(i9) United States
(12) Patent Application Publication oo) Pub. No.: US 2006/0203932 Al
Palanki et al. (43) Pub. Date: Sep. 14,2006
(54) PILOT TRANSMISSION AND CHANNEL
ESTIMATION FOR A COMMUNICATION
SYSTEM UTILIZING FREQUENCY
(76) Inventors: Ravi Palanki, San Diego, CA (US);
Aamod Khandekar, San Diego, CA
5775 MOREHOUSE DR.
SAN DIEGO, CA 92121 (US)
A transmitter generates a pilot having a constant timedomain envelope and a flat frequency spectrum based on a polyphase sequence. To generate a pilot IFDMA symbol, a first sequence of pilot symbols is formed based on the polyphase sequence and replicated multiple times to obtain a second sequence of pilot symbols. A phase ramp is applied to the second pilot symbol sequence to obtain a third sequence of output symbols. A cyclic prefix is appended to the third sequence of output symbols to obtain an IFDMA symbol, which is transmitted in the time domain via a communication channel. The pilot symbols may be multiplexed with data symbols using TDM and/or CDM. A pilot LFDMA symbol may also be generated with a polyphase sequence and multiplexed using TDM or CDM. A receiver derives a channel estimate based on received pilot symbols and using minimum mean-square error, least-squares, or some other channel estimation technique.