The present invention relates to performing measurements for inter-frequency and inter-radio access technology (inter-RAT) handover while receiving Multimedia Broadcast/Multicast Service (MBMS) data in a point-to-multipoint transmission environment.
The objective of MBMS is the efficient use of the radio resources by allowing the simultaneous distribution of identical multimedia data to multiple receivers using the same radio channel(s). MBMS defines a number of new procedures to support point-to-multipoint (p-t-m) transmission to multiple users. In addition, MBMS uses existing procedures for point-to-point (p-t-p) transmission to a single user.
It is expected that MBMS will allow operators to offer new services by allowing the efficient broadcast or multicast of popular multimedia services such as news, traffic information and sports clips. The 3rd Generation Partnership Project (3GPP) is currently standardizing the Multimedia Broadcast/Multicast Service (MBMS) as part of the new features to be included in Release 6 of its specifications.
According to the proposed standards, all user equipment (UE) or mobile units receiving MBMS share a common downlink. Thus, there is no possibility for the network to consider individually signalled measurement occasions for each user equipment. The proposed standard assumes that the number of MBMS users in a cell will be large, and thus, it will difficult if not impossible to coordinate the signalled measurement occasions between all user equipments without a loss of MBMS transmission capacity.
However, if the user equipment is focused on receiving point-to-multipoint MBMS data on a Forward Access Channel (FACH), the user equipment may not be able to perform measurements relating to inter-frequency and/or inter-RAT (Radio Access Technology). Therefore, there is a need for a system and/or method that can ensure a certain level of Quality of Service (QoS), e.g. that page messages or large amounts of MBMS-data are not lost, while performing inter-frequency/RAT measurements concurrently with point-to-multipoint MBMS data reception.
Disclosed are systems and methods that allow the user equipment to perform inter-frequency and inter-RAT measurements while receiving MBMS data. As disclosed, control of measurement occasions is decided on by the user equipment using Discontinuous Reception (“DRX”) during Forward Access Channel (“FACH”) reception. Using aspects of the disclosed embodiments, each user equipment individually decides when to perform inter-frequency/RAT measurements (provided performance requirements on cell reselection are met). Outer coding procedures may then be performed to recover data lost during the measurements.
These and other features, and advantages, will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. It is important to note the drawings are not intended to represent the only aspect of the invention.
a and 6b are methods incorporating various aspects of the present invention.
For the purposes of the present disclosure, various acronyms are used, and the definitions of which are listed below:
For the purposes of promoting an understanding of the principles of the present inventions, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the inventions as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
Turning now to
A UMTS network typically consists of three interacting domains: Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). The main function of the core network is to provide switching, routing and transit for user traffic. The core network also contains the databases and network management functions. A UTRAN 104 provides the air interface access method for User Equipment. Typically, the base stations are referred as Node-B, such as Node-B 101 and control equipment for Node-B's is called Radio Network Controller (RNC), one RNC 103 is illustrated. The network 100 also includes several mobile units or user equipment, of which only user equipment 102 is illustrated. The user equipment 102 communicates with the UTRAN 104 in a conventional manner.
To achieve a MBMS environment, a number of new capabilities are added to existing 3GPP network entities and a number of new functional entities are added. Thus, the “existing” packet-switched domain functional entities (e.g., GGSN, SGSN, UTRAN, and UE) may be enhanced to provide the MBMS Bearer Service.
As illustrated in
The SGSN 106 also communicates with a Gateway GPRS Support Node (GGSN) 110, which typically functions as a gateway between the core network or cellular network and an IP network. The role of the GGSN 110 within the MBMS environment is to serve as an entry point for IP multicast traffic, such as MBMS data. The GGSN 110 is able to request the establishment of a bearer plane for a broadcast or multicast MBMS transmission. Further, the GGSN 110 is able to tear down the established bearer plane. Bearer plane establishment for multicast services is carried out towards those SGSNs that have requested to receive transmissions for the specific multicast MBMS bearer service. The GGSN 110 is also able to receive IP multicast traffic (whether from a BM-SC 112 or other data sources, such as multi-cast broadcast source 114) and to route this data to the proper GTP tunnels as part of the MBMS bearer service.
The BM-SC 112 provides functions for MBMS user service provisioning and delivery. The BM-SC 112 may also serve as an entry point for content provider MBMS transmissions, for instance, from a content provider 116. Additionally, the BM-SC 112 may also be used to authorize and initiate MBMS bearer services within the network and can be used to schedule and deliver MBMS transmissions. The BM-SC 112 is a functional entity, which must exist for each MBMS user service.
MBMS data may be distributed to multiple users through a MBMS distribution tree that can go through many BSCs/RNCs, many SGSNs and one or more GGSNs. Furthermore some bearer resources may be shared between many users accessing the same MBMS bearer service in order to save resources. As a result, each branch of a MBMS distribution tree will typically have the same QoS for all of its branches.
