GB2435150A

GB2435150A - Load control in a cellular communication system

Info

Publication number: GB2435150A
Application number: GB0602526A
Authority: GB
Inventors: Fernando Almendros; Ignacio Rivas
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2006-02-08
Filing date: 2006-02-08
Publication date: 2007-08-15
Anticipated expiration: 2026-02-08
Also published as: GB2435150B; WO2007092687A3; GB0602526D0; WO2007092687A2

Abstract

An apparatus for load control in a cellular communication system comprises a load processor (205) for determining a load level characteristic for at least one cell of the cellular communication system. A comparison processor (207) compares the load level characteristic to a load level threshold and a congestion relief processor (209) executes a load control procedure if the load level characteristic exceeds the load level threshold. A threshold modifier processor (305 Fig 3, not shown), possibly located at a different network element, determines a modified load level threshold in response to a performance characteristic of the cellular communication system, such as a loading for a given service. The threshold processor (213) accordingly dynamically modifies the load level threshold in response to the modified load level threshold.

Description

LOAD CONTROL IN A CELLULAR COMMUNICATION SYSTEM

Field of the invention

The invention relates to load control in a cellular communication system and in particular, but not exclusively, to load control in a Universal Mobile Telecommunication System.

Background of the Invention

Currently, the most ubiquitous cellular communication system is the 2nd generation communication system known as the Global System for Mobile communication (GSM). Further description of the GSM TDMA communication system can be found in The GSM System for Mobile Communications' by Michel Mouly and Marie Bernadette Pautet, Bay Foreign Language Books, 1992, ISBN 2950719007.

3rd generation systems have relatively recently been rolled out in many areas to further enhance the communication services provided to mobile users. One such system is the Universal Mobile Telecommunication System (UMTS), which is currently being deployed. Further description of CDMA and specifically of the Wideband CDMA (WCDMA) mode of UMTS can be found in WCDMA for UMTS', Harri Holma (editor), Antti Toskala (Editor), Wiley & Sons, 2001, ISBN 0471486876. The core network of UMTS is built on the use of SGSNs and GGSN5 thereby providing commonality with GPRS.

* S S * S * * S S * * S S * * S S * S * * * S ** S * S ** * S * S S * S S S S. * *5* *S * The frequency band allocated to a cellular communication system is typically severely limited and therefore the resource must be effectively divided between mobile stations. A fundamental property of a cellular communication system is that the resource is divided geographically by the division into different cells. Thus, a certain amount of resource (for example a frequency band) may at a given time be allocated to a given cell thereby reducing the resource allocation to neighbouring cells. In order to optimise the capacity of a cellular communication system, it is important to minimise the impact of interference caused by or to other mobile stations. An important advantage of a cellular communication system is that due to the attenuation of radio signals with increasing distance, the interference caused by communication within one cell is negligible in a cell sufficiently far removed, and therefore the resource can be reused in this cell. In addition, the resource is typically divided within one cell and between cells by division of the resource in the time domain, the frequency domain and/or the code domain. Different communication systems use different principles for this division. The resource allocation may be static or dynamic dependent on the current load of the communication system, and typically a combination of static and dynamic resource allocation is used.

In order to achieve a high capacity and efficient use of the available resource, it is important to implement efficient resource allocation and management. Typically, cellular communication systems implement a number of different resource allocation and management processes which are specifically directed to provide improved performance at high loads.

S S S

* * * * S * 5 a S * * e S S * S * p S. * S * S* S S * S S * S * S S. S *55 * S Specifically, a cellular communication system typically comprises various load control processes operating a suite of cell load control algorithms that seek to maximise the resource utilization under heavy load, whilst keeping the system in stable working conditions. Those mechanisms are used when a measure of current cell load exceeds a given threshold. The threshold is conventionally set to a fixed value by manual means. In particular, the network operator typically sets a fixed threshold value for the load control processes. The configuration of the thresholds is often identical for all cells and processes but in many systems it is also possible for the operator to manually set different thresholds independently for each algorithm on a per cell or per RNC basis.

