WO2009054764A1

WO2009054764A1 - A method and a device for improved td-hsdpa radio resource handling

Info

Publication number: WO2009054764A1
Application number: PCT/SE2007/050783
Authority: WO
Inventors: Jie Mao; Jiuhui Du; Bin Xu
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2007-10-26
Filing date: 2007-10-26
Publication date: 2009-04-30
Anticipated expiration: 2010-04-26
Also published as: TW200922345A; CN101836490B; TWI436611B; CN101836490A

Abstract

A method for a TD-HSDPA system (100) with a NodeB (120) which controls traffic to and from user terminals, UEs (140), and with an RNC (110), for controlling radio resources in the system. Some radio Resource Units of a cell (130) are assigned by a NodeB (120), and the NodeB sets up (710) a connection between a UE and the system by establishing an RRC to the RNC. A first channel on a first frequency is established between the NodeB and the UE. An RAB, is established between the NodeB and the UE, and the NodeB recommends (725) the RNC a second frequency for the RAB. The NodeB performs a check (730) of the first frequency of the first channel and the second frequency recommended for the RAB, and if the two frequencies do not coincide, this information is sent (735) to the RNC.

Description

TITLE

A method and a device for improved TD-HSDPA radio resource handling.

TECHNICAL FIELD The present invention discloses a method and a device for improved radio resource handling in a wireless cellular access system of the Time Division High Speed Downlink Packet Access kind, TD-HSDPA.

BACKGROUND In modern cellular wireless access systems, use can be made of the High Speed Downlink Packet Access technology, commonly abbreviated as HSDPA. When HSDPA is applied in systems which use the Time Division Synchronous Code Division Multiple Access systems, the acronym TD- HSDPA is used for the technology in question.

Time Division - Synchronous Code Division Multiple Access, TD-SCDMA, is one of the standards within 3G₁ the third Generation mobile communication systems.

In similarity to systems which use the WCDMA, Wide-band Code Division Multiple Access, HSDPA, the TD-HSDPA technology uses link adaptation techniques such as AMC, Adaptive Modulation and Coding, and HARQ, Hybrid Automatic Repeat request, in order to enhance the capability of the TD-SCDMA RAN, Radio Access Network, to access packet services. TD- HSDPA is standardized within 3GPP, 3G Partnership Project, R5.

Within the TD-SCDMA technology, there is a specific multiple frequency technology known as N-carrier technology which is aimed at improving the system capacity and to optimize the power utilization/coverage balance between common timeslot and traffic timeslots in TD-SCDMA systems. In an N-carrier TD-HSDPA system, the RU assignment for a UE is managed by the Node-B of the cell to which the UE belongs at the moment. As an example of an RU assignment in a cell, mention can be made of the frequency or frequencies which is/are allocated for the HSDPA Radio Access Bearer, the RAB, which is a radio connection between the NodeB and an UE in a cell of the NodeB.

If we take the example of a UE which enters a cell, there is a need to establish and maintain a so called RRC link, Radio Resource Control, between the NodeB and its RNC before an RAB is established. Due to this need, a certain channel, a so called A-DCH, Assisted-DCH, which is used for signalling transmission for HSDPA RAB on a certain frequency is established prior to the HSDPA RAB, which, as will be explained later, results in a limitation of the RU assignment flexibility for NodeBs in N-carrier TD-HSDPA systems.

Turning now to the issue of problems which may be caused by current set up procedures in N-carrier TD HSDPA systems, take as an example a cell in a system in which the A-DCH is setup during the set up and connection procedures for the radio link, RL, and the RRC, procedures which take place prior to the RAB establishment.

During the RAB setup procedure, the NodeB of the cell will make a recommendation to its RNC regarding the radio resource units, RUs, of the (anticipated) HS-DSCH, i.e. the High Speed Dedicate Shared CHannel, a channel which is used for the HSDPA RAB. The recommendation will be based on, for example, the RU load status or on the RU priority setting, etc.

The recommendation will be feedback from the NodeB to the RNC in an information element, IE, of Radio Link Reconfiguration Ready. If the frequency which the NodeB anticipates using for the HS-DSCH RAB coincides with the frequency used for the A-DCH, the HS-DSCH RAB will be setup successfully. However, if the frequency which NodeB wants to use for HS-DSCH RAB does not coincide with the A-DCH frequency, an RU allocation conflict will occur. The NodeB will check the UE capacity to see if the UE in question can work simultaneously in all frequencies, and if this is the case, the HS-DSCH will be setup as recommended by the NodeB.

