Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W56/00—Synchronisation arrangements
  • H04W56/001—Synchronization between nodes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
  • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
  • H04B7/2662—Arrangements for Wireless System Synchronisation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W56/00—Synchronisation arrangements
  • H04W56/0055—Synchronisation arrangements determining timing error of reception due to propagation delay
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W92/00—Interfaces specially adapted for wireless communication networks
  • H04W92/04—Interfaces between hierarchically different network devices
  • H04W92/10—Interfaces between hierarchically different network devices between terminal device and access point, i.e. wireless air interface

Definitions

• the present invention relates in general to the mobile communications field and, in particular, to a method that can be used in a mobile communication system to detect and compensate for radio link timing errors.
• Description of Related Art The operations of certain mobile communication systems such as, for example,
• CDMA Code Division Multiple Access
• TDMA Time Division Multiple Access
• each BS can define one or more cells.
• Each cell connects the BS (and the radio network) to a particular MS via a unique radio link (radio air interface connection).
• a unique radio link radio air interface connection
• the timing between such cells may create a significant design problem.
• each MS has a "receiving time window" or interval within which all radio link transmissions are to be received.
• GPS timing signals which provide a relatively stable timing reference in all network nodes. Consequently, for example, in IS-95 and CDMA2000 systems, each BS has a relatively accurate timing reference with respect to inter-BS timing that can be used to maintain the radio link transmissions in the MSs' receiving time windows. However, the radio link transmissions can still move within the receiving time windows due to the effects of MS mobility and/or time dispersion. In any event, a significant design problem exists for those (e.g., CDMA) mobile systems that use the less accurate inter-BS time synchronization methods, because some (one or more) of the radio links in such systems can move out of the MSs' receiving time windows.
• CDMA Code Division Multiple Access
• a method for detecting and means for compensating for radio link timing errors is provided, whereby an MS determines that one or more radio link transmissions are outside or nearly outside of that MS's receiving time window, and reports such information to the network for appropriate action.
• An important technical advantage of the present invention is that a method for mobile communication network time synchronization is provided that does not require the use of an absolute timing reference such as the GPS.
• Another important technical advantage of the present invention is that a method is provided for minimizing the effects of phase drift between cells in a mobile communication system.
• Still another important technical advantage of the present invention is that a method is provided for improving the accuracy of inter-BS timing in a mobile communication system and thereby decreasing the uncertainty (for an MS) of other BS timing, which improves cell searching processes.
• FIGURES 1A, IB and 1C are related diagrams that illustrate how radio link timing errors can be detected and compensated for, in accordance with a preferred embodiment of the present invention
• FIGURES 2A and 2B are related diagrams that illustrate a second aspect of the preferred embodiment
• FIGURES 3 A and 3B are related diagrams that illustrate a third aspect of the preferred embodiment.
• FIGURES 4A and 4B are related diagrams that illustrate a fourth aspect of the preferred embodiment.
• a method for detecting and compensating for radio link timing errors is provided, whereby an MS determines that one or more radio link transmissions are outside or nearly outside of that MS's receiving time window, and reports such information to the network on the uplink for appropriate action.
• the threshold levels that are used to determine whether or not a radio link transmission is outside the MS's receiving time window, are sent to the MS from the network.
• FIGURES 1 A, 1 B and 1 C are related diagrams that illustrate how radio link timing errors can be detected and compensated for, in accordance with a preferred embodiment of the present invention.
• a section 10 of an exemplary mobile communication system is shown.
• such a system can be a CDMA system that functions in accordance with an existing or future CDMA protocol (e.g., IS-95, CDMA2000, or the so-called 3 rd Generation system).
• the present invention is not limited to a system that functions in accordance with a particular protocol and can include, for example, any telecommunication system with radio link timing problems that need to or should be resolved.
• System 10 includes a Base Station (BS) 12, which is connected via an appropriate communications link to a network.
• BS Base Station
• FIGURE IB is a timing diagram that illustrates how an MS (e.g., 16) can determine if a radio link (e.g., 14) transmission is moving out (or has nearly moved out) of the MS's receiving time window (e.g., 18), in accordance with the preferred embodiment of the present invention.
• a radio link e.g., 14
• the MS's receiving time window e.g., 18
• one downlink (forward) code is used for each radio link.
• These codes should be orthogonal with respect to a BS. Consequently, for this exemplary embodiment, a new radio link setup should be aligned to the closest 256-chip boundary. Therefore, in a 3 rd Generation CDMA system, for example, since no tight/accurate inter-BS synchronization exists, a radio link can be positioned relatively close to a border of an MS's receiving time window.
• one radio link (14) is involved. If the received radio link 14 is located relatively close to the center of the MS's timing window 18, and there is no sudden change in the MS's distance from the BS or in the radio environment, the MS can follow the downlink signal relatively slowly and accurately with the timing of the uplink transmission. However, on the other hand, if the received radio link is located far enough away from the center of the window 18, then this situation can create a more complicated problem (which, as described below, the present invention resolves).
• the MS 16 has just completed a handover from one or more other cells (not shown) to the cell associated with the BS 12 and radio link 14. Also, each of the other radio links (connected prior to the handover) has been released from its respective connection with the MS 16.
