WO2013079556A1

WO2013079556A1 - Method and system for handover control of a user equipment

Info

Publication number: WO2013079556A1
Application number: PCT/EP2012/073876
Authority: WO
Inventors: John Fitzpatrick; Stefan Schmid
Original assignee: Nec Europe Ltd.
Priority date: 2011-11-28
Filing date: 2012-11-28
Publication date: 2013-06-06

Abstract

The present invention relates to a method for handover control of a user equipment between a first mobile communication network and a second mobile communication network, wherein the user equipment is connected to a base station in the first mobile communication network and wherein the user equipment is in or nearby the coverage area of a base station of the second mobile communication network, comprising the steps of a) Measuring backhaul resource capabilities of the first and/or second mobile communication network, b) Determining a backhaul resource quality, preferably for voice calls and/or data traffic, based on the result of step a), c) Determining a handover control decision based on the determined backhaul resource quality according to step b), and d) Performing of the handover control decision according to step c), wherein determining the handover control decision includes a decision whether or not a handover of the user equipment is to be performed and/or whether or not base station parameters of the base station the user equipment being connected to or intended to be connected to are modified. The present invention relates also to a system for handover control of a user equipment.

Description

METHOD AND SYSTEM FOR HANDOVER

CONTROL OF A USER EQUIPMENT

The invention relates to a method for handover control of a user equipment between a first mobile communication network and a second mobile communication network, wherein the user equipment is connected to a base station in the first mobile communication network and wherein the user equipment is in or nearby the coverage area of a base station of the second mobile communication network, comprising the steps of

a) Measuring backhaul resource capabilities of the first and/or second mobile communication network,

b) Determining a backhaul resource quality, preferably for voice calls and/or data traffic, based on the result of step a),

c) Determining a handover control decision based on the determined backhaul resource quality according to step b), and

d) Performing of the handover control decision according to step c).

The present invention relates also to a system for handover control of a user equipment between a first mobile communication network and a second mobile communication network preferably for performing with a method according to one of the claims 1 -17, each having a base station wherein the user equipment is connected to the base station in the first mobile communication network, and wherein the user equipment is in or nearby the coverage area of the base station of the second mobile communication network, wherein

a measurement entity, preferably a base station and/or a gateway, is configured to measure backhaul resource capabilities of the first and/or second mobile communication network and wherein

a quality monitoring entity is configured to determine a backhaul resource quality, preferably for voice calls and/or data traffic, based on the measured result and wherein

a handover decision entity, preferably a base station, is configured to determine a handover control decision based on the determined backhaul resource quality, and wherein a performing entity, preferably the user equipment and/or a base station, is configured to perform the handover control decision.

Although applicable to networks in general, the present invention will be described with regard to mobile communication networks in form of macrocell and femtocell networks.

Femtocells are usually deployed by mobile network operators to increase the mobile network capacity and to enhance indoor coverage of a mobile network. Although femtocells increase the coverage for user equipment to connect to they do not necessarily increase the quality of experience for the users. Conventional femtocell deployments have a limited integration into the mobile network of the operator via a third party broadband access network over which they are backhauled. Mobile network operators cannot influence or guarantee a certain quality of service level across this backhaul link. The mobile operator has also no way to determine whether customers experience a poor quality due to congestion or other problems in the backhaul link i.e. the third party broadband access network of the femtocell. This problem is further exacerbated by unpredictable network congestions within femtocell networks inform of home or enterprise networks and across the backhaul links.

Conventional cellular handover mechanisms consider the link quality between the user equipment and a set of available network base stations as the basis for deciding whether to handover the user equipment to another base station or not under the assumption that the backhaul network is overprovisioned and will not be a bottle neck. This is true for so called macrocell networks since the mobile backhaul network is in this case owned and controlled by the same network operator. However this does not apply for femtocells. If for example a backhaul link through which a femtocell is connected is congested either in the fixed operator domain or a residential or enterprise network, then the handover to the femtocell is in most cases not desirable: This may leed to a loss of an ongoing call in the macrocell network. ln US 7,280,487 a mechanism is described to measure voice call quality in a voice over IP network using a single voice call quality test probe. Voice over IP communication devices such as gateways are deployed at various points along the border of the Voice - over - IP network and are each configured to play an embedded reference voice filed in response to test calls placed by the test probe to those devices. The test probe measures voice call quality by recording the played voice file and comparing it to the test probes own copy of the reference voice file. The comparison uses a standard voice call quality analysis algorithm such as perceptual analysis measurement system PAMS or perceptual speech quality measurement PSQM.

