WO2009135983A1 - Procédé et système de réduction de charge de rétroaction dans des systèmes sans fil mobiles - Google Patents

Procédé et système de réduction de charge de rétroaction dans des systèmes sans fil mobiles Download PDF

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Publication number
WO2009135983A1
WO2009135983A1 PCT/FI2008/050247 FI2008050247W WO2009135983A1 WO 2009135983 A1 WO2009135983 A1 WO 2009135983A1 FI 2008050247 W FI2008050247 W FI 2008050247W WO 2009135983 A1 WO2009135983 A1 WO 2009135983A1
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WIPO (PCT)
Prior art keywords
user terminals
user terminal
cluster
information
propagation information
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PCT/FI2008/050247
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English (en)
Inventor
Nenad Veselinovic
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Elektrobit Wireless Communications Ltd.
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Application filed by Elektrobit Wireless Communications Ltd. filed Critical Elektrobit Wireless Communications Ltd.
Priority to PCT/FI2008/050247 priority Critical patent/WO2009135983A1/fr
Publication of WO2009135983A1 publication Critical patent/WO2009135983A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information

Definitions

  • This invention relates to a method and a system for reducing feedback load in mobile environments. Furthermore, the invention relates to a network element and a user terminal configured to reduce feedback load in mobile environments.
  • Modern wireless communication systems deploy feedback of some form in order to achieve theoretical performance limits. This feedback is used for functions like link adaptation, power control, multiple input multiple output (MIMO) mode selection, and other such functions that are aimed to improve the system capacity, coverage or throughput.
  • the feedback concerns mostly information about propagation conditions in a radio channel between the mobile station (MS) unit and the serving base station (BS) unit.
  • each MS performs radio channel propagation measurements, such as signal strength of the serving BS, and sends this measured information on request in the uplink (UL) to the serving BS on a feedback channel.
  • Typical examples of channel propagation measurements performed by the MS are receive signal strength indicator (RSSI) and carrier-to-interference-plus-noise ratio (CINR) measurements that are reported to the BS on the feedback channel. Based on the feedback received by the BS it also receives information about the MS mobility and propagation. The BS may then start taking measures with regard to improve the propagation conditions in the radio channel.
  • RSSI receive signal strength indicator
  • CINR carrier-to-interference-plus-noise ratio
  • the amount of feedback information cannot be excessively large. If it is, then its positive effects in terms of improved channel capacity and throughput may be overweighted by the capacity needed to transmit the feedback channel. In some deployment scenarios, like e.g. mobile systems, this may become the case.
  • the number of feedback channels in an adaptive wireless communications system may become rather large, since at least one channel is needed per MS. Furthermore if the MS is moving at very high speed, the feedback channel needs to be of a high capacity in order to get up to date channel propagation measurements in the BS. This may result in significant degradation of the UL capacity of a wireless system, preventing possible usage of such a system for symmetric applications, like voice-over-IP.
  • the wireless standards usually give the framework with which it is possible to request MSs to transmit radio channel measurement on the feedback channel with a certain period.
  • the amount of feedback messages can be reduced by deploying larger feedback period.
  • a network element and a user terminal that are able to reduce the amount of feedback signalling in mobile environments.
  • the base station is configured to
  • each of said at least one delegate user terminal to report periodically feedback information in a time period depending on current mobility information of each of said at least one cluster
  • the base station is further configured to form at least one cluster of user terminals by - measuring time correlation of propagation information received from a user terminal belonging to a plurality of user terminals in order to define correlated propagation information of said user terminal, and
  • the user terminal belonging to the plurality of user terminals is configured to form a cluster of user terminals by - comparing locally said user terminalDs own propgation information and propagation information received from any adjacent user terminal belonging to the plurality of user terminals, and
  • a network element that comprises
  • cluster controller configured to form at least one cluster of user terminals belonging to the plurality of user terminals based on propagation information received from user terminals belonging to the plurality of user terminals
  • - selecting means configured to select at least one delegate user terminal from user terminals belonging to each of said at least one cluster to report feedback information
  • - requesting means configured to request each of said at least one delegate user terminal to report periodically feedback information in a time period depending on current mobility information of each of said at least one cluster
  • the network element comprises the cluster controller that is configured to
  • a user terminal belonging to a plurality of user terminals that comprises
  • - measuring means configured to measure propagation information relating to a link between the user terminal and a base station, and relating to propagation of the user terminal
  • a cluster controller configured to form a cluster of user terminals belonging to the plurality of user terminals based on propagation information received from user terminals belonging to the plurality of user terminals.
