WO2018082032A1

WO2018082032A1 - Method of rstd measurement gap for narrowband otdoa positioning

Info

Publication number: WO2018082032A1
Application number: PCT/CN2016/104678
Authority: WO
Inventors: Min Wu; Feifei SUN
Original assignee: MediaTek Singapore Pte Ltd
Current assignee: MediaTek Singapore Pte Ltd
Priority date: 2016-11-04
Filing date: 2016-11-04
Publication date: 2018-05-11
Anticipated expiration: 2019-05-04

Abstract

Methods for RSTD measurement gap of narrowband OTDOA are provided. Some disclosed embodiments describe a method for a UE to support narrowband OTDOA positioning further comprising: receiving a configuration of NRSTD measurement gap for a cell, wherein the cell is serving cell or intra-frequency neighboring cell; performing RSTD measurement on the cell during the measurement gap and no other signal transmission/reception. In one example, the measurement gap length is predefined. In another example, the measurement gap length is configurable. In one example, the measurement gap is periodic. In another example, the measurement gap is one-off. In one example, the measurement gap is triggered by UE. In another example, the measurement gap is triggered by eNB.

Description

METHOD OF RSTD MEASUREMENT GAP FOR NARROWBAND OTDOA POSITIONING

TECHNICAL FIELD

This disclosure relates generally to wireless communications and, more particularly, for RSTD (Reference Signal Time Difference) measurement gap for narrowband OTDOA (Observation Time Difference of Arrival) positioning.

BACKGROUND

In existing LTE OTDOA positioning system, UE can support simultaneous RSTD measurement and data reception when performing serving cell RSTD measurement or intra-frequency neighboring cell RSTD measurement. However, in narrowband (NB) OTDOA positioning system, an OTDOA-capable NB-IOT (Narrowband Internet of Things) UE may not be able to support parallel processing of RSTD measurement and data reception considering the low cost/complexity. A measurement gap similar to inter-frequency RSTD measurement gap should is needed for serving cell and intra-frequency neighboring cell RSTD measurement in narrowband OTDOA positioning system.

SUMMARY

Methods for a UE to support narrowband OTDOA positioning are provided.

In one novel aspect, the method is provided, wherein comprising: receiving a configuration of NRSTD (Narrowband RSTD) measurement gap for a cell, wherein the cell is serving cell or intra-frequency neighboring cell； performing NRSTD measurement on the cell during the measurement gap and no other signal transmission/reception.

Considering in-band NB-IOT scenario, there are following use cases which require a NRSTD measurement map. In one example, the PRB index used for NRSTD measurement on serving cell is different from the PRB index used for data transmission on serving cell. In one example, a NRSTD measurement is performed on multiple PRBs considering NPRS frequency hopping to improve measurement accuracy. In one example, the PRB index used for NRSTD measurement on neighboring cell is different from the PRB index used for data transmission on serving cell.

In one example, a NRSTD measurement gap includes one NPRS occasion, wherein some time is reserved for UE preparation before and after the NPRS occasion. In one example, a NRSTD measurement gap includes multiple repetitions of NPRS occasion within a NPRS period. In one example, NRSTD measurement gap length is a predefined value. In one example, NRSTD measurement gap length is configurable and depends on UE coverage level. In one example, NRSTD measurement gap follows periodic pattern with a short gap length, and the periodicity depends on NPRS periodicity. In one example, NRSTD measurement gap follows one-off pattern with a long gap length, wherein multiple NRSTD measurements on multiple cells are performed.

In one example, a UE-triggered NRSTD measurement gap is applied since eNB is not aware of NRSTD measurement requested by E-SMLC for a UE. In one example, an eNB-triggered NRSTD measurement gap is applied since eNB can be aware of NRSTD measurement requested by E-SMLC for a UE.

Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

Figure 1 illustrates a system diagram of a wireless network in accordance with embodiments of the current invention.

Figure 2 illustrates an example of configuring a NRSTD measurement gap for a UE in accordance with embodiments of the current invention.

