CHAPTER-2. LITERATURE REVIEW

Transcription

1 CHAPTER-2. LITERATURE REVIEW This section describes the brief outline of the literature survey related to the 4th generation wireless technologies such as DVB-T, DVB-S, DVB-S2, IEEE standard, Antenna Diversity techniques, BLAST structure as well as STBC coding technique which are the milestones of this research work. The book, Fundamentals of Wireless Communication mainly includes the research on basic aspects of wireless communication along with the techniques to explore the utility of it in modern communication era. The whole concepts have been structured into three levels. 1.) Channel investigations and modeling, 2.) Various communication concepts and their utility and 3.) Techniques to be applied at system level formation. Basically the most prominent limitation of wireless communication is multi path fading due to which the capacity of the system is decreasing and the error rate is increasing. The stuff presented in the book elaborates the way in which how the fading can be exploited as an advantage to improve the system performance by means of various diversity techniques. The concept of Time diversity, Frequency diversity and Antenna diversity i.e. MIMO would be the most innovative approach in the modern wireless systems to improve the capacity with the highest superior quality. To implement the diversity algorithms into the wireless systems, this is the very useful literature for the research purpose [1]. The book, Wi-Fi, Bluetooth, ZigBee and WiMAX discusses various modern wireless networking standards approved by IEEE as IEEE , IEEE and IEEE in form of their architectural aspects, functionality, frame structure, physical and MAC layer standards, Quality of Services, etc. Wi-Fi is the most important Wireless LAN standard having various updated standards like IEEE a, IEEE b, etc. IEEE and ZigBee which are concerned with wireless sensor networks. ZigBee technology enables the coordination of communication among thousands of tiny sensors, which are very low cost, with lower power consumption and low data rate. IEEE standard i.e. WiMAX is nothing but the futuristic 4G technology for mobile 6

2 communication with the features of wireless MAN (WMAN) terminology. It fills the gap between modern cellular standards i.e. 3G techniques and wireless networking standard. It provide high data rate of 70Mbps along with wider coverage area. This literature provides very good theoretical aspect to understand the modern wireless communication standards in this research work [2]. The article on Performance Analysis of VBLAST Detectors for the MIMO channel presents the various detection algorithms for advance antenna system designated by Multiple Input Multiple Output (MIMO) system. Multiple Input Multiple Output (MIMO) channels can offer high capacity to wireless systems and the capacity increases linearly with the number of antennas. There are many schemes that can be applied to MIMO systems such as space time block codes, space time trellis codes, and the Vertical Bell Labs Space-Time Architecture (V- BLAST). Among all the different signal processing algorithms that are available for the MIMO system, the VBLAST algorithm has become a potential alternative due to its excellent complexity-performance tradeoff. Through this technique, the no. of antennas can be increased beyond 2 both at the transmitter and receiver side so that the channel capacity can be increased drastically. The paper includes the detection schemes for the VBLAST coded signals such as ZF, MMSE, ML, Ordering algorithm, etc along with their comparative analysis. As this research work includes the implementation of MIMO in various wireless communication techniques, this paper provides the base for it [3]. In this research work, the investigation and modeling of efficient wireless systems would be carried out and in that one of the most important wireless communication systems is IEEE standard i.e. WiMAX. The book Mobile Broadcasting with WiMAX-Principles, Technology and Applications provides the fundamental platform to understand the basics of WiMAX. The literature includes the basic architectural study in terms of Physical layer and MAC layer of the system along with frame structure, Error checking and controlling algorithms, Various standards with their comparative analysis, implementation of advance antenna techniques in it as well as applications of WiMAX systems. WiMAX is 7

