Positioning

TECHNICAL FIELD

[0001] The disclosed embodiments relate generally to wireless communications networks and systems and techniques for mobile positioning of user equipment coupled to wireless communications networks.

BACKGROUND

[0002] Location based services (LCS) provide increased convenience and improved services to users of wireless communications networks, and are based on mobile terminal positioning. Therefore, it would be desirable to have a system and method of improved mobile positioning of user equipment coupled to wireless communications networks. More specifically, it would be desirable to have an improved system and method of determining the frequency shift of positioning reference signals used in mobile positioning, to reduce signal interference. It would also be desirable to have an improved system and method of configuring the usage of cell-specific reference signals in mobile positioning, to reduce error.

SUMMARY

[0003] In accordance with some embodiments, a method of determining frequency shifts of reference signals performed by a communications network includes dividing a plurality of frequency shift candidates into a plurality of unique sets. Each set includes at least one frequency shift candidate. The method also includes transmitting, to a user equipment, configuration information including an assignment of a first set of the plurality of unique sets to a first reference signal. A series of frequency shifts in a corresponding series of subframes of the first reference signal uses only frequency shift candidates from the first set of the plurality of unique sets.

[0004] In accordance with some embodiments, a computer system includes one or more processors, memory, and one or more programs stored in the memory, the one or more programs including instructions for dividing a plurality of frequency shift candidates into a plurality of unique sets. Each set includes at least one frequency shift candidate. The one or more programs further include instructions for transmitting, to a user equipment,

configuration information including an assignment of a first set of the plurality of unique sets to a first reference signal. A series of frequency shifts in a corresponding series of subframes of the first reference signal uses only frequency shift candidates from the first set of the plurality of unique sets.

[0005] In accordance with some embodiments, a non-transitory computer readable storage medium stores one or more programs configured for execution by a computer system, the one or more programs including instructions that, when executed by one or more processors of the computer system, cause the computer system to divide a plurality of frequency shift candidates into a plurality of unique sets. Each set includes at least one frequency shift candidate. The one or more programs also include instructions that, when executed by one or more processors of the computer system, cause the computer system to transmit, to a user equipment, configuration information including an assignment of a first set of the plurality of unique sets to a first reference signal. A series of frequency shifts in a corresponding series of subframes of the first reference signal uses only frequency shift candidates from the first set of the plurality of unique sets.

[0006] In accordance with some embodiments, a method of mobile positioning performed by a communications network includes transmitting, to a user equipment, configuration information that includes an indication of whether a cell-specific reference signal is available for use by the user equipment to determine time-of-arrival information.

[0007] In accordance with some embodiments, a computer system includes one or more processors, memory, and one or more programs stored in the memory, the one or more programs including instructions for transmitting, to a user equipment, configuration information that includes an indication of whether a cell-specific reference signal is available for use by the user equipment to determine time-of-arrival information.

[0008] In accordance with some embodiments, a non-transitory computer readable storage medium stores one or more programs configured for execution by a computer system, the one or more programs including instructions that, when executed by one or more processors of the computer system, cause the computer system to transmit, to a user equipment, configuration information that includes an indication of whether a cell-specific reference signal is available for use by the user equipment to determine time-of-arrival information.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Different aspects of the present invention as well as features and advantages thereof will be more clearly understood hereinafter as a result of a detailed description of implementations of the present invention when taken in conjunction with the accompanying drawings, which are not necessarily drawn to scale. Like reference numerals refer to corresponding parts throughout the several views of the drawings.

[0010] FIG. 1 is a block diagram illustrating an implementation of a wireless communications network, in accordance with some embodiments.

[0011] FIGS. 2A-2C illustrate a representation of resource element allocation in a physical resource block.

[0012] FIGS. 3 A-3B illustrate a flowchart representation of a method of determining the frequency shift of positioning reference signals used in mobile positioning, in accordance with some embodiments.

[0013] FIG. 4 illustrates a flowchart representation of a method of configuring the usage of cell-specific reference signals in mobile positioning, in accordance with some embodiments.

