CN1342378A - Method for detecting and compensating for radio link timing errors - Google Patents

Abstract

A method for detecting and compensating for radio link timing errors in a mobile communication system is disclosed, whereby a mobile station (16) determines that one or more radio link transmissions (14) from the network are outside or nearly outside of that mobile station's (16) receiving time window (18), and reports such information to the network for appropriate action.

Description

Detection and Compensation Method of Radio Circuit Timing Error

This patent application claims benefit of co-pending US Patent Application Serial No. 60/174,064, filed December 30, 1999, the entire contents of which are hereby incorporated by reference.

technical field of invention

The present invention relates generally to the field of mobile communications, and in particular to methods for detection and compensation of radio link timing errors.

Background technique

The operation of certain mobile communication systems, such as Code Division Multiple Access (CDMA) or Time Division Multiple Access (TDMA) mobile communication systems, relies on the use of timing references for synchronization. Locally, in the base station (BS) the timing reference is generated by an internal oscillator. However, the internal oscillator can also be locked or synchronized to an external long-term timing reference.

Certain design issues are related to the use of BS timing references for network time synchronization. For example, an oscillator used in a BS to generate an internal timing reference may have a frequency drift which will reduce the accuracy of the generated timing reference. Also, the timing of the BS (as seen by the mobile station (MS)) may shift or slip in time because the MS is moving closer to or away from the BS (mobility) or the radio environment is changing and generally varies over time ( time discrete). This problem is sometimes referred to as "MS Timing Drift" and it can be seen that in any case the propagation delay over the radio link varies with time.

In a mobile communication network, each BS may define one or more cells. Each unit connects the BS (and radio network) with a dedicated MS via a separate radio link (radio air interface connection). In general, there are no specific timing issues between different/multiple radio links belonging to one BS and directed to one MS. However, when two or more units belong to different BSs, the timing between these units can create significant design problems. For this, each MS has a "reception window" or time interval within which all radio link transmissions are to be received.

Operating under the "IS-95" and "CDMA2000" protocols Determining the timing reference for mobile systems is based on the use of highly accurate Global Positioning System (GPS) timing signals, which provide relatively stable timing at all network nodes refer to. Therefore, as in IS-95 and CDMA2000 systems, each BS has a timing reference that is relatively more precise than the BS internal timing, whereby it can be used to maintain the transmission of the radio link during the MS's receive time window. However, due to MS mobility and/or time dispersion, the radio link transmission may still move into the receive time window. In any case, there are significant design issues for these mobile systems (e.g. CDMA) that use small precision BS internal time synchronization methods, because in such systems some radio link(s) may receive Move out of the time window.

In existing and developing mobile communication systems (such as some broadband CDMA or WCDMA systems), when an MS is connected to multiple units of different BSs through radio lines, the synchronization between these units can be achieved in phase move. This problem arises because these systems do not use an absolute time reference (such as GPS) to synchronize the different BSs involved. In fact, the problem of "phase shifting" which is inappropriate in this respect can be considered to be caused by the use of non-absolute timing references for BS internal synchronization, or the use of some inappropriate method of network time synchronization (such as suboptimal or method that does not always work) caused.

The scheme of transition evolution among the very different various existing cellular systems is based on the signal power level received by the MS. However, this approach cannot generally be used in a network to determine if a radio link transmission is outside the MS reception time window. Therefore, there is clearly a great need for a mobile communication system operating without a precise network timing reference to be able to determine when one or more radio link transmissions have moved outside or close to the MS receive time window. As will be described in detail below, the present invention successfully solves this and other related problems.

Contents of the invention

According to a preferred embodiment of the present invention, there is provided a detection method for a radio link timing error and an apparatus for compensating the same, wherein it is determined by the MS that one or more radio link transmissions are outside or close to the outside of the MS reception time window, and report the information to the website for appropriate action.

An important technical advantage of the present invention is that it provides a method for time synchronization of mobile communication networks which does not require the use of an absolute timing reference, such as GPS.

Another important technical advantage of the present invention is that it provides a method for reducing the effect of phase shifts between units in a mobile communication system.

Yet another important technical advantage of the present invention is that it provides a method of improving the BS internal timing accuracy in a mobile communication system, thereby reducing the BS timing uncertainty (for the MS), which will improve the cell search process.

Description of drawings

The method and device of the present invention will be more fully understood by referring to the following detailed description in conjunction with the accompanying drawings, and the accompanying drawings are:

1A, 1B and 1C are schematic diagrams illustrating how to detect and compensate radio link timing errors according to a preferred embodiment of the present invention;

2A and 2B are schematic diagrams representing a second aspect of the preferred embodiment;

3A and 3B are schematic diagrams representing a third aspect of the preferred embodiment;

4A and 4B are schematic diagrams showing a fourth aspect of the preferred embodiment.