The configuration of thresholds for load control processes is based on engineering expertise and optimization work. It has been proven that system performance can be increased substantially by using the appropriate threshold settings and therefore a substantial amount of effort is required to optimise these thresholds. Accordingly, the operator collects statistical data for the cellular communication system and evaluates this to select appropriate thresholds and consequently the fixed thresholds are based on average traffic information for a given area.

However, such an approach tends to have a number of associated disadvantages and specifically tends to be inflexible (especially in systems using a mix of services such as circuit switched and packet switched services), to lead to suboptjmal thresholds and degraded resource S * S S * * * * q 5 * * S S S * 1 4 5 * 5* 5 S S S * S S 5S S * utilisation to be labour intensive and to lead to Suboptimal performance of the cellular communication system.

Thus, an improved load control would be advantageous.

Summary of the Invention

Accordingly, the Invention seeks to preferably mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.

According to an aspect of the invention, there is provided an apparatus for load control in a cellular communication system, the apparatus comprising: means for determining a load level characteristic for at least one cell of the cellular communication system; comparing means for comparing the load level characteristic to a load level threshold; means for executing a load control procedure if the load level characteristic exceeds the load level threshold; modifying means for determining a modified load level threshold in response to a performance characteristic of the cellular communication system; and adjusting means for dynamically modifying the load level threshold in response to the modified load level threshold.

The invention may allow improved performance of a cellular communication system. An improved load control and/or resource utilisation may be achieved. The invention may allow operation of the cellular communication system to be adapted and/or optimised for the current rather than average conditions. The invention may facilitate operation and may S * S S S * S I I. S S * . S I S. I S * S S* I. * -. I. in particular reduce the manual effort required to maintain high performance.

The load control procedure may be a procedure which modifies traffic load control and management routines such as a process modifying a parameter used by the resource management processes. Specifically, the load control procedure may be a congestion relief procedure.

According to an optional feature of the invention, the performance characteristic comprises a load indication for at least one service supported by the cellular communication systems.

This may allow improved performance and in particular a load indication for a specific service may provide a very advantageous parameter for optimising the threshold for Performing a load control procedure.

According to an optional feature of the invention, the performance characteristic comprises a load indication for at least one service supported by the cellular communication system relative to a second service supported by the cellular communication system.

This may allow improved performance and in particular a load indication for a specific service relative to another service may provide a very advantageous parameter for optimjsation of when a load control procedure should be Performed. Specifically, it may allow a trade-off between the performance of different services at high load and may I a * a a. II.

* a a * a a. a * . a $ $ $ I a..

S. a *6 * allow one service to be prioritised higher than another service.

According to an optional feature of the invention, the first service is a conversational service and the second service is a non-conversational service.

This may allow improved performance and may in particular allow a trade-off between the performance of conversational and non-conversational services at high loads and may allow e.g. a conversational service to be prioritised higher than a non-conversational service.

A conversational service may specifically be a two (or more)-way real-time communication such as a conventional phone call or a video call.

According to an optional feature of the invention, the first service is a circuit switched service and the second service is a packet switched service.

This may allow improved performance and may in particular allow a trade-off between the performance of circuit switched and packet switched services at high loads and may allow e.g. a circuit switched service to be prioritised higher than a packet switched service.

According to an optional feature of the invention, the first service is a real time service and the second service is a non-real time service.

* * S * * * S * S S S * S * * S. S * * S * * S 5 * * *S 5 * *5 * ** -_* S 5 This may allow improved performance and may in particular allow a trade-off between the performance of real time and non-real time services at high loads and may allow e.g. a real time service to be prioritised higher than a non-real time service.

A real time service may specifically be a service that has a delay quality of service requirement such as a guaranteed maximum delay.

According to an optional feature of the invention, the load control procedure is a call admission adjustment procedure.

This may allow improved performance and may in particular provide a low complexity and efficient approach for adjusting operation at high loads thereby leading to increased system capacity. The call admission adjustment procedure may for example change parameter values for the call admission algorithm.

According to an optional feature of the invention, the load control procedure comprises a call admission blocking of a service supported by the cellular communication system.

This may facilitate implementation and/or may allow efficient load Control. Specifically, the load control procedure may block new calls if the load level threshold is exceeded.

