METHOD FOR PROVIDING MULTICAST BROADCAST SERVICES
CONTINUITY IN A WIRELESS NETWORK, CORRESPONDING
NETWORK NODE AND USER EQUIPMENT
BACKGROUND OF THE INVENTION
The present invention relates in particular to a method for providing
Multicast Broadcast Services continuity towards a user equipment part of a
wireless network.
In modern communication networks as the 3G Long Term Evolution
(LTE) defined as part of the 3GPP standardization, user equipments can be
provided with either Unicast services o r Multicast Broadcast Services o r both
simultaneously.
Unicast services are services which foresee a transmission of data
and messages towards a single destination (e.g. a single mobile terminal in
the case of a wireless network). Example of Unicast services are voice call,
email, surfing o n the Internet...
Broadcast services are services where the transmitted data are
readable by any destination (e.g. all mobile terminals in the wireless
network can access these data). Example of Broadcast Services could be
any service which does not require any registration and are available to all.
GPS could be seem as such a broadcast service.
Multicast services are a middle way between Unicast and Broadcast
services. Here only a group of destinations is addressed the same data and
messages. Example of Multicast services could be TV streaming based on
registration (often based on a fee) at a specific provider.
In wireless networks, Unicast and Broadcast/Multicast services are
each associated with a bearer specifying the corresponding configuration of
the physical Layer and the layer 2 in order to fulfill Quality of Services
requirements for the different services.
The bearers are mapped onto physical carriers. One carrier may
support several multiplexed bearers. This can be represented by different
bearers are mapped on some disjoints sub frames in a radio frame. It is
foreseen that. Figure shows a radio frame where bearers of different types
(Unicast service or Broadcast Multicast services) are multiplexed on the
same carrier. Subframes #0, #4, #5, # 9 are allocated to Unicast Services
while subframes # , #2, #3, # , #7, # 8 are allocated to Broadcast
Multicast Services.
In LTE, LTE-advanced networks, the Multicast Broadcast services are
often referred as MBMS (Multimedia Broadcast Multicast Services) or e-
MBMS (extended Multimedia Broadcast Multicast Services). It will be clear
for a person skilled in the art that the present invention can be used in the
context of LTE or LTE-advanced networks as well as in the context of other
wireless communication networks which show the same multiplexing of
Unicast and Multicast/Broadcast bearers on the same carrier.
In some cases, it may happen that the resources required for
Unicast Service bearers increase leading in a congestion situation. Here a
decision has to be made if the additional resource gets granted or not. In
case the resource is granted then a further decision has to be made if other
bearers need to be switched off. When Unicast and Broadcast Multicast
services co-exist on the same carrier, prior art solutions always privilege
Unicast services and possibly discontinue the Broadcast Multicast Services in
case of resource limitation.
Especially if Broadcast Multicast Service is provided on a single
frequency carrier, the wireless network must provide Unicast services on the
same carrier for all connected user equipments which are not capable of
carrier aggregation or dual reception. Given a large portion of subframe
resources would be reserved for Broadcast Multicast Service for a lot of user
equipments, resource limitation may be experienced for Unicast services.
The network design could minimise such resource limitation for
Unicast services on carriers which simultaneously support Broadcast
Multicast Service bearers.
One way to minimise the resource limitation for Unicast Services
consists in distributing Broadcast Multicast Service bearers load on multiple
carriers. For example, a highly popular Broadcast Multicast Service could be
provided on a carrier where only a few subframes are allocated for
Broadcast Multicast Services, leaving a large portion of subframe available
for Unicast Services. Consequently, resource limitation for Unicast Services
would happened rarely and the congestion on Unicast traffic would be kept
under control. Other available Broadcast Multicast Service should
consequently be allocated to other carriers.
Even though, the network design can minimise the possible
resource limitation for Unicast services on a carrier shared with Broadcast
Multicast Service bearers, a particular object of the present invention is to
provide a method able to resolve the limitation on Unicast Service with
minimum disturbance to the user experience for Broadcast Multicast Service
experience.
