WO2015018442A1 - Method and apparatus - Google Patents

Method and apparatus Download PDF

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Publication number
WO2015018442A1
WO2015018442A1 PCT/EP2013/066523 EP2013066523W WO2015018442A1 WO 2015018442 A1 WO2015018442 A1 WO 2015018442A1 EP 2013066523 W EP2013066523 W EP 2013066523W WO 2015018442 A1 WO2015018442 A1 WO 2015018442A1
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WO
WIPO (PCT)
Prior art keywords
neighbouring cell
signal
neighbouring
strongest signal
cell
Prior art date
Application number
PCT/EP2013/066523
Other languages
French (fr)
Inventor
Klaus Ingemann Pedersen
Claudio Rosa
Simone BARBERA
Per Henrik Michaelsen
Original Assignee
Nokia Solutions And Networks Oy
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 Nokia Solutions And Networks Oy filed Critical Nokia Solutions And Networks Oy
Priority to PCT/EP2013/066523 priority Critical patent/WO2015018442A1/en
Publication of WO2015018442A1 publication Critical patent/WO2015018442A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0058—Transmission of hand-off measurement information, e.g. measurement reports
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0079—Transmission or use of information for re-establishing the radio link in case of hand-off failure or rejection
    • 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
    • H04W36/305—Handover due to radio link failure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/19—Connection re-establishment

Definitions

  • This disclosure relates to methods and apparatus and in particular but not exclusively to methods and apparatus for use where there are at least partially overlapping cells.
  • a communication system can be seen as a facility that enables communication sessions between two or more nodes such as fixed or mobile devices, machine-type terminals, access nodes such as base stations, servers and so on.
  • a communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved.
  • the standards, specifications and related protocols can define the manner how devices shall communicate, how various aspects of communications shall be implemented and how devices for use in the system shall be configured.
  • Signals can be carried on wired or wireless carriers.
  • wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN).
  • wireless communication systems include architectures that are standardized by the 3rd Generation Partnership Project (3GPP).
  • 3GPP 3rd Generation Partnership Project
  • LTE long-term evolution
  • UMTS Universal Mobile Telecommunications System
  • a communication device can be provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other devices.
  • a communication device is used for enabling receiving and transmission of communications such as speech and data.
  • a user can access wirelessly a communication system by means of an appropriate wireless communication device or terminal, often referred to as user equipment (UE).
  • UE user equipment
  • Other types of wireless communication devices are also known, for example various access points, relays, and so on that are capable of communicating wirelessly with other devices.
  • HetNet Heterogeneous Network
  • a method comprising: receiving at least one signal from at least one neighbouring cell; determining a strongest signal from the at least one neighbouring cell; determining the strongest signal from the at least one neighbouring cell meets a reporting criteria; and generating a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
  • Receiving at least one signal from at least one neighbouring cell may comprise: determining that a current cell is a smaller area cell; receiving at least one signal from at least one neighbouring cell neighbouring the smaller area cell.
  • Determining a strongest signal from the at least one neighbouring cell may comprise: generating a signal metric based on the at least one signal from at least one neighbouring cell; comparing at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
  • the signal metric may comprise at least one of: a reference signal received power (RSRP) metric; a reference signal received quality (RSRQ) metric.
  • Determining the strongest signal from the at least one neighbouring cell meets a reporting criteria may comprise at least one of: a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell.
  • the method may further comprise transmitting the radio resource management message.
  • Transmitting the radio resource management message may comprise transmitting the radio resource management message to a network controller, wherein the network controller may comprise configuring the at least one neighbouring cell to accept a re-establishment request.
  • the method may further comprise configuring the at least one neighbouring cell based on the at least one neighbouring cell with the strongest signal to accept a re- establishment request.
  • the method may further comprise: determining a radio-link failure with a current cell; generating a re-establishment request; transmitting the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
  • the method may further comprise: re-establishing communication based on the re- establishment request to the at least one neighbouring cell with the determined strongest signal.
  • an apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive at least one signal from at least one neighbouring cell; determine a strongest signal from the at least one neighbouring cell; determine the strongest signal from the at least one neighbouring cell meets a reporting criteria; generate a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
  • Receiving at least one signal from at least one neighbouring cell may cause the apparatus to: determine that a current cell is a smaller area cell; receive at least one signal from at least one neighbouring cell neighbouring the smaller area cell.
  • Determining a strongest signal from the at least one neighbouring cell may cause the apparatus to: generate a signal metric based on the at least one signal from at least one neighbouring cell; compare at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
  • the signal metric may comprise at least one of: a reference signal received power (RSRP) metric; a reference signal received quality (RSRQ) metric. Determining the strongest signal from the at least one neighbouring cell meets a reporting criteria may cause the apparatus to perform at least one of: determine a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; determine the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell. The apparatus may be caused to further transmit the radio resource management message.
  • RSRP reference signal received power
  • RSRQ reference signal received quality
  • Transmitting the radio resource management message may cause the apparatus to transmit the radio resource management message to the at least one neighbouring cell to configure the at least one neighbouring cell to accept a re-establishment request.
  • Transmitting the radio resource management message may cause the apparatus to transmit the radio resource management message to a network controller, wherein the network controller is configured to configure the at least one neighbouring cell to accept a re-establishment request.
  • the apparatus may be caused to: determine a radio-link failure with a current cell; generate a re-establishment request; transmit the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
  • a system may comprise an apparatus as described herein and at least one neighbouring cell wherein the neighbouring cell is caused to accept a re- establishment request.
  • the at least one neighbouring cell may be further caused to re-establish communication based on the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
  • an apparatus comprising: a measurement determiner configured to receive at least one signal from at least one neighbouring cell; a measurement comparator configured to determine a strongest signal from the at least one neighbouring cell and furthermore determine the strongest signal from the at least one neighbouring cell meets a reporting criteria; a message generator configured to generate a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
  • the measurement determiner may be configured to: determine that a current cell is a smaller area cell; receive at least one signal from at least one neighbouring cell neighbouring the smaller area cell.
  • the measurement determiner may be configured to generate a signal metric based on the at least one signal from at least one neighbouring cell; the measurement comparator may be configured to compare at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
  • the signal metric may comprise at least one of: a reference signal received power (RSRP) metric; a reference signal received quality (RSRQ) metric.
