REACTIVE SCHEDULING METHODS AND APPARATUS TO ENABLE PEER-TO-PEER COMMUNICATION LINKS IN A WIRELESS OFDMA SYSTEM

• US 20100189046A1
• Filed: 01/27/2009
• Published: 07/29/2010
• Est. Priority Date: 01/27/2009
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: SMITH, NATHAN J., BAKER, MICHAEL H., MICHELS, JAMES P., MANGALVEDHE, NITIN R., CALCEV, GEORGE, BONTA, JEFFREY D.
• Granted Patent: US 8,879,479 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0062 Avoidance of ingress interference, e.g. ham radio channels
• CPC Class Codes: H04L 5/0091 Signaling for the administration of the divided path
• CPC Class Codes: H04W 72/54 based on quality criteria

Abstract

Systems, methods and apparatus are provided for scheduling resources in Orthogonal Frequency-Division Multiple Access (OFDMA) communication networks for “direct link” or peer-to-peer communications among stations operating therein so that OFDMA resources can be allocated to a transmitter station for a peer-to-peer communication session with a receiver station such that near-far issues caused by peer-to-peer communication are reduced/avoided. The disclosed technologies can prevent peer-to-peer communication links using different sub-channels within the same time slot from creating near-far issues for other receiver stations that are within communication range.

Claims

1. A method for scheduling Orthogonal Frequency-Division Multiple Access (OFDMA) resources to be allocated to a transmitter station that is actively involved in a peer-to-peer communication session with a receiver station using existing OFDMA resources previously allocated by a base station, the method comprising:

generating, at the base station, a request for Quality-of-Service (QoS) performance metric measurements with respect to the existing OFDMA resources;

receiving the request at the receiver station, and determining measured values for the QoS performance metrics being requested for the existing OFDMA resources; and

determining, at the receiver station based on the measured values for the QoS performance metrics, whether to continue using the existing OFDMA resources or whether to request a new allocation of OFDMA resources.

2. A method according to claim 1, wherein the step of generating, at the base station, a request for Quality-of-Service (QoS) performance metric measurements with respect to the existing OFDMA resources, comprises:

generating, at the base station, a Grant Metric Information Element (GMIE) comprising;

an indicator of a type of Quality-of-Service (QoS) performance metric that the base station is requesting measurements for with respect to the existing OFDMA resources, and a number of OFDMA frames to average for each QoS performance metric measurement being requested by the base station for the existing OFDMA resources; and

broadcasting the GMIE.

3. A method according to claim 2, wherein the step of receiving the request at the receiver station, and determining measured values for the QoS performance metrics being requested for the existing OFDMA resources, comprises:

receiving the GMIE at the receiver station, decoding the GMIE to determine QoS performance metrics being requested by the base station for the existing OFDMA resources, and determining values for the QoS performance metrics for the existing OFDMA resources.

4. A method according to claim 3, wherein the step of determining, at the receiver station based on the measured values for the QoS performance metrics, whether to continue using the existing OFDMA resources or whether to request a new allocation of OFDMA resources, comprises:

determining, at the receiver station based on the values for the QoS performance metrics for the existing OFDMA resources, whether to continue using the existing OFDMA resources or request a new allocation of OFDMA resources for the peer-to-peer communication session.

5. A method according to claim 4, further comprising:

when the receiver station determines, based on the values for the QoS performance metrics determined for the existing OFDMA resources by the receiver station, that the receiver station will continue using the existing OFDMA resources previously allocated for the peer-to-peer communication session, transmitting a resource renewal request message (RRRM) from the receiver station to the base station to renew allocation of the existing OFDMA resources so that the receiver station can continue using the existing resource allocation for its peer-to-peer communication session with the transmitter station;

when the receiver station determines, based on the values for the QoS performance metrics determined for the existing OFDMA resources by the receiver station, that the receiver station will request a new resource allocation of OFDMA resources for the peer-to-peer communication session to prevent near/far problems, unicasting, from the receiver station to the base station, a Grant Metric Response Message (GMRM) and a request for a new resource allocation for the peer-to-peer communication session with the transmitter station, wherein the GMRM is used to report QoS performance metrics measured by the receiver station during the peer-to-peer communication session;

determining, at the base station in response to the request for a new resource allocation for the peer-to-peer communication session with the transmitter station, a new resource allocation; and

communicating the new resource allocation from the base station to the receiver station and the transmitter station.

