摘要 : For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the over-crowding of radio bands, and the other is the move to escape that congestion by exploit... 展开 For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the over-crowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they're beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment. which is determined by a host of factors, many of them random and therefore unpredictable? 收起