HK1089025A - System and method for determining measurement value for radio resource management in wireless communications - Google Patents

Description

System and method for determining radio resource management measurement in wireless communications

Technical Field

The present invention relates to wireless communication systems. More particularly, the present invention relates to wireless communication systems utilizing measurement-based radio resource management.

Background

In a wireless communication system, a primary purpose of Radio Resource Management (RRM) is to efficiently manage the utilization of radio interface resources (i.e., radio resources). Intelligent management of radio resources is a fundamental requirement to optimize the broadcast interface capability, ensure connection reliability and network stability, and reduce battery consumption of wireless transmit/receive units (WTRUs).

Typically, a Radio Resource Management (RRM) system has: (1) call admission control that will accept or reject the request for a new radio link based on system load and quality objectives; (2) an alternate control that will ensure that a call (connection) will not miss when a wireless transmit/receive unit (WTRU) moves from one cell coverage area to another; (3) power control that maintains a minimum interference level and provides acceptable connection quality; (4) radio link maintenance which ensures that the quality of service requirements of the individual radio links are met; and (5) congestion control, which maintains network stability during periods of high congestion.

Based on different inputs, Radio Resource Management (RRM) functions may be triggered and make decisions. Among these inputs, broadcast interface measurements using observations of the wireless transmit/receive unit (WTRU) and node-B have been widely used. The broadcast interface measurements may be from a wireless transmit/receive unit (WTRU) or a node-B. Wireless transmit/receive unit (WTRU) measurements and radio link-specific node-B measurements may be referred to as dedicated measurements. Cell-specific node-B measurements may be referred to as shared measurements. Both types of measurements can accurately assess the current state of the wireless environment. For example, interference measurements may determine the placement of physical resources in a time slot or frequency band.

Typical measurements upon which Radio Resource Management (RRM) functions rely to evaluate radio environment conditions may include: interference Signal Code Power (ISCP) measurements, received power measurements including individual radio link power and Received Total Wideband Power (RTWP), Received Signal Strength Indicator (RSSI), transmit power measurements including individual radio link power and transmitted total wideband power (RTWP), and signal-to-interference ratio (SIR) measurements.

As will be described later, some of the measurements may be predicted, and a combination of the most recently reported measurements and their predictions may also be used for transient conditions in the wireless communication system.

Unfortunately, the implementation of the conventional Radio Resource Management (RRM) function may have the following disadvantages. In several cases, the previously described measurements may not be available or may be efficiently obtained by embodiments of existing Radio Resource Management (RRM) functions. First, the measurements may not be reported at all, or the measurement reports may be corrupted in the broadcast interface. For example, a wireless transmit/receive unit (WTRU) measurement report is eventually sealed in a Transmission Block (TB) and Cyclic Redundancy Check (CRC) bits are appended. The node B physical layer checks the Cyclic Redundancy Check (CRC) bits to determine if an error has occurred. The node-B physical layer may send both the error transmission method (TB) and an error indication to the upper layer when an error occurs, or the node-B physical layer may indicate to the upper layer only that an erroneous transmission block exists for a particular transport channel or a set of transport channels. Such scenarios are particularly relevant when wireless transmit/receive unit (WTRU) measurements are considered, since they are sent over the broadcast interface.

Second, the measurements typically have an age threshold, and after the age threshold, the measurements are considered invalid. If the frequency of these measurement reports is not sufficient, valid measurements may eventually become invalid and no Radio Resource Management (RRM) functionality is available.

Finally, these measurements may become invalid if the wireless link or system enters a transient state to be stable. For example, the interference measurement may exhibit instability for a specified period of time (up to 1/2 seconds), followed by a radio link configuration or reconfiguration due to power control transients. Such measurements should be avoided from triggering Radio Resource Management (RRM) functions or, alternatively, from being used for decision making, since the current state of the radio link or system is not stable.

It is therefore a primary object of the present invention to provide an improved system and method for obtaining measurements, thereby resulting in more efficient Radio Resource Management (RRM).