Another object of the invention is to provide network node as well
as user equipment mechanisms to resolve the issue addressed above while
ensuring a continuity of the Broadcast Multicast Service in a wireless
network.
SUMMARY OF THE INVENTION
These objects, and others that appear below, are achieved by a
method for providing Multicast Broadcast Services continuity towards a user
equipment part of a wireless network according to claim 1, a corresponding
network Node according to claim 5 and a corresponding user equipment
according to claim .
According to the present invention, Multicast Broadcast services are
prioritized over Unicast services in case congestion would happen for
Unicast services
In a first embodiment of the invention, the User equipment sends
out an indication requesting the wireless network to prioritize the Broadcast
Multicast Services over the Unicast Service bearers.
In a second embodiment of the invention, the prioritization is
performed by assigning priorities to all bearers destined to a user
equipment, the priority assigned to Unicast services being lower than the
priority assigned to at least one Broadcast Multicast Services.
In a third embodiment of the present invention, the prioritisation is
achieved in that the wireless network sends out an indication that
congestion happens for a Unicast Services destined to the user equipment,
the user equipment being able to take the appropriate measure to keep the
continuity of the Broadcast Multicast Services.
The method according to the present invention presents the
advantage to provide user equipments a more flexible way of controlling
the kind of Services they like to prioritize, knowing that more and more
Broadcast Multicast Services may have the preference of the users over
Unicast services at some point.
Further advantageous features of the invention are defined in the
dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and advantages of the invention will appear
on reading the following description of a preferred embodiment given by
way of non-limiting illustrations, and from the accompanying drawings, in
which:
Figure 1 shows a radio frame on a carrier multiplexing
Broadcast/Multicast Service bearers subframes and Unicast Service
bearers subframes;
- Figure 2 shows a flow diagram illustrating a first embodiment of the
present invention;
Figure 3 shows a flow diagram illustrating a second embodiment of the
present invention;
Figure 4 shows a flow diagram illustrating a third embodiment of the
present invention;
- Figure 5 shows an implementation of a network node according to the
present invention;
- Figure 6 shows an implementation of a user equipment according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
The functions of the various elements shown in the Figures,
including any functional blocks labeled as 'processors', may be provided
through the use of dedicated hardware as well as hardware capable of
executing software in association with appropriate software. When provided
by a processor, the functions may be provided by a single dedicated
processor, by a single shared processor, or by a plurality of individual
processors, some of which may be shared. Moreover, explicit use of the
term 'processor' or 'controller' should not be construed to refer exclusively
to hardware capable of executing software, and may implicitly include,
without limitation, digital signal processor (DSP) hardware, network
processor, application specific integrated circuit (ASIC), field programmable
gate array (FPGA), read only memory (ROM) for storing software, random
access memory (RAM), and non volatile storage. Other hardware,
conventional and/or custom, may also be included. Similarly, any boxes
shown in the Figures are conceptual only. Their function may be carried out
through the operation of program logic, through dedicated logic, through
the interaction of program control and dedicated logic, or even manually,
the particular technique being selectable by the implementer as more
specifically understood from the context.
Figure 1 has been described in relation with the opening part of the
description.
Figure 2 shows a flow diagram illustrating a first embodiment of the
present invention. In this embodiment, user equipment UE sends to Network
Node NN an indication requesting that Multicast Broadcast Services are
prioritised over Unicast Services. Preferably, this indication is part of a R C
signalling message. The indication itself may be represented by a single bit
in the RRC message.
It will be understood by those skilled in the art that other types of
messages can be used to convey the indication from the UE to the NN.
Upon notification of the network that the prioritisation of Multicast
Broadcast Services should happen for the UE, the network node preferably
checks if a congestion situation happens on the Unicast Service Bearers. If
this is the case, the Network Nodes decides which Unicast bearers need to
be switched off or deleted to ensure that the continuity of Multicast
Broadcast Services towards the UE is not endangered.
