Abstract
The invention provides a method of assigning radio resources for transmitting and receiving measurement radio signals for determining a position of a cellular device (UE1), wherein at least one of a bandwidth, a pulse form, and a duration of the measurement radio signals is selected according to a positioning accuracy requirement of a requesting device.
Claims
1. A method of assigning radio resources for transmitting and receiving measurement radio signals for determining a position of a cellular device, wherein at least one of a bandwidth, a pulse form, and a duration of the measurement radio signals is selected according to a positioning accuracy requirement of a requesting device.
2. The method according to claim 1, wherein the duration of the measurement radio signal is selected dependent on an accuracy parameter provided in a positioning request message.
3. The method according to claim 1, wherein the pulse form is selected dependent on an estimated link quality between a base station and a user equipment device.
4. The method according to claim 1, wherein the pulse form is selected dependent on a known measurement of distance between a base station and a user equipment device.
5. The method according to claim 1, wherein the pulse form is selected from one of a plurality of predetermined pulse shapes.
6. The method according to claim 1, wherein a measurement time slot is provided for transmission of the measurement radio signals, each slot being used for the transmission of one or more measurement radio signals.
7. The method according to claim 6, wherein the number of measurement radio signals transmitted in the measurement time slot is dependent on the duration of the one or more measurement radio signals to be transmitted.
8. The method according to claim 6, wherein for providing the measurement time slot information indicating whether the measurement radio signals are to be transmitted to the same receiving device as previously transmitted measurement radio signals is taken into account.
9. The method according to claim 6, wherein the measurement time slot is located time-wise within a special subframe of a cell of a time division duplex cellular communication system, the special subframe being a time interval of absence of cellular radio signals for switching between uplink and downlink signal exchange between devices of the cell.
10. The method according to claim 1, wherein a user equipment device is assigned a predetermined number of resource blocks within one or more measurement time slots in a single positioning bandwidth part defined according to a 3GPP 5G radio standard.
11. The method according to claim 1, wherein for performing the transmission of measurement radio signals, a user equipment device is addressed using an address having fewer bits than a radio network temporary identity.
12. The method according to claim 1, wherein an addressing scheme is provided for identifying a positioning bandwidth part in the available radio resources of a cell.
13. The method according to claim 2, wherein the pulse form is selected dependent on an estimated link quality between a base station and a user equipment device.
14. The method according to claim 2, wherein the pulse form is selected dependent on a known measurement of distance between a base station and a user equipment device.
15. The method according to claim 3, wherein the pulse form is selected from one of a plurality of predetermined pulse shapes.
16. The method according to claim 2, wherein a measurement time slot is provided for transmission of the measurement radio signals, each slot being used for the transmission of one or more measurement radio signals.
17. The method according to claim 16, wherein the number of measurement radio signals transmitted in the measurement time slot is dependent on the duration of the one or more measurement radio signals to be transmitted.
18. The method according to claim 2, wherein a user equipment device is assigned a predetermined number of resource blocks within one or more measurement time slots in a single positioning bandwidth part defined according to a 3GPP 5G radio standard.
19. The method according to claim 2, wherein for performing the transmission of measurement radio signals, a user equipment device is addressed using an address having fewer bits than a radio network temporary identity.
20. The method according to claim 2, wherein an addressing scheme is provided for identifying a positioning bandwidth part in the available radio resources of a cell.
Description
[0067] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
[0068] FIG. 1 shows a schematic representation of a cellular network;
[0069] FIG. 2 illustrates a time frequency radio resources grid including position measurement occasions;
[0070] FIG. 3 shows the grid of FIG. 2 in more detail;
[0071] FIG. 4 shows measurement occasions in a time frequency grid at a resource element level;
[0072] FIG. 5 illustrates a transmission and reception of measurement radio signals between UEs and a base station;
[0073] FIG. 6 illustrates the assignment of measurement slots to UEs;
[0074] FIG. 7 is an event sequence chart showing an implementation of the invention;
[0075] FIG. 8 illustrates a relationship between signals in the time and frequency domain;
[0076] FIG. 9 shows an example of control data for controlling UE2 of FIG. 4;
[0077] FIG. 10 shows a further example of resource assignment; and
[0078] FIG. 11 shows resource assignment information elements for the resource assignment for UE2 and UE3 shown in FIG. 10.
