WO2008014818A1

WO2008014818A1 - Simulation tool and method for simulating a communication system

Info

Publication number: WO2008014818A1
Application number: PCT/EP2006/064971
Authority: WO
Inventors: Mohsen Zadeh-Koochak; Shirin Dehghan
Original assignee: Arieso
Priority date: 2006-08-02
Filing date: 2006-08-02
Publication date: 2008-02-07

Abstract

A method (500) of simulating a wireless network supporting communication between a plurality of communication units across a plurality of communication cells is described. The method comprises performing a simulation, identifying automatically a cell overshoot and automatically performing at least one automated modification to an antenna or system parameter of the first cell or one or more second cells in the simulation in response to the identified cell overshoot. The simulation is then re-run with the modified antenna or system parameter. In this manner, a time taken for a Network Operator to simulate, design or optimise overshooting cells in a wireless communication network or study the dynamic behaviour of the communication network is significantly reduced.

Description

SIMULATION TOOL AND METHOD FOR SIMULATING A COMMUNICATION SYSTEM

Field of the Invention

This invention relates to a simulation tool and resource planning in a communication system. The invention is applicable to, but not limited to, resource planning in a second and third generation wireless communication system.

Background of the Invention

Wireless communication systems, for example cellular telephony or private mobile radio communication systems, typically provide for radio telecommunication links to be arranged between a plurality of base transceiver stations (BTSs) and a plurality of subscriber units, often termed mobile stations (MSs) . Such telecommunication links are arranged to support digital and/or analogue communication signals .

Wireless communication systems are distinguished over fixed communication systems, such as the public switched telephone network (PSTN) , principally in that subscriber units/mobile stations move between coverage areas, where communications in the different coverage areas are served by different BTS (and/or different service providers) . In doing so, the subscriber units/mobile stations encounter a variable radio propagation environment.

Thus, in order for a system planner to ensure that there is acceptable communications across a wide geographical coverage area, which allows wireless communication signals to be transmitted to, and/or received from, the MSs at different geographical locations, a large number of communication parameters have to be determined. Furthermore, the system planner/network provider needs to ensure that the communication network (s) are designed such that they meet peak usage demand, so that users can make calls as and when required.

In a wireless communication system, each BTS has associated with it a particular geographical coverage area (or cell) . Primarily, a particular BTS transmitter power level, together with the type, height and directionality of the antenna that is used, defines a coverage area where a BTS can maintain acceptable communications with MSs operating within its serving cell. In addition, receiver sensitivity performance of receiving wireless communication units also affects a given coverage area. In large cellular communication systems, these cells are combined and often overlapped to produce an extensive and contiguous signal coverage area, whilst the subscriber units/mobile stations move between cells. The cell overlap region is deliberately designed into the system plan to ensure that subscriber units/mobile stations can successfully handover between cells .

A system design based on cells is typically based on an ideal cell pattern. However, an idealised cell pattern never occurs in practice, due to the nature of the terrain and the fact that cell sites and antennae are not ideally located on a regular grid pattern. Therefore, prior to system/network integration, a network designer uses radio-planning tools to estimate the radio propagation for each cell and consequently predict a corresponding coverage area. Based on these propagation models, the network designer is able to develop an initial plan for the network (prior to deployment of the network infrastructure) that is intended to minimise the expected interference. Once a specific infrastructure has been modelled, a simulation algorithm is run a large number of times, for a wide variety of subscriber distribution and parameters, i.e. location of MSs, activity status of MSs and transmit power employed by MSs operating in the network, in order to gain a statistical assessment of the network performance under the vast majority of operating conditions.

On the basis of the results of the software simulation, a variety of network parameter settings and site configurations (herein 'network parameter settings') are manually adjusted, such as a BTS antenna type, direction, power, height, location or radio resource management such as handover parameters, admission control, congestion control etc and other system parameters such as cell reselection, in order to improve the simulation results. The software simulation algorithm is then re-run, re-run and so on for further parameter alterations. Thus, the simulation phase is designed to converge to a set of parameter settings that allow the performance of the network to reach a predefined performance level, prior to network installation.

