WO2009135499A1

WO2009135499A1 - Dynamic control channel structure for flexible spectrum usage

Info

Publication number: WO2009135499A1
Application number: PCT/EP2008/003627
Authority: WO
Inventors: Frank Frederiksen; Preben Mogensen
Original assignee: Nokia Siemens Networks Oy
Priority date: 2008-05-06
Filing date: 2008-05-06
Publication date: 2009-11-12

Abstract

The present invention relates to methods, apparatuses, a system, and a computer program product for providing access to a control channel of a wireless access network. A reference point is set or defined in at least one of a time domain and frequency domain, and at least one control parameter is signaled from the wireless access network to a wireless terminal device, wherein the at least one control parameter defines a location of a control channel allocated to the wireless terminal device within a broadcast signal. The at least one control parameter can be used at the wireless terminal device to derive the location of the allocated control channel within a broadcast signal.

Description

Dynamic Control Channel Structure for Flexible Spectrum Usage

FIELD OF THE INVENTION

The present invention relates to methods, apparatuses, computer program prod- ucts, and a system for providing access to a control channel in a wireless network environment.

BACKGROUND OF THE INVENTION

The performance of digital handsets generally has been improving over the years with respect to functionality, performance, and battery life. Handset performance is being addressed by the introduction of 3^rd generation (3G) technology, with higher data rates and better provision for new services. One key consideration is the need for the 3G networks to more than just coexist but handover active calls/data sessions with the current 2/2.5G networks. Where 3G coverage is absent, the user will need to utilize the 2/2.5G network, bringing with it the requirement for the phone to support both radio access technologies (RATs). For this reason, 3G phones often support at least two RATs.

Spectral resources in wireless communications systems are assigned to operators in a fixed manner. The scarce spectral resources could be used more efficiently if the assignment to the operators could be made with some flexibility.

Flexible Spectrum Use (FSU) aims at adapting the available spectrum to a network to reflect the changes on the number of subscribers as well as on daily traffic patterns. FSU should enable more versatile operation of the networks, for example, with varying traffic loads in the networks or with some operators providing more focused coverage than others. FSU should provide enough system flexibility towards geographical differences in regulatory spectrum assignments. FSU also aims at easing the deployment of multiple RATs at the launch of the system, even when spectrum is made available gradually according to increasing traffic demands. Such flexibility may turn out to be of particular importance for the systems requiring wide spectrum bands on frequencies suitable for efficient vehicular communications, e.g., below 6 GHz. Some approaches for flexible spectrum use (FSU) are presented in IST-2003-507581 WINNER D6.3 WINNER Spectrum As- pects: Assessment report, 2005, and in IST-2001-35125 OverDRiVE D13 Specification and Performance of Dynamic Spectrum Allocation.

The FSU concept allows multiple operators to share the same frequency spectrum in a decentralized manner using policy based radio resource optimization. It is expected to be implemented in decentralized and uncoordinated manner, where there will be a lot of independent base stations (BS), potentially belonging to different operators, which are not connected to each other, but on the other hand they are targeting at sharing the same physical spectrum resources according to certain policies. The problem of having such a flexible sharing of spectrum among several operators is that the users need to be informed on the current radio parameter configuration of the BS. Further, each user will need to know when and how to access the control channel whenever communication is needed between the BS and a mobile station (MS). This requires transmission of some broadcast information, which will typically be sent on a broadcast channel (BCH). Normally, the BCH is seen as a static entity, which is sent on a constant and periodical time- frequency resource and which will contain semi-static information - at least in typical cellular network configurations like for instance GSM (Global system for Mobile communication), UMTS (Universal Mobile Telecommunication System), and LTE (Long Term Evolution).

However, in FSU, it is expected that the used frequency resources change in a more frequent manner, such that a mechanism is needed to handle the time variability of the used cell system information. Otherwise, all users may be dropped from the system whenever the cell system parameters are changed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a mechanism for handling dynamic bandwidth adjustments without dropping existing users.

This object is achieved by a method comprising:

setting a reference point in at least one of a time domain and frequency domain; and

signaling at least one control parameter from a wireless access network to a wireless terminal device; wherein said at least one control parameter defines a location of a control channel allocated to said wireless terminal device within a broadcast signal.

Furthermore, at the other transmission end the above object is achieved by a method comprising:

• setting a reference point in at least one of a time domain and frequency domain;

• receiving at least one control parameter from a wireless access network; and

• using said at least one control parameter to derive a location of an allocated control channel within a broadcast signal.

Additionally, the above object is achieved by an apparatus comprising:

• setting means for setting a reference point in at least one of a time domain and frequency domain; and

• signaling means for generating at least one control parameter which defines a location of a control channel allocated to a wireless terminal device within a broadcast signal, and for signaling at least one control parameter from a wireless access network to said wireless terminal device.