6. A method according to claim 4, wherein the step of determining, at the receiver station based on the values for the QoS performance metrics determined for the existing OFDMA resources by the receiver station, whether to continue using the existing OFDMA resources or request a new allocation of OFDMA resources for the peer-to-peer communication session to prevent near/far problems, comprises:

determining, at the receiver station, short-term QoS performance metrics over a current OFDMA frame for the existing OFDMA resources;

determining, at the receiver station, whether short-term QoS performance metrics are acceptable for the current OFDMA frame;

when the short-term QoS performance metrics are acceptable for the current OFDMA frame, determining, at the receiver station, whether a grant period for the existing resources has expired; and

when the short-term QoS performance metrics are not acceptable for the current OFDMA frame, sending, from the receiver station to the base station, a grant metric response message (GMRM) and a resource re-allocation request message (RRARM) to request a new resource allocation for the communication session between the transmitter station and the receiver station, wherein the GMRM comprises;

a total categories field indicating a number of measurement categories, and for each category;

a category measurement type field that identifies a type of QoS measurement category; and

a measurement field that specifies a measurement for the category measurement type field.

7. A method according to claim 6, further comprising:

when the grant period for the existing resources has not yet expired, continuing to monitor, at the receiver station, short-term QoS performance metrics until the grant period for the existing resources expires;

when the grant period for the existing resources has expired, sending, from the receiver station to the base station a grant metric response message (GMRM) that includes the short-term QoS performance metrics for the current OFDMA frame, wherein the GMRM comprises;

a total categories field indicating a number of measurement categories, and for each category;

a category measurement type field that identifies a type of QoS measurement category; and

a measurement field that specifies a measurement for the category measurement type field; and

determining, at the receiver station, whether there is more data for the peer-to-peer communication session.

8. A method according to claim 7, further comprising:

determining, at the receiver station, long-term QoS performance metrics for the existing OFDMA resources previously allocated by the base station for the peer-to-peer communication session, wherein the long-term QoS performance metrics are determined based on a calculations using short-term QoS performance metrics determined for each frame from a start of a grant period up to the current point in time;

determining, at the receiver station when the receiver station determines that there is more data for the peer-to-peer communication session, whether the long-term QoS performance metrics are acceptable; and

when the long-term QoS performance metrics are not acceptable, unicasting, from the receiver station to the base station, a GMRM that reports the long-term QoS performance metrics, and a resource re-allocation request message (RRARM) to request new resource allocation for the peer-to-peer communication session with the transmitter station, wherein the GMRM comprises;

a total categories field indicating a number of measurement categories, and for each category;

a category measurement type field that identifies a type of QoS measurement category; and

a measurement field that specifies a measurement for the category measurement type field.

9. A method according to claim 8, further comprising:

when the long-term QoS performance metrics are acceptable, transmitting, from the receiver station, a request to continue with the existing resource allocation for the communication session between the transmitter station and the receiver station.

10. A method according to claim 1, wherein the types of QoS performance metrics comprise:

frame error rate (FER), Signal-to-interference-plus-Noise Ratio (SINR); and

analog-to-digital converter (ADC) desense.

11. A method according to claim 8, further comprising:

generating, at the base station, a Resource Map Information Element (RMIE), wherein the RMIE comprises a Partial Resource Allocation Map (PRAM), the PRAM comprising;

selected OFDMA resources of the OFDMA frame that the base station is requesting more information about;

an indicator of at least one metric that is to be measured with respect to the selected OFDMA resources;

a number of metric measurements being requested with respect to the selected OFDMA resources; and

a metric categories field which identifies one or more metric categories to be reported with respect to the selected OFDMA resources;

broadcasting the RMIE, from the base station to recipient stations including the receiver station, to request metric measurement information from the recipient stations based on information specified in the PRAM;

receiving, at the recipient stations including the receiver station, the RMIE generated and broadcast by the base station, and

decoding, at the receiver station, the RMIE to determine a metric being requested by the base station.