In US 7,664,122 B1 a system for monitoring quality of calls in a network is described. A server receives information concerning calls which begin or end in a network and at the same time receives measurements of a quality parameter such as bandwidth. The measurement data is provided by a probe, so that the service able to correlate calls which are placed through the network with the quality of service in the network at that time. When the quality falls below a desired level, the server notifies the customer or the network operator, so that appropriate action may be taken.

In US 7,099,283 B2 a method of estimating Quality of Services for making a handoff trigger decision for remote terminal in a wireless IP network is described. Probing packets are generated with an access router from a plurality of access points. These probing packets are then sent from the access routers of a fixed core network with a plurality of routers to a correspondent access router and then back to the access routers. Further one or more collector packets are also generated and sent to follow the first and second probing packets to gather at least one predetermined Quality of Service parameter from the routers after the first and second probing packets have left the routers. The Quality of Service parameters are then processed with the access routers to make the handoff trigger decision preferentially along with layer two Quality of Service parameters of the wireless hop. However, one of the drawbacks is that only a roughly estimated Quality of Service can be determined. Another drawback is, that the described method is imprecise and inflexible since only a decision to perform a handoff or not is determined.

It is therefore an objective of the present invention to provide a method and a system for handover control of a user equipment which is more flexible.

It is a further objective of the present invention to provide a method and a system for handover control of a user equipment which enable a more precise determination of network resource quality in terms of Quality of Service for voice calls.

It is an even further objective of the present invention to provide a method and a system for a handover control of a user equipment which is easy to implement and cost effective.

The aforementioned objectives are accomplished by a method of claim 1 and of a system of claim 18.

According to claim 1 the method for handover control of a user equipment between a first mobile communication network and a second mobile communication network, wherein the user equipment is connected to a base station in the first mobile communication network and wherein the user equipment is in or nearby the coverage area of a base station of the second mobile communication network, comprising the steps of

d) Performing of the handover control decision according to step c). According to claim 1 the method is characterized in that determining the handover control decision includes a decision whether or not a handover of the user equipment is to be performed and/or whether or not base station parameters of the base station the user equipment being connected to or intended to be connected to are to be modified.

According to claim 18 the system for handover control of a user equipment between a first mobile communication network and a second mobile communication network preferably for performing with a method according to one of the claims 1 -17, each having a base station wherein the user equipment is connected to the base station in the first mobile communication network, and wherein the user equipment is in or nearby the coverage area of the base station of the second mobile communication network, wherein

a handover decision entity, preferably a base station, is configured to determine a handover control decision based on the determined backhaul resource quality, and wherein

a performing entity, preferably the user equipment and/or a base station, is configured to perform the handover control decision.

According to claim 18 the system is characterized in that the measurement entity is configured to determine the handover control decision based on a decision whether or not a handover of the user equipment is to be performed and whether or not base station parameters of the base station the user equipment being connected to or intended to be connected to are to be modified.

According to the invention it has been recognized, that handover control for mobile communication networks based on a call resource quality improves the quality of experience for users. According to the invention it has further been recognized that Quality of Services aware admission control and handovers between networks is provided. According to the invention it has further been recognized that flexible and adaptive Quality of Service based parameters of a base station, in particular according to backhaul resource availability are provided.

According to the invention it has further been recognized that load balancing is enabled with regard to available backhaul resources.

In particular the term "base station" is to be understood in the description, preferably in the claims in a broad sense, i.e. not limited to a certain type of mobile communication network. For example a base station in LTE may be a home evolved node B, in 3G a home node B, or in small cells a pico macro base station, e.g. a eNB. Mobile communication networks may be but are not limited to LTE, 3G, small cells, WLAN and/or WIMAX.

In particular in the description preferably in the claims the following abbreviations and acrynoms are used.

3GPP 3rd Generation Partnership Project

AMR Adaptive Multi-Rate

AMR-WB Adaptive Multi-Rate Wide-Band

CE Congestion Experienced

CMR Codec Mode Request

CS Circuit Switched

CSG Closed Subscriber Group

DSLAM Digital Subscriber Line Access Multiplexer

ECN Explicit Congestion Notification

eNB eNodeB

FGW Femto Gateway FT Frame Type

GGSN Gateway GPRS Support Node

GPRS General Packet Radio Service

GTP-U GPRS Tunneling Protocol (User Plane)

HeNB Home eNodeB

HeNB-

GW Home eNodeB Gateway

HO Handover

IMS IP Multimedia Subsystem

IP Internet Protocol

IPSec IP Security

ISP Internet Service Provider

ITU International Telecommunications Union

LCS Location Services

MOS Mean Opinion Score

MTSI Multimedia Telephony Service for IMS

NTP Network Time Protocol

PAMS Perceptual Analysis/Measurement System

PESQ Perceptual Evaluation of Speech Quality

P-GW Packet Data Gateway

PSQM Perceptual Speech Quality Measure

PTP Precision Time Protocol

QoS Quality of Service

Ql Quality Indicator

RAN Radio Access Network

RNC Radio Network Controller

RTCP Real Time Control Protocol

RTP Real Time Protocol

RTSP Real Time Stream Protocol S-GW Serving Gateway

Se-GW Security Gateway

TOC Table of Contents

UDP User Datagram Protocol

UE User Equipment

VAD Voice Activity Detection

Further features, advantages and preferred embodiments are described in the following subclaims.

