This paper investigates movable-antenna (MA) enabled intelligent reflecting surface (IRS)-aided integrated sensing and communication (ISAC) systems, where an MA-enabled base station (BS) serves multiple downlink communication users (CUs) and performs direction-of-arrival (DOA) estimation for a target. The goal is to improve communication performance while satisfying a Cram´er–Rao bound (CRB) requirement for sensing. To balance performance and computational complexity, two MA control schemes including element-wise and array-wise control schemes are considered, allowing antenna elements to adjust their positions individually or in groups as arrays. Two communication rate performance metrics including the sum-rate and minimum-rate are considered to evaluate the throughput and fairness of multi-user communications. To solve the non-convex optimization problems, we develop a product Riemannian manifold optimization (PRMO) method that constructs a product Riemannian manifold space (PRMS) and integrates a penalty method with a Riemannian Broyden–Fletcher–Goldfarb–Shanno (RBFGS) algorithm. Simulation results validate the effectiveness of the proposed PRMO method and show that MA offers advantages over conventional fixed-position antenna (FPA) in IRS-aided ISAC systems. Moreover, simulation results show that while the element-wise control scheme yields the best overall performance, the array-wise control reduces the execution time by over 60% while sacrificing no more than 5% of the achievable communication rate compared with the element-wise control.

Intelligent reflecting surface (IRS) and movable antenna (MA) technologies have been proposed to enhance wireless communications by creating favorable channel conditions. This paper investigates the joint beamforming and antenna position optimization for MA-enabled IRS (MA-IRS)-aided multi-user multiple-input single-output (MU-MISO) communication systems, where the MA-IRS is deployed to aid the communication between the MA-enabled base station (BS) and user equipment (UE). In contrast to conventional fixed position antenna (FPA)-enabled IRS (FPA-IRS), the positions of the reflecting elements of the MA-IRS can be controlled to enhances the wireless channel. To verify the system’s effectiveness and optimize its performance, we formulate a sum-rate maximization problem with a minimum rate threshold constraint for the MU-MISO communication. To tackle the non-convex problem, a product Riemannian manifold optimization (PRMO) method is proposed for the joint optimization of the beamforming and MA positions. Specifically, a product Riemannian manifold space (PRMS) is constructed and the corresponding Riemannian gradient is derived for updating the variables, and the Riemannian exact penalty (REP) method and a Riemannian Broyden-Fletcher-Goldfarb-Shanno (RBFGS) algorithm is exploited to obtain a feasible solution over the PRMS. Simulation results demonstrate that compared with the conventional FPA-IRS-aided communications, the reflecting elements of the MA-IRS can move to the positions with higher channel gain, thus enhancing the system performance. Furthermore, it is shown that optimizing the positions of the reflecting elements brings higher performance gain than controlling the phase shifts of the IRS, and integrating MA with IRS leads to higher performance gains compared to integrating MA with BS.

Driven by intelligent reflecting surface (IRS) and movable antenna (MA) technologies, movable IRS (MIRS) has been proposed to improve the adaptability and performance of conventional IRS, enabling flexible adjustment of the IRS reflecting element positions. This paper investigates MIRS-aided integrated sensing and communication (ISAC) systems. The objective is to minimize the power required for satisfying the quality-of-service (QoS) of sensing and communication by jointly optimizing the MIRS element positions, IRS reflection coefficients, transmit beamforming, and receive filters. To balance the performance-cost trade-off, we proposed two MIRS schemes: element-wise control and array-wise control, where the positions of individual reflecting elements and arrays consisting of multiple elements are controllable, respectively. To address the joint beamforming and position optimization, a product Riemannian manifold optimization (PRMO) method is proposed, where the variables are updated over a constructed product Riemannian manifold space (PRMS) in parallel via penalty-based transformation and Riemannian Broyden–Fletcher–Goldfarb–Shanno (RBFGS) algorithm. Simulation results demonstrate that the proposed MIRS outperforms conventional IRS in power minimization with both element-wise control and array-wise control. Specifically, with different system parameters, the minimum power is achieved by the MIRS with the element-wise control scheme, while suboptimal solution and higher computational efficiency are achieved by the MIRS with array-wise control scheme.

