Mapping of Discrete Cosine Transforms onto Distributed Hardware Architectures

We present an algorithmically-aware, high-level partitioning methodology for discrete cosine transforms (DCT) targeted to distributed hardware architectures. The methodology relies on the exploration of alternate DCT formulations as part of the partition optimization process. To the best of our knowledge, no previously proposed DCT algorithm exists that is capable of consistently producing alternate regular formulations for an n-size DCT. Hence, a new Cooley-Tukey-like DCT factorization algorithm was developed to allow exploration of alternate formulations as part of the partitioning optimization process. The use of our factorization mechanism along with a greedy strategy to explore the space of equivalent DCT formulations yielded partitioning solutions with as much as 18% reduction in latency and 83% reduction in run-time as compared to previously proposed regular DCT formulations.

All-Optical Discrete Sine Transform and Discrete Cosine Transform Based on Multimode Interference Couplers

In this letter, a novel method to realize all-optical discrete sine transform (DST) and discrete cosine transform (DCT) is proposed. The approach requires only one multimode interference (MMI) coupler and several phase shifters at the input and output ports. By properly arranging the length of the MMI coupler and adjusting the phase shifters, the DST can be directly realized all-optically. Meanwhile, the DCT is related to the DST with a simple formula. By changing the input phase and relabeling the output ports, it can also be realized on the MMI structure. The proposed methodology has no limit on the number of the inputs.      

A Comparison Study Between Pre-Equalization Schemes for Single and Multi Carrier Modulation Systems

In this paper, frequency domain pre-equalization (Pre-FDE) is developed for broadband cyclic prefix-code division multiple access (CP-CDMA) as a single carrier transmission scheme, and for multi carrier-CDMA (MC-CDMA) and orthogonal frequency division multiplexing (OFDM) as multi carrier transmission schemes. A comparison study is held between these schemes and the traditional equalization schemes. Experimental results show that pre-equalization improves significantly the performance of the single and multi carrier communication systems with a very low complexity at the receiver. The comparative study between MIMO pre-equalization for single carrier systems and for multi carrier systems shows that MIMO pre-equalization for single carrier systems outperforms that for multi carrier systems in terms of bit error rate (BER) performance since single carrier transmission has more frequency diversity than multi carrier transmission in the uncoded case.     

OFDM系统中基于局部离散余弦变换的信道估计

论述了一种新的基于局部离散余弦变换(LDCT, local discrete cosine transform)的正交频分复用(OFDM, orthogonal frequency division multiplexing)系统信道估计方法.与传统的离散傅里叶变换(DFT)和离散余弦变换(DCT)不同,LDCT基函数具有良好的时域能量集中特性,可迅速捕获信号中的时变成分,有效跟踪信号时频结构的变化,有效地抑制符号间干扰(ISI)和信道加性高斯白噪声.仿真结果表明,该方法优于基于DFT和基于DCT的信道估计,是一种可行而且有效的信道估计方法.     

Carrier Phase Error in Single Sideband-Partial Response Systems

This paper studies the effect of a demodulator carrier phase error on the performance of a synchronous data transmission system. Various single sideband-partial response systems are ranked on the basis of their sensitivity to the phase error. Mean-square distortion due to the phase error and the vertical eye opening of the resulting eye patterns are used as performance measures of comparison. The influence of system bandwidth on the system performance is also studied.     

A New Transceiver Scheme for OFDMA System Based on Discrete Cosine Transform and Phase Modulation

A high peak-to-average power ratio of the transmit signal is a major drawback of multicarrier transmissions, such as orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA). An alternative approach to mitigate the peak-to-average power ratio (PAPR) problem is based on signal transformation using phase modulation (PM). A phase modulation based systems have the advantage of constant envelope (CE) signals and the ability to improve the diversity of multipath channels. In this paper, a different implementation of discrete Fourier transform DFT-OFDMA system which is based on discrete cosine transform (DCT) is proposed. The DCT-OFDMA system is then used to develop a new transceiver system called DCT-OFDMA-PM which refers to discrete cosine OFDMA with phase modulation. The PM input signal to be modulated must be real which can be produced using DCT-OFDMA with pulse amplitude modulation (M-PAM). The new system involves a signal transformation prior to amplification. This gives the advantage of CE (i.e. 0 dB PAPR). The proposed system is implemented with frequency domain equalization (FDE) to obtain high diversity gains over the frequency multipath channel. Simulation the PM-based systems with multipath fading can outperform that with single path fading.     