  • each of said at least one delegate user terminal to report periodically feedback information in every first time period, the first time period depending on current mobility information of each of said at least one cluster
  • the invention can be applied in any wireless system whose nodes require use of feedback channel to perform certain decisions. It can be applied as a proprietary solution to be deployed in the network element of the node, e.g. in the BS or in the user terminal functioning as a node.
  • propagation information based on user terminal Ds channel measurements and/orvelocity and/or position and/or direction and/or pre-filtered information and/or advance information and/or pre- calculated scenarios effectively reduces the amount of feedback signalling.
  • figure 1 a depicts an example of a system according to an embodiment of the invention
  • figure 1 b depicts a graph of channel propagation measurements of two links in a system according to an embodiment of the invention shown in figure 1 a,
  • FIGS. 2a and 2b depict a system according to an embodiment of the invention
  • FIG. 3a and 3b depict a system according to an embodiment of the invention
  • FIGS. 4a and 4b depict a system according to an embodiment of the invention
  • figure 5 depicts a block diagram of an apparatus according to an embodiment of the invention
  • FIG. 6 depicts a block diagram of an apparatus according to another embodiment of the invention.
  • figure 7 depicts a flow chart of a method according to an embodiment of the invention.
  • figure 8 depicts a flow chart of a method according to an embodiment of the invention
  • figure 9 depicts a flow chart of a method according to an embodiment of the invention.
  • figure 10 depicts a flow chart of a method according to an embodiment of the invention.
  • FIG. 1 a shows an example of a system according to an embodiment of the invention in which feedback load can be reduced in a mobile environment.
  • the system comprises a BS 10 and a first and second user terminals 11 , 12 communicating via the BS 10 with each other or any other user terminal in the wireless communication system.
  • the first and second user terminals 11 , 12 are located in different moving objects, e.g. vehicles 15, 16, travelling ahead, e.g. on the road, and therefore they are operating in the mobile environment.
  • two radio link connections 1 , 2 are established so that the radio link connection 1 is provided between the first user terminal 11 and the BS 10, and the radio link connection 2 is provided between the second user terminal 12 and the BS 10.
  • the first user terminal 11 performs measurements on propagation conditions through the link 1 , e.g. radio channel measurements such as CINR1 , and the second user terminal 12 through the link 2, e.g. radio channel measurements such as CINR2.
  • the first and second user terminals 11 , 12 send the measured propagation information, e.g. based on CINR1 and CINR2, to the BS 10 on feedback channels of the communication links 1 , 2.
  • Figure 1 b shows propagation information of the links 1 , 2 with respect to time. It can be seen that the propagation information of the link 1 , e.g. CINR1 , and the propagation information of the link 2, e.g. CINR2, are correlated in time.
  • the average measures of propagation informations e.g. CINR1 and CINR2 are very correlated and time correlation between the average measures can be calculated. If the time difference Dt between measured propagation conditions of the links 1 , 2, e.g. between CINR1 graph and CINR2 graph, is eliminated, then the CINR1 graph and CINR2 graph are placed one on the other. While the both graphs have a similar shape, one comes to a conclusion that the similar measured propagation conditions of the links 1 , 2 show that the first user terminal 11 and the second user terminal 12 have similar mobility pattern.
  • the user terminals in the wireless communication system have similar or same mobility patterns
  • the user terminals are located near each other and/or they have similar type propagation conditions. This is the case when a plurality of user terminals are located e.g. in a bus, train, car or other vehicles travelling ahead or dedicated communication devices are moving ahead in cars along highway, pedestrians having user terminals are walking along the street in the same direction, etc.
  • User terminals having similar or same mobility patterns can therefore be seen to form a group or cluster of user terminals.
  • Due to correlated mobility patterns of the user terminals also their large scale propagation conditions, e.g. path loss, are correlated in time. This correlation in turn will have an effect on the measurements that are computed in the user terminals and fed back to the BS.
  • the BS then makes certain decisions concerning e.g. link adaptation, power control and/or MIMO mode selection based on this feedback information received through the feedback channel from the user terminals.