According to an optional feature of the invention, the load level threshold is associated with a limited geographical region. S *

* S S * * * * S * S S * * * S S *S * * * S 5 * * * S * * S. * * S. * *** S * * This may improve performance of the cellular communication system and may in particular allow local opt miseci resource utilisation reflecting the actual experienced conditions.

According to an optional feature of the invention, the load level threshold is associated with a group of cells.

This may improve performance of the cellular communication system and may in particular allow local optimised resource utilisation reflecting the actual experienced conditions in the group of cells. The group of cells may e.g. comprise a single cell or may e.g. comprise all cells served by a specific network element, such as all cells served by a Radio Network Controller (RNC).

According to an optional feature of the invention, the modifying means are comprised in a first network element of a fixed network of the cellular communication system and the adjusting means is comprised in a second network element of the fixed network.

This may facilitate implementation and/or the operation and management of the cellular communication system and/or may provide improved compatibility with existing systems.

According to an optional feature of the invention, the second network element is a Radio Network Controller.

S

* S S * * * * S * * * * S S 5 * S * * S * * * * S 5 * SS 5 * ** * *5* S S 5 According to an optional feature of the invention, the second network element is arranged to apply different load level thresholds for different cells supported by the second network element.

This may improve performance of the cellular communication system and may in particular allow local Optimised resource utilisation reflecting the actual experienced conditions in different areas or cells.

According to an optional feature of the invention, the first network element is an Operations and Maintenance Centre.

According to an optional feature of the invention, the first network element is arranged to determine different modified load level thresholds for different cell groups.

This may improve performance of the cellular communication system and may in particular allow local optimised resource utilisation reflecting the actual experienced conditions in different cell groups. The different cell groups may e.g. comprise a single cell or may e.g. comprise all cells served by a specific network element, such as all cells served by a Radio Network Controller (RNC). Specifically, each cell group may correspond to a group of cells supported by a single RNC. S *

* * * S * * S * * * S * * S * *e 5 * * S * * * S S * * *. * * * *.S -* * * According to an optional feature of the invention, the first network element is arranged to transmit configuration control messages to the second network element, the configuration control messages comprising an indication of the load level threshold, and the second network element is arranged to change the load level threshold in response to the indication.

According to an optional feature of the invention, the configuration control messages comprise Man Machine Language (MNL) commands and the second network element is arranged to change the load level threshold in response to the MML commands.

The cellular communication system may specifically be a Universal Mobile Telecommunication System (UMTS) cellular communication system.

The invention may allow improved performance of a UMTS cellular communication system and may in particular allow improved resource utilisation and specifically may provide improved resource utilisation for changing traffic conditions.

* S S S * * S * * S * * * S 5 * S * S 5 * * * * S * 55 5 * *S * *** S S According to another aspect, there is provided a method of load control in a cellular communication system, the method comprising: determining a load level characteristic for at least one cell of the cellular communication system; comparing the load level characteristic to a load level threshold; executing a load control procedure if the congestion level characteristic exceeds the load level threshold; determining a modified load level threshold in response to a performance characteristic of the cellular communication system; and dynamically modifying the load level threshold in response to the modified load level threshold.

According to another aspect, there is provided a computer program product enabling the carrying out of the above described method.

These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Brief Description of the Drawings

Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which FIG. 1 illustrates an example of a cellular communication system in accordance with some embodiments of the invention; FIG. 2 illustrates an example of a Radio Network Controller in accordance with some embodiments of the invention; * . . * * * S * * * * * * S 5 S. * * * S * * S * ** I S *.. * S a FIG. 3 illustrates an example of an Operations and Maintenance Centre in accordance with some embodiments of the invention; and FIG. 4 illustrates a specific example of an algorithm for modifying a load level threshold for circuit switched and packet switched services in accordance with some embodiments of the invention.

Detailed Description of Some Embodiments of the Invention The following description focuses on embodiments of the invention applicable to a tiNTS cellular communication system but it will be appreciated that the invention is not limited to this application but may be applied to many other cellular communication systems including for example GSM cellular communication system.

FIG. 1 illustrates an example of a tiNTS cellular communication system 100 in which embodiments of the invention may be employed.

