Orthogonal Frequency Division Multiple Access (OFDMA)

Radio is one of the wireless network system devices that is still widely used today. Transceiver was used because the radio can function as a transmitter and receiver. In this paper, half-wave dipole antenna for radio communication as a transceiver on TDMA Digital Radio was simulated. The antenna was used at 167.5 MHz and radio communication channel. In collecting the data, spectrum analyzer was used as the measuring tool. To analyze the output signal generated by TDMA Digital Radio, the data sample on both measurements. This paper compared the TDMA Digital Radio communication with simulation by using MATLAB. Analyze the Channel Power that has become the output of Spectrum Analyzer, and the measurement of Spectrum Analyzer Measurement was using MATLAB.

It is proposed a method for increase of reliability of information transmission in wireless networks, functioning in conditions of influence of deliberate noise. The method is based on additional application of uncertainty factor in case of decision making in the turbo decoder in conditions of non-stationarity of the transmission channel. In a process of adaptive regulation of turbo code decoding iterations amount is modified for each data packet basing on dynamic calculation of uncertainty factor. Simulation results show increase of signal to noise ratio results in decoding iteration decrease, and information transmission reliability increase.

Software Defined Radio (SDR) is one of possibilities to realize the structure of device with a high mobility, flexibility and reconfigurability. This technology can provide the seamless shifting between existed airinterface standards. Extending the flexibility further, a system capable to sense the spectrum space available for communication and adapt to it is Cognitive Radio. Obviously SDR in Cognitive Radio should be configured not only to independent standards, protocols and services but also to the extensively dynamic nature of bandwidth allocation. Moreover this need of dynamic allocation of Spectrum space is a must to cater to its increased demand. Cognitive radio is envisioned as the ultimate system that can sense, adapt and learn from the environment in which it operates. Sensing the available bandwidth an SDR (Software defined radio) in a Cognitive System, tunes the circuits in the System for transferring data at optimum data rates, permissible by the space available. So it ...

The aim of this paper is to study the bit-loading and power allocation problem in the presence of interference (Inter-carrier Interference (ICI) and Inter-Symbol Interference (ISI)) in Orthogonal Frequency Division Multiplexing (OFDM) systems. ISI and ICI significantly degrade the performance of OFDM systems and make the resource management optimized without the assumption of interference less efficient. To solve this problem, an initial solution based on the greedy approach is proposed in this paper. Then, several reduced complexity approaches, which yield a little degradation compared to the initial solution, have been developed. Simulation results presented in the context of Power Line Communication (PLC) show that the performance of proposed algorithms is tight with their upper bound. Moreover, these algorithms efficiently improve the system performance as compared to the constant power water-filling allocation algorithm as well as maximum power allocation algorithm.

– Emerging standards in the area of mobile services, such as Worldwide Interoperability for Microwave Access (WiMAX) and Universal Mobile Telecommunication System (UMTS), require new capabilities from mobile devices. As a result, these devices should be aware of how ...

The modulation techniques covered include AM, FM, PM, ASK, FSK, PSK, and QAM. Furthermore, the article shed light on the enabling technology in telephony and internet connectivity, specifically in 3G, 4G, 5G, WiFi 5, and WiFi 6. It then concludes that as communication technology continues to evolve, staying updated with modulation techniques and enabling technologies will be essential for optimizing communication systems and ensuring reliable and high-quality information transmission.

A turbo-equalization technique is presented for transmissions, where QAM constellations are constructed via blockpartitioning as linear combinations of rotated, separately channel-coded BPSK components. The multilevel encoded QAM can be decoded with multistage decoding level-bylevel. Iterative equalization and multistage decoding is performed via soft interference cancellation and MMSE equalization followed by soft-in-soft-out channel decoders. Due to binary channel codes both the equalizer and decoder can operate with binary likelihood values without requiring symbolibit conversion. The resulting scheme is suitable for robust transmission when transmitter has little or no knowledge of channel quality.

3GPP's Long Term Evolution is defined by the standardization body's Release 8 and 9, and provides more than a substrate for 3GPP's IMT-Advanced Candidate, namely LTE-Advanced, which is due to be defined in Release 10. Both LTE and LTE-Advanced have SC-FDMA in their uplink, a multi-carrier access technique requiring contiguous subcarrier allocations for each UE. No scheduling algorithm, however, is dictated by the standard and several proposals have hence been presented to be implemented by vendors. A definite scheduling requirement is the support of QoS attributes of different types of uplink traffic. Our intent in this study is to evaluate the connectionlevel performance of representative scheduling proposals, with focus on QoS aspects. Specifically, we utilize a mixed type of traffic flows and evaluate the schedulers in terms of per-user throughput, packet loss and fairness.

