In wireless networking, the hidden node problem or hidden terminal problem occurs when a node can communicate with a wireless access point, but cannot directly communicate with other nodes that are communicating with that AP. 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 neither packet getting through. Although some loss of packets is normal in wireless networking.
In, the exposed node problem occurs when a node is prevented from sending packets to other nodes because of with a neighboring transmitter. Consider an example of four nodes labeled R1, S1, S2, and R2, where the two receivers (R1, R2) are out of range of each other, yet the two transmitters (S1, S2) in the middle are in range of each other. Here, if a transmission between S1 and R1 is taking place, node S2 is prevented from transmitting to R2 as it concludes after that it will interfere with the transmission by its neighbor S1. However note that R2 could still receive the transmission of S2 without interference because it is out of range of S1.mechanism helps to solve this problem only if the nodes are synchronized and packet sizes and data rates are the same for both the transmitting nodes.
When a node hears an RTS from a neighboring node, but not the corresponding CTS, that node can deduce that it is an exposed node and is permitted to transmit to other neighboring nodes.If the nodes are not synchronised (or if the packet sizes are different or the data rates are different) the problem may occur that the sender will not hear the CTS or the ACK during the transmission of data of the second sender.The exposed node problem is not an issue in as the power and distance between cells is controlled to avoid it.See also. (MACAW)References.
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A problem that manifests in wireless networks where some of the nodes are unaware of each other. Specifically, it can occur when all nodes are within signal range of the network's access point, but some are out of range of each other. Because traditional networking protocols rely on a node listening to network traffic and only transmitting data when the network is momentarily idle, it is possible that two nodes unaware of each other will attempt to transmit simultaneously. The addition of handshaking to the protocols is a partial cure, but no complete solution has yet been found. Compare exposed terminal problem.