GB2341048A

GB2341048A - Method and apparatus for changing the frequency plan of a cellular communications system

Info

Publication number: GB2341048A
Application number: GB9817939A
Authority: GB
Inventors: Paul Stephens; Paul Norkus
Original assignee: Motorola Ltd
Current assignee: Motorola Solutions UK Ltd
Priority date: 1998-08-19
Filing date: 1998-08-19
Publication date: 2000-03-01
Anticipated expiration: 2018-08-19
Also published as: GB9817939D0; GB2341048B

Abstract

A system for changing a frequency plan of a cellular communications system comprises the steps of: determining a second frequency plan; transmitting corresponding frequency plan settings to components of the communications system; storing the settings at the components; and implementing the frequency plan settings in response to an initiation instruction. This allows preparation of a complete frequency plan in advance and implementing it in one step, whilst alleviating disadvantages related to shutting down all or part of the system.

Description

2341048 METHOD OF CHANGING A FREQUENCY PLAJ-Z IN. AND APPARATUS FOR, A

CELLULAR COMMUNICATIONS SYSTEM

Field of the Invention

This invention relates to a method of changing a frequency plan in a cellular communications system. The invention also relates to apparatus for a cellular communications system.

Background of the Invention

In a cellular communications system, the area over which service is provided is divided into a number of smaller areas called cells. Each cell is served from a base transceiver station (BTS) which has a corresponding antenna or antennas for transmission to and reception from a user station, normally a mobile station.

A cellular communications system is operated according to a frequency plan. A frequency plan consists of a plurality of frequency plan settings applied to the various components of the system. Such settings typically include a specific radio frequency or set of frequencies assigned to each respective BTS, which frequency or frequencies thus apply to the corresponding cell. Other frequency plan settings forming part of the frequency plan are typically a cell colour code which a given cell will transmit. One example of a cellular communications system is a global system for mobile communications (GSM) system. In a GSM system, the cell colour code is contained within the base transceiver station identity code (BSIC).

The overall specification of the above mentioned frequency plan settings constitutes a frequency plan of a cellular communications system. In known communications systems, it is often necessary or desirable to change a frequency plan from a first frequency plan, under which the system is currently operating, to a second frequency plan. There are different possible reasons as to why such a change can be required. One 2 reason can be that the system requires enlarging. An alternative reason can be that it is believed that the new frequency plan will operate better than the original frequency plan. Whatever the case, it is relevant that under all frequency plans, the frequencies used on one cell potentially interfere with the frequencies used in adjacent and other nearby cells. As such it is not possible in practice to change part of the frequency plan without affecting other parts of the system.

Known methods of changing the frequency plan in a cellular communications system are as follows.

The first known method is often referred to as a manual on-line frequency change. Under this method, direct on-line editing of individual frequencies can be carried out through an operations and maintenance centre (OMC) of the system. The disadvantage with this method is that when a single frequency is altered on its own, due to the above interference affects, other parts of the system will be affected. A further disadvantage of manual on-line frequency change whereby individual frequencies are changed one at a time is that associated parameters that ought to be changed in parallel cannot be. For example, when a frequency is changed, it may be appropriate to amend also a colour code.

Another known method of changing a frequency plan is to carry out offline frequency change. Under this method, an overall frequency plan is prepared in advance. Databases and simulation programmes can be used to estimate the interference affects of a proposed new frequency plan and improve and amend the plan ahead of its actual implementation. However, when such a technique is used under known methods, it is then necessary to close down a part or all of the communications system in order to change over the many frequency settings. Advantages of planning a complete frequency plan in advance are such that network operators do indeed in practice shut down part or all of their systems in order to 3 implement the change of a frequency plan according to such a known method. However, in doing this, a separate major disadvantage occurs, since closing down part or all of the system is inconvenient for the users of the system. In known methods, the operator of the system will balance his requirements for avoiding shut down of the system with his requirements for optimising the frequency plan, by choosing how much of the system to shut down at one time. If he shuts down small parts of the system at a time, this reduces the inconvenience or levels of inconvenience to end users, but minimises the benefits of an overall implementation. On the other hand, if he shuts down most or all of the system to achieve optimisation of the overall implementation, it then increases inconveniences to the users. A method used conventionally to alleviate the above disadvantages is to carry out any shut down of part or all of the system and implementation of the corresponding frequency plan change at a time of day when the system is under least use. This might be at 3a.m. for example. However, such a situation can be viewed merely as making the best of a bad job, in particular since many applications can be envisaged where service at 3 a.m. is still of significant benefit. Such possibilities include emergency calls and other unscheduled events, and in addition pre-planned 24 hour services such as telemetry.

