1,721,132 research outputs found
PHY-supported frame aggregation for wireless local area networks
No full textClick on the DOI link to access the article (may not be free).An aggregate medium access control (MAC) service data unit (A-MSDU) contains multiple subframes with a single sequence number. Hence, it has a major drawback in environments with high error rates because if any subframes are corrupted, then the entire A-MSDU will be lost. In addition, performance of the A-MSDU depends strongly on the choice of parameters, such as frame size, modulation level, coding rate, and spatial mode. In this paper, a novel link-adaptation mechanism, dubbed physical (PHY)-supported frame aggregation (PSFA), is proposed over IEEE 802.11 networks, and its performance is analyzed. The proposed PSFA technique is based on a cross-layer interaction that enables joint optimization of various parameters between the PHY and MAC layers. This paper derives a new packet error rate (PER) expression for convolutionally coded multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems as an example. Then, this PER expression is used to efficiently estimate the link quality, given the channel conditions and system parameters, and most importantly, it is able to facilitate a parametric study of the cross-layer interaction. In the proposed PSFA algorithm, we present a rule for selecting the parameters so that MAC throughput is maximized. It is shown analytically and verified using Monte Carlo simulations that this choice of parameters can improve throughput performance significantly and also ensure quality of service (QoS) requirements compared to existing conventional algorithms.MSIP (Ministry of Science, ICT & Future Planning), Korea in the ICT R&D Program 2013 and in part by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2005-0049408)
Flexible routing algorithm for digital intermediate frequency interoperability satellite systems using fair buffer queuing
No full textDate of Conference: 17-20 February 2025
Date Added to IEEE Xplore: 13 May 2025
Conference Location: Honolulu, HI, USAFunding Agency: 10.13039/100006831-United States Air ForceWith changes in the Digital Intermediate Frequency Interoperability (DIFI) standard, there is now a standardized way for DIFI systems to communicate various flow control details. These details can be used to increase the reliability of satellite systems in terms of packet loss and delay. We will examine a deterministic routing scenario in which a satellite is used as a relay between two earth stations. To accomplish this goal, we propose a new queuing algorithm for network scheduling called "fair buffer queuing." We will also briefly discuss situations that would allow us to further leverage the changes from the updated flow control mechanisms included in the DIFI 1.2.0
Design of Millimeter Wave Hybrid Beamforming Systems
No full textMillimeter wave (mmWave) signals experience a significant path-loss in free space. To overcome this weakness, a large number of antennas are needed to obtain a high beamforming gain. Although a large number of antennas can be implemented in small area due to the short wavelength, the digital beamforming techniques cannot be implemented easily due to the high complexity of hardwares. To solve this problem, the hybrid beamforming systems which have smaller number of radio frequency (RF) chains are proposed in the literature. Although the hybrid beamforming systems may achieve the spectral efficiencies of the digital beamforming systems closely, the spectral efficiency cannot be monotonically increase along with the number of data streams due to the limited scattering in mmWave channel. In this paper, we provide a guide for the design of mmWave hybrid beamforming systems. We find the optimal number of streams, and present the spectral efficiency achievable region in which the system guarantees the reliable communications with the lowest cost
Quantization Error Reduction Scheme for Hybrid Beamforming
No full textIn a multiple-input multiple-output (MIMO) system of a large number of antennas, the requirement of an analog to digital converter (ADC) in each antenna string causes high implementation cost and excessive signal processing. Hence, a hybrid beamforming has been proposed in the literature as a solution. However, still quantization errors introduced at the analog beamformer part can lead to performance degradation. This paper is to present a quantization error reduction scheme for a hybrid beamformer in a 2 by 2 MIMO system. The key idea is to sacrifice the data rate from a full rate to a half rate, estimate all user data in a digital baseband, and then restore the received signal at each antenna string. By using the restored received signal and the residual (which is calculated in the estimator), quantization error can be reduced. Simulation results verify that the proposed scheme can improve the bit error rate performance with a resolution of smaller number of bits
Optimal power allocation for two-way decode-and-forward relay networks with equal transmit power at source nodes
No full textThis paper proposes an optimal power allocation method for two-way decode-and-forward (DF) relay networks when transmit power values at source nodes are the same. In this paper we consider the multiple access (MAC) capacity for DF relaying scheme. Using case studies, it analytically determines the optimal power values for the two source nodes and one relay node. The achievable sum rate is maximized under a sum power constraint for given squared magnitude of the channel coefficients. Finally, numerical results show that the achievable sum rate for proposed optimum power allocation is greater than or equal to that for equal power allocation
AF MIMO Beamforming Relay Networks under Various Power Constraints
No full textThis paper studies amplify-and-forward (AF) multiple-input multiple-output (MIMO) beamforming relay networks based on the minimum mean square error (MMSE) criterion under various transmit power constraints. The primary contribution of this paper is the derivation of a set of optimal relay amplifying matrices and source-destination beamforming vectors under diverse conditions of transmit power constraints on the source and the relay for the AF MIMO wireless relay network. By comparing the bit error rate (BER) performance of each case,
an efficient design of a half-duplex AF relay system is presented
Distributed AF beamforming relay networks under transmit power constraint
No full textThis paper investigates minimum mean square error (MMSE)-based amplify-and-forward (AF) relay amplifying matrices and source/destination beamforming vectors under perfectly known channel state information by imposing constraints on the transmit power of source and relays, separately and individually. The main contribution of this paper is the derivation of a set of relay amplifying matrices and source/destination beamforming vectors under transmit power constraints on the source and relay. Additionally, the SNR and the MMSE cost function behaviors will be investigated numerically and analytically
Cooperative AF wireless relay strategy under relay power constraint
No full textThis paper presents an optimal relay amplifying matrix based on various schemes, such as zero-forcing (ZF) and minimum mean square error (MMSE), for a cooperative amplifyand-forward (AF) wireless relay network consisting of a one source-one-destination pair with a single antenna and one relay with N antennas. The total relay transmission power constraint is employed. Even though different schemes and methods are applied to determine the optimal relay amplifying matrix, the identical one is derived. By adopting the derived optimal relay
amplifying matrix, various analytical and numerical discussions, such as achievable rate (AR), are presented
Two-way amplify-and-forward relay strategies under relay power constraint
No full textThis paper proposes a two-way amplify-and-forward (AF) wireless relay network consisting of two sources with a single antenna and one relay with multiple antennas. The relay amplifying matrix under a power constraint at the relay is presented. The minimum mean square error (MMSE) criterion with self-interference cancelation is employed using vectorization and singular value decomposition (SVD) methods, while the MMSE and matched-filter (MF) criteria without self-interference cancelation are implemented. Using the derived optimal relay amplifying matrix, the average bit error rate (BER) and average mean square error (MSE) behaviors are evaluated
AF Wireless Relay Network Analysis under Receiver Power Constraint
No full textThis paper presents both cooperative and noncooperative amplify-and-forward (AF) relay networks consisting of a one-source-one-destination pair and N-relays under receiver power constraint (RPC) at the destination. The optimal AF relay amplifying matrices for the relays by minimizing the mean square error are analytically derived. This paper also shows that the performance of the optimum cooperative relay network is identical to that of the optimum noncooperative network, as long as the same receiver power constraint is applied. The purpose of the RPC is to reduce the interference level for users located in neighboring cells. Finally, using the derived optimal relay amplifying matrices, the achievable rate, the pairwise error probability, and the outage probability are investigated
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