Adaptive filtering faces significant challenges in handling complex non-Gaussian noise, while graph signal processing (GSP) excels at processing data with intricate structures. This brief introduces a novel method for solving non-Gaussian noise from the perspective of the graph domain for the first time. Specifically, we develop an online time-varying graph model based on the filter error signal and propose a corresponding graph topology transformation strategy. Utilizing a graph smoothness measure, we introduce a new adaptive filtering cost function, in which the graph Laplacian matrix plays a direct role in the filter update process. Subsequently, we derive the graph smoothness recursive adaptive filtering (GS-RAF) algorithm, rigorously analyze its theoretical performance, and validate its efficacy through simulations and echo cancellation experiments. The corresponding MATLAB (MathWorks, USA) codes of the simulations are publicly available at: https://github.com/smartXiaoz/GS-RAF.git.

In this paper, we focus on the joint beamforming for intelligent reflecting surface (IRS) aided integrated sensing and communication (ISAC) systems, where a multi-antenna base station (BS) performs multi-user multi-input single-output (MU-MISO) communication and radar sensing simultaneously. Specifically, the direction-of-arrival (DoA) estimation is considered as the task of radar sensing, and we aim to optimize the MU-MISO communication while enhancing the estimation accuracy by ensuring a Cramér-Rao bound (CRB) lower bound. First, for the CRB-constrained sum rate maximization problem, we propose a product Riemannian manifold optimization (PRMO) framework to solve the problems without relaxing the objective functions. Specifically, a product Riemannian manifold space (PRMS) is constructed to satisfy the constraints of the precoding matrix and IRS phase shifts, and the constraint of the CRB threshold is tackled by a Riemannian exact penalty (REP) method. A parallel Riemannian Broyden-Fletcher–Goldfarb-Shanno (P-RBFGS) algorithm is derived to update the parameters over the PRMS. Then, considering the fairness of the MU-MISO communication, the PRMO is further extended to tackle the CRB-constrained max-min optimization by maximizing the minimum rate among all users. Simulation results demonstrate that with the same CRB constraint, the PRMO outperforms the existing method in sum rate maximization with lower computational complexity, and the extended PRMO enables the users to obtain approximately equal rates, thus guaranteeing the fairness of the system.

Spiking Neural Networks (SNNs) have shown substantial promise in processing spatio-temporal data, mimicking biological neuronal mechanisms, and saving computational power. However, most SNNs use fixed model regardless of their locations in the network. This limits SNNs’ capability of transmitting precise information in the network, which becomes worse for deeper SNNs. Some researchers try to use specified parametric models in different network layers or regions, but most still use preset or suboptimal parameters. Inspired by the neuroscience observation that different neuronal mechanisms exist in disparate brain regions, we propose a new spiking neuronal mechanism, named learnable thresholding, to address this issue. Utilizing learnable threshold values, learnable thresholding enables flexible neuronal mechanisms across layers, proper information flow within the network, and fast network convergence. In addition, we propose a moderate dropout method to serve as an enhancement technique to minimize inconsistencies between independent dropout runs. Finally, we evaluate the robustness of the proposed learnable thresholding and moderate dropout for image classification with different initial thresholds for various types of datasets. Our proposed methods produce superior results compared to other approaches for almost all datasets with fewer timesteps. Our codes are available at https://github.com/sq117/LTMD.git.

Nodes in a wireless ad hoc network have to support routing using their limited battery power resource. The routing protocol involved should use battery power efficiently for good system performance. For systems where node location information is available, this study proposes an on-demand routing protocol for choosing a route based on maximising the minimum node battery power and minimising the total transmission power required to reach the destination. In addition, the routing protocol proposed is able to restrict control packet flooding during route discovery and pre-empt link breakages because of node mobility. A power and mobility aware optimisation problem is first formulated. For an actual practical implementation, we present a heuristic scheme, Power and Mobility Aware Routing or PMAR protocol. PMAR performs almost as well as the proposed optimisation approach in static networks. In mobile networks, PMAR performs very well in terms of network lifetime, the number of data packets carried within the network lifetime and delay performance. It is shown to be energy efficient, effective in restricting control packet flooding and able to substantially reduce the network overheads caused by link breakages.

