WO2010121642A1

WO2010121642A1 - Method and device for transmitting allocation information based on a received channel quality report

Info

Publication number: WO2010121642A1
Application number: PCT/EP2009/054646
Authority: WO
Inventors: Hans Thomas Hohne; Xin Qi
Original assignee: Nokia Siemens Networks Oy
Priority date: 2009-04-20
Filing date: 2009-04-20
Publication date: 2010-10-28

Abstract

A method for data processing in a first access point is suggested, wherein the first access point conveys an allocation information to a second access point (e.g. mobile station), wherein said allocation information is based on at least one channel quality report provided by the second access point and wherein the allocation information is encoded as a function of the at least one report comprising in particular band indices. Furthermore, a device and a communication System is suggested comprising said device.

Description

METHOD AND DEVICE FOR TRANSMITTING ALLOCATION INFORMATION BASED ON A RECEIVED CHANNEL QUALITY REPORT

The invention relates to a method and to a device for data processing in an access point.

Mobile communication systems utilize time-frequency allocations. Localized (adjacent) subcarrier allocation is a concept enabling frequency selective scheduling (FSS) and promises efficiency gains of up to 40% over distributed (permu- tated) subcarrier allocations.

Those gains can be achieved if the channel state in downlink (DL) direction is, e.g., signaled by a mobile station (MS) to a base station (BS) , and the MS is informed in return by the BS on what bands to expect data.

Because of the time delay required for such signaling, channel state information may become outdated. Hence, in environments with a moving transmitter or a moving receiver, moving even at a moderate speed, an actual gain in efficiency may be rather difficult to achieve. On the other hand, some use cases of OFDMA systems include stationary access points (APs) . Regarding, e.g., a connection between a BS and a relay, the channel change will be slow and high and persistent data volumes can be expected. Also, a laptop user connected to a BS may hardly move and may utilize a broadband connection for streaming or for downloading purposes.

The problem to be solved is to overcome the disadvantages pointed out before and in particular to reduce a traffic required for allocation signaling purposes. It is also suggested as how to reduce an amount of reported bands.

This problem is solved according to the features of the inde- pendent claims. Further embodiments result from the depending claims . In order to overcome this problem, a method for data processing in first access point is suggested,

- wherein the first access point conveys an allocation information to a second access point, wherein said allocation information is based on at least one report provided by the second access point;

- wherein the allocation information is encoded as a function of the at least one report comprising in particular band indices.

Hence, the at least one report conveys information that can be used for addressing allocation information.

This approach bears the advantage that the allocation infor- mation conveyed via an allocation message towards the first access point needs a reduced amount of data and thus reduces the signaling overhead.

The approach provided is in particular applicable to a mobile communication system with low channel variability, but high bandwidth request.

It is noted that the allocation information may comprise a frequency allocation, a band allocation and/or a channel al- location.

E.g., if the second access point (e.g., a mobile station) reports that five bands have good channel quality, e.g., sending a report comprising " [bl b2 b3 b4 b5]", the first access point (e.g., a base station) may use that report to indicate an allocation " [r2 r3]" by conveying a corresponding allocation message indicating that band 2 and band 3 have been allocated.

In an embodiment, the allocation information comprises a relative address information pursuant to the at least one report . The relative address information is in particular fed back from the second access point via said at least one report.

In a further embodiment, the function comprises a bitmap in particular indicating which of reporting bands is/are used.

It is also possible to indicate such bands that are not used or combinations of used and/or unused bands.

In a next embodiment, the at least one report comprises a sequence number.

The sequence number can be used for differentiating messages and to avoid a mix-up of messages. For example, the sequence number may be realized by one bit only.

It is also an embodiment that the allocation information comprises a sequence number.

Hence, a sequence number, in particular a sequence numbering scheme can be applicable for the allocation information and/or for the reports.

Pursuant to another embodiment, a channel report table is maintained based on the at least one report provided by the second access point.

The channel report table may be realized as any memory means (temporarily or persistently) storing data provided by said reports. The channel report table may preferably represent the latest status of the information conveyed by the reports.

According to an embodiment, the at least one report is based on a channel measurement determined by the second access point.

Such channel measurement may comprise a channel quality indicator information. According to another embodiment, the allocation information is based on a sequence conveyed with the at least one report.

Hence, such sequence can be used as a coding scheme to inform the second access point about the changes regarding an allocation conducted.

In yet another embodiment, the first access point and/or the second access point is one of the following components:

- a base station;

- a mobile station;

- a gateway;

- a relay station; - a network element of a communication system, in particular of a mobile communication system.

It is noted that the base station can be any base station conveying information towards at least one network element, e.g., towards at least one mobile station. The base station may be a NodeB, an eNodeB or any access point with a radio interface that can be utilized by the mobile terminal. It is also noted that the mobile station or the mobile terminal referred to may be any mobile device with a radio interface, in particular any mobile phone, UE, personal digital assistant, computer or processing unit.

