The present disclosure relates to a method and arrangement in a mobile communication system, in particular to methods and arrangements for providing improved signaling information when applying Multimedia Broadcast/Multicast Services (MBMS).
Multimedia Broadcast/Multicast Service (MBMS) technology was first introduced for UMTS Wideband Code Division Multiple Access (WCDMA) in Rel-6 of the 3GPP specifications in order to enhance the delivery of identical multimedia contents from one source to multiple receivers in terms of transmission resources. Meanwhile, MBMS has also been standardized for the next release, Rel-9, of the enhanced UMTS Terrestrial Radio Access Network (E-UTRAN), and is therefore also known as enhanced MBMS (eMBMS). During the standardization process of MBMS, several new logical channels were introduced. In the following description the MBMS concept will be explained by means of examples for E-UTRAN Rel-9. However, the description is also applicable for the MBMS concept as used in WCDMA according to Rel-6 of the 3GPP specifications with system specific differences using e.g. other logical, transport and physical channels.
The MBMS Control CHannel (MCCH) is needed for the User Equipment (UE) to obtain service specific information necessary for MBMS service reception, e.g. physical multicast channel (PMCH) configuration such as modulation and coding scheme, MBMS subframe allocation etc. Furthermore, the MCCH also announces session starts and session ends of services. Changes on MCCH may only be conducted at the next modification period. Thus, an MBMS User Equipment (UE) only has to wake up once within a modification period to check if there have been any changes.
Each MBMS service session is mapped to an MBMS Traffic Channel (MTCH). The Multicast Channel (MCH) is used as transport channel to carry the MBMS service data or the corresponding MTCH, respectively. Several MTCHs can be bundled and multiplexed on the same MCH if they have the same quality of service (QoS) requirements. As an MBMS UE is often only interested in a subset of the services carried on the same MCH, it is also desirable that each MCH carries scheduling information for the services mapped to that MCH. Previously, such scheduling information was denoted dynamic scheduling information (DSI) but in current development of MBMS, the scheduling information is denoted MCH Scheduling Information (MSI) and as such provides the information that it is specific for each MCH.
After reading the MSI, the UE knows when it has to wake up to receive the service(s) of its interest, while it can sleep during the transmission of other services. The MSI information is valid for one scheduling period, or more specifically the MCH scheduling period, MSP, which has a duration of typically 32 radio frames corresponding to 320 ms, but it may also be shorter or longer (up to a few seconds) in duration depending on the services' burstiness and on the limit of the delay that is introduced by the scheduling.
The MSI may be transmitted in the MAC Control Element (MAC CE) of the first transport block (TB) of a scheduling period. The radio resource, e.g. a subframe in the context of E-UTRAN in which the MSI is transmitted, is therefore known implicitly from the start of the scheduling period.
In certain systems, session ends may only be announced at the next MCCH modification period boundary. Even if the service is not scheduled, the UE has to wake up to read MSI at every scheduling period until the session end is announced on MCCH. As a result, the UE has thus to wake up at each scheduling period and consumes more battery power than necessary.
It is therefore an object of the current disclosure to provide a mechanism that obviates at least some of the drawbacks of existing solutions. Certain embodiments of the present disclosure may reduce battery power consumption in a network node or provide other benefits.
According to particular embodiments, a method in a network node for providing Multimedia Broadcast/Multicast Service (MBMS) from the network node to a user equipment (UE) in a mobile communication system includes determining a scheduling information for at least one MBMS service such that the scheduling information includes information about transmission of data of the at least one MBMS service for a scheduling period that is later than a current scheduling period. The method additionally includes transmitting data of the at least one MBMS service and the scheduling information for said at least one MBMS service, the transmission taking place in the current scheduling period and in a plurality of consecutive scheduling periods following the current scheduling period.
Additionally, according to particular embodiments, a method in a user equipment (UE) for receiving Multimedia Broadcast/Multicast Service (MBMS) from a network node in a mobile communication system includes receiving data of at least one MBMS service and scheduling information for said at least one MBMS service, the reception taking place in a current scheduling period. The method also includes determining, if a service is unscheduled, whether the received scheduling information comprises information about the reception of data of the at least one MBMS service for a scheduling period that is later than the current scheduling period. In addition, the method includes interpreting the received scheduling information and, as a consequence of the interpretation for unscheduled services, entering a sleep mode for a duration of at least one scheduling period.
Additionally, according to particular embodiments, a method for providing Multimedia Broadcast/Multicast Service (MBMS) in a mobile communication network including data transmission of such a service from a network node to a user equipment, in which the MCH scheduling information (MSI) for one or more services mapped on the same transport channel is transmitted in each scheduling period, and the MSI provides information about the data transmission of the service beyond the current scheduling period.
