Multihop lightwave networks based on De Bruijn graphs

This paper deals with the analysis of the throughput performance of various logical topologies for Multihop Networks. In particular, ShuffleNets, De Bruijn graphs and Kautz graphs are analyzed. For the comparison, routing algorithms adopting minimum path length are considered. A hot-spot traffic scenario is adopted, modeling the presence of a centralized network resource to which a quota of the internal traffic is directed or originated from. The analysis is carried out by varying the traffic unbalance degree, from a uniform traffic distribution to a completely unbalanced one (all the traffic is concentrated in the hot-spot node). For ShuffleNets, simple analytical expressions of the actual throughput limits are utilized. In the case of De Bruijn and Kautz graphs, instead, a lower bound of the throughput is utilized, which coincides with the actual throughput in a wide range of values of the network size. The results obtained show that Shuffle and Kautz graphs always outperform De Bruijn topologies. Moreover, ShuffleNets present a further advantage on the other topologies; in fact, since the nodes are topologically equivalent, the placement of the hot-spot node does not affect the throughput performance.

IEEE 802.11ah (also known as WiFi Halow) is a new WiFi standard for sub-l GHz communications intended to address key challenges of the Internet of Things. IEEE 802 working group introduces IEEE 802.11ah to overcome the disadvantages of various previously introduced protocols (more data rate and very less transmission range, and more transmission range and very less data rate) by providing much data rate and transmission range of up to 1 km and has the capacity of 8192 devices connecting simultaneously with only one access point. The IEEE 802.11ah standard was released to support Machine-to-Machine (M2M) Communication between a large number of sensor devices that are rapidly increasing with the Internet of Things (IoT). IEEE 802.11ah protocol introduces the RAW Mechanisms in the MAC layer to avoid channel contention, especially when there is a large number of stations trying to access the channel simultaneously, thereby increasing scalability in dense deployments. In this paper, we analyze the network performance in terms of throughput through the proper allocation of nodes. This article investigates the impact of the number of stations and the number of groups on network performance, specifically throughput, in wireless networks. The article examines how varying the number of stations and groups affects the network’s performance and identifies the optimal values for these parameters that can maximize the network’s throughput.

This paper presents a dynamic overlay network based on the De Bruijn graph which we call Linearized De Bruijn (LDB) network. The LDB network has the advantage that it has a guaranteed constant node degree and that the routing between any two nodes takes at most O(log n) hops with high probability. Also, we show that there is a simple local-control algorithm that can recover the LDB network from any network topology that is weakly connected.

In a multihop wireless network, the throughput performance decreases seriously because of inter-flow and intra-flow collision. The backoff algorithm is the de facto function to resolve collision in 802.11 networks. In this paper we study the impact of five back-off algorithms on the performance of 802.11-based multihop wireless networks with different network topology and flow patterns. Simulations show that the backoff algorithms have big influence on the performance of both UDP and TCP flows. But none of the current backoff algorithms can improve the throughput and fairness performance in multihop wireless networks efficiently. It shows that the traditional random backoff algorithms are no longer suitable for collision resolution in distributed multihop wireless networks.

Network coding has been as a new coding paradigm that can significantly improve the throughput performance of a wireless multi-hop network. However, most previous studies either assume a fixed transmission power or do not take the impact of transmission power/rate to the network coding into consideration. Since in many scenarios, the selection of the transmission power/rate has big impact on network coding gains due to the fact the reception and overhearing probability, spatial reuse are both rely on transmission power/rate. Therefore, how to achieve high network throughput by appropriate selection of transmit power level and its corresponding packet transmit rate, network coding gain (if any) via localized network operations has been a critical issue in distributed multihop wireless networks, or alternatively, what is the best trade-off between the space-time resource (level of spatial reuse and transmission time) and the network coding gain? In this paper, our goal is to achieve the best trade-off between transmission power/rate and coding gains. Aiming at this, we propose a decentralized network coding aware power and rate control mechanism to enable each node to adjust its transmit power and data rate such that the network coding gains and the network throughput is maximized. Simulation results show that the proposed mechanism yields higher performance in network throughput as compared with existing work.

