Description  Claims  Drawing  Cited references 

US9078153B1   [0027] 
US2014093005A1   [0029] 
US9118103B1   [0030] 

802.11ac: A Survival Guide Chapter 4. Beamforming in 802.11 ac   [0028] 
Next Generation Wireless LANs: 802.11n and 802.11 ac   [0105]