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Signum Concepts: 4G Wireless Sphere Detector

System Generator was the key to building 4G wireless sphere detector in an FPGA.

Signum Concepts, working together with Xilinx and Rice University, designed an FPGA implementation of a detector for spatial-multiplexing MIMO in 802.16e broadband wireless systems. By utilizing a channel matrix preprocessor that realizes a type of successive-interference cancellation similar in concept to BLAST processing employed in Bell Labs Layered Space Time, the detector achieves close to maximum-likelihood performance.

To implement the system, Signum Concepts used Xilinx FPGA technology. The design flow employed Xilinx System Generator for design capture, simulation, and verification. To support the different number of antenna/user and modulation orders, Signum Concepts designed the detector for the most-demanding 4x4, 64-QAM case.

The calculation of the pseudo-inverse matrix is the most-demanding component in the preprocessing algorithm. The high system latency associated with the well-known algorithms for angle estimation and planar rotations, such as CORDIC, were unacceptable for our system. Hence, the goal was to find an alternative solution for vector rotation and phase estimation using the FPGA’s embedded DSP resources. 

- Milos Trajkovic, DSP Engineer
- Slobodan Denic, Systems Engineer
- Dragan Vuletic, Vice President of Engineering Signum Concepts

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