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An equalization algorithm is proposed for DVB-T/H systems to reduce noise effect by averaging equalized results with different signal intervals for the same OFDM symbol. It has a signal-to-noise gain of 0.5 dB over conventional algorithm.
Orthogonal frequency division multiplexing (OFDM) systems may confront significant intercarrier interference (ICI) when applied in doubly selective channels. Furthermore, the insufficient cyclic prefix (CP) leads to interblock interference (IBI) which again results in ICI. These interferences cause an early error floor in conventional receivers. In this paper, we characterize the doubly selective...
Unique word - orthogonal frequency division multiplexing (UW-OFDM) is a novel OFDM concept that uses deterministic sequences, which we call unique words, as guard intervals instead of the conventional cyclic prefixes. Since unique words represent known sequences, they can advantageously be used for synchronization, channel estimation, but also for improving the bit error ratio (BER) behavior of a...
This paper introduces a technique for joint channel control signal estimation for OFDM systems. The basic idea proposed is to embed the control signal information in the pilot sequence such that when it is estimated at the receiver it can reveal both the channel response and the intended control signal information. We also provide a novel technique, which utilizes the channel''s correlation, for recovering...
In this paper we study the statistical distribution of the enhanced noise after zero forcing frequency domain equalization in an OFDM system transmitting over a Nakagami-m fading channel. With this purpose, we obtain the expression of the density function of the ratio between the modulus of a complex Gaussian random variable (i.e., a Rayleigh distributed random variable) and that of a n-dimensional...
The concept of using unique word (UW) prefixes instead of cyclic prefixes (CPs) is already well investigated for single carrier systems with frequency domain equalization (SC/FDE). In OFDM (orthogonal frequency division multiplexing), where the data symbols are specified in frequency domain, the introduction of UWs - which are specified in time domain - is not that straight forward. In this paper...
Cooperative networking schemes provide spatial diversity gain (named cooperative diversity gain) using the antennas of spatially distributed users. Consistent research has been focusing on cooperative networks using orthogonal frequency division multiplexing (OFDM) and single carrier with frequency domain-equalization (SC-FDE). Coherent detection and frequency-domain equalization (FDE) require accurate...
In this paper, we propose a novel transmit signal structure for OFDM (orthogonal frequency division multiplexing). Instead of the conventional cyclic prefix (CP), we use a deterministic sequence, which we call unique word (UW), as guard interval. We show how unique words, which are already well investigated for single carrier systems with frequency domain equalization (SC/FDE), can also be introduced...
Orthogonal Frequency Division Multiplexing (OFDM) has been widely adopted in many applications and standards for a number of benefits including high efficiency and immunity against the frequency-selective channel. Power loading, which is a technique that allocates different amount of power for each subcarrier, further enhances the system performance by maximizing mutual information, reducing Bit Error...
High Peak to Average Power Ratio (PAPR) is a critical issue in multi-carrier communication systems using Orthogonal Frequency Division Multiplexing (OFDM), as Second Generation Terrestrial Digital Video Broadcasting (DVB-T2) system. This problem can result in large performance degradation due to the non-linearity of the High Power Amplifier (HPA) or in its low power efficiency. In this paper, we evaluate...
This study proposes an orthogonal frequency division multiplexing (OFDM) transmission technique. N samples generated by the N-point inverse discrete Fourier transform at the OFDM transmitter form one transmission block. It is controlled so that the M tail samples of every N-point transmission block have the same pilot sequence. If the maximum delay spread of multipath channel does not exceed M-sample...
A crucial parameter required for adaptive transmission in orthogonal frequency division multiplexing (OFDM) systems is the signal-to-noise ratio (SNR). In this paper, certain modifications to previously proposed preamble-based SNR estimator for wireless OFDM systems are suggested in order to improve estimation performance. Proposed modifications, related to DFT interpolation, are based on the adaptive...
In the bistatic radar, it is important to suppress the undesired signals such as the direct propagated signal from transmitter and its multipath components. Conventionally, the suppression method by subtracting the replicas of the undesired signals is often used. However, it requires the precise delay times of the undesired signals. In this paper we propose a new method to detect the target without...
Multi-user multi-input multi-output (multi-user MIMO) can increase the number of users simultaneously accessing the same base station (BS) without increasing the signal bandwidth. MIMO signal detection which can provide better bit error rate (BER) performance than linear detection with less computational complexity is indispensable in order to enhance the uplink cellular capacity of multi-user MIMO...
In broadband wireless communication systems, single-carrier transmission with frequency domain equalization (SC-FDE) is regarded as an alternative modulation technique to the orthogonal frequency division multiplexing (OFDM). Compared with OFDM systems, SC-FDE has similar implementation complexity and performance. However, SC-FDE with linear equalizer will suffer from serious performance deterioration...
The frequency-domain filtered single-carrier (SC) signal transmission can achieve improved bit error rate (BER) performance due to additional frequency diversity gain while keeping a lower peak-to-average power ratio (PAPR) property than orthogonal frequency division multiplexing (OFDM). In this pa-per, we extend our recently proposed frequency-domain block signal detection (FDBD) with MLD employing...
Contraposing the diffuse characteristic of HF channel and low data rate in HF communication systems, the technology which combines AMC and OFDM was presented. The models of transmitter and receiver were also put forward. The key technologies such as time synchronization, carrier frequency offset estimation, channel estimation and PAPR reduction were analyzed and corresponding resolutions were given...
We propose a dual diagonal linear-minimum-mean-square-error (DD-LMMSE) channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems involving joint channel estimation and signal detection. Computational complexity and mean-square-error (MSE) analysis are presented to evaluate the efficiency of the proposed algorithm. Compared with the optimal LMMSE method, the proposed...
The complexity of the conventional post Discrete Fourier Transform (DFT) Maximal Ratio Combining may exceed the processing ability of a low-end OFDM receiver. In this paper, we propose a new combining architecture which can reduce the complexity by using cyclic delay combining and orthogonal design simultaneously. Simulation results show that this architecture works well in the OFDM system.
The LS channel estimation was modified by implementing space and time code via introducing cyclic conjugate to both the information sequence and the pilot sequence in the time-domain. The bit error rate (BER) performance of orthogonal frequency division multiplexing (OFDM) and of single-carrier transmission with frequency-domain equalization (SC/FDE) with the new channel estimator in MIMO channels...
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