JP2012217176A - System and method for providing selection diversity for multicasting content - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and system for providing multicasting content in a network having several cells which can communicate with one or more terminals such as user equipment.SOLUTION: The terminals are able to select which cell they desire to communicate. At least some of the cells transmitting multicasting content also transmit cell information on one or more other cells transmitting the same multicasting content. The terminals select one of the cells transmitting multicasting content which the terminals intend to receive, based on this information.

Description

  The present invention relates to a method and system for selective diversity for multicasting content, for example in WCDMA. The term multicasting content means that the content is intended for some users.

  Furthermore, the invention relates to a network entity such as a UE (user equipment), for example a mobile phone, intended to receive multicasting content and including selection means or functions.

  The technical field of the present invention relates to UMTS Terrestrial Radio Access (UTRA; UMTS = Universal Mobile Communication System), for example, future releases such as Release 6 of the 3GPP UTRA specification (3GPP = 3rd Generation Partnership Project).

  Standardization support for Multicasting, MBMS (Multimedia Broadcasting / Multicasting Service) is described.

  Multicast is based on FACH. Since handover (HO) is not supported for FACH, HO is not supported for multicast. To enable multicast HO, BTS resynchronization can be considered, but this is difficult to implement.

  The present invention is intended to solve the above problems.

  And, according to one aspect, the invention provides a method as defined in either the independent method claim or the dependent method claim.

  The invention, according to a further aspect, provides a system as defined in either the independent system claim or the dependent system claim.

  Furthermore, the present invention provides a terminal as defined in either the independent terminal claim or the dependent terminal claim.

  The present invention does not require BTS resynchronization and does not impose any extra timing requirements on the terminal, eg, user equipment (UE) or network, preferably soft handover (SHO) Systems and methods are provided.

  The present invention provides the related advantages of soft handover and soft handover in the case of multicasting transmission.

  The proposed concept is multicast, MBMS, with minimal additional network load and structure that is not complex from the point of view of the network and terminal, eg UE (User Equipment), and does not require complex timing control in the network. Enables handover for.

  One object of the present invention is to provide a system and method for providing soft handover for multicasting content. One suitable solution is based on the use of DSCH and selection diversity.

  The present invention enables a novel macro diversity method that does not require multicast content, ie Node B synchronization used to send and receive multicast messages.

  Due to the traditional maximal ratio combining method, soft handover requires that the links be time aligned in downlink transmission. This can be done for dedicated channels. However, due to multicasting content, the problem is that all UEs in the network must be considered for this, and therefore become very demanding in cell deployments where the synchronization requirements are large.

  Conventionally, only dedicated channels are considered in soft handover, and individual UEs control radio link timing. This is different when several UEs are expected to receive the same content.

  The present invention also provides better performance advantages over current broadcast solutions. No new synchronization is required for the proposed “all” macro diversity.

  According to one or several embodiments of the invention, a DSCH (Downlink Shared Channel) is used for multicasting. When there is a DCH (dedicated channel) indicated to be associated with the DSCH in question, data needs to be transmitted.

  The present invention preferably applies to CDMA (Code Division Multiple Access) or WCDMA (Wideband Code Division Multiple Access), but also applies to other network types as well.

1 illustrates a system for providing selection diversity for a multicast service according to one embodiment of the invention. FIG. 2 is a flow chart showing a decision process implemented in a system, method or subscriber terminal according to an embodiment of the present invention. 6 is a flow chart illustrating a further decision process implemented in a system, method, terminal or the like according to one embodiment of the present invention.

  According to the first basic part of the embodiment of the present invention, the multicast message is transmitted in DSCH (Downlink Shared Channel) instead of FACH (Forward Access Channel). Previously, a terminal, such as a user equipment, listened to the DSCH only from that BTS that the UE can best hear, and the RNC transmitted the DSCH only to that particular BTS.

  In one of the provided preferred solutions that are equally applicable to all other provided solutions, the RNC can have many base stations, eg, Node B or BTS (base transceiver station each transmitting a DSCH). ), Multicast content is transmitted to the DSCH. The terminal, eg UE, selects the DSCH that it can hear best. The advantage is that HO is possible in multicast.

  A DCH is associated with each DSCH for each UE separately. In a more advanced embodiment, ie the extended version, the DCH is observed by a BTS network element such as a base station that transmits the DCH or another network element such as a radio controller RNC. This and other network elements, eg, the BTS, can stop sending its DSCH that is not heard by any UE. In this extended version, knowledge of the presence of any associated DCH in the BTS is used. The relationship between DCH and DSCH is as follows. The UE cannot receive a DSCH without receiving an associated DCH. Thus, if there is no DCH associated with a DSCH, no one has received that DSCH. However, it should be noted that there can also be DCHs that are not associated with the DSCH, and for this reason there can be active DCHs in the cell. As long as none of the active DCHs are associated with a DSCH, DSCH multicasting is stopped.