In a cellular communication system, a geographical region is divided into a number of cells each of which is served by a base station. The base stations are interconnected by a fixed network which can communicate data between the base stations. A User Equipment (tiE) (e.g. a 3 Generation system UE, a subscriber unit or a mobile station) is served via a radio communication link by the base station of the cell within which the tiE is situated.

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* S S * S * * S S * * S * S. * * * S 5, * S S 5 * SI * *S 5 *_* S p As a UE moves, it may move from the coverage of one base station to the coverage of another, i.e. from one cell to another. As the UE moves towards a base station, it enters a region of overlapping coverage of two base stations and within this overlap region it changes to be supported by the new base station. As the UE moves further into the new cell, it continues to be supported by the new base station. This is known as a handover or handoff of a UE between cells.

A typical cellular communication system extends coverage over typically an entire country and comprises hundreds or even thousands of cells supporting thousands or even millions of tiEs. Communication from a tiE to a base station is known as uplink, and communication from a base station to a tiE is known as downlin]c.

In the example of FIG. 1, a first tiE 101 and a second tiE 103 are in a first cell supported by a first base station 105.

The first base station 105 is coupled to a first RNC 107. An RNC performs many of the control functions related to the air interface including radio resource management and routing of data to and from appropriate base stations.

The first RNC 107 is coupled to a core network 109. A core network interconnects RNCs and is operable to route data between any two RNCs, thereby enabling a tiE in a cell to communicate with a tiE in any other cell. In addition, a core network comprises gateway functions for interconnecting to external networks such as the Public Switched Telephone Network (PSTN), thereby allowing tiEs to communicate with

S

* S S S S * * S S. * . * S * * * a * * * I * * 5* * * SS * --landline telephones and other communication terminals connected by a landline. Furthermore, the core network comprises much of the functionality required for managing a conventional cellular communication network including functionality for routing data, admission control, resource allocation, subscriber billing, UE authentication etc. The core network 109 is further coupled to a second RNC 111 which is coupled to a second base station 113. The second base station 113 supports a third UE 115.

The cellular communication system 100 furthermore comprises an Operations and Maintenance Centre (OMC) 117. The OMC 117 provides an interface to the operator and allows the operator to control and manage the operation of the cellular communication system 100. Specifically, the OMC 117 provides means for presenting the user with operations and performance data for the cellular communication system, such as statistical performance data. Furthermore, the OMC 117 comprises means for receiving user inputs that are used by the operator to set various parameters for the operation and management of the system and individual network elements, such as individual RNCs and base stations.

To achieve efficient operation and resource utilisation it is important that cell load control algorithms are implemented that deal with dynamic variations in the demand for the communication resource. In the specific example, the RNCs 107, 111 comprise various cell load control algorithms that manage the loading of the individual cells.

I

* I. * e * I I * S S II I I * * * S S * -.. I S I. * --Optimisation of the operation of the system becomes increasingly important as the loading increases. In particular, when the loading increases to levels approaching the capacity of the cell, the ability to support the current demand becomes increasingly difficult. Therefore, the cellular communication system comprises functionality for dealing with congested cells and specifically it comprises one or more load control procedures such as congestion relief functions that modify the behaviour of the cellular communication system at higher loads.

The load control procedures can be simple procedures that are integrated with resource management and load control algorithms and which change the settings for the algorithms at higher loads. As another example, the load control procedures may be complex additional procedures that are not present at lower load levels but which substantially affect the operation at higher load levels. An example of such an algorithm may be a cell breathing algorithm that reduces the pilot tone signal of a highly loaded cell thereby reducing the cell size at these loads.

In the specific example of FIG. 1, the RNCs 107, iii implement algorithms for cell load control algorithms which include call admission control algorithms, load congestion control algorithms and load balancing algorithms. These algorithms are typically based on parameters such as power resource consumption (in the downlink) and interference levels (in the uplink). As another example, the algorithms can be based on an equivalent number of active users. a a

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Specifically, the algorithms receive common measurement reports from the base stations including e.g. Transmit Carrier Power (TCP) and Received Total Wideband Power (RTWP) signalling. This information is used by the RNC to calculate the current cell load for the uplink and downlink.