Figure 3 illustrates a use case of NRSTD measurement gap on serving cell in accordance with embodiments of the current invention.

Figure 4 illustrates a use case of NRSTD measurement gap on serving cell in accordance with embodiments of the current invention.

Figure 5 illustrates a use case of NRSTD measurement gap on intra-frequency neighboring cell in accordance with embodiments of the current invention.

Figure 6 illustrates an example of a NRSTD measurement gap including one NPRS occasion in accordance with embodiments of the current invention.

Figure 7 illustrates an example of a NRSTD measurement gap including multiple repetitions of NPRS occasion in accordance with embodiments of the current invention.

Figure 8 illustrates an example of periodic pattern of NRSTD measurement gap in accordance with embodiments of the current invention.

Figure 9 illustrates a procedure of performing multiple NRSTD measurements on multiple cells in accordance with embodiments of the current invention.

Figure 10 illustrates an example of one-off pattern of NRSTD measurement gap in accordance with embodiments of the current invention.

Figure 11 illustrates a procedure of UE-triggered request for a NRSTD measurement gap in accordance with embodiments of the current invention.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Machine type communication is a form of data communication that involves one or more entities that do not necessarily need human interaction. A service optimized for machine type communication differs from a service optimized for human-to-human (H2H) communication. Typically, MTC services are different from the current mobile network communication services because MTC services involve different market scenarios, pure data communication, lower cost and effort, and a potentially very large number of communicating terminals with little traffic per terminal. Therefore, it is important to distinguish low cost (LC) MTC from regular UEs. UE with bandwidth reduction (BR-UE) can be implemented with lower cost by reducing the buffer size, clock rate for signal processing, and so on.

The embodiments are described associated with Massive MTC (MMC) and LTE carriers, but not limitation. In the embodiments of this invention, “MMC carrier” is one description for simplification, and for the person skilled in the art, the MMC carrier could be named as MTC carrier, MMC cell, MTC cell, etc. and the operating mode is one example, and could be called as the transmission mode, operation mode, which is not limitation to the embodiments of this invention. In LTE R 13, the BW for IoT terminal is mim 180kHz. One benefits is the cost is low. And another benefits is the above BW and system bandwidth is good for the spectrum for MTC. For example, if the GSM system is out of market in the future, the 180kHz BW is compatible of the current GSM system, so the 180kHz BW of MTC carrier could be deployed in the current GSM band more easily. One of such MTC carrier is a stand-alone MTC carrier, the mode transmitting or receiving data on the stand alone carrier is called as stand-alone operating mode. In another aspect, the actual transmission BW of 180kHz BW is the same as the actual transmission unit, resource block (RB) . If the above MTC carrier is deployed inside the LTE system, and coexists with the original common channel, signals of LTE system. A first system deployed in a second system, and the system BW of the first system smaller then the second system is called as in band operating mode.

Beside, the 180kHz BW of MTC carrier could be deployed on the guard band of the LTE system, for example, maintaining the LTE modulation scheme and numerology, the one or more resources block on the guard band of LTE system could be the 180khz band. In another embodiment, the 180kHz could adopt a new MCS, or new numerology different from LTE, the numerology is for example, the carrier spacing, by filtering, making the spectrum mask meets the requirement of protocol. Virtual Resource Block (VRB) is one wireless resource definition in LTE system, wherein comprises: localized and distributed way. For one VRB pair, the two time slots in one subframe is allocated one VRB number. On DL allocation or UL grant comprises multiple basic blocks, for example, a set of PRB. In one embodiment, the MTC carriers could be with the same or different transmission format with LTE system, for example, the UL or DL, there could be different carrier spacings, for example, the MTC carrier spacing is 3.75kHz.

