Optimal Hop Count Research Articles

An adaptive congestion and energy aware multipath routing scheme for mobile ad-hoc networks through stable link prediction

Advancement in mobile ad-hoc network (MANET's) has offered solutions to wide range of real-time applications. MANET's consist of group of battery operated wireless mobile nodes that forms a dynamic topology and functions autonomously without infrastructure. Mobile nodes are limited to resource, bandwidth, energy and memory. Due to mobile nature of the nodes, mobility and resource limitations are the two major factors that affect MANET's performance. Frequent topology changes and mobility affects the link stability between two nodes, frequent link interruption results in network congestion, lead to packet drop and increase retransmission delays. During multihop data transmissions, the wireless channel is shared among neighbour nodes. Determining the channel status and predicting the quality of link is still a challenging issue. Existing MANET's routing scheme considers optimal hop count as a metric for data transmission and selects the shortest path. Due to nodes movement, frequent link failure occurs, resulting in packet loss and retransmission of packet, which restablished path avoids packets loss, and alternate paths can be discovered within time such that congestion is controlled and delay is minimised. Therefore, it is required to design routing scheme for MANET's that can adapt to network changes and conditions to support quality of service (QoS). In this paper, we propose an Adaptive Congestion and Energy Aware Multipath Routing Scheme (ACEAMR) to provision QoS requirements in MANET's. ACEAMR discovers stable, energy aware, and congestion free paths towards destination. The congestion level at node is determined by computing queue utilization through adaptive feedback mechanism. ACEAMR integrates stable link prediction (SLP) to estimate the link quality and channel availability for reliable data transmission. Energy aware nodes are computed using fitness function of nodes having sufficient energy to extend network lifetime. Simulation results show that proposed ACEAMR achieves 30 % of higher throughput, 25 % more in packet delivery ratio, 27 % less delay and 28 % energy efficient compared to LLECP-AOMDV, OLEADM and AOMDV schemes.

Joint Minimization of Wired and Wireless Traffic for Content Delivery by Multicast Pushing

As more mobile users become subscribers of content services, their subscribed content can be directly pushed from the content provider into the user equipment after the content is generated. In current and future network paradigms, a joint wired and wireless transmission design for this pushing is needed to guarantee the user experience without the extra deployment of communication infrastructures or consumption of resources. In this paper, we investigate a joint wired and wireless content delivery system that incorporates wired and wireless multicast. The users in the same group are served by wireless multicast from a base station (BS), while the BSs of the same content form a multicast tree in a backbone wired network. The sum of wired and wireless traffic is minimized by a joint design of user grouping, subchannel allocation, wired routing, and wired link usage. Exploiting the monotonicity of wired and wireless traffic with regard to the wired hop count, the original problem is converted for searching the optimal hop count vector that achieves the minimum sum of both types of traffic, which is solved by a monotonic optimization (MO)-based iterative algorithm. Compared with existing schemes and according to the numerical results, a reduction in total traffic of 43% can be achieved by our approach.

Optimal relay selection for transmission rate maximisation in multi‐hop wireless networks

A fundamental problem for wireless networks is how to select relays from all available network nodes to realise the optimal multi-hop relaying between a source node and a destination node. Mutual interference among wireless nodes makes this problem challenging. A surprising result of the reported work is that interference-free multi-hop relaying can be achieved in full-duplex decode-and-forward relaying. The broadcast nature of wireless transmissions can be exploited without suffering from mutual interference. Then, an efficient relay selection algorithm is developed that finds the optimal hop count and all the relays to maximise the source-destination multi-hop transmission rate. The complexity of the algorithm is O(N 2) only, where N is the number of available network nodes or network size. Interestingly, this wireless network algorithm is similar to the well-known Dijkstra's algorithm of wired networks. Simulations are conducted to demonstrate its optimality and efficiency.

Analysis and Modeling of Realistic Compound Channels in Transparent Relay Transmissions

Analytical approaches for the characterisation of the compound channels in transparent multihop relay transmissions over independent fading channels are considered in this paper. Compound channels with homogeneous links are considered first. Using Mellin transform technique, exact expressions are derived for the moments of cascaded Weibull distributions. Subsequently, two performance metrics, namely, coefficient of variation and amount of fade, are derived using the computed moments. These metrics quantify the possible variations in the channel gain and signal to noise ratio from their respective average values and can be used to characterise the achievable receiver performance. This approach is suitable for analysing more realistic compound channel models for scattering density variations of the environment, experienced in multihop relay transmissions. The performance metrics for such heterogeneous compound channels having distinct distribution in each hop are computed and compared with those having identical constituent component distributions. The moments and the coefficient of variation computed are then used to develop computationally efficient estimators for the distribution parameters and the optimal hop count. The metrics and estimators proposed are complemented with numerical and simulation results to demonstrate the impact of the accuracy of the approaches.