  If there is no associated DCH, there is no user receiving the DSCH. Therefore, there is no need to transmit DSCH. That is, the radio network controller, RNC, or transmitting device, preferably a network element (at least one) such as a BTS, if there is no DCH associated with the DSCH, ie the DSCH is If not, stop DSCH transmission. The possibility of monitoring DCH and stopping transmission is one advantage of using DSCH for multicast. Another advantage of using DSCH is that DSCH is point-to-multipoint.

The present invention includes several levels of possible implementation.
-Use of DSCH-Use and selection diversity of DSCH-Use of DSCH, selection diversity, closure of unused DSCH-Use of FACH, ie "normal" MBMS transmission mode and selection diversity

  In any case, the important idea of the present invention is that in the case of multicast content, information (cell information transmitted on SIB, DCCH = dedicated control channel, etc.) is the same as other multicast content that is transmitted. Necessary parameters such as spreading codes in other cells, which are parameters that allow the terminal to decode multicast content from other cells, are also supplied. The terminal can independently select which cell to receive.

  The advantage is high performance. Furthermore, since the information is available in advance, it is not necessary to read the broadcast information (SIB) before service reception can continue (after cell reselection when the user moves to another cell).

  The channels that can be used for this are preferably the FACH and DSCH (Downlink Shared Channel), which have a more detailed issue as follows.

  In DSCH, the same DSCH is transmitted from multiple cells and received by multiple users. (Conventionally, a DSCH is transmitted from one cell to only a single user at a time.)

  In FACH, when transmitting a channel with an existing DCH, the base station can know which DCH is related to FACH (MBMS) reception, and when it knows, the base station determines the transmission power based on Can be adjusted. For example,

-DCH power-Presence of associated DCH channel (when user comes)-Uplink feedback information such as SSDT (feature indicating in cell which cell is best for DCH transmission, eg primary / SSDT uplink feedback information indicating non-primary cell status), if all terminals indicate some other cell as non-primary, do not transmit or reduce TX (transmit) power Thus, the same can be considered for FACH (MBMS) transmission. (The terminal transmits an SSDT instruction indicating which cell is the strongest in the uplink.) (SSDT = site selection diversity transmission)

  The present invention can use DSCH (Downlink Shared Channel) to provide multicasting content to some users along with features added to support soft handover as follows. Now DSCH has content intended for some users. This can be achieved, for example, with small protocol level modifications.

  A DSCH is transmitted from Node B with the same MBMS content. Then, which DSCH is received by the terminal is selected based on, for example, CPICH signal strength. Here, the split mode for TFCI can also be used. This is a diversity based selection and not part of normal DSCH operation.

  Node B is notified of a plurality of DCHs related to the multicasting DSCH. And in the handover state, none of the DCH is active anymore and no DSCH needs to be transmitted. These transmissions can then be stopped by the Node B.

  If the number of UEs is high and not all UEs want to have DCH, an alternative method is to consider the use of FACH along with the selection principle. This also makes it possible to reduce the FACH power level for multicasting.

  1 through 3 show details of an embodiment of the present invention relating to the use of selective diversity. The embodiment describes the aspect of handover in selection diversity of multicast messages, eg, transmitted via MBMS.

  FIG. 1 shows a first embodiment of a method and system according to one embodiment of the present invention. This embodiment is configured to provide selection diversity in UTRAN for MBMS.

  MBMS content, ie the content of one or more multicast messages, from the core network (CN) to one or several transmission controllers such as BSC (Base Station Controller) or RNC (Radio Network Controller) 1 Sent. The controller 1 transmits this MBMS content to one or several radio transmitters 2, 3 such as BTS or Node B. All transmitters 2, 3 that receive this MBMS content send this content, ie a multicast message, to one or more terminals 4 via a common channel MBMS transmission. For example, a comparison of pilot signals on a common pilot channel (CPICH), preferably P-CPICH (primary common pilot channel) is performed, and based on the result of this CPICH or p-CPICH comparison, By performing the selection of one, preferably the strongest common channel, the terminal 4 performs the selection.

  2 and 3 show a flow chart of routines implemented in an embodiment with one or more terminals 4, e.g. a UE, and a method according to an embodiment of the present invention. The decision process performed at the terminal 4 is shown in detail.

