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Reverse channel reuse scheme in a time shared cellular communication system
| Details |
Inventors: Gardner, Steven H.; Gilbert, Sheldon L.; Hardin, Carl Thomas; Petranovich, James E.;
Assignee: Cirrus Logic, Inc. (Fremont, CA)
Primary Examiner: Eisenzopf; Reinhard J.
Assistant Examiner: Kincaid; Lester G.
Attorney, Agent or Firm: Shaw; Stephen, Jaquez; Marty
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. |
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DETAILED DESCRIPTION The present invention is 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.
That is, 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 or groups.
Several particular cell reuse patterns are taught that provide good operational characteristics and low co-channel interference.
A message-based control scheme provides for allocation of the time slots and handling certain problems with mobile subscriber unit handoff between cells.
The invention allows the use of a small number of cellular frequencies in a conventional cellular system without significant alteration of the existing system.
However, the invention is particularly useful in two-way cellular paging systems.
One alternative embodiment of the present invention increases the efficiency and data bandwidth of the reverse link.
Data bandwidth is increased by increasing the reuse of frequencies in the reverse link.
Due to transmission characteristics of the reverse link, the reuse of frequencies can be denser than the reuse of frequencies in the forward link.
Acceptable reverse link co-channel interference is achieved using dense reverse link frequency reuse groups.
The present invention uses the following three approaches for improving the reuse of frequencies in the reverse link of NPCS systems: (1) In asymmetrical NPCS systems, improved reverse link data throughput is achieved by allowing the reverse channel of a cell or base station to be used to receive signals from a plurality of mobile units whenever a corresponding forward channel of the cell or base station is active
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Cell Phones 
