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In this paper, we propose a high performance multiple-input and multiple-output (MIMO) detection algorithm for downlink multiuser MIMO (DL MU-MIMO) with practical errors in IEEE 802.11ac systems. The DL MU-MIMO system using the precoding matrix, which is generated through imperfect channel state information caused by channel estimation error and channel feedback quantization error, has severe performance...
Considering the time duplex division (TDD)-based cellular network, this paper investigates the uplink/downlink interference under the framework of centralized-radio access network (C-RAN). According to different uplink/downlink configurations within three neighboring cells, two fundamental cases are discussed, which can be further classified into several scenarios. For the sake of tackling this kind...
An autonomous downlink interference control method for closed subscriber group (CSG) Long Term Evolution (LTE) femtocells is proposed. The proposed method integrates three interference control methods — power control, timing synchronization, and resource partitioning — by leveraging measurement results in various environments. The interferences on physical downlink data channel (PDSCH) and physical...
In this paper we compare the implicit and explicit methods of providing channel state information (CSI) to the transmitter in a multi-user multiple-input-multiple-output (MU-MIMO) system as specified in the draft specification IEEE 802.11ac [1]. The comparison is made on the basis of both overhead requirements and packet-error-rate (PER) performance. We also propose a hybrid feedback scheme that combines...
In this paper, we analyze the performance of a downlink beamforming system with partitioned vector quantization (P-VQ). A multiuser multiple-input single-output (MU-MISO) downlink beamforming system with accurate channel state information (CSI) at user terminals is considered. The optimization of feedback bits allocation to different partitions and channel direction indicator (CDI), channel quality...
Indoor downlink communication contributes to a large part of the data traffic generated in today's world. Enormous high data rate supporting devices are entering todays market. They demand for high rate wireless indoor coverage for their uninterrupted service. The main challenge lies in working with the existing wireless technologies while providing a future proof centralized optical fiber indoor...
In 3GPP LTE Release-11 the Enhanced Physical Downlink Control Channel (EPDCCH) has been specified for downlink and uplink radio resource assignment notifications to User Equipments (UEs). EPDCCH has been designed to overcome several limitations of the Physical Downlink Control Channel (PDCCH) used in LTE Release 8–10. Some of the important design objectives of EPDCCH are: increased capacity for DL...
In this paper, we focus on robust design of downlink beamforming vectors for multiple antenna base stations (BSs) in a multi-cell interference network. We formulate a robust optimization problem where an individual BS within a cell designs its beamforming vectors to minimize a combination of its sum-power, used for assuring a desired quality of service at its local users, and its aggregate induced...
In this work, we present a low-complexity linear precoding scheme for downlink large-scale multiple-input multiple-output (MIMO) systems. The proposed scheme can achieve near minimum mean square error (MMSE) precoding performance in terms of the sum rate and is based on a matrix polynomial instead of matrix inversion. Simulation results show that matrix polynomials consisting of only a few terms are...
We consider the up- as well as downlink of a cellular network with multi-user multiple-input multiple-output (MIMO) communication and propose to turn the entire network into a two-hop network where a large amount of relays assist the bidirectional communication. To this end, many two-way relays are spread over the entire area of the network. In addition to introducing the concept of ubiquitous relaying,...
In this paper, we propose an enhanced multi-user eigen channel selection (E-MES) solution for multiple-input multiple-output (MIMO) multi-user downlink transmissions exploiting sequential projection and zero-forming (ZF) algorithm. In the existing solutions, eigen channel of each candidate user was pre-defined at the start of the multi-eigen selection, and this limits user's eigen channel adaptation...
In order to exploit multiuser diversity in multiuser MIMO systems with Block Diagonalization, A novel multi-user scheduling algorithm, guarantee both the fairness between users and higher capacity of the system, is proposed in this paper. We provide a number of different scheduling schemes and compare them in the terms of average capacity and the fairness as a function of the number of users. Numerical...
This paper investigates the impact of multiple BER requirements on resource allocation for orthogonal frequency division multiple access (OFDMA) downlink systems. Max-total capacity (MTC) and proportional fairness (PF) problems are considered. With the goal of maximizing either the instantaneous or long-term network capacity, we propose BER-driven resource allocation (BRA) schemes which exploit both...
In wireless resource allocation, improving system throughput and simultaneously enhancing user fairness are two fundamental but contradictory objectives. As for fairness, both short-term and long-term fairness are of significant importance. However, less effort has been dedicated to explore the optimal tradeoff between system throughput and the two mentioned fairness in terms of widely used Jain's...
In this work we study the problem of channel state feedback and user scheduling in a single cell downlink wireless network employing multiple orthogonal parallel channels. The aspect of the system we are focusing on is stability. For user scheduling for stability as a performance measure, both the queue and channel states need to be known by the base station. However channel states can be known only...
Wireless Sensor Networks (WSNs) are being considered for a wide range of applications, however, they still face various challenges, e.g. short communication range and the hidden terminal problem, to name a couple. In this paper, we build up on our previous work in [1], present a WSN prototype that demonstrates this solution, and analyze its performance in different indoor conditions by measurement...
This paper considers the problem of energy-efficient communication in the downlink of a cellular OFDMA network. User scheduling and power allocation are jointly optimized across a cluster of coordinated base stations so as to maximize the weighted sum of the energy efficiencies on the available resource slots under a per-subcarrier power constraint. The asymptotic noise-limited regime is also discussed...
The long term evolution (LTE) networks provide high data rate access to support multi-media services at the expense of more power consumption in user equipment (UE). Discontinuous reception (DRX) mechanism is one of the promising technologies for energy saving in LTE networks, which extends UE battery lifetime effectively. The DRX parameters configuration should make a compromise between power saving...
Interference management is a hot issue in Heterogeneous Networks (HetNets), which is very crucial for the performance promotion in heterogeneous cellular networks with full frequency reuse. Focusing on mitigating the interference between Macrocell and Femtocell, we propose the IM-Torch (Interference Mitigation via Traffic Offloading in Macro/Femtocell + WiFi Heterogeneous Networks) scheme to handle...
In this paper, we investigate how picocells overlaid in macrocells expand their coverage areas under different Cell Range Expansion (CRE) strategies in a macro-pico heterogeneous network. Through system level simulations, the relationships among the presented CRE strategies are specified from both qualitative and quantitative perspective, in which network topologies using different CRE strategies...
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