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Address 4G issues with SystemVue

Posted: 23 Dec 2011 ?? ?Print Version ?Bookmark and Share

Keywords:LTE-Advanced? 3GPP? EDA tools?

SystemVue's W1918 LTE-Advanced library implements a fully-coded downlink source with up to eight antennas and an LTE-A fully-coded UL source with up to 4 antennas. To assist in verifying their Release 10 algorithms, designers can replace some SystemVue components with their own algorithm components, either as MATLAB or C++ code.

Challenge 3
Addressing the added stress on the RF design caused by carrier aggregation (CA). CA is the mechanism by which LTE-A specifies spectrum allocations of up to 100MHz. It allows the aggregation of contiguous and non-contiguous component carriers to provide the wider bandwidth. Unfortunately, the increased bandwidth drives the Peak-to-Average Power Ratio (PAPR) to extreme levels and exposes frequency-dependence and other analog degradations, which cross multiple component carriers. Non-contiguous CA, the multitude of possible RF bands and the number of MIMO layers further add to the RF design challenges.

Solution: Addressing these issues requires the ability to translate real RF limitations back up to system-level performance and correlate PHY simulations with measurements. It also demands utilization of Crest Factor Reduction (CFR) and Digital Pre-Distortion (DPD) to help linearize power amplifier design, two strategies which are essential to dealing with the high PAPR resulting from the increased bandwidth enabled by CA.

SystemVue meets this need by implementing three LTE-A deployment scenarios to characterize spectrum, CCDF and PAPR. To model/correct for power amplifier nonlinearities and memory effects, SystemVue's W1716 digital pre-distortion application kit can be used. It works with test equipment and RF circuit co-simulation to quickly assess the "correctability" of a power amplifier. This enables designers to model the "dirty" power amplifier for inclusion in Layer 1 link-level architecture studies.

Challenge 4
Adequately addressing MIMO and channel considerations. Verifying LTE-A is a complicated process, one that's made even more so by the multiplicity of MIMO and having to consider the MIMO channel during simulation.

Solution: In this case, virtual design tool techniques (e.g., simulation links from a bottom-up EDA flow) offer one way to bridge the gaps, providing a surprising level of accuracy at the algorithm/architecture stage of a design. SystemVue has the ability to simulate multichannel MIMO scenarios that may be less convenient to configure as actual hardware measurements, thus providing a simulation-based alternative for early algorithmic and functional verification. The capability is available with the W1715 MIMO Channel Builder, an optional SystemVue block set that provides both WINNER II and LTE-Advanced MIMO channel models (up to 8x8 MIMO) for predictive BER/FER and throughput fading simulation of LTE, LTE-A or 802.16m systems. With this solution, the effects of imperfect antenna arrays and correlated MIMO fading and propagation can be compared directly across both simulation and at-speed hardware faders. Furthermore, the use of comparable reference algorithms throughout the design process helps ease the transition to verification.

Challenge 5
Dealing with the significant increase in verification that's needed for LTE-A. Many factors work to increase the verification task, including the various baseband PHY operating modes, RF spectral allocations/bands and analog control settings; new semiconductor processes, battery and environmental conditions; and the need for scripting, regressions, IP exchange, and testbenches across domains.

Solution: Dealing with this challenge requires next-generation EDA tools featuring a host of new capabilities geared toward simplifying and speeding verification. SystemVue, for example, supports both Fast Circuit Envelope (FCE) verification modeling and native RF system modeling. For RFIC verification, FCE behavioral models are simply exported from an RFIC circuit tool. SystemVue then provides a reliable system-level model in seconds that accounts for things like power- and frequency-dependence, nonlinear memory effects and frequency translation.

As with most emerging technologies, design challenges for LTE-A abound, particularly when it comes to the PHY architecture development. Adequately addressing these challenges is essential for any engineer looking to create superior systems designs for the emerging LTE-A standard. Next-generation EDA tools like SystemVue provide the capabilities needed to address these challenges and in turn, successfully develop and deploy LTE-A designs.

About the authors
Daren McClearnon is a product marketing manager for system-level design products within Agilent's EEsof EDA organization.?He has held engineering and management roles in the EDA industry since 1985, including field applications and field sales, customer education and product marketing for a variety of RF and system-level products.?He graduated with a BSEE from Case Western Reserve University in Cleveland, OH.

Wu Huan is a system engineer with Agilent EEsof, responsible for the development of digital signal processing algorithms for emerging wireless applications, primarily 4G and MIMO.?He began his career with Agilent in 2008 developing the industry's first ETSI compliant v8.9 LTE PHY DSP library and is currently working on the new 4G LTE Advanced PHY DSP library and Digital Pre-Distortion tool kits for Agilent SystemVue. Huan earned his master's degree in electrical engineering from Beijing University of Posts and Telecommunications.

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