DESCRIPTION OF EMBODIMENTS

[0014] Reference will now be made in detail to implementations, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous non-limiting specific details are set forth in order to assist in understanding the subject matter presented herein. It will be apparent, however, to one of ordinary skill in the art that various alternatives may be used without departing from the scope of the present invention and the subject matter may be practiced without these specific details.

[0015] FIG. 1 is a block diagram illustrating an implementation of a wireless communications network (also referred to herein as a communications network or mobile communications system), in accordance with some embodiments. In particular, FIG. 1 illustrates an implementation of an LTE system 100, in accordance with some embodiments. LTE system 100 includes wireless network 120, including at least one base station (eNB) 102, and at least one user equipment (UE) 101. User equipment UE 101 is wirelessly coupled to base station eNB 102 of wireless network 120 for obtaining wireless services. UE 101 includes a wireless module 112 for performing wireless data transmissions and receptions to and from eNB 102. In some implementations, wireless module 112 further includes a baseband unit 112-1 and a radio frequency (RF) unit 112-2. Baseband unit 112-1 contains multiple hardware devices to perform baseband signal processing, including analog to digital conversion (ADC)/digital to analog conversion (DAC), gain adjustment, modulation/demodulation, encoding/decoding, etc. RF unit 112-2 receives RF wireless signals from e B 102 and converts the received RF wireless signals into baseband signals to be processed by baseband unit 112-1. Alternatively, RF unit 112-2 receives baseband signals from baseband unit 112-1 and converts the received baseband signals into RF wireless signals to be transmitted to eNB 102. In some implementations, RF unit 112-2 also includes multiple hardware devices to perform radio frequency conversion. For example, RF unit 112-2 may include a mixer to multiply the baseband signals with a carrier oscillated at a radio frequency of the mobile communications system. In some implementations, the radio frequency may be (i) 900 MHz, 1900 MHz, or 2100 MHz utilized in WCDMA systems, (ii) 900 MHz, 2100 MHz, or 2.6 GHz utilized in LTE systems, or (iii) other frequencies depending on the radio access technology used by the wireless network 120.

[0016] In some implementations, UE 101 includes a controller module 114 for controlling the operations of wireless module 112 as well as other components in UE 101. For example, UE 101 may also include a display unit and/or a keypad serving as a human-to- machine interface 116, a storage unit 118 storing program codes supporting various applications and communication protocols, etc. Controller module 114 controls wireless module 112 to perform the random access procedure and related data exchange operations with wireless network 120 via eNB 102 as described above in connection with FIG. 1. In some implementations, wireless network 120 also includes a control node to control the operations of eNB 102 and other base stations. In some implementations, wireless network 120 complies with a predefined standard communication protocol. For example, as shown in FIG. 1, wireless network 120 is an LTE network, and UE 101 accordingly complies with the specifications of the LTE communication protocols. But it will be clear to those skilled in the art that different implementations of the present invention are not limited to the LTE network.

[0017] In some embodiments, wireless network 120 includes a plurality of cells, not shown in FIG. 1. In some embodiments, a respective cell has an associated positioning reference signal (PRS), cell-specific reference signal (CRS), and physical cell identification number (PCID). In some embodiments, the cells in wireless network 120 are macro-cells that are each subdivided into a plurality of pico-cells, where each macro-cell and pico-cell has a respective geographic location. In some embodiments, a macro-cell and its component pico- cells share the same physical cell identification number PCID and transmit the same CRS. In some embodiments, a macro-cell and its component pico-cells transmit different PRS so that the timing measurement based on a respective PRS signal is indicative of the geographic location of a specific respective cell of the macro- and pico-cells. As used herein, the term "cell" may refer to an undivided cell, a macro-cell, or a pico-cell.

