WO2013055430A2 - Procédé d'amélioration des performances de transfert intercellulaire dans des réseaux sans fil hétérogènes - Google Patents

Procédé d'amélioration des performances de transfert intercellulaire dans des réseaux sans fil hétérogènes Download PDF

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Publication number
WO2013055430A2
WO2013055430A2 PCT/US2012/048690 US2012048690W WO2013055430A2 WO 2013055430 A2 WO2013055430 A2 WO 2013055430A2 US 2012048690 W US2012048690 W US 2012048690W WO 2013055430 A2 WO2013055430 A2 WO 2013055430A2
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Prior art keywords
resources
coordinated
mobility
handover
macrocell
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PCT/US2012/048690
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English (en)
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WO2013055430A3 (fr
Inventor
Ismail Guvenc
David LOPEZ-PEREZ
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Ntt Docomo, Inc.
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Publication of WO2013055430A2 publication Critical patent/WO2013055430A2/fr
Publication of WO2013055430A3 publication Critical patent/WO2013055430A3/fr

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    • 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
    • H04W36/0085—Hand-off measurements
    • 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
    • H04W36/008375—Determination of triggering parameters for hand-off based on historical data
    • 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
    • H04W84/045—Public Land Mobile systems, e.g. cellular systems using private Base Stations, e.g. femto Base Stations, home Node B
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present invention relates to wireless communications technology. More specifically, the proposed system can be used to improve handover performance in a heterogeneous wireless network.
  • the mobile users In homogeneous networks, the mobile users typically use the same set of handover parameters while making a handover to a different cell.
  • using the same set of parameters for all cells and for all users may increase the number of handover failures (HFs) and/or ping-pongs (PPs). More specifically, if a user equipment (UE) is in a high-mobility state, a shorter time-to-trigger (TTT) should be utilized as opposed to a relatively-longer TTT for lower-mobility users.
  • TTT time-to-trigger
  • the rapid movement of the high-mobility user can significantly degrade the user's signal-to-interference-plus- noise ratio (SINR) in a relatively short amount of time.
  • SINR signal-to-interference-plus- noise ratio
  • a shorter TTT would be preferable to decrease HFs, since the SINR degradation in a smaller cell may happen at a faster rate compared to a larger cell.
  • TTT handover performance
  • UE user equipment
  • UEs with higher mobility can be configured to use shorter TTT values.
  • Doppler spread information which may then be used to configure handover parameters more efficiently.
  • Both the base station (BS) and the UE can estimate the UE mobility state so that the overall UE mobility state may be estimated by comparing the BS-derived and UE-derived estimations. Then, TTT or some other handover parameters are adapted accordingly.
  • Another prior art approach uses low, medium, and high mobility states based on tracking the number of handovers in a cellular network. Then, a scaling factor is introduced for different mobility states, which is multiplied with the TTT (i.e., a mobility-specific TTT is utilized as opposed to a cell-specific TTT).
  • handover parameters may also be optimized at the base station by tracking the measurement reports from the UEs.
  • the TTT may then be adapted based on the signal quality from different nodes.
  • handover parameters for different cells in heterogeneous network are configured differently. For example, cells may be divided into multiple handover-related classes based on their coverage areas, and each class is then assigned a unique set of handover parameters.
  • Another prior art approach uses UE measurements on the quality of the connection to the best cell. Then, a mobility-related parameter set (including discontinued reception (DRX) configurations) is selected based on this assessment. Post-handover measurements from the UE (with regard to the previous cell) are used for optimizing handover parameters in the future.
  • DRX discontinued reception
  • the communication resources (time, frequency, coding, and so on) in a heterogeneous network may be coordinated or uncoordinated.
  • An uncoordinated resource is shared equally by the various cells.
  • a coordinated resource is reserved for a certain cell class.
  • coordinated frequency sub-bands may be allocated to cell-edge vs cell-centered UEs based on quality of pilot measurements. Different sub-bands are allocated to cell-edge as opposed to cell-centered UEs, and cell-edge UEs perform measurements more frequently due to higher possibility of handover. But the use of coordinated resources often inefficiently utilizes the available resources.