Specific implementation method

The preferred embodiment of the present invention and its advantages are best understood with reference to the illustrations of Figures 1A-4B of the drawings.

Basically, in accordance with a preferred embodiment of the present invention there is provided a method of detection and compensation of radio link timing errors, wherein the MS determines that one or more radio link transmissions are outside or close to the outside of the MS receive time window, and the information Report to the network on the uplink for appropriate action. Thresholds for determining whether a radio link transmission is outside the MS reception time window are communicated by the network to the MS.

Specifically, FIGS. 1A, 1B and 1C are schematic diagrams illustrating how to detect and compensate radio link timing errors according to a preferred embodiment of the present invention. Referring to Figure 1A, there is shown an area 10 of an exemplary mobile communication system. For example, the system may be a CDMA system which operates according to existing or future CDMA protocols (eg IS-95, CDMA2000, or so called third generation systems). However, the invention is not limited to systems operating according to a specific protocol, and may include, for example, any communication system in which radio link timing issues need or should be resolved.

System 10 includes base station (BS) 12, which is connected to the network by a suitable communication link. According to the illustrated structure, BS 12 defines individual cells and associated radio links 14 . Thus, an MS 16 can be connected to the BS 12 via the radio link 14 to communicate with the network.

Figure 1B illustrates how an MS (eg, 16) can determine whether a radio link (eg, 14) transmission is moving out of (or close to being used for) the MS receive time window (eg, 18), in accordance with the preferred embodiment of the present invention. Typically, one downlink (forward) code is used for each radio link. These codes should be orthogonal to the BS. Therefore, for the exemplary embodiment, the establishment of a new radio link should be aligned with close together 256-chip boundaries. Thus in third generation CDMA systems the radio link can be located relatively close to the MS reception time window since eg there is no fixed/precise BS internal synchronization.

As shown, a radio link (14) is involved for this exemplary embodiment. If the receiving radio link 14 is located relatively close to the center of the MS receive timing window 18, and there are no sudden changes in the BS-to-MS distance or radio environment, the MS can relatively slowly and accurately follow the downlink signal with the timing of the uplink transmission. On the other hand, however, if the receiving radio link is located sufficiently far from the receive timing window 18, this situation can cause more complex problems (which are addressed by the present invention as described below).

For this exemplary embodiment, referring now to FIG. 1C, it can be assumed that MS 16 has just completed switching from one or more additional units (not shown) to units associated with B2 12 and radio link 14. And each additional radio link (connected before the switchover) has been released from its connection with MS16. The remaining radio links 14 received by the MS 16 are offset from the center of the receive time window 18, for example by 128 chips. Since the width of the reception time window from one boundary to the other is in this example slightly larger than 256 chips, the received radio link 14 is located in the vicinity of the boundary of the reception time window 18 . Thus, a slight movement of the radio link (eg due to time dispersion effects or changes in the radio environment) can cause the radio link to "slide out" of the receive time window. Therefore, according to the preferred embodiment of the present invention, the MS 16 sends a message to the network (on the uplink) which reports that the radio link 14 has moved outside the boundaries of the radio network which was previously signaled to the MS. These boundaries represent a slightly smaller window size than the MS receive time window 18 . The web can then take appropriate action in response to the report (see detailed discussion below).

Alternatively, before the radio link 14 actually moves out of the receive time window, the MS 16 can send a message to the network (on the uplink) reporting that the radio link 14 has approached the boundary of the window 18. As also discussed in more detail below, the network may take appropriate action in response to the report. For example, if the radio link transmission deviates from the center of the time window by more than selected predetermined values (ie each value corresponds to a "side" of the window), the MS can be directed to send a report message to the network. For example, a time window may include two thresholds. One of the thresholds corresponds to a "less than" report from the MS (e.g., to the left of the first boundary. The other threshold corresponds to a "greater than" report from the MS (e.g., to the right of the second boundary). Therefore, when responding, the The network takes appropriate action to adjust the timing of the radio link in order to reposition the radio link to an acceptable position within the window.

2A and 2B are schematic diagrams showing a second aspect of the preferred embodiment. In this example, referring to Figure 2A, MS 16 is connected to the network via two radio links 14 and 114 (via BS 12 and 112, respectively). However, as shown in FIG. 2B, the two radio links 14 and 114 are significantly separated in time (eg, BSs 12 and 112 are connected to different BSs). In this case, MS 16 may select one radio link to follow (eg the strongest radio link) in the receive time window. However several different timing issues may arise.

