US20040053597A1

US20040053597A1 - Method for managing processing resources in a mobile radiocommunication system

Info

Publication number: US20040053597A1
Application number: US10/250,990
Authority: US
Inventors: Pascal Agin
Original assignee: Evolium SAS
Current assignee: Evolium SAS
Priority date: 2001-01-12
Filing date: 2002-01-10
Publication date: 2004-03-18
Also published as: CN1507764A; FR2819658B1; EP1223782B1; JP3954497B2; US7477609B2; FR2819658A1; US20040066744A1; DE60225610D1; CN1784075A; JP2004525550A; EP1223782A1; ATE390026T1; CN1242646C; WO2002056628A1; DE60225610T2; CN100448323C

Abstract

A method of managing processing resources in a mobile radio system in which a first entity manages radio resources and corresponding processing resources provided in a second entity separate from the first entity, in which method:

the second entity signals to the first entity its overall processing capacity, which is also known as the capacity credit, and the amount of said overall processing capacity, which is also known as the consumption law or the cost, as a function of the resources that are necessary,

the first entity updates the capacity credit on the basis of the consumption law,

in the case of radio resources corresponding to dedicated channels, a different cost is provided for the first radio link and for additional radio links, and

in the case of radio resources corresponding to a common channel associated with a dedicated channel, said updating is effected, in the case of the first radio link, on the basis of the cost for the dedicated channel and a cost for the associated common channel and, in the case of an additional radio link, on the basis of the cost for the dedicated channel only.

Description

The present invention relates generally to mobile radio systems and more particularly to systems using the code division multiple access (CDMA) technique.

The CDMA technique is used in third generation systems such as the Universal Mobile Telecommunication System (UMTS), for example.

As a general rule, a mobile radio network includes base stations and base station controllers, as shown in FIG. 1. In the UMTS, the network is known as the UMTS Terrestrial Radio Access Network (UTRAN), a base station is known as a Node B, and a base station controller is known as a Radio Network Controller (RNC).

A mobile station is known as a User Equipment (UE), and the UTRAN communicates with mobile stations via a Uu interface and with a Core Network (CN) via an Iu interface.

As shown in FIG. 1, an RNC is connected:

to a Node B via an Iub interface,

to other RNC via an Iur interface, and

to the core network (CN) via an Iu interface.

The RNC controlling a given Node B is known as the Controlling Radio Network Controller (CRNC) and is connected to the Node B via the Iub interface. The CRNC has a load control function and a radio resource allocation and control function for each Node B that it controls.

For a given call relating to a given user equipment UE, there is a Serving Radio Network Controller (SRNC) that is connected to the core network via the Iu interface. The SRNC has a control function for the call concerned, including the functions of adding or removing radio links in accordance with the macrodiversity transmission technique, monitoring parameters likely to change during a call, such as bit rate, power, spreading factor, etc.

In CDMA systems, capacity limitations at the radio interface are fundamentally different from their counterparts in systems using other multiple access techniques, such as the Time Division Multiple Access (TDMA) technique. The TDMA technique is used in second generation systems such as the Global System for Mobile communications (GSM), for example. In CDMA systems, at any time all users share the same frequency resource. The capacity of these systems is therefore limited by interference, for which reason these systems are also known as soft limited systems.

This is why CDMA systems use algorithms such as load control algorithms to prevent, detect and where applicable correct overloads, in order to avoid degraded quality, and call admission control algorithms to decide (as a function of diverse parameters such as the service required for the call, etc.) if the capacity of a cell that is not being used at a given time is sufficient for a new call to be accepted in that cell. In the remainder of the description, these algorithms are grouped together under the generic name load control algorithms.

They ordinarily use only radio criteria and are ordinarily executed in the CRNC, which does not have any information on the processing capacity of each Node B that it controls. It can therefore happen that the CRNC accepts a new call only for the call to be finally rejected because of a shortage of processing resources in the Node B, which leads to unnecessary additional processing in the CRNC and to additional exchanges of signaling between the CRNC and the Node B.

Of course, it would be possible to avoid those problems by providing each Node B with sufficient processing resources to cover all situations, including that of maximum capacity (which corresponds to the situation of a very low level of interference). However, this would lead to costly base stations that would be rated more highly than necessary most of the time. Furthermore, in the case of progressive introduction of services offered by these systems, the processing capacity of the base stations can be limited at the start of deployment of these systems and progressively increased thereafter.

It would therefore be desirable for load control in such systems to allow for the processing capacity of each base station (Node B).