In a further step, and in case of Unicast Service congestion, the
Network Node sends a signalling message to the UE indicating one or
more Unicast Service release. One possible signalling way is to use a RRC
message.
In an advantageous embodiment, the RRC Unicast Service release
message contains the reason of the release (i.e. release because of
Multicast Broadcast Services prioritisation). This presents the advantage that
the UE would avoids any attempt to re-establish the released Unicast
Service bearer/ and or connection as part of a recovery measure.
In the following, 3 possible implementations of the Unicast Service
release will be explained.
The Unicast Service release can preferably done either at the
Unicast Service bearer level or at the Unicast Service connection level or at
both levels. In case the bearer is released the UE is still known at the
network and the network keeps the UE info: security, id, etc. In case the
connection is released, the UE doesn't have any established bearers to the
network any more. Consequently the UE is known by the wireless network
only at tracking area level since, releasing connection also clears up some
stored info about the UE at the network side.
These Unicast Service release implementations are not exhaustive
so that any other alternative obvious for a person skilled in the art in view of
invention should also fall under the scope of the present invention.
In the following the description is made with reference to the
Unicast Service bearer release. It will be clear for a person skilled in the art
that a Unicast Service connection release would also apply. For simplicity
reasons the cases of Unicast Service connection release will not be detailed
below but is part of the scope of the present invention.
In a first alternative, the Unicast Service bearer release is reached
by the Network Node requesting the UE to move to Idle mode. After
resolving the congestion, the UE is informed that it can restore the
Broadcast Multicast Service bearer. In this alternative, the UE cannot get any
unicast service (including voice calls) during the period of congestion.
In a second alternative, the Unicast Service bearer release is
reached in that all dedicated Unicast Service bearers are released but the
default bearer is kept. The traffic mapped onto the default bearer is
expected to be delivered with best effort. Some unicast Services on the
default bearer may experience unavailability while the UE is receiving
Broadcast/Multicast Services. Once congestion is relaxed, the dedicated
Unicast Service bearers can be established. In this alternative, the UE
cannot get any unicast service (including voice calls) during the period of
congestion. Compared to the option above, this option does not require
signalling of congestion in the RC message informing on unicast
connection release nor alleviation of congestion.
In a third alternative, the Unicast Service bearer release is reached
in that only some dedicated Unicast Service bearers are released when the
UE indicates its willingness to prioritise Brodacast Multicast Services over
Unicast Services. This alternative provides a more flexible solution but is
also more complex since it implies that a choice has to be done on which
Unicast Service Bearers to release and which to keep. Here an assignment
of priorities as described in the second embodiment of the present invention
(in relation with Figure 3) can be used to help selecting the bearers to
release. This method requires signalling to keep the network updated on the
dynamic priority values since the UE may change priority between the
bearers frequently.
Advantageously, the signalling message requesting the
prioritisation of Broadcast Multicast Services over Unicast may be
interpreted at the network node depending on the network/operator policy
o r user subscription information. The method has consequently the potential
to cater for each individual user requirements. Hence the unicast bearers
which are released in a congestion situation may vary for user to user.
Figure 3 shows a flow diagram illustrating a second embodiment of
the present invention. According to this embodiment, a control unit 3 1
assigns priorities to the different bearers received by a user equipment.
Typically the default bearer is assigned priority P0, Unicast bearers 1 resp 2
are assigned priority PI resp P2 and Broadcast Multicast bearer is assigned
priority Pm. In order to have Broadcast Multicast bearer prioritized over
Unicast bearers P and P2, Pm should be at least higher than PI or P2 or
higher than both.
Upon detection of congestion, the network can start releasing the
bearers having a low priority to ensure keeping continuity of Broadcast
Multicast bearer.