Physical topology is a major determinant of the system performance of optical backbone networks, and it is important to understand the relationships between physical topology features and system performance for better system design. For application in elastic optical backbone network systems, we propose a framework of correlation analysis to examine these relationships comprehensively, and we use the framework to investigate the relationships between various physical topology features and system performance. The results of numerical experiments suggest that four important physical topology features are strongly correlated with the system performance. Specifically, the average number of hops and the algebraic connectivity are strongly correlated with only the communication capacity, whereas the average path length and the geodesic distance Laplacian spectral radius are strongly correlated with both the capacity and the cost. The geodesic distance Laplacian spectral radius is a newly defined quantity that is expected to expand the possibilities of physical topology design in the future. Through combinations of these features, we classify physical topology designs and examine the relationships between the classification, real networks, and graph generation algorithms.

Multihop lightwave networks with hot potato routing offer the potential for significantly higher aggregate capacity as compared against minimum distance routing since each interconnecting link can be operated at a rate much higher than the electro-optic constraint forced by store-and-forward buffering. If the links can be operated at a speed sufficiently high as to offset the hot potato misrouting inefficiency, then a net capacity gain will be enjoyed. In this paper, we study such a network in which contention for an outbound link is resolved by assigning to each packet a priority based on its distance to destination and its age (number of misroutes previously suffered). An approximate analysis based on a reasonable set of assumptions is presented, queueing delay, packet loss performance, and network aggregate capacity (saturation throughout) are compared for distance-age prioritization, age-distance prioritization, and no prioritization. Results suggest that the lowest delay, lowest packet loss performance, and highest saturation throughput are offered by distance-age prioritization (priority given first to a packet closest to its destination and second to the oldest of multiple packets of the same distance to destination). The tails of the probability distribution for the number of hops taken by a representative packet are, however, shorter for age-distance routing. The capacity gain with link speed-up and hot potato routing can be quite significant compared to link speed-constrained store and forward buffering, and grows with both link speed-up factor and network size.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The paper presents HiPeer, a robust resource distribution and discovery algorithm that can be used for fast and fault-tolerant location of resources in P2P network environments. HiPeer defines a concentric multi-ring overlay networking topology, whereon dynamic network management methods are deployed. In terms of performance, HiPeer delivers of number of lowest bounds. We demonstrate that for any De Bruijn digraph of degree*d ≥ 2 and diameter*DDB HiPeer constructs a highly reliable network, where each node maintains a routing table with at most 2d + 2 entries independent of the number N of nodes in the system. Further, we show that any existing resource in the network with at most d nodes can be found within at most DHiPeer = logd(N(d - 1) + d) - 1 overlay hops. This result is as close to the Moore bound [1] as the query path length in other outstanding P2P proposals based on the De Bruijn digraphs. Thus, we argue that HiPeer defines a highly connected network with connectivity d and the lowest yet known lookup bound DHiPeer. Moreover, we show that any node's join or leave operation in HiPeer implies a constant expected reorganization cost of the magnitude order of O(d) control messages.

Star graph has desirable properties for WDM multihop lightwave network, such as node and edge symmetry, low diameter, simple routing, etc. A multihop lightwave network, based upon the star graphs, is studied. Schemes for embedding the star graphs and a cluster of stars in physical lightwave networks are proposed. The resulting networks have many desirable properties: high capacity, self-routing, fault tolerant and good scalability.

