Microcellular mobile communication system

• US 6,477,154 B1
• Filed: 08/14/1998
• Issued: 11/05/2002
• Est. Priority Date: 08/14/1997
• Status: Expired due to Term

• Current Assignee: SK Telecom Co., Ltd.
• Original Assignee: SK Telecom Co., Ltd.
• Inventors: Cheong, Jong Min, Kim, Tae Gue, Seo, Sang Hoon, Lim, Jae Sung, Park, Sun
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): NGUYEN, TOAN D
• Application Number:
  US09/138,470
• Time in Patent Office: 1,544 Days
• Field of Search: 370/320, 370/328, 370/331, 370/334, 370/335, 370/342, 370/467, 359/109, 359/115, 359/118, 359/135-136, 375/130, 375/140, 375/257, 455/436, 455/439, 455/442, 455/444, 455/450-452
• US Class Current: 370/328
• CPC Class Codes: H04B 10/25752 Optical arrangements for wireless networks
• CPC Class Codes: H04B 10/25753 Distribution optical network, e.g. between a base station and a plurality of remote units
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04W 16/32 Hierarchical cell structures
• CPC Class Codes: H04W 88/085 Access point devices with remote components
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A microcelluar mobile communication system which performs various functions such as a centralized management of resources, a capacity increase, a Base Station Transceiver System(BTS) miniaturization, a synchronization between micro base stations, a dynamic resource management, a softer handover between cells, a grouping and ungrouping of base stations in accordance with a traffic distribution. The microcelluar mobile communication system may increase the subscriber capacity, provide the high reliable service, extend the battery life of a personal station inducing low power communication and assure the radio channel capacity so that the radio multimedia service may be accomplished in the future, by maximizing the utility efficiency of radio frequency resource through cell miniaturization. The microcelluar mobile communication system may be installed efficiently to an indoor, a building underground, an underground tunnel as well as an outdoor, and may compose the single cell also in the indoor.

Claims

1. A micro cellular system for use in a wireless communication system based on a Code Division Multiple Access (CDMA) technology, comprising:

a micro base station controller (mBSC) ,connected to abase station controller(BSC), for receiving forward link traffic signals from the BSC, performing a spread modulation with respect to the forward link traffic signals, supporting an inter-cell handoff, combining the spread modulated signals, converting the combined signals into analog signals by using a digital modulation scheme and converting the analog signals into forward link hybrid fiber-radio(HFR) cable frequency signals in a forward link, and for receiving reverse link HFR cable frequency signals, extracting carrier signals bearing reverse link traffic signals from the reverse link HFR cable frequency signals, frequency down converting the carrier signals, converting the frequency down converted signals into reverse link digital signals by using a digital demodulation scheme, performing a spread demodulation with respect to the reverse link digital signals to thereby produce reverse link traffic signals and transmitting the reverse link traffic signals to the BSC in a reverse link;

a plurality of micro base stations, each connected to the mBSC and whole or part of the plurality of the micro base stations being included in a same micro cell, for transferring the HFR cable frequency signals including the forward link and the reverse link HFR cable frequency signals and transmitting/receiving RF (Radio Frequency) signals to/from a multiplicity of mobile stations, wherein each micro base station has one among a laser diode whose optical wavelengths are separated from each other and a light emitting diode; and

a HFR network, connecting the MBSC to the plurality of micro base stations, for converting the forward link HFR cable frequency signals into forward link optical signals, outputting the forward link optical signals via a single optical fiber core connected thereto and distributing the forward link optical signals to each micro base station in the forward link, for combining reverse link optical signals received from each micro base station, the combined reverse link optical signals being transferred via the single fiber core, converting the reverse link optical signals into electrical signals to thereby produce reverse link HFR cable frequency signals and transferring the reverse link HFR cable frequency signals to the mBSC,

wherein the micro cell is distinguished from other micro cells by its forward link and reverse link HFR cable frequency bands and the number of the frequency bands of each of the forward link and the reverse link HFR cable frequency signals ranges from one to the number of the plurality of the micro base stations.

2. The microcellular system of claim 1, wherein the mBSC includes:

a HFR network controller for generating forward link control channel signals, transmitting the forward link control channel signals to each micro base station, extracting reverse link control channel signals received from each micro base station, performing operation and management of each micro base station and interworking with HFR NMS (Network Management System) based on a GUI (Graphic User Interface),

wherein the operation and management is performed by using a polling scheme.