FIGS. 2 and 3 respectively outline the main transmit and receive processing used in a base station, for example a UMTS Node B.

FIG. 2 shows a transmitter 1 including:

channel coding means 2,

despreading means 3, and

radio frequency transmitter means 4.

These processing means are well known to the person skilled in the art and do not need to be described in detail here.

Channel coding uses techniques such as error corrector coding and interleaving to protect against transmission errors. This is also well known to the person skilled in the art.

Coding (such as error corrector coding) is intended to introduce redundancy into the information transmitted. The coding rate is defined as the ratio of the number of information bits to be transmitted to the number of bits actually transmitted or coded. Various quality of service levels can be obtained using different types of error corrector code. In the UMTS, for example, a first type of error corrector code consisting of a turbo code is used for a first type of traffic (such as high bit rate data traffic), while a second type of error corrector code consisting of a convolutional code is used for a second type of traffic (such as low bit rate data or voice traffic).

Channel coding generally also includes bit rate adaptation in order to adapt the bit rate to be transmitted to the bit rate offered for its transmission. Bit rate adaptation can include techniques such as repetition and/or puncturing, the bit rate adaptation rate then being defined as the repetition rate and/or the puncturing rate.

The raw bit rate is defined as the bit rate actually transmitted at the radio interface. The net bit rate is the bit rate obtained after deducting from the raw bit rate everything that is of no utility to the user, for example the redundancy introduced by the coding process.

Spreading uses spectrum spreading principles that are well known to the person skilled in the art. The length of the spreading code used is known as the spreading factor.

It should not be forgotten that, in a system such as the UMTS, the net bit rate (which is referred to hereinafter for simplicity as the bit rate) can vary during a call, and that the spreading factor can vary as a function of the bit rate to be transmitted.

FIG. 3 shows a

receiver

5 including:

radio frequency receiver means 6, and

received data estimation means 7, including

despreader means 8 and channel decoder means 9.

These processing means are well known to the person skilled in the art and therefore do not need to be described in detail here.

FIG. 3 shows an example of processing carried out in the despreader means 8. The processing is carried out in a rake receiver to improve the quality of received data estimation using multipath phenomena, i.e. propagation of the same source signal along multiple paths, such as results from multiple reflections from elements in the environment, for example. Unlike TDMA systems, CDMA systems can exploit the multiple paths to improve received data estimation quality.

A rake receiver has a set of L fingers 10 ₁to 10 _Land means 11 for combining signals from the fingers.

Each finger despreads the signal received via one of the paths that are taken into account, as determined by means 12 for estimating the impulse response of the transmission channel. To optimize received data estimation quality, the means 11 combine the despread signals corresponding to the paths that are taken into account.

The reception technique using a rake receiver is also used in conjunction with the macrodiversity transmission technique, whereby the same source signal is transmitted simultaneously to the same mobile station by a plurality of base stations. By using a rake receiver, the macrodiversity transmission technique not only improves receive performance but also minimizes the risk of call loss during handover. For this reason it is also known as soft handover, as compared to hard handover, in which a mobile station is connected to only one base station at any given time.

The received data estimating means can also use various techniques for reducing interference, such as the multi-user detection technique.

It is also possible to use a plurality of receive antennas. To optimize received data estimation quality, the received data estimator means then further include means for combining signals received via the multiple receive antennas.

Channel decoding includes functions such as deinterleaving and error corrector decoding. Error corrector decoding is generally much more complex than error corrector coding and can use techniques such as maximum likelihood decoding, for example. A Viterbi algorithm can be used for convolutional codes, for example.

To be able to process several users simultaneously, a base station (Node B) includes transmitters and receivers such as the transmitter and the receiver outlined above and therefore requires a high receive processing capacity for received data estimation.

As mentioned above, for monitoring the load in a system such as the UMTS, for example, it is therefore desirable to take account of the processing capacity of a base station.

For the UMTS, for example, the 3G document TS 25.433 published by the 3 ^rdGeneration Partnership Project (3GPP) specifies that, for each value of the spreading factor (SF) for which there is provision within the system, the Node B must signal to the CRNC its overall processing capacity, which is also known as the capacity credit, and the amount of that overall processing capacity, which is also known as the consumption cost, that is necessary for allocating a physical channel. The set of all consumption costs for all possible values of the spreading factor is also known as the capacity consumption law. This information is signaled by a Node B to the CRNC each time that the processing capacity of the Node B changes, using a Resource Status Indication message, or in response to a request from the CRNC, using an Audit Response message.