  • D user terminal platforms are known to refer to wide variety of consumer electronic platforms such as, but not limited to, mobile stations (MS), subscriber stations (SS), user equipment (UE), access terminals (AT), Internet terminals, terminal equipment, mobile devices, dedicated communication devices, gaming devices, personal computers, personal digital assistants (PDA), set-top-boxes, etc.
  • DBase station D refers to a generated equipment set that provides connectivity, management and control of user terminals, and is associated with a mesh network station as a node.
  • Fig. 2a shows a system according to an embodiment of the invention comprising a BS 10 and a plurality of user terminals 101 -107.
  • the system comprises a database 20 capable of storing and retrieving data to/from the BS 10.
  • Every user terminal 101-107 performs measurements on propagation conditions of the radio link between each of the user terminals 101 -107 and the BS 10 in order to produce propagation information.
  • On request of the BS 10, during time period T1 each of the user terminals 101-107 send its own measured propagation information to the BS 10 using its own feedback channel. Then, during the time period T1 , the BS 10 measures correlation of propagation information received from each of the user terminals 101 -107.
  • the BS 10 classifies the user terminals 101-107 into clusters A and B, as shown in fig. 2b, so that user terminals having similar or same correlated propagation information are classified into the same cluster of user terminals.
  • a cluster is formed if at least two user terminals of the plurality of user terminals 101-107 have similar or same correlated propagation information.
  • certain threshold values can be used to define whether or not a received propagation information is considered to be within similar or same correlated propagation information. According to fig.
  • clusters A and B are formed, where the cluster A comprises user terminals 101 -103 each having propagation information that correlates similar or same way to each other and the cluster B comprises user terminals 106-108 each having propagation information that correlates similar or same way to each other. Due to their deviating propagation information the BS 10 does not classify user terminals 104- 105 into any of the clusters A, B or form a new cluster with each other. Reason for this is that propagation information of the user terminal 104 deviates too much from propagation information of the user terminal 105 and average propagation information of the cluster A or the cluster B. Average propagation information of the cluster relates to a value of propagation information of all user terminals belonging to the cluster, and it can be e.g.
  • a threshold limit can be determined in the BS 10 in order to define whether or not propagation information of the user terminal 101 -107 is within correlated propagation information of the cluster, i.e. whether or not the user terminal 101 -107 has similar or same propagation information as the user terminals belonging to the cluster.
  • the BS 10 selects one or more delegate user terminals 102, 107 among the user terminals belonging to each cluster A, B in order to represent the whole cluster, i.e. all the user terminals belonging to the cluster.
  • Propagation information of the delegate user terminal 102, 107 represents average propagation information of the cluster A, B.
  • the BS 10 requests only the delegate user terminal 102, 107 to feedback information relating to propagation conditions in the radio channel, and this feedback information represents feedback information of all user terminals 101 -103, 106- 107 belonging to the cluster A, B.
  • the BS 10 determines a time period for requesting feedback information from the delegate user terminals 102, 107.
  • This time period defines how often the delegate user terminals 102, 107 should report propagation condition measurements on their feedback channel to the BS 10.
  • This time period depends on current mobility information of the cluster A, B, e.g. speed of the cluster.
  • the speed of the cluster can be e.g. speed of a bus that transports passages having user terminals. These user terminals inside the bus form a cluster of user terminals.
  • the time period for reporting feedback information has to be sufficient for the decisions to be made accurately given the current speed of the cluster.
  • the user terminal 104, 105 that is not classified to any cluster shall report propagation condition information on its feedback channel to the BS 10 as usually.
  • the amount of total feedback capacity needed is reduced because only the delegate user terminal 102, 107 in each cluster A, B reports the feedback information of the cluster A, B.
  • the other user terminals 101 , 103, 106 within the cluster A, B than the delegate user terminals 102, 107 must also comply with Dcluster propertiesD, i.e. propagation or mobility information of the other user terminals 101 , 103, 106 should remain within limits defined for the cluster they belong to. This is checked by detecting periodically feedback information of the other user terminals 101 , 103, 106 as well. Therefore, the BS 10 determines another time period for requesting feedback information from the other user terminals 101 , 103, 106 within the cluster A, B.
  • This another time period defines how often the other user terminals 101 , 103, 106 should report propagation condition measurements on their feedback channel to the BS 10.
