GB2525230A - Telecommunications system and method - Google Patents

Abstract

A macro base station 21 configured for use in a telecommunications network, where the network includes a core network and small base-stations 22, comprises: radio means for wirelessly communicating with the small base-stations; and control means configured to manage Radio Resource Management (RRM) communications with the small base stations independently of the core network. A particular advantage of the present invention lies in the combination of standard macrocell functionalities with the radio resource management of small cells. By making this combination, the processing power required for managing radio resources is not only now handled in a distributed manner (i.e. by the macrocells), but the inherent latency in control signals being sent to and from small cells to the core network (i.e. the MME) is significantly reduced, since these signals are now only sent between the managing macrocell and the small cell.

Description

I

TELECOMMUNICATIONS SYSTEM AND METHOD

FIELD OF THE INVENTION

The present invention relates to a mobile telecommunications network including a core and a radio access network having radio means for wir&ess communication with mobe terminals registered with the network, and to a method of configuring the same. More particularly, the present invention relates to an LTE (Long Term Evolution) telecommunications system and method, or a 4G and above system/method.

BACKGROUND

As telecommunications networks continually develop from a multitude of sources, Heterogeneous Networks (HetNets) are a natural consequence. A HetNet is a multi-freqUency, multi-technology, multi-layer, multi-architecture network. Therefore a HetNet is typically defined by a collection of different technologies, dftferent cell sizes, frequencies and site assets; such as indoor and outdoor access points and base stations. An example of a win3less heterogeneous network is one which provides a service through a wireless LAN and is able to maintain the service when switching to a cellular network.

In other words, a HetNet typically incorporates multiple types of access nodes, such as macrocells and small cells, in order to offer a wide variety of wireless coverage zones, ranging from coverage in an open outdoor environment to "indoor coverage in office buildings, homes, and underground areas.

A small cell is a low-powered radio access node that operates in licensed and/or unlicensed spectrum, and which typically has a range of 10 metres to 1 or 2 kilometres. They are small compared to a macrocell, which typically has a range of a few tens of kilometres. The expression small cell", is generally considered to be an umbrella expression, encompassing picocells, pico base stations, microcells, micro base stations, femtocefls, femto base stations, Access Points (AP5) and home access points (HAPs). All terms describe the same general apparatus which are communicable with the macro network. The expression "small cell" will be generally

used in this specification.

This use of multiple different types of access points is useful for increasing the mobile network coverage, but the use of small cells does increase the network complexity, particularly in terms of radio resource management. The aim of course with a HetNet is a seamless transition between the different network technologies from the user's perspective.

Currently, small cells are managed by a Mobility Management Entity (MME) in the same manner as macrocells, albeit with additional operating algorithms to minimise interference with macrocells. MMEs are controllers located in the core network and management the macro/small cells in the radio access network. This management of the radio access network is becoming increasingly more complex as the number of small cells increase, and network efficiencies are tested. For instance, looking at Figure 1, which shows a known configuration of a 40 network, the MME of the core network is responsible for managing signal processing and the like, and so all communications for UEs attached to small cells (i.e. treated as an eNB 10) are sent/from the MME 11. Since the eNBs are remotely located from the core network, and the network between the two is not secured, communications between the MME 11 and the eNBs 10 are sent via a Security Gateway (SeGV I 2a. The SeGW protects control and user plane traffic on the SI and X2 interfaces through IPSEC between the eNB and MME and S-GW. IPSec, is a protocol suite for securing IP communications by establishing a "tunnel" that sets the authentication parameters for a communication session. All user and control packets transmitted as part of the session are authenticating and encrypting according to the established authentication parameters. The Security Gateway is typically deployed at the edge of the Access Core Network. Typical signalling traffic to be managed includes service requests, paging and location area updates. Therefore, there is significant signalling traffic transmitted from each of the smalls cells and macrocells operating in a given region that the MME 11 has to manage.

Although Figure I illustrates only two eNBs, representing the macro and small cells (for illustration purposes only), in actuality an MME is more likely to manage hundreds of macro and smalls cells. This is just the tip of the iceberg however, as even more srnafl cefls are being introduced to the mobile network, as this technology area matures and becomes more widely accepted.

Currenfly techniques are being developed in order to reduce the amount of signafling needed by mobile terminals (UEs) in a network in order to reduce the processing requirements of MMEs.

There is therefore a need to overcome or amehorate at east one problem of the prior art. In particular, there is a need to provide an improved arrangement and method of network operation and/or configuration that better accommodates small cells, particularly from the perspective of improving radio resource management, whilst minimising operational costs and maximising coordination of radio performance with macrocells.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a macro base station as defined in claim 1 This aspect of the invention has been predicated on the discovery that by distnguishing small cells from macro cells, it becomes possible to reconfigure the mobile network, particularly in regard to redistributing processing responsibilities for small cells. It has been found to be particularly advantageous to combine the functionality of small cell management with that of a macrocells functionality. By placing the small cell management in the radio access network, not only are resources of the core network freed up, but latency is improved from the small cell's perspective, and also from a UEs perspective, as their control communications, particularly relating to radio resource management, have less distance to traveL A particular advantage of the present invention lies in the combination of standard macrocell functionalities with the management of small cells. By making this combination, the processing power required for managing radio resources is not only now handled in a distr!buted manner (i.e. by the macrocells), but the inherent latency in control signals being sent to and from small cells to the core network (i.e. the MME) is significantly reduced, since these signals are now only sent between the managing macrocell and the small cell.