多载波与单载波QAM传输系统性能比较

本文研究加性白高斯噪声信道上，多载波与单载波ＱＡＭ传输系统的性能。首先指出在发送平均功率和传输速率相同的情况下，在传输特性为理想的平的信道上，两种传输系统具有相同的误比特率，然后给出了信道特性非平（即存在码间干扰）的情况下，多载波ＱＡＭ系统的比特优化分配方法，并用蒙特卡洛方法给出了优化的多载波ＱＡＭ系统与采用判决反馈均衡的单载波ＱＡＭ系统的性能结果。结果显示，优化的多载波ＱＡＭ系统的性能要优于通常的采用判决反馈均衡的单载波ＱＡＭ系统。     

Discrete Generalized Fresnel Functions and Transforms in an Arbitrary Discrete Basis

The idea of generalized Fresnel functions, which traces back to expressing a discrete transform as a linear convolution, is developed in this paper. The generalized discrete Fresnel functions and the generalized discrete Fresnel transforms for an arbitrary basis are considered. This problem is studied using a general algebraic approach to signal processing in an arbitrary basis. The generalized Fresnel functions for the discrete Fourier transform (DFT) are found, and it is shown that DFT of even order has two generalized Fresnel functions, while DFT of odd order has a single generalized Fresnel function. The generalized Fresnel functions for the conjunctive and Walsh transforms and the generalized Fresnel transforms induced by these functions are considered. It is shown that the generalized Fresnel transforms induced by the Walsh basis and the corresponding generalized Fresnel functions are unitary and that the generalized Fresnel transforms induced by the conjunctive basis and the corresponding generalized Fresnel functions consist of powers of the golden ratio. It is also shown that the Fresnel transforms induced by the generalized Fresnel functions for the Walsh and conjunctive transforms have fast algorithms.     

Spectral Mask Compliance and Amplifier Nonlinearity in Single Carrier and OFDM Systems

In this paper we investige the comparative merits of two transmission techniques, OFDM and single carrier, with respect to spectral mask compliance when a nonlinear amplifier is utilized in transmission. Two different nonlinear power amplifier models are used for analyzing the behavior of the two techniques in terms of average transmitted power and distortion.     

Error-resistance and Low-complexity Integer Inverse Discrete Cosine Transform

In this paper, a low-complexity multiplication-free integer inverse discrete cosine transform (IDCT) based on data flow structure of improved AAN’s fast IDCT is proposed for error drifting resistance of decoder. Two algorithms are used in this integer IDCT improvement. One is common factor extraction which extracts the complicated common factors from transform kernel to scale; the other is two-stage scale which splits a more than 16-bit scale into two less than 16-bit scales. With the two algorithms, high-accuracy integer IDCT is implemented in lower complexity. The experimental results show that the proposed transform exceeds the requirements of IEEE1180-1990 significantly (about 10 times). The results of the proposed IDCT implemented into MPEG-2 and MPEG-4 decoders instead of original 64-bit floating-point IDCT also show that it reduces the error drifting of decoders efficiently.     

Compact Sine Cosine Algorithm applied in vehicle routing problem with time window

In this paper, the compact Sine Cosine Algorithm (cSCA) is proposed. The cSCA algorithm is not based on population, but simulates the behavior of the actual population through a probability model called virtual population. Compared with the original algorithm, the cSCA algorithm takes up less memory space. However, frequent sampling may lead to poor solution quality. In view of this situation, this paper introduces the intergenerational generation sampling mechanism to improve the cSCA algorithm. Through the CEC2013 function set test, compared with the original SCA algorithm and other compact algorithms, the algorithm proposed in this paper can show strong solving ability. Finally, this paper describes how to apply the proposed algorithm and the SCA algorithm to solve the vehicle routing problem with time window in transportation. The quality of the solution is further improved by introducing the relocate operator. Through Solomon standard test data, the calculation performance of the algorithms is verified.

     

一种改进的单载波频域迭代均衡算法

改进了传统频域迭代均衡算法中相关系数的计算.仿真发现,在数字电视地面广播信道,提出的算法以更低的复杂度获得了比已有算法更好的性能.     

基于正余弦计算的CORDIC旋转算法的改进与分析

该文提出了一种基于正余弦流水线CORDIC的模校正因子和级数部分的改进旋转算法,在FPGA仿真中给出了相关实验数据,结果证明了该方法可以有效减少流水级数,降低硬件复杂度,满足计算精度,改进引起的误差精度很小,在实际应用中可以忽略不计。     

Robust QoS Control for Single Carrier PMP Mode IEEE 802.16 Systems

The IEEE 802.16 WirelessMAN standard provides a comprehensive quality-of-service (QoS) control structure to enable flow isolation and service differentiation over the common wireless network interface. By specifying a particular set of service parameters, the media access control (MAC) mechanisms defined in the standard are able to offer predefined QoS provisioning on a per-connection basis. However, the design of efficient, flexible, and yet robust MAC scheduling algorithms for such QoS provisioning still remains an open topic. This paper proposes a new QoS control scheme for single-carrier point-to-multipoint mode wireless metropolitan area network (WirelessMAN) systems, which enables the predefined service parameters to control the service provided to each uplink and downlink connection. By MAC-PHY cross-layer resource allocation, the proposed scheme is robust against particular wireless link degradation. Detailed simulation experiments are presented to study the performance and to validate the effectiveness of the proposed QoS control scheme.     