  • This another time period can be different, e.g. longer, from the time period defined for the delegate user terminals to report feedback information.
  • This another time period depends on current mobility information of the other user terminal 101 , 103, 106 with respect to the cluster A, B, e.g. speed of the other user terminal 101 , 103, 106 with respect to the cluster A, B.
  • the another time period depends on propagation information of the other user terminal 101 , 103, 106 with respect to the cluster A, B.
  • any of the other user terminals 101 , 103, 106 becomes incompatible with the cluster properties, said user terminal is released from the cluster and starts sending feedback information more often in a usual way (until it joins a new cluster).
  • New candidate user terminals for the clusters are recruited so that the BS 10 requests, during time period T2, each of the candidate user terminals to send measured propagation information to the BS 10 on feedback channel. Then after measuring correlation of propagation information received from each of the candidate user terminals the BS 10 classifies the candidate user terminals in clusters.
  • Fig. 3a shows a system according to an embodiment of the invention comprising a BS 10 and a plurality of user terminals 101 -107.
  • the system comprises a database 20 capable of storing and retrieving data to/from the BS 10.
  • Each user terminal 101-107 performs measurements on propagation conditions of the radio link between each of the user terminals 101 -107 and the BS 10 in order to produce propagation information.
  • neighbouring user terminals are configured to exchange their propagation information sending them on feedback channel via the BS 10, using communication between user terminal and the BS.
  • neighbouring user terminals are configured to exchange their propagation information directly between each other instead of sending them on feedback channel to the BS 10.
  • the communication between adjacent user terminals can be accomplished using e.g.
  • the adjacent user terminals comprise means for exchanging propagation information, e.g. a short distance wireless transmitter and/or receiver.
  • the user terminal 103 requests its adjacent user terminals 101 , 102, 104, 105 to exchange propagation information and receives propagation information from those adjacent user terminals 101 , 102, 104, 105. Then the user terminal 103 compares each of the received propagation information to its own propagation information. If any of the adjacent user terminals 101 , 102, 104, 105 have similar or same propagation information than the user terminal 103, the user terminal 103 makes a decision to form a cluster together with said adjacent user terminal. In an example of fig.
  • the neighbouring user terminals 101 -103 have similar or same propagation information and therefore the user terminal 103 classifies the neighbouring user terminals 101 - 103 in the same cluster A as shown in fig. 3b.
  • the adjacent user terminals 101 , 102 when exchanging their propagation information are found to have similar or same propagation information. Therefore the adjacent user terminals 101 -103 have correlated propagation information.
  • a cluster is formed if at least two adjacent user terminals have similar or same correlated propagation information. Because propagation information of other adjacent user terminals 104, 105 deviates from propagation information of the user terminal 103 they are not classified to this same cluster. After similar functionality of the adjacent user terminals as described above there is formed as shown in fig.
  • a cluster B comprising adjacent user terminals 106, 107.
  • the BS 10 selects one or more delegate user terminals 102, 107 among the user terminals belonging to each cluster A, B, requests each of the delegate user terminal to report feedback information and detects the other user terminals within the cluster A, B as disclosed earlier in connection with figs 2a and 2b.
  • Fig. 4a shows a system according to an embodiment of the invention comprising a BS 10 and a plurality of user terminals 101 -107.
  • the system comprises a database 20 capable of storing and retrieving data to/from the BS 10.
  • Each user terminal 101-107 performs measurements on propagation conditions of the radio link between each of the user terminals 101 -107 and the BS 10 in order to produce propagation information.
  • a combination of the BS based and the user terminal based classification of user terminals is used.
  • a cluster A comprising user terminals 101 -103 is formed as described in connection with figs 2a and 2b and a cluster B comprising user terminals 106-107 is formed as described in connection with figs 3a and 3b.
  • the BS 10 is configured to request the user terminal to send feedback information of the measured propagation information of the user terminals 101-107 on a feedback channel to the BS 10.
  • the feedback channel of the user terminal 101-107 can be determined by a protocol stack of any used wireless communication standard or it can be determined by means of a proprietary protocol running over the existing protocol stack. The proprietary protocol stack would need to be implemented in both the BS 10 and the plurality of the user terminals 101 -107.
  • the BS 10 is configured to measure time correlation between propagation information received from the user terminals 101 -107 for a certain time period.
