What are the classifications and sources of wireless jamming

Wireless jamming can be divided into WLAN interference and non-WLAN interference by type. WLAN interference refers to the interference source to send the RF signal also meet the 802.11 standard, in addition to the non-WLAN interference. The interference of WLAN can be divided into same frequency interference and adjacent frequency interference according to frequency range. According to the source division, can be divided into WLAN network itself mutual interference and network interference

The same frequency interference of WLAN network with wireless jamming

The same-frequency interference refers to the mutual interference between two WLAN devices working at the same frequency. WLAN work ISM (Industry,scienceandmedicine) band, including 2.4G and 5G two bands. For some countries or regions, only 2.4G bands are available. In the 2.4G band, the frequency of non-interference is very limited, usually only 1, 6, 11 channels (as shown in Figure 1).

Therefore, for a large WLAN network, especially high-density deployed networks, the same channel often needs to be used by different APS. When there is a repeat region between these APs, there is a problem of mutual interference. Figure 2 is a student apartment AP Deployment channel arrangement diagram, due to poor wall isolation, not only the same floor of the same channel between the AP can be seen between the upper and lower floors of the same channel AP also have interference with each other.

If visible between the same frequency AP, 802.11 based WLAN, empty is the public transport media for all devices, two AP will be based on the CSMA/CA principle, the mutual avoidance, which will greatly reduce performance, two AP total performance will not exceed one channel performance.

If the same-frequency AP is not visible and the coverage area is intersected, a hidden node or exposed node problem may be formed for the client in the intersection area (as shown in Figure 3).

Hiding nodes and exposing nodes can cause two of problems. The first is that the message needs to be sent back or constantly retransmission, the second is because the message retransmission will reduce the physical rate of the message sent, resulting in an extension of the same AP, but also make the message sent to occupy more empty time, conflict probability increased, causing more retransmission.