well, i know it's working in SISO as reported in webui, but when i test a router, i test in all conditions that were studied by the producer, and so.. i tested also ext antennas, which are completely useless. (well.. i immagine that in some scenarios they could help)
Inside house, B618 is faster - no antennas
Outside, with ext antenna B618 is faster.
There is no scenario where this 3ca modem router goes faster, and it's a real pity.. because overall i liked the idea of 3ca 256QAM.