Next-generation Mobile Communication Research Articles

Carrier aggregation for LTE-advanced: uplink multiple access and transmission enhancement features

Multiple access and transmission enhancement in support of carrier aggregation techniques has been actively studied in the 3GPP LTEAdvanced standardization process of the nextgeneration mobile broadband communication systems. By means of carrier aggregation, users can access a total bandwidth of up to 100 MHz in order to meet the IMT-Advanced requirements. This article first introduces and compares several uplink multiple access schemes in LTE-Advanced standard. Technical challenges arising from the use of carrier aggregation is then addressed, with focus on reference signals design for uplink transmission. Meanwhile, various candidate options are summarized and compared in terms of their system performance, computational complexity, and design flexibility. The article further proceeds to investigate the link performance with carrier aggregation, taking into account the presence of frequency offset and fast fading in the uplink channel. Numerical results are also presented, which indicate that advanced signal processing algorithms should be further studied and optimized to ensure reliable operation of the 3GPP LTE-Advanced in high mobility.

다중 사용자 및 다중 안테나 하향링크 네트워크에서 적응적 사용자 선택 기법

ABSTRACT Multiple antenna technique is attracting attention as a core technology for next-generation mobile communication systems to accommodate explosively increasing mobile data traffic. Especially, recent researches focus on multi-user multiple input multiple output (MU-MIMO) system where base stations are equipped with several tens of transmit antennas and transmit data to multiple terminals (users) simultaneously. To enhance the performance of MU-MIMO systems, we, in this paper, propose an adaptive user selection algorithm which adaptively selects a user set according to varying channel states. According to Monte-Carlo based computer simulations, the performance of proposed scheme is significantly improved compared to the conventional scheme without user selection and approaches that of exhaustive search-based optimal scheme. On the other hand, the proposed scheme can reduce the computational complexity to    compared to the optimal scheme where  denotes the number of total users.

An S-Band Multifunction Chip with a Simple Interface for Active Phased Array Base Station Antennas

An S-band multifunction chip with a simple interface for an active phased array base station antenna for next-generation mobile communications is designed and fabricated using commercial 0.5-μm GaAs pHEMT technology. To reduce the cost of the module assembly and to reduce the number of chip interfaces for a compact transmit/receive module, a digital serial-to-parallel converter and an active bias circuit are integrated into the designed chip. The chip can be controlled and driven using only five interfaces. With 6-bit phase shifting and 6-bit attenuation, it provides a wideband performance employing a shunt-feedback technique for amplifiers. With a compact size of 16 mm2 (4 mm × 4 mm), the proposed chip exhibits a gain of 26 dB, a P1dB of 12 dBm, and a noise figure of 3.5 dB over a wide frequency range of 1.8 GHz to 3.2 GHz.

An S-Band Multifunction Chip with a Simple Interface for Active Phased Array Base Station Antennas

An S-band multifunction chip with a simple interface for an active phased array base station antenna for nextgeneration mobile communications is designed and fabricated using commercial 0.5-μm GaAs pHEMT technology. To reduce the cost of the module assembly and to reduce the number of chip interfaces for a compact transmit/receive module, a digital serial-to-parallel converter and an active bias circuit are integrated into the designed chip. The chip can be controlled and driven using only five interfaces. With 6-bit phase shifting and 6-bit attenuation, it provides a wideband performance employing a shunt-feedback technique for amplifiers. With a compact size of 16 mm 2 (4 mm × 4 mm), the proposed chip exhibits a gain of 26 dB, a P1dB of 12 dBm, and a noise figure of 3.5 dB over a wide frequency range of 1.8 GHz to 3.2 GHz.

Impact of Multiantenna Real Estate on Diversity and MIMO Performance in Mobile Terminals

In this letter, the impact of antenna real estate is investigated and generalized to multiantenna diversity and multiple- input-multiple-output (MIMO) performance. In particular, an extensive study of two-antenna capacitive coupling elements with different antenna volumes and locations in a small mobile terminal is presented. The discussion reveals the optimally compact two-antenna system that can attain promising 80% and 100% MIMO performance separately at the lower (698-960 MHz) and higher (1710-2690 MHz) frequencies for next-generation mobile communications.

