共查询到20条相似文献,搜索用时 31 毫秒
1.
Control, supervisory, and order wire signal transmission, i.e., service channel (SC) is a requirement for most microwave systems. In digital radio the data spectrum extends to the lowest baseband (BB) frequencies. Frequency translation of the SC above the data spectrum is one possibility. Another method, in frequent use, is the double modulation technique, e.g., the SC amplitude modulates the carrier that is already phase modulated by the data spectrum. A novel approach that results in significant equipment cost savings and good performance is proposed. The low-frequency power density spectrum of the random multilevel channel coded data is removed. The vacated spectrum is available for the SC. For different bit rates, the error probabilityP(e) degradation due to SC is calculated. The analysis is performed for various channel coded messages and SC spectrum utilizations. The high-pass filter that assures low-frequency data spectrum removal is optimized for the SC signal to noise ratio and dataP(e) degradation. The analysis is verified with computer simulations and actual multilevel frequency-shift keying (FSK) 6-GHz microwave hop measurements. The proposed approach is also applicable to analog microwave systems when carrying hybrid information. The hybrid system carries an SC, 6.3-Mb/s data, and 900 frequency division multiplexed voice channels in a shared BB. 相似文献
2.
It is well known that power amplifier induced non-linear distortions produce a signal spectral regrowth at the IF transmitter output of digital radio communication systems. This effect is responsible for both adjacent channel interference and BER degradation. Signal predistortion is a technique that counteracts such phenomena. Technological advances in the last decade, renewing the interest in this technique, led to the realization of digital baseband (BB) predistorters that overcome the performance of the existing analog IF (intermediate frequency) ones. However, the substitution of an analog IF predistorter with a digital BB one forces one to partially redesign the system architecture. An alternative approach is proposed in this paper, based on digital and analog techniques, which combines the precision of the digital BB solution with the practicality of an IF architecture. This solution is particularly interesting to substitute an old analog IF predistorter simply plugging-in the new digital one, without further changes in the transmitter architecture. Critical aspects, predistortion algorithms and simulation performance are presented with respect to a digital video broadcasting system which is based on an OFDM modulation and is very sensitive to non-linear distortions because of the adopted multicarrier modulation 相似文献
3.
Reflective semiconductor optical amplifier (RSOA) based wavelength division multiplexed radio-over-fiber passive optical network (WDM−RoF−PON) has been proposed and demonstrated, to transmit 2.5 Gbps baseband (BB) and 1.25 Gbps wireless data in downstream and 1 Gbps BB data signal in upstream over 25-km single-mode fiber (SMF), and wireless downstream signal over 25-km SMF as well as 5.2 m free space in air. In the downstream, 2.5 Gbps BB data and 1.25 Gbps wireless data are modulated using single-electrode Mach–Zehnder modulator (SD-MZM) based on double-sideband with optical carrier suppression (DSBCS) scheme and simultaneously transmitted by incoherent light injection technique and employing fiber Bragg grating (FBG) at the base station. RSOA is utilized at the user end to reuse the carrier for uplink transmission. High receiver sensitivity, low bit-error-rate (BER) and excellent eye-diagram, eye height are achieved in our proposed network system and the results affirm the acceptability of proposed RSOA based WDM−RoF−PON. 相似文献
4.
《Selected Areas in Communications, IEEE Journal on》2009,27(4):400-411
This study presents a healthcare monitoring architecture coupled with wearable sensor systems and an environmental sensor network for monitoring elderly or chronic patients in their residence. The wearable sensor system, built into a fabric belt, consists of various medical sensors that collect a timely set of physiological health indicators transmitted via low energy wireless communication to mobile computing devices. Three application scenarios are implemented using the proposed network architecture. The group-based data collection and data transmission using the ad hoc mode promote outpatient healthcare services for only one medical staff member assigned to a set of patients. Adaptive security issues for data transmission are performed based on different wireless capabilities. This study also presents a monitoring application prototype for capturing sensor data from wireless sensor nodes. The implemented schemes were verified as performing efficiently and rapidly in the proposed network architecture. 相似文献
5.
该文提出了一种新的分布式环境下用于QoS控制的基于模糊逻辑的动态资源调配(Fuzzy logic based Dynamic Resource Allocation,FDRA)算法。分布式环境采用集中式带宽代理(Bandwidth Brokers, BB))与分布式BB相结合的控制模式。分布式BB基于滑动窗口和滑动指针机制,在分配资源不足时向集中式BB请求追加资源,在占用资源高于需求一定阈值时滞后释放部分追加资源。追加资源块和释放资源块的大小分别由集中式BB和分布式BB根据当前网络负荷状态,采用模糊逻辑确定。模糊逻辑算法引入新的基于数据源特性的隶属度函数生成方法,提高决策的有效性。仿真结果证明,该文提出的算法性能优于已有文献的算法。 相似文献
6.
