Wireless local area network system and receiver for the same

• US 5,864,550 A
• Filed: 04/18/1996
• Issued: 01/26/1999
• Est. Priority Date: 05/05/1995
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Posti, Jarkko
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US08/634,501
• Time in Patent Office: 1,013 Days
• Field of Search: 370/338, 370/319, 370/343, 370/445, 370/313, 370/347, 370/349, 375/269, 375/219, 375/220, 375/329, 375/334, 375/200, 375/206, 375/348, 375/350, 455/422, 455/450, 455/464, 455/32.1
• US Class Current: 370/338
• CPC Class Codes: H04L 27/00 Modulated-carrier systems
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

The invention relates to a wireless local area network system having data terminals and transceivers which communicate with the data terminals and transmit and receive data, for forming a wireless link between at least two data terminals, the system transmitting data as outputs in a certain frequency range. The output has a signal (B) which is visible as a narrow-band signal in the frequency range of the output. The signal (B) can be detected from farther away than a conventional output by arranging circuits (7, 8, 9) in the local area network system for filtering and detecting the narrow-band signal of a certain frequency from the received signal.

Claims

1. A wireless local area network system comprising data terminals (D1-D6) and transceivers (TR1-TR6) that communicate with the data terminals and transmit and receive data, for forming a cordless link between at least two data terminals, the system sending data as output signals in a certain frequency range, characterized in that an output signal comprises a signal (B) that is visible as a narrow-band signal in the frequency range of the output signal, and said local area network system comprises means (7,8,9) for filtering and detecting the narrow-band signal of a certain frequency from the received signal, said narrow-band signal being detectable at a greater range by other transceivers of the same wireless local area network system than a data portion of the output signal for indicating an on-going transmission of the output signal.

2. A local area network system according to claim 1, characterized in that data is transmitted as digital bit packets and the packets comprise a bit sequence (B) which is visible as the narrow-band signal in the frequency range of the output.

3. A local area network system according to claim 2, characterized in that said bit sequence (B) is predefined.

4. A local area network system according to claim 2, characterized in that said bit sequence (B) occurs at a plurality of points in the transmitted digital bit packet.

5. A local area network system according to claim 4, characterized in that said bit sequence (B) occurs at predefined intervals in the transmitted digital bit packet.

6. A local area network system according to claim 4, characterized in that said bit sequence (B) occurs at random intervals in the transmitted digital bit packet.

7. A local area network system according to claim 1, characterized in that said signal (B) is visible as a peak in the frequency spectrum of the received signal.

8. A local area network system according to claim 2, characterized in that said bit sequence (B) comprises at least two sequential 1-bits.

9. A local area network system according to claim 2, characterized in that said bit sequence (B) comprises at least two sequential 0-bits.

10. A local area network system according to claim 2, characterized in that said bit sequence (B) comprises at least two sequential 1-bits and 0-bits.

11. A receiver of a wireless local area network, comprising means (1) for receiving a signal of a reception frequency in a reception frequency range. characterized in that said receiver comprises means (7, 8, 9) for filtering and detecting a narrow-band signal of a certain frequency from the received signal and means, responsive to detecting the narrow-band signal, for inhibiting a transmitter from transmitting a wider-band signal, wherein said narrow-band signal is detectable at a greater range by other receivers of the same wireless local area network than a data portion of the output signal for indicating an on-going transmission of the output signal.

12. A wireless local area network, comprising:

a plurality of wireless transceivers each comprised of a transmitter and a receiver;

each said transmitter being coupled to a source of digital data for transmitting the digital data as a transmission signal during a transmission period, the transmission signal comprising a digital data portion that is transmitted at a first transmission frequency and with a first bandwidth, and further comprising at least one transmission in progress indicator that is transmitted at a second frequency that deviates from the first frequency and with a second bandwidth that is narrower than the first bandwidth, the transmission in progress indicator being detectable at a greater range than the digital data portion of the transmission signal by other receivers of the same wireless local area network f or indicating an on-going transmission of the transmission signal; and

each said receiver comprising a filter having an output coupled to an input of a detector f or detecting a presence of a received transmission in progress indicator and for inhibiting an operation of the corresponding transmitter during the transmission period of another transmitter.

13. A wireless local area network as in claim 12, wherein the digital data is transmitted as packets of digital data that comprise a bit sequence that defines the at least one transmission in progress indicator.

14. A wireless local area network as in claim 13, wherein the bit sequence occurs at one of predetermined intervals or random intervals.

15. A wireless local area network as in claim 13, and further comprising means, responsive to a determination that a predetermined bit sequence occurs in the digital data of a packet, for inhibiting the transmission of the bit sequence that defines the transmission in progress indicator.

16. A wireless local area network as in claim 13, wherein the bit sequence is comprised of a plurality of one bits that are preceded by or followed by a plurality of zero bits.

17. A wireless local area network as in claim 12, wherein said receiver is comprised of an In-phase branch and a Quadrature-phase branch, wherein said filter is comprised of a narrow-band filter in each said branch, and wherein said detector is coupled to an output of each of said narrow-band filters.

18. A wireless local area network as in claim 17, wherein said detector is comprised of an Amplitude Modulation detector.