Technology Review - San Diego startup On-Ramp Wireless uses the wifi frequency, but less power, to send data signals 45 miles, thanks to algorithms that make the signals very resistant to noise.
On Ramp Wireless website
Ultra-Link Processing, transfers data at a very low rate compared with a home broadband connection. But On-Ramp intends to offer it as a way to enable "smart energy" grids, in which simple sensors installed in home energy meters, for example, report local activity back to utilities, allowing them to manage power generation and distribution more intelligently. They are targeting devices that use less than 50 bits per second.
This looks like a technology that could deliver super-cheap open spectrum short message/twitter communication devices and networks. One SMS/tweet every three seconds and replace your battery every 20 years. It would also be a useful system for communication that could be made robust against disasters.
These are the key system highlights, which set this technology apart:
* Greater than 40 miles (65 km) line-of-sight range, and up to 10 miles (16 km) to underground locations.
* RPMA, a unique multiple access method with order of magnitude capacity improvements, and demodulation of up to a thousand incoming signals, below the noise floor, every frame.
* Receive sensitivity of -142 dBm.
* Each Access Point supports up to 64,000 endpoints.
* Access Point aggregate throughput of 120 kbps (10 Mb/day).
* Each ULP Gateway can support hundreds of Access Points.
* Ultra low power consumption, allowing up to a 20-year battery-life for water meter applications.
* Security has undergone comprehensive 3rd party validation.
* Worldwide applicability in the license free spectrum (adaptive to local regulatory regimes).
* Simple and flexible integration with back-end automation systems, such as OMS, DMS and MDMS systems, process automation (e.g. OSIsoft PI™, Modbus™), and others.
* Intelligent Data Integrity throughout the entire data path.
* Simple and standardized wireless module integration.
A trial network in San Diego requires just 35 strategically located access points to collect data from smart meters and other devices equipped with On-Ramp's technology across a 4,000-square-mile area. "It boils down to a cost advantage," says Myers. "You need fewer access points this way." California utility PG&E is currently rolling out smart meters based on more established technology which will require over 1,000 access points to cover the same area.
ULP is a half-duplex system, operating in a star topology and is deployed using industry standard and time-tested modeling tools, similar to those used in the mobile telephony industry. The system delivers the lowest cost of ownership in the industry and is simple to deploy, operate, and maintain.
The On-Ramp Wireless Advantage
The On-Ramp Wireless ULP system’s advantages are derived from our unique innovation that leverages the proven technology of Direct-Sequence Spread Spectrum (DSSS) modulation. The ULP technology is optimized from the ground up to solve critical issues in applications such as the Smart Grid, industrial condition monitoring, and asset tracking. Most other attempts at solving these problems are merely adaptations of related industry standards, leading to complex network infrastructures and high costs. There are numerous technical terms in the industry to explain networking solutions in complicated detail, however, the performance of wireless systems can be effectively summarized and objectively compared by simply looking at coverage, capacity, power consumption, coexistence and security.
A radio’s ability to find weak signals over vast geographic areas in the face of high interference can be measured by receive sensitivity; an objective measure of the radio’s ability to demodulate a signal bounded by power levels. Receive sensitivity is the only way to accurately measure range and robustness of wireless systems in an apples-to-apples comparison. On-Ramp Wireless’ ability to achieve 40dB of additional receive sensitivity compared to other free spectrum radios, translates into a groundbreaking advantage in terms of both coverage and robustness. The following comparison is based on an Okumura-Hata propagation model, which is well accepted in the industry as an accurate predictive tool of coverage in various types of real-world environments.
The ULP system has an immense uplink capacity. The capacity model is specifically designed to meet the requirements of the wide area collection of sensing data, through the use of an efficient access method. The system uses Random Phase Multiple Access (RPMA) – a unique access method developed by On-Ramp Wireless – to support thousands of simultaneous connections to a single Access Point (AP). RPMA, which is patented, has similarities to CDMA, however RPMA channelizes (i.e. uniquely identifies) devices through random phase offsets in a scrambling code rather than using separate codes.
