Autonomous determination of optimal values for handover parameters

Patent metadata

Field	Value
Publication number	US-9572071-B2
Application number	US-201314436279-A
Country	US
Kind code	B2
Filing date	Oct 15, 2013
Priority date	Oct 18, 2012
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

The present invention relates to a method for adjusting handover parameters (TTT; OFF) used for handover detection within a given serving cell (CS). In accordance with an embodiment of the invention, the method comprises, for respective ones of a plurality of mobile stations (UE 1 . . . UEN) served by the serving cell, gathering measurement samples (M(i,CS,k); M(i,CN,k)) of the serving cell and of a respective neighboring cell (CN) carried out by a respective mobile station (UEi) at successive time instances (k), and determining delta values (Δ(i,CN,k)) indicative of the time-indexed difference between respective ones of the measurement samples of the serving cell and corresponding ones of the measurement samples of the neighboring cell. The method further comprises determining near-optimal values (TTT NO ; OFF NO ) for the handover parameters by statistical characterization of the ensembles of delta values for the plurality of mobile stations. The near-optimal values may be input to an iterative closed-loop optimization algorithm in order to determine optimal values (TTT O ; OFF O ) for the handover parameters. The present invention also relates to a handover configuration agent ( 150 ) implementing the proposed method.

First claim

The invention claimed is:

1. A method for jointly adjusting Time-To-Trigger (TTT) and offset handover parameters used for handover detection within a given serving cell, the method comprising:
receiving, during a preliminary sensing phase and from a plurality of mobile stations served by the serving cell, measurement samples of the serving cell and of respective neighboring cells carried out by the respective mobile stations at successive and regular time instances, the measurement samples being indicative of the respective strengths or qualities of pilot signals received by the respective mobile stations from the respective serving and neighboring cells, determining delta values indicative of the time-indexed difference between respective ones of the measurement samples of the serving cell and corresponding ones of the measurement samples of the neighboring cells; and
determining near-optimal values for the handover parameters by statistical characterization of the ensembles of delta values for the plurality of mobile stations.

2. The method according to claim 1 , wherein the method further comprises inputting the near-optimal values to an iterative closed-loop optimization algorithm in order to determine optimal values for the handover parameters.

3. The method according to claim 2 , wherein the iterative closed-loop optimization algorithm is based on a simulated annealing algorithm.

4. The method according to claim 1 , wherein the plurality of mobile stations belongs to a particular speed class, and wherein the near-optimal values for the handover parameters are determined on per speed class basis.

5. The method according to claim 1 , wherein the statistical characterization of the ensembles of delta values for the plurality of mobile stations involves the characterization of variances of the delta values for respective ones of the plurality of mobile stations over varying time windows.

6. The method according to claim 5 , wherein the method further comprises, for respective ones of the plurality of mobile stations, and from a given time index onwards, estimating variance values over a time-window of K successive delta values for respective increasing K values, and determining a minimum time-window length beyond which the so-determined variance values lies within a given small interval,
and wherein the method further comprises determining a Time-To-Trigger TTT value, during which measurement samples of the serving cell and a given target cell shall fulfill a given handover condition, by statistical characterization of the so-determined minimum time-window lengths for the plurality of mobile stations.

7. The method according to claim 6 , wherein the so-determined TTT value is such that a given proportion of the so-determined minimum time-window lengths for the plurality of mobile stations are lower than or equal to the TTT value.

8. The method according to claim 6 , wherein the method further comprises determining a nominal variance value by statistical characterization of the so-estimated variance values, and inputting the so-determined nominal variance value, along with a first upper bound for a handover detection time and a second upper bound for a false handover detection rate, to a Page Hinkley statistical test so as to determine an offset value whereby the target cell shall be measured offset-better than the serving cell for the handover condition to be fulfilled.

9. The method according to claim 8 , wherein the nominal variance value is determined such that a further given proportion of the variance values estimated for the plurality of mobile stations over time-windows of lengths equal to the TTT value are lower than or equal to the nominal variance value.

10. The method according to claim 4 , wherein the determination of the offset value is instantiated on a per neighboring cell basis,
and wherein the first upper bound is adjusted based on an inter-site distance between the serving and a given neighboring cell and on the particular speed class.

11. A configuration agent for jointly adjusting Time-To-Trigger (TTT) and offset handover parameters used for handover detection within a given serving cell, and configured:
to receive, during a preliminary sensing phase and from a plurality of mobile stations served by the serving cell, measurement samples of the serving cell and of respective neighboring cells carried out by the respective mobile stations at successive and regular time instances, the measurement samples being indicative of the respective strengths or qualities of pilot signals received by the respective mobile stations from the respective serving and neighboring cells, to determine delta values indicative of the time-indexed difference between respective ones of the measurement samples of the serving cell and corresponding ones of the measurement samples of the neighboring cell; and
to determine near-optimal values for the handover parameters by statistical characterization of the ensembles of delta values for the plurality of mobile stations.

12. A radio access node comprising a configuration agent according to claim 11 .

13. A radio access controller comprising a configuration agent according to claim 11 .

14. A network manager comprising a configuration agent according to claim 11 .

15. A non-transient computer readable medium carrying instructions which when executed by at least one processor provide a configuration agent for jointly adjusting Time-To-Trigger (TTT) and offset handover parameters used for handover detection within a given serving cell, the processor thereby being configured:
to receive, during a preliminary sensing phase and from a plurality of mobile stations served by the serving cell, measurement samples of the serving cell and of respective neighboring cells carried out by the respective mobile stations at successive and regular time instances, the measurement samples being indicative of the respective strengths or qualities of pilot signals received by the respective mobile stations from the respective serving and neighboring cells, to determine delta values indicative of the time-indexed difference between respective ones of the measurement samples of the serving cell and corresponding ones of the measurement samples of the neighboring cell; and
to determine near-optimal values for the handover parameters by statistical characterization of the ensembles of delta values for the plurality of mobile stations.

16. A radio access node comprising non-transient computer readable medium carrying instructions which when executed by at least one processor provide a configuration agent according to claim 15 .

17. A radio access controller comprising a non-transient computer readable medium carrying instructions which when executed by at least one processor provide a configuration agent according to claim 15 .

18. A network manager comprising a non-transient computer readable medium carrying instructions which when executed by at least one processor provide a configuration agent according to claim 15 .

Assignees

• Alcatel Lucent

Inventors

• Capdevielle Veronique
• Feki Afef

Classifications

• H04W36/0083

  Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists · CPC title

• H04W36/0094

  Definition of hand-off measurement parameters · CPC title

• H04W36/0005 Primary

  Control or signalling for completing the hand-off · CPC title

• H04W24/02

  Arrangements for optimising operational condition · CPC title

• H04W36/0007

  for multicast or broadcast services, e.g. MBMS (multicast or broadcast application services H04W4/06; resource management for broadcast services H04W72/30; connection management for selective distribution or broadcast H04W76/40) · CPC title