Summary of the technology
UVIGO telecom engineers have developed a novel methodology to suppress the impulsive noise present in Long Term Evolution (LTE) cell phone systems. These systems that utilize multiple-input multiple output (MIMO) techniques are already used in fourth generation (4G) cell phones and are expected to undergo further development in a near future. The presence of impulsive noise can be detected comparing the signals received by different antennas, the subsequent application of a enhanced algorithm leads readily to the suppression of the deleterious effect of the impulsive noise on the radio signal. To date, no other methods have been specifically developed for LTE.
New and innovative aspects
In comparison with current procedures: • Efficient detection and suppression of Impulsive Noise. The Bit Error Rate improves more than 10 times over the threshold detection and blanking method. • It is not necessary to implement additional hardware in the handset. • Easy algorithm, with low computational load. • Easy to incorporate in the LTE handset firmware.
Main advantages of its use
*The computational load of the method is very low because the necessary parameters of correlation and RMS signal value are already calculated in the ordinary reception algorithms of every LTE handset. * Dynamic threshold selection can be made in real time. * Up to 100 times improvement with respect to clàssic threshold suppressing methods * Low false alarm probability
A novel methodology to suppress the impulsive noise present in Long Term Evolution (LTE) cell phone systems Let us consider a LTE MIMO 2x2 downlink transmission. Two antennas, Tx1 and Tx2 at the base station transmit an OFDMA signal to the handset, which in turn has two receive antennas, Rx1 and Rx2. The signal transmitted from Tx1 and Tx2 will arrive at Rx1 and Rx2 as a sum of direct and reflected waves. The equation which defines reception at the handset is: (y1) (h11 h12) (x1) + (v1) ( ) = ( ) ( ) + ( ) (y2) (h21 h22) (x2) + (v2) Where x1 and x2 are the signals transmitted by Tx1 and Tx2, y1 and y2 are the signals received by Rx1 and Rx2, and the elements hij of matrix H represent the complex gain of the channel between the jth transmit antenna and the ith receive antenna. Therefore, the rows of H represent receive antennas and the columns represent transmit antennas. v1 and v2 are the noise contribution at Rx1 and Rx2. In this example, v1 and v2 will consist of interference from an IN event. It must be highlighted that IN is considered to be near end interference, and it does not follow the same path as the signals coming from Rx1 and Rx2. Another important feature of the IN leaking into Rx1 and Rx2 is the expected correlation between their amplitudes. The positive correlation found implies that any time we receive an IN peak in one receive antenna we will probably receive another peak with similar amplitude in the other one. That is to say, if some IN is generated near the handset then it is very probable that it receives high amplitude at both receive antennas at the same time. The patent that we present is based on these principles.