One project of in band eMTC, one signal receiving antenna the min terminal RF BW is supported as 1.4MHz, and the max 15dbm coverage enhancement, 1Mpbs data rate are supported too. In eMTC system, UE has a RF BW of 1.4MHz, so the UE may detect the synchronization signal and MIB carried in the PBCH. In one way, the UE obtains the cell ID etc information to obtain the time-frequency resource, TBS, to decoding the SIB1. And the information to decoding other SIBs could be obtained from SIB1. Besides, the future 5G system could adopt multiple different transmission formats, and the different transmission formats could be designed for different requirements. For example, one transmission format could support ultra reliable requirement, and another transmission format supports high rate requirement, for example, wide band LTE system, mmWave (MMW) system. Yet another transmission format could support ultra low latency. The embodiments of this invention could be used in 5G communication system, or used to solve the problems of coexistence of 4G and 5G systems.

Figure 1 illustrates a system diagram of a wireless network with NB IoT in accordance with embodiments of the current invention. Wireless communication system 100 includes one or more fixed base infrastructure units, such as

base stations

101 and 102, forming a network distributed over a geographical region. The base unit may also be referred to as an access point, an access terminal, a base station, a Node-B, an eNode-B, or by other terminology used in the art. The one or

more base stations

101 and 102 serve a number of

UEs

103 and 104 within a serving area, for example, a cell, or within a cell sector.

Base stations

101 and 102 can support different RATs. The two base stations simultaneously serve the UE 103 within their common coverage.

Base stations

101 and 102 transmit downlink communication signals 112, 114 and 117 to UEs in the time and/or frequency domain.

UE

103 and 104 communicate with one or

more base stations

101 and 102 via uplink communication signals 111, 113 and 116.

In one novel aspect, the UEs are NB-IoT devices. They communicate with the base stations in NB by receiving DL transmission format information through signaling channels. The UEs further decode and connect with the base stations based on the received system information.

FIG. 1 further shows simplified block diagrams of base station 101 and UE 103 in accordance with the current invention. Base station 101 has an antenna 156, which transmits and receives radio signals. A RF transceiver module 153, coupled with the antenna, receives RF signals from antenna 156, converts them to baseband signals and sends them to processor 152. RF transceiver 153 also converts received baseband signals from processor 152, converts them to RF signals, and sends out to antenna 156. Processor 152 processes the received baseband signals and invokes different functional modules to perform features in eNB 101. Memory 151 stores program instructions and data 154 to control the operations of eNB 101. Base station 101 also includes a set of control modules circuit 155 that carry out functional tasks.

UE 103 has an antenna 136, which transmits and receives radio signals. A RF transceiver module 133, coupled with the antenna, receives RF signals from antenna 136, converts them to baseband signals and sends them to processor 132. RF transceiver 133 also converts received baseband signals from processor 132, converts them to RF signals, and sends out to antenna 136. Processor 132 processes the received baseband signals and invokes different functional modules to perform features in UE 103. Memory 131 stores program instructions and data 138 to control the operations of UE 103. UE 103 also includes a set of control modules circuit 135 that carry out functional tasks.

In one embodiment, the eNB can serve different kind of UEs.

UE

103 and 104 may belong to different categories, such as having different RF bandwidth or different subcarrier spacing. UE belonging to different categories is be designed for different use cases or scenarios. For example, some use case such as Machine Type Communication (MTC) may require very low throughput, delay torrent, the traffic packet size may be very small (e.g., 1000 bit per message) , extension coverage. Some other use case, e.g. intelligent transportation system, may be very strict with latency, e.g. orders of 1ms of end to end latency. Different UE categories can be introduced for these diverse requirements. Different frame structures or system parameters may also be used in order to achieve some special requirement. For example, different UEs may have different RF bandwidths, subcarrier spacing values, omitting some system functionalities (e.g., random access, CSI feedback) , or use physical channels /signals for the same functionality (e.g., different reference signals) .