Disclosure of Invention

The present invention relates to a radio resource control system and method for managing broadcast interface resources. In accordance with the present invention, a wireless communication system determines the availability and validity of system-specific measurements to acquire Radio Resource Management (RRM) data. First, it is determined whether actual system measurements and predicted system measurements are available, and whether the actual system measurements are valid. Based on the determination, a selective combination of actual broadcast interface measurements, predicted values, and default values may be utilized. Alternatively, radio resources desired by Radio Resource Management (RRM) will not be set to utilize.

Drawings

The invention will be understood by reference to the following detailed description of preferred embodiments, when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a flow chart utilizing different types of values of Radio Resource Management (RRM) functions in accordance with a preferred embodiment of the present invention;

FIGS. 2A and 2B illustrate time varying weighting functions in accordance with a preferred embodiment of the present invention; and

FIG. 3 shows a centralized measurement control unit according to a preferred embodiment of the present invention.

Detailed Description

The preferred embodiment of the present invention is described in detail in connection with a voice or data application, which may be for regular and High Speed Downlink Packet Access (HSDPA) transmissions in accordance with a third generation partnership project (3GPP) wideband code division multiple access (W-CDMA) communication system, i.e., an embodiment of the Universal Mobile Telephone System (UMTS). Although the third generation partnership project (3GPP) technology can be applied to the present invention, the third generation partnership project (3GPP) system is only an embodiment of the present invention, and the present invention can also be applied to other wireless communication systems as long as they can provide measurement-based Radio Resource Management (RRM).

In the context of this patent specification, a "wireless transmit/receive unit (WTRU)" may include, but is not limited to, a User Equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. In addition, common types of wireless environments can include, but are not limited to, Wireless Local Area Networks (WLANs) and Public Land Mobile Networks (PLMNs). A "node B" may include, but is not limited to, a Base Station (BS), a location controller, an access point, or any type of interfacing device in a wireless environment.

Fig. 1 shows a flow chart for performing a measurement value determination procedure 20 for Radio Resource Management (RRM) functions in accordance with a preferred embodiment of the present invention. First, actual measured and predicted values, along with a timestamp of their time of receipt, are received and stored in a database (step 22). These measurements and values are received by different Radio Resource Management (RRM) functions, such as: call admission control, alternative control, power control, and radio link maintenance. Whether these measurements and values are actual system measurements or predicted values (such as, for example, call admission control functions that make system impact predictions when new calls are received), these measurements and values are stored in a database. The Radio Network Controller (RNC) maintains these measurements and values and maintains them as they are stored.

Each time the Radio Network Controller (RNC) receives a measurement or value, it stores the measurement or value in the database along with a timestamp corresponding to the time of receipt. The Radio Network Controller (RNC) may then determine in turn whether measurements or values are available (i.e., whether the measurements or values are stored in the database) and whether the age of the measurements or values is valid (i.e., whether the age of the measurements or values is less than a particular age threshold) if the measurements or values are available.

If a Radio Resource Management (RRM) measurement request is not received, as shown in step 30, the process 20 will not perform other actions, except for continuously receiving and storing actual measurement and prediction values, as shown in step 22. If a Radio Resource Management (RRM) measurement request has been received, the Radio Network Controller (RNC) checks the database for the requested RRM measurement, and determines whether the requested RRM measurement is available, as shown in step 30. Measurements may also be unavailable (i.e., they are not stored in the database) because measurement reports are not being sent or corrupted on the air interface. If the actual system measurements cannot be provided, as shown in step 34, a determination is made as to whether the predicted values can be provided (step 36).

These predicted values (M)_pREDICTED) The determination steps are as follows. When a particular Radio Resource Management (RRM) function performs an action, the RRM measurements may predict particular system measurements (such as interference or power) at which the action is performed. For example, one Radio Resource Management (RRM) function may be a Call Admission Control (CAC) algorithm. The Call Admission Control (CAC) algorithm predicts the interference and power for a call being added. If the prediction levels are acceptable, the call is added. Otherwise, if the predicted levels are not acceptable, the call is rejected. According to the invention, these predictions and power values (along with other types of predictions) are then stored and used as predictions of interference or power. Since the prediction of Radio Resource Management (RRM) values is well known in the art (and varies according to various types of RRM functions), and this particular prediction method is not the focus of the present invention, a detailed description of this particular prediction method will be omitted.

