We propose a Reinforcement Learning (RL) framework for hybrid truck-drone Last-Mile Delivery (LMD), where drones launch from a truck and either rendezvous with it or return to the depot after serving customers, subject to vehicle range limits and customer-defined deadlines. Deliveries completed after the latest allowable service time are treated as deadline violations (lateness) and are penalized in the objective. To provide an exact reference, a Mixed Integer Linear Programming (MILP) model is formulated. It serves both as a benchmark for evaluating the RL approach and as a practical method when the delivery set is small or when minimizing lateness is the primary objective, since the exact MILP solution is guaranteed to be optimal but become computationally expensive to solve as problem size grows due to the combinatorial increase in routing and coordination possibilities. The RL method is introduced as a scalable alternative for larger hybrid truck-drone deployments because it maintains practical computation times through iterative learning and avoids the exponential growth in solving effort associated with exact optimization. The RL framework employs an$\epsilon $-greedy policy with decay and a reward structure that mirrors the MILP objective. Traffic congestion is incorporated through a scaling matrix that adjusts truck travel times on road segments, while drones remain unaffected due to aerial operation. RL is further benchmarked against Genetic Algorithm (GA) and Particle Swarm Optimiztion (PSO), which are also formulated to align with the same MILP objective to ensure a consistent basis for comparison. Results show that the RL component scales more efficiently with increasing delivery size while maintaining competitive solution quality.

Closed-loop Distributed Denial-of-Service (DDoS) mitigation in Fifth Generation (5G) networks must balance attack blocking with operational safety by minimizing collateral damage to benign users. Network operators using the Network Data Analytics Function (NWDAF) face a dilemma: existing Machine Learning (ML)-based security solutions provide binary classifications but lack a mechanism to translate model outputs into quantifiable, proportional, and automated mitigation actions. This paper proposes a two-stage management framework that maps network analytics to graduated mitigation decisions using a risk-calibrated decision gate and severity-based policy thresholds. First, Isotonic Regression calibrates model outputs and triggers mitigation only for high-confidence detections, reducing false-positive harm. Second, for admitted threats, the Dynamic Mitigation Severity Score (DMSS) quantifies severity by aggregating normalized Shapley Additive exPlanations (SHAP) contributions of key 5G features. Thresholds optimized to minimize benign terminations select one of three actions: Terminate, Throttle, or Monitor. Experiments on a public 5G DDoS testbed show that, unlike deep learning baselines prone to severe collateral damage, the framework maintains high threat coverage while nearly eliminating benign terminations. Calibration further reduces Expected Calibration Error (ECE) and improves probability reliability. The DMSS ranks volumetric floods as the most severe attacks, and sensitivity analysis shows stable policy thresholds across operating points. The resulting 3rd Generation Partnership Project (3GPP)-aligned framework supports closed-loop mitigation and explicit control of the trade-off between security coverage and operational safety in 5G/Beyond 5G (B5G) networks.

The IPv6 Routing Protocol for LLNs (RPL) is fundamental to the Internet of Things (IoT), providing essential routing capabilities for devices operating in constrained environments. At the heart of RPL’s efficiency is the Trickle Algorithm (TA), designed to optimize the dissemination of control messages across networks, balancing timely updates with the imperative to conserve bandwidth and energy. This paper focuses on validating the implementation of the TA within the Latest version of Contiki-OS (Contiki-NG), a leading experimental platform for IoT networks. By comparing the results of theoretical models with practical simulations of Contiki-NG, we aim to determine the reliability of the Contiki-NG representation of the TA behaviour. Our analysis reveals a high degree of agreement between theoretical expectations and simulated results, underscoring Contiki-NG’s robustness as a simulation tool for IoT research. The findings affirm the precision of Contiki-NG implementation and highlight the platform’s value in facilitating the development and testing of IoT protocols. By ensuring the reliability of these simulations, our work strengthens the confidence of the IoT research community in using Contiki-NG as a foundation for exploring innovative solutions to the unique challenges of IoT networks.

