WO2008088592A1 - Translation dans un système de communication cellulaire - Google Patents

Translation dans un système de communication cellulaire Download PDF

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Publication number
WO2008088592A1
WO2008088592A1 PCT/US2007/079633 US2007079633W WO2008088592A1 WO 2008088592 A1 WO2008088592 A1 WO 2008088592A1 US 2007079633 W US2007079633 W US 2007079633W WO 2008088592 A1 WO2008088592 A1 WO 2008088592A1
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WO
WIPO (PCT)
Prior art keywords
network element
base stations
base station
group
relocation
Prior art date
Application number
PCT/US2007/079633
Other languages
English (en)
Inventor
David C. Padfield
Gerard T. Foster
Luis Lopes
Original Assignee
Motorola, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Motorola, Inc. filed Critical Motorola, Inc.
Publication of WO2008088592A1 publication Critical patent/WO2008088592A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/04—Reselecting a cell layer in multi-layered cells
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/302—Reselection being triggered by specific parameters by measured or perceived connection quality data due to low signal strength

Definitions

  • the invention relates to relocation in a cellular communication system and in particular, but not exclusively, to handover from a macro-cell to a pico-cell in a 3 rd Generation cellular communication system.
  • a method which has been used to increase the capacity of cellular communication systems is the concept of hierarchical cells wherein a macro-cell layer is underlayed by a layer of typically smaller cells having coverage areas within the coverage area of the macro- cell.
  • smaller cells known as micro-cells or pico-cells (or even femto-cells)
  • the micro-cells and pico-cells have much smaller coverage thereby allowing a much closer reuse of resources.
  • the macro-cells are used to provide coverage over a large area
  • micro-cells and pico-cells are used to provide additional capacity in e.g. densely populated areas and hotspots.
  • pico-cells can also be used to provide coverage in specific locations such as within a residential home or office.
  • CE16161EP macro-cell layer and the underlying layer is optimized.
  • the process of handover can be separated into three phases. Firstly, identifying that a handover might be required, secondly, identifying a suitable handover candidate and finally, switching the mobile user from one base station to another.
  • underlaying a macro-layer of a 3G network with a pico-cell (or micro-cell) layer creates several issues.
  • the introduction of a large number of underlay cells creates a number of issues related to the identification of individual underlay cells when e.g. handing over to an underlay cell.
  • 3G communication systems are developed based on each cell having a relatively low number of neighbours and extending the current approach to scenarios wherein the mobile station may need to consider large numbers of potential neighbour cells is not practical.
  • CE16161EP underlay cell and to identify all potential handover underlay cells as neighbours of the macro-cell as this would require very large neighbour lists. These large neighbour lists would e.g. result in the neighbour list exceeding the maximum allowable number of neighbours in the list, slow mobile station measurement performance as a large number of measurements would need to be made, increased resource usage etc. It would furthermore require significant operations and management resource in order to configure each macro-cell with the large number of neighbours and would complicate network management, planning and optimisation. However, sharing scrambling codes for the pilot signals of the pico-cells results in a target ambiguity and prevents the mobile station from uniquely identifying a potential handover target.
  • a mobile station detecting the presence of this shared scrambling code will be aware that a potential handover target has been detected but will not be able to uniquely identify which of the group of underlay cells has been detected.
  • an improved cellular communication system would be advantageous and in particular a system allowing increased flexibility, improved suitability for large numbers of potential handover targets/neighbour cells, improved suitability for overlay/underlay handovers, reduced neighbour lists, increased practicality, reduced measurement requirements, facilitated and/or improved handover target detection/identification and/or improved performance would be advantageous.
  • the Invention seeks to preferably mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.
  • a network element for a cellular communication system the network element being arranged to support at least a plurality of base stations having a shared pilot signal scrambling code; the network element comprising: means for receiving a relocation request message for a remote station supported by a first base station, the relocation request comprising an identification of the shared pilot signal scrambling code; determining means for determining a group of base stations as potential target base stations for the relocation request in response to the identification of the shared pilot signal scrambling code; request means for transmitting a request message to the group of base stations, the request message comprising a parameter indication for an uplink transmission from the remote station to the first base station and requesting the group of base stations to measure the uplink transmission; means for receiving measurement reports for the uplink transmission from the group of base stations; and selection means for selecting a handover target base station from the group of base stations in response to the measurement reports.
  • the invention may allow improved and/or facilitated operation in a cellular communication system and may in
  • CE16161EP particular allow improved identification of a handover target from a group of cells sharing a pilot signal scrambling code thereby improving e.g. handover performance.
  • the invention may allow improved identification of an underlay target handover cell for a remote station currently served by a macro- cell.
  • the invention may allow highly robust underlay cell identification while using a reduced amount of resources.
  • the invention may require fewer scrambling codes while still allowing a given number of underlay cells to be identified.
  • the invention may in some embodiments facilitate handover.
  • the invention may in some embodiments facilitate or enable support of large numbers of underlay cells.
  • the invention may e.g. allow improved handover in a cellular communication system.
  • the invention may facilitate or improve handovers in systems wherein a remote station may have a large number of possible handover targets.
  • the invention may allow a reduced number of measurements being required by a remote station to determine a suitable handover target, may allow reduced neighbour lists and/or may reduce the required number of scrambling codes.