Important technical advantages of certain embodiments of the present invention include providing improved techniques for communicating information regarding MBMS services. Particular embodiments may be capable of reducing power use by mobile devices. Other advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.
a is a flow chart of a method in a network node.
b is a flow chart of a method in a user equipment.
a illustrates MCH scheduling information according to prior art.
b illustrates the general structure of MSI MAC CE.
a illustrates determination of scheduling information using bitmap representation.
b is a flow chart of determination of scheduling information using bitmap representation.
a illustrates determination of scheduling information using codepoint representation.
b is a flow chart of determination of scheduling information using codepoint representation.
In
A Broadcast/Multicast Service Center (BM-SC) 107 in the core network 102 enables the network 100 to provide Multimedia Broadcast/Multicast Service (MBMS) in that it controls, i.e., the data flow of the MBMS in the core network 102. The BM-SC is coupled via the Internet 109 to a server 110 that illustrates an entity from which the mobile devices 106 may receive the MBMS discussed herein. As the skilled person realizes, the network 100 in
In some more detail, the network node 206 is configured for providing Multimedia Broadcast/Multicast Service (MBMS) from the network node 206 to a user equipment (UE) in a mobile communication system such as the UE 106 in the network 100 in
The determination circuitry (210, 211) i.e. CPU and MEM, may be configured to determine the scheduling information such that the information comprises information that indicates an end of session for the MBMS service as well as information that indicates a number of scheduling periods in which the MBMS service will not be scheduled, for example a minimum number of scheduling periods, in which the UE e.g. shall sleep without receiving any further scheduling information.
Moreover, the determination circuitry (210, 211) may be configured to determine the scheduling information such that the information comprises information about the next scheduling period in which the UE shall receive scheduling information about the sleep duration or the MBMS service. The determination circuitry (210, 211) may be configured such that it determines the scheduling information in a bitmap form, which indicates whether or not the MBMS service has ended and/or indicates whether or not the MBMS service will not be scheduled at least for the current scheduling period.
Alternatively, the determination circuitry (210, 211) may be configured such that it determines the scheduling information in a codepoint form, which indicates whether or not the MBMS service has ended and/or indicates whether or not the MBMS service will not be scheduled at least for the next scheduling period. Furthermore, the determination circuitry (210, 211) may be configured such that it determines the scheduling information in a codepoint form, which represents any of sleep duration and wake-up time point for the UE.
The network node 206 may also be configured such that the transmission circuitry is capable of transmitting of information that indicates a valid value range for the codepoint, which may indicate the sleep duration and/or the transmit time.
In some more detail, the UE 306 is configured for receiving Multimedia Broadcast/Multicast Service (MBMS) from a network node in a mobile communication system such as the node 206 (
a and 4b are flow charts that illustrate interaction between a network node and a UE, for example any of the network nodes and UE's described above in connection with
a illustrates a method in a network node in a mobile communication system for providing Multimedia Broadcast/Multicast Service (MBMS) from the network node to a user equipment (UE). The method comprises, in a transmission step 403, transmitting data of at least one MBMS service and scheduling information for said MBMS service(s). The transmission takes place in a current scheduling period and in a plurality of consecutive scheduling periods following the current scheduling period. The scheduling information is determined, in a determination step 401, such that the scheduling information comprises information about transmission of data of the at least one MBMS service for a scheduling period that is later than the current scheduling period.
a illustrates MCH Scheduling Information MAC CE, 2 bytes per service, according to prior art.
The value range for “Stop MTCH” is 0-2042, there are four reserved values ranging from 2043-2046, and the value for not scheduled is 2047.
In principle, larger savings may be achieved for lower MSPs. With shorter MSPs, not all values for the “Stop MTCH” will be used. If the MSP is rather large, e.g. 2.56 s corresponding to 2560 subframes, at most 1536 values would be needed, 1536=2560*0.6 since there are at most 6 MBSFN subframes in a radio frame, so that only values between 0-1535 would be used. The remaining values from 1536 to 2042 are categorized “invalid”. So alternatively to reserved values, which only contain four values and would not provide fine granularity and a sufficiently large value range at the same time, invalid values may be used to indicate for how many scheduling periods the UE may sleep or when it shall wake up, respectively.
Turning now to
The MSI is extended to comprise further information about unscheduled services to provide information beyond the current scheduling period. Session ends may not only be indicated on MCCH, but already in advance in the MSI. A second bitmap in addition to the first bitmap which provides whether the services are scheduled or not, may be used to indicate that the session has already ended, in order to preserve an UE to wake up at the next scheduling periods until it reads session end information on MCCH. Alternatively, another specific codepoint may be used for that purpose. In general, the MSI uses several bits data field of each service to provide information about the transmit times of the service within the scheduling period. Since such information only requires a subset of the available value range of the data field, the free values may be used as codepoints.
