Method and apparatus for simultaneous wideband and narrowband wireless communication

• US 5,640,385 A
• Filed: 01/04/1994
• Issued: 06/17/1997
• Est. Priority Date: 01/04/1994
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Elder, Robert C., Long, James F.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US08/177,363
• Time in Patent Office: 1,260 Days
• Field of Search: 370/18, 370/95.1, 370/95.3, 370/110.1, 370/68.1, 370/69.1, 370/73, 370/76, 370/11, 370/19, 370/119, 375/200, 375/205, 455/33.1, 455/33.2, 455/33.3, 379/59, 379/60
• US Class Current: 370/335
• CPC Class Codes: H04B 7/2631 for broadband transmission
• CPC Class Codes: H04B 7/2646 for broadband transmission
• CPC Class Codes: H04J 1/00 Frequency-division multiplex systems H04J14/00 takes precedence
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points

Abstract

A wireless communication system for simultaneously communicating overlapping wideband and narrowband signals. The system includes a transmitting station for embedding one or more narrowband signals (3-5) in a wideband signal (1) having a frequency spectrum encompassing the narrowband signals, and transmitting the resulting composite wideband signal (2). The system also includes a receiving station for receiving a composite wideband signal (60) and separating the embedded narrowband signal(s) (62, 63) from the wideband signal (61). In one embodiment, a cellular radiotelephone base station (35) is operable as both the transmitting and receiving station, communicating with remote subscriber units (29-31) having conventional transceivers (FDMA, TDMA and/or CDMA). The base station transmitter circuitry (10-17) includes FM and CDMA signal generators (10, 12), a combiner (15) for embedding the narrowband signal (3-5) in the wideband signal (1), and an AGC (14) and power detectors (11, 13) for controlling the narrowband signal power. The receiving circuitry includes a CDMA processing circuit having an FFT circuit (41), a threshold detector (42), a notch filter (43), and an inverse FFT circuit (44) for separating narrowband signals (62, 63) from the CDMA signal (61).

Claims

1. A wireless communication unit for sending and receiving communications by both wideband and narrowband signals, comprising:

a transmitter comprising means for generating a first narrowband modulated radio frequency signal and a first wideband modulated radio frequency signal, the first wideband modulated radio frequency signal comprising a spread spectrum signal;

a combiner responsive to the means for generating, for combining the first narrowband modulated radio frequency signal with the first wideband modulated radio frequency signal to form a first composite signal, the first composite signal having a first component derived from the first narrowband modulated radio frequency signal with a first frequency band and a second component derived from the first wideband modulated radio frequency signal with a second frequency band, the second frequency band overlapping the first frequency band, for transmission to at least one other wireless communication unit;

means for controlling signal power responsive to the means for generating, the means for controlling signal power varying signal power of the first narrowband modulated radio frequency signal in dependence on signal power of the first wideband modulated radio frequency signal; and

means for receiving a second composite signal including a second wideband signal and a second narrowband signal,

wherein the means for controlling is operable to maintain the signal power of the first narrowband modulated radio frequency signal at approximately a predetermined ratio relative to the signal power of the first wideband modulated radio frequency signal.

2. The wireless communication unit of claim 1;

wherein the means for controlling comprises;

means for detecting the signal power levels of the first narrowband signal and the first wideband signal;

means for determining the predetermined ratio of the first narrowband signal to the first wideband signal required to maintain at least a predetermined carrier to interference (C/I) level of the narrowband signal for a subscriber receiving the narrowband signal;

means for adjusting the signal power level of the narrowband signal such that the predetermined ratio is maintained.

3. A wireless communication unit for sending and receiving communications by both wideband and narrowband signals, comprising:

a transmitter comprising means for generating a first narrowband modulated radio frequency signal and a first wideband modulated radio frequency signal, the first wideband modulated radio frequency signal comprising a spread spectrum signal;

a combiner responsive to the means for generating, for combining the first narrowband modulated radio frequency signal with the first wideband modulated radio frequency signal to form a first composite signal, the first composite signal having a first component derived from the first narrowband modulated radio frequency signal with a first frequency band and a second component derived from the first wideband modulated radio frequency signal with a second frequency band, the second frequency band overlapping the first frequency band, for transmission to at least one other wireless communication unit;

means for receiving a second composite signal including a second wideband modulated radio frequency signal and a second narrowband modulated radio frequency signal, the means for receiving comprising means for determining the location of the second narrowband modulated radio frequency signal within the second wideband modulated radio frequency signal and means for filtering at least one of the second narrowband modulated radio frequency signal at the determined location and the second wideband modulated radio frequency signal around the determined location of the second narrowband modulated radio frequency signal, wherein the means for determining comprises a transform means for performing a fast Fourier transform (FFT) on the second composite signal to produce frequency domain samples of both the second wideband modulated radio frequency signal and the second narrowband modulated radio frequency signal.

