Selecting radio frequency channels for reuse in micro-cellular radio communications systems

• US 5,828,963 A
• Filed: 03/24/1995
• Issued: 10/27/1998
• Est. Priority Date: 03/24/1995
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Grandhi, Sudheer A., Madhavapeddy, Seshagiri R., Basu, Kalyan, Willhoff, Steven J., Staley, Hong D.
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): Nguyen, Lee
• Application Number:
  US08/409,802
• Time in Patent Office: 1,313 Days
• Field of Search: 455/33.1, 455/33.2, 455/33.4, 455/34.1, 455/34.2, 455/54.1, 455/56.1, 455/62, 455/63, 455/67.1, 455/422, 455/447, 455/448, 455/449, 455/450, 455/451, 455/452 , 455/453, 455/454, 455/524, 379/58, 379/59
• US Class Current: 455/450
• CPC Class Codes: H04W 16/04 Traffic adaptive resource partitioning
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 16/32 Hierarchical cell structures
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 72/563 of the wireless resources

Abstract

A micro-cellular radio communications system (microsystem) is arranged to re-use radio frequency channels which are assigned for use in a cellular radio system (macrosystem) in the same vicinity. The microsystem maintains a list of each frequency channel which is in current use in any microcell of the microsystem. In each microcell of the microsystem a signal characteristic, for example received signal strength, of each frequency channel, is repeatedly measured when the channel is not in current use in any microcell of the microsystem, and the measurements are used to determine a long-term statistical preference for re-use of a favoured set of the frequency channels in that microcell. For each microcell, the frequency channels in the favoured set are given a short-term order for actual use in dependence upon frequent measurements of the signal characteristic for the microcell regardless of whether or not the channel is in current use in any other microcell of the microsystem.

Claims

1. A method of selecting radio frequency channels, assigned for use in cells of a cellular radio communications system (macrosystem), for use in microcells of a micro-cellular radio communications system (microsystem) in the vicinity of the macrosystem, comprising the steps of:

identifying in the microsystem during operation of the microsystem each frequency channel which is in current use in any microcell of the microsystem; and

for each microcell of the microsystem,

measuring a signal characteristic for the microcell of each frequency channel when the channel is not identified as being in current use in any microcell of the microsystem;

determining a statistical preference for use of the frequency channels in the microcell in dependence upon repeated measurements of the signal characteristic; and

selecting frequency channels for use in the microcell in accordance with the statistical preference.

2. A method as claimed in claim 1 wherein the step of identifying each frequency channel which is in current use comprises maintaining a list of frequency channels in use in any microcell of the microsystem.

3. A method as claimed in claim 1 wherein, for each microcell of the microsystem, the steps of determining a statistical preference and selecting frequency channels for use in the microcell comprise identifying a favoured set of frequency channels, having a most preferred signal characteristic, and using only frequency channels in the favoured set in the microcell of the microsystem.

4. A method as claimed in claim 3 wherein the favoured set comprises a predetermined number of frequency channels.

5. A method as claimed in claim 4 wherein, for each microcell of the microsystem, the measurement of the signal characteristic for each frequency channel in the favoured set is effected more frequently than the measurement of the signal characteristic for each frequency channel which is not in the favoured set.

6. A method as claimed in claim 3 wherein, for each microcell of the microsystem, the measurement of the signal characteristic for each frequency channel in the favoured set is effected more frequently than the measurement of the signal characteristic for each frequency channel which is not in the favoured set.

7. A method as claimed in claim 6 wherein the measured signal characteristic of each frequency channel comprises a received signal strength of the frequency channel, channels having lower received signal strength measurements in each microcell being more preferred for use in the microcell.

8. A method as claimed in claim 3 and further comprising, for each microcell of the microsystem, the steps of:

measuring the signal characteristic for the microcell of each frequency channel in the favoured set regardless of whether or not the channel is identified as being in current use in any microcell of the microsystem; and

determining an order for use of the frequency channels in the favoured set in dependence upon recent measurements of the signal characteristic;

wherein the step of selecting frequency channels for use in the microcell comprises selecting frequency channels for use in the microcell in accordance with the determined order.

9. A method as claimed in claim 8 wherein, for each microcell of the microsystem, the measurement of the signal characteristic for each frequency channel in the favoured set is effected more frequently than the measurement of the signal characteristic for each frequency channel which is not in the favoured set.

