SAN JOSE, Calif. — Gerhard Fettweis believes he has the air interface for 5G, the next generation of cellular networks. The Dresden professor says Generalized Frequency Division Multiplexing (GFDM) has benefits that could enable what he calls the Tactile Internet, a future for the Internet of Things that is already attracting support from companies including Huawei, Intel, National Instruments, Vodafone and Xilinx. All sides agree 5G will need a new air interface to meet its ambitious goals, one not backward compatible with today’s 4G LTE. A half dozen major proposals have already emerged and more are expected before the 3GPP issues the first major 5G standard with its Release 15 in 2018. Most of the proposals are variations on today’s OFDM techniques that play to the strengths of their proponents. Some experts say the battle over air interfaces is not as significant as work defining brand new techniques for massive antenna arrays and support for frequencies above 6 GHz. Nevertheless, companies and research institutes are beginning to take sides among a set of air interfaces they believe sport the greatest benefits for the industry and themselves. The differences between them involve subtle trade-offs in wireless communications techniques. “It’s a bit of a beauty contest and eventually elements of multiple proposals might get adopted, but there isn’t much to play with because there are fundamental laws of physics and we can’t optimize for all the elements,” said Arogyaswami Paulraj, a veteran researcher and entrepreneur, speaking at a recent IEEE 5G Summit. John Smee, a senior director of engineering for 5G at Qualcomm Research agrees. The various proposals tweak knobs for windowing and filtering OFDM signals, he said. Nevertheless, Qualcomm recently laid out its own proposal. Its Unified OFDM interface takes a hybrid approach using multiple techniques. It supports a number of symbols that is a power of two to better suit semiconductor design. Qualcomm advocates a separate 5G approach for the resource-constrained Internet of Things. Fettweis described Qualcomm’s Unified interface as a variation on time/frequency code slicing concepts researchers have worked on for many years. He suggested the approach may not be the most energy efficient, creating relatively power hungry analog parts such as ADC and RF chips. Qualcomm laid out its views on 5G air interfaces in a recent white paper. Next Page: Mapping the air interface landscape
Companies and research institutes are beginning to take sides on a set of new air interfaces for dozenG, the successor to today's 4G mobile communications standard. While most of the half 5 or so proposals are variations of OFDM techniques, Dresden Professor Gerhard Fettweis believes that the future lies in Generalised Frequency Division Mulitplexing (GFDM). It is already attracting support and investment from big corporations, including Huawei, Intel, National Instruments and Vodafone. The benefits of GFDM, says Fettweis, is that it could lead to new kinds of uses for the Internet of Things, specifically around the concept that he coins the 'tactile internet', which could include retail product demos and a variety of remotely-managed industrial, robotic and medical controls.