[0079] FIG. 1 shows a simplified mobile communication network comprising four UEs devices (UE1, UE2, UE3 and UE4), three base stations (gNB1, gNB2 and gNB3), a core network, a location server (LCS Server) and a third party service provider (Service Provider) enabled for the inventive positioning procedure. UE1 and UE2 may be served by gNB1 indicated by an ellipsis representing the cell spanned by gNB1 while UE3 and UE4 may be served by gNB2. The LCS server is connected to the core network or it may be a part of the core network and exposed for illustration purposes only. The LCS Server is reachable from the UE device via a radio access network, e.g. one of the shown base stations or any other wireless connection, and the core network. The LCS Server is as well reachable by the service provider either directly (not shown) or indirectly via the core network.
[0080] FIG. 2 shows a simplified time-frequency-grid of a cell of the cellular mobile communication system of FIG. 1. For illustration purposes the term “measurement occasion” is introduced which is the collection of resources used for position fixes within a restricted time interval. The figure illustrates the position of three measurement occasions. These are intended for positioning signals and consist of resource for position fixes and potentially other resources. Each measurement occasion is accompanied by control resources for controlling the usage of the resources for position fixes. Between these resources, the normal communication resources of the cellular communication system are located. The measurement control is located time-wise before each measurement occasion. The measurement control field includes the resource assignment (RA), which commands the UE device to start positioning in this measurement occasion and indicates the resources within the measurement occasion to be used by the UE device, i.e. the measurement control field contains control information carried by modulated bits and no positioning signals, so the measurement control resources can also be considered as normal communication resources of the cell, yet dedicated for control of the positioning resource usage. The resources for the actual measurements can be located e.g. at the positions of the guard interval within the special subframe of the TDD-mode of LTE or NR (5G).
[0081] FIG. 3 shows more details of the three measurement occasions of FIG. 2. Each occasion is divided in multiple positioning bandwidth parts (PBWPs). Each PBWP is defined by a frequency range (bandwidth), a duration and a period, shown for PBWP #2 in FIG. 3. The different configurations enable different positioning properties, e.g. different positioning accuracy and trackability of moving devices. In this example, PBWP #1 enables the highest accuracy, as the bandwidth is the broadest allowing the shortest positioning impulses compared to the other PBWPs. PBWP #3 has the shortest positioning periodicity and enables therefore the best permanent trackability of fast moving UEs. As also depicted in FIG. 3, a measurement occasion does not necessarily bear resources for all PBWPs, each PBWP has its own periodicity and may or may not appear in an occasion. In our example, a measurement occasion is the set of resources collectively controlled by a block of control resources (PBWP-Control).
[0082] FIG. 4 shows even more details of PBWP #2 which is embedded in the mobile communication time-frequency-grid for which a single resource element (RE) is shown example wise at the bottom left. PBWP #2 is divided in measurement slots for multiple UE devices (UE1 to UE4) for measurements with respective base stations (gNB1 to gNB3). Each measurement slot in this example bears resources for a single pair of interrogator and transponder signals sent between one UE device and one base station. In another example multiple pairs for a single UE are included in one measurement slot. The measurement slots within the PBWP are typically much shorter in time compared to the symbol duration used for communication resources, i.e. the duration of the resource element (RE) as shown in FIG. 4. The duration of the PBWP-control field is equal to or a multiple of a resource element duration as it carries modulated bits like the communication resources. All resource parts that are not reserved for positioning purposes may be used for communication purposes and are using the respective resource grid, i.e. the symbol duration and the subcarrier spacing according to the resource element size.
[0083] As depicted in FIG. 4, the PBWP can be divided in time and frequency direction between different UE devices and between positioning fix iterations of a single UE device, to different or the same base stations. For different accuracy needs, different positioning impulse shapes may be used, e.g. UE2 and UE3 use half of the bandwidth of the PBWP while UE1 and UE4 use the full bandwidth. According to this invention the allocation of different amount of resources to different UE devices is a result of different positioning accuracy requirements so that UE devices UE1 and UE4 use a shorter and more precise positioning shape while UE devices UE2 and UE3 use longer impulse shape which results in half the bandwidth needs. The impulse shape and impulse bandwidth may in one example be determined by the base station before a UE device is configured and the shape and bandwidth are then configured to the UE device. Then, only the timewise occurrence of the positioning resources needs to be dynamically assigned.
