Wideband wireless base station making use of time division multiple access bus having selectable number of time slots and frame synchronization to support different modulation standards

• US 5,940,384 A
• Filed: 10/28/1996
• Issued: 08/17/1999
• Est. Priority Date: 03/13/1995
• Status: Expired due to Fees

• Current Assignee: Treble Investments LLC (Intellectual Ventures LLC)
• Original Assignee: AirNet Communications Corporation (Tecore Incorporated)
• Inventors: Williams, Terry L., Schmutz, Thomas R., Carney, Ronald R.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/740,153
• Time in Patent Office: 1,023 Days
• Field of Search: 370/320, 370/328, 370/335, 370/342, 370/347, 370/362, 370/484, 455/422
• US Class Current: 370/347
• CPC Class Codes: H04B 7/2646 for broadband transmission
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A wireless communication system basestation making use of a wideband, multichannel digital transceiver having incorporated therein a time division multiple-access (TDM) bus for providing digital samples of a plurality of wireless communication channels, wherein the time slot duration and frame rate of the TDM bus may be reconfigured. The invention allows various air interface standards, even those having different channel bandwidths, to be serviced by the same basestation, without having to install additional or different equipment, and by automatically redistributing signal processing resources, eliminating the need to reconfigure the basestation when different types of wireless signaling must be accommodated.

Claims

1. A basestation for processing signals in a multiple mobile subscriber unit wireless communication system comprising:

means for converting signals, in the form of a composite radio frequency, RF, signal sent from a plurality of the mobile units, into a first set of multiple digital channel signal outputs, each said digital channel signal output corresponding to one of the signals received from one of the plurality of mobile units;

means for selecting a modulation scheme supported by the basestation at a specific time;

a plurality of digital signal processing means, for providing digitally processed channel signal outputs according to said selected modulation scheme being supported by the basestation at a specific time;

time division multiplex switching means, disposed between the means for converting signals and the plurality of digital signal processing means, the switching means for interconnecting any one of the multiple digital channel signal outputs to any one of the plurality of digital signal processing means; and

time division multiplex synchronization timing means, coupled to control the time division multiplex means, to adjust and change a frame rate and a number of time slots per frame, depending upon a bandwidth of the selected modulation scheme being supported by the basestation.

2. The basestation according to claim 1, wherein the means for converting signals further includes:

wideband digital tuner means, for downconverting a selected bandwidth of the composite radio frequency, RF, signal to an intermediate frequency, IF, signal, and for performing an analog to digital conversion on the IF signal, to provide a wideband digital tuner output signal; and

digital channelization means, coupled to receive the wideband tuner output signal, for providing the first set of multiple digital channel signal outputs, the digital channelization means being adjustable such that each digital channel signal output to the time division multiplex switching means has a predetermined channel bandwidth, such that each digital channel signal output is output during a corresponding time slot associated with that digital signal channel output onto the time division multiplex switching means.

3. The basestation according to claim 2, wherein the digital channelization means is controlled by outputs from the time division multiplex synchronization timing means, at least one output identifying time slots occurring on the time division multiplex switching means such that there is one time slot per digital channel signal output, and at least one other output indicating when a new frame starts on the time division multiplex switching means.

4. The basestation of claim 1 wherein the signals received from the mobile units contain modulation, and the digital signal processor means include demodulators to remove the modulation.

5. The basestation of claim 1 additionally comprising signal-transport encoding means, connected to the output of the digital signal processing means, for encoding the digitally processed channel signal outputs for further transmission to a mobile telephone switching office, MTSO.

6. The basestation of claim 5 wherein the signal-transport encoding means is a T1 encoder.

7. The basestation of claim 2 additionally comprising:

second digital channelization means, being connected to receive the wideband tuner output signal, and providing a second set of multiple digital channel signal outputs, each one of the second set of the digital channel signal outputs having a predetermined channel bandwidth which is different from the predetermined channel bandwidth of said first set of digital channel signal outputs, and each one of the second set of multiple digital channel signal outputs corresponding to one of the signals received from one of the mobile units.

8. The basestation of claim 2 additionally comprising:

second wideband digital tuner means, for downconverting a second selected bandwidth of the composite radio frequency RF signal to a second intermediate frequency, IF, signal, and for performing an analog to digital conversion on the second IF signal, to provide a second wideband digital tuner output signal; and

second digital channelization means, coupled to receive the second wideband digital tuner output signal, and providing a second set of multiple digital channel signal outputs, each one of the second set of the digital channel signal outputs having a predetermined channel bandwidth which is different from the predetermined channel bandwidth of said above mentioned first set of digital channel signal outputs, and each one of the second set of digital channel signals corresponding to one of the signals received from one of the mobile units.

9. A basestation as in claim 1 wherein the first and second set of digital channel signal outputs are modulated in accordance with first and second air interface standards, respectively.

10. A basestation as in claim 9 wherein the digital signal processors include a first set of digital signal processor means for demodulating said first set of digital channel signal outputs, and a second set of digital signal processors for demodulating said second set of digital channel signal outputs.

11. A basestation as in claim 9 wherein said first and second air interface standards are each a different one of a time division multiplex, TDMA, code division multiplex, CDMA, Advanced Mobile Phone System, AMPS, Personal Communications System , PCS, or Groupe Especiale Mobile, GSM.

