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Shizhong Xu,Xiong Wang,Guangxu Yang,Jing Ren,Sheng Wang 한국통신학회 2020 Journal of communications and networks Vol.22 No.2
Distributed in-network cloud architecture is a promisingsolution to efficiently host next generation internet-of-things (IoT)services. With the rapid increase of IoT devices and applications,the backhaul or backbone networks, which transmit IoT trafficto various in-network clouds, will experience a predicted explosionin the volume of carried traffic. To guarantee the QoS of IoTcloud services and improve the network performance, it is crucialfor network operator to implement efficient routing optimizationstrategies for IoT traffic. As a promising networking paradigm,software-defined networking (SDN) has flexible and programmablecontrol capability for fine-grained flows. The emergence of SDNpaves a way for implementing high-performance routing optimizationin networks. In SDN networks, the routing strategies are realizedthrough flow rules, which are usually stored in TCAM withvery limited capacity. However, the number of IoT flows are enormous. Thus, in this paper, we address the routing optimizationproblem in SDN-based IoT with TCAM capacity constraint. Wefirst formulate the problem as a mixed integer linear programmingproblem and prove the problem is NP-hard. Then to solve theproblem efficiently, we propose several approximate algorithms,which solve the problem in two stages. In the first stage, the algorithmscalculate the routing strategies for flows without consideringthe TCAM capacity constraint. To meet the TCAM capacityconstraint, the algorithms using different strategies to adjust thepaths of some flows in the second stage. Extensive simulations areconducted on both real ISP and synthetic topologies to evaluate theperformance of the algorithms. The simulation results verify thatthe algorithms can achieve promising load balancing performancein SDN-based IoT, where the capacity of TCAM in SDN switches isvery limited.
Computationally Efficient 2-D DOA Estimation Using Two Parallel Uniform Linear Arrays
Hailin Cao,Lisheng Yang,Xiaoheng Tan,Shizhong Yang 한국전자통신연구원 2009 ETRI Journal Vol.31 No.6
A new computationally efficient algorithm-based propagator method for two-dimensional (2-D) direction-of-arrival (DOA) estimation is proposed, which uses two parallel uniform linear arrays. The algorithm takes advantage of the special structure of the array which enables 2-D DOA estimation without pair matching. Simulation results show that the proposed algorithm achieves very accurate estimation at a computational cost 4 dB lower than that of standard methods.