Wireless telephone system

• US 5,005,183 A
• Filed: 09/07/1989
• Issued: 04/02/1991
• Est. Priority Date: 02/04/1985
• Status: Expired due to Term

• Current Assignee: Mitel Telecom Ltd. (Mitel Networks Corporation)
• Original Assignee: Mitel Telecom Ltd. (Mitel Networks Corporation)
• Inventors: Carey, Michael J., Anderson, Adrian J.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US07/404,010
• Time in Patent Office: 572 Days
• Field of Search: 375/1
• US Class Current: 375/130
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 5/28 using the near field of leaky cables, e.g. of leaky coaxial cables
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker

Abstract

A wireless telephone communication system for wireless, voice, data or voice and data terminals comprising apparatus at a central location for receiving one or a plurality of signals for communication with selected ones of wireless communication terminals, apparatus for converting the signals to spread spectrum radio frequency signals, a leaky transmission line located in a communication region, apparatus for applying the spread spectrum radio frequency signals to the transmission line for electromagnetic radiation within the region, at least one wireless communication terminal adapted to receive a predetermined one of the spread spectrum radio frequency signals and for demodulating it into an intelligible signal.

Claims

1. A wireless system for telephone communication within a building, comprising:

(a) means at a central location for receiving a plurality of signals for communication with selected wireless communication terminals,

(b) means at said central location for converting said signals to spread spectrum radio frequency signals using correlation codes corresponding to particular idle channels,

(c) a leaky transmission line located in a communication region within the building,

(d) means for applying the spread spectrum radio frequency signals to said transmission line for electromagnetic radiation within said region,

(e) at least one mobile wireless communication terminal adapted to receive a predetermined one of the spread spectrum radio frequency signals within the building and for demodulating it onto an intelligible signal.

2. A system as defined in claim 1 including means for transmitting a supervisory signal on a fixed spread spectrum supervisory channel to said wireless communication terminal, means at said terminal for receiving a predetermined form of said supervisory signal designative of a particular correlation code related to a receive channel, and means for correlating the predetermined one of the spread spectrum signals using the correlation code to effect said demodulation into said intelligible signal.

3. A system as defined in claim 1 including means at the central location for receiving a signal at a particular port designative of a particular junctor or channel of an incoming signal, and means for transmitting said spread spectrum supervisory signal to said wireless terminal containing said predetermined form of said supervisory signal designative of said particular correlation code corresponding to said particular junctor or channel.

4. A system as defined in claim 1 including means at the central location for transmitting said spread spectrum communication signals to the wireless communication terminals using pseudo-random spreading codes which correspond to predetermined fixed correlation codes associated with individual ones of the wireless communication terminals.

5. A system as defined in claim 1, in which each wireless cOmmunication terminals is comprised of:

(i) a telephone set,

(ii) means for PCM encoding signals received from the telephone set,

(iii) means for spread spectrum and RF modulating the PCM encoded signals using a first pseudo-random correlation code,

(iv) means for applying the RF modulated signals to an antenna through a first filter for wireless transmission to the leaky transmission line,

(v) means for receiving RF and spread spectrum modulated signals-from the antenna via a second filter,

(vi) means for RF and spread spectrum demodulating the received signals using a second pseudo-random correlation code different from the first correlation code,

(vii) means for PCM decoding the spread spectrum demodulated signals,

(viii) means for applying the PCM decoded signals to the telephOne,

whereby wireless two-way communication via said leaky transmission line on channels designated by the correlation codes is provided.

6. A system as defined in claim 5 in which the first and second correlation codes are variable, and means for causing variation thereof whereby particular designated send and receive spread spectrum channels are established.

