Median codeword Shift (MCS) technique for PAPR reduction with low complexity in OFDM system

With the rapid development of today’s communication technology, the need for a system capable to improve spectral efficiency, high data rates and at the same time can reduce inter-symbol interference (ISI) is necessary. Orthogonal Frequency Division Multiplexing (OFDM) meet all the requirements needed. However, the high peak to average power ratio (PAPR) has become its major obstacle. This paper is focusing on the development of Median Codeword Shift (MCS), which a new PAPR reduction technique with the capability to reduce the computational complexity of the system. This can be achieved through codeword structure alterization and bit position manipulation by utilizing the circulant shift process. The simulation results revealed that the proposed technique overwhelm conventional OFDM and SCS with 24% improvement and 0.5 dB gap from SCS. In fact, the proposed technique possess a lower computational complexity by reducing 16.67% of the use of IFFT block in the system in contrast with SCS technique

Cognitive Radio Systems

Cognitive radio is a hot research area for future wireless communications in the recent years. In order to increase the spectrum utilization, cognitive radio makes it possible for unlicensed users to access the spectrum unoccupied by licensed users. Cognitive radio let the equipments more intelligent to communicate with each other in a spectrum-aware manner and provide a new approach for the co-existence of multiple wireless systems. The goal of this book is to provide highlights of the current research topics in the field of cognitive radio systems. The book consists of 17 chapters, addressing various problems in cognitive radio systems

Advanced Techniques for High-Throughput Cellular Communications

The next generation wireless communication systems require ubiquitous high-throughput mobile connectivity under a range of challenging network settings (urban versus rural, high device density, mobility, etc). To improve the performance of the system, the physical layer design is of great importance. The previous research on improving the physical layer properties includes: a) highly directional transmissions that can enhance the throughput and spatial reuse; b) enhanced MIMO that can eliminate contention, enabling linear increase of capacity with number of antennas; c) mmWave technologies which operate on GHz bandwidth to over substantially higher throughput; d) better cooperative spectrum sharing with cognitive radios; e) better multiple access method which can mitigate multiuser interference and allow more multi-users. This dissertation addresses several techniques in the physical layer design of the next generation wireless communication systems. In chapter two, an orthogonal frequency division with code division multiple access (OFDM-CDMA) systems is proposed and a polyphase code is used to improve multiple access performance and make the OFDM signal satisfy the peak to average ratio (PAPR) constraint. Chapter three studies the I/Q imbalance for direct down converter. For wideband transmitter and receiver that use direct conversion for I/Q sampling, the I/Q imbalance becomes a critical issue. With higher I/Q imbalance, there will be higher degradation in quadrature amplitude modulation, which degrades the throughput tremendously. Chapter four investigate a problem of spectrum sharing for cognitive wideband communication. An energy-efficient sub-Nyquist sampling algorithm is developed for optimal sampling and spectrum sensing. In chapter ve, we study the channel estimation of millimeter wave full-dimensional MIMO communication. The problem is formulated as an atomic-norm minimization problem and algorithms are derived for the channel estimation in different situations. In this thesis, mathematical optimization is applied as the main approach to analyze and solve the problems in the physical layer of wireless communication so that the high-throughput is achieved. The algorithms are derived along with the theoretical analysis, which are validated with numerical results

An Overview of Signal Processing Techniques for Joint Communication and Radar Sensing

Joint communication and radar sensing (JCR) represents an emerging research field aiming to integrate the above two functionalities into a single system, by sharing the majority of hardware, signal processing modules and, in a typical case, the transmitted signal. The close cooperation of the communication and sensing functions can enable significant improvement of spectrum efficiency, reduction of device size, cost and power consumption, and improvement of performance of both functions. Advanced signal processing techniques are critical for making the integration efficient, from transmission signal design to receiver processing. This paper provides a comprehensive overview of the state-of-the-art on JCR systems from the signal processing perspective. A balanced coverage on both transmitter and receiver is provided for three types of JCR systems, namely, communication-centric, radar-centric, and joint design and optimization