[0018] FIGS. 2A-2C illustrate representations of resource element allocation in physical resource blocks (PRBs, also referred to herein as resource blocks or RBs). In particular, FIGS. 2A-2C shows patterns of positioning reference signals (PRS) and cell- specific reference signals (CRS) allocated for a cell both in a subframe corresponding to one or two cell-specific reference signal (CRS) antenna ports and in a subframe corresponding to four CRS antenna ports. Each subframe corresponds to a pair of PRBs, where each PRB is represented by a rectangle block of resource elements that cross twelve subcarriers in the frequency domain and a single slot in the time domain. As shown in FIGS. 2A-2C, each slot (e.g., a respective even numbered slot or a respective odd numbered slot) contains seven orthogonal frequency-division multiplexing (OFDM) symbols for normal cyclic-prefix (CP) length. In other embodiments, not shown in FIGS. 2A-2C, each slot contains six OFDM symbols for extended CP length.

[0019] In some embodiments, positioning reference signals PRS and cell-specific reference signals CRS are used in mobile positioning to determine locations of mobile terminals such as UEs. Mobile positioning techniques include cell-ID, assisted-GPS signal, angle-of-arrival (AO A) measurement, time-of-arrival (TO A) measurement and time- difference-of-arrival (TDOA) measurement. Among them, the TDOA technique (also called Observed-Time-Difference-of-Arrival, i.e., OTDOA) based on time-of-arrival (TOA) measurements of specific downlink signals, i.e., positioning reference signal (PRS) and cell- specific reference signal (CRS), was specified in E-UTRAN LTE release 9. In some embodiments, the timing measurement in OTDOA positioning is based on PRS, CRS or the combination of both PRS and CRS. In some embodiments, a UE is configured to use a respective PRS from a respective cell for mobile positioning, and in some embodiments a UE may choose to also use CRS, e.g., corresponding to the respective PRS, for mobile positioning.

[0020] In some embodiments, a respective PRS has a respective associated pattern.

In some embodiments, a PRS pattern of a respective subframe, such as any of the PRS patterns illustrated in FIGS. 2A-2C, is repeated in a predefined number N _PRS of contiguous subframes. In some such embodiments, the predefined number N _PRS is selected from the set { 1, 2, 4, 6}. In some embodiments, a PRS pattern is repeated per PRB pair. Also, in some embodiments, the PRS pattern of a PRB pair is repeated in N^ ^s contiguous PRB pairs in the frequency domain, where N^§ ^s is a configurable parameter associated with a respective PRS.

[0021] A respective resource element in a resource block has an associated subcarrier index (selected from one of the aforementioned twelve subcarriers, for example) and an associated OFDM symbol (selected from one of the aforementioned six or seven symbols, for example). In some embodiments, therefore, a respective resource element is represented by a respective pair of indices (k, /), where k is the respective subcarrier index in the frequency domain and / is the respective OFDM symbol, and where the respective index (k, I) represents the time-frequency position of the resource element in the resource block.

[0022] In some embodiments, resource elements for a respective PRS are allocated in accordance with a cell-specific frequency shift i½ _t , which, in some embodiments, is further associated with a given physical cell identification number PCID Ν ^η . In some

embodiments, v _shi f _t is given by v _shi f _t = Ν ^η mod 6. In other words, in some

embodiments, v _shi f _t can be any integer within the range [0, 5]. In some embodiments, the same frequency shift v _shi f _t used for PRS is applied to CRS.

[0023] Accordingly, FIG. 2 A shows example PRS and CRS patterns in the normal CP length case for v _shi f _t = 0 in a subframe corresponding to one or two cell-specific reference signal (CRS) antenna ports and in a subframe corresponding to four CRS antenna ports, where the PRS corresponding to antenna port 6 is represented by Re, and the CRS

corresponding to antenna ports 0 through 3 are represented by Co through C3, respectively.

[0024] FIG. 2B shows example PRS/CRS patterns corresponding to the PRS/CRS patterns of FIG. 2A, except with v _shi f _t = 2. As shown in FIG. 2B, the PRS/CRS patterns of ^v shift = 2 is obtained in some embodiments by shifting the PRS/CRS patterns of v _shi f _t = 0 (as shown in FIG. 2A) upwards by two subcarriers.

[0025] Similarly, FIG. 2C shows example PRS/CRS patterns corresponding to the

PRS/CRS patterns of FIG. 2 A, except with v _shift = 4. As shown in FIG. 2C, the PRS/CRS patterns of v _shi f _t = 4 is obtained in some embodiments by shifting the PRS/CRS patterns of ^v shift ⁼ 0 (as shown in FIG. 2A) upwards by four subcarriers, and/or by shifting the

PRS/CRS patterns of v _shi f _t = 2 (as shown in FIG. 2B) upwards by two subcarriers.

