5 research outputs found
Development of Communication Link Perception for Decision Making in Mobile Agents
Examination and comparison of Packet Error Rate (PER), Error Burstiness (EB), and Receive Signal Strength Indicator (RSSI) as communication connectivity management metrics for multi-agent mobile robot networks are explored in this thesis. Assessment Accuracy (AA) and Time To Process (TTP) are used as parameters for the comparison of metrics given that mobile robots are required to make critical decisions rapidly. The initial investigations are done with a mobile unit making PER, EB, and RSSI measurements at an increasing distance from a base station. A relatively linear relationship between PER and EB was discovered with a R2 value of .967. Strong correlations between EB and PER were observed in areas between 0% and 50% PER. A communication aware algorithm was developed using both EB and PER to allow the mobile agent to assess the Link Quality (LQ) faster in scenarios of communication loss by scanning for error bursts
Design and Reliability Performance Evaluation of Network Coding Schemes for Lossy Wireless Networks
This thesis investigates lossy wireless networks, which are wireless communication networks consisting of lossy wireless links, where the packet transmission via a lossy wireless link is successful with a certain value of probability. In particular, this thesis analyses all-to-all broadcast in lossy wireless networks, where every node has a native packet to transmit to all other nodes in the network. A challenge of all-to-all broadcast in lossy wireless networks is the reliability, which is defined as the probability that every node in the network successfully obtains a copy of the native packets of all other nodes. In this thesis, two novel network coding schemes are proposed, which are the neighbour network coding scheme and the random neighbour network coding scheme. In the two proposed network coding schemes, a node may perform a bit-wise exclusive or (XOR) operation to combine the native packet of itself and the native packet of its neighbour, called the coding neighbour, into an XOR coded packet. The reliability of all-to-all broadcast under both the proposed network coding schemes is investigated analytically using Markov chains. It is shown that the reliability of all-to-all broadcast can be improved considerably by employing the proposed network coding schemes, compared with non-coded networks with the same link conditions, i.e. same probabilities of successful packet transmission via wireless channels. Further, the proposed schemes take the link conditions of each node into account to maximise the reliability of a given network. To be more precise, the first scheme proposes the optimal coding neighbour selection method while the second scheme introduces a tuning parameter to control the probability that a node performs network coding at each transmission. The observation that channel condition can have a significant impact on the performance of network coding schemes is expected to be applicable to other network coding schemes for lossy wireless networks
Design and Reliability Performance Evaluation of Network Coding Schemes for Lossy Wireless Networks
This thesis investigates lossy wireless networks, which are wireless communication networks consisting of lossy wireless links, where the packet transmission via a lossy wireless link is successful with a certain value of probability. In particular, this thesis analyses all-to-all broadcast in lossy wireless networks, where every node has a native packet to transmit to all other nodes in the network. A challenge of all-to-all broadcast in lossy wireless networks is the reliability, which is defined as the probability that every node in the network successfully obtains a copy of the native packets of all other nodes. In this thesis, two novel network coding schemes are proposed, which are the neighbour network coding scheme and the random neighbour network coding scheme. In the two proposed network coding schemes, a node may perform a bit-wise exclusive or (XOR) operation to combine the native packet of itself and the native packet of its neighbour, called the coding neighbour, into an XOR coded packet. The reliability of all-to-all broadcast under both the proposed network coding schemes is investigated analytically using Markov chains. It is shown that the reliability of all-to-all broadcast can be improved considerably by employing the proposed network coding schemes, compared with non-coded networks with the same link conditions, i.e. same probabilities of successful packet transmission via wireless channels. Further, the proposed schemes take the link conditions of each node into account to maximise the reliability of a given network. To be more precise, the first scheme proposes the optimal coding neighbour selection method while the second scheme introduces a tuning parameter to control the probability that a node performs network coding at each transmission. The observation that channel condition can have a significant impact on the performance of network coding schemes is expected to be applicable to other network coding schemes for lossy wireless networks
Esquemas de segurança contra ataques de poluição em codificação de rede sobre redes sem fios
Doutoramento em TelecomunicaçõesResumo em português não disponivelThe topic of this thesis is how to achieve e cient security against pollution
attacks by exploiting the structure of network coding.
There has recently been growing interest in using network coding
techniques to increase the robustness and throughput of data networks, and
reduce the delay in wireless networks, where a network coding-based scheme
takes advantage of the additive nature of wireless signals by allowing two
nodes to transmit simultaneously to the relay node. However, Network
Coding (NC)-enabled wireless networks are susceptible to a severe security
threat, known as data pollution attack, where a malicious node injects into
the network polluted (i.e., corrupted) packets that prevent the destination
nodes from decoding correctly. Due to recoding at the intermediate nodes,
according to the core principle of NC, the polluted packets propagate
quickly into other packets and corrupt bunches of legitimate packets
leading to network resource waste. Hence, a lot of research e ort has been
devoted to schemes against data pollution attacks. Homomorphic Message
Authentication Code (MAC)-based schemes are a promising solution against
data pollution attacks. However, most of them are susceptible to a new
type of pollution attack, called tag pollution attack, where an adversary
node randomly modi es tags appended to the end of the transmitted packets.
Therefore, in this thesis, we rst propose a homomorphic message
authentication code-based scheme, providing resistance against data
pollution attacks and tag pollution attacks in XOR NC-enabled wireless
networks. Moreover, we propose four homomorphic message authentication
code-based schemes which provide resistance against data and tag pollution
attacks in Random Linear Network Coding (RLNC). Our results show that
our proposed schemes are more e cient compared to other competitive tag
pollution immune schemes in terms of complexity, communication overhead
and key storage overhead