共查询到20条相似文献,搜索用时 78 毫秒
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在认知无线网络中,建立了基于认知OFDM多载波资源分配数学模型,在授权用户干扰受限条件下,以最大化传输速率为目标进行认知用户的子载波功率分配。传统注水法被证明是最优的单用户子载波功率分配算法,在传统注水法功率分配基础上,提出了两种可行的子载波功率分配改进算法,改进算法一是通过对水面值的粗略估计快速确定不分配功率子载波,改进算法二不需要通过迭代计算水面值,只通过线性计算就可以直接确定不分配功率的子载波,且对授权用户不产生干扰。仿真结果表明,在改进的两种子载波功率分配算法下,认知用户的数据传输速率优于传统注水法功率分配时认知用户的数据速率,所提改进算法具有自适应特性且计算复杂度大大降低。 相似文献
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研究了优化公平性的多用户OFDM系统下行链路的资源分配算法,根据系统各用户的业务需求,在保证用户所得数据速率满足一定比例以及系统总功率限制的前提下,提高系统总数据速率。首先,根据公平性原则进行用户的子载波分配,子载波功率分配使用注水算法;子载波分配完成后,利用贪婪功率分配算法,以最大化用户数据速率和提高功率利用率为目标,对各用户内部子载波功率和比特数进行再分配。仿真结果表明,相比参考文献[10]的算法,该算法在提高系统总速率的同时,更好地保证了用户数据速率的公平性;相比参考文献[12]的算法,该算法虽然牺牲了一定的系统总速率,但能提供更高的用户数据速率公平性。 相似文献
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在无线环境下,随着用户数的增加和速率需求的提高,基站能量消耗越来越大。因此,无线网络中能量有效化的设计变得非常必要。本文研究了一种能量有效的多用户OFDM下行链路的资源分配方案。利用分布式方式,首先根据用户的平均信道增益和最低用户比特要求,结合提出的能量有效准则思想分配子载波数;然后按照各用户分配的子载波数分配信道条件较好的信道;再对每个用户所分配的信道按照最低比特要求平均分配比特数,并利用能量有效准则做最优调整,保证功率最小。仿真结果表明,在满足各用户的误比特率及速率要求的条件下,提出的算法与静态的频分多址资源分配方式相比,功率可减小5~6 dB;同时与已有的一种经典分布式算法相比,功率可减小2~4 dB。 相似文献
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提出了一种新的基于OFDM多用户通信系统的资源分配算法。该算法在总功率限制和用户数据率要求下,通过以下两步实现子载波、比特和功率的动态分配:第一步,基于用户的平均信道增益和数据率要求进行资源初分配(每个用户分配多少个子载波、功率);第二步,对步骤1中的结果进行调整,最终决定每个用户分配到的子载波、功率以及比特载入方式。相比于Hujun Yjn等人提出的另一种基于用户需求的算法,新算法的基站发射功率略有增加,但复杂度大为降低,在实际运用中更有利用价值。 相似文献
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针对多用户正交频分复用(OFDM)系统资源分配问题,提出了一种改进的基于边缘自适应(MA)准则的子载波和比特分配算法。在采用比例公平准则为每个用户分配子载波集合基础上,以用户速率最大者-最小者(Max-Min)子载波交换为原则进行子载波调整,使用户功率递减同时兼顾用户的公平性;通过对信道状态信息进行判断,利用贪婪算法将用户子载波分配的比特取整,以实现系统功率最小化。实验结果表明,本文提出的改进次优算法的计算复杂度较传统分步算法稍高,但仍远低于最优算法,其系统性能得以提升,且接近最优算法。 相似文献
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针对多用户OFDM系统中的功率优化问题,提出了一种新的子载波、比特分配算法。利用匈牙利算法对子载波进行初始分配,然后根据信道的状态信息为每个子载波动态地分配比特,最后对分配的结果作进一步调整,直到发射总功率不再减小为止。仿真结果表明,调整后的结果比原有方法有所改善,在满足传输速率和误码率要求的条件下,有效地降低了系统发射总功率。 相似文献
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An adaptive bit allocation algorithm is proposed for multiuser transmission in OFDM/CDMA systems. The proposed scheme takes
advantage of frequency diversity to dynamically allocate a suitable number of bits/per symbol on subcarriers of each user
based on the transmitting objectives such as the required transmission rate and BER. A suboptimal solution to the problem
of the bit allocation on subcarriers for each user is derived by minimizing the interference power from each user. Then an
algorithm for adjusting the number of allocated bits is used to further reduce the interference without changing the total
transmitted data rate. The performance obtained by minimizing the interference resulting from each user is studied in terms
of BER, transmission data rate and the system capacity supporting multiple users. The theoretical analysis and simulation
results show that the proposed algorithm substantially outperforms those reported previously. 相似文献
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针对通信系统工作过程中受到外界电磁干扰而无法通信的问题,研究了基于软件无线电的电磁干扰效应及误码特征。通过分析典型软件无线电电磁信号传输特性及其信息链路电磁干扰耦合路径,设计了软件无线电通信干扰实验系统。该系统利用Simulink软件观测、记录通信信号眼图、星座图信息等受扰特征,并通过分析接收信号的误码率,给出了不同干扰信号对通信系统的影响规律:当同频干扰功率达到-40 dBm时通信开始出现误码,干扰功率每增加5 dB,误码率增加一个量级,干扰功率增加到-18 dBm时,误码率达到阈值0.25;邻频干扰误码率随干扰功率变化趋势与同频干扰一致,但出现误码的最小干扰功率更大;带外强干扰信号也会影响通信系统可靠性,在相同误码率情况下,需要更大的干扰信号功率且大小与信号频偏成正比。 相似文献
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The paper considers discrete multitone (DMT) modulation for multiuser communications when multiple users are supported by the same system, a zero-padding redundancy is employed at the transmitter output, and linear redundancy removal is used at the channel output. These users may have differing quality of service (QoS) requirements, as quantified by bit rate and symbol-error rate specifications, and are each assigned an equal number of subchannels. Our goal is to minimize the transmitted power, given the QoS specifications and subject to the knowledge of the channel and the second-order statistics of the colored interference at the receiver input. In particular, we find an optimum bit-loading scheme that distributes the bit rate transmitted across the various subchannels belonging to each user, and, subject to this bit allocation, we determine the precise subchannels assigned to each user, the optimum transceiver characterized by the input/output block transforms, and the redundancy removal operation. A major conclusion is that even though the optimum bit-rate allocation differs from the single-user case, the optimum transceiver does not. Further, it is determined entirely by the channel and interference conditions, and is unaffected by the QoS requirements. 相似文献
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Ioannis N. Stiakogiannakis Dimitra I. Kaklamani 《Wireless Personal Communications》2013,69(2):745-770