10. A method as claimed in claim 9 wherein the measured signal characteristic of each frequency channel comprises a received signal strength of the frequency channel, channels having lower received signal strength measurements in each microcell being more preferred for use in the microcell.

11. A method as claimed in claim 8 wherein the measured signal characteristic of each frequency channel comprises a received signal strength of the frequency channel, channels having lower received signal strength measurements in each microcell being more preferred for use in the microcell.

12. A method as claimed in claim 1 wherein the measured signal characteristic of each frequency channel comprises a received signal strength of the frequency channel, channels having lower received signal strength measurements in each microcell being more preferred for use in the microcell.

13. A method of selecting radio frequency channels, for use in a plurality of microcells of a microcellular radio communications system, from a set of frequency channels, comprising the steps of, for each microcell;

performing signal measurements for frequency channels in the set;

determining a favoured set of frequency channels for use in the microcell in dependence upon signal measurements performed during operation of the microsystem for each frequency channel only when the frequency channel is not in use in any microcell of the microsystem; and

selecting a frequency channel for use in the microcell from the favoured set of frequency channels in dependence upon signal measurements performed during operation of the microsystem regardless of whether or not the frequency channel is in current use in any microcell of the microsystem.

14. A method as claimed in claim 13 wherein, for each microcell, the signal measurements are performed more frequently for frequency channels in the favoured set than for frequency channels which are not in the favoured set.

15. A method of selecting radio frequency channels, assigned for use in cells of a cellular radio communications system (macrosystem), for use in microcells of a micro-cellular radio communications system (microsystem) in the vicinity of the macrosystem, comprising the steps of:

identifying in the microsystem during operation of the microsystem each frequency channel which is in current use in any microcell of the microsystem; and

for each microcell of the microsystem,

measuring a signal characteristic for the microcell of each frequency channel when the channel is not identified as being in current use in any microcell of the microsystem;

identifying a favoured set of frequency channels, having a most preferred signal characteristic, and using only frequency channels in the favoured set in the microcell of the microsystem;

measuring the signal characteristic for the microcell of each frequency channel in the favoured set regardless of whether or not the frequency channel is identified as being in current use in any microcell of the microsystem, the measured signal characteristic of each frequency channel in the favoured set comprising a received signal strength of the frequency channel;

determining an order for use of the frequency channels in the favoured set in accordance with a parameter which is increased in proportion to increases in, and decreased more slowly than decreases in, the received signal strength measurements of each frequency channel in the favoured set, the lower values of the parameter being preferred; and

selecting frequency channels for use in the microcell in accordance with the determined order.

16. A method as claimed in claim 15 wherein, for each microcell of the microsystem, the measurement of the signal characteristic for each frequency channel in the favoured set is effected more frequently than the measurement of the signal characteristic for each frequency channel which is not in the favoured set.

17. A method of selecting radio frequency channels, for use in a plurality of microcells of a micro-cellular radio communications system, from a set of frequency channels, comprising the steps of, for each microcell:

performing signal measurements for frequency channels in the set;

determining a favoured set of frequency channels for use in the microcell in dependence upon signal measurements performed during operation of the microsystem for each frequency channel when the frequency channel is not in use in any microcell of the microsystems; and

selecting a frequency channel for use in the microcell from the favoured set of frequency channels in dependence upon signal measurements performed during operation of the microsystem regardless of whether or not the frequency channel is in current use in any microcell of the microsystem, the selected frequency channel having a lowest value of a parameter which is increased in proportion to increases in, and decreased more slowly than decreases in, a received signal strength measurement of the frequency channel.

18. A method as claim 17 wherein, for each microcell, the signal measurements are performed more frequently for frequency channels in the favoured set than for frequency channels which are not in the favoured set.

19. In a micro-cellular radio communications system (microsystem) which re-uses radio frequency channels assigned for use in cells of a cellular radio communications system (macrosystem) in the same vicinity as the microsystem, and in which a plurality of frequency channels are selected for potential use in each microcell of the microsystem, a method of assigning the selected frequency channels for use in each microcell, comprising the steps of:

repeatedly measuring in the microcell during operation of the microsystem a received signal strength of each selected frequency channel regardless of whether or not the channel is in current use in the microsystem;

determining a preference for use of the selected frequency channels in accordance with a parameter which is increased in proportion to increases in, and decreased more slowly than decreases in, the received signal strength measurement of each selected frequency channel, lower values of the parameter being preferred for use in the microcell; and

assigning the selected frequency channels for use in the microcell in accordance with the determined preference.