Summary of the Invention

The present invention addresses some or all of the above disadvantages.

According to one aspect of the present invention, there is provided a method of changing a frequency plan in a cellular communications system, as claimed in claim 1.

According to another aspect of the invention, there is provided an apparatus for a cellular communications system, as claimed in claim 16.

4 According to yet another aspect of the invention, there is provided an apparatus for a cellular communications system, as claimed in claim 25.

Claims

Further aspects of the invention are as claimed in the dependent Claims.

The present invention allows the advantages of preparing a complete frequency plan in advance and implementing it in one step, whilst alleviating the above mentioned disadvantages relating to shutting down part or all of the system. The present invention also has the advantage of providing a readily available alternative frequency plan. A further advantage of a preferred version of the invention is that by virtue of a use of a change plan parameter, those components of the communications system which are required to change over to new frequency plan settings of a new frequency plan can be identified and allocated in advance, so enabling frequency planning to be refined in advance in response to changing inputs, even in advance of implementing a new frequency plan.

Similarly, a preferred version of the present invention enables further frequency plans to be saved. The information of an overall arrangement can be stored when that arrangement is found is to be of interest or satisfactory, even when such an overall arrangement consists of a mixture of unchanged components still with first frequency plan settings of a first frequency plan and changed components with newly implemented second frequency plan settings of the second frequency plan. This provides the advantage that new frequency plans can be derived on the basis that they are found in practice to be of interest, even though that particular overall arrangement might never have been planned on a theoretical basis in its exact detail.

Further advantages of another preferred version of the invention are that due to the potentially ever present availability of the different frequency plans, and the ease at which they are implemented according to the present invention, it is very straightforward to return to an original first frequency plan if a newly implemented frequency plan is found in practice to be unsuitable or unsatisfactory. 5 Yet still further advantages derive from further preferrei versions of the present invention in which frequency plan settings pertaining to neighbour cells are included in the frequency plan settings changed when changing from one frequency plan to another frequency plan. In particular, this alleviates the above mentioned disadvantages arising in known methods due to interference affects causing other parts of a system to be affected by frequency change in a particular cell.

Additional specific advantages of the present invention are apparent from the following description and figures.

Brief Description of the Drawings FIG. 1 is an illustration of part of a cellular commu 1 nications system that is in accordance with the present invention.

FIG. 2 is an illustration of the arrangement of frequency plan settings pertaining to one cell in accordance with the present invention.

FIG. 3 is a process flow chart of an embodiment of the present invention.

Description of a Preferred Embodiment of the Invention The preferred embodiment relates to a cellular communications system which is a GSM system, although it will be appreciated that the invention 6 is not limited to such a system and can equally be used in other time division multiple access (TDMA) systems, in code division multiple access (CDMA) systems, or other cellular communications systems including combined TDMA-CDMA systems. 5 FIG. 1 illustrates part of a cellular communications system 100 in which two base transceiver stations (BTS) 110 and 120 are each coupled to mobile services switching centre (MSC) 140 through one base station controller (BSC). 130. An operations and maintenance centre (OMC) 160 is also coupled to MSC 140. MSC 140 is further coupled to a public switched telephone network (PSTN) 150. BTS 110 and BTS 120 are each controlled by BSC 130. Each BTS provides a coverage area, known as a cell, of the cellular communications system. In 15 the present embodiment, the frequency plan settings of a frequency plan are all implemented within respective BTS's. It will be appreciated, however, that in other embodiments such frequency settings may be located instead or in addition in other components of a cellular communications system, according to the requirements of the particular 20 system under consideration. In the present embodiment each BTS, for the sake of simplicity, is shown to require to transmit on only up to 3 different frequencies as is indicated by the presence in each BTS of 3 transceivers. In particular, BTS 110 is shown containing transceiver 114, transceiver 116 and transceiver 118. Similarly, BTS 120 comprises transceiver 124, 25 transceiver 126, and transceiver 128. In each BTS all three transceivers are connected to a single common antenna. In the case of BTS 110, the antenna is shown as item 112. In the case of BTS 120, the antenna is shown as 122. It will be appreciated that the number of transceivers in a BTS will be dependant upon the system under consideration. In the 30 present embodiment, BTS 110 and BTS 120 each contain a respective database, which are shown as item 119 in the case of BTS 110, and as item 129 in the case of BTS 120.

