WO1998037703A2

WO1998037703A2 - Channel allocation in radio band

Info

Publication number: WO1998037703A2
Application number: PCT/FI1998/000143
Authority: WO
Inventors: Kalle Ahmavaara
Original assignee: Nokia Telecommunications Oy
Priority date: 1997-02-24
Filing date: 1998-02-17
Publication date: 1998-08-27
Also published as: AU6216298A; FI970772A; EP0962102A2; FI970772A0; WO1998037703A3

Abstract

The invention relates to a radio system and a method of optimizing channel allocation in a radio system using a selected multiple access method, such as TDMA or CDMA, at the radio interface. A suitability index, based on at least one feature to be optimized, is determined for each of the available radio channels (Yn), the index representing the suitability of the radio channel for allocation procedures. The suitability indices are utilized for selecting the most suitable radio channel (Yn) for the present allocation procedure. Thereafter the index of the selected radio channel (Yn) is updated.

Description

CHANNEL ALLOCATION IN RADIO BAND

FIELD OF THE INVENTION

The invention relates to radio systems and particularly to a method of optimizing channel allocation in a radio system. In the method, at least one feature to be optimized upon allocating radio channels is selected, and possible radio channels are determined.

BACKGROUND OF THE INVENTION

In future mobile systems, the portion of a radio resource to be allocated to different subscribers varies considerably according to the required capacity and the standard of service. The new services offered together with normal speech transmission and the requirements relating to data transmission increase the need to divide a radio band available as radio resources suited to different service situations.

In a radio system, an available radio band is allocated to users as radio channels in accordance with the selected multiple access technique. A radio channel is a frequency band employed for a radio connection or a portion separated therefrom by means of time or a user-specific code. There are several multiple access techniques for facilitating communications in which a large number of mobile user are present. These techniques include time division multiple access (TDMA), code division multiple access (CDMA) and frequency division multiple access (FDMA).

In time division multiple access (TDMA), the selected frequency band is divided into timeslots of which each radio channel is allocated its dedicated timeslots. In time division multiple access the structure of the physical layer can be described by frames composed of available timeslots (one or more).

The radio resource in each timeslot can be further divided into parts by occupying the frequency band in the timeslot with one wide-band carrier or with two or more carriers having a narrower frequency band. This case is illus- trated in Figure 1 , wherein Yn denotes the centre frequency and bandwidth of a carrier, and Xn a timeslot. The timeslots of the TDMA frame of Figure 1 employ three carrier bandwidths, e.g. 2 MHz, 1 MHz and 500 kHz. Four different carrier bandwidth combinations, i.e. 1 x 2 MHz, 2 x 1 MHz, 4 x 500 kHz or 1 x 1 MHz + 2 x 500 kHz, can be employed inside the 2-MHz frequency band of one timeslot. Each separate carrier Yn within one timeslot can be considered as a separate radio channel.

As is evident from Figure 1 , the use of one carrier within one timeslot at least partially rules out the possibility of simultaneously using other channels within the same timeslot. For example the allocation of one 2-MHz radio channel (e.g. carrier Y1 in Fig. 1) to one timeslot (e.g. X1 in Fig. 1) rules out all other radio channels from that particular timeslot. The allocation of one 500-kHz radio channel (e.g. Y6 in Fig. 1) to one timeslot (e.g. X4 in Fig. 1) prevents the simultaneous allocation of a 2-MHz channel to the same timeslot, whereas an 1-MHz radio channel (e.g. Y2 in Fig. 1) can be allocated thereto. Thus the formed radio channels are in part mutually exclusive.

