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This paper investigates the performance of delay diversity with subcarrier-based signal phase rotation in an OFDM system. Delay diversity achieves transmit diversity with channel coding by intentionally ingenerating paths which have different delays at a transmitter side. However, the correlation between subcarriers is not always low. The proposed scheme which combines the delay diversity and the...
A novel joint blind channel estimation and turbo equalization algorithm is proposed for orthogonal frequency-division multiplexing (OFDM) system in this paper. It has been proved that, blind channel estimation based on linear precoding can obtain channel information exactly. However, the precoding will cause inter-symbol interference (ISI). With the existence of ISI, the bit error rate (BER) performance...
In this report, an adaptive modulated orthogonal frequency division multiplexing (OFDM) scheme that provides efficient data transmission for correlated receiver antenna arrays is proposed. Previously reported adaptive modulation schemes generally select the modulation scheme based on the estimated carrier-to-noise ratio (CNR) on each subcarrier. However, in antenna array communication in addition...
This paper proposes a practical delay difference correction (DDC) technique that can perfectly compensate for a large delay difference due to the RoF link. Second, we show by a computer simulation of road race relay broadcasting that D-MIMO systems can achieve good coverage performance compared to centralized MIMO (C-MIMO) systems.
In a Multiple Input Multiple Output (MIMO) architecture, self-interference becomes the dominant source of impairment, particularly when correlation exists between spatial sub-channels. This paper aims to minimize the effect of self-interference by means of dynamic subcarrier allocation (DSA) and exploiting the knowledge of spatial sub-channel `quality' evaluated by an ESINR metric. The proposed system...
A novel, reduced complexity iterative channel estimation algorithm for OFDM systems using superimposed pilots is proposed. It utilizes past channel estimations of double correlated channel as a side information to reduce number of iterations. Since pilots are available at all positions of the time-frequency OFDM grid in superimposed technique, the performance of the channel estimation does not degrade...
In this paper, we will introduce Alamouti SFBC multi-antenna capabilities of Long Term Evolution's downlink channel. Alamouti's simple algorithm will be generalized by using four transmit antennas based on a combination of SFBC and Frequency Shift Transmit Diversity FSTD, and by using MIMO 2×2 transmission scheme. To prove the efficiency of these techniques, we will consider spatial correlation between...
This paper investigates the performance of multiple input multiple output orthogonal frequency and code division multiplexing (MIMO-OFCDM), where practical channel estimation is carried out with time-multiplexed pilot signals. Conditioned on each channel realization and estimation, the BER of MIMO-OFCDM is analytically evaluated, assuming zero-forcing successive interference cancellation (ZF-SIC)...
In an OFDM system, the receiver requires an estimate of the channel to recover the transmitted data. Most channel estimation methods rely on some form of training which reduces the useful data rate. In this paper, we introduce an algorithm that blindly estimates the channel by maximizing the log likelihood of the channel given the output data. Finding the likelihood function of a linear system can...
In this paper a new algorithm for adaptive dynamic channel estimation for frequency selective time varying fading OFDM channels is proposed. The new algorithm adopts a new strategy that successfully increases OFDM symbol rate. Instead of using a fixed training pilot sequence, the proposed algorithm uses a logic controller to choose among several available training patterns. The controller choice is...
Orthogonal frequency division multiplexing (OFDM) has become a key modulation format in wireless communications. Its inherent high peak to average power ratio (PAPR) severely limits the power efficiency of the operating power amplifier to alleviate nonlinear distortion effects. PAPR reduction and PA linearization have both been extensively studied to deal with this important issue. In this paper,...
In this paper, a joint adaptive modulation and multiple-input multiple-output (MIMO) transmission scheme is considered. An efficient use of radio resources shall be based on channel state information at the transmitter (CSIT) to adjust the modulation order and MIMO transmission mode. A new suboptimal algorithm is proposed for link adaptation in a MIMO-OFDMA cellular system under spatially correlated...
In this paper, we present low complexity down-sampled MMSE channel estimation. We reduced MMSE channel estimation complexity by downsampling the MMSE weight matrix. The simulation results show that the bit error rate (BER) performance significantly improved over the least square channel estimation and has comparable BER performance with MMSE channel estimation at low SNR with significant decrease...
A 64-state 16-QAM space-time trellis code (STTC), which uses two transmitting antennas, is proposed and applied to a 2??2 MIMO-OFDM system for outdoor mobile transmission in the 800-MHz band. Although STTCs have been analyzed theoretically and the error performances have been simulated by many researchers, experimental results have rarely been reported. Therefore, we evaluated the performance of our...
In this paper, an adaptive MMSE channel estimation method is proposed for UWB-OFDM system. As we known, the MMSE algorithm is dependent on the auto-correlation of the known signals and the cross-correlation between the known signals and the signals to be estimated. These parameters are difficult to obtain in practice, because it needs a long-term statistic at the cost of huge complexity and time delay...
In this paper, an interference suppression scheme by MMSE combining in OFDM-antenna array with time shifted sampling (TSS) is proposed. An array antenna at a base station has been thoroughly investigated to increase the uplink capacity. The performance of the uplink is not only limited by the correlation between the antenna elements, which strongly depends on the spatial aspects of the channel, as...
This paper presents the performance of a Fractional Sampling OFDM receiver with delay diversity. Delay diversity achieves transmit diversity by intentionally ingenerating paths which have different delays at a transmitter side. However, the correlations between subcarriers are not always low. The proposed scheme which combines the delay diversity and the FS offers diversity gain by reducing the correlation...
This paper presents an effective multiuser detector (MUD) for the uplink of dual-signaling multiple-input multiple-output (MIMO) code division multiple access (CDMA) systems over multipath fading channels, where the data are transmitted using either the spatially multiplexing (SM) or the space-time block code (STBC) scheme. The new MUD first separates users into two groups according to their transmission...
In this paper, a metric weighting scheme on a coded fractional sampling orthogonal frequency division multiplexing (FS OFDM) system is investigated. FS achieves path diversity with a single antenna through oversampling and subcarrier-based maximal ratio combining (MRC). Though the oversampling increases diversity order, correlation among noise components may deteriorate bit error rate (BER) performance...
Ultra Wideband (UWB) is an attractive technique that enable sharing spectrum with other radio systems to spread spectrum extremely wideband. However, there are potential interferences among those using in the same frequency bands and close range. This paper discusses the interference DAA (Detection And Avoidance) technique for coexisting pulse based UWB and OFDM systems. In a UWB transmitter-receiver,...
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