Common digitizing rate for multiple air interfaces for generic cell sites in cellular radio

• US 6,282,184 B1
• Filed: 12/22/1997
• Issued: 08/28/2001
• Est. Priority Date: 12/22/1997
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Lehman, Brian James, Morris, Bradley John, Monette, Gilles, Geddes, Blaine
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Duong, Frank
• Application Number:
  US08/996,133
• Time in Patent Office: 1,345 Days
• Field of Search: 370/278, 370/282, 370/290, 370/315, 370/320, 370/321, 370/342, 370/347, 370/441, 370/442, 370/501, 375/146, 375/147, 375/211, 375/219, 375/295, 375/316, 375/345, 455/422, 455/426, 455/522, 455/523
• US Class Current: 370/342
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points

Abstract

A basestation transceiver simultaneously addressing multiple air interface standards with cost-effective and efficient allocation of the resources available at the transceiver. The invention significantly reduces the redundancy of the radio frequency equipment used in the transceiver by the use of a common digitizing rate selected to simultaneously accomodate all of the air interface protocols serviced.

Claims

1. A receive section for a multichannel wireless communication system for processing a composite RF (radio frequency) signal containing RF signals each having an RF bandwidth associated with a respective air interface standard, the receive section comprising:

a first antenna for receiving the composite RF signal;

a wideband receiver connected to the first antenna for down-converting the composite RF signal to produce a down-converted signal;

an A-D (analog-to-digital) converter connected to the wideband receiver for performing an analog-to-digital conversion on the down-converted signal to produce a first composite digital signal at a common digitizing rate;

for each particular air interface standard;

a) an associated RX (receive) channelizer bank connected to receive the first composite digital signal from the A-D converter for adjusting the first composite digital signal data rate to a corresponding standard DSP (digital signal processing) data rate specified by the associated air interface standard to produce a respective adjusted composite digital signal and for extracting from the respective adjusted composite digital signal a respective set of channelized digital signals; and

b) a first set of DSP units connected to the RX channelizer bank for digitally processing and demodulating the corresponding set of channelized digital signals to produce a first set of digital channel signals each having an associated channel bandwidth corresponding to the particular air interface standard;

wherein the wideband receiver comprises an AGC (automatic gain control) circuit comprising;

a controller connected to the D-A converter to compare the D-A converter output to a predetermined reference level for providing a receiver gain setting; and

an actuator for applying the receiver gain setting, the actuator having an input port for receiving the down-converted signal, a control port for receiving the gain control setting and an output port for providing a gain controlled down-converted signal to the A-D converter.

2. The receive section of claim 1 wherein for adjusting the first composite digital signal data rate, each RX channelizer bank comprises a plurality of rate adjustment components selected from the group of decimators, rational rate converters and interpolators connected to adjust the rate from the common digitizing rate to the corresponding standard DSP data rate.

3. The receive section of claim 2 in combination with a transmit section forming a transceiver, the transmit section processing multiple second sets of digital channel signals, each second set of digital channel signals being associated with a respective air interface standard, the transmit section comprises:

for each particular air interface standard;

a) a second set of DSP units each connected to receive the corresponding second set of digital channel signals for producing a respective set of digitally processed and modulated digital channel signals;

b) an associated TX (transmit) channelizer bank connected to receive the corresponding set of digitally processed and modulated digital channel signals, the TX channelizer banks being respectively operative to adjust the data rate of each digitally processed and modulated digital channel signal to the common digitizing rate for collectively producing a second composite digital signal at the common digitizing rate which is representative of the digitally processed and modulated digital channel signals;

a D-A (digital-to-analog) converter connected to receive the second composite digital signal for performing a digital-to-analog conversion on the second composite digital signal at the common digitizing rate to produce a composite analog signal;

a wideband transmitter connected to the D-A converter for up-converting the composite analog signal to produce an up-converted signal; and

a second antenna for transmitting the up-converted signal.

4. The receive section of claim 3 wherein for adjusting the data rate of each digitally processed and modulated channel signal to the common digitizing rate, each TX channelizer bank comprises a plurality of rate adjustment components connected to adjust the rate from the corresponding standard DSP data rate to the common digitizing rate, the rate adjustment components being selected from the group of decimators, rational rate converters and interpolators.