Terrain dependant hop count selection for transparent relay transmissions

In this Letter, the selection of the best hop count for a particular topography, in the context of enhanced connectivity using multi-hop transparent relay communication is addressed. Based on the coefficient of variation and the terrain specific fading severity factor of the distribution, it is possible to estimate the optimal hop count that can provide the required performance at detector. Two distribution models, which can adequately characterise the terrain fading effects on empirical data are considered for performance comparison. The results are useful in selecting branches, with low variability and optimal hop count for connectivity, in multi-stream switched diversity combining systems.

Energy-efficient transmission scheme for mobile data gathering in Wireless Sensor Networks

Energy conservation in Wireless Sensor Networks (WSNs) has always been a crucial issue and has received increased attention in the recent years. A transmission scheme for energy-constrained WSNs is proposed in this paper. The scheme, called MIHOP (MIMO and Multi-hop), combines cluster-based virtual MIMO and multi-hop technologies. The multi-hop mode is employed in transmitting data when the related sensors are located within a specific number of hops from the sink, and the virtual MIMO mode is used in transmitting data from the remaining sensor nodes. We compare the energy consumption of different transmission schemes and propose an algorithm for determining the optimal hop count in MIHOP. A controllable mobile sink that reduces the energy consumed in sensor transmission is also adopted for data collection. The theoretical analysis and the Monte Carlo simulation demonstrate that the proposed scheme significantly outperforms individual virtual MIMO, multi-hop technologies, and double-string networks in terms of energy conservation. The energy consumption levels under the MIHOP scheme are approximately 12.98%, 47.55% and 48.30% less than that under virtual MIMO schemes, multi-hop networks and double-string networks, respectively.

On performance of multi hop CDMA wireless sensor networks with correlated interferers

Multi-hop communication in wireless sensor networks helps in attaining broader coverage and distributes the use of power throughout the hops. This paper evaluates the end-to-end performance of a CDMA-based static multi-hop wireless sensor network WSN with layered architecture in shadowed environment. End-to-end probability of outage, bit error rate BER, average energy consumption, and the associated delay for successful delivery of a packet from a source to a sink, separated by a fixed distance, are evaluated for different number of hops. An interference model for multi-hop is presented considering correlation amongst shadow faded interferers. Two different information delivery mechanisms are investigated using regenerative relays with and without error correction capability. Energy requirement, and delay for successful delivery of a data packet from a source to sink is evaluated for each packet transmission scheme considering a suitable energy model and compared under several conditions of node density, packet length, and number of hops between source and sink. Optimal hop count is estimated on the basis of energy requirement and delay for successful delivery of data from a source to sink. Analytical results are supported by simulation.

An Energy-Balanced Data Gathering Algorithm for Linear Wireless Sensor Networks

Aiming at the data unbalance of sensor nodes in the wireless sensor networks (WSN), this paper mainly studies the data gathering algorithm for linear WSNs. As the data amount varies from the time spent on data gathering of entire network minimal, it is a key factor to balance energy consumption and further prolong the network lifetime. Therefore, this paper proposes a TDMA scheduling algorithm for general k-hop networks, and takes detail performance analysis on the algorithm. Furthermore, we present the method of selecting the optimal hop-count and its formula as well as the formula of the number of timeslots required for converge-cast in order to maximize network lifetime. Finally, we obtain some general conclusions of network optimization based on the theoretical analysis and simulations. Compared with the 1-hop algorithm in (C. Florens and R. McEliece, Packets Distribution Algorithms for Sensor Networks, IEEE INFOCOM, San Diego, pp. 1063–1072, 2003), the TDMA scheduling algorithm for the general k-hop network proposed in our paper is more universal and has more practical application value.