It is further noted that the first access point may be a base station and the second access point may be a mobile station.

According to a next embodiment, the allocation information is an absolute allocation information or a relative allocation information indicating a difference with regard to a previous allocation information or with regard to a previous report.

Pursuant to yet an embodiment, the at least one report comprises an absolute information or an incremental and/or dif- ferential information indicating a difference with regard to at least one previous report.

According to another embodiment, a flag indicates whether the information is a relative information or an absolute information .

The problem stated above is also solved by a device comprising a and/or being associated with a processor unit and/or a hard-wired circuit and/or a logic device that is arranged such that the method as described herein is executable thereon .

According to an embodiment, the device is a communication de- vice, in particular a or being associated with a network element, an access point, a base station, a mobile station or any combination thereof.

The problem stated supra is further solved by a communication system comprising the device as described herein.

Embodiments of the invention are shown and illustrated in the following figures:

Fig.l shows a message chart illustrating channel measurements that are conveyed as a report from one access point to another and an allocation information being processed based on said report and conveying a corresponding allocation message (MAP) back to the first access point;

Fig.2 visualizes an example for aggregated reporting by depicting in turns downlink frames (DL) and uplink frames (UL) .

According to the approach provided, a frequency allocation information is encoded as a function of one or more channel reports . As an option, a channel report table can be set up or built in an incremental manner over time.

Fig.l shows a message chart illustrating channel measurements that are conveyed as a report from one access point to another and an allocation information being processed based on said report and conveying a corresponding allocation message (MAP) back to the first access point.

According to Fig.l, an access point API conveys a message 101 to an access point AP2 comprising, e.g., a preamble. The access point AP2 determines a channel quality indicator CQI and sends a message 102 back to the access point API comprising, e.g., a report of said CQI information. Based on said message 102, the access point API conducts a frequency allocation, wherein the allocation information is a function (fct) of the message 102, i.e.:

allocation info = fct (report) .

Said allocation information is conveyed via a message 103 to the access point AP2.

Each access point can be a network component, e.g., a mobile station or a base station. According to a particular example, the access point API can be a base station and the access point AP2 can be a mobile station.

First exemplary implementation

In an exemplary implementation, the function "allocation info = fct (report) " shown in Fig.l is a bitmap indicating which of the reported bands are to be used. In order to make the sys- tern robust against errors, sequence numbers can optionally be attached to reports as well as to allocations. When the access point API assigns bands via a bitmap, the sequence number attached to the allocation can refer to the report that the access point API has received from the access point AP2, which had the same sequence number.

Hereinafter, examples are shown for further illustration purposes. According to these particular examples, the access point API is a base station (BS) and the access point AP2 is a mobile station (MS) .

(a) Basic Scenario:

- The MS sends a report with a sequence number (seqNo) .

- The BS makes a frequency allocation and it conveys the allocation message MAP (see reference 103 in Fig.l) to the MS utilizing this seqNo.

- The MS sends a subsequent report utilizing an incremented sequence number seqNo+1.

(b) Stable channel, varying allocations (utilizing the se- quence number seqNo conveyed to the BS via report 102) :

- The MS sends a report with a seqNo.

- The BS makes a frequency allocation and it conveys the allocation message MAP (see reference 103 in Fig.l) to the MS utilizing this seqNo. - The BS makes a frequency allocation and it conveys the allocation message MAP to the MS utilizing this seqNo .

- The BS makes a frequency allocation and it conveys the allocation message MAP to the MS utilizing this seqNo.

(c) Nothing to allocate (hence, the BS may only increment the seqNo in case the MS conducted an allocation and has informed the BS accordingly) :

- The MS sends a report with a seqNo. - The BS makes a frequency allocation and it conveys the allocation message MAP (see reference 103 in Fig.l) to the MS utilizing this seqNo.

- The MS sends a report with a seqNo+1. - The MS sends a report with a seqNo+1.

- The BS makes a frequency allocation and it conveys the allocation message MAP (see reference 103 in Fig.l) to the MS utilizing this seqNo+1.

Error Behavior

In case the access point API does not receive the report 102 from the access point AP2, the access point API may continue to use the previous report (seqNo-1) . The access point AP2 then interprets the allocation bitmap with respect to the previous report.

Report band indices can be sent as MAC management messages and can thus be encapsulated with a cyclic redundancy check (CRC) .

Hereinafter, a message sequence is shown for the scenario of a lost report:

(d) Report of MS got lost:

- The MS sends a report with a seqNo.

- The BS makes a frequency allocation and it conveys the allocation message MAP (see reference 103 in Fig.l) to the MS utilizing this seqNo. - The MS sends a report with a seqNo+1; this report has been lost.

