In this thesis work, we report the design, implementation and evaluation of a timing synchronization algorithm based on the technique first proposed by Gardner , applied to wireless communication using the Alamouti spacetime code  under QPSK modulation with halfsine pulses. To achieve this, a mathematical model is introduced which includes software design of communication algorithms. In this modeling, we simulate the Gardner algorithm in MATLAB. Then, five techniques are introduced to improve the performance of the loop filter in the digital receiver, and they are successfully implemented and evaluated in Matlab. These five techniques prove that there is an improvement in digital receiver performance in terms of the convergence speed and the communication system complexity.
The estimate can be improved by averaging techniques such as least squares linear curve fitting over all pilot pairs that are su ﬃ ciently closely placed within a frame. In case of CFO, consecutive symbols within a subcarrier are rotated with respect to each other, as will soon be discussed, forcing the averaging to be independently done over the subchannels for every MC symbol time. The CFO additionally increases the additive distortion. Finally, in presence of the trans- mission channel, the (flat-fading) channel coe ﬃ cient within the subchannel of interest also multiplies the transmitted signal, introducing additional rotation. Since in general this rotation is diﬀerent at diﬀerent subcarriers, it would be expected that this method cannot be used anymore with practical transmission channels. Nevertheless, if the eﬀect of the FTD on the phase is predominant, the phase diﬀerence introduced by the channel coeﬃcients will add up as noise at the end. Consequently, we can consider ∠(H k p +Δk,n p ) = ∠(H k p ,n p ) + 2πΔkτ FTD + η ϕ , where η ϕ is an
All digital communication systems require proper synchronization for decoding of the received signal in order to obtain the original information transmitted. In Digital Audio Broadcasting (DAB), Synchronization plays an important role by locating each frame precisely. Digital Audio Broadcasting system explores the Null symbol and the phase reference symbol for synchronization purpose. Software Defined Radio-DAB is a system where components that have been traditionally implemented in hardware (example: Filters, modulators/ demodulators) are implemented by means of software on a computer or embedded system. Traditional hardware based radio devices can only be modified through physical invention. This results in higher production costs and minimal flexibility in supporting multiple waveforms standards. Whereas Software Defined Radio technology provides an efficient and comparatively inexpensive solution allowing multiple mode, multi-band and multi-functional wireless devices that can be enhanced using software upgrades. However, a pure software solution (Software Defined Radio) consumes more memory than a hardware solution. Existing techniques are still challenging in optimizing the memory requirement for Software Defined Radio to achieve overall cost effectiveness and flexibility. This work aims to produce an efficient algorithm for reducing the memory requirement for SDR DAB.
As the field of nanotechnology is increasingly gaining significance in areas such as bioscience or environmental engineering, researchers have produced diverse developments in nano-scale devices. For a possible means for nano-communication, molecular communication via diffusion (MCvD) emerged as a prime candidate technology [1–3]. In the case of the dominantly used radio-frequency (RF) communication, nano-range is difficult to implement due to the severe path-loss . The drawback of the MCvD, however, is the high level of randomness in signal propagation which creates problematic non-linear noise in macro-scale applications . Moreover, the heavy tail nature of the received signal in MCvD causes inter-symbol interference (ISI), which is detrimental to the capacity of a MCvD channel because ISI can increase the error-rate or decrease the data-rate. With a pre-decided symbol duration, ISI can be defined as one or more symbols from previous symbol periods interfering with the current symbol and causing noise at the receiver node [6–9].
At Destination, without loss of generality, let us assume that the received signal from Relay 2 is dT +τ S seconds delayed with respect to that of Relay 1, where d is an integer number and 0 T S . Thus, to avoid ISI, the cyclic-prefix length is determined as L>d. If the delay, as shown in Fig. 2, is less than one symbol duration, L=1is enough. In practice the relays do not need to know the delay and, based on the propagation environment, the maximum value of d in the network can be estimated and used to determine the cyclic prefix length.
Since the pulse-based master synchronization adopts decision feedback, its stability analysis involves the control theory. In the control theory, it is called as an act-and-wait type time-periodic control, where a more comprehensive analysis is presented in [14–16]. The stability boundaries for the given three master synchronization are analyzed and simulated. Suppose the signal period is T, Figure 3 shows the stability margin with respect to the feedback loop gain K and the delay D. The stable region is on the left-hand side of figure relative to the thick curve, and the right-hand side is unstable. The stability boundaries of sawtooth-waveform- and sine-waveform-based master synchronization is close to the result of analysis in (6). When the feedback delay increases, the gain K should be decreased to ensure the stability of the feedback loop. If we consider the fading of wireless links in practice, the above result limits the range of the stepsize of phase adjustment in master node.