[0026] In some embodiments, including those illustrated in FIGS. 2A-2C, as well as in some embodiments using extended CP length, v _shi f _t is cyclic in modulo 6. In some such embodiments, the PRS/CRS resource elements in the lower six subcarriers are cyclically shifted separately from the PRS/CRS resource elements in the upper six subcarriers.

[0027] FIGS. 3A-3B illustrate a flowchart representation of a method 300 of determining the frequency shift v _shi f _t of positioning reference signals used in mobile positioning, in accordance with some embodiments. With reference to FIG. 1, in some embodiments, method 300 is performed by a communications network, such as LTE system 100, or a component thereof such as wireless network 120. In some embodiments, v _shi f _t is determined using method 300 to reduce signal interference between a plurality of PRS from different cells received at a UE (e.g., UE 101, FIG. 1), including, for example, static interference introduced by fixed i½ t assignments (e.g., as determined by v _shi f _t =

Ν ^η mod 6) and/or random interference introduced by randomized v _shi f _t assignments. In some embodiments, method 300 is governed by instructions that are stored in a non-transitory computer readable storage medium and that are executed by one or more processors of a device. For ease of explanation, the following describes method 300 as performed by a communications network.

[0028] With reference to FIG. 3 A, in some embodiments, the communications network (e.g., LTE system 100, or a component thereof such as wireless network 120, FIG. 1) divides (302) a plurality of frequency shift candidates into a plurality of unique sets, wherein each set includes at least one frequency shift candidate. In some embodiments, the plurality of frequency shift candidates are candidate values for v _shi f _t . In some embodiments, the plurality of frequency shift candidates, e.g., the candidate values for v _shi f _t , include (304) a set of shift values {0, 1, 2, 3, 4, 5 } . It is noted that using the set {0, 1, 2, 3, 4, 5 } as candidate values for v _shi f _t is consistent with systems in which v _shi f _t can be any integer within the range [0, 5], including systems in which v _shi f _t for a respective cell is assigned a fixed value in accordance with the physical cell identification number Ν ^η of the respective cell. Moreover, limiting the candidate values to the six integer values as described is further consistent with calculation of i½u/t in modulo 6, as well as with resource allocation in accordance with twelve subcarriers including six upper subcarriers and six lower subcarriers, as discussed above with reference to FIGS. 2A-2C.

[0029] In some embodiments, for each respective set of the plurality of unique sets

(into which the plurality of frequency shift candidates are divided), the respective frequency shift candidates in the respective set have (306) a predetermined order. More specifically, in some embodiments, the respective frequency shift candidates in a respective set of two or more frequency shift candidates have a predetermined order. In some embodiments, the frequency shift v _shi f _t is time-varying, e.g., across a sequence of subframes. Thus, in some embodiments, the time-varying v _shi f _t for a sequence of subframes is selected from a respective unique set in accordance with the predetermined order of the frequency shift candidates in the respective set.

[0030] Next, the communications network transmits (308), to a user equipment (e.g.,

UE 101, FIG. 1), configuration information including an assignment of a first set of the plurality of unique sets to a first reference signal, wherein a series of frequency shifts in a corresponding series of subframes of the first reference signal uses only frequency shift candidates from the first set of the plurality of unique sets. In some embodiments, the first reference signal is (310) a positioning reference signal, i.e., a PRS. In some embodiments, the communications network transmits, and the UE receives, configuration information further including an identification number for the first reference signal. In some

embodiments in which v _shi f _t is randomly selected, the configuration information further includes a randomization seed, as described in more detail herein with reference to operations 316 and 318 of method 300.

[0031] In some embodiments, the unique sets are unique in that no frequency shift candidate appears in more than one of the sets. In some embodiments, i½u/t for a respective reference signal is selected from a respective unique set. In some embodiments, a first ^v shift,i f° ^{r a} first reference signal is selected from the frequency shift candidates in a first unique set, and a second v _shi f _ti2 for a second reference signal is selected from the frequency shift candidates in a second unique set. In some embodiments, the second unique set includes frequency shift candidates distinct from the frequency shift candidates included in the first set.

