WO2010010009A2

WO2010010009A2 - Resource allocation method and apparatus thereof

Info

Publication number: WO2010010009A2
Application number: PCT/EP2009/059000
Authority: WO
Inventors: Rolf Sigle; Ingo Karla; Ingmar Blau; Gerhard Wunder
Original assignee: Alcatel Lucent
Priority date: 2008-07-23
Filing date: 2009-07-14
Publication date: 2010-01-28
Also published as: CN101635988A; WO2010010009A3

Abstract

The invention provides a resource assignment method in a first network element of a mobile communication system, the mobile communication system comprising a first and a second radio access technologies, the first radio access technology comprising a first base station with a first a resource, the second radio access technology comprising a second base station with a second resource, and a first and a second mobile stations coupled to the first base station, the method comprising: receiving a load indicator for each radio resource of each base station, wherein the load indicator is calculated by obtaining an equal slope of a utility function for each mobile station coupled to the first base station, wherein the utility function is a function of one resource; calculating a data rate parameter for each resource as a function of a channel gain, wherein the data rate parameter is a data rate per resource unit; selecting one resource for the first mobile station by obtaining a minimum of an arithmetic operation of the data rate parameters with the load indicators.

Description

Resource allocation method and apparatus thereof

Descri ption

Field of the invention

The invention relates to a resource allocation method in a mobile communications system, to a mobile station, to a base station, and to a computer program product.

Background and related art

In today's wireless scenarios new radio access technologies and their corresponding air interfaces are constantly designed and the mobile operators introduce the new wireless systems into the market. The legacy systems continue to have strong interest in being used and therefore, it is common to foresee scenarios where an operator is in charge of multiple air interfaces with overlapping coverage area. In dense human environments, the users of mobile stations are often in the coverage of a first radio cellular system, as for example GSM, and also in the coverage of a second radio cellular system as UMTS. In these cases, if services are offered independently of the radio access technology and as terminals may support multiple wireless standards, the mobile operator has the freedom to assign users to a cell and/or interface of its choice.

Therefore, there is a need of a resource allocation method in a first network element of the mobile communication system that comprises at least first and second radio access technology, to a mobile station, to a base station and to a computer program product.

Summary of the invention

The invention provides a resource assignment method in a first network element of a mobile communication system, the mobile communication system comprising a first and a second radio access technologies, the first radio access technology comprising a first base station with a first a resource, the second radio access technology comprising a second base station with a second resource, and a first and a second mobile station coupled to the first base station, the method comprising: receiving a load indicator for each radio resource of each base station, wherein the load indicator is calculated by obtaining an equal slope of a utility function for each mobile station coupled to the first base station, wherein the utility function is a function of one or more resources; calculating a data rate parameter for each resource or each set of resources as a function of a channel gain, wherein the data rate parameter is a data rate per resource unit; selecting one resource for the first mobile station by obtaining a minimum of an arithmetic operation of the data rate parameter with the load indicators. Embodiments of the invention are advantageous in that allow a resource assignment in heterogeneous networks or distributed implementations, that guarantees service for the voice users and maximizes the sum utility of the best effort users. It also allows to compare and weight the resources of different access technologies. Embodiments formulate the assignment as a utility maximization problem, constraining the resources of the individual air-interfaces, or the minimum data requirements.

The term 'base station' is understood herein as a radio network controller, or an access point, or any network element that serves as an access to the radio access technology or air interface. A base station can be adopted to service more than one cell and it can provide support for more than one radio access technology and/or frequency. A base station can thus provide a plurality of resources that can be assigned to users.

In embodiments of the invention the first resource of the first radio access technology is power and the second resource of the second radio access technology is bandwidth. The utility function defines a fairness-throughput tradeoff of resources for the set of mobile stations coupled to the first base station.

In embodiments of the invention the first network element is the first mobile station or the first base station, wherein the first and second resource are power or bandwidth.

In embodiments of the invention the method further comprises distributing the load indicator to a second network element carrying out the selecting step; wherein the second network element is the mobile station or the base station or a third network element.

