GB/T 44068-2024Technical requirements for LTE mobile terminals supporting BDS positioning (English PDF)

5 Terminal positioning architecture

5.1 In the E-UTRAN control plane positioning architecture the user equipment receives the satellite positioning assistance information and, on the basis of it, solves the measured values of the satellite positioning signals to obtain the positioning result; the base station sends the assistance information to the terminal; the enhanced serving mobile location centre obtains the assistance information and can provide assistance data for the corresponding area according to the position of the base station, sending it to the terminal for use; and the mobility management entity triggers the positioning service and sends the positioning service request to the location centre, which triggers the related positioning process and completes the positioning of the user equipment.

5.2 In the E-UTRAN user plane positioning architecture the SUPL platform is the network-side server, whose function is to exchange information related to user plane positioning with the user equipment using the SUPL protocol.

6 Terminal positioning procedures

6.1.1 The two sides of an LPP session are called the target and the server; on the control plane they are the user equipment and the enhanced serving mobile location centre, and on the user plane the user equipment and the SUPL platform. The terminal positioning procedure of the LTE system is embodied in one or more LPP sessions, which comprise the transfer of positioning capabilities, the transfer of assistance data, the transfer of location information, error handling and session termination. The transfer of positioning capabilities is one-way and supports only the transfer of the capabilities of the target to the server, those capabilities being the ability to support different positioning methods, the ability to support different aspects of a particular method such as different types of satellite positioning assistance data, and certain capabilities common to several methods such as the ability to manage concurrent LPP sessions. The transfer of assistance data is one-way from server to target and is possible only over a unicast channel, the server being able to send further LPP messages with other assistance data besides the data matching the request of the target. The transfer of location information is one-way from target to server, the location information comprising the location estimate and the parameters used to calculate the location such as radio measurements and position measurements, and the target likewise being able to send further messages. Error handling is the notification by one side that the LPP message it has received is in error or does not match the request it sent, and may occur in both directions. Session termination is the notification by one side that it is going to terminate the LPP session in progress, and may also occur in both directions.

6.1.2 An LPP session occurs in the following conditions. For the transfer of capabilities, assistance data and location information, the session may begin with a request by one side, that side sending an LPP message requesting information and the other replying with an LPP message providing it; for assistance data and location information the replying side may provide additional information beyond the request, that information having to be of the same type as the information requested. A session may also occur without a request, one side sending a message providing information directly. To make sessions more flexible and effective, several LPP sessions may run concurrently between target and server, a new session being started before an earlier one has ended, but for one and the same positioning method only one session at a time is to be used to obtain location information.

6.1.3 The concurrent LPP session flow has four steps: the server sends the target a request for a location measurement; the target sends the server a request for particular assistance data; the server sends the target the assistance data requested; and the target calculates the location information on the basis of that assistance data and sends it to the server in response to the first step. The order of LPP sessions need not be fixed; the user equipment may request assistance data from the location centre at any time so as to calculate the location information the centre has asked for; where the location information the user equipment returns does not meet the quality of service the centre requires, the centre may issue several requests for location information such as position-related measurements and a position estimate; and where the capability information the centre has requested has not been reported in full, the user equipment may report it at any time. Although the order may vary, the preferred order is the transfer of positioning capabilities, then of assistance data, then of location information.

6.2 The positioning and data acquisition procedures between the location centre and the base station may be embodied in one or more LPPa sessions, of which there are two types, the user equipment associated session, in which information for a particular terminal such as its positioning measurements is transferred, and the non-associated session, in which information about the base station such as its timing offset is transferred. An LPPa session is to be started only by a request from the location centre and is not to occur without such a request; in a session the centre sends the base station an LPPa request message and the base station sends back an LPPa response message. Where the session is associated with a terminal the base station may send one or more response messages; where it is not, the base station is to send only one. As with LPP sessions, several LPPa sessions may run concurrently. The flow of a session for the transfer of location information has three steps: the location centre sends an LPPa message requesting location information, stating the type of information and the corresponding quality of service, the request being able to concern a particular terminal; the base station sends an LPPa message providing location information in response, which is to match the request; and where the positioning method is the enhanced cell identity, the base station may send one or more further response messages carrying other location-related information. A note states that location information here comprises the location estimate and the parameters used to calculate the location, such as radio or positioning measurements.

