# Survey of Localization for Internet of Things Nodes: Approaches, Challenges and Open Issues
## 4 Localization Techniques
### Device-Based Localization
#### 4.1.6 Tag-Based  
Tag-based localization techniques require particular hardware set up for location compatibility. Ultra-Wide Band (UWB) and Radio Frequency Identification tag-based localization methods are discussed.  
* Ultra-Wide Band Tag-Based Localization:  
The larger bandwidth of Ultra-Wide Band (UWB) permits real-time requirements and improved secrecy. The smaller fundamental frequency consents to an upgraded wave channel via diverse materials. UWB tag-based localization algorithms have provided motivating outcomes. UWB tag integrated through the pulse transmitter intermittently transmits immensely smaller pulses at a precise rate. Accordingly, accepting the conveyed pulses is the responsibility of the base station [56]. Every moving anchor node in the network possesses a tag that communicates impulses to perceive automatically nearby the base station.  
Additionally, this moving anchor node organizes and forms a self-organized wireless network. Besides, the high determination of UWB signals at various base stations can be reassembled jointly, trusting the density renewal procedure [57]. The synchronization of the clocks at the base stations is required so that the period variances of the impulses will imitate the geometrical alterations at other base stations. This process of localization is presented in Figure 11.  
* RFID Tags Localization RFID tags integrated into an object can remotely identify, track, understand the features of an object. RFID technique permits construing tags deprived of direct view, and also it passes through the fine material color coatings, snow, etc. The RFID tag compromises  
Figure 11: UWB tag-based localization.  
a chip linked to an antenna, unfold in support and interpreted by a reader, which seizures and communicates the information. Figure 12 shows the localization based on RFID tags.  
RFID tags are mainly classified into three types: read-only/immutable, read-rewrite, and write once-multiple read tags. In the third type of tag, the chip has a blank memory region to write the specific number for the particular operator. Nevertheless, this number cannot be altered once it is embedded. Besides, RFID tags can be either active or passive. Active tags are associated with onboard power sources; they have an improved range, higher cost and constrained lifetime.  
On the other hand, passive tags are cheaper, have an unlimited lifetime and require a substantial amount of energy disseminated at a smaller distance by the transmitter. In the localization approach for the objects in an office [58], every object carrying an RFID interpretation component can read passive tags mounted beside the object path. Coordinates of RFID readers are assessed by using received signal strength dispersed by the tags. RFID tags for position estimate in libraries and warehouses is proposed in [59] which equips all the moving objects with RFID chips. Tags are capable of locating objects crossing the range. This technique is economical, energy-efficient, and reference drive deployment is not required since the RFID reader must be moving continuously to scan the tags and location estimates. Tag resemblance and assembling in line with the distances measured by RSSI is used for localization [60].