共查询到20条相似文献，搜索用时 31 毫秒
1.
In 3GPP (the 3rd Generation Partnership Project) LTE (Long Term Evolution) systems, the physical uplink shared channel (PUSCH) conveys uplink control information (UCI) back to eNodeB with or without UL-SCH (uplink shared channel) data. Placeholders are inserted into the UCI to scramble in a way that maximizes the Euclidean distance of modulation symbols. Considering the attribution of encoding with placeholders, a simple and efficient decoding scheme is proposed in this paper. As shown in our simulation results, improved performance is achieved. 相似文献
2.
提出一种基于自适应波束形成循环平稳信号算法的STBC系统,首先利用信号的循环平稳性质实现自适应波束形成,然后基于对上行链路感兴趣信号的多个分量的波束形成的估计来构造一对低相关的发送波束,经STBC编码后的即可发送以同时达到分集增益和波束形成增益,并增加下行链路的SNR.提出的方法具有计算简单和快速收敛的性能,可应用于复杂干扰环境下的TDMA无线通信.仿真结果表明这个方法比常规STBC有更好的性能,在误码率为10-4时,可获得5 dB增益. 相似文献
3.
This paper investigates the interference cancellation (IC) scheme for uplink cognitive radio systems, using the spectrum underlay
strategy where the primary users (PUs) and the secondary users (SUs) coexist and operate in the same spectrum. Joint MMSE-based
parallel interference cancellation (PIC) and Turbo decoding scheme is proposed to reduce the interference to the PUs, as well
as to the SUs, in which the minimum mean square estimation (MMSE) filter is only employed in the first iteration, regarded
as the “weakest link” of the whole detection process, to improve the quality of the preliminary detections results before
they are fed to the Turbo decoder. Simulation results show that the proposed scheme can efficiently eliminate the interference
to the PUs, as well as to the SUs. 相似文献
4.
A novel architecture of wavelength-division multiplexing/optical code division multiplexing access-passive optical network
(WDM/OCDMA-PON) based on superstructure fiber Bragg grating (SSFBG) and wavelength re-modulation technology is proposed. In
this scheme, WDM is overlaid on OCDMA channel in a single network by virtue of a kind of SSFBG, and the total capacity of
hybrid PON can be extended by regulating the transmission power reasonably. Re-modulation technology is also a good method
to save wavelength-specific components at the optical network unit (ONU) and cost of wavelength management on the customer
side. In simulation system, 1.25 Gb/s up/downstream data are transported with good performance. In addition the crosstalk
penalties from adjacent wavelength channels (with the same OC) are found to be negligible in upstream and downstream transmissions. 相似文献
5.
This paper proposes a novel multichannel medium access control(MAC)protocol based on CDMA that improves network performance and reduces collision probability in wireless ad hoc networks.In the scheme,the code channel is divided into common channel,broadcast channel and several data channels.Simulation results show that the proposed protocol can achieve significantly better performance than the IEEE 802.11 standard. 相似文献
6.
研究了多用户场景下多载波码分多址系统（MC—CDMA）的下行信道和功率分配,并将吞吐最大化问题建模成一个混合整数优化问题．为了简化分析,将问题分成2个低复杂度的子问题：功率分配和信道分配．这2个子问题可分别被一个次最优自适应功率分配算法（APA）和一个最优自适应信道分配算法（ACA）解决．通过联合APA和ACA算法,进一步提出了一个自适应信道和功率的分配方案．仿真结果表明：与传统的均匀功率分配算法相比,提出的APA算法更加适用于MC—CDMA系统;此外,提出的自适应信道和功率分配方案可以显著地提高系统吞吐量性能． 相似文献
7.
分析了在公共无线局域网(PWLAN)系统中为实现对用户统一有效管理而要求应用的二层隔离技术, 同时提出通过在无线接入点(AP)的媒体接入控制(MAC)层中定义一个隔离参量dot11Isolation, 并修改MAC层协议中Distribution-Service模块的运行状态图以实现二层隔离的一种方法. 同时, 介绍了一个基于MPC860处理器并以嵌入式Linux操作系统为平台来实现二层隔离功能的WLAN AP设备实现方案. 仿真结果表明, 本文提出的二层隔离实现方法是有效可行的. 相似文献
8.