A timeslot can also be divided into separate mutually exclusive radio channels by dividing it further into subtimeslots. This kind of frame structure is illustrated in Figure 2. Each subtimeslot Yn contained in the timeslot Xn can be considered to be a separate radio channel. In the example of Figure 2, the duration of the timeslot Xn is for example 4T and three different subtimeslot types, T, 2T, and 4T, are available. Radio channels are mutually exclusive in the same way as in the previous example, i.e. the allocation of one 4T radio channel (e.g. Y1 in Fig. 2) to a timeslot (e.g. X1 in Fig. 2) rules out all other radio channels from that particular timeslot. The allocation of one T radio channel (e.g. Y6 in Fig. 2) to a timeslot (e.g. X4) prevents the simultaneous allocation of a 4T radio channel to the same timeslot, whereas the allocation of a 2T radio channel (e.g. Y2 in Fi. 2) is possible.

CDMA is a multiple access scheme based on spread spectrum communication. Unlike FDMA or TDMA, in CDMA a large number of CDMA sig- nals (users) simultaneously share a wide radio frequency band, e.g. 1.25 MHz. So called spreading codes are used to distinguish between different CDMA signals, i.e radio channels on said wide radio frequency band. A separate spreading code is used over each connection between a base station and a subscriber terminal. In other words, the narrow-band user signal is conventionally multiplied by the dedicated spreading code and thereby spread in bandwidth. The signals of the users can be distinguished from one another in the receivers on the basis of the unique spreading code of each connection, by using a correlator which accepts only a signal energy from the selected spreading code and despreads its spectrum into a narrow-band signal. The other users' signals, whose spread- ing codes do not match, are not despread in bandwidth and as a result, contribute only to the noise and represent a self-interference generated by the system. The spreading codes of the system are preferably selected in such a way that the codes used in each system cell are mutually orthogonal, i.e. they do not correlate with each other. Thus, in the CDMA systems, the spreading code unique to each user or user's signal provides a radio channel in a similar sense as a time slot in the TDMA systems. CDMA is described in more detail in the document: "An overview of the application of code division multiple access (CDMA) to digital cellular systems and personal cellular networks", Qualcomm Incorporated, 1992, USA, (Document Number EX60-10010).

In the CDMA the total radio resource available can be allocated to separate mutually exclusive radio channels by using spreading codes of different lengths. The longer the spreading code of the radio channel, the lower is the proportion of the radio capacity used by the radio channel. This may be presented by a spreading code tree. An example of a spreading code tree is shown in Fig. 10. Let us assume that a radio channel A (called 4T channel herein) having a spreading code length of 65 bits (chips) per one information symbol will use the whole radio capacity available in the selected radio frequency band, e.g. 2 MHz. Similarly, a radio channel (called 2T channel herein) having a spreading code length of 128 chips per symbol will use one half of the whole radio capacity available, a radio channel (called T channel herein) having a spreading code length of 256 chips per symbol will use a quarter of the whole radio capacity available, etc. As a result, there are four different channel combinations available within the 2 MHz band, namely 1^*4T, 2^*2T, 4^*1T, or 1*2T + 2*1 T. The code tree is configured in such a manner that codes in the same branch of the tree are non-orthogonal and the codes in the differ- ent branches of the tree are orthogonal. Allocation of a channel rules out the possibility to allocate other channels in the same branch of the code tree. Referring to Fig. 10, the allocation of channel A will rule out any other radio channels from that particular frequency band. If B is allocated, it rules out the allocation of channels A, D and E in the same branch but allows the allocation of channel C or channels F and G in the other branch.

If the principles of the CDMA are applied in a TDMA system, separate, mutually exclusive radio channels can also be provided by allocating to a TDMA timeslot spreading codes for providing a separate radio channel code-specifically. This approach is illustrated in Figure 3. Each radio resource, separated in the timeslot Xn by means of a separate spreading code, can be considered as a separate radio channel Yn. The different spreading codes may be explicitly mutually exclusive, in accordance with the above examples, or they may affect the quality of radio channels formed by means of other spreading codes in the same timeslot.

When defining the physical layer of a radio interface, e.g. all above manners of dividing a radio resource can be combined and used simultaneously. A timeslot can be divided into subtimeslots, for example, one of which can be divided into several carriers, one of which can be further divided into several radio resources by spreading codes.

