Wang Wen-bo

A frequency reuse partitioning scheme with successive interference cancellation for OFDM downlink transmission

In conventional multicell OFDMA systems, generally there is no inner cell interference (INCI). The system throughput is severely degraded by inter-cell interference (ICI), especially at cell edge. To satisfy the performance requirement, ICI must be mitigated effectively. Several schemes have been proposed to handle this problem by coordinating the way to allocate spectrum resource to each cell. Since the allocation of spectrum has effects on ICI mitigation and the spectral efficiency, a wise strategy to consider those two factors is required. In this paper, we propose a new scheme named as power division reuse partitioning scheme with successive interference cancellation (PDICS). PDICS balances ICI mitigation and spectral efficiency by appropriate frequency allocation and power distribution. To improve frequency efficiency, the frequency reuse factor is chosen as 0.5, so INCI exists. To minimize INCI, successive interference cancellation is suggested. The simulation results show that PDICS has better performance of throughput and symbol error rate (SER) than the conventional schemes.

Performance Analysis and Improvement of HARQ Techniques in TDD-HSDPA/SA System

HSDPA proposed in 3GPP is the best evolution of current UMTS to support high data rate services. It adopts numbers of enhanced techniques including AMC, HARQ, fat-pipe scheduling etc. This paper investigates the performance of different HARQ schemes considered for TDD-HSDPA system on system level. Special address is put on the affect of smart antennas. A kind of improved full IR is also proposed and investigated

A frequency reuse partitioning scheme with successive interference cancellation for OFDMA uplink transmission

Inner cell interference (INCI) is avoided in common multicell orthogonal frequency division multiplex access (OFDMA) systems but inter cell interference (ICI) still exist. The system throughput is severely degraded by ICI, especially at cell edge. Several schemes have been proposed to handle this problem by coordinating the way to allocate spectrum resource to each cell. Since the allocation of spectrum has effects on ICI mitigation and the spectral efficiency, a wise strategy to consider those two factors is required. In this paper, the power division reuse partitioning scheme with successive interference cancellation (PDICS) for OFDMA uplink transmission is discussed. PDICS balances ICI mitigation and spectral efficiency by appropriate frequency allocation and power distribution. To improve frequency efficiency, the frequency reuse factor is chosen as 0.5, so INCI exists. To minimize INCI, successive interference cancellation is suggested. The simulation results show that PDICS has better performance of throughput and symbol error rate (SER) than the conventional schemes.

Monte Carlo simulation with error classification for multipath Rayleigh fading channel

Evaluation of bit error rate (BER) of a digital communication system is usually done via simulation using Monte Carlo (MC) method. For low BER, MC method requires huge sample sizes to achieve certain efficiency. To overcome this limitation, many variance reduction techniques such as importance sampling (IS) have been proposed. In this paper, we put forward a novel simulation method - Monte Carlo simulation with error classification (EC-MC). This method can reduce the estimation variance through dividing the total errors into many sub-categories and optimizing the simulation samples for each sub-category. We apply this method in simulations of both single-path Rayleigh fading channel and multipath Rayleigh fading channel with Orthogonal Space-Time Block Coded MIMO systems. The simulation results demonstrate EC-MC method can achieve the same accuracy at smaller sample sizes and shorter simulation runtime, comparing with both conventional MC and IS methods, especially at high signal to noise ratios.

Base station and service social network and its application in cellular networks

With the rapid development of wireless networks, the fourth-generation (4G) communication network is becoming increasingly popular and the fifth-generation (5G) network is expected to be commercialized by 2020. Many types of new services are being gradually applied mobile terminals with increasingly complex data in terms of diversity, scale, and dimension. It has become a popular research topic to optimize the base station deployment as well as resource scheduling strategy to meet various service requirements based on the cognizing of cellular network service pattern. We introduce a social network analysis method and propose a novel method to build service social network and base station social network (BSSN) for typical wireless network based on a study of wireless big data in practical networks. Additionally, traffic fluctuations can be predicted based on selected several typical very important base stations (VIBS), and caching strategies for cellular network can be optimized based on BSSN. This work provides insights and possible solutions for traffic monitoring, congestion prevention, network deployment and optimization, as well as resource scheduling optimization based on the characteristics of big data in cellular network.

