Figure 3
From: Performance-Driven Symbol Mapping for Downlink and Point-to-Point MIMO Systems
Euclidean distance versus projection criterion, QPSK 
example.
Figure 3 | EURASIP Journal on Wireless Communications and Networking
From: Performance-Driven Symbol Mapping for Downlink and Point-to-Point MIMO Systems
Euclidean distance versus projection criterion, QPSK example.