12. A method according to claim 11, further comprising:

measuring the metric with respect to some of the selected OFDMA resources specified in the PRAM.

13. A method according to claim 12, wherein the step of measuring the metric with respect to some of the selected OFDMA resources specified in the PRAM comprises:

starting a resource measurement period timer at each of the recipient stations including the receiver station;

monitoring, at the recipient stations including the receiver station, an OFDMA channel for an OFDMA frame;

selecting, at the recipient stations including the receiver station, particular ones of the selected OFDMA resources from the PRAM; and

measuring, at the recipient stations including the receiver station, the metric with respect to each of the particular ones of the selected OFDMA resources that are selected by that particular recipient station.

14. A method according to claim 12, further comprising the steps of:

generating, at each of the recipient stations including the receiver station, a resource map response message (RMRM) comprising information regarding a metric measurement with respect to some of the selected OFDMA resources, wherein each RMRM comprises;

a resource type field that specifies a type of resource that the particular station is reporting in the RMRM;

a total categories field that specifies a total number of different metric categories being reported in the RMRM; and

a partial resource measurement map (PRMM) comprising;

a plurality of metric categories each including information regarding metric measurements made by the particular station for selected ones of the selected OFDMA resources specified in the PRAM, wherein the plurality of metric power categories specified in each PRMM comprise;

a high metric category used to report high power metric measurements, a medium metric category used to report medium power metric measurements, and a low metric category used to report low power metric measurements, wherein the RMRM generated by the receiver station comprises a first RMRM comprising a first PRMM;

transmitting, a RMRM to the base station from each of the recipient stations including the receiver station, wherein the receiver station transmits the first RMMM to the base station when the grant period for the existing resources has expired or when the long-term QoS performance metrics are not acceptable;

transmitting, to the base station from the receiver station, a Resource Re-allocation Request Message (RRARM) to request allocation of some of the OFDMA resources for the peer-to-peer communication session with the receiver station;

receiving, at the base station, the first RMRM comprising the first PRMM, the GMRM and the RRARM from the receiver station;

processing, at the base station, the RMRMs to determine specific ones of the OFDMA resources to be allocated to the transmitter station for the peer-to-peer communication session with the receiver station, wherein the specific ones of the OFDMA resources allocated to the transmitter station each comprise;

an allocated OFDMA sub-channel within a particular OFDMA time slot, and

wherein the specific ones of the OFDMA resources are allocated such that other stations communicating over different OFDMA sub-channels of the particular OFDMA time slots will not cause near-far problems for the receiver station, and communications by the transmitter station using the specific ones of the OFDMA resources will not cause near-far problems for the other stations communicating over different OFDMA sub-channels of the particular OFDMA time slots.

15. A method according to claim 14, wherein the step of generating, at each of the recipient stations including the receiver station, a resource map response message (RMRM), comprises:

sorting, at each of the recipient stations including the receiver station, measured metric for each of the particular ones of the selected OFDMA resources into one of a plurality of metric categories that categorize the particular ones of the selected OFDMA resources based on measured metric, wherein the plurality of metric categories comprise;

a high metric category that includes information regarding peer stations that cause high level interference;

a medium metric category that includes information regarding peer stations that cause medium level interference, and a low metric category that includes information regarding peer stations that cause low level interference;

generating, at each of the recipient stations including the receiver station, a partial resource measurement map (PRMM) comprising the plurality of metric categories, wherein each of the metric categories includes metric measurement information regarding some of the particular ones of the selected OFDMA resources; and

generating, at each of the recipient stations including the receiver station upon expiration of the resource measurement period, a RMRM comprising the PRMM as determined by that particular station, wherein the RMRMs generated by the receiver station comprises the first RMRMs including first PRMMs.