The CRNC then updates the remaining credit on each resource allocation, i.e. in the UMTS:

for the dedicated channels, during radio link set-up, radio link addition, radio link deletion and radio link reconfiguration procedures defined in the 3G document TS 25.433 published by the 3GPP, and

for the common channels, during common transport channel set-up, common transport channel deletion and common transport channel reconfiguration procedures also defined in the 3G document TS 25.433 published by the 3GPP.

These procedures are known as Node B Application Part (NBAP) procedures and the corresponding signaling messages are known as NBAP messages.

The 3G technical specification TS 25.433 defines two separate consumption laws, one for dedicated channels and one for common channels. A dedicated channel is a channel allocated to a given user, while a common channel is a channel shared between a plurality of users. For example, in the UMTS the DCH is a dedicated channel and channels such as the RACH (random access channel), FACH (forward access channel), CPCH (common packet channel), DSCH (downlink shared channel), etc. are common channels.

The Applicant has noted that the credit mechanism defined in the current version of the 3G technical specification TS 25.433 still gives rise to certain problems.

A first problem is that no account is taken of the specific nature of the DSCH.

Although the DSCH is in reality a common channel, it is always associated with a DCH, and the set-up, deletion and reconfiguration procedures that relate to the DSCH simultaneously relate to the DCH. For example, one or two operations can be executed to effect a radio link set-up operation, namely one operation for the DCH and, where applicable (if a DSCH is associated with the DCH), one operation for the DSCH.

Accordingly, although the DSCH is a common channel, it would be more logical (to simplify capacity credit updating) if it were taken into account in the consumption law for dedicated channels.

However, the allocation cost for dedicated channels is different according to whether the radio link concerned is a first radio link or not, the latter situation corresponding to that in which the UE has more than one radio link in the same Node B, i.e. in which the UE is in a situation with respect to the Node B known as softer handover. Accordingly, the 3G technical specification TS 25.433 specifies that two costs are taken into account for a first radio link, namely a radio link cost (RL cost) and a radio link set cost (RLS cost), whereas for an additional radio link only the RL cost is taken into account.

However, the soft or softer handover technique is not generally used for common channels and in particular for the DSCH. The DSCH therefore gives rise to particular problems in applying the above credit mechanism, which problems must be solved.

One object of the present invention is to solve these problems.

Thus one aspect of the present invention consists in a method of managing processing resources in a mobile radio system in which a first entity manages radio resources and corresponding processing resources provided in a second entity separate from the first entity, in which method:

According to another feature:

in the case of the dedicated channel, the cost for a first radio link includes a cost for a radio link and an additional cost and the cost for an additional radio link includes only the cost for a radio link,

in the case of a common channel associated with a dedicated channel, said cost for the associated common channel corresponds to the cost of a radio link for the dedicated channel.

According to another feature said cost for the associated common channel is specific to that channel.

According to another feature said common channel associated with a dedicated channel is a downlink shared channel (DSCH).

According to another feature the cost is a function of the spreading factor.

Another aspect of the present invention consists in mobile radio system for implementing a method of the above kind, in which system the first entity includes means for updating the capacity credit in the case of radio resources corresponding to a common channel associated with a dedicated channel on the basis of the cost for the dedicated channel and a cost for the associated common channel in the case of the first radio link and on the basis of the cost for the dedicated channel only in the case of an additional radio link.

According to another feature, said first entity is a base station controller.

According to another feature, said second entity is a base station.

Another aspect of the present invention consists in a base station controller for use in a mobile radio system for implementing a method of the above kind, said base station controller essentially including means for updating the capacity credit in the case of a common channel associated with a dedicated channel, on the basis of a cost for the dedicated channel and a cost for the associated common channel in the case of the first radio link and on the basis of the cost for the dedicated channel only in the case of an additional radio link.

A second problem is that the present versions of the technical specifications do not indicate how to take account in the above credit mechanism of a variable spreading factor and/or a variable number of spreading codes (in the case of multicode transmission).

In the case of multicode transmission in the UMTS, the spreading factor and/or the number of spreading codes used in the uplink direction can vary during the same call. The amount of processing resources needed is not the same, this amount varying with the spreading factor used and/or the number of spreading codes used. It would therefore be desirable to take account of this in the credit mechanism concerned.

Another object of the present invention is to solve this problem.

