Abstract
To the significant amount of pilot overhead of the interference cancelation methods in orthogonal frequency division multiplexing (OFDM) based on offset quadrature amplitude modulation (OFDM/OQAM) system, we proposed an improved interference cancelation method (ICM) for OFDM/OQAM system in this paper. In this method, we use the auxiliary pilot (AP) to eliminate the influence of the intersymbol interference on channel estimation, which can reduce the pilot overhead of OFDM/OQAM system significantly. At the same time, to improve the channel estimation performance, we analyze the source of the intrinsic interference of system and its distribution in time and frequency domain, then, we reset the interference cancelation range of AP, which can cancel more intrinsic interference for OFDM/OQAM system. According to the results of performance analysis, compared to the conventional interference cancelation methods, the proposed method performs better in terms of energy efficiency and spectral efficiency. Also, the simulation results of the proposed method show that the proposed method can outperform traditional interference cancelation methods in channel estimation performance.
Highlights
As an important multicarrier modulation (MCM) scheme, orthogonal frequency division multiplexing (OFDM) based on offset quadrature amplitude modulation (OFDM/OQAM) system, named OQAM system for concision in the rest of the paper, has been proved to outperform OFDM system in the terms of frequency spectrum efficiency, robustness to the interference, and the leakage of the out-band energy [1,2,3,4]
bit error ratio (BER) refers to the ratio of the number of erroneous bits recovered at the receiver to the total bits of system; normal mean square error (NMSE) is the mathematical expectation of the ratio of the square of the difference between the estimated channel value and the actual channel value to the square of the actual channel value, which can be expressed as follows: 퐻푁푀푆퐸 = 퐸
The author in [31] points out that the NMSE performance of channel estimation is related to the energy efficiency and spectral efficiency of the method; the channel estimation NMSE performance is an important embodiment of the channel estimation method in energy efficiency and spectral efficiency
Summary
As an important multicarrier modulation (MCM) scheme, orthogonal frequency division multiplexing (OFDM) based on offset quadrature amplitude modulation (OFDM/OQAM) system, named OQAM system for concision in the rest of the paper, has been proved to outperform OFDM system in the terms of frequency spectrum efficiency, robustness to the interference, and the leakage of the out-band energy [1,2,3,4]. The performance advantage is obtained at the cost of the relaxation of the orthogonal condition of OQAM system, which only satisfy the orthogonality in the real domain [5, 6] This feature causes the intrinsic interference between the real data symbol, which makes the channel estimation method of conventional OFDM system cannot be applied to OQAM system straightforwardly [7, 8]. The AP method set up one dummy symbol in the first order neighborhood of the pilot to cancel the imaginary interference, which was named AP in [13] This method can cancel mostly interference to the pilot and ensure high spectral efficiency. From the view of power efficiency, the AP takes up a significant amount of power
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