Jean-Pierre Goemaere

Optical CDMA codes for an indoor localization system using VLC

This paper describes the use of optical Code Division Multiple Access (CDMA) codes for an indoor localization system using Visible Light Communication. VLC uses Intensity Modulation and Direct Detection (IM/DD) so the CDMA codes can be used as baseband signals which makes the driving electronics less complex. In order to keep the installation cost low, a backbone network between the LEDs is not present. This makes it an asynchronous CDMA system where the cross- correlation is random and can in some cases introduces large distance errors. There are two groups of Optical CDMA codes namely uni- and bi- polar. When bipolar codes are used, the receiver should be equipped with an appropriated High Pass Filter (HPF). The results show that there is no large difference in cross- correlation between the codes but bipolar codes can reduce the distance error and so the position error even when there is static surrounding light like e.g. sunlight.

A novel indoor localization system for healthcare environments

This paper proposes a novel indoor localization system, specifically designed for use in healthcare environments. The challenge for this indoor localization project is to decide in which room or in which area of a corridor the blindfolded node is situated, and this with a 100% guarantee that the determined location complies with the actual location of the blindfolded node. We propose a decentralized localization algorithm which uses Received Signal Strength information between the beacons and blindfolded nodes, combined with a smart beacon addressing scheme which is used by the localization algorithm. These beacons are existing access points to a backbone network equipped with a wireless interface. By using a proximity-based approach, we are able to decide where a blindfolded node is situated on a low resource and decentralized basis.

Analysis of the Realistic Resolution with Angle of Arrival for Indoor Positioning

Increasing importance of localizing objects in indoor environments is the motivation for many research on localization algorithms. This paper focuses on the maximum achievable resolution for Angle of Arrival as a means to position objects inside rooms using equipment within the field of wireless sensor networks, thus dealing with restricted resources. A clear view on beam forming using antenna arrays is represented and is proven to be useful in Angle of Arrival measurements. The choice of the linear antenna array as most appropriate solution is motivated. A detailed overview of the algorithm, used to calculate the maximum realistic resolution, leads us to draw conclusions concerning the resolution. Depending on the number of anchor nodes and the composition of the antenna arrays, a reference value can be defined to calculate the realistic resolution for all room dimensions.

A Visible Light Positioning system using Frequency Division Multiple Access with square waves

In this paper, a Visible Light Positioning (VLP) system using Frequency Division Multiple Access (FDMA) with square waves is presented. For the multiple access technology, the properties of square waves in the frequency domain is exploited. Neighboring LEDs will use multiples of the ground frequency of the first LED where the receiver performs a Fast Fourier Transform (FFT) and retrieves the Received Signal Strength (RSS) for every LED. In order to facilitate implementation, the LEDs are transmitting pilot tones in a non-synchronized way to the receiver, and thus requiring no backbone network. The positioning algorithm uses the RSS to perform triangulation and finds the position by taking the least square fit. Practical results show that this VLP system has position errors smaller then 10 cm when an photodiode is used which has a Field Of View (FOV) of 70°. Simulation results show that when a photodiode with a FOV of 90° is applied, the position error can drop to a few centimeter within the entire test bench surface. The key advantage of the system is the use of unsynchronized low bandwidth transmitters, leading to an easy implementation using current high efficiency LED drivers.

On the choice of the appropriate AES data encryption method for ZigBee nodes

This paper describes the experiments that have been conducted to determine the optimal implementation method for AES Advanced Encryption Standard data encryption in a ZigBee network in terms of energy consumption. Four possible scenarios have been considered. The first one is a freely available AES-cryptographic algorithm on the processor which controls the ZigBee nodes. The second also involves the processor but is based on a proprietary, highly optimized algorithm. The other methods are based on hardware implementations. Whereas the third option is based on a cryptographic block, embedded in the ZigBee node controller, the last solution utilizes an AES128-CBC-MAC hardware co-processor embedded on a Spartan 3A FPGA. The ZigBee modules in the network contain an 8-bit microcontroller which takes care of the ZigBee protocol stack-and the encryption calculations in all but the last case. All approaches are examined and compared. We show that the usage of a microcontroller with an on-board AES processor is the optimal design choice for a new hardware platform. An optimized software library gives the best results when extending an existing platform. This paper gives developers an idea of the amount of energy they can gain/lose by choosing one of the four solutions. Copyright

