Signalling analysis for traffic class dependent routing in packet switched ISL networks

Communication challenges in ad hoc networks arise due to the mobility of nodes, causing frequent changes in connections and locations. Maintaining network equilibrium to prevent node overload and underutilization is crucial. However, imposing static behaviors on nodes to improve performance can lead to delays, especially in core nodes. Addressing these issues, this research proposes the Intermediate Node Traffic Sharing Model (INTSM) for ad hoc networks. INTSM prioritizes congestion control and load balancing during route discovery, aiming to optimize network resource utilization and traffic distribution, thereby reducing packet delays. The model employs dynamic traffic sharing algorithms that consider real-time network conditions, enabling nodes to adjust their behaviour adaptively. This approach minimizes congestion by distributing traffic loads more evenly across the network, preventing bottlenecks at central nodes. Additionally, INTSM incorporates predictive analysis to foresee potential congestion points and reroute traffic proactively, enhancing overall network stability and performance. Extensive simulations demonstrate that INTSM significantly reduces average packet delay and improves throughput compared to traditional routing protocols. The results highlight the model's efficacy in diverse scenarios, including high mobility and varying traffic loads, proving its robustness and scalability. The primary objective of this study is to enhance navigation and equilibrium mechanisms to improve the performance of ad hoc networks, contributing to more reliable and efficient wireless communication systems. The findings of this research have significant implications for the design of future ad hoc networks, particularly in applications requiring high reliability and quick adaptation to changing network conditions, such as disaster recovery, military operations, and mobile sensor networks. By addressing the critical challenges of congestion control and load balancing, INTSM offers a promising solution to enhance the resilience and efficiency of ad hoc networks.

In Network-on-chip design two of the most important performance indices are the average delay of packets and power dissipation. The first depends on the level of congestion of the communication system, the second is strongly influenced by the power dissipated by the links of a network-on-chip (NoC) which accounts for a significant fraction of the overall power dissipated by the on-chip communication fabric. Such fraction becomes more and more relevant as technology shrinks. The selection policy of the output port in the NOC router with adaptive routing function affects both the performance and power dissipation. In fact, generally a NOC with a lower average delay has a lower power dissipation on the links for transmission. The selection policies proposed in the literature have the object or the minimization of the average delay or in some cases the reduction of power dissipation. In this paper we propose a selection policy aimed at minimizing both the average delay and power consumption of the communication system of NoC based architectures. The proposed policy uses a cost function obtained using a Fuzzy Rule Base System (FRBS) with two inputs an one output. Inputs are the level of use of the buffers of the downstream routers, and the link power dissipation of the selected output. The output of FRBS is the cost function. The experimental results, obtained using a cycle accurate NoC simulator for different traffic scenarios, shows that the proposed selection policy outperforms other selection approaches both in terms of average delay and in terms on power dissipation and energy consumption.

Input queuing has become dominant and popular building blocks for high speed crossbar switches with many ports and fast line rates because they require minimum speed-up of memory bandwidth. Input Queued switches with finite Virtual Output Queues guarantees QoS performance in terms of throughput and average delay. A switch performs two functions Queuing and Scheduling. Queue Management algorithm manages the size of the queues and drops packets when necessary or appropriate. Scheduling algorithms determine next packet to transfer and solves conflicts with the switching fabric. Fairness and Starvation are another two properties of IQ switches and it is analyzed in finite VOQ in this works. Fairness performs fair allocation of bandwidth among flows and prevents flows from misbehaving flows. Starvation of VOQ prevents serving High priority queue. The motivation behind this study is to schedule the HoL packets queued in finite VOQs by Framing with Low Latency Queuing (LLQ) and Weighted Fair Queueing (WFQ). This queueing technique of VOQ is measured in terms of throughput and average delay by fair allocation of bandwidth with WFQ and Starvation-free queue with LLQ.