The simulation algorithms that are run are technology dependent. For example, different methods for assessing the network interference and quality are required for a Code Division Multiple Access (CDMA) technology, as defined for implementing the third generation (3G) mobile communication systems, as compared to the Time Division Multiple Access (TDMA) technique employed by the second generation (2G) global system for mobile communications (GSM) . An inherent feature of CDMA is that all mobile network users have access to the whole frequency- bandwidth all of the time. Thus, a frequency reuse of the network is a well-known feature of CDMA based systems. This means that the power emitted by the subscriber units and the base stations, respectively termed user equipment (UE) and Node Bs in 3G parlance, must be tightly controlled.

In order to design, plan, investigate and develop CDMA based systems, a software-based simulation of the network is carried out to ascertain, in particular, the transmit power levels employed by each Node B and each UE.

Part of a CDMA simulation involves solving certain mathematical formulations, for which there is no known ^Λclosed-form' solution. For this reason a numerical technique is employed whereby an initial solution is ^Λguessed' and is iteratively modified until the true solution is obtained. In order to ascertain when the final solution is reached, a ^convergence criterion' is defined, and the solution is then said to have Λconverged' .

A known iterative algorithm 100 used for power convergence in CDMA-based simulation applications is illustrated in FIG. 1. The iterative algorithm 100 comprises two phases:

(i) an initialisation phase 110, where all components of a network, such as communication cells and UEs etc., are executed as machine code; and

(ii) an iteration phase 150. In the initialisation phase 110, network information is read into computer memory, such as coverage information in step 115, Node B information in step 120, UE information in step 125 and network parameters in step 130.

The iteration phase 150 comprises a series of computations. In this regard, for each UE and Node B in the network in step 155, the simulation computes a new transmit power in step 160. Once the transmit powers have been computed, the simulation is able to compute the levels of interference caused within each cell and to each of the UEs, as shown in step 165. At the end of the simulation' s iteration, a determination is made as to whether the powers have converged, in step 170. If the powers have not converged, i.e. a definitive answer to the interference levels cannot be determined, the process loops 175 and one or more new transmit power level (s) for one or more UEs and/or Node Bs is/are used, as shown in step 155. However, if the powers have converged in step 170, the iterative power/interference level simulations end, as shown in step 180.

An integral part of the simulation and modelling of a wireless cell-based system involves controlling signal overshoot. Signal overshoot is defined as the power in a given area from a cell more than one tier away exceeding a given threshold, thereby creating interference and diminishing cell capacity and causing handover problems in that area. An example of an overshooting cell is shown graphically in FIG. 2. The arrows 205 in FIG. 2 illustrate the signal overshoot where one cell is overshooting and providing non-contiguous patchy coverage into an area outside its main best service area.

The flowchart 300 of FIG. 3 describes a known mechanism for handling such overshooting problems. Thus, one known mechanism is to simulate the effect of a best and second best server in such an area, as shown in step 305. The method equally applies for more than two servers . System engineers or software simulation engineers then need to visually identify an effect of a potential signal overshoot in step 310 and proceed to manually find a resolution to this problem in step 315 by, say, either reducing the transmit power of the cell in question or down-tilting the antenna.

The effect of such a simulation/modelling change then needs to be re-assessed (re-simulated) to identify whether the problem is resolved in step 320, as well as to ensure that the performance of the network is not degraded as a result of the change (s) . If the problem is resolved in step 320, then that part of the modelling/simulation is completed, in step 325. Otherwise, the process loops back to step 305, and further modelling changes are manually implemented and simulations re-run.

Thus, signal overshoot reduction is a manually intensive and significant engineering problem in first manually identifying the signal overshoot problem, and secondly modifying the simulation model in response to the identified signal overshoot problem.

It is also known that other methods of controlling signal overshoot, say through tracking of signal-to-noise ratio of transmissions, are inefficient and inadequate in that they do not ensure confinement of large cells that are generating the undesired interfering signal (s).

Thus, in summary, the known processes can take an extremely long time to resolve unknown quantities, are inefficient and do not adequately address the signal overshoot problem. In addition, in cases where there is limited time to run the simulations and modelling, it is possible that a sub-optimal network design is achieved, where the network design merely meets rather than exceeds the network provider's minimum requirements.

Thus, there exists a need in the field of the present invention for an improved method for control of overshooting cells in the resource planning in the development and design of a wireless communications network. Furthermore, there exists a need to provide a cell-based communication system that can be continuously optimised through on-going simulations, wherein the aforementioned disadvantages may be alleviated.