Routing discovery is a pivotal component of the communication stack in low-power and lossy networks (LLNs). The IPv6 routing protocol for LLNs, termed RPL, has been recently standardized to provide routing discovery in a wide range of LLN-based deployments realizing the Internet-of-Things (IoT) vision. RPL was mainly designed with the assumption that the predominant traffic flow would be gathering data toward a single destination, typically the root node. However, node-to-node (N2N) communication, where the root is neither a source nor destination, is a prime requirement in most of the LLN-based applications, such as actuating, decision making, and controlling applications. RPL in its current form does not cater well to such applications where there is a good number of inward N2N traffic flows. In this article, we propose a hybrid routing mechanism based on RPL for high N2N communications in LLNs referred to by HRPL. HRPL is implemented on Contiki and evaluated through extensive simulations on Cooja. HRPL is fully backward compatible with RPL where HRPL and RPL nodes can work together seamlessly in a hybrid network. Results show that HRPL provides a considerable improvement in the packet delivery ratio relative to the standardized RPL-based modes and to the RPL-based opportunistic routing approach. While HRPL requires a slightly larger memory footprint more than that for RPL, HRPL manages to significantly reduce the control plane packets, number of hops, and MAC transmissions needed to successfully deliver N2N data packets. Accordingly, this is translated to lower packet delay and less energy consumption.

Cloud computing is an essential technology for the future of the Information Technology (IT) industry. However, the cloud security level is identified as the biggest challenge facing cloud providers and a major concern for cloud adopters. Economic Denial of Sustainability (EDoS) attack is one of the major threats targeting the cloud. The EDoS attack exploits the cloud elasticity and auto scaling features to charge a cloud adopter bill an excessive amount of cost leading to large-scale service withdrawal or bankruptcy. A novel reactive approach referred to as the EDoS Attack Defense Shell (EDoS-ADS) is proposed to mitigate EDoS attacks while taking into account most of the existing mitigation techniques drawbacks. Specifically, the EDoS-ADS has the ability to identify the legitimacy of clients even if they belong to a Network Address Translation (NAT) based network. Thus, EDoS-ADS is the first known technique that effectively prevents an EDoS attack from blocking an entire NAT-based network from accessing the cloud. The EDoS-ADS effectiveness in terms of response time, CPU utilization, throughput, and cost is evaluated using a CloudSim simulator. The simulation results show that EDoS-ADS outperforms other mitigation techniques, and successfully differentiates between legitimate and attacker clients even when they belong to the same NAT-based network.

Time synchronization plays an important role in distributed systems. Distributed wireless sensor networks (WSN) often require accurate time synchronization for coordination and data reliability. But precision of time synchronization is limited to scope and criticality of the application. Energy, lifetime and time synchronization are important parameters of any wireless sensor network. Flooding Time Synchronization Protocol (FTSP) and Recursive Time Synchronization Protocol (RTSP) are two state of the art protocols for time synchronization in WSNs. In this paper, a comparative analysis of both protocols under two different topologies i.e. bus and tree, using message count as performance parameter. Xbee Pro and Arduino Mega are used for communication and logical design implementation of both protocols, respectively.

ABSTRACT The Internet is an interconnection of autonomous systems (ASes) that are mostly controlled by Internet service providers (ISPs). ASes use Border Gateway Protocol (BGP) to communicate routing information in the form of reachability paths. However, BGP does not guarantee that the advertised reachability paths will be exactly followed. As a result, traffic belonging to a specific network can be intentionally dropped as it is routed by BGP through a malicious ISP; a behavior we define asInternet access denial. The impact of Internet access denial, especially when performed by higher‐tier ISPs, is significant. In this work, network address translation (NAT) is used as a solution to overcome the Internet access denial problem by hiding the traffic identity. The proposed solution is scalable to fit large networks, by using pools of IP addresses across several NAT routers. Moreover, the proposed solution addresses the server reachability problem that is associated with NAT routers by introducing a novel approach. The performance degradation of introducing NAT is significantly small as shown by our experiments' results. Copyright © 2012 John Wiley & Sons, Ltd.

