Tactical Nodes Research Articles

A Strategic Multistage Tactical Two-Stage Stochastic Optimization Model for the Airline Fleet Management Problem.

This work proposes stochastic optimization for the airline fleet management problem, considering uncertainty in the demand, operational costs, and fares. In particular, a multistage tree is proposed, compounded of strategic and tactical nodes. At the former ones, fleet composition decisions are made, while at the latter ones, aircraft assignment decisions are formulated. Computational experiments are based on a small air network with seven strategic nodes and fourteen tactical nodes (i.e., seasons) where two fleet types are available to be included: Airbus 320, and Boeing 737. These results provide the optimal fleet planning and assignment at both strategic and tactical scopes. Finally, it is shown the superior performance of the stochastic version of this problem against the deterministic one.

Design of Future UAV-Relay Tactical Data Link for Reliable UAV Control and Situational Awareness

Unmanned aerial vehicles (UAVs) have recently been widely used in the military and commercial domains. UAVs, especially in the military domain, were initially used for gathering intelligence, surveillance, and reconnaissance data, and sending them to a command center. Their use was then expanded to the tactical level to perform military operations with manned platforms. Operating a UAV as a relay node in the air has many advantages, including coverage, recovery from disconnection from a relay, clear communication channel, and easy deployment. Thus, the UAV-Relay tactical network can support more effective military operations. However, reliable UAV control and situational awareness must be guaranteed for the use of tactical UAVs. In other words, all tactical nodes must be able to send their location and status periodically under the dynamic and unexpected situation of a battlefield. However, a jamming attack from the enemy can make UAV control and situational awareness impossible. Thus, we need a robust tactical data link (TDL) to guarantee reliable UAV control and situational awareness under a jamming attack. In this article, we first explain the requirements for reliable UAV control and situational awareness. We then design a future UAV-relay TDL, called link-situational awareness and control (Link-SAC), which satisfies the requirements. We also deal with the spectrum allocation and management of Link-SAC because Link-SAC requires large bandwidth under the scarcity of spectrum resource. Thus, we consider spectrum sharing to allocate an X-Band uplink to Link-SAC. Based on the interference analysis in a prior study, we show that spectrum sharing is possible. We also show how Link-SAC can manage the spectrum. Lastly, we present our concluding remarks.

단일 MAC을 이용한 자동 고장 극복 Ethernet NIC (Network Interface Card) 장치 구현

Mission critical 임무를 수행하는 Ethernet 기반 첨단 네트워크 시스템에서 자동 고장 극복 기능은 시스템의 중단 없는 운용을 위한 중요한 요구사항 중의 하나이다. 이러한 고장 극복 기능은 네트워크 시스템의 각 노드에 멀티 port를 지원하는 네트워크 인터페이스 카드 (Network Interface Card, NIC)를 설치함으로써 가능하다. 현재 가용한 NIC 장치는 두 개 또는 그 이상의 MAC (Media Access Control)을 사용하여, active port 고장 시에 MAC switching하여 자동 고장 극복 기능을 수행한다. 이러한 NIC 장치는 일반적으로 co-processor 및 이를 위한 펌웨어 (firmware)를 필요로 하며, 이에 따라 고장 극복 시간이 길어지고 throughput이 저하되는 단점이 있다. 또한 co-processor를 위한 펌웨어는 전술 환경 변화에 따라 upgrade를 해야 하므로 고장 극복 장치 가격도 상승하게 한다. 본 논문은 기존 하드웨어 방식에서 일반적으로 사용하는 co-processor와 다수 MAC 대신에, 하나의 MAC 만을 사용하는 새로운 하드웨어 방식 NIC 장치 설계 방안을 제시한다. 제시된 새로운 NIC은 단일 MAC과 일반 로직게이트 블럭으로 설계하여 고장 극복 기능을 수행한다. 제안 방식에 따라 NIC을 구현하여 성능 실험을 통해 기존 방식 대비 우수함을 입증하였다. One of the important operational requirements for mission critical Ethernet networked system is having the fault tolerant capability. Such capability can be obtained by equipping multiport Network Interface Card (NIC) in each node in the system. Conventional NIC uses two or more Media Access Controls (MACs) and a co-processor for the MAC switching whenever an active port fails. Since firmware is needed for the co-processor, longer fail-over switching and degraded throughput can be generally expected. Furthermore the system upgrading requiring the firmware revision in each tactical node demands high cost. In this paper we propose a novel single MAC based NIC that does not use a co-processor, but just use general discrete building blocks such as MAC chip and switching chip, which results in better performances than conventional method. Experimental results validate our scheme.