This paper presents an advanced architecture for residue number system (RNS)-based code-division multiple-access (CDMA) system for high-rate data transmission by combining RNS representation, phase shift keying/quadrature amplitude modulation (PSK/QAM) and orthogonal modulation. The residues obtained from a fixed number of bits are again divided into spread code index and data symbol for modulation. The modulated data symbol is spread using the indexed orthogonal codes and transmitted through a communication channel. The proposed system uses a lower number of orthogonal codes than conventional RNS-based CDMA and the performance is comparable. The computational complexity of the proposed system is compared against alternative schemes such as M-ary CDMA and conventional RNS-based CDMA. The modified system is simulated extensively for different channel conditions and the results are discussed. 相似文献
7.
本文提出一种可用于宽带数字移动通信系统的多输入多输出(MIMO)无线传输系统架构———分组的空时块编码(G-STBC)MIMO结构,即发送天线被分成若干组,组内的多根天线进行STBC编码,而各组发送的数据流相互独立。针对这一系统架构,提出了基于迫零检测的最优排序串行干扰消除(OZFSIC)接收信号检测算法的实现方案。计算机仿真结果表明,这种空时编码MIMO结构在等数据率的情况下能获得比相应的V-BLAST系统更优的性能。G-STBC-MIMO结构可以使发送天线多于接收天线,因此,对于无线通信系统下行链路以及大数据量广播业务系统(如数字高清晰度电视地面传输系统)都较V-BLAST更具有优势。 相似文献
8.
9.
Youjun Gao Hui Tian Lei Sun Haibo Xu 《Wireless Communications, IEEE》2007,14(2):57-61
Based on the requirements of beyond 3G mobile communication systems, the access network architecture and media access control technique for B3G systems are studied. The proposed novel access network architecture, which can reduce network complexity and improve system performance, is introduced. Centralized mini-slot packet reservation multiple access (CMPRMA), based on OFDMA, is proposed, which not only can inherit the advantages of MPRMA and support real-time traffic well, but can also supply the resource reservation scheme for data traffic and support transmission for data traffic efficiently 相似文献
10.
《Vehicular Technology, IEEE Transactions on》2008,57(6):3510-3524
11.
Patrick Schaumont Serge Vernalde Marc Engels Ivo Bolsens 《The Journal of VLSI Signal Processing》1998,18(2):187-197
State-of-the-art data communication systems make extensive use of digital hardware. Besides baseband modulation functions, also the frequency tuning functions are now being shifted from analog to digital implementation. Integration, cost and ease of programming are the primary motivations for doing this. This paper presents an alternative to the traditional digital frequency conversion architectures. The proposed architecture achieves low power as well as high speed operation, and achieves this dual goal by reducing programmability. A multi-rate filtering approach is used, which is applicable for both upconversion and downconversion of quadrature modulated data. 相似文献
12.
《Photonics Technology Letters, IEEE》2009,21(13):857-859
13.
Yong-Yuk Won Dong-Hyeon Kim Yin-Xing Piao Soo-Jin Park Sang-Kook Han 《Optical Fiber Technology》2009,15(2):141-144
A new architecture for bidirectional gigabit colorless wavelength division multiplexed-passive optical network system based on a reflective semiconductor optical amplifier is proposed. It uses techniques of both optical carrier suppression and subcarrier multiplexing. There is no impact of a downlink signal on an uplink one due to the wavelength reuse because a light from a single optical source is divided into two parts for uplink and downlink transmissions. One is modulated by a downlink signal and the other, which is transformed into two sidebands with a suppressed optical carrier, is utilized for an uplink transmission. An uplink data is recovered by subcarrier multiplexing technique. 1.25-Gb/s error-free transmissions of both uplink and downlink are demonstrated experimentally. 相似文献
14.