Multiple input multiple output (MIMO) - Orthogonal Frequency Division Multiple Access (OFDMA) systems have great potential for providing high spectral efficiency due to its integrated space-frequency and multi-user diversity. In this work a dynamic resource allocation scheme has been devised for MIMO-OFDMA systems in a downlink scenario. The scheme optimizes the power distribution, guarantees each user its desired quality of service (QoS), and ensures strict level of fairness to users. The available channel state information at the base station (BS) is utilized in order to help these practical schemes improve system performance, as well as satisfy various QoS constraints. The simulation results obtained show that the proposed scheme satisfies proportional data rate constraints in strict sense and achieves high system capacities.

A Mobile Ad-hoc NETwork (MANET) is an infrastructureless network consisting of self-configuring mobile nodes connected by wireless links. Nodes rely on each other to store and forward packets. Most of the proposed MANET protocols assume cooperative and friendly network context, and do not address security issues. Furthermore, MANETs are highly vulnerable for passive and active attacks because of their open medium, rapidly changing topology, lack of centralized monitoring. Encryption and authentication solutions, which are considered as the first line of defense, are not sufficient to protect MANETs from packet dropping attacks. Most of the current Intrusion Detection Systems (IDSs) for MANETS rely on the Watchdog technique. In this research we study the behavior of this technique and propose a novel mechanism, named: Adaptive ACKnowledgment (AACK), for solving two significant problems: the limited transmission power and receiver collision. This mechanism is an enhancement to the TWOACK scheme where its detection overhead is reduced while the detection efficiency is increased. NS2 is used to simulate and evaluate the proposed scheme and compare it against the TWOACK and Watchdog methods. The obtained results show that the new AACK scheme outperforms both of the TWOACK and Watchdog methods in terms of network packet delivery ratio and routing overhead.

The 3rd Generation Partnership Project (3GPP) has adopted an interworking architecture between Universal Mobile Telecommunication System (UMTS) and Wireless Local Area Networks (WLANs). This architecture imposes a set of security requirements on subscribers connecting from within interworked WLANs to be able to access their 3G home packet-switched services. Providing seamless handoff and session continuity of ongoing communication is a critical task in UMTS/WLAN integrated networks. However, the 3GPP does not specify how mobility can be supported. This paper provides a performance evaluation for the three candidate solutions: Mobile IP (MIP), Session Initiation Protocol (SIP), and mobile Stream Control Transmission Protocol (mSCTP) that may be used to provide session continuity in the integrated network. The vertical handoff delay figure is analyzed using simulations for different WLAN speeds and its major components due to the involved signaling procedures are quantified. The results are derived from our developed OPNET based simulation model that accounts for the detailed prescribed signaling procedures as per the related standards and Request for Comments (RFCs) documents, and the main network entities in the adopted architecture. The presented analysis provides insight into the potential performance bottlenecks in the integrated network. Major findings of the work show that the security related signaling and the signaling pertaining to obtaining a new Internet Protocol (IP) address, each contribute about 40% of the total delay for all the three solutions. Enhancements targeting these procedures will help reduce the overall delay while supporting seamless handoff between the two networks.

It is generally hard to find the optimal solution for sub-channel and power allocation for a multiuser Orthogonal Frequency Division Multiplexing (OFDM) system that maximizes the overall system capacity given the proportional rate constraint. Most existing solutions either utilize a suboptimal sub-channel allocation and attempt to compute the optimal power allocation or assume uniform power distribution among sub-channels and attempt to optimize using the sub-channel allocation. It is observed that derived solutions do not necessarily satisfy the proportional rate constraint, also referred to as the fairness constraint, supplied in the problem formulation. This paper proposes an iterative algorithm that computes the optimal power allocation for a given sub-channel allocation scheme. Unlike previous solutions, the proposed solution does not make any assumptions regarding the channels or regarding the proportionality constants. Furthermore, the proposed solution satisfies the proportional rate constraint in the strictest sense and therefore can provide absolute or hard rate guarantees as opposed to soft ones as the case for previous algorithms. Presented numerical example, shows that the our algorithm outperforms the original optimal power allocation algorithm and achieves strict satisfaction of the fairness constraint.

