Method and apparatus for frequency reuse in cellular communication systems

• US 6,188,903 B1
• Filed: 10/20/1999
• Issued: 02/13/2001
• Est. Priority Date: 09/25/1995
• Status: Expired due to Term

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Petranovich, James E., Hardin, Carl Thomas, Gilbert, Sheldon L., Gardner, Steven H.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Kincaid, Lester G.
• Application Number:
  US09/422,032
• Time in Patent Office: 482 Days
• Field of Search: 455/446, 455/447, 455/450, 455/452, 455/455, 455/502, 455/503, 455/509, 455/517, 455/524, 455/526, 455/62, 455/63, 370/328, 370/329, 370/330, 370/341, 370/343, 370/350, 370/431, 370/436
• US Class Current: 455/447
• CPC Class Codes: H04B 7/2615 using hybrid frequency-time division multiple access [FDMA-TDMA]
• CPC Class Codes: H04B 7/265 for channel frequency control
• CPC Class Codes: H04B 7/2693 Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 16/12 Fixed resource partitioning
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 68/00 User notification, e.g. alerting and paging, for incoming communication, change of service or the like
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems

Abstract

A time sharing method and apparatus for frequency reuse in cellular communication systems. Frequency reuse is enhanced by synchronizing cell transmit/receive base stations in a cellular system to a common time base, and then sharing the available frequencies via allocated time slots. Cells using the same frequency that may interfere with each other are activated only during selected time intervals while same-frequency cells nearby are deactivated. The deactivated cells are then in turn activated while previously activated same-frequency cells nearby are deactivated. The frequency time slots may be of equal length, or longer time slots may be allocated to cells having higher usage rates, as determined in any of a number of ways. The time slots may be mutually exclusive, or may overlap. The time sharing technique of the present invention allows design of cell systems with many reuse patterns. Several particular cell reuse patterns are disclosed that provide good operational characteristics and low co-channel interference. The invention allows the use of a small number of cellular frequencies in a conventional cellular system without significant alteration of the existing system, and is particularly useful in two-way cellular paging systems. Improved reverse link data throughput is achieved via reuse of the reverse frequency channels.

Claims

1. A method of channel reuse in a cellular communication system having a plurality of frequency channels for communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating a plurality of cellular time slots for communication on frequency channels, each cellular time slot in each frequency having a period sufficient to support a typical block transfer time in the cellular communication system, the cellular time slots responsive to the synchronizing of base stations; and

c) geographically assigning the plurality of cellular time slots to cells in the cellular communication system by substantially spacing potential co-channel interferers as far apart as possible within each cell group and substantially equally spacing potential co-channel interferers between adjacent cell groups to minimize co-channel interference and placing adjacent channel interferers in non-adjacent cells to minimize adjacent channel interference.

2. The method of claim 1 for channel reuse in a cellular communication system, wherein,

the allocation of the plurality of cellular time slots partially overlap at the beginning and ending of adjacent cellular time slots.

3. The method of claim 1 for channel reuse in a cellular communication system, wherein,

at least one of the plurality of cellular time slots have a different period than others of the plurality of cellular time slots.

4. The method of claim 1 for channel reuse in a cellular communication system, wherein,

each of the plurality of cellular time slots have equivalent periods and the allocation of the plurality of cellular time slots partially overlap at the beginning and ending of adjacent cellular time slots.

5. The method of claim 1 for channel reuse in a cellular communication system, wherein,

at least one of the plurality of cellular time slots have a different period than others of the plurality of cellular time slots and the allocation of the plurality of cellular time slots partially overlap at the beginning and ending of adjacent cellular time slots.

6. The method of claim 1 for channel reuse in a cellular communication system, wherein,

the plurality of frequency channels are shared channels for the reverse link communication from subscriber units to base stations and for the forward link communication from base stations to subscriber units within the cellular communication system.

7. The method of claim 1 for channel reuse in a cellular communication system, wherein,

the plurality of frequency channels are forward channels for communication from base stations to subscriber units within the cellular communication system.

8. The method of claim 1 for channel reuse in a cellular communication system, wherein,

the plurality of frequency channels are reverse channels for communication from subscriber units to base stations within the cellular communication system.