The development of protocol standards and the low cost of wireless equipment increased the number of wireless network installations in public (airports, universities campuses) and private (enterprises, homes) areas all over the world. This research effort examines the IEEE 802.11 protocol that dominates wireless local area networks (WLANs). Specifically, it investigates the performance of the Distributed Coordination Function (DCF) of ΙEEE 802.11 Medium Access Control (MAC) protocol. The objective of this thesis is to contribute in the research for the development of a simple and effective MAC sub-layer for WLANs that utilize the IEEE 802.11 protocol. Mathematical models are developed to calculate the following metrics in order to examine the performance of DCF that use Binary Exponential Backoff (BEB) algorithm: a) average packet delay per backoff stage and probability per backoff stage b) average packet delay, c) packet jitter, d) packet drop probability, e) average packet drop time, f) packet delay distribution, and g) cumulative packet delay distribution. An admission control algorithm is also presented. The proposed mathematical models are a) simple, as expressed with relatively simple mathematical relations, b) accurate, since they are validated by comparing analytical against simulation results and show that the proposed models are fairly accurate, and c) provide results in short period of time. Different scenarios of WLANs are examined to investigate the effect of DCF parameters in performance and to define the system parameters values that improve the performance of the IEEE 802.11 protocol. The analysis of metrics and the application of their outcomes to WLANs contribute in the design and development of more efficient access methods to wireless medium. The main contribution of this thesis is that packet delay is investigated thoroughly as a measure of WLAN performance.%%%%Η ανάπτυξη προτύπων για τα ασύρματα τοπικά δίκτυα σe συνδυασμό μe το χαμηλό κόστος της ασύρματης τeχνολογίας eπέτρeψe την ραγδαία eξαπλωση των ασυρμάτων δικτύων σe κοινόχρηστους και σe ιδιωτικούς χώρους όπως πανeπιστήμια, πλατeίeς, αeροδρόμια, γραφeία eπιχeιρήσeων, οικίeς, κλπ. Η παρούσα διατριβή μeλeτά το πρωτόκολλο ΙEEE 802.11 το οποίο κυριαρχeί στα ασύρματα τοπικά δίκτυα. Eιδικότeρα eρeυνά την απόδοση της κατανeμημένης διαδικασίας πρόσβασης DCF του υποeπιπέδου MAC του ΙEEE 802.11. Σκοπός της παρούσας eρeυνητικής προσπάθeιας eίναι η συμβολή στην έρeυνα για την ανάπτυξη eνός απλού και αποτeλeσματικού υποeπιπέδου πρόσβασης μέσου MAC στα ασύρματα δίκτυα που βασίζονται στο πρωτόκολλο ΙEEE 802.11. Αναπτύσσονται μαθηματικά μοντέλα για τον υπολογισμό των ακόλουθων μeτρικών για την απόδοση της διαδικασίας DCF που χρησιμοποιeί τον αλγόριθμο eκθeτικής οπισθοχώρησης ΒEΒ: α) την μέση καθυστέρηση των πακέτων ανά βαθμίδα οπισθοχώρησης και την πιθανότητα ανά βαθμίδα οπισθοχώρησης, β) την μέση καθυστέρηση των πακέτων, γ) την κατανομή των καθυστeρήσeων των πακέτων, δ) την αθροιστική κατανομή των καθυστeρήσeων, e) την διακύμανση των καθυστeρήσeων των…

The paper presents a new MAC protocol, rate-based headend request control (RHRC), for dual unidirectional bus networks, which overcomes the unfairness of DQDB by allowing each station to generate multiple requests while retaining most of the positive features of DQDB, including 100% bandwidth utilization and low access delay at very low load. In addition, the protocol has two attractive features. Firstly, the transmission mechanism controlling station access to the data channel is able to provide approximately equal opportunity to messages so that they experience almost the same average delay independent of their physical locations and the traffic distribution. Secondly, the bandwidth allocation mechanism can achieve fair bandwidth sharing among stations when the network is overloaded, while maintaining fairness in terms of message delay amongst the underloaded stations. This mechanism also results in a shorter transient period than the bandwidth balancing mechanism of DQDB. Simulation results are included and comparisons are made with DQDB. >

One of the major challenges in long reach passive optical network (LR-PON) is the longer end-to-end traffic delay between the central office (CO) and the end user. This longer delay significantly hampers the quality of services (QoSs) of the optical access networks. The QoSs of the LR-PON are easily affected by delaying or dropping packets as a consequence of parameters such as latency, jitter, bandwidth utilization and packet loss. Most of the studies have only focused on capacity allocation amongst the multiple optical network units (ONUs) of the network by the optical line terminal. Some research also proposed to schedule the packets in multiple threads based on the priority. However, due to the lacking of intra thread scheduling scheme the high priority (HP) data packet still suffering from more delay. In this paper, we propose a decentralized intrathread scheduling scheme that provides lower queuing delay as well as end-to-end packet delay of the HP traffic. The performance measurements involve several scenarios which combine different traffic types, intra ONU scheduling and queuing policies. The goal of this research is to identify the most suitable scenario to provide qualitative services and efficient resource utilization among different traffic types. The performances of the proposed scheme have been analyzed and compared with the existing scheme by numerical simulations. The numerical results proves the advantages of the proposed scheme over the existing one in terms of lower average packet delay of high priority data packets and higher network throughput under varying offered loads.

Performance of shared-channel multihop lightwave networks

Ant Colony Optimization (ACO) is a problem-solving technique inspired by the behavior of real-world ant colony. ACO-based routing also has high potential on balancing the traffic load in the domain of Network-on-Chip (NoC), where the performance is generally dominated by traffic distribution and routing. Since the pheromone in ACO provides both spatial and temporal network information, we find ACO-based routing suitable for reducing the probability of deadlock and its penalty. With the three schemes inspired by the behavior of ants and named as ACO-based Deadlock-Aware Routing (ACO-DAR), our simulation shows that the occurrence of deadlock can be greatly suppressed and the network performance also improves as a consequence. Moreover, ACO-DAR makes use of the existing hardware of the original ACO-based routing, so the area overhead is minor and ACO-DAR is thus cost-effective.

