WO2013114203A2 - Method and apparatus for cooperative handover across multiple mobile relays - Google Patents

Method and apparatus for cooperative handover across multiple mobile relays Download PDF

Info

Publication number
WO2013114203A2
WO2013114203A2 PCT/IB2013/000224 IB2013000224W WO2013114203A2 WO 2013114203 A2 WO2013114203 A2 WO 2013114203A2 IB 2013000224 W IB2013000224 W IB 2013000224W WO 2013114203 A2 WO2013114203 A2 WO 2013114203A2
Authority
WO
WIPO (PCT)
Prior art keywords
mobile relay
handover
following
mobile
relays
Prior art date
Application number
PCT/IB2013/000224
Other languages
French (fr)
Other versions
WO2013114203A3 (en
Inventor
Yuwen PAN
Qinglin Luo
Tao Yang
Original Assignee
Alcatel Lucent
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 Alcatel Lucent filed Critical Alcatel Lucent
Publication of WO2013114203A2 publication Critical patent/WO2013114203A2/en
Publication of WO2013114203A3 publication Critical patent/WO2013114203A3/en

Links

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
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/00837—Determination of triggering parameters for hand-off
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/042—Public Land Mobile systems, e.g. cellular systems
    • H04W84/047—Public Land Mobile systems, e.g. cellular systems using dedicated repeater stations