In the approach, the current cell load is compared to specific thresholds and if the thresholds are exceeded the corresponding load control procedure is executed (i.e. it is triggered). Thus, when the threshold is exceeded the cell is considered to be congested and a load control procedure is performed. For example, a load balancing operation may be initiated or the settings for the call admission control algorithm can be changed at higher loads to result in a different behaviour.

In conventional systems, the decision of when to modify the behaviour of the system due to high loads is based on comparing cell loads to fixed thresholds that have been set centrally and manually by the network operator. However, this is inflexible, cumbersome and leads to suboptimal performance as it is not optimjsed for the current and local conditions. Specifically, for non-constant traffic conditions a fixed thresholds solution can be ineffective.

In contrast, the system of FIG. 1 comprises functionality for dynamically varying the thresholds for the load control procedures. Specifically, the system comprises functionality for dynamically determining various performance characteristics (determined from performance statistics) and for modifying the thresholds in response thereto. Thus, an improved load control, congestion relief, load management * * S * S * S S S * S 5 * S * S S S * S * S S *S S S 5 5S * S * . S S * S * S. * *** .. . and resource utilisation can be achieved leading to an improved user experience and increased capacity of the cellular communication system as a whole.

In the specific example, the functionality is split between the RNCs 107, 111 and the OMC 117.

FIG. 2 illustrates an example of the first RNC 107 of FIG. 1.

The RNC 107 comprises a base station interface 201 which interfaces to the base stations 105 supported by the RNC 107. The base station interface 201 is coupled to a call admission processor 203 which manages the call admission for the base stations 105 supported by the RNC 107. Thus, the call admission processor 203 allocates resource and configures parameters for any new call that is requested to be set up.

The following description will focus on call load procedures associated with call admission but it will be appreciated that the principles apply to many other functions including load control functions, load balancing functions and resource allocation functions.

The base station interface 201 is also coupled to a load processor 205 which is arranged to determine a load level characteristic for at least one cell supported by the RNC 107. In the specific example, the load processor 205 determines the loading of the individual cells supported by the RNC 107.

* * S S * * S S S S S 5 5 S * S S S S S S S * 5 S S 55 5 5 S S S S 5 S S S. * *55 55 5 In other embodiments, other load level characteristics may be used such as e.g. an indication of a current relative or absolute load level of one or more cells or sectors. The load control characteristics may specifically be congestion level characteristics.

The load processor 205 is coupled to a comparison processor 207 which is arranged to compare the load level characteristic to a load level threshold. The load level threshold may specifically be a congestion level threshold.

The comparison processor 207 is coupled to a congestion relief processor 209 and is arranged to control the congestion relief processor 209 to perform a load control procedure, such as a congestion relief procedure, if the load level characteristic exceeds the load level threshold.

In the example, the congestion relief processor 209 is coupled to the call admission processor 203 and the load control procedure is arranged to modify the operation of the call admission processor 203 by changing the settings, parameters and/or the algorithms used for the call admission processing.

As a specific example, the call admission may be modified such that a certain kind of service is blocked when the cell loading increases above the load level threshold but is permitted below the load level threshold. The load control procedure run by the congestion relief processor 209 in this case changes the call admission algorithm such that all access requests for the specific service are rejected.

* S S S S * S * S * S S S S * S S S S S S S S *e S I S *S S S * S S * S S S S. * *e5 S. S The RNC 107 furthermore comprises a network interface 211 which is arranged to interface with the core network 109 and which specifically allows messages to be exchanged between the RNC 107 and the OMC 117.

The network interface 211 is coupled to a threshold processor 213 which is further coupled to the comparison processor 207. The threshold processor 213 is arranged to determine the load level threshold used by the comparison processor 207 to determine if the load control procedure is required. Furthermore, the threshold processor 213 is operable todynamically change the load level threshold. In the specific example, the determination of the appropriate value for the load level threshold is not determined in the RNC 107 but is determined in the OMC 117. Accordingly, the network interface 211 can receive control messages from the OMC 107 and feed these to the threshold processor 213 which in response sets the load level threshold to the value selected by the OMC 117.

However, it will be appreciated that in other embodiments the appropriate value of the load level threshold may directly be determined in the RNC 107.