16. A method according to claim 15, further comprising:

maintaining, at the base station, a resource allocation map comprising;

particular OFDMA resources of an OFDMA frame that have been allocated to particular stations; and

wherein each of the metric categories comprise a plurality of fields used to report information regarding metric measurements by the particular station for that metric power category, the plurality of fields comprising;

a category identifier field that identifies the particular metric category, a number measured field that specifies a number of metric measurements that are included for the particular metric category, and a category MAP data field that specifies particular resource locations in the resource allocation map for the particular metric category, wherein each particular resource location is specified as at least one specific sub-channels and at least one time slot.

17. A method according to claim 14, wherein the step of processing, at the base station, the RMRMs comprises:

determining, at the base station based on the RRARM, a packet size the transmitter station requests to transmit in the peer-to-peer communication session with the receiver station;

determining, at the base station based on the first PRMM from the first RMRM, updated peer station information for the receiver station; and

scheduling a first OFDMA resource in a first OFDMA time slot for a first transmission by the transmitter station to the receiver station during the peer-to-peer communication session;

scheduling other OFDMA resources in other OFDMA time slots for other transmissions by high metric peer stations of the receiver station having high power metric such that the first transmission is received by the receiver station at a time when the high metric peer stations of the receiver station are not transmitting so that the first transmission is isolated in the time domain from the other transmissions by the high metric peer stations of the receiver station; and

scheduling other OFDMA resources in other OFDMA time slots for other transmissions by high metric peer stations of the transmitter station having high power metric such that the first transmission is received by the receiver station at a time when the high metric peer stations of the transmitter station are transmitting so that the first transmission occurs at the same time as other transmissions by the high metric peer stations of the transmitter station.

18. A method according to claim 17, wherein each peer stations has particular station identification number, and wherein the step of determining, at the base station based on the first PRMM from the first RMRM, updated peer station information for the receiver station, comprises:

extracting, at the base station from the first PRMM that was received from the receiver station, information regarding metric measurements made by the receiver station for the selected ones of the selected OFDMA resources;

using the resource allocation map maintained at the base station to translate the selected ones of the selected OFDMA resources into corresponding peer station identification numbers;

determining, at the base station, metric categories from the first PRMM for each of the peer station indentification numbers, and assigning each particular peer station identification number to one of;

a high power metric transmitter peer list that specifies peer stations having high power metric, a low power metric transmitter peer list that specifies peer stations having low power metric, and a medium power metric transmitter peer list that specifies peer stations having medium power metric;

creating, at the base station, an entry in a peer memory map (PMM) for the receiver station, wherein the PMM comprises a plurality of rows, and a plurality of columns, the plurality of columns comprising;

a first column that lists peer station identification numbers corresponding to peer-to-peer enabled stations including the transmitter station and the receiver station, wherein each row corresponds to entry for a particular peer-to-peer enabled station that is identified in the first column by a particular peer station identification number;

a second column comprising the high power metric transmitter peer list that specifies peer stations having high power metric, wherein the second column lists peer station identification numbers for peer stations of the corresponding station in the first column;

a third column comprising the low power metric transmitter peer list that specifies peer stations having low power metric, wherein the third column lists peer station identification numbers for peer stations of the corresponding station in the first column; and

a fourth column comprising the medium power metric transmitter peer list that specifies peer stations having medium power metric, wherein the fourth column lists peer station identification numbers for peer stations of the corresponding station in the first column.

