Methods and arrangements for processing of measurement data in cellular communication systems

The problem of unsynchronized internal clocks of user equipments in a cellular communication system is addressed by a solution where a mechanism relying on a standalone clock function in user equipments is provided. Embodiments provide a network node that distributes a time reference to a user equipment (UE), and wherein the UE, using an internal clock function, time-stamps the logged measurements and/or events relative to the received time reference. When the UE has logged measurements the UE indicates to the network node that it has an available measurement log. The network node may then request several UEs to deliver their measurement log, respectively. The network node is then able to retrieve time stamped measurement information from the measurement log of each UE relative the sent time reference. Furthermore, the network node is then able to compare measurement information from each UE in a cell provided at the same time interval in all UEs.

TECHNICAL FIELD

The present invention relates to processing of measurement data. More particularly, the present invention relates to arrangements and methods for processing of measurement data in a user equipment and a network node comprised in a cellular communication system.

BACKGROUND

For next generation of mobile telecommunications systems 3rdGeneration Partnership Project (3GPP) is in the process of defining solutions for user equipment (UE) measurement logging function and immediate reporting function called Minimization of the Drive Tests (MDT). The MDT study aims at assessing the feasibility, benefits and complexity of automating the collection of UE measurements to minimize the need of manual drive-tests. The work under the MDT study should define use cases and requirements for minimizing drive-tests in next generation LTE/HSPA networks. Also, based on the defined use cases and requirements, the MDT should focus on study the necessity of defining new UE measurements logging and reporting capabilities for minimizing drive tests and analyze the impact on the UE.

The use cases for the MDT will be given as following.Radio coverage optimizationMobility optimizationNetwork capacity optimizationParameterization for common channelsQuality of Service verification

1. Radio coverage optimization; that is, information about radio coverage is essential for network planning, network optimization and Radio Resource Management (RRM) parameter optimization (e.g. idle mode mobility parameter setting, common channel parameterization), as well as backend network management activities, such as network dimensioning, CAPEX/OPEX planning and marketing. Additionally the detection of coverage problems (e.g. coverage holes, pilot pollution, low user throughput, etc.) in specific areas may be performed.

2. Mobility optimization; that is, mobility optimization is an important part of network operation. Information about mobility problems or failures can be used to identify localized lack of coverage or the need to adapt the network parameters setting, (e.g. in order to avoid too early or too late handover and to improve the handover success rate and overall network performance)

3. Network capacity optimization; that is, the operator may need to be able to determine if there is too much/little capacity in certain parts of the network. Such determination may help to determine placement of new cells, to configure common channels and to optimize other capacity related network parameters.

4. Parameterization for common channels; that is, user experience and/or network performance can be degraded by suboptimal configuration of common channels (e.g. random access, paging and broadcast channels). Detecting problems (e.g. on UL or DL common channel coverage) or analyzing the performance (e.g. connection setup delay) for the procedures associated with common channels, may help network parameter setting and configuration change for system performance optimization.

5. Quality of Service verification; that is, one of the objectives of the network performance analysis is the verification of the quality of service (e.g. user throughput). This may also allow detecting critical conditions and determining the need to change the network configuration, parameter settings or capacity extension.

In the following, UE measurement logs for minimizing drive tests will be described. The measurement logs may be taken at the occurrence of predefined “triggers”, e.g. periodic trigger, a failure event. The following UE measurements (or similar functionality) are considered for UE-internal logging:

1. Periodical downlink pilot signal strength/quality measurements of serving cell and neighbour cells on same and other radio access technologies.

2. Serving cell becomes worse than threshold; that is, radio environment measurements are logged when the serving cell metric becomes worse than the configured threshold.

3. Transmit power headroom becomes less than threshold; that is, transmit power headroom and radio environment measurements are logged when UE transmit power headroom becomes less than the configured threshold.

4. Random access failure; that is, details on the random access and radio environment measurements are logged when a random access failure occurs.

5. Paging channel failure; that is, details of the radio environment, location, time and cell identity are logged at the point when the UE fails to decode the PCCH on the Paging channel for two consecutive times.

6. Broadcast channel failure; that is, details of the radio environment, location, time, cell identity and frequency are logged at the point when the UE fails to read the relevant DL common channels to acquire required system information for camping on a cell.