A High-Speed Low-Complexity Concatenated BCH Decoder Architecture for 100?Gb/s Optical Communications 总被引:1,自引:0,他引:1
Kihoon Lee Han-Gil Kang Jeong-In Park Hanho Lee 《Journal of Signal Processing Systems》2012,66(1):43-55
This paper presents a two-iteration concatenated Bose-Chaudhuri-Hocquenghem (BCH) code and its high-speed low-complexity two-parallel
decoder architecture for 100 Gb/s optical communications. The proposed architecture features a very high data processing rate
as well as excellent error correction capability. A low-complexity syndrome computation architecture and a high-speed dual-processing
pipelined simplified inversonless Berlekamp-Massey (Dual-pSiBM) key equation solver architecture were applied to the proposed
concatenated BCH decoder with an aim of implementing a high-speed low-complexity decoder architecture. Two-parallel processing
allows the decoder to achieve a high data processing rate required for 100 Gb/s optical communication systems. Also, the proposed
two-iteration concatenated BCH code structure with block interleaving methods allows the decoder to achieve 8.91dB of net
coding gain performance at 10−15 decoder output bit error rate to compensate for serious transmission quality degradation. Thus, it has potential applications
in next generation forward error correction schemes for 100 Gb/s optical communications. 相似文献
15.
Hai-Han Lu 《Broadcasting, IEEE Transactions on》2002,48(4):370-373
An architecture of an externally modulated AM-VSB CATV 77-channel erbium-doped fiber amplifier (EDFA)-repeated system which use the combination of a single-mode fiber (SMF) and reverse dispersion fiber (RDF) as a dispersion compensation device is proposed and demonstrated. Compared to the conventional externally modulated fiber optical CATV systems with or without a dispersion compensation fiber (DCF), excellent performance of composite second order (CSO) /spl ges/ 78 dB accompanied by satisfied carrier-to-noise ratio (CNR) /spl ges/ 50 dB and composite triple beat (CTB) /spl ges/ 65 dB was obtained in the proposed system. 相似文献
16.
17.
针对可见光通信(Visible Light Communication,VLC)系统中传统非对称限幅光正交频分复用(ACO-OFDM)及直流偏置光正交频分复用(DCO-OFDM)系统存在的不足,提出了一种基于DCO-OFDM与脉冲幅度调制-离散多音频调制(PAM-DMT)混合技术传输方案,并给出了一种接收端低复杂度信号检测算法.该混合传输系统不仅可以通过改变调制方式以得到更为灵活的数据传输速率,还可以在相同数据速率下叠加较小的直流信号.最后通过蒙特卡洛仿真验证了所提设计的有效性. 相似文献
18.
J.S. Leng Y.C. Lai W. Zhang J.A.R. Williams 《Photonics Technology Letters, IEEE》2006,18(16):1729-1731
A novel architecture for microwave/millimeter-wave signal generation and data modulation using a fiber-grating-based distributed feedback laser has been proposed in this letter. For demonstration, a 155.52-Mb/s data stream on a 16.9-GHz subcarrier has been transmitted and recovered successfully. It has been proved that this technology would be of benefit to future microwave data transmission systems. 相似文献
19.
Xiqi Gao Xiaohu You Bin Sheng Han Hua Schulz E. Weckerle M. Costa E. 《Selected Areas in Communications, IEEE Journal on》2006,24(6):1189-1198
In this paper, an efficient digital implementation of multicarrier transmission scheme based on generalized discrete Fourier transform (DFT) filter banks is presented for multicarrier code-division multiple-access (MC-CDMA) systems. Generalized DFT filter banks has been traditionally discussed for very high-speed digital subscriber lines (VDSL) wireline systems, received interest also for wireless applications. The design of the generalized DFT modulated filter banks is investigated and its fast implementation is derived in the time-domain for arbitrary integer sampling rate. Through the utilization of the generalized DFT modulated filter banks, one or more subcarriers, even noncontiguous subcarriers can be easily supported by system in both uplink and downlink, which facilitates the users to access the network in a frequency-division multiple-access manner. Simulation results show that the overall bit-error-rate performance of the proposed multicarrier transmission scheme well approaches that of a single-carrier system due to the negligible intercarrier interference introduced by an appropriate design of the generalized DFT modulated filter banks. 相似文献
20.
《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1977,65(9):1283-1295
This paper examines some of the fundamental problems associated with the design and performance of integrated systems and networks that switch both voice and data. Specifically, the need for an integrated approach to the switching and transmission of voice and data is explored and alternative design considerations are discussed. One approach, described in detail, utilizes a distributed architecture to implement variable width channel allocations for the dynamic union of voice and data. Key performance criteria which aid the systems designer in evaluating the merits of a proposed unified design are identified. Examples are illustrated and supportive material is provided by a comprehensive bibliography. 相似文献