Summary of the Invention

In accordance with one embodiment of the present invention there is provided a method of simulating a wireless network supporting communication between a plurality of communication units across a plurality of communication cells, as claimed in Claim 1. The method comprises performing a simulation; identifying automatically a cell overshoot; automatically performing at least one automated modification to an antenna or system parameter of the first cell or one or more second cells in the simulation in response to the identified cell overshoot; and re-performing automatically the simulation with the modified antenna or system parameter.

Thus, the provision of a targeted solution to address the identification and resolution of a cell overshoot problem significantly reduces the time it takes a Network Operator to simulate and model an adequately performing system. Hence, employing the inventive concept leads to a higher quality radio system. Furthermore, the inventive concept may be equally applicable to automatic network optimisation techniques, to automate the whole process of radio network design for cellular operators.

In one embodiment of the present invention, the step of identifying automatically a cell overshoot may comprise setting a communication range of a first cell as a threshold radius; and identifying automatically a cell overshoot in response to detecting the threshold radius is exceeded. In one embodiment of the present invention, the step of setting a threshold radius is performed automatically. In one embodiment of the present invention, the step of setting a threshold radius automatically comprises computing a threshold for each cell based on a topology of the wireless communication network and/or based on radio environment characteristics in which the communication cell operates .

In one embodiment of the present invention, the step of identifying automatically a cell overshoot may comprise setting a communication range of a first cell as a threshold radius for a best server area. In one embodiment of the present invention, this may include setting a communication range of a first cell as a threshold radius for a best server area and a second best server area.

In one embodiment of the present invention, the step of identifying automatically a cell overshoot may comprise detecting at least one non-contiguous polygon of communication coverage from a plurality of communication cells. In one embodiment of the present invention, the one or more second cells may be adjacent the first cell.

In one embodiment of the present invention, the simulation relates to an air-interface of a wireless communication network having communication units that are capable of transmitting at differing radio frequency transmit powers, such that the step of performing a simulation comprises converging a number of the transmit powers .

In one embodiment of the present invention, the method may further comprise adapting an operational communication network, for example in a substantially real-time manner, in response to identifying automatically a cell overshoot.

In one embodiment of the present invention, the method of simulating or designing a communication network may be applied to a wireless CDMA, TDMA, FDMA or OFDMA communication network.

In one embodiment of the present invention, the method may be applied to one or more of the following: a static simulation of a wireless communication network; a dynamic simulation of a wireless communication network; an offline optimisation of a wireless communication network; or an on-line (or substantially near-real-time) optimisation of a wireless communication network.

In one embodiment of the present invention, a communication unit, such as an Operations and Management Centre (OMC) of a 3G communication network, may be adapted to support the hereinbefore described method.

In one embodiment of the present invention, a storage medium may store processor-implementable instructions for controlling a processor to carry out the hereinbefore described method.

In one embodiment of the present invention, a simulation tool for simulating or designing a communication network supporting communication between a plurality of communication units is described. The simulation tool comprises logic to identify automatically a cell overshoot; logic to perform at least one automated modification to an antenna or system parameter of the first cell or one or more second cells in the simulation in response to the identified cell overshoot; and logic to re-perform automatically the simulation with the modified antenna or system parameter.

Typically the method is applied as part of an automatic cell planning tool (ACP) or radio-planning tool or measurement post processing tool and utilised in the selection of radio base station sites, tune transmitter parameters and/or select antenna settings .

It is envisaged that data relating to the simulation may be stored in a database and relate to any, or any combination, of the following: geographical area to be covered by the network, the number of handsets for which the simulation is to be generated, the status of the handsets i.e. whether moving or static, the power emissions from the handsets and/or base stations, settings of the base stations themselves, and in general any data which can be treated as a predetermined parameter which will not in practice change or change with little or no impact on the network performance.

The simulation tool can be used to generate data results on a real time basis. As an example, if the network geographical area includes a heavily used transport link, such as a motorway, commuter route or rail line, then the usage characteristics may vary largely during any given day as a result of rush hour traffic going in a first direction at the start of the day and the reverse direction at the end of the day with, in between those times, relatively less usage. Thus, the database can hold data to allow the simulation of the use of the network at each of these different usage instances.

Thus, in accordance with one embodiment of the present invention the ^Λ signal overshoot' is detected by one or more of a number of different direct algorithms. For example, a first technique is to use a cell radius concept for best server areas to determine whether one or more cells is/are overshooting. A second technique may be to detect non-contiguous polygons of coverage from cells .