A Low-Complexity SLM PAPR Reduction Scheme for OFDMA

In orthogonal frequency division multiplexing (OFDM) systems, selected mapping (SLM) techniques are widely used to minimize the peak to average power ratio (PAPR). The candidate signals are generated in the time domain by linearly mixing the original time-domain transmitted signal with numerous cyclic shift equivalents to reduce the amount of Inverse Fast Fourier Transform (IFFT) operations in typical SLM systems. The weighting factors and number of cyclic shifts, on the other hand, should be carefully chosen to guarantee that the elements of the appropriate frequency domain phase rotation vectors are of equal magnitude. A low-complexity expression is chosen from among these options to create the proposed low-complexity scheme, which only requires one IFFT. In comparison to the existing SLM technique, the new SLM scheme achieves equivalent PAPR reduction performance with significantly less computing complexity. MATLAB tool is used for simulating the proposed work

A Low-Complexity SLM PAPR Reduction Scheme for OFDMA

In orthogonal frequency division multiplexing (OFDM) systems, selected mapping (SLM) techniques are widely used to minimize the peak to average power ratio (PAPR). The candidate signals are generated in the time domain by linearly mixing the original time-domain transmitted signal with numerous cyclic shift equivalents to reduce the amount of Inverse Fast Fourier Transform (IFFT) operations in typical SLM systems. The weighting factors and number of cyclic shifts, on the other hand, should be carefully chosen to guarantee that the elements of the appropriate frequency domain phase rotation vectors are of equal magnitude. A low-complexity expression is chosen from among these options to create the proposed low-complexity scheme, which only requires one IFFT. In comparison to the existing SLM technique, the new SLM scheme achieves equivalent PAPR reduction performance with significantly less computing complexity. MATLAB tool is used for simulating the proposed work

Nopeaan konvolutioon perustuva suodatettu OFDM ja ikkunoitu OFDM aaltomuotojen suorituskykyvertailussa 5G fyysiselle kerrokselle

