Joint design of relay and packet combining schemes for wireless industrial networks

Wireless industrial networks differ in many respects from other types of wireless networks. In particular, since many applications impose tight real-time and reliability requirements at the same time, and packet sizes tend to be small. In this paper we design a simple and practically implementable protocol in which relaying and packet combining work together to improve the probability that packets are delivered within a prescribed deadline over fading channels. The results indicate that such a combination can be fruitfully employed in wireless industrial networks.©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.</p

Efficient ARQ algorithm based on majority logic decision

Primena diverziti tehnike i majoritetnog kombinovanja paketa predstavlja jednostavno i atraktivno rešenje za kontrolu grešaka u bežičnim telekomunikacionim sistemima. Ove tehnike su posebno interesantne u paketski orijentisanim mrežama sa višestrukim putanjama i kooperativnim mrežama sa jednom ili više predajnih i prijemnih antena. Tipičan primer su bežične senzorske mreže koje često rade u ekstremno otežanim uslovima prenosa, pri čemu zahtevi za pouzdanim prenosom imaju veći prioritet od zahteva za racionalnim korišćenjem komunikacionih kapaciteta. Teorijski i aproksimativni izrazi za verovatnoću pogrešnog prenosa paketa u slučaju proizvoljnog broja kanala sa različitim verovatnoćama grešaka predstavljaju ključne parametre za procenu energetske efikasnosti senzorskih čvorova. Cilj rada: U okviru ove problematike, u tezi su postavljeni sledeći ciljevi: (i) da se dobiju teorijski izrazi za verovatnoću pogrešnog prenosa paketa u slučaju primene selektivnog i majoritetnog odlučivanja, u uslovima kada su verovatnoće grešaka različite na različitim putanjama i kada je broj mogućih paralelnih putanja proizvoljan; analitički izrazi su veoma bitni prilikom odreĎivanja optimalnog broja putanja u senzorskoj mreži sa ciljem maksimalne uštede potrošnje energije u senzorskim čvorovima, (ii) da se analizira efikasnost hibridne ARQ šeme imajući u vidu različita scenarija pristizanja paketa u odredišni čvor; naime, prisustvo prostornih putanja pri kojima su na pojedim putanjama uslovi prenosa loši, ne obezbeĎuje garantovano prepoznavanje paketa i prenos po svim putanjama, tako da se uslovi za majoritetno odlučivanje mogu obezbediti posle jedne ili više retransmisija; zbog toga, realni scenario je kombinacija prostornog i vremenskog diverzitija u korist jednog ili drugog scenarija, (iii) da se sagleda mogućnost implementacije imajući u vidu korišćenje poznatih standarda i postojećih hardverskih i softverskih rešenja koja se koriste u senzorskim mrežama; posebno težište je bilo dato modifikaciji rešenja neohodnih za implementaciju korekcije grešaka na bazi majoritetnog kombinovanja paketa...The application of diversity technique and majority packet combining is a simple and attractive solution for error control in wireless telecommunication systems. These techniques are especially interesting in packet-oriented multipath and cooperative networks with one or more transmitting and receiving antennas. A typical example is wireless sensor network which often operates in extremely harsh conditions, where requirements for reliable packet transmission have a higher priority than requirements for efficient usage of communication capacities. Theoretical and approximate expressions of packet error probabilities in the case of an arbitrary number of channels with distinct channel error probabilities are key parameters for estimation of the energy efficiency of sensor nodes. Goal of research: As part of this problem, the thesis sets the following objectives: (i) to obtain theoretical expressions for packet error probability in the case of application of selective and majority decision when the number of parallel channels is arbitrary and channel error probabilities are distinct; analitical expressions are very important in determining the optimal number of paths in a sensor network in order to achieve maximum saving of energy in sensor nodes, (ii) to analyze the throughput efficiency of a hybrid ARQ scheme, considering various scenarios of packet receiving in the destination node; namely, the presence of spatial paths, with poor transmission conditions in certain paths, does not provide guaranteed detection and transmission of frame copies via all paths, so that the conditions for majority combining may be provided after one or more retransmissions; therefore, the real scenario is a combination of space and time diversity in favor of one or the other scenario, (iii) to examine the possibility of implementation of majority combining, having in mind the known standards and the usage of existing hardware and software solutions in sensor networks; the particular focus was given to the modification of solutions required for the implementation of error correction, based on majority packet combining..

