Feature Article

June 17, 2015

Weighing in on the 'Weightless' Protocol

Interesting developments are now happening fast and furious(ly) in the lower power-wide area strategies. Several initiatives are going on with LoRa, Sigfox and Weightless. I am not a good enough engineer to get terribly into the details, and when it comes to RF my weaknesses are pretty apparent. However my experience is that good radio frequency engineers are an elite bunch, so I will aim this article at guiding the rest of us.

Weightless is a set of standards in the sub 1 GHz license spectrum. Weightless presently has two variants: Weightless N, which is architected in a star network and is suited to urban environments; and Weightless W, which works well for TV White Space solutions.

LoRa is a set of star network implementations that transmit low power, long-range microwave signals between end-devices and gateways spread out on different frequency channels and data rates. The selection of the data rate is a tradeoff between communication range and message duration. Due to the spread-spectrum technology, communications with different data rates do not interfere with each other. Implementations are categorized as “A” end devices that use an ALOHA (think Ethernet) type protocol; “B”, bidirectional with scheduled transmissions; and “C”, which transmits continuous signals.

SigFox is a company that through licensing and partnerships is an alternative to other standard technology. SigFox architecturally resembles cellular implements with Ultra Narrow Band technology. The network operates in the globally available ISM bands (license-free frequency bands) and co-exists in these frequencies with other radio technologies, but without any risk of collisions or capacity problems. SIGFOX currently uses the most popular European ISM band on 868MHz (as defined by ETSI and CEPT) as well as the 902MHz in the U.S. (as defined by the FCC), depending on specific regional regulations.

All of these implementations have merits and should be considered as complementary or competitive, and should be evaluated based on use cases. However, having said that, LTE has a volume and scale capability that makes using cellular technologies also an alternative. This includes two “standards” activities in the marketplace.

Unlicensed LTE or LTE U uses the 4G LTE radio communications technology in unlicensed spectrum such as the 5GHz band used by dual-band Wi-Fi equipment. Specifications of the standards exist in the 3GPP Release 10 documentation. Carriers see an opportunity for data offload as it has been alternatively proposed for industrial Internet requirements.

LTE-UE CAT 0 / CAT 1 are standards designed to support low transmission requirements by restricting the data transmission. In effect, these antennas will assure that carriers can support data-only solutions that will not congest the network with voice or video packets.

The rationale for writing this piece is two-fold.

First of all, with 50 billion devices coming on board, all these alternatives are going to get market share, but the carriers are going to be competitive incrementally and therefore may have pricing anomalies that should be the focus of any true net neutrality discussion, and not the nonsense brought about by John Oliver.

Second, Weightless just did an implementation in London with the Digital Catapult Centre. The focus of the implementation was not technology but the services enabled by the technology. It’s important that we have diversity in these technologies, and policies should enable and encourage alternative solutions. The Digital Catapult initiative is not based on Ofcom, but on business development by the UK. This is a great case study as to how the technology should be advanced.

Edited by Rory J. Thompson

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