When channel allocations associated with different communication needs are considerably different and the physical layer becomes more complex with the diversified and mutually exclusive channel types as described above, an immediate need arises for a method of optimal utilization of an available radio resource. In order to be able to utilize desired frame structures in implementations, a means has to be discovered for placing radio channels of different types and sizes into the available radio resource so as to utilize the resource as wisely as possible. In order to avoid delays and a complex system structure, the method should, however, be simple and operate rapidly even with a complex frame structure.

BRIEF DESCRIPTION OF THE INVENTION It is the object of the present invention to provide an efficient method which is simple to implement and by which channel allocations of different sizes and associated with different connections are carried out in a manner that utilizes the available radio resource as efficiently as possible. This is achieved by the method disclosed in claim 1. The invention further relates to radio systems disclosed in claims 15 and 27.

The invention is based on the idea that available radio channels and their mutual exclusiveness are determined system-specifically. This is used as a basis for selecting a strategy for placing the channels rationally into the available radio resources as far as the utilization of the radio resource is concerned. The strategy is used to determine a suitability index (S index), which is a general parameter representing the suitability of ^*a radio channel for procedures associated with channel allocation. It is essential that the value of the S index can be determined unambiguously on the basis of the features to be optimized for each desired radio channel or any radio resource structure, such as a timeslot or part thereof, containing the radio channel which is or is to be selected as the target for the allocation procedure.

The S indices are stored preferably in a separate index memory. The index of the radio channel or the radio resource structure comprising the radio channel being the selected target for the procedure is updated in asso- ciation with each procedure related to channel allocation. At the same time the index of the radio channel or the radio resource structure comprising said radio channels which, regarding the feature to be optimized and allowed for in the indexing, depend on the S index of the radio channel or the radio resource structure comprising the radio channel which is the target of the procedure. The index associated with the radio channel or the radio resource structure comprising it continuously depicts the allocation situation in the radio band and offers thus a handy tool in making decisions concerning procedures associated with allocation. It is an advantage of the solution of the invention that a complex procedure that continuously changes in time can be modified into an easily processable form by means of indices, whereby the decision in connection with a procedure associated with allocation can be made on the basis of the index or by means of application-specific index-based decision- making routines.

The method of the invention is suitable for utilization in allocation procedures relating to different frame structures and different radio channel types. The solution can be used when reserving new channels or when increasing transmission capacity on an existing channel. The method is also usable in releasing existing reservations, e.g. when the transmission capacity of a channel has to be decreased because traffic has exceeded the congestion value. The innovative solution is also usable when reallocating frame addresses when reserved frame addresses fill a frame unfavourably. Hereinafter the concept allocation procedure is used to refer to all procedures associated with frame address allocation, including the above examples. More generally, the concept of allocation procedure is used to refer to any channel allocation changing the reservation state of the radio resources in a radio system.

LIST OF THE DRAWINGS

In the following the invention will be described in greater detail with reference to the accompanying drawings, in which

Figure 1 illustrates a TDMA frame wherein timeslots are divided into separate radio channels by means of frequency bands of different widths (prior art), Figure 2 illustrates a TDMA frame wherein timeslots are divided into separate radio channels by means of subtimeslots of different lengths (prior art),

Figure 3 illustrates a TDMA frame wherein timeslots are divided into separate radio channels by means of separate spreading codes (prior art),

Figure 4 shows the frame structure employed in the description of the primary embodiment of the invention,

Figure 5 illustrates frequency band units to be placed into one timeslot and used in the description of the first embodiment of the invention, Figure 6 shows communication situations that are different as far as indexing is concerned and are presented in the description of the first embodiment of the invention,

Table 1 in Figure 7 shows an update table including a first updating rule for the S index and employed in the first embodiment of the invention, Table 2 in Figure 8 shows an update table including a second updating rule for the S index and employed in the first embodiment of the invention,

Figure 9 is a flow diagram illustrating the inventive method,

Figure 10 illustrates CDMA radio channels provided by spreading codes of different lengths (prior art).