黄建忠 《重庆大学学报(英文版)》2004,3(2):48-53
IntroductionAnidealstoragearchitecturewouldprovidestrongsecurity,datasharingacrossplatforms(i.e.operatingsystems),highperformance,andscalabilityintermsofthenumberofdevicesandclients.Today’sarchitecturesforcesystemdesignerstodecidewhichofthesefeaturesismostimportant,aschoosinganarchitectureinvolvesatrade-off.Thethreestoragearchitecturesincommonusetodayaredirect-attachedstorage(DAS),storageareanetworks(SANs),andnetwork-attachedstorage(NAS).Thefourtharchitecture,whichisoftencalledtheobjectst… 相似文献
9.
In this paper, a distributed compressive spectrum sensing scheme in wideband cognitive radio networks is investigated. An
analog-to-information converters (AIC) RF front-end sampling structure is proposed which use parallel low rate analog to digital
conversions (ADCs) and fewer storage units for wideband spectrum signal sampling. The proposed scheme uses multiple low rate
congitive radios (CRs) collecting compressed samples through AICs distritbutedly and recover the signal spectrum jointly.
A general joint sparsity model is defined in this scenario, along with a universal recovery algorithm based on simultaneous
orthogonal matching pursuit (S-OMP). Numerical simulations show this algorithm outperforms current existing algorithms under
this model and works competently under other existing models. 相似文献
10.
To efficiently exploit the performance of single instruction multiple data （SIMD） architectures for video coding, a parallel memory architecture with power-of-two memory modules is proposed. It employs two novel skewing schemes to provide conflict-free access to adjacent elements （8-bit and 16-bit data types） or with power-of-two intervals in both horizontal and vertical directions, which were not possible in previous parallel memory architectures. Area consumptions and delay estimations are given respectively with 4, 8 and 16 memory modules. Under a 0.18-pm CMOS technology, the synthesis results show that the proposed system can achieve 230 MHz clock frequency with 16 memory modules at the cost of 19k gates when read and write latencies are 3 and 2 clock cycles, respectively. We implement the proposed parallel memory architecture on a video signal processor （VSP）. The results show that VSP enhanced with the proposed architecture achieves 1.28× speedups for H.264 real-time decoding. 相似文献
11.
CHEN Zhi-kui 《浙江大学学报(A卷英文版)》2006,7(5):910-918
INTRODUCTION Recommendation H.264 was approved by ITU-T in May 2003 and the approved draft specifi cation is available for public review (Wiegand, 2003) The H.264 video codec has a very broad application range that covers all forms of digital compressed video from low bit rate Internet streaming applica tions to HDTV broadcast and digital cinema applica tions with near lossless coding. About 50% band width would be saved by using H.264 when compared to the existing most efficient com… 相似文献
12.
In this paper we introduce a novel energy-aware routing protocol REPU （reliable, efficient with path update）, which provides reliability and energy efficiency in data delivery. REPU utilizes the residual energy available in the nodes and the received signal strength of the nodes to identify the best possible route to the destination. Reliability is achieved by selecting a number of intermediate nodes as waypoints and the route is divided into smaller segments by the way-points. One distinct advantage of this model is that when a node on the route moves out or fails, instead of discarding the whole original route, only the two way-point nodes of the broken segment are used to find a new path. REPU outperforms traditional schemes by establishing an energy-efficient path and also takes care of efficient route maintenance. Simulation results show that this routing scheme achieves much higher performance than the classical routing protocols, even in the presence of high node density, and overcomes simultaneous packet forwarding. 相似文献
13.
A joint cooperation diversity and symbol mapping diversity （SMD） strategy is proposed for cooperative packet retransmission system with high-order modulation such as 16QAM. Substantial SER/BER （symbol error rate/bit error rate） gains result from multiple packet transmissions over independent paths and distinct bit-to-symbol mappings for each packet transmission. The SER/BER performance of relay assisted retransmission system is analyzed. Simulation results show that the joint-diversity strategy can provide more BER gains than other relaying strategies （i.e., decode-and-forward and constellation rearrangement relaying strategies） when no relay makes a decision error; but if some relays make decision errors, the joint-diversity strategy outperforms other relaying strategies only when the relays are closer to the source than to the destination. 相似文献
14.
