This paper presents a performance evaluation of OFDM LTE downlink physical layer according to the latest 3GPP specifications. Particularly, adaptive modulation and coding (AMC) is described and analyzed. This is in conjunction with the turbo decoding algorithm Max-Log-Maximum A Posteriori (Max-Log-MAP) used in soft input soft output (SISO) decoders. The performance analysis is carried out in terms of bit error rate (BER) and throughput by varying parameters such as signal to noise ratio (SNR), modulation schemes, coding rates and decoding iterations number.