A Wireless Link-Up Augmentation Design for Disaster-Resilient Optical Networks

Allawi, Yazan M.,Dujeong Lee,Rhee, June-Koo Kevin IEEE 2015 Journal of Lightwave Technology Vol.33 No.17

<P>In view of the increasing frequency and damage severity of disasters, network operators have become more concerned with providing disaster-resiliency measures for their optical network infrastructure, whereas mitigating network service interruption due to the disaster region failures in the optical physical medium merely by increasing network redundancy is deemed spatially inefficient and very costly, with recent advancements, wireless technology is a potential candidate solution for efficient medium diversification. This paper addresses the challenge of efficiently designing disaster-resilient wireless-link-augmented optical network infrastructure. We formulate this problem as an optimization model of finding the subset of links in an optical network topology whose wireless augmentation maximizes postdisaster recovery of overall network availability for a given budget constraint. To overcome the computational complexity of finding the optimal design solution, a novel greedy heuristic algorithm is proposed. Performance comparisons with an exhaustive enumeration search and simple heuristics demonstrate the efficiency and scalability of our heuristic algorithm.</P>

Cost-effective topology design for HSR resilient mesh networks

Allawi, Yazan M.,Dujeong Lee,Kyusang Lee,Rhee, June-Koo Kevin IEEE 2015 Journal of optical communications and networking Vol.7 No.1

<P>High-availability seamless redundancy (HSR) protocol provides a zero failover time protection applicable to any Ethernet topology. HSR is also capable of tolerating multiple simultaneous failures, which further promotes the application of packet-based Ethernet protection. Deploying HSR in mesh networks may incur a significant unnecessary cost if not designed carefully. This paper addresses the problem of minimizing the cost of HSR mesh networks given a network availability constraint. We first develop an enumeration-based method to find the optimal design. However, due to the NP-hard complexity of the problem, this is limited to only small networks. Hence, a novel two-step heuristic algorithm is proposed. The algorithm first searches a design of an initial mesh topology compliant with HSR survivability conditions, and then an evolution process takes place to find a modification of the initial topology that satisfies the required availability. The simulation results show that our heuristic algorithm achieves a comparable performance close to optimal while being computationally scalable.</P>

Improvement of High-Availability Seamless Redundancy (HSR) Traffic Performance for Smart Grid Communications

Saad Allawi Nsaif,이종명 한국통신학회 2012 Journal of communications and networks Vol.14 No.6

High-availability seamless redundancy (HSR) is a redundancy protocol for Ethernet networks that provides two frame copies for each frame sent. Each copy will pass through separate physical paths, pursuing zero fault recovery time. This means that even in the case of a node or a link failure, there is no stoppage of network operations whatsoever. HSR is a potential candidate for the communications of a smart grid, but its main drawback is the unnecessary traffic created due to the duplicated copies of each sent frame, which are generated and circulated inside the network. This downside will degrade network performance and might cause network congestion or even stoppage. In this paper, we present two approaches to solve the above-mentioned problem. The first approach is called quick removing (QR), and is suited to ring or connected ring topologies. The idea is to remove the duplicated frame copies from the network when all the nodes have received one copy of the sent frame and begin to receive the second copy. Therefore, the forwarding of those frame copies until they reach the source node, as occurs in standard HSR, is not needed in QR. Our example shows a traffic reduction of 37.5%compared to the standard HSR protocol. The second approach is called the virtual ring (VRing), which divides any closed-loop HSR network into several VRings. Each VRing will circulate the traffic of a corresponding group of nodes within it. Therefore, the traffic in that group will not affect any of the other network links or nodes, which results in an enhancement of traffic performance. For our sample network, the VRing approach shows a network traffic reduction in the range of 67.7to 48.4%in a healthy network case and 89.7 to 44.8%in a faulty network case, compared to standard HSR.

