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The usage of IEEE 802.11 wireless equipment has been growing in recent years. Nevertheless, the spectrum which is used by such equipment is already overcrowded and due to this, the performance of wireless devices is decreasing. Recently, IEEE 802.11 was updated with the latest IEEE 802.11ac version. IEEE 802.11ac provides higher modulation capabilities and more robustness against interference. With...
This paper proposes a new scheme for providing an additional throughput in LDM system by virtue of unique features of non-uniform constellations for low code rate. The proposed scheme provides an enhanced system throughput while any performance loss in both core- and enhanced-layer would not be induced. The proposed scheme could be applied for only limited modulation and coding combinations such as...
Free space optical link provides a number of advantages in terms of high data rate, resistance to jamming and license free data transmission. Atmospheric turbulence is a great challenge in clear sky when an optical wave is propagated through the atmosphere. Since turbulence-induced fading changes slowly, adaptive techniques can be used to mitigate the problem of fading. Compared to classical adaptive...
This paper investigates the performance of a Cognitive Radio Network, emphasizing the secondary users performance. Users are modeled by a priority M/G/1 queue, in which primary users have a higher priority than secondary users. The performance of the system is evaluated by a performance metric called Power Metric. We considered that transmissions occur over a Nakagami-m channel model. Different modulation...
In this paper, we are interested in the optimal redistribution of the available budget in average transmit power per packet among potential packet transmission attempts for improved Automatic Repeat reQuest (ARQ) protocol. A conventional ARQ protocol was combined in [5], with both Adaptive Modulation and Coding (AMC) and Power Control (PC) to improve spectral efficiency, while satisfying an average...
When communicating at high-speed environment such as high-speed rail, the signals may encounter fast fading due to the terrain changes. In such communication environment, signal prediction can help improve the system throughput and reduce packet loss. In this paper, we propose a prediction mechanism called Window Weight Moving Average (WWMA) to predict the signal strength. We also analyze the real...
Modern wireless communication systems adapt the employed Modulation and Coding Scheme (MCS) to the instantaneous channel quality in order to maximise the amount of bits correctly transmitted per time unit (i.e., the throughput). An important aspect in the study of this technique, referred to as Adaptive Modulation and Coding (AMC), is the characterisation of the link throughput performance under realistic...
In the world of telecommunication, demand for 3G mobile communication services still dominates the global market. It continues to grow despite the introduction of new technologies such as LTE and LTE-A. Hybrid Automatic Repeat Request (HARQ) and Adaptive modulation and coding (AMC) are among the key performance enhancing techniques adopted in High Speed downlink packet access (HSDPA). Limiting the...
Much work has been done in the area of telecommunications transmission parameters and, in particular, Channel Quality Indicators, to analyse the best ways to improve the performance and quality of communications. However, there is a gap in published papers when it comes to real-world experiences with CQI reports and network-side analysis of transmission parameters that can provide information about...
Long Term Evolution (LTE) developed by Third Generation Partnership Project (3GPP), is the access part of the Evolved Packet System (EPS). LTE physical layer is based on Orthogonal Frequency Division Multiple Access (OFDMA) with Quadrature Amplitude Modulation (QAM). Although there has been lots of enhancements in the LTE physical layer, yet higher order modulation schemes were not introduced in the...
Due to the exploding evolution of wireless communication systems, energy efficiency (EE) becomes the concern of many researches. In this context, we examine this metric into multiband orthogonal frequency division multiplexing ultra wideband (MB-OFDM UWB) systems. Indeed, the focus is about investigating a cross-layer design based on the joint combination between data link layer through the hybrid...
In this work we implement features for IEEE 802.11ac in the NS-3 simulator, in particular wider channels and bit-error calculations for higher modulation coding schemes. We also implement four wireless LAN deployment scenarios from the 802.11ax working group scenario document, and evaluate their performance under different operating conditions. Our simulation results demonstrate that many nodes in...
In wireless communication networks link adaptation techniques are widely used to improve the quality by adapting various parameters of channel. Adaptive modulation and coding (AMC) is one such technique which adopts various modulation techniques based on certain channel conditions like received signal power or signal strength or distance. This paper compares simulation results of adaptive modulation...
In this paper, we present a throughput optimized cross-layer design for multiple-input multiple-output (MIMO) wireless systems. The proposed design efficiently combines power control (PC), adaptive modulation and coding (AMC) and MIMO technology at the physical layer, with an automatic repeat request (ARQ) protocol at the data-link layer. Both basic ARQ and type-I hybrid ARQ are considered. More specifically,...
This paper gives an insight into IEEE 802.11ac by analysing its performance in terms of system throughput taking into consideration the key features of MAC and PHY layers. Throughput at MAC layer is calculated from transmission probability, contention window and transmission stage. Likewise, the new critical attributes of 802.11ac PHY (i.e. modulation and coding schemes, spatial streams, and channel...
This paper gives an insight into IEEE 802.11ac by analysing its performance in terms of system throughput taking into consideration the key features of MAC and PHY layers. Throughput at MAC layer is calculated from transmission probability, contention window and transmission stage. Likewise, the new critical attributes of 802.11ac PHY (i.e. modulation and coding schemes, spatial streams, and channel...
In this paper, semi-orthogonal frequency multiplexing (SOFDM) is proposed, which has doubled spectral efficiency over OFDM by halving the subcarrier spacing. SOFDM is orthogonal in real field but non-orthogonal in complex field. To cancel the inter carrier interference caused by non-orthogonality, linear equalization algorithms are introduced based on inter carrier cross-correlation matrix. However...
Packet size and modulation scheme can play an important role on optimizing the data rate of Long Term Evolution (LTE) system. The performance of the existing LTE system is evaluated in this paper in term of throughput and packet loss for Orthogonal Frequency-Division Multiple Access (OFDMA) modulation scheme with different packet sizes. The performance of LTE system for different packet size is done...
This paper presents field experiments on the downlink throughput performance of a beam tracking proof-of-concept system targeting 5G millimeter wave radio access in the following typical small cell environments: a courtyard, lobby, and underground parking area. The majority of the area in the tested environments is Line-Of-Sight (LOS) with cell radii of less than 60 m. The results show that the maximum...
In this paper, the antennas performances for the 5.2 GHz 802.11n network are compared by three different access points with 3 antenna configurations based on the simulated throughput derived from measurements in a two-storey house. The aim here is to outline a methodology for access point performance taking account client orientation, MIMO data streams that can be supported and finally a total throughput...
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