In other words, the direct physical and logical association between the macro base station and the smaH ceHs as per the present invention enables atency to be reduced, and ako radio resource and mobUity management performance to be optimised.

The macro base station with the control means in the manner of a "hub" platform accordingly connects small cells to the telecommunications network via the macro base station as a "host" in order to provide higher data rates, performance and smart neLwork capabilities. Performance and user throughput gain are achieved due to an improved backhaui atency.

in another aspect, the present invention provides a radio access network element configured for use in a telecommunications network, where the network indudes a core network and a radio access network comprising macro base-stations and small cell base-stations, the radio access network &ement including: a first interface for communicating with the core network, a second interlace for communication with other elements of the radio access network including at least one of the macro base stations; radio means for wireless communication with the small cell base-stations; and control means configured to manage communications with the small cell base stations independently of the core network. Preferably the network element further incudes macro base station functionality In a further aspect, the present invention provides a method of operating a macro base station in a telecommunications network, where the macro base station is directly associated with one or more small base stations, and comprises control means for managing radio resources associated with the one or more small base stations, the method comprising the control means: determining a plurality of network parameters associated with a communication for one of the small base stations, such that the communication is established, or to be established, via the small base station and the macro base station; processing the plurality of network parameters, independently of the core network, in order to determine a set of radio network resources suitable for enabling and/or maintaining the communication; and applying the one or more radio resource parameters in order to optimise the communication.

Other aspects of the invention are set out in the attached claim. s.

BRIEF DESCRIPTION OF THE DRAWNGS

Embodiments of the present invenLion will now be described in more detail with reference to the accompanying Figures, in which: Figure 1 illustrates a schemabc diagram of a LTEE network configuration; Figure 2 illustrates a schematic diagram of an LIE network configuration according to an embodiment of the invention Figure 3 illustrates a schematic diagram of an LIE network configuration according to a further embodiment of the invention, involving an microwave link between a macro eNB incorporating a Hub component and a plurality of small cells; Figure 4 compares the Figure 3 arrangement with a known arrangement to show the improved latency achievable by this embodiment of the invention; Figure 5 illustrates a schematic diagram of an arrangement according to an embodiment of the invention, where a macro eNB incorporates a Hub component associated with an intefligent network edge patform.

Figure 6A illustrates a first example of a HetNet cluster according to an embodiment oF the invention; Figure 6B illustrates a second example of a HetNet cluster according to an embodiment of the invention; Figure 7 illustrates a signalling diagram illustrating a handover technique according to an embodiment of the invention; Figure 8 illustrates an example of a master eNB hub controlling a number of slave eNBs and small cells and providing aH slave cells with access to a SAVi platform; a rid Figure 9 illustrates a comparative graph showing the differences of the configurations of the present invention from known arrangements.

In the Figures, where possible, like features are designated with the same reference numeral.

DETAILED DESCRIPTION

Key elements of a LTE/LTE Advanced/4G mobile telecommunications neiwork, and its operation: wifl now briefly be described with reference to Figure 1 LTE. stands for "Long Term Evoiution and refers to: -the evolution of the UMTS radio access system described as the Evolved LJTRAN (E-UTRAN); and the evolution of non-radio aspects? described as System Architecture Evolution (SAE), and includes the Evolved Packet Core (EPC).

Unlike ts predecessors, LTEE/LTE Advanced has been designed to support only packet switched services arid riot circuft-switched communications. Evolved NodeBs (eNodeBs) make up the access network in order to connect User Equipment (UEs) to a Core Network (the EPC). The interfaces interconnecting the network elements are standardised in order to enable muitkvendor interoperability. For instance, the interface interconnecting eNodeE3s 10 is the X2 interface, arid the interface between the eNodeBs and the core network is the Si interface.

The eNBs may also be called macro base stations, or equivalently macroceils, and each expression may be used in this specification interchangeably.

The main network elements of the core network are the Packet Data Network (PDN) Gateway? typically abbreviated to PGW13, the Serving Gateway (S-GW) 12 and the Mobility Management Entity (MME). The MME 11 is responsible for bearer management and connection management for establishing connections between the network and UEs. This is generally described by the umbrella term radio resource management".

Each eNodeB 10 is a macro base station or a Femtocell operating as a base station, and corresponds to a respective cell of the cellular or mobile telecommunications network and receives calls from and transmits calls to a mobile terminal (not shown) in that cell by wireless radio communication in the packet switched domain. The mobile terminal may be any portable telecommunications device? including a handheld mobUe telephone? a personal digital assistant (FDA) or a laptop computer equipped with a network access datacard In the LTE network, the Radio Access Network (RAN) comprises the eNode Bs, which s a tunctionaUy distinct from the core network in that the eNodeBs are responsible at a local level for providing the physical and transport radio ink between the mobe terminal (User Equipment, UE) and the core network. The eNode B performs the transmission and reception of data wirelessiy across the radio interface.