7. Radio link failure report; that is, radio measurements available at the UE are reported at the RLF occurrence.

The network can request the UE to perform logging of measurements. The UE executes measurements (e.g. periodical downlink pilot measurements) and logs these measurements internally in a sequential manner. Typically, the log stored internally in the UE will contain e.g. some hour of logged measurement information. For post-processing purpose, these logged measurements/events may be tagged with time information (e.g., time stamps).

When the UE has logged measurements the UE indicates to the network that it has an available measurement log. The network may then request the UE to deliver the measurement log. This procedure is illustrated inFIG. 1. The UE sends10an indication to a network node, e.g. an eNodeB or a RNC (Radio Network Controller), that it has an available measurement log. The network node then determines11whether is wants to request the measurement log. If it determines to request the measurement log it sends12a request to the UE. Thereupon the UE delivers13the measurement log to the network node.

The network collects measurement logs from several UEs in different cells. By collecting and retrieving information from the measurement logs the network is able to perform optimization of radio coverage, mobility, network capacity and to perform parameterization for common channels and verification of QoS.

It has been agreed upon to include a time stamping for the MDT measurements. However, the timestamp does not need to be very accurate. It is recognized that a simple mechanism is sufficient. For example, during a log activity of e.g. one hour, one can assume that a drift of approximately ±10 s is acceptable.

Solutions using Global Positioning System (GPS), as well as other network-broadcast time-of-day information have been discussed. A mechanism that e.g. uses System Frame Number (SFN) of the current cell as timing source has the potential of providing a very accurate time reference. However, a UE will change cells and occasionally even lose cell coverage causing problems with the time stamping during the performance of UE measurement logging function.

Most user equipments are equipped with a clock. However, in many cases the clocks of the user equipments are not synchronized with a common time base, e.g. the local time. If the UE utilizes the internal clock when time stamping measurement data, problems will arise when the network retrieves time stamped measurement information from the measurement logs and compare the time stamp measurement information from several UEs in a cell.

The document “Study on Minimization of drive-tests in Nest Generation Networks; (Release 9)”, 3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; 3GPP TR 36.805, V9.0.0, 21 Dec. 2009, pages 1-24, discusses automating the collection of UE measurements, i.e. MDT, by executing measurements in the UE. It further discloses storing the measurements in a measurement log wherein the measurements are linked to a time stamp that is available in the UE and receiving a request to deliver the log in the UE. Thereupon the log is delivered to the network node. However, the accuracy of the time information is underdetermined.

The document “Time stamp achievement and reporting in MDT”, TD TECH, 3GPP DRATFT; R2-102495, 4 Apr. 2010 relates to the issue of the accuracy of time information in MDT. It discusses a mechanism of reporting time stamp via RRC signalling. A relative time is used for the time stamp of the measurement in the UE. The relative time is linked to a counter which is turned on in the UE when measurement is triggered. However, the network node does not know the accuracy of the time information in the log.

The document “Logged MDT principles”, NOKIA SIEMENS NETWORKS et al, 3GPP DRAFT; R2-103191, 4 May 2010 relates to configuration and reporting of a measurement log for MDT but does not mention the accuracy of the time information.

SUMMARY

The object of the present invention is to address some of the problems and disadvantages outlined above, and to provide methods and arrangements that enable processing of measurement data in a cellular communication system.

The above stated object is achieved by means of the methods and the arrangements according to the independent claims.

In accordance with a first aspect of embodiments, a method in a user equipment for enabling processing of measurement data is provided. The user equipment is configured to communicate with a network node comprised in a cellular communication system. The user equipment comprises a measurement log for storing measurement data and time reference information. Furthermore, the method comprising receiving a time reference from the network node. Moreover, an internal clock function is started at the reception of the time reference. One or more measurement is then executed and measurement data is stored with a determined value of the internal clock function in the measurement log. Furthermore, the method comprising sending an indication to the network node that the measurement log is available. A request to deliver the measurement log is received from the network node. Finally, the method comprising delivering the measurement log to the network node.

In accordance with a second aspect of embodiments, a user equipment for enabling processing of measurement data is provided. The user equipment is configured to communicate with a network node comprised in a cellular communication system. The user equipment comprises a storage unit for storing a measurement log in which measurement data and time reference information are stored. The user equipment further comprises a transceiver adapted to receive a time reference from the network node and a processor unit adapted to start an internal clock function when the time reference is received, execute a measurement, and store the measurement data with a determined value of the internal clock function in the measurement log. Moreover, the transceiver is further adapted to send an indication to the network node that the measurement log is available and to receive a request to deliver the measurement log from the network node and thereupon to deliver the measurement log to the network node.

