`
`LTE-ADVANCED AND 4G WIRELESS
`
`
`
`COMMUNICATIONS: PART 2
`
`Minimization of
`
`
`Drive Tests Solution in 3GPP
`
`
`
`Wuri A. Hapsari, Anil Umesh, and Mikio lwamura, NTT DOCOMO, INC.
`
`
`
`Nokia Siemens Networks
`
`Malgorzata Tomala, 86dog Gyu/a, and Benoist Sebire,
`
`
`
`
`
`ABSTRACT
`
`tain parameters or to deploy new base stations.
`
`
`
`
`
`However, conventional drive tests consume
`
`
`
`significant time and human efforts to obtain reli­
`
`
`
`
`Providing network coverage and quality of
`
`
`
`
`
`
`service (QoS) is an important task of a cellular able data, since typically, the obtained data only
`
`
`
`
`
`covers certain area of the network, e.g., roads
`
`
`
`
`network operator. This is because cellular spec­
`
`
`
`trum is normally licensed under certain coverage
`
`and motorways. This has led to a huge amount
`
`
`
`
`
`obligations, and operators need to be competi­of OPEX and delays in detecting problems on
`
`
`
`tive in market. To improve their networks, oper­
`
`
`the network and in taking countermeasures.
`
`
`ators often send engineers in the field to collect
`
`
`These problems have also been continuously dis­
`
`
`cussed by the operators in the Next Generation
`
`radio measurements, to discover problems such
`
`
`as coverage holes in the network, and to deter­
`
`
`Mobile Networks (NGMN) alliance, a non-stan­
`
`
`mine whet.her certain parameter tuning is need­
`
`
`dardization organization from where a consoli­
`
`
`
`ed. However, such conventional "drive tests"
`
`
`dated operators' requirement for automated
`
`
`
`require large Operation Expenditure (OPEX),
`
`
`drive tests and recommendation solutions were
`
`delivered (2).
`
`
`while the collected measurements can only give
`Driven by these problems and demands, oper­
`
`
`
`
`limited snap shots of the entire network. In their
`
`
`
`Release 10 (Rel-10) specification, 3GPP studied
`
`
`
`ators proposed to standardize solutions in 3GPP
`
`
`to circumvent the cost for drive tests. In light of
`
`and specified solutions to reduce this OPEX for
`
`drive tests, under the work item named "Mini­
`
`
`such necessity, a work item called "Minimization
`
`mization of Drive Tests ( MDT)." The solution
`
`of Drive Tests (MDT)" was created in 3GPP in
`
`
`
`
`
`
`utilizes the user (customer) equipments (UEs) to March 2009 (3] scoping two Radio Access Tech­
`
`
`
`nologies (RATs), i.e., Long Term Evolution
`
`
`
`collect field measurements, including radio mea­
`
`
`
`(LTE) and Universal Mobile Telecommunica­
`
`
`
`surements and location information. This article
`
`
`
`
`
`
`
`describes in details the solution adopted in tions System (UMTS). The main concept was to
`
`
`3GPP MDT; how they were developed and
`
`
`
`exploit commercial user equipments (UEs) -
`
`their measurement capabilities and geographi­
`
`intended to be used.
`
`
`
`cally spread nature -for collecting radio mea­
`
`
`surements. The work item was finalized in March
`
`2011 as part of 3GPP Rel-10 specification.
`
`
`of MDT defined in Rel-10
`
`
`Conventional drive test is a manual process. To The key features
`
`
`
`
`collect network quality information, an operator
`are as follows:
`•The ability of the UE to include location
`
`
`
`
`
`often needs to send engineers directly to the
`
`
`
`
`concerning area and obtain radio measurements information as part of the UE radio mea­
`
`surement reporting
`
`
`
`in a hand-operated manner. Typically, a mea­
`
`
`•The ability of the UE to log radio measure­
`
`
`
`
`surement vehicle, e.g., a van equipped with spe­
`
`ments during the UE's idle state
`
`
`
`cially developed test terminals, measurement
`
`•Reuse of radio measurements to those that
`
`
`
`devices, and a Global Positioning System (GPS)
`
`anyway have to be performed as part of
`
`
`
`
`receiver to obtain geographical location, is used
`
`normal Radio Resource Management
`
`
`to check coverage outdoors (1]. With such mea­
`
`
`
`(RRM) procedures, thereby minimizing
`
`surement vehicle, engineers would perform test
`
`
`
`additional complexity and battery consump­
`
`
`
`calls in the car and record measurement results
`tion by the UE.