It is possible to develop intelligence to determine what a tier is by drawing a polygon around each site by 'connecting the dots' representing the centres of adjacent cells. It is the boundary so formed that determines a given threshold that should not be exceeded. This procedure beneficially may allow the boundary and threshold to be automatically defined.

In summary, the inventive concept of the present invention proposes an improvement to the known manual method by specifically and directly targeting and controlling overshooting cells in a deterministic, reliable and automated manner.

Brief Description of the Drawings

FIG. 1 is a flow diagram outlining the conventional iterative algorithm used in modelling a wireless communication system.

FIG. 2 illustrates a schematic diagram outlining the effects of an overshooting cell.

FIG. 3 illustrates a flow diagram outlining the approach to solving a problem in identifying and correcting an overshooting cell.

Exemplary embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:

FIG. 4 illustrates a block diagram of a cellular radio communications system adapted to support the various inventive concepts of a preferred embodiment of the present invention. FIG. 5 illustrates a flow diagram outlining the simulation algorithm employed in accordance with one embodiment of the present invention.

FIG. 6 is a diagrammatic illustration of a layout of cells including a cell boundary useful in a method embodying the invention.

Description of Preferred Embodiments

The simulation and modelling of a wireless communication system is highly complex, primarily due to the large number of wireless communication elements, such as base stations/ Node Bs and subscriber units/ user equipment (UE) . Overshooting cells is a phenomenon that is known to severely impact capacity of all adjacent cells as well as cause dropped calls in wireless communication systems.

One embodiment of the present invention is described with reference to a simulation of a 3^rd generation cellular communication system, such as a CDMA universal mobile telecommunication system (UMTS) as defined by the European Telecommunication Standards Institute (ETSI) . However, the inventive concepts are equally applicable to any other wireless access technologies, such as TDMA, FDMA, OFDMA, etc.

Simulating a CDMA network is primarily concerned with evaluating the powers transmitted by Node Bs and subscriber units . Severe interference exists between these entities. The level of interference is also dependent on their relative positions, which needs to be evaluated within the simulation. In order to combat such levels of interference, both subscriber units (UEs) and the Node Bs must adopt appropriate power levels, in order to achieve the predefined quality of service (QoS) for the end user. Furthermore, achieving the highest level of pilot dominance is of great importance in order to maximise quality and throughput in a CDMA network.

It is envisaged that the inventive concepts can be applied in a real-time manner, say, by an Operations and Management Centre (OMC) of a 3G network, to simulate a real-time performance of the network. In this manner, the OMC is able to continuously optimise the performance of the network dependent upon the prevailing and variable conditions. Alternatively, it is envisaged that the simulation aspects of the present invention can be applied by a Network Operator in the initial design of a wireless cellular communication network.

Thus, the foregoing description details how the inventive concepts can be applied to a practical 3G UMTS network, and preferably to the adaptation of system parameters in a pseudo real-time manner as a result of the simulation. Referring first to FIG. 4, a cellular-based telephone communication system 400 is shown in outline, in accordance with a preferred embodiment of the invention. In the preferred embodiment of the invention, the cellular-based telephone communication system 400 is compliant with, and contains network elements capable of operating over, a universal mobile telecommunication system (UMTS) and/or a general packet radio system (GPRS) air-interface .

In particular, the simulation aspects of the inventive concept of the present invention can be applied to the Third Generation Partnership Project (3GPP) specification for wide-band code-division multiple access (WCDMA) standard relating to the UTRAN radio Interface (described in the 3G TS 25.xxx series of specifications developed by ETSI) .

Generally, the air-interface protocol is administered from base transceiver sites, referred to under UMTS terminology as Node-Bs, within the network architecture. The Node Bs are geographically spaced apart - one Node B supporting a cell (or, for example, sectors of a cell) . A plurality of subscriber terminals (or user equipment (UE) in UMTS nomenclature) 412, 414, 416 communicate over radio links 418, 419, 420 with a plurality of Node-Bs 422, 424, 426, 428, 430, 432. The system comprises many other UEs and Node Bs, which for clarity purposes are not shown .

The wireless communication system, sometimes referred to as a Network Operator' s Network Domain, is connected to an external network 434, for example the Internet. The Network Operator' s Network Domain (described with reference to both a 3^rd generation UMTS and a 2^nd generation GSM system) includes :

(i) A core network, namely at least one Gateway GPRS Support Node (GGSN) 444 and/or at least one Serving GPRS Support Nodes (SGSN) ; and

(ii) An access network, namely:

(ai) a GPRS (or UMTS) Radio network controller (RNC) 436-440; or

(aii) Base Site Controller (BSC) in a GSM system and/or

(bi) a GPRS (or UMTS) Node B 422-432; or (bii) a Base Transceiver Station (BTS) in a GSM system.