  • While modifying handover parameters according to the above-mentioned prior art approaches may provide some gains in handover performance, there are typically some adverse effects (such as increased complexity/overhead, and degradation in some other performance metrics). For example, using shorter TTT values for high mobility users or cells with smaller coverage areas decreases the HF probability. On the other hand, a shorter TTT also implies larger number of ping-pongs, which introduces overhead on the network and may result in losing some packets (which adversely affects the call quality). Accordingly, there is a need in the art for improved handover performance in heterogeneous networks.
  • the present disclosure is directed to a heterogeneous network having macrocells and picocells with co-channel operation for both low-mobility and high-mobility users.
  • the co- channel operation occurs over both coordinated and uncoordinated resources.
  • the high-mobility user communicates with a macrocell base station in both the coordinated and uncoordinated resources. But if a handover condition to a low-power node (a picocell) arises, the high-mobility user is rescheduled to communicate only in the coordinated resources without allowing a picocell handover despite the handover condition to prevent HFs and to minimize ping-pongs.
  • low-speed users are allowed to make a handover to picocells.
  • the handover parameter set is selected more flexibly and effectively by benefiting from interference coordination, which improves the overall handover performance due to combined use of interference coordination and handover parameter optimization.
  • mobility states of the users are estimated utilizing the topology of the network, such as the number of low-power nodes that are present in the coverage area of a macrocell.
  • Figure 1 illustrates a heterogeneous network and trajectories of three different users with different mobility states.
  • Figure 2 illustrates the resource coordination for a conventional heterogeneous network.
  • Figure 3 illustrates the resource coordination for a heterogeneous network in accordance with an embodiment of the disclosure.
  • Figure 4 is a flowchart for a mobility-based interference coordination technique for handover optimization.
  • Figure 5 is a chart of handover performance without mobility-based interference coordination.
  • Figure 6 is a flowchart for a mobility state estimation technique in accordance with an embodiment of the disclosure.
  • Figure 7 is a block diagram of a base station and a UE configured to practice mobility-based interference coordination in accordance with an embodiment of the disclosure.
  • a macroccll user equipment UE
  • Determining when it is appropriate to handoff to a picocell depends upon the resource allocation for the heterogeneous network - in particular, whether the macrocells and picocells are sharing resources (co-channel) or whether they operate entirely on dedicated resources (split-channel). Since co-channel operation is more bandwidth efficient, the following discussion will assume that the macrocells and the picocells share co-channel resources.
  • the macrocell also has some dedicated resources (not shared with the picocell) that are denoted as coordinated resources.
  • the macrocell UE exploits both the coordinated and uncoordinated resources. But as a high- mobility lnacrocell UE encroaches on the coverage area of a picocell, the high-mobility macrocell UE may be rescheduled to use only the coordinated resources such that the high- mobility UE is not handed off to the picocell. Conversely, as a low-mobility macrocell UE encroaches the coverage area of a picocell, the low-mobility macrocell UE may be handed off to the picocell.
  • the handover performance method disclosed herein includes embodiments in which the handover state (whether or not a handover is indicated) for the UE is continually monitored. If the monitoring indicates that a rescheduled UE has no handover indications (it is traveling in the macrocell in an area without any picocell coverage), the non-coordinated resources are tested to determine if these resources are satisfactory. If the non-coordinated resources are satisfactory, the UE is scheduled to use both the coordinated and non-coordinated resources regardless of the current mobility state for the UE. As used herein, a UE is deemed to be rescheduled if it is communicating only over the coordinated resources and to be scheduled if it is communicating over the coordinated and uncoordinated resources.
  • FIG. 1 shows an example heterogeneous network.
  • eNBs evolved node B
  • the heterogeneous network includes a plurality of picocell base stations (picocell nodeB's (PNBs)) 104 that are placed inside the coverage areas of the macrocell eNBs 102. If no range expansion is applied, each picocell 104 has a coverage area 106, whereas with range expansion, each picocell has an expanded coverage area 108.
  • Three user equipments UE-1, UE-2, and UE-3 are initially within the macrocell controlled by eNB 101.
  • Both UE-1 and UE-2 are high-mobility UEs whereas UE-3 is a low- mobility UE.