`
`
`
`
`along the drive route. For indoor coverage engi­
`
`We describe the use case that would benefit
`
`
`
`neers perform "drive tests" on foot, using spe­
`
`from MDT. We discuss two fundamental
`
`
`
`
`cially developed measurement equipments that
`
`
`
`approaches to realizing MDT from architecture
`
`
`can be carried by hand. By analyzing these drive
`
`
`
`perspective. We explain in detail the functionali­
`
`
`test results, the operator can take necessary
`
`
`
`ties and signaling procedures adopted in 3GPP
`
`
`
`
`measures to maintain and enhance the quality of
`
`
`Rel-10, and describe the security aspects.
`
`
`
`
`the network, e.g., to decide whet.her to tune cer-
`
`INTRODUCTION
`
`28
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`0163-6804/12/$25.00 © 2012 IEEE
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`Authorized licensed use limijed to: West Virgnia University. Downloaded on January 26,2021 at 02:02 36 UTC from EEE Xplore. Restrictions apply.
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`IEEE Communications Magazine • June 2012
`
`IPR2022-00459
`Apple EX1008 Page 1
`
`

`

`RAN
`
`RAN
`
`UE
`
`UE
`
`MDT USE CASES
`
`MDT server
`
`MDT server
`
`TI1e motives bebind conventional drive test evo­
`
`
`
`
`
`lution drove further the need to understand pos­
`
`
`sible scenarios, in wbich tbe foreseen solutions
`
`
`would help to minimize the drive tests. The main
`
`
`
`triggers for drive test execution are comprised of
`[1, 5]:
`New base station deployment, where collec­
`
`
`
`
`tion of downlink/uplink (DL/UL) coverage mea­
`
`surements of the new cell a nd neighbor cells are
`
`
`
`essential for a 'coarse' tuning of the network.
`
`Construction of new highways/railways/major
`
`
`buildings, which are in fact new obstacles caus­
`
`
`
`ing additional shadowing in the existing radio
`network and new sources of network traffic.
`
`
`Drive tests are performed to check whether cov­
`
`
`erage or throughput requires improvement.
`
`
`Customer's complaint - when customers
`
`
`experience bad QoS and indicate these concerns,
`
`
`
`
`the operator perfonns measurements collection in
`
`
`the relevant area. This allows operators to identi­
`
`
`fy, understand and solve the problem, and pro­
`
`
`vide in effect high-quality service to the end user.
`Figure 1.
`
`
`
`Periodic drive tests - regular network moni­
`U-plane MDT architecture (left) and C-plane MDT architecture
`
`
`
`
`toring helps to reflect the actual performance of
`(right).
`
`"alive" net\vorks, with always changing due traf­
`
`
`fic conditions, and identify areas for improve­
`ment. This kind of drive tests is also performed
`MDT ARCHITECTURE
`on a regular basis to perform benchmarking
`INITIAL STUDIES ((-PLANE VS. U-PLANE)
`
`
`
`bet\veen operators.
`In the first phase of the study in 3GPP, the fol­
`
`
`The solutions developed in Rel-10 focus on
`
`
`lowing two architecture solutions were discussed
`
`the Coverage Optimization use case that will
`
`
`[5]: Control-plane (C-plane) based MDT archi­
`
`
`benefit operators especially in the early phase of
`
`
`tecture and User-plane (U-plane) based MDT
`
`
`net\vork deployment [6, 8]. The solutions enable
`
`
`
`architecture. Figure illustrates the two archi­
`
`collection of a set of MDT measurements that
`1
`
`
`
`will provide information for the operator to
`
`tectures. The C-plane based MDT architecture
`
`
`refers to an architecture where C-plane signaling
`
`design reliable coverage maps and consequently
`
`
`is used for sending MDT configuration to the
`
`
`to detect coverage issues. The objectives for
`
`
`UE and for reporting MDT measurements to
`
`
`measuring coverage are as follows:
`
`
`the network. In this architecture, the collected
`
`
`
`
`Coverage mapping: concerns the collection of
`
`
`MDT measurements are visible to the Radio
`
`MDT measurements in all parts of the network
`Access Network (RAN) node and Operation
`
`
`
`
`to provide an insight into the signal levels distri­
`
`bution per physical location and allow overall
`
`and Maintenance (OAM). On the other band,
`
`
`
`U-plane based MDT architecture utilizes a cer­
`
`coverage visualization
`
`
`
`tain application terminated directly bet\veen the
`
`
`Coverage hole and weak coverage detection:
`
`
`
`concerns areas where the downlink signal (of
`
`UE and the MDT server. The application data,
`
`
`which may include measurement results and
`
`
`
`
`both serving and neighbor cells) is below the
`
`
`their reporting configuration, policy setting,
`
`
`
`level needed to maintain either basic service or
`etc.,
`
`
`
`is transported using a U-plane bearer. One of
`
`
`
`to fulfill planned performance requirements
`
`t he foreseen applications was Open Mobile
`
`
`
`therefore causing discontinuous or poor service
`
`
`Alliance -Device Management (OMA-DM).
