GB2479376A - Negotiating with a femto-cell base station for access to a portion of a physical radio channel for communicating to a user station - Google Patents

Abstract

A macro-cell base station, i.e. enhanced node B (eNB), in a standard mode of communication is able to establish communication with a user station (UE) with a downlink thereto comprising signalling and data. In the event of a drop of quality of service, due for instance to the proximity of a femto-cell base station, i.e. home enhanced node B (HeNB), to the UE, the macro-cell base station negotiates access to slots in a physical channel established by the femto-cell station towards the UE, and places downlink data communication in those slots, while retaining signalling information in the original downlink. This establishes a potentially improved quality of service without relying on formal handover from the macro-cell base station to the femto-cell base station.

Description

MECHANISM OF MOBILITY MANAGEMENT THROUGH A GROUP OF FEMTO-

CELL BASE STATIONS ON OFFLOADING DATA-PACKETS

The present invention is concerned with the use of femto-cell base stations in enhancing use of mobile wireless communications equipment.

Within the confines of realistic bounds of implementation, the development of technology in the field of femto-cells has explored a wide range of possibilities. The Femto Forum has established a number of accepted standards, which have developed various technical concepts, and particularly has specified three operating modes for femto cell "Home NodeBs" (base transceiver stations intended for domestic use) which operate on the UMIS system or "Home eNodeBs" operating on the LTE system.

The first of these operating modes is named Open Subscriber Group (OSG). In the OSG mode, any UE associated with a particular operator is allowed to use the femto-cell in question.

A second mode is known as Closed Subscriber Group (CSG). In this mode, only selected UEs, for example those belonging to a particular household, may use the femto-cell operating in that mode.

A third mode is described as a hybrid mode, combining the OSG and CSG modes.

Although the hybrid mode has not yet been firmly established, it is anticipated that, a femto-cell operating in the hybrid mode, CSG users might potentially have higher priority and access to the local network than OSG users.

The most recent developments of 3GPP LTE treat fernto-celI deployments differently from other deployments. Two typical deployments are hotzone cells (which are pico cells) and are typically planned deployments and open to all UEs, and HeNB deployments, which are femto-cells and are consumer deployed and CSG mode.

This clearly demonstrates a desire to differentiate the market of the femto-cell from previous products. In future, it is expected that most customer deployed home node-B (HeNB) will be CSG mode.

As femto-cell technology becomes more and more popular, it will be apparent that many CSG mode implementations will exist in high density residential areas. This gives rise to a risk that, in such an area, a visiting UE could interfere with CSGs if signals from the visiting UE cannot be blocked. On the other hand, if all local CSGs were to block signals from a visiting UE, then that visiting UE might not be able to connect with its macrocell base station, and then the area would be considered a coverage hole for macrocell deployment.

This is evidently a substantial technical issue in the deployment of CSGs in accordance with existing technology. A typical arrangement is illustrated in Figure 1, which shows the major potential sources of interference between femto-cell base stations (HeNB5) and macrocell mobile terminals. As will be seen from the illustration. There are also other potential sources of interference, such as interference from a macrocelt base station to femto-cell terminals on a downlink, and also potentially from those femtocell terminals back to the macrocell base station on the uplink. Having said that, it will be appreciated that these sources of interference would probably be relatively small in normal circumstances.

The main sources of interference as indicated in the illustrated example of Figure 1 might either prevent communication from the femto-cell in the uplink, or block the macrocell transmission in the downlink. Consequently, there is a need to explore ways in which these sources of interference can be overcome.

An aspect of the invention attends to features of and access control and mobility management of base stations defining macrocells and/or femtocells. This enables joint operation and control of those base stations. This operation enables handover free coordination between macrocells and femto-cells, which also enables highly efficient transmission without network disturbance due to interference such as described above.

Specific embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is, as noted above, a schematic drawing of the communications network including a macrocell and a plurality of fernto-cells each operating in a CSG mode; Figure 2 illustrates a simplified version of a communications network in defining a macrocell and a single femto-celI therein; Figure 3 illustrates flow of data in a downlink from a macrocell base station to a UE in accordance with an embodiment of the invention.