5. The receive section of claim 4 wherein each TX channelizer bank further comprises a plurality of cascaded channel adders to combine in cascade the digitally processed and modulated digital channel signals respectively operating at the common digitizing rate for producing the second composite digital signal at the common digitizing rate.

6. The receive section of claim 5 wherein each TX channelizer bank further comprises a plurality of variable delays to synchronously combine in cascade the digitally processed and modulated digital channel signals for producing the second composite digital signal at the common digitizing rate.

7. The receive section of claim 6 wherein the second sets of digital channel signals processed by the multichannel communication system are received from respective ones of a plurality of multichannel networks, each multichannel network being respectively associated with a different air interface standard.

8. A transmit section for a multichannel wireless communication system for processing multiple sets of digital channel signals, each set of digital channel signals being associated with a respective air interface standard, the transmit section comprising:

for each particular air interface standard;

a) a set of DSP units each connected to receive the corresponding set of digital channel signals for providing a respective set of digitally processed and modulated channel signals;

b) an associated TX (transmit) channelizer bank connected to receive the corresponding set of digitally processed and modulated channel signals, the TX channelizer banks being respectively operative to adjust the data rate of each digitally processed and modulated channel signal received to the common digitizing rate for collectively producing a composite digital signal at the common digitizing rate which is representative of the digitally processed and modulated channel signals;

a D-A (digital-to-analog) converter connected to receive the composite digital signal for performing a digital-to-analog conversion on the composite digital signal at the common digitizing rate to produce a composite analog signal;

a wideband transmitter connected to the D-A converter for up-converting the composite analog signal to produce an up-converted signal; and

an antenna for transmitting the up-converted signal;

wherein for adjusting the data rate of each digitally processed and modulated channel signal to the common digitizing rate, each TX channelizer bank comprises a plurality of rate adjustment components connected to adjust the rate from the corresponding standard DSP data rate to the common digitizing rate, the rate adjustment components being selected from the group of decimators, rational rate converters and interpolators.

9. The transmit section of claim 8 wherein each TX channelizer bank further comprises a plurality of cascaded channel adders to combine in cascade the digitally processed and modulated channel signals respectively operating at the common digitizing rate for producing the composite digital signal at the common digitizing rate.

10. The receive section of claim 9 wherein each TX channelizer bank further comprises a plurality of variable delays to synchronously combine in cascade the digitally processed and modulated digital channel signals for producing the second composite digital signal at the common digitizing rate.

11. A method for a receive section in a multichannel wireless communication system to process a composite RF signal containing a plurality of RF signals each associated with a corresponding air interface standard, the method comprising the steps of:

receiving a band of radio frequencies containing the content of the composite RF signal;

down-converting the composite RF signal to produce a down-converted signal;

performing an analog-to-digital conversion on the down-converted signal to produce a composite digital signal at a common digitizing rate; and

for each air interface standard, adjusting the sample rate of the composite digital signal to a respective standard DSP data rate and extracting a set of digital channel signals from the adjusted composite digital signal;

wherein the common digitizing rate is selected as follows;

determining the lowest acceptable common digitizing rate based on the Nyquist theorem;

factoring each standard DSP data rate;

selecting the prime factors of the standard DSP data rate requiring the most processing;

for compliance with the Nyquist theorem, selecting further prime factors, if necessary, from the other standard DSP data rates; and

combining the selected prime factors to produce the common digitizing rate.

12. A method for a transmit section in a multichannel wireless communication system to process multiple sets of digital channel signals each associated with a corresponding air interface standard, the method comprising the steps of:

for each set of digital channel signals, adjusting the sample rate of each digital channel signal to a common digitizing rate;

combining the digital channel signals in cascade to produce a composite digital signal at the common digitizing rate;

performing a digital-to-analog conversion at a common digitizing rate on the composite signal to produce a composite analog signal;

up-converting the composite analog signal to produce an up-converted signal; and

transmitting the content of the up-converted signal;

wherein the common digitizing rate is selected as follows;

determining the lowest acceptable common digitizing rate based on the Nyquist theorem;

factoring each standard DSP data rate;

selecting the prime factors of the standard DSP data rate requiring the most processing;

for compliance with the Nyquist theorem, selecting further prime factors, if necessary, from the other standard DSP data rates; and

combining the selected prime factors to produce the common digitizing rate.