Adaptive time division duplexing method and apparatus for dynamic bandwidth allocation within a wireless communication system

• US 6,016,311 A
• Filed: 11/19/1997
• Issued: 01/18/2000
• Est. Priority Date: 11/19/1997
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Ensemble Communications
• Inventors: Klein, Israel J., Gilbert, Sheldon L., Hadar, Rami
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US08/974,376
• Time in Patent Office: 790 Days
• Field of Search: 370/280, 370/329, 370/336-338, 370/345-349, 370/468, 455/450-453
• US Class Current: 370/280
• CPC Class Codes: H04B 7/2646 for broadband transmission
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 84/14 WLL [Wireless Local Loop]; RLL [Radio Local Loop]

Abstract

An adaptive time division duplexing (ATDD) method and apparatus for duplexing transmissions on a communication link in wireless communication systems. Communication link efficiency is enhanced by dynamically adapting to the uplink and downlink bandwidth requirements of the communication channels. Time slots are flexibly and dynamically allocated for uplink or downlink transmissions depending upon the bandwidth needs of a channel. Communication link bandwidth requirements are continuously monitored using sets of pre-determined bandwidth requirement parameters. Communication channels are configured to have either symmetric or asymmetric uplink/downlink bandwidths depending upon the needs of the channel. Channel bandwidth asymmetry can be configured alternatively in favor of the uplink transmissions (i.e., more time slots are allocated for uplink transmissions than for downlink transmissions) or in favor of the downlink transmissions (i.e., more time slots are allocated for downlink transmissions than for uplink transmissions). A myriad of time slot allocation schemes are possible. One simplified time slot allocation scheme uses a "frame-based" approach. A preferred channel bandwidth analysis technique is disclosed which monitors and updates bandwidth requirement parameters associated with communication sessions, base stations and cell cluster controllers. In accordance with this technique, a communication session is preferably assigned both an "initial" and an "actual" set of bandwidth parameters.

Claims

1. A method for adaptively duplexing transmissions in a communication link using a time division duplexing scheme wherein transmissions are communicated in an uplink direction during uplink time slots and wherein transmissions are communicated in a downlink direction during downlink time slots, comprising the steps of:

(a) determining an uplink bandwidth requirement and a downlink bandwidth requirement of the communication link, wherein the uplink and downlink bandwidth requirements are determined using associated and respective uplink and downlink bandwidth utilization parameters reflective of a statistical average bandwidth utilization in the communication link, and wherein the bandwidth utilization parameters are calculated by monitoring bandwidth utilization in the communication link over a pre-determined period of time;

(b) calculating an uplink/downlink bandwidth requirement ratio based upon the uplink and downlink bandwidth requirements of the link;

(c) allocating uplink and downlink time slots in response to the calculated uplink/downlink bandwidth ratio; and

(d) periodically enabling uplink transmissions during the allocated uplink time slots and downlink transmissions during the allocated downlink time slots.

2. The method of claim 1, wherein the uplink and downlink bandwidth requirements are determined when the link is installed in the communication system.

3. The method of claim 1, wherein the uplink and downlink bandwidth requirements are determined by periodically monitoring requests for uplink and downlink transmissions in the communication link.

4. The method of claim 1, wherein the bandwidth requirements are periodically determined and the associated uplink/downlink bandwidth requirement ratio for the link is periodically updated, and wherein the uplink and downlink time slot allocations are updated periodically in response to the updated uplink/downlink bandwidth ratio.

5. The method of claim 4, wherein the uplink and downlink bandwidth requirements are periodically determined by continuously monitoring the transmissions in the communication link.

6. The method of claim 1, wherein the uplink and downlink bandwidth requirements vary depending upon the type of service provided over the communication link.

7. The method of claim 1, wherein the uplink and downlink bandwidth requirements vary depending upon the type of user of the communication link.

8. The method of claim 1, wherein the communication link comprises a wireless communication link.

9. The method of claim 1, wherein the uplink and downlink time slots are dynamically allocated using a frame-based time slot allocation approach.

10. The method of claim 9, wherein a frame comprises N time slots, and wherein the frame-based time slot allocation approach comprises allocating a first number N₁ time slots (where N is greater than or equal to N₁) for downlink transmissions only, and allocating the remaining N₂ time slots for uplink transmissions only (where N₂ equals N-N₁).