`to the end user
`
`
`
`Pilot pollution detection: concerns areas
`
`
`Since OMA-DM is terminated bet\veen the UE
`
`
`and OMA-DM server within the operator's net­
`
`
`where large overlap of different cells' coverage
`
`
`
`
`or unexpected signal propagation between cells
`work, the RAN node is unaware of the MDT
`
`
`measurements sent between the UE and OMA­
`
`
`cause excessive interference levels, high power
`DM server.
`
`
`levels, high energy consumption, and low cell
`perfonnance
`The conclusion of the study phase was that
`
`3GPP specification work is to be continued
`
`
`
`Overshoot coverage detection: concerns areas
`
`
`based on C-plane MDT architecture. TI1e main
`
`
`where coverage of a cell reaches far beyond
`
`
`reason was the visibility of the collected MDT
`
`what was initially planned
`
`
`measurements in the RAN node such that the
`U1>link coverage verification: concerns the
`
`
`
`
`
`MDT information can be used by the RAN itself
`
`detection of areas with poor uplink communica­
`
`
`
`to perform any automated network parameter
`tion and unbalanced coverage between the
`
`optimization. In fact the work on MDT in 3GPP
`
`uplink and downlink connections
`In all the cases above, t he MDT information
`
`
`was closely related to the work item for Self­
`
`
`
`should enable to detect overall network coverage
`
`
`
`Organizing Networks (SON) [4], to avoid any
`
`
`as well as reveal the locations where signal levels
`
`
`redundant features and to enable close inter­
`
`are the weakest and embed a risk for degrada­
`
`
`working between the two features.
`
`Nevertheless, 3GPP noted that the informa-
`tion of end user experience.
`
`IEEE Communications Magazine • June 2012
`
`29
`
`Authorized licensed use fim�ed to: West Virgnia University. Dow nloaded on January 26,2021 at 02:02 36 UTC from EEE Xplore. Restrictions apply.
`
`IPR2022-00459
`Apple EX1008 Page 2
`
`

`

`The so/utiom
`
`de1eloped in Rel-1 a
`Signaling-based MDT
`
`focus on the
`
`OAM
`
`Coverage
`
`
`
`Optimization use
`
`case that w11/ benefit
`
`operators to design
`
`HSS
`
`Signaling-based MDT
`
`Management/
`area-based MDT
`
`reliable coverage
`Signaling-based MDT
`
`maps and
`
`consequently to
`
`detect coverage
`
`issues.
`
`�i�i;�; ogged MDT
`h, Immediate MDT
`
`� measurement report
`
`Immediate MDT
`
`measurement report
`Logged MDT
`measurement
`� -= �� _,_---"-- _ re7port
`L09 ayail�bility
`
`� ,..,,�,, w='""
`measurement
`L ed MDT
`mdicauo'l
`configuration
`m��urement
`it
`Logged data
`l•••••••I
`
`Connected state
`Figure 2.
`
`
`
`Overn/1 MDT architecture.
`
`Idle state
`
`
`
`Connected state
`
`From network s ignaling perspective, two
`
`
`tion elements defined for JI..IDT configuratio n
`
`
`
`types of MDT were defined [8]:
`
`
`and measurements i n the C-plane architecture
`
`by other protocols/specifications
`Signaling-based MDT is used to collect mea­
`
`
`can be utilized
`
`surements from a certain/specific UE. The so­
`
`outside 3GPP, e.g., OMA-DM.
`
`
`
`called "signaling-based trace" feature [8] is used
`REL-10 MDT ARCHITECTURE
`
`
`for managing signaling-based MDT.
`Management/area-based MDT is used to col­
`
`
`Figure 2 describes the overall MDT architecture
`
`
`lect measurements from randomly chosen UEs
`
`defined in 3GPP Rel-10 for LTE. The same
`
`or a group of UEs that enter a (certain) geo­
`
`architecture applies for both LTE and UMTS.
`
`graphical area. In management/area-based MDT
`, the terminolo
`Note tJ1at in the entire article
`gy
`Node B ( eNB),"
`
`
`
`the so-called "management-based trace" or "cell
`"RAN Dode" refers to ''Evolved
`
`i.e., base station in LTE, and "Radio Network
`
`trace" feature [8] is used to manage MDT.
