GB2401748A

GB2401748A - Apparatus and method of memory allocation thereof

Info

Publication number: GB2401748A
Application number: GB0311076A
Authority: GB
Inventors: David L Bhatoolaul
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2003-05-14
Filing date: 2003-05-14
Publication date: 2004-11-17
Anticipated expiration: 2023-05-14
Also published as: GB0311076D0; GB2401748B; CN1574660A; CN100492926C

Abstract

The invention relates to memory allocation of a shared memory for acknowledge mode services using confirmation of successful transmissions from a receiver to a transmitter. A memory capability processor (403) determines a memory capability, for example of a buffer memory in a user equipment (201). A preferred allocation processor (407) determines a preferred memory allocation for a plurality of acknowledge mode services and in response a combined preferred allocation processor (409) determines the total preferred memory for the acknowledge mode services. A memory allocator (411) subsequently determines memory allocations for the acknowledge mode services in response to the memory capability and the total preferred memory allocation. Specifically, if the total preferred memory allocation exceeds the memory allocation the memory allocation for each acknowledge mode service is scaled such that the total allocated memory does not exceed the memory capability. The invention is particularly suitable for 3<rd> Generation cellular communication systems and allows for efficient sharing of a limited memory resource.

Description

CE11362EP 2401 748

APPARATUS AND METHOD OF MEMORY ALLOCATION THEREFOR

Field of the invention

The invention relates to an apparatus and a method of memory allocation therefor and in particular to an apparatus and method for allocating memory to acknowledge mode services

Background of the Invention

FIG. 1 illustrates the principle of a conventional cellular communication system 100 in accordance with prior art. A geographical region is divided into a number of cells 101, 103, 105, 107 each of which is served by base station 109, 111, 113, 115. The base stations are interconnected by a fixed network which can communicate data between the base stations 109, 111, 113, 115. A mobile station is served via a radio communication link by the base station of the cell within which the mobile station is situated. In the example of FIG. 1, mobile station 117 is served by base station 109 over radio link 119, mobile station 121 is served by base station 111 over radio link 123 and so on.

As a mobile station moves, it may move from the coverage of one base station to the coverage of another, i.e. from one cell to another. For example mobile station 125 is initially served by base station 113 over radio link 127. As it moves towards base station 115 it enters a region of overlapping coverage of the two base stations 113 and 115 and within this overlap region it changes to be supported by base station 115 over radio link 129. As the mobile station 125 moves further into cell 107, it continues to be supported by base station 115.

This is known as a handover or handoff of a mobile station between cells.

. ! . . ' CE 11 362EP A typical cellular communication system extends coverage over typically an entire country and comprises hundreds or even thousands of cells supporting thousands or even millions of mobile stations. Communication from a mobile station to a base station is known as uplink, and communication from a base station to a mobile station is known as downlink.

The fixed network interconnecting the base stations is operable to route data between any two base stations, thereby enabling a mobile station in a cell to communicate with a mobile station in any other cell. In addition the fixed network comprises gateway functions for interconnecting to external networks such as the Public Switched Telephone Network (PSTN), thereby allowing mobile stations to communicate with landline telephones and other communication terminals connected by a landline. Furthermore, the fixed network comprises much of the functionality required for managing a conventional cellular communication network including functionality for routing data, admission control, resource allocation, subscriber billing, mobile station authentication etc. In a 3rd Generation cellular communication system, the fixed network comprises a Core Network (CN) and a Radio Access Network (RAN). The core network is operable to route data from one part of the RAN to another, as well as interfacing with other communication systems. In addition, it performs many of the operation and management functions of a cellular communication system, such as billing. The RAN is operable to support wireless user equipment over a radio link being part of the air interface. The RAN comprises the base stations, which in UMTS are known as Node Bs, as well as Radio Network Controllers (RNCs) which control the Node Bs and the communication over the air interface.

The RNC performs many of the control functions related to the air interface including radio resource management and routing of data to and from À . . . À .. . CE1 1362EP appropriate Node Bs. Specifically, the RNC performs many of the functions associated with radio link control. It further provides the interface between the RAN and the CN. An RNC and associated Node Bs are known as a Radio Network System (RNS).

In 3rd Generation communication systems such as the Universal Mobile Telecommunication System (UMTS) a high variety of services are envisaged.

These different services use different radio communication characteristics to achieve a desired performance and Quality of Service (QoS).

Specifically, some services are known as acknowledge mode (AM) services. For an acknowledge mode service, data packets communicated between the fixed network and a user equipment are acknowledged by the receiving part. Thus, if an acknowledgement for a data packet is received, this indicates that the data packet has been received without errors by the receiving end. However, if no acknowledgement is received, this indicates that the data packet is unlikely to have been received by the receiving end (it is, however, also possible that the error has occurred in the transmission of the acknowledgement).

Accordingly the missing data packet is re-transmitted to the receiving end thereby ensuring successful transmission of all data packets. However, in order to implement such an acknowledge mode service, memory is required by both the transmitting and receiving end. The transmitting end utilises buffer memory to store the transmitted data packets until an acknowledgement! signal has been received. If no acknowledgement is received the data packet stored in the buffer memory is retransmitted.

Likewise, the receive end utilises a buffer to store received data packets until these are ready to be outputted. For example, the acknowledge mode service may use a scheme where new data packets are transmitted before acknowledgement of previous data packets have been received. If a data packet is lost, the receive buffer may then buffer subsequent data packets; À .. .e.e.

