Question 1: What is the main motivation for LTE?

The main motivation is the exponential growth on data transfer, on the last few years and the demand for higher connection speed due to advance of mobile technologies.

Question 2: What are the main differences between the LTE release 8 and release 10 (LTE-A)?

LTE-A is the only one between both that meets 4G requirements. Its mains advantages over release 8 are the higher data rates, for uplink and downlink, and higher spectral efficiency.

Question 3: What is the main feature of OFDMA and what are the differences between OFDMA and SC-FDMA?

OFDMA is mainly characterized by mapping the symbols into orthogonal subcarriers and attribute a subset of subcarriers to each user.

The main difference between them is the fact that, in SC-FDMA, a DFT operation is applied ti the symbol before it is mapped into subcarriers. Due to that each subcarrier contains part of each symbol.

Question 4: Highlight an important improvement on the LTE network architecture compared with CDMA networks.

The base station, called eNB, is directly connected to the core by the S1 interface. There is no network controller anymore as we had in CDMA so we have a much leaner architecture in LTE.

Question 5: What are the advantages of using MIMO?

IT makes possible an increase on the data rate or the improvement if the SNR, deoending on the mode it is operating on.