Microcellular mobile communication system

• US 5,424,864 A
• Filed: 08/02/1994
• Issued: 06/13/1995
• Est. Priority Date: 10/24/1991
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Emura, Katsumi
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): BACARES, RAFAEL D
• Application Number:
  US08/284,276
• Time in Patent Office: 315 Days
• Field of Search: 359/123, 359/124, 359/125, 359/145, 359/172, 359/173, 359/152, 370/69.1, 370/71, 370/95, 370/95.3, 455/56.1, 455/53.1, 348/6, 348/10-13
• US Class Current: 398/116
• CPC Class Codes: H04B 10/25754 Star network topology
• CPC Class Codes: H04B 10/25759 Details of the reception of RF signal or the optical conversion before the optical fibre
• CPC Class Codes: H04W 4/18 Information format or content conversion, e.g. adaptation by the network of the transmitted or received information for the purpose of wireless delivery to users or terminals
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/085 Access point devices with remote components
• CPC Class Codes: H04W 88/12 Access point controller devices
• CPC Class Codes: H04W 92/12 between access points and access point controllers

Abstract

A microcellular mobile radio communication system has a central base station and a plurality of radio base stations interconnected by a shared optical fiber transmission line. In the central and radio base stations, electrical radio signals are frequency-converted to frequencies assigned to the radio base stations and then converted into optical signals. In the central base station, the optical signals are combined for transmission through the optical fiber transmission line to the radio base stations. Alternatively, the frequency-converted electrical radio signals may first be combined and then converted into an optical signal for transmission. In the radio base stations, the electrical radio signals are converted to optical signals, which are combined and transmitted through the transmission line to the central radio station. In each radio base station, the frequency of the radio signal extracted from the received combined signal is frequency-converted to a frequency to be transmitted from its antenna, with the other signals filtered out. The central base station demodulates the received combined signal from the radio base stations into signals for the exchange office. The radio signals in different frequency bands assigned to each radio base station can simultaneously be transmitted through the shared optical fiber transmission lines between the radio and central base stations.

Claims

1. A microcellular mobile radio communication systems for radio communication with a plurality of mobile units, comprising:

a) a plurality of radio base stations (2-5) adapted to be allocated to separate microcells, each of said radio base stations comprising;

an antenna (110) for transmitting a radio signal to and receiving a radio signal from a mobile unit;

first frequency converting means (113) for converting the frequency of the radio signal received by said antenna into a predetermined frequency assigned to its own radio base station;

electrical-to-optical converter means (114) for converting the frequency-converted radio signal to an optical signal, and for transmitting the optical signal as an upstream optical signal (12);

optical-to-electrical converter means for converting downstream optical signals (11) of different frequency signals to electrical signals; and

second frequency converting means (103) for converting the frequency of one of said electrical signals which is destined for its own radio base station to a frequency assigned to the mobile unit, and for transmitting the frequency-converted signal to said antenna;

b) a central base station (20) comprising;

optical-to-electrical converter means (230) for converting the upstream optical signals from the electrical-to-optical converter means of said radio base stations to electrical signals;

demodulating means (241-244) for demodulating said electrical signals into signals to be transmitted to an exchange office (30);

frequency converting means (211, f1;

212, f2;

213, f3;

214, f4) corresponding to said second frequency converting means (103) of said radio base stations (2,3,4,5), respectively, for frequency-converting signals from the exchange office to separate electrical signals having frequencies assigned to each of said radio base stations, said assigned frequencies differing from each other, add each of said signals from the exchange office having the same frequency as the signal frequency-converted by said corresponding second frequency converting means (103); and

electrical-to-optical converter means (221-224) for converting the frequency-converted separate electrical signals to separate optical signals, and for transmitting said optical signals as said downstream optical signals to said optical-to-electrical converter means of said radio base stations, said separate optical signals having a single carrier frequency;

c) optical fiber transmission means connected between and shared by said radio base stations and said central base station, for transmitting the upstream optical signals of different frequencies assigned to each of said radio base stations from said radio base stations to said central base station, and for transmitting the downstream optical signals of different frequencies assigned to each of said radio base stations from said central base station to said radio base stations.

2. A microcellular mobile radio communication system according to claim 1, wherein said frequencies, assigned to each of said radio base stations, of the electrical signals frequency-converted by said frequency converting means of said central base station are different from the predetermined frequencies converted by the first frequency converting means of each radio base station.

3. A microcellular mobile radio communication system according to claim 1, wherein said electrical-to-optical converting means of said central base station comprises means for individually converting the separate electrical signals from said frequency converting means to the separate optical signals and combining said separate optical signals to an optical signal for transmission as said downstream optical signals through said optical fiber transmission means.

4. A microcellular mobile radio communication system according to claim 1, wherein said electrical-to-optical converter means of said central base station comprises means for combining the separate electrical signals from said frequency converting means to a combined electrical signal and converting said combined electrical signal to an optical signal for transmission as said downstream optical signals through said optical fiber transmission means.

5. A microcellular mobile radio communication system according to claim 1, wherein said frequencies, assigned to each of said radio base stations, of the electrical signals frequency-converted by said frequency converting means of said central base station are the same as the predetermined frequencies converted by the first frequency converting means of each radio base station.