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1.
We consider cyclic prefixed single carrier and adaptive multicarrier transmission over a frequency selective channel. We compare the achievable bit rate for a target bit error rate. We analytically prove that the bit rate achieved with multicarrier transmission with adaptive modulation is always higher than that obtained with single carrier transmission when a one-tap frequency domain equalizer is used. We also show that the same adaptively loaded multicarrier scheme reaches the performance of single carrier transmission with a block decision-feedback equalizer. 相似文献
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Cvetkovic Z. Vetterli M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1998,44(5):1961-1964
Accuracy of simple analog-to-digital conversion depends on both resolution of discretization in amplitude and resolution of discretization in time. For implementation convenience, high conversion accuracy is attained by refining the discretization in time using oversampling. It is commonly believed that oversampling adversely impacts rate-distortion properties of the conversion, since the bit rate, B, increases linearly with oversampling, resulting in a slow error decay in the bit rate, on the order of O(1/B). We demonstrate that the information obtained in the process of oversampled analog-to-digital conversion can easily be encoded in a manner which requires only a logarithmic increase of the bit rate with redundancy, achieving an exponential error decay in the bit rate 相似文献
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This paper investigates the notion of the probability of bit error (PBE) and its
distribution in chaos-based communication systems; these are seen as being the fundamental
quantities to both the well-known bit error rate (BER) and the new concept in
chaos communications of bit outage rate (BOR). The form of the distribution illustrates
the degree to which bit error rate is a stable representation of performance. Bit outage rate
is another measure of performance which gives practically helpful information about bit error.
For a simple coherent chaos-shift-keying system the distribution of bit error probability
is derived exactly, and theoretically exact formulas for the bit outage rate and bit error rate
are presented. Two specific cases are developed to obtain useful qualitative and quantitative
information. The cases concern independent Gaussian spreading, as a lower benchmark and
logistic map spreading, as typical of effective chaotic spreading. Comparisons are obtained
between these spreading distributions and between different extents of their spreading,
calibrated against per bit signal to noise ratio. A general conclusion is that bit outage and
bit error rates are complementary measures of performance. 相似文献
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In this paper, we present a two-stage near-lossless compression scheme. It belongs to the class of "lossy plus residual coding" and consists of a wavelet-based lossy layer followed by arithmetic coding of the quantized residual to guarantee a given L(infinity) error bound in the pixel domain. We focus on the selection of the optimum bit rate for the lossy layer to achieve the minimum total bit rate. Unlike other similar lossy plus lossless approaches using a wavelet-based lossy layer, the proposed method does not require iteration of decoding and inverse discrete wavelet transform in succession to locate the optimum bit rate. We propose a simple method to estimate the optimal bit rate, with a theoretical justification based on the critical rate argument from the rate-distortion theory and the independence of the residual error. 相似文献
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传统基于接收信号强度的物理层密钥生成方案在窃听者靠近合法方时,合法方的密钥易被窃听者获取.针对该问题,在分析密钥误比特率的基础上,提出一种基于信号传播特性的物理层密钥生成方案.方案根据接收信号强度的实测样本估计大尺度衰落模型,提取出多径效应影响下的小尺度参数量化生成密钥.实验结果表明相比于传统方案,本方案在室内环境窃听距离大于0.6倍波长以后,窃听方密钥误比特率大于0.48;在室外环境窃听距离大于1倍波长后窃听方密钥误比特率为0.47,实现了安全可靠的物理层密钥生成. 相似文献
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We propose a decision-feedback decoder for coded signals transmitted over finite-state Markov channels. The decoder achieves maximum-likelihood sequence detection (in the absence of feedback errors) with very low complexity by exploiting previous bit decisions and the Markov structure of the channel. We also propose a similar decoder, the output-feedback decoder, that does not use previous bit decisions and therefore does not suffer from error propagation. The decoder performance is determined using a new sliding window analysis technique as well as by simulation. Both decoders exhibit excellent bit error rate performance with a relatively low complexity that is independent of the channel decorrelation time 相似文献
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We examine the bit error rate (BER) of the conventional matched-filter detector for an optical code division multiple access (CDMA) system employing coherent homodyne detection. We assume a phase shift keying (PSK) modulation format where the phase is modulated by one of two methods: (1) an external phase modulator or (2) injection locking. Phase excursion is limited to ±0.42 π when using injection locking. We examine the bit error rate performance for both external modulation and modulation of the injection current and find only a moderate penalty (0.55 dB) associated with the limited phase excursion 相似文献
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Passive optical fast frequency-hop CDMA communications system 总被引:21,自引:0,他引:21
This paper proposes an all-fiber fast optical frequency-hop code division multiple access (FFH-CDMA) for high-bandwidth communications. The system does not require an optical frequency synthesizer allowing high communication bit rates. Encoding and decoding are passively achieved by Bragg gratings, Multiple Bragg gratings replace a frequency synthesizer, achieving a hopping rate in tens of GHz. A main lobe sine apodization can be used in writing the gratings to enhance the system capacity and the spectrum efficiency. All network users can use the same tunable encoder/decoder design. The simultaneous utilization of the time and frequency domains offers notable flexibility in code selection. Simulations show that the encoder efficiently performs the FFH spread spectrum signal generation and that the receiver easily extracts the desired signal from a received signal for several multiple access interference scenarios. We measure the system performance in terms of bit error rate, as well as auto-to cross-correlation contrast. A transmission rate of 500 Mb/s per user is supported in a system with up to 30 simultaneous users at 10-9 bit error rate. We compare FFH-CDMA to several direct sequence-CDMA systems in terms of bit error rate versus the number of simultaneous users. We show that an optical FFH-CDMA system requires new design criteria for code families, as optical device technology differs significantly from that of radio frequency communications 相似文献
