Method for inter-cell interference coordination with power planning for OFDM mobile communication system

• US 20050265222A1
• Filed: 04/20/2005
• Published: 12/01/2005
• Est. Priority Date: 05/04/2004
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Gerlach, Christian Georg
• Granted Patent: US 7,636,334 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A method for inter-cell interference coordination with power planning in a radio communication system employing multi-carrier techniques such as OFDM for the air interface communication between a network and a plurality of user terminals, the network comprising a plurality of base stations having means for communication with the user terminals located inside their cell service area, the cells arranged following an adjacent cell pattern, where neighbor cells do not have the same number and cells with the same number are separated by at least one cell in-between, for resource planning purposes, each cell having an inner cell region and a border cell region in which inter-cell interference is affecting the quality of service received by a user terminal.

Claims

1. Method for inter-cell interference coordination with power planning in a radio communication system employing multi-carrier techniques such as OFDM for the air interface communication between a network and a plurality of user terminals, the network comprising a plurality of base stations having means for communication with the user terminals located inside their cell service area, the cells arranged following an adjacent cell pattern, where neighbor cells do not have the same number and cells with the same number are separated by at least one cell in-between, for resource planning purposes, each cell having an inner cell region and a border cell region in which inter-cell interference is affecting the quality of service received by a user terminal, wherein

an OFDM wireless communication channel is designed so that a terminal can receive at least two pilot channels in parallel, one for each cell service area interfering at the border cell region,

an OFDM time-frequency grid is partitioned in a number of orthogonal, non-overlapping time-frequency patterns, and said time-frequency patterns are grouped in a number of disjunct subsets or time-frequency groups, the number of disjunct subsets corresponding to the number of different cells from the cell pattern for resource planning,

in each cell all time-frequency groups are used for communication with the terminals, but emission within a determined time-frequency group corresponding to the cell number is done with reduced power limited to a certain power value which is smaller than a maximum power available for transmission within the time-frequency groups,

when a terminal moves from an inner cell region of a serving cell to the border cell region of said cell and in the direction of a neighbor cell, it measures pilot signals from the interfering neighbor cells in that region and reports to the mobile radio network information about the strength of reception from these cell pilot signals,

based on the terminal information an network criteria, the mobile radio network assigns to the terminal time-frequency patterns of the time-frequency group with which said neighbor cell emits with limited power.

2. The method for inter-cell interference coordination with power planning of claim 1 characterized in that the ratio between the maximum power available for transmission with the time-frequency groups and the limited power value for transmission within a determined time-frequency group in a cell guarantees an SIR allowing satisfying transmission with said power restricted time-frequency group when used by a terminal originating from a cell, and moving into the border region in direction of a neighboring cell.

3. The method for inter-cell interference coordination with power planning of claim 1 characterized in that the time-frequency groups are further split in disjunct subsets e.g. two subsets, with different power limit above the limit power value used for power restriction of time frequency groups, dependent on the cell number, so as to deal with the interference at the cell corners of three cells.

4. The method for inter-cell interference coordination with power planning of claim 1 characterized in that the mobile radio network further uses an ARQ mechanism with the terminal, such as HARQ, to reschedule packets that were received in error when sent to the terminal.

5. The method for inter-cell interference coordination with power planning of claim 1 characterized in that the time-frequency pattern or time-frequency group assignments for the terminals in the inner cell region not using coordination are periodically changed in a random or pseudo random manner, so as to shape a caused inter-cell interference more evenly over the time-frequency pattern.

6. The method for coordinated interference avoidance of claim 1 wherein the base stations are not time synchronized.

7. The method for inter-cell interference coordination with power planning of claim 1 characterized in that the OFDM time-frequency grid is partitioned in a number of orthogonal, non-overlapping frequency patterns that use no frequency hopping.

8. The method for inter-cell interference coordination with power planning of claim 7 characterized in that the OFDM system pilot channels received by the terminal in different cells are designed in an interleaving non overlapping fashion with pilot symbols having higher energy as the data.

9. The method of claim 7 characterized in that each basic frequency pattern occupies the same locations in all cells independent of the cell specific pilot pattern and further contains sufficient place in each pattern to accommodate for the specific sending cell pilot positions leaving at least always the basic number of time-frequency locations for the basic channel data rate of such a pattern, so that a basic frequency pattern gets no interference from the sending cell pilots and just interference from neighboring cells with different pilot pattern and only maximally as much as amounts to the overhead place left for sending pilot locations i.e. the difference between the total place of the frequency pattern and the basic number of time-frequency locations for the basic channel data rate.

10. A mobile radio network comprising means for partitioning an OFDM time-frequency grid in a number of orthogonal, non-overlapping time-frequency patterns, and grouping them in a number of disjunct subsets or time-frequency groups, where a time-frequency group contains at least one of said time-frequency patterns, and assigning a user terminal one or more of said time-frequency patterns for communication;

means for transmitting inside a cell using all time-frequency groups and for limiting the power of emission for one of said groups in each cell;

means for receiving signaling information from a terminal about strength of reception measurements on cell pilot signals in a border cell region and means for analyzing said information and for assigning to the terminal a time-frequency group with which an interfering cell emits with reduced power limited by a certain power value.

11. A network element comprising means for receiving information about a determined cell pattern and/or OFDM time-frequency grid arrangement in a number of disjunct subsets or time-frequency groups, where a time-frequency group contains at least one time-frequency pattern;

means for assigning a user terminal one or more of said time-frequency patterns for communication;

means for transmitting inside a cell using all time-frequency groups and for limiting the power of emission for one of said groups in each cell;

means for receiving signaling information from a terminal about strength of reception measurements on cell pilot signals in a border cell region and means for analyzing said information and for assigning to the terminal a time-frequency group with which an interfering cell emits with reduced power limited by a certain power value.

12. A user terminal comprising means for receiving at least two OFDM pilot channels in parallel, means for negotiating one or more time frequency patterns from time-frequency groups with a mobile radio network communication;

means for measuring the OFDM pilot signals from interfering neighbor cells in a border cell region and for reporting said information to the mobile radio network.