Recently, interference alignment (IA) has emerged as a promising technique to effectively mitigate interference in wireless communication systems. It has also evolved as a powerful technique to achieve the optimal degrees of freedom of interference channel. IA can be constructed in many domains such as space, time, frequency and codes. Currently, most researches on developing IA assume that channel state information (CSI) is well-known at the transceiver. However, in practice, perfect CSI at the transceiver can¡¦t be obtained due to many factors such as channel estimation error, quantization error, and feedback error. Under our investigation, the performance of IA is very sensitive to imperfect CSI. Therefore, this thesis proposes a spatial domain IA scheme for the three-user multiple-input multiple-output (MIMO) downlink interference channels, and analyzes the effect of channel estimation errors by modeling the estimation error as independent complex Gaussian random variables. The approximated bit error rate (BER) for the system with MIMO Zero-Forcing equalizer using IA is derived.

In recent years, there has been a growing interest in wireless ad hoc network. One of the major issues in wireless network is developing efficient routing protocol. Based on the concept of designing protocol model such as OSI model, the designers distilled the process of transmitting data to its most fundamental elements and identified which networking functions had related uses and collected those functions into discrete groups that became the layers. It is not suitable to design wireless ad hoc routing protocol based on OSI model conception because the OSI model is developed from the view point of wired network and there are many different characteristics between wired and wireless environment. The main different characteristics between wired and wireless are the mobility of mobile host and the transmission medium. Such differences have great effect on network performance. Due to the differences between wired and wireless characteristics, we present a comprehensive conception of designing wireless ad hoc routing protocol. In this context, we provide a wireless ad hoc routing protocol based on physical layer characteristics, ex: bit error rate, robust link. Our routing protocol will find out a route in good transmission environment and it is efficient to improve network throughput. Furthermore, our routing protocol will decrease the number of route request packets, the amount of retransmissions, link breakage rate, and increase throughput.

In wireless Communication, the need of radio spectrum increases nowadays. But in the system we are losing approximately 82-86% of spectrum most of the time due to the absence of Primary User (PU). To overcome this issue Cognitive Radio (CR) is an admirable approach. The concept of cooperative communication needs to be considering because high data rate is the demand for wireless services. Cooperative diversity in the network realized by 3-hop Decode, Amplify and Forward (DAF) and Decode and Forward (DF) and in 2-hop DF and Amplify and Forward (AF) Protocols implemented in cognitive radio communication network using Orthogonal Space Time Block Coding (OSTBC). The communication between end points is accomplished by using Multiple Input and Multiple Output (MIMO) antenna arrangement. During the Propagation, Alamouti Space Time Block Coding is used to accomplish spatial diversity and the encoded data is transmitted through Rayleigh fading channel. CR decodes the transmitted signal using Maximum Likelihood (ML) decoding method. Afterward signal broadcast toward the destination. To check the energy level of signal, energy detection technique applies at the Cognitive Controller (CC). Finally, CC will take ultimate decision for the presence of primary user if the energy level of signal is greater than predefined threshold level, it means PU is present otherwise it is absent. The main objective of this thesis is to analyze the performance of 3-hop and 2-hop communication network using relays. The performance is compared on the bases of two parameters i.e. Bit Error Rate (BER) and Probability of Detection (PD). The results are processed and validated by MATLAB simulation.

Abstract An inevitable trend in wireless communications is the requirement for higher and higher data rates. At the same time, location awareness requires high accuracy for positioning ability. One option fulfilling both of these challenges is the use of an ultra wideband (UWB) physical layer technology due to its extremely large inherent bandwidth. From the two possible solutions to generate UWB signals, this thesis is focused on the singleband approach. This technique is closer to the original idea of impulse radio transmission than the other recently proposed multiband UWB approach. This thesis focuses on UWB coexistence with several selected radio systems; global positioning and cellular systems, and wireless local area networks. The topic was studied analytically and with experimental tests. The analytical part is divided into simulations and theoretical calculations. In the study, two different physical layer concepts, several modulation schemes and pulse waveforms have been used to find the best system performance under interference. From time hopping and direct sequence based approaches (TH and DS, respectively), the latter with binary pulse amplitude modulation was seen to outperform the former one in an interfered multipath channel if compared with bit error rate performance. Therefore, the theoretical calculations are addressed to the DS-UWB approach. The formulation defined makes it possible to rather easily calculate the upper bound for DS-UWB system performance in an AWGN channel and the results can be used to calculate reference bounds, for example, in receiver algorithm studies. The experimental part of the work focused on link level coexistence measurements between UWB and either IEEE802.11b or 3G networks. UWB can cause harmful performance degradation on the victim system if there are unrealistic numbers of active interferers in close vicinity of the victim receiver. However, increasing the separation between the UWB interferer and victim to 40 cm, or 70 cm, in the case of WLAN and 3G, respectively, the impact is insignificant. It was also shown that the activity factor of the UWB transmitter has a great impact on the victim system's performance degradation. UWB activity factors of less than about 5% can be tolerated by the studied victim systems.

This thesis concisely describes essential type of modulation technique for transmission of binary signal. In introductory part there are summarized advantages and disadvantages for each described modulation technique. There are described proceeding of modulation and demodulation too. Next part is specialized mainly to determination of incorrect receiving probability. For each modulation technique are calculated theoretical values of bit error rate and compiled graph. In practical part there are described possibilities of Matlab platform for measurement of bit error rate. In implement Simulink there is built model of communication channel with additional AWGN channel. Graphs are constructed from simulation data by the help of model’s control script. On selected modulation technique are inspected various elements which are reacted with graph. In finale part there are compared theoretical and measured values and summarized analysis.

