Mingju Li

Bio: Mingju Li is an academic researcher from NTT DoCoMo. The author has contributed to research in topics: Base station & Terminal (electronics). The author has an hindex of 9, co-authored 32 publications receiving 324 citations.

Energy Source Aware Target Cell Selection and Coverage Optimization for Power Saving in Cellular Networks

Abstract: The spread of mobile connectivity is generating major social and economic benefits around the world, while along with the rapid growth of new telecommunication technologies like mobile broadband communication and M2M (Machine-to-Machine) networks, larger number of various base stations will be employed into the network, which will greatly increase the power expense and CO2 emission. In order to degrade the system power expense, variety of researches on new energy and novel transmission technology are put in agenda. In this paper, instead of reducing the absolute power expense, the research focuses on guiding more power consumption into green source energy, which implying that the UEs (User Equipment), especially the cell edge UEs, will have preferential access to the BSs (Base Station) with natural energy supply. To realize the tendentious connection, two detailed approaches are proposed, the HO (Hand Over) parameter tuning for target cell selection and power control for coverage optimization. The system evaluation shows that, by proper setting of parameters in HO and power control, both of the two approaches can achieve good balance between energy saving effect and system throughput impact.

Component Carrier Management for Carrier Aggregation in LTE-Advanced System

Abstract: This paper focuses on investigating appropriate management of Component Carriers(CCs) in carrier aggregation( CA) system, which is identified as one of the most distinct features of 4G systems including Long Term Evolution- Advanced (LTE-A). An LTE-A user equipment (UE) is allowed to concurrently utilize multiple carriers, which leads to scalable increase in user throughput. However, in certain circumstances, aggregating entire available carriers for a UE is not meaningful due to probably low channel quality or high traffic load in some of the CCs. Therefore, how to make good use of multiple carriers in real deployment scenarios is an important issue. Based on the analysis of resource allocation across multiple carriers in Layer-2, two CC management methods in Layer- 3 are proposed. The proposed method is shown by simulation results to be effective in providing comparable user throughput with lower implementation complexity, as compared to solely ingenious resource allocation.

Switching method, mobile terminal and base station

Abstract: The invention discloses a switching method, which comprises that: when sending a switching instruction to a mobile terminal, a service base station continues to allocate an uplink transmission resource and a downlink transmission resource for the mobile terminal, so that after receiving the switching instruction, the mobile terminal can continue to maintain the data transmission with the service base station, and simultaneously execute the random access process to a target base station so as to acquire the uplink synchronization information of the target base station. The invention also discloses a mobile terminal and a base station. Through the switching method of the invention, the switching interruption time in the switching process can be shortened greatly, and the switching performance is improved.

Radio communication system, radio communication method, user terminal, and radio base station

Abstract: To perform rate matching appropriately even when downlink signals are transmitted from a plurality of transmission points to a user terminal, a radio communication system having a user terminal capable of coordinate multi-point transmission and reception with several radio base stations is provided. A radio base station transmits downlink control information including bit information defining a predetermined rate matching pattern to the user terminal. The user terminal receives the downlink control information and performs rate matching based on the bit information defining the rate matching pattern. A combination of a cell-specific reference signal pattern and an interference measurement reference signal pattern in the case of transmission from several radio base stations each using an MBSFN subframe or NCT is defined in predetermined bits. The user terminal performs rate matching based on the bit information and the subframe configuration and interference measurement reference signal pattern of the radio base station.

Handover method, mobile terminal and base station

Abstract: Disclosed is a handover method, which includes: continuing, by a serving base station, allocating an uplink and downlink transmission resource for a mobile terminal when sending a handover command to the mobile terminal, so that the mobile terminal is capable of keeping a data transmission with the serving base station after receiving the handover command, and meanwhile executes a random access process to a target base station to obtain uplink synchronization information of the target base station. This invention also provides a mobile terminal and a base station. The handover method of this invention can greatly reduce the handover interruption time of the handover process, and improve the handover performance.