9. A method of channel reuse in a cellular communication system having a plurality of frequency channels for communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating N cellular time slots for communication on M frequency channels, each of the N cellular time slots having a period sufficient to support a typical block transfer time in the cellular communication system, the N cellular time slots responsive to the synchronizing of base stations, and

c) assigning the N cellular time slots and the M frequency channels to N×

M cells and geographically arranging the N×

M cells within a cell grouping of a plurality of cell groupings within the cellular communication system such that the potential co-channel interferers are substantially spaced apart as far as possible within each cell group and are substantially equally spaced apart between adjacent cell group to minimize co-channel interference and the potential adjacent channel interferers are placed in nonadjacent cells to minimize adjacent channel interference.

10. The method of claim 9 for channel reuse in a cellular communication system, wherein,

the plurality of frequency channels are shared channels for the reverse link communication from subscriber units to base stations and for the forward link communication from base stations to subscriber units within the cellular communication system.

11. The method of claim 9 for channel reuse in a cellular communication system, wherein,

the plurality of frequency channels are forward channels for communication from base stations to subscriber units within the cellular communication system.

12. The method of claim 9 for channel reuse in a cellular communication system, wherein,

the plurality of frequency channels are reverse channels for communication from subscriber units to base stations within the cellular communication system.

13. A method of channel reuse in a cellular communication system having a plurality of frequency channels for communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating N time slots for communication on M frequency channels, each of the N time slots having a period sufficient to support a typical block transfer time in the cellular communication system, the N time slots responsive to the synchronizing of base stations;

c) geographically arranging N×

M cells within a cell grouping of a plurality of cell groupings within the cellular communication system such that the potential co-channel interferers are substantially equally spaced apart as far as possible among all cells to minimize co-channel interference and the potential adjacent channel interferers are placed in nonadjacent cells to minimize adjacent channel interference; and

,

wherein N is 2 and M is 7 such that there are 14 cells associated with seven frequency channels and two time slots within a cell grouping with each cell grouping geographically arranged within the cellular communication system as shown in FIG. 7.

14. A The method of channel reuse in a cellular communication system having a plurality of frequency channels for communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating N time slots for communication on M frequency channels, each of the N time slots having a period sufficient to support a typical block transfer time in the cellular communication system, the N time slots responsive to the synchronizing of base stations;

c) geographically arranging N×

M cells within a cell grouping of a plurality of cell groupings within the cellular communication system such that the potential co-channel interferers are substantially equally spaced apart as far as possible among all cells to minimize co-channel interference and the potential adjacent channel interferers are placed in nonadjacent cells to minimize adjacent channel interference; and

,

wherein N is 3 and M is 7 such that there are 21 cells associated with seven frequency channels and three time slots within a cell grouping with each cell grouping geographically arranged within the cellular communication system as shown in FIG. 8.

15. A method of channel reuse in a cellular communication system having a plurality of frequency channels for communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating N time slots for communication on M frequency channels, each of the N time slots having a period sufficient to support a typical block transfer time in the cellular communication system, the N time slots responsive to the synchronizing of base stations;

c) geographically arranging N×

M cells within a cell grouping of a plurality of cell groupings within the cellular communication system such that the potential co-channel interferers are substantially equall equally spaced apart as far as possible among all cells to minimize co-channel interference and the potential adjacent channel interferers are placed in nonadjacent cells to minimize adjacent channel interference; and

,

wherein N is 4 and M is 4 such that there are 16 cells associated with four frequency channels and four time slots within a cell grouping with each cell grouping geographically arranged within the cellular communication system as shown in FIG. 9.

16. A method of channel reuse in a cellular communication system having a plurality of frequency channels for communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating N time slots for communication on M frequency channels, each of the N time slots having a period sufficient to support a typical block transfer time in the cellular communication system, the N time slots responsive to the synchronizing of base stations;

c) geographically arranging N×

M cells within a cell grouping of a plurality of cell groupings within the cellular communication system such that the potential co-channel interferers are substantially equally spaced apart as far as possible among all cells to minimize co-channel interference and the potential adjacent channel interferers are placed in nonadjacent cells to minimize adjacent channel interference; and

,

wherein N is 4 and M is 3 such that there are 12 cells associated with three frequency channels and four time slots within a cell grouping with each cell grouping geographically arranged within the cellular communication system as shown in FIG. 10.

