Patent Issued for Coherent Initial Acquisition

By a News Reporter-Staff News Editor at Journal of Engineering -- A patent by the inventors Krishnamoorthi, Raghuraman (San Diego, CA); Tian, Tao (San Diego, CA); Ling, Fuyun (San Diego, CA); Huang, Yuheng (San Diego, CA), filed on September 24, 2007, was cleared and issued on December 4, 2012, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8325856 is assigned to QUALCOMM Incorporated (San Diego, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present disclosure relates generally to telecommunications, and more particularly to coherent initial acquisition of a pilot signal.

"Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique, which effectively partitions the overall system bandwidth into a large number of sub-carriers. These sub-carriers are spaced apart at precise frequencies to provide orthogonality. Content may be modulated onto the sub-carriers by adjusting each sub-carrier's phase, amplitude or both. Any suitable conventional modulation scheme may be used, such as phase shift keying (QPSK) or quadrature amplitude modulation (QAM) just to name is used, but other modulation schemes may also be used.

"In OFDM systems, content is generally broadcast in super frames. A super frame generally consists of a number of symbols that are OFDM modulated with (N+K) sub-carriers, wherein the content is modulated onto N sub-carriers and a cyclic prefix is modulated onto K sub-carriers. The first OFDM symbol in the super frame is a pilot signal. This pilot signal is generated with a pseudo-random (PN) number that is repeated multiple times across the OFDM symbol. The time domain periodic structure of the pilot may be exploited to detect the start of the OFDM super frame and correct the initial frequency offset between the transmitter frequency and the local receiver frequency.

"Heretofore, an incoherent acquisition process was used to process the pilot signal to detect the start of the super-frame and correct the initial frequency offset. Incoherent acquisition is a process whereby a delayed version of the received signal is correlated with the received signal itself. The correlator output has a high value during the pilot signal due to its periodicity. This approach, however, lacks the ability to differentiate the signal from tone interference well. In addition, the estimation of the initial frequency offset may be significantly impacted by the presence of tone interference.

"Accordingly, there is a need in the art for improvements in the processes currently used for frame synchronization and initial frequency offset estimation in OFDM systems that are also applicable to other telecommunication systems employing a periodic pilot signal."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "In one aspect of the disclosure, an acquisition module includes a coherent correlator configured to receive a transmission having a pilot signal and correlate the received transmission with a local copy of the pilot signal to produce a first output, a delayed correlator configured to delay the first output and correlate the first output with the delayed first output to produce a second output, and a detector configured to detect the pilot signal in the transmission based on the second output.

"In another aspect of the disclosure, an acquisition module includes means for receiving a transmission having a pilot signal, means for correlating the received transmission with a local copy of the pilot signal to produce a first output, means for delaying the first output, means for correlating the first output with the delayed first output to produce a second output, and means for detecting the pilot signal in the transmission based on the second output.

"In a further aspect of the disclosure a method of telecommunications includes receiving a transmission having a pilot signal, correlating the received transmission with a local copy of the pilot signal to produce a first output, delaying the first output, correlating the first output with the delayed first output to produce a second output, and detecting the pilot signal in the transmission based on the second output.

"In yet a further aspect of the disclosure, a machine-readable medium includes instructions executable by a processing system in a mobile service provider, the instructions comprising code for receiving a transmission having a pilot signal, correlating the received transmission with a local copy of the pilot signal to produce a first output, delaying the first output, correlating the first output with the delayed first output to produce a second output, and detecting the pilot signal in the transmission based on the second output.

"It is understood that other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive."

URL and more information on this patent, see: Krishnamoorthi, Raghuraman; Tian, Tao; Ling, Fuyun; Huang, Yuheng. Coherent Initial Acquisition. U.S. Patent Number 8325856, filed September 24, 2007, and issued December 4, 2012. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=41&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2024&f=G&l=50&co1=AND&d=PTXT&s1=20121204.PD.&OS=ISD/20121204&RS=ISD/20121204

Keywords for this news article include: Telecommunications, QUALCOMM Incorporated.

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