According to a preferred embodiment measuring according to step a) is performed by active probing and/or by passive measuring and that for active probing and/or for passive measuring emulated real voice calls and/or real voice call payloads are used. In particular when active probing as well as passive measuring is used in every case, e.g. when an active voice call session is present or not, measuring of the backhaul resource quality can be performed. Another advantage is that two voice quality estimates may be used for the different measurement techniques so to enable a more precise determination of the backhaul resource quality for voice calls.

According to a further preferred embodiment for determining the backhaul resource quality according to step b) a subjective analysis and/or differential analysis based on the results of the measuring with the emulated real voice calls and/or real voice call payloads is performed. With subjective analysis and/or differential analysis an even more precise determination of the backhaul resource quality is possible minimizing method inherent errors if only one analysis technique is used.

According to a further preferred embodiment base station parameters include base station output power for transmission and/or a number of nodes allowed to be connected to said base station. Base station output power can in a very easy way be modified enabling extending or shrinking the coverage area of the base station. One of the effects is that by reducing the link quality, i.e. by reducing the base station output power, to connected user equipment it may force some of the connected user equipment to handoff to another base station thereby reducing load on the current base station. Another effect is that reducing the output power also application layer adaption is induced resulting in a reduced load on the current base station.

According to a further preferred embodiment base station parameters include uplink and/or downlink rates. By modifying base station parameters in form of uplink and/or downlink rates traffic shaping may be performed at the base station so to dynamically control uplink and/or downlink rates of different traffic flows passing this base station. This may force application adaption at the user equipment or alternate traffic endpoints.

According to a further preferred embodiment the subjective analysis is performed by use of network metrics of the first and/or second mobile communication network, preferably wherein the network metrics include delay, jitter and/or packet loss. By using network metrics for the subjective analysis easy-to-determine respectively parameters, which can be easily provided or measured, are used for subjective analysis.

According to a further preferred embodiment the subjective analysis is based on a single quality metric, preferably based on the E-model. For example delay may be estimated by obtaining RTP, RTCP assuming clock synchronization between two entities which can be achieved using NTP, IEEE1588 or PTP. The ITU-T E-model or a modified variant enable a precise and reliable determination of the backhaul resource quality according to a subjective analysis.

According to a further preferred embodiment step a) is initiated according to a trigger, preferably a location based trigger and/or an activity trigger. Initiating step a) according to a trigger reduces the amount of data to be transported for determining the backhaul resource quality. For example measuring is triggered between a femtocell gateway and a specific femtocell when a specific user equipment or one of set of user equipment is in some predefined distance (location based trigger) from the femtocell and/or depending on whether a call is active or not (activity trigger). For example this set of user equipment may be all user equipment included in a subscriber list of a femtocell operating in a CSG mode. According to a further preferred embodiment steps a)-c) are performed regularly, preferably periodically. This provides a constant monitoring of the backhaul resource quality for voice calls enabling a mobile network operator to recognize areas and/or times in which a congestion of his network is likely to appear. The mobile network operator may then for example enhance the network quality by providing further network resources.