In accordance with a third aspect of embodiments, a method in a network node for processing of measurement data is provided. The network node is comprised in a cellular communication system and configured to communicate with at least two user equipments. The method comprising, for each user equipment, sending a time reference to the user equipment. Furthermore, the method comprising receiving an indication from the user equipment that a measurement log is available and sending a request to deliver the measurement log to the user equipment. Moreover, the method comprising receiving the measurement log from the user equipment and comparing the measurement logs of at least two user equipments by comparing measurement data logged at a value of time of an internal clock function of the respective user equipment with respect to the sent time references.

In accordance with a fourth aspect of embodiments, a network node for processing of measurement data is provided. The network node is comprised in a cellular communication system and configured to communicate with at least two user equipments. The network node comprises a transceiver adapted to, for each user equipment, send a time reference to the user equipment and to receive an indication from the user equipment that a measurement log is available. The transceiver is further adapted to send a request to deliver the measurement log to the user equipment and to receive the measurement log from the user equipment. The network node further comprises a processor unit adapted to compare the measurement logs of at least two user equipments by comparing measurement data logged at a value of time of an internal clock function of the respective user equipment with respect to the sent time references.

An advantage of particular embodiments is that they provide a solution to the stated object which offers simple implementation and operational simplicity without requiring complex arrangements in the user equipment or in the network.

A further advantage of particular embodiments is that they provide a solution which does not require synchronization of clocks in the user equipment and the network.

Further advantages and features of embodiments will become apparent when reading the following detailed description in conjunction with the drawings.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular sequences of steps and particular device configurations in order to provide a thorough understanding of the embodiments. It will be apparent to one skilled in the art that the embodiments may be practised in other embodiments that depart from these specific details. In the drawings, like reference signs refer to like elements.

Moreover, those skilled in the art will appreciate that the means and functions explained herein below may be implemented using software functioning in conjunction with a programmed microprocessor or general purpose computer, and/or using an application specific integrated circuit (ASIC). It will also be appreciated that while the current invention is primarily described in the form of methods and devices, the invention may also be embodied in a computer program product as well as a system comprising a computer processor and a memory coupled to the processor, wherein the memory is encoded with one or more programs that may perform the functions disclosed herein.

Embodiments are described herein by way of reference to particular example scenarios. Particular aspects are described in a non-limiting general context in relation to an LTE system. It should though be noted that the invention and its exemplary embodiments may also be applied to other types of radio access networks for processing measurement data.

In the following detailed description a number of embodiments are disclosed wherein the problem of unsynchronized internal clocks of user equipments in a cellular communication system is addressed by a solution where a mechanism relying on a standalone clock function in user equipments is provided. Embodiments described in more detail in the following provide a network node that distributes a time reference to a user equipment (UE), and wherein the UE, using an internal clock function, time-stamps the logged measurements and/or events relative to the received time reference. When the UE has logged measurements the UE indicates to the network node that it has an available measurement log. The network node may then request several UEs to deliver their measurement log, respectively. The network node is then able to retrieve time stamped measurement information from the measurement log of each UE relative the sent time reference. Furthermore, the network node is then able to compare measurement information from each UE in a cell provided at the same time interval in all UEs.

According to one exemplary embodiment, a network node comprised in a cellular communication system, e.g. a LTE system, communicates with UEs in a serving cell. The network node sends a time reference to a UE. For example, the network node could include the time reference in a MDT (Minimization of the Drive Tests) measurement configuration message sent to the UE when the network requests the UE to perform logging of measurements. The time reference could e.g. be a time-of-day and date indication. The exact content does not need not be standardized, and can instead be left for the choice of the operator of the cellular communication system. Furthermore, at reception of the MDT measurement configuration message including the time reference, the UE starts an internal clock function or a clock counter from zero, and steps it e.g. by one every second. The UE additionally stores the time reference in the measurement log. Thereupon the UE is able to “timestamp” each subsequently logged MDT measurement with the current value of the internal clock function, and adds this to the measurement log.

FIG. 2illustrates an exemplary embodiment of a structure of the measurement log stored internally in the UE and reported to the network node, including measurement and time information. The measurement log20comprises the time reference Initial MDT Time Ref21received from the network node. It further comprises a first MDT measurement22which is timestamped i.e. the MDT measurement is stored in the log with the current value of the internal clock function MDT_TIME at the time of measuring. The measurement log also comprises a second MDT measurement23which is timestamped in the same manner. The log may include several timestamped MDT measurements24as illustrated inFIG. 2. Typically, the measurement log will include e.g. some hour of logged measurement information.