In one embodiment, the wireless communication system 100 utilizes an OFDMA or a multi-carrier based architecture including Adaptive Modulation and Coding (AMC) on the downlink and next generation single-carrier (SC) based FDMA architecture for uplink transmissions. SC based FDMA architectures include Interleaved FDMA (IFDMA) , Localized FDMA (LFDMA) , and DFT-spread OFDM (DFT-SOFDM) with IFDMA or LFDMA. In OFDMA based systems, UEs are served by assigning downlink or uplink radio resources that typically comprises a set of sub-carriers over one or more OFDM symbols. Exemplary OFDMA-based protocols include the developing Long Term Evolution (LTE) of the 3GPP UMTS standard and the IEEE 802.16 standard. The architecture may also include the use of spreading techniques such as multi-carrier CDMA (MC-CDMA) , multi-carrier direct sequence CDMA (MC-DS-CDMA) , Orthogonal Frequency and Code Division Multiplexing (OFCDM) with one or two-dimensional spreading. In other embodiments, the architecture may be based on simpler time and/or frequency division multiplexing/multiple access techniques, or a combination of these various techniques. In alternate embodiments, the wireless communication system 100 may utilize other cellular communication system protocols including, but not limited to, TDMA or direct sequence CDMA.

For NB-IOT OTDOA system, NPRS subframe should avoid NPSS/NSSS, NPBCH, NPDCCH, NPDSCH subframe. And, considering backward-compatibility of Rel-13 NB-IOT UE, the NPRS subframe can only be allocated within invalid NB-IOT DL subframes. These constraints cause a small number of potential subframes to be configurable as NPRS subframe. Thus, consecutive NPRS subframe configuration within a NPRS occasion is very difficult, and there may be valid NB-IOT DL subframe (s) within a NPRS occasion. In this case, one problem is whether to need to monitor/receive NPDCCH/NPDSCH transmitted in the valid NB-IOT DL subframe (s) within a NPRS occasion when RSTD measurement is being performed. Considering buffer sharing and/or limitation of computation capability to achieve low cost/complexity, an OTDOA-capable NB-IOT UE may not be able to support simultaneous RSTD measurement and data reception.

For a UE with capability of simultaneous RSTD measurement and data reception, there is no any specification impact for serving cell RSTD measurement. However, for a UE without capability of simultaneous RSTD measurement and data reception, corresponding UE behavior should be specified to handle the issue. There are following methods.

The first method is up to UE implementation to drop either NPRS subframe or valid NB-IOT DL subframe. For example, if a NPDSCH transmission has been scheduled and overlaps a NPRS occasion, UE can drop NPRS subframe and wait for next NPRS occasion to perform RSTD measurement, as long as UE can ensure to finish RSTD measurement and report a RSTD value within a requested response time. One advantage is that there is no any specification impact and UE behavior has a complete flexibility. However, the disadvantage is that resource utilization may not be efficient considering the case that NPDCCH/NPDSCH within a NPRS occasion needs to be dropped when RSTD measurement is being performed.

The second method is to specify a priority to guide UE behavior. For example, RSTD measurement has a higher priority. When performing RSTD measurement, UE needn’ t to monitor NPDCCH and receive NPDSCH. Network should avoid schedule an OTDOA-capable Rel-14 NB-IOT UE during a NPRS occasion. On advantage is that there is no ambiguity on UE behavior and no any signaling overhead. However, the disadvantage is that the peak data rate of OTDOA-capable NB-IOT UE may be impacted. Since OTDOA positioning protocol exchanged between UE and location server is transparent to eNB, eNB cannot exactly know when UE will perform RSTD measurement. Therefore, all valid NB-IOT DL subframes within each NPRS occasion cannot be scheduled for an OTDOA-capable NB-IOT UE even though RSTD measurement is not being performed.

