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Ultra-wideband (UWB) communications can be achieved under non-line-of-sight (NLOS) propagation conditions at distances over 100 m using a single carefully designed and located microwave reflector in conjunction with a multi-carrier modulation technique such as orthogonal frequency-division multiplexing (OFDM) that is less sensitive to multipath effects than single-carrier modulation. One key factor...
This paper investigates performance tradeoffs between energy and information transfer in a relay based two-hop wireless system involving an energy harvesting receiver. The source and relay nodes of the two-hop amplify-and-forward (AF) system employ orthogonal space-time block codes along with orthogonal frequency-division multiplexing (OFDM) scheme. The joint optimal source and relay precoders over...
In this paper we propose an algorithm to achieve hard delay constraints in OFDMA systems. The resource scheduler has to ensure that delay deadlines of the packets get achieved and the resources are also not under utilized. This is a very difficult task since the channel and packet arrival in user queues are time varying in nature. The instantaneous decisions of scheduler depend on current as well...
Inter-carrier interference (ICI) caused by high Doppler frequency shift has severe impact on link performance and capacity for High-Speed Railway (HSR) communications. In this paper we investigate the ICI mitigation scheme by utilizing the estimation and pre-compensation of high Doppler shifts in Long Term Evolution for Railway (LTE-R) systems with distributed remote radio units (RRU). We propose...
This work presents an analysis of digital predistortion (DPD) architectures for radio-frequency digital-to-analog convertor (RFDAC) based direct digital to RF transmitter (DRF). The nonlinearity of the DRF frontend is determined by circuit simulation. Direct learning and indirect learning structures using least mean square (LMS) and normalized LMS (NLMS) estimation algorithm are evaluated with respect...
How to provide user-satisfied video services must be solved in the future wireless communication systems. However, most of existing works focused on the PHY-MAC cross layer schemes do not consider the end-to-end video quality of service (QoS) and hence can only provide limited user-perceived video quality improvements. In this paper, a novel video transmission scheme with guaranteed end-to-end QoS...
We propose a novel scheme to realize large group delay in a single ring resonator with an OFDM transmitter. The fundamental trade-off between transmission bandwidth and delay can be addressed with this new buffer.
In this paper, we analyze the channel estimation technique for OFDM (orthogonal frequency division multiplexing) used in VLC (Visible Light Communication system). A Post-Processing DFT (Discrete Fourier Transformation) channel estimation method was proposed to improve the system performance by eliminating the noise outside the maximum channel delay. After linear interpolation, the channel estimation...
In Orthogonal Frequency Division Multiplexing and Discrete Multitone transceivers, a guard interval called Cyclic Prefix (CP) is inserted to avoid inter-symbol interference. The length of the CP is usually greater than the impulse response of the channel resulting in a loss of useful data carriers. In order to avoid long CP, a time domain equalizer is used to shorten the channel. In this paper, we...
Single Frequency Network (SFN) is widely deployed for digital video systems, not only for classical Single Input Single Output (SISO) systems like DVB-T, but also for the latest Multiple Input Single Output (MISO) DVB-T2 system. In this paper, we propose one scheme to measure the echo power and echo delay accurately in an SFN with OFDM technology, for both pre-echoes and post-echoes, even with long...
In this contribution, we introduce an interference alignment scheme that allows the coexistence of an orthogonal frequency division multiplexing (OFDM) macro-cell and a cognitive small-cell, deployed in a two-tiered structure and transmitting over the same bandwidth. We derive the optimal linear strategy for the single antenna secondary base station, maximizing the spectral efficiency of the opportunistic...
It has been shown that due to its smaller signal bandwidth (96 KHz), DRM+ signal could suffer from flat fading degradation at low receiver speeds, particularly in urban environments. To alleviate this problem, a simple transmit delay diversity (TDD) has been proposed in the standard. This paper tries to investigate this issue by presenting the performance results of multipath fading characterizations...
This paper addresses the problem of indoor location for devices that are connected to WLAN. Nowdays most of the smart terminals: mobile phones, portable computers and tablets are WLAN enabled. Location of these devices is of interest to network security issues as well as employee and company security and reliability. Most of the algorithms on the market use triangulation as a basic rule for location...
This paper summarizes recent progress on the challenging problem of signal identification, with emphasis on the use of cyclostationarity-based features. Current trends and challenges in this research area are also highlighted.
This paper proposes a LMMSE-based channel estimator which, unlike the classical LMMSE estimator, does not require the covariance matrix of the channel nor its estimation. Actually, we add at the receiver side a fully adjustable filter, which acts like an artificial channel and hides the physical channel. We then perform an LMMSE estimation of the sum of the physical and artificial channel using the...
We Propose a 2K/4K/8K point FFT (Fast Fourier Transform) for OFDM (Orthogonal Frequency Division Multiplexing) of DVB-H (Digital Video Broadcast Terrestrial) Receiver. The proposed FFT architecture utilizes cascaded radix-4 single path feedback (SDF) structure based on the Radix-2/Radix-4 FFT algorithm.[11] We use block floating point scaling technique in order to increase SQNR. The 2K/8K FFT consists...
Filterbank Multicarrier (FBMC) modulation is a potential candidate for cognitive radio (CR) wireless networks due to its high spectrum efficiency and low interference among neighboring bands. Within the CR network it is important that the base station (BS) can localize the mobile station (MS) to better distribute radio resources. While most research has focused on interference within the FBMC network,...
There is currently an ongoing debate surrounding what would be the best choice for smart grid communication technology. One of the promising communication technologies for smart grid realization is Powerline Communication (PLC). However, because of its noisy environment and the low capacity of Narrowband Powerline Communication, its viability for smart grid realization is being questioned. To investigate...
Noncoherent UWB receivers promise low power consumption and low processing complexity but their peak data rate is limited by the delay spread of the multipath radio channel. A recently proposed multichannel autocorrelation receiver (AcR) can break this rate limit because it can demodulate multicarrier signals. The hardware implementation of this receiver architecture is addressed in this paper. We...
In this paper, we propose an enhanced eight-parallel 128/256-point mixed-radix multi-path delay commutator (MRMDC) FFT/IFFT processor for high-speed orthogonal frequency-division multiplexing (OFDM) systems to reduce the number of complex multipliers. The proposed processor can achieve a high throughput rate by using an eight-parallel data-path scheme and an efficient scheduling scheme of complex...
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