HK1127837A

HK1127837A - Measurement reporting in a telecommunication system

Info

Publication number: HK1127837A
Application number: HK09105236.4A
Authority: HK
Inventors: Salonaho Oscar; Sipilä Kari
Original assignee: Qualcomm Incorporated
Priority date: 1998-02-17
Filing date: 2009-06-10
Publication date: 2009-10-09

Description

Measurement reporting in a telecommunications system

Technical Field

The present invention relates to measurement reporting on a radio interface in a telecommunication system.

Background

In a mobile telecommunication system a mobile station MS can utilize a radio connection to use services provided by a network. The radio connection utilizes channels of a called radio interface between a mobile station and a base station of a mobile telecommunications network. Only limited bandwidth on the radio spectrum is allocated for use by the telecommunication system. In order to obtain sufficient capacity, the channel must be used as densely as possible over and over again. To accomplish this, the coverage area of the system is divided into cells, each of which is served by a base station. Therefore, mobile telecommunications systems are also often referred to as cellular systems.

The network elements and the internal relationships between the network elements of the mobile telecommunications system are illustrated in fig. 1. The network shown in the figure is in accordance with the UMTS system currently standardized by ETSI (european telecommunications standards institute). The network comprises base stations BTS (base transceiver stations) which can establish connections with mobile stations MS, radio network controllers RNC which control the use of the base stations, and mobile switching centers MSC which control the RNCs. Furthermore, the network comprises a network management system NMS, with the aid of which an operator can modify the parameters of other network elements. The interface between the MSC and the RNC is commonly referred to as the Iu interface. The interface between the RNC and the BTS is the Iubis interface, and the interface between the BTS and the MS is the radio interface. According to some proposals, an interface Iur between RNCs is specified.

Calls for the mobile station are routed from the BTS to the MSC through the RNC. The MSC hands the call over to another mobile switching center or fixed network. The call may likewise be routed to another mobile station under the same MSC, or possibly even to another mobile station under the same BTS.

The radio interface between the base station and the mobile station can be divided into channels using a number of division methods. Known partitioning methods are, for example, time division multiplexing TDM, frequency division multiplexing FDM, and code division multiplexing CDM. In TDM systems, the spectrum allocated to the system is divided into successive time frames consisting of time slots, each time slot defining a channel. In FDM a channel is defined by the frequency used in the connection. In CDM, channels are defined by spreading codes (spreading codes) used in connection. These methods may be used separately or in combination.

In order to be able to successfully communicate with a mobile telecommunications network, the mobile station continuously monitors the radio signals transmitted by the base stations. In idle mode the mobile station decodes the strongest signal received and requests, when necessary, a connection to the base station that sent the signal.

During an active connection, the connection may be moved from one base station to another. A connection can be moved from one base station to another by simply rerouting the signal, which is known as hand-over (hand). Especially in CDMA (code division multiple access) systems with CDM, system interference and thus capacity can be reduced by using soft handover in which a mobile station has simultaneous connections with a plurality of base stations, which constitute a so-called active connection group.

The handover may be:

intra-cell handover

Inter-cell handover between two base stations under the same radio network controller

inter-RNC handover between two RNCs under the same MSC, or

inter-MSC handover between two cells under different MSCs.

In addition, the handover may be divided into an intra-frequency handover, where all channels involved in the handover process are at the same frequency; and inter-frequency handover, wherein channels from at least two frequencies are involved in the handover.

In order to be able to establish a handover to the correct base station during an active connection, the mobile station continuously measures radio signals from the base stations connected to it and the neighbouring base stations of said base stations. The measurement results are sent to the network using a measurement reporting scheme specified in the system. From this report, the network initiates the handover when the mobile station has a better or at least sufficiently good radio connection to another base station.

In addition to the handover initiated by the network, the handover evaluated by the mobile station is also known. In an exemplary description of handover being evaluated by a mobile station, the mobile station monitors the signal levels received from neighboring base stations and reports those beacon signals to the network that are above or below a given set of thresholds. These thresholds may be dynamically adjusted as will be explained below. According to this reporting scheme, the network will decide whether to change the active set of connections.

Two types of thresholds are used: the first is a beacon reporting that it has sufficient power for coherent demodulation, and the second is a beacon reporting that its power has dropped to a level that is not conducive for receiving the transmitted information. Based on this information, the network instructs the MS to add or remove base station signals from its active set.

While soft handoff improves overall performance, it may negatively impact system capacity and network resources in some cases. This is due to the unnecessary branching of the active set between the MS and the base station. In the downlink direction from the base station to the mobile station, the extra branches reduce the system capacity and in the uplink direction from the mobile station to the base station, it costs more network resources.

To solve this problem, the dynamic threshold principle with respect to active group management is known in the prior art. In the method, the MS detects beacons that intersect a given static threshold T1. When this threshold is crossed, the beacon is moved to the candidate set. The beacon is then searched and tested more frequently according to a second dynamic threshold T2. A second threshold T2 will test whether this beacon is worth adding to the active set.

Adding an even poor additional finger signal will improve performance when the beacon corresponding to the finger in the active set is weak. In these cases, a relatively low value of T2 is used. When there are one or more dominant beacons, adding an additional weak branch whose beacon signal exceeds T1 will not improve performance and will use more network resources. In these cases, a higher value of T2 is used.