7 The different frequency plan settings forming a frequency plan in the present embodiment will now be explained with reference to FIG. 2. FIG. 2 shows the set of frequency plan data applicable to all the components of a single cell of the cellular communications system of the present embodiment. In the present case, FIG. 2 shows all the frequency plan settings pertaining to the cell corresponding to BTS 110 of the present embodiment. Each transceiver 114, 116, and 118 has a respective set of frequency plan settings as shown in items 210, 220 and 230 respectively of FIG. 2. Each item within the set of items for a given transceiver will now be explained individually. In the present embodiment, the first setting is a carrier type parameter determining whether that radio transceiver is one which transmits a control channel. This is shown as item 212 of FIG. 2. Since the present embodiment is a GSM one, the control channel consists of a broadcast control channel (BCCH) and the carrier type parameter is one often referred to in the art as "carrier type BCCH/carrier type nonBCCH".

The next frequency plan setting of the present embodiment is shown as item 214 of FIG. 2 and is one which indicates whether the component of the system, in this case the relevant transceiver, is operating under the respective sets of frequency plan settings of a first frequency plan or the second respective sets of frequency plan settings corresponding to have undergone implementation of a second frequency plan.

In the present embodiment another frequency plan setting is one which determines or informs the transceiver at which frequency it should transmit and/or receive when under a first frequency plan. This is shown as item 216 in FIG. 2. Since the present embodiment is a GSM one, this frequency setting will be an absolute radio frequency channel number (ARFCN).

8 Another frequency plan setting of the present embodiment is the frequency at which the transceiver is to transmit and receive when under the second frequency plan. This is shown as item 218 of FIG. 2. Again in the present embodiment, this consists of the appropriate ARFCM The corresponding frequency plan settings are applied to each of the other transceivers of BTS 110 as shown also in FIG. 2, and also similarly to transceivers 124, 126, 128 in BTS 120.

Further frequency plan settings correspond to the particular cell and are shown contained within dotted line 280 of FIG. 2. In particular, box 270 shows the frequency plan settings of the present embodiment that apply directly to the particular cell under consideration. A change plan parameter is shown as item 272 of FIG. 2. The stored value of this change plan parameter serves to determine whether the second set of frequency plan settings are implemented in this cell, that is in BTS 110, in response to an initiation instruction that will be explained later below. It is noted that the setting of the change plan parameter 272 will determine whether each of the components and boxes is shown in FIG. -2 will have their frequency settings changed when the above mentioned initiation instruction is received by the components of BTS 110. In other words, the components of the cell are arranged such that all the components in the cell undergo implementation in the case of this cell's one change plan parameter being set such as to provide implementation in response to the initiation instruction. Further shown in box 270 is an active plan parameter, item 274, which indicates whether the relevant components is operating under the first set of frequency plan settings corresponding to the first frequency plan or whether it is operating under the second set of frequency plan settings corresponding to having undergone implementation of the second frequency plan. Frequency plan settings pertaining to the cell under discussion, as shown in box 270, also include colour codes which serve to identify the particular cell of the system under 9 the relevant frequency plans. In particular, item 276 of FIG. 2 shows the location of the colour code for the cell under the first frequency plan and item 278 of FIG. 2 shows the location of the colour code for the cell under the second frequency plan. Since the present embodiment relates to a GSM system, these colour codes are each contained within corresponding base transceiver station identity codes (BSIC). The frequency plan settings are stored in a database 119 located in BTS 110. A similar database 129 is located in BTS 120.

