Cellular telecommunications networks

Abstract

The present invention relates to a method in a cellular telecommunication network having a plurality of base stations, each base station having at least one transmitter, each transmitter having at least one coverage area, the method comprising the steps of: a first transmitter operating in a first state so as to transmit within a first coverage area only according to a first cellular communication protocol; receiving a request for service according to a second cellular communication protocol in the first coverage area; and in response, the first transmitter operating in a second state so as to transmit within the first coverage area according to both the first cellular communication protocol and a second cellular communication protocol, wherein the second cellular communication protocol is a cellular communication protocol of an older generation than the first cellular communication protocol.

Description

Technical Field

[0001] The present invention relates to cellular telecommunication networks. Background Art

[0002] Cellular telecommunication networks operate according to specific protocols such as Global System for Mobile Telecommunications (GSM), Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE). Each protocol defines its transmission spectrum, which may overlap (at least partially) with the transmission spectrum of another protocol. A cellular network may include a coverage area at which a user equipment (UE) may receive transmissions from one or more base stations transmitting according to two cellular protocols, and in order to avoid interference, the network operator must allocate resources in the overlapping portion of the cellular protocol transmission spectrum to only one of these cellular protocols. These spectrum resources should be allocated to each protocol so as to fully meet the corresponding demands from the UEs communicating via that protocol. Any spectrum resources allocated to a specific protocol above the corresponding demands are considered to be wasted, since the spectrum resources could have been allocated to another protocol. Similarly, any processing resources allocated to processing transmissions according to a specific protocol exceeding the corresponding demands are also considered to be wasted.

[0003] It would therefore be desirable to alleviate some or all of the above problems. Summary of the invention

[0004] According to a first aspect of the present invention, there is provided a method in a cellular telecommunication network having a plurality of base stations, each base station having at least one transmitter, each transmitter having at least one coverage area, the method comprising the steps of: operating a first transmitter in a first state so as to transmit within a first coverage area only according to a first cellular communication protocol; receiving a request for service according to a second cellular communication protocol in the first coverage area; and, in response, operating the first transmitter in a second state so as to transmit within the first coverage area according to both the first cellular communication protocol and the second cellular communication protocol, wherein the second cellular communication protocol is a cellular communication protocol of an older generation than the first cellular communication protocol.

[0005] The method may also include the steps of determining that demand for service according to the second cellular communication protocol in the first coverage area ceases; and in response, operating the first transmitter in a first state to transmit only according to the first cellular communication protocol within the first coverage area.

[0006] The request for service using the second cellular communication protocol in the first coverage area may be based on the first transmitter being a candidate handover target for the second transmitter.

[0007] Operation in the first state may be transmission according to a first cellular communication protocol using a frequency band having a first frequency sub-band and a second frequency sub-band, and operation in the second state may be transmission according to the first cellular communication protocol using the first frequency sub-band and transmission according to a second cellular communication protocol using the second frequency sub-band.

[0008] The method may also include the following steps: identifying a second transmitter operating in a first state so as to transmit only according to a first cellular communication protocol within a second coverage area, the first coverage area and the second coverage area being adjacent coverage areas; sending an indication message to the second transmitter, the indication message causing the second transmitter to use a first transmission power for transmission in a first frequency sub-band and a second transmission power for transmission in a second frequency sub-band, wherein the first transmission power is higher than the second transmission power.

[0009] The first transmitter can be part of a first virtual base station, wherein, in a first state, the first virtual base station uses first computing resources to process communications according to a first cellular communication protocol, and in response to a request for service using a second cellular communication protocol in a first coverage area, the virtual base station can also use second computing resources to process communications according to the second cellular communication protocol.

[0010] The first transmitter may be part of a first base station and the second transmitter may be part of a second base station.

[0011] Both the first transmitter and the second transmitter may be part of a first base station.

[0012] According to a second aspect of the present invention, there is provided a computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method of the first aspect of the present invention. The computer program may be stored on a computer readable data carrier.

