公开(公告)号：EP1461924A2

公开(公告)日：2004-09-29

申请号：EP02784678.1

申请日：2002-11-27

申请人： Qualcomm, Incorporated

发明人： GUPTA, Alok

IPC分类号： H04L27/14

CPC分类号： H04L1/0066 ,  H04L1/0054 ,  H04L25/03343 ,  H04L25/067 ,  H04L25/4975 ,  H04L27/2647 ,  H04L2025/03414

摘要： An apparatus and method for recovering data transmitted in a wireless communication system is claim. A plurality of signal points, the signal point comprising a plurality of modulation symbols from a plurality of coded bits, is received (604). A first subset of signal points for which a bit is equal to a first value and a second subset of signal points for which the bit is equal to a second value is determined (608). The first and second subset are signal points from an expanded signal constelation. The probability of that the bit is equal to the first value or the second value is determined as a function of the received signal point (612). A soft decision symbol may then be determined, based on the probability that the bit is equal to the first value or the second value. The soft decision symbols may be represented as log likelihood ratios (616).

公开(公告)号：EP1854212A1

公开(公告)日：2007-11-14

申请号：EP06736722.7

申请日：2006-03-01

申请人： QUALCOMM INCORPORATED

发明人： CHUNG, Seong Taek ,  GUPTA, Alok ,  LING, Fuyun ,  MURTHY, Vinay

IPC分类号： H03J7/04

CPC分类号： H03J7/04 ,  H03J1/0083

摘要： Techniques for performing frequency control using dual-loop automatic frequency control (AFC) are described. The dual-loop AFC includes an inner loop that corrects short-term frequency variations (e.g., due to Doppler effect) and an outer loop that corrects long-term frequency variations (e.g., due to component tolerances and temperature variations). In one design, a first inner loop is implemented for frequency control of a first system (e.g., a broadcast system), a second inner loop is implemented for frequency control of a second system (e.g., a cellular system), and at least one outer loop is implemented for adjusting a reference frequency used to receive the first and second systems. Each inner loop estimates and corrects the frequency error in an input signal for the associated system and may be enabled when receiving the system. The reference frequency may be used for frequency downconversion, sampling and/or other purposes.

公开(公告)号：EP1661274A2

公开(公告)日：2006-05-31

申请号：EP04782967.6

申请日：2004-09-01

申请人： Qualcomm, Incorporated

发明人： LING, Fuyun ,  GUPTA, Alok ,  KRISHNAMOORTHI, Raghuraman ,  MURALI, Ramaswamy ,  VIJAYAN, Rajiv ,  VRCELJ, Bojan

IPC分类号： H04J1/00

CPC分类号： H04L27/2657 ,  H04L5/005 ,  H04L25/022 ,  H04L27/2613 ,  H04L27/2662 ,  H04L27/2665 ,  H04L2027/003

摘要： In an OFDM system, a transmitter (120) broadcasts a first TDM pilot on a first set of subbands followed by a second TDM pilot on a second set of subbands in each frame. The subbands in each set are selected from among N total subbands such that (1) an OFDM symbol for the first TDM pilot contains at least Sl identical pilot-1 sequences of length Ll and (2) an OFDM symbol for the second TDM pilot contains at least S2 identical pilot-2 sequences of length L2, where L2 > Ll, Sl x Ll = N, and S2 x L2 = N. The transmitter (120) may also broadcast an FDM pilot. A receiver ( 170) processes the first TDM pilot to obtain frame timing (e.g., by performing correlation between different pilot-1 sequences) and further processes the second TDM pilot to obtain symbol timing (e.g., by detecting for the start of a channel impulse response estimate derived from teh second TDM pilot).

公开(公告)号：EP1535404A1

公开(公告)日：2005-06-01

申请号：EP03752014.5

申请日：2003-09-04

申请人： QUALCOMM Incorporated

发明人： GUPTA, Alok ,  VIJAYAN, Rajiv

IPC分类号： H04B1/69 ,  H04B1/76 ,  H04B7/10

CPC分类号： H04L25/0236

摘要： An improved channel estimation is disclosed. In one embodiment, initial channel estimation is performed using known training data sequence. The data packet received is demodulated based on the initial channel estimates, de-interleaved and decoded. The decoded data is then is re-encoded, interleaved and modulated to generate additional training symbols for updating the channel estimates throughout the received data packet.

公开(公告)号：EP1869767A2

公开(公告)日：2007-12-26

申请号：EP06738527.8

申请日：2006-03-13

申请人： Qualcomm Incorporated

发明人： MURTHY, Vinay ,  GUPTA, Alok ,  CHUNG, Seong Taek ,  LING, Fuyun

IPC分类号： H03J7/04

CPC分类号： G06F1/0353 ,  H04L5/0007 ,  H04L5/0048 ,  H04L27/2659 ,  H04L27/266 ,  H04L27/2662 ,  H04L27/2675 ,  H04L27/2678

摘要： Techniques for performing frequency control in an OFDM system are described. In one aspect, frequency acquisition is performed based on a received pilot, and frequency tracking is performed based on received OFDM symbols. For frequency acquisition, an initial frequency error estimate may be derived based on the received pilot, and an automatic frequency control (AFC) loop may be initialized with the initial frequency error estimate. For frequency tracking, a frequency error estimate may be derived for each received OFDM symbol, and the AFC loop may be updated with the frequency error estimate. Frequency error in input samples is corrected by the AFC loop with the initial frequency error estimate as well as the frequency error estimate for each received OFDM symbol. In another aspect, a variable number of samples of a received OFDM symbol are selected, e.g., based on the received OFDM symbol timing, for use for frequency error estimation.