Furthermore, the second bitmap may be used to distinguish between a session end and a session silence period as illustrated in
In other words, as illustrated in
If it is found in the checking step 901 that the service is not scheduled, then the scheduled bit, bit 1, for the service is set to the value 0 in step 909. Afterwards, a check is made in a checking step 911 if the UE is supposed to sleep or if it may completely stop the reception due to a session end. If it is found in the checking step 911 that the UE is only supposed to enter a sleep mode, the sleep bit, bit 2, is set to value 1 in step 913. Then the network node checks in step 915 the silence duration for the service and sets the sleep duration in the data field accordingly.
If it is found in checking step 911 that the session of the service has ended, the sleep bit, bit 2, will be set to the value 0 in step 917 to indicate to the UE that it does not need to sleep for a restricted time, but that it may stop the reception of the service completely. The data field may be set to any arbitrary value, e.g. 0, because it will not be interpreted by the UE, as illustrated by setting a dummy value in step 919. The data field is also transmitted to the UE to keep a constant size of 2 bytes per service and byte alignment.
If the bitmap approach is not used at all, codepoints in the data fields may not only be used to indicate session ends, but also to indicate a sleep period longer than the scheduling period. Different schemes may be used to allocate the free values as codepoints to indicate the minimum or actual duration of the silence or sleep period or the next wake-up occasion. For example, with MSP=320 ms and with 11 bits available for transmit time indication which only requires a range between 0 and 192, 32 radio frames * 6 MBSFN subframes on a mixed carrier, the values between 193 and 2042 may be used as codepoints, the values 2043-2046 are reserved values and could in principle be used as well.
In order to calculate the codepoint corresponding to the actual silence/sleep duration, different methods may be applied. One possible and simple way is to use the last free value as a reference value; in this example, option 1, this would be 2042. Then, the codepoint may be calculated by using the actual sleep duration or next wake-up occasion as the minuend and the reference value as the subtrahend or the other way round, respectively. To indicate, e.g., a sleep duration of 2 scheduling periods, a codepoint set to 2040 may be used: Minuend=reference value is the maximum free value; and subtrahend=sleep duration, e.g. 2042−2=2040. It is to be noted that a sleep duration of 0 scheduling periods, i.e. the service is unscheduled only in the current scheduling period, is already reflected by the special codepoint 2047, such that 2042 would be unused. In order to indicate a session end, it is possible to set the codepoint to the next reserved value, i.e. 2046, or to the largest free value, i.e. 2042 which is not used anyway in this example. If in option 2 the next reserved value, i.e. 2046, is used, the reference value may also be increased by 1 to avoid the value 2042 to be unused, e.g. 2042+1−2=2041.
This requires that the UE knows the used reference value. This may be implicitly calculated by using the maximum number of MBSFN subframes that may be used for MBMS transmission within a radio frame and the scheduling period or by explicitly transmitting the range that is used to indicate the transmit time and/or sleep duration of the listed services on MCCH.
In other words, as illustrated in
If it is found in the checking step 1001 that the service is not scheduled, another check is made in step 1003 to check whether the UE may sleep due to a silence period or whether it may entirely cease service reception due to session end. If it is found in step 1003 that the UE is only supposed to enter a sleep mode, the sleep duration is determined in step 1005, and in the data field the codepoint is set to an appropriate value to indicate the sleep duration, in this example the backwards counting approach from the largest free value within the value range used as reference value (2042) is applied. The special codepoint with value 2047 is used to indicate a sleep duration of 0 scheduling periods according to the current 3GPP Rel-9 specification, i.e. the value 2047 indicates that the service is unscheduled only in the current scheduling period and that the UE is supposed to wake up at the next MSP of the corresponding MCH to read the MSI.
If it is found in a checking step 1003 that the UE is not supposed to sleep for a restricted number of scheduling periods, but entirely cease service reception due to a session end, the codepoint is set to a special codepoint, 2042 as the largest free value (only depicted for option 1).
According to yet another embodiment it is also possible to use the first bitmap to indicate if a service is scheduled or not and a codepoint approach to provide further information instead of using the second bitmap. In this case, if the service is unscheduled then the codepoint in the data field indicates either a session end or a particular sleep duration and if the service is scheduled then the value of the data fields indicates the transmit time.
Embodiments include those that involve short service sessions. Short sessions are transmitted in a significantly shorter period than the MCCH modification period. One example for services with very short sessions is a service mode, e.g., for download of small files, such as MMS or audio files. This takes a few seconds. Depending on the size of the file, some sessions may even require only a fraction of a second. This would be true for a small MMS file.
Service information such as session start and session end is transmitted on MCCH. So, the session end may only be announced after the modification period. After having received all data of the short session, the UE may know on application layer that, e.g., the download is complete. However, the application would need to be able to signal to lower layers that it does not have to monitor the MSI any more. However, this is up to UE implementation.
