Coexistence: The Theory and the Practice

RF coexistence, the ability of one piece of equipment to tolerate signals from another piece of equipment, is an often debated topic. Organizations from standards bodies to manufacturers to operators debate how to determine the ability to share spectrum with different technologies (CDMA, WiMAX, LTE, etc.), different duplexing schemes (FDD and TDD), and different deployments (public safety and cellular operations). Most often theoretical models are used, as measurements are often not practical. This article has performed both a theoretical and a practical (measured) analysis of CDMA-LTE coexistence in the U.S. PCS band (1850–1915/1930–1995 MHz), the result of which indicates that calculations based on standards or regulatory specifications are only directionally correct and that measurements, whenever possible, can provide a better picture of coexistence. This article validates theoretical coexistence calculations using real-world measurements and provides the methodology under which more detailed coexistence analysis can be performed. The methodology presented can be used to determine the coexistence of various wireless technologies, the results of which are directly translatable to field performance and thus practical network design. This leads to a better understanding of the challenges and solutions when disparate technologies and different network architectures attempt to share the same spectrum band.