Both the symbols in the preamble and the pilot symbols are known to the receiver. The first two OFDM frames contain ten short preambles and are used for automatic gain control, diversity selection, timing acquisition, and coarse frequency acquisition. We will focus our attention on the acquisition of timing and frequency. The zero packing has the effect of decreasing the symbol time by four, or Nfft/4, thus yielding the four copies in the time series. Thus, the short training symbols have 2.5 × Nfft symbols. In our application of OFDM, IEEE 802.11a/g, the bandwidth is 20MHz and the sample time is 1/20MHZ = 0.05μs. If we set Nfft = 64, as in IEEE802.11a, there are 16 samples in the short training symbol and so the symbol time is 16 × 0.05μs = 0.8μs. There are ten short training symbols which gives a total time of 8μs.
is down that the message signal hidden in chaotic carrier of the systems can be perfectly reconstructed, and the bandwidth, the characteristic of distortion, and the level of security are improved. The chaos masking method based on multistage chaotic synchronization system for secure communications, to some extent, enhances the degree of security, as the message is not only just added to the chaotic carrier signal twice but is also decrypted twice. For example, in , a new method of global chaos synchronization among three different structures of chaotic systems is proposed under the framework of drive-response systems based on Lyapunov stabilization theorem; then, this method is applied to secure com- munication through chaotic masking. At last, it ana- lyzes the characteristics of noise and then presents a de-noising method using wavelet transform. With the MATLAB, the effects of signal de-noising could be demonstrated.
In this thesis, I present a case study of the GMH phenomenon that emerged in 2009 from mainland China. Originally a set of homophones anonymously created online, the Mandarin tone transforms linguistic wordplay into a visual lexicon of 10 Mythological Creatures to critique internet control in mainland China. Of interest here is the way in which these symbols were generated and how and why they transitioned from symbolic online internet memes to offline symbolic use in art and design. I therefore set out to explore the new symbolism by investigating ways of deciphering online visual gestures through accessing ‘cultural keys’, as developed by Shifman (2014). The creation of the new symbolism, as discussed throughout the thesis, is rooted in political relevance and deploys practices and art forms to signal, dissolve and raise awareness of social and ideological change. My study maps the GMH phenomenon to test the claim that over time some symbols may lose potency, while others remain and propagate in online and offline visual forms. The findings have been related through a synthesis of semiotic and compositional interpretation and multimodal discourse analysis that also employs digital ethnography. The aim of the study is to deepen the Western perspective on Chinese visual culture by working with and interpreting cultural flows in the digital age. I claim that the new symbolism generated as a result of internet censorship in mainland China demonstrates a generational and ideological shift through the creation and propagation of a new visual grammar for the twenty-first century. I argue that the main symbol, the GMH, still carries potency as a freedom of expression icon, as demonstrated by its ongoing relevance to artists and designers. The overall findings suggest that, as a result of social change in China, a new set of communicators were formed and that their signification is now historicised, renewed and extended through the Chinese diaspora or people who wish to understand the complexities of China’s creativity and online cultures.
RFID system begins with an inventory round in which fundamental parameters for the communication link, such as the symbol period and modulation scheme, are determined. Specifically, tags estimate the symbol period by measuring the temporal support of the training signal sent by the inter- rogator during the initiation of the inventory round. This training signal also provides the power source required by the circuit on passive tags to backscatter their reply messages via antennas. In this paper, we refer the communication mode from tags to interrogator as the backscatter mode. All information transmitted in the link is first processed by a baseband data-encoded scheme and then modulated by either the amplitude-shift keying (ASK) or the phase- shift keying (PSK). The backscatter mode of the EPCglobal system supports two types of the baseband data-encoding schemes: (1) The FM0 baseband scheme and (2) the Miller modulation. Both schemes employ the same baseband basis functions but have di ﬀ erent data-encoding rules to represent the output data stream. Since the proposed JVSS algorithm is applicable to both baseband data-encoding schemes, this study uses the FM0 baseband scheme as the study case to describe the proposed JVSS algorithm.
