Wireless services have been around for a century. There is always the potential for interference and the service provider must engineer accordingly.
Figure 21: Interference occurs in a number of forms and interference mitigation is a matter of good engineering
Countering interference is a matter of understanding it and engineering accordingly. Interference occurs naturally in the electromagnetic spectrum. Figure 21 above shows out-of-channel interference, which comes from other transmitters that are not on the same frequency as the primary radio. A co-channel interfering transmission occurs on the same frequency as the desired signal. Step One in interference mitigation is to avoid co-channel interference through thorough frequency planning, use of licensed spectrum, and dynamic frequency selection. Step Two is to pay close attention to the link budget on the wireless network and plan power and spectrum to overcome interfering signals. Much of the im-pact of out-of-channel interference can be avoided using such technologies as OFDM, OFDMA, and a host of antenna technologies.
Solutions to Interference - OFDM
Figure 22: Multipath and intersymbol interference occur with all wireless transmissions
OFDM mitigates interference by breaking the signal into subcarriers. The loss of the data on a small percentage of the subdivided signal does not degrade the reception of the received signal.
Figure 23: OFDM and OFDMA mitigate interference by breaking the signal into mul-tiple subcarriers