Thus, when a branch of the MBMS distribution tree has been created, it is not possible for another branch (e.g. due to arrival of a new user equipment or change of location of a user equipment with removal of a branch and addition of a new one) to impact the QoS of already established branches. In other words, there is no QoS value negotiation between UMTS network elements. This implies that some branches may not be established if QoS requirement cannot be accepted by the concerned network node. Also in the UTRAN 104, there is typically no QoS (re-)negotiation feature for the MBMS bearer service. Except for various aspects disclosed herein, there is currently no special solution that allows the user equipment 102 to perform inter-frequency and inter-RAT measurements while receiving MBMS data. Currently, the user equipment 102 would either not perform measurements during MBMS reception, which impacts mobility and results in loss of MBMS data and excessive repetitions or point to point—repair.
In general, measurements occasions may be scheduled in two different ways: either autonomously by each user equipment 102, or by the UTRAN 104. This disclosure will now focus on methods and systems to enable measurement occasions scheduled by said user equipment 102.
When the user equipment 102 tunes to another frequency to conduct a measurement, i.e. to perform inter-frequency and inter-RAT measurements, while receiving MBMS data, some MBMS data loss will occur. Thus, it is desirable to have a mechanism for recovering the lost packets. One mechanism which may be used is the implementation of an outer coding to recover the partial losses. In general, any error correcting code can be used as an outer code, e.g. Convolution code, Turbo code, CRC code, Reed-Solomon code. An inner code may, e.g. be a spreading code as a specific case of a repetition code.
If discontinuous reception (DRX) on a forward access channel (FACH) is used, outer coding on radio layer can be used to compensate for the data loss during DRX occasions. Outer coding will encode a number of inner code blocks (in case of radio layer outer coding, a number of transport blocks add some parity information that is used to recover inner code block errors.)
In this example, it is the user equipment 102 that is performing the measurement actively, and the UTRAN 104 is just transmitting the MBMS service, therefore, a network node, such as Node-B 101 is relatively passive. In some embodiments, the network node is just providing the corresponding outer code during the transmitting process.
Turning now to
In step 214 they are spread by a spreading code which encodes the inner code before they are transformed into a radio signal (step 216) which is sent over an antenna.
During the time there is DTX (the time is in whole TTIs, and in this example the TTI on the FACHs are 10 ms which is the same as the radio frame length) the user equipment can do inter-RAT and inter-frequency measurements. However, in case there is also MBMS in parallel which is the case for UE1-UE3, the user equipments should autonomously also leave the MBMS channel (do DRX of that channel) because a non dual receiver user equipment can not do both the MBMS reception and the measurement at the same time on different frequencies (like when doing measurements on, e.g., GSM which is the example in
When the user equipment does the measurements, it will miss one or several parts of a inner coded block equal to one radio frame of the MBMS FACH. However, because there is outer coding performed on TTI basis this can be recovered. In this example, the 2nd and 3rd coding level (Turbo or Convolutional coding and CRC coding respectively) is used on a TTI of 80 ms basis.
User equipments with dual receivers may also be able to perform the measurements without data loss and will therefore experience a better QoS, e.g. better streaming performance, less ptp-repair.
Thus, a user may enter commands by pressing the keypad 420. Upon a series of keyboard commands, the user equipment 400 may establish a MBMS session. In this example, the UMTS receiver 512b receives the MBMS data while the GSM receiver 412a is tuned to a different frequency and performs measurement events. In this configuration, there is no loss of data.
However, dual receivers may be costly in terms of complexity and power consumption for such user equipments.
Thus, a user may enter controls by pressing the keypad 520. Upon a series of keyboard commands, the UE may establish a MBMS session. In this example, the RF receiver 512 receives the MBMS data, but temporarily switches to another frequency or RAT to perform measurements. Thus, the RF receiver 512 may be a dual UMTS/GSM receiver. During the time that the receiver has switched to perform measurements, e.g. during DRX, data on MBMS are lost, but which can be recovered by the use of outer coding as previously explained.
Turning now to
Turning now to
Since it is a MBMS point to multipoint scenario, all user equipments will see the same download delay since they all listen to the same channel. However, there could be different amount of point-to-point repair from different user equipments if they on average have received more correct blocks of the MBMS transmission. Less point-to-point repair also means less resources/interference spent on this additional traffic. It should also be noted that the use of an outer code, either on radio or application layer, will improve the performance for the end-user, since e.g., exceptionally bad radio conditions may occasionally lead to lost transport blocks.
Various disclosed aspects of this invention is relatively simple to implement, does not require extra signalling, and does not have impacts on the S-CCPCH (Secondary Common Control Channel) according to previous standardization releases within. 3GPP. Furthermore, there is no need of paging rescheduling for idle or PCH user equipments, as measurements could be performed between paging occasions. Advantageously, user equipments in FACH could perform such measurements during “FACH measurement occasions” that a user equipment anyway have available for non-MBMS measurements in CELL_FACH state, whereas user equipments in DCH could utilize compressed mode gaps. This way, MBMS data loss will be minimized.
The above description focuses on CELL_FACH state. However, as one skilled in the art would recognize, the methods disclosed above would also work in other RRC service states, such as CELL_PCH, URA_PCH and idle mode.
Number | Date | Country | Kind |
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0303031-9 | Nov 2003 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE04/01656 | 11/12/2004 | WO | 5/2/2006 |