For example, one radio link may slip away from the other due to time dispersion or mobility effects and changes in the line of sight between transmitter and receiver (i.e. radio links may change between being in and out of line of sight), Or a radio link may disappear from the window and then pop up (measured) outside the window. For this example, according to the invention, the MS can transmit a message to the network reporting that no radio link has been detected within a predetermined time interval. Notably, a design choice (but not considered as a limitation on the invention) is that two windows may be used to detect radio links. A larger window can be used whereby the MS (eg User Equipment or UE) can detect radio links within this window. A smaller window can also be used, whereby the MS can report to the network that the radio link is located near the border of the larger window. However, for this example, if the radio link suddenly moves outside the larger window, the MS will most likely not detect the radio link and therefore cannot report this information to the network.

3A and 3B are schematic diagrams showing a third aspect of the preferred embodiment. In this example, referring to FIG. 3A, MS 16 is connected to the network via three radio links 14, 114 and 214 (via BSs 12, 112 and 212, respectively). Referring to FIG. 3B, the MS can determine the action to take according to the relevant specific circumstances. Preferably, the MS reports all radio links detected to the network. Also, the network can request relevant information about the measurement unit from the MS and then decide what action to take. It should be noted that although the term "MS" is exemplified here for mobile station, mobile terminal, mobile radiotelephone, etc., the equivalent term "user equipment or UE" could also be used.

As an alternative, according to one embodiment of the invention, if the weakest radio link (eg 214) moves out of the MS reception time window, the MS (16) can send a message to the network reporting that the radio link (214) Moved out of receive window. On the other hand, if the strongest radio link (eg 14) moves out of the MS reception time window, MS 16 can be instructed by the network to maintain connection with the strongest radio link (following the window) and terminate communication with both Connection of weaker lines. Therefore, the network can interrupt the MS's radio link (or related) reporting and instruct the MS to ignore or terminate the radio link that has threatened the uplink transmission power control timing. Like the second aspect of this embodiment, the radio link can "slide out" of the receive time window.

4A and 4B are schematic diagrams showing a fourth aspect of the preferred embodiment. In this example, referring to Figure 4A, MS 16 is connected to the network via four radio links 14,114, 214 and 314. But in this case, four radio links are associated with four BSs and have two different timing domains (i.e. radio links 14 and 114 are associated with BS12 and BS112 and radio links 214 and 314 are associated with BS212 and BS312) . Referring to Fig. 4B, if two radio links (such as 214 and 314) move out of the MS's timing window, then MS 16 will send a message to the network, which can interpret the report as: two radio links can be removed from the active set of radio links remove. Notably, according to 3GPP, the noun "active set" can be defined as referring to specific communication services between both user equipment and UTRAN (Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network) entry points. A "UTRAN entry point" may be defined as a conceptual point within UTRAN that performs radio transmission and reception. A UTRAN entry point is associated with a specific unit such that there is one UTRAN entry point for each unit. A UTRAN entry point is a radio link UTRAN value endpoint.

The radio network can respond in a number of different ways when responding to a report from an MS that the radio link is at or close to being outside the MS reception time window. For example, the network may remove the radio link from the active set and wait until the MS sends a message reporting that the MS has detected a new neighbor and associated radio link to be placed in the active set. The network then connects the radio link to the MS, which receives transmissions during timing windows. Alternatively, the network is directly connected to a radio link reported to be outside the MS's timing window, and the MS is instructed to include that radio link in the active set. Therefore, the network does not need to wait for a report from the MS of a new neighbor, and the network can directly establish the radio link after it has been deleted.

As another alternative, the radio network may connect into the same cell another copy of the radio link that is reported to be outside or near the MS reception time window and then remove the first radio link from the active set. As a further alternative, the radio network can update the active set by sending a "replacement" message to the MS, then remove the first radio link and add the second radio link instead. In this case, the timing of the new radio link may differ from the timing of the first radio link.

While preferred embodiments of the method and apparatus of the present invention have been depicted in the drawings and described in the foregoing detailed description, it is to be understood that the invention is not limited to the disclosed embodiments without departing from the following claims It is susceptible to various rearrangements, modifications and substitutions without departing from the spirit of the invention as defined in the book.

Claims (24)

1. the detection of radio link timing errors and compensation method in the mobile radio communication may further comprise the steps:

Detection is from the timing of the radio link transmission of described mobile radio communication;

Whether the timing of determining the radio link transmission detected is in the outside of time of reception window; And

If the timing of the radio link of described detection transmission then sends an information to described net in the outside of described time of reception window, described information indication: the timing of the radio link transmission of described detection is in the outside of described time of reception window.