In embodiments of the invention the data rate parameter is further the function of a transmitted power of the first base station, bandwidth, interference, modulation and coding schemes, a service type and type of resources requested by the first mobile station. In embodiments of the invention a utility is a throughput-fairness tradeoff is that can be continuously tuned between maximum-minimum fairness, where all mobiles are assigned equal data rates and between maximum throughput, where only few mobiles are assigned all available resources and achieve high data rates. In embodiments of the invention the load indicator and the data rate parameter are recalculated, if a third mobile station initiate transmission with the first base station or if channel conditions changes for at least one mobile station, or if a mobile station terminates transmission with a first base station.

In embodiments of the invention the utility function is a concave, positive and increasing function; wherein the load indicator is a dual variable of an optimization theory; wherein the arithmetic operation is a multiplication or a division.

In embodiments of the invention the selecting step is triggered with a predetermined frequency intervals or if a channel gain of one mobile station crosses a certain threshold or if a session has to be dropped or if a third mobile station is assigned to the same resource.

In another aspect, the invention relates to a network element for a mobile communication system being operable to perform a method according to any of the previous embodiments; wherein the network element is a base station or a mobile station.

In another aspect, the invention relates to a computer program product stored on a storage medium, comprising executable program means for causing a base station to perform a method according to any of the preceding embodiments when the program is run on the base station.

In another aspect, the invention relates to a computer program product stored on a storage medium, comprising executable program means for causing a mobile station to perform a method according to any of the preceding embodiments when the program is run on the mobile station. Brief description of the drawings

In the following preferred embodiments of the invention will be described in greater detail by way of example only making reference to the drawings in which:

Figure 1 shows a first block diagram of a mobile communication system,

Figure 2 shows a second block diagram of a mobile communication system,

Figure 3 shows a third block diagram of a base station and a mobile station,

Figure 4 shows a flowchart of a resource allocation method in a network element.

Detailed description

Fig. 1 shows a mobile communication system 100 including a first radio access technology 101 and a second radio access technology 102. The first radio access technology comprises a first base station 103 coupled to a core network 105 and the second radio access technology comprises a second base station 104 coupled to the same core network 105. The mobile communication system 100 also includes a first and a second mobile station 106 and 107 located within the cell areas of the first and the second base station 103 and 104. The first base station 103 comprises a first resource 108 that is distributed among all the mobile stations assigned to the first base station 103 and the second base station 104 also comprises a second resource 109 that is also distributed among all the mobile stations assigned to the base station 104.

When the first mobile station 106 requests a service, for example a voice or data service within a heterogeneous mobile communication system as the one represented in fig. 1 , it may choose between at least two resources belonging to the same or different base stations of the same or different radio access technologies or of same or different frequencies. The first radio access technology 101 may be, for example a system with the power as the distributable resource, and the second radio access technology 102 may be, for example a system with the bandwidth as the distributable resource. The mobile station may support both radio access technologies, as for example the TDMA-based GSM and the CDMA-based UMTS. These two types of radio access technologies are only examples, and any combination of other radio access technologies may be used.

The service requested by the first mobile station 106 may be either a service with fixed minimum data rate requirement, for example a voice service, or a service with fixed minimum data rate requirement, whereby a higher date rate - when available - is used by the service, for example a streaming service, or a unconstrained best effort data service, or a service with a mixture of such requirements. Services that specify a mixture of such requirements can be adapted to specific user requirements.

A network element calculates a load indicator for all radio resources 108 and 109 by obtaining the maximum of the sum utility of all the users that are assigned to the base station. At this maximum, all assigned users have the same utility slope; the slope represents the load indicator. The calculation of the load may be completed independently of the other steps, so that it can be used for the selection or reselection of a radio resource, for example when a service is started. It is also possible that a first network element calculates the load indicators for the resource of the first radio access technology, and a second network element calculates the load indicator corresponding to the resources of the second radio access technology.

The utility is a function of the radio resources, for example the power or the bandwidth of the individual radio access technologies and/or base stations. An alternative constraint of the mobile stations is the minimum data rate requirements of the services requested by the mobile station. In a further step, a data rate parameter is calculated for each radio resource and for each radio access technology of the mobile stations that are potentially reassigned. Each mobile station calculates its own set of data rate parameters for all base stations 103, 104. The data rate parameter is a function of the channel gain, service type and the type of resources requested by the mobile station. The load indicator and the data rate parameter are then used to choose and select one of the radio resources 108 and 109 of one of the base stations 103 and 104. Alternatively, the base stations receive the channel gains of the mobile stations and calculate the data rate parameters. The base stations may also measure the channel gains and calculate the data rate parameters.

