高速MIMO解调器的FPGA实现

研究了高速多入多出（MIMO）解调器的实时实现，并且基于一种与信道译码器联合迭代的MIMO检测算法，提出了高效可行的FPGA实现方案。仿真分析和实验表明，硬件实现的性能与理论性能接近。完全可应用于新一代移动通信系统中完成高速MIMO解调的任务。     

MIMO及其两种应用技术

多入多出(MIMO)技术能在不增加带宽的情况下,成倍地提高通信系统的容量和频谱利用率,是新一代移动通信系统广泛采用的关键技术.本文简要介绍了MIMO及其两种应用技术,即PARC和D-TxAA,并给出了仿真结果对比.     

HSDPA的演进:基于OFDM和MIMO的HSOPA技术

文章主要介绍了基于正交频分复用（OFDM）和多入多出（MIMO）的高速OFDM分组接入（HSOPA）技术。详细阐述了其优点所在，最后对HSOPA的频谱规划提出了建议。     

4G通信系统核心技术MIMO—OFDM研究

MIMO-OFDM技术既可以为系统提供高传输速率,也能提高系统容量,降低成本,将成为第四代移动通信系统的核心技术。文章介绍了多输入多输出（MIMO）技术与正交频分复用（OFDM）技术的基本原理和特点,并对MIMO—OFDM技术的原理及其关键技术进行了详细阐述。     

MIMO技术的发展与应用

给出了多输入多输出(MIMO)技术的概念,详细叙述了MIMO技术的研究现状,阐述了MIMO的关键技术和MIMO技术的应用,研究和分析表明无线移动通信领域智能天线技术的重大突破就是多MIMO技术,它能在不增加带宽的情况下成倍地提高通信系统的容量和频谱利用率,是下一代移动通信系统中最富有竞争力的技术之一。文章最后给出了MIMO技术今后的研究方向。     

无线MIMO信道的建模与仿真研究

近年来，凭借在提高系统频谱利用率方面卓越的性能表现，多入多出MIMO技术成为了移动通信技术发展进程中广受关注的课题。为了更好的利用MIMO技术，必须对MIMO信道的特性进行研究，建立适合于多天线系统的仿真模型。通过将空间角度的概念引入到信道的仿真模型中，给出了一个完整的MIMO信道的仿真模型，并给出了相关的仿真算法。     

MIMO原理及其在移动通信中的应用

多入多出（MIMO）或多发多收天线（MTMRA）技术,是无线移动通信领域智能天线技术的重大突破,该技术能在不增加带宽的情况下,成倍地提高通信系统的容量和频谱利用率,是新一代移动通信系统采用的关键技术.     

无线通信系统中的闭环MIMO技术

多入多出（MIMO）技术被认为是下一代无线通信的关键技术之一,本文主要讨论能够进一步提升多天线系统容量的闭环MIMO技术,即带有反馈的MIMO系统。反馈的信道信息既可以提高单链路的传输性能,也可以优化多用户之间的调度问题。本文给出了几种在未来无线通信系统中可能采用的闭环MIMO方案,包括基于SVD分解和基于码本的预编码技术,分析并比较了它们的性能。仿真结果表明,闭环MIMO技术将有效地提高通信系统的性能。     

MIMO技术的发展

未来无线通信系统需要更高的数据传输速率和更好的服务质量，因此需要系统容量大幅度提高。在有限的无线频谱资源条件下，只有极大地提高频谱利用率才能使系统容量更高。采用多输入多输出（MIMO）天线技术可以满足要求。MIMO技术的主要研究方向包括：MIMO信道、MIM0收发技术、分布式MIM0和MIM0应用。MIM0技术是无线通信领域重大的技术突破，将成为未来无线觅带移动通信系统和无线宽带接入系统的关键技术。     

多天线无线信道仿真与建模方法

多入多出（MIMO）技术由于可以提高频谱利用率、系统容量和通信质量而被3G和B3G／4G系统所采用，选择合适的信道仿真模型对于测试MIMO技术在系统中的性能也就越来越重要。本文介绍了MIMO信道各种仿真与建模方法。     

