WO2022180600A1

WO2022180600A1 - Systems and methods for high precision clock synchronization in wireless communication

Info

Publication number: WO2022180600A1
Application number: PCT/IB2022/051695
Authority: WO
Inventors: Wenfeng Zhang
Original assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd.
Priority date: 2021-02-26
Filing date: 2022-02-25
Publication date: 2022-09-01

Abstract

Methods and systems for determining a local clock time difference between a first station and a second station are provided. In some embodiments, the method includes (i) transmitting, by the second station, a first first-type message to the first station, and the first first-type message is indicative of a first local clock time of the second station; (ii) receiving, by the second station, a second-type message from the first station; (iii) receiving, by the second station, a second first-type message; and (iv) determining, by the second station, the local clock time difference between the first station and the second station at least based on the second-type message and the second first-type message. The second-type message includes clock time information corresponding to the first local clock time of the first station. The second first-type message is indicative of a second local clock time of the first station.

Description

SYSTEMS AND METHODS FOR HIGH PRECISION CLOCK SYNCHRONIZATION IN WIRELESS COMMUNICATION

CROSS-REFERENCE TO RELATED APPLICATION(S)

[1] This application claims priority to U.S. Provisional Patent Application No.

63/154,558 filed on February 26, 2021, entitled “High Precision Clock

Synchronization in Wireless Communication,” and to U.S. Provisional Patent Application No. 63/210,909 filed on June 15, 2021, entitled “New Wireless Signaling for High Precision Clock Synchronization,” the contents of which are incorporated by reference herein in their entirety.

TECHNICAL FIELD

[2] The present disclosure is directed to methods and systems for synchronizing time clocks in two devices that are capable of communicating with each other wirelessly (e.g., “radio entities”). More particularly, in some embodiments, the present disclosure can be implemented in a 3GPP New-Radio (NR) system.

BACKGROUND

[3] In wireless communication systems, there are occasions where a base station (BS) and a mobile station (MS) need to synchronize to the same time clock with very high precision (e.g., with a time clock synchronization error no more than one microsecond). Time clock synchronization can be applied in higher layer applications in a wide range of use cases.

[4] In 3GPP specifications for 5G NR, a new use case called “Time- Sensitive-Networking(TSN)-5GS” needs to support TSN grandmaster clocks located in mobile stations. The clock synchronization error on a single “Uu” interface (i.e., a wireless interface between a base station and a mobile station, e.g., a Universal Mobile Telecommunications System, UMTS, interface) is set to be no larger than 275 ns (e.g., for a control-to-control scenario) and 845 ns (e.g., for a smart grid scenario). In order to meet the foregoing requirements, in 3GPP, running a propagation delay compensation in mobile stations has been proposed. The foregoing scheme takes a one-way propagation delay on downlink (e.g., the wireless link for transmissions from a base station to a mobile station, while uplink is for transmission from the mobile station to the base station) into account when determining the clock time in a mobile station based on the clock time sent by a base station.

[5] More specifically, if a mobile station receives at its local time “t” a high layer message, telling that the TSN clock time is equal to “t₀,” the mobile station should set its own TSN clock time to be “t₀+T_PD” corresponding to its local time “t”. “T_PD” is an estimated one-way propagation delay (PD) on the downlink. This propagation delay compensation can be also equivalently performed in the base station, which means that the TSN clock sent by the base station in the high layer message has already considered such delay compensation.

[6] The foregoing clock synchronization based on propagation delay compensation has two steps: (1) an estimation of the one-way propagation delay (“estimation step”); and (2) using the estimated one-way propagation delay to compensate the synchronization (“compensation step”). However, it has at least the following drawbacks.

[7] First, hardware imperfectness (e.g., a transmitter or processor in the base station, a receiver or processor in the mobile station, etc.) causes timing errors. For example, a base station processor may believe its downlink transmission occurs at time “t,” but in fact the transmission occurs at time “t+eBS_, TX" Similarly, a mobile station processor may believe that a downlink reception has been detected at time “t,” but in fact a first downlink path arrives at time “f+e_{MS ,RX}.” Both timing errors, eBS_, TX and e_{MS ,RX}, change on a per transmission/reception basis and therefore are time- varying. The foregoing arrangement results in errors in both Steps (1) and (2), which can cause significant overall clock synchronization error.

[8] A mathematic analysis shows that the errors from Steps (1) and (2) can contribute as much as to the overall synchronization error.

A fair assumption for these two hardware timing errors is and

” Then the total relevant error can be as large as “1.5x165=247.5

ns,” which already consumes a major portion of the error budget for the control-to- control scenario. [9] Second, in typical one-way propagation delay estimation, “Rx-to-Tx” or round trip time (RTT) intervals are respectively measured at the base station and the mobile station. Basically, the one-way propagation delay can be estimated as a half of the difference between the RTT measured at the base station and the RTT measured at the mobile station. However, the foregoing approach requires the two measured RTTs be consistent to each other. In other words, once one of the two RTTs is measured and recorded (i.e. , in either the base station or the mobile station), the other RTT cannot be changed before the estimation is complete. It is inefficient and not easy to implement the RTT consistency. Therefore, it is advantageous to have improved systems and methods to address the foregoing issues.

BRIEF DESCRIPTION OF THE DRAWINGS

[10] To describe the technical solutions in the implementations of the present disclosure more clearly, the following briefly describes the accompanying drawings. The accompanying drawings show merely some aspects or implementations of the present disclosure, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.

[11] Fig. 1A is a schematic diagram of a wireless communication system in accordance with one or more implementations of the present disclosure.

