Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-04-26
2001-07-31
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S342000, C375S130000, C375S150000
Reexamination Certificate
active
06269089
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to encoding/decoding of communication signals and in particular to sequences of code application to communication signals. It is particularly concerned with CDMA encoding and decoding of communication signals.
BACKGROUND OF THE INVENTION
Encoding signals in communication systems often requires the application of many codes in which a plurality of codes are applied to a signal as a sequence of overlays to accomplish several objectives in conditioning the signals to meet diverse signal transmission and switching objectives. Some encoding examples may include spreading and overspreading applied to create a CDMA signal optimized for transmission channels. Other code processes include error correction, signal correlations or de-correlations, etc.
These multiplicity of code applications must frequently be handled by a plurality of processing stations located between an originating and a terminating station. Normally the signal must be decoded and recoded at each processing station. This represents a considerable processing effort at each such station which leads to overall signal transmission inefficiencies.
In other transmission processes (i.e. CDMA), the signals may be spread or despread in several stages of successive processing stations. These processes may or may not alter the overall spreading rate dependent on the spreading processes. Spreading applications having successive layers of spreading are performed sequentially and if the original signal is to be recovered in an intermediate processing station the despreading for recovery is in reverse sequence and subsequent respreading is performed in the exact same sequence as the original spreading operation at the transmitter. Again the processing required may be instituted even though the recovery of the original signal is not needed and significantly reduce transmission efficiencies.
SUMMARY OF THE INVENTION
In accord with the invention, encoded signals, originating from transmitting stations, may be processed in intermediate stations and at receiving stations in an order different from the order of the original encoding process in order to facilitate switching, multiplexing, demultiplexing, signal regeneration, etc. In particular, the recovery of CDMA encoded signals does not require application of spreading/despreading codes in accordance with the reverse order of the original encoding order scheme or sequence of application of spreading codes. This is true for various classes of spreading in all direct sequence methods in instances using codes in which correlation despreading is employed. Moreover with like classes of code for other applications such as frequency hopping, time hopping, etc. may also be permuted.
In the illustrative embodiment, code applications may be permuted without losing the original signal which has been encoded. In such applications, not all of the encoding spreading functions result in an increased spreading rate. In theory, the permuting of code applications is predicated on the allowability of permuting the order of interated Lebesgue integrable functions while retaining the original values.
In a particular illustrative example, a particular sequence of application of despreading codes of a received signal is permuted from that of the original application of spreading codes at signal transmission. A plurality of signal processors may assume varied sequences while retaining the original signal values.
REFERENCES:
patent: 5224122 (1993-06-01), Bruckert
patent: 5325394 (1994-06-01), Buckert
patent: 5608722 (1997-03-01), Miller
patent: 5691974 (1997-11-01), Zehavi et al.
patent: 5790591 (1998-08-01), Gold et al.
Giardina Charles R.
Rudrapatna Ashok N.
AT&T Corp.
Hsu Alpus H.
Kenyon & Kenyon
Qureshi Afsar
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