• the remaining radio link 14 being received by the MS 16 is offset from the center of the receiving time window 18 by, for this example, approximately 128 chips. Since the width of the receiving time window from boundary to boundary is, for this example, slightly larger than 256 chips, the received radio link 14 is located near a boundary of the receiving time window 18.
• the MS 16 transmits a message to the network (on the uplink) which reports that the radio link 14 has moved beyond the borders that the radio network had previously signaled to the MS. These borders could represent a slightly smaller window size than that of the MS's receiving time window 18. The network can then take appropriate action in response to such a report (as discussed in detail below).
• the MS 16 can transmit a message to the network which reports that the radio link 14 is near a boundary of the window 18.
• the network can take appropriate action in response to such a report.
• the MS can be directed to transmit a report message to the network if a radio link transmission is offset from the center of the timing window by an amount which is greater than selected predetermined values (i.e., each value related to a "side" of the window).
• a timing window can contain two threshold values. One such threshold value can be related to a "less than" (e.g., located to the left of the first border) report from the MS.
• the other threshold value can relate to a "greater than” report from the MS (e.g., located to the right of the second border).
• an appropriate action by the network is to adjust the radio link timing in order to re-position the radio link to an acceptable location within the window.
• FIGURES 2A and 2B are related diagrams that illustrate a second aspect of the preferred embodiment.
• the MS 16 is connected to the network by two radio links 14 and 114 (via BS 12 and 112, respectively).
• the two radio links 14 and 114 are significantly separated in time (e.g., the BSs 12 and 112 are connected to different BSs).
• the MS 16 can select one of the radio links to follow in the receiving time window (e.g., the strongest radio link). Nevertheless, a number of different timing problems can occur.
• the MS can transmit a message to the network which reports a radio link that has not been detected for a predetermined length of time.
• one design choice (but not to be considered a limitation on the present invention) is that two windows can be used for detecting the radio link.
• a larger window can be used whereby an MS (e.g., User Equipment or UE) can detect the radio link within that window.
• a smaller window can also be used whereby an MS can report to the network that the radio link is located close to the border of the larger window. However, for this example, if the radio link pops up outside the larger window, the MS likely would not detect the radio link and, therefore, not be able to report this information to the network.
• FIGURES 3 A and 3B are related diagrams that illustrate a third aspect of the preferred embodiment.
• the MS 16 is connected to the network by three radio links 14, 114 and 214 (via BS 12, 112 and 212, respectively).
• the MS can determine what action to take depending on the particular circumstances involved.
• an MS reports all detected radio links to the network.
• the network can request relevant information from an MS about the measured cell(s) and then decide what action to take.
• MS User Equipment or UE
• the MS (16) can transmit a message to the network which reports that radio link (214) is outside the window.
• the MS 16 can be ordered by the network to maintain the connection with (and follow in the window) the strongest radio link and terminate the connections with the two weaker links.
• the network can interpret the MS's radio link (or related) report and instruct the MS to ignore or terminate a radio link that threatens the transmit power control timing to the uplink. Similar to the second aspect of the embodiment, a radio link can slide out of the receiving time window.
• FIGURES 4A and 4B are related diagrams that illustrate a fourth aspect of the preferred embodiment.
• the MS 16 is connected to the network by four radio links 14, 114, 214 and 314.
• the four radio links are associated with four BSs and two different timing domains (i.e., radio links 14 and 114 associated with BS 12 and BS 112, and radio links 214 and 314 associated with BS 212 and 312).
• the MS 16 can transmit a message to the network which the network can interpret, for example, as a report that the two radio links can be dropped from the active set of radio links.
• active set can be defined as the set of radio links simultaneously involved in a specific communication service between user equipment and a UTRAN (Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network) access point.
• UTRAN Universal Mobile Telecommunications System
• a "UTRAN access point” can be defined as a conceptual point within the UTRAN that performs radio transmission and reception.
• a UTRAN access point is associated with one specific cell, such that one UTRAN access point exists for each cell.
• a UTRAN access point is the UTRAN-side endpoint of a Radio Link.
• the radio network can respond in a number of different ways. For example, the network can delete that radio link from the active set and wait until the MS transmits a message which reports that the MS has detected a new neighbor cell and associated radio link to be placed in the active set. The network then connects that radio link to the MS, which receives the transmission in the timing window.
• the network can directly connect the radio link which was reported to be outside the timing window to the MS, and direct the MS to include that radio link in the active set. As such, the network does not have to wait for a new neighbor cell report from an MS, and the network can directly setup a radio link after it has been deleted.
• the radio network can connect another copy of the radio link which was reported outside or nearly outside the MS's receiving time window, in the same cell and then remove the first radio link from the active set.
• the radio network can update the active set by sending a "replace" message to the MS, and then removing the first radio link and adding a second radio link as a replacement. In this case, the timing of the new radio link may be different than that of the first radio link.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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• 2000
  • 2000-12-29 KR KR1020017010817A patent/KR20010104714A/ko not_active Application Discontinuation
  • 2000-12-29 AU AU27195/01A patent/AU2719501A/en not_active Abandoned
  • 2000-12-29 EP EP00990157A patent/EP1159845A1/de not_active Withdrawn
  • 2000-12-29 CN CN00804387.6A patent/CN1342378A/zh active Pending
  • 2000-12-29 WO PCT/SE2000/002692 patent/WO2001050806A1/en not_active Application Discontinuation
  • 2000-12-29 JP JP2001551058A patent/JP2003520001A/ja not_active Withdrawn

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