Definitions

  • the present invention relates to a mobile communication technology field, and more specifically, to a cooperative handover technology accross multiple mobile relays.
  • the handover signaling of MRs will increase with the increase of speed of the train.
  • the system is subjected to serious user equipment (UE) call drop caused by MR handover failure. Therefore, when the system employs multiple MRs, the handover signaling of backhaul link will be larger in amount, and the handover procedure will also be more complicated.
  • the handover procedure for mobile relays needs to be carefully designed to meet the delay and complexity requirement.
  • the mobile relay when a mobile relay hands over from a source DeNB to a target DeNB, the mobile relay communicates with the source DeNB and the target DeNB so as to send measurement reports and receive the configuration information.
  • a conventional handover procedure comprises three stages, i.e., a handover preparation stage, a handover execution stage, and a handover completion stage, respectively.
  • the handover preparation stage comprises steps S 101 -S 107, mainly involving: the source DeNB makes a handover decision for a mobile relay based on measurement reports on channel quality of backhaul link of the mobile relay, and the source DeNB obtains handover configuration information of the mobile relay from a target DeNB to which the pioneer mobile relay should be handed over;
  • the handover execution stage comprises steps S108-S111, mainly involving: the mobile relay performs RRC reconfiguration based on the handover configuration information and the target DeNB buffers user data;
  • the handover completion stage comprises steps S112-S118, mainly involving: the mobile relay gateway (Relay-SGW/PGW) switches the downlink path from the source DeNB to the target DeNB, and the source DeNB releases resources.
  • the mobile relay gateway Relay-SGW/PGW
  • 3GPP LTE handover procedure as shown in Fig. 1, measurements of channel quality of the mobile relay are made at the downlink reference symbols. These measurements include, but not limited to, pathloss, antenna gain, log-normal shadowing and fast fading averaged over all the reference symbols within a measurement channel.
  • the limited number of references symbols within the handover measurement bandwidth introduces measurement errors.
  • the increasing number of handover will increase the signaling overhead and delay. This is unacceptable for a high-speed mobile scenario such as High-Speed Train Communication (HSTC).
  • HSTC High-Speed Train Communication
  • the performance of 3GPP LTE handover procedure is investigated in terms of handover failure rate and the delay of the whole procedure. Study shows that high mobility causes large system delay and high handover failure rate.
  • An objective of the present invention aims at providing a method and apparatus for cooperative handover across multiple mobile relays.
  • a method for cooperative handover across multiple mobile relays that are installed in a moving object in sequence, wherein the method comprises the following steps: a. When a source DeNB makes a handover decision for one of the multiple mobile relays, the source DeNB determines a handover triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to the following mobile relay according to the sequence of the following mobile relay; b.
  • the source DeNB upon expiration of each first timer, obtains handover configuration information of a corresponding following mobile relay from a target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
  • a DeNB for handovering across multiple mobile relays that are installed in a moving object in sequence
  • the DeNB comprises: a first timer initiating unit for determining, when a source DeNB makes a handover decision for one of the multiple mobile relays, a handover triggering time of at least one of the mobile relays following the current mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiating and executing a first timer corresponding to the following mobile relay according to the sequence of the following mobile relay; a configuration information obtaining unit for obtaining, upon expiration of each first timer, handover configuration information of a corresponding following mobile relay from a target DeNB corresponding to the current handover mobile relay; a configuration information sending unit for sending the corresponding configuration information to the following mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
  • a mobile relay gateway for facilitating handover across multiple mobile relays that are installed in a moving object in sequence
  • the mobile relay gateway comprises: a second timer initiating unit for determining, after the current handover mobile relay completes RRC reconfiguration, a path switch triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiating and executing a second timer corresponding to the following mobile relay according to the sequence of the following mobile relay; a downlink path switching unit for switching, upon expiration of each second timer, a downlink path of a corresponding following mobile relay from a source DeNB corresponding to the current handover mobile relay to a target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to accomplish the handover and communicate with the target DeNB.
  • a mobile relay for facilitating the following mobile relays to perform handover, the mobile relay and following mobile relays being installed in a moving object in sequence, wherein the mobile relay comprises: a following relay reporting unit for sending to a source DeNB corresponding to the mobile relay, a measurement report on channel quality of the mobile relay, and information relevant to distance of the mobile relays following the mobile relay, so as to be available for the source DeNB to determine handover triggering time for the following mobile relays, wherein the measurement report is available for the source DeNB to make a handover decision for the mobile relay.
  • the present invention may determine a target DeNB to handover for a following mobile relay based on a handover decision for a pioneer mobile relay on a moving object.
  • a handover event of a following mobile relay is triggered through setting a timer at a source DeNB.
  • the measurement procedure for channel quality of the following mobile relay is eliminated, for example, periodic measurements of RSRP (reference signal received power) and RSRQ (reference signal received quality) for the following mobile relay based on the reference symbols received from the source DeNB and the neighboring DeNBs are eliminated.
  • a timer may also be set in a mobile relay gateway (Relay - SGW/ PGW), so as to be available for switching the downlink path for the following relay, such that the procedure of requesting for switching the downlink path is removed and delay is reduced.
  • the handover procedure according to the present invention reduces handover failure rate and avoids latency caused by measurement process, thereby improving handover efficiency of the system.
  • the present invention provides to a high-speed mobile scenario a cooperative handover procedure across mobile relays, overcomes the high call drop rate and high handover failure rate in a high-speed moving scenario in a conventional handover system, reduces delay in the handover procedure, and effectively improves the UE quality of service (QoS); therefore, the present invention may be applied to a reliable broadband communication for a high-speed train.
  • QoS quality of service
  • Fig. 1 shows a flowchart of a prior art method for handover across mobile relays
  • Fig. 2a shows a flowchart of a method for a pioneer mobile relay during a handover preparation stage according to one aspect of the present invention
  • Fig. 2b shows a flowchart of a method for a second mobile relay during a handover preparation stage according to one aspect of the present invention
  • Fig. 3a shows a flowchart of a method for a pioneer mobile relay during a handover preparation stage according to a preferred embodiment of the present invention
  • Fig. 3b shows a flowchart of a method for a second mobile relay during a handover preparation stage according to a preferred embodiment of the present invention
  • Fig. 4 shows an apparatus diagram of a pioneer mobile relay and a source DeNB cooperatively performing handover across multiple mobile relays according to a further aspect of the present invention
  • Fig. 5 shows an apparatus diagram of a pioneer mobile relay, a source DeNB, and a mobile relay gateway cooperatively performing handover across mobile relays according to a preferred embodiment of the present invention.
  • L3 relay was agreed to be the most suitable relay to support group mobility.
  • the mobile relay of the present invention also supports L3 relay.
  • All control planes and user plane protocols are terminated at the mobile relay.
  • a typical high-speed train is about 400 meter in length.
  • each of the cartages employs one mobile own relay to serve the UEs inside.
  • a high speed train moves at speed about 350 km h.
  • the backhaul links between one mobile relay and its DeNB is unstable especially at an extremely high speed, and when the train is crossing a tunnel with NLOS (non line of sight) between DeNB and MR. It is assume that the UEs in high speed train are not able to directly communicate with the DeNB. Once the connection between DeNB and mobile relay is dropped, UE consequently drops its phone call or other data connection. Coordination between mobile relays can be utilized to reduce the UE drop rate.
  • the above assumption of fixed relay scenario cannot be hold for mobile relay scenario.
  • the MR-DeNB link is much more unstable due to the Doppler shift effect and frequent handover. Coordination between MRs can effectively provide more reliable quality of service to UEs.
  • the present invention mainly relates to optimizing the handover preparation stage to improve the handover successful rate.
  • multiple mobile relays are sequentially installed in a moving object, for example, a high-speed train.
  • the handover preparation process for the cooperative handover across multiple mobile relays comprises: in step S201, the source DeNB sends measurement control information to a pioneer mobile relay to indicate the measurement process and reported content of the pioneer mobile relay; in step S202, the pioneer mobile relay sends measurement reports corresponding to the measurement control information and information relevant to distance of following mobile relays sequent to the pioneer mobile relay to the source DeNB; in step S203, the source DeNB makes a handover decision for the pioneer mobile relay based on the measurement reports, determines handover triggering time for the following mobile relays based on the distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a fist timer corresponding to a following mobile relay according to the sequence of the following mobile relay; in step S204,