Ever since wireless broadband communication services were introduced, its demand has been growing constantly. Over the last twenty years, wireless communications have become popular all across the world. It provides an attractive option for many private as well as administrative communication requirements due to various attributes including cost, effectiveness, and agility. The new generation mobile communication systems i.e. fourth generation (4G) are required to support multiple services in various types of environments. 4G is being developed to accommodate the quality of service and essential data rate like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV. This paper throws light on numerous multiple access techniques anticipated in 4G communication systems. Among all the multiple access (MA) techniques, it is tried to demonstrate that IDMA (Interleave Division Multiple Access) technology can competently alleviate the interference among users and provision high data rates without compromising the quality of service that is required.

Industrial networks rely on Ethernet and its complementary Time Sensitive Networking standards to support critical application requirements such as bounded latency and low jitter. To meet these requirements, precise time synchronization across wired devices is typically achieved across the wired devices via the Precision Time Protocol (PTP). PTP as a UDP-based protocol can synchronize wireless devices as well, provided that these guarantee hardware-based timestamping. On the other hand, Wi-Fi integrates time synchronization mechanisms better suited to its shared medium, such as the the Fine Time Measurement (FTM) protocol. Aiming at contributing to the time synchronization solution across multi-AP industrial environments, this paper proposes a hiearchical FTM-based synchronization approach capable of supporting time synchronization in a way compatible with Ethernet/TSN. The evaluation of the proposed solution carried out with the ns-3 DetNetWiFi framework, shows that it successfully synchronizes all devices within the networ with an accuracy of less than 5 µs and providing fairness in terms of balancing FTM requests in dense networks effectively.

This paper presents a design formulation and evaluation of a wireless co-OFDMA probabilistic algorithm aimed at optimizing resource utilization in overlapping Wi-Fi networks. The design formulation is grounded in realistic industrial application requirements, and the evaluation is conducted using the network simulator v3.0 with its DetNetWiFi module, which is capable of modeling deterministic wireless networks. The evaluation focuses on latency, jitter, and packet loss. Our findings demonstrate that co-OFDMA probabilistic approaches offer significant benefits in terms of latency in deterministic wireless environments. However, they may also introduce increased jitter compared to a static primary channel sharing scheme, aspect which may not be suitable to industrial wireless environments.

In this article, we study the energy efficiency (EE) of
orthogonal frequency-division multiple access (OFDMA) cellular
networks under the 5Grequirement ofEEenhancement.We aim to
present a power allocation scheme maximizing the EE of downlink
cellular communicationswhile avoiding numericalmethods such as
fractional programming.We focus on two EE forms; global EE and
weighted sumEE. Therefore, we propose a novel explicit expression
of the optimal power allocation related to each subcarrier. We
also present the power control with limited power budget or/and
minimal transmission rate constraint in both base station and
subcarrier perspectives. As a result, we notice the occurrence of
some transmission outage events depending on the constraints’
parameters. Fromanother side, we extend our study to analyze the
effect of the channel state information (CSI) unavailability on our
proposed power scheme. In the numerical results, we show that
our proposed power control improves the EE, especially at high
power budget regime and low minimal rate regime. We also show
that having more subcarriers enhances the OFDMA EE. Finally,
we show that EE degradation due to CSI unavailability is very
small showing the robustness of the proposed scheme against CSI
imperfectness.