CE1 1 362EP until the retransmitted lost data packet has been received. This allows for the data packets to be output in the correct sequence without requiring retransmissions of packets already successfully received. Furthermore, for some acknowledge mode services, a plurality of data packets are combined before being output. For example, the acknowledge mode services of UMTS transmits and receives data in terms of SDUs (Service Data Unit). Each SDU comprises a plurality of individually acknowledged PDUs (Packet Data Units).

Thus the receiver must buffer PDUs until all PDUs of a given SDU have been successfully received. This includes buffering PDUs until possible retransmissions have been successful. In UMTS, the control of the reception and transmission of PDUs and the combination of these into SDUs resides in the Radio Link Control (RLC) layer, which is typically implemented in an RNC.

The larger the available memory is for buffering at the receiver and/or transmitter, the better the achieved performance. However, in order to reduce the complexity and cost of e.g. user equipment and network elements, it is desirable to reduce the memory resource as much as possible. The performance and memory requirement depends on the characteristics of the specific service.

Accordingly, the 3rd Generation Partnership Project (3GPP) has e.g. specified a number of recommended memory sizes for different classes of user equipment.

For example, 3GPP prescribes that a 32 kbps class user equipment preferably has a buffer size of 10 kbytes whereas a 128 kbps class user equipment preferably has a buffer size of 50 kbytes.

This recommended memory size is a total buffer size for a given user equipment. However, a UMTS user equipment will frequently operate more than one simultaneous acknowledge mode service. For example, typically a dedicated control channel is generated as an acknowledge mode service and a user data acknowledge mode service may be operated in parallel.

Furthermore, the recommended buffer size is a shared uplink and downlink A: À:. À. .e À: CE1 1 362EP buffer size, and a user equipment running simultaneous uplink and downlink acknowledge mode services requires both a transmit and a receive buffer.

Thus, in most cases the available memory must be shared between a plurality of acknowledge mode services. This is further complicated by the optimum memory size for an acknowledge mode service depending on the data rate and Quality of Service of that service but being independent of the user equipment capability or the class of the user equipment.

Thus a limited memory resource must be allocated to acknowledge mode services. The memory allocation is a complex process and has significant impact on the achieved performance and an improved system of memory allocation is thus preferable.

For a UMTS communication system, the user equipment is operable to report an acknowledge mode service buffer capability to the RNC. The RNC may accordingly allocate memory of the buffer memory to acknowledge mode services. However, known methods of memory allocation tend to have a number of associated disadvantages resulting in sub-optimal memory allocation and accordingly sub-optimal performance of the communication system as a whole. These disadvantages include a lack of flexibility of the memory allocation, sub-optimal memory allocation for specific acknowledge mode services and a risk that insufficient memory is allocated thereby preventing acceptable performance of the acknowledge mode service.

For example, one method of memory allocation consists in allocating a predetermined memory size to an acknowledge mode service dependent on the data rate of that acknowledge mode service. For example, if an acknowledge mode service of 32 kbps is set up, 10 kbyte is allocated, and if an acknowledge mode service of 128 kbps is set up, 50 kbyte may be allocated (thus the memory sizes recommended by 3GPP for a given class of user equipment may be used). However, this has a number of disadvantages. Firstly, it may result À. ... .... ..e.

CE 11 362EP in sufficient memory being allocated for the current acknowledge mode service but prevent that sufficient memory is available for subsequent acknowledge mode services. Furthermore, the preferred memory size may be larger than the available memory thereby causing the acknowledge mode service to be rejected although it could possibly be implemented using lower memory sizes.

However, setting a lower memory allocation may result in the available memory not being used and thus buffer sizes being smaller than necessitated by the available memory. This will reduce the performance of the acknowledge mode service.

Hence, an improved system for controlling acknowledge mode services would be advantageous and in particular and improved system for memory management or allocation for a plurality of acknowledge mode services e.g. allowing for improved flexibility, efficiency, adaptability and distribution of memory would be advantageous.

Summary of the Invention

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

According to a first aspect of the invention there is provided an apparatus for a cellular communication system supporting a plurality of user equipment; the apparatus comprising: means for determining a memory capability associated with a user equipment supporting a plurality of acknowledge mode services; means for determining a preferred memory allocation associated with each of the plurality of acknowledged mode services; means for determining a combined preferred memory allocation associated with the plurality of acknowledge mode services in response to the preferred memory allocation À:..e..i Àe. hi: CE1 1 362EP associated with each of the plurality of acknowledge mode services; and means for determining a memory allocation for each acknowledge mode service in response to the memory capability and the combined preferred memory allocation.

The invention allows for an improved memory allocation for acknowledge mode services. For example, an improved sharing of a common pool of memory between a plurality of acknowledge mode services may be achieved.

Specifically, the memory allocation to a plurality of acknowledge mode services may be optimised to suit the number and characteristics of the currently allocated acknowledge mode services. The invention allows for an efficient use of a given memory resource associated with a user equipment, enabling a memory allocation which fully utilises the available memory in view of the current conditions. For example, if only a few acknowledge mode services are employed, the total preferred memory allocation for all acknowledge mode services may be within the memory capabilities and each acknowledge mode service may thus be allocated the preferred memory allocation for that service.

However, when more acknowledge mode services are set up, the combined preferred memory allocation may exceed the available memory resource and therefore the memory allocation for each acknowledge mode service may be reduced ensuring that the total allocated memory does not exceed the available memory resource. This may cause a slight degradation of each acknowledge mode service but ensures that all acknowledge mode services can be set up. Hence, the available memory may be efficiently used and optimised to suit the current conditions.

The memory capability may for example be that of a single shared buffer memory dedicated for the specific user equipment or may for example be a memory allocation of a memory shared between a plurality of user equipment.