  • RSRP reference signal received power
  • RSS reference signal received quality
  • the measurement comparator configured to determine the strongest signal from the at least one neighbouring cell meets a reporting criteria may be configured to determine at least one of: a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell.
  • the apparatus may further comprise a transmitter configured to transmit the radio resource management message.
  • the transmitter may be configured to transmit the radio resource management message to the at least one neighbouring cell to configure the at least one neighbouring cell to accept a re-establishment request.
  • the transmitter may be configured to transmit the radio resource management message to a network controller, wherein the network controller is configured to configure the at least one neighbouring cell to accept a re-establishment request.
  • the apparatus may comprise a link failure determiner configured to determine a radio-link failure with a current cell; a link failure controller configured to generate a re-establishment request; the transmitter may be configured to transmit the re- establishment request to the at least one neighbouring cell with the determined strongest signal.
  • a system may comprise the apparatus as described herein and the at least one neighbouring cell wherein the at least one neighbouring cell is configured to accept the re-establishment request.
  • the at least one neighbouring cell may be further configured to re-establish communication based on the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
  • an apparatus comprising: means for receiving at least one signal from at least one neighbouring cell; means for determining a strongest signal from the at least one neighbouring cell; means for determining the strongest signal from the at least one neighbouring cell meets a reporting criteria; means for generating a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
  • the means for receiving at least one signal from at least one neighbouring cell may comprise: means for determining that a current cell is a smaller area cell; means for receiving at least one signal from at least one neighbouring cell neighbouring the smaller area cell.
  • the means for determining a strongest signal from the at least one neighbouring cell may comprise: means for generating a signal metric based on the at least one signal from at least one neighbouring cell; means for comparing at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
  • the signal metric may comprise at least one of: a reference signal received power (RSRP) metric; and a reference signal received quality (RSRQ) metric.
  • the means for determining the strongest signal from the at least one neighbouring cell meets a reporting criteria may comprise at least one of: means for determining a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; means for determining the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell.
  • the apparatus may further comprise means for transmitting the radio resource management message.
  • the means for transmitting the radio resource management message may comprise means for transmitting the radio resource management message to the at least one neighbouring cell to configure the at least one neighbouring cell to accept a re- establishment request.
  • the means for transmitting the radio resource management message may comprise means for transmitting the radio resource management message to a network controller, wherein the network controller is configured to configure the at least one neighbouring cell to accept a re-establishment request.
  • a system may comprise the apparatus as discussed herein and the at least one neighbouring cell wherein the at least one neighbouring cell may comprise means for configuring the at least one neighbouring cell based on the at least one neighbouring cell with the strongest signal to accept a re-establishment request.
  • the apparatus may further comprise: means for determining a radio-link failure with a current cell; means for generating a re-establishment request; means for transmitting the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
  • the system comprising the at least one neighbouring cell as discussed herein wherein the at least one neighbouring cell may comprise means for re-establishing communication based on the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
  • Figure 1 shows a schematic diagram of a communication system comprising a base station and a plurality of communication devices
  • Figure 2 shows a schematic diagram of a mobile communication device according to some embodiments
  • Figure 3 shows a schematic diagram of a control apparatus according to some embodiments
  • Figure 4 shows an example radio resource measurement reporter suitable for being implemented within a mobile communications device according to some embodiments
  • Figure 5 shows a method flow of some embodiments.
  • LTE specifications include network controlled, UE assisted, mobility procedures.
  • the mobility performance of LTE is typically observed to be very good for macro-only cases, while it has been found that the mobility performance is more challenging for heterogeneous network (HetNet) scenarios with a mixture of macro and small cells.
  • HetNet heterogeneous network
  • RLF radio link failure
  • the UE attempts re-establishment to the strongest detected cell. If the re-establishment attempt is successful within a short time, the call continues without further interruptions. Otherwise, the call is dropped and the UE enters IDLE mode.
  • the re-establishment attempt is successful only if the cell where the UE requests re-establishment is prepared for UE, such that the cell "knows" the UE and its data. If the UE seeks re-establishment to a cell that is not prepared for this UE (in other words the cell is unaware of the UE), the re-establishment is unsuccessful and results in call dropping, in other words the UE transitions to IDLE mode.
  • One of the conditions for successful re-establishment is therefore coherent network and UE behaviour, meaning that the network should have prepared the cell where the UE seeks re-establishment in case it experiences RLF.
  • the concept as described herein with respect to the embodiments is the provision of improved re-establishment functionality by including enhanced coordination between the UE and network prior to the occurrence of RLF.
  • the embodiments thus as described herein are applicable to cellular systems, but particularly useful for LTE HetNet scenarios.
  • certain exemplifying embodiments are explained with reference to a wireless or mobile communication system serving mobile communication devices.
  • certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.
  • a wireless communication system mobile communication devices or user equipment (UE) 102, 103, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point.
  • UE user equipment
  • FIG. 1 an example of two overlapping access systems or radio service areas of a cellular system 100 and 1 10 provided by base stations 106 and 107 and three smaller radio service areas 1 1 5, 1 17 and 1 19 provided by remote radio heads (RRH) 1 1 6, 1 18 and 120 are shown.
  • RRH remote radio heads
  • Each mobile communication device and base station/RRH may have one or more radio channels open at the same time and may send signals to and/or receive signals from more than one source.
  • the radio service area borders or edges are schematically shown for illustration purposes only in Figure 1 .
  • a base station site can provide one or more cells.
  • a base station can also provide a plurality of sectors, for example three radio sectors, each sector providing a cell or a subarea of a cell. All sectors within a cell may be served by the same base station.
  • Base stations are typically controlled by at least one appropriate controller apparatus so as to enable operation thereof and management of mobile communication devices in communication with the base stations.
  • control apparatus 108 and 109 is shown to control the respective macro level base stations 106 and 107.
  • the control apparatus of a base station can be interconnected with other control entities.
  • the control apparatus is typically provided with memory capacity and at least one data processor.
  • the control apparatus and functions may be distributed between a plurality of control units. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller.
  • base stations 106 and 107 are shown as connected to a wider communications network 1 1 3 via gateway 1 1 2.
  • a further gateway function may be provided to connect to another network.