The third method is to introduce a measurement gap similar to the current existing inter-frequency RSTD measurement gap. Here, inter-frequency RSTD measurement means the center carrier frequency of measuring cell is different from serving cell, and carrier frequency needs to be switched for RSTD measurement. During the measurement gap, inter-frequency RSTD measurement is performing and there is no any signal transmission/reception. And, legacy mechanism/procedure of inter-frequency RSTD measurement gap can be directly reused, e.g. the UE requests a measurement gap when serving cell RSTD measurement will be performed. The requested measurement gap length is related to the UE coverage level. Similarly, UE sends a message to eNB to start/stop the measurement gap. One advantage is no ambiguity on UE behavior and the good resource utilization comparing with the previous two methods. there may be some signaling overhead for measurement gap request/configuration. However, the overall signaling overhead may be acceptable because RSTD measurement is not very frequent.

In the third method, whether to require a measurement gap for serving cell RSTD measurement depends on the capability of simultaneous RSTD measurement and data reception. If an OTDOA-capable NB-IOT UE doesn’t support simultaneous RSTD measurement and data reception, a measurement gap is required for serving cell RSTD measurement. If an OTDOA-capable NB-IOT UE supports simultaneous RSTD measurement and data reception, a measurement gap is not required for serving cell RSTD measurement. The capability on simultaneous RSTD measurement and data reception is optional and depends on the UE chipset design. And, the UE capability on simultaneous RSTD measurement and data reception can be reported to network via RRC signaling.

In the technology of OTDOA positioning, neighboring cell RSTD measurement is necessary since arrival time measurement needs to be performed on at least three different cells to derive the UE location. For intra-frequency neighboring cell RSTD measurement in in-band NB-IOT scenario, the carrier frequency of neighboring cell is same as serving cell at eNB side. However, the carrier frequency of neighboring cell may be different from serving cell at UE side. If PRB index used for neighboring cell RSTD measurement is different from the PRB index for serving cell, carrier switching is also required and data reception of serving cell cannot be continued. The case is similar to existing inter-frequency RSTD measurement. Similarly, a measurement gap similar to inter-frequency measurement gap is introduced for the case of intra-frequency neighboring cell RSTD measurement.

If PRB index used for neighboring cell RSTD measurement is same as the PRB index for serving cell, carrier switching is not required. However, there still is an issue on simultaneous RSTD measurement and data reception, which is discussed above for serving cell RSTD measurement. Similarly, for a UE without capability of simultaneous RSTD measurement and data reception, a measurement gap is introduced for the case of intra-frequency neighboring cell RSTD measurement.

As discussed above, a measurement gap similar to legacy inter-frequency RSTD measurement gap is required for both serving cell and intra-frequency neighboring cell RSTD measurement in narrowband OTDOA positioning system. To differentiate from the legacy inter-frequency RSTD measurement gap, the measurement gap is named as NRSTD (Narrowband Reference Signal Time Difference) measurement gap.

Figure 2 illustrates an example of configuring a NRSTD measurement gap for an OTDOA-capable NB-IOT UE, wherein comprising: receiving a configuration of NRSTD measurement gap for a cell by a UE, wherein the cell is serving cell or intra-frequency neighboring cell in step 210； and performing NRSTD measurement on the cell by the UE during the measurement gap and no any signal transmission/reception in step 220.

Use case for NRSTD measurement gap

Considering in-band NB-IOT scenario, one PRB within LTE system bandwidth is allocated for data service of NB-IOT UE. The PRB can be anchor PRB with the functionality of supporting initial access of NB-IOT UE, e.g. with NPSS/NSSS, NPBCH, NSIB subframe. Alternatively, the PRB can be non-anchor PRB without the functionality of supporting initial access of NB-IOT UE and just support data transmission. NPRS subframe (s) can be configured on anchor PRB or non-anchor PRB. Thus, there are following use cases for NRSTD measurement gap.

Figure 3 illustrates a use case of NRSTD measurement gap on serving cell in accordance with embodiments of the current invention. In this embodiment, the PRB index used for NRSTD measurement on serving cell is different from the PRB index for data transmission, i.e. NPDCCH/NPDSCH transmission. As illustrated in Figure 3, NPRS subframe is configured on PRB 301 for a UE. Meanwhile, NPDCCH/NPDSCH is scheduled on PRB 302 for the UE. In this case, a measurement gap is required for the UE to perform NRSTD measurement on PRB 301. In one example, PRB 301 is anchor PRB and PRB 302 is non-anchor PRB. In another example, both

PRB

301 and 302 are non-anchor PRB. In yet another example, PRB 301 is non-anchor PRB, and PRB 302 is anchor PRB.