  • neighbouring user terminals are configured to exchange their propagation information and compare correlation of propagation information of adjacent user terminals with each other.
  • a combination of above embodiments can be used.
  • This correlated propagation information form a basis for classifying the user terminals 101-107 into clusters comprising user terminals having similar or same propagation information.
  • the system is configured to measure or compare directly correlation of propagation information of the user terminals 101 -107 by observing channel measurements of candidate user terminals to form a cluster.
  • These channel measurements may comprise CINR and/or RSSI and/or other signal strength related measurements. If it is observed that results achieved from the channel measurements of candidate user terminals are the same then these candidate user terminals join the same cluster. If it is observed that results achieved from the channel measurements of candidate user terminals comply with certain same tendency, e.g. CINR decreasing or increasing at similar rate, then correlation of the results of the channel measurements are measured in the BS or compared in the user terminal communicating with the adjacent user terminal in order to define correlated propagation information of each of the candidate user terminal. Those candidate user terminals that have similar or same propagation information with respect to correlated propagation information are joining the same cluster.
  • the system is further configured to detect position, velocity and/or direction of the user terminal with respect to other user terminals belonging to the plurality of the user terminals or with respect to the BS or with respect to geographical location, e.g. a highway.
  • the system is configured to produce propagation information of the user terminal comprising information received through sensor-based measurements.
  • the means for detecting may comprise a position, motion and/or direction sensor, and/or navigation transmitter-receiver, or other such means.
  • the system further comprises protocol stack means configured to allow communication of feedback information between the BS and the user terminals.
  • Correlation of propagation information of the user terminals 101-107 is measured or compared, as described earlier above, in order to define correlated propagation information that is a basis for classifying candidate user terminals in clusters.
  • the correlated propagation information may comprise information on position, velocity and/or direction as well as information on channel measurement results, e.g. CINR, discussed above.
  • the system further comprises means for processing pre-filtered information obtained as outputs of data fusion process in order to produce propagation information of user terminals 101 -107 that is used to form clusters of user terminals.
  • the pre-filtered information may comprise information about CINR, velocity, direction and/or position, etc.
  • the user terminals 101 -107 are configured to send information obtained by data fusion process on request. Correlation of propagation information of the user terminals 101 -107 is measured or compared in order to define correlated propagation information that is a basis for classifying candidate user terminals in clusters.
  • the use of pre-filtered information obtained by data fusion process simplifies correlation measuring and comparison process and enables lower amount of feedback signalling than e.g. information obtained by CINR or velocity, direction and position separately.
  • the system further comprises means for processing advance information supplied beforehand in order to produce propagation information of user terminals 101-107 that is used to form clusters of user terminals.
  • the user terminal 101-107 is configured to send a navigation route of the user terminal on request.
  • the navigation route may also be pre-built information such as route information in public transportation systems.
  • Correlation of propagation information of the user terminals 101-107 is measured or compared in order to define correlated propagation information that is a basis for classifying candidate user terminals in clusters.
  • Propagation information comprising advance information, e.g. route information, helps to predict for how long the clusters will be unchanged. For example, when the user terminal in a car gets off the highway it also leaves the cluster and starts sending feedback information more often until it joins a new cluster. This allows the other user terminals than the delegate in a cluster further reduce the amount of their feedback signalling.
  • the user terminal 101 -107 is configured to send information about expected routes, instantaneous speeds, and other such information to the BS 10 prior to the journey in order to produce propagation information of the user terminal.
  • the BS 10 comprises means for pre-calculating to calculate deployment scenarios, e.g. mobility patterns, for the user terminals and the deployment scenarios are stored as reference values into the database 20 communicating with the BS 10. Further the means for pre-calculating may calculate deployment scenarios comprising temporal propagation information profiles for user terminals and the deployment scenarios are stored as a set of temporal propagation information into the database 20 communicating with the BS 10.
  • the set of temporal propagation information profiles for the user terminal may comprise different types of profiles based on e.g.
  • the BS 10 forms clusters according to this propagation information.
  • the user terminals including or excluding the delegate user terminal in a cluster are configured to send feedback information only if their instantaneous deployment scenarios, e.g. instantaneous mobility pattern, significantly deviates from the pre-calculated deployment scenarios, e.g. mobility pattern. This allows the user terminals including or excluding the delegate user terminal in a cluster further reduce the amount of their feedback signalling.