`(RNC)," i .e ., radio resource
`
`
`From radio configuration perspective, two
`Controller
`coll­
`
`types of MDT were defined [6]:
`
`t railer node in UMTS. The terminology "Core
`
`
`Network (CN) node" refers to "Mobility Man­
`
`Logged M])T is a type of MDT where the UE
`agement Entity (MME)" in LTE and "Serving
`
`
`stores t he collected data for a certain period of
`
`General Packet Radio Service (SGSN)" or
`
`time before the data is reported to the network.
`
`
`"Mobile services Switching Center (MSC)" in
`
`
`
`
`This type of MDT is performed when the UE is
`
`in idle state (i.e., the UE has no setup connec­
`UMTS.
`tion with the RAN node).
`MDT is always triggered by the
`network i.e.,
`
`Immediate MDT is a type of MDT wbere the
`
`
`OAM decides the configuration of MDT param­
`
`eters that need to be performed by the UE and
`
`
`
`UE promptly reports the collected data to the
`
`
`network. This type of MDT is performed when
`
`sends these parameters to the RAN node for
`
`
`MDT activation. Upon reception of these MDT
`
`the UE is in active state (i.e., the UE has a setup
`
`connection witb tJ1e RAN node).
`, the RAN node acti­
`
`configuration parameters
`
`The standard allows any combinations
`
`vates the MDT fut1ctionality in the UE by send­
`
`
`ing the MDT configuration parameters to the
`
`
`between the above MDT types. For example, the
`
`management/area-based MDT can assign the
`
`UE. After the UE performs relevant measure­
`ments, the UE reports
`
`the measurement results
`
`
`UE to perform logged or immediate MDT, and
`
`the signaling-based MDT can be used also to
`to the RAN node, which will then send these
`
`
`assign the UE to perform logged or immediate
`
`results to an MDT server, known as Trace Col­
`Entity (TCE).
`lection
`MDT.
`
`
`) network signaling purposes
`For (inter-node
`,
`
`
`
`the existing Trace procedures (i.e., procedure for
`
`MDT CONFIGURATION FROM
`
`OAM to trace radio measurements in the RAN
`
`node defined in previous 3GPP Releases) were
`
`
`OAM TO RAN
`
`reused and extended for managing M DT mea­
`MDT
`surements
`and configuration [8]. For radio inter­
`
`SIGNALING-BASED
`
`
`Figure 3 illustrates an example scenario how
`
`
`
`
`face signaling purposes, specific procedures and
`
`MDT is activated to the UE in signaling-based
`
`
`
`information elements were defined to support
`MDT [8].
`
`IvlDT configuration and reporting.
`
`30
`
`
`
`
`IEEE Communications Magazine • June 2012
`
`
`Authorized licensed use fim�ed to: West Virgnia University. Downloaded on January 26,2021 at 02:02 36 UTC from EEE Xplore. Restrictions apply.
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`
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`IPR2022-00459
`Apple EX1008 Page 3
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`

`

`UE
`
`RAN node
`
`CN node
`
`HSS
`
`OAM
`
`Idle state
`
`MDT activation
`
`(MDT configuration param ters)
`
`
`
`Storing MDT parameters
`
`User consent checking
`
`MDT confi uration a ameters
`
`
`
`Storing MDT parameters
`
`Call setup
`
`Active state
`
`
`
`MDT configuration pa ameters
`
`
`
`Storing MDT parameters
`
`
`
`M measurement confi uration
`
`
`Figure 3.
`
`Signaling-based MDT activation procedure.
`
`The MDT configura­
`
`tion parameters are
`
`sent from the OAM
`
`direct/,; to the R/lN
`
`node, and the RAN
`
`node stores these
`
`parameters for later
`
`configuration
`
`towards UEs. This
`
`type of MDT is acti-
`
`vated typically in
`
`R/lN nodes of a spe­
`
`
`
`cific area, where the
`
`area is identified by a
`
`list of cells or paging
`
`location area
`
`id€f1tities.
`
`ticipate in MDT. Roaming users and not-con­
`
`
`
`In signaling-based MDT, UE selection is
`
`sented users are excluded from any MDT cam­
`
`performed in the DAM based on a permanent
`paign.