6.3 The service layer support procedures combining LPP and LPPa cover the terminal positioning procedure for the network induced or mobile terminating location request and that for the mobile originating location request. For the first, the related services are led by the evolved packet core and the positioning procedure on that side is to conform to 3GPP TS 23.271 V16.0.0 (2020-07); the scenario described applies only to terminals in the connected state, an idle terminal being brought into the connected state by paging. The flow has four steps: the mobility management entity sends the location centre a location request for the target terminal, possibly carrying the corresponding quality of service; the centre may obtain location-related information from the terminal, from the base station or from both, starting one or more LPP sessions with the terminal to transfer its positioning capabilities, to provide it with assistance information or to obtain its location information, the terminal itself being able to start one or more sessions after receiving the first LPP message, for instance to request assistance data; where the centre obtains location-related information from the base station it may start one or more LPPa sessions, which may take place before or at the same time as the LPP sessions; and the centre obtains the location estimate from the results and sends it to the mobility management entity in response to the first step. For the mobile originating location request the services are led by the terminal and the flow has seven steps, beginning with a non-access stratum request from the terminal to the mobility management entity which may carry an LPP protocol data unit, and ending with the forwarding of the location estimate to a third party where the request so requires and with the response sent back to the terminal.

6.4 The general SLMAP procedures are the measurement request, the measurement update and the measurement termination. In the measurement request the location centre obtains a timing measurement for a particular target terminal from the location measurement unit: the centre sends the unit a measurement request stating the target terminal and the data used for the measurement, such as the sounding reference signal configuration of that terminal, and the unit sends the centre the uplink relative time of arrival measurement result. In the measurement update the centre informs the unit, during a measurement request procedure, of an update to the sounding reference signal configuration of the target terminal: where the configuration the centre sent is no longer valid the centre is to send a measurement update, and where it has already received the measurement response the update is not to be sent, the unit then continuing the measurement with the updated configuration. In the measurement termination the centre terminates a measurement request procedure in progress, for instance because the terminal has left the network or has been handed over between mobility management entities; the measurement report in progress is discarded, and where the centre has already received the measurement response the termination is not to be sent. The abbreviation SLMAP is glossed in clause 4 with an expansion that describes an authentication protocol, which does not match the use made of it in this clause as the protocol between the location centre and the location measurement unit.

6.5 The service layer support procedures combining SLMAP and LPPa again cover the network induced and mobile terminating case and the mobile originating case. In the first the flow starts when the mobility management entity sends the location centre a location request for the target terminal, possibly with the quality of service; the centre obtains the configuration information of the target terminal from the base station; where it needs measurement results from several location measurement units it is to start an SLMAP session with each of them; and it obtains the location estimate from the results and sends it back in response. In the second the flow starts from a request for the mobile originating location service by the location services client on the terminal side or by the terminal itself, its purpose being to obtain the location information of the terminal again or to send it to a third party; the terminal sends a non-access stratum request to the mobility management entity, which sends a location request to the centre, and the remaining steps follow the same pattern, ending with the forwarding of the estimate to a third party where required and the non-access stratum response carrying the location estimate to the terminal.

6.6 The global navigation satellite system is the collective name for all satellite navigation systems providing autonomous geospatial positioning with global or regional coverage, and includes BeiDou, GPS, the Galileo satellite navigation system, GLONASS, satellite based augmentation systems and the quasi-zenith satellite system. Each system may be used alone or together with others, and when different systems work together the positioning accuracy is improved. Satellite positioning uses satellites distributed in space and the intersection of the distances between the satellites and the ground point to obtain the position of that point; for effective positioning the receiver of the terminal has to receive the signals of more than four satellites. In autonomous satellite positioning the satellite navigation module of the LTE terminal does not depend on any exchange with the LTE network and can receive the satellite signals and position by itself.