  • the cells supported by the group of base stations may e.g. be micro-cells, pico-cells and/or femto-cells.
  • the cellular communication system may be a Code Division Multiple Access cellular communication system such as a Universal Mobile Telecommunication System (UMTS) .
  • UMTS Universal Mobile Telecommunication System
  • the remote station may for example be a User Equipment or a mobile communication unit, e.g. of a 3 rd generation cellular communication system.
  • the network element may in some embodiments appear to the network as a virtual Radio Network Controller (RNC) which supports a plurality of base stations sharing a pilot signal scrambling code.
  • RNC Radio Network Controller
  • the routing/handover setup may switch to the actual RNC supporting the handover target base station and a conventional handover process may e.g. be used between this RNC and the RNC supporting the remote station prior to the handover.
  • the identification of the handover target base station may result in a message being transmitted to the RNC serving the handover target base station in response to which the RNC may proceed in setting up the relocation process.
  • a relocation of a remote station may be any process or activity wherein the remote station moves from being supported by one cell to being supported by another cell.
  • the relocation request message may be any indication that a movement or switch of the remote station from the first base station to the handover target base station may be desired. This movement/switch may for example be a handover of the remote station to the handover target base station from the first cell.
  • the relocation may be associated with a modification of a routing path in the fixed network for the remote terminal (e.g. from a core network element to the handover target access point) .
  • the relocation request message may be generated internally in the network element, e.g. it may be a flag
  • CE16161EP or other indication generated by a handover evaluation functionality comprised in the network element is not limited to the network element.
  • a Code Division Multiple Access, CDMA, cellular communication system comprising a network element as previously described and further comprising: a source radio network controller for the first base station, the radio network controller being arranged to generate the relocation request message in response to receiving an indication of detection of the shared pilot signal scrambling code from the first remote station; and address means for determining an network element address of the network element in response to the shared pilot signal scrambling code; means for transmitting the relocation request message to the network element using the network element address.
  • CDMA Code Division Multiple Access
  • the generated relocation request message may be represented by different relocation messages at different locations/stages of the communication and may be modified by intervening network elements.
  • the address means and/or the means for transmitting may be located at any suitable physical or logical location in the network including in a Mobile Switching Centre (MSC) and/or in the source radio network controller.
  • MSC Mobile Switching Centre
  • the source radio network controller may generate a relocation request message in the form of a 3GPP Relocation Required message which does not specifically address any destination.
  • a serving MSC may convert this message into a relocation request message in the form of a 3GPP Relocation Request message and may
  • CE16161EP further comprise the address means arranged to address the 3GPP Relocation Request message to the network element .
  • relocation request message may be considered a common generic term comprising all specific messages used to communicate a relocation request from the source radio network controller to the network element and/or a radio network controller supporting the handover target base station. As such it encompasses different messages used at different stages of the path and/or may include a plurality of parallel messages used to indicate the request for a relocation.
  • a method of operation for a network element of a cellular communication system comprising the network element performing the steps of: receiving a relocation request message for a remote station supported by a first base station, the relocation request comprising an identification of the shared pilot signal scrambling code; determining the group of base stations as potential target base stations for the relocation request in response to the identification of the shared pilot signal scrambling code; transmitting a request message to the group of base stations, the request message comprising a parameter indication for an uplink transmission from the remote station to the first base station and requesting the group of base stations to measure the uplink transmission; receiving measurement reports for the uplink transmission from the group of
  • CE16161EP base stations and selecting a handover target base station from the group of base stations in response to the measurement reports.
  • FIG. 1 illustrates an example of a cellular communication system in accordance with some embodiments of the invention
  • FIG. 2 illustrates an example of a network element in accordance with some embodiments of the invention.
  • FIG. 3 illustrates an example of a method of operation for a network element in accordance with some embodiments of the invention.
  • CE16161EP this application but may be applied to many other cellular communication systems. Also, the description will focus on scenarios where a remote station is handing over from a macro-cell to an underlay cell such as a micro-cell or a pico-cell. However, it will be appreciated that the described principles apply equally to other scenarios including e.g. some scenarios where a handover is made to a macro-cell out of a group of macro- cells using a shared pilot signal scrambling code.
  • FIG. 1 illustrates an example of a cellular communication system which in the specific example is a UMTS cellular communication system.
  • a macro-layer is formed by macro-cells supported by base stations.
  • an underlay layer of pico-cells are supported by a large number of small base stations which henceforth will be referred to as access points.
  • each access point may have an intended coverage of a single house or dwelling, and for a typical macro-cell coverage area of 10 to 30 km there may be hundreds or even thousands of pico-cells each supported by an individual access point.
  • the macro base stations each have a cell separation code in the form of a scrambling code that is unique within a given region which e.g. may be a reuse area for the cell scrambling codes.
  • the macro base stations have an assigned scrambling code which is unique within the reuse area such that a set of defined neighbours for each cell always have unique cell scrambling codes.
  • each macro-cell base station has a unique hierarchical network address given by a unique base station ID for a given serving RNC,
  • CE16161EP which itself has a unique RNC ID for a given MSC. Furthermore, each MSC has a unique identity in the network .
