Enhanced interference management in heterogeneous wireless networks

Patent metadata

Field	Value
Publication number	US-9538415-B2
Application number	US-201514603723-A
Country	US
Kind code	B2
Filing date	Jan 23, 2015
Priority date	Jan 23, 2014
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

We show that for any given muting fraction, a more constrained version of the problem of interest can be optimally solved in an efficient manner. In addition, the obtained solution is also a near-optimal solution for the original problem (for the given muting ratio). This allows us provide an algorithm that offers a good solution to the original problem with a tractable complexity. We also derive a lower complexity greedy that offers good performance and a certain worst-case performance guarantee. Simulations over an example LTE HetNet topology reveal the superior performance of the proposed algorithms and underscore the benefits of jointly exploiting partial muting of the macro and load balancing.

First claim

The invention claimed is:

1. A computer implemented method comprising:
varying association of users to any one of multiple transmission points in a heterogeneous wireless network for managing interference of transmissions in the network, a muting fraction being one transmission point TP being inactivated or muted for a fraction of a frame duration while other transmission points TPs being active throughout the frame duration;
determining, at a coarse time-scale, at the start of each frame a choice of which muting fraction to select for a macro TP and which users to associate with each TP so that all users are associated to one TP, by solving an optimization problem;
averaging inputs to the optimization problem varying metrics that are relevant for a period longer than a backhaul latency, the varying metrics including metrics as single user rates under muting conditions and non-muting conditions with a set of muting fractions;
applying a coarse scale approach to solving the optimization problem, the coarse scale approach being based on frame level TP coordination of user association and macro partial muting; and
applying a fine scale approach to solving the optimization problem, the fine scale approach being based on sub-frame level per-TP user scheduling without coordination.

2. The computer implemented method of claim 1 , wherein the fine time scale approach comprises that in each slot each active TP independently does scheduling over a set of users associated with it, without any coordination with any of the other active TPs, based on fast changing information, such as instantaneous rate or SINR estimates, that is received directly by that TP from the users associated to it.

3. The computer implemented method of claim 1 , wherein the coarse time scale approach comprises selecting a muting fraction from a feasible set of transmission points and users that have not been picked before and determining system utility that includes user associations and an optimal allocation of a muting fraction for determined user associations.

4. The computer implemented method of claim 3 , further comprising if this is the first system utility determined or if it is the largest one yet determined, then designating it as a largest utility and storing a corresponding muting fraction and user association.

5. The computer implemented method of claim 4 , further comprising considering if all muting fractions have been considered in determining the system utility and if so outputting the muting fraction and corresponding user association that yields the largest utility of the network.

6. The computer implemented method of claim 2 , wherein the fine time scale approach comprises selecting a muting fraction from a feasible set of muting fractions, that has not been picked before, defining a muting fraction set containing all selected user and TP pairs, and setting that muting fraction set to be a null or empty set.

7. The computer implemented method of claim 6 , wherein the fine time scale approach comprises selecting and adding to the muting fraction set, the user and TP pair such that the user has not been selected before and that pair that offers the best gain in system utility among all pairs containing such users.

8. The computer implemented method of claim 7 , further comprising considering if all users have been assigned a TP and, if so, obtaining a system utility yielded by the muting fraction set of selected user and TP pairs.

9. A non-transitory storage medium configured with instructions for being implemented by a computer for carrying out the method comprising:
varying association of users to any one of multiple transmission points in a heterogeneous wireless network for managing interference of transmissions in the network, a muting fraction being one transmission point TP being inactivated or muted for a fraction of a frame duration while other transmission points TPs being active throughout the frame duration;
determining, at a coarse time-scale, at the start of each frame a choice of which muting fraction to select for a macro TP and which users to associate with each TP so that all users are associated to one TP, by solving an optimization problem;
averaging inputs to the optimization problem varying metrics that are relevant for a period longer than a backhaul latency, the varying metrics including metrics as single user rates under muting conditions and non-muting conditions with a set of muting fractions;
applying a coarse scale approach to solving the optimization problem, the coarse scale approach being based on frame level TP coordination of user association and macro partial muting; and
applying a fine scale approach to solving the optimization problem, the fine scale approach being based on sub-frame level per-TP user scheduling without coordination.

10. The non-transitory storage medium of claim 9 , wherein the fine time scale approach comprises that in each slot each active TP independently does scheduling over a set of users associated with it, without any coordination with any of the other active TPs, based on fast changing information, such as instantaneous rate or SINR estimates, that is received directly by that TP from the users associated to it.

11. The non-transitory storage medium of claim 9 , wherein the coarse time scale approach comprises selecting a muting fraction from a feasible set of transmission points and users that have not been picked before and determining system utility that includes user associations and an optimal allocation of a muting fraction for determined user associations.

12. The non-transitory storage medium of claim 3 , further comprising if this is the first system utility determined or if it is the largest one yet determined, then designating it as a largest utility and storing a corresponding muting fraction and user association.

13. The non-transitory storage medium of claim 2 , further comprising considering if all muting fractions have been considered in determining the system utility and if so outputting the muting fraction and corresponding user association that yields the largest utility of the network.

14. The non-transitory storage medium of claim 10 , wherein the fine time scale approach comprises selecting a muting fraction from a feasible set of muting fractions, that has not been picked before, defining a muting fraction set containing all selected user and TP pairs, and setting that muting fraction set to be a null or empty set.

15. The non-transitory storage medium of claim 14 , wherein the fine time scale approach comprises selecting and adding to the muting fraction set, the user and TP pair such that the user has not been selected before and that pair that offers the best gain in system utility among all pairs containing such users.

16. The non-transitory storage medium of claim 15 , further comprising considering if all users have been assigned a TP and, if so, obtaining a system utility yielded by the muting fraction set of selected user and TP pairs.

Assignees

• Nec Lab America Inc
• Nec Corp

Inventors

• Prasad Narayan
• Arslan Mustafa
• Rangarajan Sampath

Classifications

• H04W24/02

  Arrangements for optimising operational condition · CPC title

• H04L5/0058

  Allocation criteria · CPC title

• H04L5/0037

  Inter-user or inter-terminal allocation · CPC title

• H04L5/0076

  Allocation utility-based · CPC title

• H04W28/0236 Primary

  radio quality, e.g. interference, losses or delay · CPC title