System and method of integrating dynamic frequency association with channel borrowing techniques

• US 6,219,554 B1
• Filed: 09/04/1998
• Issued: 04/17/2001
• Est. Priority Date: 09/04/1998
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Eswara, Srinivas, Carter, Daniel Thomas, McCarthy, Michael John, Periyalwar, Shalini, Wilson, James Eric
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): SMITH, SHEILA B
• Application Number:
  US09/148,378
• Time in Patent Office: 956 Days
• Field of Search: 455/452, 455/444, 455/62, 455/63, 455/453, 455/454, 455/524, 455/513
• US Class Current: 455/452.1
• CPC Class Codes: H04W 16/06 Hybrid resource partitioning, e.g. channel borrowing

Abstract

A Dynamic Frequency Association (“DFA”) techniques comprising fixed channel allocation (“FCA”) and distributed channel borrowing techniques using a segregation scheme is described. The DFA technique can be used autonomously to dynamically determine the best channels for a cell cluster. Additionally, a method of minimizing search delays at channel assignment by employing a channel usage history is disclosed. In one aspect, as in FCA, each cell is assigned its nominal channels, if any, from the available frequency spectrum, with a fixed radio assigned to each of these frequencies, respectively. Additionally, in accordance with the teachings of the present invention, each cell is equipped with one or more radios designated as “DFA radios”. In operation, idle DFA radios scan channels that may be borrowed in order to build a probability matrix. This enables the cell to determine which channels to use for traffic prior to actual channel request by a mobile. This reduces the search delay experienced in classic segregation schemes.

Claims

1. A method of allocating radio frequency (“

RF”

) channels in an RF communication network including a cell during a low traffic period of said cell, said cell comprising at least one dynamic frequency association (“

DFA”

) radio, the method comprising;

creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing calls;

for each of said RF channels in said scan list, scanning said RF channel using said at least one DFA radio to determine whether said RF channel is clear;

for each of said RF channels in said scan list, calculating a probability of being clear for said RF channel based on current and previous scans of said RF channel;

constructing a clear list comprising an ordered list of each of said RF channels of said scan list determined to have at least a predetermined minimum probability of being clear, said clear list RF channels being arranged in order from a highest to a lowest probability of being clear;

when an overload condition is reached within said cell, selecting from said clear list an RF channel having said highest probability of being clear; and

associating said selected clear list RF channel to said DFA radio, at which point said at least one DFA radio is capable of servicing a call on said selected clear list RF channel.

2. The method of claim 1 wherein said scanning further comprises scanning said RF channel for a predetermined period of time to determine whether said RF channel remains clear throughout said predetermined period of time.

3. The method of claim 1 further comprising:

prior to said associating, scanning said selected clear list RF channel to determine whether said selected clear list RF channel is currently clear; and

if said selected clear list RF channel is not currently clear, selecting the next RF channel from said clear list.

4. The method of claim 1 wherein said creating, scanning, and calculating are performed while said at least one DFA radio is in a scanning mode.

5. The method of claim 4 wherein said constructing is performed while said at least one DFA radio is in said scanning mode and said selecting and associating are performed while said at least one DFA radio is in a selection mode.

6. The method of claim 5 further comprising:

when said cell exits said overload condition, handing off said call from said at least one DFA radio to a fixed radio of said cell; and

returning said at least one DFA radio to said scanning mode.

7. The method of claim 1 further comprising:

monitoring said selected clear list RF channel to which said at least one DFA radio is associated for interference during a call; and

responsive to detection of interference, determining whether there is another radio within said cell available to service said call and, if so, handing said call off to said other radio.

8. A method of allocating radio frequency (“

RF”

) channels in an RF communications network including a cell comprising at least one dynamic frequency association (“

DFA”

) radio, the method comprising;

creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing calls;

for each of said RF channels in said scan list, scanning said RF channel using said at least one DFA radio to determine whether said RF channel is clear; and

for each of said RF channels in said scan list, calculating a probability of being clear for said RF channel based on current and previous scans of said RF channel;

wherein, when a scan reveals said RF channel to be clear, said probability of being clear for said RF channel is calculated using the following equation;

$P_i=P_{i-1}*{\left(\frac{N_i}{N_i+1}\right)}^x+\left(1-{\left(\frac{N_i}{N_i+1}\right)}^x\right)$

where P_i represents the probability of being clear of the RF channel at scan i, N_i represents the scan iteration, and x is a variable exponent.

9. A method of allocating radio frequency (“

RF”

) channels in an RF communications network including a cell comprising at least one dynamic frequency association (“

DFA”

) radio, the method comprising;

creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing cells;

for each of said RF channels in said scan list, scanning said RF channel using said at least one DFA radio to determine whether said RF channel is clear; and

for each of said RF channels in said scan list, calculating a probability of being clear for said RF channel based on current and previous scans of said RF channel;

wherein, when a scan reveals said RF channel not to be clear, said probability of being clear for said RF channel is calculated using the following equation;

$P_i=P_{i-1}*\left(\frac{N_i}{N_i+1}\right)$

where P_i represents the probability of being clear of the RF channel at scan i, and N_i represents the scan iteration.