  • the neighbour lists transmitted by the base stations comprise indications of macro-cells which all have different cell scrambling codes. Furthermore, for each macro neighbour cell, a unique network address of the base station supporting the macro-cell can be determined from the detection of a specific neighbour cell pilot signal. Accordingly, a handover to a target macro-cell may be initiated with an explicit and unique identification of the handover target base station.
  • the access points (which in the specific example are base stations supporting pico-cells) use a scrambling code which is shared between a plurality of access points within the reuse area and specifically a given neighbour list may comprise indications of shared pilot signal scrambling codes for a plurality of underlay cells that are all considered as neighbours/potential handover targets for the current cell.
  • a pilot signal scrambling code between a plurality of access points, a much reduced number of scrambling codes are required by the system.
  • the number of scrambling codes by keeping the number of scrambling codes low, the number of scrambling codes that must be evaluated by the remote station for handover determination can be reduced substantially thereby reducing the measurement time, power consumption and/or complexity of the remote station.
  • CE16161EP nodes cannot uniquely identify the access point which has been detected by the remote station simply from the detected scrambling code. Rather, a remote station detecting a scrambling code does not uniquely identify a given target access point for a handover but at best identifies only a group of access points which all use the same shared pilot signal scrambling code.
  • all access points within a coverage area supported by a single macro-RNC may use the same scrambling code.
  • a plurality of shared scrambling codes may be available for the access points. Therefore, the access points may be divided into a number of groups with the access points of each group sharing a scrambling code but with different scrambling codes being used for different groups.
  • the scrambling codes may be allocated to the access points such that a reuse pattern is established with the interference between pico-cells having the same shared scrambling code being reduced or minimised.
  • one macro-base station 101 which supports a macro-cell with a typical coverage area of 10-30 kilometres is illustrated.
  • the macro base station 101 is coupled to a macro RNC 103 which is furthermore coupled to other macro base stations (not shown) .
  • the macro RNC 103 is furthermore coupled to a core network 105 which interfaces to other radio access networks and RNCs.
  • the macro RNC 103 is coupled to a first MSC 107 which is further coupled to a second MSC 109 serving a different set of RNCs than the first MSC 107.
  • CE16161EP The system furthermore comprises a large number of pico- cell base stations/access points 111, 113 (for clarity only three access points are illustrated in FIG. 1).
  • Each of the access points 111, 113 supports a pico-cell having a coverage area of typically 10 to 50 meters.
  • the access points 111, 113 implement the required functionality of a UMTS base station in order to support UMTS communications within the pico-cell.
  • the access points 109 use a common shared pilot signal scrambling code.
  • each of the access points 111, 113 comprises some RNC functionality such that the network interface to the access points 111, 113 is the same as to an RNC.
  • each access point 111, 113 appears as an RNC to the network and each access point 111, 113 has an individual RNC identity (RNC ID) .
  • RNC ID RNC identity
  • the access points/pico base stations 111, 113 are accordingly coupled directly to a serving MSC which in this case is the second MSC 109.
  • the system of FIG. 1 furthermore comprises a network element which may operate as a virtual RNC 115 for the access points 111, 113 during the initial phases of a handover. Specifically, when a remote station detects a shared pilot signal scrambling code, a relocation request message may be transmitted to the virtual RNC 115 which then may resolve the ambiguity and identify the detected access point 111, 113 as a suitable handover target.
  • a remote station 117 may initially be served by the macro base station
  • CE16161EP 101 When monitoring the pilot signals (CPICHs) of the neighbour list, the remote station 117 may detect the pilot signal of a first access point 111 of the access points 111, 113.
  • the shared pilot signal scrambling code may be decoded to provide identification data for the first access point 111.
  • the scrambling code is shared by a large number of access points 111, 113, it is not possible for the source system to uniquely determine the identity of the first access point 111.
  • the shared scrambling code may be associated with the address (RNC ID) of the virtual RNC 115.
  • the macro RNC 103 may determine the preference for a handover (based on the reported pilot signal measurements from the remote station 117) and may accordingly transmit a handover request message addressed to the virtual RNC 115.
  • this handover request message is received at the virtual RNC 115, it proceeds to determine which of the access points 111, 113 is the detected target handover access point 111.
  • the virtual RNC 115 first uses the indication of the shared pilot signal scrambling code to determine a group of base stations/ access points which are potential targets base stations/access points.
  • the group may be determined as all the access points 111, 113 using the shared pilot signal scrambling code. It will be appreciated that this may be most practical in scenarios where a relatively low number of access points share a given shared pilot signal scrambling code and that in other embodiments further measures may be taken to reduce the group of potential targets as will be described later.
  • CE16161EP The virtual RNC 115 proceeds to instruct all access points 111, 113 in the potential target group to make measurements of the uplink transmissions from the remote station 117 to the macro-base station 101.
  • the measurements may comprise a signal level measurement determined as an amplitude/power indication of a correlation of uplink pilot bits unscrambled by the remote station's uplink scrambling code. This may further be combined with the observed time difference and chip offset information which will result in a very high probability that one access point will achieve a strong correlation while all others will achieve no correlation.
  • the access points 111, 113 make these measurements and return the resulting measurement reports to the virtual RNC 115. If the pico-cells are reasonably spaced apart, it is likely that the detected access point 111 is the closest access point and that this will measure the highest signal level for the uplink transmission of the remote station 117. Accordingly, the virtual RNC 115 can select the access point measuring the highest signal level as the target handover access point 111.