In a preferred embodiment of the present invention, the default
bearer is excluded from the mechanism of priority since it should not be
released. Since however, it is foreseen that a best effort scheme applies to
the default bearer, allocating to the default bearer a higher priority than to
the Broadcast Multicast bearer would not endanger the continuity of the
Broadcast Multicast service. Background traffic (eg email, facebook, etc)
may most likely be mapped on the default bearer. The default bearer is
non-GBR (non Guaranteed Bit Rate) and the traffic is delivered according to
best effort. If resource is limited, the best effort traffic can be delayed. The
default bearer must be maintained for RRC connected UEs. Even though the
default bearer has higher priority than Broadcast Multicast services, the UE
doesn't need to be handed over to another carrier to maintain the unicast
connection since the default bearer is best effort bearer.
In LTE, Network based relative allocation/retention Priorities (ARP),
so far exclusively used in the context of Unicast bearers, could be extended
to Broadcast Multicast bearer so that a priority comparison among bearers
of different nature is possible and so that the continuity of Broadcast
Multicast bearer is ensured.
In a preferred embodiment, the priorities are controlled by an
Operation and Maintenance Module in the network, however the priorities
may be assigned by a network node or by the user equipment. In case the
user equipment is assigning the priorities a signaling mechanism should be
put in place to communicate the different priorities of the different bearers
to the network node.
In case of a resource limitation on the carrier supporting the
Broadcast Multicast bearers, the network may compare the priority of
Unicast bearers to the priority of Broadcast Multicast bearers and choose
which bearers to pre-empt. Preferably, the network is aware of the UEs who
are receiving Broadcast Multicast service so that it can focus on these UEs.
Hence, according to the present invention, the network may release some
unicast bearers with a priority lower than the one of the Broadcast Multicast
bearer.
If the resource limitation persists, and the UE finds no more Unicast
bearers with lower priority than Broadcast Multicast, the network preferably
hands over the UE to another frequency. This situation results in releasing
Broadcast Multicast bearer for the corresponding UE based on relative
priority.
Alternatively, in order to avoid the release of the Broadcast
Multicast bearer and still continue to provide continuity of the Broadcast
Multicast Service, one could use at this point a method according to the
already described first embodiment in relation with figure 2.
In a further implementation of the above solution, the priority
assigned to the Broadcast Multicast service bearers could take into account
the user subscription information. Therefore, the solution could be catered
for individual user requirements/subscription information. Additionally, it
has potential to customise the priorities for the unicast bearers for a specific
user taking into account the use of Broadcast Multicast service bearer and
the associated priority.
This solution could be further enhanced considering implicit user
selection/cooperation. For example, a user initiating a voice call is implicitly
indicating it is higher priority than Broadcast Multicast service. The user can
prioritise Broadcast Multicast service by terminating the voice call and then
the network wil move the user to the Broadcast Multicast service layer and
provide lower service for the default bearer to allow the UE to select the
Broadcast Multicast service layer. However, the implicit user interaction
assumes that direct relationship between applications and high priority
bearers is known by the user so that a user closing an application will result
in the release of a bearer and the change in priorities of the remaining
bearers.
Figure 4 shows a flow diagram illustrating a third embodiment of
the present invention. According to this embodiment, the continuity of the
Broadcast Multicast service is ensured by sending an indication of Unicast
Service congestion on the carrier shared between the congested Unicast
Service and the Broadcast Multicast Service. This congestion indication is
sent from the network node to the User equipments which are
receiving/interested in receiving a Broadcast Multicast service.
Either the congestion information can be broadcast in the cell, only
the Broadcast Multicast interested UEs being intended to use the congestion
information or the congestion information can be provided to the
corresponding UEs who are receiving or willing to receive Broadcast
Multicast service via dedicated R C signalling, these UEs being known by
the network node. The used RRC signalling could be either a dedicated RRC
signalling or a cell broadcast RRC signalling.
Upon the reception of congestion indicator on Broadcast Multicast
frequency carrier, the UEs who are willing to prioritise Broadcast Multicast
services over Unicast switch off Unicast Services which are expected to have
large amount of downlink traffic.