Semiblind Channel Estimation for MIMO Single Carrier With Frequency-Domain Equalization Systems

We propose a semiblind channel-estimation method for multiple-input multiple-output (MIMO) single carrier with frequency-domain equalization systems. By taking advantage of periodic precoding and the block circulant channel model after cyclic prefix removal, we obtain the channel-product matrices by solving a series of decoupled linear systems, which is gained from the covariance matrix of the received data. Then, the channel-impulse-response matrix is obtained by computing the positive eigenvalues and eigenvectors of a Hermitian matrix formed from the channel-product matrices. We also propose an optimal design of the precoding sequence, which minimizes the noise effect and numerical error in covariance matrix estimation, and discuss the impact of the optimal sequence on channel equalization. With the proposed framework, the method is shown to be robust with respect to channel-order overestimation, and the identifiability condition is simply that the channel-impulse-response matrix has full column rank. Due to the identifiability condition, the method is applicable to MIMO channels with more transmitters or more receivers. Simulations are used to demonstrate the performance of the proposed method.      

二维离散余弦变换及其逆变换的VLSI实现

针对适用于H.263及H.264视频压缩协议的编解码算法,二维离散余弦变换(DCT),及二维反离散余弦变换(IDCT),设计了ASIC高速电路,并完成了电路的FPGA模拟验证.在高速算法设计方面,利用一维变换来实现二维变换,通过对变换矩阵的特殊处理,使得一维变换中只含移位和加法运算;在电路设计方面,采用流水线结构并行处理数据,用寄存器堆实现矩阵的转置.对算法及电路设计的优化和改进,大大减少了完成一个矩阵二维正反变换所需要的周期数,提高了电路的吞吐率和运算速度.ASIC设计采用0.18 μm CMOS工艺,在最坏情况下,综合电路可达到的最高频率为250 MHz;FPGA模拟验证最高频率可达170 MHz.     

Hybrid Carrier and Modulation Tracking Loops

The tracking loops presented herein exploit the coherency of the observed data sidebands at the carrier frequency for improvements in phase-coherent tracking, telemetry, and command system performance. The loop is motivated by one aspect of generalized harmonic analysis, viz., the so-called cross spectrum. The basic idea of the loop centers around using the power in the composite received signal (sidebands including cross-modulation components) to enhance the signal-to-noise ratio in the carrier tracking loop, thereby reducing the noisy reference loss and ultimately the subcarrier reference jitter, the symbol sync jitter, and the error probability of the data detector. The modulation from the extracted sidebands is removed in such a way that the coherence power in the data sidebands can be used for tracking at the carrier frequency.     

基于查找表和Taylor展开的正余弦函数的实现

正余弦函数在现代数字信号处理中有着重要作用.提出一种基于查找表与Taylor展开相结合的正余弦函数的实现方法,可以完成0～360°正弦和余弦值的计算,输入有效位数为16位,输出有效位也为16位,结果精度达0.000 03.在Altera公司Stratix系列FPGA上对算法进行了验证,算法消耗的资源少,精度高,速度快.     

New Systolic Algorithm and Array Architecture for Prime-Length Discrete Sine Transform

Using a simple input-regeneration approach and index-transformation techniques, a new formulation is presented in this paper for computing an N-point prime-length discrete sine transform (DST) through two pairs of [(N-1)/4]-point cyclic convolutions, where [(N-1)/4] is an odd number. The cyclic convolution-based algorithm is used further to obtain a simple regular and locally connected linear systolic array for concurrent pipelined implementation of the DST. It is shown that the proposed systolic structure involves significantly less area-time complexity compared with that of the existing structures     

LTE-Advanced中的载波聚合技术研究

随着移动通信技术的发展,用户对数据速率的要求越来越高,与此同时频谱资源紧缺的问题日益严重。为了满足LTE-A系统对带宽的需求而提出了频谱聚合技术。与LTE系统相比,LTE-A系统需要在上下行控制信道设计、功率控制、TDD特定场景等多方面做相应的改变以支持频谱聚合的功能。