共查询到20条相似文献,搜索用时 46 毫秒
2.
抽烟,是因为手指寂寞
某年的假期我在某地长途汽车站等人,说好时间却迟迟不见接我的人,百无聊赖。我第一次花了10块钱买了一包香烟。点燃烟,每根烟只抽一口,看蓝色的烟升起。 相似文献
4.
5.
6.
7.
8.
《激光与光电子学进展》2006,43(5):62-62
目前大量新技术不断涌现,使驾驶变得轻松悠闲。DVD播放机使那些后座乘客一特别是孩子们在长途旅行时兴致盎然;同时导航系统会给驾驶员提供如何尽快到达目的地的准确信息;最新的交通情况报告会自动集成到路程计划功能中,就能有效避开交通阻塞;移动电话使人们随时随地都能联系到驾车者…… 相似文献
10.
11.
It has been a pleasure and an honor to serve for the last three years as Editor-in-Chief of the IEEE Transactions on Wireless Communications. This Transactions is clearly the leading journal in its field and continues to publish very high-quality, peer-reviewed original papers that advance the state of the art and applications in wireless communications. 相似文献
12.
13.
14.
15.
16.
Jianwei Huang Berry R.A. Honig M.L. 《Wireless Communications, IEEE Transactions on》2005,4(6):2801-2810
A model for downlink wireless scheduling is studied, which takes into account both user-channel conditions and retransmissions with packet combining hybrid [automatic repeat request (ARQ)]. Quality-of-service (QoS) requirements for each user are represented by a cost function, which is an increasing function of queue length. The objective is to find a scheduling rule that minimizes the average cost over time. We consider two scenarios: 1) the cost functions are linear, and packets arrive to the queues according to a Poisson process and 2) the cost functions are increasing, convex, and there are no new arrivals (draining problem). In each case, we transform the system model into a different model that fits into a framework for stochastic scheduling developed by Klimov. Applying Klimov's results, we show that the optimal schedulers for the transformed models in both scenarios are specified by fixed priority rules. Applying the inverse transformation in each case gives the optimal scheduling policy for the original problem. The priorities can be explicitly computed, and in the first scenario, are given by simple closed-form expressions. For the draining problem, we show that the optimal policy never interrupts the retransmissions of a packet. We also show that a simple myopic scheduling policy, called the U'R rule, performs very close to the optimal scheduling policy in specific cases. We present numerical examples, which compare the performance of the optimal scheduling rule with several heuristic rules. 相似文献
17.
现阶段在我军的边防部队装备有大量旧式模拟制无线电台,这些电台的信号质量较差,接口功能有限,无法满足部队对通信的要求。本系统通过研制扩展接口设备,将电话网通过无线电台延伸到值勤巡逻分队,使指挥员可通过电话与一线外出分队直接通信。通过使用PIC18F8720微处理器和DSP芯片实现了这个接口设备,从试验仿真和结果来看,达到了研制目的,并且研制出了样机交付部队使用。 相似文献
18.
Next-generation cellular wireless communication networks aim to provide a variety of quality-of-service (QoS)-sensitive packet-based services to downlink users. Included among these are real-time multimedia services, which have stringent delay requirements. Downlink packet scheduling at the base station plays a key role in efficiently allocating system resources to meet the desired level of QoS for various users. In this paper, we employ dynamic programming (DP) to study the design of a downlink packet scheduler capable of supporting real-time multimedia applications. Under well-justified modeling reductions, we extensively characterize structural properties of the optimal control associated with the DP problem. We leverage intuition gained from these properties to propose a heuristic scheduling policy, namely, Channel-Aware Earliest Due Date (CA-EDD), which is based on a "quasi- static" approach to scheduling. The per-time-slot implementation complexity of CA-EDD is only O(K) for a system with K downlink users. Experimental results show that CA-EDD delivers up to 50 percent of performance gains over benchmark schedulers. CA-EDD achieves these performance gains by using channel and deadline information in conjunction with application layer information (relative importance of packets) in a systematic and unified way for scheduling. 相似文献
19.
In this paper we integrate the ideas of network coding and relays into an existing practical network architecture used in
a wireless network scenario. Specifically, we use the COPE architecture to test our ideas. Since previous works have focused
on the communication aspect at the physical layer level, we attempt to take it one step further by including the MAC layer.
Our idea is based on information theoretic concepts developed by Shannon in order to reliably apply network coding to increase
the net throughput. 相似文献