7. A system as defined in claim 6 including a synchronization and control circuit, a second demodulator having its input connected to the output of said second filter for receiving a supervisory signal including synchronization signals, and providing demodulated digital supervisory signals therefrom to the synchronization and control circuit, the second demodulator using a fixed predetermined correlation code for demodulation of the supervisory signals, a second modulator having its input connected to the synchronization and control circuit for receiving supervisory signals and spread spectrum modulating said latter signals using a fixed predetermined pseudo-random code different from that of the correlation code used in the first modulator, RF modulating these signals and applying the signals via the second filter to the antenna, and means in the synchronization and control circuit for receiving supervisory signals from the telephone, generating supervisory data signals of predefined format and applying them to the second modulator, and for receiving supervisory data signals of predefined format from the second demodulator, for translating said latter supervisory signals therefrom and applying said translated signals to the telephone.

8. A system as defined in claim 7 including means at the synchronization and control circuit for deriving designated correlation codes from the received supervisory signals of predefined format and for enabling the first modulator and demodulator to use said latter correlation codes in modulation and demodulation respectively to establish the receive and transmit channels for said signals.

9. A system as defined in claim 8 including means for generating and displaying data at said wireless communication terminal, a data interface circuit connected to said data generating and displaying means, third means for spread spectrum and RF modulating data signals received via said interface circuit and applying the RF modulated signals to the first filter for transmission via the antenna to the leaky transmission line, third demodulation means having its input connected to the antenna via the second filter, and its output connected to the data interface circuit for applying demodulated data signals thereto, and means connecting the third modulator and demodulator to the synchronization and control circuit for carrying signals therefrom designative of the pseudo-random correlation codes to be used by the third modulator and demodulator.

10. A system as defined in claim 1, 5 or 9 comprising a plurality of similar circuits each comprising an interface means at the central location for connection to an individual junctor of a PABX, for receiving and transmitting communication signals from said junctor and for receiving and transmitting supervisory signals from the PABX relating to a telephone call, a central PCM encoder connected to the interface means for receiving signals to be transmitted to a wireless communication terminal, a modulator using a fixed pseudo-random correlation code associated with the junctor for spread spectrum modulating the encoded signal and generating an RF modulated signal, means for applying the latter RF modulated signal through a transmit band limiting filter to the leaky transmission line, means for receiving an RF modulated signal from the leaky transmission line through a receive band limiting filter, a central demodulator for demodulating and despreading a received RF modulated signal using a fixed pseudo-random correlation code associated with said junctor for demodulating the latter signal, a PCM decoder for receiving a spread spectrum demodulated signal and applying it to the interface means for application to said junctor.

11. A system as defined in claim 1, 5 or 9 comprising a plurality of similar circuits each comprising an interface means at the central location for connection to an individual junctor of a PABX, for receiving and transmitting communication signals from said junctor and for receiving and transmitting supervisory signals from the PABX relating to a telephone call, a central PCM encoder connected to the interface means for receiving signals to be transmitted to a wireless communication terminal, a modulator using a fixed pseudo-random correlation code associated with the junctor for spread spectrum modulating the encoded signal and generating an RF modulated signal, means for applying the latter RF modulated signal through a transmit band-limiting filter to the leaky transmission line, means for receiving an RF modulated signal from the leaky transmission line through a receive band-limiting filter, a central demodulator for demodulating and despreading a received RF modulated signal using a fixed pseudo-random correlation code associated with said junctor for demodulating the latter signal, a PCM decoder for receiving a spread spectrum demodulated signal and applying it to the interface means for application to said junctor, a plurality of unidirectional repeaters connected serially at spaced locations in the leaky transmission line whereby an input and an output to the line are defined, the output of the transmit filter being connected to the input of the transmission line and the input to the receive filter being connected to the output of the transmission line.