Figure 4 illustrates a communications network, similar to that illustrated in Figure 2, but with a plurality of local femto-cells identified in the macrocell; Figure 5 illustrates a further arrangement of a plurality of femto-cells in a macrocell, through which a UE is shown to move; Figure 6 illustrates a mobility model for movement of a UE between femto-cells; Figure 7 illustrates a method of offloading in accordance the illustrated embodiment of the invention; and Figure 8 illustrates a flow diagram representing the offloading method illustrated in Figure 7.

The specific embodiments of the invention will be described using terminology known in the invention. Thus, while macrocell base stations (BS) are well known as such, they are also known, in the context of femto-cell development, as node B" (NB) or in an enhanced implementation, as "enhanced NB" (eNB). Equally, femto-cetl base stations are known as "home node B" (HNB) or, in enhanced implementation, as "home enhanced node B" (HeNB).

As usual, mobile stations are also known as user equipment (UE) and home mobile stations are known as home user equipment (HUE).

As described previously, the present embodiment is intended to avoid the creation of a coverage hole in macrocell service to UEs which might otherwise arise due to the likely reaction of CSG mode HeNB to the existence of a "foreign" UE within range.

Figure 2 is intended to provide a simple illustration of a difficult arrangement involving a deployment of a femto-cell base station (HeNB) in a domestic environment. The square bound around the HeNB is intended to depict the walls of a domestic building (i.e. a house). A home based mobile device, associated with the HeNB is illustrated as being, alongside the HeNB and another user mobile device (UE) illustrated as moving in towards the HeNB.

The range of the HeNB is shown as a broken circle, around the limits of the building.

This is intended to illustrate reality in which the bound of a femto-cell cannot easily be limited to a particular shape of volume.

The HeNB is configured to operate in the CSG mode. This means that it permits communication with the home user equipment (HUE) but not necessarily with any other UE. Because the femto-cell is a CSG femto-cell, the UE has to communicate with the remotely located eNB defining the macrocell.

This can give rise to downlink interference. The UE might only be able to receive a very weak signal from the eNB in the region of the femto-cell. Assuming that it can communicate with the eNB at all, the downhink might contribute strong interference to the HUEs associated with the HeNB. This is because the UE and the HUE are now in the same general area. Further, the HeNB can cause severe interference to the UE, particularly when the UE moves into range of the HeNB. This might be so severed that no dated communication between the UE and the eNB will be practically possible.

Further, in an uplink direction, the UE might interfere directly with the HeNB. In addition, because the UE attempts to transmit to the distant eNB, the power transmitted by the UE must be relatively high to establish a particular quality of communication.

The transmit power of the UE might be sufficiently strong as to prevent effective transmission from the HUE to the HeNB. In essence, this involves "killing" the femto-cell service.

The present embodiment provides a mechanism for mobility management and access control, to coordinate between the eNB and the HeNB to transfer from a direct data transmission from an eNB to a UE, to an indirect transmission involving use of facilities offered by the HeNB. This uses virtual mobility control, without a true handover procedure between the eNB and the HeNB, to ensure that the CSG quality of the femto-cell mode is retained.

As currently specified in the relevant standards, an identifying label known as a CSG ID is broadcast from an HeNB in a system information block (SIB) portion of a transmission stock. Only those stations which are members of the group associated with this CSG ID can attempt to select the cavity cell concerned.

The present embodiment takes account of the fact that a UE, whether or not it is a member of a particular femto-ceIl, can see CSG IDs of femto-cells in range. A particular eNB, associated with a UE, can request measurement by the UE of the femto-cell or cells neighbouring the UE.