The GGSN/SGSN 444 is responsible for GPRS (or UMTS) interfacing with a Public Switched Data Network (PSDN) such as the Internet 434 or a Public Switched Telephone Network (PSTN) 434. A SGSN 444 performs a routing and tunnelling function for traffic within say, a GPRS core network, whilst a GGSN 444 links to external packet networks, in this case ones accessing the GPRS mode of the system

The Node-Bs 422-432 are connected to external networks, through base station controllers, referred to under UMTS terminology as Radio Network Controller stations (RNC) , including the RNCs 436, 438, 440 and mobile switching centres (MSCs), such as MSC 442 (the others are, for clarity purposes, not shown) and SGSN 444 (the others are, for clarity purposes, not shown) .

Each Node-B 422-432 contains one or more transceiver units and communicates with the rest of the cell-based system infrastructure via an I_ub interface, as defined in the UMTS specification.

Each RNC 436-440 may control one or more Node-Bs 422-432. Each MSC 442 provides a gateway to the external network 434. The Operations and Management Centre (OMC) 446 is operably connected to RNCs 436-440 and Node-Bs 422-432 (shown only with respect to Node-B 426 for clarity) . The OMC 446 administers and manages sections of the cellular telephone communication system 400, as is understood by those skilled in the art. A location registry function 480, comprising home location register and visitor location register details, is shown at a high level in the system architecture, so that the location information is system-wide. A skilled artisan would appreciate that the location registry function 480 may, in alternative embodiments, be operably coupled to lower level elements such as the SGSN 442, 444, a GGSN (not shown) or the OMC 446.

In the preferred embodiment of the present invention, the OMC 446 has been adapted to perform a real-time simulation of the UMTS network. In this regard, the OMC 446 has been adapted to recognise that overshooting cells can be described as first or second best pilot servers in an area where the cell is providing non-contiguous and patchy overlap with other cells in the area.

It is known that the power level required by any UE within the simulation may be evaluated using the following general equations .

Nbs 1 1

K= ∑P_nx—+(P_s -Pm)x—xa [2] n=\,n≠s L_n L_s

where :

P_{BS to m} signifies the required power from the Node-B to the mobile subscriber unit/UE m.

E_b /N₀ signifies the energy per bit over noise + interference spectral density; this parameter is crucial in ensuring an acceptable quality of service for mobile subscriber unit/UE m.

C signifies the chip rate for CDMA systems.

R_n signifies the data rate for mobile m.

I_n represents the interference experienced by mobile m.

L_s signifies link loss from the serving base station/Node-B of the mobile subscriber unit/UE m.

P_n signifies the total power at other base stations /Node-Bs where n=l to N bits/s which is the total number of base stations in the network being simulated where n does not equal s, which is the serving base station/ Node-B of mobile subscriber unit/UE m a is the non-orthogonality factor.

However, in accordance with one embodiment of the present invention, the identification and resolution of an overshooting problem is considered, based on the recognition that overshooting cells can be described as first /best pilot servers or, say, first and second best pilot servers in an area where the cell is providing noncontiguous and patchy overlap with other cells in the area. Best server pilot represents the pilot signal that has the strongest received signal strength at the mobile and second best pilot is the second most strong signal strength measured by the mobile.

In some embodiments of the present invention, it is envisaged that overshoot may be defined for up to an Nth server. In practice, it is most important for the best server to have limited range. Thereafter, it is important for the second server to have limited range, and so on, with the desirability to limit the range falling off rapidly for the other servers .

Furthermore, the identification and resolution of an overshooting problem is performed automatically, without the need for manual intervention.

Identification is performed by simulating the received signal strength by the mobile from all cells geographically. In one method the algorithm counts the number of geographical pixels falling outside the allowed cell radii for the specific cells. The sum of all pixels suffering from this problem may then represent a percentage area of pixels suffering from best server and second best server overshoot problem.

In one embodiment of the present invention, the algorithm then seeks to reduce this percentage to the target level set by the user by automatically tilting the overshooting cells and reconfiguring the surrounding cells to overcome lost coverage. The algorithm for automatic adjustment of parameters to overcome overshoot is best based on heuristic methods to provide the most optimum combination of configuration for resolution of the problem.