3. The microcellular system of claim 1 or 2, wherein the HFR network includes:

a frequency combiner for combining the HFR cable frequency signals from each micro base station and the forward link control channel signals from the HFR network controller;

a first E/O (Electrical to Optical) converter for converting output signals from the frequency combiner into the forward link optical signals;

a first O/E (Optical to Electrical) converter for separating the reverse link optical signals from the forward link optical signals by using optical coupling and converting the reverse link optical signals into electrical equivalents;

an optical signal distributing/combining means, connected to the single fiber core by way of at least one optical coupling for bidirectional communication, for distributing the forward link optical signals to each mBSC and combining the reverse link optical signals received from each micro base station via the single fiber core; and

a frequency divider for dividing the output signals from the first O/E converter into a plurality of reverse link HFR cable frequency signals and the reverse link control channel signals, and bandpass filtering the re-verse link HPR cable frequency signals to thereby extracting one or more micro cell designation signals, each designating a micro cell.

4. The microcellular system of claim 3, wherein the optical signal distributing/combining means supports one or both of a passive star network employing no active elements and a HFC (Hybrid Fiber-Coaxial) network employing an optical node to connect the single fiber core to a coaxial cable network.

5. The microcellular system of claim 4, wherein the HFC network has a forward link O/E converter and a reverse link E/O converter in the optical node, wherein each of the forward link O/E converter and a reverse link E/O converter is connected to the corresponding micro base station via one coaxial cable, and a forward link low noise amplifier and a reverse link line amplifier are engaged in the connection.

6. The micro cellular system of claim 3, wherein the optical signal distributing/combining means, in case that it supports both of the WLL service and the IMT-2000 service, combines signals for each service by using a wavelength coupler so that the optical wavelengths are different for each service.

7. The microcellular system of claim 1, further comprising

a Global Positioning System(GPS) receiver for receiving GPS signals and generating timing information and reference clock signals for use in synchronizing the system,

wherein the mBSC evaluates propagation delay time of signals therefrom to antennas connected to the micro base stations, and each micro cell is distinguished by applying a distinct pilot pseudo noise (PN) code offset to each micro cell in consideration for the propagation delay time including a delay time of each micro base station itself.

8. The microcellular system of claim 1, wherein said each mBSC includes:

a local controller for controlling a softer handover between each micro cell, performing a centralized dynamic resources management and controlling operation and management of the mBSC;

a channel switch, under the control of the local controller, for performing switching, combining and dividing to convert a three sector structure into N micro cells, producing the combined signals by switching and combining the spread modulated signals, converting the combined signals into analog signals by using the digital modulation scheme, converting the analog signals into the forward link HFR cable frequency signals and outputting the forward link HFR cable frequency signals to the HFR network in the forward link, for dividing, switching and spread demodulating the reverse link digital signals converted by the digital demodulation scheme, and extracting reverse link HFR cable frequency signals corresponding to each micro cell.

14. The microcellular system of claim 1, wherein each micro base station includes:

a transmitter for transmitting forward link RF signals to the mobile stations, each mobile station being air-coupled to micro base stations; and

a receiver for receiving reverse link RF signals from each mobile station;

wherein the transmitter has;

a second O/E converter for converting the forward link optical signals transmitted from them BSC via the HFR network into the electrical equivalents;

a first signal distributor for dividing the electrical signals converted at the second O/E converter;

a transmitter base station control processor for extracting the forward link control channel signals from the output from the first signal distributor and monitoring the status of or controlling the micro base station in response to the forward link control channel signals;

a forward link RF signal processor for selecting a designated forward link HFR cable frequency signal band indicated by the transmitter base station control processor, converting the selected band into the forward link RF signals and bandpass filtering the selected band into the forward link RF signals; and

a high power amplifier for amplifying the output from the forward link RF signal processor to an appropriate level to transmit by way of antenna; and

the receiver has;

a low noise amplifier for amplifying signals from the antenna of the micro base station while suppressing noise therein;

a reverse link RF processor for bandpass filtering the output from the low noise amplifier and converting the filtered output into the designated reverse link HFR cable frequency signal band;

receiver micro base station control processor for generating the reverse link control channel signal containing information on the status and control of the micro base station;

a first signal combiner for combining the output from the reverse link RF signal processor and the reverse link control channel signals; and

a second E/O converter for E/O converting the output from the first signal combiner, wherein the second E/O converter has therein as its light source one of a light emitting diode and a laser diode, wherein the laser diode having a plurality of wavelengths, each wavelength corresponding to each micro base station.

15. The microcellular system of claim 14, wherein the micro base station uses a diversity receiving path in an additional band distinct from the reverse link HFR cable frequency band to thereby support a receiver antenna diversity function.