Thus, the RNC 107 comprises functionality for dynamically and flexibly adjusting the load level threshold to suit the current conditions rather than long-term average conditions.

Thus, a more flexible and improved traffic load control can be achieved. Although the previous description has mentioned only a single load level threshold, the threshold processor 213 can in some embodiments determine a plurality of load level thresholds and apply these selectively. For example, * * S S * I * S * S S I S * I I I S S I S I

SI I I I II S S

* S S S 5! S S. a **s S. S thresholds may be determined and applied on a cell by cell basis or for a group of cells.

FIG. 3 illustrates an example of the first OMC 117 of FIG. 1.

The OMC 117 comprises an OMC network interface 301 which interfaces with the core network 109. In particular, the ONC network interface 301 is able to send and receive messages to and from the RNC 107.

The OMC network interface 301 is coupled to a performance processor 303 which determines a performance characteristic for the cellular communication system. The performance characteristic may for example be a load indication for a specific service, a distribution of services which are currently being supported by one or all cells of the cellular communication system or can e.g. be a characteristic indicating a quality of service that is currently being offered to users (of e.g. a specific service or a specific cell or cell group).

The performance processor 303 and the OMC network interface 301 are furthermore coupled to a threshold modifier processor 305 which is arranged to determine a modified load level threshold in response to the performance characteristic of the cellular communication system. The modified load level threshold may then be communicated to the RNC 107 and the threshold processor 213 may set the load level threshold used by the comparison processor 207 to Correspond to this modified load level threshold.

* * * * S * * S * S * * * S S * * 5 5 S * S S. S S S *; . S S S S 5 5 5 5* 0 *s * -Thus, the system of FIG. 1 provides for the load level thresholds to be dynamically adjusted in response to a performance characteristic of the cellular communication system.

As a specific example, the system can modify the load level thresholds on-line depending on the system performance for the current traffic conditions. This modification may be similar to the way thresholds can be manually modified by an operator from the RNC management terminal. In some cases, the dynamic threshold variation can be limited to a given range and/or a given step within a given period etc. In the example, the threshold management processes run continuously and automatically at the RNC 107 and OMC 117.

The OMC 117 can specifically continuously monitor e.g. a cluster of cells by using a set of cell statistics to determine the performance characteristic. The performance processor 303 specifically collects the statistical data (related to the selected cluster of cells) which have been uploaded from the RNC 107 to the OMC 117. The performance processor 303 and the threshold modifier processor 305 then use the statistical data to determine if the threshold should be updated.

The decision may furthermore be based on manually determined parameters or rules and accordingly the OMC 117 comprises a user interface 307 coupled to the threshold modifier processor 305 which allows the operator to set parameters for the threshold modification.

e S S

S S S S S S

I S I S a i a. S S. S. S * s a 5 0I S * If, as a result of the last collected period of statistical data, the threshold modifier processor 305 determines that the threshold should be modified, the appropriate messages are sent to the RNC 107. For example, a message instructing the RNC 107 to reduce the load level threshold by one step can be transmitted.

For instance, a downlink call admission control algorithm is set up to reject incoming call requests when the cell load exceeds a given maximum threshold. The algorithm allows that different admission thresholds can be set for e.g. conversational and non-conversational calls. Typical average values are e.g. CACCSThreshold80% (Call Admission Control Circuit Switched Threshold) for Conversational circuit switched calls and CACPSThreshold75% (Call Admission Control Packet Switched Threshold) for non-conversational packet switched calls.

Those settings are generally appropriate and widely used, as priority is usually given to voice calls over other background or interactive traffic. Hence, when the traffic in the cell exceeds a loading of 75%, the load control procedure is initiated and changes the operation such that only conversational traffic is allowed until the congestion disappears. Thus, in this mode all packet switched non-conversational call setup requests are rejected. However, if there is not much conversational traffic in the cell at this point in time, the system would be rejecting non-conversational calls, and potentially under-utilising the available resources as cell load could be increased to e.g. 80% with no risk of system instability. In this particular U r I * UI I I a a U U U I * S a a * a a If I I. a. . I situation, the CAC_PS_Threshold can therefore be increased to 80% by the threshold modifier processor 305.