The eNodeB is also the point where encryption is done before user data is sent to and from a mobe terminaL Where a Small cefl operates as a base station, the radio link between the Smafi cell and the mobUe terminal uses the same cellular telecommunication transport protocols as macrocell hut with a smafler range for example 255C)rn. .The SmaM cell appears to mobile terminals as a conventional macro base station, so no modification to the mobile terminal is required for it to operate with the Small cell.

Accordingly, the Small cell performs a role corresponding to that of traditional macrocellsleNode Bs 10 in the LTE RAN.

The Small cells would typically be configured to serve a Wireiess Local Area Network (WLAN) located in a home or office, in addition to the LIE network. The WLAN could belong to the subscriber of the mobile terminal, or he an independently operated WLAN. The owner of a Small cell can prescribe whether it is open or closed, whereby an open AR is able to carry communications from any mobile device in the LIE network, and a closed AR is only able to carry communications from specific pre-assigned mobile devices.

1) LIE Hub Embodiment With this background in mind, a first embodiment of the present invention will be described with reference to Figure 2.

In this embodiment of the invention, a differentiation is made between macrocells and small cells when operating in the radio access network. In this regard, an augmented macro base station 20 has been devised that is configured to communicate directly with one or more small cells 22 in order to manage or co--ordinate the operation of the small cells, particularly by performing Radio Resource Management for the small cells 22.

Typically these small cells will be in the vicinity of, or within the coverage area of, the augmented base station 20, so that the base station is able to coordinate its associated small cells with its own operations as a macrocell. That is, the augmented base station has a "Hub". which may act as a coordination point that manages interference and resources between itself and small cells with the same or overlapping frequency bands/spectrum allocation.

For ease of reference, the additional functionality to accommodate the small cells in the augmented base station (i.e. macrocell) will be referred to herein as a Hub component or Hub.

The Hub is configured to manage Radio Resource Management control communications relating to the small cells associated with it. The RRM control communications may be communications relating to at least one of: -mobility management (i.e. of UEs attached to the small cells); -bearer management; and/or -connection management.

Essentially the Radio Resource Management Control by the Hub relates to establishing and managing parameters necessary for a small cell, and any UEs associated with the small cell, to operate wirelessly in the radio communication network with the macro base station. That is parameters necessary for the small cell to establish a bearer for communications with one or more UEs, for the UEs to connect to the network, and to manage handoverlreselection of the UEs.

The purpose of RRM is essentially to control co-channel interference and has traditionally been managed at the core network level. RRM involves strategies and algorithms for controlling parameters such as transmit power, user allocation, beam-forming, data rates, handover criteria, modulation schemes and error coding scheme. The objective is to utilize the limited radio-frequency spectrum resources and radio network infrastructure as efficiently as possible. Therefore. RRM concerns mulfi-user and multi-cell network capacity issues, rather than the point-to-point channel capacity.

The Hub component ideally dynamically performs RRM by adaptively adjusting one or more radio network parameters, based upon the network load, user positions, user mobUity. quahty of service requrements and/or base staUon densfty, For examole. For instance, the Hub may determine that the macrocefl itsef has several IJEs directly attached to it, which are acfive, and accodinq y instruct an assocAated smafl cefl, wah an ide UE attached, to reduce its operaUng power so as to minimise interference to its active users.

The network conditions and service requirements may be determined by the Hub by any means, but wifi typicaUy he interrrdttent]y communicated to the macro base staUon/Hub component by the core network, the associated srnaU ces, UEs in the macroceUs coverage area and other macrocefls.

Preteraby dynamic RRM schemes are used by the Hub ri order to determine the appropriate adjustments to make to the radio network parameters r&ating to the ink between the macrocefi and the smaH cefl, as wefl as any UEs attached to the smaH ceft For example, predetermined power control agorithms may be used, as weH as ink adaptation algorithms.

Importanfly the augmented macro eNB retains its standard macrocefl functionality, arid can accordingly communicate directly with the core network via the Si interface, and with other macrocefls via the X2 interface and a'so directly wfth UEs, However, in terms of communications with the associated smaU cefls 22, since the Hub 20 has the required functionahty for performing radio resource management for the smafi cefls 22, no contro ayer signaffing needs to be pertormed with the core network in this regard.