However, if this is not the case, the frequency of the A-DCH will be used as the bearer of the HS-DSCH, which means that the NodeB has to use the A- DCH frequency instead of its recommendation in the Radio Link Reconfiguration Ready, which will tie the A-DCH and the HS-DSCH to one frequency, which will result in a limitation of the RU assignment flexibility for the NodeB, i.e. for a NodeB in an N-carrier TD-HSDPA system.

Accordingly, UEs which can only operate on one frequency will limit the flexibility of current systems when it comes to frequency usage.

SUMMARY

Thus, as indicated above, there is a need for a solution by means of which a

NodeB in a wireless cellular access system in a better way than previously can establish the Radio Resource Control, the RRC, and the Radio Access Bearer, the RAB, particularly in an N-carrier TD-HSDPA system. The solution should offer the NodeB a greater degree of flexibility than previous solutions, particularly with regard to UEs which can only operate on one frequency simulatenously.

Such a solution is offered by the present invention in that it discloses a method for use in a wireless cellular access system of the Time Division High Speed Downlink Packet Access kind, TD-HSDPA, in which system there can be at least a first NodeB which serves to control the traffic to and from user terminals, UEs, within a cell in the system. The system in which the invention can be applied will comprise a Radio Network Controller, an RNC, for the control of at least part of the radio resources of the system, and at least some of the radio Resource Units, the RUs, of cells in the system are assigned by the NodeB of the respective cell.

According to the method of the invention, a NodeB sets up a connection between a UE and the system by establishing an RRC link, Radio Resource Control, to the RNC, in connection to which a first channel on a first frequency is established between the NodeB and the UE, following which a Radio Access Bearer, RAB, is established between the NodeB and the UE.

In addition, according to the inventive method, the NodeB recommends the RNC a second frequency for the RAB, and the NodeB will perform a check of the first frequency used for the first channel and the second frequency recommended for the RAB, and if the two frequencies do not coincide, this information is sent to the RNC.

Thus, by means of the invention, the RNC is notified if the frequency used for the first channel and for the RAB do not coincide, and in a preferred embodiment, the RNC uses the information about the non-coinciding frequencies to take a decision to "migrate" the frequency for the first channel to the recommended frequency for the RAB and also to release RUs which are associated with the first frequency.

In a preferred embodiment of the invention, the first channel is the A-DCH, Assisted Dedicated Cannel, and the RAB is suitably established in the HS- DSCH channel, High Speed Dedicated Shared Channel.

Also, in a particular embodiment of the invention, the information about the non-coinciding frequencies is sent to the RNC as an added field in an existing information element, IE. Suitably, the existing IE is an IE in the Radio Link Reconfiguration Ready. However, it is also possible to send this information to the RNC as a separate information element, IE.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail in the following, with reference to the appended drawings, in which

Fig 1 shows an overview of a system in which the invention may be applied, and Fig 2 shows some concepts used in this text, and

Figs 3 and 4 show event diagrams of prior art, and

Figs 5 and 6 show event diagrams of the invention, and

Fig 7 shows a schematic flow chart of a method of the invention, and Fig 8 shows a block diagram of a transceiver of the invention.

DETAILED DESCRIPTION

Fig 1 shows an overview of a system 100 in which the invention may be applied. As stated previously, the invention is intended mainly for a cellular wireless access system of the TD-HSDPA kind, a system which is the HSDPA (High Speed Downlink Packet Access) version of TD-SCDMA, Time Division Synchronous Code Division Multiple Access.

As shown in fig 1 , in such a system, referred to as 100 in fig 1 , there will be a geographical area, a cell, shown as 130 in fig 1 , within which there can be a number of user terminals, UEs, one of which is shown as 140 in fig 1. The number of UEs in a cell is variable, and the amount shown in fig 1 is merely an example intended to facilitate the reader's understanding of the invention.

As is also shown in fig 1 , the system 100 will also comprise at least one so called NodeB, shown as 120 in fig 1 , which serves to control the traffic to and from user terminals, UEs, within a cell such as the cell 130 in the system. In addition, the system 100 in which the invention may be utilized will also comprise at least one Radio Network Controller, an RNC 110, which serves to control at least part of the radio resources, the RUs of the system. Examples of RUs in a system such as the system 100 of fig 1 are frequencies, time slots, channelization codes etc.