2. according to the process of claim 1 wherein that described determining step also comprises: determine whether the timing of the radio link transmission of described detection closely is positioned at the outside of described time of reception window; And

If the timing of the radio link of described detection transmission closely is positioned at the outside of described time of reception window, then send an information to described net, described information indication: the timing of the radio link transmission of described detection closely is positioned at the outside of described time of reception window.

3. according to the method for claim 1 or 2, also comprise step: respond described information, described net is regulated the timing of described radio link transmission.

4. according to the method for claim 1 or 2, also comprise step: respond described information, described net removes described radio link from effective group.

5. according to the method for claim 4, also comprise step: respond described information, described radio link is connected to travelling carriage.

6. according to the method for claim 14, also comprise step:

Respond described information, described net is connected to travelling carriage with described radio link; And

Instruct described travelling carriage with in the effective group of described radio link income.

7. according to the method for claim 1 or 2, also comprise step:

Respond described information, described net connects the circuit that duplicates of described radio link in same unit; And

Described radio link is removed from effective group.

8. according to the method for claim 1 or 2, also comprise step:

Respond described information, described net sends a replacement information and gives travelling carriage to upgrade effective group; And

Described radio link is removed from effective group; And

Effectively adding second radio link in the group.

9. according to the process of claim 1 wherein that described net comprises the CDMA net.

10. according to the process of claim 1 wherein that determining step is further comprising the steps of:

Travelling carriage receives at least one radio link transmit timing threshold value from described mobile radio communication; And

Radio link transmit timing and described at least one radio link transmit timing threshold with described detection.

11. the detection of radio link timing errors and compensation method in the mobile radio communication may further comprise the steps:

Detection is from the timing of a plurality of radio link transmission of described mobile radio communication;

Determine timing at least one inside whether of a plurality of radio links transmission of described detection at the time of reception window; And

If at least one inside of a plurality of radio link transmit timings of described detection at described time of reception window, whether second of a plurality of radio link transmit timings who then determines whether described detection be in fact from the predetermined value in the center of described time of reception window, if words, send an information to net, described information indicate described detection a plurality of radio link transmit timings described second in fact from the described predetermined value in the center of described time of reception window.

12. according to the method for claim 11, also comprise step: respond described information, described net is regulated described second timing of a plurality of radio link transmit timings of described detection.

13. according to the method for claim 11, wherein said net comprises the CDMA net.

14. according to the method for claim 11, wherein determining step is further comprising the steps of:

Travelling carriage receives at least one radio link transmit timing threshold value from described mobile radio communication; And

At least one and described at least one radio link transmit timing threshold with a plurality of radio link transmit timings of described detection.

15. according to the method for claim 11, wherein said predetermined value comprises the threshold value that is received from described mobile radio communication by travelling carriage.

16. the detection of radio link timing errors and bucking-out system in the mobile radio communication, it comprises:

Be used to detect device from the timing of the radio link transmission of described mobile radio communication;

Whether the timing that is used to determine the radio link transmission that detected is at the time of reception device of face outside window; And

When outside at described time of reception window of the timing of the radio link of described detection transmission, be used to send the device of an information to described net, described information indication: the timing of the radio link transmission of described detection is in the outside of described time of reception window.

17. according to the system of claim 16, the wherein said device that is used to determine comprises also whether the timing of the radio link transmission that is used for definite described detection closely is positioned at the described time of reception device of face outside window; And

When the timing of the radio link of described detection transmission closely is positioned at described time of reception outside window during face, be used to send the device of an information to described net, described information indication: the timing of the radio link transmission of described detection closely is positioned at the outside of described time of reception window.

18. the system according to claim 16 or 17 also comprises: be used to respond the device that described information is regulated described radio link transmit timing.

19. the system according to claim 16 or 17 also comprises: be used for responding described information from effective group of device that removes described radio link.

20. the system according to claim 16 also comprises: be used to respond the device that described information is connected to described radio link travelling carriage.

21. the system according to claim 16 also comprises: be used for responding the device that described information is connected to travelling carriage with described radio link and instructs described travelling carriage that described radio link income is effectively organized.

22. the system according to claim 16 or 17 also comprises: be used for responding described information connects described radio link in same unit the device that duplicates circuit and described radio link is removed from effective group.

23. the system according to claim 16 or 17 also comprises: be used to respond described information and send a replacement information and give travelling carriage, described radio link is removed from effective group, and in effective group, add the device of second radio link to upgrade effective group.

24. according to the system of claim 16, wherein said net comprises the CDMA net.

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