The acknowledge mode services may e.g. be any service using a confirmation protocol for communication of data including for example Automatic Repeat À. . ei. . CE1 1 362EP reQuest (ARQ) schemes or the acknowledge mode services specified by the 3rd Generation Partnership Project for 3rd Generation cellular communication systems.

The apparatus may be operable to perform a memory allocation on occurrence of an event, at regular intervals or in any suitable way. For example, the memory allocation may be performed when one or more acknowledge mode services are set up, when one or more acknowledge mode services are terminated or at regular time intervals. Thus, specifically, the apparatus may be operable to perform the memory allocation when a new acknowledge mode service is set up. The resulting memory allocation may affect the new acknowledge mode service as well as one or more of the existing acknowledge mode services. Similarly, the apparatus may be operable to perform a memory allocation for one or more existing acknowledge mode services when another existing acknowledge mode service is terminated. Thus, specifically, a new memory allocation of all current acknowledge mode services may be performed each time a new acknowledge mode service is set up or terminated thereby allowing the memory capability to be shared efficiently and dynamically between the currently active acknowledge mode services. This may allow for an efficient and dynamic adaptation of the memory capability to the current situation and specifically the currently active acknowledge mode services.

According to a feature of the invention, the means for determining a combined preferred memory allocation is operable to determine the combined preferred memory allocation as a summation of the preferred memory allocation associated with each of the plurality of acknowledge mode services. This allows for a particularly simple method of determining a measure efficiently reflecting a desired or preferred total memory allocation. The combined preferred memory allocation may thus correspond to the total memory that preferably would be allocated to all the current acknowledge mode services.

The summation may specifically be a weighted summation, for example in

. .... . .....DTD: CE1 1362EP response to a characteristic of each of the plurality of acknowledge mode services.

According to a feature of the invention, the means for determining the memory allocation is operable to determine the memory allocation of a first acknowledge mode service of the plurality of acknowledge mode services by a scaling of the preferred memory allocation of the first acknowledge mode service. This allows for a particularly suitable way of adjusting the memory allocation for the first acknowledge mode service and allows for the memory allocation to be related to the preferred memory allocation. For example, a suitable scaling factor may be determined for one, more or all of the acknowledge mode services and this scaling factor may be applied to the preferred memory allocation of the first acknowledge mode service to derive the memory allocation therefor. This allows for a memory allocation which may be as close to the preferred memory allocation as possible while taking into account a required scaling factor necessitated by the memory capability and the preferred memory allocation of other acknowledge mode services.

According to a feature of the invention the scaling is in response to a ratio between the combined preferred memory allocation and the memory capability. This provides for a particularly suitable scaling factor to be determined and allows for a memory allocation that is as close to the preferred memory allocation as possible while taking into account a required scaling factor necessitated by the memory capability and the preferred memory allocation of other acknowledge mode services.

According to a feature of the invention, the scaling is substantially equal to the ratio between the combined preferred memory allocation and the memory capability. The scaling factor may be obtained by comparing the combined preferred memory allocation, e.g. an optimum total memory requirement, against the memory capability, e.g. a total available memory resource. For : À : À À À ::. :.e. À:- : À . . . CE1 1362EP example, if the total optimum memory allocation for all acknowledge mode services is 10% higher than the available memory, the memory allocation of the first acknowledge mode service may correspond to the preferred memory allocation reduced by 10%. Thus a gradual reduction of the memory allocation may be achieved thus utilising all available memory and minimising the performance impact of insufficient memory resource.

According to a feature of the invention, the means for determining the memory allocation is operable to determine the memory allocation of all of the plurality of acknowledge mode services by the same scaling of the preferred memory allocation of each acknowledge mode service. This allows for the available memory to be distributed between the acknowledge mode services such that the relative performance impact is maintained relatively equivalent. For example, if the combined preferred memory allocation exceeds the memory capability by 10%, all acknowledge mode services may be provided with a memory allocation reduced by 10% with respect to the preferred memory allocation. This allows for all available memory to be fairly distributed between the acknowledge mode services.

According to a feature of the invention, the means for determining the memory allocation is further operable to determine the memory allocation for each acknowledge mode service in response to a priority of each acknowledge mode service. This allows for a further optimization of the available memory capability and particularly allows for the memory allocation to be in response to the relative importance of the different services.

According to a feature of the invention, the means for determining the memory allocation is further operable to determine the memory allocation of at least one priority service as the preferred memory allocation of the priority service.

This allows for a priority service to be provided with the desired and/or optimum memory allocation. Thus the impact of a limited memory capability 2. .', i. . CE1 1 362EP may be reduced or removed for priority services. For example, errors or delays of a signalling service may be significantly more damaging than for a user data service. Thus the signalling service may be designated as a priority service and the performance of this may be optimised by allocating it the preferred memory allocation.

According to a feature of the invention, the apparatus further comprises means for determining a remaining memory capability by subtracting the memory allocation of at least one priority service from the memory capability; and the means for determining the memory allocation is further operable to determine the memory allocation of a plurality of nonpriority acknowledge mode services by scaling of the preferred memory allocation of the non-priority acknowledge mode services in response to the remaining memory capability.

Advantageously, a preferred memory allocation may be allocated to a priority service and the remaining memory may be shared between nonpriority services. This allows for an advantageous distribution of available memory while ensuring that performance of priority services is optimised.

According to a feature of the invention, the memory capability associated with the user equipment comprises a buffer capability of the user equipment.

Advantageously a buffer capability of a user equipment may be allocated.

Hence, the invention allows for an improved memory allocation of a buffer of a user equipment. The buffer capability of a user equipment is typically a limiting parameter for the performance of acknowledge mode services and the communication system as a whole and accordingly an improved quality of service of acknowledge mode services may be provided.