Nykyisten mobiiliverkkojen vaatimukset kasvavat jatkuvasti, mikä johtuu pitkälti uusien mobiililaitteiden ja -palveluiden suosion kasvusta. Lisäksi matkapuhelinverkkoja on alettu käyttämään pääasiallisena internetyhteytenä, sillä nykyteknologialla on mahdollista saavuttaa kiinteään laajakaistayhteyksiin verrattavia käyttäjäkokemuksia useimmissa sovelluksissa. Nykyiset Long Term Evolution (LTE) ja LTE-Advanced ovat neljännen sukupolven (4G) teknologioita, jotka tarjoavat jo hyvin suuria tiedonsiirtonopeuksia. Tulevaisuuden palvelut vaativat kuitenkin uusia ominaisuuksia verkolta ja tämän takia uusia teknlogioita tutkitaan jatkuvasti lisää. Viidennen sukupolven (5G) teknologia pyrkii kasvattamaan tiedonsiirtonopeuksia entisestään. Lisäksi on ennustettu, että tulevaisuuden teknologiat vaativat tukea myös pienille ja viivekriittisille lähetyksille, kuten Internet of Things (IoT) ja Machineto-Machine (M2M) -tyyppisille palveluille. Tämä tarkoittaa, että verkkoon yhdistettyjen laitteiden määrä tulee kasvamaan räjähdysmäisesti. Verkossa ovat jatkossa esimerkiksi älykkäät autot, kodinkoneet, sensorit ja monet muut älykkäät laitteet, mikä vaatii mobiiliverkoilta merkittävästi suurta kapasiteettia ja joustavuutta. Tässä diplomityössä tutkitaan kahden uuden aaltomuodon soveltuvuutta 5G aaltomuodoksi: ikkunoitu CP-OFDM ja nopeaan konvoluutioon perustuva suodatettu CP-OFDM. Referenssinä on käytetty LTE-tyylistä kanavasuodatettua CP-OFDM aaltomuotoa vertaillen alltomuotojen spektraalista tehokkuutta ja vuototehoa. Aaltomuotojen suorituskykyä vertaillaan lopuksi kokonaisen tietoliikennelinkin yli. Tulosten perusteella kanavan käyttötehokkuus kasvaa uusilla aaltomuodoilla niin laaja- kuin kapeakaistalähetyksissä, mahdollistaen suurempia tiedonsiirtonopeuksia samassa kanavassa. Parannusta on havaittavissa erityisesti kapeakaistaisten lähetysten vuototehossa. Tämä sallii taajudessa lähekkäin olevien eri alikantoaaltoväliä, eri mittaisia syklisiä etuliitteitä tai eri aikasynkronisuusvaatimuksia käyytävien signaalien lähettämisen samanaikaisesti, häiritsemättä merkittävästi muita lähetyksiä.The demands for modern wireless cellular networks are increasing constantly due to the introduction of new mobile devices and services. Additionally, mobile networks are being used as a primary Internet connection as the current wireless networks are able to achieve similar user experiences than with wired connections in most applications. Long Term Evolution (LTE) and LTE-Advanced are current 4G technologies already allowing very high peak data rates. However, additional features are needed from network to satisfy traffic demands of the future and suitable technologies are in high interest in nowadays research. The fifth generation (5G) wireless system targets to increase data transmission rates further. In addition, it has been forecast that the traffic trends of the future becomes more delay-critical and small bursts communication has a bigger role. These type of services are e.g. Internet of Things (IoT) and Machine-to-Machine (M2M) communications. These increases dramatically the number of devices connected to Internet, for example smart cars, domestic appliances, sensors and other smart devices, which will require significantly improved capacity and flexibility from the forthcoming mobile communication networks. In this thesis, two waveform candidates for 5G are evaluated and compared: Windowed CP-OFDM and Fast Convolution based Filtered CP-OFDM. LTE-like channel filtered CP-OFDM is used as a reference in spectral efficiency, power leakage and overall link performance comparisons of the waveforms. It will be shown that the spectral utilization is improved with proposed waveforms in broadband and narrowband transmissions, which allows higher data rates inside the same bandwidth. The most significant improvement is observed in narrowband power leakage evaluations. Reduced power leakage allows to transmit several narrowband signals with different subcarrier spacings, cyclic prefix lengths, or different timing accuracy with tight frequency spacing without significant interference levels

Nopeaan konvolutioon perustuva suodatettu OFDM ja ikkunoitu OFDM aaltomuotojen suorituskykyvertailussa 5G fyysiselle kerrokselle

