FRACTIONAL FREQUENCY REUSE SCHEMES ASSIGNED TO RADIO NODES IN AN LTE NETWORK

• US 20150131537A1
• Filed: 11/08/2013
• Published: 05/14/2015
• Est. Priority Date: 11/08/2013
• Status: Active Grant

• Current Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Original Assignee: SpiderCloud Wireless, Inc. (Corning Incorporated)
• Inventors: Chiang, Han-Ting, Sayana, Krishna, Dunn, Brian, Nama, Hithesh, Worters, Peter J.
• Granted Patent: US 10,097,329 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04L 1/00 Arrangements for detecting or preventing errors in the information received correcting synchronisation H04L7/00
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 5/0057 Physical resource allocation for CQI
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04L 5/0076 Allocation utility-based
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

Arrangements disclosed here provide an LTE E-RAN employing a hierarchical architecture with a central controller controlling multiple LTE radio nodes (RNs). The RNs may be clustered within the small cell network. A fractional frequency reuse (“FFR”) scheme is provided that dynamically computes the FFR allocations at individual RNs and configures the corresponding schedulers within each RN to improve cell-edge users'"'"' experience. Once an FFR pattern has been generated and frequencies allocated, UE throughput can be emulated to predict the resulting bit rates for each UE. Using the prediction, a scheduler emulation may be run to predict the behavior of the system. The results of each cell may then be collected to generate the performance of the entire system, which may in turn be used to generate a new or modified FFR pattern, or new or modified clustering. Optimization of the performance results in an optimized FFR pattern.

Claims

1. A method of optimizing frequency allocation in a radio access network (RAN) that includes a plurality of RNs each associated with a cell and a SN operatively coupled to the RNs, the method comprising:

dividing the RNs in the RAN into a plurality of clusters of RNs;

generating a FFR pattern for each cluster;

allocating transmission frequencies to the RNs in each cluster in accordance with the respective FFR pattern that is generated for each cluster;

estimating bit rates of one or more user equipments (UEs) associated with each cell;

performing a scheduling emulation within each cell using the estimated bit rates for the one or more UEs; and

combining the results of the scheduling emulations for each cell to obtain a systemwide performance metric, and if the systemwide performance metric is less than a target threshold, then repeating one or more of the dividing, generating, allocating, estimating, performing, and combining steps, until the systemwide performance metric meets or exceeds the target threshold.

2. The method of claim 1, wherein the estimating bit rates includes:

calculating a SINR for each UE; and

using a SINR-to-bit-rate map to determine the bit rate for each UE.

3. The method of claim 2, wherein the calculating a SINR includes using the geometry or topology of the UEs to calculate the SINR.

4. The method of claim 1, wherein the estimating bit rates further includes improving the estimation of the bit rates by using CQI data reported by the UE.

5. The method of claim 1, wherein the systemwide performance metric refers to a downlink transmission.

6. The method of claim 1, wherein the systemwide performance metric refers to an uplink transmission.

7. The method of claim 1, wherein the estimating bit rates further includes improving an estimation of the bit rates by using measurement data on an uplink reference signal.

8. The method of claim 1, wherein the transmission frequencies are frequencies used for downlink transmission.

9. The method of claim 1, wherein the transmission frequencies are frequencies used for uplink transmission.

10. The method of claim 1, wherein the systemwide performance metric is selected from the group consisting of:

cell packet throughput, 5% cell edge user throughput, user throughput CDF, call drop ratio, call setup success rate, radio link failure rate, and handover delay.

11. The method of claim 1, wherein following the system-wide performance metric meeting or exceeding the target threshold, allocating transmission frequencies to the RNs in each cluster in accordance with the respective FFR pattern that resulted in the metric meeting or exceeding the target threshold, and performing a step of scheduling within each RN to allocate transmission frequencies to the UEs served by the RN.

12. The method of claim 11, wherein the step of scheduling directs cell edge users to high reuse bands and cell center users to low reuse bands.