On the other hand, if the traffic in the cell is mainly conversational, it would be better to lower the CAC PS Threshold below its 75% nominal value, so that resources are not taken by non-conversational calls but are left for conversational calls. The advantage is again an increase in the total carried traffic in the cell thanks to an optimisation of the parameter values to the current traffic conditions. Furthermore, an increase in the call setup success ratio can be achieved for high load conditions.

Changes in traffic conditions as in the example above, are known to happen during the day. For example, a cell may support heavy non-conversational traffic and low conversational traffic during part of the day and low non-conversational traffic and heavy conversational traffic during the rest of day. If fixed thresholds are used for algorithm configuration, the system will not be set for maximum performance. Furthermore, as the variations may not be predictable even manually setting different thresholds for different time intervals is not feasible. In contrast, the system of FIG. 1 allows the best threshold values for the current traffic conditions to be found.

Thus, the load level threshold may specifically be set depending on a load indication for a given service, and in particular a load level threshold for a given service, such as a packet switched or non-conversational service may be set depending on the loading of another service, such as a * * S * S * S S S S S * 5 S * S * S S S S S S t5 8 5 5 5* S S S S * S 5 S S S. * 555 S. S conversational and/or circuit switched service. Hence, the threshold for a lower priority service may be set depending on the loading of a higher prioritised service (and specifically the threshold for the first service may be increased for lower loading of the second service).

The threshold can thus specifically be set based on a load indication for one service relative to a second service. For example, a system may prioritise real time services higher than non-real time services. Accordingly, the load level threshold for a load control procedure which blocks non-real time services may be adjusted depending on the current loading of real time and non-real time services. E.g. if the current loading of real time services is low and the loading of non-real time services is high, the threshold may be increased to allow a higher number of non-real time services. However, if the loading of real time services is high, an increased loading of non-real time services will not result in an increased threshold but rather the threshold may be lowered even further to ensure that more non-real time services are blocked thus freeing up resource for the real time services.

As previously mentioned, different load level thresholds may be used for each individual cell, for different cell groups and/or for different services. For example, the OMC 117 can be arranged to determine individual thresholds for each supported RNC based only on statistical data for the cell group formed by the cells supported by the individual cell.

As another example, the RNC 107 can use different load level thresholds for each individual cell. Thus, each load level threshold can be associated with a limited geographical * * * * . * * * * * * * S * * S S S * * * S S S* * S S 55 5 5 * S S S S * S 5 SS* *p S region such as the region supported by the individual cell or the group of cells.

As previously described, the OMC 117 can communicate with the RNC 107 by exchanging data messages over the core network 109. These data messages can for example be configuration control messages which modify the configuration of the RNC.

The individual message may comprise a load level threshold indication which is indicative of the threshold determined by the threshold modifier processor 305. The indication can directly be the determined absolute or relative load level threshold or can be an indirect indication such as a command to increase or decrease the current threshold level.

The configuration control messages can specifically comprise data that corresponds to a data command protocol used by the RNC 107. For example, the RNC 107 may have an associated control and management terminal which allows an operator to manually and locally configure the RNC 107 by setting various parameters and characteristics. Such management terminals generally interface with the RNC 107 via a command language which specifically can be a Man Machine Language (MML). In some embodiments, the same MML can be used by the OMC 117 to control the RNC 107. Specifically the OMC 117 selects the appropriate MML commands and embeds these in the configuration control messages that are sent to the RNC 107.

The RNC 107 then extracts the MML commands and processes these in the same way as it would MML commands received from the control and management terminal. The MML commands can specifically be embodied in SNMP (Simple Network Management * S * S S S S * S S S * * * * S * S * S S * S IS S G S 55 5 5 * S S S 5 * * S. S **5 55 Protocol)coands which is the standard for OMC interface maintenance.

A specific example of an algorithm for modifying the thresholds for circuit switched and packet switched services in accordance with some embodiments of the invention are shown in FIG. 4. In FIG. 4 KPI is an acronym for Key Performance Indicator and CAC is an acronym for Call Admission Control It will be appreciated that the above description for clarity has described embodiments of the invention with reference to different functional units and processors.