The On-Ramp Wireless innovation of the RPMA receiver enables efficient demodulation of all possible phase hypotheses for all possible spreading factors to decode the messages. This requires significant amounts of computation, however through clever algorithms, the search space has been condensed to allow an implementation of the system in commodity hardware.
ULP has an extremely lightweight over-the-air (OTA) protocol, optimized for transmission of many small data packets from dispersed devices. This minimizes overhead and maximizes application throughput (i.e. goodput). Additionally, RPMA allows nodes operating under widely ranging link conditions to connect to the AP. A device with a very weak signal does not impede any other nodes in the network. It simply reverts to a higher level of processing gain and, in turn, consumes less of the overall available throughput.
ULP’s simple star topology makes it easy to manage congestion. This allows ULP to be operated with a lower margin than competing systems. For example communication in a wireless mesh environment, requires a large margin due to the inherent instability of the statistical random access methods used.
Ultimately, RPMA and the simple, but efficient, nature of the ULP system, delivers a system with enormous capacity – enough to process all the devices in the extensive coverage area.
Radios operating in unlicensed spectrum must address the issue of coexistence. ULP provides superior performance for the following coexistence requirements:
* Robustness to interference, as transmitters are regulated and the propagation environment is unpredictable and in constant flux.
* Ability to operate under strict and varying regulations.
* Not causing undue radio frequency interference.
The ULP physical layer is extremely robust to interference. The 39 dB of DSSS processing gain, inherent in the ULP physical layer, provides superior co-channel and adjacent channel rejection. This allows ULP to operate as a single frequency network, which minimizes the spectral footprint of the ULP system and enables multiple, non-coordinated ULP systems to exist in a given service area.
The system’s long symbol durations (4 milliseconds) allow for demodulation even with limitlessly strong burst interference. This robustness enables ULP to take advantage of elevated Access Point locations, such as mountain top antenna farms, mobile operator towers and tall buildings. Less robust technologies cannot use these types of sites due to the interference they receive from co-located transmitters and the surrounding areas. The ULP system uses these types of sites, which takes a nominal 600x coverage advantage due to link budget, and turns it into a 10,000x coverage advantage.
ULP can connect continuously powered (electric meter, remote monitoring unit, etc.) and battery-powered (water/gas meters, fault circuit indicators, etc.) devices. The ULP protocol is extremely efficient, which optimizes performance for battery-powered devices. Depending on the data transmission requirements, the endpoint can be in a low power (deep sleep) mode most of the time. The endpoint is awake only for a short period of time in order to receive and transmit data. Endpoints transmit at the minimum processing gain required to close link, based on a locally calculated Received Signal Strength Indicator (RSSI) inferred from parameters received in the downlink portion of the frame cycle. The endpoints have a patented low power network acquisition algorithm, which saves power through maintaining tight time synchronization to the ULP network. Furthermore, ULP uses a simple star topology, as opposed to wireless mesh, and the ULP endpoints do not have to repeat traffic.
On-Ramp Wireless has developed extremely efficient ASIC hardware for the endpoint for battery-powered applications. Low duty cycle applications, such as water/gas meters, and FCIs, can achieve a battery life of greater than 20 years.
Many of the target applications for device monitoring are critical infrastructure endpoints. Once the endpoint devices are connected, they will become the targets of hacking and cyber crime. They require a secure network, such as the ULP system, that is built using proven security algorithms. The ULP network uses NIST-approved security algorithms that have greater than 20 years of life. This makes ULP networks secure beyond 2030.
ULP security is purpose-built for use in a power-constrained, low-bandwidth wireless network with a simple star topology. It uses the following comprehensive approach to deliver this information security:
* Prevention mechanisms: Provide mutual authentication, integrity protection, confidentiality, and high availability.
* Detection mechanisms: Identify attempts to break into the system and alert operators.
* Recovery mechanisms: Ensure the system degrades gracefully and continues to operate successfully even when under attack.
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