  • the remote radio heads 1 16, 1 1 8 and 120 are connected to a respective macro cell.
  • RRH 120 is connected to macro cell base station 106 and RRHs 1 18 and 1 1 6 are connected to macro cell base station 109.
  • the RRHs are located in the respective macro cell provided by the macro cell base station to which they are connected.
  • a possible mobile communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 102.
  • a communication device is often referred to as user equipment (UE) or terminal.
  • An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals.
  • Non- limiting examples include a mobile station (MS) or mobile device such as a mobile phone or what is known as a 'smart phone', a computer provided with a wireless interface card or other wireless interface facility, personal data assistant (PDA) provided with wireless communication capabilities, or any combinations of these or the like.
  • a mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on.
  • the mobile device 102 may receive signals over an air interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals.
  • transceiver apparatus is designated schematically by block 206.
  • the transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement.
  • the antenna arrangement may be arranged internally or externally to the mobile device.
  • a wireless communication device can be provided with a Multiple Input / Multiple Output (MIMO) antenna system.
  • MIMO arrangements as such are known. MIMO systems use multiple antennas at the transmitter and receiver along with advanced digital signal processing to improve link quality and capacity.
  • multiple antennas can be provided, for example at base stations and mobile stations, and the transceiver apparatus 206 of Figure 2 can provide a plurality of antenna ports. More data can be received and/or sent where there are more antenna elements.
  • a station may comprise an array of multiple antennas. Signalling and muting patterns can be associated with TX antenna numbers or port numbers of MIMO arrangements.
  • a mobile device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices.
  • the data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204.
  • the user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like.
  • a display 208, a speaker and a microphone can be also provided.
  • a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.
  • Figure 3 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a base station.
  • base stations comprise a separate control apparatus.
  • the control apparatus can be another network element such as a radio network controller.
  • each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller.
  • the control apparatus 1 09 can be arranged to provide control on communications in the service area of the system.
  • the control apparatus 109 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. For example the control apparatus 109 can be configured to execute an appropriate software code to provide the control functions.
  • the communication devices 1 02, 1 03, 1 05 may access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA).
  • CDMA code division multiple access
  • WCDMA wideband CDMA
  • Other non-limiting examples comprise time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on.
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • IFDMA interleaved frequency division multiple access
  • SC-FDMA single carrier frequency division multiple access
  • OFDMA orthogonal frequency division multiple access
  • SDMA space division multiple access
  • An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP).
  • 3GPP 3rd Generation Partnership Project
  • LTE long-term evolution
  • LTE- A LTE Advanced
  • the LTE employs a mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN).
  • Base stations of such systems are known as evolved or enhanced Node Bs (eNBs) and may provide E-UTRAN features such as user plane Radio Link Control/Medium Access Control/Physical layer protocol (RLC/M AC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices.
  • eNBs evolved or enhanced Node Bs
  • RLC/M AC/PHY Radio Link Control/Medium Access Control/Physical layer protocol
  • RRC Radio Resource Control
  • Other examples of radio access system include those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access).
  • WLAN wireless local area network
  • WiMax Worldwide Interoperability for Microwave Access
  • Some embodiments may be used with LTE (or LTE-Advanced) co-channel deployment of macro eNBs and low power eNBs in the form of RRHs.
  • Alternatively or additionally embodiments may be used with smaller cells such as pico or femto cells and/or other relay stations.
  • the smaller cells and/or relay stations may be in communication with a macro eNB.
  • a co-channel LTE HetNet scenario This may arise where more than one transmitter is using the same channel or frequency.
  • Some embodiments may address the problem of joint multi-cell packet scheduling for the downlink of such a system, while still maintaining fairness among all users.
  • radio resource management reporter suitable for being implemented within a mobile communications device or user equipment configured to generate suitable radio resource management (RRM) reporting events according to some embodiments is described.
  • RRM radio resource management
  • the method flow or operations relating to the example radio resource measurement reporter and furthermore the network response operations are further described.
  • the term cell is used to define an access point or base station as well as the coverage area provided by the access point or base station.
  • the network is shown with respect to two base stations and a base station controller able to communicate between the two base stations.
  • at least one of the base stations can be a remote radio head (RRH) or other radio access point.
  • the network can comprise more radio access points, base stations or controlling entities such as base station controllers or radio network controllers and furthermore in some embodiments be coupled together in any suitable manner.
  • the mobile communications device or UE can be configured to provide an event triggered radio resource management (RRM) reporting event for a set of neighbouring cells.
  • RRM radio resource management
  • the radio resource management reporter comprises a measurement determiner 401 or suitable means for determining a measurement metric for signals from neighbouring base stations and/or access points.
  • the measurement determiner 401 can in some embodiments be configured to trigger a measurement operation. In some embodiments the measurement operation can be triggered based on receiving information from the transceiver 206.
  • the radio resource management reporter can be configured to trigger the measurement determiner to start determining or taking measurements of neighbouring cells when it determines that the current cell or access point is a smaller area access point.
  • the measurement determiner 401 is configured to start measuring when determining that communication is being received from a remote radio head (RRH) 1 18 or any smaller coverage area cell at the user equipment 103.
  • RRH remote radio head
  • the measurement determiner 401 can then be configured to start the measurement process.
  • the measurement determiner 401 can receive information from the transceiver 206 and from such information generate suitable radio resource management (RRM) measurements for the signals received from neighbouring cells.
  • RRM radio resource management
  • these radio resource management (RRM) measurements can be a reference signal received power (RSRP) or a reference signal received quality (RSRQ) metric.
  • RSRP reference signal received power
  • RSS reference signal received quality
  • any suitable signal strength or quality metric can be generated and used.
  • the operation of the user equipment receiving the reference signal from the neighbouring cell is shown by step 502.
  • the user equipment determines the measurement based on the reference signal in Figure 5 step 503.
  • Figure 5 shows only a single neighbouring base station 106 it would be understood that in some embodiments the signal from more than one base station is measured so that two or more neighbouring base station signal measurements are generated.
  • the measurement determiner 401 can in some embodiments be configured to output the signal measurement(s) to a measurement comparator 403.
  • the radio resource management reporter comprises a measurement comparator 403.
