OFDM Transmission Technique

2011 ◽  
pp. 151-177
Author(s):  
Hermann Rohling
Keyword(s):  
Communication Networks ◽  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Fourth Generation ◽  
Frequency Division ◽  
Carrier Synchronization ◽  
Radio Channels ◽  
Transmission Technique ◽  
Cellular Environment

The orthogonal frequency division multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA, FDMA, and CDMA approaches with the OFDM modulation procedure, which is especially important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting sub-carrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM signal. The OFDM transmission technique is used for the time being in some broadcast applications (DVB-T, DAB, DRM) and wireless local loop (WLL) standards (HIPERLAN/2, IEEE 802.11a) but OFDM has not been used so far in cellular communication networks. The general idea of the OFDM scheme is to split the total bandwidth into many narrowband sub-channels which are equidistantly distributed on the frequency axis. The sub-channel spectra overlap each other but the sub-carriers are still orthogonal in the receiver and can therefore be separated by a Fourier transformation. The system flexibility and use of sub-carrier specific adaptive modulation schemes in frequency selective radio channels are some advantages which make the OFDM transmission technique a strong and technically attractive candidate for the next generation of mobile communications. The objective of this chapter is to describe an OFDM-based system concept for the fourth generation (4G) of mobile communications and to discuss all technical details when establishing a cellular network which requires synchronization in time and frequency domain with sufficient accuracy. In this cellular environment a flexible frequency division multiple access scheme based on OFDM-FDMA is developed and a radio resource management (RRM) employing dynamic channel allocation (DCA) techniques is used. A purely decentralized and self-organized synchronization technique using specific test signals and RRM techniques based on co-channel interference (CCI) measurements has been developed and will be described in this chapter.

OFDM Transmission Technique

2009 ◽  
pp. 3561-3587
Author(s):  
Hermann Rohling
Keyword(s):  
Communication Networks ◽  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Fourth Generation ◽  
Frequency Division ◽  
Carrier Synchronization ◽  
Radio Channels ◽  
Transmission Technique ◽  
Cellular Environment

The orthogonal frequency division multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA; FDMA; and CDMA approaches with the OFDM modulation procedure; which is especially important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting sub-carrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM signal. The OFDM transmission technique is used for the time being in some broadcast applications (DVB-T; DAB; DRM) and wireless local loop (WLL) standards (HIPERLAN/2; IEEE 802.11a) but OFDM has not been used so far in cellular communication networks. The general idea of the OFDM scheme is to split the total bandwidth into many narrowband sub-channels which are equidistantly distributed on the frequency axis. The sub-channel spectra overlap each other but the sub-carriers are still orthogonal in the receiver and can therefore be separated by a Fourier transformation. The system flexibility and use of sub-carrier specific adaptive modulation schemes in frequency selective radio channels are some advantages which make the OFDM transmission technique a strong and technically attractive candidate for the next generation of mobile communications. The objective of this chapter is to describe an OFDM-based system concept for the fourth generation (4G) of mobile communications and to discuss all technical details when establishing a cellular network which requires synchronization in time and frequency domain with sufficient accuracy. In this cellular environment a flexible frequency division multiple access scheme based on OFDM-FDMA is developed and a radio resource management (RRM) employing dynamic channel allocation (DCA) techniques is used. A purely decentralized and self-organized synchronization technique using specific test signals and RRM techniques based on co-channel interference (CCI) measurements has been developed and will be described in this chapter.

scholarly journals PAPR Analysis of Fifth Generation Multiple Access Waveforms for Advanced Wireless Communication

2018 ◽  
Vol 7 (3.34) ◽  
pp. 487 ◽  
Author(s):  
Kommabatla Mahender ◽  
Tipparti Anil Kumar ◽  
K S Ramesh
Keyword(s):  
Wireless Communication ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Average Power ◽  
Cumulative Distribution ◽  
Fourth Generation ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Single Carrier

This paper describes the aspects of multiple access for emerging (5G) Wireless Communication Systems. Orthogonal Frequency Division Multiplexing (OFDM) is best suited for fourth generation (4G) but it suffers from the problem of high Peak to Average Power Ratio (PAPR) & Side band leakage. Single carrier frequency division multiple access (SC-FDMA) has worked like an alternative to OFDMA only in the uplink process and PAPR was reduced. OFDM based 4G network is not capable of supporting diverse applications and these applications can be implemented by 5G.  High traffic requirements of 5G can be evaluated by using multiple access schemes, namely filter-bank multi-carrier (FBMC), universal-filtered multi-carrier (UFMC), generalized frequency-division multiplexing (GFDM). Comparison of PAPR reduction is done based on Complementary Cumulative Distribution Function (CCDF), for various multiple access 5G waveforms.  