Fig 2 is intended to illustrate some concepts which will be used in this text: in fig 2, the "chain" between the units of fig 1 is shown, i.e. UE - Node B - RNC. Shown next to this chain are the so called RRC 190, Radio Resource Control, and the RAB 160, Radio Access Bearer. The RRC is a protocol layer which is present in both the RNC and the UE, while the RAB is a data channel which will extend from the UE via the RNC to the CN, Core Network 117.

Fig 3 shows a possible event diagram in a system according to the prior art.

The numbers to the left of the arrows in the diagrams represent messages, and the numbers to the right of the boxes in the diagram represent brief explanations of the events. The numbers correspond to the following explanatory text:

Messages

1 : RRC Connection Setup Request

2: Radio Link Setup

3: Radio Link Setup Response 4: RRC Connection Setup Complete

5: RRC connection Setup Complete

6: Radio Link Reconfiguration Prepare

7: Radio Link Reconfiguration Ready

8: Radio Link Reconfiguration Commit

Events

11 : Prepare to establish A-DCH in frequency F1 12: A-DCH in F1

13: NodeB wants to establish HS-DSCH in F1 14: NodeB wants to establish HS-DSCH in F1 and F2 15: NodeB wants to establish HS-DSCH in /F1 , F2, F3) 16: HS-DSCH in F1

17: HS-DSCH in (F1 , F2) 18: HS-DSCH in (F1 , F2, F3)

As can be seen from fig 3, the result of the sequence shown in fig 3 is that A- DCH and HS-DSCH share the same frequency, in this case frequency F1 , with HS-DSCH also being used on other frequencies, i.e. F2 and F3. In such a case, i.e. when the two channels A-DCH and HS-DSCH share a frequency, the problem which the invention wishes to solve does not arise.

However, turning now to the sequence of event shown in fig 4, another possible outcome of the case when a UE wishes to set up a connection is shown. All messages and events in fig 4 which correspond to those in fig 3 have been given the same numbering. Thus, the only added event in fig 4 is the one with the reference number 13', which represents the case that the NodeB wants to establish HS-DSCH in frequency F2. As can be seen in fig 4, since F1 is used for A-DCH, the outcome of the sequence shown in fig 4 is that A-DCH and HS-DSCH is established in F2. Thus, A-DCH and HS-DSCH are established in two different frequencies, which will limit the RU (radio Resource Units) assignment flexibility for the NodeB.

One of the goals of the present invention is to ensure that the frequencies used for A-DCH and HS-DSCH will coincide. Thus, when the NodeB makes its recommendation to the RNC regarding the frequency which is to be used for the HS-DSCH, i.e. the channel used for the RAB, the NodeB will, prior to making the recommendation to the RNC, check which frequency that is being used for the A-DCH. If the NodeB notices that the two frequencies, i.e. the frequency for the A-DCH and the frequency recommended for the HS-DSCH, do not coincide, the NodeB will inform the RNC of this.

Suitably, in order to see to it that one and the same frequency is used for the A-DCH and the HS-DSCH, the RNC will use the information from the NodeB about the non-coinciding frequencies to take a decision to move or "migrate" the frequency for the first channel, i.e. the RRC, to the recommended frequency for the RAB, and to also release the radio resource Units, the RUs, which are associated with the frequency originally used for the A-DCH.

The information about non-coinciding frequencies for A-DCH and HS-DSCH is preferably sent from the NodeB to the RNC as an added element in an existing information element, IE, but the information may naturally also be sent to the RNC as a separate information element, IE. If an existing IE is used, the IE Radio Link Reconfiguration Ready is preferably the IE which is used.

Fig 5 shows a possible sequence of events in a system in which the invention is utilized. All messages and events which correspond to those shown in previous figures have retained their reference numerals from those figures. As can be seen, at "23", the NodeB recommends the RNC to establish HS- DSCH in frequency F2, which is a recommendation sent in the message Radio Link Reconfiguration ready. However, prior to sending this message the NodeB has, according to the invention, made a comparison between the frequency which it recommends for the HS-DSCH and the frequency which is being utilized for the A-DCH.

