WO2014169476A1

WO2014169476A1 - Methods and apparatuses for updating base station configuration

Info

Publication number: WO2014169476A1
Application number: PCT/CN2013/074420
Authority: WO
Inventors: Peng Chen
Original assignee: Telefonaktiebolaget L M Ericsson(Publ)
Priority date: 2013-04-19
Filing date: 2013-04-19
Publication date: 2014-10-23

Abstract

The present disclosure relates to a method performed by a first evolved node B (40), eNB, for updating the eNB configuration of its neighboring eNBs, when the first eNB (40) is acting as a donor eNB, DeNB, for a relay cell of the mobile relay node (20). The eNB receives a signal from the mobile relay node (20) comprising a request to initiate communication between the mobile relay node (20) and the first eNB (40). Said signal comprising information elements relating to relay cells of the mobile relay node (20). The first eNB (40) sends an eNB configuration update message to all neighboring eNBs, with corresponding information elements. The neighboring eNBs than confirm that they have received the information elements and that they updated their cell relation table in accordance with the eNB configuration update message.

Description

METHODS AND APPARATUSES FOR UPDATING BASE STATION

CONFIGURATION TECHNICAL FIELD

Embodiments of the present disclosure generally relate to managing mobile relay nodes. More particularly, embodiments disclosed herein relate to a method performed by a first base station for updating base station configuration of base stations neighboring the first base station, said first base station acting as a donor base station for the mobile relay node. Embodiments herein also relate to a corresponding first base station.

BACKGROUND Today there is a quick global expansion of the use of high speed trains. This causes a big challenge when it comes to wireless communication, and in particular when performing handover when travelling on such a train. The high speed of the trains, usually around 200-350 km/h, will put demanding time constraints on the wireless network when preparing and executing handover, due to the short period of time it takes for the high speed train to run through a cell. Normally, the whole handover procedure from the detection of a strong neighboring cell to the connection to the target cell may take about 500 ms, depending on different timer settings, such as Time-to-trigger, measurement period etc. If one assumes that the cell of a radio access node has a radius of 500 meters, a high speed train will pass through as cell in about 10 to 20 seconds leading to a high volume of signaling and thus take a large portion of user equipment, UE, resources and system node resources. If the wireless network fails to meet these high time constraints it might cause a high dropping ratio or non-service from the network.

Another challenge when traveling at high speed, and especially when a larger number of users travel at high speed in the same train is that all connected users, i.e. connected UEs want to perform handover at the same time. This will cause a high volume of random access attempts and also overhead signaling. Depending on the number of users this might lead to a bottleneck in the Random Access Channel, RACH. All in all the users that are onboard a high speed train may experience frequent service interruptions or low-quality service during handover even if the handover is successful at the end.

In order to reduce frequent handovers of high speed users, attempts have been made to create a sector along the high speed railway that has an area that is shaped along the moving direction of the train. There have also been attempts to use special parameter configurations to speed up the handover procedure. Even if such attempts have reduced the above described problems to some extent, the high speed of a train still requires a rather high handover rate of the UEs and there are still a large numbers of UEs that need to be handed over at approximately the same time.

There have also been ongoing discussions to use mobile relay nodes mounted to high speed vehicles and connected wirelessly to macro cells, also called donor nodes. By using mobile relays the handover success rate may be improved since excessive handover signaling is avoided by performing a group mobility procedure instead of individual mobility procedures for every UE.

However, mobile relays also introduce some new challenges. Compared to a non-mobile relay, mobile relays cannot share the same base station identity as its donor base station, since its donor base station is constantly changing during the moving of the high speed vehicle, onto which it is mounted. If the mobile relay node instead is configured with one independent base station identity, the relationship that exists between the mobile relay node and its donor base station is not derivable from the radio access network global identifier of the mobile relay node. Thus, one UE connected to a base station directly neighboring the donor base station of a mobile relay node cannot perform handover to the mobile relay node even though connectivity has been setup between the donor base station and its neighboring base station.

For example, consider a situation where a first cell served by a first base station is a neighbor cell to a second cell served by a second base station. The first base station is also a donor base station for a mobile relay node. In such a case there does not exist any neighbor relation between any of the mobile relay node cells and the second cell. A UE served by the second cell detects one of the relay node cells and reports it back to the second cell, i.e. reports the physical cell identity, PCI and then the radio access network global identifier of that relay node cell. However, the second base station serving that second cell does not have any information that the mobile relay node is served by the first base station with which the second base station already has established connectivity. Thus, the second base station cannot handover the UE from the second cell to the relay node cell, via the first base station.