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be applied to a channel allocation radio communication systems utilizing various multiple access methods, such as TDMA or CDMA. In different multiple access methods the physical concept of radio channel varies, being primarily defined by a time slot in TDMA systems, a spreading code in CDMA systems, a carrier in FDMA systems, a combination thereof, etc. The basic concept of the present invention is, however, independent of the type of radio channel and multiple access method used.

In the following the invention will be described in association with a primary embodiment of the invention, without, however, restricting it to this alternative. In the example described, radio channels are composed of separate carriers comprised by one timeslot. An allocatable radio frame is a TDMA frame comprising five timeslots and four frequency band units. The inventive solutions could employ any other frame and timeslot structure, e.g. the alter- natives illustrated in Figures 2 and 3.

Figure 4 shows the frame structure employed in the example. The frame comprises an available radio system frequency band TF which is divided into four frequency band slots F1 to F4. A carrier is divided into five timeslots TD1 to TD5. Figure 4 shows a frame address (TD2,F3) via which information associated in the example with a radio channel CH1 is transferred in the uplink and/or downlink direction in successive frames. Figure 4 also shows a higher speed radio channel CH2 with a double carrier bandwidth compared with the channel CH1.

In the example three resources of different sizes can be allocated to a connection, the corresponding bandwidths being 1 , 2 and 4 frequency band units FU (e.g. FU = 200 kHz). Thus one timeslot can include the following channels: four 1 FU channels (e.g. 4 x 200 kHz) two 1 FU channels and one 2 FU channel (e.g. 2 x 200 kHz, 1 x 400 kHz), two 2 FU channels (e.g. 2 x 400 kHz) one 4 FU channel (e.g. 1 x 800 kHz), which have also been illustrated in Figure 5. In the example, optimization is carried out by timeslots, i.e. the channel allocations of each timeslot can be determined independently. Owing to the selected frame structure and the channel sizes in the example, indexing has to be carried out only for the timeslot halves.

Figure 6 determines all channel reservation situations for one timeslot that differ from one another in the example as far as indexing is concerned. As far as indexing is concerned, the placement of an 1 FU channel in a 2 FU empty channel is the same irrespective of into which 2 FU channel half the 1 FU channel is placed. In the Figure, the hatched bands denote reserved channels and the unhatched bands denote free channels.

In the example of Figure 6, timeslot a comprises one reserved 2 FU channel, one reserved 1 FU channel and one free 1 FU channel. Timeslot b comprises three reserved 1 FU channels and one free 1 FU channel. Timeslot c comprises two reserved 1 FU channels and two free 1 FU channels. Timeslot d comprises one reserved 2 FU channel and one free 2 FU channel. Timeslot e comprises two reserved 1 FU channels and one free 2 FU channel. Timeslot f comprises one reserved 1 FU channel, one free 1 FU channel and one free 2 FU channel. The entire timeslot g is free. Timeslot h comprises four reserved 1 FU channels. Timeslot i comprises one reserved 2 FU channel, and two reserved 1 FU channels. Timeslot j comprises two reserved 2 FU channels. Timeslot k comprises one reserved 4 FU channel.

The clarify the principle of the invention, the indices in the example are determined directly on the basis of the reservation status of the channels in the timeslot disregarding other factors. The selected indices are marked in

Figure 6 and explained in the following in association with certain allocation procedures.