InFIG. 3an exemplary embodiment of a method in a UE for enabling processing of measurement data is illustrated. The UE is configured to communicate with a network node comprised in a cellular communication system. In a first step30the UE receives a time reference Treffrom the network node. The time reference may be included in the same message which is sent to the UE from the network node requesting the UE to start logging measurements such as the MDT measurement configuration message. Then in a next step31, the UE starts an internal clock function Tintupon the reception of the time reference Tref. The UE starts executing measurements in the cell in a further step32. The measurement may be any of the measurements required for MDT functionality. For example, the measurement executed may be a downlink pilot signal strength measurement of serving or neighbour cell. It may also be a downlink pilot signal quality measurement of serving or neighbour cell. It should be noted that the measurements could be executed periodically in the UE. When the measurement is executed the UE stores33the measurement data in a measurement log in the UE. The measurement data is stored with a current value of the internal clock function Tintin the measurement log i.e. the measurement data is stored with a timestamp in the log. The UE sends34an indication to the network node that the measurement log is available. In a further step35the UE receives a request from the network node to deliver the measurement log to the network node. The UE then delivers26the measurement log comprising the timestamped measurement data and the time reference Trefto the network node.

InFIG. 4an exemplary embodiment of a method in a network node for processing of measurement data is illustrated. The network node is comprised in a cellular communication system and configured to communicate with at least two user equipments in a cell which is served by the network node. In a first step40the network node sends a time reference Trefto each UE. The time reference Trefmay be included in the same message which is sent to the UE requesting the UE to start logging measurements, such as the MDT measurement configuration message. The UE will start logging measurement data in a measurement log in accordance with the previously described method. In a further step41an indication is received from the UE that a measurement log is available in the UE. Next, the network node sends42a request to deliver the measurement log to the UE. The network node receives the measurement log in a further step43. Upon the reception of measurement logs of at least two UEs the network node can compare44the measurement logs. This step is performed by comparing measurement data logged at a value of time of an internal clock function of the respective user equipment with respect to the time references Trefsent to each UE, respectively.

FIG. 5is a schematic block diagram schematically illustrating an exemplary UE510that is configured to communicate with an exemplary network node520comprised in a cellular communication system. The UE510and network node520can be implemented using various components, both hardware and software. It should be noted that the network node may serve several UEs. However, for simplicity reasons only one UE is illustrated in the figure.

For example, as shown generally inFIG. 5, such a UE510include a processor unit512, one or more storage devices514, an operating system (not shown) running on the processor unit512as well as a corresponding application, e.g., an application which processes measurement data in the manner described above. Additionally, such a network node520include a processor unit522, one or more storage units524, an operating system (not shown) running on the processor unit522as well as a corresponding application, e.g., an application which processes measurement data in the manner described above. Both the UE510and the network node520may comprise an interface unit516,526to facilitate communications between the UE510and the network node520. For example, the interface unit516,526may include a transceiver capable of communicating wirelessly over an air interface, e.g., as specified by LTE, including hardware and software capable of performing the necessary modulating, coding, filtering and the like, as well as demodulating and decoding to process such signals.

The transceiver unit518comprised in the UE510is adapted to receive a time reference Treffrom the network node520. The processor unit512is adapted to store the received time reference Trefin a measurement log which may be comprised in the storage unit514. The processor unit512is further adapted to start an internal clock function when receiving the time reference Treffrom the network node520. Furthermore, the processor unit512is adapted to execute measurements in the cell and to store the measurement data with a determined value of the internal clock function in the measurement log comprised in the storage unit514. The transceiver518is adapted to send an indication to the network node520that the measurement log is available and to receive a request to deliver the measurement log from the network node520. Finally, the transceiver518comprised in the UE510is further adapted to deliver the measurement log to the network node520.

Moreover, the transceiver528comprised in the network node520is adapted to send a time reference Trefto the UE510. It is further adapted to receive an indication from the UE510that a measurement log is available. The transceiver528is also adapted to send a request to deliver the measurement log to the UE510and then to receive the measurement log from the same. The processor unit522comprised in the network node520is adapted to then compare the measurement logs of at least two user equipments510by comparing measurement data logged at a value of time of an internal clock function of the respective user equipment510with respect to the sent time references Tref.

The embodiments may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the embodiments described. The present embodiments are to be considered in all respects as illustrative and not restrictive.