  • UE-1 and UE-2 are traveling at a relatively high speed whereas UE-3 is traveling at a relatively low speed.
  • UE-2 and UE-3 follow paths 110 and 120, respectively, that take them through the coverage area of a picocell 1 OS.
  • UE-1 travels a path 115 that is outside of picocell coverage areas.
  • UE-1 should thus have no handover conditions and continue to operate as an unscheduled user in both the coordinated and non-coordinated macrocell resources.
  • UE-2 will experience a handover indication as it travels through picocell 105.
  • UE-2 is rescheduled to communicate with base station 101 only in the non-coordinated resources. Since UE-3 is a low-mobility user, it can be handed off to picocell 1 OS as it enters the picocell coverage area.
  • all the UEs typically use the same set of handover parameters while making a handover to a different cell.
  • using the same set of parameters for all cells and for all users may increase the number of HFs and/or ping-pongs. More specifically, if a UE is in a high-mobility state, a smaller time-to-trigger should be utilized to reduce the probability of a HF as the UE's signal to interference plus noise ratio becomes significantly degraded.
  • a smaller value of TTT would be preferable to decrease HFs, since the SINR degradation in a smaller cell may happen at a faster rate compared to a larger cell.
  • various conventional approaches adapt handover parameters using the mobility state information, measurement results, or the coverage area of cells into which the handover will be performed. This adaptation attempts to optimize handover performance.
  • Inter-cell interference coordination in combination with handover parameter optimization
  • An example set of N resources are shown in Figure 2 that are allocated in a conventional fashion. While the following discussion assumes that the N resources are time slot resources, the interference coordination disclosed herein is widely applicable to frequency allocation (e.g., component carriers), code allocation (e.g., codes as in CDMA systems), or spatial domain allocation (e.g., beam directions).
  • the conventional resource allocation shown in Figure 2 has the macrocell leave certain resources 212 dedicated to the picocell.
  • the picocell occupies all its available resources 215.
  • the picocell may schedule its own victim users (e.g., its range-expanded users) in its coordinated resources (in this case, slots R 3 and R 4 ).
  • the macrocell is excluded from resources 212, it only occupies a remaining set of resources 205.
  • the resource allocation shown in Figure 3 has its own coordinated resources 210 for the macrocell.
  • the picocell is excluded from a corresponding set of resources 220 (slots R N-1 and R N ). This is advantageous because high-mobility macrocell users may also be victim users in a heterogeneous network environment due to handover failures and ping-pongs.
  • the interference coordination approach disclosed herein reschedules the macrocell users into just the coordinated resources. Note that in a general setting, there may be more than two sets of resources with different SINR characteristics, which may e.g. be due to use of different coordinated resource patterns in different cells.
  • This interference coordination process begins with an estimation of the mobility state for a UE. While there are a number of conventional ways on how the mobility state of a UE can be estimated (where most approaches rely on handover count of a UE due to its simplicity), the interference coordination approach of the present disclosure may use an improved mobility-state estimation method for heterogeneous network scenarios as will be described further herein. Alternatively, a conventional mobility-state estimation can be performed. For example, it is known to use Doppler spread information to estimate a UE's mobility state.
  • the mobility state can be estimated in a step 300 at the UE-side (e.g., for idle mode UEs), network-side (e.g., for active mode UEs), or both.
  • the mobility state of a UE may be communicated to the cNB in the form of a single bit that indicates whether the UE is low-mobility or high-mobility.
  • the UE also sends to the serving eNB the signal measurements that are obtained from candidate cells 310 so that handover decisions can be made either at the eNB or higher up in the network.
  • the UEs are configured to send measurements collected from only one set of resources; e.g., from uncoordinated resources 205 or coordinated resources 210, depending on where it is configured to collect measurements and receive its downlink transmissions.
  • the eNB decides whether a handover is necessary for the UE in a step 320, using methods similar to those used in the prior art. If a handover is indicated for the UE, the eNB also checks the mobility state of the UE in a step 330. If the UE is a low-mobility UE, the eNB initiates the legacy handover process to the target node in a step 380. On the other hand, if the UE is a high-mobility UE, it may face with a HF before completing such a handover, or may observe ping-pongs.