- The BS makes a frequency allocation and it conveys the allocation message MAP to the MS utilizing the sequence number seqNo. - The MS sends a report with a seqNo+1.

- The BS makes a frequency allocation and it conveys the allocation message MAP to the MS utilizing this seqNo+1. Gain with respect to direct signaling

The gain for the signaling suggested may depend on several parameters .

If, e.g., 12 bands are available for allocation purposes and if a channel report from the access point AP2 indicates the 5 best bands, then 12 bits can be used for addressing the bands for allocation (in addition to 4 bits for signaling a bitmap- allocation method if implemented as defined, e.g., in IEEE 802.16eRev2/D7, chapter 6.3.2.3.38.6.2).

The approach suggested herein may utilize 5 bits for indexing and 1 bit for sequence numbering. This results in a reduction of 50% (or 1-6/16 = 62.5%) of the signaling overhead.

The effect of saving bits is of significant advantage, in particular because - it improves spectral efficiency;

- even 4 bits make already 1/3 of a slot for some modulation and coding scheme (MCS) ;

- the gains become larger, if more bands are reported or (to be) allocated, resulting in an improved and more efficient FSS;

- in case of a long-lasting data connection of high data volume, which could be allocated in a time- persistent fashion, all overhead for allocation lies in the band allocation information; - as any FSS gain depends on an accuracy of the band information and employing FSS requires balancing a trade-off between overhead for reports and gains from scheduling, the suggested scheme allows for more frequent updates with the same amount of overhead, and thus enables higher FSS gains. Implementation with regard to IEEE 802.16e

For allocation purposes, a new message may be defined. As an alternative, the existing compact allocation message MAP may be changed to indicate that Nband=15 indicates that the proposed scheme is in use, and one of the reserved bits after the "allocation mode" field may be used as sequence number. Or, Nband=15 may indicate the proposed scheme in use and a sequence number seqNo amounting to 0, whereas Nband=14 may indicate the scheme and a sequence number seqNo amounting to 1.

Compatibility with IEEE 802.16m

In 802.16m, allocation messages MAP refer to one user only.

The approach provided herewith does not interfere with such a solution .

ALTERNATIVE IMPLEMENTATION

According to another embodiment, the access point AP2 and the access point API may build a "report table" in an incremental fashion .

For example, the access point AP2 after having determined that bands 1 to 3 have not been changed, but band 4 has become stronger than before, is able to only convey the essential information.

The access point API collects the reports, and its allocation information is based on an aggregate of the reports from the access point AP2.

Fig.2 visualizes an example for aggregated reporting by de- picting in turns downlink frames (DL) and uplink frames (UL) .

The access point AP2 may convey the uplink frames to the access point API thereby providing reports to said access point API. The access point API conveys downlink frames to the access point AP2.

For example, a report 1 tells that bands [bl b2 b3] have ranks [1 2 3], and a report 2 tells that band [b6 b4] have now rank [1 4], replacing band [bl] and adding band [b4] . Then, the access point API will update its internal table to [b6 b2 b3 b4] comprising ranks [1 2 3 4] and may indicate in the next allocation message MAP to the access point AP2 that this access point AP2 should use [b6 b3] by sending a bitmap [1 0 1 0].

Therefore, an extra "absolute" flag in the reports and allocation messages can be utilized to indicate whether the re- port is absolute or incremental, and whether the allocation is referring to an absolute or incremental report.

Error Prevention

A set of rules can be established to make sure both sides

(i.e., access points) know, which bands are meant regarding allocation and/or reporting.

(1) In case the access point AP2 indicates an incremental report, but the access point API has no knowledge of an absolute report, the access point API shall send an allocation message with the absolute flag set thereby requesting an absolute report from the access point AP2.

As an option, a report response REP-RSP could be requested with an empty allocation without any reference to a report. This may indicate to the access point AP2 that an absolute report is required by the access point API.

(2) In case the access point AP2 receives an absolute allocation, but its last report was a relative one, the sub- sequent report issued by the access point AP2 could be an absolute report.

(3) The access point AP2 may send a relative report only in case it has received an absolute allocation message with a correct sequence number.

(4) The access point AP2 may only send a relative report subsequent to an allocation message obtained by the ac- cess point API.

In case more than 1 bit is used for the sequence number seqNo, the access point AP2 could send more reports without having to wait for the allocation message being conveyed by the access point API.

(5) In case the access point AP2 loses an allocation, it may next send an absolute report.

Hereinafter, examples are shown for further illustration purposes. According to these particular examples, the access point API is a base station (BS) and the access point AP2 is a mobile station (MS) . As stated above, there are two types or reports and/or allocation messages identified as "reset" (also referred to as "absolute" type) and "update" (also referred to as "relative" type) types, wherein the respective type could be indicated by a flag (e.g., 1 bit) .