In addition to the above described direct cell data contained in the form of frequency plan settings as shown in box 270 of FIG. 2, in the present embodiment further frequency plan settings pertaining to neighbour cells respective to the cell formed by BTS 110 are contained in database 119 of BTS 110. Neighbour cells of a particular cell are those other cells of the communications system that are configured at a particular time as candidate handover cells for that particular cell. The concept and implementation of neighbour cells is well known in the art and does not require description here for purposes of understanding the present invention. It is noted that many different configurations of neighbour cells can be subjected to the present invention. In the present embodiment, relevant details of neighbour cells are also included as items that have corresponding frequency plan settings altered according to which frequency plan is implemented. This provides a particular further advantage of the present invention, as it greatly increases the uniform way in which a new frequency plan can be applied to all aspects of a communications system. Not only is a cell set up and initiated with its own data, it is also immediately garnished with the data it requires to maintain system performance with respect to neighbour cell and handover procedures. In the present embodiment, it is assumed that a number of neighbour cells for which BTS holds information is a value N. In FIG. 2, neighbour 1, 2 through to N are shown with their associated frequency plan settings as per the present particular embodiment which will now be described with reference to neighbour 1 as shown in box 240 of FIG. 2. Included is an active plan parameter, item 241, which indicates whether the relevant neighbour cell, in this case neighbour 1, is operating under the first set of frequency plan settings corresponding to the first frequency plan or whether it is operating under the second set of frequency plan settings corresponding to having undergone implementation of the second frequency plan. Also included are the colour code of neighbour 1 under the first frequency plan, contained within the BSIC, item 243, and the colour code of neighbour 1 relating to the second frequency plan, contained within the BSIC, item 245. Also included are the frequency of neighbour 1 under the first frequency plan, item 247, and the frequency of neighbour 1 under the second frequency plan, item 249. In the present embodiment these frequencies of neighbour 1 apply only to the control channel frequency at which the cell identified as neighbour 1 transmits and receives.

Thus, above is described a cellular communications system 100 that is operating under a first frequency plan comprising first respective sets of frequency plan settings for respective components of the system. The method of changing the frequency plan according to the present embodiment is shown in process flow chart 300 of FIG. 3. Referring to FIG. 3, function box 310 shows the steps of determining a second frequency plan comprising second respective sets of frequency plan settings corresponding to said first respective sets of frequency plan settings. In the present embodiment, this second frequency plan is determined by an operator using standard processing means and databases located, in the present example, in OMC 160. Known frequency planning tools consisting of software protocols are also usable in step 310. As mentioned previously, the advantage to the operator is that he is able to prepare the entire frequency plan, including carrying out simulations and other estimation trials, without yet having to implement the frequency plan. Thus, it is apparent that the operator can use, inter-alia, appropriate advantageous aspects of known off-line frequency change preparation methods. It is to be 1 11 appreciated that such preparation of the frequency plan will in other embodiments be carried out in other locations of the system, even remote from the system, and using other standard or specialist equipment, according to the particular requirements of the system under 5 consideration.

The next step is that of transmitting said second respective sets of frequency plan settings to corresponding said components respectively, as shown in function box 320 of FIG. 3. In the present embodiment, such transmission of data is carried out by standard transmission means using land links that form the couplings between OMC 160, MSC 140, BSC 130, and BTS 110 and BTS 120 respectively. The sets of frequency plan settings are as described above for each BTS and as shown in FIG. 2. In the present embodiment, in addition to the frequency plan settings being transmitted to the relevant components as described above, nevertheless full details of the second frequency plan are retained at OMC 160.

The next step of the present embodiment is that of storing said second respective sets of frequency plan settings at said corresponding components as shown in function box 330 of FIG. 3. As described above, the corresponding components comprise those found in BTS 110 and BTS 120, more particularly database 119 and TRXS 114, 116 and 118, in BTS 110 and similarly database 129, and TRXS 124, 126 and 128 in BTS 120. In the present embodiment, the means used for said storing consists of standard computer memory located in the electronic controls of the transceivers and similarly in standard database memory. It will be appreciated that many alternatives exist for implementing storage of the relevant data as such, for example, specific memory components could be employed or other memory media such as disc.

The next step of the present embodiment is that of implementing said second set of frequency plan settings in the corresponding components in the case of at least one component in response to an initiation instruction, as shown at function box 360 of FIG. 3. In the present embodiment, the initiation instruction is sent from OMC 160 to all the relevant system components using the land links previously described above. On receipt of this instruction by relevant processing means in the above described components, each such component changes over to the relevant settings it has stored ready for use with the second frequency plan. Thus in the case of transceiver 114, as can be seen from reference to box 210 of FIG. 2, this transceiver will change over to the frequency allocated to it under the second frequency plan as shown at item 218 of FIG. 2, whereas before it would have been operating on the frequency ascribed to it under the first frequency plan as shown at item 216 of FIG. 2.

