Operations of cellular communications systems based on mobility and teletraffic statistics collected by mobile units

• US 5,623,535 A
• Filed: 09/08/1994
• Issued: 04/22/1997
• Est. Priority Date: 09/08/1994
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Yeung, Kwan L., Nanda, Sanjiv, Leung, Kin K.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): TROST IV, WILLIAM GEORGE
• Application Number:
  US08/303,299
• Time in Patent Office: 957 Days
• Field of Search: 379/59, 379/60, 379/63, 455/33.1, 455/33.2, 455/54.1, 455/54.2, 455/56.1
• US Class Current: 455/444
• CPC Class Codes: H04W 16/32 Hierarchical cell structures
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells

Abstract

Each mobile unit in a cellular communications system accumulates at least one mobility or communications traffic (teletraffic) statistic representative of "typical" operation of the mobile unit within the cellular communications system. The mobile units process or collect the statistics and then transmit the aggregate statistics to a microcell or macrocell base station at time of origination of a call to or from the mobile, request for a handoff of a call by the mobile unit or the registration process. Included within the characteristics which can be monitored in accordance with the present invention are the following: cell sojourn time; area sojourn time; call holding times; call throughput; number of previous handoffs in an ongoing call; time periods between two consecutive failed handoffs for the mobile unit; and, the ratio of calls originating from a mobile unit to the number of calls terminating to a mobile unit. The accumulated data representative of these characteristics are utilized by the receiving base station to assign new and handoff calls to a microcell or a macrocell, to prioritize call handling within the cellular communications system and to assign customized customer service areas.

Claims

1. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said cellular communications system comprising a layered cellular mobile network having macrocells each of which overlies a plurality of microcells, said method comprising the steps of:

controlling the connections of said plurality of mobile units from said distributed base stations based on measurable mobility and teletraffic statistics of each of said plurality of mobile units;

measuring microcell sojourn times at each of said plurality of mobile units as one of said measurable mobility and teletraffic statistics;

aggregating measured microcell sojourn times representative of mobile unit mobility at each of said plurality of mobile units; and

transmitting aggregated microcell sojourn times from said plurality of mobile units to said distributed base stations.

2. A method as claimed in claim 1 wherein said method further comprises the step of:

comparing aggregated microcell sojourn times to a threshold;

routing calls through appropriate microcells if aggregated microcell sojourn times are greater than said threshold; and

routing calls through appropriate macrocells if aggregated microcell sojourn times are less than said threshold.

3. A method as claimed in claim 2 further comprising the steps of:

performing said steps of measuring microcell sojourn times, and aggregating microcell sojourn times at each of said plurality of mobile units whenever a mobile unit is powered-up whether the unit is idle or engaged in existing calls;

performing said step of transmitting aggregated microcell sojourn times of said mobile units from said plurality of mobile units to said distributed base stations at times of initial call set-up;

performing said step of comparing aggregated microcell sojourn times to a threshold; and

setting-up initial calls on appropriate microcells if aggregated microcell sojourn times for mobile units are greater than said threshold and on appropriate macrocells if aggregated microcell sojourn times for mobile units are less than said threshold.

4. A method as claimed in claim 3 further comprising the steps of:

continuing to perform said steps of measuring microcell sojourn times, and aggregating microcell sojourn times at each of said plurality of mobile units during the progress of established calls connected over said cellular communications system;

performing said step of transmitting aggregated microcell sojourn times of said mobile units from said plurality of mobile units to said distributed base stations at times of microcell boundary crossings;

performing said step of comparing aggregated microcell sojourn times to a threshold; and

handing off established calls based on said aggregated microcell sojourn times.

5. A method as claimed in claim 4 wherein the step of handing off established calls based on said aggregated sojourn times comprises the steps of:

handing off calls from one microcell to another microcell if aggregated microcell sojourn times for mobile units is greater than said threshold;

handing up calls from one microcell to a macrocell if aggregated microcell sojourn times for mobile units is less than said threshold;

handing off calls from one macrocell to another macrocell if aggregated microcell sojourn times for mobile units is less than said threshold; and

handing down calls from one macrocell to a microcell if aggregated microcell sojourn times for mobile units is greater than said threshold.

6. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said cellular communications system comprising a layered cellular mobile network having macrocells each of which overlies a plurality of microcells, said method comprising the steps of:

controlling the connections of said plurality of mobile units from said distributed base stations based on measurable statistics of each of said plurality of mobile units;

measuring microcell sojourn times at each of said plurality of mobile units as one of said measurable statistics;

aggregating microcell sojourn times representative of mobile unit mobility at each of said plurality of mobile units is performed by determining a mobility index a_i by recursively computing a_i =α

a_i-1 +(1-α

)t_i where a_i is the mobility index, a_i-1 is the preceding mobility index, α

is a weighting factor ranging between 0 and 1, and t_i is the time the mobile unit spent in a microcell between microcell crossings i-1 and i; and

transmitting aggregated microcell sojourn times from said plurality of mobile units to said distributed base stations.