Total power of the ongoing traffic is a key element in most RRM functions, i.e. power control, call admission control (CAC), handoff control, load control, etc. An efficient RRM procedure should be able to manage all these functions efficiently which cannot be achieved without accurately characterizing the total traffic power. Nevertheless, all the proposed solutions to describe the system capacity have been developed under a set of assumptions that may or may not be valid in a practical CDMA network. Furthermore, the presented solutions to this problem are based on heuristics or simplified analytical models to simplify the computations complexity and, hence, do not accurately represent the system performance. This paper presents a novel model for characterizing the total downlink traffic power for multi-rate DS-CDMA systems. The outage probabilities are calculated as an example application of the derived model.

Mobile IP is one of the popular mobility solution and a viable candidate for the Beyond 3rd Generation (B3G) networks such as the integrated 3rd Generation Universal Mobile Telecommunications System (UMTS) and the Wireless Local Area Networks (WLANs). Mobile IP has many configuration and enhancements that are proposed by IETF such as the Care-of-Address (CoA), Collocated CoA Mobile IPv6, and route optimizations. In this paper, we present a side-by-side performance evaluation and comparisons of the UMTS to WLAN handoff delay that results from using each configuration in the lately adopted UMTS/WLAN interworking architecture by 3GPP. In addition, we analyze the delay components due to 3GPP security and Internet protocol integration requirements. Simulation results show that under low network loading all configurations yield similar performances. However, Mobile IP with IPv6 configuration is more sensitive for network loads and wireless access speeds. In fact, it produces the highest delay figures at high load. Moreover, 3GPP security procedures contribute to more than 60% of the handoff delay for all the configurations.

Fast Fourier transform (FFT) is used successfully in computing the Fourier descriptors which are used in object and character recognition. In this article, an Arabic character recognition algorithm using modified fourier spectrum (MFS) is presented. Ten descriptors are estimated from the Fourier spectrum of the character contour by subtracting the imaginary part from the real part (and not from the amplitude of the Fourier spectrum as is usually the case). Ten MFS descriptors are extracted and used for the recognition of Arabic characters. Experimental results using 10 MFS descriptors resulted in an average recognition rate of 95.9%. The analysis of the sparse matrix indicates that the major part of the errors is due to few similar characters. The new technique, based on MFS descriptors, was compared with the Fourier descriptors calculated from the amplitude of the FFT spectrum. Experimental results have shown that the MFS-based technique is faster to compute than the FFT-based technique. However, the Fourier descriptors, initially, have a better recognition rate than MFS descriptors (96.9% vs. 95.9%). Using the holes' and dots' features to resolve the problematic characters reduces the error rate of the MFS technique more than that of the Fourier descriptor technique. This article introduced MFS-based features that are faster to compute than Fourier descriptors and have fewer errors utilizing the dots and holes features of Arabic characters. Both techniques may be used in combination or in a multi-classifier system to enhance the Arabic recognition system rate.

Packet reservation multiple access (PRMA) can be considered as a merge of slotted ALOHA protocol and time division multiple access (TDMA) protocol. Independent terminals transmit packets to base station by contending to access an available time slots. A terminal that succeeds in reserving a certain time slot keeps on this reservation for transmitting its subsequent packets. Speech activity detection is used in PRMA to improve system capacity. In this work we propose a simpler contention mechanism that does not depend on a predetermined permission probability as in the original PRMA. In the new method, terminals select the contention slot uniformly from the pool of remaining free slots in the current frame. We evaluate the performance of the new contention mechanism in terms of various metrics including maximum number of carried voice calls and packet delays for a given acceptable drop rate of voice packets. We show that the new mechanism is superior to that of the original PRMA for loaded systems and is expected to be insensitive for traffic source burstiness.

The wide-band code division multiple access (WCDMA) based 3G and beyond cellular mobile wireless networks are expected to provide a diverse range of multimedia services to mobile users with guaranteed quality of service (QoS). The main contribution of this paper is to design and analyze a novel dynamic priority call admission control (DP-CAC) that can be able to achieve a better balance between system utilization and quality of service provisioning. More importantly, the analytical model of this system is valid for the real-time (RT) and non-real-time (NRT) calls having different bit- rate ( i.e. different bandwidth requirements), channel holding time , time out, and Eb/Norequirements. Its performance is compared with another two call admission control strategies, referred to as the complete partitioning CAC (CP-CAC) and the queuing priority CAC (QP-CAC). The DP-CAC analytical model can be used easily to derive the analytical model of the QP-CAC and to the CP-CAC. We present numerical examples to demonstrate the performance of the proposed CAC algorithms and we show that analytical and simulation results are in total agreement. Results also indicate the superiority of DP-CAC as it is able to achieve a better balance between system utilization and quality of service provisioning.

