Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
1999-09-17
2004-02-10
Cumming, William (Department: 2683)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
C375S214000, C375S350000, C455S011100, C455S424000, C455S561000
Reexamination Certificate
active
06690662
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to wireless communication systems. More specifically, this invention relates to remote repeaters in wireless communication systems and in particular to a method and apparatus for employing in-band signaling for downlink transmission of commands and uplink transmission of status in a wireless system repeater.
BACKGROUND OF THE INVENTION
As demand increases dramatically for wireless communication services such as Global System for Mobile Communications (GSM), Cellular Mobile Telephone (CMT), and Personal Communication Services (PCS), the operators of such systems are required to serve an increasing number of users. As a result, a type of base station equipment known as a multicarrier broadband Base Transceiver System (BTS) has been developed which is intended to serve a large number of active mobile stations in each cell. Such broadband BTS equipment can typically service ninety-six simultaneously active mobile stations, at a significant cost per channel.
A conventional cellular phone system
100
is shown in FIG.
1
. As illustrated in
FIG. 1
, the cellular phone system
100
includes a plurality of cells
110
a
,
110
b
, a mobile unit
120
, a plurality of broadband base transceiver stations (BTS)
105
a
,
105
b
, dedicated telephone lines
140
, a base station controller (BSC)
130
, an A interface
150
, a Network and Switching Subsystem (NSS)
160
and a landline switched telephone network
170
. An Operations and Maintenance Center (OMC)
180
is connected to BSC
130
through a Network Management Interface
190
.
The cellular phone system
100
has a fixed number of channel sets distributed among the BTS
105
a
,
105
b
serving a plurality of cells
110
a
,
110
b
arranged in a predetermined reusable pattern. Maximum utilization efficiency of the BTS
105
in densely populated urban environments can be obtained through an efficient frequency reuse scheme, such as that described in U.S. Pat. No. 5,649,292 entitled “A Method For Obtaining Times One Frequency Reuse in Communication Systems” issued to John R. Doner and assigned to AirNet Communications Corporation, who is the assignee of the present application. According to that arrangement, each cell is split into six radial sectors and frequencies are assigned to the sectors in such a manner as to provide the ability to reuse each available frequency in every third cell. Although this frequency reuse scheme is highly efficient, it requires at least two complete multicarrier, broadband base transceiver systems (BTS) to be located in each cell. Such a configuration results in dramatically increased hardware installation costs for each cell.
Returning to
FIG. 1
, the mobile unit
120
, in a cell
110
a
or
110
b
, communicates with the BTS
105
a
or
105
b
via radio frequency (RF) means, specifically employing one of the fixed number of channels. The BTS
105
a
,
105
b
communicate with the BSC
130
via dedicated telephone lines
140
. The BSC
130
communicates with the NSS
160
via the A interface
150
.
In the cellular phone system
100
, the cell areas typically range from 1 to 300 square miles. The larger cells typically cover rural areas, and the smaller cells typically cover urban areas. Cell antenna sites utilizing the same channel sets are spaced by a sufficient distance to assure that co-channel interference is held to an acceptably low level.
The mobile unit
120
in a cell
110
a
has radio telephone transceiver equipment which communicates with similar equipment in BTS
105
a
,
105
b
as the mobile unit
120
moves within a cell or from cell to cell.
Each BTS
105
a
,
105
b
relays telephone signals between mobile units
120
and a mobile telecommunications switching office (MTSO)
130
by way of the communication lines
140
.
The communication lines
140
between a cell site,
110
a
or
110
b
, and the MTSO
130
, are typically T
1
lines. The T
1
lines carry separate voice grade circuits for each radio channel employed at the cell site and data circuits for switching and other control functions.
While the cellular communications system arrangement of
FIG. 1
is cost effective to deploy when a large number of active mobile stations is expected in each cell, it is not particularly cost effective in most other situations. For example, during an initial system build out phase, a service provider ordinarily does not need to use a large number of radio channels. It is therefore typically not possible to justify the cost of deploying complex multicarrier broadband transceiver, system equipment based only upon the initial number of subscribers. As a result, the investment in conventional broadband multicarrier radio equipment may not be justified until such time as the number of subscribers increases to a point where the channels are busy most of the time. Furthermore, many areas exist where the need for wireless communication systems is considerable, but where signal traffic can be expected to remain low indefinitely (such as in rural freeway locations or large commercial/industrial parks). Because only a few cells at locations of high traffic demand (such as in a downtown urban location or a freeway intersection) will justify the initial expense of building out a network of high capacity broadband transceiver systems, the service provider is faced with a dilemma. He can build-out the system with less expensive narrowband equipment initially, to provide some level of coverage, and then upgrade to the more efficient equipment as the number of subscribers rapidly increases in the service area. However, the initial investment in narrowband equipment is then lost. Alternatively, a larger up front investment can be made to deploy the high capacity equipment at the beginning, so that once demand increases, the users of the system can be accommodated without receiving busy signals and the resultant blocked calls. But this has the disadvantage of requiring a larger up-front investment.
These concerns have led to the increased popularity of wireless repeaters, which can increase the capacity of cells without requiring the expense or complication of a multicarrier broadband BTS for each cell.
FIG. 2
is a block diagram of the components of a wireless communication system that makes use of wireless repeaters.
FIG. 2
illustrates a wireless communication system
200
such as a Cellular Mobile Telephone, Personal Communication System (PCS), or similar system in which employing slot-by slot diversity selection in the uplink signal paths of a wireless system repeater translator enables proper demodulation at the BTS of signals received from remote repeater base stations deployed in peripheral cells.
The system
200
provides voice and or data communication between mobile stations
210
and a Public Switched Telephone Network (PSTN) (not shown) via radio signals. In the particular embodiment of the invention being described, the radio signaling protocol, or “air interface,” uses a Time Division Multiple Access (TDMA) technique such as the GSM-1900 (formerly PCS-1900) standard promulgated by the Telecommunications Industry Association (TIA) in the United States which adopts all relevant aspects of the Global System for Mobile Communication (GSM) standard developed by the Groupe Special Mobile, and promulgated in Europe and elsewhere by the European Telecommunication Standards Institute (ETSI).
The remotely located repeaters
220
-
1
,
220
-
2
, . . . ,
120
-n (also referred to herein as the “remote base stations”) are each located in what is normally to be approximately the center of a group or cluster
240
of cells comprising individual cell sites
250
-
1
,
250
-
2
, . . . ,
250
-n. The remotely located repeaters
220
receive radio signals from the mobile stations
210
located in their respective,cells
250
and forward these signals to the associated multichannel host broadband Base Transceiver System (BTS)
260
. Likewise, radio signals originating at the host BTS
260
are forwarded by the repeaters
220
to the mobile stations
210
. As a result, th
Komara Michael A.
Overton Roger L.
Schmutz Thomas R.
Airnet Communications Corporation
Akerman & Senterfitt
Cumming William
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