Blocking optimized SIMD tree search on modern processors 总被引：2，自引：0，他引：2
Tree search is a widely used fundamental algorithm. Modern processors provide tremendous computing power by integrating multiple
cores, each with a vector processing unit. This paper reviews some studies on exploiting single instruction multiple date
(SIMD) capacity of processors to improve the performance of tree search, and proposes several improvement methods on reported
SIMD tree search algorithms. Based on blocking tree structure, blocking for memory alignment and dynamic blocking prefetch
are proposed to optimize the overhead of memory access. Furthermore, as a way of non-linear loop unrolling, the search branch
unwinding shows that the number of branches can exceed the data width of SIMD instructions in the SIMD search algorithm. The
experiments suggest that blocking optimized SIMD tree search algorithm can achieve 1.6 times response speed faster than the
un-optimized algorithm. 相似文献
15.
In this paper we present a motion compensation （MC） design for the newest Audio Video coding Standard （AVS） of China. Because of compression-efficient techniques of variable block size （VBS） and sub-pixel interpolation, intensive pixel calculation and huge memory access are required. We propose a parallel serial filtering mixed luma interpolation data flow and a three-stage multiplication free chroma interpolation scheme. Compared to the conventional designs, the integrated architecture supports about 2.7 times filtering throughput. The proposed MC design utilizes Vertical Z processing order for reference data re-use and saves up to 30% memory bandwidth. The whole design requires 44.3k gates when synthesized at 108 MHz clock frequency using 0.18-μm CMOS technology and can support up to 1920×1088@30 fps AVS HDTV video decoding. 相似文献
16.
INTRODUCTION Low latency video transmission is very de manding in terms of the performance of all layers i the protocol stack. Over the last decade, research ha focused on enhancements of each individual laye without considering cross-layer interactions. Adapt ing video coding to the channel/network condition and technologies (and vice versa) (Girod et al., 2002 via the cross-layer exchange of information has onl recently been investigated. van der Schaar et al.(200 developed a cross-laye… 相似文献
17.
ZHU Xiao-liang YANG Zong-kai DU Xu CHENG Wen-qing 《浙江大学学报(A卷英文版)》2006,7(10):1702-1708
INTRODUCTION Video streaming applications generally require continuous high bandwidth guarantees as well as stringent bounds on delays and jitters (Shen et al., 2004; Hassan and Krunz, 2004). Providing video streaming with acceptable quality degradation over wireless channels is fraught with challenges due to the adverse influence of bandwidth limitation, time variation, high error rate, and so on (Etoh and Yo- shimura, 2005; Shen et al., 2004; Chen and Zakhor, 2004; Hassan and Krunz, … 相似文献
18.
The standardized IEEE ,802. II distributed coordination function （ DCF） provides a contention-based distributed channel access mechanism for mobile stations to share the wireless medium. However, when stations are mobile or portable units, power consumption becomes a primary issue since terminals are usually battery driven. This paper proposes an analytical model that calculates the energy efficiency of both the basic and the RTS/CTS access mechanisms of the IEEE 802. II protocol. The model is validated with simulation results using NS-2 simulation package. The effects of the network size, the average packet length, the initial contention window and maximum backoff stages on the energy efficiency of both access mechanisms are also investigated. Results show that the basic scheme has low energy efficiency at large packet length and large network size, and depends strongly on the number of stations and the backoff procedure parameters. Conversely, the RTS/CTS mechanism provides higher energy efficiency when the network size is large, and is more robust to variations in the backoff procedure parameters. 相似文献
19.
Peer-to-peer （P2P） technology provides a cost-effective and scalable way to distribute video data. However, high heterogeneity of the P2P network, which rises not only from heterogeneous link capacity between peers but also from dynamic variation of available bandwidth, brings forward great challenge to video streaming. To attack this problem, an adaptive scheme based on rate-distortion optimization （RDO） is proposed in this paper. While low complexity RDO based frame dropping is exploited to shape bitrate into available bandwidth in peers, the streamed bitstream is dynamically switched among multiple available versions in an RDO way by the streaming server. Simulation results show that the proposed scheme based on RDO achieves great gain in overall perceived quality over simple heuristic schemes. 相似文献
20.
数据汇聚是降低传感器网络传输能耗的重要手段.分簇传感网数据汇聚通常包括簇内汇聚及传递汇聚结果到基站两个阶段,现有方案大多关注第二阶段数据汇聚结果传递到基站的效率.现提出一种基于位置信息的分簇传感网数据汇聚方案,通过利用位置信息选择代理点,仅与代理点有不同测量值的节点进行数据发送,有效减少了第一阶段中的数据传输.理论分析与模拟试验表明,方案簇内消息发送数优于相关方案,减少了通信开销,延长了网络生命期. 相似文献