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1.
作为一种B3G技术,HSDPA已经受到广泛的关注,该技术可以提供高速的分组下行数据传输。其关键技术包括AMC,HARQ,FCS等。AMC带来的高速率依赖于对信道质量的准确估计,所以信道质量指示(CQI)在其中发挥了关键作用。本文介绍了TD-SCDMA模式下HSDPA中CQI的工作机制和一种基于NACK的自适应信道质量反馈技术  相似文献   

2.
在高速下行分组接入(HSDPA)中,采用自适应调制编码(AMC)技术能提高下行信道传输数据的能力。仿真信道编码采用Turbo码,将自适应调制编码技术应用于VBLAST系统以进一步提高系统性能和容量。因此系统能选择调制编码方式和信道编码方式,又能对抗衰落引起的突发错误。对该系统进行仿真表明:自适应调制编码的VBLAST系统能有效地提高数据传输效率和传输质量。  相似文献   

3.
HSDPA(高速下行分组接叭)用于实现WCDMA网络高速下行数据业务,可以使下行的数据速率达到14Mbps的峰值速率。对采用多入多出(MIMO)技术的HSDPA系统,数据速率可以达到20Mbps。在HSDPA技术方案中,涉及到的关键技术主要包括四种,即自适应编码调制(AMC)、H-ASQ、快速蜂窝选择(FCS)和多入多出天线处理(MIMO)。  相似文献   

4.
在高速下行分组接入(HSDPA)中,采用自适应调制编码(AMC)技术能提高下行信道传输数据的能力.文章信道编码采用Turbo码,将自适应调制编码技术应用于VBLAST系统以进一步提高系统性能和容量.因此系统能选择调制编码方式和信道编码方式,又能对抗衰落引起的突发错误.对该系统进行仿真分析表明:自适应调制编码的VBLAS...  相似文献   

5.
余谦  刘任庆 《通信技术》2008,41(5):56-58
自适应调制编码(AMC)是高速下行分组接入(HSDPA)的关键技术之一,它可以根据信道质量情况的改变调整调制与编码方式,从而合理地利用和分配系统资源.文中概述了AMC技术原理、特点、结构和流程,对基于TD-SCDMA的AMC 技术性能进行仿真和分析.通过仿真结果,分析了在不同情况下该编码的主要技术特点,并做出了相关的结论.  相似文献   

6.
HSDPA是一些无线增强技术的集合,可以使TD—SCDMA下行数据峰值速率有很大的提高。本文主要介绍了HSDPA的物理层关键技术,包括AMC、HARQ和信道结构等。  相似文献   

7.
HSDPA是一些无线增强技术的集合,利用HSDPA技术可以在现有技术的基础上使下行数据峰值速率有很大的提高。HSDPA主要是通过引入高速下行共享信道(HS-DSCH)增强空中接口,并在UTPAN中增加相应的功能实体来完成的;引入自适应调制编码(AMC)和HARQ(混合ARQ)技术来增加数据吞吐量;增强Node B的处理功能。在Node B的MAC层中引入一个新的MAC-hs实体,专门完成HS-DSCHR的相关参数和HARQ协议等相关处理。在高层和接口加入相关操作信令。  相似文献   

8.
TD-SCDMA HSDPA/R4混合组网研究   总被引:1,自引:0,他引:1  
一、引言 基于用户对下行高速分组数据业务的需求,3GPP在Rel5中引入了HSDPA技术。基于自适应调制编码(AMC),混合自动重传请求(HARQ)等关键技术,HSDPA技术有效地提高了小区流量和峰值速率。TD—SCDMA系统是一个时分双工系统(图1),其上下行的时隙数目可以灵活配置,以支持上下行不对称数据业务。  相似文献   