6.7 Assisted satellite navigation improves positioning performance by providing the satellite navigation receiving module of the terminal with assistance information over the mobile communication network: it reduces the start-up and acquisition time of the receiver so that positioning is speeded up markedly; it increases the sensitivity of the receiver, positioning information that cannot be obtained by demodulating the satellite signal at a low signal to noise ratio being obtained from the network instead; and it lowers the power consumption of the receiving module compared with independent positioning, because the assisted module can start quickly from the idle state. The assisted terminal and the reference receiving network that provides the assistance are to be served by the same satellite. Two assisted modes are supported: the terminal assisted mode, in which the terminal makes the measurements and sends the results to the location centre for the positioning calculation and may also report measurements from sources other than the satellite system, and the terminal based mode, in which the terminal makes the measurements and calculates its own position and may likewise use other sources. Where the terminal is able to measure independently it may also position autonomously, calculating its own position from the satellite signals without assistance from the network. In the terminal assisted and terminal based modes the measurement information the terminal reports includes latitude, longitude and altitude with their uncertainties and the velocity with its uncertainty, and the terminal is also to report the satellite system types it supports and the corresponding positioning methods; in the terminal assisted mode it reports code phase, Doppler and carrier phase together with a quality estimate of each measurement. In both modes the terminal may also report the relation between satellite system time and the current air interface time of the LTE network, which the location centre uses to assist other terminals. The assistance data the centre sends the terminal comprises the reference time, the reference position, the ionospheric model, the earth orientation parameters, the time offsets between satellite systems, differential corrections, ephemeris and clock models, real-time integrity, data bit assistance, acquisition assistance, the almanac and the coordinated universal time model; part of it assists the measurement, such as the reference time, the list of visible satellites, the satellite signal Doppler and the search windows for code phase and Doppler, and part assists the calculation, such as the reference time, the reference position and the ephemeris and clock corrections. The assisted positioning procedures are the transfer of assistance data and the transfer of location information, either of which may follow a request or occur without one. In the terminal initiated assistance data transfer the terminal decides what assistance data it needs and requests it by an LPP message, and the location centre provides it in one or more LPP messages; where the data requested is not provided the terminal is to assume that it is not supported or not available at the centre, and the centre may send an LPP message stating the reason and possibly carrying other data it can provide. In the location centre initiated location information transfer the centre sends an LPP message requesting location information for satellite positioning, which may contain the positioning mode, that is terminal assisted, terminal based, terminal based preferred but terminal assisted allowed, terminal assisted preferred but terminal based allowed, or terminal autonomous, the positioning method and the measurement types required of the terminal such as fine time assistance measurements, velocity measurements, carrier phase measurements, multi-band measurements and the quality of service parameters; the terminal then makes the measurements and provides the information before the response time expires, or, where it cannot, sends a message stating why and possibly carrying the information it has obtained.

7 Functional requirements

Clause 7 states that LTE phase three mobile terminals supporting satellite positioning should support the following functions, and that LTE phase four and later smart phone terminals supporting satellite positioning are to support them: autonomous BDS positioning, where only BeiDou satellite signals are visible; autonomous GPS positioning, where only GPS signals are visible; autonomous dual-mode BDS and GPS positioning; network assisted BDS positioning, where only BeiDou signals are visible; network assisted GPS positioning, where only GPS signals are visible; and network assisted dual-mode BDS and GPS positioning.

8 Performance requirements

8.1.1 For autonomous satellite positioning the two-dimensional position error is defined as the difference in the horizontal plane, in metres, between the position obtained by the positioning calculation of the terminal and the actual position of the terminal in the test. For every global satellite constellation a minimum performance requirement is defined, and a terminal supporting several global constellations is to meet the minimum requirements of all the combined scenarios of the constellations it supports. Where a terminal supports several signals the minimum requirements may be tied to the different signals; the satellite simulator is to simulate all the signals the terminal supports, and signals it does not support need not be simulated. Table 1 gives the signal power of each signal type relative to the reference power: for Galileo, 0 dB on E1 and plus 2 dB on E5 and on E6; for GPS, 0 dB on L1C; for GLONASS, 0 dB on G1 and minus 6 dB on G2; and for BeiDou, 0 dB on B1I D1 and plus 5 dB on B1I D2. Note 1 states that the signal power in the test parameter tables is the total signal power of the satellite per channel and not the separate powers of the pilot and data channels. Note 2 states that for autonomous positioning this document lays down performance requirements only for BeiDou alone, GPS alone and the BeiDou and GPS dual mode, and not for Galileo alone, GLONASS alone or other dual-mode and multi-mode positioning. Footnote a states that the GPS constellation covered is GPS L1 C/A and does not include modernised GPS, and footnote b that in the BeiDou system D1 stands for the B1I signal type of the medium earth orbit and inclined geosynchronous orbit satellites and D2 for the B1I signal type of the geostationary satellites.