  • the virtual RNC 115 can then transmit a message to the selected target handover access point 111 identifying the source of the relocation request.
  • the target access point 111 accordingly initiates a handover procedure by directly communicating with the macro-RNC currently serving the remote station 117.
  • Such a handover process may follow a conventional handover procedure between a serving and target RNC in a UMTS system.
  • CE16161EP An exemplary handover will in the following be described in more detail with reference to FIG. 2 which illustrates the virtual RNC in more detail and FIG. 3 which illustrates an example of a method of operation for the virtual RNC 115.
  • the remote station 117 is served by the macro base station 101 and performs user data uplink transmissions supported by the macro base station 101.
  • the remote station 117 scans for the pilot signals of the cells indicated in the received neighbour list. This includes the shared pilot signal scrambling code.
  • the remote station 117 detects the presence of the shared pilot signal scrambling code and transmits a measurement report. For example, if the macro-cell level drops below a threshold and the remote station 117 measures the shared pilot signal scrambling code, the remote station 117 transmits a message which is an indication of the detection of the shared pilot signal scrambling code.
  • the message is received by the macro base station 101 and forwarded to the macro RNC 103.
  • the macro RNC 103 generates a relocation request message which is specifically implemented in the form of a UMTS Relocation Required message which is transmitted from the macro RNC 103 to the first MSC 107.
  • the Relocation Required message may not comprise any specific addressing of a target RNC (such as the virtual RNC 115) but may comprise various characterising data that allows the address of an RNC to be determined.
  • the message can specifically include a Radio Resource Control
  • CE16161EP transparent container which comprises information that may enable or assist the routing of the message and/or the identification of a suitable set of target access points and/or may assist or facilitate the measuring performed by these.
  • the RRC container comprises an identification of the detected pilot signal scrambling code, the identity of the first cell and the scrambling code used for the uplink user data transmissions to the first base station 101 from the remote station 117. It will be appreciated that the RRC container may comprise other or additional information in other embodiments. Specifically, the RRC container may comprise an indication of the frequency used for the uplink transmissions .
  • the relocation request message including the RRC transparent container is transmitted to the first MSC 107 which proceeds to determine the network element address of the virtual RNC 115 based on the information received in the RRC transparent container.
  • the virtual RNC 115 may support all access points 111, 113 that share a given shared pilot signal scrambling code and the first MSC 107 may simply comprise a list uniquely linking a given shared pilot signal scrambling code to a specific network element address for the corresponding virtual RNC 115.
  • the network element address of the virtual RNC 115 is in the example unique within the network such that the routing of the relocation request message to the
  • CE16161EP virtual RNC 115 may be performed based only on this address .
  • the same shared pilot signal scrambling code may be re-used in the cellular communication system such that different virtual RNCs may support different access points using the same shared pilot signal scrambling code.
  • the virtual RNCs will typically be distributed geographically such that all access points within a (potentially large) geographic area using the same shared pilot signal scrambling code will be served by the same virtual RNC.
  • all access points that can be accessed from a given macro- cell will typically be served by the same virtual RNC 115 and accordingly, the MSC 107 may determine the virtual RNC 115 address by a unique link from the combination of the identity of the first macro-cell and the detected shared pilot signal scrambling code.
  • the linking information may be provided manually by the network operator as part of the operations and maintenance process .
  • the relocation request message is transmitted to the virtual RNC 115 using this address.
  • the first MSC 107 generates a UMTS Relocation Request message addressed to the virtual RNC 115 and comprising the RRC transparent container received from the macro RNC 103.
  • the first MSC 107 may in some embodiments modify the transparent container and may specifically add or delete specific information elements.
  • the Relocation Request message is routed to the virtual RNC 115 via the second MSC 109.
  • the virtual RNC 115 comprises an MSC interface 201 which is arranged to exchange messages with the MSC 201.
  • the MSC interface 201 is coupled to a relocation processor 203 which executes step 301 wherein the Relocation Request message is received.
  • the relocation processor 203 extracts the information contained in the RRC transparent container. In particular, it extracts the shared pilot signal scrambling code.
  • the relocation processor 203 is coupled to a group processor 205 which executes step 303 wherein a group of base stations/access points 111, 113 is determined as potential target base stations/access points for the relocation request.
  • the group of access points are the potential target access points for the relocation request which will be requested to monitor the remote station' s 117 uplink transmissions.
  • the group processor 205 determines the potential target access points in response to the shared pilot signal scrambling code. In some embodiments, only relatively few access points share the same pilot signal scrambling code and the group processor 205 may determine the group of access points as all access point using the identified shared pilot signal scrambling code.
  • the group processor 205 may use further information comprised in
  • CE16161EP the received relocation request message to determine a reduced group of access points to instruct to perform measurements. This will reduce the amount of measurements thereby reducing the communication overhead and the measurement resource overhead.
  • the identification of the serving macro- cell comprised in the RRC transparent container can be used to determine a reduced group of access points using the shared pilot signal scrambling code.
  • the pico-cells supported by the access points using the same scrambling code may be distributed within the coverage area of a relatively large number of macro-cells.
  • a remote station within one macro-cell will only be able to detect pilot signals from pico-cells within that macro-cell (or potentially within neighbouring macro-cells if the remote station is close to the border of the macro-cell) .