[12] Fig. 1B is a schematic diagram illustrating clock time synchronization between a base station (BS) and a mobile station (MS) in accordance with one or more implementations of the present disclosure. Fig. 1B shows clock time synchronization utilizing timings obtained from a pair of independent uplink transmission/reception and downlink transmission/reception.

[13] Fig. 2 is a schematic diagram illustrating a message flow and related timing relations in clock time synchronization between two wireless communication stations in accordance with one or more implementations of the present disclosure. As shown, the message flow contains a first type message and a second type message.

[14] Fig. 3 is a schematic diagram illustrating a message flow between two wireless stations in accordance with one or more implementations of the present disclosure. As shown, the message flow averages timings associated with multiple first type message transmissions so as to reduce a clock time synchronization error. [15] Fig. 4 is a schematic diagram illustrating a message flow, where a second type message takes role and function of a first type message in accordance with one or more implementations of the present disclosure. As shown, the message flow contains “Alternative-1” message content for clock time information.

[16] Fig. 5 is a schematic diagram illustrating a message flow, where a second type message takes role and function of a first type message in accordance with one or more implementations of the present disclosure. As shown, the message flow contains “Alternative-2” message content for clock time information.

[17] Fig. 6 is a schematic diagram illustrating a message flow between two wireless communication stations in accordance with one or more implementations of the present disclosure. As shown, the message flow includes third type and fourth type messages or signaling to assist a station to know in advance the arrivals of the first type messages.

[18] Fig. 7 is a schematic block diagram of a terminal device or a mobile station in accordance with one or more implementations of the present disclosure.

[19] Fig. 8 is a flowchart of a method in accordance with one or more implementations of the present disclosure.

DETAILED DESCRIPTION

[20] The present disclosure provides a method to synchronize two clocks in two stations (e.g., a base station and a mobile station/terminal) by identifying a clock time difference between two local clocks of the two stations, without requiring estimating of a one-way propagation delay or measuring RTT in both stations.

[21] In order to synchronize the clock times in the base station and the mobile station/terminal, the present methods and systems can identify the difference between the local clock time in the base station and the local clock time in the mobile station/terminal. The present methods and systems can achieve synchronization without requiring explicit propagation delay estimation and compensation.

[22] Fig. 1A is a schematic diagram of a wireless communication system in accordance with one or more implementations of the present disclosure. The wireless communication system 100 includes a base station 101 or BS and a mobile station/terminal 103 or MS (e.g., a terminal device, user equipment, etc.). The base station 101 has a local clock 11, whereas the mobile station has a local clock 13. The base station 101 and the mobile station 103 can communicate via an uplink transmission 105 (e.g., from the mobile station 103 to the base station 101) and a downlink transmission 107 (e.g., from the base station 101 to the mobile station 103) so as to perform a clock synchronization process.

[23] Fig. 1B is a schematic diagram illustrating clock time synchronization between a base station (BS) and a mobile station (MS). For the ease of reference, in the present disclosure, the local clock time (tiocai) in the base station is denoted with “m,” and the local clock time in the mobile station is denoted with “n.” The difference between the two local clock time references (e.g., the time for “m=0” and the time for “n=0”) is denoted as “e_clk.” “UL” stands for “uplink,” and “DL” stands for “downlink.” “RX” represents “receiving/reception/receiver” and “TX” represents “transm itting/transm ission/transm itter.”

[24] As shown in Fig. 1B, MS’s local transmission clock time (“ n_{UL TX} ” at MS timing line 111) and BS’s local reception clock time (“ m_{UL RX} ” at BS timing line 113) are associated with an uplink message transmission 115. BS’s local transmission clock time (“ m_DLTX ” at the BS timing line 113) and MS’s local reception clock time (“ n_DL,RX ” at the MS timing line 115) are associated with a downlink message transmission 117. One way delay is indicated as “TPD.” In Fig. 1B, transmission/reception clock time measurement errors (“e_UL,RX” and “e_DLTX" at the BS timing line 113 and “e_ULTX" and “e_{DL RX}" at the MS timing line 111) are also shown.

[25] When the uplink message transmission 115 is performed, the mobile station MS transmits in physical layer at its “intended” local clock time “n'_{U L TX}" an uplink message to the base station BS, where the uplink message contains a clock value of “n'_{U L TX}." Due to hardware timing error, this uplink message transmission 115 “actually” occurs in physical layer at the local clock time of “n_{UL TX} " with the uplink message transmission timing error equal to “e_ULTX = n'_{U L TX} - n_ULTX."

[26] After a propagation delay of “T_PD,” the uplink message transmission 115 carrying the mentioned uplink message is “actually” received at an antenna end of the base station BS at its local clock time “m_{UL RX}." Due to a hardware timing error, the base station takes its local clock time “m'_{UL RX}" as its physical layer reception time, resulting in an uplink reception timing error equal to “e_{UL RX} = m'_{UL RX} - m_{UL RX}." [27] The timing relationship between the mobile station and the base station regarding to the uplink message transmission 115 can be formulated as:

[28] (absolute time for MS clock reference) + n_{UL TX} + T_PD =

(absolute time for BS clock reference) + m_{UL RX}

[29] As mentioned above, the difference between the absolute time for the MS clock reference and the BS clock reference can be noted as “e_cifc.” Substituting the “actual” timings of “m_{UL RX}” and “n_{UL X}" with the “intended/conceived” timings plus the timing errors yields the following equation regarding to the uplink message transmission 115:

[31] For the downlink message transmission 117, the base station transmits in physical layer at its “intended” local clock time “m'_{D L TX}" a downlink message to the mobile station. The downlink message contains either:

[32] [1 ] two values of and or

[33] [2] one value of

[34] Due to a hardware timing error, the downlink message transmission 117

“actually” occurs in physical layer at the base station’s local clock time of “m_{DL TX}" with a downlink transmission timing error equal to

[35] After the propagation delay of TPD (assuming that the propagation delay PD is the same for both downlink and uplink), the downlink message transmission 117 carrying the downlink message is “actually” received at an antenna end of the mobile station at its local clock time “n_{DL RX}." Due to a hardware timing error, the mobile station takes its local clock time “n'_{DL RX}" as the reception time in physical layer, with a downlink reception timing error equal to “e_{DL RX} = n'_{DL RX} - n_{DL RX}”.

