Performance evaluation of channel estimation techniques: for an LTE downlink system

The downlink physical shared channel contains the scrambler, the modulation mapping, the pre coder, layer mapping, resource element mapping and OFDM signal generator. This receiver processing starts from the OFDM signal reception and continuing through resource element de-mapping, channel estimation, Equalization, layer de-mapping, demodulation, descrambling, channel decoding and finally CRC detector. The resource grid is made up of several resource blocks and these are in turn made from resource elements. Even the resource element is made up of one OFDM subcarrier in frequency domain and one OFDM symbol in time domain. As can be seen from figure 2.4 the resource grid contains control and data information signals. These control signals are the user data, data control indicator (DCI), primary synchronization symbol (PSS), secondary synchronization symbol (SSS), primary matrix indicator (PMI), and cell specific reference symbol (CSR). The user data Physical Downlink Shared Channel (PDSCH), the Physical Downlink Control Channel (PDCCH) and CSR are placed in every sub frame of a resource grid. The PSS and SSS are placed in frames 0 and 5 at specific OFDM symbol.