Another identification method would be based on contiguous coverage based on evaluating neighbouring pixels and forming an enclosed polygon and assessing patchiness or otherwise of a pilot signal. This avoids the user specifying a desired cell radii and the algorithm advantageously and automatically decides if a cell is overshooting. In one embodiment of the present invention, it is envisaged that the inventive concepts can be used in a dynamic simulation of a wireless communication network. In this regard, it is envisaged that a processor in the OMC 446 runs the simulation program. However, in alternative embodiments, it is envisaged that such concepts could be implemented in software in any element operably coupled to the OMC 446. Alternatively, the improved simulation algorithm may be located within any- other element within the infrastructure, such as a separate analysis platform, or even distributed within a number of elements if appropriate. For example, the improved overshoot detection and resolution algorithm could be implemented within the radio access network (RAN) of the cellular infrastructure equipment and/or it may be implemented as a stand-alone element/function on an adjunct platform.

More generally, the improved algorithm may be programmed into, say, the OMC 446 according to the preferred embodiment of the present invention, in any suitable manner. For example, new apparatus may be added to a conventional communication unit. Alternatively existing parts of a conventional communication unit may be adapted, for example, by reprogramming one or more processors therein. As such the required adaptation may be implemented in the form of processor-implementable instructions stored on a storage medium, such as a floppy- disk, hard disk, programmable read only memory (PROM) , random access memory (RAM) or any combination of these or other storage media.

Referring now to FIG. 5, a flowchart 500 illustrates an overview of one overshoot detection and resolution algorithm within a simulation process. The simulation process comprises an initialisation phase 505, where one or more items of network information is read into computer memory, such as coverage information in step 510, Node-B information in step 515, UE information in step 520 and/or network parameters in step 525.

In accordance with one embodiment of the present invention, the software algorithm simulates a best server (and in some embodiments an additional second best server), as shown in step 530. The software algorithm then detects the overshooting cells by detecting best server or 2^nd best server beyond a user defined radius for each cell. As part of this aspect of the simulation, the software algorithm then sets a communication range for each cell, for example by setting a cell radius. The software algorithm then automatically detects those overshooting cells that transmit powers that exceed a threshold defined by the cell radius for one or both servers, as shown in step 535.

The software algorithm is then arranged to automatically modify the configuration of the identified problem cell (and potentially one or more surrounding cells) in order to eliminate any strong interfering signals outside of the allowed best server radius (i.e. the cell radius threshold as determined by the operator) . In this manner, the overshooting cell problem is reduced, and preferably minimised or eliminated, as shown in step 540.

A full and detailed simulation of the network also subsequently takes place, to ensure that other metrics of traffic, coverage and signal-to-noise ratio, etc. are not impacted by these changes . In accordance with one embodiment of the present invention, the step of identifying automatically a cell overshoot may comprise detecting at least one noncontiguous polygon of communication coverage from a plurality of communication cells. The one or more second cells may be adjacent the first cell.

FIG. 6 shows a diagrammatic layout 600 of service cells in a wireless communication system. FIG. 6 illustrates how overshoot may be determined automatically in the layout 600. Cells 601, 603, 605, 607 and 609 are included in the layout 600. Each of these cells is represented by its centre at which there is a base station, Node B or the like. In the case where overshoot from the cell 601 is being analysed, a notional polygonal boundary 611 can be constructed by joining the centres of each of the cells that are nearest neighbours of the cell 601. These nearest neighbour cells include the cells 603 and 607. The notional boundary 609 represents a limit or range to be reached with a given threshold power level from the cell 601 along a signal path 615. Thus if the power level from the cell 601 exceeds the given threshold power level in any area beyond the boundary 608 (relative to cell 601) , for example in an area indicated by dashed line 613, it is to be regarded as overshoot. The other cells may be analysed in a similar manner. The given threshold power for each cell analysed may be determiend according to system cell layout details, but may for example be - 115 dBm. The system may allocate the boundaries of each cell and the threshold power relating to the boundary automatically in the simulation procedure . In accordance with one embodiment of the present invention, the inventive concept proposes a means of achieving substantially improved pilot signal contiguous in CDMA networks, hence resulting in improved handover performance and throughput.

