At present, most publish/subscribe middlewares suppose that there are equal Quality of Service (QoS) requirements for all users. However, in many real-world Internet of Things (IoT) service scenarios, different users may have different delay requirements. How to provide reliable differentiated services has become an urgent problem. The rise of Software-Defined Networking (SDN) provides endless possibilities to improve the QoS of publish/subscribe middlewares due to its greater programmability. We can encode event topics and priorities into flow entries of SDN switches directly to meet customized requirements. In this paper, we first propose an SDN-like publish/subscribe middleware architecture and describe how to use this architecture and priority queues supported by OpenFlow switches to realize differentiated services. Then we present a machine learning method using the eXtreme Gradient Boosting (XGBoost) model to solve the difficult issue of getting the queuing delay of switches accurately. Finally, we propose a reliable differentiated services guarantee mechanism according to the queuing delay and the programmability of SDN to improve QoS, namely, a two-layer queue management mechanism. Experimental evaluations show that the delay predicted by the XGBoost method is closer to the real value; our mechanism can save end-to-end delay, reduce packet loss rate, and allocate bandwidth more reasonably.

In traditional IP-based publish/subscribe middlewares, a detour to overlay network is demanded to match events with defined filters, which introduces more latency overhead for delivering events from publishers to subscribers. The emerging Software Defined Networking (SDN) creates boundless possibilities to improve the efficiency of event delivery because of its centralized control and customized programmability. In this paper, we propose a topic-oriented bucket-based fast multicast routing to improve the efficiency of delivering events in SDN-like publish/subscribe middlewares. First, we design an SDN-like publish/subscribe middleware hierarchical architecture with an implementation framework in SDN controller to deliver events. Topic encoding, topic prefix matching, and the subscription coverage relationships between topics are considered to reduce the number of flow entries and improve the matching abilities of SDN switches. Then, a topic-oriented multicast tree construction algorithm is proposed to build publish/subscribe overlay networks with the minimal total link delay of event transmission and minimal switches in SDN controllers to deliver events fast. A topic-oriented bucket-based multicast forwarding algorithm is designed to achieve efficient multicast forwarding in SDN switches. Finally, experiments are conducted to verify that our construction algorithm has the minimal total delay of event transmission and our bucket-based multicast forwarding algorithm is effective.

Narrow band Internet of Things (IoT), based on legacy Long Term Evolution (LTE) system, is a hot cellular technology to support sensors and controllers applications. However, its paging capacity is insufficient if legacy paging mechanism is employed, due to the contradiction between the massive devices and the limited physical band resources. In this paper, a more efficient paging message is designed based on the binary tree, to significantly reduce the message size for enough paging capacity. We propose to indicate a set of value ranges encompassing the paged User Equipment (UE) identities, rather than to list all the paged UE identities as in legacy LTE system. It is verified by theoretical analyses and numerical simulations that the proposed paging message outperforms the existing approaches in statistical criteria.

In some special circumstances, e.g. tsunamis, floods, battlefields, earthquakes, etc., communication infrastructures are damaged or non-existent, as well as unmanned aerial vehicle (UAV) cluster. For the communication between people or UAVs, UAVs or mobile smart devices (MSDs) can be used to construct Mobile Ad Hoc Networks (MANETs), and Multipath TCP (MPTCP) can be used to simultaneously transmit in one TCP connection via multiple interfaces of MSDs. However the original MPTCP subpaths creating algorithm can establish multiple subpaths between two adjacent nodes, thus cannot achieve true concurrent data transmission. To solve this issue, we research and improve both the algorithm of adding routing table entries and the algorithm of establishing subpaths to offer more efficient use of multiple subpaths and better network traffic load balancing. The main works are as follows: (1) improve multi-hop routing protocol; (2) run MPTCP on UAVs or MSDs; (3) improve MPTCP subpaths establishment algorithm. The results show that our algorithms have better performance than the original MPTCP in achieving higher data throughput.

This paper proposes a micro niche evolutionary algorithm (MNEA) with lower-dimensional-search crossover for optimisation problems with constraints. The best individual in each niche is picked out and all those picked individuals compose the breeding pool of the evolutionary algorithm. Crossover operator of the algorithm searches a lower dimensional space which is determined by the parent points. Both the niche technique and the crossover technique are favourable to enhance the performance of the algorithm. The new algorithm has been tested by the 24 constrained benchmark problems and the results show that it works better than or competitive to any known effective algorithm. Notably, using this new algorithm to solve a well-known engineering problem (pressure vessel problem), its result is much better than that of any other known algorithm.