7. A method as claimed in claim 6 wherein said method further comprises the steps of:

comparing each t_i to a_i-1 ;

delaying the step of recursively computing a_i =α

a_i-1 +(1-α

)t_i until t_i+1 is determined if a t_i is substantially greater than a_i-1 ;

recursively computing a_i =α

a_i-1 +(131 α

)t_i if t_i+1 is also substantially greater than a_i-1 ; and

deleting a t_i which is substantially greater than a_i-1 prior recursively computing a_i =α

a_i-1 +(131 α

)t_i if t_i+1 is not substantially greater than a_i-1.

8. A method as claimed in claim 7 wherein the step of recursively computing a_i =α

a_i-1 +(131 α

)t_i if t_i+1 is also substantially greater than a_i-1 is performed using both t_i and t_i+1.

9. A method as claimed in claim 6 wherein said method further comprises the steps of:

comparing each t_i to a_i-1 ;

delaying the step of recursively computing a_i =α

a_i-1 +(131 α

)t_i until t_i+1 is determined if a t_i is substantially less than a_i-1 ;

recursively computing a_i =α

a_i-1 +(131 α

)t_i if t_i+1 is also substantially less than a_i-1 ; and

deleting a t_i which is substantially less than a_i-1 prior to recursively computing a_i =α

a_i-1 +(1-α

) if t_i+1 is not substantially less than a_i-1.

10. A method as claimed in claim 9 wherein the step of recursively computing a_i =α

a_i-1 +(131 α

)t_i if t_i+1 is also substantially less than a_i-1 is performed using both t_i and t_i+1.

11. A method as claimed in claim 6 further comprising the steps of:

accumulating call holding times at each of said plurality of mobile units as one of said measurable statistics;

aggregating call holding times at each of said plurality of mobile units; and

transmitting aggregated call holding times to said distributed base stations.

12. A method as claimed in claim 11 wherein the step of aggregating call holding times at each of said plurality of mobile units comprises the step of determining a weighted average by recursively computing b_i =β

b_i-1 +(131 β

)h_i where b_i is a weighted average of call holding time, b_i-1 is the preceding weighted average of call holding time, β

is a weighting factor ranging between 0 and 1, and h_i is the holding time of the i^th call.

13. A method as claimed in claim 12 further comprising the step of dividing b_i by a_i to determine a ratio representative of the expected number of handoffs for each call wherein the steps of transmitting aggregated microcell sojourn times representative of the mobilities of said mobile units from said plurality of mobile units to said distributed base stations and transmitting aggregated call holding times to said distributed base stations are combined and simplified by transmitting said ratio of b_i /a_i.

14. A method as claimed in claim 13 further comprising the steps of:

comparing said ratio of b_i /a_i to a selected handoff threshold;

assigning a call to a macrocell channel if b_i /a_i exceeds said handoff threshold; and

assigning a call to a microcell channel if b_i /a_i does not exceed said handoff threshold.

15. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said cellular communications system comprising a layered cellular mobile network having macrocells each of which overlies a plurality of microcells, said method comprising the steps of:

controlling the connections of said plurality of mobile units from said distributed base stations based on measurable statistics of each of said plurality of mobile units;

measuring microcell sojourn times at each of said plurality of mobile units as one of said measurable statistics;

aggregating measured microcell sojourn times representative of mobile unit mobility at each of said plurality of mobile units;

transmitting aggregated microcell sojourn times from said plurality of mobile units to said distributed base stations;

performing said steps of measuring microcell sojourn times, and aggregating microcell sojourn times at each of said plurality of mobile units whenever a mobile unit is powered-up;

performing said step of transmitting aggregated microcell sojourn times of said mobile units from said plurality of mobile units to said distributed base stations at times of call set-up;

comparing aggregated microcell sojourn times to an origination threshold between a low threshold and a high threshold;

routing originating calls through appropriate microcells if aggregated microcell sojourn times are greater than said origination threshold; and

routing originating calls through appropriate macrocells if aggregated microcell sojourn times are less than said origination threshold.