  • high-mobility UEs are rescheduled in the coordinated resources of macrocell in a step 340 without any handover and report their measurements only from the coordinated resources (e.g., from resources 210). Therefore, even if the macrocell UE travels into the coverage area of a picocell, it does not observe interference from the picocell, preventing any HFs due to high picocell interference. Moreover, since a potentially unnecessary handover is avoided (due to very short time of stay of the UE inside the picocell coverage), ping-pongs are prevented. Note that this rescheduled UE may also cause uplink interference to the picocell base station while inside the coverage of the picocell so that similar interference coordination mechanisms discussed in this disclosure can be applied to prevent such uplink interference.
  • the eNB first checks whether the UE is rescheduled in a coordinated resource group in a step 360. If the UE is not rescheduled in a coordinated resource group, no handover or resource scheduling of the UE is performed in a step 350 such that the eNB takes no action about this UE until the next set of measurements and mobility state information arrives at the eNB. On the other hand, if the determination in step 360 shows that the UE is rescheduled in a coordinated resource group, that UE should release the coordinated resources because there is no handover condition. The lack of a handover indication shows that UE is no longer a potential victim of a future handover
  • Whether and how such coordinated-resource UEs should release the coordinated resources depends on two issues: 1) a determination of whether the UE is a low-mobility or high-mobility UE in a step 370, and 2) a measurement report in the non-coordinated resources in steps 365 and 375. If the UE is a low-mobility UE, that would mean that the measurements in step 300 were solely in the coordinated resources (because the UE was shown to have been rescheduled in step 360 to just the coordinated resources).
  • Measurements in just the coordinated resources in step 360 could thus miss the availability of picocell coverage.
  • the UE can not simply be scheduled in the non-coordinated resources due to a potential HF.
  • the determination in step 375 is negative, a legacy handover process should be initiated to the target node in step 380. Due to the low mobility state of the UE, it can enjoy the better SINR by connecting to the low-power target node without observing HFs or ping-pongs.
  • the measurements in the non-coordinated resources are satisfactory and the UE is a low-mobility UE, it can be scheduled in the non-coordinated resources in a step 390 without triggering any handover.
  • step 370 indicates that the rescheduled UE (as used herein, a rescheduled UE refers to one that is using just the coordinated resources), the eNB also checks the rescheduled UE (as used herein, a rescheduled UE refers to one that is using just the coordinated resources).
  • step 365 involves keeping the rescheduled UE rescheduled.
  • the UEs typically report measurements only fiom a single resource group set. For example, if a UEs is rescheduled to just use coordinated resources, such a rescheduled UE does not normally report the measurements from the non- coordinated resources in order to prevent messaging overhead.
  • rescheduled UEs may be specifically configured by the eNB to obtain and transmit measurement reports in non- coordinated resources. Such measurements may occur in periodical intervals, or, as the need arises (e.g., when the coordinated resources of the eNB become highly loaded by high- mobility users).
  • a UE that is rescheduled in the coordinated resources may continue using these resources until the active call terminates.
  • the A3 offset corresponds to the hysteresis used during the handover process, and the Reference Signal Received Power (RSRP) L3 filter value is used to average out the impact of fast fading in signal measurements.
  • the handover performance results are shown in Figure 5 using the handover parameters from Table 1.
  • the range-expanded picocell UEs are scheduled at the coordinated resources of picocell (where no macrocell transmission occurs). On the other hand, there is no interference coordination for the macrocell UEs.
  • the handover performance can be improved at the cost of releasing some resources at the picocells.
  • the threshold that classifies a UE as low-mobility or high-mobility is taken as 60 km/hour. Then, if the true velocity of a UE is larger than 60 km/hour, it is rescheduled in coordinated resources of the macrocell, and no HFs or ping- pongs are observed among the macrocell and the picocell. For users with velocities lower than 60 km hour, if handover parameter set-3 is used in this scenario, maximum HF rate is 5% (decreases for higher velocities), while ping-pong rates are between 5% and 10%.