According to a feature of the invention, the means for determining the memory capability is operable to receive the buffer capability from the user equipment.

This allows for a particularly suitable way of determining the buffer capability of a user equipment and allows the invention to be used with user equipment - i.. ..i À. 2, CE1 1 362EP without requiring any characteristics or parameters of the user equipment to be known in advance.

According to a feature of the invention, the apparatus further comprises means for transmitting the memory allocations to the user equipment. This allows for a particularly suitable way of controlling the memory allocation of the buffer memory in a user equipment.

According to a feature of the invention, the apparatus is a radio network controller. A radio network controller may control a plurality of base stations.

The radio network controller may advantageously implement a significant amount of radio link control and accordingly may advantageously control the memory allocation. This allows for a centralised memory allocation which may take into account conditions or characteristics relating to a plurality of user equipment and/or cells.

According to a feature of the invention, the memory capability associated with the user equipment comprises a buffer capability of the radio network controller. The invention thus allows for an improved memory allocation of a buffer capability of a radio network controller. The buffer capability may be a buffer capability reserved for a single user equipment or a plurality of user equipment.

According to a feature of the invention, the means for determining the preferred memory allocation is operable to determine the preferred memory allocation of a second acknowledge mode service in response to a characteristic of the second acknowledge mode service. This allows for a suitable way of determining the preferred memory allocation specifically suited for the second acknowledge mode service. For example, the preferred memory allocation of the second acknowledge mode service may be determined in response to the data rate and/or Quality of Service of the second acknowledge mode service.

s 2 ' '' ' "2.

CE1 1362EP The second acknowledge mode service may be the same as the first acknowledge mode service.

According to a feature of the invention, the means for determining the preferred memory allocation is operable to determine the preferred memory allocation of the second acknowledge mode service in response to a predetermined association between the characteristic of the second acknowledge mode service and the preferred memory allocation of the second acknowledge mode service. This allows for a particularly low complexity suitable for a simple implementation. For example, the preferred memory allocation may be determined by a table look-up in a table comprising associations between characteristics of an acknowledge mode service and an optimum memory allocation.

According to a feature of the invention, the apparatus further comprises means for rejecting a third acknowledge mode service of the plurality of acknowledge mode services. This may allow for an efficient memory allocation where acknowledge mode services which cannot be adequately supported and/or would have unacceptable impact on other acknowledge mode services may be rejected. The third acknowledge mode service may be the same as the second acknowledge mode service and/or the first acknowledge mode service.

According to a feature of the invention, the means for rejecting is operable to reject the third acknowledge mode service if the combined preferred memory allocation exceeds the memory capability by more than a threshold. This allows for a suitable determination of whether the third acknowledge mode service may cause insufficient memory to be available to support all acknowledge mode service with a required performance level. For example, it may prevent that so many acknowledge mode services are allocated that there is insufficient memory to adequately support each acknowledge mode service À . . .. .' e CE1 1362EP resulting in unacceptable performance of several or all of the acknowledge mode services.

According to a feature of the invention, the means for rejecting is operable to reject the first acknowledge mode service if the scaling exceeds a threshold.

For example, if the required scaling is above 50%, corresponding to only half of the preferred memory allocation being available, the acknowledge mode service may be rejected. This allows for a suitable and easy to implement way of ensuring that the acknowledge mode services attain a certain level of 1 0 performance.

According to a feature of the invention, the communication system is a 3rd Generation cellular communication system in accordance with the specifications of the 3rd Generation Partnership Project. For example the cellular communication system may be a Universal Mobile Telecommunication System (UMTS).

According to an aspect of the invention, there is provided a communication system comprising an apparatus as described above.

According to an aspect of the invention, there is provided a method of memory allocation for a cellular communication system supporting a plurality of user equipment; the method comprising the steps of: determining a memory capability associated with a user equipment supporting a plurality of acknowledge mode services; determining a preferred memory allocation associated with each of the plurality of acknowledged mode services; determining a combined preferred memory allocation associated with the plurality of acknowledge mode services in response to the preferred memory allocation associated with each of the plurality of acknowledge mode services; and determining a memory allocation for each acknowledge mode service in .. . . CE1 1 362EP response to the memory capability and the combined preferred memory allocation.

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

Brief Description of the Drawings

An embodiment of the invention will be described, by way of example only, with reference to the drawings, in which FIG.lis an illustration of a cellular communication system in accordance with

the prior art;

FIG.2 illustrates a communication arrangement for a user equipment supporting a plurality of acknowledge mode services; FIG.3 illustrates an example of buffer memory usage for an acknowledge mode service; FIG.4is an illustration of an apparatus for memory allocation in a cellular communication system in accordance with an embodiment of the invention;and FIG.5 illustrates a method of memory allocation in accordance with an embodiment of the invention.

Detailed Description of a Preferred Embodiment of the Invention CE1 1362EP The following description focuses on an embodiment of the invention applicable to a 3rd Generation cellular mobile communication system and in particular to a UMTS communication system. However, it will be appreciated I that the invention is not limited to this application but may be applied to many other communication systems.

FIG. 2 illustrates a communication arrangement for a user equipment supporting a plurality of acknowledge mode services.

In the example of FIG. 2, a user equipment 201 comprises an antenna 203 for I communication over a radio channel 205. The user equipment may for example be a mobile station, a communication terminal, a personal digital assistant, a laptop computer, an embedded communication processor or any communication element communicating over the air interface. In the preferred embodiment, the user equipment is a UMTS user equipment comprising all the required functionality for communicating in accordance with the UMTS

specifications as defined by 3GPP.