  • the BS 10 is configured to detect periodically within each cluster A, B that the other user terminals 101 , 103, 106 belonging to the plurality of user terminals 101 -107 excluding the delegate user terminal 102, 107 also comply with average propagation information of the cluster A, B. This is done in order to detect possible changes in distribution of user terminals over clusters. Therefore, the BS 10 requests the other user terminals 101 , 103, 106 to report feedback information of the user terminal 101 , 103, 106 at certain time periods. This time period is different, e.g. longer, from the time period at which the BS 10 requests the delegate user terminal 102, 107 to report feedback information. This different, e.g.
  • time period may depend on average propagation information that comprises e.g. pre-calculated deployment scenarios for clusters as described earlier in this description.
  • the different, e.g. longer, the time period the better the other user terminals 101 , 103, 106 in the cluster A, B further reduce the amount of their feedback signalling, as earlier described.
  • the performance of the system is not degraded due to any possible outdated propagation information.
  • Time period at which the BS 10 requests the delegate user terminal 102, 107 to report feedback information depends on a current speed of the cluster A, B wherein the delegate user terminal 102, 107 belongs to.
  • Speed information of the cluster A, B is same as speed information of the delegate user terminal 102, 107 of that cluster A, B.
  • FIG. 5 shows a network element 50 according to an embodiment of the invention in which a cluster controller 52 is configured to form one or more clusters of user terminals belonging to the plurality of user terminals 101 -107.
  • the cluster controller 52 is configured to form clusters based on propagation information received from each of the user terminals belonging to the plurality of user terminals 101 -107.
  • Propagation information may comprise any information based on user terminal Ds channel measurements and/orvelocity and/or position and/or direction and/or pre-filtered information and/or advance information and/or pre- calculated scenarios as described earlier in this description.
  • the network element 50 comprises transceiver means (not shown) known in the art in order to communicate with user terminals.
  • a cluster controller 52 is further configured to measure time correlation of propagation information received from the user terminal belonging to the plurality of user terminals 101 -107 for a certain time period in order to define correlated propagation information of said user terminal. Then the cluster controller 52 is configured to classify said user terminal in one or more clusters of user terminals where each of the clusters comprises user terminals having similar or same correlated propagation information.
  • a network element 50 according to an embodiment of the invention may further comprise means for processing information 59 that is configured to process pre-filtered information obtained as outputs of data fusion process and/or advance information supplied beforehand.
  • a network element 50 may further comprise pre-calculating means (not shown) configured to calculate deployment scenarios for the user terminals, e.g. set of temporal deployment scenarios, and this obtained pre-calculated information can be processed by the means for processing information 59.
  • the means for processing information 59 is further configured to retrieve information from and store information to the database 20, where site e.g. different deployment scenarios are created using different types of propagation information.
  • a network element 50 may further comprise protocol stack means (not shown) configured to communicate feedback information between the BS 10 and the user terminals 101 -107.
  • This communication can be supported by the standard protocol stack means or proprietary protocol stack means running over the existing standard protocol stack means.
  • the proprietary protocol stack means is configured to receive feedback information that comprises information related to e.g. sensor-based measurements or pre-filtered information performed by the user terminals.
  • selecting means 54 is configured to select one or more delegate user terminals 102, 107 from user terminals belonging to each of clusters A, B. Then the network element 50 receives feedback information from the delegate user terminals 102, 107 on request of the network element 50.
  • requesting means 56 is configured to request each of the delegate user terminal 102, 107 to report periodically feedback information in a time period that depends on a current speed of the cluster A, B to which the delegate user terminal 102, 107 belongs.
  • Speed information of the cluster A, B is same as speed information of the delegate user terminal 102, 107 of that cluster A, B.
  • Speed or velocity information of the delegate user terminal 102, 107 includes in propagation information of that user terminal as explained earlier in this description.
  • the speed of the cluster can be e.g. speed of a bus that transports passages having user terminals.
  • detecting means 58 is configured to detect periodically within each of the clusters A, B that other user terminals 101 , 103, 106 than the delegate user terminal 102, 106 also comply with average propagation information of said cluster A, B. This is to ensure that all user terminals within the cluster comply with cluster properties of that cluster. Average propagation information means here that either exact values or certain threshold values can be used to define whether or not a received propagation information of the user terminal is considered to be within similar or same propagation information.