13. The method of claim 12, wherein the scheduling step is further at least partially based on UE-specific information.

14. The method of claim 13, wherein the UE-specific information includes at least one member selected from the group consisting of:

CQI, load, and QoS parameters.

15. The method of claim 1, wherein the systemwide performance metric includes the throughput of a cell edge user, and wherein the repeating the generating step includes modifying the size of the center band until the throughput of the cell edge user meets or exceeds the threshold.

16. The method of claim 1, wherein the scheduling step includes PF scheduling, round-robin scheduling, or QOS based scheduling.

17. The method of claim 1, wherein the scheduling emulation includes PF scheduling emulation, round-robin scheduling emulation, or QOS based scheduling emulation.

18. A non-transitory computer readable medium, comprising instructions for causing a computing environment to perform the method of claim 1.

19. A RN communicating with a plurality of user equipment (UE) in a radio access network, comprising:

a processor;

a first input for an FFR pattern;

a second input for data about communications performance of a plurality of UEs associated with the RN;

a scheduler module receiving data from the first and second inputs and configured to provide as output a scheduling of the plurality of UEs, such that the scheduler module is configured to direct a subset of the plurality of UEs corresponding to cell edge users to high reuse bands at least in part based on data from the second input, and further directs a subset of the plurality corresponding to cell center users to low reuse bands.

20. The RN of claim 19, wherein the data from the second input is selected from the group consisting of:

CQI, load, and QoS parameters.

21. A method of optimizing transmission resource allocation in a radio access network (RAN) that includes a plurality of radio nodes (RNs) each associated with a cell and a services node operatively coupled to the radio nodes, the method comprising:

obtaining at least one system-wide performance metric representing operational performance of the RAN;

if the system-wide performance metric is less than a target threshold, then adjusting a system-wide FFR pattern used to allocate transmission resources to the RNs until the system-wide performance metric meets or exceeds the target threshold, the system-wide FFR pattern including a plurality of cluster-based FFR patterns each being allocated to a different cluster of RNs, the RNs in the RAN being divided into a plurality of clusters.

22. The method of claim 21 wherein adjusting the system-wide FFR pattern includes adjusting FFR scheme-related parameters used to generate the system-wide FFR pattern.

23. The method of claim 21 wherein adjusting the system-wide FFR pattern includes adjusting one or more of the cluster-based FFR patterns by adjusting at least one operator-specified value selected from a plurality of parameters which are used as input data.

24. The method of claim 23 wherein the plurality of parameters includes an FFR type specifying at least one criterion for allocating edge bands to the RNs in each cluster.

25. The method of claim 24 wherein the plurality of parameters further includes a number of frequency resource blocks assigned to a center band allocated to the RNs in each cluster for use by UEs in a cell interior of each cell.

26. The method of claim 25 wherein the plurality of parameters further includes a scheduling granularity of the center band specifying a number of frequency resource blocks assigned to the center band which are scheduled together.

27. The method of claim 25 wherein the plurality of parameters further includes a scheduling granularity of the edge band specifying a number of frequency resource blocks assigned to the edge band which are scheduled together.

28. The method of claim 24 wherein the FFR type is selected from the group consisting of uniform FFR and load-based FFR, wherein uniform FFR allocates different edge bands of uniform size to each RN in a cluster and load-based FFR allocates to each RN in a cluster different edge bands having a size determined in part on load information obtained from the RNs in each cluster.

29. The method of claim 28 wherein the load information is selected from the group consisting of a load of each RN in a cluster, the number of active UEs served by each RN in a cluster, and UE-specific information, wherein the UE-specific information is selected from the group consisting of RSRP, load, QoS, sub-band channel quality indicators (CQIs), buffer status or latencies, and current or past KPIs maintained per RN or per UE.

30. The method of claim 21 wherein adjusting the system-wide FFR pattern includes adjusting RN clustering parameters.

31. The method of claim 30 wherein the RN clustering parameters include a total number of clusters into which the RNs in the RAN are to be divided.