According to a further preferred embodiment for the location based trigger a proximity estimation is performed, preferably by using a CSG proximity indication. A proximity estimation may be performed according to 3GPP release 10. A proximity estimation speeds up the detection of a CSG or hybrid cell to which the user equipment may connect since a conventional CSG identification search may take between one and ten seconds to complete and hence the handover to a femtocell may be delayed by this amount. This further enables the user equipment to determine, using autonomous search procedures, that the user equipment is near or in the coverage area of a CSG or hybrid cell whose CSG identification is in a user equipment's CSG white list. The user equipment may then provide to a base station, e.g. in form of a source evolved node B an indication of proximity. One of the further advantages is, that a proximity estimation may be used in both idle mode and activity mode. Since the CSG identification is unique to each femtocell it can be used by the source base station, e.g. the source evolved node B to identify the specific femtocell to which probing should be triggered. Further upon leaving the coverage area of a specific CSG or hybrid cell the user equipment may also issue a leaving CSG proximity indication. The proximity estimation can be used for informing the mobile communication networks to prepare for a handover and to begin the probing prior to a handover request. When for example a source base station is triggered, i.e. receives a proximity estimation it can request the corresponding user equipment to perform further measurements to obtain network information about a target cell or if this information is already provided the handover may be initiated. According to a further preferred embodiment for the location based trigger the location of the user equipment is determined using GPS and/or location services. Using GPS provides the advantage, that GPS is available worldwide and enables a sufficient precise determination of the location of a user equipment. Using location based services such as 3GPP LCS enables a number of positioning techniques to determine a user equipment location. These techniques are inter alia based upon cell coverage and radio measurements. For example, a location server maintains up-to-date information about the location of the user equipment and provides an interface to enable other nodes which act as LCS clients to query the location of user equipment. This provides in an advantageous way a mechanism for interested nodes to receive a call back when a specific user equipment enters a specific geographic region or area: For example a femtocell gateway or a femtocell registers with a LCS server and subscribes to receive location information for a user equipment in the CSG of femtocells associated with it. Once a user equipment is within a specific geographic region or area close to the femtocell in which there is a high probability that the handover to the femtocell may take place then the femtocell gateway may trigger the measuring or probing process and - based on the results - modify base station parameters to optimize Quality of Experience for the user of the user equipment.

According to a further preferred embodiment probing with the real voice calls and/or real voice call payloads includes emulation of a full duplex voice call, preferably an AMR and/or an AMR-WB voice call and/or voice activity generation for speaker behavior emulation. This enables a realistic and therefore a reliable determination of the backhaul resource quality for voice calls. Voice call payloads may be used from a known voice source, for example an AMR audio test file. When using an emulated full duplex voice call for example between a femtocell and some other network entity, in particular a femtocell gateway, this voice call probe would be identical to a normal femtocell voice call packet at all layers of a corresponding protocol stack and may emulate the codec behavior by performing codec adaption based on any adaption trigger such as using ECN. By using voice activity generation, speaker behavior can be emulated accurately. In the case of AMR or AMR-WB the voice probe may include an AMR/AMR-WB frame, RTP, UDP, IP, GTP-U and IP all transmitted through an IPSec tunnel. The AMR/AMR- WB frame payload may be obtained from a known AMR/AMR-WB encoded test file stored at both entities. At each endpoint the test audio data encapsulated in the received packet may be decoded and analyzed using a voice call quality analysis algorithm such as PESQ, PAMS or PSQM.

According to a further preferred embodiment in case the handover control decision is a rejection of a handover, a handover reject message is provided, preferably including a reason for the rejection, and preferably to the entity initiating the handover. This enables for example to indicate insufficient resources available in the backhaul link to support the current requirements of the user equipment. For example an application running on the user equipment may then reduce required resources, indicate the reduced resources with a corresponding message to a user so that - provided that the user accepts or approves the reduced resource availability - the user equipment may then try a second handover with reduced required resources.

According to a further preferred embodiment for step c) congestion indication information of the first and/or second mobile communication network is used. This information may then be used by a network entity handling a handover request enabling the network entity to make a more intelligent and comparative handover control decision. Such indications may provided by ECN according to RFC 3168 or other Radio access related congestion information from a base station. For example codec adaption may be forced by a femtocell base station or a femtocell gateway by setting the ECN bit of the RTP session even when the femtocell backhaul network does not support ECN. Upon receipt of the ECN bit a user equipment may reduce its source encoding rate thereby reducing network load and/or begin traffic shaping. According to a further preferred embodiment the call quality of ongoing voice calls is continually determined and preferably, if the call quality degrades a predefined threshold, a codec adaption on the user equipment is induced. By continually determining the call quality of ongoing voice calls this information may be used for network quality monitoring fault diagnosis. Preferably if the call quality degrades a predefined threshold, a codec adaption on the user equipment is induced. This enables reduced network load or begin of traffic shaping.

According to a further preferred embodiment the codec adaption is prior to a handover. This reduces the number of handovers if the call quality is degrading.

According to a further preferred embodiment the first mobile communication network is provided in form of a macrocell network and the second mobile communication network is provided in form a femtocell or smallcell network. This enables mobile network operators to increase network capacity and enhance indoor coverage of the macrocell network by the use of femtocells or smallcells.

According to a further preferred embodiment of the system according to claim 18 the measurement entity is configured to actively probe and/or passively measure the backhaul resource capabilities and to use for active probing and/or passively measuring emulated real voice calls and/or real voice call payloads. In particular when the measurement entity performs active probing as well as passive measuring in every case, e.g. when an active voice call session is present or not, measuring of the backhaul resource quality can be performed. Another advantage is that two voice call quality estimates may be used for the different measurement techniques so to enable a more precise determination of the backhaul resource quality for voice calls.

