Method and apparatus for operating an indoor CDMA telecommunications system

• US 6,101,176 A
• Filed: 03/12/1997
• Issued: 08/08/2000
• Est. Priority Date: 07/24/1996
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones Incorporated (Nokia Corporation)
• Inventors: Ma, Lin, Sunay, Oguz, Honkasalo, Zhi-Chun, Hottinen, Ari, Honkasalo, Harri
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Previl, Daniel
• Application Number:
  US08/815,727
• Time in Patent Office: 1,245 Days
• Field of Search: 370/335, 370/336, 370/337, 370/342, 370/345, 370/347, 370/350, 370/203, 370/206, 370/280, 370/331, 370/332, 375/200, 375/206, 375/346, 455/501, 455/502
• US Class Current: 370/335
• CPC Class Codes: H04B 7/2618 using hybrid code-time division multiple access [CDMA-TDMA]
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 16/16 for PBS [Private Base Station] arrangements

Abstract

A method and apparatus is provided for the overlaid operation of two or more wireless communication systems where one of the two systems is a small-scale or indoor system and the other is a large-scale or outdoor system. The indoor system monitors the operation of the outdoor system and detects which part of the available radio resources are temporarily not in use or interference-free in the outdoor system. The indoor system dynamically selects an unused outdoor channel for indoor operation. The indoor radio traffic is divided into TDD time slots with the slots being used for monitoring the existing radio communication on other outdoor channels so that fast changes according to changing traffic and interference conditions are possible. Synchronization, timing and phase control may be added to assist in the maintenance of an error-free communication network.

Claims

1. An indoor CDMA communication system operable within the coverage area of an outdoor communication system, the outdoor communication system using an uplink frequency band for uplinking signals and a downlink frequency band for downlinking signals, the indoor CDMA communication system comprising:

at least one mobile station transceiver;

an indoor base station transceiver operating transparently within the coverage area of the outdoor communication system, the indoor base station transceiver comprising;

monitoring means for periodically monitoring the uplink frequency band and the downlink frequency band;

means for determining a plurality of candidate frequencies on one of either the uplink frequency band or the downlink frequency band based upon a pre-determined acceptable interference level;

means for selecting one candidate frequency from said plurality of candidate frequencies for use in bi-directional communication between said indoor base station transceiver and said at least one mobile station transceiver.

2. The indoor CDMA communication system of claim 1, wherein said bi-directional communication is a time division duplex (TDD) format.

3. The indoor CDMA communication system of claim 2, wherein said TDD format comprises:

a transmit time slot wherein either said indoor base station transceiver or said at least one mobile station transceiver transmits information over said one candidate frequency;

a receive time slot wherein either said indoor base station transceiver or said at least one mobile station transceiver receive information over said one candidate frequency; and

a monitor time slot utilized by the monitoring means wherein neither said indoor base station transceiver nor said at least one mobile station transceiver transmit or receive information, and instead monitor the usage or interference dynamically changing interference levels on said plurality of candidate frequencies.

4. The indoor CDMA communication system of claim 1, wherein the outdoor communication system is a CDMA-based system.

5. The indoor CDMA communication system of claim 4, wherein the indoor CDMA communications system and the outdoor communication system operate according to an IS-95-based standard.

6. The indoor CDMA communication system of claim 4, wherein the indoor CDMA communications system and the outdoor communication system operate according to an ANSI J-STD-008 standard.

7. The indoor CDMA communication system of claim 1 further comprising means responsive to selection of said one candidate frequency for selecting a forward link component of said one candidate frequency, said forward link component falling within said downlink frequency band.

8. The indoor CDMA communication system of claim 1, wherein said plurality of candidate frequencies comprises low-use frequencies.

9. The indoor CDMA communication system of claim 1, wherein said plurality of candidate frequencies comprises non-interfering frequencies.

10. A communication system transparently operable within the coverage area of a second communication system, the second communication system using a first frequency band for uplinking signals and a second frequency band for downlinking signals, the communication system comprising:

a base station transceiver within the coverage area of the second communication system, wherein the second communication system remains unaffected by the operation of the communication system;

a mobile station transceiver for communicating with the base station transceiver;

a monitoring means associated with the base station for monitoring the first frequency band and the second frequency band to determine a plurality of candidate spreading codes orthogonal to those used in the second communication system of one of either the first frequency band or the second frequency band; and

a means for selecting one spreading code of said plurality of candidate spreading codes for use in the communication between said base station transceiver and said mobile station transceiver.

11. A method of minimizing interference in a first communication system operable within the coverage area of a second communication system using a spreading code to identify a channel within a first frequency band for uplinking signals and a second frequency band for downlinking signals, said first communication system comprising a base station transceiver and a mobile station transceiver, the method comprising:

(a) monitoring the first frequency band and the second frequency band by said base station transceiver to determine a plurality of candidate frequencies;

(b) selecting one candidate frequency of said plurality of candidate frequencies for use in communication between said base station transceiver and said mobile station transceiver;

(c) communicating information about said one candidate frequency from said base station transceiver to said mobile station transceiver;

(d) communicating in a TDD format between said base station 16 transceiver and said mobile station transceiver using said one candidate frequency; and

(e) repeating steps (a) through (d) during a periodic time frame to allow the second communication system to re-select the one candidate frequency in response to use of the selected one candidate frequency by the first communication system.

12. The method of claim 11, further comprising the step of selecting a forward link band of said one candidate frequency after the step of selecting one candidate frequency.

13. The method of claim 12, wherein the steps of communicating use the forward link band of said one candidate frequency, the forward link band falling within the second frequency band.

14. The method of claim 12, further comprising the steps of:

measuring a first interference level within the forward link band;

comparing the first interference level to a pre-determined threshold; and

switching to a reverse link band of said one candidate frequency if the first interference level exceeds the pre-determined threshold so that the steps of communicating uses the reverse link band of said one candidate frequency, the reverse link band falling within the first frequency band.

15. The method of claim 11, wherein said plurality of candidate frequencies comprises low-use frequencies.

16. The method of claim 11, wherein said plurality of candidate frequencies comprises non-interfering frequencies.

17. The method of claim 11, further comprising:

monitoring the first frequency band and the second frequency band by said mobile station transceiver to determine additional candidate frequencies;

recording said additional candidate frequencies; and

communicating said additional candidate frequencies from said mobile station transceiver to said base station transceiver.

18. A method establishing a communication between a base station and a mobile station transceiver of a first communication system operating within a coverage area of a second communication system, the second communication system using a first frequency band for uplinking signals and a second frequency band for downlinking signals, the method comprising:

monitoring the first frequency band and the second frequency band by said base station transceiver to determine a strongest interfering signal from the second communication system;

identifying a first phase which the strongest interfering signal from the second communication system reaches said mobile station transceiver;

identifying a second phase which a signal transmitted from said base station transceiver reaches said mobile station transceiver;

calculating a phase error which indicates a difference between the first phase and the second phase; and

adjusting a transmission timing of said base station transceiver to minimize any difference between said phase error and a predetermined optimal phase difference; and

establishing communication between said base station transceiver and said mobile station transceiver by synchronizing the communication with the strongest interfering signal from the second communication system, wherein the base station transceiver utilizes the adjusted transmission timing.

19. The method of claim 18 wherein said optimal phase difference is 90 degrees so that said signal from said base station transceiver is orthogonal to a signal received from the second communication system.