Based on measurements received from the UE, the eNB can determine operational situation between the UE and its neighbouring femto-cell or cells. When the UE moves close to a femto-cell, the eNB is informed as to the interference level from the HeNB to the UE (on the downlink) and accordingly it is able to predict the potential interference level to the HeNB (on the uplink) based upon its knowledge of possible transmission power of the HeNB and the UE. This transmission power of the HeNB might be fixed, or it might be dynamic and determined in accordance with the particular operation. The dynamic power allocation of an HeNB might be obtained through backhaul connection, such as from a femto-cell gateway (not illustrated).

Based upon the measurement, the eNB selects one target femto-cell in the event that there are multiple femto-cells in range of the UE. When the interference level increases to a predetermined threshold, the eNB begins negotiation with the elected HeNB by means of signalling. Thus, the present embodiment defines two thresholds: 1. A threshold for starting negotiation between the eNB and the HeN B; and 2. A threshold for transferring data transmission from a direct mode B to an indirect mode, and vice versa.

By the point of starting negotiation, the eNB may have full knowledge of the HeNB.

Thus, the first threshold is likely to be initially based on UE reporting, and the second threshold is likely to be mainly based on information received from the HeNB. The HeNB, will be understood, may take its own measurements on signals and interference.

The negotiation between the eNB and the HeNB concerns the identification of available eNB radio resource, backhaul resource availability, plus, quality of service to the UE and so on. The purpose of this stage of negotiation is to enable the eNB to request the HeNB to pass one or more data packages to the UE through radio transmission, without any additional control applied to the data packages by the HeNB. In other words, the HeNB acts as a layer 1 relay (that is, in the PHY layer) and not as a true layer to relay.

In a particular implementation of this embodiment, it might increase the efficiency of negotiation to assign a priority to this level negotiation between eNB and HeNB, to avoid unnecessary disruption on both the macrocell and femto-cell level, because of the interference between each other. This priority issue may be important in the invent of use of a femto-ceIl which cannot make particularly sophisticated measurements of its operation. In the case that the operation of the eNB has high priority, the eNB can force operation in the proposed manner on the targeted femto-ceII base station.

The outcome of the first stage of negotiation is agreement between the eNB and the HeNB as to the portion of radio resource on the HeNB at PHY level.

The intention of the negotiation is that by the time that the second threshold is reached, the eNB has informed the HeNB on the need to transfer and has informed the UE of the radio resource mapping for transmission and reception of signals. The UE transfers to the radio resource defined by the negotiation. As far as it is concerned, it is still communicating directly with the HeNB. However, in fact, the UE has transferred its communication from direct communication with the eNB, to indirect communication via the HeNB. So, as far as the UE is concerned there is no handover. The UE does not need to perform handover initiation or request, authorisation, registration, and so on.

The UE is also not handed over from the eNB to the HeNB. In contrast, the UE is still registered in the macrocell defined by the eNB, with all signalling control remaining at the eNB. The UE is in fact only receiving data packets through the HeNB at the high level. This does not disturb either systems operation.

This implicit relationship transmission of signalling and control and data packets on the downlink transmission is shown in Figure 3. In this figure, after negotiation between the eNB and the HeNB, it is shown that the eNB only transmits signaliing and control to the UE, while the HeNB only passes data packets to the UE through the defined radio resource. It should be emphasised that, in Figure 3, only of portion of signalling and control and data packets are illustrated.

By the action of this embodiment, all of the gambling interference as indicated in Figure 2 no longer applies. Therefore, the downlink transmission is now effectively interference free. This can improve UE operation, taking advantage of the radio resource locally implemented in the HeNB, and thus allowing potentially a higher operational throughput at data.

There may also be practical advantages in the uplink. In the uplink, the UE transmits normally, without any awareness of interference and any difference of network operation. This is also achieved by the negotiation between the eNB and HeNB, to allocate the transmission slot for the UE uplink, filtered by the HeNB and the eNB. As for the downlink, the uplink data part will go through the HeNB. The signalling part will, in accordance with this embodiment, be directly detected by the eNB.

Transfer of the signalling parts in either direction implies a more concrete, and higher layer, handover, which is not part of the present embodiment of the invention.