If predictive values are available, then these predictive values may be utilized (step 38). Otherwise, if the predicted value is not available, a default value is available (step 40).

A predetermined value is established based on historical conditions or a series of measurements/evaluations. Basically, a predetermined value can be pre-stored and retrieved as required by the actual situation. Usually, the selection of the default value is based on a conservative operation of Radio Resource Management (RRM) function as a main principle.

If actual system measurements are available, as shown in step 34, a determination is made as to whether the actual system measurements are valid (step 42). As previously mentioned, the actual system measurements may be invalid due to having an old age, or may be invalid due to the system being in a transient state, with respect to their effectiveness. Thus, these actual system measurements are not necessarily indicative of the state of the system.

Regarding a measured age, when the Radio Network Controller (RNC) database receives a measurement report, the measurement report is assigned a timestamp. The timestamp corresponds to the time of receipt of the measurement report. When the measurement is read from memory, the corresponding timestamp of the measurement is also read. If this timestamp indicates that: the measurement is deemed invalid if the age of the measurement is greater than a particular measurement age threshold (e.g., 1 second).

In the case where a measurement is invalid due to the system being in a transient state, as previously described, each Radio Resource Management (RRM) function is associated with one or more RRM measurements, respectively. Whenever a Radio Resource Management (RRM) function performs an action in the system, the execution time of the action is also determined. This time corresponds to the state of the "" transient period "". The transition time lasts for a certain length, and the system then goes back to steady state again. The length of the transient period depends on the type of action performed by the Radio Resource Management (RRM) function. The length of the transient period is a design parameter.

If the Radio Resource Management (RRM) function results in a particular RRM measurement during the transient, the particular RRM measurement is considered invalid. In addition, the determination of whether the Radio Resource Management (RRM) measurement occurs during the transient period can be made as follows. In a first method, each Radio Resource Management (RRM) measurement stored in the database is associated with an indication of whether the RRM measurement occurred during a transient. Although these measurements are still stored in the database, they are considered invalid.

In the second method, a start timestamp of each Radio Resource Management (RRM) transient is stored in the database. When a Radio Resource Management (RRM) measurement is retrieved from the database, the timestamp of the retrieved RRM measurement is compared to the timestamp of the transient period. If the time stamp of the acquisition Radio Resource Management (RRM) measurement falls within the transient period (i.e., the time stamp of the start of the acquisition RRM measurement plus the length of the transient period), the acquisition RRM measurement is deemed invalid.

In a third method, the actual measurement may be invalidated based directly on whether a predicted measurement exists in the database, and the timestamp of the measurement determined if the predicted measurement exists in the database. This method is based on the assumption that the transient period will start just when the predetermined measurement is written into the database. However, these methods are merely illustrative and not restrictive, as many other methods may be used to determine invalidity.

The system determines the validity of an actual measurement based on the age of the actual measurement and the stability of the system. If the actual measurement is valid, as shown in step 42, the actual measurement may be utilized (step 44).

If the actual measurement is deemed invalid (step 42), a determination is made as to whether a predicted value is available (step 46). If a predicted value is available, as shown in step 46, the actual measurement may be combined with the predicted value (step 48).

Actual measurementAnd the predicted values, as shown in step 48, are described below. Although one skilled in the art can combine the values in different ways, in the preferred embodiment of the invention, the invention can combine the actual measurements (M) in the following way_ACTUAL) And a predicted value (M)_PREDICTED)：

M(t)＝α(t)M_PREDICTED+(1-α(t))M_ACTUAL (1)

Where α (t) is a time-varying weighting function, and t represents the elapsed time from the start of the transient period (i.e., the transient period starting at t-0). M (t) indicates that the radio resource management (rrm) function provides a combined measure at time t. Typically, α is a monotonically decreasing function between 1 and 0. Preferably, α (t) at the beginning of the transient period (t ═ 0) should be equal to 1, and α (t) at the end of the transient period (when the actual measurement is stable) should be equal to 0.