Moreover, at the other transmission end the above object is achieved by an apparatus comprising:

• setting means for setting a reference point in at least one of a time domain and frequency domain;

• receiving means for receiving at least one control parameter from a wireless access network; and

• access control means for using said at least one control parameter to derive a location of an allocated control channel within a broadcast signal. - A -

The above methods may be implemented as a computer program product comprising code means for producing the respective above steps when run on a computer device.

The above apparatuses may be implemented as network elements or nodes, ac- cess devices, fixed or mobile terminal devices, or as modules, chips or chip sets provided in these nodes, elements or devices.

Accordingly, flexible and easy adjustment of data channel bandwidth can be provided without the need to inform other terminal devices about the change of sys- tern bandwidth. Basically, control bandwidth and data bandwidth are disconnected, which allows for the needed flexibility. Dynamic bandwidth adjustments can be handled without dropping existing users in the system. An access device (e.g. base station or the like) can change the borders of resource allocation (as long as the reference point is kept constant), as the terminal device will search for alloca- tion grants from a set of candidates which are defined from the reference point. In this way, it is possible for the access device to change spectrum usage according to various access conditions, e.g. current load condition. In addition, minimum impact is provided to the majority of terminal devices when an access device changes the used system bandwidth.

A kind of fixed control channel definition can thus be provided to all connected terminal devices while at the same time allowing for relatively fast updates of the used system bandwidth. Furthermore, each control channel can be self-defined based on some initial parameters. The definition of the control channel can de- pend only on the starting or reference point (and not on the currently used bandwidth), and a marginal or minimal scheduling of the control channel can be provided.

The allocated control channel may be provided in an at least temporarily fixed pattern of control channels allocated to terminal devices connected to the wireless access network. It may point to at least one physical resource provided for data transmission, e.g. uplink transmission and/or downlink transmission.

In a specific example, the control parameter may be adapted to define the location of the control channel relative to a location of a broadcast channel or relative to a predetermined system offset signaled over the broadcast channel. Further advantageous modifications are defined in dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described based on embodiments with reference to the accompanying drawings in which:

Fig. 1 shows a schematic diagram indicating a network architecture in which the present invention can be implemented;

Fig. 2 shows schematic block diagrams of a terminal device and an access device according to embodiments of the present invention;

Fig. 3 shows a flow diagram of a transmitting-end processing according to an embodiment of the present invention;

Fig. 4 shows a flow diagram of a receiving-end processing according to an embodiment of the present invention;

Fig. 5 shows a schematic representation of a control channel structure according to an embodiment; and

Fig. 6 shows a schematic block diagram of a software-based implementation according to an embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENT

In the following, embodiments of the present invention will be described based on an FSU system with broadcast control channel in a wireless communication network.

Fig. 1 shows a schematic diagram of a general network architecture in which the present invention can be implemented. A radio access network 300, e.g., a cellular Universal Mobile Telecommunications System (UMTS) Terrestrial Access Network (UTRAN) according to the Long Term Evolution (LTE) or 3^rd Generation Partnership Project (3GPP) Release 8 standard, provides access to a user equipment (UE) or - more generally - a MS 10 via a first access device 20, such as a GSM and/or UMTS base station device (e.g. Node B) of a first operator, and a second access device 30, such as an enhanced Node B (eNB) according to LTE of a second operator. It is noted that other access devices can be provided, which are not shown here.

In an embodiment, a control channel structure is defined and provided e.g. for the downlink direction from the radio access network 300 to the UE 10, which control channel allows for a variable number of control channels to exist independent of the used bandwidth. The intention is to have a concept which will provide minimum impact to the majority of MS's when an access device (e.g. BS or the like) changes the used system bandwidth. As such the introduced concept will sacrifice frequency diversity on the control channel for a unitary definition of physical resources defined for each control channel. More specifically, the control channel is suggested to be defined relative to a reference point (in the time or frequency domain) instead of relative to the total used bandwidth.

From a conceptual level, it is assumed that an access device will be able to adjust the used system bandwidth in a dynamic manner. Thus, the proposed control channel layout is configured to provide a fixed definition to all connected MSs while at the same time allowing for relatively fast updates of the used system bandwidth. Requiring all connected MSs to simply decode the broadcast channel all time would significantly increase power consumption of the connected MSs - especially if they are only needing traffic on a seldom basis (e.g., voice over internet protocol - VoIP).

According to the embodiment, each control channel is adapted to be self-defined based on some initial parameters (that is, for example, relative to the location of the BCH or relative to a given system offset which could be communicated/indicated over the BCH or any other suitable parameter).

