Two-dimensional channel bonding in a hybrid CDMA/FDMA fixed wireless access system to provide finely variable rate channels

• US 20020051435A1
• Filed: 04/09/2001
• Published: 05/02/2002
• Est. Priority Date: 10/27/2000
• Status: Active Grant

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Griffin, Dan M., Hall, Eric K., Giallorenzi, Thomas R., Ertel, Richard B., Stephenson, Philip L., Butterfield, Lee A.
• Granted Patent: US 7,190,683 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 7/2621 using frequency division multiple access [FDMA] H04B7/2615 takes precedence
• CPC Class Codes: H04B 7/2634 for channel frequency control

Abstract

A communications system employs the use of both synchronous CDMA and FDMA to provide a variable bandwidth waveform with multiple bonded transmitters and receivers that are agile in both frequency and PN code to permit a variable bandwidth and variable rate multiple access system. In a first aspect the teachings provide the use of both CDMA and FDMA together to enable an improved concentration efficiency by making a larger pool of bandwidth available to each user. In a second aspect these teachings enable channel bonding across both code space and frequency space, thus making the system capable of operating within a variable (not necessarily contiguous) bandwidth and at a finely variable rate.

Claims

1. A method for operating a communication system, comprising steps of:

defining the system as a combined Code Division Multiple Access CDMA and Frequency Division Multiple Access FDMA system; and

using a variable bandwidth waveform with multiple bonded transmitters and receivers that are each agile in both frequency and code to provide a variable bandwidth and variable rate multiple access system.

2. A method as in claim 1, wherein the use of both CDMA and FDMA together provides an improved concentration efficiency by making a larger pool of bandwidth available to each user.

3. A method as in claim 1, wherein channel bonding across both code space and frequency space enables the system to operate in at least one of a variable, contiguous or non-contiguous bandwidth at a finely variable rate.

4. A synchronous Code Division Multiple Access CDMA and Frequency Division Multiple Access FDMA communications system, comprising:

a base site comprising a transmitter for transmitting a waveform and further comprising a plurality of frequency agile and PN code agile data modulators having an output coupled to a radio channel; and

a subscriber unit comprising a receiver for receiving the transmitted waveform from the radio channel and further comprising a plurality of frequency agile and PN code agile data demodulators.

5. A CDMA and FDMA communications system as in claim 4, wherein there are N modulators and N demodulators each operable for communicating at data rates that are power of two multiples of a basic rate on a plurality of frequency subchannels within a channel.

6. A CDMA and FDMA communications system as in claim 5, wherein said N modulators and N demodulators operate with power of two multiples of the basic rate from a minimum rate to a maximum rate at a granularity that is an integer multiple of the basic rate.

7. A CDMA and FDMA communications system as in claim 4, wherein statistical concentration is achieved when the system has Y Mbps of aggregate capacity allocatable to X users simultaneously at rates of Y/X Mbps each, and by tuning said modulators and demodulators to any one of Z frequency subchannels, the useable bandwidth is Z times the Y Mbps bandwidth of any one channel, and Z*X users are supported simultaneously at rates of Y/X Mbps.

8. A CDMA and FDMA communications system as in claim 4, wherein a bandwidth of any one subchannel is X MHz, and at least some of said plurality of modulators and demodulators are tuned to different ones of contiguous or non-contiguous X MHz sub-channels within a Y MHz channel, where Y>

X.

9. A CDMA and FDMA communications system as in claim 8, wherein X=3.5 and where Y=14.

10. A CDMA and FDMA communications system as in claim 4, wherein input data to said plurality of modulators is a punctured convolutional code.

11. A CDMA and FDMA communications system as in claim 4, wherein input data to said plurality of modulators is a rate ½

, constraint length 7 code that is punctured to increase the rate.

12. A CDMA and FDMA communications system as in claim 11, wherein the puncturing rate is made adaptive to mitigate fading conditions.

13. A CDMA and FDMA communications system as in claim 11, wherein said output of said modulators is coupled to said radio channel through an end-to-end raised-cosine Nyquist pulse shape filter.