Presentation is loading. Please wait.

Presentation is loading. Please wait.

Wireless Systems Research Department AT&T Labs - Research The Mobile MIMO Channel and Its Measurements Jack H. Winters [Carol Martin, Nelson Sollenberger.

Similar presentations


Presentation on theme: "Wireless Systems Research Department AT&T Labs - Research The Mobile MIMO Channel and Its Measurements Jack H. Winters [Carol Martin, Nelson Sollenberger."— Presentation transcript:

1 Wireless Systems Research Department AT&T Labs - Research The Mobile MIMO Channel and Its Measurements Jack H. Winters [Carol Martin, Nelson Sollenberger (Mobilelink)] AT&T Labs - Research Middletown, NJ

2 AT&T Labs - Research OUTLINE Introduction Test Setup Performance Measures Results Conclusions

3 AT&T Labs - Research MIMO Capacity Increase Multiple antennas at both the base station and terminal can significantly increase data rates if the multipath environment is rich enough –With M antennas at both the base station and the mobile, M independent channels can be provided in the same bandwidth –sufficient multipath  low correlation  high spectral efficiency With 4 transmit and receive antennas, 4 independent data channels can be provided in the same bandwidth Data rates as high as 1.5 Mbps (4x384 kbps) may be possible for EDGE, 216 Mbps WLAN (802.11a), or 20 Mbps for Wideband OFDM

4 AT&T Labs - Research Mobile MIMO Radio Channel Measurements Objectives –Characterize the mobile MIMO channel to determine feasibility of MIMO approach in a typical cellular environment sufficient multipath  low correlation  high spectral efficiency With 4 transmit/receive antennas, theoretically up to a 3.77-fold increase is possible Approach –Conduct field tests to show the potential increase in capacity using 4 transmit and 4 receive antennas at both the base station and terminal For reliable measurement at mobile speeds, collect data continuously and simultaneously on all 4 transmit and 4 receive antennas Collect data on drive routes at low to moderate speeds plus pedestrian and indoor tests in suburban environment Collect data for different antenna configurations –Measure 30 kHz complex channel with IS-136 Smart Antenna Test Bed

5 AT&T Labs - Research MIMO Channel Testing Tx W1W1 W2W2 W3W3 W4W4 LO Synchronous test sequences Rx Perform timing recovery and symbol synchronization Record 4x4 complex channel matrix Evaluate capacity and channel correlation LO Mobile Transmitter Test Bed Receiver with Rooftop Antennas Base Station Antenna Configurations 1.25 ft 1.5 ft 11.3 ft Space diversity Space / polarization diversity Space / polarization / pattern diversity Terminal Antenna Configurations

6 AT&T Labs - Research MIMO Channel Measurement System Transmitter 4 antennas mounted on a laptop 4 coherent 1 Watt 1900 MHz transmitters with synchronous waveform generator Receive System Dual-polarized slant 45° PCS sector antennas separated by 11 feet and fixed multibeam antenna with ° beams 4 coherent 1900 MHz receivers with real-time baseband processing using 4 TI TMS320C40 DSPs

7 AT&T Labs - Research Rx MIMO Channel Testing W1W1 W2W2 W3W3 W4W4 LO Synchronous test sequences Rx Perform timing recovery and symbol synchronization Record 4x4 complex channel matrix Evaluate capacity and channel correlation LO Mobile Transmitters Test Bed Receivers with Rooftop Antennas Terminal Antennas on a Laptop Tx Rooftop Base Station Antennas 11.3 ft Prototype Dual Antenna Handset Mobile Transmitters

8 AT&T Labs - Research MIMO Testing Drive Routes Drive routes within coverage of test sector Non line-of-sight conditions along route Suburban environment with gently rolling terrain Maximum downrange distance of 2.5 miles Peak speed of 45 mph, average speed of 30 mph in residential area Peak speed of over 60 mph along highway Pedestrian and indoor tests

9 AT&T Labs - Research Performance Measures Complex channel measurement: H = [ H ij ] for the i th transmit and j th receive antenna Capacity (instantaneous and averaged over 1 second): C = log 2 (det[1 +  H † H]) =  log 2 (1 +  /4 i ) where  is the signal-to-noise ratio and i is the i th eigenvalue of H † H To eliminate the effect of shadow fading, the capacity is normalized to the average capacity with a single antenna: C n =  log 2 (1 +  /4 i ) / (1/16)  log 2 (1 +  H ij )