As a UE moves out of femto-cell coverage, the reverse procedure of the above should be applied. The reader should find this relatively straightforward to follow. The only difference is that, on the definition of the thresholds, the second threshold referred to above is now the first threshold as signal quality drops. As for the previously described procedure, measurement reporting on the UE is still controlled by the eNB.

The mechanism of the mobility control can be described as follows: * eNB initially sets up thresholds (minimum 2) for measurements upon to the UE's QoS requirements, for instance, the measurement might be on received single strength. In case of 2 thresholds, the 1 threshold is to indicate a noted degradation, the 2' threshold is to indicate a possible service drop.

* eNB request its serving UE to do measurement, such as neighbouring measurement, and report back. For a UE, its neighbouring measurement is to measure its neighbouring base stations including femto-cell base stations.

* Based on measurement reporting, eNB closely monitors the status of UE's connection. When research to the 1st threshold, eNB initiates the negotiation to HeNB.

* The negotiation is mainly on the possibility of offloading data packets transmission to UE from eNB to HeNB with available radio resource on HeNB.

* Upon the success of the negotiation, eNB is able to request measurements from both HeNB and the UE.

* While the UE is moving closer to the HeNB that reach the 2 threshold, eNB asks HeNB to allocate the radio resource agreed between eNB and HeNB.

* eNB needs to inform the UE on the radio resource for the transmission.

* Meanwhile, eNB needs to set up security thread on those data packet transmission before the data packets released from the backhaul to HeNB.

* HeNB transmits the data packets on its allocated radio resource(s) while eNB continues its signalling and control on the UE.

* After the UE received the data packets, the UE acknowledges eNB on receiving.

Note that, for security reasons, the HeNB does not need to be aware of the UE within this proposed mechanism and procedure. Security must be taken into account and it should be the responsibility on eNB. However, this could be an implementation issue on operations (upon to different operators).

On purely PHY transmission on uplink, the HeNB might be able to help to detect the success and/or failure of the received data packet from the UE to the HeNB before passing the data packet onto the network. More specifically, if successfully received the data packet at the HeNB, it continues delivering the data packet to the network: in contrast, if the failure of the transmission is determined, the HeNB might be able to discard the data packet and inform the eNB and the eNB might request retransmission from the UE.

An operation procedure of the proposed scheme is depicted in Figure 4. We emphasised in the figure that the procedure is always initiated by eNB. Through the whole procedure, the UE should not be aware of any difference on its transmission as the UE is always controlled by the eNB on communications.

A dynamic monitored set might be needed for both macro-cell and femto-cell on this operation. One significant problem in the handover procedure involves defining or knowing the femtocells in the Neighboring Cell Lists in the macro network. The number of femto cells is estimated to be at least in the magnitude of tens of thousands [USA7,613,444]. Different from those conventional techniques, such as the (USA7,613,444], we do not require UE to report all the femto-cells around on the neighbouring list but in contrast a specific UE might only report back those femto-cells who cause interference to it over the 1st threshold. This will highly limits the number of femto-cell on the reporting list.

However, it is possible for a UE to report several femto-cells around it according to the criteria we set up here. One example is shown in figure 5 that a few femto-cells base station equally distributed around tM UE. In this case, eNB might need to negotiate those femto-cell HeNBs and the offloading could be operated by those HeNBs together on the same radio resource to achieve coordinative transmission (e.g. diversity), or, on separated radio resources to support the UE sequentially (upon to implementation).

Figure 6 illustrates a further practical scenario, whereby a UE moves between several femto-cells. In this scenario, conventional mobility management might give rise to frequent handover. However, if femto-cells are in the CSG mode, no handover might be allowed, and thus the communications in both the macro-cell and the relevant femto-celI might be interrupted frequently.

The present embodiment performs virtual mobility control in order to enable smooth transfer during the UE movement, as also presented in figure 6.