After detecting a base station signal exceeding T2, the MS reports it back to the network. The network will then set up the care-of resource and instruct the MS to coherently demodulate the signals of this additional branch.

The beacons may be subtracted from the active set according to the same principles. When the beacon strength falls below the dynamic threshold T3, the handoff connection is removed and the beacon is moved back to the candidate set. The threshold T3 is a function of the total energy of the beacon in the active set. When the beacons in the active set are weak, removing an even weak branch will degrade performance. In these cases, a relatively low value of T3 is used. When there are one or more dominant fingers, removing the weaker signals will not degrade performance, but makes more efficient use of network resources. In these cases, a higher value of T3 is used. Branches that do not contribute enough to the total received energy will be subtracted. When further dropping below the static threshold T4, this beacon is removed from the candidate set.

In order to be able to control the connection, the network requires different kinds and different amounts of measurement information in different situations. The more information that is sent, the more efficient the handover algorithm. However, the more information the mobile station sends to the network, the more radio resources are consumed. Therefore, the measurement reporting schemes according to the prior art always trade off between efficiency of the handover algorithm and utilization of radio resources.

Due to the use of mobile telecommunication systems and the increasing use of multimedia applications requiring large bandwidths, the current methods are no longer sufficient and thus limit the performance of mobile telecommunication networks. The object of the present invention is a flexible measurement reporting scheme that solves this problem.

Disclosure of Invention

The basic idea of the invention is to specify at least two different triggers for sending a measurement report from a mobile station to a network. According to the invention, the network provides for these triggers to be used for different measurement report types. These triggers are preferably upper or lower thresholds for parameters such as radio signals, timer conditions, etc. In response to detecting that the measurement value has exceeded its upper threshold or fallen below its lower threshold, the mobile station sends a measurement report to the network.

In particular, the present invention provides a method of measurement reporting in a telecommunication system comprising a mobile station and a network comprising a base station, wherein a handover decision on establishing or dropping a link between the mobile station and the base station is made in the network based on a measurement report sent from the mobile station to the network, characterized in that the method comprises the steps of: specifying, by the network, a plurality of parameters for the mobile station; transmitting parameters to the mobile station; determining, by the mobile station, a plurality of independent measurement report trigger conditions using the network specified parameters; monitoring at the mobile station characteristics of a plurality of radio signals received from respective base stations; checking, by the mobile station, whether a measurement report triggering condition is satisfied; generating a measurement report at the mobile station comprising information about the monitored radio signal when one of said trigger conditions is fulfilled; and transmitting the generated measurement report to the network.

The invention also provides a telecommunications network for a telecommunications system comprising a mobile station and a network comprising a base station, in which system the mobile station monitors radio signals transmitted by the base station and in which network a handover decision regarding establishment or deactivation of a link between the mobile station and the base station is made on the basis of a measurement report transmitted from the mobile station to the network, characterized in that the network comprises: determining means for determining a plurality of parameters of a mobile station for use by the mobile station in determining a plurality of independent measurement report trigger conditions; and transmitting means, responsive to said determining means, for transmitting the determined parameters to the mobile station.

The invention further provides a network element for a telecommunication network of a telecommunication system comprising a mobile station and a network comprising base stations, in which system the mobile station monitors radio signals transmitted by the base stations and in which network a handover decision on establishing or dropping a link between the mobile station and a base station is made on the basis of a measurement report transmitted from the mobile station to the network, characterized in that the network element comprises: determining means for determining a plurality of parameters of a mobile station for use by the mobile station in determining a plurality of independent measurement report trigger conditions; and transmitting means, responsive to said determining means, for transmitting the determined parameters to the mobile station.

The present invention still further provides a mobile station for use in a telecommunications system comprising a mobile station and a network comprising a base station, in which system a handover decision regarding establishment or deactivation of a link between the mobile station and the base station is made in the network based on a measurement report sent from the mobile station to the network, characterized in that the mobile station comprises: receiving means configured to receive a plurality of parameters from the network (10); means for determining a plurality of independent measurement report trigger conditions using the received parameters; monitoring means for monitoring characteristics of a plurality of radio signals received from respective base stations; a plurality of checking means for checking whether a measurement report triggering condition is satisfied; a plurality of reporting means, responsive to said checking means, for establishing a measurement report when one of the trigger conditions is met, the measurement report including information about the monitored radio signal; and transmitting means for transmitting the measurement report to the network.

According to a preferred embodiment, the network may deactivate one or more triggers. However, at least one flip-flop must always be active.

According to a preferred embodiment, the triggers, i.e. the thresholds, are defined for the downlink and uplink directions, respectively. Furthermore, it is specified how the outputs of these flip-flops are combined. For example, it may be determined whether the measurement report is sent when both uplink and downlink conditions are met, when either of them is met, entirely according to the downlink conditions, or entirely according to the uplink conditions.

In a preferred embodiment, one of the measurement report types is a mobile station evaluation handover measurement report. Such a report is triggered in the mobile station when at least one upper threshold value of the radio signal parameters for the mobile station to evaluate handover is exceeded or falls below a lower threshold value.

According to another preferred embodiment, one of the measurement report types is a periodic handover measurement report. Such a report is triggered periodically according to a period set by the network.