Figure 4 illustrates a use case of NRSTD measurement gap on serving cell in accordance with embodiments of the current invention. In this embodiment, NPRS subframe is configured on multiple PRBs for frequency hopping to improve NRSTD measurement accuracy. As illustrated in Figure 4, NPRS subframe is configured on

PRB

401 and 402 for a UE. Meanwhile, NPDCCH/NPDSCH is scheduled on PRB 402 for the UE. In this case, a measurement gap is required for the UE to perform NRSTD measurement on

PRB

401 and 402. In one example, PRB 401 is anchor PRB and PRB 402 is non-anchor PRB. In another example, both

PRB

401 and 402 is non-anchor PRB. In yet another example, PRB 401 is non-anchor PRB, and PRB 402 is anchor PRB.

In one case, the PRB index used for NRSTD measurement on serving cell is exactly same as the PRB index used for data transmission, and the PRB may be anchor PRB or non-anchor PRB. In this case, carrier frequency switching is not required at UE side when performing serving cell NRSTD measurement. However, for a UE without capability of simultaneous NRSTD measurement and data reception to achieve low cost/complexity, a measurement gap is also required for the UE to perform NRSTD measurement.

Figure 5 illustrates a use case of NRSTD measurement gap on intra-frequency neighboring cell in accordance with embodiments of the current invention. In this embodiment, the PRB index used for RSTD measurement on intra-frequency neighboring cell is different from the PRB index for data transmission on serving cell. As illustrated in Figure 5, NPRS subframe is configured on PRB 501 of neighboring cell for a UE. Meanwhile, NPDCCH/NPDSCH is scheduled on PRB 502 of serving cell for the UE. And, the center carrier frequency of neighboring cell is the same as that of serving cell at eNB side. In this case, a measurement gap is required for the UE to perform NRSTD measurement on PRB 501 of neighboring cell. In one example, PRB 501 is anchor PRB and PRB 502 is non-anchor PRB. In another example, both

PRB

501 and 502 is non-anchor PRB. In yet another example, PRB 501 is non-anchor PRB, and PRB 502 is anchor PRB.

In one case, the PRB index used for NRSTD measurement on intra-frequency neighboring cell is same as the PRB index for data transmission on serving cell. In this case, carrier frequency switching is not required at UE side when performing neighboring cell NRSTD measurement. However, for a UE without capability of simultaneous NRSTD measurement and data reception to achieve low cost/complexity, a measurement gap is also required for the UE to perform intra-frequency NRSTD measurement on neighboring cell.

NRSTD measurement gap pattern

As discussed above, in general, introducing NRSTD measurement gap is used for two cases. The first case is that carrier frequency switching is required when performing NRSTD measurement. In the case, switching time should be included in NRSTD measurement gap, e.g. 1ms switching time is required for NB-IOT UE. The second case is that UE cannot support simultaneous NRSTD measurement and data reception due to some limitation on buffer size and/or computation ability for low cost/complexity. In this case, processing time of data reception and/or processing time of NRSTD measurement should be included in NRSTD measurement gap. For example, when receiver processing is switched to NRSTD measurement from data reception, processing time of data reception should be reserved in the front of NRSTD measurement gap. When the receiver processing is switched to data reception from NRSTD measurement, processing time of NRSTD measurement should be reserved in the end of NRSTD measurement gap. In addition, possible timing offset of NPRS subframe on different cells is included in NRSTD measurement gap when performing neighboring cell NRSTD measurement. And, 1ms is sufficient for the purpose of timing offset.