Handouts: The lecturer will give to students handouts to help them focus more on their research for specific functions and commands. Multimedia: Students will use multimedia tools on the e-learning package to discuss the issues and ideas as a group. The digital tools will allow the incorporation of sound into lessons, moving pictures, and animation, which gives students a more active role in the learning environment. They can watch practices in action, see small things up close, and use the keyboard or mouse to navigate interactive materials, simulations, and images. The use of multimedia helps to transfer information effectively and quickly to all students, and can keep students interested. The lecturer can blend video, audio, text, simulations, images and multimedia into a single online environment via a Moodle application available to students from school or home.It is more important to review and inspect each material before providing it to students; this stage can be used to pilot-test the lesson materials
Timing recovery as a process of sampling at the right time are critical in digital communication receivers. The problem is formulated through maximum likelihood (ML) . In direct application of ML method, message sym- bols and timing offset are estimated jointly. However, this solution conveys the exhaustive search methods that imposes a lot of computations and it makes the solution impractical. To avoid the complexity due to the exhaustive search in ML problem, iterative solutions are introduced [2–4]. The general idea of iterative timing recovery scheme is to improve the timing estimation accuracy by multiple exploiting the timing information provided by a set of samples and application of this estimation to regen- erate a new set of samples that iteratively approaches to the local maximum of the likelihood function. ML- based timing recovery methods usually ignore the time
Massive MIMO is the best energy efficient technique for 5G cellular communications . But in massive MIMO a large amount of antennas are used which increase the power consumption. So the selection of antenna is quite challenging. Moreover massive MIMO require complex architecture. A huge amount of power is also consumed in multiplexing and de-multiplexing unit. It also increases the overall system cost. Energy harvesting techniques are also used to make cellular networks energy efficient but they are not reliable. In case of solar energy, the required amount of power cannot be generated during cloudy weather. As the energy cannot be encrypted so the energy state of devices in a cellular network is open to security attacks. This is also a challenging task for the researchers and the industries.
negated copies of the synchronization pattern. The synchroniza- tion algorithm at the receiver needs no knowledge of the em- ployed synchronization pattern, hence this sequence could be used for channel sounding training sequences or for base station identification signals. Note that there are three hierarchical pe- riodic time-domain structures in the proposed framing scheme: the short-term intrinsic periodicity in the reference symbol of Fig. 4, the medium-term periodicity associated with the quasi- periodic extension of the OFDM symbols, and the long-term pe- riodicity of the OFDM frame structure, repeating the reference symbol every 64 OFDM symbols, as portrayed in Fig. 3. The long-term reference symbol periodicity is exploited to main- tain OFDM frame synchronization, while the medium-term syn- chronism of the cyclic extension assists in the process of OFDM symbolsynchronization. A detailed discussion of this figure will be provided during our further discourse. Let us initially con- sider the macroscopic structure of the synchronization system in the next section.
experimental test-bed. Various analytical approaches were found in the time synchronizationtechniques exclusively for single hop network for the purpose of defining the accuracy features of the discussed synchronizationtechniques. Unfortunately, in case of multi-hop network, there was no evidence of any analytical model that could be adopted for further extension of future research work. It is already known that standard routing protocols that have higher supportability of multihop in wireless sensor network is very limited and no evidence of time synchronization technique considering multihop has added to a significant research gap. This fact needs to be addressed in the future study direction that emergence of increased error rate in time synchronization is quite high when two sensor nodes attempts to perform synchronization in multihop network. Although, effect of time synchronization of multihop network doesn’t have much significant effect in pair-wise error evaluation, but still the scope of evaluation in same is extremely few to find in existing studies. Such research gap calls for performing an extended study as well as problem investigation in the line of both single and multihop synchronizationtechniques in distributed wireless sensor network. The most frequently adopted RBS scheme was found with a significant issue when the identiﬁcation or the discovery process of the sensor node to be acting as beacon sender evolved. This is a challenging issue as if there is presence of more number of beacons in a single neighborhood, it may lead to evolution of message redundancy as well as control overhead too. This fact will also lead to maximize the consumption of constrained resource available within the sensor nodes. Moreover, such facts could be possibly more investigated
2) Signal Transitions: For purposes of synchronization we are often less concerned with the signal level than with the times at which the signal changes state. In digital systems this time of change would be called an edge or transition of the signal. The notion of the transition time ignores rise-time effects. In fact, the transition time is subject to interpretation. Transition times are a useful abstraction for the case where the rise times are very short in relation to the interval between transitions, with the result that the variation in the transition time is negligibly small over the set of all possible definitions of the transition time. Rise-time is governed by underlying physical phenomena, such as transmission line dispersion, and can be decreased by using wider bandwidth drivers or intermediate repeaters. As system clock rates increase, however. for a given interconnect style the behaviour ignored by this abstraction inevitably becomes essential.
2. Md. Tofazzal Hossain, Sithamparanathan Kandeepan and David Smith, “Decode- and-Forward Cooperative Communications: Performance Analysis with Power Constraints in Presence of Timing Error”, in Proceedings of International Workshop on Cognitive Radio and Cooperative Strategies for Power Saving collocated with MOBIMEDIA 2010, Lisbon, Portugal, Sept. 2010.