station and to mobile station are 50dB and 70dB

19. Evaluation Methodology and Simulation Parameters (cont’d)
The received power in downlink or uplink (BS-BS)
where PTx and PRx are the transmitted and received signal power.
GTx and GRx present the transmitted and received antenna gain.

20. Evaluation Methodology and Simulation Parameters (cont’d)
Interference Models and Power Control Mechanism
WCDMA system interference models
The SINR calculation in uplink
PRx: received power, N0: thermal noise.
Iown : the interference generated by other users that are connected to the same BS
β represents an interference reduction factor due to the use of Multi User Detection (MUD) in uplink

21. Evaluation Methodology and Simulation Parameters (cont’d)
Iother means the interference from other cells of WCDMA system, and also includes the interference coming from the WiMAX system, which is decreased by ACIR (dB).
The SINR calculation in downlink
α is the orthogonal factor, which takes into account the fact that the downlink is not perfectly orthogonal due to multipath propagation. In this simulation, α = 0.4

22. Evaluation Methodology and Simulation Parameters (cont’d)
WiMAX system interference model
WiMAX system adopts Orthogonal Frequency Division Multiple Access (OFDMA) technology
IC,i denotes the co-channel interference received from the ith transmitter
NC represents the number of co-channel interfering transmissions
IA,i is the adjacent channel interference received from the jth transmitter which reduced by ACIR (dB)
NA is the number of adjacent channel interfering transmissions.

23. Evaluation Methodology and Simulation Parameters (cont’d)
Interference factor
When WCDMA system is interfered by WiMAX system
TDD system’s interference to certain direction of FDD system exists for some periods other than the whole time.
The interference from TDD should multiply k, the interference factor and assumes uplink/downlink ratio as ½.
Interference (WiMAX BSWCDMA BS & MS)
k is 0.67
Interference (WiMAX MSWCDMA BS and MS)
k is 0.33

24. Evaluation Methodology and Simulation Parameters (cont’d)
Performance Evaluation Criteria
WCDMA performance evaluation criteria
Nsingle is defined as the number of users per sector in single system case (i.e. the case without interfering system)
In multi-system case, when considering additional interference from WiMAX system, Nmulti users per sector is distributed in WCDMA system.

25. Evaluation Methodology and Simulation Parameters (cont’d)
WiMAX performance evaluation criteria
The modulation efficiency (ME) of each link in WiMAX system could be acquired from physical layer performance table
The average modulation efficiency is
ME is modulation efficiency of the ith link, N is the number of total links.
The loss in the modulation efficiency is calculated by

26. Simulation Results and Analysis
Different offsets between two systems
evaluate the impacts on coexistence caused by different offsets between the two systems
WCDMA MS interfering with WiMAX BS

27. Simulation Results and Analysis (cont’d)
As the distance between the two systems increasing
More users in WCDMA cell edge are likely to locate near WiMAX base station
These users will transmit at higher power in order to guarantee their link qualities in WCDMA system,
Results in sever interference to WiMAX BSs and decrease of WiMAX uplink modulation efficiency.

28. Simulation Results and Analysis (cont’d)
Uplink power control mechanism used in WiMAX system
an important technology in reducing the interference to other cells or systems
The initial transmitted power for a user is the maximum MS transmit power.
Using the current SINR (SINRcurrent) as index to lookup the physical layer performance table, we choose the lower SINR value close to the current one as the target SINR.

29. Simulation Results and Analysis (cont’d)

30. Simulation Results and Analysis (cont’d)
The data show that using power control mechanism may adjust transmitted power of WiMAX users, as well as effectively reduce their interference to WCDMA systems.

31. Simulation Results and Analysis (cont’d)
Two frequency reuse schemes
Frequency reuse is implemented to assure edge-user connection quality and throughput
Two interference scenarios
From WiMAX MS to WCDMA BS
From WCDMA BS to WiMAX BS.
The frequency reuse mechanism may significantly reduce the transmitted power for users at cell edge and the interference to WCDMA system

32. Simulation Results and Analysis (cont’d)

33. Mitigation Techniques
Reduce the interference between TDD and FDD systems operating on adjacent frequencies
antenna separation
improving the RF equipment performance
using proper guard-bands between two systems
adopting channel filter for the base station to improve the ACLR (adjacent channel leakage ratio) and ACS (adjacent channel selectivity) performance.

34. Conclusion Detailed interference environment analysis
including several interference scenarios, network deployment, propagation models and interference models
Typical interference scenarios are simulated and evaluated from three different respects

35. Comments
Learn about much interference knowledge about WiMAX with WCDMA system
Lack of detail simulation procedure
If using the CSCC Etiquette Protocol in WiNAX and WCDMA system