Marco Ghibaudi

Performance evaluation of FEC techniques based on BCH codes in video streaming over wireless sensor networks

Video streaming in wireless sensor networks is a promising and challenging application. The reduced amount of available bandwidth, as well as the low-computational power available for acquiring and processing video frames on tiny devices, imposes the transmission of low resolution video frames at a low frame rate. In such a scenario the amount of information carried by each video frame must be preserved as mush as possible in order to avoid possible artifacts in the reconstructed dynamics of the scene. In this paper we first evaluate the impact of the bit error rate on the quality of the received video stream, then we propose a forward error correction technique based on the use of BCH codes to preserve the video quality. The proposed technique, fully compliant with the IEEE802.15.4 standard, reaches a PSNR improvement of 1.95 dB, with respect to the plain transmission, while requiring an additional minimal overhead of 22.51% in the number of transmitted bits. When a higher protection level is exploited a PSNR improvement of 3.72 dB has been experienced at the cost of 40.74% additional overhead.

Video streaming in wireless sensor networks with low-complexity change detection enforcement

Video streaming applications in wireless sensor networks are attractive for enabling new pervasive high value services. The reduced amount of available bandwidth in such networks imposes the transmission of small size video frames at very low frame rates. Moreover, when compression techniques cannot be applied, due to constrained computational capabilities of sensor nodes, and uncompressed video frames must be sent through the network, lower image sizes and frame rates must be adopted. In such a scenario, when higher frame rates are required or multiple video streams must be enabled the required transmission bandwidth of each stream must be reduced. In this paper we present a low-complexity algorithm based on change detection which reduces the transmission bandwidth of a video stream based on raw images. Performance results show how the proposed technique can reduce the transmission bandwidth up to 87.22% and 66.78%, with respect to a flat video stream transmission, when low and high changes are experienced in the monitored scene.

SPEED routing protocol in 6LoWPAN networks

The integration of the Wireless Sensor Networks (WSNs) technology in the Internet world is one of the biggest challenges to enable the Internet of Things (IoT) vision. In order to really benefit of such kind of integration the IPv6 addressing method and communication protocols adopted in the IoT must be modified to match the WSNs scenario. This adaptation has been standardized with the name of IPv6 over Low power Wireless Personal Area Networks (6LoWPAN). In this paper the first adaptation of the SPEED geographic routing algorithm in a 6LoWPAN scenario is presented and its experimental validation in a real testbed is shown as compared with the AODVprotocol. Avoiding route creation time and showing reduced memory occupation, load balancing and flow shaping properties SPEED is an effective solution to support packet routing in 6LoW-PAN networks.

Real-time voice streaming over IEEE 802.15.4

Audio and video applications over wireless sensor networks have recently emerged as a promising research field. However, the limits in terms of communication bandwidth and transmission power have withstood the design of low-power embedded nodes for voice communication. In this work we describe the implementation details of an embedded system for the wireless broadcasting of audio signals over the low datarate IEEE 802.15.4 standard, which is widely adopted to build Wireless Personal and Sensor Networks. The resulting device has been developed from scratch by combining several techniques with the goal of obtaining the most suitable implementation on a low-cost and low-power 16-bit microcontroller. We used a realtime operating system, a well-known psychoacoustic model based on FFT signal decomposition and the Haar wavelet transform to create a novel audio compression algorithm targeted to embedded systems with limited computational capabilities. The result is a fully-functional embedded system which is able to stream voice in real-time over IEEE 802.15.4 with an acceptable audio quality.

Free space optical communication in the visible bandwidth for V2V safety critical protocols

Vehicular Communication Systems are an emerging type of networks in which vehicles and roadside units are the communicating nodes, providing each other with information, such as safety warnings and traffic information. Vehicle-to-vehicle message exchange is considered the preferred pattern for safety-critical communication (e.g. in anti-collision active systems). Recently, LED-based optical wireless communication has been also proposed for car to car message delivery. This option turns to be particularly effective in short range direct communications to exploit its line-of-sight feature and overcome the issues related to the isotropic nature of radio waves. In this paper we experimentally address this case study making use of two low cost On-Board Unit prototypes, equipped with a common Light Emitting Diode (LED) component at the transmitter and a common PIN photodiode at the receiver.

Perceptual voice communications in IEEE802.15.4 networks for the emergency management support

Voice communication in IEEE802.15.4 networks is an attractive application for the emergency management support when a disaster occurs. Although this application can be of extreme utility in the immediate consequence of the disaster, it must take into account the bandwidth limitations of the IEEE802.15.4 standard, which allows the simultaneous transmission of a small number of voice streams. When more voice streams must be transmitted through the network, a bandwidth reduction of each speech flow must be performed. In this paper we first present an algorithm for the perceptual selection of voice data aiming at reducing the speech flow bandwidth while preserving as much as possible the end-to-end speech quality, then we propose a voice data protection technique based on speech perceptual importance and able to preserve speech quality against packet losses. The perceptual selection algorithm can reach a 30.8% reduction in bandwidth occupancy, with respect to a full rate voice communication, still maintaining an end-to-end speech quality between good and fair according to the Mean Opinion Score scale defined by the International Telecommunications Union. The protection technique, jointly adopted with the perceptual selection, can reach better end-to-end speech quality values with respect to a full rate voice communication while requiring a lower amount of transmission bandwidth.

SPEED-3D: a geographic routing protocol for 6LoWPAN networks

The integration of the wireless sensor network WSN technology in the internet world is a necessary step towards the full accomplishment of the internet of things IoT vision. In order to reach a seamless integration of tiny mote devices in internet, the IPv6 addressing method and communication protocols developed for the IoT must be modified or adapted to match the WSN requirements. This adaptation process is started in the 2007 with the standardisation of the IPv6 protocol over low power wireless personal area networks 6LoWPAN. In such a scenario, we propose SPEED-3D, an extension of the SPEED geographic routing algorithm, adapted to 6LoWPAN networks that caters for 3D routing. SPEED-3D avoids the creation of routing tables, and has a very low memory occupation; it also supports load balancing and flow shaping; finally, thanks to the presented extension, it is able to work seamlessly in a 3D setting e.g., a tall building. In the paper, we first present SPEED-3D in 6LoWPAN networks by detailing the encapsulation of all messages in the IEEE802.15.4 medium access control MAC protocol and the new functionality provided thanks to the IPv6 standard, then we present its implementation on a real-time kernel and its performance in a realistic indoor scenario.