It is &so to be appreciated that in this embodiment of the invention, the security functionality of the SeGW is also preferably managed by the Hub at a control pane level. That is, the Hub is also preferably responsible for managing the encrypt!on of contro packets, rather than the SeGW. This woud again improve latency, particuarly as the Se-GW may be ocated between 10-200 kHometres away from a macrocell: the resultant RTT could therefore be of the order of 7ms from a core transport eve, User pane packets will typicafly stifl need to be secured via the SeGW, particuary when a UE associated with a given augmented rriacro eNB is communicating with a second UE in a different network. n view of the second UE being in a different network, these packets wouid need to be routed via the core network anyway (so that the second UE can decrypt them), so there would be little advantage in removing this functionality from the SeGW, By connecting small cells directly to a Hub associated with macro cell functionality, it advantageously becomes possible to coordinate the two HetNet layers in a faster or tighter manner, based on L3 or L2 switching (i.e. the eNB coordinator controls small cells within its coverage area via an L21L3 switch). The interface between the Hub and the small cells may involve existing interfaces or evolved or new interfaces. For example, a Common Public Radio Interface (CPRI) may be used or an evolved one based upon a split protocol stack Packet Data Convergence Protocol (PDCP), Radio Link Control (RLC) and Medium Access Control (MAC) interface.

In short, since the Hub manages radio resource and mobility management for its associated small cells, RRM signalling does not need to be sent to and from the core network, which reduces the number of hops for a given communication and according reduces latency and provides higher data rates and performance.

The relocation of the radio resource management functionality in the Hub component has the potential advantage of reducing connection failures and speeding up reconnection in the event of actual connection failure by reducing the number of hops in the control and user plane interfaces. This would particularly be applicable in fast fading environments such as dense urban areas.

For instance, in an urban environment, where there are tall buildings that can easily get in the way of the LOS connection between a UE and its serving eNB, where the serving eNB is a small cell, if a handover is needed from this cell due to a tall building getting in the way (for example), since the mobility management is handled at the Hub, which is fewer communication hops away from the UE than the core network (as per the current approach), the Hub is able to act faster to effect handover, thereby reducing the likelihood of a connection failure for the UE. In other words, the Hub is able to reduce the time needed for handover preparation, thereby reducing the probability of radio link failure.

Similarly, in terms of handover recovery, should a communication for a UE drop out, the location of the mobility management in the Hub enables the communications necessary to reconnect the UE to occur with fewer communication hops (and thereby a shorter length of time).

This primary embodiment of the invention provides a particularly advantageous arrangement since it serves to minimise link latency (delay) through direct physical and logical connection of the small cells with the macrocell. That is, the number of hops is minimised for communications with the small cells, which, since each hop adds precious microseconds, results in an improved latency.

In this regard, ideally the Hub is in the proximity or coverage area of the small cells, as a local macrocell, which means that costs for deployment of the system are minimised, as fewer towers would need to be constructed (since microwave links require Line of Sight (LOS) connections), and consequently, less maintenance of the system would be required.

This is illustrated in Figure 3, which illustrates three small cells in LOS with a microwave tower, via Point to Point (PTP) or Point to Multipoint (PTM) communications. These signals are then fed to the Hub via a backhaul connection.

The Hub then provides master radio RRM coordination using its high powered processing capabilities. This arrangement advantageously has low latency via the logical and physical connectivity.

The latency advantage achieved using the arrangement shown in Figure 3 is illustrated in Figure 4. Figure 4 compares the current embodiment of the invention, incorporating the Hub with a microwave connection to three small cells (i.e. to the left of the diagram), with a standard arrangement (i.e. to the right of the diagram). From this Figure it is clear that this embodiment of the invention reduces latency by decreasing the hop count, as in the current arrangement, for example between 3 and 9 hops across the access core backhaul transport network are added. The number of hops depends upon the number of switches, routers and transmission technologies need to be traversed to reach the Security Gateway and return for an X2 interface for example. The number of hops can vary and involve very extended distances considering neighbouring cells can be on different transmission rings or point of concentrations or involve third party transmission networks even though physically they may be deployed relatively closely.

2) CoMP Embodiment Latency is an important consideration in all networks, and is introduced through other factors, despite the direct physical and logical interconnection made possible in the first embodiment of the invention, For example, in a more specific embodiment of the present invention a microwave system is preferably used for communications between the Hub and the small cefls.

Firstly, it is to be appreciated that the use of microwave systems operating below 40GHz are known for estabUshing point-topoint connectivity between two locations.

However, link latencies can vary significantly during operation of these systems, particularly due to the effects of atmospheric conditions and weather, which are quite significant in the 3-30 GHz frequency band.

There are two main types of attenuations that will affect the power margins of a microwave ink. One is atmospheric gaseous absorption, while another is rain attenuation. Additional environmental phenomena, such as coud, fog. ice, snow, precipitation, scintWlation, aerosol, and dust can also cause severe signal impairment, particularly as the operating frequency increases.

Further, several anomalous propagation modes, such as ducting and tropospheric scatter, also create interference, albeit over smaller time periods than the environmental attenuations referred to above.

Where a microwave connection is utilised to interconnect the small cells to the Hub/macro eNB, the small cells are likely to be installed with a low elevation angle relative to the microwave transceiver for the network. Such a low elevation angle is likely to exacerbate atmospheric scintUlation and multi-path fading, thereby increasing the likelihood of losses being incurred on transmitted signals.