[0032] In some such embodiments, selecting v _shi f _t for the first and second reference signals from among the frequency shift candidates in distinct first and second sets, respectively, results in v _shi f _{t l} for the first reference signal having a different value from ^v shift,2 f° ^r the second reference signal. In some embodiments, selecting v _shi f _t in this manner reduces signal interference, including at least static interference, between the reference signals. In some embodiments in which v _shi f _t for one or more reference signals is also time-varying, the value for v _shi f _t for a respective reference signal is limited to the frequency shift candidates from the respective set assigned to the respective reference signal, thereby also reducing random interference between the reference signals. In some embodiments, for example, the first reference signal may be associated with a first cell, and the second reference signal may be associated with a second cell distinct from the first cell. In some other embodiments, the first and second reference signals may be associated with the same cell. For example, one of the first and second reference signals may be a reference signal with a time-varying frequency shift, and the other may be a legacy reference signal with time-invariant frequency shift.

[0033] In some embodiments, v _shi f _t is time-varying and its value deterministically selected from the first set of the plurality of unique sets that is assigned to the first reference signal. For example, in some embodiments, a respective frequency shift in a respective corresponding subframe of the first reference signal has (312) a respective index m in the first set, Sj, determined using a function of the form m = f(t, N _I ^PRS , N _i \ where t represents a respective subframe time index for the respective corresponding subframe, represents an identification number for the first reference signal, and N _t represents a total number of frequency shift candidates in the first set S ₁ . In some embodiments, the respective frequency shift for the respective subframe is determined (314) using a function of the form m = fi Ni) = (t + Nf _D ^RS ) mod Ni.

[0034] In some embodiments, the output of the function f t, Ni) is the index m of frequency shift in the first set S ₁ . Accordingly, the output is an integer value that satisfies

0≤f(t, Nf _D ^RS , N _i ) < N _i and the respective frequency shift for the first reference signal in a respective subframe is given by v _shi f _t = 5 _X [m] . Those skilled in the art will recognize that, in some embodiments, the output of the function f t, Nj) is the frequency shift itself rather than an index of a frequency shift in a respective set. As an illustrative example, in some embodiments, v _sh ift = f(t, N _I ^p _D ^RS , N _i ), and in some such embodiments, f(t, Ni) takes as an input N _t a set of frequency shift candidates, e.g., the first set S ₁ . [0035] In some embodiments, a UE measures a plurality of reference signals in the same subframe. Thus, in some embodiments, two or more reference signals having their frequency shift selected from the same set each have a unique identification number N^ ^s ' ¹ . For example, for a first reference signal with a first identification number Ν^' ¹ , and a

PRS 2

second reference signal with a second identification number N _ID ' , where both the first and second reference signals have their frequency shift selected from the same set:

Thus, when selected from a set that includes two or more frequency shift candidates, v _shi f _til for the first reference signal and v _shi f _{t 2} for the second reference signal are distinct. Those skilled in the art will recognize that other methods may similarly be used to deterministically select v _shift .

[0036] In some embodiments, v _shi f _t is time-varying and its value randomly (or pseudo-randomly) selected from the first set of the plurality of unique sets that is assigned to the first reference signal. For example, in some embodiments, a respective frequency shift in a respective corresponding subframe of the first reference signal has (316) a respective index m in the first set S _t determined using a function of the form m = f(t _l Nfj? ^s _l N _seedl N _i \ where t represents a respective subframe time index for the respective corresponding subframe, represents an identification number for the first reference signal, N _seed represents a randomization seed, and N _t represents a total number of frequency shift candidates in the first set S ₁ .

[0037] In some embodiments, the output of the function f t, N ^s , N _seed , Ni) is the index m of frequency shift in the first set S ₁ . Accordingly, the output is an integer value that satisfies

0≤f(t, Nf _D ^RS , N _seed , N _i ) < N _i and the respective frequency shift for the first reference signal in a respective subframe is given by v _shift = SJm] .

