METHOD FOR COORDINATING INTER-CELL INTERFERENCE IN HETEROGENEOUS NETWORK AND HETEROGENEOUS NETWORK

• US 20140169275A1
• Filed: 07/09/2012
• Published: 06/19/2014
• Est. Priority Date: 07/13/2011
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Nagata, Satoshi, Wang, Jing, Jiang, Yu, She, Xiaoming, Chen, Lan, Suda, Hirohito
• Granted Patent: US 9,307,423 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 72/27 between access points
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Provided are a method for coordinating inter-cell interference in a heterogeneous network (HetNet) and the heterogeneous network. The method includes: forming M normal base stations and low-power nodes within coverage of the respective normal base stations in the heterogeneous network into a coordinated group; combining mute/non-mute states of bandwidths of the M normal base stations to obtain a plurality of states of the coordinated group; a user of each of the normal base stations feeding at least one first CQI back to the normal base station; a user of each of the low-power nodes feeding one or more second CQIs back to the low-power node; using the first CQI and the second CQIs as a basis to make capacity estimation of the coordinated group; and setting the mute/non-mute states of the bandwidths of the M normal base stations in accordance with a state of the coordinated group corresponding to an optimal system capacity so as to perform data transmission. In the method for coordinating interference provided by the present invention, M transmission points each including one or more normal base stations and low-power nodes covered by the respective normal base stations can be formed into a coordinated group, thereby extending processing for the normal base stations up to all the transmission points in the coordinated group.

Claims

1. A method for coordinating inter-cell interference in a heterogeneous network (HetNet), comprising:

a step A of forming M normal base stations (M is greater than

     1) and low-power nodes within coverage of the respective normal base stations in the heterogeneous network into a coordinated group;

a step B of combining mute/non-mute states of bandwidths of the M normal base stations to obtain a plurality of states of the coordinated group;

a step C of a user of each of the normal base stations in the coordinated group, feeding at least one first channel quality indicator (CQI) corresponding to the states of the coordinated group back to the normal base station;

a step D of a user of each of the low-power nodes covered by the normal base stations in the coordinated group, feeding one or more second CQIs corresponding to the states of the coordinated group back to the low-power node;

a step E of using the at least one first CQI and the one or more second CQIs as a basis to make capacity estimation of the coordinated group and obtaining a plurality of system capacities corresponding to the respective states of the coordinated group; and

a step F of setting the mute/non-mute states of the bandwidths of the M normal base stations in accordance with a state of the coordinated group corresponding to an optimal system capacity so as to perform data transmission.

2. The method of claim 1, wherein

the states of the coordinated group in the step B include a state where the M normal base stations are all non-mute and a state where the M normal base stations are all mute,

in the step C, the user of the normal base station feeds back the first CQI of the state where the M normal base stations are all non-mute,

in the step D, the user of the low-power node feeds back two second CQIs of the state where the M normal base stations are all non-mute and the state where the M normal base stations are all mute, and

the first CQI and the second CQIs are all related to interference strength outside the coordinated group.

3. The method of claim 1, wherein

the states of the coordinated group in the step B include any combinations of the mute/non-mute states of the M normal base stations,

in the step C, the user of each of the normal base stations decides M first CQIs, the first CQIs being related to signal strength of j-th (j=1, 2, . . . , M) normal base stations and interference strength outside the coordinated group, and

in the step D, the user of each of the low-power nodes decides M+1 second CQIs, the second CQIs being related to signal strength of the low-power node, signal strength of the respective normal base stations in the coordinated group and the interference strength outside the coordinated group.

4. The method of claim 3, wherein the step E comprises:

each of the normal base stations in the coordinated group updating the M first CQIs fed back from the user of own station to be CQIs in one-to-one correspondence with the mute/non-mute sates of any combinations of the mute/non-mute states of other normal base stations in the coordinated group;

each of the low-power nodes updating the M+1 second CQIs fed back from the user of own station to be CQIs in one-to-one correspondence with the states of the coordinated group; and

estimating the system capacities of the coordinated group in the respective states based on the updated CQIs.

5. The method of claim 1, wherein

the states of the coordinated group in the step B are determined by a number of mute normal base stations and the number of mute normal base stations corresponding to an i-th state of the coordinated group is i (i=0, 1, . . . , M),

in the step C, the user of each of the normal base stations decides M first CQIs and an i-th first CQI (i=0, 1, . . . , M−

1) is related to signal strength of the normal base station to which the user belongs, signal strength of another non-mute normal base station in the i-th state of the coordinated group and interference strength outside the coordinated group;

in the step D, the user of each of the low-power nodes decides M+1 second CQIs and an i-th second CQI (i=0, 1, . . . , M) is related to signal strength of the low-power node, the signal strength of the non-mute normal base station in the i-th state of he coordinated group, and the interference strength outside the coordinated group.

