WiMAX technology is considered one of the most important solutions capable to provide a Broadband Wireless Access in metropolitan areas. Mobility issues have become challenging for the rollout for WiMAX networks in or...
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WiMAX technology is considered one of the most important solutions capable to provide a Broadband Wireless Access in metropolitan areas. Mobility issues have become challenging for the rollout for WiMAX networks in order to compete against the other competitive technologies such as 3.5G and LTE. In this paper, a unified approach to derive the overall BER and data rate for mobile WiMAX (in uplink direction) will be introduced. This approach will take into consideration different operational scenarios such as time varying channels with different values of channel estimation precision values, different number of subcarriers, and different symbol durations. An analytical expression for the effect of ICI power on the bit error probability and effective bit rate will be obtained for BPSK, QPSK, and 16QAM in presence of AMC. This paper also investigates the effect of the use of AMC techniques on the obtained system performance.
In the present and future generation of wireless networks, link adaptation is used for better channel efficiency. With link adaptation the modulation and coding scheme used for transmissions to a particular user is ad...
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In the present and future generation of wireless networks, link adaptation is used for better channel efficiency. With link adaptation the modulation and coding scheme used for transmissions to a particular user is adjusted based on the user's channel conditions. However, because of delays and measurement errors in the reported channel quality information, the actual transmission may experience a significantly different channel than anticipated. This can either lead to transmission errors (if the channel has deteriorated) or wasted transmission resources (if the channel is actually better than predicted). To avoid the former scenario, a conservative mapping from channel quality information to modulation and coding scheme is used. However, the degree of this conservatism depends on the Doppler Frequency of the channel with higher values requiring a more conservative mapping. In this paper we propose an algorithm for dynamically adjusting the mapping from channel quality reports to the modulation and coding scheme. Hybrid ARQ is assumed and we use the outcome of the first transmission to adjust the mapping. Simulation results are used to illustrate the effectiveness of the approach.
The adaptive modulation and coding can provide robust and spectrally efficient transmission over generalized ¿-¿ (or generalized gamma) wireless fading channels. The key idea of our proposal is to transmit t...
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The adaptive modulation and coding can provide robust and spectrally efficient transmission over generalized ¿-¿ (or generalized gamma) wireless fading channels. The key idea of our proposal is to transmit the low-density parity-check (LDPC) encoded sequence over the generalized fading channel, feedback the channel state information of by an RF feedback channel, and adapt the powers and rates of so that the channel capacity is maximized. The optimal power adaptation policy maximizing the channel capacity is derived. We show that deep fades can be tolerated with proposed scheme.
Wireless communication using multiple-input multiple-output (MIMO) systems improves throughput and enhances reliability for a given total transmit power. Achieving a higher data rate in MIMO systems requires utilizing...
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ISBN:
(纸本)9781424458257
Wireless communication using multiple-input multiple-output (MIMO) systems improves throughput and enhances reliability for a given total transmit power. Achieving a higher data rate in MIMO systems requires utilizing an effective space-time coding and modulation scheme. The appropriate algorithm to use for a system will depend on parameters such as the number of transmit/receive antennas, target spectral efficiency, complexity limitations, channel environment, and other factors. In this paper, we examine the performance of various two-transmit and four-transmit space-time coding schemes under different channel types and target data rates. We compare the performance of state of the art space-time coding schemes including direct non-binary LDPC GF(q) modulation, bit interleaved coded modulation using iterative detection, and space-time trellis coded modulation. We obtain a tradeoff between performance and complexity of these various schemes.
As the demand of high quality service in next generation wireless communication systems, a high performance of data transmission requires an increase of spectrum efficiency and an improvement of error performance in w...
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As the demand of high quality service in next generation wireless communication systems, a high performance of data transmission requires an increase of spectrum efficiency and an improvement of error performance in wireless communication systems. In this paper, we propose a multi-user multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system with adaptive modulation and coding to improve system capacity with maintaining good error performance. The results of computer simulation show the improvement of system capacity in Rayleigh fading channel.
Packet retransmission strategies are presented for MIMO eigenmode transmission where adaptive modulation and coding (AMC) is implemented. The retransmission design is based on weighted linear MMSE. It includes the tra...