This work proposes a radio resource management framework employing game theoretic concepts for orthogonal frequency division multiple access, the most prevalent multiple access technique for the next generation wireless networks. The subcarrier allocation problem is encountered as a combinatorial auction, where the base station auctions the subcarriers and the users bid for and buy bundles of subcarriers, aiming at minimising their required transmit power. Subsequently, each allocated subcarrier is loaded with a number of bits, decided by each user independently, and the power control process is set up as a non-cooperative game. Each user responds to the interference sensed in his environment and, through a best responses process, the game converges to the unique, Pareto optimal, Nash equilibrium. In order to guarantee convergence, a limit is imposed to the maximum modulation level for each subcarrier. Simulation results show that the auction algorithm follows closely the performance of the optimal algorithm, whereas it is of lower computational complexity and requires less feedback information. Similarly, the proposed distributed bit loading and power control scheme achieves lower transmit power per offered bit rate unit. However, the distributed nature of the algorithm results in lower total offered bit rate, because of the partial knowledge and exploitation of channel state information. 相似文献
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《Signal Processing, IEEE Transactions on》2005,53(9):3572-3582
We consider the design of biorthogonal, as opposed to orthonormal, discrete multitone (DMT) systems supporting multiple services in a single antennae setting. The services may have differing quality of service (QoS) requirements, quantified by bit rate and symbol error rate specifications. Different users on the system can be potentially assigned different number of subchannels. Our goal is to minimize the transmitted power given the QoS specifications for the different users, subject to the knowledge of the channel and colored interference at the receiver input of the DMT system. We find an optimum bit loading scheme that distributes the bit rate transmitted across the various subchannels, where the precise subchannels are assigned to each user, and an optimum transceiver. Key conclusions are i) relaxing the orthonormality constraint yields no performance improvement; ii) the optimum transceiver is unaffected by changing service characteristics, and depends only on the channel and interference conditions; iii) the QoS requirements, the number of users, and the number of subchannels assigned to the different users only affect bitloading and subchannel assignment. 相似文献
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A model for a multiple spot beam digital satellite employing an active phased array antenna with frequency reuse is proposed and applied to study the power limited down-link bit error rate performance. Since the power amplifier preceding each antenna element is generally nonlinear, intermodulation distortion is produced among the various spot beams, degrading performance. Expressions for the bit error rate are derived, averaged over an ensemble of random arrays. Typical results indicate a degradation of 1-5 dB relative to a horn-reflector antenna of the same total effective aperture with a single channel per transponder, as the number of cochannel signals and the number of antenna elements are respectively varied between 10 and 30, and 500 and 10 000. The degradation is shown to result from nonlinearly induced signal suppression and cochannel interference. 相似文献
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This correspondence considers an interference suppression scheme for a direct-sequence code-division multiple-access overlay system operating in a multipath Nakagami fading environment. The receiver employs suppression filters and diversity to mitigate the effect of multipath and narrow-band jammer interference. The system performance is presented in terms of the bit error rate with different system parameters such as bit energy, jammer-to-signal power, multipath, diversity, ratio of interference bandwidth to spread-spectrum bandwidth, and number of active users. Numerical results indicate substantial improvement in system performance. 相似文献
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Kyuntak Kim 《International Journal of Electronics》2013,100(8):1377-1387
In this paper, we propose an inter-lighting interference cancellation (ILIC) scheme to reduce the interference between adjacent light-emitting diodes (LEDs) and enhance the transmission capacity of multiple-input–single-output (MISO)-visible light communication (VLC) systems. In indoor environments, multiple LEDs have normally been used as lighting sources, allowing the design of MISO-VLC systems. To enhance the transmission capacity, different data should be simultaneously transmitted from each LED; however, that can lead to interference between adjacent LEDs. In that case, relatively low-received power signals are subjected to large interference because wireless optical systems generally use intensity modulation and direct detection. Thus, only the signal with the highest received power can be detected, while the other received signals cannot be detected. To solve this problem, we propose the ILIC scheme for MISO-VLC systems. The proposed scheme preferentially detects the highest received power signal, and this signal is referred as interference signal by an interference component generator. Then, relatively low-received power signal can be detected by cancelling the interference signal from the total received signals. Therefore, the performance of the proposed scheme can improve the total average bit error rate and throughput of a MISO-VLC system. 相似文献