  RAN (Radio Access Network), e.g., base transceiver station (BTS) or system information block with cell information including channelization code, e.g. spreading code for each cell for which the nodes B2, 3 transmit the same MBMS content (SIB) is transmitted. The SIB is preferably transmitted on a broadcast channel in the cell. This information can be transmitted on other channels as well.

  Cell selection / reselection is not service driven in embodiments.

  Existing cell selection rules are not violated.

  In the embodiment shown in FIG. 2, FACH (Forward Access Channel) is used to transmit the System Information Block (SIB). The FACH can also be used in some or all other embodiments.

  In step S21, the terminal 4, for example, the UE, decides to participate in the multicast service and registers there (service participation). In step S22, the terminal 4 reads the SIB and notification transmitted on the broadcast channel. Notifications can also be sent on another channel. The SIB includes cell information that includes channelization codes for each cell that transmits the same MBMS content. In step S23, the terminal 4 decodes the received multicast message (decodes MBMS data).

  In step S24, pilot signals received from different cells are compared to determine a better channel, eg, a channel received with greater power or less error. As an example, received pilot strengths or low errors are compared with each other to find one or more received pilot signals with higher strength or reduced error rate, and the like. In step S25, a determination is made. If there is no better, for example, a stronger pilot (signal) is found in step S24. In order to repeat steps S23, S24, S25, the routine loops back to step S23.

  When a better, eg, stronger, pilot (signal) is found at step S24, the routine proceeds from step S25 to step S26, where it has a better or best (strongest or least error-prone) pilot detected. It is checked whether the cell provides the same multicasting content, ie whether it provides the same multicast service provided by the cell selected by the user and actually heard by the terminal 4 in step S21. .

  If the answer in step S26 is yes, the routine proceeds to step S27. There, the MBMS data from the new cell that transmits the detected stronger or better pilot signal is decoded. That is, the terminal 4 is handed over, i.e. switched, to a new cell in order to receive the multicast message.

  For example, if the terminal is moving, the routine preferably returns from step S27 to comparison step S24 and decision step S25 in order to detect a stronger or better pilot signal continuously or repeatedly.

  In step S26, when the system detects that the cell transmitting the pilot signal better received by the terminal does not provide the same multicast content, the cell reselection function or means is activated in step 28 Is done. New cells better received by the terminal 4 are instructed by the network management or controller to additionally transmit MBMS content that the terminal 4 wants to receive. Accordingly, the SIB is adapted to additionally indicate or include cell information including the channelization code of the new cell. The process proceeds from step 28 to step 22, where the SIB is read again by terminal 4, and terminal 4 preferably selects a new cell to decode the multicast message, MBMS data. Instructed. As an alternative, the program also skips the return to step 22 after performing the cell reselection process or step S28, and directly allows the terminal 4 to decode the multicast content from the new cell. Indicates to select a cell. Thereafter, steps S24, S25, etc. are executed again as described above.

  In the embodiment shown in FIG. 3, there is a dedicated channel, DCH, and the MBMS content is in a DSCH (downlink shared channel) or a cell in the DCH activity set on the FACH (not necessarily all). To be transmitted in parallel. FIG. 3 relates to the terminal determination process, which is DCH activity.

  The network transmits cell information for cells (within the active set) that transmit the same MBMS content (including spreading codes etc.). This information can be transmitted in SIB or DCCH (Dedicated Control Channel).

  Steps S31 to S37 shown in FIG. 3 are substantially the same as steps S21 to S27 of FIG. For this reason, the above description of these steps also applies to steps S31 to S37, with the following exceptions. In step 32, the information transmitted on the SIB or DCCH is read by the terminal 4 to detect information about the cell (within the active set) transmitting the same MBMS content (including spreading code etc.).

  When in step 36 it is determined that the cell transmitting the pilot signal better received by terminal 4 does not provide the same multicast content that terminal 4 wants to receive, the program routine Proceed to step 33 so that is read again from the same cell as before. Therefore, cell reselection is not executed by the terminal 4.

  However, if there is no new cell in the activity set that is found with a better pilot in step S36 and is sending this better pilot, the normal reporting and mobility management rules include, for example, the new cell as well. Can be used to update the activity group. That is, the activity group can be updated. After such an update, when looping again through steps S34, S35, and S36, the answer to step S36 is yes, and then the process is switched to step S37. That is, the MBMS data from the new cell is decoded.

  Therefore, the embodiment provides selection diversity for MBMS, for example, in UTRAN.