9.
高速下行分组接入技术(HSDPA)通过使用自适应调制编码、混合自动重传请求、快速凋度等关键技术,可以大大提高下行数据的传输速率。为了充分利用这些技术网络侧必须配置仅供HSDPA用户使用的PDSCH码道,因为PDSCH码道的共享性和普通R4码道的专用性,TD-SCDMA系统中必须在建立小区的时候建立PDSCH码道,一旦某些码道被HSDPA占用就不能再在这些码道上接入普通的R4业务。但系统对HSDPA下行流量的需求是时变的,因此固定不变的PDSCH码道配置就有可能造成码道资源的浪费。本文从侧重实现的角度提出了一种基于LMS自适应算法的HSDPA动态码道分配方法,可以由系统根据当前下行数据流量自行调整HSDPA码道配置,提高了TD-SCDMA系统中HS-PDSCH物理信道的利用效率和系统容量。  相似文献   

10.
3GPP在R5版本中提出了HSDPA(高速下行分组接入)。HSDPA通过采用AMC、HARQ、高阶调制(16QAM)等技术,在基站侧实现快速调度,从而可以快速自适应地反映用户信道的变化,获得较高的用户峰值速率和小区数据吞吐量。HSDPA的单载波(上下行时隙比例为1:5)理论峰值速率可达2.8Mb/s。烽火  相似文献   

11.
HSDPA (high-speed downlink packet access) is an evolved UMTS packet scheme that delivers increased user peak data rates and quality of service. A key technique supporting HSDPA is adaptive modulation and coding (AMC), in which the modulation scheme and the coding rate are changed adaptively according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes channel adaptive CQI reporting schemes in which UEs report the CQI value intelligently by using information about channel quality. With the proposed schemes, the battery capacity of UE can be conserved and the uplink interference can be lowered by filtering off redundant CQI reports or the transmission error rate can be lowered by fast CQI reports.  相似文献   

12.
A major evolution of UMTS standard is the high speed downlink packet access (HSDPA). One of key techniques supporting HSDPA is the adaptive modulation and coding (AMC) in which the modulation scheme and the coding rate are adaptively changed according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes an enhanced CQI reporting scheme that can be used when a proportional fair scheduling algorithm (PFA) is used as a packet scheduling algorithm. The proposed scheme uses a dynamic threshold to filter off redundant CQI reports. With the proposed scheme, the battery capacity of UK can be conserved, maintaining the performance of traditional CQI reporting scheme.  相似文献   

13.
We propose an unbiased signal‐to‐interference ratio (SIR) estimator for the high speed downlink packet access (HSDPA) system. The proposed SIR estimator solves the problem of underestimation present in conventional SIR estimators and is suitable for channel quality measurement in the adaptive modulation and coding scheme of HSDPA, which requires accurate SIR estimation for optimum adaptive modulation and coding selection. Our analysis and simulation results demonstrate the improved estimation performance of the proposed SIR estimator.  相似文献   

14.
An opportunistic feedback technique is proposed for proportional fair (PF) scheduling in a downlink multi-user system. This technique requires each mobile station, the scheduling metric of which is higher than a threshold, to send one-bit feedback for PF scheduling. The scheduler determines the optimal modulation and coding scheme for a scheduled user based on channel quality indicator (CQI) update, which is sent on a longer period than the scheduling period. The simulation results indicate that PF scheduling with the proposed update scheme can achieve similar performance as PF scheduling with full CQI feedback. The feedback overhead can be reduced in comparison with typical PF scheduling provided that an optimal CQI update period is chosen.  相似文献   

15.
Resource allocation in OFDMA systems involves the application of adaptive modulation/coding (AMC). AMC provides the flexibility to match the modulation-coding scheme (MCS) to each user’s channel conditions. In order to accurately determine the appropriate MCS level, full channel state information (CSI) is required by the base-station (BS). Full CSI feedback requires bandwidth to be reserved in the OFDM frame which is occupied by the users to transmit channel quality information (CQI) to the BS. Allocations and deallocations of channels reserved for CQI feedback require expensive signaling messages between the base stations and the mobile stations, and therefore should be minimized. In this paper, we show that the amount of bandwidth consumed for this type of signalling can be significantly reduced by selecting the users with the lowest average SNR to periodically feedback their instantaneous channel state information. These benefits become more evident at low values of the user velocity.  相似文献   