[36] Similarly, the timing relationship between the base station and the mobile station regarding to the downlink message transmission 117 can be formulated as:

[37] (2)

[38] Combining Equations (1) and (2) can reach a close-form of the clock difference “e_clk” as:

[40] As shown in Equation (3), the propagation delay (TPD) is not shown in

Equation (3), and therefore the present methods and systems do not need to perform a propagation delay estimation and compensation to determine the clock difference.

[41] Further, based on Equations (1) and (2), a close-form on one-way delay

“ T_PD can be shown as:

[43] Although “ TPD” in Equation (4) may appear to reflect the principle of one way propagation delay estimation based on RTT measurements, nevertheless, this is just one special case of one-way propagation delay estimation where the RTT measurements in the two stations are based on the same pair of downlink transmission and uplink transmission. It is apparent that the present methods and systems follow the principle and operations that are different from those of the one way propagation delay compensation.

[44] In some embodiments, the roles of the base station and the mobile station in determining “e_clk” can be swapped with each other. In addition, the present methods can be implemented not only for the clock synchronization between a base station and a mobile station, but also for the clock synchronization between two mobile stations that communicate with each other on a side-link or between two base stations that communicate with each other on a wireless backhaul link.

[45] In some embodiments, the downlink message can include two pieces of information:

[46] [1] The timing difference ( m'_{UL RX} - n'_{UL TX}) between the local clock time in the mobile station for the uplink message transmission and the local clock time in the base station for the uplink message reception. This timing difference can be considered a “response” to the message of “n'_ULTX" in the uplink message. [47] [2] The local clock time in the base station for the downlink message transmission ( m_{'D L TX} ), which enables a receiving station to measure its local clock time for upon reception (i.e. , the same purpose as the clock time in the uplink message (n_{'U L X})).

[48] In some embodiments, the downlink message can be split into two messages: one message takes the format clone from the uplink message (e.g., to carry m_{'D L TX}), and the other message serves as a response to the uplink message (to carry m'_{UL RX} — n'_{UL TX}).

[49] Fig. 2 is a schematic diagram illustrating a message flow and related timing relations in clock time synchronization between two wireless communication stations in accordance with one or more implementations of the present disclosure. In the illustrated embodiments of Fig. 2, each of the two stations individually transmits, at a given local clock time of its own ( t_TX ), a first type message 201 to the other station. The first type message 201 includes information of given local clock time of the transmitting station ( t_TX ), at which the first type message is transmitted. In some embodiments, the first type message 201 can be carried in either Radio Resource Control (RRC) signaling or Medium Access Control layer Control Element (MAC-CE) signaling.

[50] Once successfully receiving the first type message 201 , at least one of the receiving stations (e.g., Station 1 in Fig. 2) identifies its local clock time ( t_RX ), at which the first type message 201 is received. Later, the receiving station transmits a second type message 203 to the station (e.g., Station 2 in Fig. 2) from which the first type message 201 is received. The second type message can include information for both t_RX and t_TX. In some embodiments, such information can include:

[51] [a] two values corresponding to t_RX and t_TX, or

[52] [b] one value corresponding to ( t_RX - t_TX).

[53] In some embodiments, the purpose for sending t_TX back to the station where t_TX is determined is to identify the pairing between t_RX and t_TX that associate with the same first type message 201 in case multiple first type messages are transmitted in an earlier step. In some embodiments where there is no need to identify the pairing between t_RX and t_TX, “ t_TX " can be dropped so that the second type message 203 contains information corresponding to either t_RX alone or ( t_RX - t_TX). In some embodiments, the second type message 203 can be carried in either RRC signaling or MAC-CE signaling.

[54] In some embodiments, for a station receiving at least one first type message 201 and at least one second type message 203 (e.g., Station 2 in Fig. 2), the first type message 201 and the second type message 203 can be received in separate message signaling or in one combined message signaling. The receiving station (e.g., Station 2 in Fig. 2) can derive the difference between its local clock time and the local clock time in the other station according where

'^s based on the information contained in the received second type

message 203, is the information contained in the received first type message

201 is the local clock time at which the first type message 201 is received.

[55] In some embodiments, referring to Equation (3), a total error term in an estimated clock time difference can be determined_. This

total error term (or a residue error) is caused by the timing errors generated in the transmitters and receivers in both stations. As shown, the total error term includes two transmitting timing errors (e_{UL TX} and e_{DL TX} ) and two receiving timing errors ( e_UL,_RX and e_{DL RX}). The four error components shown in the total error term are time- varying, which means each error component shows randomly a positive value at a moment while randomly a negative value at another moment - this is especially true for the two receiving timing errors ( e_{UL RX} and e_{DL RX} ). This randomness characteristic makes it feasible to somehow reduce the overall error statistically by an averaging technique. Embodiments described in Fig. 3 can serve as an example.