According to another embodiment, one of the measurement report types is a measurement report based on a change in conditions. In this type of reporting, the transmission of measurement reports is triggered by a change in the radio signal parameters exceeding a threshold given by the network.

Drawings

The invention is described in more detail below with reference to the attached drawing figures, wherein:

fig. 1 illustrates a telecommunications system;

figure 2 shows a measurement reporting scheme;

FIG. 3 shows the structure of an MEHO algorithm;

figures 4, 5, 6, 7 and 8 each show a decision flow diagram,

fig. 9 shows functional entities in a telecommunications network; and

fig. 10 shows functional entities in a mobile station.

Detailed Description

The basic idea of the invention is schematically shown in fig. 2. In step (stage) G00, a plurality of triggers are defined in the network, three triggers being defined in the exemplary embodiment shown in the figure, trigger 1, trigger 2 and trigger 3. It must be noted here, however, that the invention is not limited to the use of exactly three flip-flops, the number of which may be any number equal to or greater than 2. The mobile station is informed about these triggers.

The mobile station continuously measures radio signals from the neighboring base stations (step G01). In these measurements, the mobile station obtains the information necessary to compare the measurement results with the triggers.

At step G02, the measurement result is compared with flip-flop 1, and if the condition for activating the flip-flop is met (decision step G03), then at step G10, a measurement report of type 1 is sent to the network, and the process continues to step G01. If the condition is not met, the process continues to step G04.

At step G04, the measurement result is compared with flip-flop 2, and if the condition for activating the flip-flop is met (decision step G04), then at step G20, a measurement report of type 2 is sent to the network and the process continues to step G01, if the condition is not met, then the process continues to step G06.

In step G06, the measurement result is compared with the trigger 3. If the condition for activating the trigger is met (decision step G07), then at step G30, a measurement report of type 3 is sent to the network, and the process continues to step G01.

According to a preferred embodiment, the network may deactivate one or more triggers. Thus, the network is able to flexibly adjust the reporting scheme. For example, when inside a cell, the mobile station has a very good link with the base station, in which case it is sufficient for the mobile station to inform the network when the link is worse than a given threshold. In this case, only one trigger condition is valid, which threshold condition is met when the mobile station reaches the border area of the cell, and the mobile station sends a measurement report to the network. Based on this received report, the network decides that the mobile station should be tracked more closely and commands the mobile station to start sending measurement reports periodically once the link monitor meets the second threshold condition. Now the condition of both flip-flops is valid. However, in all cases, the condition of at least one flip-flop must be valid.

In fig. 2, the comparisons in steps G02, G04 and G06 are shown in series. However, they may equally be implemented as parallel processes.

In the following, the three best types of measurement reports will be explained in more detail. These types are particularly preferred when a Wideband CDMA (WCDMA) system with soft handover is employed. The report types are mobile station evaluated handover (MEHO), periodic measurement reports, and measurement reports based on a change in conditions.

Handover of mobile station evaluation

In this respect, handover of mobile station evaluation means that a handover measurement algorithm located in the mobile station triggers a handover report. The actual HO decision is always implemented by the network. The handover report type may be further divided into an intra-frequency handover report type and an inter-frequency handover report type.

In-frequency handover

The algorithm presented hereinafter includes the possibility to utilize information about Downlink (DL), Uplink (UL) or both as HO report trigger. This arrangement also provides a flexible means of controlling the information content of the HO report. Such actual thresholds and timers are selected in the algorithm so that a wide variety of HO algorithms can be constructed by setting them appropriately.

The mobile station continuously performs measurements of the radio signals from the different BTSs according to the procedure to be described below.

Mobile station measuring received data for BTS_iThe power of the beacon channel. This power is marked as P_rx，i(mW). The mobile station performs this measurement for a time period t, a parameter that is set by the network priority.

P_rx，iThe values are averaged over the measurement period. The result of this operation is labeled P _ ave_rx，i. When the measurement is complete, the label L is calculated according to the following formula_iPath loss estimate of (dB):

in (1), P _ beacon_tx，iThe unit of (2) is mW.

During the same measurement period t, the MS also estimates the beacon channel interference power before or after correlating the received sum signal with the spreading code, which is a parameter preferably specified by the network. The difference in the values calculated before and after the correlation is due to the fact that: the correlation significantly reduces the interference caused by other connections. This interference is marked I_i(mW). The interference is also averaged over the measurement period. After the averaging is complete, the average is converted to dBm. This average is labeled I _ ave_i。

The MS also receives the BTS, e.g., on a beacon channel_iIs marked as DL _ offset_i(dB), which is a relatively stable parameter and therefore does not need to be re-received for each measurement period. The purpose of this base station specific parameter is to specify different cell sizes. The mobile station is more likely to be handed over from the first set of cells than from the second set of cells. The cells of the first group are thereforeSmaller than the cells of the other groups. The offset value can be considered as an additional base station specific part of the threshold value, which is given in more detail shortly.

From the above information, the MS calculates a DL HO measurement sample S_dl，iThe following were used:

S_dl，i＝L_i+I_ave，i+DL_offset_i (2)

thus S_dl，iIs a measure of the carrier-to-interference ratio, CIR, in the measured signal. It is to be noted that S_dl，iThe larger the value, the worse the link from the base station to the mobile station. The scope of the invention is not limited to the use of this particular metric, and other metrics of link quality may be used as well when practicing the invention. As an example, the bit error rate BER in the received radio signal may be used as the measure.

