  The space-based laser interferometers, LISA, Taiji and TianQin, are targeting
to observe milliHz gravitational waves (GWs) in the 2030s. The joint
observations from multiple space-based detectors yield significant advantages.
In this work, we recap the studies and investigations for the joint space-based
GW detector networks to highlight: 1) the high precision of sky localization
for the massive binary black hole (BBH) coalescences and the GW sirens in the
cosmological implication, 2) the effectiveness to test the parity violation in
the stochastic GW background observations, 3) the efficiency of subtracting
galactic foreground, 4) the improvement in stellar-mass BBH observations. We
inspect alternative networks by trading off massive BBH observations and
stochastic GW background observation.