RESERVATION OF 1 FU CHANNEL

In the example, the reservation is carried out by searching the index memory for an S index with the smallest value inside the range associated with each size of the channel to be reserved. As can be seen from Figure 6, the smallest S index associated with an 1 FU channel is 0 (one free 1 FU channel) and the maximum is 7 (the entire timeslot is free). According to the selected allocation strategy, it would be most advantageous to place the 1 FU channel into timeslot a and this traffic situation has been given the index 0. If the frame does not comprise such a traffic situation, the next most advantageous alternative is timeslot b which has been given the index 1 , etc. If the entire frame is full, the value of each index exceeds 7, and no reservation is made. If the system finds the index 0, it places the new channel into that particular timeslot and consequently the indices of the timeslot are updated to correspond to the new situation. After the reservation, the timeslot comprises one reserved 2 FU channel and two reserved 1 FU channels. This corresponds to timeslot i in Figure 6, i.e. when an 1 FU channel is reserved, the in- dexing of the timeslot changes and no longer corresponds to timeslot a (0/12) but instead to timeslot i (11/14).

RESERVATION OF 2 FU CHANNEL

As can be seen from Figure 6, when a 2 FU channel is reserved, the smallest possible S index value is 4 (one 2 FU free channel) and the maximum is again 7. Thus the system searches the index memory for the smallest possible S index which is more than or equal to 4 but less than or equal to 7. If for example the smallest S index found by the system within the range is 6 (corresponding to timeslot f in Figure 6), the new channel is placed into that particular timeslot and the indices of the timeslot are again updated to correspond to the new situation. After channel allocation, the timeslot com- prises one reserved 2 FU channel, one reserved 1 FU channel and one free 1 FU channel. This corresponds to timeslot a in Figure 6, i.e. when a 2 FU channel is allocated, the indexing of the timeslot changes and no longer corresponds to timeslot f (3/3) but instead to timeslot a (0/12).

RESERVATION OF 4 FU CHANNEL

As to the allocation of a 4 FU channel, the only possible S index value is 7. Should this value not be found in the index memory, no allocation is carried out. If the index S=7 is found, allocation is carried out, and consequently the indexing of the timeslot changes and no longer corresponds to timeslot g (7/7) but instead to timeslot k (16/16).

The S index update rules can be advantageously presented in the form of a table. In the following update rule tables are illustrated for a timeslot which has been divided into two halves, each with dedicated S indices, such as e.g. in Figure 6. Table 1 in Figure 7 illustrates the table employed in the up- date of the S index of the timeslot half subjected to an allocation procedure in the example. The rows of the table illustrate three possible allocation procedures, in which

0 = reservation of an 1 FU channel

1 = reservation of a 2 FU channel 2 = reservation of a 4 FU channel.

The columns of Table 1 show the present value of the S index before allocation (the topmost value in the column) and the new value after each different type of allocation procedure (1 FU, 2 FU, 4 FU). In the first example described above, the reservation of an 1 FU channel (row 0) consequently changes the value of the S index of the timeslot half from the present value 0 (column 0) to the value 11 (arrow A). Similarly, the reservation of a 2 FU channel (row 1) to a timeslot half with a present S index of 6 (column 6) gives a new S index value 12 (arrow B), etc. On the basis of the update rules of Table 1 , a new S index can be determined unambiguously for the timeslot when the present S index and the type of allocation procedure (1 FU, 2 FU, 4 FU) are known.

The S indices of the magnitude to be optimized, i.e. in this case the part (e.g. the second half) sharing the same timeslot with the target channel of the allocation procedure, depend on the S index of said channel, and a corre- sponding table can be drawn up for their update rules. Table 2 in Figure 8 shows the rules for updating the S index of the second half of the same time- slot in the example when the index of the first half is modified as a result of an allocation procedure (e.g. in accordance with Table 1 ). Corresponding to Table 1 , the rows of Table 2 show the allocation procedures (1 FU = 0, 2 FU = 1 and 4 FU = 2) and the columns show topmost the present S index value before al- location and below the new S index value after each update. In the first example, the reservation of an 1 FU channel (row 0) to the part sharing the same timeslot (arrow A in Table 1) changes the S index of the adjacent half of the same timeslot from the present value 12 (column 12) to the value 14 (arrow C). In the second example, the reservation of a 2 FU channel (row 1) to the first part of the timeslot (arrow B in Table 1) changes the S index of the part sharing the same timeslot from the present value 3 (column 3) to the value 0 (arrow D). On the basis of the update rules of Table 2, the new S index of the second timeslot half can be determined unambiguously when the present S index and the type of allocation procedure the first half is subjected to are known.