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Packet retransmission strategies are presented for MIMO eigenmode transmission where adaptive modulation and coding (AMC) is implemented. The retransmission design is based on weighted linear MMSE. It includes the transmit and receiver filter, the power and eigenmode allocation and AMC level when new packets are transmitted. The weight matrix of WMMSE is used to appropriately weight streams with different AMC levels in order to maximize the system throughput. Simulations show that the choice of the weight factors has a major impact on the performance.
To meet growing target data rates, future wireless networks will be heterogeneous with macro and pico base stations (BSs). Allocating resources and managing interference between various types of BSs are of primary imp...
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To meet growing target data rates, future wireless networks will be heterogeneous with macro and pico base stations (BSs). Allocating resources and managing interference between various types of BSs are of primary importance for achieving acceptable throughput in cell edges. In this work, we propose the interference canceling block modulation (ICBM) scheme for interference management in heterogeneous networks. We provide analytical design methods for ICBM and study the application of ICBM in heterogeneous wireless networks. Our results essentially show that ICBM acts as a virtual resource, significantly improving the data rates for cell-edge users as well as the cell average throughput over the conventional techniques in typical interference scenarios arising in heterogeneous networks.
An error correcting capable 2/4 modulation code scheme is proposed in holographic data storage (HDS) systems. We adopt trellis coded modulation (TCM) to obtain a good error correcting capability without loss of data r...
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An error correcting capable 2/4 modulation code scheme is proposed in holographic data storage (HDS) systems. We adopt trellis coded modulation (TCM) to obtain a good error correcting capability without loss of data rate in the HDS systems. To overcome loss of a data rate caused by a 1/2-rate convolutional code, we extend a 2/4 modulation code set the 3/4 modulation code set as high-order modulation in the proposed scheme. Additionally, we find an optimal mapping method of index numbers to maximize the free distance on the trellis and calculate the free distance according to each constraint length. The simulation results show that the proposed scheme with the same data rate has about 4 dB coding gains compared to the conventional 2/4 modulation coding scheme. (C) 2012 The Japan Society of Applied Physics
The performance of bit-interleaved coded modulation in multiple-input multiple-output (BICM-MIMO) systems using an iterative channel estimator is analysed. In a conventional iterative channel estimator, after initiali...
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The performance of bit-interleaved coded modulation in multiple-input multiple-output (BICM-MIMO) systems using an iterative channel estimator is analysed. In a conventional iterative channel estimator, after initialisation with the training phase, the channel estimator switches to the data phase. However, such a conventional iterative channel estimator does not always improve the performance of the receiver. In order to guarantee the performance improvement, a condition on when the output of the decoder should be used by the estimator is determined. Such a condition is related to the reliability of the soft information utilised by the channel estimator. The key in establishing this relationship is to use the mutual information (MI) that the observation vector has about the channel gains given the output of the decoder at each iteration. In this switch-augmented conventional iterative channel estimator, referred to as SAICE, the condition is theoretically found and indicates the needed reliability of the soft information for the channel estimator at the switching time. The switch-augmented scheme guarantees performance improvement of the iterative receiver with each iteration, however, it might need many iterations to converge for moderate to low signal-to-noise ratios (SNRs). A less computationally intensive approach is to use both the training and data segments of the observation. This approach produces a combined iterative channel estimator (CICE) for BICM-MIMO systems. The performance behaviour of the BICM-MIMO system is illustrated through the extrinsic information transfer (EXIT) chart with imperfect channel state information (CSI). Analytical results are verified with computer simulations.
Recent work has shown that chaos-based communication systems can yield performances as good as their non-chaotic counterparts in additive white Gaussian noise (AWGN), and behave even better in flat-fading channels. Ho...
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Recent work has shown that chaos-based communication systems can yield performances as good as their non-chaotic counterparts in additive white Gaussian noise (AWGN), and behave even better in flat-fading channels. However, much of this work relies on computer simulations and there is still a need to study in depth the implementation issues of such systems. The authors address for the first time a fixed-point arithmetic implementation of the iterative decoding algorithm for a recently proposed and successful class of parallel concatenated chaos-based coded modulations. The novel digital signal processor (DSP) results demonstrate that it is possible to implement in standard hardware competitive chaos-based communication systems.
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