http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Dynamic cross-layer transmission control for station-assisted satellite networks
Changhee Joo,Choi, Jihwan P. IEEE 2015 IEEE transactions on aerospace and electronic syst Vol.51 No.3
<P>In addition to sending signals directly to end-user terminals, the multibeam satellite can benefit from path diversity by routing to ground stations, which relay signals to the end users through terrestrial networks. We investigate a cross-layer dynamic transmission control in station-assisted satellite networks and develop an optimal solution that is amenable to implementation with a simple queue structure.We demonstrate the impact of ground stations and power control on the performance of multibeam satellite networks.</P>
Local Greedy Approximation for Scheduling in Multihop Wireless Networks
Changhee Joo,Shroff, Ness B. IEEE 2012 IEEE TRANSACTIONS ON MOBILE COMPUTING Vol.11 No.3
<P>In recent years, there has been a significant amount of work done in developing low-complexity scheduling schemes to achieve high performance in multihop wireless networks. A centralized suboptimal scheduling policy, called Greedy Maximal Scheduling (GMS) is a good candidate because its empirically observed performance is close to optimal in a variety of network settings. However, its distributed realization requires high complexity, which becomes a major obstacle for practical implementation. In this paper, we develop simple distributed greedy algorithms for scheduling in multihop wireless networks. We reduce the complexity by relaxing the global ordering requirement of GMS, up to near zero. Simulation results show that the new algorithms approximate the performance of GMS, and outperform the state-of-the-art distributed scheduling policies.</P>
Joo, Changhee,Eryilmaz, Atilla Institute of Electrical and Electronics Engineers, 2018 IEEE/ACM transactions on networking Vol.26 No.6
<P>We consider the problem of scheduling in wireless networks with the aim of maintaining up-to-date and synchronized (also called, <I>aligned</I>) information at the receiver across multiple flows. This is in contrast to the more conventional approach of scheduling for optimizing long-term performance metrics such as throughput, fairness, or average delay. Maintaining the age of information at a low and roughly equal level is particularly important for distributed cyber-physical systems, in which the effectiveness of the control decisions depends critically on the freshness and synchrony of information from multiple sources/sensors. In this paper, we first expose the weakness of several popular MaxWeight scheduling solutions that utilize queue-length, delay, and age information as their weights. Then, we develop a novel age-based scheduler that combines age with the interarrival times of incoming packets in its decisions, which yields significant gains in the information freshness at the receiver. We characterize the performance of our strategy through a heavy-traffic analysis that establishes upper and lower bounds on the freshness of system information.</P>
Joo, Changhee,Lin, Xiaojun,Ryu, Jiho,Shroff, Ness B. Institute of Electrical and Electronics Engineers, 2016 IEEE/ACM transactions on networking Vol.24 No.3
<P>It has been known that scheduling algorithms designed to achieve throughput optimality and good delay performance often require solving the Maximum Weighted Independent Set (MWIS) problem. However, under most realistic network settings, the MWIS problem is known to be NP-hard. In non-fading environments, low-complexity scheduling algorithms have been provided that converge either to the MWIS solution in time or to a solution that achieves at least a provable fraction of the achievable throughput. However, in more practical systems the channel conditions can vary at faster time-scales than convergence occurs in these lower-complexity algorithms. Hence, these algorithms cannot take advantage of opportunistic gains, and may no longer result in achieving good performance. In this paper, we propose a low-complexity scheduling scheme that performs provably well under fading channels and is amenable to implement in a distributed manner. To the best of our knowledge, this is the first scheduling scheme under fading environments that requires only local information, has a low complexity that grows logarithmically with the network size (provided that the conflict graph has bounded maximum vertex degree), and achieves provable performance guarantees (arbitrarily close to that of the well-known centralized Greedy Maximal Scheduler). We verify that the throughput and the delay of our proposed scheme are close to those of the optimal MaxWeight that solves MWIS at each time. Further, we implement our algorithm in a testbed by modifying the existing IEEE 802.11 DCF. The experiment results show that our implementation successfully accounts for wireless fading, attains the short-term opportunistic gains in practice, and hence substantially outperforms IEEE 802.11 DCF.</P>