3 seen to be the 4G standard anticipating larger coverage area along with the highest speed among the all existing 3G technologies [4]. The book, Wireless Communications, Principles and Practice, elaborates the basics of traditional wireless communication technology. It includes the invention of wireless and cellular technology along with the basic architecture of traditional cellular systems i.e. GSM. Further the major hurdle in the growth of wireless communication i.e. multi path fading and its effects have been very well covered. In the cable less environment, the signals can take any path from the transmitter to reach to the receiver. The components of the signal take various paths and form the multi path structure and will arrive at the receiver with different strength and at different time intervals causing distortion in amplitude, phase and frequency which turns into fading. According to the variations in the distance between transmitter and receiver as well as nature of fluctuations, two types of fading would occur as small scale and large scale fading which limits the system capacity and data rate and introduces errors in the information. As this research work is towards making the wireless systems more efficient by eliminating the effect of fading, this book makes the concept of fading and its causes much clear [5]. The paper, Terrestrial Digital Video Broadcasting Technology basically discusses the most emerging technology of digital video broadcasting technique i.e. terrestrial digital video broadcasting system (DVB-T). In DVB-T digital signal processing it is necessary to perform source coding, compression techniques, modulation, channel coding, multiplexing and multiple accesses, frequency spreading and synchronization. This paper consists of various video compression and coding techniques such as JPEG, MPEG-I, II, IV, DCT, etc with their applications and comparative analysis. In digital video broadcasting image data compression is very crucial issue, especially in transmission and storage of image data. Its aim is to minimize the requirement of transmission bandwidth and the storage memory. The MPEG standards for video coding addresses the combining of more elementary streams of video, audio, text, still pictures, graphics and other data into a single or multiple streams which are suitable for 8

4 transmission, storage and users interaction. Also video coding is one of the key technologies in digital video broadcasting era and its standardization is essential for efficient interchange of audio-visual information. Hence this paper provides very fruitful analysis of complete DVB-T system for this research [6]. The paper on Design and Implementation of H.264-based Video Decoder for Digital Multimedia Broadcasting has presented the world s first real-time video decoder for the Digital Multimedia Broadcasting system. The video decoder was built based on the Baseline profile of MPEG-4 Part10 AVCIH.264 at Level 1.3. This paper comprises of a brief overview of the H.264 video coding standard and the DMB system, the design issues and presents the hardware architecture of H.264 and the performance of the video decoder in terms of the average decoding time and the system s operation clock frequency. In H.264, the overall gain in coding efficiency results from a plurality of small improvements in the Video Coding Layer (VCL). The H.264 video codec enhances the motion-prediction by employing a new set of techniques such as variable block-size motion compensation, quarter-sample-accurate motion vectors, multiple reference pictures, and spatial prediction for intra coded pictures. The complete design and architecture of H.264 Video decoder is the most beneficial aspect of this paper for the research work [7]. This paper on Influence of the FEC Channel Coding on Error Rates and Picture Quality in DVB Baseband Transmission presents the simulation model of general DVB system which includes basic transmission blocks along with source, channel and link coder and decoder systems with their parameters. Basically as a channel encoder and decoder, pair of inner and outer encoder/decoder has been chosen in cascade combination. As an inner coder convolution coder and as an outer coder reed solemn encoder has been taken. The whole simulation model has been analyzed by changing various parameters of RS coder and Convolution coder so as to achieve the different values of BER and SER. The aim of the analysis is to determine the influence of channel encoder parameters on achieved error rates and objective PQE metrics by passing the image signal through it which is the quite handy utilization of the paper in this research work [8]. 9

5 The paper Simulation of Lithuanian Version of DVB T System illustrates the complete modeling of DVB-T system with matlab simulink. The model includes the various blocks of channel encoder/decoder, source encoder/decoder, modulation/demodulation as well as OFDM encoder/decoder. By changing the signal to noise ratio of AWGN channel as a transmission medium, the error rate performance of the system can be carried out by plotting the graphs of BER v/s SNR. This paper plays a key role in understanding the basics of DVB-T system for this research work [9]. This paper DVB-T Channel Coding Implementation in MATLAB is based on the coding of complete DVB-T system with MATLAB tool. The DVB-T (Digital Video Broadcasting Terrestrial) is ETSI EN standard of European digital television for the terrestrial transmission to fixed, portable and mobile receivers. The DVB-T Standard specifies the framing structure, channel coding and modulation for digital terrestrial broadcasting. This paper includes MATLAB coding of various blocks of DVB-T system such as randomization/derandomization, inner coding/decoding, and outer coding/decoding, interleaving/deinterleaving, modulation/demodulation and OFDM. By considering AWGN as a channel, for different MER values the performance of the system has been analyzed with constellation diagrams [10]. In this work, the performance of a MIMO antenna system that is a hybrid of transmit diversity and spatial multiplexing has been evaluated. Two receiver structures for this hybrid BLAST-STBC transmission scheme have been proposed by the researcher. Multiple-input multiple-output (MIMO) wireless channels are known to offer better link and/or capacity gains, which can be exploited by employing antenna arrays at both ends of the link. An efficient way of exploiting the MIMO channel is the use of spatial multiplexing or V-BLAST (Vertical Bell Labs Layered Space-Time) that aims at providing higher data rates with no sacrifice in bandwidth. Another approach that benefits from exploiting the MIMO channel is the use of transmit diversity by means of space-time block-coding (STBC), where the idea is to obtain diversity gains at the receiver, with simplified receiver processing. The paper on Performance of MIMO Systems with a Hybrid 10