(a) Basic scenario, varying allocation, the BS uses the lat- est received report:

- The MS sends a reset report.

- The BS makes a frequency allocation and it conveys the allocation message "reset alloc" (indicating an absolute allocation based on the reset report ob- tained by the MS) to the MS.

- The BS makes a frequency allocation and it conveys the allocation message "reset alloc" (indicating an absolute allocation based on the reset report obtained by the MS) to the MS.

- The MS sends an update report indicating the relative changes based on its previous reset report. - The BS makes a frequency allocation based on the update report and it conveys the allocation message "update alloc" (indicating the relative allocation conducted based on the update report) to the MS.

(b) Nothing to allocate (the MS cannot send two updates without any BS allocation in between; example chosen for a sequence number seqNo of 1 bit) :

- The MS sends a reset report with a sequence number (seqNo) . - The BS makes a frequency allocation and it conveys the allocation message "reset alloc" (indicating an absolute allocation based on the reset report obtained by the MS) to the MS utilizing this seqNo.

- The MS sends an update report with a seqNo+1 indicat- ing the relative changes based on its previous reset report .

- The MS sends a reset report with a seqNo+1 (as there is no allocation conveyed from the BS since the last report, the MS now sends an absolute report, said i.e. reset report).

- The BS makes a frequency allocation and it conveys the allocation message "reset alloc" utilizing the sequence number SeqNo+1 (indicating an absolute allocation based on the reset report obtained by the MS) to the MS.

(c) Report of MS got lost:

- The MS sends a reset report with a sequence number (seqNo) . - The BS makes a frequency allocation and it conveys the allocation message "reset alloc" (indicating an absolute allocation based on the reset report obtained by the MS) to the MS utilizing this seqNo. - The MS sends an update report with a seqNo+1 indicating the relative changes based on its previous reset report .

- The BS makes a frequency allocation update utilizing the update report with the sequence number seqNo+1 and it conveys an update allocation message with this sequence number seqNo+1 to the MS.

- The MS sends an update report with a seqNo+2 indicating the relative changes based on its previous reset report. This report got lost (never arrives at the

BS) .

- The BS makes a frequency allocation update utilizing the update report with the sequence number seqNo+1 and it conveys an update allocation message with this sequence number seqNo+1 to the MS (as the BS did never become aware of the previous update report with seqNo+2) .

- The MS sends an update report with a seqNo+2 indicating the relative changes based on its previous reset report.

- The BS makes a frequency allocation update utilizing the update report with the sequence number seqNo+2 and it conveys an update allocation message with this sequence number seqNo+2 to the MS .

The gain of the alternative implementation may depend on the occurrence of band changes and an average amount of incrementally reported bands.

In case the access point API requests an allocation of non- reported bands, an additional signaling can be provided, which may either be appended to the existing allocation or a control bit can be added (e.g., in downlink direction). List of Abbreviations:

AP access point

CRC cyclic redundancy check DL downlink

FSS frequency selective scheduling

MAC message authentication code

MAP allocation message

MCS modulation and coding scheme MS mobile station

UL uplink

Claims

Claims :

1. A method for data processing in a first access point,

2. The method according to claim 1, wherein the allocation information comprises a relative address information pursuant to the at least one report.

3. The method according to any of the preceding claims, wherein the function comprises a bitmap in particular indicating which of reporting bands is/are used.

4. The method according to any of the preceding claims, wherein the at least one report comprises a sequence number .

5. The method according to claim 4, wherein the allocation information comprises a sequence number.

6. The method according to any of the preceding claims, wherein a channel report table is maintained based on the at least one report provided by the second access point .

7. The method according to any of the preceding claims, wherein the at least one report is based on a channel measurement determined by the second access point.

8. The method according to any of the preceding claims, wherein the allocation information is based on a se- quence conveyed with the at least one report.

9. The method according to any of the preceding claims, wherein the first access point and/or the second access point is one of the following components:

- a base station; - a mobile station;

- a gateway;

- a relay station;

- a network element of a communication system, in particular of a mobile communication system.

10. The method according to any of the preceding claims, wherein the allocation information is an absolute allocation information or a relative allocation information indicating a difference with regard to a previous allocation information or with regard to a previous report.

11. The method according to any of the preceding claims, wherein the at least one report comprises an absolute information or an incremental and/or differential information indicating a difference with regard to at least one previous report.

12. The method according to any of claims 10 or 11, wherein a flag indicates whether the information is a relative information or an absolute information.

13. A device comprising a and/or being associated with a processor unit and/or a hard-wired circuit and/or a logic device that is arranged such that the method according to any of the preceding claims is executable thereon .

14. The device according to claim 13, wherein the device is a communication device, in particular a or being associ- ated with a network element, an access point, a base station or a mobile station.

15. Communication system comprising the device according to any of claims 13 or 14.