[0013] According to a third aspect of the present invention, there is provided a network node of a cellular telecommunication network, the network node comprising a transmitter, a processor and a memory, the transmitter, the processor and the memory being configured to cooperate to perform the steps of the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to better understand the present invention, embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0015] Figure 1 is a schematic diagram of an embodiment of a cellular telecommunication network of the present invention;

[0016] Figure 2 yes Figure 1 A schematic diagram of a base station of a cellular network;

[0017] Figure 3a to Figure 3g is a schematic diagram of a cellular network adapted by an embodiment of the method of the present invention; and

[0018] Figure 4 is a flow chart illustrating an embodiment of the method of the present invention. DETAILED DESCRIPTION

[0019] exist Figure 1 1. A cellular telecommunication network 1 is shown in FIG. The cellular network 1 comprises first to eleventh base stations 10a to 10k (i.e. 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i, 10j, 10k), whose coverage areas are shown by their respective enclosing hexagons.

[0020] like Figure 2 As shown, the first base station 10a includes a first communication interface 11a configured to communicate with a user equipment (UE), a processor 13a, a memory 15a, and a second communication interface 17a for communicating with a cellular core network, all of which are connected via a bus 19a. The communication interface, the processor, and the memory are configured to collaborate to define a software defined network (SDN) working environment, thereby allowing the first base station 10a to be reconfigured on demand. In addition, the processor 13a implements network function virtualization (NFV) to establish a first communication processing environment for communicating with the first UE via a first communication protocol (e.g., LTE), and a second communication processing environment for communicating with the second UE via a second communication protocol (e.g., GSM). In order to achieve these communications, the first communication interface 11a can cooperate with several antennas, wherein each antenna works according to a specific protocol. In addition, the first base station 10a may include an NFV coordinator 14a for determining resource (e.g., spectrum resource) allocation, and a virtualized infrastructure manager (VIM) 16a for implementing the decision of the NFV coordinator. In this embodiment, the NFV coordinator 14a and the VIM 16a determine and implement allocation of spectrum resources in overlapping portions of respective transmission spectrums of the first communication protocol and the second communication protocol.

[0021] The second base station 10b to the eleventh base station 10k are similar to the first base station 10a, so that they all include a communication interface, a processor and a memory, which are adjusted to collaborate to define an SDN working environment to allow them to be reconfigured on demand, and also implement NFV to establish multiple communication processing environments so that they can communicate with the first UE via a first communication protocol and communicate with the second UE via a second communication protocol.

[0022] Now refer to Figure 3a to Figure 3g as well as Figure 4 The first embodiment of the present invention is described by the flowchart of FIG. Figure 3a As shown, the first base station 10a of the cellular network 1 operates according to both the LTE protocol and the GSM protocol (indicated by the coverage area of ​​the first base station having cross-hatching in its hexagonal coverage area). Therefore, the first communication interface 11a of the first base station is adjusted to send and receive transmissions according to the LTE and GSM protocols (for example, by connecting to a first antenna that is adjusted to send and receive transmissions using the LTE protocol, and also connecting to a second antenna that is adjusted to send and receive transmissions via the GSM protocol), and the processor 13a of the first base station can implement a first communication processing environment that processes communications according to the LTE protocol and a second communication processing environment that processes communications according to the GSM protocol. In addition, the NFV coordinator and VIM of the first base station are configured to determine and implement resource allocation between the first communication processing environment and the second communication processing environment, including resource allocation in the overlapping portion of the LTE transmission spectrum and the GSM transmission spectrum.

[0023] In this initial configuration, the first base station 10a serves the first UE 20 only via the LTE protocol. However, the first base station 10a has active GSM services (via the second antenna and the second communication processing environment), for example because the network operator is obliged to provide GSM services in the coverage area of ​​the first base station.

[0024] The second base station 10b to the eleventh base station 10k of the cellular network 1 operate only according to the LTE protocol (designated by having positive diagonal hatching in their respective hexagonal coverage areas). Therefore, the first communication interface of each base station is adjusted to send and receive transmissions according to the LTE protocol (for example, by connecting to a first antenna that is adjusted to send and receive transmissions using the LTE protocol). In addition, the processor of each base station implements a first communication processing environment that is configured to process transmissions of the LTE protocol. As described above, these base stations are capable of communicating with UEs via the GSM protocol (for example, by using their respective second antennas that are adjusted to communicate via the GSM protocol and their respective second communication processing environments that are configured to process transmissions of the GSM protocol), but since no UE requires GSM service and the cellular network is not obligated to provide GSM service in these coverage areas, Figure 3a The initial configuration shown is without these second antennas and second communications processing environment in use.

