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Since 2016, 3GPP has continued to carry out research on 3G and 4G indoor positioning technology enhancement in R13 and R14
versions, enhancing RAT (RadioTechnology) positioning methods, improving non-RAT indoor positioning methods, etc. Positioning
enhancements in the R14 standard include the following:
1. Observed Time Differenceof Arrival OTDOA (Observed Time Differenceof Arrival) is enhanced in shared Physical Cell Identifier
(PCI) scenarios. In R14, the terminal can distinguish between different transmission nodes in shared PCI scenarios, increasing the
number of measurement nodes that can be located on the terminal side, thus improving location accuracy.
2, the beacon R14 based on the positioning reference signal introduces a transmission node that only transmits the positioning
reference signal, which enables the terminal to identify additional positioning reference signals, thereby improving the positioning
accuracy.
3, positioning ReferenceSignal combined with CRS (Cell ReferenceSignal, cell reference signal) measurement terminal can combine
positioning reference signal and cell reference signal to obtain RSTD (ReferenceSignal Time Difference), This improves OTDOA
accuracy.
4. In Time of Arrival (TOA) R14 under multi-path, the terminal can report the TOA under multi-path to the network side, and the network
side can use this information to compensate the measurement error caused by multi-path fading, thus improving the positioning
accuracy. In June 2019, 3GPP's Rel.15 version TR38.885 described positioning as: for general users, the horizontal positioning
accuracy is not less than 50 meters in 80% of cases, the vertical accuracy is 5 meters, the end-to-end delay is less than 30 seconds,
and for commercial users, the horizontal positioning accuracy is not less than 3 meters indoors, not less than 10 meters outdoors,
and the vertical accuracy is not less than 3 meters. End-to-end delay is less than 1 second. Rel.16 plans to achieve a minimum
outdoor positioning accuracy of 3 meters for commercial users, with an end-to-end delay of less than 1 second. Originally expected
to be released by the end of March this year, but the epidemic disrupted the schedule, and it is estimated that the R16 version will
not be completed until the end of September. Version 17 is planned to achieve sub-meter positioning, end-to-end latency of less than
100 milliseconds, and is expected to be released by the end of 2021. The R16 version also supports the Japanese QZSS SSR
information, which is acceptable, but requires a special decoder.
PRS (positioning reference signal)
SRS (sounding reference signal)
LPP (LTE Positioning Protocol)
User based (UE) location measurement reports are included below
•Downlink reference signal referencepower (downlink reference signal level DL RSRP) per beam/gNB
•Downlink reference signal timedifference (DLRSTD)
•UE RX-TX time difference Time for receiving and transmitting data
gNB- based position measurement report
• Uplink angle-of-arrival (UL-AoA)
• Uplink reference-signal receive power (Uplink reference signal level value UL-RSRP)
• UL relative time of arrival (UL-rTOA)
• gNB RX-TX time difference
5G has five major advantages in positioning,
One is high carrier frequency
The second is high bandwidth
Third, the number of antennas is extremely large
The fourth is D2D direct communication
Fifth, the network density is very high
These five advantages eventually became UL-RTOA and UL-AoA. TDOA (TimeDifference of Arrival) and AOA (Angle of Arrival) are
two basic wireless positioning technologies. From the theoretical analysis, on the one hand, 5G uses high-frequency or millimeter
wave communication, and millimeter wave communication has very good directivity, which can achieve higher precision ranging and
Angle measurement; On the other hand, 5G uses large-scale antenna technology, has a higher resolution beam, and can also achieve
higher precision ranging and Angle measurement characteristics. Therefore, the positioning method based on AOA will have higher
accuracy than 4G. In addition, because 5G uses low-delay, high-precision synchronization and other technologies, it is also helpful to
improve TDOA positioning accuracy. The error source of TDOA is mainly clock error, and high-precision crystal vibration can be used
to reduce clock error, but this improvement is limited, and the cost is high to greatly increase. The error of AOA is a linear function of
the distance between the base station and the terminal, which is easy to compensate later and has low cost. So AOA is the main direction.
What 5G is best at is indoor positioning, because 5G penetration is relatively poor, and large-scale positioning is not 5G's strong point.
The location of the underground parking lot with autonomous valet parking is the most advantageous, and the physical location accuracy,
stability and robustness of the communication are 100 times stronger than the camera solution that relies entirely on the probabilistic
algorithm. The underground parking lot has low illumination and drastic changes in light, which is very unsuitable for camera-based
solutions. There is also the indoor positioning based on the logistics warehouse, the horizontal and vertical accuracy is required to be
5-10 cm, which is far from what the camera can do, and the UWB scheme is more expensive and has spectrum problems.
On February 29, 2020, Huawei held an online conference on 5G indoor coverage new products and solutions, and launched a 5G indoor
digital family series of new products and solutions, including upgraded 5G LampSite and 5G LightSite. And LampSiteEE (Enterprise
Edition), a 5G indoor coverage solution. The LampSite EE solution released by Huawei for industry scenarios includes five function sets:
5G indoor ultra-wideband, 5G indoor precision positioning, 5G industrial ultra-low latency, 5G indoor high reliability, and 5G industrial
high-density concurrent connection.
On March 19, 2020, Qualcomm published its own indoor positioning video. There are a total of five TRPS (transmit and receive points)
in the room, each using a directional antenna, 4X4MIMO array, 400MHz bandwidth, and a center frequency of 6.225GHz.
The horizontal positioning accuracy is basically maintained at about 10 cm, and the vertical positioning accuracy is slightly lower.