4. The wireless communication unit of claim 3, wherein the transform means is further operable for determining which samples have magnitudes exceeding a first predetermined threshold.

5. The wireless communication unit of claim 4, wherein the means for filtering is operable for filtering those samples determined to have magnitudes exceeding the first predetermined threshold from the those samples having magnitudes less than the first predetermined threshold.

6. The wireless communication unit of claim 5, wherein the means for filtering is further operable for adaptively notch filtering those samples determined to have magnitudes exceeding the first predetermined threshold such that the magnitudes of those samples are reduced approximately to a magnitude equal to the first predetermined threshold.

7. The wireless communication of claim 6, wherein the means for filtering is further operable for dynamically filtering narrowband signals based on their signal energy per bit per noise density (E_b /N₀).

8. The wireless system of claim 3, wherein the means for determining is operable for determining the location of the second narrowband modulated radio frequency signal using predetermined frequency reuse information.

9. A cellular radiotelephone system for communicating wideband and narrowband signals between at least one base station and subscribers, the system comprising:

a base station comprising;

a wideband modulated radio frequency signal generator for generating a first signal having a first frequency band, the first signal comprising a spread spectrum signal;

a narrowband modulated radio frequency signal generator for generating a second signal having a second frequency band, the second frequency band being narrower than the first frequency band;

a combiner combining the first and second signals to form a composite modulated radio frequency signal;

a transmitter transmitting the composite modulated radio frequency signal to a plurality of subscribers;

means for controlling signal power of the second

wherein the means for controlling signal power comprises;

means for detecting signal power of the second signal and signal power of the first signal, and

means for controlling the narrowband modulated radio frequency signal generator for adjusting the signal power of the second signal so as to maintain the signal power of the second signal within a predetermined range of ratios to the signal power of the first signal required to maintain at least a predetermined carrier to interference (C/I) level of the second signal for a subscriber receiving the second signal.

10. The system of claim 9, wherein the means for controlling the narrowband modulated radio frequency signal generator is operable for maintaining the signal power of the second signal at least 1 dB greater than the signal power of the first signal.

11. A cellular radiotelephone system for communicating wideband and narrowband signals between at least one base station and subscribers, the system comprising:

a base station comprising;

a wideband modulated radio frequency signal generator for generating a first signal having a first frequency band, the first signal comprising a spread spectrum signal;

a narrowband modulated radio frequency signal generator for generating a second signal having a second frequency band, the second frequency band being narrower than the first frequency band;

a combiner combining the first and second signals to form a composite modulated radio frequency signal;

a transmitter transmitting the composite modulated radio frequency signal to a plurality of subscribers; and

means for reassigning a subscriber receiving communications via the second signal to receive communications via a narrowband signal having a third frequency band which is outside of the first frequency band.

12. The system of claim 11, wherein the means for reassigning is further operable for handing-off the subscriber to another base station.

13. A system for receiving communications via wideband signals from wideband signal subscribers to a fixed station, and via narrowband signals from narrowband signal subscribers to the fixed station, the system comprising:

a receiver detecting a composite wideband spread spectrum modulated radio frequency signal composed of at least a first one of the narrowband signals having a frequency band, and a first one of the wideband signals from a first one of the wideband signal subscribers, the first one of the wideband signals having a frequency band wider than and overlapping the frequency band of the first narrowband signal; and

separating means including a first filter and a second filter, the separating means connected to the receiver means for separating and recovering the first narrowband signal and the first wideband signal,

wherein the first filter comprises a first digital processor for frequency transforming the composite wideband spread spectrum modulated radio frequency signal, determining a frequency of the first narrowband signal, filtering the transformed composite wideband spread spectrum modulated radio frequency signal at the determined frequency of the first narrowband signal, and inverse transforming the filtered composite wideband spread spectrum modulated radio frequency signal to recover the first wideband signal.

14. The system of claim 13, wherein the first digital processor frequency transforms the composite wideband spread spectrum modulated radio frequency signal by a fast Fourier transform.

15. The system of claim 14, wherein the first digital processor filters the transformed composite wideband spread spectrum modulated radio frequency signal by reducing any frequency component of the transformed composite wideband spread spectrum modulated radio frequency signal having an amplitude above a first predetermined amplitude level to a reduced amplitude which is no more than a second predetermined amplitude level.

16. The system of claim 15, wherein the second predetermined amplitude level is an average amplitude level of any frequency components of the transformed composite wideband spread spectrum modulated radio frequency signal which are less than the first predetermined amplitude level.

17. The system of claim 13, wherein the frequency of the first narrowband signal is determined from an assigned channel frequency for a subscriber sending the first narrowband signal.

18. The system of claim 13, wherein the second filter means comprises a second digital processor means for digitally downmixing and decimation filtering the composite wideband signal to recover the first narrowband signal.