The present embodiment is one wherein said second set of frequency plan settings are implemented in the corresponding component in the case of all said components, in response to said initiation instruction. Thus, in the present embodiment all the components shown in BTS 110 and BTS 120 are changed over to the second frequency plan. This embodiment produces significant advantages over known methods. In particular, the operator has been able to plan the second frequency plan in totality with consequent possibilities for optimisation and general improvement of intercell effects by use of simulation and other known methods. In addition, the plan can if desired be implemented concurrently in each cell and each component of each cell. What is meant by concurrently is that it may be as near as simultaneous as is allowed by the restraints of physical transmission of an electronic initiation instruction and likewise, the restraint of time required for processing means to receive said instructions and to activate the above described changes. Even if instead said changes occur over a period of time slower than the absolute fastest times possible under electronic signal restraints, nevertheless the present invention and its advantages still apply in that the time required will still be less than would be required to change each item one after another as is the case in known methods.

13 In the present embodiment, further steps can be carried out between the above described steps of storing and implementing. The step of selecting and transmitting a respective change plan parameter to certain of said components is shown at function box 340 of FIG 3 and takes place after the storing step shown at function box 330. Thereafter, the next step is that of storing said change plan parameter at the corresponding components, which is shown at function box 350 of FIG. 3. These steps are carried out such that the respective stored change plan parameter serves to determine in which of said components of said system said second set of frequency plan settings are implemented in response to said initiation instruction. The change plan parameter is, in the present embodiment, located in the database of each BTS of the system. For example, change plan parameter 272 is shown in box 270 of FIG. 2, corresponding to being located physically in database 119 of BTS 110 of FIG. 1. This parameter can be set as part of the second frequency plan to either "yes" or "no" or, equivalent coding possibilities under the coding method employed in a particular system under consideration. In the present embodiment, the operator will set such parameter as "yes" or "no", based on his intentions with respect to the second frequency plan. The parameter settings are transmitted to BTS 110 where it is stored in database 119. The effect over the whole system is that the system is pre-loaded with a pre-determined pattern of which cells will be switched over to new frequency settings on receipt of the initiation instruction. Thus, it can be seen that in the present embodiment the question of which components undergo implementation in response to said initiation instruction is determined on a cell by cell basis. Moreover, in the present embodiment, the system is arranged such that if change plan parameter 272 of FIG. 2 is set at "Yes", then on receipt of the initiation instruction, all the components represented in FIG. 2 will have the second frequency plan initiated therein on receipt of the initiation instruction. Thus the present embodiment is one wherein one said change plan parameter is stored in one component of each cell of said system and the 14 components of a cell are arranged such that all the components in said cell undergo implementation in the case of that cell's one said change plan parameter being set such as to provide implementation in response to said initiation instruction. An advantage arising from the ability to determine in advance which cells will change over to the second frequency plan is that the operator has the flexibility to try out the new frequency plan in certain areas of the overall system. This can be carried out on the basis of repeated implementations over respective parts, the system being divided into parts on either a geographical basis or a system logic basis.

It will be clear from the above that some of the many advantages of the present invention are derived from the aspect of flexibility given to the operator of the system with respect to planning in advance a frequency change and also flexibility with respect to his considering the best ways of implementing said frequency plan change-over. Further optional aspects of the. present invention are included in the present embodiment, which provide the operator with yet more powerful capabilities in this area. In such a preferred version of the present embodiment, at least some of said components indicate whether they are operating under their first respective sets of frequency plan settings corresponding to said first frequency plan or whether they are operating under their second respective sets of frequency plan settings corresponding to having undergone implementation of said second frequency plan. This is implemented in the present embodiment by means of the active plan parameter previously described above and shown as items 214, 241 and 274 in FIG. 2. In the present embodiment, each relevant component has this feature. However, an alternative version would be for this feature to be present in only some of the components, according to the requirements of the particular system under consideration.

