Coexistence in heterogeneous networks Discuss the interference issue Spectrum Co-existence of IEEE 802.11b and 802.16a 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

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, 2008. VTC2008 Presenter: Han-Tien Chang

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

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

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 802.16d 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 2500-2690 MHz operating in adjacent bands and in the same geographical area,” 2004.

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

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.

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

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

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

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

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.

Evaluation Methodology and Simulation Parameters (cont’d)

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

Evaluation Methodology and Simulation Parameters (cont’d)

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)

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.

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

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.

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

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

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.

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

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.

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

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

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.

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.

Simulation Results and Analysis (cont’d)

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.

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

Simulation Results and Analysis (cont’d)

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.

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

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