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In this paper we consider two alternate packet structures for estimating the multi-input multi-output (MIMO) powerline channel and their impact on achievable application throughputs. In the first packet structure, an orthogonal pair of OFDM symbols is used to estimate the channel. When compared to single-input single-output (SISO) transmissions that use one OFDM symbol to estimate the channel, there...
In this paper we analyze the performance of advanced OFDM packet scheduling techniques based on 3GPP UTRAN Long Term Evolution (LTE) framework for high velocity scenarios. Based on our previous investigations in system performance analysis, we demonstrate that packet scheduler being part of the whole radio resource management (RRM) process has a major impact on it. On the other hand high user velocities...
This paper presents results from a novel OFDMA multi-cell mobile broadband system level simulator. The tool is used to statistically characterize uplink and downlink inter-cell interference. Without suitable interference management, multi-billion dollar networks can collapse under the strain of heavy traffic loads. Fully loaded interference studies cannot be performed on the network until it has been...
MIMO, OFDMA and cooperative relaying are the key technologies in future wireless communication systems. However, under the usage of these technologies, resource allocation becomes a more crucial and challenging task. In multi-user MIMO-OFDMA relay-enhanced cellular networks, we formulate the optimal instantaneous resource allocation problem including user group selection, path selection, power allocation,...
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...
In this paper, we present a performance evaluation for six scheduling algorithms over a MIMO-OFDM based cellular system. We have selected a set of scheduling algorithms that may use information about the instantaneous channel conditions, status of transmission queues, QoS requirements or pending HARQ retransmissions. Performance evaluation is focused on average delay under different cell load conditions,...
Machine learning algorithms have recently attracted much interest for effective link adaptation due to their flexibility and ability to capture more environmental effects implicitly than classical adaptation algorithms. However, past applications are limited to rather simple configurations such as identifying channel condition or link adaptation in fixed or slowly varying channels. Recently, more...
This paper presents system level downlink performance evaluation results for the TDD based LTE-Advanced networks utilizing some of the most recent technologies for mobile systems. The main enhanced technology components used in the systems include multi-user (MU)-MIMO, intra-site coordinated multipoint (CoMP) transmission and space-time-frequency proportional fair scheduling. Performance comparison...
When fast and accurate channel state information (CSI) at the transmitter is available, opportunistic power control (OPC) is an attractive alternative to signal-to-interference-and-noise ratio (SINR) target following approaches, because it maximizes throughput by taking advantage of fast channel variations. On the other hand, in multiple-input multiple-output (MIMO) systems, open loop schemes such...
Due to the growing demand of transmission capacity of the wireless communication system, multiple-input multiple-output orthogonal-frequency-division-multiplexing (MIMO-OFDM) communication system requires more and more MIMO antennas and a large number of OFDM subcarriers. Thus, the QR decomposition becomes one of the computational bottlenecks in the QR-based MIMO detection. The proposed Givens-Rotation-based...
The use of decision directed (DD) channel estimation in a MIMO-OFDM downlink receiver with a LTE pilot structure is studied in this paper. The space-alternating generalized expectation-maximization (SAGE) algorithm is used to improve the receiver performance from the one obtained by using the pilot symbol based least-squares (LS) channel estimator. The DD channel estimation improves the performance...
In this paper, we propose a sum rate maximizing ordering method for hard decision successive interference cancellation receiver of MIMO-OFDM systems. Compared with conventional ordering methods developed for open loop MIMO systems, the proposed scheme shows considerable improvement in throughput capacity. We propose two simplified methods with considerable complexity reduction and negligible performance...
Multiple-antenna systems have been shown to provide significant performance improvements over single-antenna systems. Theoretical analysis, simulation and experimental testing corroborate improvements in capacity and transmit power/energy savings. Unfortunately, co-located MIMO radios have numerous disadvantages compared to single-antenna radios; such as more complex RF and modem signal processing,...
A link adaptation scheme for MIMO-OFDM systems over high speed rail environment is addressed in this paper. In this study, a selection method of MIMO transmission mode and the modulation and coding scheme (MCS) according to the Rician channel K-factor from our previous work is considered. A hidden Markov model of time-varying Rician channel K-factor is constructed by using the real measured channel...
In this paper, we propose a bit and power allocation strategy for adaptive modulation and coding (AMC) based spatial multiplexing multi-input-multi-output (MIMO) orthogonal frequency division multiple access (OFDMA) systems. This strategy aims to maximize the average system throughput by allocating the available resources optimally among the utilized bands depending on the corresponding channel conditions...
This paper proposes a differential codebook-based method to reduce the feedback overhead for closed-loop MIMO-OFDM systems. With the assumed multimode transmit precoding, both the number of data streams (rank) and the index of precoding matrix are fed back to the transmitter at each sub-band. By exploiting the channel correlation in frequency domain, an enhanced differential codebook (a subset of...
This paper presents throughput performance of 2 × 2 multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) using a testbed in line with the Long Term Evolution (LTE) numerology. Then, this paper clarifies the relation among the throughput, modulation schemes and antenna polarization. The field experiments clearly demonstrate that a measured throughput exceeding 200...
The LOS components of the base station (BS) can provide a high SNR to mobile stations (MSs), but they cannot achieve a high spatial multiplexing gain in the MIMO-OFDMA system. The spatial multiplexing gain is obtained by degrees of freedom between MIMO antenna arrays. MIMO channels should be uncorrelated to achieve the maximum degrees of freedom, and it depends on rich scattering environments which...
This paper proposes a new wireless scheduling methodology which takes advantage of future predictions of data rate for the several users competing for physical access. Based on a system which allows low-cost 3D mapping of an environment in real-time, the predictions are obtained via either low-resolution path-loss prediction given the physical structure of the surroundings or by reference to data...
The MIMO-OFDM Adaptive MCM System changes MIMO scheme, channel coding rate, and modulation scheme, adaptively, according to the channel conditions. And the addition of Pre-coding and Antenna Subset Selection assures a better performance and higher data rate. The MIMO-OFDM Adaptive MCM System achieves a better average throughput performance than a Non Adaptive-MCM system; as SNR increases, the throughput...
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