A modular test platform for evaluation of security protocols in NFC applications

In this paper we present the advantages and possibilities of a modular test platform for the evaluation of security protocols in NFC applications. Furthermore, we also depict some practical implementation results of this modular system. The scope of the platform is to provide a highly modular system. Adding or removing certain functionality can be done without the need of rebuilding the entire system. Security measures in hardware as well as software can be tested and evaluated with this platform. It can serve as a basis for a broad range of security related applications, NFC being our domain of interest, but even so in other domains.

Flexible design of a modular simultaneous exponentiation core for embedded platforms

In this paper we present a flexible hardware design for performing Simultaneous Exponentiations on embedded platforms. Simultaneous Exponentiations are often used in anonymous credentials protocols. The hardware is designed with VHDL and fit for use in embedded systems. The kernel of the design is a pipelined Montgomery multiplier. The length of the operands and the number of stages can be chosen before synthesis. We show the effect of the operand length and number of stages on the maximum attainable frequency as well as on the FPGA resources being used. Next to scalability of the hardware, we support different operand lengths at run-time. The design uses generic VHDL without any device-specific primitives, ensuring portability to other platforms. As a test-case we effectively integrated the hardware in a MicroBlaze embedded platform. With this platform we show that simultaneous exponentiations with our hardware are performed 70 times faster than with an all-software implementation.

Using a decision tree for real-time distributed indoor localization in healthcare environments

Decision trees can be of great importance when trying to perform indoor localization on room level basis. These decision trees enable mobile nodes with limited computational resources to locate themselves inside a building without the need of heavy computations. This paper elaborates on the use of a decision tree for tracking moving mobile nodes inside healthcare facilities with possibly thousands of mobile nodes which need to be tracked at the same time. By avoiding a centralized localization attempt for all of the mobile nodes, we prove a distributed localization algorithm based on a decision tree can enable the tracking and tracing of this amount of mobile nodes. The same decision tree is used for determining if indoor localization without Line-Of-Sight between beacons and mobile nodes is feasible, for instance when people are standing between a mobile unit and a fixed beacon.

Optimized shape of a parametric designed HF loop antenna

The design of loop antennas is no longer limited to circular and square shapes. Adapting the shape of the antenna to its environment is needed to increase the reliability of the application, especially when we have to place the antenna in an atypical environment or orientation. We will evaluate an HF loop antenna which differs in shape from commercially available antennas. This work demonstrates how the knowledge of the designer and the use of an optimization tool can create an antenna shape with specific goals. The optimization tool combines MATLAB® and CST EM Studio®. The dedicated antenna shape is implemented in a practical environment, e.g., a metallic drawer for medication storage. The results of the simulations are presented and are verified experimentally. These measurements confirm the simulation results, leading to the realisation of a very reliable, dedicated RFID solution with an atypical antenna shape.

Influence of MAI in a CDMA VLP system

In this paper, we study a Visible Light Positioning (VLP) system using Code Division Multiple Access (CDMA). In order to facilitate implementation, the LEDs are transmitting data in a non-synchronized way to the receiver requiring no backbone network. The positioning algorithm uses the received optical power calculated from the auto- correlation peak value. Because of the asynchronous system Multiple Access Interference (MAI), random interference with the auto- correlation peak, will occur and cause position errors. Practical results show that a CDMA VLP system can have position errors smaller then 40 cm and not be influenced by synchronization problems due to MAI. The positioning error and synchronization arent only determined by the MAI but also the receiver Field Of View (FOV) is an important parameter. Depending on the CDMA code, the LEDs still have 97% of the illumination functionality compared when there is no communication.