`
`
`UE identity, which uniquely identifies the UE
`
`
`in the network, s uch as International Mobile
`
`
`
`Subscriber Identity (IMSI) or International
`MDT CONFIGURATION FROM
`
`
`
`Mobile Equipment Identity and Software Ver­
`sion (IMEI SV). From OAM the MDT configu­
`RAN TO UE
`ration parameters are sent to the H ome
`LOGGED MDT
`
`
`
`Subscriber Service (HSS), where decision is
`
`
`
`
`taken whether MDT can be activated for a UE, In logged MDT, measurements are configured
`
`
`
`
`
`
`based on whether the corresponding end user t o the UE "in advance," i.e., tbe received MDT
`
`
`
`
`
`has consented to contribute to MDT. The HSS configuration is stored in the UE and becomes
`
`
`
`performs MDT activation towards the relevant
`
`only valid when the UE releases the connection
`
`CN node e.g., MME in case of LTE. This acti­
`
`
`and enters idle state [6]. The logging operation
`
`
`
`
`
`
`vation is typically done when the UE initially itself is therefore performed by the UE in idle
`
`state. For tbe UE to log MDT measurements,
`
`
`
`attaches to the network or updates its paging
`
`l ocation area, but the MDT configurat ion the UE must be able to detect,
`
`
`track, and mea­
`
`
`parameters can be propagated also as a stan­
`
`
`
`sure radio signals from base stations, i.e., the sig­
`nal level has t o be abov e the UE receiver
`
`dalone procedure at any time. This activation
`
`
`
`
`of MDT from CN to RAN is performed when a sensitivity. Once the signal level from all cells
`
`has dropped below the minimum level for camp­
`
`call or session is established.
`
`
`
`ing, the UE encounters a "coverage hole." To
`MANAGEMENT/AREA-BASED MDT
`
`
`sav e the amount of data, tbe UE performs no
`
`
`The procedure used for activating MDT in man­
`
`logging while in a coverage hole. The UE sensi­
`
`
`
`tivity would be inferior compared to specialized
`
`
`agement/area-based MDT is shown in Fig. 4 [8].
`
`
`
`
`
`The MDT configuration parameters are sent equipment in conventional drive tests, as s uch
`
`
`equipment is normally designed to have higher
`
`from the OAM directly to the RAN node, and
`
`
`
`
`
`
`the RAN node stores these parameters for later sensitivity and accuracy in measuriDg low level
`
`
`configuration towards UEs. This type of MDT is
`
`
`signals. However, in MDT the UE has the ability
`
`
`
`
`
`
`activated typically in RAN nodes of a specific to log measurements for a period of 10 s in LTE
`(or 12 s in UMTS) from the time the UE enters
`
`area, where the area is identified by a list of cells
`
`a coverage hole.
`
`
`or paging location area identities.
`By statistically analyzing these measurement
`
`
`
`
`One of the differences between signaling­
`logs, an operat or can detect nearly where the
`
`
`based MDT and management/area-based MDT
`
`
`coverage hole is. Such information would also
`
`
`is how the UE selection is performed. In man­
`
`
`provide a hint how to improve coverage, e.g.,
`
`agement/area-based MDT, selection of UEs to
`
`which base stations need parameter adjustments
`commit to MDT is done by the RAN node,
`
`and which base stations would become neighbors
`
`
`based on the received parameters from DAM,
`
`if a new base station is placed on the dark spot.
`
`UE radio capability, and the "MDT allowed
`
`
`If the operator has other carrier frequencies or
`flag" received from the CN node during call
`
`systems that cover the area, handover thresholds
`setup. This flag is set by the CN node based
`
`
`can be adjusted such that inter-frequency or
`
`
`on the UE's roaming status and whether the
`
`
`inter-system handover can be triggered before
`
`
`corresponding end user bas consented to par-
`
`IEEE Communications Magazine • June 2012
`
`31
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`Authorized licensed use fim�ed to: West Virgnia University. Dow nloaded on January 26,2021 at 02:02 36 UTC from EEE Xplore. Restrictions apply.
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`IPR2022-00459
`Apple EX1008 Page 4
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`

`

`The RAN node is not
`
`required to retrieve
`
`UE
`
`RAN node
`
`CN node
`
`HSS
`
`OAM
`
`the logged data
`
`Active state
`directr; after the log
`
`availability is received
`
`MDT activation
`
`(MD configuration parame ers)
`
`from the UE. The
`
`RAN node can initi­
`
`ate data retrieval
`at
`
`
`
`any time while the
`
`UE is connected.
`
`Hence, the UE is
`
`required to keep the
`
`non-retrieved report
`
`
`
`Storing MDT parameters
`
`Call setup
`
`Context setup
`
`uration parameters, M T allowed bit)
`
`UE selection
`
`for 48 hours from
`
`the moment the log­
`
`
`
`M measurement conf guration
`
`ging duration timer
`Management/area-based MDT activation procedure.