  • the measurement comparator or suitable means for comparing measurements or triggering event messages is configured to receive the various signal measurement(s) from the neighbouring cells (or base stations and/or access points) to the user equipment.
  • the measurement comparator 403 can then be configured to compare the measurements from the neighbouring cells and determine the neighbouring cell with the strongest signal, for example the neighbouring cell with the highest RSRP or RSRQ.
  • the measurement comparator 403 can be configured to compare the determined strongest neighbour signal measurement against a threshold criteria to determine whether the radio resource management reporter is configured to report the determined strongest neighbour signal measurement.
  • the threshold comprises a time component.
  • the measurement comparator 403 can be configured to communicate with a timer 402.
  • the timer 402 can be configured to provide a timing value relative to the last reporting message sent, or the last handover.
  • the timing value exceed a time-to-trigger threshold value then the measurement comparator 403 can be configured to trigger the message generator by outputting the determined strongest neighbour value. In such a manner the timing criteria limits the number of reporting messages sent.
  • the threshold comprises a signal component.
  • the measurement comparator 403 can be configured to communicate with a memory 404 comprising a previous strongest neighbour signal measurement or metric and compare the current determined strongest neighbour signal measurement against the previous determined strongest neighbour signal measurement or metric. In some embodiments the comparison is such that the threshold value is one of the previous strongest neighbour signal measurement and an offset margin. In such embodiments when the current strongest neighbour signal measurement exceeds (or at least equals) the previous determined strongest neighbour signal measurement then the measurement comparator 403 outputs the determined strongest neighbour value or in other words triggers the message generator to generate the reporting event message.
  • the criteria detemination can comprise both of the example criteria thresholds (signal and time).
  • the operation of determining the strongest neighbour signal measurement or metric and furthermore that the strongest neighbour signal measurement or metric measurement matches the reporting criteria is shown in Figure 5 by step 505.
  • the radio resource management reporter comprises a message generator 405.
  • the message generator 405 can in some embodiments be configured to receive the output of the measurement comparator 403. In other words receive an indication when the new strongest neighbour cell meets the criteria for generating a reporting event message.
  • the identifier can in some embodiments be the determined strongest neighbour identifier.
  • the identifier can comprise the determined strongest neighbour signal measurement or metric for use in self-organising power control mechanisms.
  • the message generator 405 can then be configured to generate a suitable radio resource management (RRM) reporting event message for configuring the network and specifically the determined strongest neighbour base station or access point that the user equipment is potentially to request re-establishment with the access point.
  • RRM radio resource management
  • step 507 The operation of generating a suitable RRM reporting event message is shown in Figure 5 by step 507.
  • the message generated by the message generator 405 is passed to the transceiver 206.
  • the transceiver 206 can in some embodiments be configured to transmit the RRM message to the current cell or access point.
  • the current cell or access point which in this example is base station 1 1 07 can in some embodiments be further configured to pass the RRM message to the network which forwards the message onto the strongest signal neighbouring cell or base station such as the base station 2 106.
  • the operation of transmitting the RRM message from the current cell or access point (the base station 1 107) to the determined strongest neighbour cell or base station or access point (the base station 2 107) that the user equipment is potentially to request re-establishment with the cell or access point and to configure itself to enable such a re-establishment to succeed is shown in Figure 5 by step 510.
  • the communication is not a direct one as shown in Figure 5 but can be via further entities such as for example a controlling entity (such as a base station controller 109 or radio network controller).
  • the determined strongest neighbour cell or base station or access point (the base station 107) can then be configured to configure itself to be able to accept a re- establishment from the user equipment.
  • Figure 5 shows that after a time period, indicated by the break, that the user equipment suffers from a radio-link failure.
  • the user equipment radio-link failure is shown in Figure 5 by step 515.
  • the user equipment following the radio-link failure, can be configured to request re- establishment with the determined strongest neighbouring cell (or base station or access point).
  • the operation of generating a re-establishment request is shown in Figure 5 by step 517. Furthermore the operation of transmitting the re-establishment request to the determined strongest neighbour cell or base station or access point (the base station 2 106) is shown in Figure 5 by step 518.
  • the determined strongest neighbour cell (or base station or access point), which as shown in Figure 5 is the base station 2 106, can then be configured to accept the re- establishment request from the user equipment and re-establish the communication between the user equipment and the network.
  • step 51 9 The operation of re-establishing the communication between the user equipment and the network is show in Figure 5 by step 51 9.
  • the network has the required feedback from the user equipment to prepare a good cell for the user equipment in case of radio-link failure (RLF). Then should radio-link failure occur the user equipment can then attempt re-establishment towards the prepared neighbouring cell. This would significantly increase the probability of successfully re-establishing communication between the user equipment and network or effectively reducing the risk of experience a call dropped.
  • RLF radio-link failure
  • the required data processing apparatus and functions of a base station apparatus, a communication device and any other appropriate apparatus may be provided by means of one or more data processors.
  • the described functions at each end may be provided by separate processors or by an integrated processor.
  • the data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples.
  • the data processing may be distributed across several data processing modules.
  • a data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can also be provided in the relevant devices.
  • the memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.
  • the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof.
  • Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.

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Abstract

A method comprises receiving at least one signal from at least one neighbouring cell; determining a strongest signal from the at least one neighbouring cell; determining the strongest signal from the at least one neighbouring cell meets a reporting criteria; generating a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.

Description

METHOD AND APPARATUS
Field This disclosure relates to methods and apparatus and in particular but not exclusively to methods and apparatus for use where there are at least partially overlapping cells.
Background
A communication system can be seen as a facility that enables communication sessions between two or more nodes such as fixed or mobile devices, machine-type terminals, access nodes such as base stations, servers and so on. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how devices shall communicate, how various aspects of communications shall be implemented and how devices for use in the system shall be configured.
Signals can be carried on wired or wireless carriers. Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Furthermore examples of wireless communication systems include architectures that are standardized by the 3rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. A communication device can be provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other devices. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. A user can access wirelessly a communication system by means of an appropriate wireless communication device or terminal, often referred to as user equipment (UE). Other types of wireless communication devices are also known, for example various access points, relays, and so on that are capable of communicating wirelessly with other devices.
Some systems may have a number of small-cells overlying larger or macro-cells, a so called Heterogeneous Network (HetNet).