[56] Referring to Fig. 3, multiple first type messages 301 can be sent on the same radio link direction from one station to another station, resulting in multiple pairs of <t_TX, t_RX>. Then the station receiving these multiple first type messages 301 uses an average of {t_TX} and an average of {t_RX}, or an average of {t_RX - t_TX}, to construct a second type message 303 or calculate the clock time difference e_clk. As shown in Fig. 3, the averaging is performed over two first type messages 301 received per transmission direction. [57] In some embodiments, multiple second type messages 303 can also be sent on the same radio link direction from one station to another station. Then the station receiving these multiple second type messages retrieves multiple pairs of {t_TX, t_RX} or multiple {t_RX - t_TX} from these messages, and uses the average of {t_RX - t_TX} to calculate the clock time difference e_clk.

[58] In some embodiments, the total error term in

Equation (3) may not depict the overall error effect in the derived clock time difference e_{clk .} For example, in addition to the timing errors relating to the transmissions/receptions of the messages, quantization errors for the clock time information contained inside those messages can also contribute to the total error according to the following formulation:

[60] In Equation (5a), e_{st1 TX} and e_{st1 RX} are the transmission timing error and reception timing error, respectively (e.g., in Station 1). In some cases where Station 1 is a base station, the 3GPP RAN1 standard has the following assumptions:

[61] In Equation (5a), e_{st2 X} and e_{st2 RX} are the transmission timing error and reception timing error, respectively (e.g., in Station 2). In some case where Station 2 is to a mobile station, the 3GPP RAN4 standard outlines a requirement of

for the subcarrier spacing equal to 15kHz, which is

the main application scenario for clock time synchronization.

[62] “T_g” is the quantization granularity of the signaling delivering the clock time between the two stations, which results in a quantization error of per single

quantization. The coefficient of 3 in corresponds to three quantizations

performed on <a1>, <b1-a1> and <b2> in three messages shown in Fig 2. The existing “3GPP RRC message” of “ReferenceTimelnfo” has the granularity of 10 ns.

[63] Therefore, the total clock synchronization error ( Err_total ) is upper- bounded by which is larger than the available error

budget of 280 ns for control-to-control scenario. In order to meet the 280 ns error budget, the quantization granularity T_g needs to satisfy T_g < 2.9ns. The reduction of reporting granularity from 10 ns to less than 2.9 ns may introduce extra requirements on hardware measurement.

[64] In order to meet the error budget for control-to-control scenario and meanwhile to avoid reducing T_g to a low value, the present disclosure provides a solution to reduce the number of quantization error. More particularly, instead of delivering the clock time between the two wireless stations in a series of three messages including <a₁>, <b₁-a₁> and <b₂>, there are two messaging alternatives that can reach the same clock time difference calculation These

two alternatives are described below with reference to Fig. 4 (“Alternative-1”) and Fig. 5 (“Alternative-2”).

[65] Alternative-1

[66] Referring to Fig. 4, following the message

flow can include:

[67] [1] Station 2 sends to Station 1 a first type message 401 containing which is the local clock time in Station 2 for transmitting the first type

message 401 .

[68] [2] Station 1 measures the reception timing o upon receiving

the first type message 401 (which includes t_TX = a₁) and sends back to Station 2 a second type message 403 containing b₁ + b₂ - a₁ where b₂ is the local clock time in Station 1 for the transmission of the second type message 403.

[69] [3] Station 2 calculates the clock time difference between the two stations as wherein “a₂” is the local clock time in Station 2 for the

reception of the second type message 403 that contains

[70] In the embodiments illustrated in Fig. 4, the first type message 401 of

<a₁> (from Station 2 to Station 1 ) and the second type message 403 of <b + b₂ - a₁> (from Station 1 to Station 2) are delivered with clock time quantization. The total clock time synchronization error can be shown as:

[72] Alternative-2

[73] Referring to Fig. 5, following the message flow can include:

[74] [1] Station 2 sends to Station 1 a first type message 501 containing either no clock time information or t_TX = a₁ which is the local clock time in Station 2 for transmitting the first type message 501.

[75] [2] Station 1 measures the reception timing of t_RX = b upon receiving the first type message 501 and sends back to Station 2 a second type message 503 containing b + b₂ or where b₂ is the local clock time in Station 1 for

transmitting the second type message 503.

[76] [3] Station 2 calculates the clock time difference between the two stations as where

a₁ is the local clock time in Station 2 for the

transmission of the first type message sent earlier, and a₂ is the local clock time in Station 2 for the reception of the second type message 503 that contains b + b₂ or

[77] In the embodiments illustrated in Fig. 5, the message flow includes one time clock time delivery with one quantization, i.e. , the second type message 503 of

<b + b₂> or (from Station 1 to Station 2). Accordingly, the total clock time

synchronization error for Alternative-2 can be shown as:

[79] In Equation (5c), “α = 1/2” if the second type message contains b + b₂ and “α = 1” if the second type message contains

[80] The error performances for the two Alternatives are calculated in Table 1. It can be seen that the granularity in clock time delivery can be larger than 2.9 ns, e.g., “T_g = {4, 8}ns,” when meeting total error budget of 280 ns.

[81] Table 1 : Performance of new clock time synchronization methods

[82] In the embodiments discussed in Fig. 4 (Alternative-1), both the first type message 401 and the second type message 403 can be delivered in either MAC-CE or RRC signaling. For RRC signaling, the “ReferenceTimelnfo IE” with modified clock time granularity can be used. [83] In the embodiments discussed in Fig. 5 (Alternative-2), the first type message 501 that does not need to carry any clock time can be in format of MAC-CE, RRC message or even a physical layer channel/signal whose transmission and reception can be unambiguously identified by the two wireless stations.

