Spatial Channel Model for Link Level Simulations Younglok Kim July 14, 2004

Outline Importance of spatial channel model (SCM) Spatial model implementation Old spatial correlation model Time-invariant correlation Time-varying correlation MIMO spatial channel model by 3GPP-3GPP2 More spatial parameters for BS and UE Discussions

Channel Models for Multiple Antennas The spatial properties of channels are extremely important in determining the performance of multiple antenna systems Each diversity scheme has own channel model description Need to consider Time-varying angular spread Angular distribution with plane wave assumptions Adaptive array antenna geometries Various estimations of spatial correlation based on various assumptions Must verify models by field measurements [R1-01-1132] If we adopt more than two antenna elements for TxD scheme, SCM description is important to evaluate the performances of various different schemes.

Spatial Correlated Channel Model Assumptions Long-term properties of the channel remain unchanged over time Independence between different taps Spatial covariance matrices are equal for each tap Spatially correlated multiple channels can be generated by the linear transformation of the same number of uncorrelated channels

Block Diagram for SCM Generation

Alternative Modification for Rx Diversity Simulations Assumption: spatial covariance matrices are equal for each tap Equivalent simulation method without change the channel impulse responses by transformation of Received signal before AWGN Antenna weight

Spatial Correlation Coefficients Spatial correlation matrix for 4 antenna case Spatially uncorrelated channels: a=b=c=0 Correlation coefficients are given in TSGR1#17(00)1358

Recommended Correlation Parameters Environment Parameters Recommended path model Angular spread Macro cell (Rural area) a=0.97 exp(-0.8 j) b=0.94 exp(-1.6 j) c=0.88 exp(-2.4 j) 1-path Rayleigh Vehicular A 10° AS 70° AoA Micro cell (Urban area) a=0.7 exp(-2.2 j) b=0.1 exp(-1.2 j) c=0.2 exp(-3.0 j) Pedestrian A 45° AS 60° AoA Pico cell or uncorrelated a, b, c = 0 Large angular spread

PSD of Macro Cell Model: 70 AoA, 10 AS AoA is around 15° but not 70 ° Long-term average power profile according to angle Beam pattern of the dominant eigenvector Dominant eigenvector is associated with 99.9% power

Eigenbeam Patterns of Macro Model 0.1% 99.9% 0 % 0 %

PSD of Micro Cell Model: 60 AoA, 45 AS Dominant eigenvector is associated with 96% of total power

Eigenbeam Patterns of Micro Cell 38.7% 57.2% 3.7 % 0.4 %

Time Varying Correlation Model Discrete uniform distribution model

Time Varying Correlation Model… Angle of sub-paths: Angle of center: Steering vector of ULA:

Steering Vector of ULA Phase Difference between two adjacent antenna

Time Varying Model Parameters Propagation Environment Macro Cell Micro Cell Distance from BS to UE 2000 m 500 m Angular spread 10 ° 45 ° Channel models & UE velocities (km/h) 1-path Rayleigth: 3,10,40,120 Vehicular A: 10,40,120 Pedestrian A: 3, 10, 40 Number of sub-paths (Q) 10 100 Closed loop feedback error rate 4 %

Time Varying Coeffs (Macro Cell) Power of dominant eigenvector is about 99.9%

Time Varying Coeffs (Micro Cell) Power of dominant eigenvector ranges from 75.4 to 99.7%

Comments on Previous Channel Model Only eigenbeamformer scheme has adopted this spatial channel model Uniformly distributed power on an angular region Very limited simulation environments can be considered Constant time-invariant AoA can be assumed Since it is a slow varying effect similar to shadow fading Time varying AoA will not included in link level simulations Common & more reliable simulation spatial channel model is required Need specific descriptions of more channel parameters, AOA, PAS, AS, etc

Spatial Channel Model by AHG Text description: SCM-077 11/2002 Recommended to use MIMO physical layer channel model proposed SCM AHG (AH-62) from 3GPP & 3GPP2 Develop and specify parameters and methods associated with Link level spatial channel model For calibration only System level spatial channel model Define physical parameters and system evaluation methodology

Link level channel model Only for calibration purposes Reflect only one snapshot of the channel behavior Do not account for system attributes such as scheduling and HARQ Only for comparison of performance results from different implementation of a given algorithm Status: 95% completed

System level channel model Required for the final algorithm comparison Define the methodology for generating the spatial channel coefficients between BS and MS 95% completed

Terminologies MS = UE = terminal = subscriber unit BS = Node-B = BTS AS = angle spread = azimuth spread = PAS Path = Ray Path component = Sub-ray PAS = power azimuth spectrum DoT = direction of travel AoA = angle of arrival AoD = angle of departure PDP = power delay profile

