Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Reexamination Certificate
2000-08-01
2002-07-23
Ghebretinsae, Temesghen (Department: 2631)
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
C375S298000, C375S364000, C370S510000
Reexamination Certificate
active
06424678
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to multi-carrier communication systems, including but not limited to radio frequency (RF) communication systems. More particularly, this relates to a scalable pattern methodology for multi-carrier communication systems.
BACKGROUND OF THE INVENTION
Multi-carrier communication systems are well known in the art. Pursuant to many such systems, an information-bearing signal, such as serial digitized voice or digital data is subdivided into a plurality of bit streams, each of which is encoded into symbols (e.g., 16QAM symbols) to form a corresponding plurality of symbol streams. Synchronization and pilot symbols are inserted into each of the plurality of symbol streams, yielding a plurality of composite symbol streams. The composite symbol streams are used to modulate separate carrier signals, yielding a corresponding plurality of sub-channels each occupying a discrete frequency band and carrying a portion of the information in the original information-bearing signal. The plurality of sub-channels are combined into a composite signal that is transmitted over an RF channel from a first location to a second location. At the second location, a receiver performs generally the inverse operations, demodulating and detecting each sub-channel separately. Pilot interpolation is performed to determine the carrier's phase and to estimate the effects of channel impairments, such as fading, multi-path effects, etc., and errors are corrected to overcome the effect of the channel impairments and reconstruct the original information signal.
Generally, the amount of information that may be carried by any communication system is a function of the available bandwidth. One of the advantageous aspects of multi-carrier communication systems is that different channel types (e.g., having larger bandwidths) may be accommodated by increasing the number of sub-channels, to the extent that the bandwidth of the total number of sub-channels do not exceed the available bandwidth. Heretofore, however, the sequences of synchronization and pilot symbols inserted among the data symbols for particular numbers of sub-channels, corresponding to particular bandwidths were uniquely defined without regard to scalability. Consequently, unique pilot interpolation techniques were required for different receivers adapted to detect information in the different numbers of sub-channels, corresponding to the different bandwidths. Generally, the greater the number of sub-channels and the greater the corresponding bandwidth, the greater computational complexity was required in the receiver. A multi-carrier communication system that simplifies the complexity of the receiver would be an improvement over the prior art.
Accordingly, there is a need for a method of defining patterns of synchronization, pilot and data symbols usable in a multi-carrier communication system that scales readily between different numbers of sub-channels and different corresponding bandwidths. Advantageously, the pattern methodology should define a pattern of synchronization, pilot and data symbols for a first number of sub-channels that is scalable to multiple numbers of sub-channels and allows for using similar pilot interpolation techniques for any of the scaled versions. The present invention is directed to satisfying or at least partially satisfying these needs.
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Crochiere and Rabiner, “Multirate Digital Signal Processing.,” 1983, pp. 297-324.
Doberstein Kevin G.
Hiben Bradley M.
Ghebretinsae Temesghen
Motorola Inc.
Santema Steven R.
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