  • the detecting means 58 is configured to request the other user terminals 101 , 103, 106 to report feedback information of the user terminal 101 , 103, 106 at certain time periods.
  • This time period is different, e.g. longer, from the time period at which the requesting means 56 requests the delegate user terminal 102, 107 to report feedback information.
  • This different, e.g. longer, time period may depend on average propagation information that comprises e.g. pre-calculated deployment scenarios for clusters that are retrievable from the database 20.
  • Figure 6 shows a user terminal 101-107 according to an embodiment of the invention that comprises means 66 for measuring propagation conditions of a channel link between the user terminal and the BS 10 as well as propagation of the user terminal in order to produce propagation information.
  • the means 66 for measuring is configured to perform radio channel measurements, e.g. CINR and/or RSSI.
  • the means 66 for measuring further comprises sensor-based detecting means (not shown) configured to perform measurements of velocity and/or position and/or direction of the user terminal with respect to other user terminals and/or the BS 10.
  • the means 66 for measuring further comprises processing means 64 for processing pre-filtered information e.g. through data fusion procedure.
  • the user terminal 101-107 comprises transceiver means (not shown) known in the art in order to communicate with other user terminals and the BS 10.
  • the user terminal 101 -107 according to an embodiment of the invention further comprises protocol stack means (not shown) configured to send feedback information to the BS 10. This communication can be supported by the standard protocol stack means or proprietary protocol stack means running over the existing standard protocol stack means.
  • the proprietary protocol stack means is configured to receive feedback information that comprises information related to e.g. sensor-based measurements or pre-filtered information performed by the user terminals.
  • the proprietary protocol stack means is further configured to exchange information relating to propagation information with adjacent user terminals 101 -107. Then neighbouring user terminals are configured to exchange their propagation information sending them on feedback channel via the BS 10, using communication between user terminal and the BS. Alternatively, then neighbouring user terminals are configured to exchange their propagation information directly between each other instead of sending them on feedback channel to the BS 10.
  • the communication between adjacent user terminals can be accomplished using e.g. a short distance wireless link or other such communication technology.
  • the adjacent user terminals comprise means for exchanging propagation information (not shown), e.g. a short distance wireless transmitter and/or receiver.
  • a cluster controller 62 is configured to form a cluster of user terminals belonging to the plurality of user terminals 101-107.
  • the cluster controller 62 is configured to form clusters based on propagation information received from the user terminal belonging to the plurality of user terminals 101 -107.
  • the cluster controller 62 is further configured to compare locally its own propagation information and propagation information received from any adjacent user terminal belonging to the plurality of user terminals 101 -107. For example, the user terminal 103 requests its adjacent user terminals 101 , 102, 104, 105 to exchange propagation information and receives propagation information from those adjacent user terminals 101 , 102, 104, 105.
  • the user terminal 103 compares each of the received propagation information to its own propagation information in order to classify user terminals in a cluster comprising adjacent user terminals. If any of the adjacent user terminals 101 , 102, 104, 105 have similar or same propagation information as the user terminal 103, the user terminal 103 makes a decision to form a cluster together with said adjacent user terminal.
  • the user terminal 101 -107 may further comprise a navigation transmitter/receiver or other such elements known in the art to define location of the user terminal.
  • Figure 7 shows a flow diagram of a method according to an embodiment of the invention for reducing feedback load in a mobile environment.
  • step 710 measurements relating to a communication link between a user terminal and a base station, and measurements relating to propagation of the user terminal, are performed in order to produce propagation information of the user terminal.
  • step 712 propagation information is received by a network node.
  • the method comprises in step 714 forming at least one cluster of user terminals belonging to a plurality of user terminals based on propagation information received from user terminals belonging to the plurality of the user terminals.
  • step 716 a decision is made to select at least one delegate user terminal from user terminals belonging to each of said at least one cluster to report feedback information.
  • step 718 there is requested each of said at least one delegate user terminal to report periodically feedback information in every first time period, the first time period depending on current mobility information of each of said at least one cluster.
  • step 720 there is detected periodically, within each of said at least one cluster, that other user terminals than said at least one delegate user terminal to comply with average propagation information of said at least one cluster.