Thus another aspect of the present invention consists in a method of managing processing resources in a mobile radio system in which a first entity manages radio resources and corresponding processing resources provided in a second entity separate from the first entity, in which method:

the second entity signals to the first entity its overall processing capacity, which is also known as the capacity credit, and the amount of said overall processing capacity, which is also known as the consumption law or the cost, for different values of the spreading factor,

in the case of a variable spreading factor and/or a variable number of spreading codes, said updating is effected in accordance with a reference spreading factor and/or a reference number of spreading codes.

According to another feature, said reference spreading factor is a minimum spreading factor.

According to another feature, said number of reference spreading codes is a maximum number of spreading codes.

According to another feature, the minimum spreading factor has a predetermined value.

According to another feature, said predetermined value is a function in particular of the type of service.

According to another feature, said predetermined value is adjustable by operation and maintenance means.

According to another feature, said first entity comprising a controlling radio network controller (CRNC) and said predetermined minimum spreading factor value being determined in a separate entity comprising a serving radio network controller (SRNC), said predetermined minimum spreading factor value is signaled by the SRNC to the CRNC.

According to another feature, said minimum spreading factor has a calculated value.

According to another feature, said calculated value is obtained from a transport format combination set (TFCS) parameter.

According to another feature, said first entity comprising a controlling radio network controller (CRNC), said calculated value is calculated in the CRNC from said parameter signaled to the CRNC by a separate entity comprising a serving radio network controller (SRNC).

According to another feature, said first entity comprising a controlling radio network controller (CRNC), said calculated value is signaled to the CRNC by a serving radio network controller (SRNC) that calculates it itself from said parameter.

Another aspect of the present invention consists in a mobile radio system for implementing a method of the above kind, in which system the first entity includes means for effecting said updating on the basis of a reference spreading factor and/or a reference number of spreading codes if the spreading factor and/or the number of spreading codes is variable.

According to another feature, said first entity is a base station controller.

According to another feature, said second entity is a base station.

Another aspect of the present invention consists in a base station controller for mobile radio systems for implementing a method of the above kind, said base station controller essentially comprising means for effecting said updating on the basis of a reference spreading factor and/or a reference number of spreading codes.

According to another feature, said means for effecting said updating include means for receiving a predetermined reference spreading factor value and/or a predetermined reference number of spreading codes value signaled to said base station controller (CRNC) by a separate base station controller (SRNC).

According to another feature, said means for effecting said updating include means for calculating a reference spreading factor value from a parameter signaled to said base station controller (CRNC) by a separate base station controller (SRNC).

According to another feature, said means for effecting said updating include means for receiving a reference spreading factor value signaled to said base station controller (CRNC) by a separate base station controller (SRNC) which calculates it itself.

A third problem is that the current technical specifications do not indicate how the above credit mechanism should take account of multicode transmission.

Now, as mentioned above, in the UMTS, multicode transmission can be used in the uplink or downlink direction, and the amount of processing resources required is not the same, varying with the number of spreading codes used. It would therefore be desirable to take it into account in the credit mechanism concerned.

An object of the present invention is to solve this problem.

the second entity signals to the first entity its overall processing capacity, which is also known as the capacity credit, and the amount of said overall processing capacity, which is also known as the consumption law or the cost, for different spreading factor values,

the first entity updates the capacity credit on the basis of the consumption law, and

in the case of multicode transmission using N spreading codes, said updating is effected on the basis of the cost for at least one of the N spreading codes.

According to another feature, the cost for the N codes corresponds to the sum of the costs for each of the N codes.

According to another feature, the cost for the N codes is determined from the cost for one code.

According to another feature, the cost for the N codes corresponds to N times the cost for one code.

According to another feature, the cost for the N codes corresponds to the cost for the minimum spreading factor code.

Another aspect of the present invention consists in a mobile radio system for implementing a method of the above kind, in which system the first entity includes means for effecting said updating on the basis of the costs for at least one of the N spreading codes in the case of multicode transmission using N spreading codes.

According to another feature, said first entity is a base station controller.

According to another feature, said second entity is a base station.

Another aspect of the present invention consists in a base station controller for a mobile radio system for implementing a method of the above kind, said base station controller essentially comprising, in the case of multicode transmission using N spreading codes, means for effecting said updating on the basis of the cost for at least one of the N spreading codes.

Another object of the present invention is to propose a load control method and/or a call admission control method allowing for the processing capacity of a base station determined in accordance with the above credit mechanism.