In this particular case, as is also evident from fig 5, the comparison shows that the two frequencies are not the same, i.e. they do not coincide. Thus, the NodeB informs the RNC of this, and the RNC may use this information in order to see to it that the two channels are established on one and the same frequency. This is shown at "24" in fig 5, where the NodeB prepares to establish the HS-DSCH in F2, and also prepares to shift the A-DCH to F2. This is done by the NodeB as the result of an instruction to that effect from the RNC, which may, for example, be received in the message Radio Link Reconfiguration Commit, "18" in figs 3-5. Thus, at "25" in fig 5, both A-DCH and HS-DSCH are established in F2. Also, the NodeB has released all RUs which were attached to the previous frequency of the A-DCH, i.e. F1.

Fig 6 shows a slight variation of the event diagram of fig 6. A-DCH is established in F1 , and the NodeB wishes to establish HS DSCH in F2 and F3, shown as "33" in fig 6. As with the previous examples, A-DCH is established in F1. Thus, at "33", the NodeB informs the RNC of this, and the RNC, at "34", recommends the NodeB to shift the A-DCH to frequency F3, which the RNC informs the NodeB of at "34" in the message Radio Link Reconfiguration Commit, "18", and at "35", the A-DCH is established in F3, and HS DSCH in F2 and F3.

Fig 7 shows a rough flow chart of a method 700 of the invention. Steps which are options or alternatives have been shown with dashed lines in fig 7. Thus, as shown in fig 7, according to the method 700 a NodeB sets up, as shown in step 710, a connection between a UE and the system by establishing an RRC link, Radio Resource Control, to the RNC.

In connection to this, as shown in step 715, a first channel on a first frequency is established between the NodeB and the UE, following which, step 720, a Radio Access Bearer, RAB, is established between the NodeB and the UE.

In addition to this, step 725, the NodeB recommends the RNC a second frequency for the RAB, and as shown in step 730, the NodeB checks the first frequency used for the first channel and the second frequency recommended for the RAB, and if these two frequencies do not coincide, this information is sent, step 735, to the RNC. As shown in step 740. in one embodiment of the invention, the RNC uses the information from the NodeB about the non-coinciding frequencies to take a decision to migrate the frequency for the first channel to the recommended frequency for the RAB, and to release RUs which are associated with the first frequency.

Step 745 shows that the first channel is preferably the A-DCH, the Assisted Dedicated Cannel. As shown in step 750, the RAB may in one embodiment of the invention be established in the HS-DSCH channel, the High Speed Dedicated Shared Channel.

Step 755 shows that the information about the non-coinciding frequencies is sent to the RNC as an added element in an existing information element, an IE, which may be the IE Radio Link Reconfiguration Ready. However, in another embodiment, this information may be sent as a separate information element, a separate IE.

Fig 8 shows a rough block diagram of a "base station" or a transceiver 800 of the invention, for use as a eNodeB as described above. As can be seen in fig

8, the eNodeB 800 of the invention comprises an antenna 810 for communicating with the UEs in one or more cell, and also comprises a transmitter 830 and a receiver 820 for said communication. In addition, the eNodeB 800 also comprises control means such as for example a microprocessor 840, as well as comprising a memory 850. In addition, the transceiver 800 may comprise an interface, "Int", 860, towards another node, such as the RNC.

The transceiver 800 basically comprises means for functioning according to the method described above, and is thus intended for use as a NodeB in a wireless cellular access system of the Time Division High Speed Downlink Packet Access kind, TD-HSDPA, and has means for: • controlling the traffic to and from user terminals, UEs, within a cell (130) in the system. These means may comprise the controller 840, the memory 850, the transmitter 830 and the antenna 810.

• communicating with a Radio Network Controller, an RNC (110), which controls at least part of the radio resources of the system. These means are suitably the interface 860, which may be assisted by, for example, the controller 840.

• assigning at least some of the radio Resource Units, the RUs, of a cell in the system. These means may comprise the controller 840, the memory 850, the transmitter 830 and the antenna 810.

• setting up a connection between a UE and the system by establishing an RRC link, Radio Resource Control, to the RNC. These means may comprise the controller 840, the memory 850, the transmitter 830 and the antenna 810. • establishing a first channel on a first frequency between the NodeB and the UE. These means may comprise the antenna 810, the receiver 820, the transmitter 830, the controller 840 and the memory 850.

• establishing a Radio Access Bearer, a RAB, between the NodeB and the UE. These means may comprise the antenna 810, the receiver

820, the transmitter 830, the controller 840 and the memory 850.

• recommending the RNC a second frequency for the RAB, which may be done via the interface "Int". 860.