The MS also receives the BTS, e.g., on a beacon channel_ITotal interference power of (1)_ul，i(dBm) and BTS_iUL offset value UL _ offset of_i(dB). The MS then calculates the value of one UL HO measurement sample as follows:

S_ul，i＝L_i+I_ul，i+UL_offset_i (3)

when it is for BTS_iHas been completed, the MS places these results as first elements into the vector L _ fact_i(for L)_iValue), S _ vect_dl，i(for S)_dl，iValue) and S _ vect_ul，i(for S)_ul，iValue) of (a). The last elements of these vectors are discarded. The vector includes a history of measurements. The saved history length, specified by the length n of these vectors, is a network parameter.

After performing the measurements on the base station signals, the MS checks whether or not a MEHO report is to be sent, according to the HO algorithm described in the following section. The argument of the algorithm may be, for example, the vector S _ vent_dl，iAnd S _ vect_ul，iMedian or mean, maximumAs well as specified by the network. In addition, the MS starts to measure by the next BTS_i+1The transmitted beacon signal.

The HO algorithm is used to trigger the sending of MEHO measurement reports. In this algorithm, the UL and DL transmission directions are handled separately. The two algorithms may actually function independently in the MS. The network may instruct the MS to use either or both of them to trigger the sending of the measurement report. It should be noted, however, that the active set is always the same for both directions of transmission.

The algorithm includes the following thresholds:

1. branch increase threshold, denoted BA _ abs in this document_thAnd BA _ rel_th，

2. Branch delete threshold, denoted BD _ abs in this document_thAnd BD _ rel_thAnd are and

3. branch replacement threshold, labeled BR rel in this document_th。

For thresholds 1 and 2, both absolute and relative thresholds are specified. Separate values may be specified for the uplink and downlink directions. These thresholds are used in the Branch Addition (BA), Branch Deletion (BD) and Branch Replacement (BR) decision units. These units may be implemented in the form of hardware units, software blocks or a combination thereof.

The basic structure of these algorithms is shown in fig. 3, and an uplink comparison unit ULU compares the measurement results of the uplink radio signals with triggers defined by thresholds set for these signals and outputs a logical true value. The downlink comparison unit DLU compares the measurement results of the downlink radio signals with the triggers specified by the thresholds set for these signals and outputs a logical true value. The results of the ULU and DLU are combined into one logic signal using a logic function. The logical value may be, for example, an AND (AND) OR (OR) function, OR a function that directly outputs one of the input values of the component. The TRUE value of this signal is checked, e.g. if the TRUE value is TRUE, a report is sent. Of course, using different logic functions when combining the outputs of the ULU and DLU, it may be specified that a report is sent if the true value is FALSE.

The parallel decision units BA, BD and BR shown in fig. 3 are used for different scenarios. When the base station is not in the active connection group and the number of links between the MS and the BTSs in the active group is less than a given limit N_AS，maxBA is used. N is a radical of_AS，maxThe values are preferably parameters set by the network.

The BD is used when the base station is in the active connection group. To prevent the ping-pong effect, the logistic functions of the components BA and BD must be consistent so that the same measurement value for the link between the MS and the BTS is unlikely to cause both components to trigger a measurement report that suggests the addition or deletion of the same link. For example, if the logic functions AND OR are used, the value OR cannot be used in both decision blocks.

When the base station is not in the active connection group and the number of links between the MS and the BTS in said active connection group is equal to the limit value N_AS，maxBR is used. Such a decision unit is used to replace a link of the active link set with another link having better radio characteristics.

An algorithm implementation of the downlink comparison unit DLU of the branch addition algorithm BA is shown in fig. 4. The algorithm is used for beacon signals from base stations that do not belong to the active set. In step a1, it is checked whether the number of base stations in the active set is below a predefined limit value, i.e. whether the active set is full. As an example, a "limit value of 3" may be used herein. If the active set is full, a branch replacement algorithm is selected instead of the branch addition algorithm (step A10).

If the active set is not full, the process proceeds to steps A2, A3, and A4, wherein

Checking whether a new measurement has been received (step a2),

mixing S_i，DLAnd absolute threshold value BA _ abs_th，DLMaking a comparison of, and

mixing S_i，DLAnd threshold S _ best_i，DL+BA_rel_th，DLMake a comparison in which

S_best_i，DLIs the value measured for the best effective branch.

If a new result has been received and the threshold value BA _ abs has been set_th，DLAnd S _ best_i，DL+BA_rel_th，DLBoth are higher than S_i，DLThen the output of the DLU is set to TRUE.

The uplink branch may be implemented using a similar algorithm. If a new result for the uplink has been received and the threshold value BA _ abs_th，ULAnd S _ best_i，UL-BA_rel_th，ULBoth are higher than S_i，ULThe output of the ULU is set to TRUE. Threshold values BA _ abs for use in different directions_th，DL/BA_abs_th，ULAnd BA _ rel_th，DL/BA_rel_th，ULMay be different from or the same as each other.

The values of the DUL and ULU algorithms are input into a logic function, as shown in fig. 3, and if the function outputs a value TRUE, a MEHO measurement report is sent. For example, if the logical value used is AND, a MEHO measurement report is sent when both the ULU AND DLU have the value TRUE.

