Cooperative Perception for Connected and Automated Vehicles using V2X Communications

Programa de Doctorado en Tecnologías Industriales y de TelecomunicaciónLos vehículos autónomos hacen uso de múltiples sensores para detectar su entorno. Los sensores utilizados (cámaras, radares o lidars) han mejorado significativamente su capacidad de detección en los últimos años. Sin embargo, sus capacidades aún están limitadas ante la presencia de obstáculos o condiciones climáticas adversas, entre otros factores. Una opción para mitigar estos retos es la percepción cooperativa o colectiva, la cual permite a los vehículos intercambiar información sobre los objetos detectados por sus sensores utilizando las comunicaciones V2X (Vehicle-to-Everything). De esta forma, los vehículos disponen de información no sólo de los objetos detectados por sus propios sensores sino también de los detectados por los sensores de los vehículos cercanos. De esta forma, la percepción cooperativa permite que los vehículos mejoren su rango de detección más allá de las capacidades de sus sensores locales. La percepción cooperativa también puede ayudar a mejorar la precisión y confianza en la detección de objetos, y ayuda a mitigar el impacto negativo de las condiciones climáticas o de visibilidad adversas. ETSI y SAE están definiendo actualmente nuevos estándares V2X para la percepción cooperativa. SAE aún no ha publicado su estándar, mientras que ETSI ha publicado un Informe Técnico sobre percepción colectiva que incluye aspectos importantes como el formato del Mensaje de Percepción Colectiva (CPM) y las reglas de generación de mensajes para decidir cuándo debe generarse un nuevo CPM y qué información debe incluir. ETSI está actualmente en proceso de finalizar un primer estándar sobre percepción colectiva, y asociaciones industriales como el CAR 2 CAR Communication Consortium (C2C-CC) y 5G Automotive Association (5GAA) han incluido la percepción cooperativa en sus hojas de ruta. Todos estos esfuerzos destacan el interés industrial y el potencial de las comunicaciones V2X para apoyar el desarrollo y despliegue de la percepción cooperativa en vehículos conectados y autónomos. A pesar de los avances realizados hasta la fecha, el concepto de percepción cooperativa es relativamente novedoso y se requiere un profundo estudio de su funcionamiento y rendimiento antes de considerar su despliegue comercial. La percepción cooperativa permite intercambiar de forma frecuente actualizaciones sobre los objetos detectados por los sensores con el fin de aumentar la precisión de la detección. Sin embargo, las actualizaciones frecuentes aumentan la carga en los canales de comunicación, y suponen un reto para la escalabilidad de la red de comunicaciones V2X y la efectividad de la percepción cooperativa. Además, pueden generar altos niveles de redundancia pues muchos vehículos cercanos pueden detectar un mismo objeto y reportarlo simultáneamente. Este reporte simultáneo puede, hasta cierto punto, mejorar la precisión en la detección. Sin embargo, un alto nivel de redundancia puede sobrecargar el canal de comunicaciones y afectar al funcionamiento y efectividad de la percepción cooperativa ante la imposibilidad de transmitir los mensajes críticos por la saturación del canal de comunicaciones. El desafío general en la percepción cooperativa ocurre principalmente cuando el mensaje de la percepción cooperativa no está bien organizado. Por ejemplo, podría ser muy ineficiente generar un mensaje de percepción cooperativa que contenga una pequeña cantidad de objetos detectados, lo que también podría aumentar la carga del canal de comunicaciones y podría afectar la percepción cooperativa. Esta tesis estudia y evalúa exhaustivamente el funcionamiento y rendimiento de la percepción cooperativa, y propone diferentes soluciones para mejorar su eficiencia y escalabilidad. Para ello, en primer lugar, la tesis realiza un estudio de dimensionado para comprender mejor el funcionamiento de la percepción cooperativa, e identificar las posibles ineficiencias existentes. Este estudio evalúa las reglas de generación de mensajes de percepción cooperativa propuestas en ETSI, y analiza en detalle el impacto de diferentes configuraciones de sensores, densidades de tráfico y tasas de penetración de la tecnología en el mercado. Esta tesis también investiga por primera vez el impacto del control de congestión en la percepción cooperativa. Este estudio es muy relevante ya que los