[0084] In the current embodiment, all measurement slots are of equal duration while in other embodiments it may be foreseen that the measurement slot duration is variable. It may for example depend on the duration of the impulse shape and in some embodiments the time of flight of the signal, i.e. the estimated distance between UE and base station. As this distance can hardly be estimated before the resource allocation, the preferred embodiment is a fixed length measurement slot as depicted in FIG. 4.
[0085] A measurement slot may be long enough in time to fit multiple position fixes, but because of the unknown or not precisely known time of flight of positioning impulses, the number of position fixes fitting into an allocated measurement slot or into multiple consecutive slots assigned to a single UE device may not be known beforehand. One embodiment could foresee that a UE device having the role of an interrogator, i.e. initiating a position fix, may transmit a first interrogator signal and receive the corresponding transponder signal within the allocated resources and measure the time between this transmission and the related reception. The UE device may then determine whether the time elapsed between transmission and reception fits another time into the allocated resources, i.e. into one or more consecutively assigned measurements slots, and if so, perform another positioning fix with the same base station. This procedure may be repeated until no position fix can be performed within the remaining part of the assigned resources. In a positioning system similar to that described in DE 102015013453 B3 this process allows several iterations of position fixes and thus a very accurate position estimation within one assigned block of measurement slots.
[0086] In case the UE device has the role of the transponder it may be foreseen that the UE device is prepared to receive interrogator signals and respond with respective transponder signals during the complete duration of the assigned resources so that a base station can decide how many repeated position fixes to perform with the UE device within the assigned resources.
[0087] The PBWP-control resource block as shown in FIG. 4 must use resources that lay time-wise before the PBWP. The control block may comprise control information for multiple PBWPs that are not shown in FIG. 4, e.g. for PBWP #1 and PBWP #3 of FIG. 3.
[0088] As one example, a part of control data for UE2 according to FIG. 4 is shown in FIG. 9. The control data is assigned to UE2 in a first information element identifying the UE device with its RNTI. In a following information element that may for example be four bits long, the PBWP is identified which is to be used by the UE device for position fixes and which is addressed for the following assignment. The next information element may indicate the number of measurement blocks, each block comprising one or more immediately consecutive measurement slots assigned to UE2; in this example two blocks according to FIG. 4 are assigned to UE2. For each of these blocks a start slot number is indicated in following information elements, in the example these are measurement slot number 2 and 6 and for the first block, a number of consecutively assigned measurements slots, in the example 1, is indicated. Similar information may be signalled by the base station for further PBWPs used by UE2 and for further UE devices for position fixes.
[0089] FIG. 10 depicts details of the resource assignment of a different system in a different example. In this example UE2 is assigned three consecutive measurement slots, the first for a position fix with base station gNB1, and the second and third for position fixes with gNB2, respectively. Also, FIG. 10 shows the resource assignment to UE3 which is assigned two consecutive measurement slots for position fixes with base station gNB3 and one following measurement slot for position fixes with base station gNB1. In contrast to the example shown in FIG. 4 and FIG. 9, in this example the assigning base station informs the UE about whether a measurement slot is for a different or the same base station as the preceding position fix. FIG. 11 shows the resource assignment information elements in this example for UE2 and UE3. These are very similar to those of the last example shown in FIG. 9. FIG. 10 differs in depicting the assignment data for assigning one block of three measurement slots to UE2 (upper part) and UE3 (lower part), respectively. The new aspect introduced by this new example is depicted in a new information element in the assignment data, here called New BS bitmap. The bitmap indicates for each of the assigned measurement slots, whether it is for position fixes with a new base station or it is for continued measurement fixes with the preceding base station. As a result, the respective UE device can, as described for example in DE 102015013453 B3, reset their registers that are maintained over position fixes with the same base station and which need resetting whenever the positioning is started with a new base station.
[0090] The information elements of FIGS. 9 and 11 are only examples to illustrate the proposed control mechanism for position resources. Various other forms of control signalling can be used to implement the various aspects of the current invention.
[0091] FIG. 5 depicts the transmission and reception of positioning impulses between UE devices UE1 to UE4 and one base station (gNB1) assuming a resource assignment according to FIG. 4. The figure focuses on resource usage with regards to gNB1 while other resources used for position fixes with other base stations are not shown. As usual in cellular mobile communication systems, the resource grid and respective allocation and assignment of resources to different UE devices is described at the location and with the timing of the base station. The base station assigns resources timewise according to the transmission and reception point in time at the base station.
