Building Blocks for a 24 GHz Phased-Array Front-End in CMOS Technology for Smart Streetlights

According to a recent European Union report, lighting represents a significant share of electricity costs and the goal of reducing lighting power consumption by 20% demands the coupling of light-emitting diode (LED) lights with smart sensors and communication networks. In this context, this paper proposes the integration of these three elements into a smart streetlight, incorporating a 24 GHz phased-array (Ph-A) front-end (FE). The main building blocks of this Ph-A FE integrated in a low cost 90 nm complementary metal-oxide-semiconductor (CMOS) technology are fully characterized. The selected FE’s architecture allows the implementation of transceivers as well as Doppler radar sensors functionalities. More specifically, the Ph-A technology is applied to a Doppler radar sensor in order to realize multi-lane road scanning and pedestrian detection. That way, the smart streetlight can become eco-friendly by turning on the LEDs only when necessary as well as to measure traffic parameters such as vehicle speed, type and direction. Intercommunication between the smart streetlights is based on a time-sharing mechanism that uses the same FE reconfigured as transceiver. Thanks to this functionality, the recorded traffic information can be relayed through adjacent streetlights to a control center, and control commands and warnings can be spread through the network. The system requirements are derived assuming a simplified model of the operating scenario with a typical inter-light distance of 50 m and line-of-sight between lights. The radar range is around 60 m, which allows for continuous coverage from one streetlight to the adjacent one. Meanwhile, a communication range of 140 m is derived as a fundamental requirement for reliable communication between streetlight sensors because it allows bypassing of one node in case of failure. For the developed building blocks — a low-noise amplifier, a variable-gain amplifier, a voltage-controlled oscillator and a vector modulation phase shifter — the design methodology is presented together with measurement results. The system power, consumption, noise figure and gain are estimated by means of a system analysis based on the measured data from the implemented blocks and the state of the art performances for the missing parts. It is shown that the requirements can be fulfilled with a total power consumption of around 375 mW in Doppler radar sensor mode and around 190 mW in transceiver mode. To the authors’ knowledge, this kind of integration is new and overcomes some limitations of the currently used solutions based on infrared sensors and low-throughput communications.

A 24 GHz Phased-Array Doppler Radar Sensor and Transceiver Front-End for Smart Streetlights

Ban Wang

Recently, European Union advocates the smart Solid-State Lighting (SSL). The key factors are a smart-control scheme and an interaction with other networks, such as communication networks and traffic monitoring sensor networks. Public lighting represents a significant share of city total electricity costs, accounting for up to 60% of the budget. The adoption and deployment of new technologies, such as SSL that is based on Light-Emitting Diodes (LED), offer great opportunities to improve efficiencies and reduce costs. When combined with smart light management systems, SSL can save up the electricity used for lighting and significantly reduce energy and maintenance costs compared to current lighting installations. Moreover, streetlights are the infrastructures erecting beside or in the middle of the streets, so they seem to be the ideal observers of the traffic situations. Even though, other functional sensors, e.g., for measuring temperatures, CO2 and even particulate matter 2.5 (PM2.5), could be integrated in the smart-streetlights. Nowadays there are no sensors embedded in commercial available streetlights, except for the infrared motion sensor used only for pedestrian detection since their range is limited to about 10 meters, as well as there are limited networking capabilities, both in data-rate and functionalities, e.g. it is possible the dimming of only the entire file of streetlights. Hence, the idea to develop aWireless Sensor Front-End (WSFE), which is capable of working as motion sensor, namely a Doppler radar sensor, to monitor the road traffic as well as transceiver to communicate with the other network nodes. Such kind of WSFE could enable many streetlights futures, for example the lighting can be adapted to the traffic conditions and the presence of pedestrians on the sideways. Meanwhile, the communication function can build up a wireless network that can be used to manage the streetlight infrastructure and to collect information on traffic conditions, sensor reading, network status and so on. This thesis proposes a 24GHz 4-channel Phased-Array (Ph-A) front-end for smart-streetlight applications. The design exploits a 90nm Complementary Metal-Oxide-Semiconductor (CMOS) technology to benefit of the low-cost offered by CMOS technology. The architecture of the selected front-end allows the implementation of transceivers as well as Doppler radar sensors. Furthermore, the Ph-A technology is applied to the Doppler radar sensor in order to realizemulti-lane road scanning and pedestrian detection. The intercommunication between streetlights is based on a time-sharing mechanism and uses the same FE reconfigured as transceiver.[...]