protocolos de control de congestión pueden modificar la generación y transmisión de mensajes cuando el canal radio está congestionado, y por lo tanto alterar el funcionamiento de la percepción cooperativa. El estudio considera el sistema de control de congestión (DCC, control de congestión descentralizado) estandarizado por ETSI y que abarca varias capas de la pila de protocolos. El estudio realizado demuestra el impacto de la configuración DCC en el funcionamiento y efectividad de la percepción cooperativa. En base a los resultados del estudio de dimensionado, esta tesis proponen dos técnicas para mitigar las ineficiencias identificadas en el proceso de percepción cooperativa, la técnica Look-Ahead y una técnica de mitigación o control de redundancia. La técnica de mitigación de redundancia reduce la redundancia en la red de comunicaciones eliminando del mensaje de percepción cooperativa los objetos detectados que no han cambiado significativamente su posición, velocidad y rumbo desde la última vez que fueron recibidos como parte de un mensaje de percepción cooperativa enviado por otro vehículo cercano. La evaluación muestra que la técnica de control de redundancia propuesta reduce significativamente la redundancia y la carga del canal de comunicaciones, y mantiene la capacidad de percepción para distancias cortas y medias críticas para la seguridad. La técnica Look-Ahead reorganiza la transmisión de objetos en el mensaje de percepción cooperativa con el fin de reducir el overhead en las comunicaciones V2X. Para ello, la técnica incluye objetos en el mensaje de percepción cooperativa actual que predice se incluirían en el siguiente mensaje de percepción cooperativa. Esta reorganización busca reducir el número de mensajes de percepción cooperativa generados haciendo que cada mensaje incluya información sobre una mayor cantidad de objetos detectados. Los resultados del análisis muestran que Look-Ahead reduce el overhead y la carga del canal de comunicaciones V2X a la vez que mejora la percepción de los vehículos. Por último, la tesis propone métodos para combinar las técnicas propuestas (Look-Ahead y mitigación de redundancia) con el fin de mejorar aún más la efectividad de la percepción cooperativa y la escalabilidad del sistema. Este estudio considera la combinación de las dos técnicas con y sin control de congestión DCC, y muestra que las combinaciones propuestas reducen la carga del canal y mejoran la escalabilidad de los servicios de percepción cooperativa.Automated vehicles make use of multiple sensors to detect their surroundings. The sensing technology has significantly improved over the last years. However, the capabilities of onboard sensors like cameras, radars, or lidars are still limited under the presence of obstacles or adverse weather conditions, among other factors. Cooperative perception (a.k.a. collective perception or cooperative sensing) has been proposed to help mitigate these challenges by exchanging sensor data among vehicles using V2X (Vehicle-to-Everything) communications. V2X communications allow vehicles to exchange information about detected objects, and hence improve their sensing range beyond the capabilities of their local sensors thanks to cooperative perception. Cooperative perception can also help improve the vehicles’ sensor detection accuracy and increase the confidence about the detected objects. It can also help mitigate the negative impact of adverse weather conditions or the negative effect of lighting conditions on the sensitivity. ETSI and SAE are currently defining new V2X standards for cooperative perception. SAE has not yet published its standard. On the other hand, ETSI has published a Technical Report on collective perception that includes important aspects such as the Collective Perception Message (CPM) format and the message generation rules to decide when a new CPM should be generated and what information it should include. ETSI is now finalizing the standardization of the Technical Specification on collective perception. Industrial associations such as the C2C-CC and the 5GAA have included cooperative perception in their roadmaps. All these efforts highlight the industrial interest and potential of V2X communications to support the development and deployment of cooperative perception in connected and automated vehicles. Despite the advances made to date, the concept of cooperative perception is relatively new and an in-depth study of its operation