In the present embodiment, a further step can be carried out, namely that of, after implementation of said second set of frequency plan settings in the case of certain components of said system, saving the resulting system arrangement, comprising a mixture of unchanged components still with first frequency plan settings and changed components with newly implemented second frequency plan settings, as a further frequency plan, as shown in function box 370 of FIG. 3. Standard data processing means or computer means can be used for saving such data. An advantage arising from this further optional step is that resulting plans which in practice turn out to be of interest can be saved as full-blown theoretical frequency plans, even if they were never purposely developed as such. In other words, if it is found that a partially implemented second frequency plan working alongside the remaining parts of the original frequency plan turn out to be particularly advantageous, such overall arrangement can be saved as a preferred theoretical frequency plan, perhaps for use at a later date, either in the original system or in a different system. Alternatively, the operator may in fact intentionally make use of this facility when planning future frequency plans. In other words, he may intentionally decide to implement part of a second frequency plan step wise until he finds an overall behaviour that he decides is acceptable, in this case perhaps on the basis of expecting such a successful outcome.

In the present embodiment yet further steps can be carried out. As shown at decision box 380 of FIG. 3, after implementing the second frequency plan, whether that be in all components of the system or instead in some components of the system using the change plan parameter option described above, the operator or equivalent can determine or assess whether the new arrangement is satisfactory. If the new arrangement is found to be satisfactory, then it can be left in place, as shown by outcome cc yes" from decision box 380 of FIG. 3. If, on the other hand, the outcome is that the new arrangement is not found to be satisfactory, then a further step can be carried out, namely that of implementing said first frequency plan according to a further initiation instruction, as shown in function box 390 of FIG. 3. In other words, the new unsatisfactory arrangement is 16 effectively rejected and the system is returned to the original first frequency plan. However, it is noted that the process of returning the system to the original first frequency plan is particularly advantageously easily carried out according to the present embodiment because the original first frequency plan is still held stored and ready at each component of the system. For example, the relevant frequencies to be used by the transceivers, and the relevant BSIC identities to be used by each cell and so on, as shown in FIG. 2, still remain stored at the relevant components. Thus, returning to the initial frequency plan under the present invention is very straightforwardly carried out simply by transmission of a further initiation instruction. This capability provides yet further general advantages. New frequency plans can be tried out on the understanding that it is easy to return to an original frequency plan. Similarly, the second frequency plan can be implemented as some type of default or stand-by frequency plan since it is so straightforward to return to the original frequency plan.

It is noted in fact, that the possibility of the second frequency plan being a stand-by or default frequency plan is actually an advantage that can apply to even the simplest embodiment of the present invention. It is further noted that the advantage of easy return to the initial frequency plan is particularly advantageous when combined with the above described advantage relating to being able to implement the second frequency plan in only certain parts of the system. It will be appreciated that a number of advantages of the present invention will be pursued by the skilled person according to his particular requirements relating from the particular system under consideration, and this may involve normal procedures of trade-:off between competing advantages.

The above embodiment has been described in terms of a first frequency plan and a second frequency plan. It is to be appreciated that the present invention is not limited to the case of where only one new frequency plan 1 17 can have its values transmitted and stored to the relevant components in advance of possible implementation in response to an initiation instruction. On the contrary, the present invention also applies to the case where a plurality of frequency plans, including said second frequency plan, are implemented in corresponding fashion to the above embodiment. In other words, a third frequency plan can be envisaged with its corresponding frequency settings which would each be placed in the relevant components in addition to the frequency settings already described above. In this case, box 210 of FIG. 2 would show a further frequency setting, F3, below item 218, and this would represent the frequency at which the corresponding transceiver, namely transceiver 114, would transmit and/or receive if instructed to go over to the third frequency plan. In such an overall arrangement, it would be possible that certain components would be instructed to go over to the third frequency plan, certain components would be instructed to go over to the second frequency plan, and certain components would be instructed to remain on the original first frequency plan, according to the values set at the change plan parameter 200, such as that shown as item 272 in FIG. 2. In this event, the change plan parameter would not be simply "yes" or "no", it would rather consist of "no" or "yes plan 2" or "yes plan 3", or similar logical equivalents. In such a multiple frequency plan version, it can be seen that with a parameter as just described, a single initiation instruction would serve to implement both new frequency plans, i.e. the second frequency plan and the third frequency plan, using the same initial instruction. Clearly, a vast number of possibilities exist for implementing the present invention in a more complicated fashion using further frequency plans and/or more complicated change plan parameters. The question of implementing such embodiments will be assessed by theskilled person using standard tradeoff considerations applicable to the particular system and requirements under consideration.

is It is also to be appreciated that the different optional aspects mentioned in the above description of the preferred embodiment can be combined in numerous ways whist implementing the invention. It will be apparent that the exact means of implementing the above described method steps will vary according to the exact system requirements and the existing technology within the applicable system. In a GSM system as described above, the various steps of storing and implementing can be performed using software, hardware or a combination of software and hardware, or by direct operator influence.