The application layer of the UE communicates to the network node
the switching off of Unicast Services which eventually results in release of
the associated bearers. This is performed at the application layer and may
advantageously use IP-CAN bearer setup/mod if ication/ release procedure.
When the congestion is relaxed on the carrier, the UE should be
informed in order to turn on the application released due to the congestion.
This third embodiment purely relies on the UE to switch off the
unicast bearers. If any of the unicast bearers is not released, (except the
default bearer) the network is required to handover the UE to another
carrier to maintain the unicast connection.
To improve the performance, the network could indicate to the UE
the release of which bearers may assist the resolving the congestion. Thus,
the user makes the decision to switch off the application based on its
interest (assuming the user is aware of the mapping between bearer and
application).
It will be clear for those skilled in the art that any combination of
two or more of the presented embodiments would solve the technical
problem and is part of the scope of the present invention. For example, in
addition to releasing some bearers based on priorities, the UE could also be
informed of the congestion situation.
Figure 5 shows an implementation of a network node 50 according
to the present invention. The Network Node is part of a wireless network
and adapted to support Multicast Broadcast Services continuity towards a
user equipment. The Multicast Broadcast Services are supported by at least
one Multicast Broadcast Services bearer. The wireless network further
provides Unicast Services to the user equipment. The Unicast Services are
supported by at least one Unicast Service bearer. The Multicast Broadcast
Services bearers are multiplexed with Unicast Services bearers on at least
one carrier. According to the present invention the network node 50
comprise a control unit 5 1 adapted to prioritise the Multicast Broadcast
Services over said Unicast services.
In a first embodiment, the control unit 5 1 reaches the prioritisation
by assigning a priority to each bearer supporting a service at the user
terminal. At least one of said Multicast Brodacast Services bearer is given a
higher priority than the Unicast Services bearers. The priority is taken into
account by the network node 50 for releasing bearers in case of congestion
on said carrier, bearers with lower priority being released first.
In a second embodiment the control unit 5 1 reaches prioritisation
by sending an indication of Unicast Service bearer congestion on the carrier
shared with the Broadcast Muluticast Service to the user equipment.
Network Node 50 performs method steps as described in relations
with the description of figure 2, 3, 4 .
Figure 6 shows an implementation of a user equipment 60
according to the present invention. The user equipment is part of a wireless
network and adapted to support Multicast Broadcast Services continuity. The
Multicast Broadcast Services being supported by at least one Multicast
Broadcast Services bearer. The user equipment is further provided with
Unicast Services, the Unicast Services being supported by at least one
Unicast Service bearer. The Multicast Broadcast Services bearers are
multiplexed with Unicast Services bearers on at least one carrier. The user
equipment comprises a module 6 1 adapted to request prioritisation of the
Multicast Broadcast Services over said Unicast services. The module 6 1
comprises means for sending an indication to a network node requesting
the Multicast Broadcast Services to be prioritised over the Unicast Services.
User Equipment 60 performs method steps as described in relations
with the description of figure 2, 3, 4 .
CLAIMS
/ Method for providing Multicast Broadcast Services continuity towards a
user equipment (60) part of a wireless network, said Multicast Broadcast
Services being supported by at least one Multicast Broadcast Services
bearer, said wireless network further providing Unicast Services to said user
equipment (60), said Unicast Services being supported by at least one
Unicast Service bearer, said Multicast Broadcast Services bearers being
multiplexed with Unicast Services bearers on at least one carrier, said
method comprising the steps of:
- prioritising said Multicast Broadcast Services over said Unicast
services wherein said prioritising consists in sending an indication
from said user equipment (60) to said wireless network requesting
said Multicast Broadcast Services to be prioritised over said Unicast
Services, and wherein in case of congestion of Unicast Services on
said carrier, said network releases at least one Unicast service bearer
and/or one Unicast Connection.