In this paper, we propose a topology-based Multicast-Capable (MC) nodes placement heuristic - Power Attenuation Constrained Placement (PACP) in amplifier-less power attenuation constrained all- optical metropolitan area network (AL-MAN). We define a selection function in our algorithm to find the 'best' locations in the network for a given number of MC nodes to achieve good performance in overall cost competitiveness (CC) while ensuring that power constraint is always satisfied. Through our simulation studies, we show that PACP is able to construct power constrained trees with cost close to the optimal cost, and also able to improve the CC as high as 6% compared to latest topology-based algorithm. The simulation results conclude that PACP is cost-resilient for amplifier-less optical multicast networks with small number of MC nodes, and with multicast sessions with low source power output.

This paper addresses the problem of dynamic multicast routing and wavelength assignment in delay constrained wavelength-routed WDM network. Current algorithms focus in minimizing blocking probability or wavelength numbers used, but not on the number of wavelength conversions. Wavelength conversions on either optical or electronics plane are costly and time consuming, hence should be minimized to ensure good transmission quality and manageable cost. In this paper, we proposed an algorithm on generic layered auxiliary graph to construct delay constrained dynamic multicast trees with minimal conversions and low blocking, and compared it with existing optimal algorithms through simulations. The results indicate that our proposed algorithm is able to achieve near optimal performance in terms of blocking, wavelength conversions and delays between source and members.

We propose an efficient heuristic algorithm to rearrange multicast trees proactively in delay constrained dynamic membership multicast networks. The objective is to construct low cost multicast tree with controlled number of disrupted members within a very short rearrangement time when a member joins and leaves the tree. In addition, a heuristic algorithm to obtain near-optimal solution to the problem is introduced as the benchmark. A new performance index to gauge the efficiency of the proposed heuristics more accurately is also introduced. Better performance is obtained when compared with existing methods using simulations.

A simplified parallel step-by-step decoding algorithm is proposed for decoding Reed-Solomon (RS) codes. It uses new method to calculate the determinants of the temporarily changed syndrome matrices, based on the property of these matrices determined in this paper. By using the proposed method, the calculations of the determinants of the temporarily changed syndrome matrices become much simpler and thus the computational complexity of the step-by-step decoding algorithm is significantly reduced.

Distributed lightpath establishment in wavelength- routed networks requires up-to-date link-state information to achieve blocking performance target. Invalid routing and wavelength assignment decisions caused by inaccurate link-state information may degrade network performance significantly as the lightpaths become more and more dynamic. In this paper, we evaluate the performance of periodic link-state update, where link-state information is exchanged between network nodes at regular intervals. By proposing an accurate analytical model as well as by carrying out extensive simulations, we show how different components of network blocking probability are affected by inaccurate information under different traffic loads, and provide insights into the high sensitivity of blocking performance to link- state update interval under light traffic loads. We demonstrate how the sensitivity could be affected by network connectivity as well.

The Ethernet passive optical network (EPON) has recently attracted more attentions from the academic research and industry since it could be a perfect candidate for next generation access networks. Supporting differentiated services is an important issue for service providers to design an EPON system. In this paper, we propose an urgency fair queuing (UFQ) scheme to support DiffServ among multiple users in EPONs. It can achieve fairness by providing better services to best-effort users while guaranteeing the services for QoS users. The simulation results show that the UFQ scheme can effectively provide differentiated services for different classes of traffic

In this paper, we study the benefits of advertising wavelength availability in a distributed lightpath establishment environment by extensive simulations. Various cases with different routing methods, densities of wavelength conversions, and degrees of network connectivity are evaluated. In all these cases, we show that advertising wavelength availability can only improve network blocking performance under light traffic load. In addition, we demonstrate how the performance gain is affected by routing methods, wavelength conversion, and network connectivity.