Random access transport capacity

We develop a new metric for quantifying end-to-end throughput in multihop wireless networks, which we term random access transport capacity, since the interference model presumes uncoordinated transmissions. The metric quantifies the average maximum rate of successful end-to-end transmissions, multiplied by the communication distance, and normalized by the network area. We show that a simple upper bound on this quantity is computable in closed-form in terms of key network parameters when the number of retransmissions is not restricted and the hops are assumed to be equally spaced on a line between the source and destination. We also derive the optimum number of hops and optimal per hop success probability and show that our result follows the well-known square root scaling law while providing exact expressions for the preconstants as well. Numerical results demonstrate that the upper bound is accurate for the purpose of determining the optimal hop count and success (or outage) probability.

단방향 이중연결 CC-NUMA 시스템의 동적 부하 대응 경로 설정 기법

높은 클럭으로 동작하는 고속의 프로세서를 다수 이용한 다중프로세서 시스템 성능은 프로세서 자체의 성능보다 상호연결망의 트랜잭션 처리 능력 및 지연에 의하여 큰 영향을 받게 된다. 따라서 상호연결망의 성능은 대역폭 및 지연시간 측면으로 시스템 성능에 큰 비중을 차지한다. 단방향 이중 연결을 이용한 CC-NUMA 구조는 이중 연결을 이용한 대역폭 증가효과와 고속 단방향 링크를 이용한 적은 지연시간으로 인하석 고성능 시스템에서 많이 채용되고 있다. 한편, 이중 연결구조로 인하여 시스템의 상호연결망의 최단 경로는 단일하게 형성되지 않으며, 여러 개의 최단 경로가 구성될 수 있다. 그러나 실제 응용프로그램을 수행할 때, 동일한 홉 수를 나타내는 경로일지라 하더라도 각 연결 링크의 부하 및 경쟁에 따른 지연 시간의 차이를 나타내게 되며, 만일 노드간의 트랜잭션 전달 경로가 정적으로 구성되어 있을 경우, 실제 프로그램의 수행에서 균일하지 못한 연결 링크 부하에 따른 지연 시간의 차이가 나타날 수 있음을 의미한다. 이는 곧 고속의 상호연결망 전체의 대역폭을 균일하게 사용하지 못함으로 나타나는 부가적 지연 시간으로 볼 수 있으며, 이로 인한 응용 프로그램의 수행 성능이 저하될 수 있음을 의미한다. 본 논문은 기존 연구된 단방향 이중 연결을 이용한 CC-NUMA 시스템에서, 노드간 트랜잭션 전달 경로가 정 적으로 구성될 경 우 발생될 수 있는 성능 저하를 평가하고, 정적 경로와 동일한 홉 수의 경로를 나타내며 링크 부하에 따라서 동적으로 전달되도록 부하에 따르는 동적 경로 설정 방법을 제시하였다. 논문에서 제시하는 방법은 기존 경로설정 방법에 대하여 동일한 홉 수를 나타내며, 링크 부하에 따라서 동적으로 경로를 설정함으로써 실시간 경로 분배가 자연스럽게 이루어지도록 하였고, 링크 경쟁을 완화함으로써 보다 균일한 링크 사용을 나타냈고, 링크 획득 실패로 인한 지 연시간을 감소시켰다. 프로그램 구동 시뮬레이션을 통한 성능 검증 결과, 논문에서 제시한 동적경로 설정 방법은 기존 정적 경로 설정 방법에 비해 링크점유시간 편차가 <TEX>$1{\~}10\%$</TEX> 낮게 나타났고, 링크의 획득 실패 횟수가 <TEX>${\~}3\%$</TEX> 감소하였으며, 그 결과 <TEX>$1{\~}6\%$</TEX>의 수행 시간 감소를 나타냈다. Throughput and latency of interconnection network are important factors of the performance of multiprocessor systems. The dual-link CC-NUMA architecture using point-to-point unidirectional link is one of the popular structures in high-end commercial systems. In terms of optimal path between nodes, several paths exist with the optimal hop count by its native multi-path structure. Furthermore, transaction latency between nodes is affected by congestion of links on the transaction path. Hence the transaction latency may get worse if the transactions make a hot spot on some links. In this paper, I propose a dynamic transaction routing algorithm that maintains the balanced link utilization with the optimal path length, and I compare the performance with the fixed path method on the dual-link CC-NUMA systems. By the proposed method, the link competition is alleviated by the real-time path selection, and consequently, dynamic transaction algorithm shows a better performance. The program-driven simulation results show <TEX>$1{\~}10\%$</TEX> improved fluctuation of link utilization, <TEX>$1{\~}3\%$</TEX> enhanced acquirement of link, and <TEX>$1{\~}6\%$</TEX> improved system performance.