Sunday, 5 April 2015

Antennae Market: Benefit of MIMO

  • 1. Antenna Market Overview June 2014
  • 2. Presentation Outline • The benefits and shortcomings of MIMO • LTE network performance and the need for higher capacity / better edge of cell throughput • Mobile device performance implications – “it takes two to tango” • Final thoughts
  • 3. The Impact of MIMO on Data Rates  Test conducted in our hotel room  Logged using Accuver XCAL drive test software  Occurred while operator / vendor turned on MIMO at 6 AM
  • 4. Results from each test were fairly consistent!
  • 5. MIMO gains varied as a function of SINR (no surprise)  The benefits of MIMO are most evident with SINR >20 dB  At 15 dB the impact of MIMO on end user data rates is only modest  Below 10 dB the availability of MIMO could actually degrade performance
  • 6. Is the Glass half-empty or half-full?  At least 40% of the time TM 3 increased user throughput by at least 20%  At least 50% of the time the availability of TM 3 would only have a modest improvement on throughput while 30-40% of the time it could degrade performance  In all likelihood, SINR will only get worse, not better
  • 7. Actual MIMO Utilization is much lower!  Results based on network-level testing at multiple sites and for extended lengths of time  Logged using the Sanjole IntelliJudge test platform  Likely due to a combination of poor network conditions and user / application behavior  The typical data connection consumes very little data
  • 8. Actual MIMO Utilization is much lower!  A mobile device is far more likely to use transmit diversity versus MIMO (Rank Indicator 2)  Device performance (as we’ll see in a bit) could have been a contributing factor  Device location (and application behavior), combined with network design criteria was also a likely contributing cause
  • 9. Spectral Efficiency isn’t what we think it is!  Median efficiency across all tests was 1.16 bps/Hz  Vendor differentiation is evident  Most device interactions with the network involve minimal amounts of transferred data while network design also played a likely role
  • 10. Mobile Devices don’t perform the same  OTA testing in an anechoic chamber done with Spirent and ETS-Lindgren  All devices use LTE chipsets from the same manufacturer  Major differences in performance likely due to poor RF front-end design  Challenges escalate with multi-band (7+ band) devices
  • 11. Mobile Devices don’t leverage MIMO to the same degree Device 1 Device 2 Device 3 Device 4 Device 5  Simulated network conditions were good, but by no means ideal  RSTP = -80 dBm  Uncorrelated MIMO signals with UMi channel model  Device 2 outperforms all other devices by a considerable margin  ~120% higher throughput than worst performing device
  • 12. Mobile Devices don’t leverage MIMO to the same degree  Best performing device leveraged MIMO fairly extensively and with success  Two devices barely used MIMO, if at all  Up to 2 unit differential in reported median CQI values Device 1 – CW0 Device 1 – CW1 Device 3 – CW0 Device 3 – CW1 Device 5 – CW0 Device 5 – CW1 Device 2 – CW0 Device 2 – CW1 Device 4 – CW0 Device 4 – CW1
  • 13. Where do we go from here?  Vendors and operators are moving from 2x2 to 4x2 MIMO with Closed Loop MIMO now becoming more prevalent  Preliminary analysis of test results suggests it offers a compelling gain at edge of cell (uplink) and in some cases even at the center of the cell  4x4 MIMO has promise based on test results we’ve seen, but market opportunity is limited by device support  Impact of higher order MIMO schemes on devices cannot be ignored – they are already struggling to keep up  More “complex” antenna technologies, such as 8T8R, are being deployed in support of LTE TDD – largely to compensate for higher frequencies  Multi-user MIMO and/or beamforming will help drive capacity gains – good news is no impact on devices w.r.t. feature requirements