11. The method of claim 9, wherein a frame comprises N time slots, and wherein the frame-based time slot allocation approach comprises allocating a first number N₁ time slots (where N is greater than or equal to N₁) for downlink transmissions only, and allocating the remaining N₂ time slots for both uplink and downlink transmissions (where N₂ equals N-N₁).

12. The method of claim 9, wherein a frame comprises N time slots, and wherein the frame-based time slot allocation approach comprises allocating a first number N₁ time slots (where N is greater than or equal to N₁) for uplink transmissions only, and allocating the remaining N₂ time slots for downlink transmissions only (where N₂ equals N-N₁).

13. The method of claim 9, wherein a frame comprises N time slots, and wherein the frame-based time slot allocation approach comprises allocating a first number N₁ time slots (where N is greater than or equal to N₁) for uplink transmissions only, and allocating the remaining N₂ time slots for both uplink or downlink transmissions (where N₂ equals N-N₁).

14. The method of claim 1, wherein the uplink and downlink bandwidth requirements are determined using associated and respective uplink and downlink rejected session parameters reflective of a statistical average of bandwidth requirements of transmissions rejected in the communication link.

15. The method of claim 14, wherein the rejected session parameters are calculated by monitoring transmissions rejected in the communication link over a pre-determined period of time.

16. The method of claim 1, wherein the bandwidth utilization parameters comprise both an initial and actual set of statistical parameters, the actual set of statistical parameters being reflective of the statistical average bandwidth utilization in the communication link.

17. The method of claim 16, wherein the initial set of statistical parameters are set when the communication link is installed, and wherein the actual set of statistical parameters are periodically updated as the uplink and downlink bandwidth utilization of the communication link varies.

18. The method of claim 17, wherein the initial set of statistical parameters are based upon an estimate of the number of users and the type of user of the communication link.

19. A method for monitoring and updating uplink and downlink bandwidth requirements of a selected base station in a wireless communication system, wherein the communication system includes a plurality of base stations arranged into a plurality of associated cell clusters, and wherein the uplink and downlink transmissions of each base station within a cell cluster is controlled by an associated cell cluster controller, comprising the steps of:

(a) initializing the selected base station with an initial set of bandwidth utilization parameters for the base station, wherein the initial bandwidth utilization parameters comprise an estimate of the uplink and downlink bandwidth requirements of the selected base station;

(b) updating the initial set of bandwidth utilization parameters with an actual set of bandwidth utilization parameters reflective of an actual bandwidth utilization of the selected base station, wherein the actual set of bandwidth parameters are calculated as follows;

##EQU9## wherein α

_M <

1, M>

1 ##EQU10## and wherein α

₁ <

1, M=1;

and wherein U.sup.(M)_n, D.sup.(M)_n comprise uplink and downlink filtered moments, respectively, of order M at an instant n, and wherein U_n, D_n respectively comprise an uplink and downlink accumulated bandwidth requirement influenced by the actual bandwidth utilization of the selected base station, and;

(c) updating the cell cluster controller associated with the selected base station with the actual set of bandwidth parameters calculated in step (b).

20. The method of claim 19, wherein the cell cluster controller is updated with the actual set of bandwidth parameters whenever the cell cluster controller initiates an update request.

21. The method of claim 19, wherein the cell cluster controller is periodically updated with the actual set of bandwidth parameters calculated in step (b).

22. The method of claim 19, further comprising the step of monitoring transmissions rejected by the selected base station, wherein the following parameters are updated when transmissions are rejected:

##EQU11## wherein γ

₁ <

1; and

wherein U'"'"'_n, D'"'"'_n comprise a moving average of the uplink and downlink bandwidth requirements of rejected sessions.

23. The method of claim 19, further comprising the step of monitoring transmissions rejected by the selected base station, wherein the following parameters are updated when transmissions are not rejected by the selected base station:

##EQU12## and wherein U'"'"'_n, D'"'"'_n comprise a moving average of the uplink and downlink bandwidth requirements of rejected sessions.