Dynamic Hyperchaotic Key Generation Using Optical Orthogonal Frequency Division Multiplexing-based Visible Light Communication Networks

2021 ◽  
Author(s):  
Mohammed Alresheedi ◽  
YAHYA AL-MOLIKI ◽  
Yahya Al-Harthi ◽  
Ali Alqahtani
Keyword(s):  
Visible Light ◽  
Communication Networks ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Visible Light Communication ◽  
Frequency Division Multiplexing ◽  
Key Generation ◽  
Frequency Division ◽  
Degree Of Protection ◽  
Communication Time

Abstract This paper introduces an optical orthogonal frequency division multiplexing (OFDM)-based hyperchaotic key generation encryption approach that can improve confidentiality in visible light communication (VLC) networks. Using a hyperchaotic four-dimensional method, the bipolar real-valued OFDM signal can be used for constructing dynamic cypher keys modified at every frame over the communication time, resulting in a superior degree of protection against statistical and correlation attacks. In accordance with our findings, this approach decreases the ratio of peak-to-average power of the transmitted signal, and enhances the bit error rate efficiency and secrecy capacity of the OFDM-based VLC network, which improves confidentiality.

scholarly journals Hardware Prototyping and Modelling of Prototype Filter for FBMC

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Bircan Çalişir ◽  
Ayhan Akbal
Keyword(s):  
Communication Networks ◽  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Filter Design ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Mobile Telecommunication ◽  
Guard Band ◽  
Filter Bank Multicarrier ◽  
Band Limited

Filter bank multicarrier (FBMC) is one of the effective candidates for the fifth generation of wireless communication networks. 5G (5th-generation wireless systems) is accepted as the next major stage of mobile telecommunication technology. The extent of 5G will be expanded mobile broadband services to next-generation automobiles and connected machines. In particular, filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) is determined as the future generation 5G air interface by researchers recently. Filter bank multicarrier (FBMC) is admitted as one of the alternative technologies for multicarrier modulation. Compared to orthogonal frequency-division multiplexing (OFDM), FBMC has better spectrum shape and supports mobility. Therefore, efficient hardware implementations have highly interested researchers. Cyclic prefix (CP) and guard band are used for orthogonal frequency-division multiplexing (OFDM) and this causes loss of spectral efficiency, but FBMC applications do not need CP and guard band. Due to the fact that FBMC has offset QAM (OQAM) and band-limited filtering features on each subcarrier, the need for CP and guard band is eliminated. In this paper, novel pipelined hardware architecture of the filter design of FBMC/OQAM modulator has been proposed.

scholarly journals APR Reduction Technique based on OFDM Pilot Filter Bank Limiting for Satellite Mobile Communications

2018 ◽  
Vol 246 ◽  
pp. 03002
Author(s):  
Tianfang Dai
Keyword(s):  
Mobile Communications ◽  
Bit Error Rate ◽  
Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Hardware Implementation ◽  
Reduction Technique ◽  
Papr Reduction ◽  
Frequency Division Multiplexing ◽  
Frequency Division

Combined with OFDM (Orthogonal Frequency Division Multiplexing), satellite mobile communications will effectively achieve on-demand communication in areas with an ultra-low density of users. With OFDM multiple access optimization, the bandwidth utilization efficiency can be increased by 5 to 10 times. However, satellites are power-constrained systems, so higher PAPR requires greater power backoff, resulting in a decline in satellite transmission capacity. To use OFDM technology in satellites, there are problems such as reduced transmission capacity resulted from high PAPR, complication of lowering PAPR, and difficulty in hardware implementation. In order to deal with the problem of high bit error rate and hardware implementation difficulties in PAPR reduction technique of non-orthogonal frequency division multiplexing, this paper proposes a limiting PAPR reduction technique with OFDM pilot filter banks for satellite mobile communications. Firstly, the applicability of OFDM in satellite mobile communications is analyzed, and the influence of high PAPR on satellite power utilization and the influence of frequency shift sensitivity on inter-satellite communication interference are obtained. Then design the PAPR reduction technique based on the pilot filter bank. By setting the tunable filter bank to the pilot, the sideband power suppression in the OFDM frequency domain is realized, and the PAPR of the OFDM signal is reduced. Finally, the experimental results show that the PAPR performance is improved by 3dB without reducing the bit error rate.