According to embodiments of the present invention, some suitable terminal functions or functionality for multicast selection diversity and handover (HO), eg, for MBMS HO, are:
The strongest common channel is selected (eg, on P-CPICH, based on selection), and for example, either DSCH or FACH can be used.

  Receive two common channels in the asynchronous network during the selection diversity process (if the stronger cell is more advanced in SFN timing, at least during the switching process during the timing difference period), this Is an optional feature that may or may not be implemented, for example, depending on QoS (Quality of Service) requirements. When one or more 10 ms frame losses are acceptable (eg, if Node B timing is within 10 ms), parallel reception of two common channels is not necessary. In either case, there is usually some frame loss.

  The node S decodes the related SIB that notifies the terminal 4 that transmits data.

  Previously, there was no requirement for parallel DCH / FACH reception. Nevertheless, if the terminal can receive DCH / FACH simultaneously, receiving two FACHs does not increase complexity. Otherwise, the terminal can be adapted to receive DCH / FACH in parallel. If the MBMS content is also considered for DCH / DSCH or DCH / FACH, the terminal is adapted to receive two common channels in addition to DCH (for a while). This requirement can be eliminated if the network is within Node B timing, eg, 10 ms timing, since MBMS transmissions and one frame loss due to switching are acceptable. The requirements for reception resources are the same as those for DCH / FACH or DCH / DSCH capable terminals.

  Due to selection diversity, P-CPICH is preferably measured. Extra processing is provided depending on the requirements. If the requirement is at a similar level or not exceeded, the requirement is set for the SSDT feature and does not add additional complexity. Terminal 4 can monitor P-CPICH from up to 6 cells at a time, and can consider cells that are within the active set of DCHs to be considered, assumed to include 6 cells surrounding terminal 4 .

  It is the UE's ability to receive DCH + MBMS content simultaneously.

According to an embodiment of the present invention, a suitable network function for multicast handover, eg, MBMS HO, is
A new Node B function for MBMS in selection diversity is not required. The only possible timing issues are:

  According to the 10 ms timing assumption, MBMS content is preferably aligned in time either in the RNC or in the Node B (meaning a buffer that is together because some delay needs to be introduced).

  There is no need for new functionality of the core network (CN), for example for the HO support option on the RAN side. In general, every cell that can provide MBMS content has a corresponding RNC along with available MBMS content.

  The preferred embodiments have been described above, but the present invention is not limited thereto. For example, one or more features of one or more embodiments can be combined with those of another embodiment. Another aspect can be realized by combining one or a plurality of features in an arbitrary form.

Claims (36)