The illustrated operation enables femto-cell base station to pass on data transmission from macro-cell base station without actual handover. The macro-cell mobile terminal is always connected and controlled by the macro-cell base station. The macro-cell base station might only request the femto-cell base station to transmit the macro-cell user's data packets with no need for the UE to handover to the femto-celI.

As already mentioned, the UE might not even be aware of any operational difference, as no handover procedure is imposed on the UE. In addition, the UE does not need to access the femto-ceIl, and thus the CSG characteristic of the femto-cell can be maintained.

From the network perspective, none of the UEs in the network will be interrupted either.

The eNB still takes responsibility for the UEs even though the data packets might pass through a HeNB.

Further to the above, advantage can be taken of existing features of the femto-cell.

Considering the transmission format of a femto-ceIl, the femto-cell is requested to pass data packets from the macro-cell to the macro mobile terminal, and so the femto-cell is effectively operating as a relay. This is alluded to in US7,594,010. However, the communications between eNB and HeNB can be performed through air interface or backhaul, which distinguishes the present case from a relay. A relay does not have any access to a backhaul, so that all data and signals to be relayed have to be obtained from a base station.

Furthermore, the eNB and the HeNB should share the same backhaul (as the definition of a femto-cell within a macro-cell, so the data packets of the UE might not need to be transmitted from the eNB to the HeNB. The communications between the eNB and the HeNB might only be the signalling part on negotiation. Consequently, this might be transmitted through the air interface without lowering efficiency upon the air interface design. An example is presented herein with consideration of signalling through the backhaul. However, the present invention is not dependent upon the availability of a radio interface between eNB, HeNB, Femto GW, S-GW, etc. Furthermore, the mechanism and operation of the present embodiment are not limited to only CSG mode femto-cells. Embodiments of the invention could also suitably be applied to OSG or hybrid mode femto-cells, following the same concept and similar approaches.

In the hybrid mode, as currently specified, a femto-cell is asked to accept users temporarily, in the event of severe interference and/or blocking, as members' on a list to access that femto-cell, but this then requires UE handover. An embodiment of the invention can alternatively be employed, as mentioned above, to avoid frequent handover.

As described above, data packets are passed through the femto-cell base station. This might not only avoid the interference between the femto-cell and macro-cell but also enhance the efficiency of transmission (e.g. transmit power efficiency). In order to demonstrate the potential, a simple model is adopted as shown in figure 7. Nodes A and B are transmitters and node C is a receiver.

y1 = P1H1x1 + y2=P2H2x2+n2 (1) = P3H3x3 + where x1, x2, x3 are data packets from node A and B respectively; H1, H2, H3 are normalised channels; F, P, P are received powers; node B receives a signal from node A, and node C receives two signals as -received signal at B node -received signal at C node -received signal at C node While the three nodes are far apart as in Error! Reference source not found.(a), ideally: -* F; required power level 1*0; Now, by introducing one more node 0', which is within the coverage of node B, or say, a UE served by node B, y4 is the received signal at node D node such that, y4=P4H4x4+n4 (2) Following the same concept, now ideally: M_req; required received power level on macro-cell P3-* 0; 1 -Freq; required received power level on femto-cell However, as node-C is moving into the femto serving area, so it follows that: J-* PorP4P orP-*P3 In conventional operation, this would produce a severe conflict on operation criteria and environment conditions. In an extreme case, if node A continues to support node C on data-transmission and the same for node B supporting node 0, both node C and node D might be disabled simultaneously.

In contrast, by stopping transmission on node A, say, by offloading data packets transmission from node A to node B: 1 =] = 0; Freq' required received power level on femto-cell Also, due to the short distance, transmission power on node B might be much lower than that on node A for a similar quality of service to both node D and node C. Besides the effective interference avoidance and high power efficiency, the described mechanism also saves signalling loading, achieving lower overhead on signalling for the offloading as described previously. As an example, a possible offloading procedure with signalling and data transmission through backhaul is shown in figure 8.