24. A method for monitoring and updating uplink and downlink bandwidth requirements of a plurality of communication links in a wireless communication system, wherein the communication system includes a plurality of base stations arranged into a plurality of associated cell clusters, and wherein the uplink and downlink transmissions of each base station within a cell cluster are controlled by an associated cell cluster controller, and wherein the transmissions occur during frames comprising N time slots wherein N₁, N₂, . . . N_M are positive integers, and wherein ##EQU13## comprising the steps of:

(a) summing all of the uplink bandwidth requirements of each base station within a selected cell cluster as follows;

for each integer value of k between 1 and ##EQU14## (b) summing all of the downlink bandwidth requirements of each base station within the selected cell cluster as follows;

for each integer value of k between 1 and M, ##EQU15## (c) calculating an estimated bandwidth allocation scheme as follows;

##EQU16## (d) comparing the estimated bandwidth allocation scheme calculated in step (c) with the allocation scheme currently used by the cluster controller associated with the selected cell cluster, wherein the allocation scheme currently used by the cluster controller is defined as N_d, N_u ; and

(e) replacing N_d and N_u with the estimated bandwidth allocation scheme calculated in step (c) if |N_d -N_d |≧

μ

, wherein μ

comprises a predetermined threshold.

25. The method of claim 24, further comprising steps for monitoring transmissions rejected by base stations in the selected cell cluster.

26. The method of claim 25, wherein the steps for monitoring transmissions rejected by base stations in the selected cell cluster comprise the steps of:

(a) summing all of the rejected uplink bandwidth requirements of each base station within the selected cell cluster as follows;

S'"'"'_u =Σ

U'"'"';

(b) summing all of the rejected downlink bandwidth requirements of each base station within the selected cell cluster as follows;

S_d '"'"'=Σ

D'"'"'; and

(c) calculating an expected allocation scheme as follows;

##EQU17##

27. The method of claim 26, further comprising steps for updating the bandwidth allocation scheme of the selected cluster controller when the number of rejected transmissions exceeds a predetermined threshold.

28. The method of claim 27, wherein the bandwidth allocation scheme of the selected cluster controller is updated in accordance with the following steps:

(a) determining if Max(S_u '"'"',S_d '"'"')>

S_o, wherein S_o is a constant, if so then proceeding to step (b);

(b) determining if |N_d -N_d |>

μ

, wherein μ

is a constant, if so then proceeding to step (c),

(c) determining if N_d >

N_d and N_d <

N-δ

, wherein δ

is a constant, if so then updating the downlink allocation N_d as follows;

N_d ←

N_d +δ

;

(d) determining if N_d <

N_d and N_d >

δ

, if so then updating the downlink allocation N_d as follows;

N_d ←

N_d -δ

;

(e) updating the uplink allocation N_u for the selected cell cluster whenever the downlink allocation is updated in either steps (c) or (d) as follows;

space="preserve" listing-type="equation">N.sub.u ←

N-N.sub.u ;

(f) updating the bandwidth allocation parameters of all of the base stations associated with the selected cell cluster whenever the values of N_d and N_u are updated; and

(g) alerting the wireless communication system of the selected cell cluster'"'"'s capacity limitations if Max(S_u '"'"',S_d '"'"')>

T, wherein T is a predetermined threshold value.

29. An apparatus for adaptively duplexing transmissions in a communication link of a wireless communication system using a time division duplexing scheme wherein transmissions are communicated in an uplink direction during uplink time slots and wherein transmissions are communicated in a downlink direction during downlink time slots, comprising:

(a) means for determining an uplink bandwidth requirement and a downlink bandwidth requirement of the communication link, wherein the uplink and downlink bandwidth requirements are determined using associated and respective uplink and downlink bandwidth utilization parameters reflective of a statistical average bandwidth utilization in the communication link, and wherein the bandwidth utilization parameters are calculated by monitoring bandwidth utilization in the communication link over a predetermined period of time;

(b) means, responsive to the determining means, for calculating an uplink/downlink bandwidth requirement ratio based upon the uplink and downlink bandwidth requirements of the link;

(c) means, responsive to the calculating means, for allocating uplink and downlink time slots; and

(d) means for periodically enabling uplink transmissions during the allocated uplink time slots and downlink transmissions during the allocated downlink time slots.

30. The apparatus of claim 29, wherein the determining, calculating and allocating means comprise a computer program executing on a programmable processor.

