Multicast services need to satisfy all mobile devices even under very bad channel conditions. However, the method for accommodating this will result in the throughput of the service being determined and limited by the channel state of the mobile device with the worst channel conditions. In this way, the capacity of mobile devices under a good channel state is determined based on the capacity of the mobile device under the worst channel state. To overcome the capacity limitation and achieve throughput maximization, we propose two different scenarios for resource management of a multiple carrier component (CC) wireless system. The first scenario manages resources with a two-step approach to support every mobile device and solve the throughput maximization feasibly for the primary CCs. A power control algorithm and admission control for minimizing the BS power is applied under the second scenario to mitigate interference.

In this paper, a novel observe-and-forward (OF) cooperative scheme is proposed for relay-enhanced wireless cooperative systems. In this scheme, the codewords transmitted from the source are regenerated by the decoder at the relay and forwarded without re-encoding or interleaving. The decoding processes for different streams of a transmitted codeword can be parallel, which greatly reduces the relaying latency and the complexity of the relay. Furthermore, classical Viterbi algorithm (VA) decoding is adopted at the destination while a Turbo decoding is necessary in decoded-and-forward with coded cooperation (DF-CC) scheme. Union bounds on error performances and the achievable rates are analyzed for the OF scheme. Both the analysis and simulation show that the proposed OF scheme works as well as the classical DF scheme and even better than the DF-CC scheme in some scenarios. The features of the proposed OF scheme are smaller relaying latency and lower complexity, which facilitate the application of this relaying scheme.

In fast moving environment, the inter-carrier interference (ICI) due to Doppler spread will degrade the performance of OFDM system severely. Using Jakes' model for the Doppler power spectrum and linear model for time-varying channel during an OFDM symbol interval, the analytical closed- form expression of ICI power, signal-to-interference ratio (SIR) and signal-to-interference-plus-noise ratio (SINR) are given without assumption on the statistical characteristic of ICI. Moreover, the effect on bit error probability (BEP) performance by the number of concerned interfering subcarriers is analyzed, which helps to choose the number of concerned interfering subcarriers according to the Doppler spread to greatly reduce the complexity of ICI mitigation method with little performance penalty. The simulation results show that the ICI analysis and SIR expression are efficient, and the concerned number of interfering subcarriers should be more with the increase of Doppler spread when ICI mitigation is adopted.

In current wireless system performance evaluation, separate link and system level simulators are needed due to less computation complexity. The link-to-system (L2S) interface method to interconnect two simulators is essential and need careful definition. Exponential effective signal-to-interference-and-noise ratio mapping (EESM) is a typical L2S interface method suitable for evaluation of orthogonal frequency division multiplexing systems. When itpsilas used in simulation, all the sub-carriers for one user have to use the same modulation and coding scheme. In this paper, two modified L2S interface EESM methods are presented based on the idea that a high-level modulation symbol could be equivalently converted to several low-level modulation symbols with different reliability. As a result, usage of EESM can be extended to the situation that sub-carriers for one user use different modulation schemes.

The time-variation of channels during one OFDM symbol destroys the orthogonality among subcarriers and results in intercarrier interference (ICI), which may detail substantial error performance. Assumed channels vary in linear fashion during one OFDM symbol, we propose an iterative partial-ICI-cancellation (PIC) based detector for OFDM systems with linear modulation over doubly-selective Rayleigh fading channels. The tentatively detected information of channel and data are fed back to regenerate the ICI and then partially subtracted from the received signals. The optimal partial ICI cancellation factor (PICF) is determined by minimizing the mean square error (MSE) of data estimation. The proposed detector iteratively renews the channel estimation and data detection after PIC, and results in performance enhancement. Based on Jake's model for the Doppler effects, the bit error ratio (BER) performance of the proposed detector is illustrated for OFDM systems with phase-shift keying (PSK) and quadrature-amplitude modulation (QAM) in Rayleigh fading channels at several speeds.

WiBro (wireless broadband), the standard of high-speed portable internet (HPI) based on OFDMA/TDD and IP network in Korea, is the subset of consolidated version of IEEE 802.16e wireless MAN standard. In this paper, the architecture and key physical layer technologies of WiBro are briefly introduced, whereas the convolutional turbo code (CTC) with high-order modulation is presented in detail. The performance of convolutional Turbo coded WiBro system with QPSK, 16QAM and 64QAM over ITU-R channel models is simulated, where pilot tones aided channel estimation and 1-tap equalization are applied. Simulation results show that the good BER performances of CTC with short code block size in WiBro systems, which facilitates the flexibility of channel resource allocation. Given the same code block size, CTC outperforms TC (turbo codes) and CC (convolutional codes).