Figure 6 illustrates an example of NRSTD measurement gap including one NPRS occasion. In the figure, the length of NRSTD measurement gap 601 is larger than the length of NPRS occasion 602, and there are at least one reserved time for UE preparation at the two side of NRSTD measurement gap,

e.g. time gap

603 and 604 before the starting subframe of NPRS occasion and after the ending subframe of NPRS occasion. The reserved time should include one or multiple of following factors: carrier frequency switching time, possible timing offset, processing time of NRSTD measurement, and processing time of data reception. In one example, the reserved time is at least 2ms. In another example, the reserved time is at least 10ms.

In one embodiment, NRSTD measurement gap length is a predefined value, e.g. 10ms, 20ms, or 40ms. In another embodiment, NRSTD measurement gap length is configurable and selected from a predefined set.

Figure 7 illustrates an example of a NRSTD measurement gap including multiple repetitions of NPRS occasion in accordance with embodiments of the current invention. In narrowband OTDOA positioning system, NPRS occasion is repeated within a NPRS period to support some UE in worse coverage level. And, the repetition number of NPRS occasion within a NPRS period should be configurable and depends on the maximum coverage level supported by the cell. For a UE in coverage extension (CE) , a configured NRSTD measurement gap should include multiple repetitions of NPRS occasion within a NPRS period, as illustrated in Figure 7.

In one example, there are three level of NRSTD measurement gap length. The first level of NRSTD measurement gap length is for normal coverage (NC) , wherein the NRSTD measurement gap includes one NPRS occasion. The second level of NRSTD measurement gap is for extended coverage (CE) , wherein the NRSTD measurement includes a middle level of repetitions of NPRS occasion. The third level of NRSTD measurement gap is for extreme coverage, wherein the NRSTD measurement includes a large level of repetitions of NPRS occasion. For a UE in good coverage, a short NRSTD measurement gap length can be configured. For a UE in worse coverage, a long measurement gap length can be configured.

In one example, the length of NRSTD measurement gap is determined by UE according to its coverage level. In another example, the length of NRSTD measurement gap is determined by eNB according to UE coverage level assuming the UE coverage level is known by eNB.

Figure 8 illustrates an example of a periodic pattern of NRSTD measurement gap. In one embodiment, NRSTD measurement gap occurs per period. In one example, the period of NRSTD measurement gap is predefined. In another example, the period of NRSTD measurement gap is configurable and selected from a predefined set. And, the period of NRSTD measurement gap is related to NPRS period configured for NRSTD measurement, e.g. 160ms, 320ms, 640ms, or 1280ms.

Figure 9 illustrates a procedure of performing multiple NRSTD measurements on multiple cells in accordance with embodiments of the current invention. In figure 9, UE sends a message to eNb to request a first NRSTD measurement gap for the first cell in step 910. In step 920, UE performs the first NRSTD measurement on the first cell. In step 930, UE sends a message to eNB to step the first NRSTD measurement gap when the measurement task is finished. In step 940, UE sends a message to eNb to request a second NRSTD measurement gap for a second cell. In step 950, UE performs the second NRSTD measurement on the second cell. In step 960, UE sends a message to eNB to stop the second NRSTD measurement gap when the measurement task of the second cell is finished. In this embodiment, a message to stop NRSTD measurement gap should be sent by UE to eNB if NRSTD measurement task is finished, i.e. the step 930 and step 960.

Generally, a NRSTD measurement gap corresponds to one special offset of NPRS subframe, i.e., the occurrence time of NRSTD measurement gap should be matched to time resources location of the NPRS subframe used for NRSTD measurement. In order to derive UE location, multiple NRSTD measurements on different cells are necessary. If NPRS subframe on the multiple cells are not aligned, i.e., the location of NPRS subframe is different, the multiple NRSTD measurements require multiple NRSTD measurement gap. If NPRS subframe on the multiple cells are aligned, i.e. the location of NPRS subframe is the same, the multiple NRSTD measurements can share one NRSTD measurement gap. Thus, only one NRSTD measurement gap is requested when performing the multiple NRSTD measurements.