2/ Method according to claim 1, wherein a Unicast Service bearer is
defined as default bearer for said user equipment (60), said default bearer
still keeping priority over said Multicast Broadcast Services bearers.
3/ Method according to claim 1, wherein said indication is sent through
C signalling.
4/Method according to claim 1, wherein said user equipment (60) is
informed through signalling that the Unicast service bearer has been
released because of said prioritising of said Multicast Broadcast Services
over said Unicast Services, said method further comprising the step of
avoiding any attempt by said user equipment (60) to re-establish said
Unicast bearer as part of a recovery measure.
5/Method according to claim 1, wherein said user equipment (60) is
informed through signalling that the Unicast connection has been released
because of said prioritising of said Multicast Broadcast Services over said
Unicast Services, said method further comprising the step of avoiding any
attempt by said user equipment (60) to re-establish said Unicast connection
as part of a recovery measure.
6/ Method according to claim , wherein said prioritising consists in
assigning a priority to each bearer at said user terminal, said bearer being
either a Multicast Broadcast Services bearer or a Unicast Services bearer, at
least one of said Multicast Broadcast Services bearer having a higher
priority than said Unicast Services bearers, said priority being taken into
account for releasing bearers in case of congestion on said carrier, bearers
with lower priority being released first.
7/ Method according to claim 6, wherein said priorities are assigned by the
operation and maintenance module of said wireless network.
8/ Method according to claim 6, wherein in case of congestion of Unicast
Services on said carrier, said network releases at least one Unicast Service
bearer having a low priority.
9/ Method according to claim 1, wherein said prioritising consists in
sending an indication of Unicast Service bearer congestion on said carrier,
said user equipment (60) performing the step of switching off at least one
Unicast Service bearer on said carrier upon reception of said indication of
congestion.
0/ Method according to claim 9, wherein said indication of congestion is
sent through dedicated RRC signalling.
11/ Method according to claim 9, wherein said indication of congestion is
sent through cell broadcast RRC signalling.
2/ Method according to claim 9, wherein said user equipment 60)
releases at least one of said Unicast service bearers upon reception of said
indication of congestion.
13/ Network Node (50) part of a wireless network adapted to support
Multicast Broadcast Services continuity towards a user equipment (60), said
Multicast Broadcast Services being supported by at least one Multicast
Broadcast Services bearer, said wireless network further providing Unicast
Services to said user equipment (60), said Unicast Services being supported
by at least one Unicast Service bearer, said Multicast Broadcast Services
bearers being multiplexed with Unicast Services bearers on at least one
carrier, said network node (50) comprising:
a control unit (51 ) adapted to prioritise said Multicast Broadcast Services
over said Unicast services, said prioritisation being obtained by assigning a
priority to each bearer supporting a service at said user terminal, at least
one of said Multicast Broadcast Services bearer having a higher priority
than said Unicast Services bearers, said priority being taken into account by
said wireless network for releasing bearers in case of congestion on said
carrier, bearers with lower priority being released first ORsaid prioritisation
being obtained by sending an indication of Unicast Service bearer
congestion on said carrier to said user equipment (60).
14/ User equipment (60) part of a wireless network adapted to support
Multicast Broadcast Services continuity, said Multicast Broadcast Services
being supported by at least one Multicast Broadcast Services bearer, said
user equipment (60) being further provided with Unicast Services, said
Unicast Services being supported by at least one Unicast Service bearer,
said Multicast Broadcast Services bearers being multiplexed with Unicast
Services bearers on at least one carrier, said user equipment (60)
comprising a module (61 ) adapted to request prioritisation of said Multicast
Broadcast Services over said Unicast services, said module (61) comprising
means for sending an indication to said wireless network requesting said
Multicast Broadcast Services to be prioritised over said Unicast Services,
wherein in case of congestion of Unicast Services on said carrier, said
network releases at least one Unicast service bearer and/or one Unicast
Connection.