16. A method as claimed in claim 15 further comprising the steps of:

continuing to perform said steps of measuring microcell sojourn times, and aggregating microcell sojourn times at each of said plurality of mobile units during the progress of established calls connected over said cellular communications system;

performing said step of transmitting aggregated microcell sojourn times of said mobile units from said plurality of mobile units to said distributed base stations at times of microcell boundary crossings; and

handing off established calls based on said aggregated microcell sojourn times.

17. A method as claimed in claim 16 wherein said origination threshold is between a low threshold less than said origination threshold and a high threshold greater than said origination threshold, and the step of handing off established calls based on said aggregated microcell sojourn times comprises the steps of:

comparing aggregated microcell sojourn times to said low threshold;

comparing aggregated microcell sojourn times to said high threshold;

handing off calls from one microcell to another microcell if aggregated microcell sojourn times for mobile units are greater than said low threshold;

handing up calls from one microcell to a macrocell if aggregated microcell sojourn times for mobile units are less than said low threshold;

handing off calls from one macrocell to another macrocell if aggregated microcell sojourn times for mobile units are less than said high threshold; and

handing down calls from one macrocell to a microcell if aggregated microcell sojourn times for mobile units are greater than said high threshold.

18. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said cellular communications system comprising a layered cellular mobile network having macrocells each of which overlies a plurality of microcells, said method comprising the steps of:

controlling the connections of established calls on said plurality of mobile units from said distributed base stations based on measurable mobility and teletraffic statistics of each of said plurality of mobile units;

accumulating the number of previous handoffs for each call at each of said plurality of mobile units as one of said measurable mobility and teletraffic statistics;

transmitting the number of previous handoffs with each request for a handoff;

comparing the number of previous handoffs for each call to a defined threshold; and

allocating a macrocell channel to calls in which the number of previous handoffs exceeds a defined handoff threshold.

19. A method as claimed in claim 18 further comprising the steps of:

accumulating call holding time for each call;

dividing the previous number of call handoffs by the call holding time to determine the number of previous handoffs per unit time per call; and

utilizing the number of previous handoffs per unit time per call for macrochannel allocation.

20. A method as claimed in claim 18 further comprising the steps of:

averaging the number of handoffs per call;

accumulating call holding time for each call;

dividing the average number of call handoffs by the call holding time to determine the average number of handoffs per unit time per call; and

utilizing the average number of handoffs per unit time per call for macrochannel allocation.

21. A method as claimed in claim 19 wherein the step of utilizing the number of previous handoffs per unit time per call for macrochannel allocation comprises the step of comparing the number of previous handoffs to a corresponding handoff threshold and allocating a macrochannel if the number of previous handoffs exceeds said handoff threshold.

22. A method as claimed in claim 20 wherein the step of utilizing the average number of handoffs per unit time per call for macrochannel allocation comprises the steps of:

comparing the average number of handoffs per unit time per call to a corresponding handoff threshold;

assigning a macrochannel if the corresponding threshold is exceeded; and

assigning a microchannel if the corresponding threshold is not exceeded.

23. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said method comprising the steps of:

controlling system resource allocation for each of said plurality of mobile units from said distributed base stations based on measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units;

collecting measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units at each of said plurality of mobile units;

transmitting said measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units from said plurality of mobile units to said distributed base stations; and

setting a customer service area based on said measurable mobility and teletraffic communications statistics.

24. A method as claimed in claim 23 wherein the step of collecting said measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units at each of said plurality of mobile units comprises the step of collecting call holding times for each of said plurality of mobile units.

25. A method as claimed in claim 24 wherein the step of setting a customer service area is based on collected call holding times.

26. A method as claimed in claim 23 wherein the step of collecting said measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units at each of said plurality of mobile units comprises the step of collecting call types for each of said plurality of mobile units.

27. A method as claimed in claim 26 wherein the step of setting a customer service area is based on collected call types.

28. A method as claimed in claim 23 wherein the step of collecting said measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units at each of said plurality of mobile units comprises the step of collecting the number of calls originated by each of said plurality of mobile units and the number of calls received by each of said plurality of mobile units.

29. A method as claimed in claim 28 wherein the step of setting a customer service area is based on the collected number of calls originated by each of said plurality of mobile units and the number of calls received by each of said plurality of mobile units.

30. A method as claimed in claim 23 wherein the step of collecting said measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units at each of said plurality of mobile units comprises the step of collecting call throughput for each of said plurality of mobile units.

31. A method as claimed in claim 30 wherein the step of setting a customer service area is based on the collected call throughput for each of said plurality of mobile units.

32. A method as claimed in claim 23 wherein the step of collecting said measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units at each of said plurality of mobile units comprises the step of collecting network service area sojourn times.