6 of Transmit Diversity and Spatial Multiplexing presents two schemes of hybrid structure in which the first hybrid receiver structure (HR-1) is designed to operate on flat-fading channels while the second hybrid one (HR-2) is designed for ISI channels. The performance of the hybrid transmission scheme is compared to that of pure transmit diversity and pure spatial multiplexing schemes in terms of biterror-rate (BER). The simulation results show that the performance of the hybrid scheme along with the proposed receivers is excellent, outperforming pure BLAST-based systems in terms of BER and providing higher data rates than a pure STBC system. For this research work, this paper provides the fundamental idea for developing the MIMO system [11]. The paper on Combined Spatial Multiplexing and STBC to Provide Throughput Enhancements to Next Generation WLANs describes the wireless LAN standards. Current WLAN systems such as IEEE a and g Wireless Local Area Networks (WLANs) employ Coded Orthogonal Frequency Division Multiplexing (COFDM) and provide data rates of up to 54 Mbps in a 20MHz bandwidth. But the recent trend demands for the higher data rate with the lowest value of error rate. To solve the purpose, the antenna diversity technique abbreviated as MIMO system with the hybrid combination of spatial multiplexing and space time coding is the emerging technology which is the central theme of this paper. In this paper a hybrid 4x4 scheme is investigated that combines spatial multiplexing and STBC to provide both increased throughput and diversity to future generation WLANs. For this study, a WLAN physical layer simulator employing MIMO techniques was developed to evaluate the PER and throughput of WLANs for the 2x2, 4x2 and 4x4 MIMO cases with and without the hybrid algorithm. As one of the main part of this research work is to study and implement MIMO with alamouti and blast structure, this paper provides the most useful information [12]. This paper Multi layered Space Time Block Codes for OFDM System correlates three most emerging techniques of wireless communication to achieve high data rate with low bit error rate and high capacity i.e. Alamouti coding, BLAST structure and OFDM system. This paper includes the simulation of 11

7 different wireless channels with the implementation of suitable above mentioned techniques to achieve great throughput. The researcher has proposed two schemes aiming at achieving high data rate with reliable transmission. VBLAST-STBC is used in flat fading channels, and VBLAST-STBCOFDM is used in frequency selective fading channels. Simulations showed a great improvement in the Bit Error Rate for the mentioned schemes over the original VBLAST architecture, either fixing the number of transmit and receive antennas or fixing the bit rate. The above conclusion is very beneficial for this research work for developing the efficient wireless communication system [13]. The paper Capacity and V-BLAST Techniques for MIMO Wireless Channel analyses the behavior of V-BLAST system. In wireless communication, the major problem lies with the system is the scarcity of the bandwidth which puts the limitation on throughput of the system in terms of data rate as well as error rate. But the remedial solution for the above is the latest trends in antenna systems that are Multiple Input Multiple Output system. It has been demonstrated that multiple antenna system provides very promising gain in capacity without increasing the use of spectrum, reliability, throughput, power consumption and less sensitivity to fading, hence leading to a breakthrough in the data rate of wireless communication systems. There are many schemes that can be applied to MIMO systems such as space time block codes, space time trellis codes, and the Vertical Bell Labs Space-Time Architecture (V-BLAST). In this paper, the study of the performance of general MIMO system, the general V-BLAST architecture with Maximum Likelihood (ML), the Successive Interference Cancellation (SIC), Zero-Forcing (ZF), Minimum Mean- Square Error (MMSE) and Maximal Ratio Combining (MRC) detectors in fading channels have been carried out which is the stepping stone for this research work [14]. This paper New Rate-2 STBC Design for 2 TX with Reduced-Complexity Maximum Likelihood Decoding discusses the design of a closed-form rate-2 space-time block code for two transmit antennas through a judicious application of rotation and linear combination operations on two parallel Alamouti codes to achieve maximum diversity or maximum capacity while achieving optimized 12