6. The method of claim 5, wherein

the i-th first CQI is a minimal CQI in the i-th state of the coordinated group measured by the user of the normal base station, and

the i-th second CQI is a minimal CQI in the i-th state of the coordinated group measured by the user of the low-power node.

7. The method of claim 1, wherein

each of the states of the coordinated group in the step B corresponds to one of selections by, once a number N_close of mute normal base stations is decided, selecting N_close normal base stations arbitrarily from the M normal base stations and making the N_close normal base stations mute, a value of N_close being any of 1, . . . , M−

1,

in the step C, the user of each of the normal base stations decides M first CQIs, each of the first CQIs being related to signal strength of the normal base station to which the user belongs, signal strength of another non-mute normal base station in the corresponding state of the coordinated group, and interference strength outside the coordinated group, and

in the step D, the user of each of the low-power nodes decides M+1 second CQIs, the second CQIs being related to signal strength of the low-power node, signal strength of non-mute normal base stations in the corresponding state of the coordinated group, the interference strength outside the coordinated group.

8. The method of claim 3, wherein

the step C further comprises the user of each of the normal base stations feeding the determined M first CQIs back to the normal base station, and the step D further comprises the user of each of the low-power nodes feeding the determined M+1 second CQIs back to the low-power node, or

the step C further comprises the user of each of the normal base stations grouping and comparing the determined M first CQIs, selecting a minimal first CQI from each group and feeding the first CQI back to the normal base station, and the step D further comprises the user of each of the low-power nodes grouping and comparing the determined M+1 second CQIs, selecting a minimal second CQI from each group and feeding the second CQI back to the low-power node.

9. The method of claim 2, wherein the interference strength outside the coordinated group is actual interference strength measured with actual mute/non-mute states of normal base stations outside the coordinated group by a corresponding user, or estimated interference strength measured by the corresponding user assuming the normal base stations outside the coordinated group are all non-mute.

10. The method of claim 1, wherein

the step C further comprises the user of each of the normal base stations assuming a plurality of states of the coordinated group shiftable from a state of the coordinated group at a last transmission time as the states of the coordinated group at a current feedback time and feeding first CQIs corresponding to the states of the coordinated group at the current feedback time back to the normal base station, and

the step D further comprises the user of each of the low-power nodes assuming a plurality of states of the coordinated group shiftable from the state of the coordinated group at the last transmission time as the states of the coordinated group at the current feedback time and feeding second CQIs corresponding to the states of the coordinated group at the current feedback time back to the low-power node.

11. The method of claim 1, wherein

the step C further comprises the user of each of the normal base stations deciding N_feed1 first CQIs to feed back, selecting strongest n1 (n1 meets N_feed1>

n1≧

1) first CQI from the N_feed1 first CQIs and feeding the strongest n1 first CQI back to the normal base station, and

the step D further comprises the user of each of the low-power nodes deciding N_feed2 second CQIs to feed back, selecting strongest n2 (n2 meets N_feed2>

n2≧

1) second CQI from the N_feed2 second CQIs and feeding the strongest n2 second CQI back to the low-power node.

12. The method of claim 1, wherein the step B further comprises dividing a whole band of each of the normal base stations into K subband groups (K is greater than 1), each of the subband groups including one or a plurality of subbands, and combining the mute/non-mute states of the M normal base stations in each of the subband groups to obtain the states of the coordinated group.

13. The method of claim 1, wherein

the step A further comprises providing a control section configured to be shared by the M normal base stations, and

the step E further comprises:

one of each of the low-power nodes, a normal base station that covers the low-power node and the control section, using the one or more second CQIs fed back from the user of the low-power node as a basis to make capacity estimation of the low-power node in the states,

the normal base station or the control section, using the at least one first CQI fed back from the user of the normal base station and a capacity estimation result of the low-power node covered by the normal base station as a basis to make capacity estimation of the normal base station in the states of the coordinated group, and

the control section using the capacity estimation result of each of the normal base stations as a basis to make capacity estimation of the coordinated group and obtain the system capacities corresponding to the states of the coordinated group.

14. The method of claim 1, wherein

the step A further comprises selecting a decision normal base station from the M normal base stations and setting each normal base station other than the decision normal base station to be another normal base station, and

the step E further comprises:

one of each of the low-power nodes, a normal base station that covers the low-power node and the decision normal base station, using the one or more second CQIs fed back from the user of the low-power node as a basis to make capacity estimation of the low-power node in the states,

the other normal base station or the decision normal base station, using the at least one first CQI fed back from the user of the other normal base station and a capacity estimation result of the low-power node covered by the other normal base station as a basis to make capacity estimation of the other normal base station in the states of the coordinated group, and

the decision normal base station using the at least one first CQI fed back from the user of own station and a capacity estimation result of the low-power node covered by the decision normal base station as a basis to make capacity estimation of the decision normal base station in the states of the coordinated group and using a capacity estimation result of each of the normal base stations as a basis to make capacity estimation of the coordinated group and obtain the system capacities corresponding to the states of the coordinated group.