31. The apparatus of claim 30, wherein the programmable processor is in a cluster controller, and wherein the cluster controller controls a plurality of base stations in the wireless communication system, and wherein one selected base station controls transmissions in the communication link.

32. The apparatus of claim 31, wherein the communication link comprises a wireless communication between the selected base station and a CPE.

33. A method for duplexing transmissions in a communication link using a time division duplexing scheme wherein transmissions are communicated in an uplink direction during uplink time slots and wherein transmissions are communicated in a downlink direction during downlink time slots, comprising the steps of:

(a) establishing an uplink/downlink bandwidth requirement ratio based upon initial and actual uplink and downlink bandwidth requirements of the communication link, wherein the actual bandwidth requirements are determined using bandwidth utilization parameters reflective of a statistical average bandwidth utilization in the communication link, and wherein the bandwidth utilization parameters are calculated by monitoring bandwidth utilization in the communication link over a predetermined period of time;

(b) allocating uplink and downlink time slots in response to the uplink/downlink bandwidth ratio; and

(c) periodically enabling uplink transmissions during the allocated uplink time slots and downlink transmissions during the allocated downlink time slots.

34. The method of claim 33, wherein the uplink and downlink bandwidth requirements are determined when the link is installed in the communication system.

35. The method of claim 33, wherein the actual bandwidth requirements are determined using rejected session parameters reflective of a statistical average of bandwidth requirements of transmissions rejected in the communication link.

36. A method for adaptively duplexing uplink and downlink transmissions of a selected base station in a wireless communication system, wherein the communication system includes a plurality of base stations arranged into a plurality of respective and associated cell clusters, and wherein the uplink and downlink transmissions of each base station within a cell cluster are controlled by an associated cell cluster controller, comprising the steps of:

(a) initializing the selected base station with an initial set of bandwidth utilization parameters for the base station, wherein the initial bandwidth utilization parameters comprise an estimate of the uplink and downlink bandwidth requirements of the selected base station;

(b) updating the initial set of bandwidth utilization parameters with an actual set of bandwidth utilization parameters reflective of an actual bandwidth utilization of the selected base station, wherein the actual set of bandwidth parameters comprise a statistical average of the actual bandwidth utilization in the uplink and downlink of the selected base station, and wherein the statistical average of the actual bandwidth utilization is calculated by monitoring the actual bandwidth utilization over a predetermined time period;

(c) updating the cell cluster controller associated with the selected base station with the actual set of bandwidth parameters calculated in step (b);

(d) calculating an uplink/downlink bandwidth ratio for the selected base station based upon the actual set of bandwidth parameters;

(e) allocating uplink and downlink time slots in response to the calculated uplink/downlink bandwidth ratio; and

(f) periodically enabling uplink transmissions during the allocated uplink time slots and downlink transmissions during the allocated downlink time slots.

37. The method of claim 36, wherein a cell cluster controller calculates an uplink/downlink bandwidth ratio in step (d) for each base station within the cell cluster controlled by the cell cluster controller.

38. The method of claim 37, wherein the cell cluster controller calculates the bandwidth ratio for each base station by monitoring actual bandwidth utilization in the uplink and downlink of each base station over a pre-determined time period.

39. An apparatus for adaptively duplexing uplink and downlink transmissions of a selected base station in a wireless communication system, wherein the communication system includes a plurality of base stations arranged into a plurality of respective and associated cell clusters, and wherein the uplink and downlink transmissions of each base station within a cell cluster are controlled by an associated cell cluster controller, comprising:

(a) means for initializing the selected base station with an initial set of bandwidth utilization parameters for the base station, wherein the initial bandwidth utilization parameters comprise an estimate of the uplink and downlink bandwidth requirements of the selected base station;

(b) means, operatively coupled to the selected base station, for calculating an actual set of bandwidth utilization parameters reflective of an actual bandwidth utilization of the selected base station, wherein the actual set of bandwidth parameters comprise a statistical average of the actual bandwidth utilization in the uplink and downlink of the selected base station, and wherein the statistical average of the actual bandwidth utilization is calculated by monitoring the actual bandwidth utilization over a pre-determined time period; and

(c) a cell cluster controller coupled to and in communication with the selected base station, wherein the cell cluster controller is periodically updated with the actual set of bandwidth utilization parameters calculated by the calculating means, and wherein the cell cluster controller controls the uplink and downlink transmissions of the selected base station based upon the actual set of bandwidth utilization parameters.