Thus another aspect of the present invention consists in a load control method and/or a call admission control method for use in a mobile radio system in which a first entity manages radio resources and corresponding processing resources provided in a second entity separate from the first entity, in which method:

the second entity signals to the first entity its overall processing capacity, which is also known as the capacity credit, and the consumption law, i.e. the amount of the overall processing capacity, which is also known as the consumption cost, as a function of the necessary resources,

if the capacity credit in the uplink and/or downlink direction falls below a given first threshold, a new call is rejected until the capacity credit rises above a given second threshold higher than or equal to the first threshold.

Another aspect of the present invention consists in a mobile radio system for implementing a method of the above kind, in which system the first entity includes means for rejecting a new call if the capacity credit in the uplink and/or downlink direction falls below a given first threshold until the capacity credit rises above a given second threshold higher than or equal to the first threshold.

According to another feature, said first entity is a base station controller.

According to another feature, said second entity is a base station.

Another aspect of the present invention consists in a base station controller for use in a mobile radio system for implementing a method of the above kind, said base station controller essentially comprising means for, if the capacity credit in the uplink and/or downlink direction falls below a given first threshold, rejecting any new call until the capacity credit rises above a given second threshold higher than or equal to the first threshold.

Another aspect of the present invention is a load control method and/or a call admission control method for use in a mobile radio system in which a first entity manages radio resources and corresponding processing resources provided in a second entity separate from said first entity, in which method:

the second entity signals to the first entity its overall processing capacity, which is also known as the capacity credit, and the consumption law, i.e. the amount of said overall processing capacity, which is also known as the consumption cost, as a function of the necessary resources,

if the capacity credit falls below a given threshold, an overload control procedure is initiated.

Another aspect of the present invention consists in a mobile radio system for implementing a method of the above kind, in which system the first entity includes means for initiating an overload control procedure if the capacity credit falls below a given threshold.

According to another feature, said first entity is a base station controller.

According to another feature, said second entity is a base station.

Another aspect of the present invention consists in a base station controller for use in a mobile radio system for implementing a method of the above kind, said base station controller essentially comprising means for initiating an overload control procedure if the capacity credit falls below a given threshold.