10. A system for allocating radio frequency (“

RF”

) channels in an RF communications network including a cell during a low traffic period of said cell, said cell comprising at least one dynamic frequency association (“

DFA”

) radio, the system comprising;

means for creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing calls;

means for scanning each of said RF channels in said scan list using said at least one DFA radio to determine whether said channel is clear;

means for calculating a probability of being clear for each of said RF channels in said scan list, based on current and previous scans of said RF channel;

means for constructing a clear list comprising an ordered list of each of said RF channels of said scan list determined to have at least a predetermined minimum probability of being clear, said clear list RF channels being arranged in order from a highest to a lowest probability of being clear;

means for selecting from said clear list an RF channel having said highest probability of being clear when an overload condition is reached within said cell; and

means for associating said selected clear list RF channel to said DFA radio, at which point said at least one DFA radio is capable of servicing a call on said selected clear list RF channel.

11. The system of claim 10 wherein said means for scanning further comprises means for scanning said RF channel for a predetermined period of time to determine whether said RF channel remains clear throughout said predetermined period of time.

12. The system of claim 10 further comprising:

means for scanning said selected clear list RF channel to determine whether said selected clear list RF channel is currently clear prior to said associating; and

means for selecting the next RF channel from said clear list if said selected clear list RF channel is not currently clear.

13. The system of claim 10 wherein said creating, scanning, and calculating are performed while said at least one DFA radio is in a scanning mode.

14. The system of claim 13 wherein said constructing is performed while said DFA radio is in said scanning mode and said selecting and associating are performed while said at least one DFA radio is in a selection mode.

15. The system of claim 14 further comprising:

means for handing off said call from said at least one DFA radio to a fixed radio of said cell when said cell exits said overload condition; and

means for returning said at least one DFA radio to said scanning mode.

16. The system of claim 10 further comprising:

means for monitoring said selected clear list RF channel to which said at least one DFA radio is associated for interference during a call; and

means responsive to detection of interference for determining whether there is another radio within said cell available to service said call and, if so, handing said call off to said other radio.

17. A system for allocating radio frequency (“

RF”

) channels in an RF communications network including a cell comprising at least one dynamic frequency association (“

DFA”

) radio, the system comprising;

means for creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing calls;

means for scanning each of said RF channels in said scan list using said at least one DFA radio to determine whether said RF channel is clear; and

means for calculating a probability of being clear for each of said RF channels in said scan list, based on current and previous scans of said RF channel;

wherein, when a scan reveals said RF channel to be clear, said probability of being clear for said RF channel is calculated using the following equation;

$P_i=P_{i-1}*{\left(\frac{N_i}{N_i+1}\right)}^x+\left(1-{\left(\frac{N_i}{N_i+1}\right)}^x\right)$

where P_i represents the probability of being clear of the RF channel at scan i, N_i represents the scan iteration, and x is a variable exponent.

18. A system for allocating radio frequency (“

RF”

) channels in an RF communications network including a cell comprising at least one dynamic frequency association (“

DFA”

) radio, the system comprising;

means for creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing calls;

means for scanning each of said RF channels in said scan list using said at least one DFA radio to determine whether said RF channel is clear; and

means for calculating a probability of being clear for each of said RF channels in said scan list, based on current and previous scans of said RF channel;

wherein, when a scan reveals said RF channel not to be clear, said probability of being clear for said RF channel is calculated using the following equation;

$P_i=P_{i-1}*\left(\frac{N_i}{N_i+1}\right)$

where P_i represents the probability of being clear of the RF channel at scan i, and N_i represents the scan iteration.

19. A radio frequency (“

RF”

) communications network comprising;

a mobile switching center (“

MSC”

);

a base station controller (“

BSC”

) electrically connected to said MSC;

a cell having a base station connected to said BSC; and

a dynamic frequency association (“

DFA”

) radio connected to said BSC;

wherein, during a low traffic period of said cell, said DFA radio operates in a scanning mode in which said DFA radio;

creates a scan list comprising a list of RF channels potentially available for use by said DFA radio for servicing calls;

for each of said RF channels in said scan list, scans said RF channel to determine whether said RF channel is clear;

for each of said RF channels in said scan list, calculates a probability of being clear for said RF channel based on current and previous scans of said RF channel; and

constructs a clear list comprising an ordered list of each of said RF channels of said scan list determined to have at least a predetermined minimum probability of being clear, said clear list RF channels being arranged in order from a highest to a lowest probability of being clear; and

wherein, when an overload condition is reached within said cell, said DFA radio operates in a selection mode in which said DFA radio;

selects from said clear list an RF channel having said highest probability of being clear; and

associates said selected clear list RF channel to said DFA radio, at which point said DFA radio is capable of servicing a call on said selected clear list RF channel.