8.1.2 For network assisted positioning, the measurement parameters of terminal based assisted positioning are contained in the location information element carried in the provide location information LPP message and consist of the horizontal position estimate reported by the terminal, expressed as latitude and longitude; those of terminal assisted positioning are contained in the signal measurement information element of the same message, the code phase measurements conforming to 3GPP TS 36.302 V16.1.0 (2020-07) and 3GPP TS 36.214 V16.2.0 (2021-03) and the procedures to annex F of 3GPP TS 36.171 V16.2.0 (2021-06). The maximum response time is defined as running from the moment the terminal has received a request location information LPP message to the moment it begins to send a provide location information LPP message on the Uu interface. Unless otherwise stated, the response time specified for all tests is the time to first fix, that is the terminal is not to reuse any information about satellite time, position or other assistance data obtained, calculated or stored earlier; the dedicated test message that resets the stored positioning information of the terminal is to conform to 6.9 of 3GPP TS 36.509 V16.1.0 (2021-06) and, in detail, to B.1.10 of annex B of 3GPP TS 36.171 V16.2.0 (2021-06). Two kinds of time assistance are available: coarse time assistance, always provided by the network, which gives the terminal the current satellite system time within 2 s of the true system time by means of the day number and time of day fields of the system time information element; and fine time assistance, provided optionally, which gives the terminal the relation between satellite system time and the current E-UTRAN time to within 10 microseconds of the actual accuracy, by means of the system time information element and the reference time for cells information element. The satellite system time is defined by the time identifier field of the system time information element, and where several satellite systems are used in a test only one such identifier is used to determine the time of day; for all constellations the time model information element is to be available in the system simulator in accordance with annex E of 3GPP TS 36.171 V16.2.0 (2021-06). Even where the network signals fine time assistance, its use is optional for the terminal although it can improve performance, so a minimum performance requirement set is laid down for all terminals and the additional minimum requirements for the fine time assistance case apply only to terminals supporting that capability. The minimum assisted positioning requirements of 8.5, 8.6 and 8.7 apply to terminals in the RRC connected state, the test and verification procedure conforming to annex B of 3GPP TS 36.171 V16.2.0 (2021-06). For assisted positioning the two-dimensional position error is defined as the difference in the horizontal plane, in metres, between the ellipsoid point reported or calculated through the provide location information LPP message and the actual position of the terminal in the test. The rules on terminals supporting several constellations and several signals repeat those of 8.1.1, table 2 repeating the relative signal powers of table 1 with the same notes, except that here signals the terminal does not support are not to be simulated; the reference signal power defined for each test scenario of 8.5, 8.6 and 8.7 is the reference power of each satellite, and the simulated power of each satellite signal is to be set to that reference power plus the relative power of table 2.

8.2 to 8.4 Autonomous positioning is verified by a nominal accuracy test in which the receiver of the terminal has no valid almanac, ephemeris, time or approximate own position, under static ideal signal conditions, so that the performance of the cold start position estimate is verified. For autonomous BDS positioning the simulator generates six satellites with an additive white Gaussian noise channel model; the test parameters of table 3 are six BeiDou satellites, a horizontal dilution of precision from 1.4 to 2.1, the noise channel and a reference signal power of minus 128.5 dBm, and the minimum requirement of table 4 is a success rate of 95 %, a two-dimensional position error of 15 m and a maximum cold start time to first fix of 120 s. For autonomous GPS positioning the simulator generates eight satellites; the test parameters of table 5 are eight GPS satellites, a horizontal dilution of precision from 1.1 to 1.6, the noise channel and a reference signal power of minus 130 dBm, and the minimum requirement of table 6 is a success rate of 95 %, a two-dimensional position error of 30 m and a maximum cold start time to first fix of 120 s. For autonomous dual-mode positioning the simulator generates six satellites; the test parameters of table 7 are six satellites in all, three BeiDou and three GPS, a horizontal dilution of precision from 1.4 to 2.1, the noise channel and a reference signal power of minus 128.5 dBm for both BeiDou and GPS, and the minimum requirement is the same as for autonomous BDS positioning.