Other objects and features of the present invention become apparent on reading the following description of embodiments of the invention, which is given with reference to the accompanying drawings, in which: [0126]
FIG. 1, described above, outlines the general architecture of a mobile radio system such as the UMTS, [0127]
FIGS. 2 and 3, also described above, outline the main transmit and receive processing effected in a base station, such as a UMTS Node B, and [0128]
FIG. 4 is a diagram illustrating one embodiment of a method of the invention.[0129]
Thus one object of the present invention is to solve problems to which the credit mechanism described in the current version of the 3G technical specification TS 25.433 gives rise. [0130]
A first problem is that no account is taken of the specific nature of the DSCH. [0131]
The solution in accordance with the invention to this first problem can be explained in the following manner. [0132]
Because the DSCH is always associated with a DCH, it may be preferable to take its processing cost into account in the consumption law for the dedicated channels. [0133]
A number of solutions can be adopted: [0134]
A specific cost is added in the consumption law for the DSCH, either for a few spreading factor values or for all possible spreading factor values (the second solution, i.e. a cost for each spreading factor, is preferable, as in the case of the DCH). [0135]
One of the costs specified for the downlink DCH (DL DCH), referred to as the DL RL cost, is taken into account (it will be noted that only one cost for the downlink direction has to be taken into account, since the DSCH is a downlink only channel and the processing for the Node B transmitter and receiver is usually significantly different). [0136]
As soft handover cannot be used for the DSCH, no additional resource is used for the DSCH when a new radio link is added. If the NBAP messages concern a first radio link the preferred solution is therefore to add/change/remove a cost for the DSCH only once. [0137]
To be more precise: [0138]
for a radio link set-up procedure, the DSCH cost (either a specific cost or the DL RL cost for the DCH, see above) is debited from the capacity credit (it is debited only once, regardless of the number of radio links, unlike the DCH cost), [0139]
for a radio link addition procedure, the capacity credit is not modified because of the DSCH (but may change to take account of DCH processing), and [0140]
for a radio link re-configuration procedure, if the new DSCH cost is different from the old one, the capacity credit is modified because of the DSC only once, regardless of the number of radio links. [0141]
Generally speaking, to solve this first problem for a common channel that is associated with a dedicated channel, the invention essentially effects said updating on the basis of the cost for the dedicated channel and a cost for the associated common channel in the case of the first radio link and on the basis of the cost for only the dedicated channel in the case of an additional radio link. [0142]
In an advantageous embodiment of the invention, if a physical downlink shared channel (PDSCH) is allocated in the radio link set-up procedure, the processing cost associated with the PDSCH, which is equal to the DL RL cost, is debited from the capacity credit, in addition to the radio link processing cost. Similarly, this cost is debited from the capacity credit if a PDSCH is deleted and the difference between the new cost and the old cost is debited from the capacity credit if a PDSCH is reconfigured (or credited to the capacity credit if the difference is negative). [0143]
FIG. 4 is a diagram showing one example of the means to be provided in a base station (or a UMTS Node B) and in a base station controller (or a UMTS RNC) to implement a method in accordance with the invention as defined above. [0144]
A base station (Node B) thus includes, in addition to other means which can be conventional means, means [0145] 13 for signaling to a base station controller its overall processing capacity, which is also known as the capacity credit, and the amount of that overall processing capacity, which is also known as the cost, as a function of the resources that are necessary.
A controlling radio network controller (CRNC) thus includes, in addition to other means that can be conventional means: [0146]
means [0147] 14 for receiving from a base station its overall processing capacity, which is also known as the capacity credit, and the amount of that overall processing capacity, which is also known as the cost, as a function of the resources that are necessary,
means [0148] 15 for updating the capacity credit on the basis of the consumption law, said updating being effected, in the case of a first radio link, on the basis of the cost for the dedicated channel and a cost for the associated common channel and, in the case of an additional radio link, on the basis only of the cost for the dedicated channel.
The above means can operate in accordance with the method described above; their specific embodiment representing no particular problem for the person skilled in the art, such means do not need to be described here in more detail than by stating their function. [0149]
In the above description, the cost can be a function of the spreading factor, as specified in the current version of the technical specifications referred to above. However, the principle as described is not limited to that situation, and applies also to a situation in which the cost is a function of one or more other parameters, such as the bit rate. [0150]
A second problem is that at present the technical specifications do not cover the variable spreading factor and/or the variable number of spreading factors. [0151]
The solution in accordance with the invention to this second problem can be explained in the following manner. [0152]
In the uplink direction, the spreading factor can vary as a function of the amount of data that the UE has to transmit (the way of choosing the spreading factor and the number of spreading codes is standardized). The CRNC has no a priori knowledge of the spreading factor and cannot take account of the spreading factor in updating the capacity credit. [0153]
The proposed solution is to update the capacity credit on the basis of a reference spreading factor. Said reference spreading factor is advantageously the minimum spreading factor. This can be determined relatively easily since it depends primarily on the maximum bit rate, which is part of the definition of the service (it will be noted that the choice of the minimum spreading factor is not standardized, and therefore depends on the manufacturer). [0154]
In a first embodiment of the invention, the minimum spreading factor has a predetermined value, which is a function of the type of service, for example. For more flexibility, the predetermined value can be adjusted, in particular by operation and maintenance (O&M) means. [0155]