  • handover parameter set-2 yields slightly larger HF rates, but yields almost no ping- pongs. Therefore, both ping-pong and handover performance can be improved with the proposed approach compared to using interference coordination only at the picocells as in Figure 5. Moreover, using set-2 would be preferable when ICIC is applied, while set-3 (which yields lower number of HFs at higher velocities) would be preferable with no ICIC. Hence, the use of interference coordination may change the ideal set of handover parameters for the best handover performance.
  • the interference coordination and improved handover performance for heterogeneous networks disclosed herein requires the release of certain resources at the picocells, which introduces some degradation in the performance (e.g., capacity, measurement report quality due to less averaging, etc.) of picocell users.
  • resources at the picocells which introduces some degradation in the performance (e.g., capacity, measurement report quality due to less averaging, etc.) of picocell users.
  • releasing only a small portion of a picocell's resources may yield important gains in the performance of high-velocity macrocell users.
  • An adaptive resource partitioning where the amount of resources released at the picocell varies depending on the number of high-velocity users in the macrocell may also be possible.
  • the eNB may jointly optimize/configure the handover parameter sets and the interference coordination ratio and pattern.
  • the eNB may con igure the picocells not to release any resources (e.g., over the X2 interface in LTE).
  • an optimum handover parameter set also depends jointly on whether the ICIC is utilized or not at a macrocell.
  • the blank resource pattern used by the picocell is designed in a way such that it minimizes the interference to crucial resources of macrocell.
  • an LTE picocell may align its blank subframes with the primary/secondary synchronization channel, physical broadcast channel, and system information block of the macrocell.
  • the blank subframe pattern at picocell may also be designed jointly with one or more macrocells. Improvement of Mobility State Estimation in Heterogeneous Networks:
  • Performance of the proposed interference coordination approach relies on the accuracy of the mobility state estimation technique (step 300 in Figure 4).
  • a mobility state estimation threshold should ideally be modified based on the number of picocells and their range expansion bias values inside a macrocell.
  • An example look-up table is shown in Table 2, which shows the dependence of mobility state threshold on number of picocells per sector and the range expansion bias.
  • the look-up table may also involve parameters other than the number of picocells per sector and the range expansion bias.
  • the table shows how the handover count threshold (which if exceeded, is used to denote a UE as a high-mobility UE) increases as the number of picocells is increased from zero to four. In addition, the table shows how the handover count threshold is increased in response to picocell range expansion for those macrocells having three or more picocells.
  • the duration of the sliding time window within which the total number of handovers are counted may also be adjusted in some embodiments. This would enable quicker mobility state estimates in denser heterogeneous network deployments, since smaller window duration to count the number of handovers would be sufficient to have a reliable mobility state estimate due to the larger number of handovers.
  • FIG. 6 A flowchart that summarizes how a lookup table such as Table 2 can be used for improving the mobility state estimation of UEs is shown in Figure 6.
  • the UE receives the relevant cell-specific information such as the number of picocells and their range expansion bias configurations within a given sector in a step 302.
  • the serving eNB may also directly calculate the threshold value and communicate the threshold to the UE.
  • These cell-specific data may be transmitted by the system information broadcast of the serving eNB.
  • an appropriate mobility-state threshold value is selected from the look-up table in a step 304 (along with a selection of an appropriate time window).
  • the UE estimates its mobility state based upon the selected threshold value and notifies the eNB of the estimated mobility in a step 306.
  • the look-up table may also return the duration for the sliding time window.
  • An example value of a sliding window in a homogeneous network may be 30 seconds, but for heterogeneous network environments, smaller time windows can be used.
  • the eNB decides on the mobility state of the UE in a step 308. Note that this procedure may be applied both for idle-mode and active-mode UEs. If the UE is in active mode, the network already has the information on the number of handovers for the given UE.
  • the mobility state may be directly estimated at the eNB, which removes the requirement for the UE to transmit its mobility state to the eNB.
  • the mobility state may be estimated both at the UE- side and network-side, to obtain a more reliable mobility state decision at the e B.
  • FIG. 7 A block diagram for a macrocell base station 500 and a UE 550 that implements the proposed mobility-based interference coordination method is shown in Figure 7.