Turbo-coded burst-by-burst adaptive orthogonal frequency division multiplex (AOFDM) wide-band speech transceivers are proposed. A constant throughput adaptive OFDM transceiver was designed and benchmarked against a time-variant rate scheme. The proposed joint adaptation of source-codec, channel-codec, and modulation regime results in attractive, robust, high-quality audio systems, capable of conveying near-unimpaired wide-band audio signals over fading dispersive channels for signal-to-noise ratios (SNR) in excess of about 5 dB. Index Terms-Adaptive OFDM, audio compression, transmission, wide-band speech compression. I. BACKGROUND AND MOTIVATION B URST-BY-BURST adaptive quadrature amplitude modulation (AQAM) transceivers [1] have recently generated substantial research interests in the wireless communications community [2]-[4]. The transceiver reconfigures itself on a burst-by-burst basis, depending on the instantaneous perceived wireless channel quality. More explicitly, the associated channel quality to be experienced by the next transmission burst is estimated on the basis of the current received burst and the specific modulation mode, which is expected to achieve the required performance target is then selected for the transmission of the next burst. In other words, modulation schemes of different robustness and of different data throughput are invoked [5], [6]. In the event of an anticipated error burst due to a low expected instantaneous channel quality, the transmitter can also be temporarily disabled, while the data are delayed and buffered, until the channel quality improves, provided that the associated delay is not excessive for the service supported. Due to this feature, the distribution of channel errors becomes typically less bursty, than in conjunction with nonadaptive modems. This is an attractive feature in conjunction with channel coding, resulting in potentially increased coding gains [5]. Furthermore, the soft-decision channel codec metrics can also be invoked in estimating the instantaneous channel quality [5]. Recently, block turbo-coded AQAM transceivers have also been proposed for dispersive wide-band channels in conjunction with conventional decision feedback equalizers (DFE) [5], where the mean squared error (MSE) at the DFE's output was used as the channel quality metric, controlling the choice of modem modes. An alternative neural-network radial basis function (RBF) DFE-based AQAM modem design was Manuscript

The current US MIL-STD-188-110B [1] is being revised and will include an appendix defining a family of wideband HF data waveforms supporting bandwidths from 3 kHz to 24 kHz in increments of 3 kHz. This family of waveforms, designed by engineers at Harris Corporation and Rockwell Collins, extends the high performance serial tone modem technology of the current MIL-STD-188-110B standard, which was designed primarily to operate in a 3 kHz sideband, to wider bandwidths and much higher data rates. The waveforms can provide user bit rates up to 120,000 bps, and allow users the option of selecting the bandwidth and modulation to optimize modem performance based on the HF channel characteristics. The NATO Beyond Line-Of-Sight Communications Ad Hoc Working Group (BLOS Comms AHWG) is currently monitoring this development and may include this wider-bandwidth capability in a future NATO STANAG. This paper begins with a brief discussion of the HF data communications and networking requirements that led to a waveform design effort considering higher bandwidths. This is followed by a detailed discussion of the key design decision and tradeoffs involved in designing a family of waveforms for radio bandwidths of 3 to 24 kHz, where it is necessary to provide reliable communications connectivity under a wide range of expected channel impairments. Next, the paper examines the system implications of these design decisions, considering how this new wideband capability can be best integrated and applied in a tactical military radio usage scenario, the implications of these wideband waveforms for Automated Link Establishment (ALE), and the potential applicability of cognitive radio techniques in areas such as intelligent selection of the communications bandwidth and other waveform parameters. The paper concludes with a discussion of the results of preliminary on-air testing of the new waveforms. Links tested include a relatively short east-west link in western New York State and a long north-south link between New York and Florida.

A detailed study of the performance of MIMO-OFDM transmission on WLAN physical layer specified in IEEE 802.11n, Wi-MAX (IEEE 802.16-2009) physical layer specified in 802.16 and LTE downlink physical channel (PDSCH) has been carried out using MATLAB Simulink. The WLAN and Wi-MAX system incorporates Convolution coding with 1/2 and 2⁄3 rated codes. The LTE incorporates Turbo coding with 1/2 and 2/3 rated codes. Orthogonal Frequency Division Multiple (OFDM) accesses uses adaptive modulation technique such as QPSK,16-QAM and 64-QAM, on the physical layer of WLAN, Wi-MAX and LTE and the concept of cyclic prefix that adds additional bits at the transmitter end. The Error Rate (BER) derived from simulation results show that the implementation with interleaved Convolution coding and Turbo coding under QPSK modulation technique is found to be highly efficient for WLAN, Wi-MAX and LTE wireless network system. The Implementation of MIMO-OFDM multiplexing on WLAN networks with QPSK modulation at BER ~10-3 dB, exhibits significant improvement in SNR ~ 2.75 dB, Wi-MAX network SNR ~ 3.75 dB and LTE network SNR ~7.55 dB. The improvement of SNR ~4.8 dB displayed between the MIMO-OFDM implementation on WLAN and LTE network can be attributed to the Turbo coding techniques adopted in LTE networks.