It is known to use advanced coding technologies, such as higher order QAM modulation to improve spectral effects, as Nell as error correcting techniques, such as ARO and FEC. Further, when these techniques are combined with dual-polarised antennas, even better performance can be achieved. Unfortunately, however, signal processing, coding and error correction schemes adversely impact the latency of higher capacity microwave links.

Accordingly, where a microwave connection is used, the Hub ideally has the additional functionality of configuring the link between the Hub and the small cells in a manner dependent upon the link conditions at the time.

Therefore, in order to better control latency, network conditions should be monitored and appropriate adjustments made where possible. To achieve this according to this embodiment of the invention, Coordinated Multipoint (C0MP) functionalities are managed by the Hub.

CoMP involves uplink CoMP reception and downlink CoMP transmission. Uplink CoMP reception improves cell-edge user throughput through user data being sent to the central eNB Hub from multiple sources.

The main idea of CoMP is based on the fact that when a UE is in a cell edge region, it will typically be able to receive signals from multiple cells sites, and vice versa. The related signals between the UE and the various neighbouring cells can therefore be aggregated and exploited as required.

Downlink CoMP transmission is made up of Joint Transmission (JP), Coordinated Scheduling (CS) and Coordinated Beamforming (CB). CS/CB are used to reduce intercell interference.

This information could be used to appropriately control the cluster of small cells. The co-ordinated scheduling (CS), coordinated beam-forming (CB), joint transmission (JT) or combinations thereof could also be used in combination with carrier aggregation (CA) functions (i.e. intercell functions such as dual cell connectivity, dynamic ICIC). A particularly advantageous implementation of this embodiment of the invention would be to switch any or all of the small cells between different radio technologies (e.g. WiFi or LTE) or switched from/to Common Public Radio Interface (CPRI) operation. Similarly UEs in the network may be able to connect to both the macrocell and a small cell at the same time (dual connectivity) Accommodating these functions in the augmented eNB may involve changes, extensions or modifications to X2 inter-eNB interfaces. Alternatively, this may involve a new interface between the macro and small cell, xn for the case of carrier aggregation or COMP-like interface for Joint Transmission.

This functionality is provided at* -he Hub: in other words the Hub hosts the synchronisation of these Co-operative Muftipoint (CoMP) features. This embod!ment of the invention essentiafly implements a form of coordinated multi-point processing in order to improve the spectral efficiency between the Hub and the duster of smafi cefls. That is, CS/CB requires the macro/smafl cefls to be interconnected in order to exchange scheduHng and beam forming information so that a dynamic multF-site scheduhng can be performed from a single entity (i.e. the Hub).

This processing of CoMP information in the eNB Hub may also be used by the Hub to perform scheduhng determinations for its associated smaU cefls. That is, the Huh can devise scheduUng rules n relation to the transmission characteristics and requirements (eg of slots and packets), which are provided to the smaU caDs associated wEth the macroceD in the form of schedufing rues, In this regard, a fast and secure atency when sharing information between cefls is critical for schedulers to co-operate more effidently. It also enables greater net-benefit of overafi resources and end user throughput gains.

Scheduhng is generaDy performed by each eNB according to rules devised by the core network. This embodiment accordingly differs, since the eNB Hub is managing one or more smaD cefls. The eNB Hub instead performs a central coordinated scheduling on behalf of the one or more associated small cells, by defining rules that will then be utihsed by the small cells in their communications with the network.

Afternativ&y, or in addition to using CoMP data, the Hub may he made aware of the inter-node latencies of the transmission links between the cells it is coordinating by static pre-configuration, being measured at initiation of an X2 interface, or routinely updated over time. This link latency information can also be advantageously used by the macro eNB hosting the Hub to improve the scheduling and coordination of radio resources, by making superior scheduling decisions.

3) Routing Embodiment In a further alternative embodiment, additional functionality that is performed by the hub component of the eNE3 is that of traffic routing, parhcularly at the lP transport layer utilising Multi-Protocol Label Switching (MPLS).

As we described in the previous embodiment of the invention, the Hub component of tile augmented eNS is provided with network information, and particularly information relating to traffic, environmental conditions and the ike. so the Hub is able to make an educated assessment of latency, particularly for packets to be routed back to the EAC (i.e. core network).

MPLS is a scalable. protocokndependent mode of routing where packets are assigned labels, and packettorwarding decisions are made solely on the contents of this label, without the need to examine the packet itse 1. In other words, MALS uses the labels to direct data from one network node to the next, rather than long network addresses dentifying the endpoint. This allows end4o-end circuts to be created across any type of transport medium:, using any protocol. Accordingly, MPLS essentially creates virtual inks' between distant nodes.

MPLS is an important advance for telecommunications companies, as it enables voice, data and multimedia traffic to he converged onto a single, secure network. For a packet to be transmitted to given destination, a source entity (e.g. a abel edge router) associates the packet with a label stack, with each label relating to a "hop" to the eventual destination, according to the route determined by the label edge router.