In this first embodiment of the invention, the minimum spreading factor can be fixed by the SRNC and signaled to the CRNC at the Iur interface (if the SRNC is different from the CRNC) using the radio link addition request message and the radio link set-up request message, the corresponding information element (IE) being the minimum UL channelization code length IE. The CRNC then also signals the minimum spreading factor to the Node B by means of messages of the same type at the Iub interface. [0156]
In a second embodiment of the invention, the minimum spreading factor is calculated, for example on the basis of a transport format combination set (TFCS) parameter that is usually signaled for the dedicated channels (or radio link procedures) or for the common transport channels, in accordance with procedures provided by the corresponding standards. [0157]
One of the features of a system like the UMTS is the possibility of transporting a plurality of services on the same connection, i.e. a plurality of transport channels (TrCH) on the same physical channel. The transport channels are processed separately in accordance with a channel coding scheme (including error detector coding, error corrector coding, bit rate adaptation and interleaving, see FIG. 2) before they are time division multiplexed to form a coded composite transport channel (CCTrCH) to be transmitted on one or more physical channels. For more information on these aspects of the UMTS, see the 3G document TS 25.212 V3.0.0 published by the 3GPP. [0158]
Another feature of a system like the UMTS is that it allows users to use bit rates that can vary during a call. The data transported by the transport channels is organized into data units known as transport blocks that are received periodically at a transmission time interval (TTI). The number and the size of the transport blocks received for a given transport channel vary as a function of the bit rate. The transport format is defined as the known number and size of the transport blocks (and thus the instantaneous bit rate) for a given transport channel. The transport format combination (TFC) is defined as a combination of transport formats authorized for different transport channels to be multiplexed onto the same coded composite transport channel. Finally, the transport format combination set (TFCS) is defined as the set of all possible combinations of transport formats. For more information on these aspects of the UMTS see the 3G document TS 25.302 V3.7.0 published by the 3GPP. [0159]
The 3G technical specification TS 25.212 specifies how to choose the uplink spreading factor as a function of the TFC. Accordingly, the CRNC can also calculate from the TFCS the minimum spreading factor for all the TFC in the TFCS, or more generally the CRNC can calculate a reference spreading factor on the basis of the TFCS, regardless of the calculation method used. [0160]
This second embodiment of the invention is slightly more complex, but it may be the only solution when the minimum spreading factor is not fixed, as is the case for the physical common packet channel (PCPCH), for example. [0161]
In the same way, the capacity credit can be updated on the basis of a reference number of spreading codes, which in this example is the number of dedicated uplink physical data channels (DPDCH), the reference number advantageously being a maximum number which the SRNC signals to the CRNC using the maximum number of UL DPDCH IE. The number of uplink DPDCH can also vary and is therefore not known a priori to the CRNC either. [0162]
Generally speaking, to solve this second problem in the case of a variable spreading factor and/or a variable number of spreading codes, the invention essentially provides for said updating to be effected on the basis of a reference spreading factor and/or a reference number of spreading codes. [0163]
In an advantageous embodiment of the invention, the uplink reference spreading factor is the minimum spreading factor signaled in the radio link setup request message (minimum UL channelization code length IE). [0164]
Similarly, the uplink reference number of spreading codes is the maximum number signaled in the radio link set up request message (maximum number of UL DPDCH IE). [0165]
It will also be noted that what has been stated above for the uplink direction can also apply to the downlink direction or simultaneously to the uplink and downlink directions. [0166]
FIG. 4 can also be used to illustrate one example of the means to be provided in a base station (or a UMTS Node B) and in a base station controller (or in a UMTS RNC) to implement the above kind of method of the invention. [0167]
Thus a base station (Node B) includes, in addition to other means that can be conventional means, means [0168] 13 for signaling to a base station controller its overall processing capacity, which is also known as the capacity credit, and the amount of that overall processing capacity, which is also known as the cost, for different spreading factor values.
Thus a base station controller CRNC (controlling radio network controller) includes, in addition to other means that can be conventional means: [0169]
means [0170] 14 for receiving from a base station its overall processing capacity, which is also known as the capacity credit, and the amount of that overall processing capacity, which is also known as the cost, for different spreading factors, and
means [0171] 15 for updating the capacity credit on the basis of the consumption law, said updating being effected, in the case of a variable spreading factor and/or a variable number of spreading codes, on the basis of a reference spreading factor and/or a reference number of spreading codes.
In a first embodiment of the invention, the [0172] means 15 can include means for receiving a predetermined value of the reference spreading factor and/or reference number of spreading codes signaled to the base station controller (CRNC) by a separate base station controller (SRNC).
In a second embodiment of the invention, the [0173] means 15 can include means or calculating a reference spreading factor value from a parameter signaled to the base station controller (CRNC) by a separate base station controller (SRNC).
Another option is for the [0174] means 15 to include means for receiving a reference spreading factor value signaled by a separate base station controller (SRNC) that calculates it itself.
The above means can operate in accordance with the method described above; their particular implementation representing no particular problem for the person skilled in the art, such means need not be described here in more detail than by stating their function. [0175]
A third problem is that multicode transmission is currently not covered by the technical specifications. [0176]
The solution of the invention to this third problem can be explained in the following manner. [0177]
Multicode transmission corresponds to the use of a plurality of spreading codes, which are also known as channelization codes, for the same coded composite transport channel (CCTrCh). [0178]
The simplest solution is to consider that the cost for N codes is simply the sum of the costs of the individual codes (N times the cost of one code if the spreading codes have the same spreading factor), or more generally to derive the cost for N codes as a function of the cost for one code. This would avoid additional signaling and would provide a simpler way of taking account of multiple codes. [0179]