Statement
According to a first aspect, there is provided a method comprising: receiving at least one signal from at least one neighbouring cell; determining a strongest signal from the at least one neighbouring cell; determining the strongest signal from the at least one neighbouring cell meets a reporting criteria; and generating a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
Receiving at least one signal from at least one neighbouring cell may comprise: determining that a current cell is a smaller area cell; receiving at least one signal from at least one neighbouring cell neighbouring the smaller area cell.
Determining a strongest signal from the at least one neighbouring cell may comprise: generating a signal metric based on the at least one signal from at least one neighbouring cell; comparing at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells. The signal metric may comprise at least one of: a reference signal received power (RSRP) metric; a reference signal received quality (RSRQ) metric.
Determining the strongest signal from the at least one neighbouring cell meets a reporting criteria may comprise at least one of: a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell.
The method may further comprise transmitting the radio resource management message.
Transmitting the radio resource management message may comprise transmitting the radio resource management message to a network controller, wherein the network controller may comprise configuring the at least one neighbouring cell to accept a re-establishment request.
The method may further comprise configuring the at least one neighbouring cell based on the at least one neighbouring cell with the strongest signal to accept a re- establishment request.
The method may further comprise: determining a radio-link failure with a current cell; generating a re-establishment request; transmitting the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
The method may further comprise: re-establishing communication based on the re- establishment request to the at least one neighbouring cell with the determined strongest signal. According to a second aspect there is provided an apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive at least one signal from at least one neighbouring cell; determine a strongest signal from the at least one neighbouring cell; determine the strongest signal from the at least one neighbouring cell meets a reporting criteria; generate a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
Receiving at least one signal from at least one neighbouring cell may cause the apparatus to: determine that a current cell is a smaller area cell; receive at least one signal from at least one neighbouring cell neighbouring the smaller area cell.
Determining a strongest signal from the at least one neighbouring cell may cause the apparatus to: generate a signal metric based on the at least one signal from at least one neighbouring cell; compare at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
The signal metric may comprise at least one of: a reference signal received power (RSRP) metric; a reference signal received quality (RSRQ) metric. Determining the strongest signal from the at least one neighbouring cell meets a reporting criteria may cause the apparatus to perform at least one of: determine a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; determine the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell. The apparatus may be caused to further transmit the radio resource management message. Transmitting the radio resource management message may cause the apparatus to transmit the radio resource management message to the at least one neighbouring cell to configure the at least one neighbouring cell to accept a re-establishment request. Transmitting the radio resource management message may cause the apparatus to transmit the radio resource management message to a network controller, wherein the network controller is configured to configure the at least one neighbouring cell to accept a re-establishment request. The apparatus may be caused to: determine a radio-link failure with a current cell; generate a re-establishment request; transmit the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
A system may comprise an apparatus as described herein and at least one neighbouring cell wherein the neighbouring cell is caused to accept a re- establishment request.
The at least one neighbouring cell may be further caused to re-establish communication based on the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
According to a third aspect there is provided an apparatus comprising: a measurement determiner configured to receive at least one signal from at least one neighbouring cell; a measurement comparator configured to determine a strongest signal from the at least one neighbouring cell and furthermore determine the strongest signal from the at least one neighbouring cell meets a reporting criteria; a message generator configured to generate a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
The measurement determiner may be configured to: determine that a current cell is a smaller area cell; receive at least one signal from at least one neighbouring cell neighbouring the smaller area cell. The measurement determiner may be configured to generate a signal metric based on the at least one signal from at least one neighbouring cell; the measurement comparator may be configured to compare at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
The signal metric may comprise at least one of: a reference signal received power (RSRP) metric; a reference signal received quality (RSRQ) metric.
The measurement comparator configured to determine the strongest signal from the at least one neighbouring cell meets a reporting criteria may be configured to determine at least one of: a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell.
The apparatus may further comprise a transmitter configured to transmit the radio resource management message. The transmitter may be configured to transmit the radio resource management message to the at least one neighbouring cell to configure the at least one neighbouring cell to accept a re-establishment request. The transmitter may be configured to transmit the radio resource management message to a network controller, wherein the network controller is configured to configure the at least one neighbouring cell to accept a re-establishment request.
The apparatus may comprise a link failure determiner configured to determine a radio-link failure with a current cell; a link failure controller configured to generate a re-establishment request; the transmitter may be configured to transmit the re- establishment request to the at least one neighbouring cell with the determined strongest signal. A system may comprise the apparatus as described herein and the at least one neighbouring cell wherein the at least one neighbouring cell is configured to accept the re-establishment request.
The at least one neighbouring cell may be further configured to re-establish communication based on the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
According to a fourth aspect there is provided an apparatus comprising: means for receiving at least one signal from at least one neighbouring cell; means for determining a strongest signal from the at least one neighbouring cell; means for determining the strongest signal from the at least one neighbouring cell meets a reporting criteria; means for generating a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request. The means for receiving at least one signal from at least one neighbouring cell may comprise: means for determining that a current cell is a smaller area cell; means for receiving at least one signal from at least one neighbouring cell neighbouring the smaller area cell.
The means for determining a strongest signal from the at least one neighbouring cell may comprise: means for generating a signal metric based on the at least one signal from at least one neighbouring cell; means for comparing at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
The signal metric may comprise at least one of: a reference signal received power (RSRP) metric; and a reference signal received quality (RSRQ) metric. The means for determining the strongest signal from the at least one neighbouring cell meets a reporting criteria may comprise at least one of: means for determining a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; means for determining the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell.
The apparatus may further comprise means for transmitting the radio resource management message.
The means for transmitting the radio resource management message may comprise means for transmitting the radio resource management message to the at least one neighbouring cell to configure the at least one neighbouring cell to accept a re- establishment request. The means for transmitting the radio resource management message may comprise means for transmitting the radio resource management message to a network controller, wherein the network controller is configured to configure the at least one neighbouring cell to accept a re-establishment request.
A system may comprise the apparatus as discussed herein and the at least one neighbouring cell wherein the at least one neighbouring cell may comprise means for configuring the at least one neighbouring cell based on the at least one neighbouring cell with the strongest signal to accept a re-establishment request.