12. A basestation as in claim 1 additionally comprising:

basestation controller means, connected to the time division multiplex switching means and the digital signal processing means, for maintaining a list of unused digital signal processing means that are not presently interconnected through the time division multiplex switching means to one of the digital channel signal outputs, and for dynamically allocating digital signal processing means from the list of unused digital signal processing means to be interconnected to one of the digital channel signal outputs only when the digital channel output contains an active signal being transmitted by the mobile unit which has not yet been assigned to one of the digital signal processing means.

13. A basestation as in claim 1 wherein the time division multiplex switching means further comprises:

a time division multiplex, TDM, data bus including data lines;

basestation controller means, connected to the TDM bus, and to generate TDM bus synchronization signals and driver address signals, the TDM bus synchronization signals used to identify access timeslots on the TDM bus; and

TDM bus driver means, connected to the TDM bus, the basestation controller means, and at least one of the digital channel output signals, for receiving the TDM bus synchronization signals and the driver address signals, for storing the driver address signals, and for asserting the at least one digital channel output signal on the TDM bus when the value of driver address signals corresponds to the value of the bus synchronization signals, thereby indicating that a timeslot associated with the at least one digital channel output signal is currently active.

14. A basestation as in claim 13 wherein the basestation controller means, connected to the TDM bus, additionally generates receiver address signals, and the time division multiplex switching means additionally includes:

TDM bus receiver means, connected to the TDM bus, the basestation controller means, and at least one of the digital signal processor means, for receiving the TDM bus synchronization signals and the receiver address signals, for storing the receiver address signals, and for reading a signal asserted on the TDM bus and providing such asserted signal to the digital signal processor means when the value of receiver address signals corresponds to the value of the bus synchronization signals, indicating that a timeslot associated with the digital signal processor is currently active.

15. A basestation as in claim 8 wherein the first and second channelizers each comprise:

a convolutional digital filter, connected to receive the respective one of the digitized wideband signals; and

a fast Fourier transform, FFT, processor, connected to receive the output of the convolutional digital filter, and to provide the digital channel signal outputs.

16. A basestation as in claim 1, further comprising:

a second plurality of digital signal processing means, connected to receive digital input signals from a communication signal source;

a wideband digital combiner, being connected to receive a second plurality of digital channel signals, and to provide a composite digital signal for transmission;

wherein the time division multiplex switching means is also disposed between the second plurality of digital signal processors and the wideband digital combiner, the switching means connecting any one of the second set of digital signal processors to any one of the digital channel signals input to the combiner;

a wideband digital exciter, connected to receive the composite digital signal and to provide a combined RF signal; and

a transmit antenna, connected to receive the combined RF signal and the radiate the combined RF signal.

17. A basestation as in claim 16, additionally comprising:

basestation controller means, connected to the time division multiplex switching means and the first and second plurality of digital signal processing means, for maintaining a list of all unused digital signal processing means that are not presently interconnected through the time division multiplex switching means to one of the digital channel signal outputs, and for dynamically allocating digital signal processing means from the list of unused digital signal processing means to function as one of the first or second digital signal processing means only when the digital channel signal output contains an active signal being transmitted by the mobile unit which has not yet been assigned to one of the digital signal processing means, or when the digital input signals from the communications source are active.

18. A basestation for processing signals in a multiple mobile subscriber unit wireless communication system, comprising:

means for selecting a modulation scheme supported by the basestation at a specific time;

digital channelization means, connected to receive a composite signal containing signals received from a plurality of mobile subscriber units, for filtering the composite signal to generate a plurality of digital channel signal outputs in response thereto, the digital channelization means having a selectable channel bandwidth for each such digital channel signal output depending upon an air interface standard being supported by the basestation;

a plurality of digital signal processing means, for providing digitally processed channel signal outputs according to said selected modulation scheme being supported by the basestation at said specific time;

time division multiplex switching and synchronization means, disposed between the digital channelization means and the plurality of digital signal processing means and interconnecting any one of the plurality of digital channel signal outputs to any one of the plurality of digital signal processing means;

wherein the digital channelization means and the time division multiplex switching and synchronization means are coupled such that each is driven by common parameters including a frame rate and a number of time slots per frame, the common parameters determining which digital channel signal is interconnected between the digital channelization means and a digital signal processing means at any one moment in time, and said parameters being determined by the air interface standard being supported by the basestation.

19. The basestation according to claim 18, wherein:

the time division multiplex switching and synchronization means includes;

a time division multiplex synchronization means; and

a time division multiplex switching means; and

wherein the common parameters are produced by a time division multiplex synchronization means and synchronize the digital channelization means and the time division multiplex switching means such that the digital signal channel outputs are multiplexed onto the time division multiplex switching means at a predetermined rate, depending upon the bandwidth of channels allocated in the modulation scheme being supported; and

wherein the common parameters may be changed to allow the basestation to implement reception and transmission of a varying number of signals having varying bandwidth requirements, depending upon different air interface standards being supported by the basestation.

20. The basestation according to claim 19, wherein the common parameters may be adjusted to reconfigure the basestation to support at least two different air interface standards.

21. The basestation according to claim 20, wherein said at least two different air interface standards include at least one selected from the group comprising the IS-54B TDMA standard, the IS-95 CDMA standard, an Advanced Mobile Phone System, AMPS, standard, a Personal Communications System, PCS, standard, and a Groupe Especiale Mobile, GSM, standard.