User terminal, radio base station and radio communication method

Abstract: The present invention is designed to provide a user terminal, a radio base station and a radio communication method of novel structures that can achieve a good communication environment. A radio base station non-orthogonal-multiplexes downlink signals for a plurality of user terminals over a given radio resource, a user terminal having received the downlink signals for the plurality of user terminals decodes downlink signal for another user terminal, judges whether or not the downlink signal for the other user terminal has been successfully received, based on the decoding result of the downlink signal, reports a judgement result as to whether or not the downlink signal for the other user terminal has been successfully received and a judgement result as to whether or not a downlink signal for the user terminal has been successfully received, to the radio base station, and then the radio base station executes retransmission control of downlink signals based on reports from the user terminal.

User terminal, wireless base station, and wireless communication method

Abstract: In order that a user terminal properly identifies a connection cell in a radio communication system (LTE-U) for operating LTE in an unlicensed band, a user terminal for communicating with a radio base station in an unlicensed band is provided with a detection section that detects a synchronization signal transmitted from a radio base station using a dummy cell ID used in common among a plurality of radio base stations, an estimation section that performs channel estimation using a reference signal, and a reception processing section that performs reception processing of system information transmitted from a radio base station using a channel estimation result.

On Optimizing Green Energy Utilization for Cellular Networks with Hybrid Energy Supplies

Abstract: Green communications has received much attention recently. For cellular networks, the base stations (BSs) account for more than 50 percent of the energy consumption of the networks. Therefore, reducing the power consumption of BSs is crucial to achieve green cellular networks. With the development of green energy technologies, BSs are able to be powered by green energy in order to reduce the on-grid energy consumption, thus reducing the CO2 footprints. In this paper, we envision that the BSs of future cellular networks are powered by both on-grid energy and green energy. We optimize the energy utilization in such networks by maximizing the utilization of green energy, and thus saving on-grid energy. The optimal usage of green energy depends on the characteristics of the energy generation and the mobile traffic, which exhibit both temporal and spatial diversities. We decompose the problem into two sub-problems: the multi-stage energy allocation problem and the multi-BSs energy balancing problem. We propose algorithms to solve these sub-problems, and subsequently solve the green energy optimization problem. Simulation results demonstrate that the proposed solution achieves significant on-grid energy savings.

Powering mobile networks with green energy

Abstract: Explosive mobile data demands are driving a significant growth in energy consumption in mobile networks, and consequently a surge of carbon footprints Reducing carbon footprints is crucial in alleviating the direct impact of greenhouse gases on the earth environment and the climate change With advances of green energy technologies, future mobile networks are expected to be powered by green energy to reduce their carbon footprints This article provides an overview on the design and optimization of green energy enabled mobile networks, discusses the energy models for the analysis and optimization of the networks, and lays out basic design principles and research challenges on optimizing the green energy powered mobile networks

A Survey of Radio Resource Management for Spectrum Aggregation in LTE-Advanced

Abstract: In order to satisfy the requirements of future IMT-Advanced mobile systems, the concept of spectrum aggregation is introduced by 3GPP in its new LTE-Advanced (LTE Rel. 10) standards. While spectrum aggregation allows aggregation of carrier components (CCs) dispersed within and across different bands (intra/inter-band) as well as combination of CCs having different bandwidths, spectrum aggregation is expected to provide a powerful boost to the user throughput in LTE-Advanced (LTE-A). However, introduction of spectrum aggregation or carrier aggregation (CA) as referred to in LTE Rel. 10, has required some changes from the baseline LTE Rel. 8 although each CC in LTE-A remains backward compatible with LTE Rel. 8. This article provides a review of spectrum aggregation techniques, followed by requirements on radio resource management (RRM) functionality in support of CA. On-going research on the different RRM aspects and algorithms to support CA in LTE-Advanced are surveyed. Technical challenges for future research on aggregation in LTE-Advanced systems are also outlined.