8 coding gain and reduced-complexity maximum likelihood (ML) decoding. The maximum transmit diversity (MTD) construction provides a diversity order of 2Nr for any number of receive antennas Nr at the cost of channel capacity loss. The maximum channel capacity (MCC) construction preserves the mutual information between the transmit and the received vectors while sacrificing diversity. So this paper suggests the effective simulation of the combination of the two techniques [15]. Recently, the increasing demands of multimedia services and high speed wireless communications have lead to great interest multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM). The efficient MIMO technique can be implemented in two ways: one by means of spatial multiplexing i.e. BLAST structure and the other is by means of Space Time Block Coding i.e. Alamouti coding. The first one provides the greater capacity but sacrifices diversity while the later one provides high diversity gain but sacrifices system capacity. So the hybrid technique which is the combination of SM and STC along with MIMO-OFDM provides the solution to achieve both greater system capacity along with less error rate. This paper A Novel Efficient Detection Scheme for Hybrid STBC in MIMO-OFDM System proposes efficient detection scheme for MIMO-OFDM system with hybrid STBC symbols which is the important point from this research work point of view [16]. This paper Multiuser Detection of Alamouti Signals proposes a low complexity Alamouti BLAST-MMSE (A-BLAST) receive algorithm. The performance of the A-BLAST Algorithm is determined by the quaternionic angle (the inner product of two quaternionic vectors) between the desired Alamouti signal and interference. In combination with the A-BLAST Algorithm, this led to introduce a new adaptive modulation strategy that is called code diversity for single-user point-to-point system or multiuser MAC system. Using the Alamouti code as a building block, different ways of decoupling transmission signals (by exploiting the algebraic structure of quaternion) at the receiver have been developed, which are then decoded using BLAST. In particular, the paper presents a BLAST receive 13

9 algorithm for Alamouti signals based on the Minimum Mean Squared Error (MMSE) filter, which is called the Alamouti BLAST-MMSE (A-BLAST) Algorithm. The paper will be useful for innovation in BLAST and Alamouti technique implementation in this research work [17]. The paper Interference Cancellation Receiver for Space Time Block Coded Systems over Frequency Selective Channels describes the version of MIMO system. An efficient way of exploiting the MIMO channel is the use of spatial multiplexing or V-BLAST (Vertical Bell Labs Layered Space-Time) that aims at providing higher data rates with no sacrifice in bandwidth. Another approach that benefits from exploiting the MIMO channel is the use transmit diversity by means of space-time block-coding where the idea is to obtain diversity and coding gains at the receiver with simple linear processing. In mobile communication systems, STBC is being considered as an attractive solution to provide diversity gain on downlink path, i.e., at the mobile terminal. For the recent era, the utilization of available bandwidth is the most important aspect. And with this it should also be kept in mind that with reduction in bandwidth requirement co channel interference (CCI) as well as inter symbol interference (ISI) should also remained enough low for better system performance. This work proposes an effective receiver structure for space-time block-coded systems capable of performing CCI cancellation and ISI equalization in a two-stage approach. The receiver is based on a minimum mean square error (MMSE) spatial filter for CCI cancellation and a modified space-time decoder connected to a non-linear equalizer for ISI equalization [18]. The paper On the Adaptive DVB-S2 Physical Layer: Design and Performance presents the design of DVB-S2 system. The digital video broadcasting-satellite (DVB-S) standard is now the most widely adopted transmission protocol for broadcasting by satellite. This fact has prompted the development of the evolved standard identified as DVB-S2 which promises to yield very significant system capacity gains, as well as the extension of the set of services and applications that can be delivered to an enlarged mass market. This article provides general guidelines for the implementation of an adaptive physical layer compliant with 14

