Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-10-21
2001-07-31
Maung, Nay (Department: 2744)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S349000, C455S561000
Reexamination Certificate
active
06269255
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to masthead units for base stations used in cellular communication networks. More particularly, a self-contained modular masthead unit and methods for changing the cell size by swapping masthead units are described.
The popularity of cellular telephones has been increasing dramatically in recent years. With the increased demand for cellular services, there has been an explosive growth in the infrastructure that is required to support these cellular services. Most cellular networks are organized substantially as illustrating in FIG.
1
. As seen therein, a mobile switching center (MSC)
10
communicates with a plurality of base station controllers
12
which in turn each communicate with one or more base stations
14
. The base stations
14
are directly coupled to one or more antennas (transceivers)
16
and are responsible for transmitting or receiving the radio signals that are used to support cellular communications. The mobile switching center
10
operates as the nerve center for the entire network and communicates with the base station controllers (BSC)
12
by an established protocol. There are a variety of different protocols that have been defined for cellular services, as for example, the GSM (Global Systems for Mobile Communications) protocol, the CDMA (Code Division Multiple Access) and the TDMA (Time Division Multiple Access) protocols. These various protocols dictate the nature of the communications between the MSC, the BSCs, and the BTSs and are well known to those skilled in the art.
Conventional base station controllers are primarily responsible for dictating the size of the associated cell. That is, the area that is covered by a particular base station. There are no fixed specifications as to the size of the cells, but in current usage, it is common to refer to macro cells, mini cells, and micro cells. The range of the various cells tends to vary with their size and by way of example in current usage, macro cells typically have antennas that output on the order of 20-50 watts of energy and tend to have ranges on the order of 5-40 kilometers. Mini cells typically have power outputs on the order of 10 watts and corresponding ranges in the vicinity of 2-5 kilometers. Micro cells typically have power consumption on the order of 2-8 watts with ranges of less than a kilometer or so. Of course as signal processing capabilities in antenna designs improve, the distinctions between the various sizes blurs but in concept, the cell size may always be varied.
One problem frequently encountered by systems having relatively larger cell sizes is that the antenna must be placed on a tower in order to obtain the desired range. Referring next to
FIG. 2
, one conventional tower arrangement will be briefly described. In the illustrated arrangement, the antenna
16
is mounted on a tower structure
20
while the associated base station
14
is located in the building structure at the base of the tower
20
. If the tower
20
is relatively tall, a relatively long feed cable
22
must be provided between the base station
14
and the antenna
16
. Generally the feed cable
22
includes a pair of coax cables with one of the coax cables (a transmit line) being arranged to carry the transmit signal and one of the coax cables (a receive line) being arranged to carry the receive signal.
A relatively long feed cable
22
presents a number of difficulties in terms of both signal intensity losses and the introduction of noise to the received signal. One approach to reducing the problems encountered by long feed lines is to provide a masthead unit
24
that is mounted on the tower
20
at a position relatively closer to the antenna
16
. The masthead unit typically includes a duplexer that is arranged to apply the transmitted signals to the antenna and to split the received signals onto a receive line. The split received signals are then passed through a low noise amplifier which amplifies the received signals making them substantially less susceptible to degradation by noise picked up by the feed cable
22
.
When the feed cable is particularly long there may be relatively significant power losses in the transmit signal carried on the transmit line as well. Accordingly, some designs have incorporated a linear power amplifier into the masthead design as well. Such power amplifiers are fed by a power supply located in the base station.
As cellular technology improves and its popularity increases there are increased needs to alter the size and/or shape of particular cells. In some cases it is desirable to increase the size of a cell to provide improved range. At the same time, in other situations it is desirable to reduce the size of a cell to permit the introduction of additional cells in order to handle higher usage. Although the present designs work well, they are not particularly modular in that if it is desirable to change the size of a cell for any reason, it is necessary to replace the entire base station
14
. Since base stations are relatively expensive units it would be desirable to provide a base station architecture which permits the base station hardware to be reused even if the cell size or cell geometry needs to change.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, an improved modular masthead unit for use in cellular communications networks is provided. The modular masthead unit is configured for insertion into a communication path between the base station and the antenna. The modular masthead unit communicates with the antenna via an antenna line and communicates with a base station by distinct transmission and receiver lines. The masthead unit includes a power amplifier arranged to amplify the power of outgoing communication signals received from the base station. A duplexer is configured for electrical communication with the antenna via an antenna line and is arranged to receive the amplified transmit signals and to output the amplified transmit signals to the antenna line. The duplexer also receives incoming communication signals from the antenna line and outputs the received incoming communication signals on a receiver line that is distinct from the transmission line. A power supply is provided within the masthead unit for supplying power to the power amplifier. With this arrangement, the masthead unit forms a modular unit that is distinct from the base station such that the modular masthead unit may be replaced independently of the base station. In a preferred embodiment, the masthead unit also includes a low noise amplifier for amplifying the received incoming communication signals and passing the amplified incoming communication signals to the base station.
The masthead unit may be used in a cellular communications network that includes a mobile switching center, a base station controller that communicates with the mobile switching center and a base station that communicates with a base station controller and operates in accordance with an established cellular communications protocol such as the GSM protocol.
In a separate method aspect of the invention, a method of changing the range of a cell within a cellular network is provided. Initially, a masthead unit associated with a particular base station is replaced by a masthead unit having a different power supply and power amplifier output thereon in order to change the associated cell range. Additionally, at least one radio range parameter in an operations registry associated with a mobile switching center that controls the affected base station is also changed. With this arrangement, the range of the cell within the cellular network may be changed without changing any hardware in the base station.
REFERENCES:
patent: 4592093 (1986-05-01), Ouchi et al.
patent: 5436822 (1995-07-01), West, Jr.
patent: 5502715 (1996-03-01), Penny
patent: 5548813 (1996-08-01), Charas et al.
patent: 5758287 (1998-05-01), Lee et al.
patent: 6047199 (2000-04-01), DeMarco
patent: 0639035A1 (19
Flehr Hohbach Test Albritton & Herbert LLP
interWAVE Communications International, Ltd.
Maung Nay
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