The apparatus may further comprise: means for determining a radio-link failure with a current cell; means for generating a re-establishment request; means for transmitting the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
The system comprising the at least one neighbouring cell as discussed herein wherein the at least one neighbouring cell may comprise means for re-establishing communication based on the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
Summary of Figures
Some embodiments will now be described with reference to the accompanying figures in which:
Figure 1 shows a schematic diagram of a communication system comprising a base station and a plurality of communication devices;
Figure 2 shows a schematic diagram of a mobile communication device according to some embodiments;
Figure 3 shows a schematic diagram of a control apparatus according to some embodiments; Figure 4 shows an example radio resource measurement reporter suitable for being implemented within a mobile communications device according to some embodiments; and
Figure 5 shows a method flow of some embodiments.
Description of Example Embodiments
Current LTE specifications include network controlled, UE assisted, mobility procedures. The mobility performance of LTE is typically observed to be very good for macro-only cases, while it has been found that the mobility performance is more challenging for heterogeneous network (HetNet) scenarios with a mixture of macro and small cells. In particular there has been shown to be a problem with respect to small cell outbound handover with the associated higher risk of experiencing radio link failure (RLF). In case of RLF, the UE attempts re-establishment to the strongest detected cell. If the re-establishment attempt is successful within a short time, the call continues without further interruptions. Otherwise, the call is dropped and the UE enters IDLE mode. The re-establishment attempt is successful only if the cell where the UE requests re-establishment is prepared for UE, such that the cell "knows" the UE and its data. If the UE seeks re-establishment to a cell that is not prepared for this UE (in other words the cell is unaware of the UE), the re-establishment is unsuccessful and results in call dropping, in other words the UE transitions to IDLE mode. One of the conditions for successful re-establishment is therefore coherent network and UE behaviour, meaning that the network should have prepared the cell where the UE seeks re-establishment in case it experiences RLF.
The concept as described herein with respect to the embodiments is the provision of improved re-establishment functionality by including enhanced coordination between the UE and network prior to the occurrence of RLF. The embodiments thus as described herein are applicable to cellular systems, but particularly useful for LTE HetNet scenarios. In the following certain exemplifying embodiments are explained with reference to a wireless or mobile communication system serving mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.
In a wireless communication system mobile communication devices or user equipment (UE) 102, 103, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. In the Figure 1 an example of two overlapping access systems or radio service areas of a cellular system 100 and 1 10 provided by base stations 106 and 107 and three smaller radio service areas 1 1 5, 1 17 and 1 19 provided by remote radio heads (RRH) 1 1 6, 1 18 and 120 are shown. Each mobile communication device and base station/RRH may have one or more radio channels open at the same time and may send signals to and/or receive signals from more than one source. It is noted that the radio service area borders or edges are schematically shown for illustration purposes only in Figure 1 . It shall also be understood that the sizes and shapes of radio service areas may vary considerably from the shapes of Figure 1 . A base station site can provide one or more cells. A base station can also provide a plurality of sectors, for example three radio sectors, each sector providing a cell or a subarea of a cell. All sectors within a cell may be served by the same base station.
Base stations are typically controlled by at least one appropriate controller apparatus so as to enable operation thereof and management of mobile communication devices in communication with the base stations. In Figure 1 control apparatus 108 and 109 is shown to control the respective macro level base stations 106 and 107. The control apparatus of a base station can be interconnected with other control entities. The control apparatus is typically provided with memory capacity and at least one data processor. The control apparatus and functions may be distributed between a plurality of control units. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller.
In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 1 1 3 via gateway 1 1 2. A further gateway function may be provided to connect to another network.
The remote radio heads 1 16, 1 1 8 and 120 are connected to a respective macro cell. Thus RRH 120 is connected to macro cell base station 106 and RRHs 1 18 and 1 1 6 are connected to macro cell base station 109. The RRHs are located in the respective macro cell provided by the macro cell base station to which they are connected.
A possible mobile communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 102. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non- limiting examples include a mobile station (MS) or mobile device such as a mobile phone or what is known as a 'smart phone', a computer provided with a wireless interface card or other wireless interface facility, personal data assistant (PDA) provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content include downloads, television and radio programs, videos, advertisements, various alerts and other information. The mobile device 102 may receive signals over an air interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.
A wireless communication device can be provided with a Multiple Input / Multiple Output (MIMO) antenna system. MIMO arrangements as such are known. MIMO systems use multiple antennas at the transmitter and receiver along with advanced digital signal processing to improve link quality and capacity. Although not shown in Figures 1 and 2, multiple antennas can be provided, for example at base stations and mobile stations, and the transceiver apparatus 206 of Figure 2 can provide a plurality of antenna ports. More data can be received and/or sent where there are more antenna elements. A station may comprise an array of multiple antennas. Signalling and muting patterns can be associated with TX antenna numbers or port numbers of MIMO arrangements. A mobile device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto. Figure 3 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a base station. In some embodiments, base stations comprise a separate control apparatus. In other embodiments, the control apparatus can be another network element such as a radio network controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 1 09 can be arranged to provide control on communications in the service area of the system. The control apparatus 109 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. For example the control apparatus 109 can be configured to execute an appropriate software code to provide the control functions.
The communication devices 1 02, 1 03, 1 05 may access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other non-limiting examples comprise time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on. An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The various development stages of the 3GPP LTE specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE- A). The LTE employs a mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Base stations of such systems are known as evolved or enhanced Node Bs (eNBs) and may provide E-UTRAN features such as user plane Radio Link Control/Medium Access Control/Physical layer protocol (RLC/M AC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices. Other examples of radio access system include those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access). Some embodiments may be used with LTE (or LTE-Advanced) co-channel deployment of macro eNBs and low power eNBs in the form of RRHs. Alternatively or additionally embodiments may be used with smaller cells such as pico or femto cells and/or other relay stations. The smaller cells and/or relay stations may be in communication with a macro eNB. One example of is a co-channel LTE HetNet scenario. This may arise where more than one transmitter is using the same channel or frequency. Some embodiments may address the problem of joint multi-cell packet scheduling for the downlink of such a system, while still maintaining fairness among all users. With respect to Figure 4 an example radio resource management reporter suitable for being implemented within a mobile communications device or user equipment configured to generate suitable radio resource management (RRM) reporting events according to some embodiments is described. Furthermore with respect to Figure 5 the method flow or operations relating to the example radio resource measurement reporter and furthermore the network response operations are further described. In the following examples the term cell is used to define an access point or base station as well as the coverage area provided by the access point or base station. Furthermore in the following examples the network is shown with respect to two base stations and a base station controller able to communicate between the two base stations. However it would be understood that in some embodiments at least one of the base stations can be a remote radio head (RRH) or other radio access point. Furthermore it would be understood that the network can comprise more radio access points, base stations or controlling entities such as base station controllers or radio network controllers and furthermore in some embodiments be coupled together in any suitable manner.