Nykyisten mobiiliverkkojen vaatimukset kasvavat jatkuvasti, mikä johtuu pitkälti uusien mobiililaitteiden ja -palveluiden suosion kasvusta. Lisäksi matkapuhelinverkkoja on alettu käyttämään pääasiallisena internetyhteytenä, sillä nykyteknologialla on mahdollista saavuttaa kiinteään laajakaistayhteyksiin verrattavia käyttäjäkokemuksia useimmissa sovelluksissa. Nykyiset Long Term Evolution (LTE) ja LTE-Advanced ovat neljännen sukupolven (4G) teknologioita, jotka tarjoavat jo hyvin suuria tiedonsiirtonopeuksia. Tulevaisuuden palvelut vaativat kuitenkin uusia ominaisuuksia verkolta ja tämän takia uusia teknlogioita tutkitaan jatkuvasti lisää. Viidennen sukupolven (5G) teknologia pyrkii kasvattamaan tiedonsiirtonopeuksia entisestään. Lisäksi on ennustettu, että tulevaisuuden teknologiat vaativat tukea myös pienille ja viivekriittisille lähetyksille, kuten Internet of Things (IoT) ja Machineto-Machine (M2M) -tyyppisille palveluille. Tämä tarkoittaa, että verkkoon yhdistettyjen laitteiden määrä tulee kasvamaan räjähdysmäisesti. Verkossa ovat jatkossa esimerkiksi älykkäät autot, kodinkoneet, sensorit ja monet muut älykkäät laitteet, mikä vaatii mobiiliverkoilta merkittävästi suurta kapasiteettia ja joustavuutta. Tässä diplomityössä tutkitaan kahden uuden aaltomuodon soveltuvuutta 5G aaltomuodoksi: ikkunoitu CP-OFDM ja nopeaan konvoluutioon perustuva suodatettu CP-OFDM. Referenssinä on käytetty LTE-tyylistä kanavasuodatettua CP-OFDM aaltomuotoa vertaillen alltomuotojen spektraalista tehokkuutta ja vuototehoa. Aaltomuotojen suorituskykyä vertaillaan lopuksi kokonaisen tietoliikennelinkin yli. Tulosten perusteella kanavan käyttötehokkuus kasvaa uusilla aaltomuodoilla niin laaja- kuin kapeakaistalähetyksissä, mahdollistaen suurempia tiedonsiirtonopeuksia samassa kanavassa. Parannusta on havaittavissa erityisesti kapeakaistaisten lähetysten vuototehossa. Tämä sallii taajudessa lähekkäin olevien eri alikantoaaltoväliä, eri mittaisia syklisiä etuliitteitä tai eri aikasynkronisuusvaatimuksia käyytävien signaalien lähettämisen samanaikaisesti, häiritsemättä merkittävästi muita lähetyksiä.The demands for modern wireless cellular networks are increasing constantly due to the introduction of new mobile devices and services. Additionally, mobile networks are being used as a primary Internet connection as the current wireless networks are able to achieve similar user experiences than with wired connections in most applications. Long Term Evolution (LTE) and LTE-Advanced are current 4G technologies already allowing very high peak data rates. However, additional features are needed from network to satisfy traffic demands of the future and suitable technologies are in high interest in nowadays research. The fifth generation (5G) wireless system targets to increase data transmission rates further. In addition, it has been forecast that the traffic trends of the future becomes more delay-critical and small bursts communication has a bigger role. These type of services are e.g. Internet of Things (IoT) and Machine-to-Machine (M2M) communications. These increases dramatically the number of devices connected to Internet, for example smart cars, domestic appliances, sensors and other smart devices, which will require significantly improved capacity and flexibility from the forthcoming mobile communication networks. In this thesis, two waveform candidates for 5G are evaluated and compared: Windowed CP-OFDM and Fast Convolution based Filtered CP-OFDM. LTE-like channel filtered CP-OFDM is used as a reference in spectral efficiency, power leakage and overall link performance comparisons of the waveforms. It will be shown that the spectral utilization is improved with proposed waveforms in broadband and narrowband transmissions, which allows higher data rates inside the same bandwidth. The most significant improvement is observed in narrowband power leakage evaluations. Reduced power leakage allows to transmit several narrowband signals with different subcarrier spacings, cyclic prefix lengths, or different timing accuracy with tight frequency spacing without significant interference levels

Comparison of 3GPP LTE and 3GPP2 UMB

In the last years, technology evolution in mobile communications is mainly motivated by three relevant agents: (1) the market globalization and liberalization and the increasing competence among vendors and operators coming from this new framework, (2) the popularization of IEEE 802 wireless technologies within the mobile communications sector and, finally, (3) the exponential increase in the demand for advanced telecommunication services. Concerning the last item, the envisaged applications to be supported by current and future cellular systems include Voice over IP (VoIP), videoconference, push-to-talk over cellular (PoC), multimedia messaging, multiplayer games, audio and video streaming, content download of ring tones, video clips, Virtual Private Network (VPN) connections, web browsing, email access, File Transfer Protocol (FTP). Thus, the race towards IMT-Advanced was officially started in March 2008, when a Circular Letter was distributed asking for the submission of new technology proposals. Previous to this official call, the 3rd Partnership Project (3GPP) established the Long Term Evolution (LTE) and the 3rd Partnership Project 2 (3GPP2) established the Ultra Mobile Broadband. In this paper we have conducted a comparative study between UMB and 3GPP LTE by focusing on their first layers, i.e. Physical layer. The comparison specifically includes system architecture, radio aspects of the air interface such as radio access modes, multiple access technologies, multiple antenna technologies, modulation and mobility