The current focus on the Internet of Things (IoT) has led to the emergence of many network scenarios with unlimited use cases, including smart homes, smart cities, smart agriculture, and more. Unmanned aerial vehicles (UAVs), also known as drones, have become increasingly popular due to their versatility and ability to collect and transmit data through various sensors and cameras. With real-time data transmission, autonomy, and cost-effectiveness, UAVs have become valuable tools for different applications, including disaster management, agriculture monitoring, and remote area control. Low-power wide-area network (LPWAN) technology plays a crucial role in enabling IoT, and LoRaWAN is one of the specific LPWAN communication technologies that can provide low power consumption and coverage over a wide range. During a catastrophe, wireless communication is critical for analyzing damaged regions, coordinating rescue and relief team actions, saving lives, and reducing economic losses. UAVs can partially replace damaged or overloaded wireless networks as an alternative wireless network provider. This thesis aimed to simulate a LoRa network and investigate the relationship between the UAV coverage radius and elevation angle, as well as the effect of multipath distortion and signal attenuation on UAV and user distance. By calculating signal-to-noise ratio (SNR) and bit error rate (BER) for LoRa in a line-of-sight (LoS) and non-line-of-sight (NLoS) environment, we provided a comprehensive analysis of LoRaWAN performance in real-life environments for long distances. The results indicate that LoRaWAN communication is reliable in various environments, making it a promising technology for emergency and medical communications. / Det nuvarande fokuset på Internet of Things (IoT) har lett till uppkomsten av många nätverksscenarier med obegränsade användningsfall, inklusive smarta hem, smarta städer, smart jordbruk och mer. Obemannade flygfarkoster (UAV), även kända som drönare, har blivit allt populärare på grund av deras mångsidighet och förmåga att samla in och överföra data genom olika sensorer och kameror. Med realtidsdataöverföring, autonomi och kostnadseffektivitet har UAVs blivit värdefulla verktyg för olika applikationer, inklusive katastrofhantering, jordbruksövervakning och fjärrkontroll av områden. Low-power wide-area network (LPWAN)-teknik spelar en avgörande roll för att möjliggöra IoT, och LoRaWAN är en av de specifika LPWAN-kommunikationsteknikerna som kan ge låg strömförbrukning och täckning över ett brett spektrum. Under en katastrof är trådlös kommunikation avgörande för att analysera skadade regioner, koordinera räddnings- och hjälpteams åtgärder, rädda liv och minska ekonomiska förluster. UAV:er kan delvis ersätta skadade eller överbelastade trådlösa nätverk som en alternativ leverantör av trådlöst nätverk. Detta examensarbete syftade till att simulera ett LoRa-nätverk och undersöka sambandet mellan UAV-täckningsradien och höjdvinkeln, såväl som effekten av flervägsdistorsion och signaldämpning på UAV och användaravstånd. Genom att beräkna signal-brusförhållande (SNR) och bitfelsfrekvens (BER) för LoRa i en siktlinje (LoS) och icke-siktlinje (NLoS) miljö, gav vi en omfattande analys av LoRaWAN prestanda i verkliga miljöer för långa avstånd. Resultaten indikerar att LoRaWAN-kommunikation är tillförlitlig i olika miljöer, vilket gör den till en lovande teknik för akut- och medicinsk kommunikation.

No / A proposed method for cancelling or reducing the effect of the transmitted power within the transceiver MIMO unit is investigated and discussed using a feedback signal process between the elements. Several parameters including the level of feedback power mismatch, the transmitted power and the received power are considered in this work to test the performance of the system in term of the bit error rate (BER) versus signal to noise ratio (SNR). A new software programme using MATLAB is implemented to evaluate the proposed method. The results showed that the performances of the system are heavily dependent on the amount of the transmitted power, the received power, and the mismatch in the feedback component.

No description available.

<p>In this thesis, we consider a coherent MIMO system, emphasizing on the simplicity of implementation at both the code generator and the receiver. Specifically, we consider the transmission of a space-time block code (STBC) that is a linear combination of coding matrices weighted by the information symbols through a receiver-correlated flat-fading channel and received by a linear ZF detector. Our target is the design of a code which, while maintaining full data-transmission rate, minimizes the asymptotic average (over all the random channel coefficients) bit error probability of an ZF detector. To this end, we first ensure that the full data rate of symbols is maintained, and then, based on the BER for 4-QAM signals, we derive the conditions for optimal codes and establish a code structure that minimizes the asymptotic average bit error probability. We also prove that the diversity gain of our M × N MIMO system is N − M + 1. The resulting optimum code structure requires the individual coding matrices to be mutually orthogonal when vectorized and is related to covariance matrix of correlated channel. The first optimum structural characteristics of the coding matrices is described as trace-orthogonal. A new approach to express expected value of random correlated channel has been proposed as well. From simulation results we can see that advantage of optimum code over uncoded system is more apparent as channel correlation is higher.</p> / Master of Applied Science (MASc)

No / Multi-antenna(MIMO) techniques are reported to improve the performance of radio communication systems in terms of their capacity and spectral efficiency. In combination with appropriate receiver technologies they can also provide savings in the required transmit power with respect to target bit error rate. Long Term Evolution(LTE), one of the candidates for fourth generation(4G) mobile communication systems has MIMO as one of its underlying technologies and ITU defined channel models for its propagating environment. This paper undertakes a comprehensive verification of the performance of transmit diversity MIMO in the downlink sector of LTE. It uses models built using MATLAB to carry out simulations. It is deduced that generally increasing transmit diversity configuration from 2x2 to 4x4 offers SNR savings in flat fading channels though with a user equipment moving at 30km/hr, deploying 2x2 offers higher SNR saving below 7dB. Furthermore bandwidth variation has minimal effect on the BER performance of transmit MIMO except at SNR values above 9dB while the gains of higher modulation schemes come with a transmit power penalty.