`Figure 4.
`
`expires.
`
`ration (i.e., one MDT context) at a time.
`
`
`the UE enters the coverage hole. The logged
`
`
`
`Thus, if other RAT or PLMN provides a new
`
`
`measurements would allow the operator t o
`
`logged MDT configuration to the UE, the
`
`decide which base stations need such parameter
`
`
`UE overwrites the previously received con­
`tuning.
`figuration.
`
`
`The overall principle of logged MDT opera­
`The UE reports the logged data upon
`
`
`
`tion is illustrated in Fig. 5. The measurement
`
`r equest from the network. The RAN node
`
`configuration for logged MDT sent from the
`
`
`requests reporting based on indication from
`RAN node to the UE is created based on the
`
`
`the UE, upon connection establishment, of
`
`
`
`MDT configuration parameters received from
`
`
`OAM [7, 8]. The followings are the configura­
`
`the availability of logged data. The RAN node
`is not require d t o retrieve the logged data
`tion parameters:
`
`
`directly after the log availability is received
`
`
`• Logging interval which defines the periodic­
`
`ity of the measurements that should be
`
`from the UE. The RAN node can initiate data
`logged
`
`retrieval at any time while the UE is connect­
`•Logging rlnration which determines how
`
`
`
`ed. Hence, the UE is required to keep the
`
`non-retrieved report f or 48 hours from the
`
`long the logged MDT configuration is valid
`
`moment the logging duration timer expires.
`
`
`• Trace Reference which identifies the Trace
`
`
`The 48-hour timer can also be started when
`
`Session used for the MDT
`
`the logged data volume exceeds the available
`•Trace Recording Session Reference which is
`
`
`
`
`storage space in the UE reserved f or MDT
`
`
`used together with the Trace Reference for
`
`
`purposes. AUE supporting R el-10 MDT is
`
`
`correlating the collected log data of an
`
`equipped with a minimum of 64 kB memory
`
`MDT session and the UE
`for log storage.
`• TCE ID identifi e s the TCE to where the
`
`MDT measurements should be sent. This
`With this reporting mechanism, the amount
`
`
`
`
`
`of signaling is reduced compared to immediate
`
`parameter is sent back by the UE within
`
`MDT, as the UE reports all logs in one report.
`
`the log data to the network.
`
`
`
`However, logged MDT requires additional mem­
`
`
`The measureme11t results are tagged with
`
`
`
`ory for log storage and specific procedures for
`
`
`
`available location information, i.e., location
`log r eporting.
`
`i nformation that happened to have been
`acquired by the UE at the time of measure­
`ment.
`IMMEDIATE MDT
`The UE stores the received co11figuration
`Immediate MDT utilizes procedures defined for
`
`
`
`
`
`regardless of a state change (idle to active
`
`RRM in previous 3GPP Releases to a great
`
`extent. The RAN node translates the MDT con­
`
`and vice versa) within the logging duration
`
`
`figuration parameters received from the
`timer. This applies also f or a change of
`
`OAM/CN node into RRM measurement config­
`
`
`camped operator network, i .e., Public Land
`
`
`uration before sending to the UE [7, 8]. The
`Mobile Network (PLMN) and RAT (i.e.,
`
`main change introduced for immediate MDT
`
`LTE and UMTS). In case of PLMN, RAT or
`
`
`state change, the logging by the UE is sus­
`
`
`was the configuration and reporting of location
`
`
`information. The followings are the configura­
`
`
`
`pended. Effectively, logged MDT will resume
`tion parameters:
`when the UE returns to idle state or comes
`
`•List of measurements which identifies what
`
`back to the RAT that configured MDT. The
`
`measurements the UE should collect
`
`UE maintains only one logged MDT configu-
`
`32
`IEEE Communications Magazine • June 2012
`
`
`Authorized licensed use fim�ed to: West Virgnia University. Dow nloaded on January 26,2021 at 02:02 36 UTC from EEE Xplore. Restrictions apply.
`
`IPR2022-00459
`Apple EX1008 Page 5
`
`

`

`•Report interval which defines the interval of
`
`UE
`
`RAN node
`
`Active state
`
`
`Logged MDT measurement configuration
`
`
`
`Log availability indication
`
`
`
`Logged measurement request
`
`
`
`Logged measurement report
`
`•Reporting Trigger which determines
`
`
`
`whether periodical or event based reporting
`is requested
`
`
`
`
`periodical measurements
`
`•Report amount which indicates the number
`
`
`of measurement reports to be sent with
`
`periodical measurements
`
`•Event threshold indicates the threshold
`
`
`(against s ignal quality) for event based
`reporting
`•Area scope if present in
`
`management/area-based MDT, this indi­
`cates to the RAN node in which cells MDT
`
`
`should be activated; if present in signaling­
`
`based MDT, this indicates that the mea­
`
`
`
`surement c onfiguration is sent to the
`
`
`selected UE only if it is connected in the
`cell which is part of the area scope.
