Estimation Based On Two-dimensional Pilot LTE System Channels

In new generation wireless mobile communication systems, to facilitate the operation of coherent detection, demodulation and decoding of data, channel quality measurements, etc. It’s a must to obtain the channel state information from channel estimation. Therefore, channel estimation is a very important part for cellular wireless communication systems such as the LTE system. The performance of channel estimation will directly affect the performance of the whole cellular wireless communication systems. In the LTE system, channel estimation based on Demodulation Reference Signal (DM-RS) and the effect of pilot pattern have been studied. This thesis mainly includes three aspects as follows:1) This paper analyzed the design features of the LTE physical layer, and proposed a simulation analysis method based on multiple Code Blocks (CBs), which can help analyze the effect of pilot pattern on the channel estimation performance of different CBs. In a LTE system, current coding scheme adopts the way of segmenting the Transmission Block (TB) into several CB to encode and decode. Once any CBs corresponding to the TB fails in decoding, the TB will be retransmitted using HARQ. Therefore, it’s important to keep the balance of decoding performance for each CB, otherwise the worst performance of a certain CB will become the bottleneck of the whole TB.2) The design of DM-RS in LTE is discussed in detail from the aspect of pilot generation and pilot mapping, and the channel estimation based on DM-RS pilot pattern (we call it Legacy) is further studied. The results show that the unbalanced distribution of DM-RS pilots in a Resource Block Pair (RBP) leads to the poor channel estimation of some CBs. Specifically, the performance of the CB locating at the left part is the bottlenecks of the whole RBP for Legacy pilot pattern. Two representatives of pilot patterns called Baseline and Ericsson from3GPP proposals are studied. Results show that among the three pilot patterns: Ericsson channel estimation performance is the best, Baseline take second place, and the Legacy the worst.3) In order to improve the performance of channel estimation, this thesis proposes an algorithm based on the Legacy pilot pattern that treats the successfully decoded data in the middle and right part of the RBP as pilots to help the channel of the left part of the RBP. Four Data-assisted Pilot Pattern scenarios are presented and their performances are evaluated via simulations. Results show that considering the performance and computational complexity the second scheme with Data-assisted Pilots (Pattern B) is the best.