RLP : An Efficient HSR Traffic Reduction Algorithm

Saad Allawi NSAIF,Je Hyun JUN,Je Hyun JUN,Jong Myung RHEE 통신위성ㆍ우주산업연구회 2012 한국위성정보통신학회논문지 Vol.7 No.3

RMT: A Novel Algorithm for Reducing Multicast Traffic in HSR Protocol Networks

Nsaif, Saad Allawi,Rhee, Jong Myung The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.1

The high-availability seamless redundancy (HSR) protocol is one of the most important redundancy IEC standards that has garnered a great deal of attention because it offers a redundancy with zero recovery time, which is a feature that is required by most of the modern substation, smart grid, and industrial field applications. However, the HSR protocol consumes a lot of network bandwidth compared to the Ethernet standard. This is due to the duplication process for every sent frame in the HSR networks. In this paper, a novel algorithm known as the reducing multicast traffic (RMT) is presented to reduce the unnecessary redundant multicast traffic in HSR networks by limiting the spreading of the multicast traffic to only the rings that have members associated with that traffic instead of spreading the traffic into all the network parts, as occurs in the standard HSR protocol. The mathematical and the simulation analyses show that the RMT algorithm offers a traffic reduction percentage with a range of about 60-87% compared to the standard HSR protocol. Consequently, the RMT algorithm will increase the network performance by freeing more bandwidth so as to reduce HSR network congestion and also to minimize any intervention from the network administrator that would be required when using traditional traffic filtering techniques.

Optimal dynamic subcarrier allocation for dual-band OFDMA-PON supporting integrated fronthaul and backhaul in 5G networks

Yazan M. Allawi,김근영,Jungbum Cho,Ahmad G. Reza,나용수,이준구 한국통신학회 2018 ICT Express Vol.4 No.3

We propose a novel dynamic subcarrier allocation (DSCA) design for dual-band orthogonal frequency division multiple access passive optical network (DB-OFDMA-PON), supporting integrated fronthaul and backhaul services, given their stringent requirements in emerging 5G networks. An optimization problem is formulated to maximize both the bandwidth utilization and QoS guarantees. The simulation results show that our proposed DSCA achieves the desired statistical multiplexing gain and high performance in terms of throughput and delay.

Improvement of High-Availability Seamless Redundancy (HSR) Traffic Performance for Smart Grid Communications

Nsaif, Saad Allawi,Rhee, Jong Myung The Korea Institute of Information and Commucation 2012 Journal of communications and networks Vol.14 No.6

High-availability seamless redundancy (HSR) is a redundancy protocol for Ethernet networks that provides two frame copies for each frame sent. Each copy will pass through separate physical paths, pursuing zero fault recovery time. This means that even in the case of a node or a link failure, there is no stoppage of network operations whatsoever. HSR is a potential candidate for the communications of a smart grid, but its main drawback is the unnecessary traffic created due to the duplicated copies of each sent frame, which are generated and circulated inside the network. This downside will degrade network performance and might cause network congestion or even stoppage. In this paper, we present two approaches to solve the above-mentioned problem. The first approach is called quick removing (QR), and is suited to ring or connected ring topologies. The idea is to remove the duplicated frame copies from the network when all the nodes have received one copy of the sent frame and begin to receive the second copy. Therefore, the forwarding of those frame copies until they reach the source node, as occurs in standard HSR, is not needed in QR. Our example shows a traffic reduction of 37.5%compared to the standard HSR protocol. The second approach is called the virtual ring (VRing), which divides any closed-loop HSR network into several VRings. Each VRing will circulate the traffic of a corresponding group of nodes within it. Therefore, the traffic in that group will not affect any of the other network links or nodes, which results in an enhancement of traffic performance. For our sample network, the VRing approach shows a network traffic reduction in the range of 67.7 to 48.4%in a healthy network case and 89.7 to 44.8%in a faulty network case, compared to standard HSR.

