Method and apparatus for determining an interference relationship between cells of a cellular communication system
The invention relates to a system for determining an interference relationship between cells of a cellular communication system comprising at least a first cell and a second cell. A method comprises the step of dividing ( 205 ) an evaluation interval into a plurality of sub-intervals. For each sub interval, the method proceeds to determine ( 209 ) a sub-interval simultaneous occupancy related to the correlation between communication in the first and second cell. The sub-interval simultaneous occupancy is determined from an occupancy of each of the first cell and the second cell. A sub-interval potential interference is then determined ( 209 ) in response to the interference characteristics in each sub-interval. An interference relationship is subsequently determined from the sub-interval potential interferences and the sub-interval simultaneous occupancies. The interference relationship provides a measure of the impact of interference between the first and second cell suitable for frequency planning.
1 . A method of determining an interference relationship between cells of a cellular communication system comprising at least a first cell and a second cell; the method comprising the step of:
determining an interference relationship between the first cell and the second cell in response to a potential interference relationship between the first and the second cell and a simultaneous occupancy of the first cell and the second cell.
2 . A method as claimed in claim 1 further comprising the steps of:
dividing an evaluation interval into sub-intervals;
for each sub-interval determining a sub-interval potential interference in response to the interference characteristics in each sub-interval; and
determining the potential interference relationship for the evaluation interval in response to the sub-interval potential interferences.
3 . A method as claimed in claim 1 wherein the step of determining a simultaneous occupancy comprises the steps of:
dividing an evaluation interval into sub-intervals;
for each sub-interval, determining a sub-interval simultaneous occupancy by determining an occupancy of each of the first cell and the second cell; and
determining the simultaneous occupancy for the evaluation interval in response to the sub-interval simultaneous occupancies.
4 . A method as claimed in claim 1 further comprising the steps of:
dividing an evaluation interval into a plurality of sub-intervals;
for each sub-interval performing the steps of:
determining a sub-interval simultaneous occupancy by determining an occupancy of each of the first cell and the second cell,
determining a sub-interval potential interference in response to the interference characteristics in each sub-interval, and
determining a sub-interval interference relationship in response to the sub-interval simultaneous occupancies and the sub-interval potential interferences; and
wherein the interference relationship is determined in response to the sub-interval interference relationships.
5 . A method as claimed in claim 3 wherein the step of determining the simultaneous occupancy for the evaluation interval comprises determining the simultaneous occupancy as an average of the sub-interval simultaneous occupancies
6 . A method as claimed in claim 3 wherein the occupancy of at least one of the first cell and the second cell is determined from network statistics.
7 . A method as claimed in claim 6 wherein the network statistics comprise a measurement report quantity characteristic.
8 . A method as claimed in claim 1 wherein the potential interference relationship is determined in response to a measurement of a signal level in the second cell associated with a transmission in the first cell.
9 . A method as claimed in claim 1 wherein the potential interference relationship is associated with assignment of co-channel carriers in the first and the second cell.
10 . A method as claimed in claim 1 wherein the potential interference relationship is associated with assignment of adjacent channel carriers in the first and the second cell.
11 . A method as claimed in claim 1 wherein the potential interference relationship is in response to a ratio of communication units of the second cell for which an interference from the first cell will cause a quality level below a given threshold.
12 . A method as claimed in claim 1 , further comprising the step of frequency planning for the cells of the cellular communication system, frequency planning including the substeps of:
for the combinations of two cells determining a penalty associated with a corresponding frequency allocation in response to the interference relationship of that combination of two cells; and
allocating carrier frequencies to the plurality of cells in response to the penalty values.
13 . A method as claimed in claim 12 wherein the frequency allocation is such that the sum of penalty values is minimised.
14 . A method as claimed in claim 12 wherein the penalty values are associated with corresponding frequency allocations of co-channel frequencies.
15 . A method planning as claimed in claim 12 wherein the penalty values are associated with the corresponding frequency allocations of adjacent channel frequencies.
16 . A method according to claim 1 wherein the cellular communication system is a GSM communication system.
17 - 18 . (canceled)
19 . An apparatus for determining an interference relationship between cells of a cellular communication system comprising at least a first cell and a second cell; the apparatus comprising:
means for determining an interference relationship between the first cell and the second cell in response to a potential interference relationship between the first and second cell and a simultaneous occupancy of the first and the second cell.