The radio transmission from the user equipment 201 is received by a base station (or Node B) 209 having an antenna 207. The radio signal is demodulated and decoded by the base station as is well known in the art. The received data packets, known as Packet Data Units (PDUs) in UMTS, are fed to a Radio Network Controller (RNC) 211 coupled to the base station 209.

In the described embodiment, the user equipment is supporting a plurality of acknowledge mode services. For example, the user equipment may have set up i one signalling or control acknowledge mode service and two user data acknowledge mode service. In the preferred embodiment, the acknowledge mode service communicates in accordance with the acknowledge mode : , . ... .... . CE1 1362EP communication protocol as specified in 3GPP Technical Specification TS25.322

- Radio Link Control Protocol Specification.

In order to support the acknowledge mode services, both the user equipment and the RNC comprise buffer memory which is operable to temporarily store PDUs of the acknowledge mode services. It should be noted that the acknowledge mode services may be in the uplink and/or downlink direction, and that the buffer memory is typically shared between uplink and downlink acknowledge mode services. The available buffer memory is allocated to the individual acknowledge mode services and thus the pool of available memory is shared between the different acknowledge mode services including between the uplink and downlink acknowledge mode services. Thus, in the preferred embodiment, the buffer memory may be allocated as receive buffers or as transmit buffers for the respective uplink and downlink services.

FIG. 3 illustrates an example of buffer memory usage for an acknowledge mode service. FIG. 3 illustrates a transmit buffer 301 and a receive buffer 303.

In the case of an uplink acknowledge mode service, the transmit buffer 301 may reside in the user equipment and the receive buffer 303 may reside in the RNC.

In the example of FIG. 3, a number of PDUs have been transmitted by the transmitter. Specifically, PDUs 1 to 4 have been transmitted and PDU 5 is currently being transmitted. However, no acknowledgement from the receiver has been received for these PDUs. Accordingly, the transmit buffer has stored a copy of PDU 1 305, PDU 2 307, PDU 3 309, PDU 4 311 and PDU 5 313.

When an acknowledgement for a PDU is received, the corresponding PDU is deleted from the transmit buffer 301. However, if no acknowledgement is received within a given time interval or if an acknowledgement of a subsequent PDU is received, the corresponding PDU is retransmitted.

À . . . À. . CE1 1 362EP In the shown example, the receiver has received PDUs 1, 2 and 4 and is currently receiving PDU 5. However, PDU 3 was lost in the transmission and has not been successfully received by the receiver. In the specific example, PDUs 1 to 5 are all required to generate an SDU. Thus, the receive buffer 303 stores a copy of PDU 1 315, PDU 2 317, PDU 4 319 and PDU 5 321. The receiver transmits an acknowledgement signal for each of the PDUs 1, 2 and 4.

When the transmitter receives the acknowledgement for PDU 1 and 2, it deletes these from the transmit buffer 301. However, when it receives the acknowledgement of PDU 4, it retransmits PDU 3 (e.g. after the transmission of PDU 5 is completed). The receiver then receives the retransmitted PDU 3 and uses the stored versions of PDUs 1, 2, 4 and 5 to generate the SDU of PDU 1 to 5.

As illustrated, buffer memory is intensively used for acknowledge mode services. Clearly, increased memory allocations for transmit and receive buffers allow for improved performance, for example by allowing for increased number of retransmissions before the receive or transmit buffer fills. However, the memory available for buffers is typically significantly limited and is furthermore shared between a plurality of different PDUs. Thus an efficient memory allocation is important for optimum performance of the acknowledge mode services and thus the communication system as a whole.

It will be apparent to the person skilled in the art that FIG. 3 illustrates a single example of how an acknowledge mode communication may use buffers and that many other alternatives and variations are possible.

FIG. 4 is an illustration of an apparatus for memory allocation in a cellular communication system in accordance with an embodiment of the invention. In the described preferred embodiment, the apparatus is specifically an RNC 400 of a UMTS cellular communication system.

À . . . . À : À À . . CE1 1362EP The RNC 400 comprises a memory capability processor 401 which is operable to determine a memory capability associated with a user equipment. In the described embodiment, the memory capability is the available buffer memory of a user equipment supporting a plurality of acknowledge mode services. Thus the memory capability processor 401, in the preferred embodiment, determines the size of a memory resource in user equipment which is available for buffering of acknowledge mode services.

In the preferred embodiment, the memory capability processor 401 is coupled to a receiver 403 which is operable to receive the memory capability of the user I equipment from the user equipment (via the base station). Thus, the available buffer memory of a user equipment is communicated from the user equipment to the receiver 403 and fed to the memory capability processor 401, which accordingly sets the memory capability to this value. Thus the memory capability may correspond to the memory resource or pool available for sharing between the acknowledge mode services.

The RNC 400 furthermore comprises an acknowledge mode service controller 405 which is operable to control the set-up, maintenance and disconnection of acknowledge mode services. Thus the acknowledge mode service controller 405 comprises functionality for performing the required control and maintenance of acknowledge mode services as specified in 3GPP Technical Specification TS25.322 - Radio Link Control Protocol Specification.

Specifically, the acknowledge mode service controller 405 is responsible for setting up and terminating acknowledge mode services, and it further maintains information of the characteristics of the current acknowledge mode services.

The acknowledge mode service controller 405 is coupled to a preferred allocation processor 407 which is operable to determine a preferred memory À . . . . À . . À À . CE 11 362EP allocation associated with each of the plurality of acknowledged mode services allocated to (or about to be allocated to) the user equipment. Thus the acknowledge mode service controller 405 feeds the required information of the current acknowledge mode services to the preferred allocation processor 407 which then for each acknowledge mode service determines a preferred or optimal memory allocation.