15. The method of claim 1, wherein in the step F, an actual CQI is decided corresponding to the state of the coordinated group of the optimal system capacity and data scheduling and transmission is performed in accordance with the actual CQI.

16. The method of claim 1, further comprising:

deciding a degree of importance of the first CQI or the second CQIs;

setting a feedback cycle of each of the first CQI and the second CQIs in accordance with the degree of importance in such a manner that the feedback cycle of a CQI of higher degree of importance is short and the feedback cycle of a CQI of lower degree of importance is long;

or

using the CQI of higher degree of importance as a reference CQI to send feedback directly to a corresponding transmission point and to send a difference between the reference CQI and the CQI of lower degree of importance as feedback to a corresponding transmission point.

17. The method of claim 1, wherein the step A further comprises forming M normal base stations co-located in the heterogeneous network and corresponding low-power nodes into the coordinated group or forming neighbor M normal base stations in the heterogeneous network and corresponding low-power nodes into the coordinated group.

18. The method of claim 1, further comprising:

calculating actual transmission power of the normal base stations as P (P falls within [0, I])×

specified transmission power and deciding the mute/non-mute state based on the actual transmission power.

19. A heterogeneous network comprising:

at least one coordinated group including M normal base stations (M is greater than

     1) and low-power nodes within coverage of the respective normal base stations; and

a control section configured to be shared by the M normal base stations, wherein at least one normal base station of the normal base stations in the coordinated group covers one or a plurality of low-power nodes,

each of the normal base stations in the coordinated group receives at least one first channel quality indicator (CQI) corresponding to a plurality of states of the coordinated group fed back from a user of own station to the normal base station, the states of the coordinated group being obtained by combining mute/non-mute states of bandwidths of the M normal base stations,

each of the low-power nodes covered by the respective normal base stations in the coordinated group receives one or more second CQIs corresponding to the states of the coordinated group fed back from a user of own station to the low-power node, and

the control section uses the at least one first CQI and the one or more second CQIs as a basis to make capacity estimation of the coordinated group, obtains a plurality of system capacities corresponding to the respective states of the coordinated group, and sets the mute/non-mute states of the bandwidths of the M normal base stations in accordance with a state of the coordinated group corresponding to an optimal system capacity so as to perform data transmission.

20. The heterogeneous network of claim 19, wherein

each of the low-power nodes performs calculation and updating of the one or more second CQIs fed back from the user of own station, uses the updated CQIs as a basis to make capacity estimation of the low-power node and provides a capacity estimation result of the low-power node in the states of the coordinated group to the normal base station that covers the low-power node,

each of the normal base stations performs calculation and updating of the at least one first CQI fed back from the user of own station, uses the updated CQI and the capacity estimation result of the low-power node covered by the normal base station as a basis to make capacity estimation of the normal base station and provides a capacity estimation result of the normal base station in the states of the coordinated group to the control section, and

the control section uses the capacity estimation result of each of the normal base stations as a basis to make capacity estimation of the coordinated group and obtains the system capacities corresponding to the respective states of the coordinated group.

21. A heterogeneous network comprising:

at least one coordinated group including M normal base stations (M is greater than

     1) and low-power nodes within coverage of the respective normal base stations, wherein one of the normal base stations is a decision normal base station and each normal base station other than the decision normal base station is another normal base station,

at least one normal base station of the normal base stations in the coordinated group covers one or a plurality of low-power nodes,

each of the normal base stations in the coordinated group receives at least one first channel quality indicator (CQI) corresponding to a plurality of states of the coordinated group fed back from a user of own station to the normal base station, the states of the coordinated group being obtained by combining mute/non-mute states of bandwidths of the M normal base stations,

each of the low-power nodes covered by the respective normal base stations in the coordinated group receives one or more second CQIs corresponding to the states of the coordinated group fed back from a user of own station to the low-power node, and

the decision normal base station uses the at least one first CQI and the one or more second CQIs as a basis to make capacity estimation of the coordinated group, obtains a plurality of system capacities corresponding to the respective states of the coordinated group, and sets the mute/non-mute states of the bandwidths of the M normal base stations in accordance with a state of the coordinated group corresponding to an optimal system capacity so as to perform data transmission.