  • the group processor 205 can determine the group of access points which are potential targets as the access points which are located within the currently serving macro-cell (and possibly within the neighbouring macros cells) . However, any access points located further away can be discarded as they currently cannot be potential handover targets for the remote station.
  • the group processor 205 uses the indication of the currently serving cell to determine a reduced group of potential target access points .
  • the group processor 205 is coupled to a request processor 207 which is arranged to execute step 305 wherein the virtual RNC 115 transmits a request message to the identified group of access points 111, 113.
  • the request
  • CE16161EP message instructs the group of access points 111, 113 to make measurements of the uplink transmission from the remote station 117 to the first base station 101.
  • the request message includes a parameter indication for the uplink transmission which may be used by the access points 111, 113 to adapt the measurements to the uplink transmission.
  • the request processor 207 may include the uplink scrambling code used by the remote station 117 for the communication to the first base station 101.
  • the information of the uplink scrambling code received in the RRC transparent container may be forwarded to the access points 111, 113 and used to set the chip code used by a RAKE measurement receiver.
  • the request processor 207 is coupled to the MSC interface 201 and in the specific example the measurement request message is transmitted to the access points 111, 113 via the second MSC 109.
  • the virtual RNC 115 may be physically, logically or structurally located elsewhere.
  • the virtual RNC 115 may be located in the path between the second MSC 109 and the access points 111, 113 and the request message may be sent directly to the access point 111, 113.
  • the measurement request message may be transmitted as a broadcast message which is received by all the relevant access points 111, 113 or may e.g. be transmitted by a plurality of messages each of which may be individually addressed to a specific access point 111, 113.
  • the access points 111, 113 When the access points 111, 113 receive the measurement request message, they proceed to scan for the uplink transmissions. Specifically, the access points 111, 113
  • CE16161EP begin to determine a received signal level for the uplink signal of the remote station 117 using the specified uplink scrambling reported in the request message.
  • the measurement request message may in some embodiments comprise an indication of a frequency of the uplink transmission and the access points 111, 113 can accordingly tune to this frequency when making the measurements.
  • the measured signal level is then reported to the virtual RNC 115 by the transmission of one or more measurement reports from each of the access points 111, 113.
  • each of the identified group of potential target access points 111, 113 will measure a received signal level for a received signal which has parameters corresponding to the uplink transmission as indicated by the parameter indication.
  • the exact timing of the uplink scrambling code may not be known and the access point 111, 113 may accordingly perform a search to synchronise the measurements to the uplink transmissions.
  • a remote station detects the presence of a pilot signal from a pico-cell it will be located very close to that pico-cell and substantially further away from any other pico-cell using the same shared pilot signal scrambling code (e.g. a reuse pattern for a plurality of shared pilot signal scrambling codes may be applied) . Accordingly, the uplink transmission from the remote station is likely to be received at a high signal level at only one of the pico-cells. Furthermore, even if the uplink transmission was detected with a high signal level at more than one access point, this is likely to be due to the remote station being located close to more
  • CE16161EP than one access point with all of these access points being likely to be acceptable handover targets.
  • the virtual RNC 115 specifically comprises a measurement processor 209 coupled to the MSC interface 201.
  • the measurement processor 209 executes step 307 wherein the measurement reports are received from the access points 111, 113.
  • the measurement processor 209 is coupled to a selection processor 211 which executes step 309 wherein a handover target access point 111 is selected from the group of potential target access points 111, 113 in response to the measurement reports. Specifically, the selection processor 211 compares the received signal levels and selects the access point 111 having the highest measured receive level as the handover target base station.
  • the selection processor 211 then proceeds to transmit a relocation message to the radio network controller which supports the handover procedures for the selected target access point 111.
  • each of the access points 111, 113 comprise RNC functionality and the relocation message may therefore be transmitted directly to the target access point 111.
  • the relocation message is in the specific example the UMTS Relocation Request message which was received by the virtual RNC 115 from the first MSC 107.
  • the target RNC i.e. the RNC functionality of the access point 111 or an RNC supporting the selected access point
  • the target RNC i.e. the RNC functionality of the access point 111 or an RNC supporting the selected access point
  • CE16161EP the first MSC 107.
  • the target RNC can transmit a relocation acknowledge message (e.g. a Relocation Request Acknowledge) to the macro-RNC thereby initiating a handover procedure generally following a conventional approach.
  • a relocation acknowledge message e.g. a Relocation Request Acknowledge
  • the routing path may be changed to use the network address of the target RNC.
  • the target RNC when receiving the Relocation Request message, allocates resources in the target pico-cell for the incoming hard handover and returns the matching configuration in e.g. a Physical Channel Reconfiguration message in an RRC transparent container to the macro RNC 103 (possibly via the virtual RNC 115) .
  • the macro RNC 103 then passes the reconfiguration to the remote station 117 which then attempts to access the target access point using the specified configuration.
  • the source RNC i.e. the macro RNC 103 transmits an access characteristic for the handover target base station to the remote station 117 when receiving the relocation acknowledge message from the target RNC.
  • the remote station 117 then initiates an attachment to the target access point 111 using the indicated configuration/access characteristic .
  • the single selected access point 111 then receives an access from the remote station 117 and specifically the access point 111 detects uplink synchronisation at layer 1 and then receives the RRC reconfiguration confirm
  • CE16161EP message from the remote station 117.
