Hideki Minami

IQ imbalance compensation scheme in the presence of frequency offset and dynamic DC offset for a direct conversion receiver

A direct conversion architecture reduces the cost and power consumption of a receiver. However, a direct conversion receiver may suffer from direct current (DC) offset, frequency offset, and IQ imbalance. This paper presents an IQ imbalance estimation scheme for orthogonal frequency division multiplexing (OFDM) direct conversion receivers. The proposed IQ imbalance estimation scheme operates in the presence of dynamic DC offset and frequency offset. The proposed scheme calculates IQ imbalance from a simple equation. It employs the knowledge of the preamble symbols of the IEEE 802.11 a/g standards, while it does not require the impulse response of the channel. Numerical results obtained through computer simulation show that the bit error rate (BER) performance for the proposed IQ imbalance estimation scheme has a degradation of about 4 dB with a large DC offset, frequency offset, and IQ imbalance.

Frequency Offset Estimation Scheme in the Presence of Time-Varying DC Offset for OFDM Direct Conversion Receivers

This paper presents a frequency offset estimation scheme for Orthogonal Frequency Division Multiplex (OFDM) direct conversion receivers. The key idea is to use a differential filter for reduction of DC offset. Frequency offset is estimated in the presence of time-varying DC offset. In order to overcome the varying DC levels under automatic gain control (AGC) circuits, a threshold level is set for the output of the differential filter. The proposed compensation scheme offers superior frequency offset estimation when compared with a conventional scheme with a high pass filter.

Frequency Offset Estimation Scheme in the Presence of Time-Varying DC Offset and IQ Imbalance for OFDM Direct Conversion Receivers

In WLAN systems, direct conversion architecture has been implemented. Though this architecture reduces the cost and power consumption, it may suffer from DC offset, frequency offset, and IQ imbalance. This paper presents a frequency offset estimation scheme for OFDM direct conversion receivers. In this paper, a frequency offset estimation scheme in the presence of time-varying DC offset and IQ imbalance is proposed. The novelty of this scheme is in its usage of a differential filter to reduce DC offset. Evaluation of the presented estimation scheme was carried out on an OFDM communication system designed to the specifications of the IEEE 802.11a/g standard for WLANs. Numerical results through computer simulation show that the proposed frequency offset estimation scheme works well even with large DC offset and IQ imbalance.

IQ Imbalance Compensation Scheme in the Presence of Frequency Offset and Dynamic DC Offset for a Direct Conversion Receiver

A direct conversion architecture reduces the cost and power consumption of a receiver. However, a direct conversion receiver may suffer from direct current (DC) offset, frequency offset, and IQ imbalance. This paper presents an IQ imbalance estimation scheme for orthogonal frequency division multiplexing (OFDM) direct conversion receivers. The proposed IQ imbalance estimation scheme operates in the presence of dynamic DC offset and frequency offset. The proposed scheme calculates IQ imbalance from a simple equation. It employs the knowledge of the preamble symbols of the IEEE 802.11 a/g standards, while it does not require the impulse response of the channel. Numerical results through computer simulation show that the bit error rate (BER) performance for the proposed IQ imbalance estimation scheme has a degradation of about 4 dB with a large DC offset, frequency offset, and IQ imbalance.

Modified Direct Insertion/Cancellation Method based Sample Rate Conversion for Software Defined Radio

In this paper, a new fractional sample rate conversion (SRC) scheme based on direct insertion/cancellation technique is proposed. This technique is suitable for signal that is sampled with high sample rate and converted to lower sample rate. The direct insertion/cancellation technique may achieve low-complexity and lower power consumption as compared to other SRC techniques. However, the direct insertion/cancellation technique may suffer from high aliasing and distortion. Therefore, a modified direct insertion/cancellation scheme is proposed in order to realize high performance resampling.

Modified Direct Insertion/Cancellation Method Based Sample Rate Conversion for Software Defined Radio

In this paper, a new fractional sample rate conversion (SRC) scheme based on direct insertion/cancellation technique is proposed. This technique is suitable for signal that is sampled with high sample rate and converted to lower sample rate. The direct insertion/cancellation technique may achieve low-complexity and lower power consumption as compared to other SRC techniques. However, the direct insertion/cancellation technique may suffer from high aliasing and distortion. Therefore, a modified direct insertion/cancellation scheme is proposed in order to realize high performance resampling.

High‐performance soft decision decoding method using table‐aided algorithm for block code

Although various methods exist in soft decision decoding methods for block codes, of those that can be applied to linear and nonlinear coding, there are not many with low levels of computation that provide high levels of performance. In this paper, a method is proposed that reduces computation requirements while maintaining performance close to that of maximum likelihood decoding by a decision-making procedure in which a candidate codeword table is referenced by performing Euclidean distance comparisons on the received signals hard decision binary sequence. The computation requirements and the block error rate performance are investigated through computer simulation to demonstrate the effectiveness of the proposed method in nonlinear β codes in additive Gaussian noise channels and fading channels. These results show that the block error rate performance of the proposed method in the additive Gaussian noise channel is about the same as the performance of the Chase 11 algorithm and is only slightly inferior to that of maximum likelihood decoding. Concerning the amount of computations, it is possible to reduce the complexity down to about 1% of that required by maximum likelihood decoding, and also the complexity can be reduced below that of the Chase II algorithm. On the other hand, in the fading channel, the block error rate performance of the proposed method, when compared to maximum likelihood decoding performance, reveals a decrease in Eb/N0 of about 1 dB, and it is seen to have good performance compared to the Chase II algorithm. Also, application toward quasi-cyclic coding/4-ary ASK coding using a candidate word table with respect to a 4-ary sequence applied with BCH coding is investigated, and superior results are obtained.

High performance soft decision decoding using a table-aided algorithm for block-coded 16 QAM in land mobile communications

This paper proposes soft decision decoding using a table-aided algorithm which has much lower computational complexity than maximum likelihood (ML) decoding. The bit error rate (BER) performance of block-coded 16 QAM applied to land mobile communications is evaluated. Computer simulations show that the proposed method can achieve performance close to that of ML decoding and that the amount of computation for decoding is about 1% that of ML decoding.