For example, in the case of a transient having a length of 1 second, the alpha weighting function can be represented as fig. 2A and 2B. In fig. 2A, the time variation of α is substantially a linear function, however, in fig. 2B, the time variation of α exhibits an initial slow decrease and a subsequent fast decrease. The model of the time variation of α can be expressed exponentially or geometrically, as the case may be.

In addition, follow-up may also occur during this transient (i.e., before α becomes 0). When a Radio Resource Management (RRM) function performs a subsequent action, the system directly enters a "new" transient period. The time t is typically predicted due to specific Radio Resource Management (RRM) functions₁The value following the execution of the action, so that the calculation of the predicted value is based on M (t)₁). In this case, the numerical value (M) is predicted_PREDICTED) The calculation is based on M (t)₁) Wherein, t₁Is the trigger time of the subsequent operation.

In addition, when the follow-up action is completed (i.e., when the new moment is reached)At the beginning of the transition period), t is also reset to 0. That is, when a new transient period begins, it is performed at time t₂Any subsequent Radio Resource Management (RRM) will utilize the time t₁As the start of this new transient period. Therefore, t in equation (1) can be expressed as t ═ t₂-t₁。

Next, referring again to fig. 1, if the actual measurement is deemed invalid (step 42) and the predetermined value is not available (step 46), the RNC can choose to perform the following four steps (step 50): (1) using the preset value, as shown in step 402; (2) combining actual measured and predicted values; (3) adding a boundary to the actual measurement; or (4) making an announcement that the resource is not available.

Regarding the first step (i.e., using a predetermined value), this step will be described with reference to step 40.

Regarding the second step (i.e. combining the actual measurements with the default values), the Radio Network Controller (RNC) combines the actual measurements with the default values in different ways depending on the reason why the actual measurements are deemed invalid. If the actual measurement is deemed invalid because the latest actual measurement of this database is too old, equation (2), similar to equation (1), will be available:

M(t)＝α(t)M_AUTUAL+(1-α(t))M_DEFAULT (2)

in equation (2), the decreasing time α (t) is applied to the actual measurement M_AUTUALAnd t represents the elapsed time since the actual measurement was stored in the database. Preferably, the α function is different from equation (1) because the α function should make the decrement speed slower.

If the actual measurement is deemed invalid because the system is in the transient state and an updated actual measurement is still available, a weighted combination of the actual measurement and the default value can be used:

M＝AM_AUTUAL+BM_DEFAULT (3)

where a + B is 1, and the weighting factors a and B are configurable parameters that are optimized based on system simulation or observation. It is noted that different measurements may result in different weighting factors.

Regarding the third step (i.e., adding a boundary to the actual measurement), preferably, a time varying error boundary is added to the actual measurement, as shown in equation (4):

M＝M_ACTUAL+MARGIN (4)

in this case, MARGIN is the time-varying boundary, which is maximum at the beginning of the transient (t 0) and monotonically decreases to 0 at the end of the transient. As shown in equation (1), equation (4) will be performed when the actual measurements can be provided, but are not considered invalid because they are during transients or have an old time stamp. It should be noted that this method only occurs when the actual measurement or metric monotonically increases or decreases to a converging value. This approach is not ideal in situations where the actual measurement or metric oscillates around a converged value.

The method has the advantages that: the presence of a predicted value need not be inferred during this transient. Equation (1) can also be performed when the prediction value is available, and equation (4) can also be performed when MARGIN is considered the best "prediction".

In connection with the last method of step 50 (i.e., making an announcement that resources are not available), if actual measurements, predicted values, adding bounds to actual measurements, or any combination of these methods are not satisfactory, the system may directly deny transmission of a Radio Resource Management (RRM) measurement, and the required resources for the RRM measurement may be deemed unavailable. Therefore, these resources will not be utilized.

The results of determining whether to utilize the actual measurements (step 44), whether to utilize the predicted values (step 38), whether to utilize the default values (step 40), whether to utilize a combination of the actual measurements and the predicted values (step 48), or whether to utilize either method (step 50) may then be used to determine the required Radio Resource Management (RRM) measurements.