[84] For example, the first type message 501 in Alternative-2 can be the last physical layer transmission from Station 2 to Station 1 before the second type message 503 delivered from Station 1 to Station 2, or a signal in an identifier channel (e. g., a MAC-CE or RRC message with an unique message identification). The second type message 503 in Alternative-2 can be delivered in either MAC-CE or RRC signaling. For RRC signaling, the “ReferenceTimelnfo IE” with modified clock time granularity can be used.

[85] In some embodiments, the clock times in the procedures discussed herein (such as and can use either the same or a different clock

time format from the one used by the higher layer clock time. For example, in 3GPP specification, there is a higher layer clock time format with following ASN.1 definition in unit of 10 ns:

[86] In some embodiments, instead of adopting the clock time format as in

ReferenceTime-r16, the clock times (such as and can use a

different clock time format as long as the clock time difference on this clock time format matches the clock time difference on ReferenceTime-r16. For example, the method provided in this application can adopt a local clock time format that contains <refSFN, refTc>, where refSFN indicates the system-frame-number of the local radio frame whose beginning boundary or ending boundary is the starting reference for refTc, and refTc indicates the time in unit of T_c. T_c is the physical layer time unit in 5G New Radio and is defined as T_c=1/(480000*4096)≈5.1 x10¹⁰(second). Each radio frame contains 19660800 T_c.

[87] In some embodiments, if the first type message adopts the message format as defined in “ReferenceTime-r16,” the second type message can use a format based on “ReferenceTime-r16” as well, with following choices:

[88] [1] One second type message contains two “ReferenceTime-r16” fields, one another for

[89] [2] One second type message contains two fields, one field in

“ReferenceTime-r16” format to indicate the absolute value of difference between and and another field of 1-bit to indicate the sign of

[90] In some embodiments, the transmission clock time and the reception clock time of the first or second type messages may not be the exact clock times at which the transmission and reception of the message are performed. However, some clock times have fixed timing relationships with the exact clock times at which the message transmission and reception are performed. For example, the transmission clock time for the first or second type message can be the local clock time corresponding to the starting boundary or the ending boundary of the time- domain frame structure unit in which the first or second type message is transmitted.

[91] In some examples, the frame structure unit can be a radio frame, a subframe or a time slot. Similarly, the reception clock time for the first or second type message can be the local clock time corresponding to the starting boundary or the ending boundary of the time-domain frame structure unit in which the first or second type message is received.

[92] In some embodiments, different message flows can share one common characteristics: assuming that Station 2 is the entity that determines the local clock time difference between Station 1 and Station 2, after the reception of a first type message (or signal and channel) transmitted from Station 2, Station 1 can send the clock time information corresponding to the local clock time of the first-type message reception back to Station 2 in a second type message. The clock time information contained in the second type message and corresponding to the local clock time (denoted as b ) of the first-type message reception can be in various forms, including:

[93] [1 ] b₁ (see, e.g., the embodiments illustrated in Fig. 2);

[94] [2] b - a₁ (see, e.g., the embodiments illustrated in Fig. 2);

[95] [3] < b₁, b₂ > or b₁ + b₂ or (b₁ + b₂ /2 (see, e.g., the embodiments illustrated in Fig. 5); and

[96] [4] b₁ + b₂ - a₁ (see, e.g., the embodiments illustrated in Fig. 4).

[97] Time a₁ is the local clock time in Station 2 for transmitting the first type message for which the local reception clock time in Station 1 is b₁ and b₂ is the local clock time in Station 1 for the transmission of the second type message containing the above listed clock time information of b_2. In some embodiments, the clock time information contained in the second type message can relate to “local clock time in one station”, which is distinctive from the idea of “clock time interval in one station” that is used in prior art as Rx-to-Tx (RTT) time interval.

[98] The present methods and systems can effectively address the following issues. In practice it may be difficult for one wireless station to identify the reception time for a message containing a specific information, especially given the identification of reception time is done in the physical layer processing which occurs in an earlier stage of receiver processing while the interpretation of message information is done in the higher protocol layer which occurs in the later stage of receiver processing. Identification of reception time of a specific message based on message content can be feasible only if the station records the reception time for every received message, which could be challenging because of the transparency of higher layer message to the physical layer processing as well as the implementation complexity. Therefore, it is beneficial to make the receiving station know in advance the time in transmission unit, at which it can expect the arrival of a first type message, so that the station can measure and record the reception time accordingly.

[99] In order to make the station be aware in advance of the reception for which the reception time should be measured, either: [100] [a] The station intending to transmit a first type message sends a third type message or signaling to the peer receiving station to inform of the upcoming transmission of the first type message, where the third message or signaling can be carried in physical layer control channel information, MAC-CE or RRC signaling; or

[101] [b] The station intending to receive a first type message sends a fourth type message or signaling to the peer station to request or schedule a transmission of the first type message at a requested transmission time unit (e.g., a time slot).

[102] Embodiments of a message flow involving third and fourth types of messages are discussed in detail with reference to Fig. 6. The message flow can include a first type message 601 , a second type message 603, a third type message 605, and a fourth type of message 607. As shown in Fig. 6, the fourth type message 607 can be sent from Station 1 (e.g., the station intending to receive the first type message 601) to Station 2. The fourth message 607 is to request or schedule a transmission of the first type message 601.