8.5 Network assisted BDS positioning. The minimum requirements assume that the terminal has received all the relevant and available assistance data needed to make the measurements or to calculate the position, conform to annexes D and E of 3GPP TS 36.171 V16.2.0 (2021-06) and do not include the delays simulated by the various network interface signalling. The sensitivity test verifies the performance of the receiver under weak satellite signal conditions and is run on the noise channel so that the harshest signal level is tested, both for the case in which only coarse time assistance is provided and for the case in which fine time assistance is added. With coarse time assistance the simulator generates six satellites; the test parameters of table 8 are six BeiDou satellites in all, one with a high power signal and five with a low power signal, a horizontal dilution of precision from 1.4 to 2.1, the noise channel, a coarse time assistance error range of plus or minus 2 s, a reference high signal power of minus 136 dBm and a reference low signal power of minus 145 dBm; the minimum requirement of table 9 is a success rate of 95 %, a two-dimensional position error of 100 m and a maximum response time of 20 s. With fine time assistance, which applies to terminals supporting that capability, the test parameters of table 10 are six BeiDou satellites, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, a fine time assistance error range of plus or minus 10 microseconds and a reference signal power of minus 147 dBm; the minimum requirement of table 11 is the same as that of table 9. The nominal accuracy test verifies the accuracy of the position estimate under ideal conditions and the performance of the first fix; the test parameters of table 12 are six BeiDou satellites, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s and a reference signal power of minus 133 dBm, and the minimum requirement of table 13 is a success rate of 95 %, a two-dimensional position error of 15 m and a maximum response time of 20 s. The dynamic range test makes sure that the receiver works well when the powers of the visible satellite signals differ widely and is run on the noise channel so that the requirement is not relaxed by the extra margin a fading channel would give; the test parameters of table 14 are six BeiDou satellites in all, two with a high power signal and four with a low power signal, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, a reference high signal power of minus 133.5 dBm and a reference low signal power of minus 145 dBm, and the minimum requirement of table 15 is a success rate of 95 %, a two-dimensional position error of 100 m and a maximum response time of 20 s. The multipath test verifies the tolerance of the receiver to multipath while keeping the test set-up simple; the simulator generates six satellites, some with a single path channel representing the line of sight signal and others with a two path channel whose first path is the line of sight signal and whose second path is a reflected and attenuated signal in accordance with C.2 of annex C of 3GPP TS 36.171 V16.2.0 (2021-06). The test parameters of table 16 are six BeiDou satellites in all, two with a single path channel and four with a two path channel, the same dilution of precision, the noise channel, a coarse time assistance error range of plus or minus 2 s and a reference signal power of minus 133 dBm, and the minimum requirement of table 17 is a success rate of 95 %, a two-dimensional position error of 100 m and a maximum response time of 20 s. The moving scenario and periodic update test verifies the ability of the terminal to measure or to position while it is on a vehicle travelling normally at constant speed and then decelerating, turning or accelerating, the terminal moving on a rectangular track imitating city streets on the noise channel; no time to first fix test is run. The test parameters of table 18 are six BeiDou satellites, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s and a reference signal power of minus 133 dBm, the terminal reporting its position periodically at an interval of 2 s, and the minimum requirement of table 19, applying after the first position estimate has been reported, is a success rate of 95 % and a two-dimensional position error of 50 m at a periodic reporting interval of 2 s. The clause states that the track parameters and the track diagram of the terminal are the same as for autonomous BDS positioning, although clause 8.2 contains no moving scenario.