Adaptive channel assignment for different types of traffic in DS‐CDMA cellular systems

The link capacity of DS‐CDMA cellular systems is limited by the interference contained in the link. This link interference is affected by many environment factors and thus the link capacity varies with the environment. Since link capacity changes with the varying interference and different traffic types mutually interfere with each other, it is difficult to use link capacity efficiently. Static channel assignment (SCA) based on fixed link capacity is inefficient for DS‐CDMA cellular systems. To improve system capacity, channel assignments need to be adapted to variations in interference. In this paper, we propose an adaptive channel assignment (ACA) for different types of traffic. The proposed ACA is based on the reverse link power received at the base station and is adaptable to dynamically varying environments. It consists of two schemes: nonprioritized and prioritized. In the nonprioritized scheme, there is no difference in channel assignments between calls. In the prioritized scheme, however, the number of nonpriority calls acceptable is limited. In both schemes, a channel is assigned if the link power after assigning the channel is less than the power allowed in the link. The performance is evaluated in terms of link capacity and service grade. Utilizing the proposed algorithm yields more link capacity than using SCA in such environment changes as nonhomogeneous traffic load or varying path loss. Service grade is also improved by properly limiting the number of nonpriority channels. This revised version was published online in August 2006 with corrections to the Cover Date.     

Interference-based channel assignment for DS-CDMA cellular systems

Link capacity is defined as the number of channels available in a link. In direct-sequence code-division multiple-access (DS-CDMA) cellular systems, this is limited by the interference present in the link. The interference is affected by many environmental factors, and, thus, the link capacity of the systems varies with the environment. Due to the varying link capacity, static channel assignment (SCA) based on fixed link capacity is not fully using the link capacity. This paper proposes a more efficient channel assignment based on the interference received at the base station (BS). In the proposed algorithm, a channel is assigned if the corresponding interference margin is less than the allowed interference, and, thus, channels are assigned adaptively to dynamically varying link capacity. Using the proposed algorithm yields more channels than using SCA in such an environment changes with nonhomogeneous traffic load or varying radio path loss. The algorithm also improves service grade by reserving channels for handoff calls     

基于资源分配和功率控制的D2D中继选择

为优化蜂窝用户通信与设备直传(D2D)中继通信共存下的同频干扰问题,满足蜂窝用户容量要求,提出了一种基于能效的联合资源分配和功率控制的D2 D中继选择算法.该算法首先对等效D2 D中继链路进行资源分配,减小算法复杂度的同时使得D2 D链路对蜂窝链路产生的干扰最小;然后以资源分配结果和功率控制算法为依据进行中继选择.该方案不仅考虑了D2 D中继链路的能效问题,而且还同时考虑到了对蜂窝链路的干扰问题.通过仿真验证,所提算法不仅能有效提升D2 D中继链路的能效值,同时降低了对蜂窝用户的干扰.     

On the Capacity Enhancement of a Cellular CDMA Channel with Asymmetrical Bandwidth Allocation

Capacity enhancement of cellular CDMA is analyzed using an asymmetrical-bandwidth-allocation approach. Cellular CDMA systems with and without successive interference cancellation are considered. The main source of interference is interuser interference and, in particular, a 9-cell configuration is employed to account for interference from surrounding cells. By transferring more bandwidth or, equivalently, processing gain from the forward link to the reverse link, we have effectively balanced their performance and raised the overall capacity of the cellular system. The optimum bandwidth allocation is easily obtained from the performance curves of both links. For a typical cellular CDMA with a bit error rate of 10-³, the capacity gain of this approach is about 40%. If successive interference cancellation is employed and both links have the same quality, then both links should have equal bandwidth. However, in a situation where imperfect power control occurs, our studies indicate that using interference cancellation alone achieves a 25% increase in capacity, while enhancement with an asymmetrical bandwidth allocation overlay raises this gain to 68%.     