  • the source DeNB obtains handover configuration information of the following mobile relay from the target DeNB of the pioneer mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
  • the information relevant to distance of the following mobile relays includes, but not limited to, identification information of the following mobile relays, the distance information between the pioneer mobile relay and each of the following mobile relays, and the distance information between every two of the following mobile relays, etc.
  • the information relevant to motion of the moving object includes, but not limited to, location information and movement speed information of the moving object, which may be obtained from a measurement device, such as GPS, motion sensor, etc, installed on the moving object.
  • the source DeNB may periodically obtain the information relevant to motion of the moving object from the measurement device or obtain the information relevant to motion of the moving object in the event that a handover triggering time of the following mobile relay is determined.
  • the solution in which the source DeNB sequentially initiates and executes the first timer of the following mobile relay in the multiple mobile relays is merely an example for the purpose of illustrating the present invention, and should not be regarded as any limitation to the present invention.
  • the cooperative handover procedure in the present invention may start from any mobile relay among the sequentially arranged multiple mobile relays, without the need of starting from the first mobile relay.
  • the source DeNB makes a handover decision for any mobile relay among the multiple mobile relays, it initiates a first timer for a following mobile relay relative to the current handover mobile relay, i.e., the pioneer mobile relay, so as to trigger a handover event of the following mobile relay.
  • the present invention is mostly described with initiating the first timer of the following mobile relay sequent to the pioneer mobile relay when a handover decision is made for the pioneer mobile relay; however, those skilled in the art should understand that the scenario of starting the cooperative handover procedure of the present invention from any mobile relay among the multiple mobile relays should still fall within the protection scope of the present invention.
  • the source DeNB may initiate and execute a corresponding first timer for each of the following mobile relays in sequence, so as to trigger a corresponding handover event of the following mobile relay; or initiate and execute the corresponding first timer for a part of the following mobile relays in accordance with their corresponding sequence, so as to trigger the handover event for each of the part of following mobile relays.
  • the part of following mobile relays may be determined by the source DeNB or the pioneer mobile relay, and based on the distance between multiple mobile relays and the information relevant to motion of the moving object, such as the location information and speed information of the moving object, the source DeNB determines the handover triggering time for each following mobile relay which has a handover event to be triggered, so as to initiate and execute a first timer of a corresponding following mobile relay.
  • the handover triggering time for each following mobile relay may be identical or different, dependent on the arrangement position of the each following mobile relay in the moving object, the motion speed of the moving object, etc.
  • the source DeNB initiates and executes the first timer for the corresponding mobile relay based on the sequent of the each following mobile relay; upon expiration of the first timer, the source DeNB obtains the handover configuration information of the corresponding following mobile relay from the target DeNB of the pioneer mobile relay, and meanwhile repeats the above procedure for a next sequential mobile relay, i.e., initiating and executing its first timer for the next mobile relay and obtaining the corresponding handover configuration information upon expiration, thereby eliminating the measurement control and report process of the following mobile relays.
  • a source DeNB makes a handover decision for a pioneer mobile relay, determines a target DeNB to which the pioneer mobile relay should be handed over and meanwhile initiates and executes a first timer of each following mobile relay, so as to trigger a handover event for the corresponding following mobile relay. Because the train length is determined, the distance between every two mobile relays is also determined.
  • a GPS receiver installed on the high-speed train reports the location related information of the high-speed train to the source DeNB via a dedicated control channel; or a motion sensor installed on the high-speed train detects and reports the location related information of the high-speed train to the source DeNB.
  • the source DeNB determines the handover triggering time of each mobile relay following the pioneer mobile relay, and initiates and executes its corresponding first timer in accordance with the sequence of the each following mobile relay.
  • Each following mobile relay upon expiration of its corresponding first timer, should arrive at a time point/ location that requires handover to the target DeNB; therefore, upon expiration of the first timer, the source DeNB obtains handover configuration information from the target DeNB for the corresponding following mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
  • the present invention may further optimize the handover competition stage so as to improve the successful rate.
  • the handover preparation procedure for cooperative handover across multiple mobile relays comprises: in step S301, the source DeNB sends measurement control information to a pioneer mobile relay to indicate the measurement process and reported content for the pioneer mobile relay; in step S302, the pioneer mobile relay sends measurement reports corresponding to the measurement control information and information relevant to distance of following mobile relays sequent to the pioneer mobile relay, in step S303, the source DeNB makes a handover decision for the pioneer mobile relay based on the measurement reports, determines handover triggering time for the following mobile relays based on the distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to a following mobile relay in accordance with the sequence of the following mobile relay; in step S304, the source DeNB sends a handover request to a target DeNB to which the pioneer mobile relay should be handed over
  • the pioneer mobile relay enters into the handover execution stage to perform steps S308-S311 so as to complete RRC reconfiguration based on the handover configuration information, and then enters into the handover completion stage to perform steps S312-S318 so as to accomplish the handover to the target DeNB.
  • the mobile relay gateway After the pioneer mobile relay completes RRC reconfiguration, the mobile relay gateway, after receiving a downlink path switch request from the target DeNB, initiates and executes a second timer corresponding to the following mobile relay in accordance with the sequence of the following mobile relay, wherein the switch triggering time of the second timer for each following mobile relay is identical to the handover triggering time of the first timer.
  • the source DeNB obtains handover configuration information for the following mobile relay from the target DeNB of the pioneer mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration. Afterwards, the following mobile relay completes RRC reconfiguration and enters into the handover completion stage.
  • the mobile relay gateway switches the downlink path of the following mobile relay from the source DeNB to the target DeNB, so as to be available for the following mobile relay to accomplish the handover and communicate with the target DeNB.
  • multiple mobile relays are installed on a high-speed train in sequence.
  • the source DeNB makes a handover decision for the pioneer mobile relay, and the pioneer mobile relay continues its handover procedure; meanwhile, the source DeNB initiates the first timer of the second mobile relay; upon expiration of the first timer of the second mobile relay, the source DeNB obtains handover configuration information for the second mobile relay from the target DeNB of the pioneer relay, the second mobile relay continuing its handover procedure; after expiration of the first timer of the second mobile relay, the source DeNB initiates and executes the first timer of the third mobile relay so as to trigger a handover event of the third mobile relay; by this, the source DeNB initiates and executes a corresponding first timer for each mobile relay following the pioneer mobile relay so as to obtain the corresponding handover configuration information for each following mobile relay from the target DeNB of the pioneer mobile relay.
  • the mobile relay gateway After the pioneer mobile relay enters into the handover completion stage, the mobile relay gateway, after receiving a downlink path switch request from the target DeNB, initiates a second timer of the second mobile relay; and upon expiration of the second timer of the second mobile relay, the mobile relay network switches the downlink path from the source DeNB to the target DeNB, and the handover procedure of the second mobile relay continues till completion; upon expiration of the second timer of the second mobile relay, the mobile relay gateway initiates and executes a second timer for the third mobile relay so as to trigger a downlink path switch for the third mobile relay; by this, the mobile relay gateway initiates and executes the corresponding second timer for each mobile relay following the pioneer mobile relay, so as to trigger the downlink path switch for each following mobile relay from the target DeNB.
  • the handover triggering time of the first timer and the switch triggering time of the second timer are identical.
  • Fig. 4 shows an apparatus diagram according to one embodiment of the present invention, illustrating a pioneer mobile relay and a source DeNB cooperating to perform cooperative handover across multiple mobile relays.
  • the multiple mobile relays are installed on a moving object in sequence, wherein the pioneer mobile relay 11 comprises a following relay reporting unit 411 ; a source DeNB 20 comprises an uplink information receiving unit 421, a first timer initiating unit 422, a configuration information obtaining unit 423, and a configuration information sending unit 424.
