Editing Hidden node problem (section)

{{Use American English|date = March 2019}}
{{Short description|Problem in wireless networking}}
[[Image:Wifi hidden station problem.svg|right|thumb|250px|In one scenario, Station A can communicate with Station B. Station C can also communicate with Access Point Station B. However, Stations A and C cannot communicate with each other as they are out of range of each other, and thus start to transmit simultaneously preventing B from receiving messages intended for it.]]
In [[wireless networking]], the '''hidden node problem''' or '''hidden terminal problem''' occurs when a [[Node (networking)|node]] can communicate with a [[wireless access point]] (AP), but cannot directly communicate with other nodes that are communicating with that AP.<ref>{{cite book|last1=Buehrer|first1=R. Michael|title=Code Division Multiple Access (CDMA)|date=2006|publisher=Morgan & Claypool Publishers|location=[San Rafael, Calif.]|isbn=1598290401|pages=16–19|edition=1st}}</ref> This leads to difficulties in [[medium access control]] sublayer since multiple nodes can send data packets to the AP simultaneously, which creates interference at the AP resulting in no packet getting through.

Although some loss of packets is normal in wireless networking, and the higher layers will resend them, if one of the nodes is transferring a lot of large packets over a long period, the other node may get very little [[goodput]].

Practical protocol solutions exist to the hidden node problem. For example, [[IEEE 802.11 RTS/CTS|Request To Send/Clear To Send (RTS/CTS)]] mechanisms where nodes send short packets to request permission of the access point to send longer data packets. As responses from the AP are seen by all the nodes, the nodes can synchronize their transmissions to not interfere. However, the mechanism introduces [[Network delay|latency]], and the [[Protocol overhead|overhead]] can often be greater than the cost, particularly for short data packets.