22. The heterogeneous network of claim 21, wherein

each of the low-power nodes performs calculation and updating of the one or more second CQIs fed back from the user of own station, uses the updated CQIs as a basis to make capacity estimation of the low-power node and provides a capacity estimation result of the low-power node in the states of the coordinated group to the normal base station that covers the low-power node,

the other normal base station uses the at least one first CQI fed back from the user of own station and the capacity estimation result of the low-power node covered by the other normal base station as a basis to make capacity estimation of the other normal base station and provides a capacity estimation result of the other normal base station in the states of the coordinated group to the decision normal base station, and

the decision normal base station uses the at least one first CQI fed back from a user of own station and a capacity estimation result of a low-power node covered by the decision normal base station as a basis to make capacity estimation of the coordinated group and obtains the system capacities corresponding to the respective states of the coordinated group.

23. A method for coordinating inter-cell interference in a heterogeneous network (HetNet), comprising the steps of:

a step A2 of forming a first normal base station and one or a plurality of low-power node covered by the first normal base station in the heterogeneous network into a coordinated group;

a step B2 of a user of the first normal base station measuring signal strength of the first normal base station and signal strength of one or more interference normal base stations around the user and feeding back a plurality of corresponding third channel quality indicators (CQIs);

a step C2 of a user of each low-power node covered by the first normal base station measuring signal strength of one or a plurality of normal base stations around the user and feeding back a plurality of corresponding fourth CQIs;

a step D2 of using the third CQIs and the fourth CQIs as a basis to make capacity estimation of the first normal base station in each of a mute state and a non-mute state, selecting a state of higher system capacity out of the mute state and the non-mute state and setting the state as an actual transmission state of the first normal base station; and

a step E2 of the first normal base station obtaining an actual transmission state of each interference normal base station, using the third CQIs and the fourth CQIs as a basis to decide actual CQIs corresponding to the actual transmission state of the first normal base station and the actual transmission state of the interference normal base station and performing data scheduling and transmission in accordance with the actual CQI.

24. The method of claim 23, wherein the step B2 further comprises setting a measurement feedback group in advance for all users of the first normal base station and measuring signal strength of the normal base station in the measurement feedback group so that each of the users of the first normal base station can feed back the corresponding third CQIs.

25. The method of claim 23, wherein the step E2 further comprises, when the third CQIs and the fourth CQIs are the actual CQIs corresponding to the actual transmission state of the first normal base station and the actual transmission state of the interference normal base station, performing user scheduling of the first normal base station in accordance with the third CQIs and performing user scheduling of each of the low-power nodes covered by the first normal base station in accordance with the fourth CQIs.

26. The method of claim 23, wherein the step E2 further comprises performing calculation and updating of the third CQIs and the fourth CQIs to obtain actual CQIs corresponding to the actual transmission state of the first normal base station and the actual transmission state of the interference normal base station.

27. A method for coordinating inter-cell interference in a heterogeneous network (HetNet), comprising the steps of:

a step A3 of forming M transmission points (M is greater than

     1) into a coordinated group, each of the M transmission points including one or a plurality of normal base stations and low-power nodes covered by the respective normal base stations;

a step B3 of combining mute/non-mute states of bandwidths of the M transmission points to obtain a plurality of states of the coordinated group;

a step C3 of a user of each of the transmission points in the coordinated group feeding at least one channel quality indicator (CQI) corresponding to the states of the coordinated group, back to the transmission point;

a step D3 of making capacity estimation of the coordinated group based on the fed-back CQI to obtain a plurality of system capacities corresponding to the respective states of the coordinated group; and

a step E3 of setting the mute/non-mute states of the bandwidths of the M transmission points in accordance with a state of the coordinated group corresponding to an optimal system capacity so as to perform data transmission.

28. The method of claim 27, wherein

the states of the coordinated group in the step B3 include any combination of the mute/non-mute states of the M transmission points, and

in the step C3, a user of each of the transmission points decides M CQIs and each of the CQIs is related to signal strength of the corresponding transmission point and interference strength outside the coordinated group.

29. The method of claim 27, wherein

the states of the coordinated group in the step B3 are decided by a number of mute transmission points and the number of mute transmission points corresponding to an i-th state of the coordinated group is i (i=0, 1, . . . , M−

1), and

in the step C3, the user of each of the transmission points decides M CQIs and each of the CQIs is related to signal strength of the transmission point to which the user belongs, signal strength of another non-mute transmission point in the i-th state of the coordinated group and interference strength outside the coordinated group.

30. The method of claim 27, wherein

each of the states of the coordinated group in the step B3 corresponds to one of selections by, once a number N_close of mute transmission points is decided, selecting N_close transmission points arbitrarily from the M transmission points and making the N_close transmission points mute, a value of N_close being any of 1, . . . , M−

1, and

in the step C3, the user of each of the transmission points decides M CQIs, each of the CQIs being related to signal strength of the transmission point to which the user belongs, signal strength of another non-mute transmission point in the corresponding state of the coordinated group signal, and interference strength outside the coordinated group.