8.6 Network assisted GPS positioning follows the same structure. For the sensitivity test with coarse time assistance the simulator generates eight satellites and the test parameters of table 20 are eight GPS satellites, a horizontal dilution of precision from 1.1 to 1.6, the noise channel, a coarse time assistance error range of plus or minus 2 s, a reference high signal power of minus 142 dBm and a reference low signal power of minus 147 dBm, the minimum requirement of table 21 being a success rate of 95 %, a two-dimensional position error of 100 m and a maximum response time of 20 s. With fine time assistance the parameters of table 22 are eight GPS satellites, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, a fine time assistance error range of plus or minus 10 microseconds and a reference signal power of minus 147 dBm, and the minimum requirement of table 23 is the same. For nominal accuracy the parameters of table 24 are eight GPS satellites, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s and a reference signal power of minus 130 dBm, the minimum requirement of table 25 being a success rate of 95 %, a two-dimensional position error of 30 m and a maximum response time of 20 s. For dynamic range, where strong satellite signals may affect the acquisition of weak ones because of cross-correlation products, the simulator generates six satellites and the parameters of table 26 are six GPS satellites, a horizontal dilution of precision from 1.4 to 2.1, the noise channel, a coarse time assistance error range of plus or minus 2 s and satellite signal powers of minus 129 dBm for satellite one, minus 135 dBm for satellite two, minus 141 dBm for satellite three and minus 147 dBm for satellites four, five and six, the minimum requirement of table 27 being a success rate of 95 %, a two-dimensional position error of 100 m and a maximum response time of 20 s. For the multipath test the simulator generates five satellites, two of which have a single path channel representing the line of sight signal and three a two path channel, and the parameters of table 28 are five GPS satellites, satellites one and two not affected by multipath and satellites three, four and five affected, a coarse time assistance error range of plus or minus 2 s, a horizontal dilution of precision from 1.8 to 2.5, a reference signal power of minus 130 dBm for satellites one and two and, for satellites three, four and five, minus 130 dBm for the line of sight signal and minus 136 dBm for the multipath signal; the minimum requirement of table 29 is a success rate of 95 %, a two-dimensional position error of 100 m and a maximum response time of 20 s. For the moving scenario and periodic update the simulator generates five satellites and the parameters of table 30 are five GPS satellites, a horizontal dilution of precision from 1.8 to 2.5, the noise channel and a reference signal power of minus 130 dBm, the terminal reporting its position every 2 s, and the minimum requirement of table 31 is a success rate of 95 % and a two-dimensional position error of 100 m at a periodic reporting interval of 2 s.

8.7 Network assisted dual-mode BDS and GPS positioning again assumes that all the relevant assistance data has been received and conforms to annexes D and E of 3GPP TS 36.171 V16.2.0 (2021-06). For the sensitivity test with coarse time assistance the simulator generates six satellites and the parameters of table 32 are six satellites in all, three BeiDou, one GPS satellite with a high power signal and two GPS satellites with a low power signal, a horizontal dilution of precision from 1.4 to 2.1, the noise channel, a coarse time assistance error range of plus or minus 2 s, a BeiDou reference signal power of minus 145 dBm, a GPS reference high signal power of minus 142 dBm and a GPS reference low signal power of minus 147 dBm; the minimum requirement is the same as for network assisted BDS positioning. With fine time assistance the parameters of table 33 are six satellites in all, three BeiDou and three GPS, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, a fine time assistance error range of plus or minus 10 microseconds and reference signal powers of minus 147 dBm for both BeiDou and GPS, the minimum requirement again being that of network assisted BDS positioning. For nominal accuracy the parameters of table 34 are six satellites in all, three BeiDou and three GPS, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, a BeiDou reference signal power of minus 133 dBm and a GPS reference signal power of minus 128.5 dBm. For dynamic range the parameters of table 35 are six satellites in all, one BeiDou satellite with a high power signal and two with a low power signal and one GPS satellite with a high power signal and two with a low power signal, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, BeiDou reference powers of minus 133.5 dBm high and minus 145 dBm low, and GPS reference powers of minus 129 dBm high and minus 147 dBm low. For the multipath test the parameters of table 36 are six satellites in all, one BeiDou satellite with a single path channel and two with a two path channel and one GPS satellite with a single path channel and two with a two path channel, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, a BeiDou reference signal power of minus 133 dBm and a GPS reference signal power of minus 128.5 dBm. For the moving scenario and periodic update the parameters of table 37 are six satellites in all, three BeiDou and three GPS, the same dilution of precision and channel, a coarse time assistance error range of plus or minus 2 s, a BeiDou reference signal power of minus 133 dBm and a GPS reference signal power of minus 128.5 dBm, the terminal reporting its position every 2 s. In every one of these six cases the minimum requirement is stated to be the same as the corresponding requirement for network assisted BDS positioning.

9 Interface requirements

Clause 9 states that the LTE positioning protocol is a point-to-point positioning protocol which defines the positioning-related signalling between the user equipment and the enhanced serving mobile location centre, and that the related signalling is to conform to 3GPP TS 36.355 V15.5.0 (2019-09).