In modern, competitive, and dynamic access networks the underlying bandwidth distribution mechanism has to be capable of understanding user requirements, meeting stringent quality of service (QoS) demands, and satisfying a broad spectrum of user traffic dynamics. Undoubtedly, optical fiber is the dominant transmission medium enabling practical and cost-effective optical infrastructures in the last mile. Passive optical networks (PONs) represent one of the most promising player towards the fiber to the home (FTTH) vision allowing users to experience high quality, demanding multimedia services and applications. The 10-gigabit-capable passive optical network (XG-PON), one of the latest PON standard, incorporates a set of profound conditions a contemporary PON should ensure. Fairness provisioning constitutes one of the most critical features a PON should provide. However, ensuring fairness in an access network with numerous different users, requesting multiple traffic flows in any time, is not a straightforward task. In this work, we focus on the fairness issue by devising an adaptive, efficient, and fair dynamic bandwidth allocation (DBA) scheme called Insistent FAIr STrategy prOcesS (IFAISTOS). IFAISTOS investigates and maintains user traffic profiles. Overloaded users are carefully treated by gaining greater granting windows than other users; however bandwidth monopolization is prevented. Fairness is ensured for all users in terms of traffic load and average delay. A steering, adaptive mechanism records user traffic profiles by changing and defining bandwidth weights proportional to individual traffic needs. Extensive simulation results reveal the efficacy of the proposed DBA in terms of fairness and average packet delay.

An integrated scheduling and buffer management scheme for input queued switches with finite buffer space

One unique architectural benefit of Named Data Networking (NDN) is adaptive forwarding, i.e., the forwarding plane is able to observe data retrieval performance of past Interests and use it to adjust forwarding decisions for future Interests. To be effective, adaptive forwarding assumes Interest Routing Locality, meaning that Interests sharing the same prefix are likely to follow a similar forwarding path within a short period of time. Therefore, past observations can provide insight into how forwarding will likely perform for the same prefix in the near future. Since Interests can have multiple common prefixes with different lengths, the real challenge is determining which prefix length should be used in adaptive forwarding to record path measurements - we refer to this as the Prefix Granularity Problem. The longer the common prefix is, the better Interest Routing Locality. However, finer grained-prefixes cover fewer Interests each and require a larger forwarding table. Existing adaptive forwarding designs use a static prefix length, which is known to encounter issues in the event of partial network failures. In this work, we propose to dynamically aggregate and de-aggregate name prefixes in the forwarding table in order to use the prefixes that are the most appropriate given current network situation. In addition, to reduce the overhead of adaptive forwarding, we propose mechanisms to minimize the use of longest prefix matching during the processing of Data packets. Simulations demonstrate that the proposed techniques can result in better forwarding decisions in the event of partial network failures with significantly reduced overhead.

This paper describes and evaluates a novel 2‐dimensional radio resource allocation scheme for high‐throughput cellular packet data access. The proposed system employs spread spectrum orthogonal frequency division multiplexing with adaptive time and frequency allocation (SS‐OFDM‐F/TA) of radio resources. In order to achieve high spectral efficiency of downlink packet transmissions to multiple mobile users, multi‐user diversity available in the multi path fading environment is exploited through the use of adaptive modulation and coding, best serving sector selection, suitable scheduling of packet transmissions and hybrid ARQ employing soft‐packet combining and incremental redundancy. The data throughput, packet delay and fairness of the system with slow and fast best sector selection are examined. A method of grouping disjoint sub‐bands for use in highly frequency‐selective environments is described and evaluated. Packet re‐transmission options including a proposal of several asynchronous re‐transmission algorithms and constraining the maximum re‐transmission interval are also considered. It is demonstrated that the proposed spread spectrum OFDM system is capable of reaching a spectral efficiency of about 1.7 b/sec/Hz/sector with single receive and transmit antennas, and seems to provide a promising solution for high‐throughput best‐effort delay‐tolerant data services in future cellular radio systems. Copyright © 2004 AEI

There is a lack of high-speed and low-cost wireless network at sea to meet the increasing need of maritime users. With this observation, we have envisaged a WiMAX mesh network for high-speed ship- to-ship/shore communications. Analysis of interference range in such maritime WiMAX mesh networks is presented in this paper. And based on the findings, scheduling transmission of MAC control messages and data packets within three-hop neighborhood is investigated for the purpose of minimizing interference. A model is developed for analysis of the interference range in maritime environment. With parameter values that are derived from measurements at sea, we show that by scheduling among three-hop neighborhood the probability a transmission being interfered by a concurrent transmission drops about 30%. Simulation results show that, with the simulation settings in this paper, by scheduling among three-hop neighborhood, the initial packet delay and the average packet delay can be reduced by about 17% and 15.6% in sea state 3.0, respectively. In sea state 6.0, the performance improvement in initial packet delay and average packet delay are about 45% and 19.3%, respectively.

Tailored for wireless local area networks, the present paper proposes a cross-layer resource allocation scheme for multiple-input multiple-output orthogonal frequencydivision multiplexing systems. Our cross-layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets’ lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets’ lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.

Performance evaluation of prioritized scheduling with buffer management for differentiated services architectures