Browse Prior Art Database

METHOD OF IMPROVING IN-BUILDING COVERAGE FOR CDMA SYSTEMS

IP.com Disclosure Number: IPCOM000009900D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-26
Document File: 2 page(s) / 99K

Publishing Venue

Motorola

Related People

Doug Reed: AUTHOR

Abstract

Traditional cellular systems make use of spatial separation to provide sufficient co-channel interference protection to allow frequency reuse. CDMA uses spreading codes to provide the needed co~channel separation between users, who all operate on the same frequency.

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This is the abbreviated version, containing approximately 50% of the total text.

MOTOROLA

Technical Developments

METHOD OF IMPROVING IN-BUILDING COVERAGE FOR CDMA SYSTEMS

by Doug Reed

Traditional cellular systems make use of spatial separation to provide sufficient co-channel interference protection to allow frequency reuse. CDMA uses spreading codes to provide the needed co~channel separation between users, who all operate on the same frequency.

Generally improvements can be made in system capacity by adding base antenna directivity, which is another type of separation, since the nominal signal to interference ratio is improved, allowing more users in the same physical area.

This works sufficiently well for users on the ground when the propagation law is 3.5 to 4.5 or more, however when the user goes to high floors of an office building, there are line-of-site paths to tnany base sites. Line-of -site paths quickly degrade the performance of a user because there are too many strong interference sources in view, making it difficult to maintain a nominal signal to noise ratio needed to make a call.

The technique described herein provides a method of improving in-building coverage to users on high floors of office buildings by directing more signal at the desired buildings from the primary serving base site. This is accomplished by employing a high gain directional antenna pointed at the upper floors of a building, or a cluster of buildings, which need the improvement.

A slight up-tilt of the antenna pointing direction is used to reduce the effects of unwanted reflections off of the buildings since the reflections will be directed upwards, in proportion to the up-tilt angle, rather tMn toward the ground where it might inter~ fere with other users. By using this approach to boost the signa] strength to the upper floors of selected buildings, a number of important improve~

Motorola. Inc. 2000

ments occur. The signal-to- noise ratio is increased.

the boosted signal now becomes the dominate signal which results in fewer handoffs, the subscriber can power down reducing interference into other cells on the reverse link, and the in-building coverage is improved for the users on high floors.

As an example, consider a 200' off...