DocumentCode :
41023
Title :
A Cost-Effective Preamble-Assisted Engine With Skew Calibrator for Frequency-Dependent I/Q Imbalance in 4x4 MIMO-OFDM Modem
Author :
Wei-Chi Lai ; Yuan-Te Liao ; Terng-Yin Hsu
Author_Institution :
Dept. of Comput. Sci., Nat. Chiao Tung Univ., Hsinchu, Taiwan
Volume :
60
Issue :
8
fYear :
2013
fDate :
Aug. 2013
Firstpage :
2199
Lastpage :
2212
Abstract :
Variations in I/Q gains, phases, and filters of the RF frontend, namely frequency-dependent I/Q imbalance (FDI), are an important factor in OFDM-based wireless access. To enable the proper function of a 4 × 4 MIMO-OFDM receiver this work proposes a low-complexity preamble-assisted solution using only one complex divider and one complex multiplier to handle significant FDI distortions. An all-digital multiphase and multi-rate clock generator (MPRCG) was built to support fast dynamic frequency scaling for FDI estimation and compensation and for efficient implementation. Based on the proposed MPRCG, a skew calibration was also realized to tune I/Q timing coherently via multiphase A/D clocking. Performance evaluation showed that the proposed approach incurs an SNR loss of 1.5 dB to maintain a packet-error rate of less than 10% under a 1 dB gain error, 15 phase error and worse filter mismatch. Thus, this solution not only provides adequate performance, but also makes FDI estimation and compensation more cost-effective.
Keywords :
MIMO communication; OFDM modulation; clocks; dividing circuits; error statistics; filters; modems; multiplying circuits; radio receivers; FDI compensation; FDI distortions; FDI estimation; I/Q gains; I/Q timing; MIMO-OFDM modem; MIMO-OFDM receiver; MPRCG; OFDM-based wireless access; RF frontend; SNR loss; all-digital multiphase; complex divider; complex multiplier; cost-effective preamble-assisted engine; dynamic frequency scaling; filters; frequency-dependent I/Q imbalance; loss 1.5 dB; low-complexity preamble-assisted solution; multiphase A/D clocking; multirate clock generator; packet-error rate; performance evaluation; phase error; skew calibration; Clocks; Engines; Estimation; Frequency domain analysis; OFDM; Receivers; Timing; Clock generator; I/Q mismatch; MIMO-OFDM; dynamic frequency scaling; frequency-dependent I/Q imbalance;
fLanguage :
English
Journal_Title :
Circuits and Systems I: Regular Papers, IEEE Transactions on
Publisher :
ieee
ISSN :
1549-8328
Type :
jour
DOI :
10.1109/TCSI.2013.2239431
Filename :
6428662
Link To Document :
بازگشت