Feedback Overhead in the FDD Downlink Massive MIMO System

Table 5

Compression rate of the conventional Givens rotation and the proposed Givens rotation with AC and LZW algorithms in different MMIMO-OFDM configurations. , , and , respectively, stand for the number of antennas at the BS, the number of antennas at each UE, the number of UEs, and the number of OFDM subcarriers.

MMIMO; OFDM	Feedback amount in bits	Amount with GR in bits	Compression rate	Amount with amount with GR & LZW in bits	Compression rate	Amount with amount with GR & AC in bits	Compression rate
	524288	196608	62.5%	26784	94.89%	80504	83.18%
	1048576	393216	62.5%	38304	96.35%	179104	83.15%
	2097152	786432	62.5%	60480	97.12%	340472	83.37%
	4194304	1572864	62.5%	86080	97.95%	679576	83.17%
	1048576	393216	62.5%	53568	94.89%	170920	83.38%
	2097152	786432	62.5%	76608	96.35%	356848	83.29%
	4194304	1572862	62.5%	120960	97.12%	679584	83.25%
	8388608	3145728	62.5%	257730	96.93%	1423304	83.26%
	1048576	458752	56.25%	76296	92.72%	317552	70.25%
	2097152	917504	56.25%	109120	94.80%	624176	70.31%
	4194304	1835008	56.25%	155140	96.30%	1244040	70.50%
	8388608	3670016	56.25%	203970	97.57%	2519568	70.36%
	2097152	1179648	56.25%	196420	90.63%	626720	69.99%
	4194304	1835008	56.25%	218240	94.80%	1249128	70.68%
	8388608	3670016	56.25%	310470	96.30%	2509384	70.56%
	16777216	7430032	56.25%	487050	97.10%	4829072	70.56%.