10 the DVB-S2 standard. The complete design of DVB-S2 system along with various coding/decoding techniques and adaptive modulation techniques described in this paper provides the handy information for the research work [19]. This article on Transmission techniques for Digital Terrestrial TV Broadcasting discusses potential transmission techniques for digital terrestrial TV broadcasting. The single carrier transmission with frequency domain equalization opens up new perspectives for digital terrestrial TV broadcasting. This paper illustrates the basic OFDM system along with its implementation in terrestrial digital TV system along with frequency domain equalization for better channel capacity with reduced error rates. Finally the simulation can be carried out to compare the performance of OFDM and single carrier transmission using a number of channels [20]. This technical paper on 4GWireless Begins to Take Shape explores the idea of 4 th generation wireless systems. As always, service providers and users are looking for wireless technologies that offer better performance and more advanced capabilities than their predecessors and that thereby better approximate the experience of using wire line technologies. Basically there are two trends driving the development of 4G technologies: the continuing growth of wireless usage and the rise of household broadband Internet subscriptions. Many users want wireless technologies that approximate the experience they have at home with their high-speed wire line services. There is also demand for the services such as better-quality, faster video viewing and quicker online content downloading, even for mobile users with handheld devices that 4G would enable. WiMAX is the only 4G approach built on an existing OFDMA technology. It is based on IEEE e, which added mobility to the previous WiMAX standard, designed mainly for fixed operations. IEEE is a longrange, fixed and wireless, metropolitan-area communications technology also known as WiMAX (worldwide interoperability for microwave access). As this research work is on the modeling of modern wireless communication systems, the paper plays the very important role [21]. 15

11 The paper 4G Wireless Technologies: When will it happen? What does it offer? gives the overview of the latest wireless technologies. As the name itself suggests that the paper is about to have need for the best technology in the current era for faster data transfer with very low error rate and with very less requirement of bandwidth. Consumer expectations for mobile handsets and similar products are becoming more and more sophisticated. Consumers are demanding a better user experience along with more advanced and useful applications on a more ergonomic device. Devices continue to shrink in size while growing in processing power. Next generation mobile networks, like 4G wireless technologies, will need to meet these user expectations if they are to succeed. The move to 4G networks will allow service providers to offer the impressive applications that will drive users to upgrade to the new phones. This paper basically discusses the features, supporting technologies and requirement of 4G technologies which provides the fundamental idea in this research work [22]. This paper An Empirical Feasibility Study of 4G s Key Technologies has attempted to highlight the key challenges in migrating to 4G mobile communication systems. The paper also discusses in short the various key technologies required for implementing for fourth generation mobile communication systems. 4G will be an IP based wireless network replacing the old Signaling System 7 (SS7) telecommunications protocol. Several upcoming technologies are considered to be the 4G technologies such as OFDM, OFDMA, MIMO, Ultra Mobile Wideband, UMTS, E-UTRA air interface, SDR, etc. which have been discussed in the paper along with their illustrations and parameters. For this research work, this paper provides very good theoretical background [23]. To cope up with the current trends of modern wireless communication systems, its mandatory to have the system which fulfils the requirements of high system throughput along with the lowest error rates. MIMO-OFDM is the technique which is the most promising technology which seems to satisfy the current demand. This paper Approaching MIMO-OFDM Capacity With Zero-Forcing V-BLAST Decoding and Optimized Power, Rate, and Antenna-Mapping Feedback presents a practical partial-channel-feedback scheme to support 16