More generally, it is noted that the present invention is applicable to communications system other than those described in the present embodiment above. In particular, digital communications systems other than GSM can be considered, including other TDMA system, CDM.A systems and hybrid TDMA/CDMA systems, and also analogue systems. Indeed any system which includes the use of distributed frequency plan will derive benefit from the present invention. Furthermore, the invention is applicable to communications systems wherein the infrastructure and components is other than as particularly described in the embodiments above.

19 Claims 1. A method of changing a frequency plan in a cellular communications system, wherein the system is operating under a first frequency plan comprising first respective sets of frequency plan settings for respective components of said cellular communications system; the method comprising the steps of. - determining a second frequency plan comprising second respective sets of frequency plan settings corresponding to said first respective sets of frequency plan settings; - transmitting said second respective sets of frequency plan settings to corresponding said components respectively; - storing said second respective sets of frequency plan settings at said corresponding components; - implementing said second set of frequency plan settings in the corresponding component in the case of at least one component, in response to an initiation instruction.
2. A method according to claim 1, wherein said second set of frequency plan settings are implemented in the corresponding component in the case of all said components, in response to said initiation instruction.
3. A method according to claim 1 or 2, further comprising the steps of selecting and transmitting a respective change plan parameter to certain of said components, and storing said change plan parameter at the corresponding components, such that the respective stored change plan parameter serves to determine in which of said components of said system said second set of frequency plan settings are implemented in response to said initiation instruction.
4. A method according to claim 3, wherein which components undergo implementation in response to said initiation instruction is determined on a cell by cell basis.
5. A method according to claim 4, wherein one said change plan parameter is stored in one component of each cell of said system and the components of a cell are arranged such that all the components in said cell undergo implementation in the case of that cell's one said change plan parameter being set such as to provide implementation in response to said initiation instruction.
6. A method according to any preceding claim, wherein at least some of said components indicate whether they are operating under their first respective sets of frequency plan settings corresponding to said first frequency plan or whether they are operating under their second respective sets of frequency plan settings corresponding to having undergone implementation of said second frequency plan.
7. A method according to any preceding claim, comprising the further step of, after implementation of said second set of frequency plan settings in the case of certain components of said system, saving the resulting system arrangement, comprising a mixture of unchanged components still with first frequency plan settings and changed components with newly' implemented second frequency plan settings, as a further frequency plan.
8. A method according to any preceding claim, comprising the further step of, after implementation of said second set of frequency plan settings in the case of at least one component, implementing said first frequency plan according to a further initiation instruction.

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9. A method according to any preceding claim, wherein a plurality of frequency plans, including said second frequency plan, are implemented in corresponding fashion.
10. A method according to any preceding claim, wherein the frequency plan settings of those of said components which serve to identify a particular cell of said system comprise a respective cell colour code which that cell has under the corresponding frequency plan.
11. A method according to any preceding claim, wherein a said component of a first cell contains frequency plan settings pertaining to neighbour cells.
12. A method according to claim 11, wherein said frequency plan settings pertaining to neighbour cells include respective cell colour codes which the respective neighbour cells have under the corresponding frequency plan.
13. A method according to claim 11 or 12, wherein said frequency plan settings pertaining to neighbour cells include respective control channel frequencies of said neighbour cells.
14. A method according to any preceding claim, wherein one type of said component is a radio transceiver and its corresponding frequency plan settings include that frequency at which it transmits and/or receives.
15. A method according to any preceding claim, wherein one type of said component is a radio transceiver and its corresponding frequency plan settings include a carrier type parameter determining whether that radio transceiver is one which transmits a control channel.