The minimum of an arithmetic operation, that can be for example a multiplication or a division, between the data rate parameter and the load indicator, is used for the selecting step. Then, the resource is distributed among all the mobile stations coupled to the base station. This may require a redistribution of the previously assigned resources. The selection of the radio resources might be carried out after a service is requested. Further triggers, like e.g. crossing a threshold of the channel gain or dropping of the session, might trigger a reselection of the radio resources for the mobile. It is also possible that any other trigger affecting the load indicator might also trigger a reselection of the radio resources.

The load indicator calculated for each radio resource provides a way of comparison and a weight parameter for radio resources belonging to different radio access technologies and therefore for different types of resources, as it might be the power or the bandwidth. The utility function relates the assigned resources or data rates to a utility for each service type or user type, such as user satisfaction or earnings. This allows controlling the priorities between the services and the users. It can also be used to model the priorities of the system or to model the fairness-throughput tradeoff. The tradeoff may be implemented for mobile stations with a utility function that are able to handle different data rates; or for mobile stations with a fixed data rate requirement to be guaranteed by the system. Also, a combination of the service types is possible, with a flexible rate and a utility function and a guaranteed minimum data rate.

The utility function is a concave, positive and increasing function and the load indicator is the result of a dual variable of an optimization theory. The data rate parameter may also be a function of the transmitted power of the base station, the bandwidth, the inter-cell interference and intra-cell interference, the modulation and the coding schemes. The data rate parameter is a measure which data rate a user obtains per assigned resource unit.

The selection of the radio resources follows a problem formulation of the heterogeneous scenario in the convex form, and a decentralized algorithm within network elements of the communication system that solves the optimization problem and obtains simple assignment rules using the dual representation of the utility problem.

Fig. 2 shows the same mobile communication system 100 represented in fig. 1 including the reference of the elements of the drawing. In fig. 2, the first mobile station 106 has changed position to the left and the second mobile station 107 has further moved to the right. Also, a third mobile station 201 is requesting for one of the available services. As the channel conditions of the system have changed, including a new channel gain, the load indicators and the data rate parameters are recalculated. As a consequence, a new assignment of the resources is completed in order to achieve the optimum distribution of the resources.

If the channel conditions change quickly, triggers may be used to select new resources on a predetermined frequency basis, ensuring an optimum resource assignment for the mobile stations. The update and recalculation of the distribution of each of the resources between the mobile stations assigned to one of the resources is executed each time the channel gain of one of these mobile stations change, or when a user leaves or requests new services, as it is the case of a third mobile station 201. The reselection and selection of the radio resource is an independent step based on the data rate parameters for all candidate radio access technologies of one mobile station and the corresponding load indicators. On the other hand, the distribution of the radio resources is completed in all base stations. Alternatively, the distribution can be completed in an independent network element. This is based on the data rate parameters of all mobile stations assigned to that radio access technology. The network element that performs the calculations and the selection of the radio resource may be a base station, a mobile station, a third network element, or a combination of both mobile and base station. The base station may for example broadcast the load indicator to the mobile station and the mobile station may perform a whole set of data rate parameter calculations, one for each resource and complete the selection of the radio resource. If the base station or a third network element carries out the selection of the radio resource, the base station has to forward the load indicators to the corresponding network element (i.e. the neighbor's base stations controllers or a separate node) and no broadcast is necessary, and the mobile station, the base station or and independent third network element has to calculate the data rate parameter based on channel gains measured and reported by the mobile and forward it to the node carrying out the selection of the radio resources.

Fig. 3 shows a block diagram 300 comprising a first network element 301 adapted for coupling to a second network element 302. The first network element comprises the means for calculating a load indicator 303; the means for calculating a data rate parameter 304, the means for selecting the radio resource 305 and the computer program product 306. The first network element may be a base station or radio access network. The second network element may include the means for receiving the calculated load indicator 307, the means for calculating a data rate parameter 308, the means for selecting the radio resource 309 and the computer program product 310. The second network element may be a mobile station, a base station or a radio access network. Alternatively, a third network element not depicted in the figure 3 may comprise the means for selecting the radio resource 309.