In addition, the inventive NodeB comprises means such as the controller 840, and the memory 850 for performing a check of the first frequency used for the first channel and the second frequency recommended for the RAB, and if the two frequencies do not coincide, means such as the interface 860 and the controller 840 for sending this information to the RNC. In another embodiment, all or parts of the invention can be realized as computer executable software, SW, which may be stored on or in a storage media such as an optical or magnetic disc, magnetic tape, E-PROM or E²- PROM memories etc. If the invention, or parts of it, is/are realized as SW, the SW may also be stored on or in one or more node(s) in a system in which the invention is applied. For example, it would be possible to let nodes such as the RNC and the NodeB have the appropriate parts of the SW stored, and to let those nodes execute the SW during the operation of the system.

The invention is not limited to the examples of embodiments described above and shown in the drawings, but may be freely varied within the scope of the appended claims.

Claims

1. A method (700) for use in a wireless cellular access system (100) such as a Time Division High Speed Downlink Packet Access system, a TD-HSDPA system, in which system there can be at least a first NodeB (120) which serves to control traffic to and from user terminals, UEs (140), within a cell (130) in the system, the system also comprising a Radio Network Controller, an RNC (110), for control of at least part of the system's radio resources, in which system at least some radio Resource Units, RUs, of a cell (130) are assigned by the NodeB (120) of the cell (130), according to which method (700) a NodeB sets up (710) a connection between a UE and the system by establishing an RRC link, Radio Resource Control, to the RNC, in connection to which (715) a first channel on a first frequency is established between the NodeB and the UE, following which (720) a Radio Access Bearer, RAB, is established between the NodeB and the UE, and according to which method the NodeB recommends (725) the RNC a second frequency for the RAB, the method being characterized in that the NodeB performs a check (730) of the first frequency used for the first channel and the second frequency recommended for the RAB, and if the two frequencies do not coincide, this information is sent (735) to the RNC.

2. The method of (700, 740) claim 1 , according to which the RNC uses the information about the non-coinciding frequencies to take a decision to migrate the frequency for the first channel to the recommended frequency for the RAB and to release RUs which are associated with the first frequency.

3. The method (700, 745) of claim 1 or 2, according to which the first channel is the A-DCH, Assisted Dedicated Cannel.

4. The method (700, 750) of any of claims 1-3, according to which the RAB is established in the HS-DSCH channel, High Speed Dedicated Shared Channel.

5. The method (700, 755) of any of the previous claims, according to which said information is sent to the RNC as an added field in an existing information element, IE.

6. The method (700, 755) of claim 4, according to which the existing IE is Radio Link Reconfiguration Ready.

7. The method (700) of any of claims 1-4, according to which said information is sent to the RNC as a separate information element, IE.

8. A transceiver (800) for use as a NodeB (120) in a wireless cellular access system (100) such as a Time Division High Speed Downlink Packet Access system, a TD-HSDPA system, the transceiver (800) having means for: • controlling (840, 850, 830, 810) traffic to and from user terminals, UEs

(140), within a cell (130) in the system,

• communicating (860) with a Radio Network Controller, an RNC (110), which controls at least part of the system's radio resources,

• assigning (840, 850. 830, 810) at least some of said cell's (130) radio Resource Units, RUs,

• setting up (840, 850, 860, 810) a connection between a UE and the system by establishing an RRC link, Radio Resource Control, to the RNC,

• establishing (810, 820, 830, 840, 850) a first channel on a first frequency between the NodeB and the UE,

• establishing (810, 820, 830, 840, 850) a Radio Access Bearer, a RAB, between the NodeB and the UE,

• recommending (860) the RNC a second frequency for the RAB, the transceiver being characterized in that it comprises means (840, 850) for performing a check of the first frequency used for the first channel and the second frequency recommended for the RAB, and if the two frequencies do not coincide, for (840, 860) sending this information to the RNC.

9. The transceiver (800) of claim 8, in which the first channel is the A-DCH, the Assisted Dedicated Cannel.

10. The transceiver (800) of claim 8 or 9, which establishes the RAB in the HS-DSCH channel, the High Speed Dedicated Shared Channel.

11. The transceiver (800) of any of the claims 8-10, which comprises means for sending said information to the RNC as an added element in an existing information element, IE.

12. The transceiver of claim 11 , in which the existing IE is Radio Link Reconfiguration Ready.

13. The transceiver of any of claims 8-11 , which can send said information to the RNC as a separate information element, IE.