Approach for determining the optimum pilot placement in orthogonal frequency division multiplexing systems

Abstract

One of the major concerns in wireless communications is multipath fading that causes some adverse effects and significantly limits the performance of a system. To overcome these effects in orthogonal frequency division multiplexing, system channel estimation must be performed. Pilot arrangement is very crucial in pilot aided channel estimation. There is an inevitable trade-off between the number of pilot symbols used in channel estimation, the accuracy of such estimation, and spectral efficiency. In this study, the analytical formulation of the channel estimation mean squared error based on a channel's sampled power density is presented. A novel mathematical rule for the optimum pilot symbol interval and a novel adaptive pilot placement are proposed to improve channel estimation quality and bandwidth efficiency. The optimum pilot symbol intervals which are related to channels' coherence times and coherence bandwidths can be calculated easily with the use of the proposed method. As the proposed method effectively reduces the number of searches for the optimum pilot symbol interval, it gives rise to simply constructing adaptive pilot placement in realtime systems. Compared with fixed pilot placement, the proposed adaptive placement shows obvious improvement up to 6% in bandwidth efficiency while maintaining the bit error rate performance.

New precoding blind channel estimation and channel order estimation algorithm in OFDM systems with cyclic prefix

“…Depending on the SNR value, each curve exhibits a linear relationship till specific limit. For SNR < 20 dB and employing (2) A at 0.1, 0.3 r = and (3) A at 0.1 r = yields the best performance, and for greater SNR values, the results that surpass all other results. In Fig.…”

“…) generally results in the best performance. The matrix (2) A at 0.6 r = is superior to the other values with higher SNR. At the same value of r , using matrix (1) A shows an impact in BER over the other cases at 0.1 r = , 0.3 r =…”

“…In non-blind or pilot based channel estimation, the received value in the receiver is compared to the value of previously known pilot bits that are placed into the transmitted signal. One-dimensional (block and comb) and two-dimensional (comb) pilot insertion techniques are utilized [2]. Because fewer pilots are used, semi-blind channel estimate results in higher bandwidth efficiency than pilot-based channel estimation.…”

“…Many papers [2,11] have used this design of precoding matrix to estimate the OFDM channel as in Eq. Ошибка!…”

Channel Estimation Techniques for MIMO-OFDM Systems over Frequency Selective Fading Channels

“…Channel estimation algorithms can be categorized into three groups [4]. In pilot based channel estimation, value of previously known pilot bits are inserted into the transmitted signal is compared to the received value in the receiver and in pilot based channel estimation one dimensional pilot placement (block and comb) and two dimensional pilot placement (rectangular and diamond) are used [5]. In blind channel estimation, algorithms often exploit the second-order stationary statistics with high computational complexity.…”