  • a relocation detect and relocation complete is then signalled to the core network .
  • a second rapid relocation (without the remote station 117 being involved) can be executed to relocate the Iu signalling connection from the virtual RNC 115 to the target RNC.
  • the virtual RNC 115 may instead of (or as well as) transmitting the relocation message to the target RNC, transmit a relocation message back to a network element supporting the macro base station 101 with an identification of at least one network element supporting communications in the target cell.
  • the selection processor 111 may generate a message which comprises the network address of the target RNC and transmit this message to the first MSC 107.
  • the first MSC 107 may initiate a retransmission of the original UMTS Relocation Request message but this time directly addressing the appropriate target RNC. A conventional handover process between the source and the target network elements may then proceed.
  • the serving base station identity and the uplink scrambling code was used to assist the relocation. However, it will be appreciated that in other embodiments, only one or none of these may be used. Also, it will be appreciated that other information may alternatively or additionally be used.
  • the relocation request message may comprise an indication of a timing characteristic for the uplink transmission by the remote station 117.
  • the indication may for example be included in the RRC transparent container.
  • the timing characteristic may specifically be a timing offset such as a frame timing offset and specifically a System Frame Number offset.
  • the RRC transparent container can comprise an SFN-SFN observed time difference between the SFNs of the macro-cell and the detected pico-cell.
  • This information may be used to identify an appropriate virtual RNC. For example, if a given shared pilot signal scrambling code may be used by access points served by different virtual RNCs, the first MSC 107 may build up a database indicative of a current frame timing offset (SFN offset) for different access points (e.g. based on previous relocations) and may compare the current offset to the stored data to select the appropriate virtual RNC. Alternatively or additionally, the SFN offset may be compared to stored values by the group processor 205 and used to select a subset of potential target access points. Alternatively or additionally, the SFN offset may be fed to the potential target access points and used by these to perform suitable measurements. For example, the detection of the uplink transmissions may be verified by determining if the current measured frame synchronisation offset between the uplink signal and the access point corresponds to that of the SFN offset indicated in the relocation message.
  • SFN offset current frame timing offset
  • CE16161EP It will be appreciated that a chip offset of the current macro-cell uplink transmissions by the remote station 117 may be used in a similar way.
  • the relocation request message may comprise an indication of a propagation delay for the uplink transmission between the remote station 117 and the macro base station 101.
  • This propagation delay may for example be used to determine the group of target base stations. Specifically, the propagation delay will typically be indicative of a distance from the base station to the remote station. Typically, the location of the access points are known by the virtual RNC and the propagation delay that is likely to be experienced by a transmission to the macro base station for a remote station within a given pico-cell can thus be determined. Accordingly, the virtual RNC can compare the received propagation delay to determine which pico-cells (and thus access points) are likely to be close to the remote station and thus are likely to be the access point currently detected.
  • the propagation delay may be fed to the group of potential target access points and used to synchronise the measurements e.g. by setting the initial timing for a search for the uplink scrambling code .
  • the source MSC 107 processes the message from the macro RNC 103 in order to address the virtual RNC 115, and in some cases in order to provide additional information.
  • CE16161EP the MSC 107 may e.g. be arranged to merely forward messages from the macro RNC 103 without processing these. Specifically, the macro RNC 103 may generate the message comprising all relevant information and directly address this to the virtual RNC 115. This data packet may be routed unmodified to the virtual RNC 115 via the macro MSC 107.
  • the macro base station 101 may be a UMTS base station whereas the access point 111 may be a GSM base station capable of supporting GSM air interface communications but not UMTS air interface communications.
  • the access point 111 may still transmit a pilot signal using the shared pilot signal scrambling code which can be detected by the remote station 117.
  • the access point 111 may be arranged to monitor for the UMTS uplink transmission to determine a signal level.
  • the remote terminal 117 is a dual mode remote station and the handover is an intersystem handover where the remote terminal 117 hands over from UMTS to GSM.
  • CE16161EP appreciated that the described principles are equally applicable to a situation where these are integrated in the same physical or logical network element.
  • a virtual RNC may be built into a macro RNC.
  • the detection of the shared pilot signal scrambling code by a remote station may be evaluated by a subroutine which generates a relocation request message (e.g. by setting a flag) if the pilot signal is detected.
  • another routine can initiate the transmission of measurement requests to the access points and proceed to use these to identify the appropriate handover target. Once, the handover target is identified the handover can be performed.
  • the invention can be implemented in any suitable form including hardware, software, firmware or any combination of these.
  • the invention may optionally be implemented at least partly as computer software running on one or more
  • CE16161EP data processors and/or digital signal processors may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit or may be physically and functionally distributed between different units and processors .
  • CE16161EP Furthermore, the order of features in the claims does not imply any specific order in which the features must be worked and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un élément de réseau (115) prenant en charge des stations de base (111, 113) avec un code d'embrouillage de signal pilote partagé. L'élément de réseau (115) reçoit un message de demande de translation qui comprend une identification du code d'embrouillage partagé. Un processeur de groupe (205) détermine ensuite un groupe de stations de base cibles potentielles (111, 113). Un processeur de demande (207) transmet un message de demande aux stations de base cibles (111, 113) qui comprend une indication de paramètre pour une transmission de liaison montante depuis la station distante (117) vers la station de base (101) et demande aux stations de base cibles (111, 113) de mesurer la transmission de liaison montante. Un processeur de mesure (209) reçoit des rapports de mesure pour la transmission de liaison montante des stations de base cibles et un processeur de sélection (211) sélectionne une station de base cible de transfert intercellulaire (111) sur la base des rapports de mesure.