  • the following relay reporting unit 411 of the pioneer mobile relay 11 sends a measurement report on channel quality of the pioneer mobile relay 11 and information relevant to distance of the following mobile relays sequent to the pioneer mobile relay 11 to a source DeNB corresponding to the pioneer mobile relay 11, so as to be available for the source DeNB to determine handover triggering time for the following mobile relays, wherein the measurement report is for the source DeNB to make a handover decision for the pioneer mobile relay 11 ;
  • the uplink information receiving unit 421 of the source DeNB 20 receives from the pioneer mobile relay 11 the measurement report on channel quality of the pioneer mobile relay 11 and information relevant to distance of the following mobile relays;
  • the information relevant to distance of the following mobile relays includes, but not limited to, identifier information of the following mobile relays, distance information between the following mobile relays and the pioneer mobile relay, and distance information between every two of the following mobile relays, etc.
  • the information relevant to motion of the moving object includes, but not limited to, location information and movement speed information of the moving object, which may be obtained from a measurement device, such as GPS, motion sensor, etc, installed on the moving object.
  • the source DeNB 20 further comprises an object moving object unit (not shown).
  • the object moving obtaining unit may periodically obtains the information relevant to motion of the moving object from the measurement device, or may obtain the information relevant to motion of the moving object in the event that a handover triggering time of the following mobile relay is determined.
  • the information relevant to distance of the following mobile relays, the information relevant to motion of the moving object, and their obtaining manners are only examples, and other existing or possibly evolved future information relevant to distance of the following mobile relays, information relevant to motion of the moving object, or their obtaining manners, if applicable to the present invention, should also be included within the protection scope of the present invention and incorporated here by reference.
  • the source DeNB 20 makes a handover decision for the pioneer mobile relay 11
  • the solution in which the first timer initiating unit 422 sequentially initiates and executes the first timer of the following mobile relay 12-ln following the pioneer mobile relay 11 is merely an example for the purpose of illustrating the present invention, and should not be regarded as any limitation to the present invention.
  • the cooperative handover procedure in the present invention may start from any mobile relay among the multiple mobile relays mounted in sequence, and it is not needed to start from the first mobile relay 11.
  • the first timer initiating unit 422 initiates a first timer for a following mobile relay following the current handover mobile relay, i.e., the pioneer mobile relay, so as to trigger a handover event of the following mobile relay.
  • the present invention is mostly described with initiating the first timer of the following mobile relay sequent to the pioneer mobile relay when a handover decision is made for the pioneer mobile relay; however, those skilled in the art should understand that the scenario of starting the cooperative handover procedure of the present invention from any mobile relay among the multiple mobile relays should still fall within the protection scope of the present invention. Likewise, the cooperative handover procedure of the present invention is also applicable for all or a part of the following mobile relays following the pioneer mobile relay 11.
  • the first timer initiating unit 422 of the source DeNB 20 may initiate and execute a corresponding first timer for each following mobile relay In (n>l) in sequence, so as to trigger a handover event of the corresponding mobile relay; or may initiate and execute the corresponding first timer for a part of following mobile relays in accordance with the corresponding sequence, so as to trigger the handover event of each of this part of the following mobile relays.
  • this part of following mobile relays may be determined by the source DeNB 20 or the pioneer mobile relay 11 ; based on the distance between multiple mobile relays and information relevant to motion of the moving object, such as the location information and speed information and the like of the moving object, the first timer initiating unit 422 of the source DeNB 20 determines the handover triggering time of each following mobile relay which has a handover event to be triggered, so as to initiate and execute the first timer of a corresponding following mobile relay.
  • the handover triggering time for each following mobile relay may be identical or different, dependent on the arrangement position of the each following mobile relay on the moving object, and the motion speed of the moving object, etc.
  • the first timer initiating unit 422 of the source DeNB 20 initiates and executes its first timer for a corresponding following mobile relay in accordance with the sequence of the each following mobile relay; upon expiration of the first timer, the configuration information obtaining unit 423 obtains the handover configuration information of the corresponding following mobile relay from a target DeNB of the pioneer mobile relay 11, and meanwhile, the source DeNB 20 repeats the above procedure for a next sequential mobile relay, i.e., initiating and executing its first timer for the next mobile relay and obtains the corresponding handover configuration information upon expiration, thereby eliminating the measurement control and report process of the following mobile relays.
  • Fig. 5 shows an apparatus diagram of another embodiment of the present invention, illustrating a pioneer mobile relay, a source DeNB, and a mobile relay gateway cooperating to accomplish a cooperative handover across multiple mobile relays.
  • the multiple mobile relays are installed on a moving object in sequence, wherein the pioneer mobile relay 11 comprises a following relay reporting unit 511 ; the source DeNB 20 comprises an uplink information receiving unit 521, a first timer initiating unit 522, a configuration information obtaining unit 523, and a configuration information sending unit 524; and the mobile relay gateway 30 comprises a second timer initiating unit 531 and a downlink switching unit 532.
  • the pioneer mobile relay 11 comprises a following relay reporting unit 511 ;
  • the source DeNB 20 comprises an uplink information receiving unit 521, a first timer initiating unit 522, a configuration information obtaining unit 523, and a configuration information sending unit 524;
  • the mobile relay gateway 30 comprises a second timer initiating unit 531 and a downlink switching unit 532.
  • the following relay reporting unit 511 of the pioneer mobile relay 11 sends a measurement report on channel quality of the pioneer mobile relay 11 and information relevant to distance of the following mobile relays sequent to the pioneer mobile relay 11, so as to be available for the source DeNB 20 to determine handover triggering time for the following mobile relays, wherein the measurement report is available for the source DeNB 20 to make a handover decision for the pioneer mobile relay 11; the uplink information receiving unit 521 of the source DeNB 20 receives the measurement report on channel quality of the pioneer mobile relay 11 and the information relevant to distance of the following mobile relays; the first timer initiating unit 522 of the source DeNB 20, when making a handover decision for the pioneer mobile relay 11, determines the handover triggering time of at least one of the following mobile relays following the pioneer mobile relay 11 based on the distance between multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to a following mobile relay in accordance with the sequence of the following mobile relay; the configuration information obtaining unit 523, upon expir
  • the path switch triggering time of the second timer of the following mobile relay may be computed by the second timer initiating unit 531 in accordance with the distance between the multiple mobile relays and information relevant to motion of the moving object, or may directly employ the handover triggering time of the first timer of the corresponding following mobile relay, i.e., for each following mobile relay, the handover triggering time of the first timer and the switch triggering time of the second timers is identical.
  • multiple mobile relays are installed on a high-speed train in sequence; wherein a following relay reporting unit 511 of a pioneer mobile relay 11 reports a measurement report and information relevant to distance of its following mobile relays to the source DeNB; the source DeNB 20 makes a handover decision for the pioneer mobile relay 11, the pioneer mobile relay 11 continuing its handover procedure; meanwhile, the first timer initiating unit 522 initiates a first timer of a second mobile relay 12; upon expiration of the first timer of the second mobile relay 12, the configuration information obtaining unit 523 obtains the handover configuration for the second mobile relay 12 from the target DeNB of the pioneer relay 11, the second mobile relay 12 continuing its handover process; after the first timer of the second mobile relay 12 expires, the first timer initiating unit 522 initiates and executes a first timer for a third mobile relay 13, so as to trigger a handover event of the third mobile relay 13; by this, the source DeNB 20 initiates and executes a corresponding first timer of each mobile relay In (n>l)
  • the second timer initiating unit 531 initiates a second timer of the second mobile relay 12; upon expiration of the second timer of the second mobile relay 12, the downlink switching unit 532 switches the downlink path from the source DeNB to the target DeNB, and the handover procedure of the second mobile relay 12 continues till completion; after expiration of the second timer of the second mobile relay 12, the second timer initiating unit 531 initiates and executes the second timer for the third mobile relay 13 so as to trigger a downlink path switch of the third mobile relay; by this, the mobile relay network 30 initiates and executes a corresponding second timer for each mobile relay following the pioneer mobile relay 11 one by one, so as to trigger the downlink path switch of the target DeNB for each following mobile relay.
  • the handover triggering time of the first timer and the switch triggering time of the second timers is identical.
  • the present invention may also be applicable for mobile relay handover with some modification of the conventional handover procedure for UE in LTE system.
  • the target DeNB before the handover execution stage, not only needs the information of the mobile relays, but also needs the information of the user equipment served by the mobile relays. Additionally, the mobile relays also need to execute the downlink path switch procedure for the serving user equipment.