As each node in the route receives the packet with the MPLS label stack, the top label is typically removed and the packet routed to the next node revealed on the subsequent label. It is to be appreciated that this is a generalisation of the MPLS procedure. it is intended essentially to portray the routing technique, and variations are of course possible (e.g. in terms of label swapping, pushing or popping).

According to this embodiment of the invention, the hub eNB operates as a label edge router, particularly for packets being routed from small cells it is associated with, so as to apply an MPLS label stack to the packet. utilising its knowledge of network information, so that the packet is sent on the best path known to the hub eNB, particularly from a latency viewpoint.

For nstance. the hub eNS can choose to route background traffic back to the E.PC via multiple hops with low latency, or for highly guaranteed services and distributed content hosting, the shortest path possible could be allocated. This embodiment of the invention is particularly advantageous when utilised in conjunction with hub clusters as the scale of routing can justify a higher functonal switch.

4) SAV1 Embodiment In a still further embodiment of the invention, additional functionality that is incorporated into the Hub 20 is that of a smart network capability in order to additionally host content and services for the small cells. In particular, such a smart network capability is known as SAVi (Smart Access vision) and is described in Patent Applications GB2481 723, 0B2473717, EP 2403186 and EP231 5412 which are incorporated herein by reference.

SAVi is a platform that has been designed for more traditional network arrangements of macrocells, where functions such as caching, routing, optimisation and offload/return decision functionality have been integrated into macrocell eNBs in the radio network architecture. However, the integration of the SAVi platform into networks incorporating small cells is more difficult.

For example, it is envisaged that small cells will be deployed in public sites in large volumes. For this to be achievable, not only will the large number of these small cells make the inclusion of a SAVi platform prohibitively expensive, but the small cells themselves are constrained because of their size, weight and power so these are again other factors that would make it prohibitively costly for a SAV1 platform to be integrated into small cells, in the same manner as has been done for macrocells.

Furthermore small cells may not have the same processing capabilities as macrocells in order to support the SAVi platform Advantageously, it has been found that the configuration of the embodiment shown in Figure 2 provides a novel architecture that enables a SAVi platform to be incorporated into the Hub 20 and accordingly provide small cells with the SAVi functionalities. In other words, the Hub has the SAVi functionality, and feeds or anchors the necessary content and applications to the small cells 22 as required.

Although not essential, the small cells may be provided with a "SAVi Light platform that provides an interface with the SAVi platform on the Hub 20. It is to be appreciate that this platform is a cut-down version of the main SAVi platform and accordingly does not host large scale content of applications: as the use of the word "light" suggests, it has lower processing capabilities and is essentially an interface to appropriately use final content provided by the main SAVi platform hosted by the Hub eNB. This embodiment of the invention is illustrated in Figure 5.

By associating the Hub with the SAV1 platform on the macroceU, the smafl ceUs are able to utffise the applications associated wdh the SAVi platform. For instance, the Hub can aggregate arid route Apphcation Programming Interfaces (APIs) to the srnafl cefls, to provide various functionalities for the smafl cells themselves and/or users camped on the small cells.

To provide a better understanding of the how the SAVi platform integrates into the network. an annex A is attached with provides a detailed outline. This detailed outline also explains the useful application of the SAVi platform which may equally be utihsed in the present embodiment of the invention, where the SAVi platform is integrated into the macro base station hub, directly controlling one or more small cells.

One example of a functionality that could be provided could be that of enabling advanced video optimisation for users camped on the small cells: this is a functionality that otherwise would not easily be provisioned via small cells. Also, the Hub combined with the SAVi platform could be used to aggregate and suiiplify export of APIs (e.g. video optimisation) to the core network.

It is to be appreciated that in this embodiment, the SAVi Light platform on the small cefls is not hosting SAVi but instead acts as an interface by connecting back to the macrocell to access the SAVi functionalities. A further functionality that may be provided by the SAVi platform is that of service continuity for small cells associated with the Hub. For example, the Hub can provide service continuity for handover by exposing a mobility event triggered by the SAE-GW of the core network. or by the source eNB.

For example, the Hub associated with a SAVi interface could assist in the situation of a handover to a target eNB where the target eNB is a small eNB. That is, where a tiE is being handed over from a rriacrocell source eNB to a small cell target eNB, the original source eNB is required to support X2 handover for the new target eNB to maintain service continuity of anchored content. This requires the source eNB to have visibility of the small cell on the Si and X2 interface. Therefore new Si X2 procedures are required, since the target small cell eNB is not directly connected to the X2 interface. The new procedures are needed in order to maintain service continuity of content and applications hosted on the original source Macro eNB.

The target small cell eNB could be adapted to support complex tromboned X2 interfaces (i.e. with other neighbouring macrocells or small cells that it could receive handovers from), but this would be a highly complex and degraded performance solution. Also, without a more suitable solution, the UE could be expected to perform multiple and consecutive (failed) handovers whilst the source content was still being served at the original source eNB, Therefore, according to this further embodiment of the invention, the SAVi platform associated with the Hub is configured in order to support last-caching in order to enable small cell mobility. Fast caching is described in Annex A. The small cells associated with the host macro eNB utilise the SI and X2 gateways/interfaces of the macrocell in order to make the necessary communications with source macro eNB and the core network, and utilises a fast cache of the SAVI platform to anchor content. This fast cache is usable by all small cells associated with the Hub/host macro eNB.