Cooperative Location Management for a Cellular Network with Ad Hoc Communication

The cellular network with ad hoc communication has been foreseen in the next-generation mobile communication system. For such a network, a distance-based (DB) location management scheme cooperated with the ad hoc assistance node (DBCAN) is proposed in this paper. Allowing a mobile terminal to pass its mobility information to the ad hoc assistance node (AAN) with appropriate location updating, DBCAN can effectively reduce the paging cost and limit the paging delay. Moreover, DBCAN includes a method to determine whether AANs should be utilized or not to make cost effective. Our simulation results show that DBCAN can effectively reach cost reduction and still get performance improvement even if the probability to successfully deliver mobility information to AANs falls to the median level.

Ex-ante evaluation of the consumers' preference for the 4th generation mobile communications service

Research about next-generation mobile communications (MCs) technology has become an issue in these days since MCs bear a close relationship to our daily lives. The third generation (3G) MCs technology is now evolving into the fourth generation (4G) MCs technology. An initial analysis of potential consumer preferences for the technology is essential to ensure successful strategies and changes. This paper attempts to apply a choice experiment to evaluating consumers' willingness to pay (WTP) for each attributes of the 4G technology. The experiment encompasses five attributes: data rates, the quality of communications service, the number of broadcasting channels, video-on-demand (VOD) service, and supplementary services. We consider the trade-offs between the price and attributes of the 4G for selecting a preferred alternative and derive the marginal WTP (MWTP) estimate for each attribute. The results indicate that the average MWTP for the improved communications service is KRW 4443 (USD 4.03) and the average MWTP for one more broadcasting channel is KRW 67 (USD 0.06). The average MWTPs for VOD and supplementary services is KRW 1932 (USD 1.75) and KRW 1601 (USD 1.45), respectively.

China Next-Generation Information Technology (NGIT) Networks Implementation

In March 2011, China released its 12th Five-Year Plan, (FYP, 2011-2015) which contains road maps and goals to guide industries and local government for the implementation of the plan and the outcome will then be evaluated. Willy Shih, professor of Harvard Business School, listed eleven items for the Next Generation Information Technology (NGIT), which is one of the seven Strategic Emerging Industries (SEIs) that government will support in this plan and it is expected these targeted seven priority industries will increase GDP contribution from 2% to 8% by 2016 and 15% by 2020, and will be supported by a budget allocation of RMB 10 trillion (USD. 1.52 trillion) over the five year period. The main NGIT items include: Next-generation mobile communications, Next-generation core Internet equipment, Convergence of Telecom/ Cable TV/ Internet networks, Cloud Computing, etc. From a user point of view: Users today will want information available right away, and don’t care how the digital data is transferred or through which channels. Therefore, we looked at this as one giant system functioning together. The whole system’s functionality, including the policy, is the main reason for attaining the sustainability of the telecom industry’s future growth. The Objective of this paper is to try to examine the sustainability for future China telecom operators’ growth, and the China NGIT future operations will depend on the policies and regulations that government will practice. The sustainability can be categorized under several areas: the new technology including new standards has to be feasible, new services and new content has to be generated, new customers have to be created and most importantly new regulations and policies have to be in place. The sustainability relies also on the social-technical-economic factors; the new policies on these related areas in the 12th FYPs will be discussed. The Actor-Network Theory (ANT) used as an important tool for the case study in this paper it will be used to explain how the China governmental departments worked together to create a new policy or made new decisions in the past? The formation of the 12th FYPs and its main content along with three related cases studies will be discussed. Will these current Chinese ways still be sustainable in the future? Suggestions will be made followed by the Fair Division Problem Solution of the Corporative Game Theory to fit the special competition environment that China had. For example: three Telecom Operators working under the supervision of government and possessing most of the resources of the country for transferring information including: spectrums/ fiber backbones (land & ocean), but the division for the subscribers of these three telecom operators was not equally spread. (By March, 2012. Mobile Subscribers for China Mobile were 667million, China Unicom had 209million, China Telecom had 135million.) The Chinese government’s main concern was security of the information, for example, in China officially there was neither 3 X movies nor violent ones and the content on the web would be blocked if it was deemed inappropriate. The government also seriously monitored the telecom market’s healthy competition environment. Will this be enough for growth?The heuristic analysis and insights in this paper are based on achievable public information and documents such as China Daily, Marbridge Daily, available Web pages and interviews. The interesting trend predicted was that the three telecom operators seemed to be moving towards the Golden Rule from the subscriber number division? China is a developing country, the political system and economic path were all different from others, but still many ways and experiences can be shared and lessons can be learned for other countries. Investor opportunity is huge, but the mind set has to change and a new way of thinking adopted.