Naturally, when the second timeslot half is subjected to an allocation procedure, its S index is changed in accordance with Table 1 , and that of the first half in accordance with Table 2. Should the timeslot have several parts with a dedicated S index, a rule table corresponding to Table 2 can be drawn up for each part.

It should be noted that the update tables presented above have been created in order to illustrate the preferred embodiment described in the first example, and consequently they do not restrict the definition of the update rules or the storage format to the format presented above. The structure and headings of the tables can also be implemented in several ways, one of which has been selected as an example. It is an advantage of the table presented in the example that although the physical layer becomes substantially more complex, the inventive function is still achieved by means of this relatively simple table. The flow diagram of Figure 9 illustrates the method of the invention in association with the reservation procedures presented above. In point 10 the system checks the size of the channel the subscriber wishes to reserve. Once the size of the channel is known, a search is made for a range within which the S index associated with said channel size can vary (point 20). The index memory is then searched for the smallest possible S index value within the range (point 30). Should no suitable index value for the range be found (point 40), no allocation is carried out. If the index is found, the reservation is made (point 50) and the indices in both timeslot halves are updated (point 60). The method of the invention provides a means for selecting a frame address for actual channel allocation carried out separately as a dedicated function. The channel allocation and the determination and storage of S indices according to the invention can be carried out in any network element. Most advantageously said network element is the one responsible for call control. In modem mobile networks such an element is typically an exchange, a base station controller or a separate controller, but in future networks these func- tions may be decentralized.

In the above example, the determination of the S indices was based only on the reservation status of the radio channels in a timeslot. Application- specifically, S indexing can be specified so as to allow for other factors, such as e.g. the allocation status in adjacent timeslots or in the entire frame, com- munication circumstances in the channels to be allocated etc.

The more factors are included, the more S index values are needed. Even a continuous variable value, calculated on the basis of all included factors, can be used as the S index. In this case the value of the variable can e.g. be changed discretely in association with allocation procedures and continuously on the basis of measurements concerning transmission. In that case, if two channels are available whose S indices are the same on the basis of allocations, but of which one is weaker judged by communication circumstances, the system is able to select the channel with superior conditions by means of the S index. In the above example, owing to the employed bandwidth choices, the S indices had to be determined for timeslot halves only. However, an S index can be determined similarly for other timeslot parts, too, depending on the structure of the physical layer and the required accuracy of allocation optimization. It is essential in S index determination that the value of an S index can be determined unambiguously in association with each change concerning allocation.

When a radio channel is deallocated (e.g. as a call terminates), the tables are used inversely for index updating. Referring to Table 1 in the above examples, when one 1 FU radio channel (row 0) is deallocated from a timeslot half whose index is 11 , the new updated S index becomes 0 (column 0) (arrow A'). When one 2 FU (row 1) channel is deallocated from a timeslot half whose index is 12, the new updated S index becomes 6 (row 6) (arrow B'). The S index of the other timeslot half is updated similarly by means of Table 2.

The S index may also be employed as a support for decision- making when channels are being deallocated, e.g. when the data transmission capacity allocated to a subscriber is being decreased because of increased traffic or when a subscriber him/herself indicates a change in data transmission need. In this case the system e.g. goes through the frame addresses associated with the subscriber connection, searches the index memory for the S indices associated with each frame address and the S indices of frame ad- dresses that e.g. share the same frame layer and depend on said S indices. The system then determines new indices, possibly following an update, for each alternative and selects from the retrieved alternatives the most suitable. The principle for selecting the channels to be deallocated on the basis of the S index is selected application-specifically. If in the above example a subscriber has a channel composed of e.g. three 1 FU allocations, one of which should be deallocated, the table serves to search for the indices of the timeslots in which 1 FU allocations have been carried out and corresponding indices for the other timeslot half. The system determines new indices following the deallocation, compares the ob- tained index combinations and deallocates the 1 FU timeslot half selected on the basis of the comparison. After the deallocation, the value of the S index in the timeslot subjected to the allocation procedure is updated.

