The goal of 6G is to make far-reaching changes in communication systems with stricter demands, such as high throughput, extremely low latency, stronger security, and ubiquitous connectivity. Several promising techniques, such as reconfigurable intelligent surfaces (RISs), have been introduced to achieve these goals. An RIS is a 2D low-cost array of reflecting elements that can adjust the electromagnetic properties of an incident signal. In this paper, we guarantee secrecy by using an irregular RIS (IRIS). The main idea of an IRIS is to irregularly activate reflecting elements for a given number of RIS elements. In this work, we consider a communication scenario in which, with the aid of an IRIS, a multi-antenna base station establishes a secure link with a legitimate single-antenna user in the presence of a single-antenna eavesdropper. To this end, we formulate a topology-and-precoding optimization problem to maximize the secrecy rate. We then propose a Tabu search-based algorithm to jointly optimize the RIS topology and the precoding design. Finally, we present simulation results to validate the proposed algorithm, which highlights the performance gain of the IRIS in improving secure transmissions compared to an RIS. Our results show that exploiting an IRIS can allow additional spatial diversity to be achieved, resulting in secrecy performance improvement and overcoming the limitations of conventional RIS-assisted systems (e.g., a large number of active elements).

Software-defined networking (SDN) is the key technology to enable network softwarization by offering a programable and flexible network control capabilities. In order to dynamically manage and reconfigure the underlying network through SDN, network-based monitoring functionality needs to be in place. However, existing network monitoring schemes are normally heavyweight which can cause substantial monitoring overhead when dealing with entire network infrastructure and complex policies. Such a limitation can be critical in a software-based network system that enables the construction of multiple networks with various network policies designed by a network operator. In this article, we propose a new lightweight monitoring mechanism referred to as Active-port Aware Monitoring (APAM) in order to support the monitoring of complex networks with substantially reduced overhead. APAM typically monitors active ports which are the switch ports utilized by current flow rules. These active ports are dynamically monitored with reconfigurable monitoring intervals according to their port utilization. The measurement results show that APAM adapts varying traffic route due to a change of flow rules and also adjusts its monitoring performance according to network traffic dynamicity, which reduces the monitoring overhead and also improves monitoring accuracy.

The advent of Programming Protocol-independent Packet Processors (P4) enables the programmability of data planes, which provides not only further flexibility but also the possibility of the emergence of new features. With programmable data planes, network monitoring functionalities can be evolved beyond the conventional mechanism of Software-Defined Networks (SDN) which is polling-based monitoring based on OpenFlow. Although the polling-based method is easy and simple to collect monitoring information, it can cause substantial monitoring overhead on both the controller side and the switch side. Unlike the OpenFlow-based SDN which has one option to collect pre-defined information using the polling-based method, monitoring performance can be improved by applying new monitoring approaches based on P4. In this paper, a novel mechanism referred to as P4-based Proactive Monitoring (PPM) is proposed in order to enhance the efficiency of monitoring collection operations. PPM scheme adopts a proactive approach which allows programmable switches to proactively forward monitoring information to the controller after the controller enables PPM. The measurement results show that PPM can not only enhance the efficiency of collecting monitoring information by applying a proactive mechanism but also minimize the general monitoring overhead compared to the polling-based method.

This letter proposes a new receiver-based retransmission scheme for efficient retransmission with TFRC. The proposed scheme consists of an adaptive packet loss (APL) detection method and a receiver-based retransmission mechanism that efficiently accomplishes retransmission. Simulation results show that the proposed scheme not only improves effective retransmission but also reduces unnecessary retransmissions.