Optimal transmission scheduling over a fading channel with energy and deadline constraints

We seek to maximize the average data throughput of a single transmitter sending data over a fading channel to a single user class. The transmitter has a fixed amount of energy and a limited amount of time to send data. Given that the channel state determines the throughput obtained per unit of energy expended, the goal is to obtain a policy for scheduling transmissions that maximizes the expected data throughput. We develop a dynamic programming formulation that leads to an optimal transmission schedule, first where the present channel state is known just before transmission, and then to the case where the current channel state is unknown before transmission, but observed after transmission and evolves according to a Markov process. We then extend our approach to the problem of minimizing the expected energy required to send a fixed amount of data over a fading channel given deadline constraints.     

基于磁耦合谐振的无线电能传输装置

在基于耦合谐振技术上,设计一种无线电能传输装置,采用软件对所设计的耦合谐振电路进行了建模与仿真,在此基础上实际制作了无线电能传输装置,实测效果良好.该设计方法简洁实用,但从效率角度考虑,有进一步改进的空间.     

A novel slot scheduling technique for duty-cycle based data transmission for wireless sensor network

The duty cycling process involves turning a radio into an active and dormant state for conserving energy. It is a promising approach for designing routing protocols for a resource-constrained Wireless Sensor Networks (WSNs). In the duty cycle-based WSNs, the network lifetime is improved and the network transmission is increased as compared to conventional routing protocols. In this study, the active period of the duty cycle is divided into slots that can minimize the idle listening problem. The slot scheduling technique helps determine the most efficient node that uses the active period. The proposed routing protocol uses the opportunistic concept to minimize the sender waiting problem. Therefore, the forwarder set will be selected according to the node's residual active time and energy. Further, the optimum routing path is selected to achieve the minimum forwarding delay from the source to the destination. Simulation analysis reveals that the proposed routing scheme outperforms existing schemes in terms of the average transmission delay, energy consumption, and network throughput.     

Energy-efficient scheduling with individual packet delay constraints over a fading channel

This article focuses on energy-efficient packet transmission with individual packet delay constraints over a fading channel. The problem of optimal offline scheduling (vis-à-vis total transmission energy), assuming information of all packet arrivals and channel states before scheduling, is formulated as a convex optimization problem with linear constraints. The optimality conditions are analyzed. From the analysis, a recursive algorithm is developed to search for the optimal offline scheduling. The optimal offline scheduler tries to equalize the energy-rate derivative function as much as possible subject to causality and delay constraints, in contrast to the equalization of transmission rates for optimal scheduling in static channels. It is shown that the optimal offline schedulers for fading and static channels have a similar symmetry property. Combining the symmetry property with potential idling periods, upper and lower bounds on the average packet delay are derived. The properties of the optimal offline schedule and the impact of packet sizes, individual delay constraints, and channel variations are demonstrated via simulations. A heuristic online scheduling algorithm, assuming causal traffic and channel information, is proposed and shown via simulations to achieve energy and delay performances comparable to those of the optimal offline scheduler in a wide range of scenarios.

Location and calculation-free node-scheduling schemes in large wireless sensor networks

In wireless sensor networks that consist of a large number of low-power, short-lived, unreliable sensors, one of the main design challenges is to obtain long system lifetime without sacrificing system original performance (sensing coverage and sensing reliability). To solve this problem, one of the potential approaches is to identify redundant nodes at the sensing interface and then assign them an off-duty operation mode that has lower energy consumption than the normal on-duty mode. In our previous work [J. Wireless Commun. Mobile Comput. 3 (2003) 271; Processing of ACM Wireless Sensor Network and Application Workshop 2002, September 2002], we proposed a node-scheduling scheme, which can provide a 100% sensing coverage preservation capability. This, however, requires each node to be aware of its own and its neighbors’ location information. Also, in that scheme, each node has to do accurate geometrical calculation to determine whether to take an off-duty status. In this paper, we propose and study several alternative node-scheduling schemes, which cannot completely preserve the original system coverage, but are nonetheless light-weighted and flexible compared with the previous one. Our simulation results compare these schemes with the previous one and demonstrate their effectiveness.     

Physical and chemical analysis of advanced interconnections using energy filtering transmission electron microscopy

Our newest method for interconnection analysis using focused ion beam (FIB) specimen thinning and energy filtering transmission electron microscopy (EFTEM) is presented. It is shown that using the site-specific capability and the controlled thinning effect of the FIB in addition with the high spatial resolution of the EFTEM technique, fast chemical analysis of materials with nanometre spatial resolution can be obtained. This is the only method for the observation of very thin diffusion barriers and interfaces in the presence of drastic topography. Application examples are given concerning firstly, the in-depth analysis of tungsten aluminum technology, barrier integrity and interdiffusion of elements near interfaces and secondly, the surface contamination of copper in copper interconnection technology with high aspect ratio contacts. In this case, photoresist spin-coating is carried out prior to FIB thinning. This method is an alternative to surface analysis techniques and offers the best spatial resolution without topography limitations.     

Asymptotically optimal transmission power and rate control for CDMA channels with MF and MMSE receivers

The asymptotically combined optimal transmission power and rate control policy is derived for a DS-CDMA time varying fading channel with multiple user classes, random spreading codes and a receiver using either a conventional matched filter (MF) or a minimum mean square error (MMSE) multiuser detector. For a general objective function, the optimal policies are given by closed form functions of a single Lagrangian multiplier. The optimal policies are demonstrated by an application, where the transmission power is adapted to the channel fade variations, and the transmission rates are adapted to the tier containing the mobile. The effect of the number of tiers on the optimal transmission rate are presented for MF and MMSE receivers in an environment with Lognormal and Rayleigh fading. It is shown that with an MMSE receiver, there is a substantial increase in the total transmission rate, whereas only a negligible increase exists with a MF receiver. Zvi Rosberg received the B.Sc., M.A. and Ph.D. degrees from the Hebrew University of Jerusalem. During his graduated studies he was a senior system analyst in the Central Computing Bureau of the Israeli government, where he was one of the chief designers of a new on-line Israeli population registration system. After graduation he held a research fellowship at the Center of Operation Research and Econometric (C.O.R.E.), Belgium and a visiting assistant professorship at the department of Business Administration, University of Illinois. At 1980 he joined the Computer Science department, Technion, Israel where he was until 1990. From 1990 to 1999 he was with the Haifa Research Laboratory, Science and Technology, IBM Israel, holding a position of a Program Manager of Communication Networks. From 2000 to 2001 he was with Radware Ltd., holding the chief scientist position. During the year of 2002 he visited the ARC Special Research Centre for Ultra-Broadband Information Networks (CUBIN), University of Melbourne. Currently he is an Associate/Professor at the Department of Communication Systems Engineering, Ben Gurion University, Beer-Sheva. Since 1980 he held summer research positions and a two year visiting position in IBM Thomas J. Watson Research Center, Yorktown Heights. He also had summer research positions in the Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, Department of Electrical Engineering and Computer Science, University of California, Berkeley, the Radio Communication Systems, Royal Institute of Technology (KTH) in Stockholm, the ARC Special Research Center for Ultra-Broadband Information Networks (CUBIN), University of Melbourne, and the Department of EEE, City University, Hong Kong. Presently, he is serving on the editorial board of the Wireless Networks (WINET) and the International Journal of Communication Systems. His research interest, where he has published numerous papers, include: Narrowband and spread spectrum wireless communication, Radio resource allocation and planning in cellular networks, Scheduling in wireless networks, Optical and ultra high speed networks, Control in queueing networks, Analysis of algorithms in communication and computing systems and Internet technologies