This paper addresses one of the potential graph-based problems that arises when an optimal shortest path solution, or near optimal solution is acceptable, namely the Single Source Shortest Path (SSP) problem. To this end, a novel Heuristic Genetic Algorithm (HGA) to solve the SSSP problem is developed and evaluated. The proposed algorithm employs knowledge from deterministic techniques and the genetic mechanism to achieve high performance and allow consistent convergence. In addition, the proposed HGA is implemented and evaluated using a developed software tool that is easily amenable for future extensions and variations of our HGA. The schema introduced in this proposal depends on starting with initial population of candidate solution paths constraints as an alternative of a randomly generated one. To preserve the high performance candidate solutions, the HGA also uses a new heuristic order crossover (HOC) operator and mutation (HSM) operator to keep the search limited to feasible search domain. Simulation results indicate that the developed HGA is highly efficient in finding an optimal also quantify the effect initial population size and the increase of generation numbers.

Sharing of 3G network infrastructure among operators offers an alternative solution to reducing the investment in the coverage phase of WCDMA. For radio access network (RAN) sharing method each operator has its own core network and only the RAN is shared. Without an efficient RRM, one operator can exhausts the capacity of others. This paper proposes and analyzes an efficient uplink-scheduling scheme in case of RAN sharing method. We refer to this new scheme as multi-operators code division generalized processor sharing scheme (M-CDGPS). It employs both adaptive rate allocation to maximize the resource utilization and GPS techniques to provide fair services for each operator. The performance analysis of this scheme is derived using the GPS performance model. Also, it is compared with static rate M-CDGPS scheme. Numerical and simulation results show that the proposed adaptive rate M-CDGPS scheduling scheme improves both system throughput and average delays.

Increasing speed of hardware device and versatile functionalities of small equipments e.g. laptop, PDA etc. are introducing various voice oriented applications with mobility. Like other computer networks, in Mobile Ad-hoc Network (MANET) voice transmission is very much demanding and necessary. In this research paper we have a feasibility analysis of voice transmission over MANET. Since voice applications consume more energy than typical applications, we use an energy aware routing protocol known as WEAC for the study. We have a comparative study among several audio codecs (G. 711, G. 729 and G 723.1) and by simulation we show that the G 729 codec is suitable to use for voice transmission over MANET in terms of latency. We show that it is possible to launch voice transmission with acceptable quality over MANET using G 729 and WEAC protocol.

Much research is going on to enhance the distributed coordination function (DCF) of the IEEE 802.11 as to support quality of service (QoS) requirements needed by real time services. This is achieved by enhancing the throughput and delay characteristics of the DCF. The throughput of DCF degrades in high loaded situations. Most analyses study the network in a saturation state where each station is always transmitting. In this paper, we propose and evaluate a novel and simple algorithm to enhance the backoff procedure of DCF and provide QoS differentiation. The new algorithm attempts to adoptively control the DCF contention window in order to alleviate congestion through an easy to set parameter referred to as q. In our study, we evaluate the DCF and the new under non saturation condition where each station receives frames from upper layers according to a Poisson process. Simulation results indicate that better throughput and delay figures are obtained using the proposed algorithm. Moreover, the proposed algorithm shows less sensitivity to the number of active nodes especially for low number of active nodes. This feature is very important for WLAN service provider.

The characterization of downlink traffic power is an important issue for the design of efficient call admission control (CAC) and radio resource management (RRM) procedures. In this paper an analytic model is presented to solve the power-rate assignment problem and to approximate the probability distribution function for the cell site downlink traffic power for a multi-rate CDMA based network. The model accounts for both the radio frequency propagation model and the large signal variations represented by the signal shadowing process. As one application, the model is utilized in calculating the probability of cell site power outage as a function of the system rates and the number of supported bursts. The study compares between model based results and results obtained using conventional Monte- Carlo simulations. Comparisons indicate the model provides an adequate approximation for outage probability figure.

