Coverage area sectorization in time division multiple access/frequency-time division duplex communications systems

#The present invention relates to communications systems, and more particularly, to the sectorization of cells, or coverage areas, in time division multiple access (TDMA) radio communications systems.

#Most time-division multiple-access wireless communications systems employ either a time-division duplex (TDD) scheme or a frequency-division duplex (FDD) scheme to separate uplink and downlink transmissions. Since both duplex schemes provide certain advantages and disadvantages, both schemes are routinely utilized in wireless communications applications.

#For example, in the Personal Wireless Telecommunication (PWT) standard, time-division multiple-access with time-division duplex is used for frequency planning as well as signal packet and time slot assignment. Such a time-division multiple-access/time-division duplex scheme is well suited for many business wireless communication applications (e.g., small-campus systems with micro or pico cells).

#FIG. 1 depicts an exemplary wireless communications system in which the teachings of the invention can be implemented.

#FIG. 2A depicts a base station and a terminal communicating in accordance with a conventional time-division multiple-access/time-division duplex scheme.

#FIG. 2B depicts an exemplary time slot arrangement in a conventional time-division multiple-access/time-division duplex system.

#FIG. 1 depicts a wireless communications system 100 in which the teachings of the present invention can be implemented. As shown, the exemplary wireless system includes ten cells or coverage areas C-C10, ten base stations B1-B10, a timing master TM and ten mobile stations M1-M10. Such a wireless system can be constructed, for example, in accordance with the Personal Wireless Telecommunication (PWT) standard, and can therefore be used, for example, to provide mobile communications within a building or throughout a campus including many buildings and open areas. Generally, a wireless system can include far more than ten cells, ten base stations and ten mobile stations; however, ten of each is sufficient for illustrative purposes.

#As shown, one or more base stations can be situated in each of the cells. Although FIG. 1 shows the base stations located toward the cell centers, each base station can instead be located anywhere within a cell. Base stations located toward a cell center typically employ omni-directional antennas, while base stations located toward a cell boundary typically employ directional antennas. The timing master TM, or radio exchange, maintains timing synchronization between the base stations as is known in the art. The timing master can be connected to the base stations by cable, radio links, or both.

#Each base station and each mobile station includes a transceiver for transmitting and receiving communications signals over the air interface. Typically, the base and mobile stations communicate using a form of time, frequency or code division multiple access (i.e., TDMA, FDMA or CDMA) as is known in the art. As the mobile stations move within a cell and from cell to cell, communication with at least one base station is always possible. As a result, mobile station users are able to place, receive and conduct calls anywhere within the overall system coverage area.