During communication, allocations and deallocations change continuously. If e.g. previous channel allocations fill a frame disadvantageously or if a channel has for some reason had to be placed badly, channels can be reallocated by means of the S index. This can be accomplished by e.g. first selecting by means of the S index a new place for the transferable channel in the manner described in the above reservation example, and by transferring the channel to a new place and then updating the S indices as usual. The principle for reallocating the channels by means of the S index is selected application- specifically.

The above described allocation schemes based on the suitability index S are also directly applicable to other types of radio channels, such as CDMA. For example, the S index updating rules described above with refer- ence to Figs. 4 to 9 can be used as such, when 1 FU, 2FU and 4FU channels are replaced by the 1T, 2T and 4T CDMA channels of Fig. 10. In pure CDMA, when there is no time-division multiplexing of the 2 MHz band (i.e. no time-slots), the allocation of 1T, 2T and 4T CDMA channels may be analogous to the allocation of 1 FU, 2FU and 4FU channels within a single time slot in the above described TDMA embodiments. The drawings and the related description are only intended to illustrate the inventive idea. The details of the solution of the invention may vary within the scope of the claims. Although the invention has been described above in association with the placement of radio channels composed of carriers having different bandwidths, the described method can also be employed in the above described manner in association with other radio channel and frame types.

Claims

1. A method of allocating a radio channel in a radio system, the method comprising the step of: determining possible radio channels (Yn), characterized in that the method further comprises the steps of: determining a suitability index, based on at least one feature to be optimized, for each of the available radio channels (Yn) or for any radio resource structure comprising said available radio channels, the index repre- senting the suitability of the respective radio channel or the respective radio resource structure for allocation procedures, utilizing said suitability indices in allocation procedures for selecting the one of said available radio channels which is suitable for the respective allocation procedure, and updating the suitability index of at least the selected radio channel

(Yn) or the respective radio resource structure comprising said selected radio channel in association with the respective allocation procedure.

2. A method as claimed in claim 1, characterized in that said radio resource structure includes timeslots (Xn) comprising said radio channels or parts of timeslots comprising said radio channels.

3. A method as claimed in claim 1 or 2, characterized in that the features to be optimized include at least the TDMA timeslot reservation status as far as utilization of the radio system bandwidth resource is concerned.

4. A method as claimed in claim 3, characterized in that one or more of at least two different radio channels with mutually different carrier bandwidths can be allocated simultaneously to said timeslot.

5. A method as claimed in claim 3, characterized in that one or more of at least two different radio channels whose associated sub- timeslots have durations that are of mutually different lengths and that do not exceed said timeslot can be allocated simultaneously to said timeslot.

6. A method as claimed in claim 3, characterized in that one or more of at least two different radio channels with mutually different spreading codes can be allocated simultaneously to said timeslot.

7. A method as claimed in any one of the previous claims, characterized in that a TDMA timeslot is divided into two or more parts, each having a suitability index representing the suitability of the radio channel or radio channels of said timeslot part for an allocation procedure.

8. A method as claimed in any one of the previous claims, characterized in that the suitability indices of different radio channels or timeslot parts inside the same timeslot are interdependent.

9. A method as claimed in claim 8, characterized by updating the suitability index of the timeslot part or the radio channel which is selected for the respective allocation procedure according to a first update rule and the other suitability indices of the same timeslot according to a second update rule.

10. A method as claimed in any one of the previous claims, characterized by determining the updated value of a suitability index according to the present value of the suitability index and the type of the allocation procedure.