Fig. 2 shows schematic block diagrams of a terminal device or terminal (e.g. the MS 10) and a network node or network device (e.g. first or second access devices 20, 30) according to the embodiment of the present invention. At the MS 10, a received information is checked by a parameter detection (PD) functionality or unit 15 for provision of a predetermined access control parameter, e.g., based on a predetermined bit pattern, location, or other dedicated characterizing feature of a received data stream. The parameter detection functionality or unit 15 may be provided as a part of an RRC functionality which controls reception operation of a receiver part of a radio frequency (RF) front-end unit 16 which enables wireless transmission and reception via an antenna. A detected access control parameter is forwarded to an access controller or control unit 14 which derives the allocated control channel based on the access control parameter and under consideration of a pre-defined reference point which has been set previously or which is pro- vided as a default parameter.

At the first and second access devices 20, 30, the access control parameter is selected or set in a signaling functionality or unit (Sl) 22 which is controlled by a control parameter functionality or unit (CP) 21 , e.g., in response to a correspond- ing control input which could for example be supplied by the network operator or stored in a suitable memory device (not shown). The control parameter is incorporated in or added to a control message (e.g. in an access control message or any other suitable message or signaling) in a message control information (MCI) functionality or unit 23 and transmitted via an RF front-end unit 24 and an antenna.

Fig. 3 shows a flow diagram of a transmitting-side processing according to an embodiment of the present invention, which could be implemented based on a processing routine in the MS 10 for uplink transmissions or in the access devices 20, 30 for downlink transmissions.

In step S101 , a control channel is allocated or an allocated control channel is determined based on a received or set information. Then, in step S102, the access control parameter is determined based on the allocated control channel and the pre-defined reference point. Finally, in step S103, the access control parameter is signaled in a suitable message to the other transmission end, and it is checked in step S102 whether a sharing indicator is provided. The access control parameter may be part of a dedicated access control signalling to the other transmission end.

Fig. 4 shows a flow diagram of a receiving-side processing according to an embodiment of the present invention, which could be implemented based on a proc- essing routine in the MS 10 for downlink transmissions or in the access devices 20, 30 for uplink transmissions.

In step S101 , the access control parameter is detected in a received message or data stream. Then, in step S102, an allocated control channel is derived from the access control parameter based on the pre-defined reference point. Finally, in step S103, the allocated control channel is accesses to derive transmission resources to be used for network connections. Fig. 5 shows a schematic representation of a control channel structure according to an embodiment. As can be gathered from this representation, a set of vertically stacked control channels is indicated on the left side next to a stack of available physical user payload resources which may correspond to different frequencies, channels, time slots, codes, which each points to a set of physical resources for data transmission. In Fig. 5, the vertical direction may thus correspond to the frequency domain, time domain, code domain or any other domain suitable to differentiate channels and transmission resources. Additionally, the first block in Fig. 5 may represent a set of resources that are constructed using any combination of time, frequency, and code domains. In Fig. 5, a first control channel C1 is defined, which starts directly after the reference point and which points to the similarly vertically hatched resource regions. Additionally, a successive second control channel C2 is defined which points to similar non-vertically hatched resource regions. Fur- ther, it should be observed that each of the control channels may contain a number of sub-channels each capable of pointing to similar non-vertically hatched resource regions. Such a configuration allows to define a set of mother control channel regions, where each mother control channel can carry multiple subchannels for control.

In the embodiment, it is expected that a reference point is defined in the time/frequency domain such that each MS listening for the broadcast channel can drive where its allocated or a desired control channel 'starts'. Given this information, the control channels can be defined in a manner suitable to be derivable from the signalled access control parameter. As an example for the frequency domain, the control channels may be defined in a linear manner with increasing/decreasing frequency, such that one control channel element is not scattered over a large bandwidth. This concept provides the advantage that the definition of the control channel is only dependent on the starting or reference point (and not on the cur- rently used bandwidth), and a marginal or minimal scheduling of the control channel can be provided (as long as channel quality information for different MS is available at the respective access device). To alleviate the problem of less frequency diversity, the proposed concept could be operated in small scale environments where coverage is less of an issue.

Further, by knowing the reference or starting point of the control channel structure, it is still possible to employ increased coding on top of this such that a control channel for a single user can be constructed by using aggregation of multiple elements for a single control channel.

As indicated above, the proposed channel access concept can be applied to both uplink and downlink allocations, so that the borders of allocation can be adjusted (as long as the reference point is kept constant). Allocation grants can be searched from a set of candidates which are defined from the reference point. In this way it is possible to change the spectrum usage according to the current load or other channel conditions.

It should be noted that this structure for the control channel will require some overhead of the control channel, as each single control channel should be able to address the full potential used system bandwidth, while schemes with more information on the actually used bandwidth will be able to utilize more compression on the signalling.

In the example of Fig. 5, other control channel(s) could be added above the C2 allocation, if a new user is added in the system. If the used bandwidth is to be reduced for the current active access device, control channel(s) above the non- vertically hatched area could be omitted, so as to reduce data payload carriers (resources) accordingly.

