Abstract:In modulated scattering antenna array (MSAA) system it has at the receiver side encountered low levels of scattering signals [1,2] and interferences in addition to the desired signal. In this paper, we propose to utilize the frequency hopping scheme to improve the performance of scattering signals under the influence of narrow band strong interferences. From the numerical results, it concludes that with larger hopping range it improves the ability of anti-interference effects.

When a carrier aggregation communication system suffers from receiving power imbalance (RPI) in its antenna array due to design flaw, operator's negligence etc. the system performance may be degraded to an unacceptable level. Specifically in this paper a carrier aggregation communication system with two carrier links while one link suffers RPI is considered, various modulation techniques, such as QPSK, 16 QAM and 64 QAM and/or coding schemes, Convolution Code (CC) and Low Density Parity Check Code (LDPC) are implemented in the system performance simulation to investigate the system behavior when it has the design request to maintain the same system performance in each link when the RPI has values of 7 or 10 dB.

In this paper we simulate and analyze the system performance of implementing two Hybrid Automatic Retransmission Request (HARQ) architectures for IEEE 802.16m system, one is a modified Type I HARQ architecture with adaptive modulation and coding (AMC) scheme and the other is the Chase Combining. In the simulation, the buffer size of HARQ has been set to certain limit and under the condition of having the packet error ratio (PER) limited by 10% then the selection of proper HARQ structure with suitable AMC scheme for IEEE 802.16m system has been proposed for mobile speeds at 3 km/hr, 80 km/hr or 350 km/hr and with a distance of 300m between the mobile station and its serving base station.

Abstract:In this paper the implementation of hierarchicalmodulated pilot signals for carrier frequency drift estimation in high mobility multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system is introduced. Specifically for a hierarchical-modulated 64QAM-OFDM system in which three Layers with two bits in each Layer are defined from the constellation point and the carrier frequency drift estimation is facilitated from every Layer instead of using all six constellation bits to possibly simplify the design and reduce the time in the estimation process. The carrier frequency drift estimation by using only one Layer and the system performance at the receiver terminal by utilizing this Layer's estimated carrier frequency drift are simulated and compared for various high mobile speeds in Rayleigh fading channels.

Abstract:The received power imbalance (RPI) effect exists in multiple antennas wireless communications system due to design flaw, operator's negligence etc. The range of RPI can be from −10 dB to 0 dB and if the RPI information is not available at the receiver terminal, it can implement turbo iterative receiver by concatenating multi-input and multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) demodulation (MIMO OFDM demodulation, MOD) serially by channel decoder such as low density parity check (LDPC) decoder or Convolution code (CC) decoder to mitigate the RPI effect and to maintain the system performance at certain acceptable level. Keywords: array antenna, received power imbalance (RPI), turbo iterative receiver, low density parity check (LDPC), convolution code (CC) Classification: Microwave and millimeter wave devices, circuits, and systems References[1] B. Lu, G. Yue, and X. Wang, "Performance analysis and design optimization of LDPC-coded MIMO OFDM systems,"