[0025] In this embodiment, the first step ( Figure 4In step S1), the first base station 10a starts to serve the second UE 30 via the GSM protocol (for example, the second UE 30 is powered on and establishes communication with the first base station 10a, or the second UE 30 switches from the "idle" working mode to the "connected" working mode). In step S3, the first base station 10a identifies one or more possible handover targets for the second UE 30. The first base station 10a can identify the possible handover targets as one or more base stations among its neighboring base stations. To achieve this, the first base station 10a (for example, based on the information in its neighbor relationship table NRT) identifies all neighboring base stations, and in this embodiment, a subset of these neighboring base stations is identified as a possible handover target based on a comparison of the location of each neighboring base station in the neighboring base stations with the location of the second UE 30. For example, the second UE 30 can report its location to the first base station 10a, and the first base station 10a can identify the n nearest neighboring base stations as possible handover targets based on a comparison of the location of the second UE with the locations of these neighboring base stations (known or queried by the first base station 10a). In another example, the first base station 10a may determine that the second UE 30 is following a known route (e.g., a road or railway track), and therefore identifies one or more neighboring base stations having a coverage area along the route as possible handover targets. However, in a simpler implementation, the first base station 10a may identify all of its neighboring base stations as possible handover targets. In this example, the first base station 10a identifies the third base station 10c and the fourth base station 10d as possible handover targets.

[0026] In step S5, the first base station 10a establishes an X2 connection with the third base station 10c and the fourth base station 10d (in the case where one connection has not yet been established), and sends an X2 message including: a) a request for service according to the GSM communication protocol, and b) identifiers of all other base stations that have been identified as possible handover targets of the second UE 30 (from step S3). In step S7, the third base station 10c and the fourth base station 10d respond to the request for service via the GSM protocol by being reconfigured to operate according to both the LTE and GSM communication protocols. In this example, this is achieved by having their respective processors establish a second communication processing environment that is adjusted to process communications according to the GSM protocol (this is in addition to the first communication processing environment that is adjusted to process communications according to the LTE protocol) and having their respective first communication interfaces connected to a second antenna that is configured to communicate via the GSM protocol (in addition to being connected to a first antenna that is configured to communicate via the LTE protocol). Since the third base station 10c and the fourth base station 10d previously used the entire LTE transmission spectrum for communication, their respective NFV coordinators must allocate resources in the overlapping portion of the LTE and GSM spectrum to the LTE spectrum or the GSM spectrum for use by their first antenna or second antenna, respectively (implemented by VIM). At this stage when there is no actual demand for services via GSM (because the second UE 30 is still served by the first base station 10a at this time), only the resources of the GSM protocol required for establishing communication with the second UE 30 in the overlapping portion of the LTE transmission spectrum and the GSM transmission spectrum are allocated for communication according to the GSM protocol. All remaining resources in the overlapping portion of the LTE and GSM transmission spectrum are allocated for LTE communication.

[0027] After this reconfiguration, the cellular network 1 is in the state Figure 3b The state shown in FIG. 1 is a state in which the first base station 10a, the third base station 10c and the fourth base station 10d are adjusted to communicate via LTE and GSM, and the second base station 10b, the fifth base station 10e to the eleventh base station 10k are adjusted to communicate only via LTE. In step S9, the second UE 30 moves into the coverage area of ​​the third base station 10c, and the first base station 10a and the third base station 10c complete the handover, so that the third base station 10c now serves the second UE 30 (using the GSM protocol). This is Figure 3c At this point, the NFV coordinator and VIM of the third base station may reallocate resources in the overlapping portions of the respective spectrums of GSM and LTE between GSM and LTE in proportion to the current (or estimated) demand for services via these protocols.