Landscapes

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

Abstract

An objective of the present invention aims at providing a method and apparatus for cooperative handover across multiple mobile relays. Herein, when a source DeNB makes a handover decision for one of the multiple mobile relays, the source DeNB determines a handover triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to the following mobile relay according to the sequence of the following mobile relay; upon expiration of each first timer, the source DeNB obtains handover configuration information of a corresponding following mobile relay from a target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to perform RRC reconfiguration and communicate with the target DeNB Through cooperative handover across multiple mobile relays, the amount of handover signaling and handover latency will be both reduced, thereby effectively avoiding handover failure and improving user experience.

Description

Method and Apparatus for Cooperative Handover across Multiple Mobile Relays Technical Field The present invention relates to a mobile communication technology field, and more specifically, to a cooperative handover technology accross multiple mobile relays.
Background art Wireless broadband has become a reality in recent years. Online multimedia, gaming, mobile application downloading, etc., become dominating traffic of the mobile network. To provide data-intensive applications to passengers on a train, for example a China Railways High-speed (CRH) train between Beijing and Shanghai at a speed of 350km/h, it is desirable to develop an access network characterized by high bandwidth and resilience to high mobility. Employing mobile relays (MR) inside the high speed train is regarded as a feasible technique to provide multiple services of good quality to users. Since the CRH train length is around 400 meters, in order to cover the whole train, multiple MRs are required to be placed in the train to maintain smooth backhaul link transmissions. However, when multiple MRs are employed in a high-speed train, the handover signaling of MRs will increase with the increase of speed of the train. The system is subjected to serious user equipment (UE) call drop caused by MR handover failure. Therefore, when the system employs multiple MRs, the handover signaling of backhaul link will be larger in amount, and the handover procedure will also be more complicated. The handover procedure for mobile relays needs to be carefully designed to meet the delay and complexity requirement.
As shown in Fig. 1, in the existing mobile relay handover procedure, when a mobile relay hands over from a source DeNB to a target DeNB, the mobile relay communicates with the source DeNB and the target DeNB so as to send measurement reports and receive the configuration information.
Specifically, still refer to Fig. 1, a conventional handover procedure comprises three stages, i.e., a handover preparation stage, a handover execution stage, and a handover completion stage, respectively. Herein, the handover preparation stage comprises steps S 101 -S 107, mainly involving: the source DeNB makes a handover decision for a mobile relay based on measurement reports on channel quality of backhaul link of the mobile relay, and the source DeNB obtains handover configuration information of the mobile relay from a target DeNB to which the pioneer mobile relay should be handed over; the handover execution stage comprises steps S108-S111, mainly involving: the mobile relay performs RRC reconfiguration based on the handover configuration information and the target DeNB buffers user data; the handover completion stage comprises steps S112-S118, mainly involving: the mobile relay gateway (Relay-SGW/PGW) switches the downlink path from the source DeNB to the target DeNB, and the source DeNB releases resources.
In 3GPP LTE handover procedure as shown in Fig. 1, measurements of channel quality of the mobile relay are made at the downlink reference symbols. These measurements include, but not limited to, pathloss, antenna gain, log-normal shadowing and fast fading averaged over all the reference symbols within a measurement channel. The limited number of references symbols within the handover measurement bandwidth introduces measurement errors. And, the increasing number of handover will increase the signaling overhead and delay. This is unacceptable for a high-speed mobile scenario such as High-Speed Train Communication (HSTC). Further, the performance of 3GPP LTE handover procedure is investigated in terms of handover failure rate and the delay of the whole procedure. Study shows that high mobility causes large system delay and high handover failure rate.
Summary of the Invention
An objective of the present invention aims at providing a method and apparatus for cooperative handover across multiple mobile relays.
According to one aspect of the present invention, there is provided a method for cooperative handover across multiple mobile relays that are installed in a moving object in sequence, wherein the method comprises the following steps: a. When a source DeNB makes a handover decision for one of the multiple mobile relays, the source DeNB determines a handover triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to the following mobile relay according to the sequence of the following mobile relay; b. upon expiration of each first timer, the source DeNB obtains handover configuration information of a corresponding following mobile relay from a target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
According to another aspect of the present invention, there is further provided a DeNB for handovering across multiple mobile relays that are installed in a moving object in sequence, wherein the DeNB comprises: a first timer initiating unit for determining, when a source DeNB makes a handover decision for one of the multiple mobile relays, a handover triggering time of at least one of the mobile relays following the current mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiating and executing a first timer corresponding to the following mobile relay according to the sequence of the following mobile relay; a configuration information obtaining unit for obtaining, upon expiration of each first timer, handover configuration information of a corresponding following mobile relay from a target DeNB corresponding to the current handover mobile relay; a configuration information sending unit for sending the corresponding configuration information to the following mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
According to a further aspect of the present invention, there is further provided a mobile relay gateway for facilitating handover across multiple mobile relays that are installed in a moving object in sequence, wherein the mobile relay gateway comprises: a second timer initiating unit for determining, after the current handover mobile relay completes RRC reconfiguration, a path switch triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiating and executing a second timer corresponding to the following mobile relay according to the sequence of the following mobile relay; a downlink path switching unit for switching, upon expiration of each second timer, a downlink path of a corresponding following mobile relay from a source DeNB corresponding to the current handover mobile relay to a target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to accomplish the handover and communicate with the target DeNB.
According to a still further aspect of the present invention, there is further provided a mobile relay for facilitating the following mobile relays to perform handover, the mobile relay and following mobile relays being installed in a moving object in sequence, wherein the mobile relay comprises: a following relay reporting unit for sending to a source DeNB corresponding to the mobile relay, a measurement report on channel quality of the mobile relay, and information relevant to distance of the mobile relays following the mobile relay, so as to be available for the source DeNB to determine handover triggering time for the following mobile relays, wherein the measurement report is available for the source DeNB to make a handover decision for the mobile relay.
Compared with the prior art, the present invention may determine a target DeNB to handover for a following mobile relay based on a handover decision for a pioneer mobile relay on a moving object. Through cooperative handover across multiple mobile relays, the amount of handover signaling and handover latency will be both reduced, thereby effectively avoiding handover failure and improving user experience. According to the present invention, a handover event of a following mobile relay is triggered through setting a timer at a source DeNB. In this scenario, the measurement procedure for channel quality of the following mobile relay is eliminated, for example, periodic measurements of RSRP (reference signal received power) and RSRQ (reference signal received quality) for the following mobile relay based on the reference symbols received from the source DeNB and the neighboring DeNBs are eliminated. Further, a timer may also be set in a mobile relay gateway (Relay - SGW/ PGW), so as to be available for switching the downlink path for the following relay, such that the procedure of requesting for switching the downlink path is removed and delay is reduced. The handover procedure according to the present invention reduces handover failure rate and avoids latency caused by measurement process, thereby improving handover efficiency of the system.
The present invention provides to a high-speed mobile scenario a cooperative handover procedure across mobile relays, overcomes the high call drop rate and high handover failure rate in a high-speed moving scenario in a conventional handover system, reduces delay in the handover procedure, and effectively improves the UE quality of service (QoS); therefore, the present invention may be applied to a reliable broadband communication for a high-speed train.
Description of Drawings Through reading the detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objectives and advantages of the present invention will become more apparent:
Fig. 1 shows a flowchart of a prior art method for handover across mobile relays;
Fig. 2a shows a flowchart of a method for a pioneer mobile relay during a handover preparation stage according to one aspect of the present invention;
Fig. 2b shows a flowchart of a method for a second mobile relay during a handover preparation stage according to one aspect of the present invention;
Fig. 3a shows a flowchart of a method for a pioneer mobile relay during a handover preparation stage according to a preferred embodiment of the present invention; Fig. 3b shows a flowchart of a method for a second mobile relay during a handover preparation stage according to a preferred embodiment of the present invention;
Fig. 4 shows an apparatus diagram of a pioneer mobile relay and a source DeNB cooperatively performing handover across multiple mobile relays according to a further aspect of the present invention;
Fig. 5 shows an apparatus diagram of a pioneer mobile relay, a source DeNB, and a mobile relay gateway cooperatively performing handover across mobile relays according to a preferred embodiment of the present invention.
Same or like reference numerals in the accompanying drawings represent same or like components. Specific Embodiments
Hereinafter, the present invention will be further described in detail with reference to the accompanying drawings.
In 3GPP TR36.806 (Release 9), LI/ L2/ L3 relay classifications were discussed. For mobile relay scenario, L3 relay was agreed to be the most suitable relay to support group mobility. Thus, the mobile relay of the present invention also supports L3 relay. On the Un interface between UE and mobile relay, all control planes and user plane protocols are terminated at the mobile relay.
A typical high-speed train is about 400 meter in length. In order to cover the whole train, more than one mobile relay should be mounted on the train, for example, each of the cartages employs one mobile own relay to serve the UEs inside. Generally a high speed train moves at speed about 350 km h. The backhaul links between one mobile relay and its DeNB is unstable especially at an extremely high speed, and when the train is crossing a tunnel with NLOS (non line of sight) between DeNB and MR. It is assume that the UEs in high speed train are not able to directly communicate with the DeNB. Once the connection between DeNB and mobile relay is dropped, UE consequently drops its phone call or other data connection. Coordination between mobile relays can be utilized to reduce the UE drop rate. Cooperative transmissions for fixed relays have been investigated a lot in literatures to improve the UE throughput. The difference from mobile relay case is that in fixed relay scenario, the DeNB to fixed relay link is generally assumed to have high SNR. This assumption is rational, as in fixed relay scenario, relay is usually fixed at a position with LOS (line of sight) to the DeNB in order to provide UE enhancement.
However, the above assumption of fixed relay scenario cannot be hold for mobile relay scenario. Especially in high mobility situation, the MR-DeNB link is much more unstable due to the Doppler shift effect and frequent handover. Coordination between MRs can effectively provide more reliable quality of service to UEs.
The present invention mainly relates to optimizing the handover preparation stage to improve the handover successful rate. In one embodiment of the present invention, multiple mobile relays are sequentially installed in a moving object, for example, a high-speed train. With reference to Fig. 2a, the handover preparation process for the cooperative handover across multiple mobile relays comprises: in step S201, the source DeNB sends measurement control information to a pioneer mobile relay to indicate the measurement process and reported content of the pioneer mobile relay; in step S202, the pioneer mobile relay sends measurement reports corresponding to the measurement control information and information relevant to distance of following mobile relays sequent to the pioneer mobile relay to the source DeNB; in step S203, the source DeNB makes a handover decision for the pioneer mobile relay based on the measurement reports, determines handover triggering time for the following mobile relays based on the distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a fist timer corresponding to a following mobile relay according to the sequence of the following mobile relay; in step S204, the source DeNB sends a handover request message to a target DeNB to which the pioneer mobile relay should be handed over; in step S205, the target DeNB performs access control for the pioneer mobile relay; in step S206, the target DeNB sends a handover request acknowledge message to the source DeNB; correspondingly, the source DeNB obtains handover configuration information of the pioneer mobile relay from the handover request acknowledge message; in step S207, the source DeNB sends the handover configuration information to the pioneer mobile relay, so as to be available for the pioneer mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