`Unlike logged MDT, the TCE ID, Trace Ref­
`
`
`erence and Trace Recording Session Reference
`
`parameters are not sent to the UE, since those
`
`
`are already known by the network and the UE
`
`
`bas continuous connection with the network.
`
`
`Once the UE receives the configuration, the
`
`
`
`UE applies it immediately and starts sending
`
`
`measurement reports when the reporting condi­
`Figure 5. Logged MDT configuration and reporting.
`
`tions are met. Based on the conventional mea­
`
`
`surement capabilities for RRM, two reporting
`trigg ers have been identified
`for MDT purposes:
`Event A2 (i.e., the quality of serving cell
`LOCATION INFORMATION FOR
`MDT
`
`becomes less than a threshold) and periodical
`PRINCIPLES OF
`
`
`
`reporting. The overall principle of immediate
`
`
`MDT operation in RAN is illustrated in Fig. 6.
`
`LOCATION INFORMATION IN MDT
`
`With immediate MDT the UE may also send
`Inclusion of location information in MDT
`
`
`
`
`
`separate reports on connection failures (e.g.,
`
`
`radio link failures or handover failures). Sucb
`
`
`
`reports is essential in MDT. Location informa­
`
`
`
`Radio Link Failure (RLF) reporting requires no
`
`tion for MDT can be categorized into the fol­
`lowings:
`
`
`prior configuration. That is, a UE supporting the
`Detailed location information is geographical
`
`
`
`
`
`
`feature autonomously collects data related to the
`
`
`
`location information which at least consists of
`
`failure and sends them to the network upon
`
`latitude and longitude. This t ype of location
`
`
`
`request after recovery. The data consist of radio
`
`
`information gives the exact geographical point of
`
`
`
`measurement results available at the time of
`
`
`connection failure, tagged by available location
`
`the earth where the radio measurement sample
`
`was taken (subject to the positioning method
`
`
`information and identification of cells involved
`
`
`
`
`accuracy). Detailed location information is typi­
`
`in the event. Reporting is performed in a similar
`
`cally obtained by GPS or Global Navigation
`
`
`way to logged MDT, i.e., the UE indicates first
`
`
`the availability of an RLF report after successful
`
`
`
`Satellite System (GNSS) positioning method, but
`
`connection recovery, upon which the RLF report
`
`
`can also be obtained by other positioning meth­
`
`can be retrieved by the RAN node.
`
`
`ods supported by the UE and the network, e.g.,
`
`
`Observed Time Difference of Arrival (OTDOA),
`
`
`
`Assisted -GNSS (Assisted-GPS), Enhanced Cell
`
`
`ID (E-CID) or even Secure User-Plane Location
`(SUPL).
`In general, MDT does not introduce additional
`
`
`RF fingerprint refers to t he profile of mea­
`
`
`
`
`sured quality of signals from the neighboring
`requirements for UE measurements handling
`
`cells. This information can be used by the net­
`
`
`during handover. In signaling-based MDT, since
`
`
`
`the purpose is to collect measurements from a
`
`
`
`work to calculate the approximate location of
`
`the UE by means of e.g., triangulation of the
`
`
`particular UE, the MDT configuration and
`
`
`geographical location of the cell or the base sta­
`
`
`reporting are continued during and after han­
`tion.
`
`
`dover. MDT configuration is transferred from
`In Rel-10 MDT, inclusion of detailed location
`
`
`
`the handover source RAN node to the target
`
`
`
`information is based on 'best effort', i.e., includ­
`
`RAN node, as the target RAN node also needs
`
`to be aware of what measurements are b eing
`
`ed only if it happens to be available in the UE at
`
`the time wben the UE performs radio measure­
`
`
`continued in the UE, so that any further recon­
`
`
`ments. Its availability depends on the ongoing
`
`
`
`figurations can be performed as necessary. In
`
`
`
`location services, e.g., map application and loca­
`contrast in management/area-based MDT,
`
`tion search application, which are independent
`
`
`
`since the purpose is to collect measurements in a
`from MDT control.
`
`
`certain area, the configuration and measure­
`
`The main benefit of this best effort approach
`
`
`ments do not continue upon handover.
