Yuro Lee

Additional Diversity Gain in OFDM Receivers under the Influence of IQ Imbalances

In this paper, we analyze the effects of IQ (in-phase/ quadrature-phase) imbalances at both transmitter and receiver of OFDM (orthogonal frequency division multiplexing) system and show that more diversity gain can be achieved even though there are unwanted IQ imbalances. When mixed sub-carriers within an OFDM symbol due to the IQ imbalances undergo frequency selective channels, additional diversity effects are expected during the demodulation process. Simulation results on the symbol error rate (SER) performance with ML (maximum likelihood) and OSIC (ordered successive interference cancellation) receiver show that significant performance gain can be achieved with the diversity gain caused by the IQ imbalances combined with the frequency selective channels.

A New MIMO System for Gbps Transmission

In this paper, a receiver algorithm for an 8times8 MIMO system is considered for Giga-bps data transmission, in which the decoding complexity and latency are crucial factors for implementation of MIMO system with large number of transmit and receive antennae. To reduce computational complexity and the decoding latency, a 3-stage receiver algorithm is proposed. The MIMO receiver consists of multi-dimensional detection, partial interference cancellation and the weighted zero-forcing equalization, where the transmit antennae are divided into two group. The first group is encoded by a lower rate code and multi-dimensional search algorithm is used for demodulation and decoding, while the second group is encoded by higher rate code and weighted zero-forcing equalization is used. Once the first group is decoded successfully, they are cancelled out from the received vector for the decoding of the second group. The complexity and the error rate performance are investigated and compared with a well-known sphere decoding algorithm.

Obtained Diversity Gain in OFDM Systems under the Influence of IQ Imbalance

In this paper, we analyze the effects of IQ (In-phase/Quadrature-phase) imbalance at both transmitter and receiver of OFDM (Orthogonal Frequency Division Multiplexing) system and show that more diversity gain can be achieved even though there are unwanted IQ imbalance. When mixed sub-carriers within an OFDM symbol due to the IQ imbalance undergo frequency selective channels, additional diversity effects are expected during the demodulation process. Simulation results on the symbol error rate (SER) performance with ML (Maximum Likelihood) and OSIC (Ordered Successive Interference Cancellation) receiver show that significant performance gain can be achieved with the diversity gain caused by the IQ imbalance combined with the frequency selective channels.

Obtaining Diversity Gain Coming from IQ Imbalances in OFDM Receivers

In this paper, we analyze the effects of IQ (in-phase/quadrature-phase) imbalances at both transmitter and receiver of OFDM (orthogonal frequency division multiplexing) system and show that more diversity gain can be achieved even though there are unwanted IQ imbalances. When mixed sub-carriers within an OFDM symbol due to the IQ imbalances undergo frequency selective channels, additional diversity effects are expected during the demodulation process. Simulation results on the symbol error rate (SER) performance with ML (maximum likelihood) and OSIC (ordered successive interference cancellation) receiver show that significant performance gain can be achieved with the diversity gain caused by the IQ imbalances combined with the frequency selective channels.

A new MIMO algorithm for high data rate transmission

In this paper, a receiver algorithm for an 8x8 MIMO system is considered for Giga-bps data transmission, in which the decoding complexity and latency are crucial factors for implementation of MIMO system with large number of transmit and receive antennae. To reduce computational complexity and the decoding latency, a 3-stage receiver algorithm is proposed. The MIMO receiver consists of multidimensional detection, partial interference cancellation and the weighted zero-forcing equalization, where the transmit antennae are divided into two group. The first group is encoded by a lower rate code and multidimensional search algorithm is used for demodulation and decoding, while the second group is encoded by higher rate code and weighted zero-forcing equalization is used. Once the first group is decoded successfully, they are cancelled out from the received vector for the decoding of the second group. The complexity and the error rate performance are investigated and compared with a well-known sphere decoding algorithm.

Multi-rate QR-MDD for High Data Rate Transmission in Nomadic Local Wireless Access

In this paper, we propose a new MIMO algorithm for giga-bps data transmission. To reduce computational complexity and the decoding latency, a 3-stage receiver algorithm, namely multi-rate QR-MDD is proposed. The MIMO receiver consists of multi-dimensional detection, partial interference cancellation and the weighted zero-forcing equalization, where transmit antennas are divided into two group. The first group is transmitted using lower modulation level and lower code rate and the MDD (multi-dimensional detection) algorithms is used for demodulation and decoding, while the second group is transmitted using higher modulation order and higher code rate and the WZF algorithms is used. Once the first group is decoded, they are cancelled out from received signal for demodulation and decoding of the second group. The complexity and the error rate performance are investigated and compared with MLD (Maximum Likelihood Detection) and ZF (zero forcing). The error performance is slightly worse performance than that of MLD. And computational complexity viewpoint of the required number of real multiplications is approximately 2 times the complexity level of ZF.

A New MIMO Algorithm for Gbps Transmission in Nomadic Local Wireless Access

In this paper, we propose a new MIMO receiver algorithm for 8x8 MIMO system based on hybrid detection to reduced computational complexity for Giga-bps data transmission. The proposed MIMO detector, multi-rate QR-MDD consists of MDD (multi-dimensional detector), DSC (decision symbol cancellation) and WZF (weighted zero forcing) where the transmit streams are divided into two groups. The first group is transmitted using lower modulation level and lower code rate and the MDD algorithms is used for demodulation and decoding, while the second group is transmitted using higher modulation order and higher code rate and the WZF algorithms is used. Once the first group is decoded, they are cancelled out form received signal for demodulation and decoding of the second group. The error performance is slightly worse performance than that of MLD (maximum likelihood detection). And computational complexity viewpoint of the required number of real multiplications is approximately 2 times the complexity level of WZF.

Performance of Antenna Permutation for Multi-rate Gigabit MIMO-LDPC

ETRI has developed and successfully demonstrated a mobile communications technology dubbed New Nomadic Local Area Wireless Access (NoLA) that will allow users to download data at 3.6 Gbps. NoLA is designed as an 8times8 MIMO-OFDM system. NoLA transmits two lower rate streaming signals and six higher rate streaming signals through eight transmit antennas. After QR-decomposition of the received multi-rate signals, the lower rate streaming signals are decoded by multi-dimensional detector and removed by the successive interference cancellation scheme. The remaining six higher rate streaming signals are decoded using a weighted zero-forcing detector. Besides, NoLA adopts an independent LDPC coding scheme to process high-speed decoding at gigabit. In this paper, we propose an antenna permutation scheme for multi-rate MIMO systems with an independent LDPC coding scheme like NoLA. The simulation results show that the higher rate streaming signals achieve higher performance gain than the lower rate streaming signals by only a simple modification of the MIMO-OFDM system.