There are several ways how to design and further develop the teaching of the present invention in an advantageous way. To this end it is to be referred to the patent claims subordinate to patent claim 1 and patent claim 18 on the one hand and to the following explanation of preferred embodiments of the invention by way of example, illustrated by the figure on the other hand. In connection with the explanation of the preferred embodiments of the invention by the aid of the figure, generally preferred embodiments and further developments of the teaching will we explained. In the drawing

Fig. 1 shows a method according to a first embodiment of the present invention; Fig. 2 shows a method according to a second embodiment of the present invention;

Fig. 3 shows a method according to a third embodiment of the present invention;

Fig. 4 shows a system according to a fourth embodiment of the present invention and

Fig. 5 shows a system according to a fifth embodiment of the present invention.

Fig. 1 shows a method according to a first embodiment of the present invention.

In Fig. 1 a proximity detection based triggering of a probe is shown. A user equipment UE is connected via a source evolved node B eNodeB to a macrocell network. Further a femtocell network including a Home evolved node B HeNodeB is connected to a femtocell gateway.

In the following steps for a handover proximity triggered are described.

In a first step 101 a measurement control according to measurement type CSG Proximity Detection is sent from a source eNodeB to a user equipment UE. In a second step 102 a measurement report including a CSG proximity indication is sent from the user equipment to the source eNodeB.

In a third step 103 a measurement control message is sent from the source eNodeB to the user equipment UE. As a reply the user equipment UE sends in a fourth step 104 a measurement report including PCS cell identity and CSG member indication to the source eNodeB.

In a fifth step 105 a CSG proximity indication including CSG identification is sent from the source eNodeB to the Femtocell gateway. In a sixth step 106 probing is initiated. ln a seventh step 107 an emulated AMR voice call is sent from the Femtocell gateway to the home evolved node B HeNodeB. In an eight step 108 the HeNodeB sends an emulated AMR voice call to the Femtocell gateway. In a ninth step 109 the Femtocell gateway computes MOS & PESQ score. In a tenth step 1 10 the Femtocell gateway sends a message to reconfigure the home evolved node B HeNodeB to accept or reject calls to the HeNodeB.

In an eleventh step 1 1 1 a handover request message is sent from the source eNodeB to the HeNodeB. In a twelfth step 1 12 the home evolved Node B HeNodeB performs admission control for handover

In a thirteenth step 1 13 a handover request acknowledgement message is sent from the HeNodeB to the source eNodeB.

In a fourteenth step 1 14 normal handover procedures are continued.

In Fig. 1 the proximity indication 102 and an associated CSG identification 105 are forwarded to the femtocell gateway. Instead of a femtocell gateway also another network entity may be used. The measurement report according to the fourth step 104 is being received from the user equipment causing the source eNodeB to issue a proximity indication 105 to the femtocell gateway in order to initiate the probing mechanism according to the steps 106, 107 and 108. Based on the measurements received from this probing the femtocell gateway reconfigures in the tenth step 1 10 the home involved HeNodeB to either accept or reject voice call handover requests.

Fig. 2 shows a method according to a second embodiment of the present invention.

In Fig. 2 LCS based triggering of a probing is shown.

In Fig. 2 a user equipment UE is connected via a source evolved Node B to a macrocell network. A Home evolved node B HeNB is connected to a femtocell gateway in a femtocell network. The femtocell gateway is further connected to a LCS server.

In a first step 201 a femtocell gateway sends a core network location request to a LCS server. In a second step 202 the LCS server sends a location report back to the Femtocell gateway.

In a third step 203 probing is initiated. In a fourth step 204 an emulated AMR voice call is sent from the Femtocell gateway to the HeNodeB.

In a fifth step 205 the HeNodeB sends an emulated AMR voice call to the Femtocell gateway. In a sixth step 206 the Femtocell gateway computes a MOS & PESQ score. In a seventh step 207 the Femtocell gateway reconfigures or initiates reconfiguring of the HeNodeB to accept and/or reject calls. In an eighth step 208 the source eNodeB sends a measurement control message to the user equipment UE.

In a ninth step 209 the user equipment sends a measurement report including PSC, cell identity, CSG member indication to the source eNodeB. The source eNodeB sends a handover request message in a tenth step 210 to the HeNodeB.

The home evolved node B HeNodeB performs in an eleventh step 21 1 an admission control for a handover of the user equipment. In a twelfth step 212 the HeNodeB sends a handover request acknowledgement message to the source eNodeB.