Fig. 4 shows a flowchart of a resource allocation method in a network element of the mobile communication system. The mobile communication system comprises a first and a second radio access technology, each radio access technology comprises a base station, and each base station comprises at least a resource and is coupled to a set of mobile stations. The method in a first network element comprises calculating a load indicator in a first step 401 ; calculating data rate parameters in a second step 402 and selecting a radio resources in a third step 403. The first network element may be for example a base station or radio access network.

The method in the base station may include a fifth step where the load indicator is distributed to a second network element that carries out the selecting step. In this case, the method 400a in the second network element comprises receiving a calculated load indicator in a first step 401 a, receiving a calculated data rate parameter in a second step 402a, and selecting a radio resource in a third step 403a. The second network element may be a mobile station, a base station or a radio access network.

L ist of Referen ce N u m era l s

Claims

1. A resource assignment method in a first network element of a mobile communication system (100), said mobile communication system (100) comprising a first (101 ) and a second (102) radio access technologies, said first radio access technology (101 ) comprising a first base station (103) with a first a resource (108), said second radio access technology (102) comprising a second base station (104) with a second resource (109), and a first (106) and a second mobile station (107) coupled to said first base station (103), the method comprising:

- receiving a load indicator for each resource (108,109) of each base station (106,107), wherein said load indicator is calculated by obtaining an equal slope of a utility function for each mobile station (106) coupled to said first base station (103), wherein said utility function is a function of one resource;

- calculating a data rate parameter for each resource (108,109) as a function of a channel gain, wherein said data rate parameter is a data rate per resource unit;

- selecting one resource (108) for said first mobile station (106) by obtaining a minimum of an arithmetic operation of said data rate parameters with said load indicators.

2. The method of claim 1 , wherein said first resource (108) of said first radio access technology (101 ) is power and said second resource (109) of said second radio access technology (102) is bandwidth.

3. The method of claim 1 , wherein said utility function defines a fairness-throughput tradeoff of resources for said first (106) and second mobile station (107) coupled to said first base station (103).

4. The method of claim 1 , wherein said first network element is said first mobile station or said first base station, wherein said first and second resource are power or bandwidth.

5. The method of claim 1 , wherein said method further comprises distributing said load indicator to a second network element carrying out the selecting step; wherein said second network element is said mobile station or said base station or a third network element.

6. The method of claim 1 , wherein said data rate parameter is further said function of a transmitted power of said first base station (103), bandwidth, interference, modulation and coding schemes, a service type and type of resources requested by said first mobile station.

7. The method of claim 3, wherein in a utility a throughput-fairness tradeoff can be continuously tuned between maximum-minimum fairness, where all mobiles are assigned equal data rates and between maximum throughput, where only few mobiles are assigned all available resources and achieve high data rates.

8. The method of claim 1 , wherein said load indicator and said data rate parameter are recalculated, if a third mobile station initiate transmission with said first base station (103) or if channel conditions changes for at least one mobile station, or if said first base station (103) terminates transmission.

9. The method of claim 1 , wherein said utility function is a concave, positive and increasing function; wherein said load indicator is a dual variable of an optimization theory; wherein said arithmetic operation is a multiplication or a division.

10. The method of claim 1 , wherein said selecting step is triggered with a predetermined frequency intervals or if a channel gain of one mobile station crosses a certain threshold or if a session has to be dropped or if a third mobile station is assigned to the same resource.

11. A network element for a mobile communication system being operable to perform a method according to any of the claims 1 to 10.

12. The network element of claim 11 , wherein said network element is a base station or a mobile station.

13. A computer program product stored on a storage medium, comprising executable program means for causing a base station to perform a method according to any of the preceding claims 1 to 10 when the program is run on the base station.

14. A computer program product stored on a storage medium, comprising executable program means for causing a mobile station to perform a method according to any of the preceding claims 1 to 10 when the program is run on the mobile station.