Cohere Technologies, which has high hopes of seeing its modulation scheme adopted in future 5G standards, has a new chairman and CEO, Ray Dolan. He joined last year but has only just been publicly announced as the new chief, with dual remits to build up commercial equipment sales, and drive patent licensing, for Cohere’s OTFS (orthogonal time frequency and space) air interface technology.
Dolan comes from being CEO at IP core and signalling specialist Sonus, which merged with Genband in late 2017 to form Ribbon. Dolan was designated to be CEO of the combined company, but he left only a month after the merger completed and apparently took a break from the industry until turning up at Cohere. This brings him back into the broadband wireless technology territory he occupied in a former role as CEO of start-up Flarion, which was acquired by Qualcomm in 2006.
Cohere’s OTFS technology was supported 3GPP RAN1 by AT&T, China Mobile, Deutsche Telekom, Telefonica and Telstra as an alternative air interface to OFDMA, for 5G New Radio standards. In the end, the 3GPP Release 15 specifications played it safe and stuck with extensions of OFDMA, but many expect that Release 16 will have to introduce one or more additional technologies, in order to fulfil its remit of optimizing 5G for ultra-low latency and other IoT-related capabilities. Some experts also believe an OFDM alternative would support millimeter wave frequencies optimally.
Cohere VP Anton Monk described the first wave of Release 15 as “LTE with Massive MIMO and beamforming — nothing really new except for including Huawei’s polar codes in the control channel and using LDPC (low density parity check) everywhere else.”
Having failed at the 3GPP, Cohere focused on building equipment that incorporates OTFS, particularly for fixed wireless access (which has the advantage of not requiring standardized devices like mobile cellular). Its technology has been trialled by Telefónica, Telstra, Altice, Sprint, Deutsche Telekom and Charter.
OTFS sits on top of OFDM and claims to be significantly more reliable. It creates a two-dimensional view of the delay and signal fading of a wireless channel. spreading information across time and frequency. This allows signals to benefit from diversity in the channel while also penetrating through concrete and glass, and to achieve high levels of immunity to fading, multipath and other signal impairments.
All that adds up to higher data rates, greater spectral efficiency and reduced interference, claims the company, which says that, in its first trials in 2015-16, it tested its technology among tall buildings and mountains and in moving vehicles, and the OTFS radios never faded, even over distances above four kilometers, as OFDM ones would have done. A minimum of 4bps/Hz was achieved in 10 MHz of spectrum in the 3.5 GHz band during those initial trials, driving speeds of 120Mbps to 320Mbps. Those rates will be much increased as Cohere is incorporating Massive MIMO radios with 64×64 arrays into its plans, as well as implementation in millimeter wave bands.
Cohere stresses that its technology can coexist with OFDM to support smooth migration from current networks, or coexistence between different 5G flavors. Indeed, OTFS is not an entirely new modulation scheme as it sits on top of OFDM, but is a “scheme for diversity that adds to MIMO with an equalization technique”, as Phil Marshall of Tolaga Research explained.