Title :
SIR Analysis and Interference Cancellation in Uplink OFDMA with Large Carrier Frequency and Timing Offsets
Author :
Raghunath, K. ; Chockalingam, A.
Author_Institution :
Dept. of ECE, Indian Inst. of Sci., Bangalore
Abstract :
In uplink OFDMA, carrier frequency offsets (CFO) and/or timing offsets (TO) of other users with respect to a desired user can cause multiuser interference (MUI). In practical uplink OFDMA systems (e.g., IEEE 802.16e standard), effect of this MUI is made acceptably small by requiring that frequency/timing alignment be achieved at the receiver with high precision (e.g., CFO must be within 1 % of the subcarrier spacing and TO must be within l/8th of the cyclic prefix duration in IEEE 802.16e), which is realized using complex closed-loop frequency/timing correction between the transmitter and the receiver. An alternate open-loop approach to handle the MUI induced by large CFOs and TOs is to employ interference cancellation techniques at the receiver. In this paper, we first analytically characterize the degradation in the average output signal-to-interference ratio (SIR) due to the combined effect of large CFOs and TOs in uplink OFDMA. We then propose a parallel interference canceller (PIC) for the mitigation of interference due to CFOs and TOs in this system. We show that the proposed PIC effectively mitigates the performance loss due to CFO/TO induced interference in uplink OFDMA.
Keywords :
OFDM modulation; interference suppression; multi-access systems; radiofrequency interference; SIR analysis; carrier frequency offset; closed-loop frequency/timing correction; frequency/timing alignment; interference cancellation; multiuser interference; parallel interference canceller; timing offset; uplink OFDMA; Base stations; Communications Society; Degradation; Interference cancellation; OFDM; Performance loss; Signal analysis; Throughput; Timing; Transmitters;
Conference_Titel :
Wireless Communications and Networking Conference, 2007.WCNC 2007. IEEE
Conference_Location :
Kowloon
Print_ISBN :
1-4244-0658-7
Electronic_ISBN :
1525-3511
DOI :
10.1109/WCNC.2007.189