Modified iterative sphere decoding algorithm in LTE system

In the long-term evolution (LTE) system, channel equalization makes compensation to restore the original signal, the paper puts forward iteration sphere decoding algorithm which combines traditional sphere decoding and the improved QR based on the conventional QR decomposition detection algorithm. It can effectively reduce the system complexity. At the same time, in QPSK and 16QAM, the simulation results show that the improved QR iterative sphere decoding algorithm performance is better with higher SNR in AWGN channel. Introduction In LTE system, the receiver uses signal detection and estimation methods to retrieve information from the received data to recover the transmitted signals. This process is referred to as channel equalization. This paper expounds the principle of decomposition algorithm and improved QR decomposition iterative detection algorithm. An improved algorithm is presented by combining QR algorithm with sphere decoding methodology. In addition, the improved algorithm will be compared with the Maximum Likelihood (ML). This paper is organized as follows: the QR decomposition detection principles will be described in section 2. Section 3 will present the improved iterative QR decomposition detection method. The combination of sphere decoding methodology and improved QR decomposition detection method will be given in section 4. Section 5 shows the simulation results, conclusions are drawn in section 6. QR decomposition detection principle Channel model: Y=HX+N.QR will decompose the channel impact response matrix H at (k, l). The result is the unitary matrix Q and the upper triangular matrix R, and then the matrix QH left multiplied by the received vector Y, after conversion. The result is received vector y . after conversion expressions are as follows: H H y Q Y RX Q n RX η = = + = +  (1) After decomposing, we can obtain the equations: , nT nT nT nT nT y r x η = +  1 1, 1 1 1, 1 nT nT nT nT nT nT nT nT y r x r x η − − − − − − = + + 