Adaptive Antenna Subarray Formation for MIMO Systems

MIMO systems with reduced hardware complexity have attracted researchers' attention due to their high efficiency and low cost. Sub-optimum algorithms for antenna subset selection have been intensively studied in the literature. In this paper we present a new technique to maximize the capacity of multiple antenna wireless systems with reduced available RF chains. The technique is based on the adaptive formation of subarrays, i.e. the grouping of antenna elements and the application of appropriate element weights. The elements of each subarray and their weights are dynamically selected by an evolutionary optimization technique using the link capacity as a cost function     

Cellular CDMA capacity with out-of-band multihop relaying

In this paper, we consider the capacity of cellular code division multiple access (CDMA) when there is out-of-band ad hoc traffic relaying. The mobile stations (MSs) are dual-mode, having both ad hoc and cellular CDMA radios. An active MS is free to choose any available relay station (RS) within its ad hoc radio coverage area for dual-hop communication with the CDMA base station (BS). Communications between the RSs and the MSs use bandwidth which is available to the ad hoc radio and does not consume the CDMA capacity. Using this mechanism, CDIVIA interference can be reduced by dynamically selecting RSs which have more favorable CDMA link characteristics. Several relay station selection criteria are considered, namely, ad hoc relaying with low relative interference (ARRI), with best link gain (ARLG), and with shortest distance (ARSD). The relay station selection protocols are compatible with existing wireless local area network (WLAN) standards such as IEEE 802.11. An analytic model is used to compute the effects on uplink and downlink CDMA capacities when out-of-band relaying is added. The results show that very significant capacity improvements are possible by using these criteria compared with conventional CDMA with hard or soft handoff. Ad hoc relaying which dynamically tracks CDMA link quality can achieve greater capacity improvements than that using a distance-based relay station selection. Relaying, which considers both signal and interference conditions, achieves better capacity than that based on signal link quality alone.     

基于优化多带复小波的多载波CDMA及反向链路性能

在分析多载波码分多址的原理基础上,利用优化生成的多带复小波,提出了一种基于优化多带复小波的多载波CDMA系统反向链路模型,并采用基于多天线的空间分集合并(SDC)技术进一步完善所提系统.该系统可利用优化多带复小波的优良特性来避免通常多载波CDMA由于插入循环前缀所带来的频谱效率的下降,在此基础上我们研究了所提系统采用空间分集合并技术时在瑞利衰落信道下的反向链路性能;给出相应的误比特率分析.理论分析和仿真结果表明采用基于最大比合并的SDC技术可显著提高所提系统抗空间衰落和各种干扰的能力,而且基于SDC技术的所提系统要好于同样基于SDC技术的通常多载波CDMA系统和基于实小波包的多载波CDMA系统.     

Erlang capacity of a power controlled CDMA system

This work presents an approach to the evaluation of the reverse link capacity of a code-division multiple access (CDMA) cellular voice system which employs power control and a variable rate vocoder based on voice activity. It is shown that the Erlang capacity of CDMA is many times that of conventional analog systems and several times that of other digital multiple access systems     

国外多种数据链综合应用研究

从网络中心战对数据链发展的要求出发,结合外军数据链发展情况及特点,着重论述了多种数据链综合应用所面临的技术挑战及解决途径。分析了建设全球信息栅格面临的技术困难,并提出我军数据链综合应用需从以主用数据链为主实现多数据链信息共享、数据链距离扩展及数据链、与计算机互联网络的互联等方向的几点启示。     

Reverse link capacity analysis of a CDMA cellular system with mixedcell sizes

The demands for mobile communication services are growing rapidly. In heavily populated areas, cell splits are unavoidable to increase the capacity of the cellular system. Cell splitting makes a cellular system have mixed cell sizes. For cell planning, it is necessary to analyze the reverse link capacity of a code-division multiple-access (CDMA) cellular system with mixed cell sizes. In this paper, we propose a method to calculate the reverse link capacity of a CDMA cellular system with mixed cell sizes. When a macro cell is split into three micro cells, as an example, we calculate the reverse link capacities for the three micro cells and the neighboring macro cells. The results show that as the radius of a micro cell decreases, the reverse link capacity of the micro cell increases, while those of the neighboring macro cells decrease