and performance is required before considering its commercial deployment. Cooperative perception allows frequent exchange of updates on the sensors detected objects to increase detection accuracy. However, the frequent updates increase the channel load on the communications channels, and pose a challenge for the scalability of the V2X communications network and the effectiveness of cooperative perception. In addition, they can generate high levels of object redundancy since many nearby vehicles can detect the same object and report it simultaneously. This simultaneous reporting of objects can improve detection accuracy to some extent. However, a high level of redundancy can overload the communications channel and affect the operation and effectiveness of the cooperative perception given the impossibility of transmitting critical messages due to the saturation of the communications channel. The general challenge in cooperative perception occurs mainly when the cooperative perception message is not well organized. It might be very inefficient to generate a cooperative perception message that contains a small number of detected objects, which could also increase the load on the communications channel and affect cooperative perception. This thesis extensively studies and evaluates the performance and operation of cooperative perception solutions and proposes different techniques to address the identified challenges, fulfilling the existing literature gaps. To this aim, the thesis presents first a dimensioning study to identify any inefficiencies in existing cooperative perception solutions and support the design of more advanced and scalable techniques. This dimensioning study evaluates the cooperative perception message generation rules proposed at ETSI and compares them with periodic generation policies to analyze its effectiveness and identify existing limitations. Then the impact of different sensor configurations, traffic densities and market penetration rates are analyzed in detail. The study also investigates the impact of congestion control on cooperative perception, since congestion control protocols can modify message generation and transmission when the radio channel is congested. ETSI has standardized a DCC (Decentralized Congestion Control) framework for V2X communications that spans over multiple layers of the protocol stack. To the author’s knowledge, this is the first study that evaluates the combination of the ETSI defined DCC Access and DCC Facilities on cooperative perception. The study demonstrates the importance of the DCC configuration for the operation of the V2X network and the effectiveness of cooperative perception. Based on the findings of the dimensioning study, different techniques are proposed in this thesis to mitigate the inefficiencies identified. This thesis mainly proposes two different techniques, namely the look-ahead technique and redundancy mitigation or control technique. The redundancy mitigation proposal is designed to reduce the redundancy in the network by filtering the detected objects reported in cooperative perception messages that have not significantly changed their position, speed, and heading since the last time they were received as part of a cooperative perception message from other vehicles. The evaluation shows that the proposed redundancy mitigation technique significantly reduces the redundancy and channel load without degrading the perception for safety-critical short and medium distances. The Look-Ahead proposal reorganizes the transmission of objects in the cooperative perception message. It includes objects in the current cooperative perception message that are predicted to be included in the following cooperative perception message. This reorganization results in vehicles transmitting fewer messages, and each message includes information about a higher number of detected objects. This approach reduces the communications overhead and the channel load, and improves the perception. Finally, the thesis proposes methods to combine the proposed techniques (Look-Ahead and redundancy mitigation) to further improve the effectiveness of cooperative perception and the system’s scalability. The different combinations are evaluated with and without DCC, and the conducted study shows that combining the two proposals can further reduce the channel load and improve the scalability of cooperative perception services without degrading the perception