[103] As also shown in Fig. 6, the third message 605 is for informing an upcoming transmission of the first type message 605. The third message 605 and the first message can be transmitted at the same time if the third message 605 is a physical layer control signaling.

[104] In some embodiments, since the first type message transmission is bi directional between two stations, both the third type and the fourth type messages or signaling can apply in the same message flow between two stations in a single derivation of the clock time difference.

[105] In some embodiments, the application of the third type message or the fourth type message can be independent from whether or not the related first type message is transmitted together with the second type message in a single combined message body.

[106] In some embodiments, a wireless station can measure and record the reception time of the first type message(s) by confining the corresponding transmission(s) and reception(s) of the first type message(s) within a time period. In other words, the starting time instance and ending time instance of the first type message are made known to the wireless station. The wireless station can simply measure and record the reception times for all successful receptions performed within the time period. To establish a starting time and an ending time, a message of “Request to start” and a message of “Confirmation to complete” can be respectively transmitted from any station to another before the beginning and after the ending of the message flow described herein (e.g., Fig. 2).

[107] In some embodiments, the described architecture, 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 and microprocessors. In a communication system of 3GPP New-Radio, the clock time synchronization and related signaling flow and process may be implemented in form of software instructions or firmware instructions for execution by a processor in the transmitter and receiver or the transmission and reception controller. In operation, the instructions are executed by one or more processors to cause the transmitter and receiver or the transmission and reception controller to perform the described functions and operations.

[108] Fig. 7 is a schematic block diagram of a terminal device (or a mobile station) 700 in accordance with one or more implementations of the present disclosure. As shown, the terminal device 700 includes a processing unit 710 (e.g., a DSP, a CPU, a GPU, etc.) and a memory 720. The processing unit 710 can be configured to implement instructions that correspond to the methods described herein. It should be understood that the processor in the implementations of this technology may be an integrated circuit chip and has a signal processing capability. During implementation, the steps in the foregoing method may be implemented by using an integrated logic circuit of hardware in the processor or an instruction in the form of software. The processor may be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or another programmable logic device, a discrete gate or transistor logic device, and a discrete hardware component. The methods, steps, and logic block diagrams disclosed in the implementations of this technology may be implemented or performed. The general-purpose processor may be a microprocessor, or the processor may be alternatively any conventional processor or the like. The steps in the methods disclosed with reference to the implementations of this technology may be directly performed or completed by a decoding processor implemented as hardware or performed or completed by using a combination of hardware and software modules in a decoding processor. The software module may be located at a random-access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, or another mature storage medium in this field. The storage medium is located at a memory, and the processor reads information in the memory and completes the steps in the foregoing methods in combination with the hardware thereof.

[109] It may be understood that the memory in the implementations of this technology may be a volatile memory or a non-volatile memory, or may include both a volatile memory and a non-volatile memory. The non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM) or a flash memory. The volatile memory may be a random-access memory (RAM) and is used as an external cache. For exemplary rather than limitative description, many forms of RAMs can be used, and are, for example, a static random-access memory (SRAM), a dynamic random-access memory (DRAM), a synchronous dynamic random-access memory (SDRAM), a double data rate synchronous dynamic random-access memory (DDR SDRAM), an enhanced synchronous dynamic random-access memory (ESDRAM), a synchronous link dynamic random-access memory (SLDRAM), and a direct Rambus random-access memory (DR RAM). It should be noted that the memories in the systems and methods described herein are intended to include, but are not limited to, these memories and memories of any other suitable type.

[110] Fig. 8 is a flowchart of a method 800 in accordance with one or more implementations of the present disclosure. The method 800 can be implemented by a system (such as the wireless communication system 100), a terminal device, a mobile station, a radio entity (e.g., a device capable of communicate via wireless radio communications) etc. The method 800 is for determining a local clock time difference between a first station and a second station. In various embodiments, the first station can be a base station, a network device, etc. In some embodiments, the second station can be a mobile station, a mobile terminal, a terminal device, user equipment, etc.

[111] The method 800 includes, at block 801, transmitting, by the second station, a first first-type message to the first station. The first first-type message is indicative of a first local clock time (e.g., “a₁” of Station 2 timing shown in Figs. 2-6) of the second station (e.g., Station 2). Embodiments of the first-type message include first type messages 201, 301, 401, 501, and 601 transmitted by Station 2. Embodiments of the first first-type message can include “t_TX=a₁” shown in Figs. 2-6.

[112] At block 803, the method 800 continues by receiving, by the second station, a second-type message from the first station. The second-type message includes clock time information corresponds to the first local clock time of the first station. Embodiments of the second-type message include second type messages 203, 303, 403, 503, and 603. As illustrated in Figs. 2-6, the second type message can include clock time information corresponding to a first local clock time (e.g., “b₁” of Station 1 timing shown in Figs. 2-6) of the first station (e.g., Station 1 ).

[113] At block 805, the method 800 continues by receiving, by the second station, a second first-type message from the first station. The second first-type message is indicative of a second local clock time of the first station. Embodiments of the second first-type message include first type messages 201, 301, 401, 501, and 601 transmitted by Station 1.

