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Personal and local area networks include technologies such as IEEE 802.11 (WLAN), Bluetooth, Zigbee, Ultra‐Wideband (UWB), and RFID.

WLAN APs are ubiquitous in indoor environments, where they are used to provide Wi‐Fi Internet services to users with a range of approximately 50–100 m per Wi‐Fi access point. Therefore, Wi‐Fi signals represent some of the most widely available RF signals in indoor environments. Not surprisingly, a majority of triangulation and fingerprint‐based indoor localization techniques (discussed in more detail in Section 37.5) utilize Wi‐Fi signals. The 802.11 Wi‐Fi family consists of several standards. The 802.11b and 802.11g standards use the 2.4 GHz industrial, scientific, and medical radio (ISM) radio band, and employ direct‐sequence spread spectrum (DSSS) and orthogonal frequency‐division multiplexing (OFDM) signaling methods to limit occasional interference from microwave ovens, cordless telephones, and Bluetooth devices. The 802.11a standard uses the 5 GHz U‐NII band, which for much of the world, offers at least 23 non‐overlapping channels rather than the 2.4 GHz ISM frequency band offering only 3 non‐overlapping channels, where other adjacent channels overlap. The 802.11n standard allows using either the 2.4 GHz or the 5 GHz band, while 802.11ac uses only the 5 GHz band. Note that as the segment of the RF spectrum used by 802.11 varies between countries, indoor localization solutions that utilize WLAN signals may need to be adjusted when deployed in different countries.

Bluetooth is a wireless standard for wireless personal area networks (WPANs), for exchanging data over short distances (using short‐wavelength RF waves in the ISM band from 2.4 to 2.485 GHz). Almost all Wi‐Fi‐enabled mobile devices available in the market today (e.g. smartphones, tablets, laptops) have an embedded Bluetooth module. Bluetooth has a smaller coverage area than Wi‐Fi (typically 10–20 m). In [14] it was shown that the Bluetooth Low Energy (BLE; Bluetooth 4.0) propagation model can better relate RSSI to range than Wi‐Fi, which indicates that BLE can be more accurate when used in localization scenarios. However, Wi‐Fi has a much wider coverage than BLE, so BLE‐based localization solutions will require more anchors/beacons compared to Wi‐Fi APs, for the same coverage area.

Zigbee is another short‐range wireless technology based on the IEEE 802.15.4 specification and mainly designed for applications which require low power consumption but do not require large data throughput. It operates in the 2.4 GHz ISM band in most jurisdictions worldwide, 784 MHz in China, 868 MHz in Europe, and 915 MHz in the United States and Australia. Zigbee implementations are typically more economical, more energy efficient, and have higher coverage (~100 m) than Bluetooth implementations. However, Zigbee support is less common in mobile devices than Bluetooth support. Moreover data rates for Zigbee vary from 20 kbit/s (868 MHz band) to 250 kbit/s (2.4 GHz band), which are much lower than the data rates achievable with Bluetooth (1–25 Mbit/s).

RFID systems are commonly composed of one or more reading devices that can wirelessly obtain the ID of tags present in the environment. When the reader transmits an RF signal, RFID tags in the environment reflect the signal, modulating it by adding a unique identification code [15]. The tags can be active, that is, powered by a battery, or passive, drawing energy from the incoming radio signal. The detection range of passive tags is therefore more limited compared to that of active tags. RFID technology is used in a wide range of tracking applications in the automobile assembly industry, warehouse management systems, and across supply chain networks, where LOS contact is difficult or even impossible [16]. Passive RFID systems typically make use of four frequency bands: LF (125 kHz), HF (13.56 MHz), UHF (433, 868–915 MHz), and microwave frequency (2.45 GHz, 5.8 GHz). Active RFID systems use similar frequency ranges, except for the low‐frequency and high‐frequency ranges.

UWB radio technology is designed for short‐range, high‐bandwidth communication, with the desirable properties of strong multipath resistance. Unlike narrowband wireless technologies such as Wi‐Fi, which beam signals within a defined frequency band (e.g. the 2.4 GHz or 5 GHz band), UWB scatters its transmissions over several gigahertz of the spectrum (from 3.1 to 10.6 GHz in the United States as restricted by the FCC; 6.0 to 8.5 GHz in Europe as restricted by the ECC) using short pulses (typically <1 ns). UWB waves typically occupy a much larger frequency bandwidth (>500 MHz) than narrowband operation. Due to its spectrum‐scattered approach to communication, UWB is theoretically less susceptible to interference. UWB short‐duration pulses are easy to filter, to determine which signals are correct and which are generated from multipath. UWB signals also pass easily through walls, equipment, and clothing, but metallic and liquid materials can still cause UWB signal interference. A major advantage of using UWB for distance measurements is that large bandwidth translates into a higher resolution in time and consequently in distance than other technologies.