In an alternative embodiment of applying the aforementioned inventive concept in a preliminary network design simulation process, as compared to a real-time monitoring and adjustment of system parameters as described above, it is envisaged that the configuration of the hardware or software or firmware platform need not be static. In this regard, by arranging for the configuration of the network to vary in time, according to a pre-programmed sequence of events stored in the computer, the time-varying dynamic nature of the network can be precisely studied.

In this case, the operator defines a dynamic scenario by specifying the manner in which one or more parameter (s) of the network changes with time, or alternatively the behaviour is predicted using location based information of the mobiles or is determined from network data logged as the network is operating. The sequence is then stored in computer memory.

In one embodiment of the present invention, the at least one antenna or system parameter that is modified in response to a determination of a cell overshoot condition, may comprise one or more of the following: BTS antenna type, direction, power, height, location or radio resource management such as one or more handover parameters, admission control, congestion control, etc. and other system parameters such as cell reselection, in order to reduce or minimise the cell overshoot problem.

One embodiment of the present invention has been described with regard to a cellular telephony communication system, such as the universal mobile telecommunications standard (UMTS) . It is envisaged that the invention is equally applicable to other wireless CDMA, TDMA, FDMA or OFDMA communication systems. It is also within the contemplation of the invention that alternative radio communication architectures, such as private or public mobile radio communication systems could benefit from the inventive concepts described herein.

It is also within the contemplation of the present invention that the inventive concepts are not limited to use in simulating a wideband CDMA network. It is envisaged that the inventive concepts are equally- applicable to any scenario where there exists a need to solve recursive equations similar to the ones detailed here. In particular, it is envisaged that the inventive concepts can be applied to any radio network, such as : static simulation of radio networks, dynamic simulation of radio networks, off-line optimisation of radio networks, on-line (or near-real-time) optimisation of radio networks, etc.

Clearly, a skilled artisan would appreciate the vast array of applications and opportunities that are made available to users through the inventive concepts described herein. In this regard, the examples provided above highlight only a snapshot of these. It will be understood that the wireless communication system, improved OMC and improved method for resource (re-) planning, as described above, provides at least one or more of the following advantages that could not be reliably obtained using existing radio planning methods:

(i) It significantly reduces the time it takes a Network Operator to detect and thereafter reduce, minimise or eliminate overshoot problems. Hence, employing the inventive concept leads to a higher quality- radio system.

(ii) The inventive concept is equally applicable to automatic network optimisation techniques, to automate the whole process of radio network design for cellular operators .

(iii) The inventive concept is equally applicable to on-going and substantially real-time adjustment of a wireless communication network, a feature that cannot be envisaged in today's large wireless networks.

(iv) It significantly reduces the time it takes a Network Designer to design and study the dynamic behaviour of the network.

It will be appreciated that any suitable distribution of functionality between different functional units or controllers or memory elements, may be used without detracting from the inventive concept herein described. Hence, references to specific functional devices or elements 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.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. 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 a single unit or IC, in a plurality of units or ICs or as part of other functional units .

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 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 performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to "a", "an", "first", "second" etc. do not preclude a plurality.

Thus, a communication system, improved OMC and a method for simulator-driven cell configuration (re-) planning have been provided wherein the aforementioned disadvantages associated with prior art arrangements have been substantially alleviated.

Claims

1. A method (500) of simulating or designing a wireless communication network supporting communication between a plurality of communication units across a plurality of communication cells, wherein the method comprises : performing a simulation; wherein the method is characterised by: identifying automatically a cell overshoot; automatically performing at least one automated modification to an antenna or system parameter of the first cell or one or more second cells in the simulation in response to the identified cell overshoot; and re-performing automatically the simulation with the modified antenna or system parameter.

2. The method (500) of simulating or designing a wireless communication network according to Claim 1, wherein the step of identifying automatically a cell overshoot is further characterised by setting a communication range of a first cell as a threshold radius; and identifying automatically a cell overshoot in response to detecting the threshold radius is exceeded.

3. The method (500) of simulating or designing a wireless communication network according to Claim 2, wherein the step of identifying automatically a cell overshoot is further characterised by setting a communication range of a first cell as a threshold radius for a best server area.

4. The method (500) of simulating or designing a wireless communication network according to Claim 3, wherein the step of identifying automatically a cell overshoot is further characterised by setting a communication range of a first cell as a threshold radius for at least one of a best server area and a second best server area.