Any suitable method of determining the preferred memory allocation for an acknowledge mode service may be used but in the preferred embodiment a simple determination based on the data rate of the acknowledge mode service is used. Specifically, the preferred memory allocation is set as the memory size recommended in table 5.2.1.1 of 3GPP Technical Specification TS25.306 - UE Radio Access Capabilities. Thus if the acknowledge mode service is 32 or 64 kbps, the preferred memory allocation is set to 10 kLytes, if it is 128 or 384 kbps the preferred memory allocation is set to 50 kbytes, etc. The preferred allocation processor 407 is coupled to a combined preferred allocation processor 409 which is operable to determine a combined preferred memory allocation associated with the plurality of acknowledge mode services.

The combined preferred memory allocation is determined in response to the preferred memory allocation associated with each of the plurality of acknowledge mode services.

In the preferred embodiment, the combined preferred memory allocation is simply determined by adding the preferred memory allocation of each of the current acknowledge mode services together. Thus the combined preferred memory allocation corresponds to the total memory that needs to be allocated for all acknowledge mode services to receive their preferred or optimum allocation.

À . . . . À . . À À . À À . CE1 1 362EP The combined preferred allocation processor 409 is coupled to a memory allocator 411 which is further coupled to the memory capability processor 401.

The memory allocator 411 is operable to determine a memory allocation for each acknowledge mode service in response to the memory capability and the combined preferred memory allocation.

Any suitable method or algorithm for determining a memory allocation of the acknowledge mode services in response to the memory capability and the combined preferred memory allocation may be employed. In the preferred embodiment, the memory allocator 411 determines if the combined preferred memory allocation exceeds the memory capability. If not, the preferred memory allocation is allocated to each acknowledge mode service. However, if the memory capability is exceeded, memory is allocated to the acknowledge mode services such that the total memory capability is not exceeded. The reduction of memory allocated is dependent on the preferred memory allocation of each service - preferably by reducing each by a similar relative amount.

Thus the memory allocator 411 will allocate memory to the acknowledge mode services such that the available memory is preferably optimally utilised yet ensuring that the impact of insufficient memory is distributed fairly over the acknowledge mode services taking into account the relative performance impact on each service.

The memory allocator 411 is coupled to the acknowledge mode service controller 405 which is operable to control the configuration of the memory in accordance with the determined memory allocation. In the preferred embodiment, the acknowledge mode service controller 405 is coupled to a transmitter 413 which is operable to transmit the determined memory allocation to the user equipment which then allocates the memory accordingly.

À . . À . À À - : : e. :e:: CE1 1 362EP FIG. 5 illustrates a method of memory allocation in accordance with an embodiment of the invention. The method is applicable to the RNC 400 of FIG. 4 and will be described with reference to this.

In step 501, the memory capability associated with the user equipment is determined by the memory capability processor 401. If the relevant memory is that of the user equipment, the memory capability is preferably communicated from the user equipment to the memory capability processor 401 as previously described.

In other embodiments, the memory allocation is of memory associated with the user equipment but is not memory of the user equipment. For example, the memory may be memory of the RNC 400 used for buffering of acknowledge mode services. The memory may thus be memory shared between a plurality of user equipment and in this case the memory capability processor 401 may determine the memory capability by determining a share (or likely share) of the memory pool which has been allocated for this user equipment. For example, the memory capability processor 401 may determine the memory capability as the total memory divided by the number of user equipment currently operating one or more acknowledge mode services.

Step 501 is followed by step 503 wherein the preferred allocation processor 407 determines a preferred memory allocation associated with each of the acknowledge mode services of the user equipment.

In the preferred embodiment, the preferred memory allocation is determined in response to a characteristic of the acknowledge mode service. As previously mentioned, the characteristic may preferably be the data rate of the acknowledge mode service. However, in other embodiments other characteristics may be used or a plurality of characteristics may be used.

Thus, in some embodiments other Quality of Service (QoS) parameters may be . . . . ...

A:: A. ':e:: CE1 1362EP 23: used in determining the preferred memory allocation including for example a required data error rate or a delay requirement.

In the preferred embodiment, the preferred memory allocation is determined by a table look up on the basis of the given characteristic. Thus, an association between one or more characteristics of an acknowledge mode service and a corresponding preferred memory allocation is predetermined and stored in a table. During memory allocation, the preferred allocation processor 407 may access the table based on a characteristic provided by the acknowledge mode service controller 405 (e. g. the data rate) and the corresponding preferred memory allocation may be retrieved. In other embodiments, an equation may I be used to determine the preferred memory allocation based on one or more characteristics, e.g. based on one or more service descriptors.

The associations between the characteristics and the preferred memory allocation may be determined in any suitable way. A simple method is to use the recommendations of buffer size provided by 3GPP. However, more suitable and advantageous values may be obtained through trial and error or simulations as will be apparent to the person skilled in the art.

Step 503 is followed by step 505 wherein the combined preferred allocation processor 409 determines the combined preferred memory allocation. In the preferred embodiment, the combined preferred memory allocation simply corresponds to the total amount of memory that would ideally be allocated.

Thus the combined preferred memory allocation is simply determined by adding up the preferred memory allocation of all the acknowledge mode services.

Step 505 is followed by step 507 wherein the memory allocator 411 determines a memory allocation for each acknowledge mode service. The memory d À, s. a CE11 362EP allocation of each service is determined in response to the memory capability and the combined preferred memory allocation.

In the preferred embodiment, it is first determined if the combined preferred memory allocation exceeds the memory capability. If not, the preferred memory allocation is allocated to each acknowledge mode service.