  • Figure 8 shows a flow diagram of a method according to an embodiment of the invention in which the step of forming further comprises step 810 of measuring time correlation of propagation information received from a user terminal belonging to a plurality of user terminals, step 811 of defining correlated propagation information for said user terminal, and step 812 of classifying said user terminal in a cluster comprising user terminals that belong to the plurality of user terminals and have similar correlated propagation information as said user terminal.
  • step 813 there is checked whether more user terminals belong to the plurality of user terminals. If so steps 810-812 are repeated to each of them.
  • step 814 a decision is made to select one or more delegate user terminals from user terminals belonging to each of said at least one cluster to report feedback information.
  • step 815 there is requested each of said at least one delegate user terminal to report periodically feedback information in every first time period, the first time period depending on current mobility information of each of said at least one cluster.
  • the step of detecting further comprises step 816 of requesting within each of said at least one cluster other user terminals excluding said at least one delegate user terminal to report periodically feedback information in every second time period, the second time period being different, e.g. longer, to the first time period.
  • step 817 there is checked whether propagation information relating to mobility and propagation of said other user terminal does comply with cluster properties of the cluster where it belongs. If propagation information of said other user terminal is becoming incompatible with cluster properties then said other user terminal will exit its current cluster and start sending feedback information more often in a normal way. Then again through steps 810-812 said other user terminal has a possibility to join a new cluster. If in step 817 propagation information of said other user terminal complies with the cluster properties, it continues according to step 815-816 within the current cluster.
  • Figure 9 shows a flow diagram of a method according to other embodiment of the invention in which the step of forming further comprises step 910 of receiving propagation information from any adjacent user terminal belonging to the plurality of user terminals, step 911 of comparing locally propagation information of a user terminal belonging to the plurality of user terminals with propagation information of the adjacent user terminal belonging to the plurality of user terminals, and step 912 of classifying said user terminal in a cluster that comprises adjacent user terminals belonging to the plurality of user terminals and having similar propagation information as said user terminal.
  • Steps 913-917 are equivalent with steps 813-817 of figure 8.
  • Figure 10 shows a flow diagram of a method according to an embodiment of the invention which forms a combination of previous embodiments of figures 8 and 9.
  • steps 1001 and 1002 are performed, said steps corresponding to steps 910- 911 of figure 9.
  • steps 1003 and 1004 are performed, said steps corresponding to steps 810-
  • Step 1005 corresponds to steps 812 and 912 in figures 8 and 9 respectively.
  • Step 1006 corresponds to steps 813 and 913 in figures 8 and 9 respectively.

Abstract

La présente invention concerne la façon de réduire, de façon significative, le niveau de signalisation de rétroaction dans des environnements mobiles sans pour autant diminuer la performance d’un système de communication sans fil. Le système comprend au moins un ensemble de terminaux d’utilisateur (101-107) et une station de base (10) contenant un élément de réseau. Le système est configuré pour former une ou plusieurs grappes (A, B) de terminaux d’utilisateur appartenant à la pluralité des terminaux d’utilisateur en fonction de l’information de propagation reçue des terminaux d’utilisateur. Dans le système, la station de base (10) est configurée pour sélectionner un ou plusieurs terminaux d’utilisateur délégués (102, 107) dans chaque grappe (A, B) afin de rapporter l’information de rétroaction. La station de base (10) est également configurée pour demander à chacun des terminaux d’utilisateur délégués (102, 107) de rapporter périodiquement des informations de rétroaction dans un délai déterminé par l’information de mobilité en cours de chacune des grappes. Enfin, la station de base (10) est configurée pour détecter périodiquement si les terminaux d’utilisateur dans chacune des grappes (A, B) satisfont aux propriétés de grappe de la grappe actuelle.
PCT/FI2008/050247 2008-05-07 2008-05-07 Procédé et système de réduction de charge de rétroaction dans des systèmes sans fil mobiles WO2009135983A1 (fr)

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WO2021154144A1 (fr) * 2020-01-30 2021-08-05 Telefonaktiebolaget Lm Ericsson (Publ) Configuration de rapport de mesure

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US20070076670A1 (en) * 2005-10-04 2007-04-05 Ravi Kuchibhotla Group scheduling in wireless communication systems
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WO2021154144A1 (fr) * 2020-01-30 2021-08-05 Telefonaktiebolaget Lm Ericsson (Publ) Configuration de rapport de mesure

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