For current and next 3G and beyond wideband code-division multiple access (WCDMA) cellular networks, sharing the radio access network has become an important issue for 3G mobile operators. Sharing of network infrastructure among operators offers an alternative solution to reducing the investment in the coverage phase of WCDMA. In radio access network (RAN) sharing method, which is our focus in this study, each operator has its own core network and only the RAN is shared. It implies that multiple operators fully share the same RAN. This paper tackles an uplink efficient scheduling to provide maximum system throughput and proportional fairness in accordance with operator capacity share through adaptive resource allocation scheme. We refer to this new scheme as multi-operators code division generalized processor sharing scheme (M-CDGPS). It employs both adaptive rate allocation to maximize the resource utilization and GPS techniques to provide fair services for each operator. The simulation results show that the proposed scheme improves both system utilization (throughput) and average delays.

In current and next 3G and beyond mobile wireless systems, sharing the radio access network has become an important issue for 3G mobile operators. Sharing network infrastructure amongst operators offers an alternative solution to reduce the investment in the coverage phase of WCDMA, allows increased coverage, reduces time to market, and allows earlier user acceptance for WCDMA and its related services. In this paper a novel radio resource management strategy known as adaptive partitioning with borrowing (APB) is proposed to cope with the implied new architectural changes. This strategy is devoted to achieve an efficient usage of the available pool of radio resources while satisfying the required quality of service (QoS) in heterogeneous traffic 3G wireless networks. Grade of service (GoS) and resources utilization are considered in this study to evaluate the network performance. Simulation results indicate that the proposed APB resource allocation provides higher resource utilization under all load conditions leading in turn to increased revenue. Moreover it provides the best balance between the system utilization and the required QoS

CDMA network is well known for its interference- limited performance. Minimizing the interference and achieving high throughput along with fairness is still the objective of many research efforts. This paper investigates this issue through exploring the relation between scheduling interval and power assignment on the performance of downlink slotted CDMA networks for different scheduling criteria. The proposed scheduler is a power based scheduler. It shall assign "channels" to contending users based on their power requirements and QoS constraint. The scheduler will choose first the user that requests the minimum power level as far as its maximum delay threshold is not reached and it continues in serving minimum power users until all allocated power or set of codes is exhausted. The scheduler is examined for different scheduling intervals, delay thresholds and different levels of burstiness. We compare through system level simulations of the downlink channel the enhancements provided by the proposed scheme with Power Earliest Deadline First (PEDF). The simulation results show outstanding performance for the proposed algorithm in terms of higher throughput, much lower packet delay and comparable fairness index figures under a wide range of traffic loads.

An adaptive polling scheme for multiple access in a broadband wireless local area networks (LANs) is proposed. It is designed to accommodate asynchronous transfer mode (ATM) traffic with a large and variable range of bit rates. The radio architecture is microcellular, with switched sectored-beam antennas and a small frequency reuse factor. Features of the multiple access scheme include polling rate depending on a terminal's average bit rate, fixed-length frames divided into segments corresponding to base antenna sectors, and automatic-repeat-request (ARQ) for error control, combined with randomized sector segment ordering. The steady-state performance (cell loss, call blocking and dropping probabilities, waiting time, and buffer occupancy) are evaluated by simulation for an open indoor environment, and for handoff, ARQ, and simple power control enhancements; focusing mainly on the effects of the propagation and interference conditions.

An adaptive polling scheme for multiple access in a broadband wireless local area networks (LANs) is proposed. It is designed to accommodate asynchronous transfer mode (ATM) traffic with a large and variable range of bit rates. The radio architecture is microcellular, with switched sectored-beam antennas and a small frequency reuse factor. Features of the multiple access scheme include polling rate depending on a terminal's average bit rate, fixed-length frames divided into segments corresponding to base antenna sectors, and automatic-repeat-request (ARQ) for error control, combined with randomized sector segment ordering. The steady-state performance (cell loss, call blocking and dropping probabilities, waiting time, and buffer occupancy) are evaluated by simulation for an open indoor environment, and for handoff, ARQ, and simple power control enhancements; focusing mainly on the effects of the propagation and interference conditions.