Diversity Evaluation of Two-Port Antenna System for a Mobile Terminal

Next-generation mobile communication systems require high data transmission rate and low bit error rate, but multi-path fading still stands as a major problem. Antenna diversity techniques can overcome the problem. In this paper, we thoroughly study the antenna diversity performance on a mobile terminal through theoretical analysis, computer simulations, and practical prototype measurements. Specifically, a genetic methodology is developed to accurately evaluate the diversity gain achieved in the mobile terminal from both power level approach and correlation approach. Throughout the simulations and measurements, we demonstrate that it is beneficial to implement antenna diversity on mobile terminal side, and high diversity gain can be achieved when the antennas are placed in the terminals properly. Moreover, further improvement of the diversity gain can be obtained from the implementation of the matching networks.

무선이동통신 제어환경에서 전파특성 및 알고리즘 분석에 관한 연구

Users of the Information Age, IT usage patterns of the wired broadband information services and various forms of the same quality wireless multimedia services are required. Changes of these times the next-generation mobile communications (IMT-Advanced) has emerged as the necessity of developing its current voice and packet data communications on the move in the high-speed 100Mbps, 1Gbps in stationary and slow data transmission rates up to fixed-mobile convergence based on needed to provide ubiquitous service platform for the realization of IMT-Advanced is the time for preparation. In particular, 3-5GHz band, focused on mobile communications can be used to secure the necessary frequency band relocated and the existing crosstalk analysis methodology developed for the services rendered, and the frequency of such results to obtain new spectrum for IMT-Advanced for the country to secure the frequency characteristics and IMT-Advanced 3-5GHz band for the radio frequency of the characterization techniques necessary to develop a national wireless communication interference and frequency-based technology acquisition and management skills were identified.

Design and Flight Test Results of Robust Attitude Controller for the ETS-VIII Spacecraft

AbstractThis paper reports the flight test results of robust attitude controller for Engineering Test Satellite VIII (ETS-VIII) spacecraft. The main mission of ETS-VIII is to support next-generation mobile digital communications, and for this purpose it is equipped with two large deployable antenna reflectors and a pair of large solar paddles that rotate around the pitch axis. For the spacecraft, the authors have proposed and demonstrated several control methods based on the advanced control theories for the linear parameter varying multi-input multi-output system. The aim is to develop a baseline for future controller design technology for this class of satellite instead of existing classical PID control laws. This paper describes the on-orbit experiment results and compares these controllers performance.

