无线通信中的空时分组码

空时分组码技术结合信道编码、调制和天线分集技术,当发送天线一定时,他的解码复杂度正比于发送速率,在3G标准中,该技术有着重要的地位。对空时分组码及相关知识进行了介绍,并对可变速率的空时分组码设计进行了探讨,最后展望了空时分组码技术的应用前景。     

Variable-rate convolutional network coding

Four types of variable-rate convolutional network codes are investigated over a single-source finite cyclic network.It is found that variable-rate generic,dispersion and broadcast can be implemented on the same network without changing the local encoding kernels of the non-source nodes.The efficient implementation has the advantage that each non-source node only needs to store one copy of the local encoding kernel within a session.However,it is also shown by an example that variable-rate multicast may not always be implemented under the above condition.     

Combined Speech and Channel Coding for Wireless Communications

In this paper, we propose acombined variable-rate code-excited linearly predictive (QCELP)speech coding and unequal error protection (UEP) channel codingsystem for wireless communications. In contrast to theconventional schemes, our system employs a concatenatedsuper-imposed rate-compatible punctured convolutional (SI-RCPC)channel coding scheme which can provide UEP with respect to notonly the bit-significance of speech packets but also the speechactivity and local channel characteristics. Verified by thesimulation results, the combined system achieves an averagetransmission rate less than 8 kb/s as well as an average 2 dBsignal-to-noise ratio (SNR) gain over the conventional equal errorprotection system.     

New algorithm for variable-rate linear broadcast network coding

To adjust the variance of source rate in linear broadcast networks,global encoding kernels should have corresponding dimensions to instruct the decoding process.The algorithm of constructing such global encoding kernels is to adjust heterogeneous network to possible link failures.Linear algebra,graph theory and group theory are applied to construct one series of global encoding kernels which are applicable to all source rates.The effectiveness and existence of such global encoding kernels are proved.Based o...     

流星突发通信中的变速率编码方案研究

流星突发通信是一种利用流星余迹进行通信的短时、突发通信方式。如何在较短通信时间内尽可能多的实现数据的可靠传输,始终是研究者关注的问题。传统的固定速率编码方案无法很好地适应信道变化,因此提出变速率编码以提高系统性能。通过对两种方案研究,对变速率编码算法进行了改进。仿真结果表明,改进后的变速率编码方案可明显改善系统性能。     

线性网络编码的类型保持转换矩阵

提出了类型保持转换矩阵的概念,用以描述为同一网络构建的类型相同、速率不同的线性网络编码间的转换关系,并为四类线性网络编码证明了其类型保持转换矩阵的存在性。进而,提出了一种变速率线性网络编码的构建框架。当在网络上实现由此框架构建的任意类型的变速率线性网络编码时,仅信源节点需要根据发送速率的变化采用相应的类型保持转换矩阵改变其局部编码核,而网络中任意非源节点上进行的网络编码操作均无需改变。     

一种femto-macro异构网络多业务资源公平管理算法

摘要：针对毫微微蜂窝（femtocell）网络中多种业务（固定速率业务和可变速率业务）环境下如何公平分配毫微微蜂窝基站（femtocell base station, FBS）资源的问题,提出了一种基于比例公平算法的femto-macro异构网络资源分配算法。该算法以基于比例公平法则的可变速率用户的吞吐量为优化目标,并以每个用户的服务质量（quality of service, QoS）、FBS的下行传输总功率和宏蜂窝（macrocell）用户的跨层同频干扰门限值为约束组成优化问题。在上述资源分配最优化问题为凸优化问题的基础上,采用对偶分解算法进行求解。仿真结果表明,提出的算法在保证不同用户 QoS 的同时,不仅能够有效地公平分配资源给可变速率用户,而且降低了macrocell用户受到来自FBS的跨层同频干扰。     

基于自适应变速率编码的VoIP网关的研究与应用

针对当前VoIP语音质量易受网络带宽影响的问题，提出了一种基于自适应变速率编码的VoIP网关。通过实时监测RTP语音分组的丢包率，并分析服务质量，自适应地选择最适合当前网络状况的编码速率，以提供一种语音质量和网络状况的最佳组合，从而降低语音分组的丢包率、有效地保障语音服务质量。结合开源项目Asterisk，实现了基于自适应变速率编码的VoIP网关。     