[0038] In some embodiments, the respective frequency shift for the respective subframe is determined (318) using a function of the form m = / ^" (t, N£ ^R , N _seed , Ni) = [Nf _D ^RS + g(t, N _seed , mod N where g(t, N _seed , N ) is a function of a plurality of parameters including at least t, N _seed , and Ni, and where g(t, N _seed , N ) cannot be decomposed into a sum of a first additive term that does not depend on N _seed and a second additive term that does not depend on t. More specifically, g(t, N _seed , N ) cannot be decomposed into two additive terms as g(t, N _seed , Ni) = [g^t. Ni + g ₂ (N _seed , Ni)] mod , where g _\ (t, Ni) does not depend on (i.e., is independent of) N _seed and g2 (N _seed , N^) does not depend on t. One implementation example of g(t, N _seed , N^) is to make it equal to the multiplication of a first multiplicative term that at least depends on t and a second

multiplicative term that at last depends on N _seed . More specifically, in some embodiments (320), g(t, N _seed , Ni) = [gfi fo -Vi) x g ₂ (N _seed , Ni)] mod N;, and, as an example (322), g(t, N _seed , Ni) = [t x N _seed ] mod N;.

[0039] In some embodiments in which a UE measures a plurality of reference signals, the reference signals all have the same randomization seed N _seed . In some such

embodiments, the reference signals have different N™ for generating distinct v _shi f _t values for the plurality of reference signals, reducing collision in any respective subframe.

[0040] FIG. 4 illustrates a flowchart representation of a method 400 of configuring the usage of cell-specific reference signals in mobile positioning, in accordance with some embodiments. With reference to FIG. 1, in some embodiments, method 400 is performed by a communications network, such as LTE system 100, or a component thereof such as wireless network 120. As described above with reference to FIGS. 1 and 2A-2C, in some

embodiments, a UE is configured to use PRS for mobile positioning and may choose whether to also use a corresponding CRS for mobile positioning. In some embodiments, using a corresponding CRS in addition to a PRS improves mobile positioning, such as by enabling improved determination of time-of-arrival information. In some embodiments, however, a macro-cell and its component pi co-cells share the same PCID and transmit the same CRS. Thus, in embodiments where identical CRS based on the same PCID are transmitted by multiple cells at different geographic locations, and where this condition is unknown to the UE, the timing measurements by the UE based on these CRS result in distance ambiguity and large positioning error. [0041] With reference to FIG. 4, in some embodiments, the communications network

(e.g., LTE system 100, or a component thereof such as wireless network 120, FIG. 1) transmits (402), to a user equipment, configuration information that includes an indication of whether a cell-specific reference signal is available for use by the user equipment to determine time-of-arrival information. In some embodiments, the configuration is transmitted as a configuration information element (IE). In some embodiments, the configuration information includes the PCID Ν ^η of a cell.

[0042] With respect to the indication of whether a CRS is available for use by the UE in determining TOA information, in some embodiments in which a unique CRS is transmitted by a single undivided cell with a unique geographic location, for example, the configuration information includes an indication that a CRS is available for measurement and/or use in mobile positioning. On the other hand, in some embodiments in which the same CRS is transmitted by multiple cells, such as a macro-cell and its component pico-cells, the configuration information includes an indication that a CRS is not available for use in mobile positioning. In such embodiments, the UE is thereby informed whether the CRS is available for use in positioning. In some embodiments, a CRS is not transmitted by a PRS-only beacon, and therefore is not available for use in mobile positioning.

[0043] In some embodiments, in accordance with the indication indicating that a cell- specific reference signal is not available for time-of-arrival measurement (404), the user equipment does not use a cell-specific reference signal to determine time-of-arrival information.

[0044] In some embodiments, in accordance with the indication indicating that a cell- specific reference signal is available (406), the user equipment determines whether to use the cell-specific reference signal to determine time-of-arrival information. In some embodiments in which a CRS is available, the UE is not required to use the CRS in positioning, but may exercise discretion whether to use the CRS.

