Making wireless MIMO equalization more efficient with a multiprocessor DSP SoC

Dmitry Lachover, Avi Gal, and Ran Zamir - Freescale Semiconductor
Embedded.com (January 1, 2013)

To meet growing demand for advanced 4G services, wireless infrastructure equipment manufacturers increasingly require components that offer exceptional performance and flexibility. 4G services require multi-RAT (Radio Access Technology) devices to fully support Baseband Physical Layer and higher layer requirements for FDD-LTE, TDD-LTE and LTE-Ad base stations. To enable these technologies, the processor used has to provide low latency and high throughput communications at an affordable price. In addition, a balance of high-performance, low power processing with sufficient programmability is needed.

To explain the requirements for 4G services, as an example we examine a 4x4 LTE MIMO Equalizer implementation of the Qonverge B4860 system-on-chip (SoC) with integrated StarCore SC3900 DSP cores. The Equalizer’s offloading to the processor’s high-speed Equalizer Processing Element (MAPLE-B3 EQPE) accelerator will be described in detail.

The LTE Equalizer is one of the key functions in a LTE receiver and is based on a complex algebra-like matrix of multiplication, decomposition and inversion. Offloading of compute intensive functions such as the Equalizer is of great importance to the performance and efficiency of the SoC used in a LTE base station.

This article describes in detail the LTE Equalizer performance and implementation on DSP cores embedded on a SoC. In addition, an alternative is presented for offloading the LTE Equalizer to the dedicated MIMO accelerator (Equalizer Processing Element or EQPE) that can handle complex antenna MIMO configurations of two, four, or eight in-parallel. The EQPE capabilities is presented in terms of low latency, high throughput, and optimized control; combined, these efficiently meet increasing data rate requirements. The solution delivers significant reduction in cost per megabit for the growing data traffic in cellular LTE networks.

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