19. A system for receiving communications via wideband signals from wideband signal subscribers to a fixed station, and via narrowband signals from narrowband signal subscribers to the fixed station;

the system comprising;

a receiver detecting a composite wideband spread spectrum modulated radio frequency signal composed of at least a first one of the narrowband signals having a frequency band, and a first one of the wideband signals from a first one of the wideband signal subscribers, the first one of the wideband signals having a frequency band wider than and overlapping the frequency band of the first narrowband signal; and

separating means including a first filter and a second filter, the separating means connected to the receiver means for separating and recovering the first narrowband signal and the first wideband signal;

wherein the second filter comprises a second digital processor for frequency transforming the composite wideband spread spectrum modulated radio frequency signal, determining a frequency of the first narrowband signal, filtering the transformed composite wideband spread spectrum modulated radio frequency signal at the determined frequency of the first narrowband signal, and inverse transforming the filtered composite wideband spread spectrum modulated radio frequency signal to recover the first narrowband signal.

20. The system of claim 19, wherein the second digital processor means is operable for filtering the transformed composite wideband spread spectrum modulated radio frequency signal by digital downmixing the transformed composite wideband spread spectrum modulated radio frequency signal and bandpass filtering the downmixed signal around the determined frequency of the first narrowband signal.

21. The system of claim 20, wherein the frequency of the first narrowband signal is determined from an assigned channel frequency for a subscriber sending the first narrowband signal.

22. A system for receiving communications via wideband signals from wideband signal subscribers to a fixed station, and via narrowband signals from narrowband signal subscribers to the fixed station, the system comprising:

a receiver detecting a composite wideband spread spectrum modulated radio frequency signal composed of at least a first one of the narrowband signals having a frequency band, and a first one of the wideband signals from a first one of the wideband signal subscribers, the first one of the wideband signals having a frequency band wider than and overlapping the frequency band of the first narrowband signal;

separating means connected to the receiver means for separating and recovering the first narrowband signal and the first wideband signal; and

means for reassigning a subscriber transmitting communications via the first narrowband signal to receiving communications via a second narrowband signal having a frequency band which is outside of the frequency band of the first wideband signal.

23. The system of claim 22, wherein the means for reassigning is further operable for handing-off the subscriber to another base station.

24. A cellular radiotelephone system for simultaneously communicating wideband and narrowband signals between at least one base station and subscribers, the system comprising:

a base station transmitter circuitry comprising;

a wideband signal generator operable for generating a first wideband signal characterized by a first frequency band;

a narrowband signal generator operable for generating a first narrowband signal characterized by a second frequency band within the first frequency band;

a combiner coupled to the wideband and narrowband signal generators, being operable for combining the first narrowband and first wideband signals and outputting a first composite wideband signal;

an amplifier and antenna connected to the combiner, being operable for amplifying the first composite wideband signal and transmitting the amplified first composite wideband signal to a plurality of subscribers; and

a base station receiver circuitry comprising;

an RF front end circuitry operable for receiving a second composite wideband signal having at least a second narrowband signal embedded in a second wideband signal;

an analog to digital converter connected to the RF front end circuitry operable for outputting a digitized second composite wideband signal;

a narrowband signal processing circuit connected to the analog to digital converter, and comprising a downmixing and decimation filter operable for recovering the second narrowband signal; and

a wideband signal processing circuit connected to the analog to digital converter, and comprising a transformation circuit connected to the converter operable for transforming the digitized second composite wideband signal into a frequency domain composite signal, a narrowband signal detector connected to the transformation circuit operable for determining the frequency of the second narrowband signal, a filter connected to the narrowband signal detector operable for filtering the frequency domain composite signal at the determined frequency of the second narrowband signal and outputting a frequency domain representation of the second wideband signal, and inverse transformation circuitry connected to the filter operable for inverse transforming the frequency domain representation of the second wideband signal to recover the second wideband signal.

25. A method for wireless communications, comprising:

modulating first information into a narrowband signal for communication with a first remote unit having a narrowband demodulator;

modulating second information into a wideband signal for communication with a second remote unit having a wideband demodulator;

embedding the narrowband signal within the wideband signal to form a composite wideband signal;

transmitting the composite wideband signal to the first and second remote units;

detecting signal power levels of the narrowband signal and the wideband signal;

determining a predetermined ratio of the signal power level of the narrowband signal to the signal power level of the wideband signal required to maintain at least a predetermined carrier to interference (C/I) level of the narrowband signal for a subscriber receiving the narrowband signal; and

adjusting the signal power level of the narrowband signal such that the predetermined ratio is maintained.

26. The method of claim 25, further comprising the steps of:

receiving at the second remote unit the composite wideband signal having said predetermined ratio between the signal power levels of the narrowband and wideband signals;

processing the composite wideband signal to recover the wideband signal; and

demodulating the recovered wideband signal to recover the second information.

27. The method of claim 25, further comprising reassigning the first remote unit to receive communications via a further narrowband signal having a frequency band which is outside of a frequency band of the wideband signal.