[0045] As discussed above, in some embodiments, the communications network includes a plurality of cells. Thus, in some embodiments, the configuration information includes (408), for a respective cell of one or more cells, a respective configuration information element including a respective indication of whether a cell-specific reference signal for the respective cell is available for use by the user equipment to determine time-of- arrival information for the respective cell. In accordance with the respective indication corresponding to the respective cell indicating that a respective cell-specific reference signal is not available for measuring the time-of-arrival for the respective cell, the user equipment does not use a cell-specific reference signal to determine time-of-arrival information for the respective cell, for example by not requesting a CRS.

[0046] The indication of whether CRS is available may be implicit or explicit. In some embodiments, for an explicit indication, the configuration information includes an additional bit to indicate whether CRS is available for use in mobile positioning. In some embodiments, the indication includes (410) a Boolean variable.

[0047] In some embodiments, the configuration information includes (412) a positioning reference signal identification number (e.g., N ^s ) used in generating a positioning reference signal, and in some such embodiments the indication is based on whether the configuration information further includes a physical cell identification number (e.g., a PCID Ν β ^η ). In some embodiments, the generation of a PRS depends on the positioning reference signal identification number N™ but not on the PCID (which is sometimes associated instead with CRS generation, as discussed above). Thus, in some embodiments, for an implicit indication, the configuration information includes a PCID if a cell-specific reference signal is available for use in determining TOA information, and the configuration information does not include a PCID if a cell-specific reference signal is not available for use in determining TOA information. The absence of the PCID indicates to the UE that a CRS is not available for use in determining TOA information, in accordance with which the UE does not request or use CRS for positioning.

[0048] In some implementations, the above-described methods and their variations may be implemented as computer software instructions or firmware instructions. Such instructions may be stored in an article with one or more machine-readable storage devices connected to one or more computers or integrated circuits or digital processors such as digital signal processors, microprocessors, or micro-control units (MCU). In addition, the method may be applied to any mobile communications device supporting the WCDMA technology and/or the LTE technology. Other variations and enhancements are possible based on what is mentioned here.

[0049] While particular implementations are described above, it will be understood it is not intended to limit the invention to these particular implementations. On the contrary, the invention includes alternatives, modifications and equivalents that are within the spirit and scope of the appended claims. Numerous specific details are set forth in order to provide a thorough understanding of the subject matter presented herein. But it will be apparent to one of ordinary skill in the art that the subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the

implementations.

[0050] Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, first ranking criteria could be termed second ranking criteria, and, similarly, second ranking criteria could be termed first ranking criteria, without departing from the scope of the present invention. First ranking criteria and second ranking criteria are both ranking criteria, but they are not the same ranking criteria.

[0051] The terminology used in the description of the invention herein is for the purpose of describing particular implementations only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "includes," "including," "comprises," and/or "comprising," when used in this specification, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof.

[0052] As used herein, the term "if may be construed to mean "when" or "upon" or

"in response to determining" or "in accordance with a determination" or "in response to detecting," that a stated condition precedent is true, depending on the context. Similarly, the phrase "if it is determined [that a stated condition precedent is true]" or "if [a stated condition precedent is true]" or "when [a stated condition precedent is true]" may be construed to mean "upon determining" or "in response to determining" or "in accordance with a determination" or "upon detecting" or "in response to detecting" that the stated condition precedent is true, depending on the context.

[0053] Although some of the various drawings illustrate a number of logical stages in a particular order, stages that are not order dependent may be reordered and other stages may be combined or broken out. While some reordering or other groupings are specifically mentioned, others will be obvious to those of ordinary skill in the art and so do not present an exhaustive list of alternatives. Moreover, it should be recognized that the stages could be implemented in hardware, firmware, software or any combination thereof.

[0054] The foregoing description, for purpose of explanation, has been described with reference to specific implementations. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The

implementations were chosen and described in order to best explain principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various implementations with various modifications as are suited to the particular use contemplated. Implementations include alternatives, modifications and equivalents that are within the spirit and scope of the appended claims. Numerous specific details are set forth in order to provide a thorough understanding of the subject matter presented herein. But it will be apparent to one of ordinary skill in the art that the subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the implementations.