When the session has ended already, UE will in general wake up at every scheduling period until it finds session end indication on MCCH. The larger the modification period, the larger unnecessary UE energy consumption will be. Since MCCH information is transmitted in RRC messages, there will be some further decoding delay until the UE notices that the session has ended.
Under the assumptions listed in the table above, the UE would need 4 scheduling intervals to download the complete file. In the remaining 28 scheduling intervals, the UE has to wake up to find out that the service is not scheduled. If the session end is indicated in the MSI already, the UE could sleep almost 90% of the time during which MSI is transmitted.
Since the sessions are very short, it is quite probable that it only requires very few scheduling intervals to be completely transmitted. As soon as session start has been announced on MCCH, it is most efficient to distribute the service data in the first scheduling intervals. Otherwise, if the service is not scheduled e.g. in the first 30 scheduling intervals, the UE would have to read unnecessary scheduling information at the beginning of the MCCH modification period before it may actually receive the MBMS data. Thus, it may maximize its sleep duration.
Hence, it is possible to indicate in MSI that a service has already ended as described above in connection with
Embodiments include those that involve intermittent services/sessions. Sessions of intermittent services may remain ongoing but not scheduled for some time. Services are updated very frequently and consequently scheduled very frequently as well. Information updates within the service may be in the order of a few seconds or larger, but not significantly larger than multiple MCCH modification periods. In such a case, the update intervals would be too small that a session start/session end procedure would pay off.
The stock ticker service is one example of intermittent services which may have updates every few seconds. It is assumed that consumers may want to receive brand new information with very low latencies, which requires avoiding MBMS session starts and session stops.
The UE has to wake up at every scheduling period, although the service is only scheduled in a small fraction of all scheduling periods.
Extend bitmap/additional codepoint: The application layer often knows when new information will be fetched and updated. Both schemes may contain an information on the (minimum) number of scheduling periods to sleep. The eNB must know at least the earliest time at which new data for these services will be transmitted or even the periodicity of service transmission. This requires from BM-SC that it indicates some kind of update periodicity, e.g. service-specific update intervals.
It may be difficult to convey per packet when the next packet transmission from the BM-SC will take place, so that dynamic sleep information may be difficult to realize. It appears more realistic to configure a periodic sleep pattern already when the session is established. A sleep pattern may be defined by the number of consecutive scheduling intervals where the service is/is not scheduled.
Hence, it is possible to indicate the sleep duration for MBMS UE in MSI, e.g. in terms of multiple of MSI periods.
The signalling of sleep periods may be realized as an extension to the session end signalling. The second bitmap may be used to distinguish between a session end and a session silence period as illustrated in
If no bitmap is used at all, another codepoint may indicate a sleep period longer than the scheduling period, as described above in connection with
Embodiments include those that involve short carrousel services. Short carrousel services are characterized by repetitions between actual information updates to allow any new-coming user to receive the latest information as soon as possible, service mode 3. If the repetitions are smaller or in the order of few modification periods it does not make any sense to have short session durations with frequent session starts and stops as described above. Note that the options described below assume that the minimum duration between service updates is known, e.g. configured in the service layer. Furthermore, it is assumed that the UE does not want to receive any repetitions.
One option is then that the MCCH provides information about the service repetition period and number of repetitions.
A second option is then to add information in MSI to indicate if it has scheduled a new or a repeated transmission, maybe use new data indicator. This requires the extension of the bitmap or the addition of a codepoint, respectively.
If the UE receives new and not repeated data, it knows the minimum time to sleep until it has to wake up to read the MSI. This is sub-optimal if the UE does not receive the new data. Then it would also have to wake up at the next service repetition periods.
Another option is to indicate the sleep duration until the service is updated.
Alternatively, the MSI could directly indicate the minimum sleep duration until the service is updated. After each repetition, the value would be reduced accordingly. The advantage of this scheme is that it may be used for both intermittent as well as short carrousel services.
Hence, it is possible to indicate the sleep duration until the service is updated. Thus, no extra information is needed on MCCH. An example for such a service is traffic information with different kinds of messages, such as e.g. traffic jam.
To conclude, in order to improve the UE power saving for short, intermittent and carrousel services, the following examples are useful regarding signalling in the MSI: indicate session end in MSI, consider introducing sleep duration for MBMS UE in case of intermittent services, add information in MSI to indicate if it has scheduled a new or a repeated transmission, may be use new data indicator, in case of carrousel services, while no extra information shall be transmitted on MCCH.
This application claims the benefit of U.S. Provisional Application No. 61/248,633, filed Oct. 5, 2009, the disclosure of which is incorporated herein by reference.
Number | Date | Country | |
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61248633 | Oct 2009 | US |