Neural Networks and Wireless Communications Modeling

This paper presents a free software tool that supports the next-generation Mobile Communications, through the automatic generation of models of components and electronic devices based on neural networks. This tool enables the creation, training, validation and simulation of the model directly from measurements made on devices of interest, using an interface totally oriented to non-experts in neural models. The resulting model can be exported automatically to a traditional circuit simulator to test different scenarios.&#61472

On distributed antenna systems with limited feedback precoding: Opportunities and challenges

The distributed antenna system is a promising technique to enhance system performance in next-generation broadband wireless mobile communications. The application of linear precoding with space time codeword based on channel state information can further enhance the link quality and reduce the receiver complexity in DASs. However, designing the optimal codebook for DAS to convey the precoding information remains an open issue. This article provides a tutorial addressing various issues of DASs with limited feedback, focusing on the challenges in its codebook design. A suboptimal codebook design is then proposed, suitable for DAS. Furthermore, an effective feedback reduction strategy without performance loss is presented by exploiting the channel correlation property. Numerical results are given to demonstrate the effectiveness of the proposed scheme.

Performance of iteratively decoded bit-interleaved coded modulation with chaos based interleaving strategies

Bit-interleaved coded modulation with iterative decoding (BICM-ID) is a bandwidth efficient transmission scheme which is well suitable for next-generation mobile communications. The interleaver design is critical to the high performance of BICM-ID. In this paper we investigate the application of the chaos theory to the interleaver design to further improve the performance of BICM-ID. A new interleaving scheme based on the chaos theory is proposed. Compared with the random interleaver, the proposed approach has the advantages including lower system delay and higher transmission efficiency. Simulation results in both additive white Gaussian noise (AWGN) channel and Rayleigh fading channel are provided, which demonstrates that the new interleaver is better than the random interleaver and exhibits excellent performance when applied to the BICM-ID system.

Path Morphology 개념을 이용한 MIMO 채널 모델링

차세대 이동 통신 시스템에서는 높은 주파수 대역, 광대역, 다중 안테나(MIMO antenna)의 사용이 예상된다. 또한 무선 통신의 급격한 수요와 이동 통신 서비스의 폭발적인 증가로 인해 차세대 이동 통신 시스템의 최적화를 위한 검증 모델 개발 연구가 필요하다. 기존 MIMO 채널 모델의 경우 도심, 부도심, 시골, 개활지 등으로 포괄적으로 전파 환경을 분류하여 연구를 수행하였으나, 이러한 접근 방법은 예를 들어 도심 환경 내에서도 다양한 morphology가 존재할 수 있기 때문에 모델링 정확도 측면에서 취약성을 가질 수 있다. 본 논문에서는 path morphology 개념을 도입하여 전파 환경을 송 수신기 사이의 건물의 높이, 밀집도 등을 고려하여 세부적으로 분류하는 방법을 제안하였다. 광선 추적(ray tracing) 기법을 이용하여 각 환경별 delay spread(DS), AoD와 AoA의 angular spread(AS)를 분석하고, 이를 바탕으로 국내 환경에 적합한 MIMO 채널 모델을 제시하였다. The use of high frequency band, broad band and MIMO antenna is expected in the next generation mobile communication system. By the rapid increase of demand for wireless communications and the explosive increase of the mobile communication services, researches for optimization of next-generation mobile communication system are required. In the existing MIMO channel models, propagation-environments are commonly classified into urban, suburban, rural area, etc. However such approaches can have drawbacks in that many different morphologies may exist even in the urban area, for example. In this paper, we introduced path morphology concept, and proposed the method of morphology classification considering the building height, density, etc. Delay spread(DS), angular spread(AS) of AoD and AoA analyzed for each environment using the ray tracing technique. Based on the analysis, a MIMO channel model appropriate in domestic environment was suggested.

Reduced-Complexity ML Signal Detection for Spatially Multiplexed Signal Transmission Over MIMO Systems With Two Transmit Antennas

In this paper, we address spatially multiplexed (SM) multiple-input-multiple-output (MIMO) systems that are expected to be used in next-generation mobile communication systems that require high-speed data transmission. The data-transmission rate of an SM MIMO system increases in proportion to the number of spatial streams it transmits. However, it is hard to implement large numbers of spatial streams due to the spatial limits of mobile units and the high cost of installing many antennas. In this paper, we focus on the case of two spatial streams and propose a novel signal-detection technique. We first define the bidirectional detectability of a 2-D complex vector, and using the fact that only a small number of vectors, including the maximum-likelihood (ML) solution vector, satisfy the bidirectional detectability, we reduce the search space, thereby enabling efficient ML signal detection at the receiver.