[0028] After this handover, even though the second UE 30 is now located within the coverage area of ​​the third base station 10c, when the second UE 30 is located within the coverage area of ​​the source base station (i.e., the fourth base station 10d), the source base station (i.e., the first base station 10a) and other base stations identified as possible handover targets for the second UE 30 initially continue to communicate via both the LTE protocol and the GSM protocol. After reading the following description, how and when the source base station and the possible handover target base stations that have not become the target base stations switch back to LTE-only communication will become apparent.

[0029] In step S11, the third base station 10c identifies one or more possible handover targets for the second UE 30 at the new location in the coverage area of ​​the third base station. In this example, this includes the first base station 10a, the fourth base station 10d and the sixth base station 10f. In step S13, the third base station 10c then determines whether any other base stations should switch back to communicating via LTE only (i.e., and therefore reallocate all resources to LTE communication). This is achieved by the third base station 10c by identifying any of the following base stations: 1) a source base station (i.e., the first base station 10a in this iteration) that is handed over to the third base station 10c, but the source base station is not one of the possible handover targets (the first base station 10a, the fourth base station 10d, and the sixth base station 10f) newly identified for the second UE 30 based on the coverage area of ​​the third base station, or 2) any of the other possible handover target base stations for the second UE 30 when the second UE 30 is served by the source base station (i.e., the fourth base station 10d in this iteration), but any of the base stations is not one of the possible handover targets (the first base station 10a, the fourth base station 10d, and the sixth base station 10f) newly identified for the second UE 30 based on the coverage area of ​​the third base station. In this iteration, no base station that meets at least one of these criteria is identified.

[0030] However, when the third base station 10c explicitly identifies a possible handover target, the process loops back to step S5, in which the third base station 10c sends a message to these identified base stations, the message including: a) a request for service via the GSM protocol; and b) identifiers of all identified possible handover targets (the first base station 10a, the fourth base station 10d and the sixth base station 10f). Since the first base station 10a and the fourth base station 10d are already providing GSM services, they ignore the request for service via the GSM protocol, but the sixth base station 10f responds to this request by establishing communication via both the LTE protocol and the GSM protocol (step S7). After this reconfiguration, the cellular network 1 is in a state as shown in FIG. Figure 3dThe state shown in FIG. 1 is a state in which the first base station 10a, the third base station 10c, the fourth base station 10d and the sixth base station 10f are adjusted to communicate via LTE and GSM, and the second base station 10b, the fifth base station 10e and the seventh base station 10g to the eleventh base station 10k are adjusted to communicate only via LTE. In the second iteration of step S9, the second UE 30 moves into the coverage area of ​​the sixth base station 10f, and the third base station 10c and the sixth base station 10f complete the handover, so that the sixth base station 10f now serves the second UE 30 (using the GSM protocol). This is Figure 3e Shown in.

[0031] In a second iteration of step S11, the sixth base station 10c identifies one or more possible handover targets for the second UE 30 at a new location in the coverage area of ​​the sixth base station. In this example, this includes the third base station 10c, the fourth base station 10d, the seventh base station 10g, the ninth base station 10i and the tenth base station 10j. In the second iteration of step S13, the sixth base station 10f then determines whether any other base station should switch back to communicating via LTE only by identifying any of the following base stations: 1) the source base station handed over to the sixth base station 10f (i.e., the third base station 10c in this iteration), but the source base station is not one of the possible handover targets (the third base station 10c, the fourth base station 10d, the seventh base station 10g, the ninth base station 10i and the tenth base station 10j) newly identified for the second UE 30 based on the coverage area of ​​the sixth base station 10f, or 2) any of the other possible handover target base stations for the second UE 30 when the second UE 30 is served by the source base station (i.e., the first base station 10a and the fourth base station 10d in this iteration), but any of the said base stations is not one of the possible handover targets (the third base station 10c, the fourth base station 10d, the seventh base station 10g, the ninth base station 10i and the tenth base station 10j) newly identified for the second UE 30 at the new position in the coverage area of ​​the sixth base station. In this second iteration, the first base station 10a is identified as a base station that should switch back to communicating only via LTE. Therefore, in step S15, the sixth base station 10f sends a message to the first base station 10a (e.g., via X2) indicating that the first base station 10a can switch back to communicating only via LTE. In response, the first base station 10a determines whether it can switch back to communicating only via LTE (i.e., disabling GSM communications). In this example, the first base station 10a has an obligation to provide GSM services, so the message is ignored.

