Centrally located equipment for wireless telephone system

Details Centrally located equipment for wireless telephone system Centrally located equipment for wireless telephone system

1998-02-19

2001-10-09

Jung, Min (Department: 2663)

Multiplex communications

Communication over free space

Combining or distributing information via frequency channels

C370S480000

Reexamination Certificate

active

06301240

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to wireless communications systems, and more particularly to improved centrally located equipment for a wireless telephone system that incorporates an existing broadband distribution network, such as cable television network cable, to carry communication signals between wireless telephones and the centrally located equipment.
BACKGROUND OF THE INVENTION
The prior art teaches the use of an existing broadband distribution network to carry telephony signals between an existing telephone network and remote transceivers sites in defined cells or sectors. The remote transceivers, sometimes called Remote Antenna Drivers (RADs), are used to establish wireless telephony communication links with wireless telephones operating with an area covered by each RAD. Such broadband distribution networks include, but are not limited to, fiber-optic cable, coaxial cable, and radio links.
Between the telephone network and the broadband distribution network is centrally located equipment for carrying the telephony signals between the telephone network and the broadband network. This centrally located equipment typically includes multiple Base Transceiver Stations (BTS) and multiple Remote Antenna Signal Processors (RASPs). Each BTS is connected to the telephone network and to the RASPs. Each RASP is connected to the broadband network.
In typical operation, an audio telephony signal from the existing telephone network, and directed to a wireless telephone, is input to a BTS where it is encoded for use in one of the known wireless telephone systems, which include GSM, CDMA and CT2. The encoded telephony signal is used to modulate a radio frequency carrier signal of an intermediate frequency (IF) before being processed further. Before being transmitted to a RASP the IF signal is frequency translated to a higher radio frequency (RF) carrier signal for transmission to a RASP. When the encoded telephony signal, now being carried by the RF carrier signal, is received by the RASP, it is frequency translated back to an IF carrier signal and control signals are added. After this processing the encoded signal and control signals are frequency translated to another RF carrier frequency used for transmission over the broadband distribution network to the Remote Antenna Drivers (RADs) in the cells or sectors. Such transmission over the broadband network is typically over fiber-optic cable or over coaxial cable.
Similarly, encoded telephony and control signals received by the RASPs over the broadband distribution network from the Remote Antenna Drivers (RADs) are first converted to an IF carrier signal. The IF carrier signal is initially signal processed in the RASP to remove the control signals, and the IF carrier signal is then translated to an RF signal for transmission to a BTS. In each BTS the RF carrier signal carrying the telephony signal is first converted to an IF carrier signal before the telephony signal is extracted and converted into an analog or digital signal, depending on the type of system, and the encoded telephony signal is then sent to the telephone network.
SUMMARY OF THE INVENTION
The prior art systems described above utilize much frequency translation of the carrier signal as it passes through the Remote Antenna Signal Processor (RASP) and Base Transceiver Station (BTS). Thus, there is a need in the wireless telephony art for improved, simplified central equipment, such as the RASPs and BTSs, for processing and carrying telephony signals between an existing telephone network and wireless telephones.
The above described need in the wireless telephony art is satisfied by the present invention. The improvement comprises simplifying the Base Transceiver Stations (BTS) and the Remote Antenna Signal Processors (RASPs). This simplification lowers the cost of the BTS and RASP equipment, and decreases their complexity, which improves their reliability.
This simplification consists of reducing the number of frequency translation steps utilized in the BTS and RASP equipment. More particularly, for telephony signals originating at the telephone network and terminating at a wireless telephone, the IF carrier signal in each BTS is not translated to an RF carrier signal before being transmitted to a RASP. In addition, the IF carrier signal in each RASP is not translated to an RF carrier signal before being transmitted to a BTS. Rather, the frequency of the IF carrier signal in the RASPs and BTSs is the same, and the IF carrier signals are transmitted between the BTSs and the RASPs. This result is a significant savings in the complexity and cost of the RASPs and BTSs.
Since each prior art BTS and RASP has a number of telephony signal channels, each of which has the above described RF/IF translations, there is a large reduction in the number of frequency translation stages in this equipment. All IF to RF, and all RF to IF frequency translation stages at the RASP to BTS interface are eliminated.


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