PCT/US2007/079633 2007-01-19 2007-09-27 Translation dans un système de communication cellulaire WO2008088592A1 (fr)

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GB0701060A GB2445987B (en) 2007-01-19 2007-01-19 Relocation in a cellular communication system

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WO2010013032A1 (fr) * 2008-07-31 2010-02-04 Ubiquisys Limited Établissement de seconde cellule co-implantée à l'aide d'un second code de brouillage par une station de base à femtocellules
WO2010042861A2 (fr) * 2008-10-09 2010-04-15 Qualcomm Incorporated Système et procédé employant des ressources pré-affectées pour prendre en charge le transfert d’une station mobile d’une macro-station de base à une femto-station de base
EP2197228A1 (fr) * 2008-12-12 2010-06-16 Alcatel, Lucent Procédé d'identification d'une station de base femtocell en tant que cible de transfert, et appareil associé
EP2268079A1 (fr) 2009-05-07 2010-12-29 Alcatel Lucent Identification d'une station de base parmi des stations de base candidates au transfert qui utilisent le même code de brouillage principal
WO2011035557A1 (fr) * 2009-09-28 2011-03-31 大唐移动通信设备有限公司 Procédé, système et appareil de mise en oeuvre d'un transfert intercellulaire de service
EP2330850A1 (fr) * 2009-12-07 2011-06-08 Alcatel Lucent Contrôle de transfert
WO2011133926A1 (fr) * 2010-04-23 2011-10-27 Qualcomm Incorporated Identification unique d'une femtocellule cible facilitant le transfert actif à l'aide de la technologie femto
EP2395790A1 (fr) * 2010-06-10 2011-12-14 Alcatel Lucent Noeud de réseau et procédé de transfert d'une connexion d'appel
EP2451104A1 (fr) * 2010-11-05 2012-05-09 Alcatel Lucent Nýuds de réseau et procédés
CN101860930B (zh) * 2009-04-07 2012-09-05 中兴通讯股份有限公司 一种移动通信系统中的重定位方式
JP2013528958A (ja) * 2010-01-08 2013-07-11 アルカテル−ルーセント マクロセルからフェムトセルへの移動局のハンドオーバーを管理するための方法および装置
CN103974352A (zh) * 2013-01-28 2014-08-06 中兴通讯股份有限公司 一种网络侧设备及宏基站到微基站的切换方法
US8838117B2 (en) 2010-04-23 2014-09-16 Qualcomm Incorporated Active macro-femto hand-in with help from out-of-band proxy
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KR101488264B1 (ko) * 2008-10-13 2015-01-30 삼성전자주식회사 펨토 기지국으로의 핸드 오버를 위한 무선 통신 시스템 및 이를 위한 방법
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WO2015198101A1 (fr) * 2014-06-27 2015-12-30 Telefonaktiebolaget Lm Ericsson (Publ) Synchronisation de canal de transport inter-rnc
EP2432279A4 (fr) * 2009-07-21 2016-07-27 Zte Corp Procédé et système pour un équipement utilisateur sélectionnant un n ud domestique
EP3386238A1 (fr) * 2008-11-21 2018-10-10 QUALCOMM Incorporated Procédé et appareil de communication sans fil
EP2375807B1 (fr) * 2008-12-10 2018-10-31 Huawei Technologies Co., Ltd. Procédé de traitement de transfert, passerelle pour station de base locale et système de réseau

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WO2009006041A1 (fr) * 2007-06-29 2009-01-08 Motorola, Inc. Relocalisation dans un système de communication cellulaire
WO2010013032A1 (fr) * 2008-07-31 2010-02-04 Ubiquisys Limited Établissement de seconde cellule co-implantée à l'aide d'un second code de brouillage par une station de base à femtocellules
US8559345B2 (en) 2008-07-31 2013-10-15 Percello Ltd. Establishing colocated second cell using a second scrambling code by a femto base station
WO2010042861A2 (fr) * 2008-10-09 2010-04-15 Qualcomm Incorporated Système et procédé employant des ressources pré-affectées pour prendre en charge le transfert d’une station mobile d’une macro-station de base à une femto-station de base
WO2010042861A3 (fr) * 2008-10-09 2010-07-01 Qualcomm Incorporated Système et procédé employant des ressources pré-affectées pour prendre en charge le transfert d’une station mobile d’une macro-station de base à une femto-station de base
KR101488264B1 (ko) * 2008-10-13 2015-01-30 삼성전자주식회사 펨토 기지국으로의 핸드 오버를 위한 무선 통신 시스템 및 이를 위한 방법
EP3386238A1 (fr) * 2008-11-21 2018-10-10 QUALCOMM Incorporated Procédé et appareil de communication sans fil
EP2375807B1 (fr) * 2008-12-10 2018-10-31 Huawei Technologies Co., Ltd. Procédé de traitement de transfert, passerelle pour station de base locale et système de réseau