[0032] When the sixth base station 10f explicitly identifies the possible handover targets, the process loops back to step S5, where the sixth base station 10f sends a message to these identified base stations, the message including: a) a request for service via the GSM protocol; and b) identifiers of all identified possible handover targets (the third base station 10c, the fourth base station 10d, the seventh base station 10g, the ninth base station 10i and the tenth base station 10j). In steps S7 to S15, the process continues to establish communications via LTE and GSM protocols among these identified possible handover targets to complete the handover of the second UE 30 (in the third iteration, to the tenth base station 10j), to identify any base stations that are possible handover targets when the second UE 30 is now served by the tenth base station 10j, and to determine whether any other base stations can switch back to LTE-only communications (in this third iteration, the third base station 10c and the fourth base station 10d). Therefore, the third base station 10c and the fourth base station 10d react to the message from the sixth base station 10f (in step S15) by reconfiguring their respective processors to switch back to LTE-only communication by discarding their second communication environment (so that only their first communication environment via the LTE protocol is retained) and no longer connecting to their second antennas. Figure 3f Shown in.

[0033] Thus, this embodiment of the method works in an iterative manner to dynamically reconfigure base stations in the cellular network 1 to enable communications via a particular protocol when the base station is serving a UE via that particular protocol or will soon be serving a UE via that particular protocol. This allows the base station to completely disable communications via a protocol that is not being used, thereby allowing all spectrum resources in the overlapping portions of that protocol with any other protocol to be reallocated to other protocols, and allowing all processing resources to be allocated to other protocols. This is not achieved in the prior art of monitoring demand for a particular protocol and allocating resources proportionally, because the base station must use some resources in those overlapping portions of its respective spectrum to enable such monitoring to occur.

[0034] In an improvement to the above embodiment, any neighboring base stations of a base station transmitting using both the first protocol and the second protocol are configured to mitigate interference in the overlapping portion of the transmission spectrum of these first and second protocols. This is done by making these neighboring base stations (e.g., Figure 3gThe second base station 10b, the third base station 10c, the fourth base station 10d, the fifth base station 10e and the eighth base station 10h) reduce the transmit power of transmissions in the overlapping parts of the transmission spectrum (this is illustrated by having reverse diagonal hatching in their hexagonal coverage areas). This can be a reduction to a specific percentage of the transmit power of the non-overlapping parts of their transmission spectrum, or a reduction to avoid using these overlapping parts altogether. In addition, the reduction in transmit power can be in one or both of downlink transmissions and uplink transmissions. However, this feature is not required.

[0035] Those skilled in the art will also appreciate that it is not necessary to virtualize the base station to achieve the advantages of the present invention. That is, the base station may have physical hardware dedicated to each protocol, and the base station may then enable and disable communications via a particular protocol in response to a request for service according to that protocol. Furthermore, it is not necessary that the first protocol and the second protocol be sent from the same transmitter of a particular base station, and may be sent from different transmitters of the same or different base stations (as long as they cover a particular coverage area).

[0036] In the above embodiment, the base station receives a request for service via the second protocol in response to determining that the base station may be a handover target for a UE using the second protocol. However, this is not required. For example, only when the UE is present in the coverage area of ​​the base station without a transfer event (for example, the UE switches inside the coverage area of ​​the base station), the UE is provided with service via the second protocol in a base station operating according to the first protocol, and the base station may receive a request for service via the second protocol from a neighboring base station, which receives a signal from the UE. Alternatively, the base station may operate a periodic timer that triggers a request for service via the second protocol at the base station when it expires, so as to establish communication with the UE. In another example, the request for service may be based on another trigger, such as a prediction or determination that a UE configured for the second protocol is about to switch in the coverage area of ​​the base station.