Next, with reference to Fig. 2b, when the first timer expires, the source DeNB obtains handover configuration information of the following mobile relay from the target DeNB of the pioneer mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
Here, the information relevant to distance of the following mobile relays includes, but not limited to, identification information of the following mobile relays, the distance information between the pioneer mobile relay and each of the following mobile relays, and the distance information between every two of the following mobile relays, etc.
The information relevant to motion of the moving object includes, but not limited to, location information and movement speed information of the moving object, which may be obtained from a measurement device, such as GPS, motion sensor, etc, installed on the moving object. The source DeNB may periodically obtain the information relevant to motion of the moving object from the measurement device or obtain the information relevant to motion of the moving object in the event that a handover triggering time of the following mobile relay is determined.
Those skilled in the art should understand that the information relevant to distance of the following mobile relays, the information relevant to motion of the moving object, and their obtaining manners are only examples, and other existing or possibly evolved future information relevant to distance of the following mobile relays, information relevant to motion of the moving object, or their obtaining manners, if applicable to the present invention, should also be included within the protection scope of the present invention and incorporated here by reference.
Here, when the source DeNB makes a handover decision for the pioneer mobile relay, the solution in which the source DeNB sequentially initiates and executes the first timer of the following mobile relay in the multiple mobile relays is merely an example for the purpose of illustrating the present invention, and should not be regarded as any limitation to the present invention.
For the present invention, the cooperative handover procedure in the present invention may start from any mobile relay among the sequentially arranged multiple mobile relays, without the need of starting from the first mobile relay. For example, when the source DeNB makes a handover decision for any mobile relay among the multiple mobile relays, it initiates a first timer for a following mobile relay relative to the current handover mobile relay, i.e., the pioneer mobile relay, so as to trigger a handover event of the following mobile relay. For the sake of simplicity, the present invention is mostly described with initiating the first timer of the following mobile relay sequent to the pioneer mobile relay when a handover decision is made for the pioneer mobile relay; however, those skilled in the art should understand that the scenario of starting the cooperative handover procedure of the present invention from any mobile relay among the multiple mobile relays should still fall within the protection scope of the present invention.
Likewise, the cooperative handover procedure of the present invention is also applicable to all or a part of following mobile relays relative to the pioneer mobile relay. The source DeNB may initiate and execute a corresponding first timer for each of the following mobile relays in sequence, so as to trigger a corresponding handover event of the following mobile relay; or initiate and execute the corresponding first timer for a part of the following mobile relays in accordance with their corresponding sequence, so as to trigger the handover event for each of the part of following mobile relays.
Further, in a scenario in which only the corresponding handover events for a part of the following mobile relays are triggered, the part of following mobile relays may be determined by the source DeNB or the pioneer mobile relay, and based on the distance between multiple mobile relays and the information relevant to motion of the moving object, such as the location information and speed information of the moving object, the source DeNB determines the handover triggering time for each following mobile relay which has a handover event to be triggered, so as to initiate and execute a first timer of a corresponding following mobile relay. In a scenario in which multiple following mobile relays have handover events to be triggered, the handover triggering time for each following mobile relay may be identical or different, dependent on the arrangement position of the each following mobile relay in the moving object, the motion speed of the moving object, etc. The source DeNB initiates and executes the first timer for the corresponding mobile relay based on the sequent of the each following mobile relay; upon expiration of the first timer, the source DeNB obtains the handover configuration information of the corresponding following mobile relay from the target DeNB of the pioneer mobile relay, and meanwhile repeats the above procedure for a next sequential mobile relay, i.e., initiating and executing its first timer for the next mobile relay and obtaining the corresponding handover configuration information upon expiration, thereby eliminating the measurement control and report process of the following mobile relays.
For example, multiple mobile relays are installed on a high-speed train in sequence, a source DeNB makes a handover decision for a pioneer mobile relay, determines a target DeNB to which the pioneer mobile relay should be handed over and meanwhile initiates and executes a first timer of each following mobile relay, so as to trigger a handover event for the corresponding following mobile relay. Because the train length is determined, the distance between every two mobile relays is also determined. A GPS receiver installed on the high-speed train reports the location related information of the high-speed train to the source DeNB via a dedicated control channel; or a motion sensor installed on the high-speed train detects and reports the location related information of the high-speed train to the source DeNB. Based on the location related information of the high-speed train and the distance between mobile relays, the source DeNB determines the handover triggering time of each mobile relay following the pioneer mobile relay, and initiates and executes its corresponding first timer in accordance with the sequence of the each following mobile relay. Each following mobile relay, upon expiration of its corresponding first timer, should arrive at a time point/ location that requires handover to the target DeNB; therefore, upon expiration of the first timer, the source DeNB obtains handover configuration information from the target DeNB for the corresponding following mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
The present invention may further optimize the handover competition stage so as to improve the successful rate.
In another embodiment of the present invention, multiple mobile relays are sequentially installed in a moving object in sequence, for example, a high-speed train. With reference to Fig. 3a, the handover preparation procedure for cooperative handover across multiple mobile relays comprises: in step S301, the source DeNB sends measurement control information to a pioneer mobile relay to indicate the measurement process and reported content for the pioneer mobile relay; in step S302, the pioneer mobile relay sends measurement reports corresponding to the measurement control information and information relevant to distance of following mobile relays sequent to the pioneer mobile relay, in step S303, the source DeNB makes a handover decision for the pioneer mobile relay based on the measurement reports, determines handover triggering time for the following mobile relays based on the distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to a following mobile relay in accordance with the sequence of the following mobile relay; in step S304, the source DeNB sends a handover request to a target DeNB to which the pioneer mobile relay should be handed over; in step S305, the target DeNB performs access control for the pioneer mobile relay; in step S306, the target DeNB sends a handover request acknowledge message to the source DeNB, and correspondingly, the source DeNB obtains handover configuration information of the pioneer mobile relay from the handover request acknowledge message; in step S307, the source DeNB sends the handover configuration information to the pioneer mobile relay, so as to be available for the pioneer mobile relay to perform RRC reconfiguration and communicate with the target DeNB . Next, the pioneer mobile relay enters into the handover execution stage to perform steps S308-S311 so as to complete RRC reconfiguration based on the handover configuration information, and then enters into the handover completion stage to perform steps S312-S318 so as to accomplish the handover to the target DeNB. After the pioneer mobile relay completes RRC reconfiguration, the mobile relay gateway, after receiving a downlink path switch request from the target DeNB, initiates and executes a second timer corresponding to the following mobile relay in accordance with the sequence of the following mobile relay, wherein the switch triggering time of the second timer for each following mobile relay is identical to the handover triggering time of the first timer.
Next, referring to Fig. 3b, for the following mobile relay, when the first timer corresponding to the following mobile relay expires, the source DeNB obtains handover configuration information for the following mobile relay from the target DeNB of the pioneer mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration. Afterwards, the following mobile relay completes RRC reconfiguration and enters into the handover completion stage. When the second timer corresponding to the following mobile relay expires, the mobile relay gateway switches the downlink path of the following mobile relay from the source DeNB to the target DeNB, so as to be available for the following mobile relay to accomplish the handover and communicate with the target DeNB.
For example, multiple mobile relays are installed on a high-speed train in sequence. When the pioneer mobile relay reports its measurement report and information relevant to distance of the following mobile relays to the source DeNB, the source DeNB makes a handover decision for the pioneer mobile relay, and the pioneer mobile relay continues its handover procedure; meanwhile, the source DeNB initiates the first timer of the second mobile relay; upon expiration of the first timer of the second mobile relay, the source DeNB obtains handover configuration information for the second mobile relay from the target DeNB of the pioneer relay, the second mobile relay continuing its handover procedure; after expiration of the first timer of the second mobile relay, the source DeNB initiates and executes the first timer of the third mobile relay so as to trigger a handover event of the third mobile relay; by this, the source DeNB initiates and executes a corresponding first timer for each mobile relay following the pioneer mobile relay so as to obtain the corresponding handover configuration information for each following mobile relay from the target DeNB of the pioneer mobile relay.
After the pioneer mobile relay enters into the handover completion stage, the mobile relay gateway, after receiving a downlink path switch request from the target DeNB, initiates a second timer of the second mobile relay; and upon expiration of the second timer of the second mobile relay, the mobile relay network switches the downlink path from the source DeNB to the target DeNB, and the handover procedure of the second mobile relay continues till completion; upon expiration of the second timer of the second mobile relay, the mobile relay gateway initiates and executes a second timer for the third mobile relay so as to trigger a downlink path switch for the third mobile relay; by this, the mobile relay gateway initiates and executes the corresponding second timer for each mobile relay following the pioneer mobile relay, so as to trigger the downlink path switch for each following mobile relay from the target DeNB. Here, for each following mobile relay, the handover triggering time of the first timer and the switch triggering time of the second timer are identical.
Fig. 4 shows an apparatus diagram according to one embodiment of the present invention, illustrating a pioneer mobile relay and a source DeNB cooperating to perform cooperative handover across multiple mobile relays. Specifically, the multiple mobile relays are installed on a moving object in sequence, wherein the pioneer mobile relay 11 comprises a following relay reporting unit 411 ; a source DeNB 20 comprises an uplink information receiving unit 421, a first timer initiating unit 422, a configuration information obtaining unit 423, and a configuration information sending unit 424.