However, it will be apparent that any suitable distribution of functionality between different functional units or processors may be used without detracting from the invention. For example, functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controllers. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

The invention can be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors. The elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in S S S * S * S * S * S * * S * S S 5 a S S * S S S * ** * S * a S S * * S S. S aSS *5 * a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit or may be physically and functionally distributed between different units and processors.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term comprising does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also the inclusion of a feature in one category of claims does not imply a limitation to this category but rather indicates that the feature is equally applicable to other claim categories as appropriate. Furthermore, the order of features in the claims does not imply any specific order in which the features must be worked and in particular the order of individual steps in a method claim does not imply * * * S * * * * * S * * S S * . S S * * S S * 5 * S ** 5 * * S S S * S S 5* S **s 5. 5 that the steps must be performed in this order. Rather, the steps may be performed in any suitable order.

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Claims

CLAIMS

1. An apparatus for load control in a cellular communication system, the apparatus comprising: means for determining a load level characteristic for at least one cell of the cellular communication system; comparing means for comparing the load level characteristic to a load level threshold; means for executing a load control procedure if the load level characteristic exceeds the load level threshold; modifying means for determining a modified load level threshold in response to a performance characteristic of the cellular communication system; and adjusting means for dynamically modifying the load level threshold in response to the modified load level threshold.

2. The apparatus of claim 1 wherein the performance characteristic comprises a load indication for at least one service supported by the cellular communication systems.

3. The apparatus of any previous claim wherein the performance characteristic comprises a load indication for at least one service supported by the cellular communication system relative to a second service supported by the cellular communication system.

4. The apparatus of claim 3 wherein the first service is a conversational service and the second service is a non-conversational service.

0 * * 0 * * S * S. * a * * * * a * * * 0 0 4 * . S * ** * 4 a S I S a S 5. The apparatus of claim 3 or 4 wherein the first service is a circuit switched service and the second service is a packet switched service.

6. The apparatus of any previous claim 3 to 5 wherein the first service is a real time service and the second service is a non-real time service.

7. The apparatus of any previous claim wherein the load control procedure is a call admission adjustment procedure.

8. The apparatus of any previous claim wherein the load control procedure comprises a call admission blocking of a service supported by the cellular communication system.

9. The apparatus of any previous claim wherein the load level threshold is associated with a limited geographical region.

10. The apparatus of any previous claim wherein the load level threshold is associated with a group of cells.

11. The apparatus of any previous claim wherein the modifying means are comprised in a first network element of a fixed network of the cellular communication system and the adjusting means is comprised in a second network element of the fixed network.

12. The apparatus of claim 11 wherein the second network element is a Radio Network Controller.

* * * . * * * . . S S 5 0 S S S * S S e S SS S S 5 5I S S * S S S * S S S. p *** S. S 13. The apparatus of claims 11 or 12 wherein the second network element is arranged to apply different load level thresholds for different cells supported by the second network element.

14. The apparatus of the previous claims 11 to 13 wherein the first network element is an Operations and Maintenance Centre.

15. The apparatus of any of the previous claims 11 to 14 wherein the first network element is arranged to determine different modified load level thresholds for different cell groups.

16. The apparatus of any previous claim wherein the first network element is arranged to transmit configuration control messages to the second network element, the configuration control messages comprising an indication of the load level threshold, and the second network element is arranged to change the load level threshold in response to the indication.

17. The apparatus of any previous claim wherein the configuration control messages comprise Man Machine Language (MML) commands and the second network element is arranged to change the load level threshold in response to the MML commands.

18. The apparatus of any previous claim wherein the cellular communication system is a Universal Mobile Telecommunication System (UMTS) cellular communication system.

* * * S S * * * S * S S I S * * * S * S S S S S. S S 0 ** * . * S * S S S * *S S.55 55 * 19. A method of load control in a cellular communication system, the method comprising: determining a load level characteristic for at least one cell of the cellular communication system; comparing the load level characteristic to a load level threshold; executing a load control procedure if the load level characteristic exceeds the load level threshold; determining a modified load level threshold in response to a performance characteristic of the cellular communication system; and dynamically modifying the load level threshold in response to the modified load level threshold.

20. A computer program product enabling the carrying out of a method according to claim 19.

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