Fig. 6 shows a schematic block diagram of an alternative software-based implementation of the above embodiment and its implementation examples for achiev- ing a dynamic control channel structure. The required functionalities can be implemented in a processing unit 210, which may be any processor or computer device with a control unit which performs control based on software routines of a control program stored in a memory 212. The control program may also be stored separately on a computer-readable medium. Program code instructions are fetched from the memory 212 and are loaded to the control unit of the processing unit 210 in order to perform the processing steps of the above functionalities of Figs. 2 to 4, which may be implemented as the above mentioned software routines. The processing steps may be performed on the basis of input data Dl and may generate output data DO. At the transmitting side the input data Dl may cor- respond to a desired control channel allocation to be signalled by the access control parameter, and at the receiving side the input data Dl may correspond to the received data stream or message. Furthermore, at the transmitting side the output data DO may correspond to a message or signalling with the added access control parameter and at the receiving side the output data DO may correspond to the derived control channel.

Consequently, the above embodiments may be implemented as a computer pro- gram product comprising code means for generating each individual processing step when run on a computer device or data processor of the first and second access devices 20, 30 or terminal device (e.g. MS 10), respectively.

In summary, methods, apparatuses, a system, and a computer program product for providing access to a control channel of a wireless access network have been described. A reference point is set or defined in at least one of a time domain and frequency domain, and at least one control parameter is signaled from the wireless access network to a wireless terminal device, wherein the at least one control parameter defines a location of a control channel allocated to the wireless terminal device within a broadcast signal. The at least one control parameter can be used at the wireless terminal device to derive the location of the allocated control channel within a broadcast signal.

It is apparent that the invention can easily be extended to any transmission link for any kind of wireless network which supports usage of control channels. Specifically, the present invention is not intended to be restricted to cellular networks. The embodiment may thus vary within the scope of the attached claims. Furthermore, while the invention has been described mainly for the case of access devices 20, 30 and the MS 10 is a terminal device, other devices can take the re- spective role as well.

Claims

1. A method comprising:

a) setting a reference point in at least one of a time domain and frequency domain; and

b) signaling at least one control parameter from a wireless access network (300) to a wireless terminal device (10);

c) wherein said at least one control parameter defines a location of a control channel allocated to said wireless terminal device within a broadcast signal.

2. A method comprising:

a) setting a reference point in at least one of a time domain and frequency domain;

b) receiving at least one control parameter from a wireless access network (300); and

c) using said at least one control parameter to derive a location of an allocated control channel within a broadcast signal.

3. The method according to claim 1 or 2, wherein said allocated control channel is provided in an at least temporarily fixed pattern of control channels allocated to terminal devices connected to said wireless access network (300).

4. The method according to any one of the preceding claims, wherein said control parameter defines the location of said control channel relative to a location of a broadcast channel or relative to a predetermined system offset signaled over said broadcast channel.

5. The method according any one of the preceding claims, wherein said allocated control channel points to at least one physical resource provided for data transmission.

6. The method according to claim 5, wherein said data transmission is an uplink transmission.

7. The method according to claim 5, wherein said data transmission is a downlink transmission.

8. An apparatus comprising:

a) setting means for setting a reference point in at least one of a time domain and frequency domain; and

b) signaling means for generating at least one control parameter which defines a location of a control channel allocated to a wireless terminal de- vice (10) within a broadcast signal, and for signaling at least one control parameter from a wireless access network (300) to said wireless terminal device (10).

9. An apparatus comprising:

a) setting means for setting a reference point in at least one of a time domain and frequency domain;

b) receiving means for receiving at least one control parameter from a wireless access network (300); and

c) access control means for using said at least one control parameter to derive a location of an allocated control channel within a broadcast signal.

10. The apparatus according to claim 8 or 9, wherein said allocated control channel is provided in an at least temporarily fixed pattern of control channels allocated to terminal devices connected to said wireless access network (300).

11. The apparatus according to any one of claims 8 to 10, wherein said control parameter defines the location of said control channel relative to a location of a broadcast channel or relative to a predetermined system offset signaled over said broadcast channel.

12. The apparatus according any one of claims 8 to 11 , wherein said allocated control channel points to at least one physical resource provided for data transmission.

13. The apparatus according to claim 12, wherein said data transmission is an uplink transmission.

14. The apparatus according to claim 12, wherein said data transmission is a downlink transmission

15. A computer program product comprising code means for generating the steps of method claim 1 or 2 when run on a computer device.

16. A system for providing access to a control channel, said system comprising at least one apparatus according to claim 8 and at least one apparatus according to claim 9.

17. A network access device comprising an apparatus according to claim 8 or 9.

18. A mobile terminal device comprising an apparatus according to Claim 8 or 9.

19. A chip device comprising an apparatus according to claim 8 or 9.