Analysis of Advantages of Single Layer Vs Double Layer Anastomosis of Bowel

INTRODUCTION: In the modern day surgical practice, we come across situations in abdominal surgery, where we require resection and anastomosis of bowel. In small bowel resection and anastomosis, conventionally, two layer suturing technique i.e., inner layer with absorbable suture material in continuous fashion and outer layer with non absorbable suture material in a continuous or interrupted fashion, was considered secure. Recently, it has been advocated that anastomosis of small bowel with a single layer suturing using a non absorbable monofilament suture material in a continuous fashion has the same outcome when compared to double layer suturing technique. AIMS AND OBJECTIVES: 1. Complications of Single layer technique and the Double layer technique in emergency and elective surgeries. 2. Time consumption for performing single layer anastomosis as well as double layer anastomosis. 3. Cost effectiveness of single layer anastomosis. MATERIALS & METHODS: All adult patients requiring intestinal anastomosis at Govt. Rajaji Hospital from July 2008 to June 2010 were considered eligible. Totally 60 patients were included in our study. 30 patients under went single layer anastomosis and 30 patients underwent double layer anastomosis. Patients who underwent elective or emergency surgery were included in our study. Based on a careful history and meticulous physical examination, combined with adjunctive investigations, a decision to operate urgently or electively was taken. Baseline laboratory parameters like blood urea, blood sugar, serum creatinine, serum electrolytes, blood grouping and typing were done in all the cases, to rule out co morbid conditions. Evaluation of patients with Acute abdomen: Immediately after receiving the patient, primary survey was done, which included resuscitation secondary survey included definitive management. DISCUSSION: Our study assessed the efficacy and safety of single and double layer anastomosis after intestinal resection, in emergency and elective situations. Generally, conventional two layered technique is being practised. But this causes excessive mucosal inversion, causing narrowing of lumen and may lead to ischaemia of anastomotic site. To overcome this problem little mucosal and complete serosal continuous suturing technique was tried. It has the advantage of good opposition of serosal surfaces, no luminal narrowing and less damage to submucosal vascular plexus. In our study, anastomotic leakage in single layer group was 3.3% which is consistent with the other studies which showed leakage in the range of 1.3 to 7.7%. In emergency situations the anastomotic leak rate in single layer group is 5% The double layer group shows anastomotic leakage around 3.3% again which is consistent with the other studies. In emergency situations the anastomotic leak rate in double layer group 5%. CONCLUSION: Among the two methods of small intestinal bowel anastomosis which we have studied, our observations are ; 1. There is no much difference in the development of the complication in both the methods. However the development of complications in emergency situation is more marked in both the methods. 2. The time required to construct a single layer anastomosis is lesser than that of the double layer anastomosis. 3. Narrowing of the lumen of the bowel is lesser in single layer anastomosis when compared to double layer anastomosis. 4. Bowel movements recovered early in single layer anastomosis when compared to double layer anastomosis. 5. Finally, construction of single layer anastomosis of small bowel is cost effective when compared to that of double layer anastomosis

Expanded porphyrins as third order non-linear optical materials: some structure-function correlations

In this paper, the non-linear optical properties of representative core-modified expanded porphyrins have been investigated with an emphasis on the structure-property relationship between the aromaticity and conformational behaviour. It has been shown that the measured two-photon absorption cross section (σ2) values depend on the structure of macrocycle, its aromaticity and the number of π-electrons in conjugation

Generation of Cooperative Perception Messages for Connected and Automated Vehicles

Connected and Automated Vehicles (CAVs) utilize a variety of onboard sensors to sense their surrounding environment. CAVs can improve their perception capabilities if vehicles exchange information about what they sense using V2X communications. This is known as cooperative or collective perception (or sensing). A frequent transmission of collective perception messages could improve the perception capabilities of CAVs. However, this improvement can be compromised if vehicles generate too many messages and saturate the communications channel. An important aspect is then when vehicles should generate the perception messages. ETSI has proposed the first set of message generation rules for collective perception. These rules define when vehicles should generate collective perception messages and what should be their content. We show that the current rules generate a high number of collective perception messages with information about a small number of detected objects. This results in an inefficient use of the communication channel that reduces the effectiveness of collective perception. We address this challenge and propose an improved algorithm that modifies the generation of collective perception messages. We demonstrate that the proposed solution improves the reliability of V2X communication and the perception of CAVs

Cooperative Perception for Connected and Automated Vehicles: Evaluation and Impact of Congestion Control

Automated vehicles make use of multiple sensors to detect their surroundings. Sensors have significantly improved over the years but still face challenges due to the presence of obstacles or adverse weather conditions, among others. Cooperative or collective perception has been proposed to help mitigate these challenges through the exchange of sensor data among vehicles using V2X (Vehicle-to-Everything) communications. Recent studies have shown that cooperative perception can complement on-board sensors and increase the vehicle's awareness beyond its sensors field of view. However, cooperative perception significantly increases the amount of information exchanged by vehicles which can degrade the V2X communication performance and ultimately the effectiveness of cooperative perception. In this context, this study conducts first a dimensioning analysis to evaluate the impact of the sensors' characteristics and the market penetration rate on the operation and performance of cooperative perception. The study then investigates the impact of congestion control on cooperative perception using the Decentralized Congestion Control (DCC) framework defined by ETSI. The study demonstrates that congestion control can negatively impact the perception and latency of cooperative perception if not adequately configured. In this context, this study demonstrates for the first time that the combination of congestion control functions at the Access and Facilities layers can improve the perception achieved with cooperative perception and ensure a timely transmission of the information. The results obtained demonstrate the importance of an adequate configuration of DCC for the development of connected and automated vehicles