40. The apparatus of claim 39, wherein the cell cluster controller further controls the uplink and downlink transmissions of the selected base station by:

(a) calculating an uplink/downlink bandwidth ratio for the selected base station based upon the actual set of bandwidth utilization parameters;

(b) allocating uplink and downlink time slots responsive to the calculated uplink/downlink bandwidth ratio; and

(c) periodically enabling uplink transmissions during the allocated uplink time slots and downlink transmissions during the allocated downlink time slots.

41. A method for monitoring and updating uplink and downlink bandwidth requirements of a selected base station in a wireless communication system, wherein the communication system includes a plurality of base stations arranged into a plurality of respective and associated cell clusters, and wherein the uplink and downlink transmissions of each base station within a cell cluster are controlled by an associated cell cluster controller, comprising the steps of:

(a) initializing the selected base station with an initial set of bandwidth utilization parameters for the base station, wherein the initial bandwidth utilization parameters comprise an estimate of the uplink and downlink bandwidth requirements of the selected base station;

(b) updating the initial set of bandwidth utilization parameters with an actual set of bandwidth utilization parameters reflective of an actual bandwidth utilization of the selected base station, wherein the actual set of bandwidth parameters are determined from a statistical average of the actual bandwidth utilization in the uplink and downlink of the selected base station, and wherein the statistical average of the actual bandwidth utilization is determined by monitoring the actual bandwidth utilization for a pre-determined time period; and

(c) updating the cell cluster controller associated with the selected base station with the actual set of bandwidth parameters determined in step (b).

42. The method of claim 41, further comprising the steps of monitoring sessions rejected by the selected base station, and updating the cell cluster controller with bandwidth parameters reflective of the rejected sessions.

43. A method for monitoring and updating uplink and downlink bandwidth requirements of a plurality of communication links in a wireless communication system, wherein the communication system includes a plurality of base stations arranged into a plurality of respective and associated cell clusters, and wherein the uplink and downlink transmissions of each base station within a cell cluster are controlled by an associated cell cluster controller, and wherein the transmissions occur during frames comprising N time slots, comprising the steps of:

(a) summing all of the uplink bandwidth requirements of each base station within a selected cell cluster;

(b) summing all of the downlink bandwidth requirements of each base station within the selected cell cluster;

(c) calculating an estimated bandwidth allocation scheme reflective of the uplink and downlink bandwidth requirements summed in the summing steps (a) and (b);

(d) comparing the estimated bandwidth allocation scheme calculated in step (c) with an allocation scheme currently used by a cluster controller associated with the selected cell cluster, wherein the allocation scheme currently used by the cluster controller is defined as N_d, N_u ; and

(e) replacing N_d and N_u with the estimated bandwidth allocation scheme calculated in step (c) if the estimated bandwidth allocation differs from the allocation currently used by the cluster controller by more than a pre-determined threshold.

44. The method of claim 43, further comprising the steps of monitoring transmission sessions rejected by each base station in the selected cell cluster, summing all of the uplink and downlink bandwidth requirements associated with the rejected sessions, and updating the bandwidth allocation scheme currently used by the cluster controller when the summed rejection session bandwidth requirements exceeds a predetermined threshold.

45. An apparatus for adaptively duplexing transmissions in a communication link of a wireless communication system using a time division duplexing scheme wherein transmissions are communicated in an uplink direction during uplink time slots and wherein transmissions are communicated in a downlink direction during downlink time slots, comprising:

(a) means for determining an uplink bandwidth requirement and a downlink bandwidth requirement of the communication link using associated and respective uplink and downlink rejected session parameters reflective of a statistical average of bandwidth requirements of transmissions rejected in the communication link;

(b) means, responsive to the determining means, for calculating an uplink/downlink bandwidth requirement ratio based upon the uplink and downlink bandwidth requirements of the link;

(c) means, responsive to the calculating means, for allocating uplink and downlink time slots; and

(d) means for periodically enabling uplink transmissions during the allocated uplink time slots and downlink transmissions during the allocated downlink time slots.