32. The method of claim 21 wherein the transmission resources are resources used for downlink transmission.

33. The method of claim 21 wherein the transmission resources are resources used for uplink transmission.

34. The method of claim 21 wherein the transmission resources are resources used for uplink and downlink transmission.

35. The method of claim 34 wherein, for at least one of the clusters, the cluster-based FFR pattern generated for uplink transmission is the same as the cluster-based FFR pattern generated for downlink transmission.

36. The method of claim 21, wherein the system-wide performance metric is selected from the group consisting of:

cell packet throughput, 5% cell edge user throughput, and user throughput CDF, call drop ratio, call setup success rate, radio link failure rate, and handover delay.

37. A non-transitory computer readable medium, comprising instructions for causing a computing environment to perform the method of claim 21.

38. A services node controlling a plurality of radio nodes (RNs) in a radio access network (RAN), the plurality of radio nodes communicating with a plurality of user equipment (UE) in the radio access network, comprising:

a processor; and

a performance evaluation module operatively associated with the processor, the performance module having an input for obtaining at least one system-wide performance metric representing operational performance of the RAN, the performance evaluation module being configured such that if the system-wide performance metric is less than a target threshold, then adjusting a system-wide FFR pattern used to allocate transmission resources to the RNs until the system-wide performance metric meets or exceeds the target threshold, the system-wide FFR pattern including a plurality of cluster-based FFR patterns each being allocated to a different cluster of RNs, the RNs in the RAN being divided into a plurality of clusters.

39. A method for obtaining system performance metrics for a mobile communications system that includes a radio access network (RAN) having a plurality of radio nodes (RNs) each associated with a cell and services node operatively coupled to the RNs, comprising:

obtaining an FFR pattern for the RAN;

receiving from UEs operational in the cells a measurement of signal strength;

based at least in part on the FFR pattern and the measurement of signal strength, emulating scheduling functionality performed by the RNs for allocating transmission resources to the UEs;

based at least in part on the emulation, determining at least one performance metric for each of the cells in the RAN.

40. The method of claim 39 further comprising:

determining, for different levels of interference, an SINR for each of the UEs from the measurement of signal strength and the FFR pattern;

mapping each of the SINRs to a per-subcarrier bit rate, wherein emulating the scheduling functionality is performed using the per-subcarrier bit rates.

41. The method of claim 39 wherein the measurement of signal strength includes UE RSRPs.

42. The method of claim 39 wherein the at least one performance metric is selected from the group consisting of a cell packet throughput, 5% cell-edge user throughput and a user throughput cumulative distribution function (CDF), call drop ratio, call setup success rate, radio link failure rate, and handover delay.

43. The method of claim 39 further comprising aggregating the at least one performance metric for each of the cells to obtain at least one predicted key performance indicator (KPI) for the mobile communications system.

44. The method of claim 39 further comprising receiving from the UEs operational in the cells channel quality information (CQI), wherein emulating the scheduling functionality performed by the RNs for allocating transmission resources to the UEs is also based at least in part on the CQI.

45. The method of claim 39 wherein the FFR pattern for the RAN is a system-wide FFR pattern that includes a plurality of FFR patterns that are each associated with a different subset of the RNs each defining a cluster of RNs, wherein each cluster is selected such that interference between RNs within a cluster is greater than interference between RNs in different clusters.

46. A services node controlling a plurality of radio nodes (RNs) in a radio access network (RAN), the plurality of radio nodes communicating with a plurality of user equipment (UE) in the radio access network, comprising:

a processor;

a UE SINR calculator module operatively associated with the processor for determining, for different levels of interference, an SINR for each of the UEs from (i) a measurement of signal strength received from the UEs and/or (ii) a measurement of signal strength from the UEs measured on uplink reference signals and (iii) an FFR pattern used to allocate transmission frequencies to the RNs;

an SINR bit rate mapping module operatively associated with the processor for mapping each of the SINRs to a per-subcarrier bit rate; and

a scheduler emulation module operatively associated with the processor for emulating scheduling functionality performed by each of the RNs for allocating transmission resources to the UEs based at least in part on the per-subcarrier bit rates.