However, if the combined preferred memory allocation exceeds the memory capability, the memory allocation for at least one acknowledge mode service is determined by a scaling of the preferred memory allocation for that acknowledge mode service.

Specifically, the scaling is preferably such that the preferred memory allocations of all or some of the acknowledge mode services are scaled proportionally such that the total memory allocation does not exceed the memory capability. In the preferred embodiment, all acknowledge mode services are scaled by the same factor equivalent to the ratio between the combined preferred memory allocation and the memory capability.

Thus, as a specific example, three acknowledge mode services may be set up for a given user equipment. Two of these acknowledge mode services may be 768 kbps services having a recommended memory allocation of 100 kbytes each, and a third acknowledge mode service may be a 128 kbps service having a recommended memory allocation of 50 kbytes. Thus the combined preferred memory allocation may be determined by summing these, resulting in a combined preferred memory allocation of 250 kbytes. However, in the specific example, the user equipment only has 200 kbytes of buffer memory available.

Thus the memory capability is in the example determined as 200 kbytes.

In this case each of the acknowledge mode services may be allocated a memory allocation corresponding to the preferred memory allocation scaled by the ratio À < l a À CE1 1362EP between the combined preferred memory allocation and the memory capability. This ratio is in the present case 250kbytes/200kbytes=1.25.

Therefore the preferred memory allocation is scaled by a factor of 1.25 yielding a memory allocation of 100/1.25=80 kLytes for each 768 kbps service and 50kLytes/1.25= 40kLytes for the 128 kbps service. Accordingly, the memory capability of 200kbytes is not exceeded but the available memory is fully utilised. Furthermore, as the memory limitation is distributed over a plurality of acknowledge mode services, each acknowledge mode service only experiences a slight degradation which may only very occasionally impact the operation.

In other embodiments, more advanced scaling than a simple linear scaling may be employed. For example, the scaling factor may be dependent on the value of the preferred memory allocation such that small preferred memory allocations are scaled less than larger preferred memory allocations. It is within the contemplation of the invention that any suitable method or algorithm for scaling the preferred memory allocations may be employed.

In some embodiments, the memory allocator 411 is further operable to determine the memory allocation in response to priorities of the acknowledge mode services.

In one such embodiment, the memory allocator 411 is operable to allocate the full preferred memory allocation to one or more acknowledge mode services which are designated as priority services. In this embodiment, the memory allocation may thus first allocate memory to all priority acknowledge mode services. These services will be allocated the individual preferred memory allocation. Thus performance will be optimised for the priority services and the lack of sufficient buffer memory will not impact the priority services.

À'2.2;.e.'...

CE1 1362EP 26 1 Once the memory for the priority services has been allocated, a remaining memory capability may be calculated by subtracting the memory allocation of the priority services from the memory capability. The remaining memory capability thus corresponds to the memory available after the priority services have been allocated.

The memory allocation then preferably proceeds to share the remaining memory between the remaining acknowledge mode services using the same principles as previously discussed. Thus the memory allocation of nonpriority acknowledge mode services may be determined by scaling of the preferred memory allocation of these services. This scaling is in response to the remaining memory capability and may specifically be by scaling the preferred memory allocation of the non-priority services by a ratio corresponding to the ratio between the remaining memory capability and the sum of the preferred memory allocation of the remaining services.

This will allow for optimization of performance for priority services while minimising impact of insufficient memory on the remaining acknowledge mode services. This may be specifically advantageous for ensuring high performance of priority services such as signalling services.

In some embodiments, the apparatus may further comprise functionality for rejecting acknowledge mode services. Specifically, a new acknowledge mode service may be rejected if it could not be sufficiently supported by the available memory or if it would cause a memory sharing that would result in unacceptable degradation of another acknowledge mode service.

In one such embodiment, an acknowledge mode service is rejected if the combined preferred memory allocation exceeds the memory capability by more than a threshold. Thus if the combined preferred memory allocation of all the acknowledge mode services is too large with respect to the available memory, . .. .. . : À:e À À À À À r À À À À. À À À r À À CE1 1 362EP 27 1 the sharing of the available resource is likely to result in unacceptable performance of most or all of acknowledge mode services. Therefore, it is preferable to reject one or more of the acknowledge mode services such that the remaining acknowledge mode services can be operated with acceptable performance. ! The value of the threshold at which an acknowledge mode service may be rejected can be selected by the person skilled in the art dependent on the characteristics and requirements of the communication systems. The threshold may specifically be determined by a trial and error approach or by use of simulation techniques. A suitable threshold for many situations and cellular communication systems may be for a combined preferred memory allocation being around 25% to 50% higher than the memory capability.

In embodiments wherein the memory allocation comprises a scaling of the preferred memory allocations, a decision whether to reject an acknowledge mode service may be based on the scaling factor resulting from accepting the service. Specifically, the RNC may determine a scaling factor for the acknowledge mode services assuming the given acknowledge mode service is accepted. The resulting scaling factor may be compared to a threshold and if the threshold is exceeded (i.e. if a higher degree of scaling is required), the given acknowledge mode service is rejected. Thus this approach provides for a simple way of ensuring that the allocated memory is above a certain ratio of the preferred memory allocation. For example, all acknowledge mode services resulting in a scaling of more than 25% (equivalent to 80% of the preferred memory allocation) may be rejected. Thus, a simple approach may be implemented that ensures that an acknowledge mode service is always allocated at least 80% of the preferred memory allocation.