[114] At block 807, the method 800 proceeds to determine, by the second station, the local clock time difference between the first station and the second station at least based on the second-type message and the second first-type message. Embodiments of the local clock time difference include the clock difference “e_clk" described in Equations (3) and other relevant descriptions. For example, the first portion of Equation (3) “ is known and

can be provided by Stations 1 and 2. As described above, the second portion of Equation (3) can be determined based on two transmitting

timing errors (e_{UL X} and e_{DL TX}) and two receiving timing errors (e_{UL RX} and e_{DL RX}). As a result, the clock difference “e_clk” can be determined. [115] In some embodiments, the first local clock time of the second station includes a local clock time when the first first-type message is transmitted by the second station (e.g., t_TX=a₁ in Fig. 2). In some embodiments, the second local clock time of the first station includes a local clock time when the second first-type message is transmitted by the first station (e.g., t_TX=b₂ in Fig. 2). In some embodiments, the first and second first-type messages can include a signal in an identifiable channel (e.g., in Fig. 5, the first type message can include no clock time).

[116] In some embodiments, the clock time information of the second-type message includes an average of local clock times in the first station when one or more of first-type messages are received (e.g., an average of “bi” values received by Station 1 ). In some embodiments, the clock time information of the second-type message includes an average of one or more (b - a₁) values (e.g., Fig. 2, Fig. 3, and Fig. 6). “a₁’ value corresponds to when one or more of first-type messages are transmitted by the second station, and “b₁ value corresponds to when the one or more of first-type messages are received by the first station.

[117] In some embodiments, the second first-type message and the second- type message can be combined by the first station into a single modified second- type message (e.g., Fig. 4 and Fig. 5). The single modified second-type message includes value

and value b₂, wherein the value b₁ is a local clock time of the first station when the first first-type message is received, wherein the value b₂ is a local clock time of the first station when the single modified second-type message is transmitted. In some embodiments, clock time information contained in the single modified second type message is α(b₁ + b₂), and a can be either 0.5 or 1 (e.g., Equation (5c)).

[118] In some embodiments, the local clock time difference can be determined by the second station a (e.g., Fig. 4 and Fig. 5). Value <¾ is a local clock

time of the second station when the first first-type message is transmitted by the second station, wherein value b is a local clock time of the first station when the first first-type message is received by the first station. Value b₂ is a local clock time of the first station when the second first-type message is transmitted by the first station. Value a₂ is a local clock time of the second station when the second first-type message is received by the second station. [119] In some embodiments, the second station is a mobile terminal, and wherein the first station is a base station. In other embodiments, the first and second stations can both be base stations or both be mobile terminals.

[120] In the illustrated embodiments, the method 800 is implemented by a mobile terminal, mobile station, or a terminal device. In other embodiments, the steps described in the method 800 can also be implemented by a base station (e.g., replacing a “transmitting” step by a “receiving” step or vice versa). The method 800 provides examples of the present methods and in no way limits the present methods.

[121] The above Detailed Description of examples of the disclosed technology is not intended to be exhaustive or to limit the disclosed technology to the precise form disclosed above. While specific examples for the disclosed technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the described technology, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative implementations may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified to provide alternative implementations or sub-combinations. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed or implemented in parallel, or may be performed at different times. Further, any specific numbers noted herein are only examples; alternative implementations may employ differing values or ranges.

[122] In the Detailed Description, numerous specific details are set forth to provide a thorough understanding of the presently described technology. In other implementations, the techniques introduced here can be practiced without these specific details. In other instances, well-known features, such as specific functions or routines, are not described in detail in order to avoid unnecessarily obscuring the present disclosure. References in this description to “an implementation/embodiment,” “one implementation/embodiment,” or the like mean that a particular feature, structure, material, or characteristic being described is included in at least one implementation of the described technology. Thus, the appearances of such phrases in this specification do not necessarily all refer to the same implementation/embodiment. On the other hand, such references are not necessarily mutually exclusive either. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more implementations/embodiments. It is to be understood that the various implementations shown in the figures are merely illustrative representations and are not necessarily drawn to scale.

[123] Several details describing structures or processes that are well-known and often associated with communications systems and subsystems, but that can unnecessarily obscure some significant aspects of the disclosed techniques, are not set forth herein for purposes of clarity. Moreover, although the following disclosure sets forth several implementations of different aspects of the present disclosure, several other implementations can have different configurations or different components than those described in this section. Accordingly, the disclosed techniques can have other implementations with additional elements or without several of the elements described below.

[124] Many implementations or aspects of the technology described herein can take the form of computer- or processor-executable instructions, including routines executed by a programmable computer or processor. Those skilled in the relevant art will appreciate that the described techniques can be practiced on computer or processor systems other than those shown and described below. The techniques described herein can be implemented in a special-purpose computer or data processor that is specifically programmed, configured, or constructed to execute one or more of the computer-executable instructions described below. Accordingly, the terms “computer” and “processor” as generally used herein refer to any data processor. Information handled by these computers and processors can be presented at any suitable display medium. Instructions for executing computer- or processor-executable tasks can be stored in or on any suitable computer-readable medium, including hardware, firmware, or a combination of hardware and firmware. Instructions can be contained in any suitable memory device, including, for example, a flash drive and/or other suitable medium.

[125] The term “and/or” in this specification is only an association relationship for describing the associated objects, and indicates that three relationships may exist, for example, A and/or B may indicate the following three cases: A exists separately, both A and B exist, and B exists separately.

[126] These and other changes can be made to the disclosed technology in light of the above Detailed Description. While the Detailed Description describes certain examples of the disclosed technology, as well as the best mode contemplated, the disclosed technology can be practiced in many ways, no matter how detailed the above description appears in text. Details of the system may vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the disclosed technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the disclosed technology with which that terminology is associated. Accordingly, the invention is not limited, except as by the appended claims. In general, the terms used in the following claims should not be construed to limit the disclosed technology to the specific examples disclosed in the specification, unless the above Detailed Description section explicitly defines such terms.