Thus, there is a need to find new ways to improve cellular communications for passengers, i.e. UEs, travelling on high speed vehicles and especially how to make use of mobile relay nodes.

SUMMARY In view of the above, an improved way to utilize mobile relay nodes for use on high speed vehicles, such as high speed trains, would be advantageous.

It is therefore a general object of embodiments of the present disclosure to improve the management of mobile relay nodes and its donor base station such that it is possible for base stations neighboring the donor base station of the mobile relay node to obtain cell information of the relay cell.

According to an aspect a method is provided that is performed by a first base station, for updating a base station configuration of its neighboring base stations. The first base station is acting as a donor base station and serving a relay cell of the mobile relay node. The method comprises receiving a signal from the mobile relay node comprising a request to initiate communication, via an interface, between the mobile relay node and the first base station. The first base station then receives information elements from the mobile relay node relating to relay cell of the mobile relay node. The first base station sends a base station configuration update message to all neighboring base station, said message comprising information elements relating to the relay cell that is served by the first base station. In various embodiments of the method the first base station receives an updating signal from the neighboring base stations comprising information elements, informing the first base station that the neighboring base stations, respectively, have updated their cell relation table in accordance with the base station configuration update message. The first base station and each neighboring base station may be an evolved node B, eNB, and the interface may be an X2 interface.

In other embodiments of the method performed by the first eNB the information elements relating to the relay cell served by the first eNB may be configured as an extension of the eNB configuration update message and/or may comprise a list of relay cells to add, relay cells to modify and relay cells to delete in the cell relation table of the neighboring eNBs. The information about relay cell may comprise the radio access network global identifier of the relay cell. According to a further aspect a first base station is configured to update a base station configuration of its neighboring cells, act as a donor base station and serve a relay cell of a mobile relay node. The first base station comprises a communication interface arranged for wireless communication; a processor; and a memory for storing computer program code which, when run in the processor will cause the first base station to receive, by means of the communication interface, a signal from the mobile relay node comprising a request to initiate communication between the mobile relay node and the first base station, to receive, by means of the communication interface, information elements from the mobile relay node relating to the relay cell of the mobile relay node and to send a base station configuration update message to all neighboring base stations

said message comprising information elements relating to the cell that is served by the first base station.

In various embodiments the first base station is further configured to receive, by means of the communication interface, an updating signal from the neighboring base stations comprising information elements, informing the first base station that the neighboring base stations, respectively, have updated their cell relation table in accordance with the base station configuration update message. The first base station and each neighboring base station may be an evolved node B, eNB, and the interface may be an X2 interface.

In various other embodiments of the first eNB, the information elements relating to the relay cell served by the first eNB, may be configured as an extension of the eNB configuration update message and/or comprise a list of relay cells to add, relay cells to modify and relay cells to delete in the cell relation table of the neighboring eNBs.

Furthermore the information about relay cell may comprise the radio access network global identifier of the relay cell.

An advantage of embodiments herein is that in the perspective of the UE it is now possible to perform a handover from a base station, on which the UE is camping directly to a mobile relay node, since the base station has received information elements related to relay cells. Heretofore this was not possible since the base station on which the UE is camping did not have any information about the donor node of the mobile relay node even if it was a neighboring cell.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects, features and advantages of embodiments of the present disclosure will be apparent and elucidated from the following description of various embodiments, reference being made to the accompanying drawings, in which:

Fig. 1 is a schematic diagram illustrating an exemplary embodiment of a first eNB;

Fig. 2 is a schematic diagram illustrating the procedure of updating the eNB configuration of neighboring eNBs; and

Fig. 3 is a flow chart showing an exemplary method.

DETAILED DESCRIPTION Various embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those persons skilled in the art. Like numbers refer to like elements throughout the description.

As mentioned above the present disclosure is generally directed towards managing mobile relay nodes, and in particularly how to update the base station configuration with information regarding relay cells. To this end an exemplary embodiment of a first base station will be described in more detail in conjunction with Figure 1. However, the description of the first base station is also applicable for a second base station or any other base station in a telecommunication system. In this example the base station will be a Long Term Evolution, LTE, base station, i.e. an evolved node B, eNB. However, it should be understood that it could be a base station in any present or future radio access network.