An algorithm implementation of the downlink comparison unit DLU of the branch deletion algorithm BD is shown in fig. 5. This algorithm is used for beacon signals from base stations belonging to the active set.

It is first checked whether a new measurement has been received (step D2). Measuring the result S_i，DLAnd a threshold BD _ abs_th，UL(step D3) and S _ best_i，DL+BD_rel_th，UL(step D4) for comparison. If any of these thresholds is below S_i，DLThen the DLU is set to TRUE (step D5). Otherwise, the DLU is set to FALSE (step D10) and the next beacon signal in the active set is measured.

A similar comparison is made between the uplink measurement and the uplink threshold to determine the ULU value. The DLU and the ULU are combined using a network-specified logic function to decide whether to send or not send MEHO measurement reports. To prevent ping-pong effects, the logic functions used are chosen such that the same measurement result never results in a BA request plus one branch and in the BD deleting the same branch. To meet this requirement, only one of the logical functions used in the BA and BD algorithms according to the same reporting option may be a logical OR function.

An algorithm implementation of the downlink comparison unit DLU of the finger replacement algorithm BR is shown in fig. 6. The algorithm is used for beacon signals from base stations not belonging to the active set. In step R1 it is checked whether the number of base stations in the active set equals a predefined limit value, that is to say whether the active set is full. As an example, limit value 3 may be used here. If the active set is not full, a branch addition algorithm is selected instead (step R10).

If the active set is full, the process proceeds to a step of checking whether a new measurement has been received (step R2). If no new measurements are received, the next beacon signal is investigated. If a new measurement result S has been received_i，DLThen it is compared to the measured value of the worst link in the active set S _ worst at step R3_i，DLFor comparison. If S _ worst_i，DLExceeds S_i，DLWith a margin (margin) of BR _ rel_thThen the DLU is set to TRUE (step R4). Otherwise the ULU is set to FALSE (step R20) and the measurement results for the next BTS not belonging to the active set are investigated.

Uplink forking can be implemented using a similar algorithm. In the comparison, S_i，ULThe worst link S _ worst in the active set_i，DLFor comparison. If S is_i，DLOver S _ worst_i，DLHas a margin of BR _ rel_thThen the DLU is set to TRUE. Preferably, the margin value BR _ rel is in the downlink and uplink direction_thAre identical, but may also be used in different directionsThe same value. This is a network-specified parameter. The DLU and the ULU are combined using a logic function to decide whether to send MEHO measurement reports or not. The logic function is preferably a logic AND function, AND in another preferred embodiment the network is free to adjust the logic function. The output of the logic function may be, for example, the true value of a DLU or ULU.

When the MEHO algorithm in the mobile station triggers a measurement report, the status of the M best cells/sectors is sent. The transmitted measurement report always includes an appropriate value for the active set. Utilizing S according to whether DL or UL algorithm triggered this report_i，dlOr S_i，ulThe values determine the M best cells/sectors. The content of the report is preferably determined by means of a message sent from the network. The measurement report includes, for example, the following values for each cell/sector reported. These values are filtered values.

1.S_i，dl

2.S_i，ul

3.L_i

It should be noted that the measurement report may include only information about neighboring BTSs for which the beacon signal has been decoded. The handover report must include information on the number of BTSs being reported.

The information contained in the measurement report is preferably specified by the network. For example, the number of beacon signals whose power levels are to be reported in a measurement report is preferably specified by the network.

Inter-frequency HO

The inter-frequency measurements are always initiated by the network. Thus, the mobile station may perform an inter-frequency MEHO only after the network has first commanded the MS to start inter-frequency HO measurements.

There are at least three different reasons for inter-frequency HO:

1. coverage. For example, the MS is exiting the coverage area of a microcell and must be handed off to a macrocell. This situation may be relatively simple. For example, if a finger deletion has triggered a measurement report and only one finger is active, then the conclusion made by the network is that the MS is exiting coverage. The network responds to this by sending a message 'start i-f measurement'. This message contains the possible candidate BTSs. The mobile then begins searching for stronger BTSs at other frequencies. The sending of the measurement report is triggered when the MS finds a candidate BTS on another (new) frequency that is stronger than the best active branch on the current frequency.

2. And (4) loading. An inter-frequency HO may be appropriate if for some reason the load on the used frequency is higher than on some other available frequency. This situation is likely to be known only to the network. After the network has detected the overload condition, the operation is the same as in case 1.

3. The speed of movement. If the MS is connected to the microcell layer, the speed of the MS is so high that an excessive handover amount is required. This is a further study item. The most critical issue is the detection of the MS velocity. That is, there is a method of reliably estimating the speed of the MS? Can the received beacon power be measured often enough to use a fast fading based method? What signaling the MS uses to indicate its speed if the estimation is made in the mobile station?

After the network has ordered the MS to start inter-frequency measurements, the MS will make measurements on the frequencies given in the start measurement order.

This algorithm is used to trigger the sending of inter-frequency measurement reports. In the algorithm, the UL and DL transmission directions are handled separately. Therefore, in practice the two decision algorithms (DLU and ULU) function independently in the MS. The outputs of these algorithms are combined as shown in fig. 3 to make the final decision about sending a measurement report. The network may instruct the MS to use either or both of them to trigger the sending of the measurement report. It should be noted, however, that the active set is always the same for both transport directions.