In a thirteenth step 213 normal handover procedures are continued. In summary with regard to Fig. 2, the location server maintains up-to-date information about the location of user equipment and provides an interface to enable other nodes which act as LCS clients to query the location of the user equipment, as depicted in Fig. 2, step 201. The LCS server also provides a mechanism for nodes to receive a callback when a specific user equipment UE enters a specific geographic region, as shown in Fig. 2, step 202. The femtocell gateway or the femtocell registers with the LCS server and subscribes to receive location information for user equipment UE in the CSG of the femtocells associated with it.

Once the user equipment UE is the femtocell specific geographic region close to the femtocell with the HeNodeB in which there is a high probability that the handover to the femtocell may take place, then the femtocell gateway triggers the probing process as depicted in Fig. 2 by steps 203, 204 and 205 and based on the results reconfigures the HeNodeB, shown in Fig. 2, step 207.

Fig. 3 shows a method according to a third embodiment of the present invention.

In Fig. 3 a flowchart of the mechanism used to make the admission control decision is shown.

In a first step S1 a user equipment enters a defined geographic area. In a second step S2 the user equipment, a HeNodeB, a HeNodeB gateway or another network entity triggers probing.

In a third step S3 the HeNodeB, the HeNodeB gateway or the other network entity exchange an emulated voice call probe. In a fourth step S4 the HeNodeB gateway or the other network entity computes network metrics and a PESQ score. In a fifth step S5 the HeNodeB is reconfigured considering the results of the probing by for example reducing the number of supported user equipment, by reducing the output power, etc.. In a sixth step S6 it is decided whether voice calls can be supported or not. If not in a first seventh step S7a all handover requests of active voice calls are rejected. If voice calls can be supported, all handover requests of active calls are accepted in a second seventh step S7b. ln Fig. 3 based upon the results obtained from the probe it can be determined if a voice call can be supported at reasonable quality. If no voice calls can be supported then all handover requests can be rejected. The handover reject message may optionally contain information regarding the reason for the rejected handover, for example insufficient resources are available in the backhaul network to support current requirements of the user equipment. Furthermore the initial handover request may optionally contain information regarding the congestion level of the current cell of the femtocell base station. This information can then be used by a network entity handling the handover requests to make a more intelligent and comparative handover decision.

Furthermore the femtocell parameters and configuration, i.e. of the home evolved node B HeNodeB can also be adapted depending on the estimated backhaul capacities and resource availability. For example the femtocell base station can dynamically adjust/adapt the femtocell base station output power. A femtocell base station can also be reconfigured to perform a traffic shaping to dynamically control the uplink and downlink data rates of different traffic flows to force application adaption at the user equipment or alternate traffic endpoint. The femtocell respectively the femtocell base station and/or the femtocell gateway may continually monitor a number of voice call specific metrics. These may include AMR/AMR-WB encoded test file, CMR, end-to-end or two-waydelay, jitter and packet loss and both uplink and downlink. These metrics may then optionally be combined using an algorithm such as a modified variant of the ITU-T E-model for voice quality assessment to obtain a single metric as an estimate to the voice call quality being achieved between the femtocell base station and the femtocell gateway or another network entity.

At the femtocell a Quality of Service agent may monitor respectively capture all ongoing downlink voice call flows and extracts pertinent information from the passing voice calls. This information or metrics are then processed fully in order to compute a Quality of Service value for the downlink or only partially before being forwarded to a Quality of Service agent in the femtocell gateway or another network entity. The femtocell gateway or the other network entity may capture respectively monitor all pertinent Quality of Service information for the uplink voice flows. This information may then be used to monitor the quality of the ongoing voice flows and may be logged for network quality monitoring and fault diagnosis. The femtocell or femtocell gateway may provide an IPSec tunnel originating and terminating by these entities and as such have full access to all packets.

Alternative to Fig. 3 and by using architecture similar to Fig. 3, the HeNodeB gateway, i.e. a femtocell gateway may register with a LCS server to receive a callback when specific user equipment in a CSG of a specific femtocell enter a predefined geographic area or are within a predefined distance relative to a corresponding femtocell basestation. The HeNodeB gateway may then perform a check to determine if the user equipment UE has an active voice session. If a voice session is active a probing session between the HeNodeB gateway and the femtocell basestation is initiated.

If no such check is possible in the existing network, then it may be assumed that there is an active voice call and (active) probing is performed. This probing and voice quality assessment may then be used to estimate the MOS that will be achieved in the backhaul network in case the voice call is handed over to the femtocell.

If the voice call quality falls below some predefined minimum of a threshold then the femtocell base station or femtocell gateway may deny any handover requests from a user equipment. The femtocell base station or the femtocell gateway may still enable user equipment having no active voice calls to be handed in. In this case the femtocell base station may wait until a handover request is received and based on this request it will know if there is an active voice call at the user equipment. If yes, the handover request may be denied. Fig. 4 shows a system according to a fourth embodiment of the present invention.