19. A method according to claim 18, further comprising:

processing, at the base station, the first PRMM provided in the first RMRM and other PRMMs provided in other RMRMs from other recipient stations, to generate;

a high impact peer set that identifies stations in the high power metric transmitter peer list of the receiver station that are susceptible to near-far issues when one station that belongs to the high impact peer set transmits while another station that belongs to the high impact peer set is receiving a different transmission from another station that does not belong to the high impact peer set, and a low impact peer set that identifies stations in the low power metric transmitter peer list of the receiver station that are not susceptible to near-far issues when one station that belongs to the low impact peer set transmits while another station that belongs to the low impact peer set is receiving a different transmission from another station that does not belong to the low impact peer set;

using information in the resource allocation map, the high impact peer set and the low impact peer set to determine preferred OFDMA time slots (TS_p) of the OFDMA frame and excluded OFDMA time slots (TS_x) of the OFDMA frame, and marking the preferred OFDMA time slots (TS_p) and excluded OFDMA time slots (TS_x) in the resource allocation map maintained at the base station;

estimating, at the base station, a resource allocation size (RAS) for the peer-to-peer communication session between the transmitter station and the receiver station; and

determining, at the base station based on the estimated RAS, a resource allocation comprising at least one of the preferred OFDMA time slots (TS_p) and at least one sub-channel in that preferred OFDMA time slot (TS_p) to allocate for the peer-to-peer communication session between the transmitter station and the receiver station.

20. A method according to claim 19, wherein the step of using information in the resource allocation map, the high impact peer set and the low impact peer set to determine preferred OFDMA time slots (TS_p) of the OFDMA frame and excluded OFDMA time slots (TS_x) of the OFDMA frame, and marking the preferred OFDMA time slots (TS_p) and excluded OFDMA time slots (TS_x) in the resource allocation map maintained at the base station, comprises:

marking, at the base station, any time slots where peer stations in a high impact peer set of the transmitter station are allocated to transmit as preferred OFDMA time slots (TS_p) of the OFDMA frame;

marking, at the base station, any time slots where peer stations in the high impact peer set of the transmitter station are allocated to receive as excluded OFDMA time slots (TS_x) of the OFDMA frame;

marking, at the base station, any time slots where peer stations in the high impact peer set of the receiver station are allocated to transmit as excluded OFDMA time slots (TS_x) of the OFDMA frame; and

when the high impact peer set of the receiver station includes no peer stations, marking, at the base station, any time slots allocated to peer stations in a low impact peer set of the transmitter station as preferred OFDMA time slots (TS_p) of the OFDMA frame.

21. A method according to claim 20, when an OFDMA time slot is marked as being both an excluded time slot (TS_x) and preferred time slot (TS_p), further comprising:

marking the OFDMA time slot;

as a preferred OFDMA time slot (TS_p) of the OFDMA frame when the receiver station is a member of the high impact peer set of the transmitter station, or as an excluded OFDMA time slot (TS_x) of the OFDMA frame when the receiver station is not a member of the high impact peer set of the transmitter station.

22. A method according to claim 12, wherein the metric comprises a radio frequency (RF) quality metric.

23. A method according to claim 22, wherein the RF quality metric comprises:

receive signal strength (RSS) power levels.

24. A method according to claim 22, wherein the RF quality metric comprises:

Signal-to-interference-plus-Noise Ratio (SINR).

25. A method according to claim 22, wherein the RF quality metric comprises:

Signal-to-Noise Ratio (SNR).

26. A method according to claim 22, wherein the RF quality metric comprises:

range.

27. A method according to claim 1, wherein each of the OFDMA resources is a OFDMA frequency sub-channel within an OFDMA time slot.

28. A method according to claim 1, wherein the QoS performance metric measurements reflect quality of the communication link between the transmitter station and the receiver station and allow the base station to monitor adequacy of the existing OFDMA resources allocated to the transmitter station.

29. A method for scheduling Orthogonal Frequency-Division Multiple Access (OFDMA) resources, the method comprising:

generating, at a base station, a request for Quality-of-Service (QoS) performance metric measurements with respect to existing OFDMA resources allocated to a transmitter station for a peer-to-peer communication session with a receiver station;

receiving the request at the receiver station, and determining measured values for the QoS performance metrics being requested by the base station for the existing OFDMA resources; and

determining, at the receiver station based on the measured values for the QoS performance metrics, whether to request a new allocation of OFDMA resources.