  A method for providing multicasting content in a network having several cells capable of communicating with one or more terminals, wherein the terminal can select which cell it wishes to communicate and transmits the multicasting content Multicasting that the terminal intends to receive based on this information also transmits cell information about one or more other cells where at least some of the cells are transmitting the same multicasting content Selecting one of the cells transmitting the content.   The method of claim 1, wherein the cell information is transmitted as a system information block (SIB).   The method of claim 1, wherein cell information is transmitted on a broadcast channel in the cell.   The method of claim 1, wherein the cell information is transmitted on a dedicated control channel (DCCH).   The method of claim 1, wherein the cell information includes a channelization code for each of the cells transmitting the same multicasting content.   The method of claim 1, wherein at least two cells transmit the same multicasting content on a downlink shared channel (DSCH) received by at least two terminals.   A radio network controller (RNC) transmits multicast content on the DSCH to at least two base stations in the cell each broadcasting a downlink shared channel (DSCH), and the terminal can receive with sufficient or strongest power The method of claim 1, wherein the DSCH is selected.   The method of claim 1, wherein at least two cells transmit the same multicasting content on a forward access channel (FACH) received by at least two terminals.   The method according to claim 1, wherein the base station of the cell is informed about a dedicated channel (DCH) associated with a forward access channel (FACH) used for transmission of multicast content. The cell base station
-Detected DCH power, or-presence of associated DCH channel, or-SSDT (Site Selective Diversity Transmission) uplink feedback information indicating primary / non-primary cell status,
10. The method of claim 9, wherein the adjustment is based on   The method of claim 9, wherein the DCH is associated separately with each DSCH for each terminal, the DCH associated with the DSCH is observed, and transmission of the DCH with no associated DCH is stopped.   The terminal is adapted to compare the quality of reception of information from at least two cells and to select a cell that provides better or stronger reception for receiving multicasting content. The method described.   A pilot signal that the terminal compares with the strength or power of pilot signals received from several cells and is received with a strength or power higher than the pilot signal strength or power of the currently listening cell When a cell is detected, it is checked whether it provides the same multicasting content as the cell it is currently listening to, and if yes, the multicasting from the cell The method of claim 12, wherein content decoding is initiated.   Cell reselection procedure in which when a terminal detects that a cell does not provide the same multicasting content as the cell it is currently listening to, the cell is instructed to start transmitting multicasting content 14. The method of claim 13, wherein the method begins.   The method of claim 12, wherein the terminal compares the strength or power of pilot signals received from several cells on a primary common pilot channel (P-CPICH).   A system that provides multicasting content in a network having several cells that can communicate with one or more terminals, and can select which cell the terminal wants to communicate with and transmit the multicasting content Multicasting that the terminal intends to receive based on this information also transmits cell information about one or more other cells where at least some of the cells are transmitting the same multicasting content A system that selects one of the cells sending content.   The system according to claim 16, wherein the cell information is transmitted as a system information block (SIB).   The system of claim 16, wherein cell information is transmitted on a broadcast channel in the cell.   The system of claim 16, wherein the cell information is transmitted on a dedicated control channel (DCCH).   The system of claim 16, wherein the cell information includes a channelization code for each of the cells transmitting the same multicasting content.   The system of claim 16, wherein at least two cells transmit the same multicasting content on a downlink shared channel (DSCH) received by at least two terminals.   A radio network controller (RNC) transmits multicast content on the DSCH to at least two base stations in the cell each broadcasting a downlink shared channel (DSCH), and the terminal can receive with sufficient or strongest power The system of claim 16, wherein the DSCH is selected.   The system of claim 16, wherein at least two cells transmit the same multicasting content on a forward access channel (FACH) received by at least two terminals.   The system according to claim 16, wherein the base station of the cell is informed about a dedicated channel (DCH) associated with a forward access channel (FACH) used for transmission of multicast content. The cell base station
-Detected DCH power, or-presence of associated DCH channel, or-SSDT (Site Selective Diversity Transmission) uplink feedback information indicating primary / non-primary cell status,
25. The system of claim 24, wherein the system adjusts based on:   A DCH is separately associated with each DSCH for each terminal, at least one network element is adapted to observe the DCH associated with the DSCH, and that network element or another network element is not associated with the DCH The system according to claim 24, wherein transmission of DSCH is stopped.   17. The terminal is adapted to compare the quality of reception of information from at least two cells and select a cell that provides better or stronger reception for receiving multicasting content. The described system.   A pilot signal that the terminal compares with the strength or power of pilot signals received from several cells and is received with a strength or power higher than the pilot signal strength or power of the currently listening cell When a cell is detected, it is checked whether it provides the same multicasting content as the cell it is currently listening to, and if yes, the multicasting from the cell 28. The system of claim 27, wherein content decoding is initiated.   Cell reselection procedure in which when a terminal detects that a cell does not provide the same multicasting content as the cell it is currently listening to, the cell is instructed to start transmitting multicasting content 30. The system of claim 28, wherein the system begins.   28. The system of claim 27, wherein a terminal compares the strength or power of pilot signals received from several cells on a primary common pilot channel (P-CPICH).   In a network having several cells that can communicate with the terminal, the terminal for receiving the multicasting content, which terminal can select which cell the terminal wants to communicate with, and which cell the terminal has transmitted from the cell A terminal that selects one of the cells that are transmitting the multicasting content that is intended to be received based on the cell information indicating whether or not the same multicasting content is transmitted.   The terminal according to claim 31, wherein the multicast content is transmitted on the downlink shared channel (DSCH) by at least two base stations of the cell and the terminal selects a DSCH that can be received with sufficient or strongest power. .   The terminal is adapted to compare the quality of reception of information from at least two cells and to select a cell that provides better or stronger reception for receiving multicasting content. The listed terminal.   A pilot signal that the terminal compares with the strength or power of pilot signals received from several cells and is received with a strength or power higher than the pilot signal strength or power of the currently listening cell When a cell is detected, it is checked whether it provides the same multicasting content as the cell it is currently listening to, and if yes, the multicasting from the cell The terminal according to claim 33, which starts decoding content.   Cell reselection procedure in which when a terminal detects that a cell does not provide the same multicasting content as the cell it is currently listening to, the cell is instructed to start transmitting multicasting content 35. The terminal of claim 34, which begins.   The terminal of claim 33, wherein the terminal compares the strength or power of pilot signals received from several cells on a primary common pilot channel (P-CPICH).

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