[0092] UE devices are configured with a timing advance (TA) value representing an estimation of the time of flight of signals between the UE device and the base station. UE devices transmit signals at a time advanced by TA compared to the received DL timing to ensure the signals are received in-sync at the base station. UE devices expect signals sent by the base station to arrive at the UE by TA later. As depicted in FIG. 5, on the time axes of gNB1 three blocks of resources are present, a first communication block for mobile communication shaded in grey, a measurement occasion for PBWP #2, and a second communication block for mobile communication again shaded in grey. Within PBWP #2, measurement slots are shown, namely slot 1, 2, 3 and 6 whereas slots 4, 5 and further slots after 6 are indicated by three dots “ . . . ”.
[0093] According to FIG. 4 a first measurement slot of PBWP #2 is assigned to a positioning fix of UE1 with the UE being the interrogator, thus transmitting a positioning impulse (1) in UL. As depicted in FIG. 5, the impulse is received by gNB1 and a transponder signal is transmitted back in DL. The next measurement slot (2) is assigned to UE2 and UE3, respectively on different frequency ranges and intended for different gNBs. FIG. 5 only depicts the positioning impulses for gNB1. Measurement slot (3) is assigned to UE5 for a position fix with gNB1 as shown in FIGS. 4 and 5. Measurement slots (4) and (5) are assigned to UE1 and UE4 for position fixes with gNB2 and gNB3, respectively, so that gNB1 does not receive or transmit any signals in these resources. The next transmission towards gNB1 is according to FIG. 4 in measurement slot #6 by UE3 as shown in FIG. 5.
[0094] FIG. 6 shows another example of resource assignment with a longer measurement slot to illustrate the embodiment of a UE device, in this case UE1, performing multiple position fixes within one measurement slot. The UE device can perform the additional position fix after determining that a second interrogator signal sent from UE1 will be received in the gNB within the assigned measurement slot. The determining may take into account measurement slot duration, the time elapsed between transmission of the interrogator signal and reception of the transponder signal in the first position fix, and/or the TA configured to the UE device. The same determination leads to UE devices 2 and 3 in the example of FIG. 6 to only perform a single position fix within their assigned measurement slot as obvious from the figure.
[0095] One specific embodiment of the current invention is the allocation and configuration of resources for position fixes, e.g. in a PBWP, so, that the resources fit into the guard interval of the so called special subframe of a time duplex communication system, e.g. LTE TDD or NR TDD. This guard interval has a length of 1 to 10 symbols which mark the transformation between the DL usage of the resources and the UL usage. Within this guard interval, neither UE devices nor the base station transmits signals except for the UE devices transmitting UL signals of the subsequent subframe advanced by their timing advance within the special subframe. The guard interval is generally free of signals at the gNB and can be used by the current invention to carry a PBWP for position signals. There is no need to instruct other UEs to free these resources. Only the involved UEs may be instructed to shorten the DL reception immediately before a positioning impulse is sent. E.g. UE1 in FIG. 6 may shorten DL reception and the gNB will shorten DL transmission for this UE to avoid the shown overlap between the DL and the positioning impulse. For UE2 and UE3 this shortening is not required, as can be seen in FIG. 6. The shortening of DL reception can easily be taken into account in the scheduling of DL communication resources by the base station, so that this aspect does not have any drawback for the system.
[0096] In order to enable a reliable reception of the PBWP-control field, the PBWP-control field is scheduled so that an interval of time appears after the PBWP-control field before the related PBWP, as depicted in FIG. 4. This is configured to be about the maximum TA value of the involved UEs. The proposed scheduling will prevent an overlap at the UEs of the PBWP-control field and the transmission of an interrogator impulse.
[0097] In case the special subframe is used as measurement occasion, the control information having the assignment data is sent before the special subframe, preferably in the last subframe before the special subframe. The invention would then claim a base station to configure both a special subframe with silence for changing from DL to UL transmission and a PBWP at the same or at least an overlapping time interval for exchange (UL and DL) of position signals.
