1. Federal University of Rio Grande do Norte (UFRN); Av. Senador Salgado Filho, 3000, Natal, RN, CEP: 59072-970 Brazil
2. Communication Engineering Department; Federal University of Rio Grande do Norte (UFRN); Av. Senador Salgado Filho, 3000, Natal, RN, CEP: 59072-970 Brazil