Are 1-bit ADCs Sufficient?

A series of recent papers,

suggest the use of 1-bit ADCs in Massive MIMO base station receivers. Important studies of a concept, that offers great potential for cost saving and simplification of transceiver hardware.

One-bit ADCs
One-bit ADCs quantize the sign of the real and imaginary part of the complex baseband signal.


Granted, much lower resolution will be sufficient in Massive MIMO than in conventional MIMO, but will one bit be sufficient? These papers indicate that the price to pay is not insignificant: the number of antennas may have to be doubled in some cases. Also, while the use of symbol-sampled models as in these studies may give correct order-of-magnitude estimates of capacity, much future work appears to remain to understand the effects of digital channelization/prefiltering and sampling rate conversion if 1-bit frontends are going to be used.

Massive MIMO in Mobile Environments

An impressive experiment, recently reported by colleagues at Univ. of Lund and Univ. of Bristol, shows TDD (reciprocity-based) Massive MIMO multiplexing to mobile terminals:

The interesting part starts at 2:48, with the terminals onboard cars. While it has been contested whether Massive MIMO can work in mobility (because of channel aging) this experiment confirms that it does — as predicted by theory for a long time. In fact, at 3.7 GHz carrier and with a slot length of 0.5 ms, the maximum permitted mobility (assuming a two-ray model with Nyquist sampling, and a factor-of-two design margin) is over 140 km/h. So the experiment is probably still not close to the physical limits.