[0098] FIG. 8 shows the relation of signal duration and bandwidth for three different impulse shapes. At the top of FIG. 8 on the left an arbitrary impulse with a defined signal duration is shown in the time domain. This pulse corresponds to the shape given on the top right of the figure in the frequency domain having a resulting bandwidth. The example impulses and shapes are not exact, they are just selected to illustrate the physical principle that is the base for the current invention. In the mid left of the figure a similar impulse, yet with a longer duration in the time domain, is shown and evidently this pulse corresponds to a shape in the frequency domain with a smaller bandwidth as shown in the mid right of FIG. 8. A third example is a chirp impulse in the time domain as shown in the bottom left. The signal duration may be longer than the first example pulse, yet the bandwidth of that impulse is still larger than that of the first and second example impulses. The figure thus illustrates, that the bandwidth of an impulse is inversely proportional to the signal duration and also depends on the impulse shape.
[0099] A method for positioning resource allocation and assignment proposed in this invention is shown in FIG. 7. It comprises the following steps: [0100] the base station receives a positioning request comprising a requested positioning parameter indicating a requested accuracy of the positioning fix, [0101] the base station determining a position impulse shape (duration, bandwidth, form) for the UE device's positioning fixes, [0102] the base station optionally grouping UE devices with at least one common parameter regarding the impulse shape or regarding their distance to the base station into a first group of UE devices, [0103] the base station determining a measurement slot duration from the requested accuracy and from further conditions (e.g. signal quality and rough base station to UE distance) and optionally a measurement resource frequency from the requested trackability, [0104] the base station allocating first resources for positioning fixes and second resources for control of the first resources, including a resource periodicity for recurring resources, to UE devices of the first group, [0105] the base station configuring the UE devices accordingly, [0106] the base station scheduling positioning fixes in the allocated first resources and indicating these by transmitting control information on the second resources to the respective UE devices, thereby assigning scheduled position fixes one or more measurement slots of the determined measurement slot duration, [0107] the base station (as interrogator) transmitting position measurement impulses to a UE device of the first group and thereafter being prepared to receive a transponder signal from the UE device; or the base station acting in the opposite direction as transponder. [0108] the UE device receiving a configuration from a base station, the configuration comprising [0109] first resources for positioning fixes, [0110] second resources for reception of control information regarding the first resources, [0111] a positioning impulse shape (duration, bandwidth and/or shape), [0112] a measurement slot duration (if not fixed system wide), and (optionally) an indication of a role as interrogator or transponder the UE device shall take. [0113] the UE device receiving on the second resources an indication of measurement slots assigned to the UE device, and [0114] the UE (as interrogator) transmitting position measurement impulses according to the configured impulse shape to the base station and thereafter being prepared to receive a transponder signal according to the configuration from the base station; or the UE device acting in the opposite direction as transponder.
[0115] While the above method configures and assigns radio resources to UE devices for position fixes with a single base station, e.g. with the base station that allocates, configures and assigns the radio resources, this will result in an estimation of the distance between a UE device and the base station. For an estimation of the geographical position, however, multiple such distance measurements with different reference points are necessary. The reference points can be other base stations, e.g. pico base stations or macro base stations, or any other reference points that are able to perform the position fix using interrogator and transponder signals.
[0116] The UE device, configured with resources for position fixes and individually assigned such resources for actual performance of a position fix, does not need to distinguish between different base stations. That is, resources assigned to an individual UE device for position fixes can be used to perform position fixes to multiple different base stations. Depending on the method applied for the position fix, the UE device may not even need to know that positioning is done with different base stations, e.g. when using the method described in DE 102015013453 B3 and the UE device is the transponder. Alternatively, e.g. when the same method is applied and the UE device is the interrogator, the UE device may simply need to know for consecutive position resource assignments, whether they are for continued position fixes with the same base station or they are for a first position fix with a new base station. It is thus an aspect of this invention to include in the resource assignments sent by the base station to the UE device a “new base station” flag indicating to the UE device that the respective position fix is not related to the base station used previously but to a new base station. In this case the UE will reset the previously derived timings relating to the previous base station.
[0117] The base stations involved in position fixes, however, need to align their timing and the resource configuration for position fixes. The resource configuration needs to be done by a single base station, i.e. the serving base station, here called primary base station, because only that base station can communicate with the UE device and configure it. Other base stations involved, here called secondary base stations, need to perform their position fixes with the UE device at exactly the timing assigned to the UE device by the primary base station. It is thus another aspect of this invention to have PBWPs allocated by a primary base station to a UE device communicated by the primary base station to a secondary base station to firstly silence the secondary base station with regard to their cellular data communication and secondly provide measurement slot timing to the secondary base stations for position fixes between the secondary base stations and the UE device.
