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Deployment of femtocell in macrocell cellular network which forms two-tier femtocell-macrocell cellular network faces more complicated interference problems, since it uses the same licensed frequency spectrum as its macrocell. This paper addresses the interference problems for downlink transmission in such two-tier cellular communication network. In this paper, interference management using power...
The surge of mobile data traffic has spurred academia and industries to begin developing 5G networks. 5G is meant to overcome limitations of 4G cellular technology relying on the dominant trend of mobile network densification with the deployment of small cell base stations. To accelerate this process, low complexity and inexpensive remote radio heads (RRHs) are deployed massively and connected to...
In this paper, an alternative jointly optimized transceiver scheme is proposed to reduce the multi-user interference in the distributed antenna system (DAS). First a joint design for the pre-coders and combiners is proposed based on the signal-to-leakage-plus-noise ratio (SLNR) maximization and the receive signal-to-interference-plus-noise ratio (SINR) maximization, respectively. Then a modified weighted...
We consider the robust beamforming problem under imperfect channel state information (CSI) subject to SINR constraints in a downlink multiuser MISO system. One popular approach to solve this nonconvex optimization problem is via semidefinite relaxation (SDR). In this paper, we prove that the SDR method is tight when the channel uncertainty bound is small or when the base station is equipped with two...
In this paper we study joint transmitter adaptation and power control in downlink wireless systems with target values imposed on the signal-to-interference+noise-ratios (SINR) at the receiver terminals. We use a general framework based on block transmissions and linear precoders that is applicable to a wide range of wireless systems to formulate this as a constrained optimization problem for which...
Base station coordination has received much attention as a means to reduce the inter-cell interference in cellular networks. However, this interference reducing ability comes at the expense of increased feedback, backhaul load and computational complexity. The degree of coordination is therefore limited in practice. In this paper we explore the trade-off between capacity and feedback load in a cellular...
The major problem of multiuser MIMO precoding and scheduling is the required Channel State Information (CSI) at the base station which needs to be provided to the base station via a feedback channel in case of frequency division duplex. Each user quantizes the channel direction information and computes a Channel Quality Indicator (CQI), e.g., based on the Signal-to-Interference-and-Noise Ratio (SINR),...
This paper focuses on the feedback scheme for downlink Multi-User Multiple-Input Multiple-Output (MU-MIMO) transmission with linear precoding. When the maximum transmission rank per user is limited to one, the multiple-antenna receiver uses a weight vector to transform MIMO channel matrix into an equivalent Multiple-Input Single-Output (MISO) channel vector. Then a Channel Directional Index (CDI)...
This paper is concerned with the game-theory approach in designing the multiuser downlink beamformers in multicell systems. Sharing the same physical resource, the base station of each cell wishes to minimize its transmit power subject to a set of target signal-to-interference-plus-noise ratios (SINRs) at the multiple users in the cell. In that process, each base station determines its optimal downlink...
In this paper, we have discussed the effects of channel interference and evaluated the signal-to-interference plus noise ratio (SINR) for the cognitive radio (CR) network. The cognitive radio is a novel concept of reusing licensed spectrum with unlicensed manner. The most challenging part is the introduction of cognitive radio in the primary user spectrum without causing interference to it. The SINR...
In this paper we consider the Downlink Beamforming (DLBF) and resource allocation problem in MIMO-OFDMA systems. We consider the sum-power minimization or margin adaptive problem. This is a variable Signal to Interference and Noise Ratio (SINR), non-convex optimization problem and many aspects of this problem are not well understood. By using uplink downlink duality we first obtain the expression...
The architecture for the Beyond 3rd Generation or 4th Generation wireless networks aims at integrating various heterogeneous wireless access networks over an IP backbone. To provide seamless mobility, one of the design issues is the vertical handoff support. In this paper, we propose a SINR (Signal to Interference plus Noise Ratio) and AHP (Analytic Hierarchy Process) based SAW (Simple Additive Weighting)(SASAW)...
IEEE 802.16j is an amendment to the IEEE 802.16 broadband wireless access standard to enable the operation of multi-hop relay stations (RS). The relays of IEEE 802.16j include transparent relay and non-transparent relay with scheduling function located in the base station (centralized scheduling) or in the relay station (distributed scheduling). IEEE 802.16j aims to enhance the coverage, user throughput...
In this paper, we consider user equipment which is not yet connected to a given UMTS-FDD network. We propose an algorithm which allows to the user equipment to estimate bit error rate (BER) of a potential downlink in term of the spreading factor and of the power that could be allocated by a base station to this virtual link. This problem is motivated by the context of cognitive radio. Our approach...
In this paper, we study low feedback user grouping in downlink cooperative transmission multi-antenna systems. Users in the same group are served on the same frequency and time resource by multiple cooperative BSs using the zero-forcing precoder. We first derive the user's average received signal to interference and noise ratio (SINR). It shows that each user's SINR is an increasing function of the...
We present field experiment results on multiple input multiple output (MIMO) precoding using orthogonal frequency division multiple access (OFDMA) in the E-UTRA downlink. We measured the throughput performance of 4??4 MIMO precoding with 1- to 4-stream transmission. Time variation characteristics of throughput, SINR, and antenna correlations are compared to evaluate the selection criteria for the...
A joint linear precoding and power allocation scheme based on users' QoS requirement was proposed for the downlink of multi-user MIMO systems. The scheme is developed as follow, on the basis of the precoding, the transmit power allocation for different user will be optimized to maximize the channel capacity and to meet the users' service requirement. The simulation result shows that the algorithm...
In this paper, a novel channel allocation method is proposed to reduce the time-varying effects in downlink OFDMA systems. This method makes use of a Kalman filter in order to predict the user SINR and rate in the next time slot. Based on this estimated rate, the available subcarriers are assigned according to a rate greeding algorithm. Compared with the rate-craving greedy (RCG) algorithm and the...
This paper examines linear beamforming methods for secure communications in a multiuser wiretap channel with a single transmitter, multiple legitimate receivers, and a single eavesdropper, where all nodes are equipped with multiple antennas. No information regarding the eavesdropper is presumed at the transmitter, and we examine both the broadcast MIMO downlink with independent information, and the...
Closed loop transmit diversity has already been adopted by 3GPP for MIMO HSDPA in the form of TxAA and its dual stream counterpart, D-TxAA. While both these transmission techniques provide performance gains for single user (SU) scenarios, they both introduce multi-user interference in the downlink in multi-user (MU) scenarios. In this paper, we study the extension of these transmission techniques...
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