The first eNB 40 depicted in Figure 1 comprises a controller (CTL) or a processor 44 that may be constituted by any suitable Central Processing Unit, CPU, microcontroller,

Digital Signal Processor, DSP, etc., capable of executing computer program code. The computer program may be stored in a memory (MEM) 46. The memory 46 may be any combination of a Read And write Memory, RAM, and a Read Only Memory, ROM. The memory 46 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory. The first eNB 40 further comprises a communication interface (i/f) 42 arranged for wireless communication with other devices or nodes. The interface may comprise an X2 interface for direct communication between different eNBs, also including mobile relay nodes. With direct communication is meant neighboring eNBs are connected directly to each other via a transport network, i.e. without the need to use any other radio access network or core network. Turning now to Figure 2 the basic problem of using mobile relay nodes efficiently will be described. Figure 2 depicts a mobile relay node 20 a first eNB 40 and second eNB 50. Consider now a situation where a first cell is served by the first eNB and a second cell is served by the second eNB. The first eNB also serves as a donor eNB, DeNB, for the mobile relay node 20. If now the UE that is served by the second eNB detects one of the cells of the mobile relay node 20 and reports it back to the second cell of the second eNB, i.e. reports the PCI and the evolved universal terrestrial radio access network cell global identifier ECGI of the detected relay node cell, the second eNB will have problem with determining that the mobile relay node is served by the first eNB. The reason for this is that there is no such information in the eNB configuration of the first eNB. It is by realizing this problem, i.e. that the relationship that exists between the mobile relay node 20 and its DeNB can not be derieved from the ECGI of the relay cells, that the inventor understood that the eNB configuration was the solution to the problem. When the mobile relay node 20 attaches to or is handed over to the first eNB 40, the mobile relay node 20 will initiate an X2 setup procedure towards its DeNB, i.e. in the case depicted in Figure 2, the first eNB 40. The DeNB 40 will in turn initiate an X2 eNB configuration update procedure, and send an eNB configuration update message towards all of its neighboring eNBs in order to notify the neighboring eNBs about the relay cell information. In order to do this a new eNB configuration update message is foreseen. By extending the eNB configuration update message to contain lists of Relay Cells to Add, Relay Cells to Modify and Relay Cell to Delete the eNB configuration message now includes information about the mobile relay cells. In a preferred embodiment the information elements, IE, relating to the relay cells that are served by the first eNB 40, i.e. the DeNB, may have the definition as specified in Table 1 below.

Table 1 Definition of information elements relating to the

relay cells that are served by the DeNB. The relay cells to add are relay cells served by the first DeNB 40 and which have been newly added since the last X2 eNB configuration update message was sent. This will be the case when a new mobile relay node 20 attaches to or is handed over to the DeNB 40. The relay cells to modify may be updated if the mobile relay node for some reason changes its configuration, for example its transmission bandwidth. Relay cells to delete may be updated when the mobile relay node 20 detaches from the present DeNB 40 or is handed over to a new DeNB.

Based on the new and extended eNB configuration update message, the procedure to exchange associated relay cell information between DeNBs and its neighboring eNBs may be performed as depicted in Figure 2. When the second eNB receives the eNB configuration update message, the second eNB will parse the IE of Relay Cells to Add, Relay Cells to Modify, and Relay Cells to Delete, and will update its Cell Relation Table. The cell relation table may be defined as shown below in Table 2, below. In the cell relation table the eNB may look up the Donor Identity, ID, when it receives a measurement report from a UE indicating that the target cell is pointing to one cell of the mobile relay node. This may be achieved in that the mobile relay node broadcasts an indicator in the system information block 1 , SIB 1 , whether the cell is an relay cell or not. The UE may then set a relay node indicator in the Measurement Report to TRUE if the target cell is a relay cell.