The exact scaling threshold at which a given acknowledge mode service is rejected may be determined by the person skilled in the art in view of the

. A. . :.:e À À . e.. À À À Àe :. e.. : :.. :e CE1 1362EP characteristics and requirements of the specific embodiment. Specifically, the i threshold may be determined by a trial and error or simulation approach...DTD: The invention can be implemented in any suitable form including hardware, software, firmware or any combination of these. However, preferably, the invention is implemented as computer software running on one or more data processors and/or digital signal processors. The elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit or may be physically and functionally distributed between different units and processors. I Although the present invention has been described in connection with the preferred embodiment, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. In the claims, the term comprising does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. Thus references to "a", "an", "first", "second" etc do not preclude a plurality.

À . . . . . . À À . À. : : . À : : . .

Claims

CE1 1 362EP CLAIMS

1. An apparatus for a cellular communication system supporting a plurality of user equipment; the apparatus comprising: means for determining a memory capability associated with a user equipment supporting a plurality of acknowledge mode services; means for determining a preferred memory allocation associated with each of the plurality of acknowledge mode services; means for determining a combined preferred memory allocation associated with the plurality of acknowledge mode services in response to the preferred memory allocation associated with each of the plurality of acknowledge mode services; and means for determining a memory allocation for each acknowledge mode service in response to the memory capability and the combined preferred memory allocation.

2. 2.i.2. .e -e

2. An apparatus as claimed in claim 1 wherein the means for determining a combined preferred memory allocation is operable to determine the combined preferred memory allocation as a summation of the preferred memory allocation associated with each of the plurality of acknowledge mode services.

3. An apparatus as claimed in any of the previous claims wherein the means for determining the memory allocation is operable to determine the memory allocation of a first acknowledge mode service of the plurality of acknowledge mode services by a scaling of the preferred memory allocation of the first acknowledge mode service.

4. An apparatus as claimed in claim 3 wherein the scaling is in response to a ratio between the combined preferred memory allocation and the memory capability.

À , , . .e.e e. ' Àe À Àe: :e CE1 1 362EP An apparatus as claimed in claim 4 wherein the scaling is substantially I equal to the ratio between the combined preferred memory allocation and the memory capability.

6. An apparatus as claimed in any of the previous claims 3 to 6 wherein the means for determining the memory allocation is operable to determine the memory allocation of all of the plurality of acknowledge mode services by the same scaling of the preferred memory allocation of each acknowledge mode service.

7. An apparatus as claimed in any of the previous claims wherein the means for determining the memory allocation is further operable to determine the memory allocation for each acknowledge mode service in response to a priority of each acknowledge mode service.

8. An apparatus as claimed in 7 wherein the means for determining the memory allocation is further operable to determine the memory allocation of at least one priority service as the preferred memory allocation of the priority service.

9. An apparatus as claimed in 7 or 8 further comprising means for determining a remaining memory capability by subtracting the memory allocation of the at least one priority service from the memory capability; and wherein the means for determining the memory allocation is further operable to determine the memory allocation of a plurality of non-priority acknowledge mode services by scaling of the preferred memory allocation of the non-priority acknowledge mode services in response to the remaining memory capability.

10. An apparatus as claimed in any previous claim wherein the memory capability associated with the user equipment comprises a buffer capability of the user equipment.

. . . e. .e... ' Be. ... : :e CE1 1362EP 11. An apparatus as claimed in claim 10 wherein the means for determining the memory capability is operable to receive the buffer capability from the user equipment.

12. An apparatus as claimed in any previous claim 10 to 11 further comprising means for transmitting the memory allocations to the user equipment.

13. An apparatus as claimed in any previous claim wherein the apparatus is a radio network controller.

14. An apparatus as claimed in claim 13 wherein the memory capability associated with the user equipment comprises a buffer capability of the radio network controller.

15. An apparatus as claimed in any previous claim wherein the means for determining the preferred memory allocation is operable to determine the preferred memory allocation of a second acknowledge mode service in response to a characteristic of the second acknowledge mode service.

16. An apparatus as claimed in claim 15 wherein the means for determining the preferred memory allocation is operable to determine the preferred memory allocation of the second acknowledge mode service in response to a predetermined association between the characteristic of the second acknowledge mode service and the preferred memory allocation of the second acknowledge mode service.

17. An apparatus as claimed in any of the previous claims further comprising means for rejecting a third acknowledge mode service of the plurality of acknowledge mode services. À .

CE1 1362EP 18. An apparatus as claimed in claim 17 wherein the means for rejecting is operable to reject the third acknowledge mode service if the combined preferred memory allocation exceeds the memory capability by more than a threshold.

19. An apparatus as claimed in claim 17 as dependent on any of the claims 4 to 6 wherein the means for rejecting is operable to reject the first acknowledge mode service if the scaling exceeds a threshold. i

20. A apparatus as claimed in any of the previous claims wherein the communication system is a 3rd Generation cellular communication system in accordance with specifications of the 3rd Generation Partnership Project.

21. A communication system comprising an apparatus as claimed in any of the previous claims.

22. A method of memory allocation for a cellular communication system I supporting a plurality of user equipment; the method comprising the steps of: determining a memory capability associated with a user equipment supporting a plurality of acknowledge mode services; determining a preferred memory allocation associated with each of the plurality of acknowledged mode services; determining a combined preferred memory allocation associated with the plurality of acknowledge mode services in response to the preferred memory allocation associated with each of the plurality of acknowledge mode services; and determining a memory allocation for each acknowledge mode service in response to the memory capability and the combined preferred memory i allocation.

: a: : : À:: À À . .: CE1 1 362EP 23. A computer program enabling the carrying out of a method according to claim 22.

24. A record carrier comprising a computer program as claimed in claim 23.