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This work explores the theoretical and practical performances of the two most recent IEEE standards, 802.11n and 802.11ac. Experiments were conducted to measure data rates to characterize performance effects of distance and interference between different channels. We conclude that the majority of test cases show 802.11ac achieved higher data rates than its predecessor, as expected. However, performance...
The growth of wireless technology made opportunistic scheduling awidespread theme in recent research. Providing high systemthroughput without reducing fairness allocation is becoming a verychallenging task. The purpose of this work is twofold. On the onehand, we proposed a new optimization problem called SatisfactionProbability which consists in maximizing the number of satisfiedusers. On the other...
The performance of ad hoc networks depends greatly on the network topology. Thus, deploying relays or controlling the position of network nodes may impact the performance. Unmanned Aerial Vehicles (UAVs) and other elevated platforms may improve the ground network performance when used as network relays, due to better Line-of-Sight (LoS) conditions. In addition, UAVs can easily move to better locations...
MIMO-OFDM is the generally accepted standard in all WLAN systems. However, this method increases training signals required to estimate the propagation matrix of multi-antenna system. In this study, we investigate methods of shortening VHT-LTF training signal in WLAN systems. Simulation results have shown that 1/2 and 3/4 reduction in VHT-LTF training signal is possible while maintaining a considerable...
This paper analyses the very high system throughput of IEEE 802.11ac by taking into consideration the key features of MAC and PHY layers under a Multiple In Multiple Out (MIMO) channel. Throughput at the MAC layer is calculated from the transmission probability, contention window and transmission stage. Likewise, the new critical attributes of 802.11ac PHY (i.e. modulation and coding schemes, spatial...
Systems comprised of Cognitive Radio Networks (CRN) have been gaining attention in the current literature, given their ability to reduce spectrum scarcity by reusing parts of the spectrum band, while at the same time ensuring a minimum Quality of Service (QoS) margin. In this regard, it becomes important to consider the CRN's usage of multiple access protocols. In this paper, we consider a CRN with...
Performance anomaly is a well-known problem in 802.11 networks. It refers to the case where the aggregated throughput of the multirate network is degraded by slow rate links due to the fair sharing of transmission opportunities. As a result of growing heterogeneity in 802.11 hardware, the coexistence of slow rate and fast rate links are more common and performance anomaly is considered severer. In...
Cognitive Radio (CR) is a promising technology for improving spectrum utilization. When combined with multiple input multiple output (MIMO) technology, which achieves high spectral efficiency, CR MIMO can serve as a solution to the ever increasing demand for spectrum. Antenna selection is a signal processing technique that improves the performance of MIMO systems and reduces their hardware complexity...
In vehicle-to-infrastructure (V2I) communications, continuity and reliability are the most severe issues. Owing to the high-speed mobility of vehicles and frequent hand-off, the connection between vehicle and access point (AP) could not be kept stable. According to the number of APs and the adaptive data rate transmission, we investigate the performance of the proposed method which provides reliable...
This paper presents a comprehensive cross-layer analysis framework on the performance of transmission control protocol (TCP) over free-space optical (FSO) links, which employ the automatic repeat request (ARQ) and adaptive modulation and coding (AMC) schemes. From the framework, we quantify the impacts of different parameters/settings of ARQ, AMC and FSO links on TCP throughput performance. We also...
An EUTRAN offers Multi-Point connectivity from base station (eNB) toward the UE for reliable connection under mobility. This enhances the user experience with committed throughput. Radio resource allocation is a complex arrangement of resources in multiuser scenario, and it became more cumbersome if UE offer optional or alternative path to connect the network. Generally in network radio resources...
This paper provide the performance comparison of the IEEE 802.11n and IEEE 802.11ac Wireless Local Area Network (WLAN). The IEEE 802.11ac protocol currently has been used widely. Network Simulator (NS-3) is used to simulate it. The advantages of the research using Network Simulator are shorter time to explore, low cost and flexibility on scenario developed. Our project analyzes and compares the 802...
In this paper, we propose two novel physical layer aware adaptive network coding schemes for time variant channels, one aiming to maximize the energy efficiency, the other exploiting also the variable modulation order, in an adaptive way. The proposed schemes have been applied to different satellite communications scenarios with different Round Trip Times (RTT). Compared to adaptive network coding,...
Adaptive modulation and coding (AMC), power control (PC) and automatic repeat request protocols (ARQ) represent very important link adaptation (LA) techniques for future generations of wireless communication systems. In order to improve the efficiency of these systems, some combination schemes of these LA techniques have been proposed in the literature. Most of these schemes were interested in the...
The impact of the amplifier noise figure (NF) on the optical network throughput is quantified from an information viewpoint. For every dB of NF decrease, throughput gains between 4% and 7% are reported.
This paper presents our research in developing high performance but low complexity MIMO decoders for the newest WLAN, i.e. 802.11ac. K-best and Trellis methods are proposed to develop the MIMO decoders. Their performances are observed and compared to MIMO decoders which are based on linear and optimal methods, i.e. ZF, MMSE, and ML. Run test of 2×2 MEMO, 64-QAM, Coding rate 3/4, and 40MHz of bandwidth...
In this paper, we consider the multicast resource allocation problem for video streaming in Orthogonal Frequency Division Multiple Access (OFDMA) systems. The video streams are encoded into base layer (BL) and enhancement layer (EL) data by the hierarchical video coding (HVC) scheme. The basic resource unit is a set of contiguous subcarriers (chunk). The problem is formulated to maximize the sum of...
Faster-than-Nyquist (FTN) system provides higher throughput and spectrum efficiency, which is pivotal in future communication. Traditionally in Nyquist system, orthogonality of shaping waveforms is required in order to avoid inter-symbol interference (ISI). However, ISI is permitted in FTN system and thus the advantages of nonorthogonal pulses can be utilized. In this paper, two innovative ones, namely...
Asymmetric data transmission is a challenge factor in wireless communication channel. In this paper, we study the issue of data processing in asymmetric data transmission from different sources in wireless communication channel, and propose a Joint Hierarchical Modulation and Network Coding (JHMNC) scheme. In the proposed scheme, the procedure of JHMNC is analyzed and compared with the traditional...
This paper presents the performance of scheduling for adaptive modulation and coding based on the dynamic margin control. To cover various wireless channel conditions and requirements for multimedia traffic QoS, the selection of suitable MCS (Modulation and Coding Scheme) is important technique in real deployment and management fields. In this paper, we propose dynamic margin control schemes based...
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