Analysis of hybrid-ARQ based relaying protocols under modulation constraints

In a seminal paper published in 2001, Caire and Tuninetti derived an information theoretic bound on the throughput of hybrid-ARQ in the presence of block fading. However, the results placed no constraints on the modulation used, and therefore the input to the channel was Gaussian. The purpose of this thesis is to investigate the impact of modulation constraints on the throughput of hybrid-ARQ in a block fading environment. First, we consider the impact of modulation constraints on information outage probability for a block fading channel with a fixed length codeword. Then, we consider the effect of modulation constraints upon the throughput of hybrid-ARQ, where the rate of the codeword varies depending on the instantaneous channel conditions. These theoretical bounds are compared against the simulated performance of HSDPA, a newly standardized hybrid-ARQ protocol that uses QPSK and 16-QAM bit interleaved turbo-coded modulation. The results indicate how much of the difference between HSDPA and the previous unconstrained modulation bound is due to the use of the turbo-code and how much is due to the modulation constraints. (Abstract shortened by UMI.)

IST-2000-30148 I-METRA: D3.1 Design, analysis and selection of suitable algorithms

This deliverable contains a description of the space-time coding algorithms to be simulated within the I-METRA project. Different families of algorithms have been selected and described in this document with the objective of evaluating their performance. One of the main objectives of the I-METRA project is to impact into the current standardisation efforts related to the introduction of Multiple Input Multiple Output (MIMO) configurations into the High Speed Downlink and Uplink Packet Access concepts of UMTS (HSDPA and HSUPA). This required a review of the current specifications for these systems and the analysis of the impact of the potential incorporation of the selected MIMO schemes.Preprin

Interference-Mitigating Waveform Design for Next-Generation Wireless Systems

A brief historical perspective of the evolution of waveform designs employed in consecutive generations of wireless communications systems is provided, highlighting the range of often conflicting demands on the various waveform characteristics. As the culmination of recent advances in the field the underlying benefits of various Multiple Input Multiple Output (MIMO) schemes are highlighted and exemplified. As an integral part of the appropriate waveform design, cognizance is given to the particular choice of the duplexing scheme used for supporting full-duplex communications and it is demonstrated that Time Division Duplexing (TDD) is substantially outperformed by Frequency Division Duplexing (FDD), unless the TDD scheme is combined with further sophisticated scheduling, MIMOs and/or adaptive modulation/coding. It is also argued that the specific choice of the Direct-Sequence (DS) spreading codes invoked in DS-CDMA predetermines the properties of the system. It is demonstrated that a specifically designed family of spreading codes exhibits a so-called interference-free window (IFW) and hence the resultant system is capable of outperforming its standardised counterpart employing classic Orthogonal Variable Spreading Factor (OVSF) codes under realistic dispersive channel conditions, provided that the interfering multi-user and multipath components arrive within this IFW. This condition may be ensured with the aid of quasisynchronous adaptive timing advance control. However, a limitation of the system is that the number of spreading codes exhibiting a certain IFW is limited, although this problem may be mitigated with the aid of novel code design principles, employing a combination of several spreading sequences in the time-frequency and spatial-domain. The paper is concluded by quantifying the achievable user load of a UTRA-like TDD Code Division Multiple Access (CDMA) system employing Loosely Synchronized (LS) spreading codes exhibiting an IFW in comparison to that of its counterpart using OVSF codes. Both system's performance is enhanced using beamforming MIMOs

Space-Time Trellis and Space-Time Block Coding Versus Adaptive Modulation and Coding Aided OFDM for Wideband Channels

Abstract—The achievable performance of channel coded spacetime trellis (STT) codes and space-time block (STB) codes transmitted over wideband channels is studied in the context of schemes having an effective throughput of 2 bits/symbol (BPS) and 3 BPS. At high implementational complexities, the best performance was typically provided by Alamouti’s unity-rate G2 code in both the 2-BPS and 3-BPS scenarios. However, if a low complexity implementation is sought, the 3-BPS 8PSK space-time trellis code outperfoms the G2 code. The G2 space-time block code is also combined with symbol-by-symbol adaptive orthogonal frequency division multiplex (AOFDM) modems and turbo convolutional channel codecs for enhancing the system’s performance. It was concluded that upon exploiting the diversity effect of the G2 space-time block code, the channel-induced fading effects are mitigated, and therefore, the benefits of adaptive modulation erode. In other words, once the time- and frequency-domain fades of the wideband channel have been counteracted by the diversity-aided G2 code, the benefits of adaptive modulation erode, and hence, it is sufficient to employ fixed-mode modems. Therefore, the low-complexity approach of mitigating the effects of fading can be viewed as employing a single-transmitter, single-receiver-based AOFDM modem. By contrast, it is sufficient to employ fixed-mode OFDM modems when the added complexity of a two-transmitter G2 scheme is affordable