As shown in Fig. 4, the following relay reporting unit 411 of the pioneer mobile relay 11 sends a measurement report on channel quality of the pioneer mobile relay 11 and information relevant to distance of the following mobile relays sequent to the pioneer mobile relay 11 to a source DeNB corresponding to the pioneer mobile relay 11, so as to be available for the source DeNB to determine handover triggering time for the following mobile relays, wherein the measurement report is for the source DeNB to make a handover decision for the pioneer mobile relay 11 ; the uplink information receiving unit 421 of the source DeNB 20 receives from the pioneer mobile relay 11 the measurement report on channel quality of the pioneer mobile relay 11 and information relevant to distance of the following mobile relays; the first timer initiating unit 422, when making the handover decision for the pioneer mobile relay 11, determines the handover triggering time of at least one of the following mobile relays following the pioneer mobile relay 11 based on the distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to a following mobile relay in accordance with the sequence of the following mobile relay; a configuration information obtaining unit 423, upon expiration of each first timer, obtains handover configuration information of the corresponding following mobile relay from a target DeNB corresponding to the pioneer mobile relay 11 ; the configuration information sending unit 424 sends the corresponding handover configuration information to the following mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB. Here, the embodiment mainly relates to accomplishing cooperative handover across multiple mobile relays with cooperation between the multiple mobile relays and the source DeNB, so as to optimize the handover preparation stage and improve the handover successful rate.
In this embodiment, the information relevant to distance of the following mobile relays includes, but not limited to, identifier information of the following mobile relays, distance information between the following mobile relays and the pioneer mobile relay, and distance information between every two of the following mobile relays, etc.
The information relevant to motion of the moving object includes, but not limited to, location information and movement speed information of the moving object, which may be obtained from a measurement device, such as GPS, motion sensor, etc, installed on the moving object.
Preferably, the source DeNB 20 further comprises an object moving object unit (not shown). The object moving obtaining unit may periodically obtains the information relevant to motion of the moving object from the measurement device, or may obtain the information relevant to motion of the moving object in the event that a handover triggering time of the following mobile relay is determined.
Those skilled in the art should understand that the information relevant to distance of the following mobile relays, the information relevant to motion of the moving object, and their obtaining manners are only examples, and other existing or possibly evolved future information relevant to distance of the following mobile relays, information relevant to motion of the moving object, or their obtaining manners, if applicable to the present invention, should also be included within the protection scope of the present invention and incorporated here by reference. Besides, when the source DeNB 20 makes a handover decision for the pioneer mobile relay 11, the solution in which the first timer initiating unit 422 sequentially initiates and executes the first timer of the following mobile relay 12-ln following the pioneer mobile relay 11 is merely an example for the purpose of illustrating the present invention, and should not be regarded as any limitation to the present invention.
For the present invention, the cooperative handover procedure in the present invention may start from any mobile relay among the multiple mobile relays mounted in sequence, and it is not needed to start from the first mobile relay 11. For example, when the source DeNB 20 makes a handover decision for any mobile relay among the multiple mobile relays, the first timer initiating unit 422 initiates a first timer for a following mobile relay following the current handover mobile relay, i.e., the pioneer mobile relay, so as to trigger a handover event of the following mobile relay. For the sake of conciseness, the present invention is mostly described with initiating the first timer of the following mobile relay sequent to the pioneer mobile relay when a handover decision is made for the pioneer mobile relay; however, those skilled in the art should understand that the scenario of starting the cooperative handover procedure of the present invention from any mobile relay among the multiple mobile relays should still fall within the protection scope of the present invention. Likewise, the cooperative handover procedure of the present invention is also applicable for all or a part of the following mobile relays following the pioneer mobile relay 11. The first timer initiating unit 422 of the source DeNB 20 may initiate and execute a corresponding first timer for each following mobile relay In (n>l) in sequence, so as to trigger a handover event of the corresponding mobile relay; or may initiate and execute the corresponding first timer for a part of following mobile relays in accordance with the corresponding sequence, so as to trigger the handover event of each of this part of the following mobile relays.
Further, in a scenario of only triggering corresponding handover events for a part of the following mobile relays, this part of following mobile relays may be determined by the source DeNB 20 or the pioneer mobile relay 11 ; based on the distance between multiple mobile relays and information relevant to motion of the moving object, such as the location information and speed information and the like of the moving object, the first timer initiating unit 422 of the source DeNB 20 determines the handover triggering time of each following mobile relay which has a handover event to be triggered, so as to initiate and execute the first timer of a corresponding following mobile relay.
In a scenario in which multiple following mobile relays have handover events to be triggered, the handover triggering time for each following mobile relay may be identical or different, dependent on the arrangement position of the each following mobile relay on the moving object, and the motion speed of the moving object, etc. The first timer initiating unit 422 of the source DeNB 20 initiates and executes its first timer for a corresponding following mobile relay in accordance with the sequence of the each following mobile relay; upon expiration of the first timer, the configuration information obtaining unit 423 obtains the handover configuration information of the corresponding following mobile relay from a target DeNB of the pioneer mobile relay 11, and meanwhile, the source DeNB 20 repeats the above procedure for a next sequential mobile relay, i.e., initiating and executing its first timer for the next mobile relay and obtains the corresponding handover configuration information upon expiration, thereby eliminating the measurement control and report process of the following mobile relays.
Fig. 5 shows an apparatus diagram of another embodiment of the present invention, illustrating a pioneer mobile relay, a source DeNB, and a mobile relay gateway cooperating to accomplish a cooperative handover across multiple mobile relays. Specifically, the multiple mobile relays are installed on a moving object in sequence, wherein the pioneer mobile relay 11 comprises a following relay reporting unit 511 ; the source DeNB 20 comprises an uplink information receiving unit 521, a first timer initiating unit 522, a configuration information obtaining unit 523, and a configuration information sending unit 524; and the mobile relay gateway 30 comprises a second timer initiating unit 531 and a downlink switching unit 532. As shown in Fig. 5, the following relay reporting unit 511 of the pioneer mobile relay 11 sends a measurement report on channel quality of the pioneer mobile relay 11 and information relevant to distance of the following mobile relays sequent to the pioneer mobile relay 11, so as to be available for the source DeNB 20 to determine handover triggering time for the following mobile relays, wherein the measurement report is available for the source DeNB 20 to make a handover decision for the pioneer mobile relay 11; the uplink information receiving unit 521 of the source DeNB 20 receives the measurement report on channel quality of the pioneer mobile relay 11 and the information relevant to distance of the following mobile relays; the first timer initiating unit 522 of the source DeNB 20, when making a handover decision for the pioneer mobile relay 11, determines the handover triggering time of at least one of the following mobile relays following the pioneer mobile relay 11 based on the distance between multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to a following mobile relay in accordance with the sequence of the following mobile relay; the configuration information obtaining unit 523, upon expiration of each of the first timers, obtains the handover configuration information of the corresponding following mobile relay from the target DeNB corresponding to the pioneer mobile relay 11 ; the configuration information sending unit 524 sends corresponding handover configuration information to the following mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB; the second timer initiating unit 531 of the mobile relay gateway 30, after the pioneer mobile relay 11 completes RRC reconfiguration, determines the path switch triggering time of at least one following mobile relay following the current handover mobile relay based on the distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes the second timer corresponding to the following mobile relay in accordance with the sequence of the following mobile relay; the downlink path switching unit 532, upon expiration of each of the second timers, switches the downlink path of the corresponding following mobile relay from the source DeNB corresponding to the current handover mobile relay to the target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to accomplish the handover and communicate with the target DeNB. Here, this embodiment mainly relates to cooperating across multiple mobile relays, a source DeNB, and a mobile relay gateway to accomplish cooperative handover across multiple mobile relays, so as to optimize the handover preparation stage and the handover completion stage and improve the handover successful rate.
In this embodiment, the path switch triggering time of the second timer of the following mobile relay may be computed by the second timer initiating unit 531 in accordance with the distance between the multiple mobile relays and information relevant to motion of the moving object, or may directly employ the handover triggering time of the first timer of the corresponding following mobile relay, i.e., for each following mobile relay, the handover triggering time of the first timer and the switch triggering time of the second timers is identical.
For example, multiple mobile relays are installed on a high-speed train in sequence; wherein a following relay reporting unit 511 of a pioneer mobile relay 11 reports a measurement report and information relevant to distance of its following mobile relays to the source DeNB; the source DeNB 20 makes a handover decision for the pioneer mobile relay 11, the pioneer mobile relay 11 continuing its handover procedure; meanwhile, the first timer initiating unit 522 initiates a first timer of a second mobile relay 12; upon expiration of the first timer of the second mobile relay 12, the configuration information obtaining unit 523 obtains the handover configuration for the second mobile relay 12 from the target DeNB of the pioneer relay 11, the second mobile relay 12 continuing its handover process; after the first timer of the second mobile relay 12 expires, the first timer initiating unit 522 initiates and executes a first timer for a third mobile relay 13, so as to trigger a handover event of the third mobile relay 13; by this, the source DeNB 20 initiates and executes a corresponding first timer of each mobile relay In (n>l) following the pioneer mobile relay 11, so as to obtain corresponding handover configuration information for each following mobile relay In from the target DeNB of the pioneer mobile relay 11.
After the pioneer mobile relay 11 enters into the handover completion stage, when the mobile relay gateway 30 receives a downlink switch request from the target DeNB, the second timer initiating unit 531 initiates a second timer of the second mobile relay 12; upon expiration of the second timer of the second mobile relay 12, the downlink switching unit 532 switches the downlink path from the source DeNB to the target DeNB, and the handover procedure of the second mobile relay 12 continues till completion; after expiration of the second timer of the second mobile relay 12, the second timer initiating unit 531 initiates and executes the second timer for the third mobile relay 13 so as to trigger a downlink path switch of the third mobile relay; by this, the mobile relay network 30 initiates and executes a corresponding second timer for each mobile relay following the pioneer mobile relay 11 one by one, so as to trigger the downlink path switch of the target DeNB for each following mobile relay. Here, for each following mobile relay, the handover triggering time of the first timer and the switch triggering time of the second timers is identical.
Besides, the present invention may also be applicable for mobile relay handover with some modification of the conventional handover procedure for UE in LTE system. For example, before the handover execution stage, the target DeNB not only needs the information of the mobile relays, but also needs the information of the user equipment served by the mobile relays. Additionally, the mobile relays also need to execute the downlink path switch procedure for the serving user equipment.
To those skilled in the art, it is apparent that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or essential features of the present invention, the present invention may be implemented by other specific forms. Thus, regardless of from which aspect, the embodiments should be regarded as illustrative, not limitative, and the scope of the present is defined by the appended claims instead of the above depictions; therefore, all variations intended to fall within the meaning and scope of equivalent elements of claims should be included within the present invention. Any reference numerals in claims should be not regarded as limiting the involved claims. Besides, it is apparent that the terms "comprise" and "include" do not exclude other elements or steps, a singular form does not exclude the plural form. Multiple units or means as stated in the system claims may also be implemented by one unit or means through software or hardware. The terms "first" and "second" and the like are used to indicate names, instead of any specific sequence.