12 capacity-approaching spatial multiplexing for the frequency-selective fading MIMO OFDM channel. The proposed scheme is a closed-loop extension of the well-known V-BLAST transmission scheme. Though the conventional open-loop V-BLAST is severely compromised in practice owing to its poor diversity performance and error propagation, the proposed closed-loop V-BLAST overcomes these difficulties by adaptively assigning transmit powers, rates, and antenna mappings at all OFDM tones. For the implementation of V-BLAST structure with the advancement in the modern wireless systems which is one of the objective of this research work, this paper will be very useful stuff [24]. The paper Performance of LDPC Code Based D-BLAST System represents the overview of one of the most important channel coding technique. Recently, many researchers have focused on multiple input multiple-output (MIMO) system to achieve large capacity and to combat fading environment. Many transmission schemes have been proposed for the modeling and analysis of MIMO system. Among those, Bell Labs Layered Space-Time (BLAST) is one of the transmitreceive architecture using spatial multiplexing and sub-optimal processing to detect transmitted signal from each transmit antenna. It gives a reasonable tradeoff between complexity and performance. One of the BLAST system is Diagonal BLAST (D-BLAST) which spreads each layer in space and time, and relies on layer s encoding to achieve transmit diversity gain. This paper describes the BLAST architecture along with LDPC coding. LDPC. In fading channel, LDPC codes can significantly reduce the error floor with a modest computational complexity. For nurturing the various algorithms of the MIMO in the research work, this paper is very beneficial [25]. The paper DVB-S2 Benefits for Military Broadcast Systems focuses on the technology and waveform efficiency of the DVB-S2 standard in military satellite communication (MILSATCOM) applications and provides a clear description of the status and authority of this evolving standard. DVB-S2 combines DVB-S and DVB-Digital Satellite News Gathering (DVB-DSNG) with advancements in coding technology and interactive services to provide capacity and reliability enhancements for a variety of applications. This paper is very useful for the 17

13 research work as it gives the comparative analysis of DVB-S and DVB-S2 system on the basis of every parameter. Moreover it illustrates the real time application of DVB-S2 in Military which includes the study of uplink, downlink frequency, encoding/decoding algorithm, multiple modulation schemes, etc [26]. The paper on DVB-S/S2 Satellite Television Broadcasting Measurement and Comparison compares two versions of DVB-S system. With the current trend in the digitization, the Digital Video Broadcasting has been emerging as the most promising technique which can offer best transmission performance approaching the Shannon limit, total flexibility and reasonable receiver complexity. The system is structured as a toolkit to allow the implementation of the following satellite applications: TV and audio broadcasting, interactivity and professional services, such as TV contribution links and digital satellite news gathering. This paper gives the overview of 1 st and 2 nd generation digital video broadcasting techniques for satellite communication i.e. DVB-S and DVB-S2 along with the real time application of it. As a digital satellite signal source were used a 90cm diametric parabolic antenna in top of DREL BUT destined to satellite ASTRA 3A 23,5 East longitude for DVB-S signal and to satellite ASTRA 1E 19,2 East longitude for DVB-S2 signal. Through this paper the keen comparative analysis can be done which would be the most important parameter for the research work [27]. This paper System-level Modeling of IEEE e Mobile WiMAX Networks: Key Issues basically deals with network level analysis of WiMAX system by evaluating the layer by layer working of the whole system. WiMAX system comprises of mainly two operational layers i.e. Physical layer and MAC layer which are individually modeled in this paper so as to get the view of system level parameters. The readings and observations generated at the abstract level are the very useful outcomes for this research work [28]. As one of the major unit of my research work the numerical modeling of WiMAX system which is considered to be the most recent wireless communication technique, this paper Simulation of WiMAX Systems plays the key role for the same. The paper describes the MATLAB model of WiMAX system along with 18

14 the advance features such as OFDM, MIMO with STBC and MIMO with BLAST. The simulation results derived from the modeling of WiMAX system related to bit error rate are very useful for this research work to expect the system performance of the WiMAX system with advance features. The paper provides the hard core reference for the progress of my research work [29]. The paper Rayleigh Fading Channel Model versus AWGN Channel Model in Audio Watermarking gives the comparative analysis of two wireless channels. For the fruitful wireless communication system, its not only sufficient to have the perfect transmitter and receiver sections, but to have efficient modeling of the medium i.e. virtual wireless channel. The modeling and analysis of wireless channel plays the important role in deciding the effectiveness of the wireless system as it is the main component which decides the error rate and data rate of the whole system. This paper puts the emphasis on the utility of two different wireless channels i.e. AWGN channel and Rayleigh channel by considering the real time application of Audio watermarking in mp3 system. As this research work is to develop the numerical modeling of modern wireless systems, the paper illustrates the choice of various wireless channels under different scenarios to get best performance [30]. 19