Vývoj standardů mobilních sítí

Import 21/10/2013This bachelor thesis deals primarily with a development of LTE technologies and its possibilities of deployment in the Czech Republic and abroad. The thesis is initially focused on the development of mobile network standards since the advent of 3rd generation networks in Release 99 up to the newest Release 12 where the main telecommunication technologies are continuously described along with their advantages. As the LTE represents next evolution step in a field of mobile data transmission, the comparison of LTE and HSPA+ physical layers is also included. Among other it describes information blocks from transport channel over the transmission path and regaining of user data. The development of LTE networks in the world deals with an actual progress of the deployment of this technology. In detail, there are described countries where the LTE is in a commercial service among with a comparison of used frequency bands. Addressing with issue of development and deployment of LTE in the Czech Republic is a content of the last part. With regard to the current network state of each provider, it is also focused on legislation, backbone networks and frequency planning which is closely related to the forthcoming auction of the Digital Dividend.Tato bakalářská práce pojednává především o vývoji LTE technologíí a jejich možnostech nasazení v České Republice a ve světě. Práce se nejprve zaměřuje na vývoj mobilních standardů od nástupu sítí třetí generace, Release 99, až po doposud nejnovější Release 12, kde jsou postupně probrány vrcholové telekomunikační technologie a jejich přednosti. V práci jsou dále popsány rozdíly fyzických vrstev mezi technologiemi HSPA+ a LTE, jelikož se jedná o další evoluční krok v oblasti datových přenosů. Popis obsahuje blokové srovnání od samotné inicializace transportního kanálu, po přenosovou cestu a opětovného získání užitečné informace. Vývoj LTE sítí ve světě pojednává o aktuálním stavu vývoje a rozšíření této technologie. Podrobně jsou zde popsány země, kde se LTE používá spolu se srovnáním použitých frekvenčních pásem. Poslední část řeší otázku vývoje a nasazení LTE v České Republice. S ohledem na aktuální stav sítí jednotlivých operátoru je sekce zaměřena také na legislativu, páteřní sítě a frekvenční plánování, s čímž souvisí také očekáváná aukce z digitální dividendy.440 - Katedra telekomunikační technikyvelmi dobř

Turbo Decoding and Detection for Wireless Applications

A historical perspective of turbo coding and turbo transceivers inspired by the generic turbo principles is provided, as it evolved from Shannon’s visionary predictions. More specifically, we commence by discussing the turbo principles, which have been shown to be capable of performing close to Shannon’s capacity limit. We continue by reviewing the classic maximum a posteriori probability decoder. These discussions are followed by studying the effect of a range of system parameters in a systematic fashion, in order to gauge their performance ramifications. In the second part of this treatise, we focus our attention on the family of iterative receivers designed for wireless communication systems, which were partly inspired by the invention of turbo codes. More specifically, the family of iteratively detected joint coding and modulation schemes, turbo equalization, concatenated spacetime and channel coding arrangements, as well as multi-user detection and three-stage multimedia systems are highlighted

Link level performance evaluation and link abstraction for LTE/LTE-advanced downlink

Els objectius principals d'aquesta tesis són l'avaluació del rendiment a nivell d'enllaç i l'estudi de l'abstracció de l'enllaç pel LTE/LTE-Advanced DL. S’ha desenvolupat un simulador del nivell d'enllaç E-UTRA DL basat en la tecnologia MIMO-OFDM. Es simulen els errors d'estimació de canal amb un model d'error de soroll additiu Gaussià anomenat CEEM. El resultat d'aquest simulador serveix per avaluar el rendiment a nivell d'enllaç del LTE/LTE-Advanced DL en diferents entorns . La idea bàsica dels mètodes d'abstracció de l'enllaç és mapejar el vector de SNRs de les subportadores a un valor escalar, l'anomenada ESNR, la qual és usada per a predir la BLER. Proposem un innovador mètode d'abstracció de l'enllaç que pot predir la BLER amb bona precisió en esvaïments multicamí i que inclouen els efectes de les retransmissions HARQ. El mètode proposat es basa amb l'estimació de la informació mútua entre els bits transmesos i els LLRs rebuts.The main objectives of this dissertation are the evaluation of the link level performance and the study of link abstraction for LTE/LTE-Advanced DL. An E-UTRA DL link level simulator has been developed based on MIMO-OFDM technology. We simulate channel estimation errors by a Gaussian additive noise error model called CEEM. The result of this simulator serves to evaluate the MIMO-OFDM LTE/LTE-Advanced DL link level performance in different environments. The basic idea of link abstraction methods is to map the vector of the subcarrier SNRs to a single scalar, the ESNR, which is then used to predict the BLER. We propose a novel link abstraction method that can predict the BLER with good accuracy in multipath fading and including the effects of HARQ retransmissions. The proposed method is based on estimating the mutual information between the transmitted bits and the received LLRs.Postprint (published version

Effect of multiple simultaneous HSDPA users on HSDPA end-user performance for non-real time services in one cell system

HSDPA networks are currently being deployed; however, there is little knowledge about how these networks perform and behave, and which will the Quality of Service and Quality of Experience that users will achieve due to the fact that UEs share the downlink channel. Furthermore, HSDPA planning and dimensioning is being done through the traditional mechanisms to plan and dimension UMTS networks. These mechanisms do not provide, though, accurate results for HSDPA. This thesis will focus on doing progress in these two areas. A HSDPA simulator was built to find some answers. This simulator used a simplistic model to simulate the radio environment and HSDPA features at Node B. Besides, the simulator dynamically created web browsing traffic according to the traffic patterns specified by the 3GPP. Three main simulations were performed. First, the maximum number of HSDPA users that a HSDPA network can support was obtained for different mean cell throughputs. Results also showed that the relationship between the mean cell throughput and the maximum number of users is linear. Second, the effect of the amount of UEs in a HSDPA network was studied. Results showed how the network and end-user performance changed when the number of UEs differed from the maximum number of UEs. Simulations demonstrated that network and end-user performance decreases rapidly and significantly when the maximum number of UEs was exceeded. Finally, the mean session inter-arrival time was modified to observe how this traffic parameter affected the network and the end-user performance. Furthermore, different sets of number of UEs were used to find out any correlation between the number of UEs and the mean session inter-arrival time. Results showed how the mean session inter-arrival time was much more relevant for the network and end-user performance when the maximum number of UEs had been exceeded. Results will give a glimpse of how HSDPA can perform in real networks. Besides, this simulator can help operators and providers to plan and dimension HSDPA networks more accurately