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In wireless networks, the exposed node problem occurs when a node is prevented from sending packets to other nodes because of co-channel interference 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 ...
A wireless site survey, sometimes called an RF (Radio Frequency) site survey or wireless survey, is the process of planning and designing a wireless network, to provide a wireless solution that will deliver the required wireless coverage, data rates, network capacity, roaming capability and quality of service (QoS). [1]
It is particularly important for wireless networks, where the alternative with collision detection CSMA/CD, is not possible due to wireless transmitters desensing (turning off) their receivers during packet transmission. CSMA/CA is unreliable due to the hidden node problem. [3] [4] CSMA/CA is a protocol that operates in the data link layer.
In the typical case of a WiFi network, increasing transmission power on the access point only will not solve the problem because typically the hidden nodes are the clients (e.g. laptops, mobile devices), not the access point itself, and the clients will still not be able to hear each other. Increasing transmission power on the access point is ...
This effect was first seen in networks using CSMA/CD on Ethernet. Because of this effect, the most data-intense connection dominates the multiple-access wireless channel. [12] This happens in Ethernet links because of the way nodes "back off" from the link and attempt to re-access it.
Interference alignment was eventually established as a general principle by Jafar and Viveck R. Cadambe in 2008, when they introduced "a mechanism to align an arbitrarily large number of interferers, leading to the surprising conclusion that wireless networks are not essentially interference limited." This led to the adoption of interference ...
Link adaptation, comprising adaptive coding and modulation (ACM) and others (such as Power Control), is a term used in wireless communications to denote the matching of the modulation, coding and other signal and protocol parameters to the conditions on the radio link (e.g. the pathloss, the interference due to signals coming from other ...
For wider area communications, wireless local area network (WLAN) is used. WLANs are often known by their commercial product name Wi-Fi. These systems are used to provide wireless access to other systems on the local network such as other computers, shared printers, and other such devices or even the internet.