Multiplex communications – Communication techniques for information carried in plural... – Transmission bandwidth conservation
Reexamination Certificate
1999-11-04
2001-05-08
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Transmission bandwidth conservation
C370S529000, C370S535000, C375S262000, C375S267000, C714S790000, C714S795000
Reexamination Certificate
active
06229824
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and apparatus for concatenated convolutional encoding and interleaving of a source data stream for transmission.
BACKGROUND OF THE INVENTION
Radio frequency transmissions are often subjected to multipath fading. Signal blockages at receivers can occur due to physical obstructions between a transmitter and the receiver or service outages. For example, mobile receivers encounter physical obstructions when they pass through tunnels or travel near buildings or trees that impede line of sight (LOS) signal reception. Service outages can occur, on the other hand, when noise or cancellations of multipath signal reflections are sufficiently high with respect to the desired signal.
Communication systems can incorporate two or more transmission channels for transmitting the same program or data to mitigate the undesirable effects of fading or multipath. For example, a time diversity communication system delays the transmission of program material on one transmission channel by a selected time interval with respect to the transmission of the same program material on a second transmission channel. The duration of the time interval is determined by the duration of the service outage to be avoided. The non-delayed channel is delayed at the receiver so that the two channels can be combined, or the program material in the two channels selected, via receiver circuitry. One such time diversity system is a digital broadcast system (DBS) employing two satellite transmission channels.
Interleaving of data symbols on the transmission channels of a time diversity system can be employed to mitigate, in particular, the effects of a slow deep fade. An interleaver rearranges a set of consecutive coded data symbols in a data stream to be transmitted such that symbols in the set extend for a duration of time greater than the duration of a slow deep fade. A receiver having a de-interleaver rearranges received symbols to their original order. The interleaved data symbols that are being de-interleaved, however, are subject to independent fades that may not be mitigated by the interleaver due to size constraints of the interleaver.
In addition, a DBS generally has a requirement for protection against an outage of selected minimum duration when both satellite channels are available. Thus, a need exists for a communication system which provides such outage protection. In addition, a need exists for a communication system which provides maximum outage protection within reasonable memory and delay constraints of the interleaver when only a single satellite channel is available.
SUMMARY OF THE INVENTION
The above-described disadvantages are overcome and a number of advantages are realized with the method and apparatus provided by the present invention for encoding a source data stream via convolutional encoding. Plural encoded data streams are interleaved and transmitted on plural transmission channels. Data groups generated via convolutional encoding are interleaved in accordance with a plurality of time-interleaving functions to disperse selected bits within puncture groups of the data groups, to disperse bits in between data groups, as well as to disperse bits in selected sets of data groups, and thereby facilitate reconstruction of the source data stream from at least a portion of the interleaved data stream received on at least one transmission channel.
In accordance with another aspect of the present invention, two or more transmission channels are employed. The time-interleaving functions are selected to facilitate reconstruction of the source data stream from at least a portion of the interleaved data stream received on at least one of the transmission channels following a continuous blockage of the transmission channels.
In accordance with yet another aspect of the present invention, each of the puncture groups comprises subsets of bits in the data groups. The subsets of bits are selected such that only a minimum number of the subsets are required to reconstruct the source data stream from more than one of the transmission channels.
In accordance with still yet another aspect of the present invention, the subsets of bits are selected such that multiple combinations of the subsets can be received on both of the interleaved transmission channels and allow reconstruction of the source data stream therefrom following blockage of one of the transmission channels.
In accordance with still yet another aspect of the present invention, decoding at the receiver is performed using convolutional decoding. Decoding is preferably performed using a Viterbi decoder.
In accordance with another aspect of the present invention, the time-interleaving functions are selected to optimize error correction during Viterbi decoding.
In accordance with another aspect of the present invention, the encoded signals are interleaved and then demultiplexed for transmission on plural channels.
In accordance with another aspect of the present invention, the encoded signals are demultiplexed and then interleaved prior to transmission.
In accordance with an embodiment of the present invention, a method of interleaving a source data stream for transmission is provided comprising the steps of: (1) encoding a source data stream to generate an output data stream using a convolutional coding scheme having a selected code rate, the output data stream being characterized as a series of data groups, each of the data groups comprising a plurality of punctured data groups, each of the punctured data groups having a reduced code rate with respect to the selected code rate; (2) interleaving the data groups in accordance with a plurality of time-interleaving functions to disperse the bits in the data groups within the output data stream and generate an interleaved data stream; and (3) demultiplexing the interleaved data stream for transmission on separate transmission channels, the time-interleaving functions being selected to disperse different groups of bits in the output data stream selected from the group consisting of bits in one of the punctured data groups, bits in adjacent data groups, and bits in selected sets of data groups to facilitate reconstruction of the source data stream from at least a portion of the interleaved data stream received on at least one of the transmission channels.
The time-interleaving functions are selected in accordance with the present invention to facilitate reconstruction of the source data stream from at least a portion of the interleaved data stream received on at least one of the transmission channels following a continuous blockage of the transmission channels. The punctured data groups each comprise subsets of bits in the data groups. The subsets of bits are selected in accordance with the present invention such that only a minimum number of the subsets are required to reconstruct the source data stream from more than one of the transmission channels. The subsets of bits are also selected such that multiple combinations of the subsets can be received on both of the interleaved transmission channels and allow reconstruction of the source data stream therefrom following blockage of one of the transmission channels.
The interleaved data stream is decoded using the selected code rate in accordance with the present invention. Decoding is preferably performed using convolutional decoding such as via a Viterbi decoder. The time-interleaving functions are selected in accordance with the present invention to optimize error correction during Viterbi decoding.
REFERENCES:
patent: 4429390 (1984-01-01), Sonoda et al.
patent: 4622598 (1986-11-01), Doi et al.
patent: 4881241 (1989-11-01), Pommier et al.
patent: 5191576 (1993-03-01), Pommier et al.
patent: 5197061 (1993-03-01), Halbert-Lassalle et al.
patent: 5228025 (1993-07-01), Le Floch et al.
patent: 5278863 (1994-01-01), Briskman
patent: 5283780 (1994-02-01), Schuchman et al.
patent: 5305353 (1994-04-01), Weerackody
patent: 5319673 (1994-06-01), Briskman
patent: 5485485 (1996-01-01), Briskman et al.
patent: 5592471 (
Kizou Hassan
Pezzlo John
Roylance Abrams Berdo & Goodman
XM Satellite Radio Inc.
LandOfFree
Method and apparatus for concatenated convolutional... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for concatenated convolutional..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for concatenated convolutional... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2520127