Context-based Broadcast Acknowledgement for Enhanced Reliability of Cooperative V2X Messages

Most V2X applications/services are supported by the continuous exchange of broadcast messages. One of the main challenges is to increase the reliability of broadcast transmissions that lack of mechanisms to assure the correct delivery of the messages. To address this issue, one option is the use of acknowledgments. However, this option has scalability issues when applied to broadcast transmissions because multiple vehicles can transmit acknowledgments simultaneously. To control scalability while addressing reliability of broadcast messages, this paper proposes and evaluates a context-based broadcast acknowledgement mechanism where the transmitting vehicles selectively request the acknowledgment of specific/critical broadcast messages, and performs retransmissions if they are not correctly received. In addition, the V2X applications/services identify the situations/conditions that trigger the execution of the broadcast acknowledgment mechanism, and the receiver(s) that should acknowledge the broadcast messages. The paper evaluates the performance of the context-based broadcast acknowledgment mechanism for a Collective Perception Service. The obtained results show the proposed mechanism can contribute to improve the awareness of crossing pedestrians at intersections by increasing the reliability in the exchange of CPM messages between vehicles approaching the intersection. This solution is being discussed under IEEE 802.11bd, and thus can be relevant for the standardization process.10.13039/501100000780-European Commission;10.13039/501100007170-Ministry of Econom

Comparative Studies on Application of Various Adsorbents in Textile Waste Water

This thesis aims to explore the potential of employing natural adsorbents, such as cashew nut shells, date seeds, orange peels, and coir pith, to mitigate COD levels in textile wastewater. The wastewater used for the study was sourced from a textile industry located in Salem. The investigation involved batch studies, wherein the effectiveness of each selected absorbent in reducing COD was assessed to determine the most efficient among the four sorbents. The initial concentration from the batch research served as a basis for identifying the optimal adsorbent, with the COD of the textile wastewater maintained consistently along with the initial dye concentration. To conduct the study, the adsorbent was incrementally introduced in 10 g portions into conical flasks. Over a10-minute period following a 20-minute contact time, the supernatant liquid from each conical flask was collected using syringes. The COD concentration in the obtained samples was determined using a standard methodology. Results revealed that date seeds exhibited the highest percentage of COD removal at 67%, followed by cashew nut shells at 45%, coir pith at 33%, and orange peels at 23%. The data obtained indicated that cashew nut shells and date seeds achieved the highest percentages of COD reduction, respectively. On the other hand, the Orange Peel Adsorbent displayed the least reduction in COD. Based on the collected findings, date seeds emerge as a promising adsorbent for effectively lowering COD in the treatment of textile wastewater

The Two Forms of Lysine Decarboxylase; Kinetics and Effect of Expression in Relation to Acid Tolerance Response in E. coli

Lysine decarboxylase has gained importance recently due to its involvement in acid tolerance response in some pathogenic bacteria. Two forms of the enzyme exist. One, CadA, is part of an operon and is induced by changes in external pH. The other form, Ldc, is constitutively expressed. The differences between the two enzymes have not been understood fully. CadA has been studied more extensively whereas Ldc has not received much attention. The enzymes Ldc and CadA were purified individually using Ni-affinity chromatography from over expressing clones and it was found that their Km for lysine were 0.84mM and 0.27mM respectively. Their velocities, Vmax, were 27.21nmol cadaverine/min/µg of enzyme, and 8.148nmol cadaverine/min/µg of enzyme respectively. Epsilon aminocaproic acid (EACA), benserazide, carbidopa and voveran were added to the enzyme. Voveran inhibited only the inducible form of the enzyme. The assay of activity of each of these enzymes during growth of E.coli suggests that the two forms of the enzyme might be expressed at various phases of growth. This might be the probable reason for the presence of two enzymes which catalyse essentially the same reaction.ÂÂ