Aiming at the problems of the Internet of Vehicles routing algorithm in specific mobile communication scenarios of cars, buses and pedestrians, this paper presents a routing algorithm based on bus behavior (BBR). The movement patterns and routes of public transport vehicles have certain regularities. Using these regularities, this paper constructs an abstract network model, and based on the model, proposes a packet routing algorithm that keeps approaching public transport vehicles. A series of simulation experiments are carried out on the Bus Behavior algorithm and the classical routing algorithm by the ONE simulation tool. The simulation results show that the BBR performs well in the four performance indicators of message transmission success rate, load rate, average delay, and average number of hops. It shows that the algorithm has a high transmission success rate, low network load and delay, and good network stability, which is suitable for the urban traffic communication scenario studied in this paper.

Virtual topologies of WDM-based multihop networks can be arranged by assigning wavelengths to tunable transceivers of nodes. An optimal node arrangement problem in multihop lightwave networks with linearly virtual topologies is considered. For a given traffic matrix, this problem is to arrange node locations to adapt traffic patterns and optimise network performance. However, the problem of node arrangement for constructing optimised linear virtual topologies has been proved as NP-complete. Two lower bounds are proposed for this problem according to the traffic-weighted mean hop distance and the maximum link flow, respectively. An efficient node arrangement algorithm, called k-ENA, is also proposed. The performance of the k-ENA algorithm is compared with the best algorithms in previous work. Simulation results indicate that the k-ENA algorithm generally yields the best solutions.

The performance of a multihop wireless network is typically affected by the interference caused by transmissions in the same network. In a statistical fading environment, the interference effects become harder to predict. Information sources in a multihop wireless network can improve throughput and delay performance of data streams by implementing interference-aware packet injection mechanisms. Forcing packets to wait at the head of queues and coordinating packet injections among different sources enable effective control of copacket interference. In this paper, throughput and delay performance in interference-limited multihop networks is analyzed. Using nonlinear probabilistic hopping models, waiting times which jointly optimize throughput and delay performances are derived. Optimal coordinated injection strategies are also investigated as functions of the number of information sources and their separations. The resulting analysis demonstrates the interaction of performance constraints and achievable capacity in a wireless multihop network.

Aiming at the limitations of existing solutions for network bottleneck caused by the gap between the network transmission capacity and the processing capability of the current Internet architecture, this paper presents a novel cloud routing protocol named LD-CR based on limited deflection mechanism. A router running this protocol logically separates data forwarding and processing, which could share cloud processing resources with other nodes by using extra bandwidth. This method could effectively alleviate single-node congestion by leverage of the capability of electronic processing and optical transmission capacity at the same node. Analysis and simulation results show the simple LD-CR protocol could improve network performance in packet loss rate and network throughput obviously compared with OSPF protocol. Meanwhile, this method could also avoid performance rapid deterioration under the condition of heavy traffic load by using traditional deflection routing technology.

This paper focuses on the deafness problem in cognitive radio networks and presents a collision-free resident channel selection based distributed solution. Simulation results show that the proposed solution to the problem of deafness has an excellent performance in the overall network throughput and end-to-end delay characteristics, thus improving the network capacity and utilization of spectrum holes to provide quality of service in cognitive radio networks.

Clustering is an effective method for reducing energy consumption in wireless sensor networks (WSNs). In a multihop clustered network scenario, each sensor node transmits data to its own cluster head (CH), and the CH aggregates the data from its member nodes and forwards it to the base station (BS) via other CHs. However, the “hot spot” problem is prone to occur in clustered WSNs because CHs closer to the BS have heavier intercluster forwarding tasks. To address this problem, this paper proposes an unequal clustering algorithm based on interval type-2 TSK fuzzy logic theory (UCT2TSK). The relative distance to the BS (RDB), residual energy (RE), and node density (ND) are considered as the inputs of an interval type-2 fuzzy logic system (FLS). Through fuzzy reasoning, outputs are acquired that can be used to optimize the CHs and determine the cluster sizes. Simulation results verify that UCT2TSK can effectively balance energy consumption and enhance energy efficiency because it has better performance in network lifetime and network throughput than other classical and recent clustering algorithms.