Parameters of Link Level SCM Multipath fading propagation conditions Model Case I Case II Case III Case IV 3GPP Case B Case C Case D Case A 3GPP2 Model A, D, E Model C Model B Model F PDP Mod. Pedestrian A Vehicular A Pedestrian B Single path Speed (Km/h) 1) 3 2) 30, 120 3, 30, 120 3 # of paths 1) 4 + 1 (LOS on, K=6 dB) 2) 4 (LOS off) 6 1 Relative path power (dB) & Delay (ns) LOS on 0.0 -6.51 -16.21 -25.71 -29.31 LOS off –Inf -9.7 -19.2 -22.8 110 190 410 -1.0 -9.0 -10.0 -15.0 -20.0 310 710 1090 1730 2510 -0.9 -4.9 -8.0 -7.8 -23.9 200 800 1200 2300 3700

Parameters of Link Level SCM… Spatial parameters for NodeB Model Case I Case II Case III Case IV Topology Reference: ULA with 0.5, 4, 10 spacing N/A PAS Laplacian distribution with RMS angle spread of 2 or 5 degrees per path depending on AoA/AoD AoD/AoA (degrees) 50 for 2 RMS AS per path 20 for 5 RMS AS per path Antenna gain pattern 3 or 6 sector antenna pattern (For diversity oriented applications rather than beamforming applications)

Parameters of Link Level SCM… Spatial parameters for UE Model Case I Case II Case III Case IV Topology Reference 0.5 N/A PAS 1) LOS on: Fixed AoA for LOS component, remaining power has 360 degree uniform PAS. ( RMS angle spread of 104 degrees) 2) LOS off: Laplacian distribution with RMS angle spread of 35 degrees per path Laplacian distribution with RMS angle spread of 35 degrees per path OR 360 degree uniform PAS ( RMS angle spread of 104 degrees) DoT (degrees) 22.5 -22.5 AoA 22.5 (LOS component) 67.5 (all other paths) 67.5 (all paths) 22.5 (odd paths) -67.5 (even paths) Antenna gain pattern Omni directional with -1 dBi gain

Assumptions of Link Level SCM Spatial channel parameters per path Each resolvable path is characterized by spatial channel parameters: AS, AoA, PAS All paths are assumed independent Array Topologies Allow any type of antenna configuration, but must be shared to reproduce and verify the results ULA with element spacing of 0.5, 4, 10 wavelengths

Antenna Gain Patterns UE: -1 dBi gain omni-direction Node B uplink/downlink Only for diversity oriented implementations (large spacing) Need different antenna patterns for beamforming applications 3 sector cell Bandwidth 70°, Maximum attenuation 20 dB, 14 dBi gain 6 sector cell Bandwidth 35°, Maximum attenuation 23 dB, 17 dBi gain Sector antenna formula in dB scale

Sector Antenna Patterns at BS…

Sector Antenna Patterns at BS…

Average Received Power Laplacian distributed PAS Angle of Arrival RMS angle spread Normalization factor Antenna gain in linear scale

Average Received Power at BS 3 sectored antenna with AoA = 20 and RMS AS = 5

Average Received Power at MS Laplacian distributed PAS with omni-directional gain

Average Received Power at MS… 22.5 AoA & 35 RMS AS

Average Received Power at MS… 22.5 AoA & 104 RMS AS (uniform over 360 degree PAS)

Doppler Spectrum at UE Dependent on DoT PAS AoA

Generation of link level channel model Average received power Angle theta represents path components Its distribution is TBD Uniformly distribution over [-180 180] degrees Channel implementation techniques Correlation based Ray based Details are TBD Reference correlation values are provided Nokia to provide formulas for computing correlation matrices

Future Plan & Discussions SCM generation and verification by using MatLab UE BS Study on system level spatial channel model

References Old 3GPP Model: MIMO Model: Tx Div Model: TSGR1#14(00)0867 0765, 770 TSGR1#29(02) 1139,1419,1440 1441 (TR25.869) MIMO Model: TSGR1#22(01)1132 TSGR1#22(01)1136 TSGR1#23(01)1179 TSGR1(02)0141 SCM-077, November 2002 by 3GPP-3GPP2

Standard for Space Channel Model Common & more reliable simulation spatial channel model is required Need specific descriptions of more channel parameters, AOA, PAS, AS, etc Spatial channel model by 3GPP-3GPP2 More spatial parameters for BS and UE SCM Text V7.0, 8/2003 ftp://ftp.3gpp2.org/TSGC/Working/2003/3GPP_3GPP2_SCM_(Spatial_Modeling)/ConfCall-16-20030417/