[127] A person of ordinary skill in the art may be aware that, in combination with the examples described in the implementations disclosed in this specification, units and algorithm steps may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether the functions are performed by hardware or software depends on particular applications and design constraint conditions of the technical solutions. A person skilled in the art may use different methods to implement the described functions for each particular application, but it should not be considered that the implementation goes beyond the scope of this application.

[128] Although certain aspects of the invention are presented below in certain claim forms, the applicant contemplates the various aspects of the invention in any number of claim forms. Accordingly, the applicant reserves the right to pursue additional claims after filing this application to pursue such additional claim forms, in either this application or in a continuing application.

Claims

CLAIMS I/We claim:

1. A method for determining a local clock time difference between a first station and a second station, comprising: transmitting, by the second station, a first first-type message to the first station, wherein the first first-type message is indicative of a first local clock time of the second station; receiving, by the second station, a second-type message from the first station, wherein the second-type message includes clock time information corresponding to a first local clock time of the first station; receiving, by the second station, a second first-type message from the first station, wherein the second first-type message is indicative of a second local clock time of the first station; and determining, by the second station, the local clock time difference between the first station and the second station at least based on the second- type message and the second first-type message.

2. The method of claim 1 , wherein the first local clock time of the second station includes a local clock time when the first first-type message is transmitted by the second station.

3. The method of claim 1 , wherein the second local clock time of the first station includes a local clock time when the second first-type message is transmitted by the first station.

4. The method of claim 1, wherein the first and second first-type messages include a signal in an identifiable channel.

5. The method of claim 1, wherein the clock time information of the second-type message includes an average of local clock times in the first station when one or more of first-type messages are received by the first station.

6. The method of claim 1, wherein the clock time information of the second-type message includes an average of one or more (b₁ - a₁) values, wherein a₁ value corresponds to the first local clock time of the second station when one or more of first-type messages are transmitted by the second station, wherein

value corresponds to the first local clock time of the first station when the one or more of first-type messages are received by the first station.

7. The method of claim 1 , wherein the second first-type message and the second-type message are combined by the first station into a single modified second-type message, wherein the single modified second-type message includes value and value b₂, wherein the value b is the first local clock time of the first station when the first first-type message is received by the first station, wherein the value b₂ is the second local clock time of the first station when the single modified second-type message is transmitted by the first station.

8. The method of claim 7, wherein clock time information contained in the single modified second type message is α(b + b₂ ), and wherein a is either 0.5 or 1.

9. The method of claim 1, wherein the local clock time difference is determined by the second station wherein value a₁ is a local clock

time of the second station when the first first-type message is transmitted by the second station, wherein value b_t is the first local clock time of the first station when the first first-type message is received by the first station, wherein value b₂ is the second local clock time of the first station when the second first-type message is transmitted by the first station, and wherein value a₂ is a second local clock time of the second station when the second first-type message is received by the second station.

10. The method of claim 1 , wherein the second station is a mobile terminal, and wherein the first station is a base station.

11. An apparatus for determining a local clock time difference with an external device, comprising: a processor; and a memory configured to store instructions, when executed by the processor, to: transmit a first first-type message to the external device, wherein the first first-type message is indicative of a first local clock time of the apparatus; receive a second-type message from the external device, wherein the second-type message includes clock time information corresponding to a first local clock time of the external device; receive a second first-type message from the external device, wherein the second first-type message is indicative of a second local clock time of the external device; and determine the local clock time difference between the apparatus and the external device at least based on the second-type message and the second first-type message.

12. The apparatus of claim 11, wherein the first local clock time of the apparatus includes a local clock time when the first first-type message is transmitted by the apparatus, and wherein the apparatus is a mobile terminal.

13. The apparatus of claim 11, wherein the second local clock time of the external device includes a local clock time when the second first-type message is transmitted by external device, and wherein the external device is a base station.

14. The apparatus of claim 11, wherein the clock time information of the second-type message includes an average of local clock times in the external device when one or more of first-type messages are received by the external device.

15. The apparatus of claim 11, wherein the clock time information of the second-type message includes an average of one or more

b₁ - a₁) values, wherein a₁ value corresponds to the first local clock time of the apparatus when one or more of first-type messages are transmitted by the apparatus, wherein

value corresponds to the first local clock time of the external device when the one or more of first-type messages are received by the external device.

16. A base station for facilitating a terminal device to determine a local clock time difference, comprising: a processor; and a memory configured to store instructions, when executed by the processor, to: receive a first first-type message from the terminal device, wherein the first first-type message is indicative of a first local clock time of the terminal device; transmit a second-type message to the terminal device, wherein the second-type message includes clock time information corresponding to a first local clock time of the base station; and transmit a second first-type message to the terminal device, wherein the second first-type message is indicative of a second local clock time of the base station; wherein the second-type message and the second first-type message are for the terminal device to determine the local clock time difference between the terminal device and the base station.

17. The base station of claim 16, wherein the first local clock time of the terminal device includes a local clock time when the first first-type message is transmitted by the terminal device.

18. The base station of claim 16, wherein the second local clock time of the base station includes a local clock time when the second first-type message is transmitted by base station.

19. The base station of claim 16, wherein the clock time information of the second-type message includes an average of local clock times in the base station when one or more of first-type messages are received by the base station.

20. The base station of claim 16, wherein the clock time information of the second-type message includes an average of one or more

b₁ - a₁) values, wherein a₁ value corresponds to the first local clock time of the terminal device when one or more of first-type messages are transmitted by the terminal device, wherein

value corresponds to the first local clock time of the base station when the one or more of first-type messages are received by the base station.