In Fig. 4 a system architecture for call quality monitoring is shown. ln Fig. 4 an user equipment UE is connected to a base station BS. The base station BS is connected via a DSLAM and via the internet to a security gateway GW and a femtocell gateway FGW in an evolved packet core EPC. In the evolved packet core EPC a Quality of Service agent is running. The Quality of Service agent may be run in AMR mode, CMR mode and may analyze delay, jitter and loss.

Further at the evolved packet core EPC the Quality of Service computation is performed receiving corresponding information from a monitoring and management interface. The monitoring and management interface uses logged data exchanged between the base station BS and the evolved packet core EPC. For assessment of a Quality of Service at the base station BS also a further Quality of Service agent may run in AMR mode or CMR mode determining delay, jitter and/or loss. For example a Voice over IP probe including an AMR/WR encoded test file, a VAD emulation and a codec adaption is exchanged between the base station BS and the evolved packet core EPC.

Between the user equipment UE and the evolved packet core EPC data is or may be exchanged according to IPSec, IP, UDP, GTP-U, IP/UDP/RTP and AMR wherein AMR includes CMR, FT, TOC and Test/Voice Payload enabling call quality monitoring via the Quality of Service agent(s). A voice call packet includes IPSec, IP, UDP, GTP-U, IP/UDP/RTP and AMR.

Fig. 5 shows a system according to a fifth embodiment of the present invention. In Fig. 5 user equipment are connected to a macrocell base station MBS. The macrocell base station MBS is connected to a mobility server, a femtocell gateway and a location server. The mobility server, the femtocell gateway FemtoGW and the location server are located in the core network of the mobile communication network. Further a femtocell base station FBS is connected by a fixed broadband access network FBAN and a security gateway to the femtocell gateway and the location server. Between the femtocell base station FBS and the femtocell gateway a voice probe packet including IPSec, IP, UDP, GTP-U, IP/UDP/RTP and AMR is exchanged. In Fig. 5 a voice call quality is determined passively. According to Fig. 5 an ongoing voice call is assumed to be present and therefore be used for determining voice call quality. The network metrics, for example loss, delay, jitter, codec modes are monitored at both the femtocell base station FBS and the femtocell gateway FemtoGW. These metrics are used to estimate the voice call quality, for example by using the E-model, to determine if any further calls should be allowed to hand in. If the call quality of ongoing calls falls or is below predefined threshold any further handover requests that are received are or can be rejected. If the results of probing or passively monitoring of existing ongoing voice calls or other data traffic indicate that no further calls can be supported, the femtocell base station may reduce its output power to force some of the attached user equipment to reconnect to an alternate femtocell basestation or to the macrocell base station MBS. This reduces the load on the current femtocell base station FBS and the corresponding backhaul link and lower the probability of receiving handover requests. If the backhaul link quality of the femtocell base station FBS via their fixed broadband access network FBAN is very poor, the femotcell base station FBS may opt to completely disable access radio until the backhaul link quality of the fixed broadband access network FBAN is above a predefined threshold.

It is further possible when continuously monitoring the quality of ongoing voice calls via their femtocell base station, Quality of Service based handoffs from a femtocell base station are enabled. For example if the voice call quality of a voice call via the femtocell base station FBS degrades, the femtocell base station FBS transmitted power may be reduced to initially trigger application adaption at the corresponding user equipment and forcing the use of a more error resilient encoding mechanism or to force the user equipment to perform a handoff to an alternative available base station, either another femtocell base station or to the macrocell base station.

In summary the present invention enables a handover control and optimization for cellular networks, in particular femtocell networks and macrocell networks, based on backhaul resource availability to improve Quality of Experience for users. Further the present invention enables voice call quality monitoring in order to make sure voice services do not degrade as a result of a handover that is not necessary. Furthermore the present invention provides Quality of Service aware admission control and handovers for femtocell networks. Even further the invention provides adaptive Quality of Service based power control for femtocell base stations and load balancing of mobile terminals according to backhaul recource availability.

The present invention improves Quality of Experience in cellular networks with resource limited backhaul links. One of the further advantages of the present invention is that the present invention provides a mechanism to achieve quality based handovers in cellular networks, in particular femtocell networks as well as macrocell networks preventing handovers to radio cells which are not able to support a high level of voice quality. Even further one of the advantages of the present invention is that load balancing from the perspective of the backhaul resource is enabled.