[0037] In the above embodiments, the first protocol is LTE, and the second protocol is GSM. However, those skilled in the art will appreciate that any two protocols may be used to achieve the benefits of the present invention, and it will also be appreciated that the first protocol may be considered a preferred protocol relative to the second protocol, so that the second protocol is used only when there is a demand for the second protocol. The preferred first protocol may be a newer generation (e.g., the nth generation) than the second protocol (e.g., the (n-1)th generation or the (nx)th generation). In addition, benefits may also be achieved when the two protocols do not have any overlapping portions in their respective coverage areas, because the present invention will at least mitigate any waste of processing resources when the two protocols are used unnecessarily. Those skilled in the art will also appreciate that the present invention may be implemented for base stations that are adjusted for transmission according to two or more protocols.

[0038] The above embodiments are practiced in a distributed manner, so that all messaging is between base stations and all decisions are made by the base stations. However, those skilled in the art will also appreciate that a centralized version of the method may also be used, in which some or all messaging is sent via one or more control entities and some or all decisions are made by one or more control entities.

[0039] Furthermore, in the above embodiment, all neighboring base stations of the base station serving the second UE become possible handover targets. However, this is not necessary, and a subset of these neighboring base stations may be identified (eg, excluding those base stations that are highly unlikely to become handover targets).

[0040] Those skilled in the art will understand that any combination of features is possible within the scope of the invention.

Claims

1. A method in a cellular telecommunication network having a plurality of base stations, each base station having at least one transmitter, each transmitter having at least one coverage area, the method comprising the following steps: a first transmitter of a first base station of the plurality of base stations operating in a first state so as to transmit only within a first coverage area according to a first cellular communication protocol; receiving a request for service in accordance with a second cellular communication protocol in said first coverage area; and in response, the first transmitter being operative in a second state to transmit within the first coverage area according to both the first cellular communication protocol and a second cellular communication protocol, wherein the second cellular communication protocol is an older generation cellular communication protocol than the first cellular communication protocol, wherein the request for service is received at the first base station from a second base station, wherein the second base station operates according to the second cellular communication protocol.

2. The method according to claim 1, further comprising the steps of: determining that demand for service according to the second cellular communication protocol in the first coverage area ceases; And, in response, The first transmitter operates in the first state to transmit only in accordance with the first cellular communication protocol within the first coverage area.

3. The method according to claim 1 or 2, wherein: The request for service using the second cellular communication protocol in the first coverage area is based on the first transmitter being a candidate handover target for a second transmitter.

4. The method according to claim 1, wherein: Operation in the first state is to transmit according to the first cellular communication protocol using a frequency band having a first frequency sub-band and a second frequency sub-band, and operation in the second state is to transmit according to the first cellular communication protocol using the first frequency sub-band and to transmit according to the second cellular communication protocol using the second frequency sub-band.

5. The method according to claim 4, further comprising the steps of: identifying a second transmitter operative in the first state to transmit only in accordance with the first cellular communication protocol within a second coverage area, the first coverage area and the second coverage area being adjacent coverage areas; An indication message is sent to the second transmitter, the indication message causing the second transmitter to use a first transmission power for transmission in the first frequency sub-band and a second transmission power for transmission in the second frequency sub-band, wherein the first transmission power is higher than the second transmission power.

6. The method according to claim 1, wherein: The first transmitter is part of a first virtual base station, wherein, in the first state, the first virtual base station uses first computing resources to process communications according to the first cellular communication protocol, and in response to the request for service using the second cellular communication protocol in the first coverage area, the virtual base station also uses second computing resources to process communications according to the second cellular communication protocol.

7. The method according to claim 3, wherein: The second transmitter is part of a second base station.

8. The method according to claim 3, wherein: Both the first transmitter and the second transmitter are part of a first base station.

9. A computer program comprising instructions which, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 8.

10. A computer-readable data carrier having the computer program according to claim 9 stored thereon.

11. A network node of a cellular telecommunication network, the network node comprising a transmitter, a processor and a memory, the transmitter, the processor and the memory being configured to cooperate to perform the steps of any one of claims 1 to 8.

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