In some embodiments the mobile communications device or UE can be configured to provide an event triggered radio resource management (RRM) reporting event for a set of neighbouring cells. In some embodiments the radio resource management reporter comprises a measurement determiner 401 or suitable means for determining a measurement metric for signals from neighbouring base stations and/or access points. The measurement determiner 401 can in some embodiments be configured to trigger a measurement operation. In some embodiments the measurement operation can be triggered based on receiving information from the transceiver 206.
For example in some embodiments the radio resource management reporter can be configured to trigger the measurement determiner to start determining or taking measurements of neighbouring cells when it determines that the current cell or access point is a smaller area access point. For example in some embodiments the measurement determiner 401 is configured to start measuring when determining that communication is being received from a remote radio head (RRH) 1 18 or any smaller coverage area cell at the user equipment 103. The operation of receiving communication from a base station or cell at the user equipment 103 in Figure 5 by step 500.
The measurement determiner 401 can then be configured to start the measurement process.
The operation of starting a measurement process is shown in Figure 5 by step 501 . In some embodiments the measurement determiner 401 can receive information from the transceiver 206 and from such information generate suitable radio resource management (RRM) measurements for the signals received from neighbouring cells. In some embodiments these radio resource management (RRM) measurements can be a reference signal received power (RSRP) or a reference signal received quality (RSRQ) metric. However any suitable signal strength or quality metric can be generated and used. In the example shown in Figure 5 the operation of the user equipment receiving the reference signal from the neighbouring cell (base station 1 06) is shown by step 502.
Furthermore the user equipment determines the measurement based on the reference signal in Figure 5 step 503.
Although Figure 5 shows only a single neighbouring base station 106 it would be understood that in some embodiments the signal from more than one base station is measured so that two or more neighbouring base station signal measurements are generated.
The measurement determiner 401 can in some embodiments be configured to output the signal measurement(s) to a measurement comparator 403.
In some embodiments the radio resource management reporter comprises a measurement comparator 403. The measurement comparator, or suitable means for comparing measurements or triggering event messages is configured to receive the various signal measurement(s) from the neighbouring cells (or base stations and/or access points) to the user equipment. The measurement comparator 403 can then be configured to compare the measurements from the neighbouring cells and determine the neighbouring cell with the strongest signal, for example the neighbouring cell with the highest RSRP or RSRQ. Furthermore the measurement comparator 403 can be configured to compare the determined strongest neighbour signal measurement against a threshold criteria to determine whether the radio resource management reporter is configured to report the determined strongest neighbour signal measurement.
In some embodiments the threshold comprises a time component. For example in some embodiments the measurement comparator 403 can be configured to communicate with a timer 402. The timer 402 can be configured to provide a timing value relative to the last reporting message sent, or the last handover. When the timing value exceed a time-to-trigger threshold value then the measurement comparator 403 can be configured to trigger the message generator by outputting the determined strongest neighbour value. In such a manner the timing criteria limits the number of reporting messages sent.
In some embodiments the threshold comprises a signal component. For example in some embodiments the measurement comparator 403 can be configured to communicate with a memory 404 comprising a previous strongest neighbour signal measurement or metric and compare the current determined strongest neighbour signal measurement against the previous determined strongest neighbour signal measurement or metric. In some embodiments the comparison is such that the threshold value is one of the previous strongest neighbour signal measurement and an offset margin. In such embodiments when the current strongest neighbour signal measurement exceeds (or at least equals) the previous determined strongest neighbour signal measurement then the measurement comparator 403 outputs the determined strongest neighbour value or in other words triggers the message generator to generate the reporting event message.
In some embodiments it would be understood that the criteria detemination can comprise both of the example criteria thresholds (signal and time). The operation of determining the strongest neighbour signal measurement or metric and furthermore that the strongest neighbour signal measurement or metric measurement matches the reporting criteria is shown in Figure 5 by step 505. In some embodiments the radio resource management reporter comprises a message generator 405. The message generator 405 can in some embodiments be configured to receive the output of the measurement comparator 403. In other words receive an indication when the new strongest neighbour cell meets the criteria for generating a reporting event message. The identifier can in some embodiments be the determined strongest neighbour identifier. Furthermore in some embodiments the identifier can comprise the determined strongest neighbour signal measurement or metric for use in self-organising power control mechanisms.
The message generator 405 can then be configured to generate a suitable radio resource management (RRM) reporting event message for configuring the network and specifically the determined strongest neighbour base station or access point that the user equipment is potentially to request re-establishment with the access point.
The operation of generating a suitable RRM reporting event message is shown in Figure 5 by step 507.
In some embodiments the message generated by the message generator 405 is passed to the transceiver 206. The transceiver 206 can in some embodiments be configured to transmit the RRM message to the current cell or access point.
The transmission of the RRM message from the UE to the current access point the base station 1 1 07 is shown in Figure 5 by step 508.
The current cell or access point, which in this example is base station 1 1 07 can in some embodiments be further configured to pass the RRM message to the network which forwards the message onto the strongest signal neighbouring cell or base station such as the base station 2 106.
The operation of transmitting the RRM message from the current cell or access point (the base station 1 107) to the determined strongest neighbour cell or base station or access point (the base station 2 107) that the user equipment is potentially to request re-establishment with the cell or access point and to configure itself to enable such a re-establishment to succeed is shown in Figure 5 by step 510. It would be understood that in some embodiments the communication is not a direct one as shown in Figure 5 but can be via further entities such as for example a controlling entity (such as a base station controller 109 or radio network controller).