5. The method (500) of simulating or designing a wireless communication network according to Claim 4, wherein the step of setting a threshold radius is performed automatically.

6. The method (500) of simulating or designing a wireless communication network according to Claim 5, wherein the step of setting a threshold radius automatically comprises computing the said threshold for each cell based on a topology of the wireless communication network and/or based on radio environment characteristics in which the communication cell operates.

7. The method (500) of simulating or designing a wireless communication network according to Claim 1, wherein the step of identifying automatically a cell overshoot further comprises detecting at least one noncontiguous polygon of communication coverage from a plurality of communication cells.

8. The method (500) of simulating or designing a wireless communication network according to any preceding Claim, wherein the one or more second cells are adjacent the first cell.

9. A method (500) of simulating or designing a wireless communication network according to any preceding Claim, wherein the simulation relates to an air-interface of a wireless communication network (400) having communication units that are capable of transmitting at differing radio frequency transmit powers, such that the step of performing a simulation comprises converging a number of the transmit powers .

10. A method (500) of simulating or designing a wireless communication network according to any preceding Claim, wherein the method is further characterised by the step of: adapting an operational communication network (400) , for example in a substantially real-time manner, in response to identifying automatically a cell overshoot .

11. A method (500) of simulating or designing a wireless communication network (400) according to any of the preceding Claims, wherein the method is applied to a wireless CDMA, TDMA, FDMA or OFDMA communication network.

12. A method (500) of simulating or designing a wireless communication network (400) according to any- preceding Claim, wherein the method is applied to one or more of the following:

(i) A static simulation of a wireless communication network;

(ii) A dynamic simulation of a wireless communication network;

(iii) An off-line optimisation of a wireless communication network; or

(iv) An on-line (or substantially near-real-time) optimisation of a wireless communication network.

13. A wireless communication network (200) adapted to support the method steps of any of preceding Claims 1 to 12.

14. A wireless communication unit, such as an Operations and Management Centre (OMC) of a 3G communication network, adapted to support the method steps of any of preceding Claims 1 to 12.

15. A storage medium storing processor-implementable instructions for controlling a processor to carry out the method steps of any of preceding Claims 1 to 12.

16. A simulation tool, adapted to support the method steps of any of preceding Claims 1 to 12.

17. A simulation tool, for simulating or designing a wireless communication network (400) supporting communication between a plurality of communication units, wherein the simulation tool is characterised by: logic to identify automatically a cell overshoot; logic to perform at least one automated modification to an antenna or system parameter of a first cell or one or more second cells in a simulation in response to the identified cell overshoot; and logic to re-perform automatically the simulation with the modified antenna or system parameter.

18. The simulation tool according to Claim 17, wherein the logic to identify automatically a cell overshoot comprises logic to set a communication range of a first cell as a threshold radius; and the logic to perform at least one automated modification to an antenna or system parameter of the first cell or one or more second cells performs the at least one automated modification in response to detecting the threshold radius is exceeded.

19. The simulation tool according to Claim 18, wherein the logic to set a communication range of a first cell as a threshold radius comprises logic to compute a threshold for each cell based on a topology of the wireless communication network and/or based on radio environment characteristics in which the communication cell operates.

20. The simulation tool according to any of preceding Claims 17 to 19, wherein the logic to identify automatically a cell overshoot comprises logic to set a communication range of a first cell as a threshold radius for a best server area.

21. The simulation tool according to Claim 20 wherein the logic to identify automatically a cell overshoot comprises logic to set at least one communication range of a first cell as a threshold radius for a best server area and a second best server area.

22. The simulation tool according to Claim 17 to 19 wherein the logic to identify automatically a cell overshoot comprises logic to detect at least one noncontiguous polygon of communication coverage from a plurality of communication cells.

23. The simulation tool according to any of preceding Claims 17 to 22 wherein the one or more second cells are adjacent the first cell.

24. The simulation tool according to any of preceding Claims 16 to 23 wherein the simulation tool is located in an Operations and Management Centre (446) of a wireless communication network (400) .

25. The simulation tool according to any of preceding Claims 16 to 24 wherein the simulation tool is arranged to adapt an operational communication network for example in a substantially real-time manner, in response to identifying automatically a cell overshoot.

26. A cellular communication system (400) adapted to employ the simulation tool of any of preceding Claims 16 to 25.

27. Apparatus for use in a cellular communication system (400) adapted to employ the simulation tool of any of preceding Claims 16 to 25.