Many modifications and other embodiments of the invention set forth herein will come to mind the one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

C l a i m s

1. A method for handover control of a user equipment between a first mobile communication network and a second mobile communication network, wherein the user equipment is connected to a base station in the first mobile communication network and wherein the user equipment is in or nearby the coverage area of a base station of the second mobile communication network, comprising the steps of a) Measuring backhaul resource capabilities of the first and/or second mobile communication network,

b) Determining a backhaul resource quality, preferably for voice calls and/or data traffic, based on the result of step a)

d) Performing of the handover control decision according to step c), characterized in that

determining (1 10) the handover control decision includes a decision whether or not a handover of the user equipment (UE) is to be performed and whether or not base station parameters of the base station (MBS, FBS) the user equipment being connected to or intended to be connected to are to be modified.

2. The method according to claim 1 , characterized in that measuring according to step a) is performed by active probing (106) and/or by passive measuring and that for active probing and/or for passive measuring emulated real voice calls and/or real voice call payloads (107, 108) are used.

3. The method according to claim 2, characterized in that for determining the backhaul resource quality according to step b) a subjective analysis and/or a differential analysis based on the results of the measuring with the emulated real voice calls and/or real voice call payloads is performed.

4. The method according to claim 1 -3, characterized in that base station parameters include base station output power for transmission and/or a number of nodes allowed to be connected to said base station (MBS, FBS).

5. The method according to claim 1 -4, characterized in that base station parameters include uplink and/or downlink rates.

6. The method according to one of the claims 1 -5, characterized in that the subjective analysis is performed by use of network metrics of the first and/or the second mobile communication network, preferably wherein the network metrics include delay, jitter and/or packet loss.

7. The method according to one of the claims 1 -6, characterized in that the subjective analysis is based on a single quality metric, preferably based on the E- model.

8. The method according to one of the claims 1 -7, characterized in that step a) is initiated according to a trigger, preferably a location based trigger and/or an activity trigger.

9. The method according to one of the claims 1 -8, characterized in that steps a)-c) are performed regularly, preferably periodically.

10. The method according to one of the claims 1-9, characterized in that for the location based trigger a proximity estimation is performed, preferably by using a CSG proximity indication.

1 1. The method according to one of the claims 1 -10, characterized in that for the location based trigger the location of the user equipment (UE) is determined using GPS and/or location services.

12. The method according to one of the claims 1 -1 1 , characterized in that probing with the emulated real voice calls and/or real voice call payloads includes emulation of a full duplex voice call, preferably an AMR and/or an AMR-WB voice call and/or voice activity generation for speaker behavior emulation.

13. The method according to one of the claims 1 -12, characterized in that in case the handover control decision is a rejection of a handover, a handover reject message is provided, preferably including a reason for the rejection, and preferably to the entity initiating the handover.

14. The method according to one of the claims 1 -13, characterized in that for step c) congestion indication information of the first and/or second mobile communication network (MCN) is used.

15. The method according to one of the claims 9-14, characterized in that the call quality of ongoing voice calls is continually determined and preferably if the call quality degrades a predefined threshold, a codec adaption on the user equipment (UE) is induced.

16. The method according to claim 15, characterized in that the codec adaption is performed prior to a handover.

17. The method according to one of the claims 1 -16, characterized in that the first mobile communication network (MCN) is provided in form of a macrocell network and the second mobile communication network (FCN) is provided in form of a femtocell or smallcell network.

18. A system for handover control of a user equipment (UE) between a first mobile communication network (MCN) and a second mobile communication network (FCN) preferably for performing with a method according to one of the claims 1 -17, each having a base station (MBS, FBS) wherein the user equipment (UE) is connected to the base station (MBS) in the first mobile communication network (MCN), and wherein the user equipment (UE) is in or nearby the coverage area of a base station (FBS) of the second mobile communication network (FCN), wherein

a measurement entity (BS, SeGw), preferably a base station (BS) and/or a gateway (SeGw, FGW), is configured to measure backhaul resource capabilities of the first and/or second mobile communication network (MCN, FCN) and wherein a quality monitoring entity (FBS) is configured to determine a backhaul resource quality preferably for voice calls and/or data traffic based on the measured result and wherein

a handover decision entity (FBS), preferably a base station, is configured to determine a handover control decision based on the determined backhaul resource quality, and wherein

a performing entity, preferably the user equipment (UE) and/or a base station (FMS, MBS), is configured to perform the handover control decision,

characterized in that

the measurement entity (BS, SeGw) is configured to determine the handover control decision based on a decision whether or not a handover of the user equipment (UE) is performed and whether or not base station parameters of the base station (MBS, FBS) the user equipment being connected to or intended to be connected to are to be modified.

19. The system of claims 18, characterized in that the measurement entity (BS, SeGw) is configured to actively probe and/or passively measure the backhaul resource capabilities and to use for active probing and/or for passively measuring emulated real voice calls and/or real voice call payloads.