Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-07-23
2001-04-24
Bost, Dwayne D. (Department: 2744)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S450000, C455S453000, C455S509000, C455S513000
Reexamination Certificate
active
06223041
ABSTRACT:
BACKGROUND
1. Technical Field
The invention relates generally to wireless communication systems; and more particularly to a wireless communication system and an associated method of operation in which radio resources are dynamically allocated to reduce system interference within the wireless communication system.
2. Related art
A wireless communication system is generally known in the art to service wireless communications with wireless mobile units operating within a respective service area. The construction of a wireless communication system typically includes a plurality of base stations dispersed throughout the service area. The base stations couple to base station controllers, with each base station controller serving a plurality of base stations. Each base station controller couples to a mobile switching center that also couples to the public switched telephone network and to other mobile switching centers. When being serviced, the mobile units establish wireless communications with one or more of the base stations.
The wireless communication system operates within an allocated frequency band. The allocated frequency band is subdivided into a plurality of channels with each channel occupying a respective bandwidth of the frequency band. Each of the base stations is allocated at least one channel in which all communications with proximate mobile units are carried. In most wireless communication systems, each base station supports a plurality of sectors, with each sector allocated at least one channel. Allocation of channels is performed so that the base stations can adequately service each of the mobile units operating in their proximity.
The capacity of prior wireless communication systems was fixed. Base stations and the supporting infrastructure was initially installed and channels were assigned to service a projected loading across the systems. As loading increased, additional base stations were installed and/or additional channels were allocated to existing base stations to service the additional load. Such initial allocations and subsequent additional allocations for each cell/sector were made to serve a peak loading interval for the respective cell/sector.
However, loading patterns do not correspond to the fixed capacity of prior wireless communication systems. As is known, loading across any wireless communication system varies significantly by time of day and day of week with such loading patterns not being proportional across the system. Some portions of the system are more heavily loaded during working hours, some during evening hours, some during commuting hours and some over the weekend. Thus, because resources within the wireless communication system are deployed to meet the greatest loading period for each base station/sector within the wireless communication system, substantial resources remain unused during most loading periods. These allocated resources are extremely expensive and, when not fully used to service calls, generate no revenue for the service provider. Further, when additional channels are allocated, system interference is increased. Thus, it has been advantageous for most operators of wireless communication systems to deploy minimal resources that provide a minimal acceptable service quality during most time periods but unacceptable service quality during peak loading periods.
Thus, there is a need in the art for a wireless communication system and method of operation that manages resources to assign resources when capacity is needed, does not assign the resources when they are not needed, and manages such assignments to minimize interference within the system to maximize grade of service.
SUMMARY OF THE INVENTION
Thus, in order to overcome the above-described shortcomings and additional shortcomings related to radio resource assignment in a wireless communication system, the method and apparatus of the present invention dynamically assigns radio resources (channels) among a plurality of intercoupled base stations based upon historical loading so as to reduce both localized and system interference.
According to the method, a plurality of loading intervals are first determined that span a loading interval sequence. The loading intervals may correspond to time based periods such as fifteen-minute, thirty-minute, hour or other time intervals. The loading interval sequence may correspond to a weekday, a weekend day or such other loading period within which loading resembles a pattern. Once the loading intervals and the loading interval sequence are determined, an analysis is made for each loading interval so that a channel assignment is made that reduces localized and system interference.
Each loading interval is considered separately in making the channel assignments. When considering a particular loading interval, estimated loading for each base station cell/sector for the loading interval is first determined. Such loading patterns typically are obtained from previously gathered loading information for each base station cell/sector of the wireless communication system. Then, a number of channels required to service the load for the loading interval are determined for each cell/sector to meet a minimal service level.
Once channel requirements have been determined, an initial assignment of channels among the cells/sectors of the base stations of the wireless communication system is made to satisfy localized radio interference criteria. Such an assignment will typically be made to preclude local reuse of channels. Then, the assignments are reconsidered from the standpoint of system interference and the channels are reassigned to minimize system interference. In reassigning channels among the cells/sectors, radio propagation and, cell/sector proximity are considered so as to most accurately predict performance when the assignments are implemented.
Once the channel assignments have been determined for the loading interval sequence(s), the wireless communication system is operated according to the channel assignments. With the dynamic radio allocation, significant savings over static radio assignments are realized. Because, for any loading interval, fewer radio channel allocations are required system resources are conserved and grade of service is met using a smaller resource set. Further, because fewer radio resources are allocated, voice quality increases through the decrease of interference from radio channels which are not be needed during a particular period.
Moreover, other aspects of the present invention will become apparent with further reference to the drawings and specification which follow.
REFERENCES:
patent: 5134709 (1992-07-01), Bi et al.
patent: 5448621 (1995-09-01), Knudsen
patent: 5448750 (1995-09-01), Eriksson et al.
patent: 5752194 (1998-05-01), Lin et al.
patent: 5901356 (1999-05-01), Hudson
patent: 6023622 (2000-02-01), Plaschke et al.
patent: 6023623 (2000-02-01), Benkner et al.
patent: 6049717 (2000-04-01), Dufour et al.
Egner Will A.
Prabhu Vasant
Bost Dwayne D.
Garlick Bruce E.
Harrison James A.
Nortel Networks LTD
Persino Raymond B.
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