  This paper presents a tutorial for network multiple-input and multiple-output
(netMIMO) in wireless local area networks (WLAN). Wireless traffic demand is
growing exponentially. NetMIMO allows access points (APs) in a WLAN to
cooperate in their transmissions as if the APs form a single virtual MIMO node.
NetMIMO can significantly increase network capacity by reducing interferences
and contentions through the cooperation of the APs. This paper covers a few
representative netMIMO methods, ranging from interference alignment and
cancelation, channel access protocol to allow MIMO nodes to join ongoing
transmissions, distributed synchronization, to interference and contention
mitigation in multiple contention domains. We believe the netMIMO methods
described here are just the beginning of the new technologies to address the
challenge of ever-increasing wireless traffic demand, and the future will see
even more new developments in this field.