16.
This paper focuses on the effect of circuit switched (CS) services on high speed downlink packet access (HSDPA) packet services in the context of the UMTS FDD system. An objective of the analysis is to provide guidelines for the UMTS planning process to prioritize services when resources are dynamically shared between circuit and packet services. An analytical model, taking into account some of the features introduced in HSDPA (namely adaptive modulation and coding (AMC), hybrid automatic repeat request (HARQ) and fast cell selection) and the interaction between CS services and HSDPA, is proposed to approximate the HSDPA cell capacity. Simulation results to assess the efficiency of the analytical model are also reported.  相似文献   

17.
For the efficacy of radio resource management in downlink wireless relay networks, the channel quality indicator (CQI) between a mobile station (MS) and a relay station (RS) should be fed back from the RS to its base station (BS), at the cost of additional feedback overhead. In this letter, we propose an efficient feedback scheme based on network coding between a pilot sequence and the CQI of MS-RS link, through which the BS can have both CQIs of MS-RS and RS-BS links without overhead. Numerical results reveal that the proposed CQI reporting scheme has as good feedback performance as conventional one which generally requires additional feedback burden.  相似文献   

18.
Cross-layer techniques represent efficient means to enhance throughput and increase the transmission reliability of wireless communication systems. In this paper, a cross-layer design of aggressive adaptive modulation and coding (A-AMC), truncated automatic repeat request (T-ARQ), and user scheduling is proposed for multiuser multiple-input–multiple-output (MIMO) maximal ratio combining (MRC) systems, where the impacts of feedback delay (FD) and limited feedback (LF) on channel state information (CSI) are also considered. The A-AMC and T-ARQ mechanism selects the appropriate modulation and coding schemes (MCSs) to achieve higher spectral efficiency while satisfying the service requirement on the packet loss rate (PLR), profiting from the feasibility of using different MCSs to retransmit a packet, which is destined to a scheduled user selected to exploit multiuser diversity and enhance the system's performance in terms of both transmission efficiency and fairness. The system's performance is evaluated in terms of the average PLR, average spectral efficiency (ASE), outage probability, and average packet delay, which are derived in closed form, considering transmissions over Rayleigh-fading channels. Numerical results and comparisons are provided and show that A-AMC combined with T-ARQ yields higher spectral efficiency than the conventional scheme based on adaptive modulation and coding (AMC), while keeping the achieved PLR closer to the system's requirement and reducing delay. Furthermore, the effects of the number of ARQ retransmissions, numbers of transmit and receive antennas, normalized FD, and cardinality of the beamforming weight vector codebook are studied and discussed.   相似文献   

19.
Adaptive Bit-Interleaved Coded OFDM With Reduced Feedback Information   总被引:1,自引:0,他引:1  
If the channel is static and is perfectly known to both the transmitter and the receiver, the water-filling technique with adaptive modulation is known to be optimal (Gallager, 1968). However, for orthogonal frequency-division multiplexing (OFDM) systems, this requires intensive traffic overheads for reporting channel state information on all subcarriers to the transmitter. In this paper, we consider an adaptive modulation and coding scheme for bit-interleaved coded OFDM with reduced feedback information satisfying a specified quality of service level. We propose a rate adaptation scheme, which utilizes the estimated bit error rate for supportable transmission rates. In this scheme, a user equipment chooses a modulation and coding scheme (MCS) level, which can provide the maximum spectral efficiency based on one OFDM symbol rather than on all subchannels. Then the user needs to send back only the selected MCS level index. The proposed scheme does not require the water-filling procedure, and the amount of the feedback information reduces to a single integer value irrespective of the number of subcarriers. Simulation results show that the proposed scheme can significantly reduce the system complexity while minimizing the performance loss compared to the optimum water-filling scheme.  相似文献   

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