10 AT&T Labs - Research Performance Measures (cont.) For the multibeam antenna, we normalize the capacity by the average capacity of the strongest beam: C n =  log 2 (1 +  /4 i ) / (1/4)  log 2 (1 +  H ijmax ) Correlation (averaged over 1 second): –Transmit signal correlation  i1,i2 = | [H † H] i1,i2 / ([H † H] i1,i1 [H † H] i2,i2 ) 1/2 | –Receive signal correlation  j1,j2 = | [HH † ] j1,j2 / ([HH † ] j1,j1 [HH † ] j2,j2 ) 1/2 |

11 AT&T Labs - Research Effect of Time Averaging on Capacity Simulation results with independent- Rayleigh-fading equal-power channels Distribution of capacity does not vary significantly with averaging –100 fades during 1 second average at 30 mph Spatial averaging reduces the effect of fading Capacity for pedestrians is similar to mobile users

12 AT&T Labs - Research Simulation results with independent- Rayleigh-fading equal-power channels Distribution of correlation does vary significantly with averaging Correlation decreases with: –Speed –Terminal antenna rotation –Low signal level Relative correlation only should be considered to identify antennas causing capacity reduction Effect of Time Averaging on Correlation

13 AT&T Labs - Research Amplitudes of 16 channels between the 4 transmit and 4 receive antennas 1 second average Channel powers are approximately equal for dual-polarized transmit and receive antennas MIMO Field Test Results

14 AT&T Labs - Research Field Test Results Dual-polarized, spatially-separated base station and terminal antennas Instantaneous normalized capacity Spatial averaging reduces variations due to Rayleigh fading Capacity increase is close to 4 times that of a single antenna 50% and 90% of the signal correlations are less than 0.23 and 0.47, respectively

15 AT&T Labs - Research Correlation distribution - 1 second average Dual-polarized, spatially- separated base station and terminal antennas Tx antennas: 30% decrease in correlation for spatially- separated antennas Rx antennas: 60% decrease in correlation for cross-pol, spatially- separated antennas

16 AT&T Labs - Research Measured capacity distribution is close to the ideal for 4 transmit and 4 receive antennas MIMO Field Test Results

17 AT&T Labs - Research Field Test Results Dual-polarized multibeam base station antenna (2 center beams) and dual-polarized terminal antennas Instantaneous normalized capacity Capacity increase is close to 2 times that of a single antenna 50% and 90% of the Rx signal correlations are less than 0.61 and 0.87, respectively

18 AT&T Labs - Research Correlation distribution - 1 second average Dual-polarized multibeam base station antenna (2 center beams) and dual-polarized terminal antennas Correlations between co-pol beams are high

19 AT&T Labs - Research Field Test Results Measured capacity distribution is close to the ideal for 4 transmit and 4 receive antennas with dual- polarized, spatially-separated base station and terminal antennas (cases 1-4) Capacity gain is 2 times a single antenna with the dual-polarized multibeam antenna (case 8) Capacity gain is 1.4 times a single antenna with the orthogonally- polarized multibeam antenna (case 7), and slightly lower with vertically- polarized multibeam antenna (cases 5,6)

20 AT&T Labs - Research Conclusions Conducted the first field tests to characterize the mobile MIMO radio channel in a typical cellular environment With 4 transmit and 4 receive antennas close to 4 times the capacity of a single antenna can be supported –Dual-polarized spatially-separated base station and terminal antennas Multibeam antenna has lower capacity - only twice the gain Capacity distribution is close to the ideal and is nearly independent of terminal speed –Capacity for pedestrians is similar to mobile users Correlation results can be used to compare antenna diversity performance Field test data and results are valuable inputs to design and deployment of mobile MIMO systems Future work: Wideband channel measurements

21 AT&T Labs - Research MIMO Field Test Results Pedestrian Tests Mobile Tests Amplitudes of 16 channels between the 4 transmit and 4 receive antennas No averaging Channel characteristics vary for pedestrian and mobile users Capacity for pedestrians is similar to mobile users - spatial averaging reduces the effect of fading

22 AT&T Labs - Research MIMO Field Test Results Instantaneous normalized capacity Spatial averaging reduces variations due to fading Potential capacity increase is close to 4 times that of a single antenna


Download ppt "Wireless Systems Research Department AT&T Labs - Research The Mobile MIMO Channel and Its Measurements Jack H. Winters [Carol Martin, Nelson Sollenberger."

Similar presentations


Ads by Google