The algorithm includes the followingAnd (4) a threshold value. For the threshold, an absolute threshold and a relative threshold CF _ abs are specified_thAnd CF _ rel_th. A decision flow diagram for the DLU unit of the algorithm is shown in fig. 7.

If a new measurement has been made on a new frequency not belonging to the active set, the link loss experienced by the beacon signal is compared to an absolute threshold CF _ abs_thFor comparison. If the quality of the link is sufficient, it is compared to the best link in the active set. If the quality is better than the predefined threshold, the output of the DLU algorithm is set to TRUE.

A similar algorithm ULU is applied for the downlink direction. The outputs of the DLU and ULU are combined using a logic function as previously described.

When the HO algorithm triggers inter-frequency measurement reporting, the status of the M best cells/sectors is sent. Based on whether the report is triggered by DL or UL algorithm, S is utilized_i，dlOr S_i，ulTo determine the M best cells/sectors. The content of the report is determined using a message sent from the network. The measurement report includes, for example, the following values for each reported cell/sector. These values are filtered values.

1.S_i，dl

2.S_i，ul

3.L_i

It has to be noted that the possible logic functions are not limited to those presented in the above examples. For example, if the outputs of the DLU and ULU functions are not binary but have multiple levels, or even continuous functions triggered by certain events with respect to radio signals in various directions, a fuzzy logic function may be utilized when making a decision whether to send a measurement report or not based on the outputs of the functions DLU and ULU. The fuzzy logic function is preferably given by the network.

Periodic handover reports

The MS continuously performs pairs in a periodic measurement schemeMeasurement of radio signals. Measurement reports are periodically sent by the MS to the network. The transmission period is specified by a parameter T _ report set by the network. It should include M best cells/sectors. The transmitted measurement reports always also include appropriate values for the active set. The order of the sectors being set by the network S_i，dlOr S_i，ulAnd (4) setting.

The measurement report includes, for example, the following filtered values for each reported cell/sector. These values are filtered values.

1.S_i，dl

2.S_i，ul

3.L_i

It should be noted that the measurement report may include only information about neighboring BTSs for which the beacon signal has been decoded. Therefore, the handover report must include information on the number of BTSs being reported. The parameters specified by the network are preferably similar to those specified in the MEHO case set forth above.

HO reporting scheme based on condition change

If the condition changes by a sufficient amount, then a measurement report based on the change in condition is triggered to be sent. The number of changes required is set by the network and marked as Change_th(dB)。

In this reporting scheme, the MS maintains a list of N (preferably one parameter specified by the network) best BTSs. In which order passes or makes use of S_i，ulOr by S_i，dl(preferably an option set by the network). When S of one of these BTSs_i，ulOr S_i，dlChange of value of_thA measurement report is sent comprising the new value of the changed amount. If a comparison occurs with the worst BTS in the list (depending on how the BTSs are arranged in order, S will be_i，ulOr S_i，dlValue of (d) for said comparison) is better than Replace_th(dB) new BTS, then measurement reports are also sent. At most every Tms (this is a network)Parameters) sends a measurement report once.

This method requires that the MS stores in memory the parameter values sent in previous measurement reports in tabular form. That is, the MS must keep in memory the conditions seen by the network from the measurement reports sent by the MS. The table must include in its elements the values of the required (by the network) reported quantities and a set of reported base stations, i.e. those whose beacon signal measurements are reported. For example, the format of this table, i.e., the HO _ table, is as follows:

one decision diagram embodiment for sending measurement reports based on changes in conditions is shown in fig. 8. After measuring the signal (step C1) and sending a measurement report (step C2), the process waits for a delay T specified by the network (step C3). In step C4, the best of those beacon signals that do not belong to the reported group of base stations, i.e., the candidate base station, is compared to the worst of those beacon signals that belong to the reported group of base stations. If the signal quality of the candidate base station exceeds the signal quality of the worst reported base station by a margin replace-th specified by the network, the worst base station is replaced with the candidate base station in the set of reported base stations (step C10). The HO-tab is updated (step C11) and a measurement report is sent (step C12).

If the reported base station list does not need to be updated, the change in the measured signal value is compared to a given threshold at step C5. If the threshold is not exceeded, the process returns to step C4. If at least one of the thresholds is exceeded, a measurement report is generated (step C11) and sent (step C12).

The content of the measurement report may be associated with its measured value (S)_i，ulOr S_i，dl) Elements in the HO _ table of the BTS that has been changed are the same. The measurement report/HO _ table may include, for example, the following for eachReported filtered values of cell/sector:

1.S_i，dl

2.S_i，ul

3.L_i

the inter-frequency scheme is the same as the intra-frequency scheme for the reporting scheme based on the change of conditions, except that the network commands the MS to initiate measurements only when needed.

The network function according to the invention is shown in fig. 9, the network comprising:

determining means for determining a plurality of independent trigger conditions

Transmitting means, responsive to the determining means, for transmitting the determined trigger condition to the mobile station.

For example, the transmitting apparatus may transmit the threshold value to the corresponding mobile station using a dedicated control channel DCCH associated with the connection to the mobile station communication service. These means are preferably implemented in a single network element of the network, e.g. a radio network controller RNC.