  • the UE is initially connected to the serving eNB. On the other hand, it also receives signal
  • the UE receives a downlink signal 640 from the serving eNB as well as downlink signals 605, 615, and 625 from the nearby network nodes. Based on these measurements, the UE checks whether certain conditions are satisfied, e.g., if the link quality of serving node 500 is worse than the link quality of one of the target nodes 600, 610. 620 plus a given threshold.
  • This measurement report processing is performed in a measurement processing engine in the UE in an analogous fashion to prior art report processing and communicated to a handover decision engine 535 in the serving eNB. Note that the logical links between different engines are shown in dashed lines, while the information exchange actually happens through scheduling of the corresponding messages at the UE and the eNB, and transmission/reception through antennas 515 and 555.
  • the UE may estimate its mobility state using a mobility state estimation engine 585, such as through tracking the total number of handovers within a given sliding time window and using the look-up table to adjust its mobility state estimation parameters.
  • the eNB may broadcast mobility state estimation parameters in its system information broadcast, which can be used by the UE for improved mobility state estimation.
  • Final decision for the mobility state of a UE is made at a mobility state decision engine 540 of the eNB. Instead of getting a mobility state estimate from the UE, the eNB may also directly utilize a similar approach for counting the number of handovers and deciding on the mobility state of the UE. Once an estimate for the mobility state of a UE is available, it is used jointly with the received measurement reports for deciding whether a handover is needed for the UE.
  • Hie base station receives upstream communication from an operator network 545 as known in the base station arts.
  • An interference coordination engine 530 in the eNB can configure the ratio of coordinated resources that would be required for mobility-based interference coordination. Depending on the number of high-mobility UEs, it may configure more or less resources as blank in the picocells (e.g., through the X2 interface in LTE).
  • a scheduler 525 schedules the UEs in coordinated or non-coordinated resources based on the measurement reports and mobility state information, such as discussed with regard to Figure 4.
  • a scheduler 575 in the UE responds accordingly such that the UE is either rescheduled or uses both the coordinated and uncoordinated resources.
  • the base station includes a signal generator 505 and a transceiver 510 for its RF communications with the UE.
  • the UE includes both a signal generator 570 and a transceiver 565 for its RF communications with both the macrocell base station and the picocell base station.
  • the measurements are collected only from those resources in the eNB, before being processed in a measurement processing engine 580 of the UE.

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

L'invention porte sur un réseau hétérogène comprenant des macrocellules et des picocellules à fonctionnement dans le même canal pour des utilisateurs aussi bien à faible mobilité qu'à forte mobilité. Le fonctionnement dans le même canal s'effectue sur des ressources aussi bien coordonnées que non coordonnées. Durant un fonctionnement normal sans aucune condition de transfert intercellulaire, l'utilisateur à forte mobilité communique avec une station de base macrocellulaire dans les ressources aussi bien coordonnées que non coordonnées. Mais si une condition de transfert intercellulaire vers un nœud basse puissance (une picocellule) apparaît, l'utilisateur à forte mobilité est replanifié pour communiquer seulement dans les ressources coordonnées sans autoriser un transfert intercellulaire vers la picocellule en dépit de la condition de transfert intercellulaire afin de prévenir des échecs de transfert intercellulaire (HF) et de réduire au minimum des phénomènes de ping-pong. D'autre part, des utilisateurs à faible mobilité sont autorisés à effectuer des transferts intercellulaires vers des picocellules.
PCT/US2012/048690 2011-10-12 2012-07-27 Procédé d'amélioration des performances de transfert intercellulaire dans des réseaux sans fil hétérogènes WO2013055430A2 (fr)

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US9544827B2 (en) 2011-09-12 2017-01-10 Ntt Docomo, Inc. Enhanced local access in mobile communications with FDD resource allocation
US9584976B2 (en) 2015-06-24 2017-02-28 The Florida International University Board Of Trustees Specific velocity estimation of wireless network devices
EP3183929A4 (fr) * 2014-08-20 2018-04-18 Telefonaktiebolaget LM Ericsson (publ) Procédé et appareil destinés à coordonner des ressources
US10454829B2 (en) 2011-06-01 2019-10-22 Ntt Docomo, Inc. Enhanced local access in mobile communications using small node devices

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