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A WiMedia ultrawideband (UWB) frequency synthesizer is designed for band group #1. A very fast hopping is achieved by using a delay-locked loop (DLL) architecture which utilizes a novel variable gain voltage-controlled delay line (VCDL) scheme to compensate the phase error generated at the hopping instant. Fast-settling DLL allows an injection-locked oscillator (ILO) to be employed to reduce the current...
This paper presents a low-power MMSE MIMO detector using a dynamic voltage wordlength scaling (DVWS) technique for 4×4 MIMO-OFDM systems. A MIMO MMSE detector requests high performance computing for real-time processing. A pipelined MMSE detector using Strassen's algorithm has been developed in our previous work. However, it consumes significant power and thus, we have to consider a low-power solution...
Active and passive detection using CP-OFDM modulated signals traditionally assume that targets do not move significantly during the entire observation period. In this paper, a “time-shift” model that compensates for the motion of targets between pulses during the observation period is introduced. Matched filtering based upon this model can be efficiently performed using a combination of the chirp-z...
To combat Inter-Carrier Interference (ICI) in mobile OFDM systems, ICI can be reconstructed and removed from the received signal with the aid of channel estimation and decision-feedback. Successful ICI cancellation hinges on accurate channel estimation, which includes both the channel gains and ICI gains, the multiplicative coefficients to the neighbor subcarrier signals representing their power leakage...
Distributed space-time block coding with orthogonal frequency division multiplexing (DSTBC-OFDM) and distributed space-frequency block coding with orthogonal frequency division multiplexing (DSFBC-OFDM) are introduced in this paper. Unlike the original DSTBC scheme which was designed for networks with a fixed number of relays operating in frequency-nonselective channels with insignificant Doppler...
In this paper the hardware setup and a field trial of a transmitter delay diversity (DD) system for DRM+ (Digital Radio Mondiale, Mode E) in ‘urban’ areas in the city of Hannover are presented. DD should help against destructive interferences resulting in signal dropouts, especially for slow receiver velocities. A closer look is taken on the spatial correlation of the channel paths and their influence...
This paper deals with the Hybrid Cramer-Rao bound (HCRB) for the estimation of Rayleigh channel and carrier frequency offset (CFO) in data-aided (DA) and non-data-aided (NDA) OFDM systems. The random part (channel) and the deterministic part (CFO) of the hybrid vector to be estimated are statistically independent. The channel estimation function is based on the equivalent discrete-time channel taps...
This paper focuses on the compensation of carrier frequency offsets (CFO) for spatial multiplexing multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with distributed transmit antennas, where the CFOs between the receiver and each transmit antenna are possibly different and the zero-forcing (ZF) detection is used. Rather than the conventional linear frequency-domain...
Orthogonal Frequency Division Multiplexing (OFDM) is considered as an effective method for overcoming problems such as noise, multi-path propagation and frequency selective fading in low voltage power-line communication (PLC). However, OFDM system is sensitive to the error of synchronization. Accurate symbol timing and carrier frequency offset estimation are crucial to the PLC system based on OFDM...
An overview of the unique challenges in underwater acoustic (UWA) communication in ocean environment is presented. The UWA channel is compared with conventional RF channels. Several design considerations applicable to the physical layer design of a UWA communication system is described based on field measurements. The unique problems in synchronization under high Doppler are described highlighting...
Radio technology has been developed extensively for mobile communications and wireless LANs. In a wireless communication channel, we have multipath propagation due to reflections and scatterings. When the delay difference between multipath waves is large, we have frequency selective fading. Thus far, a frequency correlation defined for a single antenna has been used for evaluating the frequency selectivity...
The fourth generation mobile communication system is expected to be implemented on a frequency band higher than the bands already assigned for IMT-2000. Therefore, to compensate propagation loss, relay schemes have been investigated. Amplify-and-Forward (AF) relay has advantages on complexity and time slot usage. However, the coupling effect between transmit and receive antennas in the relay station...
Three ONU auto-discovery schemes are proposed to reestablish connections between ONUs and OLT in network failure restoration for OFDMA-PONs. Simulation is conducted to compare the performances of these schemes.
Reduction of peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) system using the partial transmit sequence (PTS) approach. In PTS, the total search for the number of subblocks and the rotation factors must be accomplished. As the number of subblocks and rotation factors increases, PAPR reduction improves. The number of calculation increases as the number of subcarriers...
Single-carrier (SC) waveform has a lower peak-to-average power ratio than multi-carrier waveform. Furthermore, it can exploit the channel frequency-selectivity through frequency-domain equalization (FDE) to improve the transmission performance. SC-FDE is a block transmission. The cyclic prefix (CP) is inserted in front of each data block. Instead of CP insertion, the known training sequence (TS) insertion...
The Filter Bank MultiCarrier (FMBC) concept can be seen as an extension of the Orthogonal Frequency Division Multiplex (OFDM) principle. Indeed, in the case where each sub-carrier uses an Offset Quadrature Amplitude Modulation (OQAM), we get with the FBMC/OQAM system a multicarrier modulation scheme with relaxed orthogonality constraints so that, differently from OFDM, a cyclic prefix (CP) is no longer...
In this paper, we study the cross-layer resource allocation for the secondary users (SUs) supporting heterogeneous services in interference-limited spectrum sharing system. Two classes of SUs are considered: delay-tolerant SUs (DT-SUs) and delay- sensitive SUs (DS-SUs). With the queue theory, the delay requirements of DS-SUs are transformed into constant rate requirements. Unlike most previous works,...
This paper describes both link budget analysis and field experimental results on a mobile WiMAX system deployed in Azumino city, the city scale of which is corresponding to suburban. Firstly, in this paper, the link budget analysis is performed in order to evaluate the system performance based on propagation distance, delay spread, average BER (Bit Error Rate) under a multipath fading environment,...
In this work, a network simulator for power line communications based in the Homeplug-AV technology is presented. The simulator implements both the physical and the MAC layers, along with an in-home power line channel generator, which makes it very useful in a wide variety of network optimization procedures. To the authors' knowledge, performance evaluation of the MAC layer of Homeplug-AV by means...
The recently proposed edge windowing technique provides a new degree of freedom between spectral efficient sidelobe suppression and controllable inter-symbol-interference (ISI) for orthogonal frequency division multiplexing (OFDM) based systems. By combining the introduced degree of freedom of edge windowing and the dependency of the channel dispersive characteristics to the distance between transmitter...
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