The determined strongest neighbour cell or base station or access point (the base station 107) can then be configured to configure itself to be able to accept a re- establishment from the user equipment.
The operation of configuring the determined strongest neighbour cell or base station or access point (which in Figure 5 is the base station 2 106) to accept a re- establishment from the user equipment is shown in Figure 5 by step 513.
Furthermore Figure 5 shows that after a time period, indicated by the break, that the user equipment suffers from a radio-link failure.
The user equipment radio-link failure is shown in Figure 5 by step 515.
The user equipment, following the radio-link failure, can be configured to request re- establishment with the determined strongest neighbouring cell (or base station or access point).
The operation of generating a re-establishment request is shown in Figure 5 by step 517. Furthermore the operation of transmitting the re-establishment request to the determined strongest neighbour cell or base station or access point (the base station 2 106) is shown in Figure 5 by step 518.
The determined strongest neighbour cell (or base station or access point), which as shown in Figure 5 is the base station 2 106, can then be configured to accept the re- establishment request from the user equipment and re-establish the communication between the user equipment and the network.
The operation of re-establishing the communication between the user equipment and the network is show in Figure 5 by step 51 9.
In such a way the network has the required feedback from the user equipment to prepare a good cell for the user equipment in case of radio-link failure (RLF). Then should radio-link failure occur the user equipment can then attempt re-establishment towards the prepared neighbouring cell. This would significantly increase the probability of successfully re-establishing communication between the user equipment and network or effectively reducing the risk of experience a call dropped.
It is noted that whilst embodiments have been described in relation to LTE, similar principles may be applied to any other communication system or to further developments with LTE. Therefore, although certain embodiments are described above by way of example with reference to certain exemplifying architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.
The required data processing apparatus and functions of a base station apparatus, a communication device and any other appropriate apparatus may be provided by means of one or more data processors. The described functions at each end may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can also be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed there is a further embodiment comprising a combination of one or more of any of the other embodiments previously discussed.

Claims

1 . A method comprising:
receiving at least one signal from at least one neighbouring cell;
determining a strongest signal from the at least one neighbouring cell;
determining the strongest signal from the at least one neighbouring cell meets a reporting criteria; and
generating a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria,
wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
2. The method as claimed in claim 1 , wherein determining a strongest signal from the at least one neighbouring cell comprises:
generating a signal metric based on the at least one signal from at least one neighbouring cell; and
comparing at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
3. The method as claimed in claim 2, wherein the signal metric comprises at least one of:
a reference signal received power (RSRP) metric;
a reference signal received quality (RSRQ) metric.
4. The method as claimed in any of claims 1 to 3, wherein determining the strongest signal from the at least one neighbouring cell meets a reporting criteria comprises at least one of:
a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different cell than the at least one neighbouring cell.
5. The method as claimed in any of claims 1 to 4, further comprising transmitting the radio resource management message.
6. The method as claimed in claim 5, wherein transmitting the radio resource management message comprises transmitting the radio resource management message to a network controller, wherein the network controller is configured to configure the at least one neighbouring cell to accept a re-establishment request.
7. The method as claimed in any of claims 1 to 6, further comprising configuring the at least one neighbouring cell based on the at least one neighbouring cell with the strongest signal to accept a re-establishment request.
8. The method as claimed in any of claims 1 to 7, further comprising:
determining a radio-link failure with a current cell;
generating a re-establishment request;
transmitting the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
9. The method as claimed in claim 8, further comprising:
re-establishing communication based on the re-establishment request to the at least one neighbouring cell with the determined strongest signal.
10. An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:
receive at least one signal from at least one neighbouring cell; determine a strongest signal from the at least one neighbouring cell;
determine the strongest signal from the at least one neighbouring cell meets a reporting criteria; and
generate a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria,
wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
1 1 . The apparatus as claimed in claim 10, wherein determining a strongest signal from the at least one neighbouring cell causes the apparatus to:
generate a signal metric based on the at least one signal from at least one neighbouring cell;
compare at least two signal metrics associated with different neighbouring cells to determine the strongest signal from the different neighbouring cells.
12. The apparatus as claimed in claims 1 1 , wherein the signal metric comprises at least one of:
a reference signal received power (RSRP) metric;
a reference signal received quality (RSRQ) metric.
13. The apparatus as claimed in any of claims 10 to 12, wherein determining the strongest signal from the at least one neighbouring cell meets a reporting criteria causes the apparatus to perform at least one of:
determine a time associated with the strongest signal from the at least one neighbouring cell occurs a determined time period following a reporting time; and determine the signal strength from the at least one neighbouring cell is greater than a determined offset more than a previously determined strongest signal from a different one of the at least one neighbouring cell.
14. An apparatus comprising: a measurement determiner configured to receive at least one signal from at least one neighbouring cell;
a measurement comparator configured to determine a strongest signal from the at least one neighbouring cell and furthermore determine the strongest signal from the at least one neighbouring cell meets a reporting criteria; and
a message generator configured to generate a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
15. An apparatus comprising:
means for receiving at least one signal from at least one neighbouring cell; means for determining a strongest signal from the at least one neighbouring cell;
means for determining the strongest signal from the at least one neighbouring cell meets a reporting criteria; and
means for generating a radio resource management message based on the strongest signal from the at least one neighbouring cell meeting the reporting criteria, wherein the radio resource management message is configured to enable the at least one neighbouring cell to accept a re-establishment request.
PCT/EP2013/066523 2013-08-07 2013-08-07 Method and apparatus WO2015018442A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100278150A1 (en) * 2007-12-31 2010-11-04 Gi Won Park Method for inter rat handover
US20110039546A1 (en) * 2009-08-17 2011-02-17 Motorola, Inc. Method and apparatus for radio link failure recovery
WO2012019339A1 (en) * 2010-08-11 2012-02-16 Huawei Technologies Co., Ltd. Method for providing information in a cellular wireless communication system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100278150A1 (en) * 2007-12-31 2010-11-04 Gi Won Park Method for inter rat handover
US20110039546A1 (en) * 2009-08-17 2011-02-17 Motorola, Inc. Method and apparatus for radio link failure recovery
WO2012019339A1 (en) * 2010-08-11 2012-02-16 Huawei Technologies Co., Ltd. Method for providing information in a cellular wireless communication system

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