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A method of passively estimating the resource block (RB) utilization rate of a serving cell according to radio-quality information measured by a user terminal is proposed. The estimated RB utilization rate can be regarded as the traffic load on the base station. The contribution of this paper is twofold: first, a method for passively estimating a traffic load on a base station via a user terminal...
Rapid growth in data traffic necessitates a proportional growth and improvement in the capacity of cellular networks. A heterogeneous network in which macro cells are overlaid with small cells is a cost efficient and effective paradigm shift for increasing the network traffic capacity. Unplanned deployment of low power base stations with divergent power levels introduces new challenges in heterogeneous...
Significant throughput gains can be achieved in a multi-user MIMO (MU-MIMO) wireless system by exploiting the combination of multi-user scheduling and multi-user diversity. Open-loop MU-MIMO (OL-MU-MIMO) is a codebook based precoding technique where precoders are fixed a priori at the base station (BS) in a known fashion and the user needs to feedback which precoding vector is to be chosen referred...
In Multi-user MIMO (MU-MIMO), the Base Station (BS) schedules multiple users simultaneously on the same resources. Closed loop MU-MIMO uses explicit feedback from each of these users for scheduling and allocation of resources. In this scheme, an estimate of the SINR experienced is fed back by each user and is known as the CQI (Channel Quality Information). This CQI is used by the BS for link adaptation...
Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity to one antenna. Recently, a new class of methods called cooperative communication has been proposed that enables single antenna mobiles in a multiuser environment to share their antennas and generate a virtual multiple-antenna transmitter that allows...
This paper studies the performance of a superposition based approach for multi-user access in the uplink of a wireless cell. The approach uses non-orthogonal signaling and multi-user detection on top of an orthogonal multiple-access method like OFDMA. Path losses depending on the distance between a terminal and the base station and cancellation errors during multi-user detection are taken into account...
In this paper, a quality of service (QoS) based resource allocation for orthogonal frequency division multiplexing (OFDM)-based Cognitive Radio (CR) System with mixed services is proposed. We consider the resource allocation problem for downlink with unoccupied frequency sensed by CR users (CRUs) and total transmission power constraint of the CR base station. In mixed services CR system, the objective...
In the cooperative system with a large number of users, the base station may select a subset of users to serve in order to maximize the total throughput. The brute-force search for the optimal user set, however, is computationally prohibitive. We propose a clustering algorithm for cooperative communication systems, whose objective is to increase the cellular network throughput and further improve...
This paper proposed a joint adaptive soft frequency reuse and virtual cell power control (JAP) algorithm for relay enhanced cellular (REC) system in LTE-A. The JAP algorithm allocates bandwidth to base station and relay node adaptively according to user distribution and target data rate and achieves frequency reuse factor be one among sectors. Furthermore, the JAP algorithm controls transmit power...
This paper addresses the power allocation problem on relaying channels with user-cooperation for multi-user orthogonal frequency division multiplexing (OFDM) systems. The proposed problem is based on dual-mode mobile stations (MSs), where one interface is used to receive signals from a base station (BS) and the other is used to forward the signals to nearby MSs through out-of-band relaying. This dual-mode...
In this paper, we propose a new limited channel feedback algorithm for Orthogonal Frequency Division Multiple Access (OFDMA) systems. The proposed method reports channel information of relative maximum and minimum points of the channel gain from users to base station (BS). Based on the feedback information, BS reconstructs the channel for all the subcarriers using linear interpolation. Compared with...
Cooperative communication in multi-user orthogonal frequency division multiplexing (MU-OFDM) networks is a promising solution to combat wireless channel fading and to increase system throughput. In this paper, with the instantaneous channel state information (CSI) available at base station, the optimal resource allocation strategy is considered in MU-OFDM networks, which is to maximize throughput...
Most of the existing scheduling algorithms in OFDMA and TDMA systems assume the availability of perfect channel quality indicator (CQI) at the transmitter. Unfortunately, this is unrealistic since the receiver (e.g. mobile users) estimates the CQI at time t - ?? and feed back this CQI estimate to the transmitter (e.g. base station). The scheduler uses then this outdated CQI at time t to make the allocation...
An adaptive resource allocation scheme is proposed for regenerative relay-based orthogonal frequency division multiplexing access systems. This scheme allocates subchannels to guarantee fairness between users, and also saves energy by minimising the transmission power. The subchannel allocation for data rate fairness is considered between direct link users and relay stations in the first time subslot...
This paper investigates the resource allocation problem in the downlink of OFDMA cooperative relaying networks with one source (base station) and multiple relay and destination nodes. Assuming that the base station knows all the instantaneous channel gains of all links, we propose a dynamic joint subchannel and power allocation (SPA) scheme whose objective is to maximize the worst user's data rate...
IEEE 802.16 wireless networks, known as WiMAX, employ a mechanism for guaranteed time allocation to mobile stations in order to meet the different quality of service requirements for service flows. The base station allocates contention-based time slots for the stations to transmit their requests for additional bandwidth. Each contention time slot can accommodate a single transmission if there is no...
In this paper, we propose a novel channel quality indicator (CQI) feedback reduction scheme. In the proposed scheme, the base station (BS) calculates the urgency information of each user according to the quality of service (QoS) and queue conditions and informs users of their urgency information, then the users will send the CQI feedback information with different feedback schemes which are threshold...
An adaptive power allocation algorithm called two-hop power allocation (THPA) is proposed to guarantee two-hop data rate balance in regenerative OFDM relay systems. The aim of this algorithm is power efficiency at the transmission node. The base station (BS) or relay station (RS) adjust power adaptively in terms of the difference between the first hop link data rate and the second hop link data rate...
We consider a multiuser MIMO-OFDM downlink system with single antenna mobile terminals (MTs) where channel state information at the base station is provided through limited uplink feedback (FB). In order to reduce the FB rate and signal processing complexity, the available bandwidth is divided into resource blocks (RBs) whose number of subcarriers reflects the coherence bandwidth of the channel. This...
In this paper, power allocation scheme for clusters by mobile station (MS) is investigated in the uplink of a multi-user multiple-input multiple-output (MU-MIMO) and orthogonal frequency division multiplexing access (OFDMA) cellular system. In system level simulation works, without the knowledge of how many clusters will be assigned to a MS, it is a puzzle to decide how much transmission power should...
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