To enhance measurement management, the Radio Network Controller (RNC) may also utilize a centralized measurement control unit. This centralized control unit may implement the following functions, including: (1) storing the received measurements in a centralized structure; and (2) performing measurement processing including: measurement filtering, tracking measurement age and validity (e.g., assigning a time stamp upon receipt and performing an age threshold comparison), selecting or combining predicted values and actual measurements.

FIG. 3 shows a centralized measurement control unit 80 according to a preferred embodiment of the present invention. The measurement control unit 80 has a measurement setting unit 81, a measurement receiving and storing unit 82, a measurement processing unit 83, and a measurement output unit 84.

The measurement setup unit 81 performs measurement setup procedures for wireless transmit/receive units (WTRUs) and node-bs. The measurement setup unit 81 is responsible for performing measurement setup and configuration. In particular, the measurement configuration unit 81 communicates with the Radio Resource Control (RRC) layer of the node-B and wireless transmit/receive unit (WTRU) to configure, adjust, and terminate measurements to provide all measurement configuration details (e.g., averaging period, reporting condition/period).

The measurement receiver and memory unit 82 organizes the actual and predicted wireless transmit/receive unit (WTRU) and node-B measurements. The measurement receiver and storage unit 82 assigns time stamp information to track the age of the measurement as it is received.

The measurement processing unit 83 filters the received measurements, verifies the validity and/or availability of the measurements, and combines actual measurements, predicted values, and default values as the case may be. The measurement processing unit 83 is responsible for all measurement processing described in the preferred embodiment of the present invention.

The measurement output unit 84 provides appropriate measurements to the Radio Resource Management (RRM) function, as required, namely: providing an actual measurement (when valid), a predicted measurement (when not available or invalid), or a combination of an actual measurement, a predicted value, or a predetermined value (as shown in steps 38, 40, 44, 48, 50 of fig. 1). The measurement output unit 84 may also be selectively responsible for triggering Radio Resource Management (RRM) functions if the measurement exceeds a predetermined threshold.

Claims (10)

1. A radio resource control unit that monitors broadcast interface resources and provides a radio resource management output, the radio resource control unit comprising:

a broadcast interface measurement unit for obtaining broadcast interface measurements;

a storage unit for storing the broadcast interface measurements; and

a processing unit for processing the broadcast interface measurements to provide the output;

whereby at least a portion of the broadcast interface measurements are predictive measurements.

2. The control unit of claim 1, wherein at least a portion of the broadcast interface measurements are actual measurements.

3. The control unit of claim 2, wherein the actual measurement and the predicted measurement are selectively combined using the processing unit.

4. The control unit of claim 1 wherein the storage unit also stores a time stamp for each stored broadcast interface measurement, the time stamp corresponding to the time of storage of the broadcast interface measurement.

5. A method for obtaining rrm data, comprising the steps of:

obtaining a broadcast interface measurement;

storing the broadcast interface measurements;

generating and storing a time stamp indicating a storage time measured for each broadcasting interface; and

processing the broadcast interface measurements to provide output data;

whereby at least a portion of the broadcast interface measurements are predicted values.

6. The method of claim 5 wherein the processing step compares the corresponding time stamp to a threshold to determine whether a broadcast interface measurement is valid, and determines that the broadcast interface measurement is invalid when the time stamp is older than the broadcast interface threshold.

7. The method of claim 5, wherein the processing step comprises:

determining the occurrence of a transient period; and

comparing the time stamp of a broadcast interface measurement with the occurrence of the transient to determine whether the broadcast interface measurement is valid, and determining that the broadcast interface measurement is invalid when the time stamp is in each transient.

8. The method of claim 7 wherein the determining step is performed while the broadcasted interface measurements are stored, and a corresponding validity indicator is also stored with the broadcasted interface measurements.

9. The method of claim 5, wherein the output data comprises a predetermined value.

10. The method of claim 5 wherein the output data includes a combination of predicted values and actual values.