In the embodiment of figure 9, the location of NPRS subframe is not aligned for the two cells. In one example, the center carrier frequency of the two cells is the same, i.e. intra-frequency. However, the PRB index for NRSTD measurement is different for the two cells. In one example, the center carrier frequency of the two cells is different, i.e. inter-frequency.

Figure 10 illustrates an example of a one-off pattern of NRSTD measurement gap with an ultra-long gap length. In the example, multiple NRSTD measurements on multiple cells are performed during the long NRSTD measurement gap 1001. For the one-off NRSTD measurement gap, UE needn’ t send a message to eNB to stop measurement gap, i.e. in

step

930 and 960 of figure 9. However, the multiple NRSTD measurement tasks should be ensured to be finished during the ultra-long measurement gap.

Procedure of configuring NRSTD measurement gap

Figure 11 illustrates a procedure of configuring a NRSTD measurement gap for a UE, comprising: sending a message to eNB by the UE to start a NRSTD measurement gap for a cell in step 1110, wherein the cell is serving cell or intra-frequency neighboring cell； receiving RRCConnectionReconfiguration on the requested NRSTD measurement gap by the UE in step 1120； performing NRSTD measurement on the cell during the measurement gap and no any signal transmission/reception in step 1130； sending a message to eNB to stop the NRSTD measurement gap if the measurement task is finished in step 1140.

In one embodiment, eNB is not aware of an OTDOA measurement request, since the measurement request via LPP (LTE Positioning Protocol) is transparent to eNB. In order to configure a NRSTD measurement gap for a given UE when performing NRSTD measurement, eNB has to be aware of whether an OTDOA positioning measurement is requested by E-SMLC (Evolved Serving Mobile Location Center) for this UE. A UE-triggered measurement gap request message is sent by UE to eNB. If LPP layer indicates to start performing NRSTD measurement, and the UE requires a measurement gap for the NRSTD measurement while measurement gap is either not configured or not sufficient, a message to request NRSTD measurement gap should be sent by the UE to eNB. If the measurement task is finished, a message to stop NRSTD measurement gap should be send by the UE to eNB.

In another embodiment, eNB is aware of an OTDOA measurement request, e.g. some signaling is exchanged between eNB and E-SMLC. In order to configure a NRSTD measurement gap for a given UE when performing NRSTD measurement, E-SMLC needs to send a message to eNB to make eNB be aware of an OTDOA measurement requested by E-SMLC for this UE. An eNB-triggered measurement gap configuring message is sent by eNB to the UE.

Claims

A method for a UE to support narrowband OTDOA positioning, the method comprising:

receiving a configuration of NRSTD measurement gap for a cell, wherein the cell is serving cell or intra-frequency neighboring cell； and

performing NRSTD measurement on the cell during the measurement gap and no other signal transmission/reception.
The method of claim 1, wherein the UE doesn’ t support simultaneous NRSTD measurement and data reception, and the capability is reported to network.
The method of claim 1, wherein the PRB index used for serving cell NRSTD measurement is different from the PRB index used for data transmission in in-band NB-IOT scenario.
The method of claim 1, wherein the PRB index used for neighboring cell NRSTD measurement is different from the PRB index used for data transmission in in-band NB-IOT scenario.
The method of claim 1, wherein the length of measurement gap is predefined or the length of measurement gap is configurable.
The method of claim 5, wherein the length of measurement gap is related to coverage level of the UE.
The method of claim 1, wherein the NRSTD measurement gap occurs every period.
The method of claim 7, wherein the value of period for NRSTD measurement gap is configurable, and the value of period for NRSTD measurement gap is related to NPRS periodicity of the cell.
The method of claim 1, wherein the RSTD measurement gap is one-off.
The method of claim 9, wherein multiple cells RSTD measurements are performed during the one-off measurement gap.
The method of claim 1, wherein the NRSTD measurement gap is triggered by UE or the eNB.