Cellular communications system with sectorization

Abstract

A method and apparatus for sectorizing coverage of a cellular communications area includes providing a remote unit having microcell antenna units. Each microcell antenna unit is configured to cover a particular sector. The remote unit is connected to a sectorized base station unit which is connected to a mobile telecommunications switching office. Separate digitized streams representative of telephone signals received from the mobile telecommunications switching office are generated corresponding to the microcell antenna units and the separate digitized streams are multiplexed and transmitted to the remote unit. The remote unit demultiplexes the multiplexed digitized streams into the separate digitized streams corresponding to the microcell antenna units and the separate digitized streams are converted to RF signals for coverage of a particular sector by the corresponding microcell antenna unit. Separate digitized streams are separately generated for each microcell antenna unit representative of RF signals received at the microcell antenna unit for a particular sector. The separately generated digitized streams are multiplexed at the remote unit and transmitted to the sectorized base station unit. At the sectorized base station unit, the multiplexed digitized streams are demultiplexed into the separate digitized streams corresponding to microcell antenna units and the separate digitized streams are converted to RF signals for provision to the mobile telecommunications switching office. Diversity at the remote units is also provided.

Description

[0001]This Reissue Application is a continuation of Reissue application Ser. No. 11 / 937,255, filed on Nov. 8, 2007, which is a continuation of Reissue application Ser. No. 09 / 747,273, filed Dec. 22, 2000, which is a reissue of application Ser. No. 08 / 299,159, filed Aug. 31, 1994, (U.S. Pat. No. 5,852,651), which is a division of application Ser. No. 08 / 204,660, filed Mar. 2, 1994 U.S. Pat. No. 5,627,879, which is a continuation-in-part of U.S. application Ser. No. 08 / 183,221, filed Jan. 14, 1994, now abandoned, which is a continuation-in-part of U.S. application Ser. No. 08 / 068,389, filed May 28, 1993, now abandoned, which is a continuation-in-part of U.S. application Ser. Nos. 07 / 946,402, 07 / 946,964, 07 / 946,931, and 07 / 946,548, all filed Sep. 17, 1992, all of which are now abandoned. More than one reissue application has been filed for U.S. Pat. No. 5,852,651. Specifically, Reissue application Ser. No. 09 / 747,273 was filed Dec. 22, 2000, Reissue application Ser. No. 11 / 937,255 was ...

AI Technical Summary

Benefits of technology

The present invention provides a better coverage and capacity in a microcell system without needing to deploy individual base stations in each microcell area. It uses a digital transport to improve signal quality and range. The invention also allows for the transmission of control and monitoring information between the microcell antenna unit and the base station. An all-digital embodiment is also provided where the base stations are fully digital, eliminating the need for RF equipment. A method is also provided to allow for the rapid deployment of a system with analog-type base stations while easily upgrading them to all digital technology. The method allows for the full benefit of the all-digital base station without the expense of modifying existing installed microcell antenna units.

Problems solved by technology

In densely populated urban areas, the capacity of a conventional system 5 is severely limited by the relatively small number of channels available in each cell 11, 16.

Moreover, the coverage of urban cellular phone systems is limited by blockage, attenuation and shadowing of the RF signals by high rises and other structures.

This can also be a problem with respect to suburban office buildings and complexes.

While such “microcell” systems are a viable solution to capacity and coverage problems, it can be difficult to find space at a reasonable cost to install conventional base station equipment in each microcell, especially in densely populated urban areas.

Furthermore, maintaining a large number of base stations spread throughout a densely populated urban area can be time consuming and uneconomical.

The ability to analog modulate and demodulate light, the limitations imposed by line reflections, and path loss on the fiber all introduce significant distortion and errors into an analog modulated signal and therefore limit the dynamic range of the signals which can be effectively carried via an analog system, especially in the uplink direction.

These factors limit the distance from the base station to the antenna sites.

Moreover, in AM systems an out-of-band signal is required to transmit control and alarm information to and from the antenna sites, again adding to the expense of the modulation and demodulation equipment.

Moreover, provision of other services such as paging systems, personal communications networks (PCN's) or mobile data services are not easily added to analog AM systems such as that shown in AT&T's European application.

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