Suppression of Cyclic Prefix in Down-Link LTE like Systems to Increase Capacity

In this paper it is presented a proposal to increase the capacity of Down-Link (DL) transmissions in Long Term Evolution (LTE) like systems based on Multiple-Input Multiple-Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM). The augment of the data rate is achieved with the total or partial suppression of the Cyclic Prefix (CP), which requires the use of a variable number of samples without conveying any information. The proposal is based on an iterative cancellation of the main impairments that the CP suppression supposes, the Inter Symbol and Inter Carrier Interferences. The interference mitigation procedure demands adequate channel estimations obtained in two different stages. Firstly, this new scheme requires the utilization of a preamble symbol appended to the beginning of the data transmission, which enables an initial Maximum Likelihood channel estimation. Secondly, time-variant channels will be estimated using a Least Squares estimator by the use of scattered pilots within the LTE frame structure. Through simulations it has been demonstrated that, despite the interferences arisen due to the CP suppression, our proposal attains adequate channel estimations which converge to theoretical bounds and the overall system obtains values of Bit Error Rate similar to the ideal situation of not suppressing the CP. It is also presented that considering the typical values of CP in the LTE standard the increment of the capacity employing this strategy can range between 7% and 25%.