Measurement Journal Issue 6

Reviewing detailed 4G performance requirements Besides the headline peak data rates, 4G — unlike 3G — is setting targets for average spectral efﬁciency and cell-edge performance. This is a welcome development and these ﬁgures can be seen in Table 1. The ﬁrst point of note is that the peak efﬁciency targets for LTE-Advanced are substantially higher than the targets for 4G — thus the focus on peak performance is maintained despite the averages being very similar. That said, 3GPP have emphasized that the average and cell-edge targets are more important than the peaks. The LTE targets are based on 2x to 4x improvements to Release 6 HSPA (single-stream downlink with diversity UE receiver), which produces a microcell average efﬁciency of around 0.53 b/s/Hz/cell.4 At 2.6 b/s/Hz/cell the targets for 4G and LTE-Advanced are around ﬁve times higher and, should they be met, would truly be worth the investment. However, we are still some way from demonstrating cost-effective technology that can deliver on the lower 1.86 b/s/Hz/cell LTE target. The industry knows how to increase the peak ﬁgures by adding more bandwidth or higher-level modulation and less coding (with consequential negative impact on coverage), but with targets for average performance there is nowhere to hide. Consider this automotive example: Let’s say the average speed of metropolitan rush-hour trafﬁc is 20 mph. Compare the difﬁculty of designing a car that can travel at ten times the average speed with no environmental restrictions (e.g., assume perfect roads and no trafﬁc) versus designing an entire trafﬁc system — not just a car — that can double the average speed during rush hour. This offers a qualitative feel for the enormity of the challenge 4G is setting in improving on today’s average wireless performance by a factor of ﬁve. Aggregating bandwidth Those familiar with today’s spectrum allocations might well be wondering where space for the 100-MHz channels needed for 1 Gbps will be found. Some new IMT spectrum was identiﬁed at the World Radio Conference in 2007 (WRC-07) but there are still only a few places where continuous blocks of 100 MHz might be found (e.g., at 2.6 GHz or 3.5 GHz). One possibility would be to encourage network sharing, which reduces fragmentation caused by splitting one band between several operators; however, sharing the spectrum, as opposed to just the sites and towers, is a considerable step up in difﬁculty. The ITU recognizes the challenge that wide-bandwidth channels present and so it is an expectation that the required 100 MHz can be created by the aggregation of non-contiguous channels from different bands in a multi-transceiver mobile device. Table 1. LTE, LTE-Advanced and IMT-Advanced performance requirements Item Peak spectral efﬁciency (b/s/Hz) Downlink cell spectral efﬁciency (b/s/Hz/cell) Microcellular 3 km/h Downlink cell-edge spectral efﬁciency (b/s/Hz/user)* Sub-category Downlink Uplink (2x2 MIMO) (4x2 MIMO) (4x4 MIMO) (2x2 MIMO) (4x2 MIMO) (4x4 MIMO) LTE (3.9G) target4 16.3 (4x4 MIMO) 4.32 (64QAM SISO) 1.69 1.87 2.67 0.05 0.06 0.08 LTE-Advanced (4G) target 2 30 (up to 8x8 MIMO) 15 (up to 4x4 MIMO) 2.4 2.6 3.7 0.07 0.09 0.12 IMT-Advanced (4G) requirement 5 15 (4x4 MIMO) 6.75 (2x4 MIMO) 2.6 0.075 *5 percentile, 10 users 55 Agilent Measurement Journal

Table of Contents Feed for the Digital Edition of Measurement Journal Issue 6

Measurement Journal Issue 6 Using a Few Words to Convey a Deeply-Held Spirit Charting a Unique Path to Technology Innovation Contents Announcing First Commercial GC/MS Metabolites Library Assessing Nonlinear Behavior Testing Combines Form and Function Testing Multiplay Networks Higher Sensitivity LC/MS Easing Military Radio Test Stepping Up Calibration Accuracy Increasing Spectrum Analyzer Bandwidth 3GPP Tool Supports TS 36 Standards The Olympic Story Spotlights Agilent's Continuing Contribution to Technology Innovation Ensuring a Level Playing Field in Competitive Sports GPS: Coming of Age Resolving Design Issues in HSPA Mobile Devices Achieving Accurate Results with Oscilloscope-Based Jitter-Analysis Software RF Handheld Testers Guarantee Traffic Stability Under Olympic-Sized Stress Conditions Utilizing LAN-Based Instrumentation to Measure Total Harmonic Distortion in Remote Facilities IMT-Advanced: 4G Wireless Takes Shape in an Olympic Year EPO Doping: A Speed Engine, Turbo-Charged by Chemistry

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