Anas Muhamad Bostamam

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.

Direct-Sequence/Spread-Spectrum Communication System with Sampling Rate Selection Diversity

In this paper, sampling rate selection diversity (SRSD) scheme for Direct-Sequence/Spread-Spectrum (DS/SS) is proposed. In DS/SS communication systems, oversampling may be employed to increase the signal-to-noise ratio (SNR). However, oversampling enlarges the power consumption because signal processing of the receiver has to be carried out at a higher clock rate. Higher sampling rate does not always maximize the SNR. In the proposed SRSD scheme, the power consumption can be reduced by selecting the optimum sampling rate depending on the characteristics of the channel. The proposed SRSD scheme can also reduce the BER more than the conventional oversampling scheme under certain channel conditions.

Experimental investigation of undersampling for adjacent channel interference cancellation scheme

In this paper an adjacent channel interference (ACI) cancellation scheme for multi-channel reception with undersampling and investigated. Low-IF receiver architecture is used in the multi-channel reception scheme. However, in this system, the signal in the adjacent channel causes interference to the desired signal. ACI cancellation scheme with analog filter bank has been proposed to mitigate the influence from the adjacent channel. Undersampling technique is applied in this system in order to lower the required sampling frequency and power consumption. The effects of the adjacent channel to the undersampling technique in this scheme is investigated through the experiment

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.

Performance of frequency offset estimation in the presence of IQ imbalance for OFDM direct conversion receivers

In WLAN receivers, a direct conversion architecture has been implemented in recent years. Though this architecture reduces cost and power consumption, it may suffer from direct current (DC) offset and frequency offset. To reduce the effect of DC offset, a frequency offset estimation scheme with a differential filter for orthogonal frequency division multiplexing (OFDM) direct conversion receivers has been proposed. However, the receiver may also suffer from IQ imbalance, which deteriorates the performance of frequency offset estimation. In this paper, the performance analysis of the frequency offset estimation scheme with the differential filter in the presence of IQ imbalance is derived. The numerical results obtained through computer simulations show that the derived analysis provides close approximation to the performance of the frequency offset estimation scheme. It also clarifies the dependency of the mean square error on the waveform of the preamble symbols, which is caused by 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.

Sampling Rate Selection Path Diversity for a RAKE Receiver in DS/SS

In this paper, sampling rate selection path diversity (SRSPD) scheme for direct-sequence/spread-spectrum (DS/SS) is proposed. In DS/SS communication systems, oversampling may be employed to increase the signal-to-noise ratio (SNR). However, oversampling enlarges the power consumption because signal processing of the receiver has to be carried out at a higher clock rate. In order to reduce the power consumption, the proposed SRSPD scheme selects the tap positions of the RAKE receiver and the sampling rate depending on the characteristics of the channel.