0. How to obtain the complete source code
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The received signal of the MIMO-OFDM system is the linear superposition of the fading and additive noise of the signals sent by multiple transmit antennas. If the estimation algorithm of the usual SISO-OFDM system or MIMO system is used to estimate the channel, it will bring a large estimation error. For the consideration of design and implementation, this paper mainly studies the channel estimation algorithm of MIMO-OFDM system based on training sequence in a relatively mature slowly changing environment. This chapter will mainly discuss the design of special training sequences and the selection of channel estimation algorithms for MIMO-OFDM systems.
Compared with the single-antenna system, the channel estimation algorithm of the multi-antenna system has greater complexity, because the received signal is a superimposed signal of multiple transmit signals. a receiving antenna. Therefore, to correctly identify multiple transmit signals from a superimposed signal, a channel estimation algorithm needs to be able to estimate the channel characteristics of multiple parallel channels between each transmit antenna and the same receive antenna . The channel estimation between any transmit antenna and any receive antenna can refer to the algorithm of the single-antenna system.
Channel estimation algorithms can be mainly divided into two types: blind estimation algorithms and non-blind estimation algorithms. The blind channel estimation algorithm does not need to insert the training sequence in the transmitted information, which saves the bandwidth. The implementation of the blind estimation algorithm needs to utilize the statistical information contained in the transmitted information. This usually requires complex mathematical operations on the received signal at the receiving end, and the computational workload of the algorithm is generally large, which is not suitable for real-time systems that require relatively high delays. The non-blind estimation algorithm inserts the information known in advance by both the transceiver and the receiver into the transmitted signal. After receiving the known information, the receiver estimates the channel's effect on the transmitted information by the amplitude, carrier frequency or phase change of the information. fading impact. The algorithm is widely used and can be applied to almost all wireless communication systems.