Figure 8(a) illustrates the offloading which is performed through two paths: * Signalling path: transmit signalling from S-GW to eNB to UE; Data-packet path: offloading data-packet from eNB to HeNB through backhaul; Error! Reference source not found.(b) presents the operation procedure of the proposed offloading. Compared to conventional handover procedures, it does not need any operations between the HeNB and the UE.

The foregoing description of specific embodiments of the invention is illustrative, and not prescriptive of the essential elements of the invention, and should not be used as inference of any requirement of a particular technical feature to be provided for the invention to be worked. On the contrary, the invention should be determined from the scope of the claims appended hereto. The claims may be read in conjunction with the above description, but not limited thereby, with reference to the accompanying drawings.

Claims (20)

1. CLAIMS: 1. A method of establishing communication in a network comprising a network base station, a user station and a local station, said network base station being capable of emitting signals in range of said user station and said local station, said local station being capable of emitting signals in range of said user station, comprising negotiating with said local station for access to a portion of a physical radio channel defined by said local station and, on the basis of said negotiating, using said portion of said physical radio channel for communication to said user station in lieu of a communication from said network base station to said user station.
2. 2. A method in accordance with claim 1 and including measuring quality of service between said base station and said user station and commencing said negotiating if said quality of service falls below a first threshold.
3. 3. A method in accordance with claim 2 and including using said portion in the event that quality of service drops below a second threshold, said second threshold being below said first threshold.
4. 4. A method in accordance with claim 3 and including discontinuing said use in the event that said quality of service then rises above said second threshold.
5. 5. A method of establishing communication between a data node and a user station in a network further comprising a network base station and a local station, the base station and the local station each being in communication with said data node, wherein said communication can be in a first mode wherein a data downlink is maintained using a physical radio channel defined between the base station and the user station, or a second mode wherein a data downlink is maintained using a physical radio channel defined between the local station and the user station, the method comprising, in said first mode, monitoring quality of service to said user station and, in the event of deterioration thereof, negotiating with said local station for access to a physical radio medium defined thereby and on gaining access thereto switching to said second mode.
6. 6. A method in accordance with claim 5 wherein said monitoring comprises determining if said quality of service is below a first threshold and then commencing said negotiating.
7. 7. A method in accordance with claim 6 wherein said monitoring comprises determining if said quality of service is below a second threshold, lower than said first threshold, and then performing said switching.
8. 8. A method in accordance with any one of claims 5 to 7 and comprising, in said second mode, defining a data communications downlink from said data node to said user station by means of a backhaul connecting said data node with said local station, and a radio signal emitted by said local station receivable by said local station, and defining a signalling downlink from said data node to said user station by means of a radio signal emitted by said base station and receivable by said user station.
9. 9. A method in accordance with claim 8 and comprising, in said second mode, defining a signalling and data communications uplink from said user station to said data node by means of a radio signal emitted by said user station and receivable by said base station.
10. 10. A communications network comprising a network base station, a user station and a local station, said network base station being capable of emitting signals in range of said user station and said local station, said local station being capable of emitting signals in range of said user station, comprising negotiating means for negotiating with said local station for access to a portion of a physical radio channel defined by said local station such that, on the basis of said negotiating, said portion of said physical radio channel is used for communication to said user station in lieu of a communication from said network base station to said user station.
11. 11. A network in accordance with claim 10 wherein said user station is operable to measure quality of service between said base station and said user station and wherein said negotiating means is operable to commence said negotiating if said quality of service falls below a first threshold.
12. 12. A network in accordance with claim 11 and operable to commence using said portion in the event that quality of service drops below a second threshold, said second threshold being below said first threshold.
13. 13. A network in accordance with claim 12 and operable to discontinue said use in the event that said quality of service then rises above said second threshold.
14. 14. A communications network comprising a data node, a user station, a network base station and a local station, the base station and the local station each being in communication with said data node, wherein said network being capable of establishing communication between the data node and the user station in a first mode using a physical radio channel defined between the base station and the user station, or a second mode using a physical radio channel defined from the local station to the user station, the network comprising monitoring means for monitoring, in said first mode, quality of service to said user station and negotiating means operable, in the event of deterioration thereof, to negotiate with said local station for access to a physical radio medium defined thereby and on gaining access thereto switching to said second mode.
