Fractional frequency reuse in heterogeneous networks

1. A method of operating a heterogeneous radio access network, the heterogeneous radio access network comprising a macro layer including at least one macro cell served by a macro base station node and a micro layer comprising at least one micro cell served by a micro base station node, the heterogeneous radio access network comprising plural macro cells and plural micro cells within each of the plural macro cells, the method comprising:

dividing a frequency bandwidth usable by the heterogeneous radio access network into a frequency-partitioned portion which is less than the entire frequency bandwidth;

assigning a frequency of the frequency-partitioned portion to a wireless terminal in an edge region of the micro cell;

assigning a frequency of the frequency bandwidth to a wireless terminal which is in a center region of the micro cell or at least within a center region of the macro cell;

dividing the frequency bandwidth usable by the heterogeneous radio access network into plural partitions including a first partition and a second partition;

dividing the plural partitions into plural sub-partitions;

assigning a frequency of a second partition to a wireless terminal in an edge region of one of the plural micro cells by:

assigning a frequency of a first sub-partition of the second partition if the wireless terminal is in an edge region of a micro cell in the first macro cell; and

assigning a frequency of a second sub-partition of the second partition if the wireless terminal is in an edge region of a micro cell in the second macro cell;

assigning a frequency of a first partition to a wireless terminal in one of the plural macro cells by:

assigning a frequency of a first sub-partition of the first partition if the wireless terminal is in a first macro cell and interferes with any micro base station node;

assigning a frequency of a second sub-partition of the first partition if the wireless terminal is in a second macro cell and interferes with any micro base station node.

2. The method of claim 1 , wherein in the frequency bandwidth the first sub-partition of the first partition is separated from the first sub-partition of the second partition by at least the second sub-partition of the first partition.

3. A method of operating a heterogeneous radio access network, the heterogeneous radio access network comprising a macro layer including at least one macro cell served by a macro base station node and a micro layer comprising at least one micro cell served by a micro base station node, the heterogeneous radio access network comprising plural macro cells and plural micro cells within each of the plural macro cells, the method comprising:

dividing a frequency bandwidth usable by the heterogeneous radio access network into a frequency-partitioned portion which is less than the entire frequency bandwidth;

assigning a frequency of the frequency-partitioned portion to a wireless terminal in an edge region of the micro cell;

assigning a frequency of the frequency bandwidth to a wireless terminal which is in a center region of the micro cell or at least within a center region of the macro cell;

dividing the frequency bandwidth usable by the heterogeneous radio access network into plural partitions including a first partition and a second partition;

dividing the plural partitions into plural sub-partitions;

assigning a frequency of a second partition to a wireless terminal in and edge region of one of the plural micro cells by:

assigning a frequency of a first sub-partition of the second partition if the wireless terminal is in an edge region of a micro cell in the second macro cell; and

assigning a frequency of the second sub-partition of the second partition if the wireless terminal is in an edge region of a micro cell in the second macro cell;

assigning a frequency of the second partition to a wireless terminal in one of the plural macro cells if the wireless terminal is in a macro cell and does not substantially interfere with any micro base station node.

4. The method of claim 3 , further comprising assigning a frequency of to the wireless terminal in one of the plural macro cells by:

assigning a frequency of a first sub-partition of the second partition if the wireless terminal is in a first macro cell and does not substantially interfere with any micro base station node;

assigning a frequency of a second sub-partition of the second partition if the wireless terminal is in a second macro cell and does not substantially interfere with any micro base station node.

5. The method of claim 3 , wherein in the frequency bandwidth the first sub-partition of the first partition is separated from the first sub-partition of the second partition by at least the second sub-partition of the first partition.

6. A base station node of a heterogeneous radio access network, the heterogeneous radio access network comprising a macro layer including at least one macro cell served by a macro base station node and a micro layer including at least one micro cell served by a micro base station node, wherein the heterogeneous radio access network comprises plural macro cells and plural micro cells within each of the plural macro cells, wherein a frequency bandwidth usable by the heterogeneous radio access network is divided into plural partitions and the plural partitions are divided into plural sub-partitions, wherein a first partition is associated with the plural macro cells and a second partition is associated with the plural micro cells, wherein the base station node serves a particular macro cell comprising the plural macro cells, the base station node comprising:

a terminal locator configured to obtain an indication of location of a wireless terminal in a cell served by the base station node;

a scheduler configured to use the indication of location to assign to the wireless terminal a frequency of the frequency bandwidth usable by the heterogeneous radio access network, the scheduler being configured to assign a frequency from a frequency-partitioned portion of the frequency bandwidth if the wireless terminal is in an edge region of the cell served by the base station node, the frequency-partitioned portion being less than the entire frequency bandwidth, and wherein the scheduler is further configured to assign to the wireless terminal a frequency of the second partition if the wireless terminal substantially interferes with a macro cell other than the particular macro cell and does not substantially interfere with a micro cell.

7. The base station node of claim 6 , wherein the scheduler is further configured to assign to the wireless terminal a frequency of a selected one of the sub-partitions of the second partition, and wherein the selected one of the sub-partitions of the second partition is associated with the particular macro cell.