12. A system as defined in claim 1, 5 or 9 comprising a plurality of similar circuits each comprising an interface means at the central location for connection to an individual junctor of a PABX, for receiving and transmitting communication signals from said junctor and for receiving and transmitting supervisory signals from the PABX relating to a telephone call, a central PCM encoder connected to the interface means for receiving signals to be transmitted to a wireless communication terminal, a modulator using a fixed pseudo-random correlation code associated with the junctor for spread spectrum modulating the encoded signal and generating an RF modulated signal, means for applying the latter RF modulated signal through a transmit band limiting filter to the leaky transmission line, means for receiving an RF modulated signal from the leaky transmission line through a receive band limiting filter, a central demodulator for demodulating and despreading a received RF modulated signal using a fixed pseudo-random correlation code associated with said junctor for demodulating the latter signal, a PCM analog decoder for receiving a spread spectrum demodulated signal and applying it to the interface means for application to said junctor, a plurality of unidirectional repeaters connected serially at spaced locations in the leaky transmission line whereby an input and an output to the line are defined, the transmit filter being connected to the input of the transmission line and the receive filter being connected to the output of the transmission line, the frequency of the R.F. modulated signals being between approximately 150 MHz and 1000 MHz.

13. A system as defined in claim 1, 5 or 9 comprising a plurality of similar circuits each comprising an interface means at the central location for connection to an individual junctor of a PABX, for receiving and transmitting communication signals from said junctor and for receiving and transmitting supervisory signals from the PABX relating to a telephone call, a central PCM encoder connected to the interface means for receiving signals to be transmitted to a wireless communication terminal, a modulator using a fixed pseudo-random correlation code associated with the junctor for spread spectrum modulating the encoded signal and generating an RF modulated signal, means for applying the latter RF modulated signal through a transmit band limiting filter to the leaky transmission line, means for receiving an RF modulated signal from the leaky transmission line through a receive band limiting filter, a central demodulator for demodulating and despreading a received RF modulated signal using a fixed pseudo-random correlation code associated with said junctor for demodulating the latter signal, a PCM decoder for receiving a spread spectrum demodulated signal and applying it to the interface means for application to said junctor, the transmission line being coaxial cable having a shield containing gaps sufficient to allow RF energy to radiate therefrom, a plurality of unidirectional repeaters connected serially at spaced locations in the leaky transmission line whereby an input and an output to the line are defined, the output of the transmit filter being connected to the input of the transmission line and the input of the receive filter being connected to the output of the transmission line, the frequency of the R.F. modulated signals being between approximately 150 MHz and 1000 MHz.

14. A system as defined in claim 1 or 5 including a plurality of unidirectional repeaters connected serially at spaced locations in the leaky transmission line.

15. A system as defined in claim 1 or 5 in which the transmission line is comprised of coaxial cable having a shield containing gaps sufficient to allow RF energy to radiate therefrom, and in which a plurality of unidirectional repeaters are connected serially at -spaced locations in the leaky transmission line.

16. A local telephone system comprising:

(a) a central switching system having a plurality of line circuits,

(b) means for converting signals carried by at least certain ones of said line circuits to spread spectrum RF signals, each signal carried by said certain line circuits having a different spreading code,

(c) first means for wireless transmitting said spread spectrum RF signals,

(d) one or a plurality of mobile telephone sets, for receiving, decoding and reproducing said signals carried by the line circuits and for wireless transmitting to said central switching system spread spectrum RF signals originating at said mobile sets, each said latter signal being transmitted using a spreading code different in each mobile set from other mobile sets.

17. A telephone system as defined in claim 16 in which the spread spectrum RF signals transmitted by said first means are in a first frequency band having one centre frequency, and in which the spread spectrum RF signals transmitted by the mobile sets are in a second frequency band having a different centre frequency.

18. A telephone system as defined in claim 16 further including a supervisory channel associated with the central switching system for providing spread spectrum RF signals carrying digital control data receivable by the mobile sets for controlling the transmit and receive spreading and despreading codes of the mobile sets which correspond to the receive and transmit despreading and spreading codes associated with respective ones of said line circuit.

19. A telephone system as defined in claim 16, 17 or 18 in which the means for wireless transmitting and receiving are comprised of antennae.

20. A telephone system as defined in claim 16, 17 or 18 in which the means for transmitting and receiving associated with the mobile sets are comprised of antennae, and the means for transmitting and receiving associated with the central switching system is comprised of one or more leaky cable transmission lines.