Since the SAVi platform caches the content on behalf of the small cell, all content to and from the 81 and X2 interfaces is routed via the Hub (i.e. which is associated with the SAVi platform). This is particularly advantageous in order to allow lawful interception, as also described in Annex 1. For example, all COPY packets sent by the SAVi platform on the source eNB are routed by the Hub to the S-GW/P-GW.

This configuration enables handover to occur between small cells associated with a particular Hub, by the Hub anchoring the content and allowing the handover procedures and policy to be valid for all small cells connected to the macro Hub component. The Hub component of course would ensure that traffic was seamlessly routed between the source and target. Location information would need to be updated internally within the Hub (i.e. in the policy), but X2 packet forwarding (i.e. to external eNBs) would be minimised.Advantageously, this configuration has no impact on the core network operation during handover, Figure 7 illustrates an example of the signalling that would be required in order to implement a handover from a UE attached to a small cell associated with a Hub, to an external cell (i.e. the eNB target).

As can be seen in this Figure, local content is served via the Hub associated with the SAVi platform at the source eNB, where a handover event to the target eNB is triggered. Wth this architecture, aM Si and X2 interfaces for the source eNB (i.e. the srnafl ceU) are managed by the host macro eNB and routed via the Hub. This provides the flexibWty to support mobffity for SAVi injected content. During handover, packets are forwarded over X2 to the target eNS (which may he another smafl cefi) wth reduced delay.

At the point of handover, the SAE-GW of the core network sends a mobflity event, for example a GTFw End Marker, and the policy instafled at the source macro eNS gets updated with the cefi ID of the target ceft.

AU further packets r&ates to this flow may be routed from the target eNS via the Hub to the core. In this way, the edge content dehvery of packets to the target eNB continues without any interruption. Alternatively, the source macro eNS could expose the mobihty event, so as to aVow packets to be routed directly to the target eNS.

The target eNS in the Figure 7 example does not have a SAVi platform for content or application hosting. However, the Hub could route a handover to other ceUs that are indirectly integrated (i.e. ogicafly connected) to the Hub (e.g. to slave macroceUs as described further in the HetNet Cluster embodiment below).

In generaL in this embodiment of the invention, the macro base station is configured to facilitate hosted content and apphcations to enable seamless mobilily to connected small cells.

5) HetNet Cluster Embodiment In a further embodiment of the present invention, the Hub is utilised to form HetNet clusters of cells. In this way, the Hub provides a mechanism to cluster the smah cells and adjacent Macro eNBs into a central point, thereby enabling the small cells to be coordinated relative to one another, as well as with other macrocells. That is, an enlarged cluster of cefls enables dynamic or overlapping control over a wider area.

Examples of HetNet clusters are illustrated in Figures 6A and 6B. Figure 6A illustrates a first cluster arrangement according to this embodiment of the invention.

In this arrangement, a ring of macroceli eNBs are illustrated that all have Hub components and are associated with their own smafl cefl eNBs. In this embodiment of the invention, the two macrocefl eNBs are interhnked. In a first aspect of this nterhnked arrangement, one of the macroacH eNBs (e.g. the highUghted one) acts as a master eNB, in the case of centrahsed co-ordination or fixed point control, so that it controls not only its own srnafl ceH eNBs, but aH of the other macrocell eNBs and their small cells (i.e. the other eNB/Hubs are slaves).

Alternatively, both Hubs in the macrocefls could coordinate and provide approphate control cooperatively in the case of distributed co-ordination, in the case of distributed co-ordination or dynamic multi-point control. This is illustrated in Figure 6B.

In a still further alternative, a master eNB/Huh could be designated, hut changed as required. That is, a first of the two Hubs could be acting as the master, but if the operating situation changes in the example of moving traffic and time of day traffic patterns (i.e. train station in the morning to the oflice mid-morning), the second of the two Hubs could be made master (and the first Huh status changed to slave).

It is to be appreciated that the examples above have described just two macrocell eNBs with Hubs forming a cluster for ease of reference. Any number of macrocell eNBs, however could be integrated into a cluster.

A particularly useful application of a cluster of HetNet cells formed about the Hub, is that the Hub could be used as a fixed centric point of control, such as for CoMP features for all of the clustered cells.

Alternatively, the clusters could be formed on the basis for users or user groups, in order to enable coordinated control therefor.

Advantageously, in this embodiment, a master macro base station is configured so as to enable a cluster of small cells and adjacent macro cells to operate within a wider orchestration of network resources referred to as fixed or multi-point control.

This embodiment may also be utilised in conjunction with the other embodiments oF the invention described herein. In particular the SAVi service continuity functionality is particularly advantageous when implerriented in conjunction with a HetNet cell cluster. An example of such an arrangement is illustrated in Figure 8.