Global Control of Robotic Highway Safety Markers: A Real-time Solution

This paper presents the design and implementation of a real-time solution for the global control of robotic highway safety markers. Problems addressed in the system are: (1) poor scalability and predictability as the number of markers increases, (2) jerky movement of markers, and (3) misidentification of safety markers caused by objects in the environment.An extensive analysis of the system and two solutions are offered: a basic solution and an enhanced solution. They are built respectively upon two task models: the periodic task model and the variable rate execution (VRE) task model. The former is characterized by four static parameters: phase, period, worst case execution time and relative deadline. The latter has similar parameters, but the parameter values are allowed to change at arbitrary times.The use of real-time tasks and scheduling techniques solve the first two problems. The third problem is solved using a refined Hough transform algorithm and a horizon scanning window. The approach decreases the time complexity of traditional implementations of the Hough transform with only slightly increased storage requirements.Supported, in part, by grants from the National Science Foundation (CCR-0208619 and CNS-0409382) and the National Academy of Sciences Transportation Research Board-NCHRP IDEA Program (Project #90).Jiazheng Shi received the B.E. and M.E. degrees in electrical engineering from Beijing University of Posts and Telecommunications in 1997 and 2000, respectively. In 2000, he worked with the Global Software Group, Motorola Inc. Currently, he is a Ph.D. candidate in the Computer Science and Engineering Department at the University of Nebraska–Lincoln. His research interests are automated human face recognition, image processing, computer vision, approximate theory, and linear system optimization.Steve Goddard is a J.D. Edwards Associate Professor in the Department of Computer Science & Engineering at the University of Nebraska–Lincoln. He received the B.A. degree in computer science and mathematics from the University of Minnesota (1985). He received the M.S. and Ph.D. degrees in computer science from the University of North Carolina at Chapel Hill (1995, 1998).His research interests are embedded, real-time and distributed systems with emphases in high assurance systems engineering and real-time, rate-based scheduling theory.Anagh Lal received a B.S. degree in Computer Science from the University of Mumbai (Bombay), Mumbai, in 2001. He is currently a graduate research assistant at the University of Nebraska–Lincoln working on a M.S. in Computer Science, and a member of the ConSystLab. His research interests lie in Databases, Constraint Processing and Real Time Systems. Anagh will be graduating soon and is looking for positions at research institutions.Jason Dumpert received a B.S. degree in electrical engineering from the University of Nebraska–Lincoln in 2001. He received a M.S. degree in electrical engineering from the University of Nebraska-Lincoln in 2004. He is currently a graduate research assistant at the University of Nebraska-Lincoln working on a Ph.D. in biomedical engineering. His research interests include mobile robotics and surgical robotics.Shane M. Farritor is an Associate Professor in the University of Nebraska–Lincolns Department of Mechanical Engineering. His research interests include space robotics, surgical robotics, biomedical sensors, and robotics for highway safety. He holds courtesy appointments in both the Department of Surgery and the Department of Orthopaedic Surgery at the University of Nebraska Medical Center, Omaha. He serves of both the AIAA Space Robotics and Automation technical committee and ASME Dynamic Systems and Control Robotics Panel. He received M.S. and Ph.D. degrees from M.I.T.     

Design of efficiently encodable nonbinary LDPC codes for adaptive coded modulation

This paper is concerned with constructions of nonbinary low-density parity-check （LDPC） codes for adaptive coded modulations （ACM）. A new class of efficiently encodable structured nonbinary LDPC codes are proposed. The defining parity-check matrices are composed of scalar circulant sub-matrices which greatly reduce the storage requirement when compared with random LDPC codes. With this special structure of parity- check matrix, an efficient encoding algorithm is presented. Based on the proposed codes, a family of variable- rate/variable-field nonbinary LDPC codes is designed for the ACM system. When combined with matched-size signal constellations, the family of constructed codes can achieve a wide range of spectral efficiency. Furthermore, the resultant ACM system can be implemented via a set of encoder and decoder. Simulation results show that the proposed nonbinary LDPC codes for the ACM system perform well.