EPFL2014

24 GHz LNA and Vector Modulator Phase Shifter for Phased-Array Receiver in CMOS Technology

Cyril Botteron, Pierre-André Farine, Gabriele Tasselli, Ban Wang

With the rapid development of the applications in short range communication, phased-array receiver working at 24 GHz can provide enhanced gain performance at desired transmission direction. Also there is the wide signal bandwidth, i.e. 250 MHz free licensed spectrum at this frequency. In the phased-array front-end, the key component is the phase shifter, which decides the tuning resolution of beam-forming. The challenge of the design work comes from the low-power, low-noise and low-cost requirement. This paper explores the design procedure of a Vector Modulation Phase Shifter (VMPS), consisting of a 90 degree hybrid, a variable gain amplifier and the Wilkinson combiner. The variable gain amplifier is fabricated in 90 nm complementary metal-oxide-semiconductor technology, and the passive hybrid and the Wilkinson combiner are designed on the printed circuit board with RO4003 substrate. After combining the measurement results of each block, the VMPS shows 45 degree phase shifts with 7 degree phase error, and 9 mW consumption.

2013

A Publish/Subscribe Approach to Processing Continuous Queries over Sensor Streams

Oana Anca Jurca

With technological advances, the sources of available information have become more and more diverse. Recently, a new source of information has gained growing importance: sensor data. Sensors are devices sensing their environment in various ways and reporting in general a numeric result. A sensor continuously reports values, thus the flow of information is also continuous, like a stream. As the field has developed, the usage paradigm has shifted from stand-alone sensors to interconnected sensors, or sensor networks. Sensors became more complex, generating larger quantities of data and having wireless communication modules for transmitting their data. Initially, data from sensor networks was first stored, and then processed. Thus, classical database technologies could be used. However, the focus has soon shifted towards reacting to sensor data in real time. A user query reacting in real time to a stream of data is called a continuous query, and to answer such a query requires that it is continuously processed, as new values appear in the sensor stream. As sensor networks and sensor based applications become more popular, users identified the need to query sensor data pertaining to different sensor networks. This setting, of interconnected sensor networks, consists of more powerful computational devices, connected with a wired communication, which can process and relay sensor data. Users can launch queries at any node to query sensor events coming from any part of the interconnected network. In this setting, the number of data sources (sensors) is orders of magnitude smaller than the number of user queries, which themselves are orders of magnitude smaller than the full content of the (sensor) data streams, and the communication becomes by far the greatest communication bottleneck. In this thesis, we present our research for reducing communication cost generated by applications accessing large scale interconnected sensor networks. Our first contribution is a probabilistic algorithm for detecting and exploiting subsumption of queries over correlated data sources. This technique reduces the communication traffic generated by query forwarding in an interconnected sensor network, by filtering out queries subsumed by a set of existing queries. In addition, this reduces the number of results that need to be transmitted. We propose an efficient forwarding algorithm of the elements of the result sets, by employing a publish/subscribe data dissemination. To support the general setting of distributed data sources in an interconnected sensor network, we propose a Filter-Split-Forward approach that adapts set subsumption to the case of join queries over distributed data sources. We base our approach on the concept of filter-split-forward phases for efficient query filtering and placement inside the network, and an efficient, publish/subscribe forwarding of matching events. We also propose distributed adaptations of state of the art solutions for continuous query processing over multiple data sources. We adapt these techniques to require only local interactions between nodes, without relying on global knowledge or a centralized server. We show how our approach achieves lower traffic through query subsumption and efficient event dissemination. In many applications using sensor data, users are only interested in the most relevant events. To that end, we present our solutions for processing top-k queries over distributed sensor data streams in the presence of query subsumption. We analyze the impact of query subsumption on top-k processing. We propose different strategies for incorporating query subsumption into top-k processing, in order to obtain sufficiently accurate result sets, while keeping network traffic low. We show that the best tradeoff is achieved by updating throughout the network the values of k for the queries resulting from splitting a query between nodes and also for the set of queries subsuming a query. By this work we contribute a framework for increasing the efficiency of continuous query processing over distributed data sources for a wide range of applications, such as environmental and living spaces monitoring, network and traffic monitoring, and in general for all sensor enhanced monitoring applications.