Integrated Framework For Mobile Low Power IoT Devices

Ubiquitous object networking has sparked the concept of the Internet of Things (IoT) which defines a new era in the world of networking. The IoT principle can be addressed as one of the important strategic technologies that will positively influence the humans’ life. All the gadgets, appliances and sensors around the world will be connected together to form a smart environment, where all the entities that connected to the Internet can seamlessly share data and resources. The IoT vision allows the embedded devices, e.g. sensor nodes, to be IP-enabled nodes and interconnect with the Internet. The demand for such technique is to make these embedded nodes act as IP-based devices that communicate directly with other IP networks without unnecessary overhead and to feasibly utilize the existing infrastructure built for the Internet. In addition, controlling and monitoring these nodes is maintainable through exploiting the existed tools that already have been developed for the Internet. Exchanging the sensory measurements through the Internet with several end points in the world facilitates achieving the concept of smart environment. Realization of IoT concept needs to be addressed by standardization efforts that will shape the infrastructure of the networks. This has been achieved through the IEEE 802.15.4, 6LoWPAN and IPv6 standards. The bright side of this new technology is faced by several implications since the IoT introduces a new class of security issues, such as each node within the network is considered as a point of vulnerability where an attacker can utilize to add malicious code via accessing the nodes through the Internet or by compromising a node. On the other hand, several IoT applications comprise mobile nodes that is in turn brings new challenges to the research community due to the effect of the node mobility on the network management and performance. Another defect that degrades the network performance is the initialization stage after the node deployment step by which the nodes will be organized into the network. The recent IEEE 802.15.4 has several structural drawbacks that need to be optimized in order to efficiently fulfil the requirements of low power mobile IoT devices. This thesis addresses the aforementioned three issues, network initialization, node mobility and security management. In addition, the related literature is examined to define the set of current issues and to define the set of objectives based upon this. The first contribution is defining a new strategy to initialize the nodes into the network based on the IEEE 802.15.4 standard. A novel mesh-under cluster-based approach is proposed and implemented that efficiently initializes the nodes into clusters and achieves three objectives: low initialization cost, shortest path to the sink node, low operational cost (data forwarding). The second contribution is investigating the mobility issue within the IoT media access control (MAC) infrastructure and determining the related problems and requirements. Based on this, a novel mobility scheme is presented that facilitates node movement inside the network under the IEEE 802.15.4e time slotted channel hopping (TSCH) mode. The proposed model mitigates the problem of frequency channel hopping and slotframe issue in the TSCH mode. The next contribution in this thesis is determining the mobility impact on low latency deterministic (LLDN) network. One of the significant issues of mobility is increasing the latency and degrading packet delivery ratio (PDR). Accordingly, a novel mobility protocol is presented to tackle the mobility issue in LLDN mode and to improve network performance and lessen impact of node movement. The final contribution in this thesis is devising a new key bootstrapping scheme that fits both IEEE 802.15.4 and 6LoWPAN neighbour discovery architectures. The proposed scheme permits a group of nodes to establish the required link keys without excessive communication/computational overhead. Additionally, the scheme supports the mobile node association process by ensuring secure access control to the network and validates mobile node authenticity in order to eliminate any malicious node association. The purposed key management scheme facilitates the replacement of outdated master network keys and release the required master key in a secure manner. Finally, a modified IEEE 802.15.4 link-layer security structure is presented. The modified architecture minimizes both energy consumption and latency incurred through providing authentication/confidentiality services via the IEEE 802.15.4