Method and apparatus for duplex communication in hybrid fiber-radio systems

Abstract

An apparatus and method for enabling cost-effective duplex communication by diplexing one of down stream signals for frequency up-conversion in a hybrid fiber-radio system includes diplexing an unmodulated mode signal among beating signals between a master laser and an injection-locked slave laser and using the diplexed signal for down-conversion in upstream transmission, thereby eliminating the need for expensive high-frequency local oscillators for frequency conversion. Higher radio frequency signals can be generated using beating between basic modes and satellite modes such as FWM conjugates of the master laser and slave laser. Cost-effective systems, stabilization of a light source and improved transmission performance may be achieved by using a diplexer instead of an expensive high-frequency local oscillator.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This is a divisional application based on pending application Ser. No. 10 / 423,760, filed Apr. 25, 2003, the entire contents of which is hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a method and apparatus for enabling cost-effective duplex communication by diplexing one of down stream signals for frequency upconversion in a hybrid fiber-radio system.[0004]2. Description of the Related Art[0005]Increasing demands for new mobile internet services including video and interactive services have resulted in the exhaustion of the available frequency band for wireless communications, and so triggered the development of the 4th generation wireless communication system. As the next generation communication system of the IMT-2000 (International Mobile Telecommunication), micro / millimeter-wave communication utilizing signals in the band of 3 GHz to 300 GHz is drawing a...

AI Technical Summary

Benefits of technology

[0012]To solve the above-described problems, it is a feature of an embodiment of the present invention to provide an apparatus and method for enabling duplex communication by generating and diplexing optical micro / millimeter signals in a hybrid fiber-radio system. In particular, it is a feature of an embodiment of the present invention to provide an efficient method for enabling duplex communication by generating signals in a carrier frequency mode and in side-band modes. One of the generated modes is diplexed with a diplexer, and is used for down-conversion in upstream transmission, thereby eliminating the need for expensive high-frequency local oscillators for frequency conversion.

Problems solved by technology

However, because of its limitation on the transmission distance and need for high-frequency sources, the micro / millimeter-wave communication system must be hybrided with existing wire systems.

A main issue in hybrid fiber-radio transmission systems is signal band conversion into a carrier frequency, because up / down conversion between baseband and carrier frequency in micro / millimeter-wave systems requires expensive equipment.

A disadvantage of baseband transmission is the necessary use of highly complex outdoor base stations including full SDH / SONET compliant equipment.

A disadvantage of the IF feeder system is the use of moderately complex outdoor base stations including RF up / down conversion.

For high radio frequency systems, however, both the baseband transmission and IF feeder transmission methods require many local oscillators to up / down convert signal frequencies into carrier frequencies.

Despite its many advantages, the optical micro / millimeter-wave transmission system has problems in upstream transmission from a subscriber to a head end, because in upstream transmission, it is necessary to generate an optical micro / millimeter-wave in a remote base station, which may increase the cost of RSs.

Therefore, it is difficult to apply the optical micro / millimeter-wave transmission system to duplex communication systems.

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