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We report an investigation of a multimode EDFA used as an optically preamplified receiver. A two-stage amplifier pumped at 982 nm shows gain of up to 40 dB at 1553 nm. We study the communications performance of the receiver at 10 Gb/s and compare it with theory. The measured sensitivity is 220 photons per bit at a bit error rate of 10/sup -9/ and data rate of 10 Gb/s. This is 4.5 dB from the quantum limit of 75 photons per bit for a 56 mode amplifier. 相似文献
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一种甚低速率语音编码的抗误码算法 总被引:1,自引:0,他引:1
为满足在高误码率的窄带信道上进行语音通信的需求,本文研究了一种适用于甚低速率语音通信的抗误码参数估值算法。在一定的解码状态下,声码器通过计算最小均方误差(MMSE)估计的方法估计最优参数,充分降低信道误码对重建语音质量的影响。对于解码状态参数,通过计算最大后验转移概率的方法作最佳估计,并给出了一种简化的计算方法。这种抗误码算法复杂度低。计算机仿真结果表明,在不同误码率下该算法恢复出的语音的平均谱失真(ASD)低于帧删除方法的谱失真最大可达0.4dB。 相似文献
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Type-II Hybrid-ARQ (Type-II HARQ) has been shown, under certain circumstances, to increase the efficiency and reduce loss of data transmissions over a wireless channel. However, it is difficult to predict how it will perform when transmission symbol errors are correlated. We present a computationally efficient approach to the performance evaluation of packet transmissions over a wireless link employing Type-II HARQ error mitigation when the physical channel is subject to correlated transmission symbol errors. This provides a tool for static or online optimization of system parameters. We present numerical results for a wide range of channel statistics, illustrating the effect of bit error correlation, bit error rate, and block size on packet latency and loss rate. 相似文献
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该文针对通信系统中的干扰抑制问题,提出一种基于最低误码率准则的Volterra均衡器.区别于以往研究中采用最小均方误差准则估计Volterra核,本文采用最低误码率准则.仿真表明:对于扩展的二元相移键控信号,在相对强的窄带干扰下,匹配滤波器和基于最小均方误差准则的线性均衡器已失效,而基于最低误码率准则的Volterra均衡器仍能表现出良好的性能,也大大优于最小均方误差准则的Volterra均衡器;并且在计算复杂度与误码率性能的权衡中,奇次三阶Volterra均衡器更有实用价值. 相似文献
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We present a new turbo-coding method which parses the input block into n-bit symbols and interleaves on a symbol-by-symbol basis. This is used in conjunction with different modulation techniques to take advantage of tradeoffs between bit error rate performance, code-rate, spectral efficiency, and decoder complexity. The structure of the encoder and decoder of these codes, which We call symbol-based turbo codes, are outlined. The bit error rate performance of a few specific codes are examined. A discussion on decoder complexity is also included. Symbol-based turbo codes are good candidates for low delay transmission of speech and data in spread spectrum communication systems 相似文献
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Gottesman D. Hoi-Kwong Lo 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(2):457-475
Shor and Preskill (see Phys. Rev. Lett., vol.85, p.441, 2000) have provided a simple proof of security of the standard quantum key distribution scheme by Bennett and Brassard (1984) by demonstrating a connection between key distribution and entanglement purification protocols (EPPs) with one-way communications. Here, we provide proofs of security of standard quantum key distribution schemes, Bennett and Brassard and the six-state scheme, against the most general attack, by using the techniques of two-way entanglement purification. We demonstrate clearly the advantage of classical post-processing with two-way classical communications over classical post-processing with only one-way classical communications in quantum key distribution (QKD). This is done by the explicit construction of a new protocol for (the error correction/detection and privacy amplification of) Bennett and Brassard that can tolerate a bit error rate of up to 18.9%, which is higher than what any Bennett and Brassard scheme with only one-way classical communications can possibly tolerate. Moreover, we demonstrate the advantage of the six-state scheme over Bennett and Brassard by showing that the six-state scheme can strictly tolerate a higher bit error rate than Bennett and Brassard. In particular, our six-state protocol can tolerate a bit error rate of 26.4%, which is higher than the upper bound of 25% bit error rate for any secure Bennett and Brassard protocol. Consequently, our protocols may allow higher key generation rate and remain secure over longer distances than previous protocols. Our investigation suggests that two-way entanglement purification is a useful tool in the study of advantage distillation, error correction, and privacy amplification protocols. 相似文献
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Error rate and outage of dual‐hop DF relay system with selection combining over Rice fading
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Performance of dual‐hop decode‐and‐forward relay system with selection‐combining receiver is analyzed over Rice fading channels. The following closed‐form expressions of performance metrics are derived: moment generating function for selection‐combining receiver output signal‐to‐noise ratio, exact average bit error rate of noncoherent modulations, approximate average symbol error rate for coherent modulations, and outage probability. We also obtain simple asymptotic expressions for moment generating function, exact average bit error rate, average symbol error rate, and outage probability, which are useful to characterize the diversity order and the coding gain. The optimal power allocation analysis suggests that the optimal power allocation factor is independent of total signal‐to‐noise ratio and source‐to‐destination link fading parameters. The accuracy of the obtained analytical expressions are supported by computer simulation results. 相似文献