It would also be possible to consider that the cost of N codes corresponds to the cost of whichever of the N codes has the lowest spreading factor, although this seems less logical because the processing of N codes can be very different from the processing of one code. [0180]
Another option is to signal the various costs for different numbers N of codes, one for each number of codes and for each spreading factor. This would necessitate more signaling, however. It could nevertheless be possible in the uplink direction, because multiple codes are authorized only for the minimum spreading factor. Thus limited signaling would be necessary. [0181]
Generally speaking, to solve this third problem, in the case of multicode transmission using N spreading codes the invention essentially provides for said updating to be effected on the basis of the cost for at least one of the N spreading codes. [0182]
In an advantageous embodiment of the invention, the costs for the dedicated channels given in the consumption law are a cost for each spreading code (channelization code). If multiple spreading codes are used either by the radio links (dedicated channels) or by the PDSCH, the cost credited to or debited from the capacity credit is taken as N times the cost of one code, where N is the number of codes. [0183]
Similarly, in an advantageous embodiment of the invention, the costs for the common channels given in the consumption law are a cost for each spreading code (channelization code). If multiple spreading codes are used by a physical channel, the cost credited to or debited from the capacity credit is taken as N times the cost of one code, where N is the number of codes. [0184]
FIG. 4 can also serve as an illustration of an example of the means to be provided in a base station (or a UMTS Node B) and in a base station controller (or a UMTS RNC) to implement the above kind of method of the invention. [0185]
A base station (Node B) then includes, in addition to other means that can be conventional means, means [0186] 13 for signaling to a base station controller its overall processing capacity, which is also known as the capacity credit, and the amount of that overall processing capacity, which is also known as the cost, for different values of the spreading factor.
A base station controller (CRNC: controlling radio network controller) thus includes, in addition to other means that can be conventional means: [0187]
means [0188] 14 for receiving from a base station its overall processing capacity, which is also known as the capacity credit, and the amount of that overall processing capacity, which is also known as the cost, for different spreading factors values,
means [0189] 15 for updating the capacity credit on the basis of the consumption law, said updating being effected, in the case of multicode transmission using N spreading codes, on the basis of the costs for at least one of the N spreading codes.
The above means can operate in accordance with the method described above; their particular implementation representing no particular problem for the person skilled in the art, such means do not need to be described here in more detail than by stating their function. [0190]
It will be noted that the term “updating” used throughout the foregoing description in respect of the capacity credit is intended to encompass not only operations which debit the capacity credit, if new radio resources are required, but also operations which credit the capacity credit, if radio resources are no longer necessary and are therefore returned. [0191]
In particular: [0192]
for the radio link set-up, radio link addition and common transport channel set-up procedures the capacity credit is debited, [0193]
for the radio link deletion and common transport channel deletion procedures the capacity credit is credited, [0194]
for the radio link reconfiguration and common transport channel reconfiguration situation the capacity credit is debited or credited according to whether the difference between the allocation cost for the new bit rate and for the old bit rate is negative or positive. [0195]
Moreover, another object of the present invention is to propose a load and/or call admission control method taking account of the processing capacity of a base station determined in accordance with the above credit mechanism. [0196]
Essentially, according to this method: [0197]
if the capacity credit in the uplink and/or downlink direction falls below a given first threshold, the call admission control procedure can reject any new call until the capacity credit rises above a given second threshold higher than or equal to the first threshold, [0198]
furthermore, if the capacity credit falls below a given threshold, which can be equal to one of the previous thresholds, an overload control procedure can be initiated. [0199]
The present invention also provides a mobile radio system and a base station controller for implementing a method of the above kind. [0200]
In the above description, the cost can be a function of the spreading factor, as specified in the current versions of the technical specifications referred to above. However, the principle so described is not limited to that situation, and applies equally to a situation in which the cost is a function of one or more other parameters, such as the bit rate in particular. [0201]

Claims

1. A method of managing processing resources in a mobile radio system in which a first entity manages radio resources and corresponding processing resources provided in a second entity separate from the first entity, in which method:

2. A method according to claim 1, wherein:

3. A method according to claim 1, wherein said cost for the associated common channel is specific to that channel.

4. A method according to any one of claims 1 to 3, wherein said common channel associated with a dedicated channel is a downlink shared channel (DSCH).

5. A method according to any one of claims 1 to 4, characterized in that the cost is a function of the spreading factor.

6. A mobile radio system for implementing a method according to any one of claims 1 to 5, in which system the first entity includes means for updating the capacity credit in the case of radio resources corresponding to a common channel associated with a dedicated channel on the basis of the cost for the dedicated channel and a cost for the associated common channel in the case of the first radio link and on the basis of the cost for the dedicated channel only in the case of an additional radio link.

7. A base station controller for use in a mobile radio system for implementing a method according to any one of claims 1 to 5, said base station controller including means for updating the capacity credit in the case of a common channel associated with a dedicated channel, on the basis of a cost for the dedicated channel and a cost for the associated common channel in the case of the first radio link and on the basis of the cost for the dedicated channel only in the case of an additional radio link.