An Introduction to NLOS Identification and Localization

Document Type

Book Chapter

Publication Date



Department of Electrical and Computer Engineering


This chapter reviews many non-line-of-sight (NLOS) identification and localization techniques. NLOS identification techniques can be categorized into cooperative and noncooperative. Cooperative localization techniques use multiple nodes to identify NLOS measurements. Noncooperative NLOS identification is based on single-node channel measurement. These techniques are based on (1) the range statistics; (2) channel characteristics, such as received signal power, Rician K-factor and features extracted from the power delay profile; and (3) the consistency between the time-of-arrival (TOA) measurement and path loss for line of sight (LOS)/NLOS, and the consistency between the direction of departure (DOD) and direction-of-arrival (DOA). The NLOS localization techniques can be cooperative and noncooperative. These techniques are categorized into (1) NLOS localization using TOA, DOA measurements, and the environment map; and (2) localization using the measurements from reflectors. The chapter discusses the advantages and disadvantages of these techniques and the complexity and performance of each technique.

Publication Title

Handbook of Position Location: Theory, Practice, and Advances