`
`HANDLING OF
`
`MDT CONFIGURATION UPON HANDOVER
`
`IEEE Communications Magazine • June 2012
`
`33
`
`
`
`Authorized licensed use fim�ed to: West Virgnia University. Dow nloaded on January 26.2021 at 02:02 36 UTC from EEE Xplore. Restrictions apply.
`
`
`
`IPR2022-00459
`Apple EX1008 Page 6
`
`

`

`UE
`
`RAN node
`
`measurements. Since there is no 'interval'
`
`
`defined for this kind of triggers, u alike logged
`
`
`MDT, the reporting interval cannot be used as
`
`
`
`guidance for assessing the validity of detailed
`
`
`
`location information. To address this problem,
`
`
`the GPS timestamp (if available) can also be
`
`
`
`reported as part of location information. With
`
`
`the assumption that the network is also aware of
`Active state
`
`
`the GPS timing, the network can judge the valid­
`Immediate MDT measurement configuration
`
`
`
`ity by comparing the GPS timestamp from the
`
`(using RRM procedure)
`
`
`UE to the GPS timestamp maintained in the
`
`
`
`network. The same mechanism also applies to
`Immediate MDT measurement configuration
`
`
`
`
`acknowledgement (using RRM procedure)
`
`periodical reporting.
`
`Reporting trigger (event/
`
`
`
`report interval) met
`
`
`
`Measurement report
`
`Figure 6. Immediate MDT configuration. and reporting.
`
`SECURITY ASPECT OF MDT
`
`
`
`Security aspects of MDT can be classified into
`
`
`
`the u ser perspective and the operator network
`perspective.
`From the user perspective, a user might not
`
`
`
`want his/her handset to be used for MDT pur­
`
`
`
`poses due to various reasons, e.g., not willing to
`
`
`
`reveal its location. The MDT mechanism speci­
`
`
`fied in 3GPP provides the following security pro­
`tection towards the user: user data
`
`
`confide11tiality, user data anonymity a11d privacy,
`is limited UE impact. No additional battery con­
`
`
`
`
`
`
`sumption nor additional processing is incurred,
`
`and co11sent-based MDT activation.
`since the UE does not need to start any posi­
`
`
`Confidentiality of user data is achieved by
`
`
`tioning function to obtain its detailed location
`
`
`
`sending the MDT related signaling using integri­
`
`
`when an MDT measurement is taken. The speci­
`
`
`ty protected protocols, both in radio interface
`
`
`
`fications were intentionally defined as sucb to
`
`
`
`and network interface. Data anonymity and pri­
`
`lower the hurdle for implementing MDT fea­
`
`
`vacy is achieved by assuring that the collected
`
`tures in the UE, as MDT is more useful in the
`
`data cannot be linked to a real user identity, e.g.,
`
`IMSI. Thus, the CN node is forbidden to send
`
`
`
`initial phases of network deployment and the
`
`
`number of participating UEs is essential to
`
`
`any user identity, e.g., IMSI, to the TCE.
`
`
`achieve reliability. However, this has created
`To address the user consent requirement, a
`
`
`
`some disadvantages for MDT as a system, since
`
`
`
`mechanism is adopted to ascertain that the oper­
`
`not every MDT measurement sample is associat­
`
`ator can only utilize the UE of those users who
`
`
`
`ed with detailed location information, and not
`
`
`have given tbei.r consent. This consent for MDT
`
`
`
`all location infonnation associated to MDT sam­
`
`can be part of user subscription and can be
`
`ples are accurate enough to point the exact loca­
`
`revoked anytime by the user. For signaling-based
`tion where the sample was taken.
`
`MDT, the HSS makes sure that MDT activation
`
`signaling is sent to the RAN node, only if the
`
`
`In this approach, validity of the location
`
`
`information becomes an important factor. To
`
`
`user data in HSS indicates that the user bas
`
`
`
`decide whether the obtained location informa­
`
`
`
`already given his/her consent to the operator to
`
`
`
`
`perform MDT using his/her UE. For manage­
`
`
`tion is valid for reliable use, a network operator
`
`
`needs to carefully consider the time difference
`ment/area-based MDT, the RAN node decides
`
`between when tbe location information was
`
`
`
`whether configuration of MDT is allowed for a
`
`
`obtained and when the radio measurement was
`
`UE, based on the "MDT allowed flag" reflecting
`obtained.
`
`
`the user conse11t status as explained in 4.2.
`
`
`From the operator perspective, the network
`LOCATION INFORMATION FOR LOGGED MDT
`
`
`
`
`quality information can be sensitive information.
`
`For logged MDT, sta