US8345633B2 (en) 2008-12-12 2013-01-01 Alcatel Lucent Method of identification of a femtocell base station as a handover target, and apparatus therefor
US20100150109A1 (en) * 2008-12-12 2010-06-17 Alcatel-Lucent Method of identification of a femtocell base station as a handover target, and apparatus therefor
CN101754303B (zh) * 2008-12-12 2013-12-25 阿尔卡特朗讯公司 用于将毫微微小区基站标识成切换目标的方法及其设备
EP2197228A1 (fr) * 2008-12-12 2010-06-16 Alcatel, Lucent Procédé d'identification d'une station de base femtocell en tant que cible de transfert, et appareil associé
CN101860930B (zh) * 2009-04-07 2012-09-05 中兴通讯股份有限公司 一种移动通信系统中的重定位方式
EP2268079A1 (fr) 2009-05-07 2010-12-29 Alcatel Lucent Identification d'une station de base parmi des stations de base candidates au transfert qui utilisent le même code de brouillage principal
EP2432279A4 (fr) * 2009-07-21 2016-07-27 Zte Corp Procédé et système pour un équipement utilisateur sélectionnant un n ud domestique
WO2011035557A1 (fr) * 2009-09-28 2011-03-31 大唐移动通信设备有限公司 Procédé, système et appareil de mise en oeuvre d'un transfert intercellulaire de service
US9078178B2 (en) 2009-12-07 2015-07-07 Alcatel Lucent Handover control
JP2013513325A (ja) * 2009-12-07 2013-04-18 アルカテル−ルーセント ハンドオーバ制御
EP2330850A1 (fr) * 2009-12-07 2011-06-08 Alcatel Lucent Contrôle de transfert
CN102754480A (zh) * 2009-12-07 2012-10-24 阿尔卡特朗讯 切换控制
WO2011069612A1 (fr) * 2009-12-07 2011-06-16 Alcatel Lucent Commande de transfert intercellulaire
JP2015136133A (ja) * 2009-12-07 2015-07-27 アルカテル−ルーセント ハンドオーバ制御
KR101473683B1 (ko) * 2009-12-07 2014-12-17 알까뗄 루슨트 핸드오버 제어
JP2013528958A (ja) * 2010-01-08 2013-07-11 アルカテル−ルーセント マクロセルからフェムトセルへの移動局のハンドオーバーを管理するための方法および装置
US9148834B2 (en) 2010-01-08 2015-09-29 Alcatel Lucent Method and apparatus for managing handover of a mobile station from a macro cell to a femto cell
WO2011133926A1 (fr) * 2010-04-23 2011-10-27 Qualcomm Incorporated Identification unique d'une femtocellule cible facilitant le transfert actif à l'aide de la technologie femto
US8838117B2 (en) 2010-04-23 2014-09-16 Qualcomm Incorporated Active macro-femto hand-in with help from out-of-band proxy
US8954051B2 (en) 2010-04-23 2015-02-10 Qualcomm Incorporated Uniquely identifying target femtocell to facilitate femto-assisted active hand-in
EP2395790A1 (fr) * 2010-06-10 2011-12-14 Alcatel Lucent Noeud de réseau et procédé de transfert d'une connexion d'appel
US9072032B2 (en) 2010-10-15 2015-06-30 Qualcomm Incorporated Femtocell indication of mobile device proximity and transmission of mobile identity to assist in resolving femtocell disambiguation
US9781659B2 (en) 2010-10-15 2017-10-03 Qualcomm Incorporated Proximity detection for femtocells using out-of-band links
EP2600550A1 (fr) * 2010-11-05 2013-06-05 Alcatel Lucent Nýuds de réseau et procédés
US20130294364A1 (en) * 2010-11-05 2013-11-07 Alcatel Lucent Network nodes and methods
EP2451104A1 (fr) * 2010-11-05 2012-05-09 Alcatel Lucent Nýuds de réseau et procédés
US9894530B2 (en) 2010-11-05 2018-02-13 Alcatel Lucent Network nodes and methods
WO2012059214A3 (fr) * 2010-11-05 2012-08-16 Alcatel Lucent Nœuds de réseau et procédés
CN103974352B (zh) * 2013-01-28 2018-03-20 中兴通讯股份有限公司 一种网络侧设备及宏基站到微基站的切换方法
US9674741B2 (en) 2013-01-28 2017-06-06 Zte Corporation Network side device and macro base station-to-micro base station switching method
EP2943009A4 (fr) * 2013-01-28 2016-03-02 Zte Corp Dispositif côté réseau et procédé de commutation de macro-station de base à micro-station de base
CN103974352A (zh) * 2013-01-28 2014-08-06 中兴通讯股份有限公司 一种网络侧设备及宏基站到微基站的切换方法
WO2014168526A1 (fr) * 2013-04-08 2014-10-16 Telefonaktiebolaget L M Ericsson (Publ) Noeud de réseau radio, station de base et procédés correspondants
WO2015198101A1 (fr) * 2014-06-27 2015-12-30 Telefonaktiebolaget Lm Ericsson (Publ) Synchronisation de canal de transport inter-rnc
US10779249B2 (en) 2014-06-27 2020-09-15 Telefonaktiebolaget Lm Ericsson (Publ) Inter-RNC transport channel synchronization

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