Finally, Figure 9 illustrates a comparative graph showing the differences of the eNB Hub configurations of the present invention from known arrangements. It illustrates that where the present invention is utilised, small cells or eNBs can combine access technologies, specifically LTE and WFi, for the purpose of fast switching between technologies to take full advantage of licenced and unlicenced spectrum. As illustrated in the final image, the eNB Hub can be utilised so that a single bearer or a single SI interface is provisioned between the eNB and the SAE Gateway to allow fast switching between a multiplicity of access types. This enables full flexibility between switching between access technology types and allowing reduced complexity for the core network. The hub can facilitate the integration of bonding of LTE/WFi access from the Macro eNB (or Hub) where the hub would route SI traffic into the WFi controller or access point directly via the small cell without any core impacts.

The embodiments described in this application are to be considered illustrative of the invention and not limitative.

For instance, although the small cells are illustrated as not being in communicable relation, it is wholly within the scope of the invention for the small cells to be in direct communication with one another via an appropriate interface.

Further, even though the invention has been described with reference to communications between the Hub and the small cells, it is to be appreciated that the same inventive concept relates to communications between the Hub and UEs attached to the small cells.

The embodiments of the invention have also been described in relation to the present incamation of LTE, however, it also has application to existing packet data access technologies like GERAN, UTRAN and W-Fi, future versions of LTE and future mobile telecommunications network developments, where the corresponding functionality is maintained, albeit with different protocols and the like. For instance, the present invention has been described with particular reference to use of the X2 and SI interlaces, however, the present invention will also be usable with future incarnations of this interface, such as the Xn interlace, currently under development, and likely to replace the X2/SI interfaces.

The Xn interface is described in TR 3GPP 36.842, and all of the above embodiments of the invention can be used in conjunction with the architectures described therein.

Also, the hub component of the macro base station may be integral therewith, or a separate entity that is functionally associated with it. Importantly it provides co-ordination between the two HetNet layers between the small cells and macro cells based on the most latency efficient method. There are also operational and deployment benefits of the hub providing operational efficiencies in reducing the complexity of HetNet networks through the hub creating a layer of abstraction for the core network.

Further, the headings in this patent specification are provided for ease or reference and should not affect the interpretation of any part of this patent specification.

Claims (14)

1. CLAIMS1. A macro base station configured for use in a telecommunications network, where the network includes a core network and small base-stations, the macro base station including: radio means for wirelessly communicating with the small base-stations; and control means configured to manage Radio Resource Management, RRM, communications associated with the small base stations independently of the core network.
2. 2. The macro base station of claim 1 wherein the control means is configured to manage RRM communications by dynamically adjusting parameters relating to the operation of the small cells providing communication links to the network for one or more user terminals.
3. 3. The macro base station of any one preceding claim wherein the control means is further configured to perform Co-operative Multipoint (CoMP) processing in relation to the operation of the macro base station and its associated small cells.
4. 4. The macro base station of any one preceding claim wherein the control means is configured to control its one or more associated small cells by switching each small cell between different radio technologies, including between WiFi and a cellular network technology.
5. 5. The macro base station of any one preceding claim wherein the control means is further configured to manage packet routing for its one or more associated small cells, particularly using Multi-Protocol Label Switching, MPLS.
6. 6. The macro base station of any one preceding claim further including a smart network capability, which provides an application programming interface so as to enable application functionality to be provided to the small cells from remotely located applications.
7. 7. A network including a plurality of macro base station as claimed in any one preceding claims] wherein the macro base stations are interlinked and one of the macro base stations is a master which provides master control for all of the small base stations associated with the plurality of macro base stations.
8. 8. The network of claim 7, wherein the role of master is interchangeable or dynamic among the macro base stations.
9. 9. A method of operating a macro base station in a telecommunications network, where the macro base station is directly associated with one or more small base stations, and comprises control means for managing radio resources associated with the one or more small base stations, the method comprising the control means: determining a plurality of network parameters associated with a communication for one of the small base stations, such that the communication is established, or to be established, via the small base station and the macro base station; processing the plurality of network parameters, independently of the core network, in order to determine a set of radio network resources suitable for enabling and/or maintaining the communication; and applying the one or more radio resource parameters in order to optimise the communication.
10. 10. The method of claim 9 further including the control means applying the one or more radio resource parameters by dynamically adjusting parameters relating to the operation of the small cell, such that the small cell provides communication links to the network for one or more user terminals.
11. 11. The method of claim 9 or 10 further including the control means performing Co-operative Multipoint (C0MP) processing in relation to the operation of the macro base station and its associated small cells.
12. 12. The method of claim 9, 10 oril further including the control means controlling the one or more small cells associated with the macro base station by switching each small cell between different radio technologies, including between WiFi and a cellular network technology.
13. 13. The method of any one of claims 9 to 12 further including the control means managing packet routing for the one or more small cells associated with the macro base station, particularly where the routing uses Multi-Protocol Label Switching, MPLS.
14. 14. The method of any one of claims 9 to 13 wherein the control means further includes a smart network capability with an application programming interface and provides application functionality to the one or more small cells from remotely located applications.