Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-04-10
2004-06-08
Gelin, Jean (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S562100, C455S013300
Reexamination Certificate
active
06748218
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to wireless communications, and more particularly, to wireless communication methods and systems using multiple sectored cells.
DESCRIPTION OF THE RELATED ART
The communications industry has long sought increased capacity communication systems that could bring robust communications to the world's population. Much of today's communication traffic is in the form of information carriers that are encoded with digital data representing information to be transported across a communication link. The information transported across the link may often include, for example, voice or video information, as well as textual information or raw data for a particular application.
With the increased use of the Internet and other forms of data communication in recent years, there has been an exponential increase in worldwide data traffic. The increased demand for data communications has essentially outpaced the capacity of existing systems, creating a need for higher capacity communication systems. The capacity of a communication link generally refers to the amount of data that can be reliably transported over the link per unit time and is typically measured in terms of data bits per second (bps).
Wireless communication systems are recognized as an effective method of interconnecting users. Wireless communication systems may be preferable, particularly in geographic locations such as congested urban areas, remote rural areas, or areas having difficult terrains, where it may be difficult and/or cost-prohibitive to deploy wire conductors or fiber optics. Rather than transporting information on carriers over a physically “tangible” communication link such as a wire conductor or fiber optic cable, wireless systems radiate information carriers in “open space” throughout a coverage area. The communication link in wireless systems generally may be defined by the spatial profile of the radiated information carriers.
Generally, the information carriers radiated in wireless communication systems have particular carrier frequencies and predetermined bandwidths within a designated frequency spectrum for a given communication link. In particular, a given information carrier may represent a single channel over which to transport information, or may represent a “channel set” including several channels over which to transport information. For example, a frequency band (i.e., a portion of the designated frequency spectrum) centered around a particular carrier frequency may be divided into a number of smaller bandwidth frequency channels, wherein each channel may carry unique information. Such a scheme commonly is known as Frequency Division Multiple Access (FDMA). Alternatively, an information carrier having a particular carrier frequency may be divided into a number of time slots, wherein each time slot represents a channel that may carry unique information. Such a scheme commonly is known as Time Division Multiple Access (TDMA). Yet other examples of techniques to partition a frequency band into a set of channels include various coding schemes to uniquely identify channels within a set, such as Code Division Multiple Access (CDMA) which uses a unique pseudo-noise digital code (PN code) to encode and decode each channel of a channel set, and various Orthogonal Frequency Division Multiplexing (OFDM) techniques (including VOFDM, COFDM, SC-OFDM, etc.).
Historically, wireless communication systems have found great applicability for communicating with mobile users. Generally, conventional mobile wireless communication systems are designed by dividing a coverage area into a number of cells in a honeycomb-like manner. For purposes of illustration, the cells in the coverage area often are represented as either essentially circular or hexagonal in shape. For purposes of this disclosure, it should be appreciated that one or both of a circular or hexagonal cell shape may be used interchangeably in the drawings to represent a typical cell in a wireless communication system coverage area.
FIGS. 1A and 1B
show two examples of common arrangements of cells in a conventional mobile wireless communication system. Generally, it is assumed that each cell in such an arrangement has essentially a same radius and covers an approximately circular area, as shown in
FIGS. 1A and 1B
. From
FIGS. 1A and 1B
, it should be readily apparent that each cell in an inner portion of the coverage area is surrounded by 6 other cells.
For wireless communication systems in general, frequency spectrum is a valuable commodity. Typical goals of a wireless communication system designer include reaching as many users as possible via broadband high capacity communication links, and doing so by using as little frequency spectrum as possible. In view of the foregoing, a variety of frequency spectrum reuse plans and cell layouts have been developed, primarily for use in mobile wireless communication systems, to reuse portions of frequency spectrum in a number of cells in a coverage area while attempting to minimize interference amongst cells in which the same frequency spectrum is used. By dividing a coverage area into a number of cells, and reusing portions of frequency spectrum in some of the cells, the information carrying capacity of the reused portions of frequency spectrum is essentially multiplied by the number of cells in which the portions are used.
FIGS. 1A and 1B
show two common frequency spectrum reuse plans for conventional mobile wireless communication systems. In each of the cells shown in
FIGS. 1A and 1B
, radiation (i.e., representing one or more information carriers) is transmitted from approximately the center of the cell in an omnidirectional manner throughout the cell. The radiation transmitted in each cell is allocated a particular frequency band within the allotted frequency spectrum for the system. The cells are arranged relative to one another such that neighboring cells do not use the same frequency band.
FIG. 1A
shows a coverage area that employs a frequency spectrum reuse plan using three different frequency bands, A, B, and C. The use of three different frequency bands in the cell arrangement of
FIG. 1A
insures that no two adjacent cells use the same frequency band. The three different frequency bands each may be reused a number of times to build up the honeycomb pattern of the coverage area shown in FIG.
1
A. It is noteworthy in
FIG. 1A
that, starting from a center cell
20
which uses the frequency band A, the nearest cells
21
1
-
21
6
which also use the frequency band A are removed from the center cell
20
by one “layer” of intervening cells that surround the center cell
20
.
Another possible frequency spectrum reuse plan for the cells of
FIG. 1A
is to employ different radiation polarizations amongst cells using a same frequency band. For example, the A cells may use a first frequency band having a first polarization, the B cells may re-use the first frequency band with an orthogonal polarization to the first polarization, and the C cells may use a second frequency band. Alternatively, cells using a same frequency band may use different time slots or channel codes, as discussed above, to differentiate the information channels amongst the cells. In view of the foregoing, the designations A, B, and C in
FIG. 1A
each may refer to one of three different cell “configurations,” wherein each cell configuration may be uniquely identified from another cell configuration by at least one of frequency band, polarization, time slot, or channel code, for example. Accordingly, as seen in
FIG. 1A
, in a coverage area having a honeycomb pattern cell arrangement employing three different cell configurations, a “buffer layer” of one cell is insured between two cells having the same configuration (e.g., using the same frequency band).
FIG. 1B
shows a similar honeycomb pattern arrangement of cells in a coverage area employing seven different cell configurations (e.g., seven different frequency bands). In particular, a center cell
22
of
FIG. 1B
is designated as h
Harrison Daniel
Johnson Thomas J.
Moritz Christopher M.
Gelin Jean
Remec, Inc.
Wolf Greenfield & Sacks P.C.
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