Claims

Claims
What is claimed is: 1. A method for cooperative handover across multiple mobile relays that are installed in a moving object in sequence, wherein the method comprises the following steps: a. When a source DeNB makes a handover decision for one of the multiple mobile relays, the source DeNB determines a handover triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiates and executes a first timer corresponding to the following mobile relay according to the sequence of the following mobile relay; b. upon expiration of each first timer, the source DeNB obtains handover configuration information of a corresponding following mobile relay from a target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
2. The method according to claim 1, wherein before step a, the method further comprises:
- the current handover mobile relay sends to the target DeNB a measurement report on channel quality of the current handover mobile relay, and information relevant to distance of the following mobile relays, wherein the measurement report is available for the source DeNB to make a handover decision for the current handover mobile relay.
3. The method according to claim 2, wherein the information relevant to distance of the following mobile relays includes at least one of the following items: - identification information of the following mobile relays;
- distance information between the following mobile relays and the current handover mobile relay;
- distance information between every two of the following mobile relays.
4. The method according to any one of claims 1 to 3, wherein the method further comprises:
- obtaining the information relevant to motion of the moving object.
5. The method according to claim 4, wherein the information relevant to motion includes at least one of the following items:
- location information of the moving object;
- movement speed information of the moving object.
6. The method according to any one of claims 1 to 5, wherein the method further comprises: - when the source DeNB makes the handover decision for the current handover mobile relay, the source DeNB obtains handover configuration information of the current handover mobile relay from the target DeNB to handover;
- the current handover mobile relay performs RRC reconfiguration based on the handover configuration information and communicates with the target DeNB.
7. The method according to any one of claims 1 to 6, wherein the method further comprises:
- after the current handover mobile relay completes RRC reconfiguration, a mobile relay gateway initiates and executes a second timer corresponding to the following mobile relay according to the sequence of the following mobile relay, wherein the switch triggering time of the second timer of each following mobile relay is identical to the handover triggering time of the first timer;
- upon expiration of each second timer, the mobile relay gateway switches a downlink path of a corresponding following mobile relay from the source DeNB to the target DeNB, so as to be available for the following mobile relay to accomplish the handover and communicate with the target DeNB.
8. A DeNB for handovering across multiple mobile relays that are installed in a moving object in sequence, wherein the DeNB comprises: a first timer initiating unit for determining, when a source DeNB makes a handover decision for one of the multiple mobile relays, a handover triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiating and executing a first timer corresponding to the following mobile relay according to the sequence of the following mobile relay; a configuration information obtaining unit for obtaining, upon expiration of each first timer, handover configuration information of a corresponding following mobile relay from a target DeNB corresponding to the current handover mobile relay; a configuration information sending unit for sending the corresponding configuration information to the following mobile relay, so as to be available for the following mobile relay to perform RRC reconfiguration and communicate with the target DeNB.
9. The DeNB according to claim 8, wherein the DeNB further comprises: an uplink information receiving unit for receiving from the current handover mobile relay a measurement report on channel quality of the current handover mobile relay, and information relevant to distance of the following mobile relays, wherein the measurement report is available for the source DeNB to make a handover decision for the current handover mobile relay.
10. The DeNB according to claim 9, wherein the information relevant to distance of the following mobile relays includes at least one of the following items:
- identification information of the following mobile relays;
- distance information between the following mobile relays and the current handover mobile relay;
- distance information between every two of the following mobile relays.
11. The DeNB according to any one of claims 8 to 10, wherein the DeNB further comprises: an object motion obtaining unit for obtaining the information relevant to motion of the moving object.
12. The DeNB according to claim 11, wherein the information relevant to motion includes at least one of the following items:
- location information of the moving object;
- movement speed information of the moving object.
13. A mobile relay gateway for facilitating handover across multiple mobile relays that are installed in a moving object in sequence, wherein the mobile relay gateway comprises: a second timer initiating unit for determining, after the current handover mobile relay completes RRC reconfiguration, a path switch triggering time of at least one of the mobile relays following the current handover mobile relay based on distance between the multiple mobile relays and information relevant to motion of the moving object, and initiating and executing a second timer corresponding to the following mobile relay according to the sequence of the following mobile relay; a downlink path switching unit for switching, upon expiration of each second timer, a downlink path of a corresponding following mobile relay from a source DeNB corresponding to the current handover mobile relay to a target DeNB corresponding to the current handover mobile relay, so as to be available for the corresponding following mobile relay to accomplish the handover and communicate with the target DeNB.
14. A mobile relay for facilitating the following mobile relays to perform handover, the mobile relay and following mobile relays being installed in a moving object in sequence, wherein the mobile relay comprises: a following relay reporting unit for sending to a source DeNB corresponding to the mobile relay, a measurement report on channel quality of the mobile relay, and information relevant to distance of the mobile relays following the mobile relay, so as to be available for the source DeNB to determine handover triggering time for the following mobile relays, wherein the measurement report is available for the source DeNB to make a handover decision for the mobile relay.
15. The mobile relay according to claim 14, wherein the information relevant to distance of the following mobile relays includes at least one of the following items:
- identification information of the following mobile relays;
- distance information between the following mobile relays and the mobile relay;
- distance information between every two of the following mobile relays.
PCT/IB2013/000224 2012-02-03 2013-02-01 Method and apparatus for cooperative handover across multiple mobile relays WO2013114203A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN201210024595.5 2012-02-03
CN201210024595.5A CN103249105B (en) 2012-02-03 2012-02-03 A kind of cooperation changing method for multiple mobile relay and device

Publications (2)

Publication Number Publication Date
WO2013114203A2 true WO2013114203A2 (en) 2013-08-08
WO2013114203A3 WO2013114203A3 (en) 2014-02-20

Family

ID=48142014

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2013/000224 WO2013114203A2 (en) 2012-02-03 2013-02-01 Method and apparatus for cooperative handover across multiple mobile relays

Country Status (2)

Country Link
CN (1) CN103249105B (en)
WO (1) WO2013114203A2 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110622559A (en) * 2017-03-22 2019-12-27 Idac控股公司 Delayed handover execution in wireless networks based on trigger conditions
US11503550B2 (en) 2015-04-24 2022-11-15 Beijing Zhigu Rui Tuo Tech Co., Ltd Information transmission method and apparatus for mobile terminal
US11985559B2 (en) 2017-03-22 2024-05-14 Interdigital Patent Holdings, Inc. System and methods for phased reconfiguration in wireless systems
US12035187B2 (en) 2018-03-22 2024-07-09 Interdigital Patent Holdings, Inc. Delayed handover execution in wireless networks based on a trigger condition

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106817737B (en) * 2016-12-22 2019-03-08 电信科学技术研究院有限公司 A kind of method and device switched over using mobile relay
CN112859928B (en) * 2021-02-19 2022-09-16 苏州市大智无疆智能科技有限公司 Unmanned aerial vehicle cruise control method and device and cloud server

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0901298A1 (en) * 1997-09-08 1999-03-10 Alcatel Base station and method for controlling the communications in a cell of a cellular digital radio communication network
CN1130088C (en) * 1997-12-10 2003-12-03 西尔可穆无线公司 Communication system and method for addressing multiple capacity wireless trunk
JP3465703B2 (en) * 2001-07-18 2003-11-10 日本電気株式会社 Common channel flow control method
CN100459788C (en) * 2004-12-24 2009-02-04 华为技术有限公司 Method and device for implementing centralized mobility management

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
3GPP TR36.806 (RELEASE 9

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11503550B2 (en) 2015-04-24 2022-11-15 Beijing Zhigu Rui Tuo Tech Co., Ltd Information transmission method and apparatus for mobile terminal
CN110622559A (en) * 2017-03-22 2019-12-27 Idac控股公司 Delayed handover execution in wireless networks based on trigger conditions
US11985559B2 (en) 2017-03-22 2024-05-14 Interdigital Patent Holdings, Inc. System and methods for phased reconfiguration in wireless systems
US12035187B2 (en) 2018-03-22 2024-07-09 Interdigital Patent Holdings, Inc. Delayed handover execution in wireless networks based on a trigger condition

Also Published As

Publication number Publication date
CN103249105B (en) 2016-01-13
WO2013114203A3 (en) 2014-02-20
CN103249105A (en) 2013-08-14

Similar Documents

Publication Publication Date Title
CN103797846B (en) improved switching robustness in cellular radio communications
US9055505B2 (en) Method and apparatus in which a terminal transmits a channel estimation result in a mobile communication system
WO2021159283A1 (en) Non-terrestrial network (ntn) switching method, and device and storage medium
CN103703858B (en) Exchange of mobility information in cellular radio communications
JP2019532604A (en) Cell handover method, apparatus, and system
CN109275168B (en) System and method for optimizing switching parameter settings of terminals on public transportation platform
JPWO2016021541A1 (en) Communications system
US10390266B2 (en) Method and apparatus for inter-radio access network mobility
US9907005B2 (en) Handover event prioritization
CN102763454A (en) Detection of radio link failure (rlf) for recovery
JP2011193375A (en) Relay station, and communication control method
CN116686336A (en) Method, apparatus and computer storage medium for communication
EP2934043A1 (en) System and method for identifying target denb cell
US11310706B2 (en) Radio link setup signaling in cellular system
WO2013114203A2 (en) Method and apparatus for cooperative handover across multiple mobile relays
WO2013143084A1 (en) Method and apparatus for handover
WO2020259811A1 (en) Sidelink-aided handover
Fei et al. Position-assisted fast handover schemes for LTE-advanced network under high mobility scenarios
JP6170905B2 (en) Communication control method, base station, and processor
EP3703422B1 (en) Identifying a moving state of a user device
Tesema et al. Multiconnectivity for mobility robustness in standalone 5G ultra dense networks with intrafrequency cloud radio access
US20140080486A1 (en) Wireless communications system, communication apparatus, and wireless communications method
WO2018077416A1 (en) Pro-active transmission of system information to reduce interruption time after radio link failure for wireless networks
WO2014090032A1 (en) Method and device for handover statistics
Tomasov et al. LTE fixed-point handover algorithm for high-speed railway scenario

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 13717300

Country of ref document: EP

Kind code of ref document: A2

122 Ep: pct application non-entry in european phase

Ref document number: 13717300

Country of ref document: EP

Kind code of ref document: A2