Behavior of CFRP strengthened RC multicell box girders under torsion

Abeer A. Majeed,Abbas A. Allawi,Kian H. Chai,Hameedon W. Wan Badaruzzam 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.3

The use of fiber reinforced polymer (FRP) for torsional strengthening of reinforced concrete (RC) single cell box beams has been analyzed considerably by researchers worldwide. However, little attention has been paid to torsional strengthening of multicell box girders in terms of both experimental and numerical research. This paper reports the experimental work in an overall investigation for torsional strengthening of multicell box section RC girders with externally-bonded Carbon Fiber Reinforced Polymer CFRP strips. Numerical work was carried out using non-linear finite element modeling (FEM). Good agreement in terms of torque-twist behavior, steel and CFRP reinforcement responses, and crack patterns was achieved. The unique failure modes of all the specimens were modeled correctly as well.

High-availability Seamless Redundancy(HSR) Protocol for Automobile Networks

박진표,사아드 나자이프,이종명,Park, Jin-Pyo,Nsaif, Saad Allawi,Rhee, Jong-Myung Korea Society of Satellite Technology 2014 한국위성정보통신학회논문지 Vol.10 No.1

Ethernet 기반 차량 네트워크 구성 시 신뢰성은 요구조건 중 하나이다. 이를 위해 차량 네트워크 구조에 High-availability Seamless Redundancy (HSR) protocol (IEC 62439-3 clause 5)를 사용할 수 있다. HSR 프로토콜은 프레임을 전송할 때 서로 다른 경로에 각각의 복제된 프레임들을 제공한다. 이는 전송 오류로 인해 하나의 경로에서 프레임을 전송받지 못하더라도 목적지 노드는 다른 경로를 통해 적어도 하나의 프레임을 받을 수 있어 네트워크의 고장 발생 시에도 네트워크의 중단이 없음을 의미한다. 고장 발생 시에도 목적지 노드는 Zero-recovery time으로 하나의 프레임을 받을 수 있기 때문에 표준 Ethernet 과는 달리 보낸 프레임의 손실시 네트워크를 재구성하는 시간이 필요 없다. 하지만 HSR 프로토콜은 복제 전송하는 프레임으로 인해 불필요한 트래픽을 발생시키는 단점이 있다. 이에 HSR 프로토콜의 성능을 향상시키기 위해 QR, VRing, RURT, DVP와 같은 방법들이 이미 제안되었다. 본 논문에서는 차량 네트워크에 HSR 프로토콜을 적용한 3가지 구조를 제안하였고 여기에 트래픽 향상을 위해 QR, VRing을 적용하였으며 이 구조들의 트래픽 성능을 측정 및 비교하였다. QR과 VRing을 적용할 때 표준 HSR 프로토콜에 비해 48-75%의 트래픽 감소를 보여주었다. 이는 차량에서 신뢰성 향상을 위해 HSR 프로토콜은 Ethernet을 대신하여 사용할 수 있음을 의미한다. One of the most important requirements for the Ethernet-based automobile is the reliability. In order to achieve this goal, we propose using the High-availability Seamless Redundancy (HSR) protocol (IEC 62439-3 clause 5) in these networks. The HSR protocol provides duplicated frame copies for each sent frame, which means that the destination node will receive at least one copy in case the second copy is lost due to a failure. In other words, there will be no network stoppage even if failure occurs. Moreover, the destination node will receive at least one frame copy with zero-recovery time (seamless) and it will not need to wait to receive the other copy if the first one is lost, which occurs it in the Ethernet standard, as a result of reconfiguration of the network paths. However, the main drawback of the HSR protocol is the unnecessary redundant traffic that is caused by the duplicated frames. Several solutions, including QR, VRing, RURT, and DVP, have already been proposed to improve the traffic performance of the HSR protocol. In this paper, we propose three automobile network topologies. each of which has pros and cons depending on the automobile requirements. Then we applied the HSR protocol with and without the QR and VRing approaches to each scenario. The comparison among these topologies depend on the traffic performance result for each of them. The QR and VRing approaches give a better traffic reduction percentage, ranging from 48% to 75% compared to the standard HSR protocol. Therefore they could limit the redundant traffic in automobile networks when the HSR protocol is used instead of the Ethernet network, which does not provide any seamless recovery if a failure occurs.