In general, multi-input multi-output (MIMO) channel is correlated by an amount that depends on the propagation environment as well as the polarization of the antenna elements and the spacing between them. In this paper, an exact error probability of orthogonal space-time block codes is considered in spatially correlated Rayleigh fading channels. We derive a general formula for the symbol error probability (SEP) of orthogonal space-time block codes for general PSK/PAM/QAM over spatially correlated Rayleigh fading channels.

This paper presents an optimized channel usage between simulator and accelerator when the simulator models transaction-level SoC while accelerator models RTL sub-blocks. Conventional simulation accelerators synchronize the progresses of simulator and accelerator at every simulation time, which results in poor performance by splitting transactions on the simulator-to-accelerator channel into pieces. Occasional synchronization with predictions and recoveries makes it possible to merge multiple transfers yielding substantial performance gain compared to the conventional method.

This paper presents new technology that accelerates system verification. Traditional methods for verifying functional designs are based on logic simulation, which becomes more time-consuming as design complexity increases. To accelerate functional simulation, hardware acceleration is used to offload calculation-intensive tasks from the software simulator. Hardware accelerated simulation dramatically reduces the simulation time. However, the communication overhead between the software simulator and hardware accelerator is becoming a new critical bottleneck. We reduce the communication overhead by exploiting burst data transfer and parallelism, which are obtained by splitting testbench and moving a part of testbench into hardware accelerator. Our experiments demonstrated that the proposed method reduces the communication overhead by a factor of about 40 compared to conventional hardware accelerated simulation while maintaining the cycle accuracy and compatibility with the original testbench.

Functional coverage is a technique for checking the completeness of test vectors in HDL simulation. Temporal events are used to monitor the sequence of events in the specification. In this paper, automatic generation of temporal events for functional coverage is proposed. The HiTER is the graph where nodes represent basic temporal properties or subgraph and edges represent time-shift value between two nodes. Hierarchical temporal events are generated by traversing HiTER such that invalid, or irrelevant properties are eliminated. Concurrent edge groups make it possible to generate more comprehensive temporal properties and hierarchical structure makes it easy to describe large design by combining multiple subgraphs. Automatically enerated temporal events describe almost all the possible temporal properties of the design under verification.

This work presents the automated process of translating behavioral testbench into synthesizable one for the hardware-accelerated simulation. Testbench is mainly implemented in unsynthesizable HDL description such as time delay, event control, non-static loops and sequential statements. Nonetheless, FPGA-based accelerator is limited to synthesizable design. To apply hardware acceleration to behavioral testbench, the proposed method automatically translates testbench into equivalent hardware by emulating the standard simulation reference model. By mapping testbench into hardware accelerator to be merged with the design under verification, we can accelerate behavioral testbench and remove the communication overhead between the software simulator and hardware accelerator. Our experiments demonstrated that the simulation time is reduced by a factor of about 1000 as compared to the conventional hardware accelerated simulation.

A smart antenna system using virtual array elements is proposed to increase the channel capacity of mobile communication systems. The proposed smart antenna system increases the degree of freedom using virtual array elements generated by complex conjugations of real array elements signals and sign compensations using the orthogonality between the user identification codes in the I and Q channels. The performance of the proposed system is analyzed under cdma2000 specifications in urban cell environments.

Deciding a proper metric for crisp values are well established and the results are clear, but the operation on fuzzy values are inherently ambiguous because the fuzzy values include uncertainty. This paper deals with this distance metric on a set of crisp/fuzzy values with different viewpoints. A bounded pseudo-metric function (distance function) for a set of crisp/fuzzy values is proposed. The distance function is based on the satisfaction function on continuous domain with a viewpoint. The viewpoint was adopted to incorporate user's preferences on the domain of discourse. The proposed distance function on a set of fuzzy values becomes a bounded metric function when the set of fuzzy values only contains crisp values. Then the role of viewpoints on the distance function is discussed. Finally, the relation between the proposed distance function and defuzzification is shown.

This paper proposes a new scheme for an ATM OAM performance management function, hybrid performance management scheme. The performance management OAM function monitors network performance using OAM cells and executes mechanisms to prevent traffic congestion with relation to traffic control functions. For this purpose, the proposed scheme enables the switching system to perform different performance monitoring mechanisms according to the OAM management boundary of end-to-end or segment definition and also makes it possible to provide the detail information in traffic control functions detail.