In a preferred embodiment, one of the determining means determines the threshold for triggering the sending of the measurement report in the mobile station when at least one upper threshold for handover of mobile station evaluation is exceeded or falls below a lower threshold. Examples of suitable parameters for such a threshold are given above.

In a preferred embodiment, one of the determining means determines a trigger condition for periodically sending measurement reports in the mobile station. In this case, the determination means determines an appropriate period for measurement reporting.

Preferably said determining means is arranged to specify the activity of the respective trigger condition and said transmitting means is arranged to transmit such information to the mobile station.

According to another embodiment, one of the determining means determines a threshold for triggering the sending of the measurement report in the mobile station, said triggering being caused by a change in radio resources exceeding a threshold given by the network. Examples of suitable parameters for such a threshold are given above.

A mobile station MS according to the invention is shown in fig. 10. The mobile station comprises

Receiving means for receiving from the network a trigger condition for sending a measurement report,

monitoring means for monitoring the radio signal,

a plurality of checking means responsive to the receiving means and to the monitoring means and having the function of checking whether a triggering condition for sending a measurement report of a specified type is fulfilled,

a plurality of reporting means responsive to the testing means for establishing measurement reports, and

-sending means, responsive to the reporting means, for sending the measurement report to the network.

The mobile station preferably further comprises:

determination means (DLU, ULU) for checking the triggering conditions of the uplink and downlink measurements, respectively, in order to produce two different checking results, and

combining means responsive to said determining means to combine said test results and decide whether to send a measurement value, as shown in figure 3.

The measurement reporting scheme according to the present invention provides a flexible means for reporting measurement results. The advantage of flexibility is that the measurement reports can be adjusted to provide the necessary information to the network while minimizing the amount of radio resources consumed for measurement reporting.

The present invention has been described above by way of preferred embodiments illustrating the principles of the invention. The invention may vary in its details within the scope of the attached claims. For example, the trigger condition for sending a measurement report may be a threshold value of a linear combination of downlink and uplink measurement results. In this case, the function that specifies the linear combination is preferably specified by the network.

Claims

1. A method of measurement reporting in a telecommunication system (10) comprising a mobile station and a network comprising base stations (BS11, BS12), wherein in the network a handover decision on establishing or dropping a link between the Mobile Station (MS) and a base station (BS11, BS12) is made on the basis of a measurement report sent from the Mobile Station (MS) to the network,

the method is characterized by comprising the following steps:

specifying (G00), by a network, a plurality of parameters for a Mobile Station (MS), the parameters being configured to specify a plurality of independent measurement report triggering conditions

Sending (G00) the parameters to the Mobile Station (MS), and

a measurement report is received from the mobile station indicating compliance with a triggering condition according to the parameters.

2. A method according to claim 1, characterized in that:

one of the parameters is configured to specify a trigger condition for a value of a timer.

3. A method according to claim 1, characterized in that: one of the trigger conditions is a threshold value for a radio signal parameter or a function thereof.

4. A method according to claim 3, characterized in that: the radio signal parameter is the power level of the received signal or a function thereof.

5. A method according to claim 3, characterized in that: the radio signal parameter is interference in the received radio signal or a function thereof.

6. A method according to claim 5, characterized in that:

the network uses a CDMA air interface in which connections are separated by different spreading codes, and

the value of the interference is an estimate of the interference power.

7. A method according to any one of the preceding claims, characterized in that the method further comprises the steps of:

the validity of the measurement report trigger conditions is specified by the network such that at least one trigger condition is valid and the remaining trigger conditions are invalid if there are remaining trigger conditions, thereby specifying the measurement report trigger conditions to be applied by the mobile station.

8. A method according to any of claims 3-6, characterized in that the parameters comprise:

a base station specific offset value corresponding to the base station to be monitored by the mobile station is used by the mobile station to check whether the measurement report triggering condition has been met.

9. A method according to claim 8, characterized in that the offset value is dynamically defined by the network.

10. The method according to any of claims 3-6, characterized in that: the one triggering condition comprises a threshold for a change of a radio parameter or a function thereof.

11. The method according to any of claims 3-6, characterized in that:

specifying a first set of trigger conditions for radio signals in the uplink direction and specifying a second set of trigger conditions for radio signals in the downlink direction, an

A logic function is defined for combining the first and second sets of trigger conditions such that the Mobile Station (MS) determines the state of each trigger condition, combines the states using the logic function, and sends a measurement report according to the conditions of the logic function.

12. A method according to claim 1, characterized in that:

defining a first set of trigger conditions for radio signals in the uplink direction, and defining a second set of trigger conditions for radio signals in the downlink direction,

defining a logic function for combining the first and second sets of trigger conditions for enabling the Mobile Station (MS) to determine the state of each trigger condition, combining the states using the logic function, and sending measurement reports according to the conditions of the logic function, and the method further comprises:

the first and second sets of trigger conditions are dynamically specified by the network.

13. A method according to claim 1,

defining a logic function for combining the first and second sets of trigger conditions such that the Mobile Station (MS) determines the status of each trigger condition, combining the statuses using said logic function and sending measurement reports according to the conditions of the logic function, and

a logic function is specified by the network.

14. A method according to claim 12 or 13, characterized in that:

defining a first combination of a first and a second set of trigger conditions and a logic function for radio signals from or to active base stations having active links linked with said Mobile Station (MS),

a second combination and logic function defining a first and a second set of trigger conditions for radio signals from or to candidate base stations not having an active link with said Mobile Station (MS), and

a Mobile Station (MS) is caused to use a first combination for radio signals from or to an active base station and a second combination for radio signals from or to a candidate base station.

