The combination of 2x20 MHz LTE, Category 4 devices, and Closed Loop MIMO with four transmit/receive antennas at the cell site delivers a number of noteworthy benefits. The headline peak data rate of 143.8 Mbps in the downlink (per TTI) and 46.93 Mbps in the uplink (per second) are noteworthy, but the real benefits are observed elsewhere.
Due to the presence of four receive antennas at the cell sites, we documented substantial benefits in the uplink performance, including much higher user data rates, far more efficient scheduling of network resources, and clear indications that the battery life of the mobile device was greatly enhanced. Generally, the benefits increased the further the mobile device was from the center of the cell, but the improvements in battery life were observed throughout a large portion of the cell. We also identified meaningful benefits in the downlink performance, again closer to the edge of the cell. And since all LTE mobile devices inherently support the 4x2 cell site configuration, the benefits of 4x2 are immediate and applicable to the entire installed base of mobile devices.
Although we haven't quantified the economic benefits associated with the 4x2 cell site configuration, it is difficult to imagine a scenario in which the ROI wouldn't be extremely favorable. The ease of upgrade for legacy hardware, the impact on the cell site, including the logistics of mounting the new hardware (if required) and the impact on the lease agreement, could be mitigating factors that should be considered. Nonetheless, the triple whammy of higher user data rates, increased network efficiency, and a longer battery life shouldn't be dismissed.
When operators first launched LTE starting back in late 2009 they used a standard 2x2 MIMO implementation, meaning two transmit / receive antennas at the cell site and two receive antennas in the mobile devices. And until last year they also relied on Cat 3 (Category 3) devices which under certain circumstances became the bottleneck that limited downlink data rates in a 2x20 MHz network. The resultant data rates were still very impressive and dramatically higher than they were with DC-HSDPA - thanks, in large part to the wider channel bandwidths - but in hindsight they could have been even better.
Key Topics Covered:
1.0 Executive Summary
2.0 Key Conclusions and Observations
3.0 Detailed Results - Uplink Performance
4.0 Detailed Results - Downlink Performance (4x2 CL-MIMO versus 2x2 OL-MIMO)
5.0 Detailed Results - Downlink Performance (4x2 CL-MIMO versus 4x2 Transmit Diversity)
6.0 Test Methodology
7.0 Final Thoughts
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SOURCE Research and Markets