The model of large-scale mobile user behavior and energy efficiency resource allocation method

For the existence of user social patterns, the traffic characteristics and user behavior in complex cellular mobile network show clustering behavior regularity characterized by groups in multi-dimensional distributions, such as time, space, and content. Previous static, island-like network resource allocation methods lead to a massive waste of network resources. Thus, the use of user behavior characteristics can have a huge impact on energy efficiency and resource utilization. Based on data collection and measurements from real cellular mobile communication systems, we analyze the behavior of user group aggregation in spatial, time, and other dimensions, to obtain traffic distributions across base stations in the space, time, and spatio-temporal domains. The study shows that traffic distribution in the space domain conforms to a Log-normal distribution and that its parameters are related to typical region types. The number of users and the amount of traffic they produce show regularity over time, and the Sine superposition model can reflect changes in the traffic volumes in a network. Next, through joint analysis of the space and time domains, we obtain a spatio-temporal joint distribution model that can accurately predict changes in base station traffic. When compared with real data, it is shown that the accuracy of the model reaches over 93%. In order to characterize user group clustering more clearly, we use the Gini coefficient to present a mathematical definition and quantitative description of user group behavior. Finally, based on the proposed spatio-temporal model and user group behavior model, we propose several energy-efficient wireless network resource allocation methods, transmission control methods, and a base station hierarchical sleep strategy for exploring new approaches using user group behavior regularity to improve wireless network energy efficiency.

An enhanced algorithm for the transmission mode switching in TD-LTE downlink systems

Downlink beamforming is an efficient technique in TD-LTE systems to provide the diversity or multiplexing gains when suitable antenna mode switching algorithm is applied. Since the radio channel information is not perfectly obtained at the transmitter, the antenna mode decided by the base station (BS) is not often suitable, and the cell throughput decreases especially when the user equipment (UE) with high speed mobility and there is a large feedback delay. To solve this problem, a dynamic antenna mode switching (DAMS) algorithm is proposed for the downlink transmission in TD-LTE systems, where a cell-specific offset and a UE-specific offset are utilized to adjust the channel quality indicator (CQI) fed back from UE and determine the suitable antenna mode. According to the simulation results, compared with the conventional mode switching (CMS) algorithm, the proposed DAMS algorithm enhances both the cell spectrum efficiency and the initial transmission success ratio (ITSR) dramatically.Downlink beamforming is an efficient technique in TD-LTE systems to provide the diversity or multiplexing gains when suitable antenna mode switching algorithm is applied. Since the radio channel information is not perfectly obtained at the transmitter, the antenna mode decided by the base station (BS) is not often suitable, and the cell throughput decreases especially when the user equipment (UE) with high speed mobility and there is a large feedback delay. To solve this problem, a dynamic antenna mode switching (DAMS) algorithm is proposed for the downlink transmission in TD-LTE systems, where a cell-specific offset and a UE-specific offset are utilized to adjust the channel quality indicator (CQI) fed back from UE and determine the suitable antenna mode. According to the simulation results, compared with the conventional mode switching (CMS) algorithm, the proposed DAMS algorithm enhances both the cell spectrum efficiency and the initial transmission success ratio (ITSR) dramatically.

Capacity Evaluation of Cellular TDD-CDMA Systems Deploying Multi-frequency

Both uplink and downlink capacity of cellular time duplex division-code division multiple access (TDD-CDMA) systems deploying multi-frequency are analyzed theoretically. The impact of multi-user detection, inter-frequency interference and different traffic types on multi-frequency TDD-CDMA system capacity are discussed. Simulation is done to evaluate the theoretical analysis and a good concordance is observed. Simulation and theoretical results show that adjacent channel leakage ratio should at least 10 dB to achieve higher capacity by deploying multi-frequency. When adjacent channel leakage ratio is bigger than 30 dB, the capacity of N frequency system is exact N times that of single frequency system. The conclusions are true for both uplink and downlink.

Performance analysis of MC DS-CDMA in the presence of partial band interference

We have analyzed the performance of multicarrier (MC) DS-CDMA mode and its impact on system performance in the presence of partial band interference (PBI). It is shown that the MC DS-CDMA system has a narrow band interference suppression effect and robustness to multipath fading. We compare this system with a single carrier RAKE receiver system. When there is no PBI, the two systems show a similar performance, but when there is, the MC DS-CDMA system outperforms the other system greatly. The analysis results show that a system using MC DS-CDMA mode is suitable for future mobile communications systems.

Theory and design of uniform filter banks using all-pass filters

In this paper, the theory of uniform filter banks using all-pass tilters is further developed. A new structure of two stage filter banks using all-pass filter is proposed. The prestage is half-band filter with period, the post-stage is two sets of band-pass filter banks. The pre-stage filter stop-band just controls the don’t-care-band of the post-stage filter banks using all-pass polyphase, so as to realize a continuous stop-band property. Moreover, a method of synthesizing filter bank is derived, which eliminates aliasing and amplitude distortions of the analysis/synthesis system. Finally, an example is given.