15. A method according to claim 1, characterized in that:

defining a second combination of the first and second set of trigger conditions and a logic function for radio signals from or to candidate base stations not having an active link with the Mobile Station (MS),

having the Mobile Station (MS) use the first combination for radio signals from or to the active base station and the second combination for radio signals from or to the candidate base station, and

when the network receives a measurement report from a Mobile Station (MS) triggered by the candidate base station, an active link is established between the Mobile Station (MS) and the candidate base station which does not have an active link with the Mobile Station (MS).

16. A method according to claim 14, characterized in that:

when the network receives a measurement report from a Mobile Station (MS) triggered by said active base station, the active link between the Mobile Station (MS) and the base station is deleted.

17. A method according to claim 15, characterized in that: the two different logic functions are such that when a base station is in the active set, the measurement report is not triggered with the radio signal of the base station for the same set of radio characteristics as the base station would trigger the transmission of the measurement report when in the candidate set.

18. A method according to claim 17, characterized in that:

a logic function is specified for use when the number of base stations in the active set is equal to a predefined maximum number,

defining first and second sets of trigger conditions based on radio signal characteristics of the active base station having the worst signal conditions, an

The mobile station is caused to trigger the sending of the measurement report with the radio signal of the candidate base station to cause the worst base station to be replaced by said candidate base station.

19. A method according to claim 18, characterized in that: the maximum number is dynamically specified by the network.

20. A method according to claim 1, characterized in that: the network informs the Mobile Station (MS) what information to include in the measurement report.

21. A method according to claim 20, characterized in that: the mobile station is provided with conditions for ordering radio signals and in a measurement report from the Mobile Station (MS) information is received about the characteristics of a predefined number of best radio signals depending on the provided conditions.

22. A method according to claim 20, characterized in that: the number of radio signals to be reported is specified by the network.

23. A method according to claim 20, characterized in that: the value of the path loss of the reported signal or a function thereof is obtained from the measurement report.

24. A method according to claim 20, characterized in that: values of carrier-to-interference ratios of the reported signals or functions thereof are obtained from the measurement reports.

25. A method in a Mobile Station (MS) for use in a telecommunication system (10), which system comprises the mobile station and a network comprising base stations (BS11, BS12), and in which system handover decisions regarding the establishment or the withdrawal of a link between the Mobile Station (MS) and a base station (BS11, BS12) are made in the network on the basis of measurement reports sent from the Mobile Station (MS) to the network, characterized by:

receiving a plurality of parameters from the network (10),

using the received parameters to determine a plurality of independent measurement report triggering conditions,

monitoring characteristics of a plurality of radio signals received from respective base stations (BS11, BS12),

it is checked whether a measurement report triggering condition has been met,

in response to said checking, establishing a measurement report when one of the trigger conditions is fulfilled, the measurement report comprising information about the monitored radio signal, and

sending a measurement report to the network.

26. A method in a mobile station according to claim 25, characterized by: receiving at least first and second different sets of trigger conditions for uplink and downlink signals and a logic function for combining the sets of trigger conditions,

determining the state of each trigger condition and combining the states in accordance with the logic function, an

The measurement report to be transmitted is established in terms of the conditions of the logic function.

27. A method in a mobile station according to claim 25 or 26, characterized by:

receiving information from the network indicating at least one trigger condition as valid, indicating remaining report trigger conditions (if any) as invalid, and

the generated measurement report is sent if at least one valid trigger condition has been met.

28. A method in a mobile station according to claim 26 or 27, characterized by:

receive a base station specific offset value, and

the base station specific offset value is used when checking whether the trigger condition has been met.

29. A judging unit, characterized by:

a receiving unit configured to receive a plurality of parameters from the network (10),

a determining unit configured to determine a plurality of independent measurement report trigger conditions using the received parameters,

a monitoring unit configured to monitor characteristics of a plurality of radio signals received from respective base stations (BS11, BS12),

a checking unit configured to check whether a measurement report triggering condition has been satisfied,

a setup unit configured to setup a measurement report in response to said checking, the measurement report comprising information on the radio signal monitored when one of the trigger conditions has been met, an

A transmitting unit configured to transmit the measurement report to a network.

30. The judging unit according to claim 29, characterized in that:

the receiving unit is further configured to receive at least first and second different sets of trigger conditions for the uplink and downlink signals, and a logic function for combining the sets of trigger conditions,

the determination unit is further configured to determine the state of each trigger condition and combine the states in accordance with the logic function, an

The establishing unit is further configured to establish the measurement report transmitted by said transmitting device (105) in dependence of a condition of a logic function.

31. The judgment unit according to claim 29 or 30, characterized by:

the receiving unit is further configured to receive such information from the network: indicating at least one trigger condition as valid, indicating remaining reporting trigger conditions (if any) as invalid, and

the sending unit is further configured to send the generated measurement report if at least one valid trigger condition is fulfilled.

32. The determination unit according to any one of claims 29 to 30, characterized by:

the receiving unit is further configured to receive a base station specific offset value, and

the checking unit is further configured to use the base station specific offset value when checking whether a trigger condition has been fulfilled.