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16. An apparatus for a cellular communications system, wherein the system is operable under a first frequency plan comprising first respective sets of frequency plan settings for respective components of said cellular communications system; the apparatus comprising: - means for determining a second frequency plan comprising second respective sets of frequency plan settings corresponding to said first respective sets of frequency plan settings; - means for transmitting said second respective sets of frequency plan settings to corresponding said components respectively; - means for transmitting an initiation instruction to said components for implementing said second set of frequency plan settings in the corresponding component in the case of at least one component in response to said initiation instruction.
17. An apparatus according to claim 16, wherein said second set of frequency plan settings are implemented in the corresponding component in the case of all said components, in response to said initiation instruction.
18. An apparatus according to claim 16 or 17, further comprising means for selecting and transmitting a respective change plan parameter to certain of said components, and means for storing said change plan parameter at the corresponding components, such that the respective stored change plan parameter serves to determine in which of said components of said system said second set of frequency plan settings are implemented in response to said initiation instruction.
19. An apparatus according to claim 18, wherein which components undergo implementation in response to said initiation instruction is determined on a cell by cell basis.

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20. An apparatus according to claim 19, wherein one said change plan parameter is stored in one component of each cell of said system and the components of a cell are arranged such that all the components in said cell undergo implementation in the case of that cell's one said change plan parameter being set such as to provide implementation in response to said initiation instruction.
21. An apparatus according to any of claims 16-20, further comprising means for indicating in the case of at least some of said components whether they are operating under their first respective sets of frequency plan settings corresponding to said first frequency plan or whether they are operating under their second respective sets of frequency plan settings corresponding to having undergone implementation of said second frequency plan.
22. An apparatus according to any of claims 16-21, comprising further means for, after implementation of said second set of frequency plan settings in the case of certain components of said system, saving the resulting system arrangement, comprising a mixture of unchanged components still with first frequency plan settings and changed components with newly implemented second frequency plan settings, as a further frequency plan.
23. An apparatus according to any of claims 16-22, comprising further means for, after implementation of said second set of frequency plan settings in the case of at least one component, implementing said first frequency plan according to a further initiation instruction.

24. An apparatus according to any of claims 16-23, wherein the frequency plan settings of those of said components which serve to identify a particular cell of said system comprise a respective cell colour code which that cell has under the corresponding frequency plan.
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25. An apparatus for a cellular communications system, wherein the system is operable under a first frequency plan comprising first respective sets of frequency plan settings for respective components of said cellular communications system; the apparatus comprising: - means for receiving second respective sets of frequency plan settings; - means for storing said second respective sets of frequency plan settings; - means for implementing said second set of frequency related settings in response to receiving an initiation instruction.
26. An apparatus according to claim 25, further comprising means for receiving and storing a respective change plan parameter, such that the stored change plan parameter serves to determine whether said apparatus implements said second set of frequency plan settings in response to receiving said initiation instruction.
27. An apparatus according to claim 26, wherein said component corresponds to a cell of said cellular communications system.
28. An apparatus according to claim 27, further comprising means for propagating implementation of said second frequency plan into other components of said cell in response to said apparatus receiving said initiation instruction.
29. An apparatus according to any of claims 25-28, further comprising means for indicating whether said component is operating under the first respective sets of frequency plan settings corresponding to said first frequency plan or whether it is operating under the second respective sets of frequency plan settings corresponding to having undergone implementation of said second frequency plan.
30. An apparatus according to any of claims 16-29, comprising means for implementing in corresponding fashion a plurality of frequency plans including said second frequency plan.
31. An apparatus according to any of claims 16-30, wherein said component comprises means for identifying a particular cell of said system and said frequency plan settings of said component comprise a respective cell colour code which that cell has under the corresponding frequency plan. 10
32. An apparatus according to any of claims 16-31, wherein said frequency plan settings include frequency plan settings pertaining to neighbour cells. 15
33. An apparatus according to claim 32, wherein said frequency plan settings pertaining to neighbour cells include respective cell colour codes which the respective neighbour cells have under the corresponding frequency plan. 20
34. An apparatus according to any of claims 32 or 33, wherein said frequency plan settings pertaining to neighbour cells include respective control channel frequencies of said neighbour cells.
35. An apparatus according to any of claims 16-34, wherein one type of 25 said component is a radio transceiver and its corresponding frequency plan settings include that frequency at which it transmits or receives.
36. An apparatus according to any of claims 16-35, wherein one type of said component is a radio transceiver and its corresponding frequency 30 plan settings include a carrier type parameter determining whether that radio transceiver is one which transmits a control channel.

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37. A method of changing a frequency plan in a cellular communications system substantially as hereinbefore described and with reference to the accompanying drawing of FIG. 3.
38. An apparatus for a cellular communications system substantially as hereinbefore described and with reference to the accompanying drawings of FIGS. 1 or 2.