11. A method as claimed in claim 10, characterized in that the type of the allocation procedure depends on the bandwidth of the radio channel to be allocated.

12. A method as claimed in claim 10, characterized in that the type of the allocation procedure depends on the duration of the timeslot of the radio channel to be allocated.

13. A method as claimed in claim 10, characterized in that the type of the allocation procedure depends on the spreading code of the radio channel to be allocated.

14. A method as claimed in claim 1, characterized in that the radio channels are CDMA radio channels provided by different spreading codes.

15. A radio system using the TDMA timeslot structure on the radio path, characterized by allocatable radio channels (Yn), timeslots (Xn) comprising said radio channels or parts of the timeslots comprising said radio channels having suitability indices representing the suitability of the radio channels (Yn), the timeslots (Xn) comprising said radio channels or the parts of the timeslots comprising said radio channels for allocation procedures as far as a selected feature to be optimized is concerned, being arranged to direct the allocation procedure to a radio channel

(Yn) which, according to the suitability index, is suited to said allocation proce- dure, being arranged to update, upon each allocation procedure, the suitability index of at least the radio channel (Yn), the timeslot (Xn) comprising said radio channel or the part of the timeslot comprising said radio channel which is the target of the procedure.

16. A radio system as claimed in claim 15, characterized in that the features to be optimized comprise at least the reservation status of a TDMA timeslot as regards the utilization of the radio system bandwidth resource.

17. A radio system as claimed in claim 16, characterized in that one or more of at least two different radio channels with mutually different carrier bandwidths can be allocated simultaneously to said timeslot.

18. A radio system as claimed in claim 16, characterized in that one or more of at least two different radio channels whose associated subtimesiots have durations that are of mutually different lengths and that do not exceed said timeslot can be allocated simultaneously to said timeslot.

19. A radio system as claimed in claim 16, characterized in that one or more of at least two different radio channels with mutually different spreading codes can be allocated simultaneously to said timeslot.

20. A radio system as claimed in any one of claims 15 to 19, characterized in that the timeslot is divided into two or more parts, each having a suitability index representing the suitability of the radio channel or radio channels of said timeslot part for allocation procedures.

21. A radio system as claimed in any one of claims 15 to 20, characterized in that the suitability indices of different timeslot parts or radio channels inside the same timeslot are interdependent.

22. A radio system as claimed in claim 21, characterized in that radio system is arranged to update the index of at least the radio channel or the timeslot part comprising said radio channel which is the target of the al- location procedure according to a first update rule and the other suitability indices of the same timeslot according to a second update rule.

23. A radio system as claimed in any one of claims 15 to 25, characterized in that the updated value of a suitability index is determined according to the present value of the suitability index and the type of the allocation procedure.

24. A radio system as claimed in claim 23, characterized in that the type of the allocation procedure depends on the radio channel bandwidth to be allocated.

25. A radio system as claimed in claim 23, characterized in that the type of the allocation procedure depends on the duration of the timeslot of the radio channel to be allocated.

26. A radio system as claimed in claim 23, characterized in that the type of the allocation procedure depends on the spreading code of the radio channel to be allocated.

27. A radio system having means for dynamically allocating radio channels, characterized by: means for determining a suitability index, based on at least one feature to be optimized, for each of available radio channels (Yn), said suitability index representing the suitability of the respective radio channel for different allocation procedures, said means for allocating being arranged to allocate the one of said available radio channels which is suitable for the respective allocation procedure, based on said suitability indices, and means for updating the suitability index of at least the selected radio channel (Yn) in response to the respective allocation procedure.

28. A radio system as claimed in claim 27, characterized in that the radio system comprises radio channels of different bandwidths, and that the at least one feature to be optimized includes the utilisation of the available bandwidth in the radio system.

29. A radio system as claimed in claim 27 or 28, characterized in that the radio channels are CDMA channels provided by different spreading codes.