20. The network of claim 19 wherein said DFA radio scans said RF channel for a predetermined period of time to determine whether said RF channel remains clear throughout said predetermined period of time.

21. The network of claim 19 wherein said DFA radio:

scans said selected clear list RF channel to determine whether said selected clear list RF channel is currently clear prior to said associating; and

selecting the next RF channel from said clear list if said selected clear list RF channel is not currently clear.

22. The network of claim 19 wherein when said cell exits said overload condition, said call is handed off from said DFA radio to a fixed radio of said cell and said DFA radio is returned to said scanning mode.

23. The network of claim 19 wherein said DFA radio further monitors said selected clear list RF channel to which said DFA radio is associated for interference during a call, and responsive to detection of interference, determines whether there is another radio within said cell available to service said call and, if so, hands said call off to said other radio.

24. The network of claim 19, wherein, when a scan reveals said RF channel to be clear, said probability of being clear for said RF channel is calculated using the following equation:

$P_i=P_{i-1}*{\left(\frac{N_i}{N_i+1}\right)}^x+\left(1-{\left(\frac{N_i}{N_i+1}\right)}^x\right)$

where P_i represents the probability of being clear of the RF channel at scan i, N_i represents the scan iteration, and x is a variable exponent.

25. The network of claim 19, wherein, when a scan reveals said RF channel not to be clear, said probability of being clear for said RF channel is calculated using the following equation:

$P_i=P_{i-1}*\left(\frac{N_i}{N_i+1}\right)$

where P_i represents the probability of being clear of the RF channel at scan i, and N_i represents the scan iteration.

26. The network of claim 19 wherein, during said scanning mode, said DFA radio constructs a clear list comprising an ordered list of each of said RF channels of said scan list determined to have at least a predetermined minimum probability of being clear, said clear list RF channels being arranged in order from a highest to a lowest probability of being clear.

27. A method of allocating radio frequency (“

RF”

) channels in an RF communications network including a cell comprising a base station which includes at least one dynamic frequency association (“

DFA”

) radio, the method comprising;

creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing calls;

for each of said RF channels in said scan list, scanning said RF channel using said at least one DFA radio to determine whether said RF channel is clear;

for each of said RF channels in said scan list, calculating a probability of being clear for said RF channel based on current and previous scans of said RF channel by said base station.

28. The method of claim 27 further comprising:

constructing a clear list comprising an ordered list of each of said RF channels of said scan list determined to have at least a predetermined minimum probability of being clear, said clear list RF channels being arranged in order from a highest to a lowest probability of being clear;

when an overload condition is reached within said cell, selecting from said clear list an RF channel having said highest probability of being clear; and

associating said selected clear list RF channel to said DFA radio, at which point said at least one DFA radio is capable of servicing a call on said selected clear list RF channel.

29. The method of claim 28 further comprising:

prior to said associating, scanning said selected clear list RF channel to determine whether said selected clear list RF channel is currently clear; and

if said selected clear list RF channel is not currently clear, selecting the next RF channel from said clear list.

30. The method of claim 29 further comprising:

monitoring said selected clear list RF channel to which said at least one DFA radio is associated for interference during a call; and

responsive to detection of interference, determining whether there is another radio within said cell available to service said call and, if so, handing said call off to said other radio.

31. A system for allocating radio frequency (“

RF”

) channels in an RF communications network including a cell comprising a base station which includes at least one dynamic frequency association (“

DFA”

) radio, the system comprising;

means for creating a scan list comprising a list of RF channels potentially available for use by said at least one DFA radio for servicing calls;

means for scanning each of said RF channels in said scan list using said at least one DFA radio to determine whether said RF channel is clear;

means for calculating a probability of being clear for each of said RF channels in said scan list, based on current and previous scans of said RF channel by said at least one DFA radio of said base station.

32. The system of claim 31 further comprising:

means for constructing a clear list comprising an ordered list of each of said RF channels of said scan list determined to have at least a predetermined minimum probability of being clear, said clear list RF channels being arranged in order from a highest to a lowest probability of being clear;

means for selecting from said clear list an RF channel having said highest probability of being clear when an overload condition is reached within said cell; and

means for associating said selected clear list RF channel to said DFA radio, at which point said at least one DFA radio is capable of servicing a call on said selected clear list RF channel.

33. The system of claim 32 further comprising:

means for scanning said selected clear list RF channel to determine whether said selected clear list RF channel is currently clear prior to said associating; and

means for selecting the next RF channel from said clear list if said selected clear list RF channel is not currently clear.

34. The system of claim 33 further comprising:

means for handing off said call from said at least one DFA radio to a fixed radio of said cell when said cell exits said overload condition; and

means for returning said at least one DFA radio to said scanning mode.

35. The system of claim 34 further comprising:

means for monitoring said selected clear list RF channel to which said at least one DFA radio is associated for interference during a call; and

means responsive to detection of interference for determining whether there is another radio within said cell available to service said call and, if so, handling said call off to said other radio.