15. 15. A network in accordance with claim 14 wherein said monitoring means comprises determining means operable to determine if said quality of service is below a first threshold, said negotiating means being operable to commence said negotiating on the basis of such a determination..
16. 16. A network in accordance with claim 15 wherein said monitoring means comprises determining means for determining if said quality of service is below a second threshold, lower than said first threshold, said network being operable to switch from said first mode to said second mode on such a determination.
17. 17. A network in accordance with any one of claims 14 to 16 wherein, in said second mode, said network is operable to define a data communications downlink from said data node to said user station by means of a backhaul connecting said data node with said local station, and by means of a radio signal emitted by said local station receivable by said local station, and operable to define a signalling downlink from said data node to said user station by means of a radio signal emitted by said base station and receivable by said user station.
18. 18. A network in accordance with claim 17 and wherein, in said second mode, said network is operable to define a signalling and data communications uplink from said user station to said data node by means of a radio signal emitted by said user station and receivable by said base station.
19. 19. A communications apparatus operable to establish a range of communication, and operable, in the presence of a local base station and a user station in said range, to manage communication of signalling and data with said user station, the apparatus comprising communication means operable to communicate with said user station to determine a quality of service measure for service by said apparatus of said user station, negotiation means operable to establish access to a physical channel defined from the local base station to the user station, and operable, should said quality of service be below a threshold, to cause establishment of a data communications downlink to the user station using negotiated access to said physical channel from said local station to said user station, while maintaining a signalling communications downlink from said apparatus to said user station.
20. 20. A computer program product comprising computer executable instructions operable to cause a computer to perform a method in accordance with any one of claims 1 to 9.Amendments to the Claims have been filed as follows CLAIMS: 1. A method of establishing communication in a network comprising a network base station, a user station and a local station, said network base station being capable of emitting signals in range of said user station and said local station, said local station being capable of emitting signals in range of said user station, comprising negotiating by said network base station with said local station for access to a portion of a physical radio channel defined by said local station and, on the basis of said negotiating, using said portion of said physical radio channel for data communication between said local station and said user station in lieu of a communication from said network base station to said user station, while defining a signalling downlink from said network base station to said user station by means of a radio signal emitted by said base station and receivable by said user station.2. A method in accordance with claim I and including measuring quality of service between said base station and said user station and commencing said negotiating if said quality of service falls below a first threshold.3. A method in accordance with claim 2 and including using said portion in the event that quality of service drops below a second threshold, said second threshold being below said first threshold.4. A method in accordance with claim 3 and including discontinuing said use in the * * event that said quality of service then rises above said second threshold.* 5. A communications network comprising a network base station, a user station a.....* and a local station, said network base station being capable of emitting signals in range ":" of said user station and said local station, said local station being capable of emitting * signals in range of said user station, said network base station comprising negotiating * 30 means for negotiating with said local station for access to a portion of a physical radio channel defined by said local station such that, on the basis of said negotiating, said portion of said physical radio channel is used for data communication from said local station to said user station in lieu of a communication from said network base station to said user station, while a signalling downlink is defined, in use, from said network base station to said user station by means of a radio signal emitted by said base station and receivable by said user station.6. A network in accordance with claim 5 wherein said user station is operable to measure quality of service between said base station and said user station and wherein said negotiating means is operable to commence said negotiating if said quality of service falls below a first threshold.7. A network in accordance with claim 6 and operable to commence using said portion in the event that quality of service drops below a second threshold, said second threshold being below said first threshold.8. A network in accordance with claim 7 and operable to discontinue said use in the event that said quality of service then rises above said second threshold.9. A computer program product comprising computer executable instructions operable to cause a computer to perform a method in accordance with any one of claims 1 to 4. S... * * **5S*S* * * ***. * . S...*5..** * I S.....SI