33. A method as claimed in claim 32 wherein the step of setting a customer service area is based on the collected network service area sojourn times for each of said plurality of mobile units.

34. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network and wherein said cellular communications system comprises a layered cellular mobile network comprising macrocells each of which overlies at least two microcells, said method comprising the steps of:

controlling system resource allocation and connections for each of said plurality of mobile units from said distributed base stations based on measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units;

collecting mobility data representative of measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units at each of said plurality of mobile units

transmitting said mobility data representative of measurable mobility and teletraffic communications statistics representative of each of said plurality of mobile units from said plurality of mobile units to said distributed base stations;

comparing said mobility data to a threshold;

routing calls through an appropriate microcell if mobility data for mobile units is greater than said threshold; and

routing calls through an appropriate macrocell if mobility data for mobile units is less than said threshold.

35. A method as claimed in claim 34 further comprising the steps of:

performing said step of collecting data representative of said measurable mobility and teletraffic statistics of each of said plurality of mobile units at each of said plurality of mobile units whenever a mobile unit is powered-up whether the unit is idle or engaged in existing calls;

performing said step of transmitting data representative of said measurable mobility and teletraffic statistics of each mobile unit at time of call set-up; and

performing said step of comparing mobility data to a threshold such that initial call set-up is determined based on said mobility data to set-up calls on an appropriate microcell if mobility data for mobile units is greater than said threshold and to set-up calls on an appropriate macrocell if mobility data for mobile units is less than said threshold.

36. A method as claimed in claim 34 further comprising the steps of:

continuing to perform said step of collecting data representative of said measurable mobility, and teletraffic statistics of each of said plurality of mobile units at each of said plurality of mobile units during established calls;

performing said step of transmitting data representative of said measurable mobility and teletraffic statistics of each mobile unit at times of microcell boundary crossings;

performing said step of comparing mobility data to a threshold; and

handing off established calls based on said mobility data.

37. A method as claimed in claim 36 wherein the step of handing off established calls based on said mobility data comprises the steps of:

handing off calls from one microcell to another microcell if mobility data for mobile units is greater than said threshold;

handing up calls from one microcell to a macrocell if mobility data for mobile units is less than said threshold;

handing off calls from one macrocell to another macrocell if mobility data for mobile units is less than said threshold; and

handing down calls from one macrocell to a microcell if mobility data for mobile units is greater than said threshold.

38. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said method comprising the steps of:

controlling connections of said plurality of mobile units from said distributed base stations based on measurable mobility and teletraffic statistics of each of said plurality of mobile units;

accumulating microcell sojourn times at each of said plurality of mobile units as one of said measurable mobility and teletraffic statistics;

taking a weighted average of microcell sojourn times representative of mobile unit mobility at each of said plurality of mobile units;

transmitting weighted averages of microcell sojourn times representative of the mobilities of said mobile units from said plurality of mobile units to said distributed base stations; and

prioritizing the order of performing connections of said plurality of mobile units based on said weighted averages of microcell sojourn times.

39. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said method comprising the steps of:

controlling connections of said plurality of mobile units from said distributed base stations based on measurable mobility and teletraffic statistics of each of said plurality of mobile units;

accumulating time intervals between two consecutive calls at each of said plurality of mobile units as one of said measurable mobility and teletraffic statistics;

taking a weighted average of accumulated time intervals between two consecutive calls at each of said plurality of mobile units;

accumulating time intervals between two consecutive calls which fail at handoff at each of said plurality of mobile units;

taking a weighted average of the time intervals between two consecutive calls which fail at handoff at each of said plurality of mobile units;

transmitting the ratio of weighted averages of accumulated time intervals between two consecutive calls to weighted averages of time intervals between two consecutive calls which fail at handoff from said plurality of mobile units to said distributed base stations; and

prioritizing the order of performing connections of said plurality of mobile units based on the ratio of said weighted averages of accumulated time intervals between two consecutive calls to weighted averages of time intervals between two consecutive calls which fail at handoff.

40. A method of operating a cellular communications system wherein distributed base stations couple a plurality of mobile units to a fixed switching network, said method comprising the steps of:

controlling connections of said plurality of mobile units from said distributed base stations based on measurable mobility and teletraffic statistics of each of said plurality of mobile units;

accumulating mobility data at each of said plurality of mobile units as one of said measurable mobility and teletraffic statistics;

taking a weighted average of accumulated mobility data at each of said plurality of mobile units;

transmitting the weighted averages of accumulated mobility data from said plurality of mobile units to said distributed base stations; and

prioritizing the order of performing connections of said plurality of mobile units based on the weighted averages of accumulated mobility data.