16. The microcellular system of claim 1, wherein a part of the plurality of micro base stations are grouped together such that the micro base stations belonging to the part select signals having the same HFR cable frequency signal band, and the grouping is adjustable by an operator.

9. The micro cellular system of claim 26, where in the HFR cable frequency signals include:

forward link control channel signals and reverse link control channel signals, each for use in monitoring status of each micro base station and adjusting variables by using ID numbers incorporated therein;

forward link and reverse link HFR cable frequency signals for transferring the carrier signals between the mBSC and the plurality of micro base stations, wherein each of the forward link and the reverse link HFR cable frequency signals has therein the RF signals or IF(Intermediate Frequency) signals.

10. The microcellular system of claim 9, wherein the forward link HFR cable frequency signals further include CW (Continuous Wave) reference frequency signals for frequency coherence of the HFR network and the micro base stations.

11. The microcellular system of claim 10, wherein each micro base station has:

a transmitter for transmitting forward link RF signals to the mobile stations, each mobile station being air-coupled to the micro base stations; and

a receiver for receiving reverse link RF signals from each mobile station;

a reference frequency signal generator for receiving the CW reference frequency signals, receiving the reference frequency signals from the transmitter and reproducing the reference frequency signals;

a forward link RF signal processor, under the control of the micro base station, for receiving the output from the reference frequency signal generator and selecting frequency bands of the forward link HFR cable frequency; and

a reverse link RF signal processor, under the control of the micro base station, for receiving the output from the reference frequency signal generator and selecting frequency bands of the reverse link HFR cable frequency.

12. The microcellular system of claim 9, wherein the HFR cable frequency signals include any one of service carrier signals among WLL (Wireless Local Loop) service carrier signals and IMT-2000 (International Mobile Telecommunications-2000) service carrier signals.

13. The microcellular system of claim 9, wherein the forward link and the reverse link HFR cable frequency signals have transmission bandwidth wider than or equal to the bandwidth of the RF signals.

17. A HFR interface architecture for use in a CDMA-based wireless communication system, transferring signals between a BTS (Base Station Transceiver Subsystem) and a plurality of micro base stations, each micro base station being connected to the BTS and air coupled with a plurality of mobile terminals, wherein forward link electrical signals are transferred from the BTS to the plurality of micro base stations after being converted into forward link optical signals and reverse link electrical signals from each micro base station are collectively transferred to the BTS after being converted into reverse link optical signals therein, each of the signals being used in defining micro cells and/or sectors, the architecture comprising:

a BTS adapter, in a forward link, for receiving output from the BTS, converting the output into forward link HFR cable frequency signals and converting the forward link HFR cable frequency signals into the forward link optical signals, and in a reverse link, for receiving the reverse link optical signals including the reverser link cable frequency signals from the plurality of micro base stations, converting the reverse link optical signals into reverse link HFR cable frequency signals and providing the reverse link HFR cable frequency signals as input signals to the BTS, wherein the number of the forward link and the reverse link HFR cable frequency bands ranges from one to the number of the plurality of the micro base stations;

a plurality of micro base station interface units, each having one among a laser diode whose optical wavelengths are separated from each other and a light emitting diode, for converting the forward link optical signals received from the BTS adapter into the forward link electrical signals in the forward link and for converting the reverse link electrical signals received from the plurality of micro base stations into the reverse link optical signals; and

a cable means for transfers the forward link and the reverse link optical signals between the BTS adapter and the plurality of micro base station interface units via a single fiber core and including therein more than one optical couplers connecting more than one micro base stations.

18. The HFR interface architecture of claim 17, wherein signals transferred between the BTS and the BTS adapter are RF signals, frequencies of the RF signals is the same as the frequencies of the RF signals used in communicating between the micro base stations and the mobile stations, and the frequencies of the HFR cable frequency signals transferred between the BTS adapter and the micro base station interfacing units has frequency bands are one of the RF signals and IF signals.

19. The HFR interface architecture of claim 17, wherein the forward link HFR cable frequency signals include carrier signals carrying traffic signals and forward link control channel signals;

and the reverse link HFR cable frequency signals include primary signals and the reverse link control channel signals, wherein the carrier signals have the bandwidth wider than or equal to the bandwidth of the RF signals.

20. The HFR interface architecture of claim 19, wherein the forward link HFR cable frequency signals further include reference frequency signals for frequency coherence of the HFR network and the micro base stations.

21. The HFR interface architecture of claim 19, wherein the reverse link HFR cable frequency signals further include diversity signals in an additional band distinct from the reverse link HFR cable frequency band to thereby support a receiver antenna diversity function.