Timing Offset Interference Canceller in Multi-Link Transmission for OFDM-Based Cellular Radio Communications

In next-generation mobile communications, it is important to improve the throughput of the cell edge as well as that of the whole cell. Multi-link transmission from two adjacent BSs has been studied for improving the throughput at the cell edge in OFDM-based cellular systems, which are major candidates for next-generation mobile communication systems. In multi-link transmission, an MS at a cell edge receives signals from both adjacent BSs by orthogonally multiplexing those signals in the frequency domain. Therefore, the cell-edge MS can utilize the frequency and power resources of both adjacent BSs, which improves the cell-edge throughput. However, when the received timing difference between the signals from both BSs exceeds the maximum permissible value, adjacent-channel interference is caused by the collapse of the orthogonality. In this paper, to resolve this issue, we propose a novel timing-offset interference canceller. To clarify the performance of the proposed canceller, this paper evaluates its performance with respect to the residual interference power and the BER by computer simulation.

On-Orbit Experiment Results of Robust Symmetric Attitude Controller for ETS-VIII Spacecraft

AbstractThis paper reports results of an on-orbit experiment using Engineering Test Satellite VIII (ETS-VIII) spacecraft. The ETS-VIII was launched into geostationary orbit by the Japan Aerospace Exploration Agency in December 18 2006. The main mission is to support next-generation mobile digital communications, and for this purpose it is equipped with two large deployable antenna reflectors and a pair of large solar paddles that rotate around the pitch axis. For the spacecraft, the authors have proposed several control methods by applying advanced control theories for the linear parameter varying multi-input multi-output system. Among them, this paper describes the results using two degrees-of-freedom control system based on symmetric feedback control.

Technologies and standards forTD-SCDMA evolutions to IMT-advanced

The current TD-SCDMA commercialization in China brings about many issues concerning the implementation of TD-SCDMA technology, the market, and its applications. In order to make TD-SCDMA successful, evolution from the current TD-SCDMA standards to international mobile telecommunications-advanced are anticipated. TD-SCDMA standards and technologies will take a home-made evolution path in China, aiming at a smooth migration to the next-generation mobile communication system. This article provides a brief description of the evolution strategies of both the standards and key technologies, in which the evolution is divided into three phases. The state of the art of TD-SCDMA evolution is surveyed, and its technologies and standards in different evolution phases are characterized. Single- and multi-carrier high-speed packet access is specified in the first evolution phase for guaranteeing the high transmission bit rate of packet services. Meanwhile, broadcast services are supported, and the HSPA evolution is also incorporated in this phase. Long term evolution is defined in the second evolution phase for approaching similar performance as mobile WiMAX, where channel-reciprocity- based multiple antenna techniques are utilized. The last phase is the revolution to the IMT-Advanced system and becoming one alternative standard in beyond 3G systems, which is based on the evolution of TD-LTE. The difference of standardizations between 3GPP and local standard releases are introduced. Some challenging work and open issues in different evolution phases are discussed as well.

Relay technologies for WiMax and LTE-advanced mobile systems

Relay technologies have been actively studied and considered in the standardization process of next-generation mobile broadband communication systems such as 3GPP LTE-Advanced, IEEE 802.16j, and IEEE 802.16m. This article first introduces and compares different relay types in LTE-Advanced and WiMAX standards. Simulation results show that relay technologies can effectively improve service coverage and system throughput. Three relay transmission schemes are then summarized and evaluated in terms of transmission efficiency under different radio channel conditions. Finally, a centralized pairing scheme and a distributed pairing scheme are developed for effective relay selection. Simulation results show that the proposed schemes can maximize the number of served UE units and the overall throughput of a cell in a realistic multiple-RS-multiple-UE scenario.