Previous work on space-frequency coded multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) has been restricted to idealistic propagation conditions. In this paper, using a broadband M...
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Previous work on space-frequency coded multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) has been restricted to idealistic propagation conditions. In this paper, using a broadband MIMO channel model taking into account Ricean K-factor, transmit and receive angle spread, and antenna spacing, we study the impact of the propagation environment on the performance of space-frequency coded MIMO-OFDM. For a given space-frequency code, we quantify the achievable diversity order and coding gain as a function of the propagation parameters. We find that while the presence of spatial receive correlation, affects all space-frequency codes equally, spatial fading correlation at the transmit array can result in widely varying performance losses. High-rate space-frequency codes such as spatial multiplexing are typically significantly more affected by transmit correlation than low-rate codes such as space-frequency block codes. We show that in the MIMO Ricean case the presence of frequency-selectivity typically results in improved performance compared to the frequency-flat case.
This paper considers the problem of space-frequency code design for frequency-selective multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) modulation. We show that space-time codes...
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This paper considers the problem of space-frequency code design for frequency-selective multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) modulation. We show that space-time codes achieving full diversity in quasistatic flat fading environment can be used to construct space-frequency codes that can achieve the maximum diversity available in frequency-selective MIMO fading channels. Since the codes are constructed via a simple mapping from space-time codes to space-frequency codes, the abundant classes of existing space-time block and trellis codes can be used for full diversity transmission in MIMO-OFDM systems. The proposed mapping provides a tradeoff between the achieved diversity order and the symbol rate. Moreover, we characterize the performance of the space-frequency codes obtained via the mapping by finding lower and upper bounds on their coding advantages as functions of the coding advantages of the underlying space-time codes. This result will allow us to investigate the effects of the delay distribution and the power distribution of the channel impulse responses on the performance of the resulting space-frequency codes. Extensive simulation results are also presented to illustrate and support the theory.
We introduce a novel space-time coding scheme, called space-time cyclic-delay coding (STCDC), for multiple input multiple output orthogonal frequency-division multiplexing (MIMO-OFDM) systems over frequency-selective ...
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ISBN:
(纸本)0780381637
We introduce a novel space-time coding scheme, called space-time cyclic-delay coding (STCDC), for multiple input multiple output orthogonal frequency-division multiplexing (MIMO-OFDM) systems over frequency-selective fading channels. The scheme exploits the redundancy introduced by channel coding. The transmitter antennas send the cyclically delayed copies of OFDM symbols, and the receiver uses the maximum likelihood estimation method to estimate the transmitted sequence. We show that STCDC-OFDM can achieve the maximum diversity, which is the product of the number of transmitter antennas (N-l), the number of receiver antennas (N-r) and the channel length (L), if the error control code has at least a free distance of NlL. Compared with the existing space-time coding and space-frequency coded MIMO-OFDM techniques, the proposed scheme has the advantages of being independent from the number of transmit antennas and having a lower implementation complexity. Keywords: Cyclic delay coding, OFDM, space-time coding, space-frequency coding.
In this letter we show that when the number of receive antennas is large, the Euclidean distance among codewords dominates the performance of space-frequency codes, the same result as for space-time codes. Therefore, ...
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In this letter we show that when the number of receive antennas is large, the Euclidean distance among codewords dominates the performance of space-frequency codes, the same result as for space-time codes. Therefore, in the presence of a large number of receive antennas, space-frequency codes can be optimized by using the Euclidean-distance criterion valid for additive white Gaussian noise channels. Simulation results show that this conclusion is also valid when the number of antennas is small.
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