Table 2 Cell Relation Table

The new elements in the cell relation table are the elements of the relay eNB Id and the donor eNB Id to support tracking associated with mobile relay nodes of neighboring eNBs. The cell relation table shows the binding relationship between one mobile relay node and its Donor eNB. The binding relationship is as mentioned above updated by the eNB configuration update message received from a neighboring Donor eNB. Turning now to figure 3, the method performed by the first eNB 40 for updating the eNB configuration of its neighboring eNBs will be described. As mentioned above the first eNB is acting as a DeNB, and serving a relay cell of the mobile relay node 20. In step 300 the eNB 40 is receiving a signal from the mobile relay node 20 comprising a request to initiate communication between the mobile relay node 20 and the first eNB 40. The communication may be done via the X2 interface, i.e. directly between the mobile relay node 20 and the first eNB. Step 300 may then be seen as an X2 setup procedure between the mobile relay node 20 and the first eNB, which in step 302 is receiving information about the relay node such as the relay eNB Id and other information relating to the relay cells of the mobile relay node 20. In step 304 the first eNB 40 is sending an eNB configuration update message to the neighboring eNBs. This message comprises information elements relating to the relay cells that are served by the first eNB 40. These information elements may be configured as an extension to the eNB configuration update message that is used today, see standard 3GPP 36.423, section 9.1.2.8, version 11.3.0. In a preferred embodiment the information elements relating to the relay cells served by the first eNB 40 comprise a list of relay cells to add, relay cells to modify and relay cells to delete in the cell relation table of the neighboring eNBs. After sending the eNB configuration update message the first eNB receives, in step 306, an updating signal from the neighboring eNBs comprising information elements, informing the first eNB 40 that the neighboring eNBs, respectively, have updated their cell relation table in accordance with the eNB configuration update message.

Although the present disclosure has been described above with reference to specific exemplary embodiments, it is not intended to be limited to the specific form set forth herein. In the pending claims, the term "comprise/comprises" does not exclude the presence of other elements or steps. Furthermore, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion of different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. Reference signs in the claims are provided merely as a clarifying example and should not be construed as limiting the scope of the claims in any way.

Claims

CLAIMS 1. A method performed by a first base station (40) for updating a base station configuration of its neighboring base stations, said first base station (40) acting as a donor base station and serving a relay cell of a mobile relay node (20), said method comprising,

- receiving (300) a signal from the mobile relay node (20) comprising a request to initiate communication, via an interface, between the mobile relay node (20) and the first base station (40),

- receiving (302) information elements from the mobile relay node (20) relating to the relay cell of the mobile relay node (20), and

- sending (304) a base station configuration update message to the neighboring base stations, said message comprising information elements relating to the relay cell that is served by the first base station (40).

2. A method according to claim 1, further comprising

- receiving (306) an updating signal from the neighboring base stations comprising information elements, informing the first base station (40) that the neighboring base stations, respectively, have updated their cell relation table in accordance with the base station configuration update message.

3. A method according to claim 1 or 2, wherein the first base station (40) and each neighboring base station is an evolved node B, eNB, and the interface is an X2 interface.

4. The method according to claim 3, wherein the information elements relating to the relay cell served by the first eNB (40), is configured as an extension of a eNB

configuration update message.

5. The method according to claim 3 or 4, wherein the information elements relating to the relay cell served by the first eNB (40), comprises a list of relay cells to add, relay cells to modify and relay cells to delete in the cell relation table of the neighboring eNBs.

6. The method according to any of the previous claims, wherein the information about the relay cell comprises the evolved universal terrestrial radio access network global identifier, ECGI, of the relay cell.

7. A first base station (40) configured to update a base station configuration of its neighboring base stations, act as a donor base station and serve a relay cell of a mobile relay node (20), said first base station (40) comprising,

- a communication interface (42) arranged for wireless communication; a processor (44); and a memory (46) storing computer program code which, when run in the processor (44), will cause the first eNB (40) to:

- receive, by means of the communication interface (42), a signal from the mobile relay node (20) comprising a request to initiate communication between the mobile relay node (20) and the first base station (40),

- receive, by means of the communication interface (42), information elements from the mobile relay node (20) relating to the relay cell of the mobile relay node (20), - send, by means of the communication interface (42), a base station

configuration update message to the neighboring eNBs, said message comprising information elements relating to the relay cell that is served by the first base station (40).

8. The first base station (40) according to claim 7, further configured to

- receive, by means of the communication interface (42), an updating signal from the neighboring base stations comprising information elements, to inform the first base station (40) that the neighboring base stations, respectively, have updated their cell relation table in accordance with the base station configuration update message.

9. The first base station (40) according to claim 7 or 8, wherein the first base station (40) and each neighboring base station is an evolved node B, eNB, and the interface is an X2 interface.

10. The first eNB (40) according to claim 9, wherein the information elements relating to the relay cell served by the first eNB, are configured as an extension of the eNB configuration update message.

11. The first eNB (40) according to any of claims 9 or 10, wherein the information elements relating to the relay cell served by the first eNB (40), comprise a list of relay cells to add, relay cells to modify and relay cells to delete in the cell relation table of the neighboring eNBs.

12. The first eNB (40) according to any of claims 7 to 1 1, wherein the information about the relay cell comprises the evolved universal terrestrial radio access network global identifier, ECGI, of the relay cell.