scholarly journals Performance analysis of OFDMA and SC-FDMA

2017 ◽  
Vol 8 (2) ◽  
pp. 113-116 ◽  
Author(s):  
M. Al-Rawi
Keyword(s):  
Carrier Frequency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
High Speed ◽  
Minimum Mean Square Error ◽  
Frequency Division ◽  
International Telecommunication Union ◽  
Single Carrier ◽  
Main Challenge ◽  
Better Than

The main challenge in any high-speed digital communication system is how to maximize the data rate with minimizing the bit error rate. Several techniques have been developed to achieve this point. Some of these techniques are orthogonal frequency division multiplexing (OFDM), single-carrier frequency domain equalization (SC-FDE), orthogonal frequency division multiple access (OFDMA), and single-carrier frequency division multiple access (SC-FDMA). These four techniques are described briefly in this paper. Also, the paper measures the performances of OFDMA and SC-FDMA systems over international telecommunication union (ITU) vehicular-A channel using minimum mean square error (MMSE) equalization. Simulation results show that the performances with interleaved mapping outperform that with localized mapping. Also, the performances with quadrature phase shift keying (QPSK) are better than that with 16-ary quadrature amplitude modulation (16QAM). In addition, the performance of SC-FDMA is better than that of OFDMA, when QPSK is used, but the latter is little bit better than that of SC-FDMA when 16QAM is used.

scholarly journals NOMA for Multinumerology OFDM Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Ayman T. Abusabah ◽  
Huseyin Arslan
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Superposition Coding ◽  
Promising Technique ◽  
Successive Interference Cancelation ◽  
Power Domain ◽  
Multiple Access Schemes ◽  
Spectrally Efficient

Nonorthogonal multiple access (NOMA) is a promising technique which outperforms the traditional multiple access schemes in many aspects. It uses superposition coding (SC) to share the available resources among the users and adopts successive interference cancelation (SIC) for multiuser detection (MUD). Detection is performed in power domain where fairness can be supported through appropriate power allocation. Since power domain NOMA utilizes SC at the transmitter and SIC at the receiver, users cannot achieve equal rates and experience higher interference. In this paper, a novel NOMA scheme is proposed for multinumerology orthogonal frequency division multiplexing system, that is, different subcarrier spacings. The scheme uses the nature of mixed numerology systems to reduce the constraints associated with the MUD operation. This scheme not only enhances the fairness among the users but improves the bit error rate performance as well. Although the proposed scheme is less spectrally efficient than conventional NOMA schemes, it is still more spectrally efficient than orthogonal multiple access schemes.

scholarly journals Experimental Studies on the Effect of Antenna Orientations to the Performance of OFDM-based System

2018 ◽  
Vol 8 (4) ◽  
pp. 2588
Author(s):  
J. Muslimin ◽  
A. L. Asnawi ◽  
A. F. Ismail ◽  
A. Z. Jusoh ◽  
N. A. Malek ◽  
...  
Keyword(s):  
System Performance ◽  
Software Defined Radio ◽  
Orthogonal Frequency Division Multiplexing ◽  
Development Process ◽  
Low Cost ◽  
Experimental Studies ◽  
Empirical Evaluation ◽  
Packet Error Rate ◽  
Frequency Division ◽  
Transmission Technique

<span>Software-defined radio (SDR) is an emerging and promising high re-configurable platform for rapid prototyping inreal environment applications. It offers both flexibility and low cost to facilitate the development process of agile communication system, such as Orthogonal Frequency Division Multiplexing (OFDM). Other than modulation and transmission technique like OFDM, antenna orientations play a significant importance in wireless communication. The availabililty of SDR platform like USRP has enabled the empirical evaluation of antenna orientation to the system performance. The performance has been evaluated in terms of throughput and packet error rate. The findings show the antenna orientation affect the system performance significantly.</span>

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