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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...
This paper presents a preliminary study on a non-line-of-sight (NLOS) identification technique that exploits space-frequency correlation features of multiple-output orthogonal frequency division multiplexing (OFDM) systems. Here, space correlation refers to the correlation across antenna elements and frequency correlation refers to the correlation across subcarriers. In this technique, a measure,...
In the IEEE802.11n WLAN standard, orthogonal frequency division multiplexing (OFDM) modulation is employed. Diversity techniques are implemented to overcome multipath fading in the OFDM systems. A fractional sampling (FS) scheme is one of the diversity techniques with a single antenna. This scheme also can be applied in a MIMO-OFDM system to increase its capacity. In this paper, the effect of FS in...
A new synchronization method for MIMO-OFDM systems with CAZAC sequence is presented in this paper. Frame timing objective functions is sharpen by using CAZAC Sequence, and its accuracy is also improved. Combing frame and symbol synchronization, only one step is needed for timing algorithm. Reducing the computation load and defining the first channel path accurately. Integral frequency offset correction...
We address pilot aided channel estimation (PACE) for MIMO-OFDM operating in diverse deployment scenarios, ranging from outdoor macro-cells to indoor office environments. In macro-cells high mobile velocities and large cell sizes result in high Doppler and channel delay spreads, while transmit antenna elements are typically spatially correlated. On the other hand, in indoor environments spatial correlation...
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)...
With standardization of MIMO-OFDM spatial multiplexing in IEEE 802.11n, the interest of the industry in chances and risks of this technology is growing. Experiences with planar transmit antennas applied with an experimental MIMO radio system and changing transmitter side interantenna spacing are reported in this paper for an indoor aircraft environment. Different transmission scenarios are described...
In this paper, cyclostationarity of the V-BLAST MIMO OFDM signal is examined based on the model of MIMO OFDM systems in the wireless communication channel and the theory of cyclostationarity. Mathematical deduction and simulation results are both shown that the received MIMO OFDM signals is cyclostationary in the wireless communication channel. Meanwhile, if the received signal is sampled at the data...
In communication systems that use orthogonal frequency-division multiplexing and multiple transmit and receive antennas, beamforming (BF) is conventionally carried out on a subcarrier basis. The computational requirements are high as dedicated discrete Fourier transform (DFT) processors are needed for each antenna. Considerable complexity reductions can be achieved by symbol-wise BF, which performs...
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...
A new and novel spread spectrum approach employing orthogonal frequency coding (OFC) for a SAW sensor/tag is presented. This approach provides ultra wide band operation, multi-device interrogation, and reduced loss as compared to conventional SAW CDMA approaches. A traditional SAW CDMA tag consists of an input transducer that launches a surface wave on the substrate towards an array of single frequency...
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 considers the practical multiple-input multiple-output systems with orthogonal frequency division multiplexing (MIMO-OFDM) and bit-interleaved coded modulation (BICM) in spatially correlated broadband channels. Using link adaption techniques, the MIMO scheme that better exploits the space and frequency characteristics of the encountered channel condition is selected. It is shown that the...
This paper proposes a frequency synchronization algorithm for time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system with multiple antenna transmit diversity. The training sequences used in the transmit diversity TDS-OFDM system are orthogonal and have near-optimal autocorrelation property, and the carrier frequency offset (CFO) estimation algorithm is based on these...
The long term evolution of evolved universal mobile telecommunications system terrestrial radio access, is based on OFDM techniques owing to its inherent flexibility and attractive implementation potential. This paper addresses the issue of time synchronization which is imposed severely challenges particularly in the downlink of LTE systems and the means of time offset estimation exploring different...
This paper presents field experiments on open-loop precoding multiple input multiple output (MIMO) using a testbed targeting International Mobile Telecommunication - Advanced (IMT-Advanced) systems. Open-loop MIMO is realized by applying Rotational OFDM (R-OFDM) to MIMO transmission. MIMO R-OFDM is more robust with respect to correlated channels than conventional open-loop MIMO-OFDM as was shown by...
We address pilot aided channel estimation (PACE) for MIMO-OFDM operating in spatially correlated channels. Pilot symbols are only inserted on selected transmit antennas, and the channel response on the remaining transmit antennas is obtained by means of interpolation. By extending the principle of channel estimation by interpolation to the spatial domain, three dimensional (3D) PACE operates in time,...
In this paper, the Cramer-Rao lower bound (CRLB) for spatial correlation matrices is derived based on a rigorous model of the doubly selective fading channel for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Adopting an orthogonal pilot pattern for multiple transmitting antennas and assuming independent samples along the time, the sample auto-correlation...
Although uncorrelated channels are commonly assumed in cyclic delay diversity (CDD) based multiple input and multiple output (MIMO) orthogonal frequency division mutiplexing (OFDM) systems, correlated channels can evolve due to closeness of antennas or lack of scatterers in the environment. To mitigate the correlation effect, a random continuous phase offset is induced into the transmitting symbols...
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