Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-06-05
2001-02-13
Urban, Edward F. (Department: 2746)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S507000, C455S560000, C455S001000, C370S280000
Reexamination Certificate
active
06188912
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the implementation of wireless systems in a local telephone loop environment in what is usually called a Wireless Local Loop (WLL). The present invention particularly addresses a base station architecture used in the implementation of a Wireless Local Loop.
BACKGROUND OF THE INVENTION
The local loop of a telephone system is what some have termed the “last mile” or the “last 1000 feet”. This local loop is essentially the copper wire that connects the customer premises (i.e., a house or business) to the telecommunications network. The cost of laying down the copper wire can be very expensive (ie, over $1 per foot). Where communities are rural in nature as in some parts of the United States or in developing countries, laying down such an infrastructure can be prohibitively expensive.
As an alternative to installing a wire or cable infrastructure, these rural communities are turning to wireless solutions for their telecommunication needs. However, conventional wireless telecommunication technologies suffer from a number of disadvantages. Often times, because of the quality of the service, modem connections are frequently difficult to establish and maintain. Even where modem connection are possible, data rates are often prohibitively slow.
A further disadvantage of conventional wireless telecommunication technologies relate to their inefficient use of their RF spectrum resources. Subscribers transferring data over the network occupy channels that would otherwise be available for voice communication. In instances in which many subscribers are, for example, accessing the internet, these conventional wireless technologies suffer from a serious degradation in Grade of Service (GOS) resulting in a increase in the percentage of calls blocked (i.e., Erlang B).
These deficiencies are particularly troublesome in view of the fact that data usage is bursty in nature. Analysis of internet data usage indicates that approximately 95-97% of time, the data network is idle. The aggregate throughput to a user is typically less than 5 kilobits per second.
Therefore, there is a need for a wireless telecommunication system to replace the local loop which more efficiently allocates resources between voice and data communications yet maintains a desirable high GOS. In implementing a wireless telecommunication system, it is critical that a base station be able to communicate in an efficient manner with various subscriber stations.
It is also an object of the present invention to provide a base station architecture that allows the central office and antenna to be conterminous.
It is a further object of the present invention to provide a base station architecture to remotely locate a wireless portion of a base station to be better situated in a wireless system, away from the central office.
It is a further object of the present invention to provide an internal channel concentration capability to reduce the cost and complexity of back haul to the remote base stations.
It is a further object of the present invention to provide a base station architecture that permits wired access to subscribers in one location and wireless access to subscribers in a second location.
It is a further object of the present invention to provide a base station architecture having redundancy and protection switching.
It is a further object of the present invention to provide a base station architecture having, in addition to a low tier communication service capable of providing less than 256 KBPS to the subscriber, a high tier access system such as ADSL channel banks and primary rate ISDN banks capable of providing greater than 256 KBPS access to the subscriber and multiple MBPS interfaces.
It is a further object of the invention to provide a base station system that allows individual subscribers in an area of service seamless telecommunications access (i.e., POTS (plain old telephone system), ISDN (Integrated Services Digital Network), data, multimedia, etc. to a telecommunications network. This system facilitates full voice, data, and fax utilization. This system is designed to replace existing local loops or provide infrastructure for those communities with no local loop in place. In this type of system a subscriber has a corresponding subscriber station and the central office (CO) has a corresponding base station.
SUMMARY OF THE INVENTION
These and other objects are achieved by a base station architecture having a front end and a back end. The front end includes a wideband bus and performs network interface, compression, and concentration functions. The back end includes a subscriber bus and a baseband modem bus and performs modulation and demodulation functions. The back end may also provide wired access to subscribers. The wideband and subscriber buses include a plurality of communication channels for carrying subscriber traffic. The number of communication channels on the wideband bus exceeds the number of communication channel on the subscriber bus. The front end of the base station includes one or more switches capable of mapping traffic from the wideband bus onto the subscriber bus. The back end of the base station includes one or more modems for modulating traffic on the subscriber bus for wireless transmission to a subscriber and for demodulating a wireless transmission from a subscriber onto the subscriber bus.
The present invention provides a base station architecture that permits a high degree of flexibility in how the base station may be configured to accommodate a variety of deployment scenarios. In a first deployment scenario in which demography permits coincident location of the central station and antenna, the front end and back end of the base station are conterminous. In a second deployment scenario in which demography dictates that the antenna be remotely located away from the central station, the front end of the base station is located in the central station and the back end of the base station is located in a remote location. A communication link is provided between the front end of the base station and the back end of the base station. This communication link can include, for example, a microwave back haul, a HDL-driven copper cable, or fiber optic cable. Alternatively, satellite communication link may be provided.
In a further deployment scenario, the base station according to the present invention provides wired access to a first group of subscribers and wireless access to a second group of subscribers. In this alternative embodiment, a POTS channel bank or DLC is provided by replacing the modem portions of the back end of the base station architecture with multi-channel POTS cards and providing a shelf extension. The wideband bus can be used to support up to 128 POTS channels.
The base station architecture provides various capabilities. The base station interfaces to the network with 8 E
1
/T
1
or single SDH/Sonet ring interface. The base station also provides for unconcentrated E
1
V5.1 and T
1
TR-008, and concentrated E
1
V5.2 and T
1
TR-303. Concentration of 240 users to the shelf traffic CDMA channel pool (typically 24 channels) is provided. Separation of the concentration and control and back haul to the MODEM and RF reduces back haul costs. The system has optional redundancy and protection switching along with flexible shelf architecture for POTS and DLC applications. Provisioning is provided for Packet Data transport and Frame Relay Network interfaces.
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Hudson Thomas C.
Struhsaker Paul F.
Long Aldridge & Norman LLP
Tran Congvan
Urban Edward F.
World Access, Inc.
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