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In this paper, a novel rapid varying doubly-selective channel estimator for OFDM systems has been proposed, in which channel is modeled by basis expansion model (BEM). Unlike traditional BEM channel estimation algorithms, in which the comb-pilot is used and the large path delay is not considered, the proposed algorithm uses firstly block-type pilot to estimate the BEM coefficients of fast-varying...
In this paper, the performance of parallel interference cancellation (PIC) multiuser detector in orthogonal frequency division multiple access (OFDMA) mobile communication systems is investigated. In multiuser systems, the multi-user interference (MUI) degraded the system performance, especially in near-far effect environments. The PIC scheme is proposed to reduce the MUIs and to improve the bit error...
In this paper, the impact of both time offsets (TOs) and carrier frequency offsets (CFOs) on the average output signal-to-interference-plus-noise ratio (SINR) in a frequency selective channel is investigated with a novel approach. First, TOs are partitioned into five cases based on how they occur. Then the mathematical models for different cases are derived. Considering CFOs and benefiting from the...
in this paper, a Space-Time-Frequency block code (STFBC) based on Quasi-Orthogonal designs is proposed over a frequency selective Rayleigh fading channel. The proposed code achieves rate-one and full diversity offered by the MIMO-OFDM channel. For quasi-static channel over adjacent OFDM symbol durations, as numerical results demonstrate, the proposed code introduces a significant performance gain...
MIMO-OFDM technology make full use of space and spectrum resources, it can exponentially increase the channel capacity, so it is one of the core technology of next generation mobile communication systems. In order to estimate the time domain (or frequency domain) response of MIMO-OFDM systems fast and accurately, the traditional SVD estimator is modified in this paper. To reduce the time to compute...
SC-FDMA is a multiple access technique adopted in LTE uplink transmission. SC-FDMA, as well as OFDMA, can improve system throughput by assigning different frequency portions of system bandwidth to different user equipments (UEs) adaptively based on their channel quality information. In SC-FDMA uplink cellular system, interference arising from UEs in neighboring cells degrades system performance, especially...
Future communication systems for car-to-x (C2X) applications have to meet stringent requirements regarding reliability issues. Channel estimation (CE) - as one of the key tasks that affect the system performance - has to be able to cope with the rapidly changing channel conditions. Applying a Wiener filter (WF) is one very efficient method to reduce the estimation error of any channel estimation approach...
In a typical wireless communication environment, radio channels need to be estimated for systems employing coherent detection. For implementation simplicity, Pilot-Assisted Channel Estimation (PACE) techniques have been widely used. An efficient interpolation method helps to estimate the channel fading coefficients between consecutive pilots with minimised pilot overhead. The simple linear interpolation...
In SFN (Single Frequency Network) broadcasting systems the equivalent CIR (Channel Impulse Response) can be very long but typically it has a sparse nature. This means that the equivalent CIR has several clusters of paths, each one associated to the CIR between a given transmitter and the receiver. These clusters have several multipath components and are typically well separated in time. In this paper...
CoMP (Coordinated Multiple Point transmission) is being discussed in 3GPP (3rd Generation Partnership Project) to improve the cell edge performance as well as the total cell throughput of mobile systems. In this paper, we focus on the control architecture to realize downlink CoMP JT (joint transmission) with inter eNB (evolved NodeB) coordination. We have designed the control architecture with a distributed...
In this paper, we propose a novel method to generate the cyclostationary signature for Orthogonal Frequency Division Multiplexing (OFDM) signals with a low overhead of signature (i.e. number of signature subcarriers) and a good performance of the signature detection under frequency-selective fading channel, for dynamic spectrum access (DSA) networks. Moreover, we also present how to employ the proposed...
This paper deals with the symbol timing issue of an OFDM system in frequency selective fading scenarios. A modified symbol timing offset estimator based on an energy transition metric is proposed. This metric can also be applied to estimate the maximum channel delay spread. Benefiting from the knowledge of the maximum channel delay spread, the modified estimator shows its advantage in a relatively...
Channel estimation techniques for Multi Input Multi Output Orthogonal Frequency Division Multiplex (MIMO-OFDM) systems based on a pilot arrangement are investigated. Training based Channel estimation with a block type pilot arrangement is studied through an algorithm for determination of efficient number of pilot symbols in an OFDM symbol by adding a feedback branch and employment of the Maximal Ratio...
In this paper, we present a sparse channel estimator for zero-padded orthogonal frequency division multiplexing (ZP-OFDM) modulation in clustered sparse underwater acoustic (UWA) channels. The proposed channel estimator consists of two stages. In the first stage, channel prediction from the previous block to the current block is carried out to generate artificial measurements on OFDM subcarriers....
A Sensor Network Aided Cognitive Radio Network uses the concept of a wireless sensor network that assists a cognitive radio network by providing information about the current primary spectrum occupancy. In this paper we study the performance of the cognitive network for various cell sizes and transmit power levels when deployed co-located with a mobile primary system that uses a cellular reuse pattern...
High-frequency (HF) radio communication has been recognized as the primary means for long-range wireless communications since the advent of radio. With its unique features, HF communication continues to be used for a wide range of civilian, government and military applications as a powerful alternative to a myriad of more sophisticated communication systems. However demanding requirements of high-speed...
This paper proposes the implementation of an Orthogonal Frequency-Division Multiplexing (OFDM) Ultra-wideband (UWB) multiple-input multiple-output (MIMO) transceiver employing a novel design of Wave-Radio Interferometer (WRI) circuit as a direct down-converter. In order to investigate the performance of the system in a realistic environment, the transceiver is simulated and tested in laboratory using...
In this paper the potential of downlink frequency selective scheduling (FSS) is addressed based on measurements in an experimental 3GPP Long Term Evolution (LTE) system setup. We find that scheduling on the best sub-band has the potential to improve channel conditions by up to 2 Channel Quality Indicator (CQI) units, which represents around 4 dB channel gain improvement. The time-frequency fading...
Inter carrier interference (ICI) is deemed as a critical issue in orthogonal frequency division multiple access (OFDMA) systems. Though ICI caused by Doppler spread is negligible in femtocell systems, frequent reception of signals over misaligned subcarriers will introduce severe ICI. Successive interference cancellation and decision feedback equalizers are some of the techniques proposed to mitigate...
The multicarrier modulations (MCM) became widely used and have been applied to wire and wireless transmission systems in recent years. This modulation techniques enable a near-perfect utilization of the provided frequency band on metallic cables and they also eliminate multipath propagation effect in terrestrial transmission. Mainly used implementations of MCM are Discrete MultiTone (DMT) and Orthogonal...
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