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

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.[...]

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

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

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.

2014

Routing and search on large scale networks

Dominique Florian Tschopp

In this thesis, we address two seemingly unrelated problems, namely routing in large wireless ad hoc networks and comparison based search in image databases. However, the underlying problem is in essence similar and we can use the same strategy to attack those two problems. In both cases, the intrinsic complexity of the problem is in some sense low, and we can exploit this fact to design efficient algorithms. A wireless ad hoc network is a communication network consisting of wireless devices such as for instance laptops or cell phones. The network does not have any fixed infrastructure, and hence nodes which cannot communicate directly over the wireless medium must use intermediate nodes as relays. This immediately raises the question of how to select the relay nodes. Ideally, one would like to find a path from the source to the destination which is as short as possible. The length of the found path, also called route, typically depends on how much signaling traffic is generated in order to establish the route. This is the fundamental trade-off that we will investigate in this thesis. As mentioned above, we try and exploit the fact that the communication network is intrinsically low-dimensional, or in other words has low complexity. We show that this is indeed the case for a large class of models and that we can design efficient algorithms for routing that use this property. Low dimensionality implies that we can well embed the network in a low-dimensional space, or build simple hierarchical decompositions of the network. We use both those techniques to design routing algorithms. Comparison based search in image databases is a new problem that can be defined as follows. Given a large database of images, can a human user retrieve an image which he has in mind, or at least an image similar to that image, without going sequentially through all images? More precisely, we ask whether we can search a database of images only by making comparisons between images. As a case in point, we ask whether we can find a query image q only by asking questions of the type "does image q look more like image A or image B"? The analogous to signaling traffic for wireless networks would here be the questions we can ask human users in a learning phase anterior to the search. In other words, we would like to ask as few questions as possible to pre-process and prepare the database, while guaranteeing a certain quality of the results obtained in the search phase. As the underlying image space is not necessarily metric, this raises new questions on how to search spaces for which only rank information can be obtained. The rank of A with respect to B is k, if A is B's kth nearest neighbor. In this setup, low-dimensionality is analogous to the homogeneity of the image space. As we will see, the homogeneity can be captured by properties of the rank relationships. In turn, homogeneous spaces can be well decomposed hierarchically using comparisons. Further, it allows us to design good hash functions. To design efficient algorithms for these two problems, we can apply the same techniques mutatis mutandis. In both cases, we relied on the intuition that the problem has a low intrinsic complexity, and that we can exploit this fact. Our results come in the form of simulation results and asymptotic bounds.

EPFL2010

Function Computation over Networks

Chien-Yi Wang

This thesis looks at efficient information processing for two network applications: content delivery with caching and collecting summary statistics in wireless sensor networks. Both applications are studied under the same paradigm: function computation over networks, where distributed source nodes cooperatively communicate some functions of individual observations to one or multiple destinations. One approach that always works is to convey all observations and then let the destinations compute the desired functions by themselves. However, if the available communication resources are limited, then revealing less unwanted information becomes critical. Centered on this goal, this thesis develops new coding schemes using information-theoretic tools. The first part of this thesis focuses on content delivery with caching. Caching is a technique that facilitates reallocation of communication resources in order to avoid network congestion during peak-traffic times. An information-theoretic model, termed sequential coding for computing, is proposed to analyze the potential gains offered by the caching technique. For the single-user case, the proposed framework succeeds in verifying the optimality of some simple caching strategies and in providing guidance towards optimal caching strategies. For the two-user case, five representative subproblems are considered, which draw connections with classic source coding problems including the Gray-Wyner system, successive refinement, and the Kaspi/Heegard-Berger problem. Afterwards, the problem of distributed computing with successive refinement is considered. It is shown that if full data recovery is required in the second stage of successive refinement, then any information acquired in the first stage will be useful later in the second stage. The second part of this thesis looks at the collection of summary statistics in wireless sensor networks. Summary statistics include arithmetic mean, median, standard deviation, etc, and they belong to the class of symmetric functions. This thesis develops arithmetic computation coding in order to efficiently perform in-network computation for weighted arithmetic sums and symmetric functions. The developed arithmetic computation coding increases the achievable computation rate from

\Theta((\log L)/L)

\Theta(1/\log L)

, where

L

is the number of sensors. Finally, this thesis demonstrates that interaction among sensors is beneficial for computation of type-threshold functions, e.g., the maximum and the indicator function, and that a non-vanishing computation rate is achievable.

EPFL2015