This paper addresses Multicast-Nodes (MC-nodes) and Wavelength Converting-Nodes (WC-nodes) placement problem in Multicast Optical Virtual Private Network (M-OVPN). This problem is motivated by the high cost incurred in the usage of optical splitters and converters in the VPN due to complexity and power considerations. An analytical model for computing the approximate blocking probability in MOVPN with wavelength conversion has been developed. The placement is determined using our proposed innovative Removal algorithm together with the blocking performance computed. We perform simulation studies of our algorithms using NSFNET. The results show that the Removal heuristic is able to locate the optimal placement location within a much shorter time and with higher efficiency compared to existing heuristic. In addition, we also show the flexibility of the heuristics by introducing the hybrid (Combined Removal) and dual (Concurrent Removal) removal mode.

The problem of how to design a survivable optical network under single and multiple link failures has been studied quite extensively; however, there are few studies on the design of optical networks that could survive single node failures. We design a dynamic wavelength routing scheme that will set up a primary path as well as a node-disjoint shared protection path for each connection using as few wavelength channels as possible by allowing multiple protection paths to share wavelength channels. Sharing full link state information among all network nodes will incur heavy processing overhead and increase routing traffic significantly. We propose a novel scheme that uses three vectors to convey incomplete information of link state. The scheme can be implemented by extending the OSPF protocol. As it is important to network service provider, we also compare the capacity requirement between link failure protection scheme and node failure protection scheme.

Multiple access control is an important issue in Ethernet passive optical networks (EPON). It is needed for traffic from different ONUs to share the upstream channel. The IEEE 802.3ah Ethernet in the first mile (EFM) task force has specified a multipoint control protocol (MPCP) for this purpose. We propose a novel multiple access control scheme consisting of a parameter-based call admission control (CAC) mechanism, the evenly distributed algorithm (EDA), and the bandwidth guarantee polling (BGP) algorithm. Our scheme can guarantee bandwidth for high-demand customers while providing best-effort service to low-demand customers according to the service level agreement (SLA). Simulation results show that the proposed scheme is very efficient.

We investigate timing properties of the timed token protocol that are necessary to guarantee synchronous message deadlines. A tighter upper bound on the elapse time between the token's lth arrival at any node i and its (l + /spl nu/)th arrival at any node k is found. A formal proof of this generalized bound is presented.

A limited-wavelength-interchangeable cross-connect (L-WIXC) is considered in this paper. While a (fully) wavelength-interchangeable cross-connect (WIXC) is functionally equivalent to a conventional switching matrix, the modeling of L-WIXC will differ from that of WIXC due to limitations in the wavelength interchange capability. We propose an analytical model for describing the connection setup in various L-WIXCs. Two methods for evaluating the blocking performances of L-WIXCs based on this model are introduced and applied for the analysis of four classes of L-WIXC.

One of the key issues related to deadline guarantees of synchronous messages in FDDI networks is the feasibility test of synchronous bandwidth allocation (SBA). Much work has been done on how to allocate synchronous bandwidth properly in order to guarantee synchronous messages transmission before their deadlines, and as a result quite a few SBA schemes have been proposed. In contrast, limited research has been done on how to effectively test the feasibility of a given allocation of synchronous bandwidths (i.e., whether or not a given allocation can guarantee the synchronous message set considered), and the existing approach cannot always give an effective test and may even produce wrong testing results. This paper presents an algorithm of polynomial time worst-case complexity which ensures the correctness and effectiveness of the testing for any given synchronous message set with message deadlines equal to periods.

This paper focuses on the use of discrete event simulation techniques for the performance evaluation of FDDI networks interconnected via the ATM WAN. The simulation enables us to obtain relevant data on such performance evaluators as the end-to-end delay and throughput for the traditional TCP/IP traffic over the internetwork. The qualitative analysis provides a basis to formulate the delay and throughput approximations and reveals the intrinsic behaviour of these networks. The detailed network model has been developed in the C language. OPNET, a Unix-based communication systems simulation tool which supports the hierarchical object-oriented model is used in this simulation. The FDDI-ATM internetwork performance results are presented.