Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1997-07-15
2002-03-26
Bost, Dwayne (Department: 2681)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S424000, C455S062000, C455S063300, C370S334000, C370S480000
Reexamination Certificate
active
06363263
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to wireless communication systems and, more particularly, to systems and methods for improving signal quality by providing select signals to a wireless communication system.
BACKGROUND OF THE INVENTION
As originally implemented, cellular communications systems were broken down into omni-trunks where each cell was able to use each channel in a 360° radius. Because of overlap in the area serviced by cells, a caller utilizing one cell in the penumbra between two cells could interfere with a caller utilizing the other cell if both were on the same channel. To avoid this interference the channel utilized by a caller in one cell would have to be disabled for any other callers in any adjacent cells. Disabling such a channel on all adjacent cells would cause many more cells than actually utilized to have the caller's channel unavailable for use by other callers. Such disabling of channels to avoid interference was recognized to lead to under-utilization of cell resources as well as depletion of available channels.
One solution to reduce the interference problems caused by other users in the omni-trunk 360° configuration, has been to break down cells into 120° sectors such that each channel available at the cell only communicates in an area of 120° radial coverage about the cell. Through the use of such sectors, mobile units operating within an adjacent cell or the same cell, but within a different sector, may utilize a different communication channel and, therefore, substantially avoid interfering with other callers in the cell.
A problem with going from the omni-trunk 360° configuration to the sector system, however, is that as a result of splitting of the cell into 120° sectors only a third of the channels are available in each sector. This results in a reduced call capacity in any particular cell sector as compared to that available in the omni-trunk 360° configuration.
In order to maintain call capacity throughout the cell, other solutions to these interference problems have included the use of so called “smart antennas,” or switchbeam systems, providing multiple antenna beams throughout the cells. Systems implementing multiple antenna beams, such as twelve narrow beams, are described in U.S. Pat. No. 5,563,610, entitled “NARROW BEAM ANTENNA SYSTEM WITH ANGULAR DIVERSITY,” incorporated herein by reference, and the associated above-referenced co-pending and commonly assigned continuation-in-part U.S. Patent application entitled “APPARATUS, SYSTEMS AND METHODS FOR MULTIPLE ANTENNA TRANSMISSION IN WIRELESS COMMUNICATIONS SYSTEMS.”
In such systems, a controller is operable to determine a narrow beam upon which a mobile is operating and couple that beam's signal to the proper communication input at the base transceiver station (BTS). Therefore, the smart antenna system is able to target particular mobile units to the exclusion of others and, as a result, reduce interference caused by the mobile units not targeted. However, the ability to mitigate interference in such systems as they exist today is limited by the fact that selection of a beam for a certain channel not only provides that channel to the BTS radio, but all channels on that beam are also sent down to the BTS radio. This problem is compounded in digital systems where the same channel may be utilized on multiple beams and, thus, have increased opportunity for interfering signals to appear within the selected beams. Therefore, the amount of interference rejection that is obtained, in either an analogue or digital implementation, is not as great as could be if only the channel that was desired was sent to the radio.
Moreover, although typically providing improved signal quality over the 360° omni-trunk configuration, both the sectored and smart antenna systems have their drawbacks to implementation. For example, since its introduction for use by the general public in the early 1980's, mobile communications utilizing cellular telephone technology has experienced phenomenal growth. This growth has resulted in a vast base of existing BTS sites already installed and equipped throughout many cellular service areas. These BTS sites may be equipped with any number of different technologies, such as the omni-trunk, sectored cell, or smart antenna, discussed above.
In order to improve signal quality at existing BTS sites, installed without the benefit of recent communication technology improvements, it would be advantageous to provide a reduction in interference, such as through the use of the solutions above. However, the above mentioned solutions require extensive modification to existing BTS sites in order to be implemented. For example the three sectored system typically requires the addition of radio units to individually process the signals associated with the three sectors in addition to replacing the existing antenna structure. Similarly, the smart antenna typically requires modifications at the BTS site, such as usurping the operation of existing equipment, in addition to replacing the existing antenna structure in order to function properly.
The necessity to add communication equipment to provide additional functionality or in order to usurp existing functionality causes there to be a cost barrier with respect to equipping existing BTS sites with such improved technology. Moreover, as there are a plethora of different manufacturers and configurations of existing equipment, the upgrade equipment must typically be specially configured or adapted in order to upgrade a particular BTS site configuration.
Therefore, a need exists in the art for an air interface system and method which is adaptable to existing wireless communication hardware in order to provide improved signal quality at existing BTS sites.
A further need exists in the art for an air interface system and method which is universally adaptable to a variety of existing wireless communication hardware such that its installation on different configurations of systems requires little or no modification.
A still further need exists in the art for an air interface system and method which, when coupled with existing wireless communication equipment, provides improved signal quality while replacing or usurping a minimum of existing hardware.
SUMMARY OF THE INVENTION
These and other objects, needs and desires are obtained in a system and method utilizing an air interface controller to provide select signals appearing within the radiation pattern of cell to communication equipment associated with an existing BTS site. Through the provision of only select signals to the inputs of the BTS communication equipment, the present invention is capable of targeting particular mobile units to the exclusion of other mobile units. This provides for improved signal quality as the number of potential interfering signals is reduced.
Preferably, the air interface controller of the present invention provides the select signals to the exclusion of others through the use of adjustable filters. As the air interface controller determines which signals are to be provided to the communication equipment, a filter in the signal path is adjusted or selected to allow the associated frequency band, or channel, to pass.
Preferably, the air interface controller monitors the BTS in order to determine which signals are to be provided to the BTS. For example, the air interface controller may intercept BTS scan receiver commands in order to determine what communication channels to pass, through the use of the above mentioned filtering, to the BTS. It shall be appreciated that, by utilizing information already available at the BTS in order to make its determination of what signals to pass, the present invention does not require duplication or usurpation of the existing BTS control systems. Furthermore, by simply requiring connection to already existing, commonly available, control signals, rather than usurping various control systems, the present invention does not require significant modification to couple with a variety of
Peterson Curt
Reudink Douglas O.
Reudink Mark
Bost Dwayne
Craver Charles
Fulbright & Jaworski L.L.P.
Metawave Communications Corporation
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