17. A method of forward channel reuse and reverse channel reuse in a cellular communication system having a plurality of forward frequency channels for communication from base stations to subscriber units and a plurality of reverse frequency channels for communication from subscriber units to base stations, the method comprising:

a) synchronizing base stations in the cellular communications system to a common time base;

b) allocating N cellular time slots for communication on M forward frequency channels and allocating X cellular time slots for communication on Y reverse frequency channels, each of the N and X cellular time slots respectively having a period sufficient to support a typical forward block transfer time and reverse block transfer time in the cellular communication system, the N and X cellular time slots responsive to the synchronizing of base stations; and

c) assigning the N cellular time slots and the M forward frequency channels to N times M cells and geographically arranging the N times M cells within a cell grouping of a first plurality of cell groupings within the cellular communication system such that the potential forward co-channel interferers are substantially spaced apart as far as possible within each cell group and are substantially equally spaced apart between adjacent cell groups to minimize forward co-channel interference and the potential adjacent forward channel interferers are placed in non-adjacent cells to minimize adjacent channel interference;

d) assigning the X cellular time slots and the Y reverse frequency channels to X times Y cells and geographically arranging the X times Y cells within a cell grouping of a second plurality of cell groupings within the cellular communication system such that the potential reverse co-channel interferers are substantially spaced apart as far as possible within each cell group and are substantially equally spaced apart between adjacent cell groups to minimize reverse co-channel interference and the potential adjacent reverse channel interferers are placed in nonadjacent cells to minimize adjacent channel interference.

18. A method for forward channel reuse and reverse channel reuse in a cellular communication system having a plurality of forward frequency channels for communication from base stations to subscriber units and a plurality of reverse frequency channels for communication from subscriber units to base stations, the method comprising:

a) synchronizing base stations in the cellular communications system to a common time base;

b) allocating N time slots for communication on M forward frequency channels and allocating X time slots for communication on Y reverse frequency channels, each of the N and X time slots respectively having a period sufficient to support a typical forward block transfer time and reverse block transfer time in the cellular communication system, the N and X time slots responsive to the synchronizing of base stations;

c) geographically arranging N times M cells within a cell grouping of a first plurality of cell groupings within the cellular communication system such that the potential forward co-channel interferers are substantially equally call spaced apart as far as possible among all cells to minimize forward co-channel interference and the potential adjacent forward channel interferers are placed in non-adjacent cells to minimize adjacent channel interference;

d) geographically arranging X times Y cells within a cell arousing of a second plurality of cell grouping within the cellular communication system such that the potential reverse co-channel interferers are substantially equally spaced apart as far as possible among all cells to minimize reverse co-channel interference and the potential adjacent reverse channel interferers are placed in nonadjacent cells to minimize adjacent channel interference; and

,

wherein N and X are 4 and M and Y are 3 such there are 12 cells associated with three forward and reverse frequency channels and four forward and reverse time slots within a cell grouping with each cell grouping geographically arranged within the cellular communication system as shown in FIG. 10.

19. A method of reverse channel reuse in a cellular communication system having a plurality of reverse channels and a plurality of forward channels for data communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating a plurality of forward frequency time slots for communication on forward frequency channels, each time slot in each frequency having a period sufficient to support a typical block transfer time in the cellular communication system, the forward frequency time slots responsive to the synchronizing of base stations;

c) allocating a plurality of reverse frequency time slots for communication on forward frequency channels, each time slot in each frequency having a period sufficient to support a typical block transfer time in the cellular communication system, the reverse frequency time slots responsive to the synchronizing of base stations;

d) geographically assigning the plurality of frequency time slots to cells in the cellular communication system by substantially equal spacing co-channel interferers as far apart as possible among all cells to minimize co-channel interference and placing adjacent channel interferers in non-adjacent cells to minimize adjacent channel interference; and

e) allowing base stations to transmit data to subscriber units for forward link data transmission over the reverse frequency time slots normally used for the reverse link.

20. A method of forward channel reuse in a cellular communication system having a plurality of reverse channels and a plurality of forward channels for communication between base stations and subscriber units, the method comprising:

a) synchronizing base stations in the cellular communication system to a common time base;

b) allocating a plurality of forward frequency time slots for communication on forward frequency channels, each time slot in each frequency having a period sufficient to support a typical block transfer time in the cellular communication system, the forward frequency time slots responsive to the synchronizing of base stations;

c) allocating a plurality of reverse frequency time slots for communication on forward frequency channels, each time slot in each frequency having a period sufficient to support a typical block transfer time in the cellular communication system, the reverse frequency time slots responsive to the synchronizing of base stations;

d) geographically assigning the plurality of frequency time slots to cells in the cellular communication system by substantially equal spacing co-channel interferers as far apart as possible among all cells to minimize co-channel interference and placing adjacent channel interferers in non-adjacent cells to minimize adjacent channel interference; and

e) allowing subscriber units to transmit date to base stations for reverse link data transmission over the forward frequency time slots normally used for the forward link.