‘‘If I have seen farther, it is by standing on the shoulders of giants.’’ is very truly coated by Sir Isaac Newton. Ideas gave way to idea. When Marconi invented wireless communication 100 years ago, we had no idea that one day life will seem to be impossible without it. It has penetrated each and every aspect of human life and has resulted into endless demands on bandwidth and spectrum. And by standing on the shoulders of giants, Teletarand Foschinigave the technique of MIMO system which would increase the spectral efficiency of the wireless system to its maximum compared to all the current technologies. Multiple antennas are used for transmission and reception to increases the capacity of the wireless channel.Capacity is expressed as the maximum achievable data rate for an arbitrarily low probabilityof error. Thistechnology received a fillip when TarokhEtA introduced their space-timetrellis coding techniques and Alamouti introduced his space-time block codingtechniques to improve link-level performance based on diversity. Another boost came in form of BLAST Technology. But in this paper, our focus will lie basically on the MIMO wireless channel and how to determine its capacityunder different conditions. And space-time blocks coding techniques. We will discuss the benefits of the topic discussed and future prospects to enhance the usage of limited available spectrum.
MIMO
Before we precede our discussion to MIMO Antennas, we should know a bit about Multi- Antenna System. Single-input single-output (SISO) is the well-known wireless configuration,single-input multiple-output (SIMO) uses a single transmitting antenna and multiplereceive antennas, multiple-input single-output (MISO) has multipletransmitting antennas and one r...
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...for wireless multiple-antenna systems without channel state information (CSI) at the transmitter has been also studied.The most prominent space-time block codes (STBCs) are orthogonal STBCs (OSTBCs) and the most popular OSTBC is the Alamouti code.The future research scope includes simulation to obtain quasi-orthogonal space time block code having full diversity gain with full transmission rate. There should also scope of research of developing orthogonal space time block code having full diversity gain with full transmission rate for more than two transmit antenna. There should be more number of quasi-orthogonal space time matrixes for large number of antenna at the transmitter and receiver antennas. There should be more research to obtain the orthogonal space time block code and quasi-orthogonal space time block code that minimize the effect of fading.
Research suggests that managers and employees in the wireless industry have faced tough challenges in their daily work. Managers have had the difficult job of crafting appropriate business strategies and human resource practices in the face of technological uncertainty, volatile demand, and heightened price competition in markets plagued by overcapacity (Batts, Colvin, Katz & Keefe (2005). This paper will examine the challenges facing the wireless industry the near future and recommend ways in which my new organization, Twenty1Wirless, can meet those challenges. First we will discuss the challenges we are facing as an organization. Next, we will explore the opportunities Twenty1 Wireless has to overcome these challenges. Finally, we will discuss
Modulation is a process of changing the characteristics of a radio wave to encode an information signal and sending that information to the other end. Readers send a continuous radio wave and the tags modulate this base band signal by adding encoded information into it, which the readers decode. Modulation schemes used for RF communication are amplitude shift keying (ASK), frequency shift keying (FSK) and phase shift keying (PSK). The modulation technique’s choice is based on the power consumption, reliability and available bandwidth. ASK is most commonly used in load modulation and PSK for backscattering.
Many wireless systems used today have improved data capacity using the multi-antenna system. However, not all MIMO wireless systems are suitable for spatial multiplexing. In order to accommodate this benefit, the wireless channel must have the appropriate antenna configuration and have the ability to accurately recover the channel coupling matrix coefficients. As mentioned before, engineers face many complexities when dealing with wireless channels. Among those complexities include channel correlation and interference/noise rates. That is where the condition number calculation comes in handy. The condition number is a deterministic calculation that evaluates the performance of a wireless channel while estimating for SNR demodulation for a LTE MIMO system. The aim would be to get a condition number as close as 0 dB as possible and try to avoid any values greater than 10 dB.
There are four popular techniques of feeding antenna which are microsrip line, coaxial probe, aperture coupling and proximity coupling. They are further divided into two main groups which are contacting (microstrip line and coaxial probe) and no contacting (aperture coupling and proximity coupling). For contacting method, the RF power is fed directly to the radiating patch while no contacting method an electromagnetic field coupling is done to transfer power between the microstrip line and the radiating patch [ ]
Abstarct- In this paper microstrip stacked patch antenna with 10mm air gap using aperture coupling technique at frequency of 5.8 GHz has been discussed. Microstrip antennas suffer from a biggest drawback of narrow bandwidth and this can be improved by a technique called aperture coupling and further by stacking of antennas without increase in surface area of antenna. Without stacking bandwidth comes out to be 310 MHz and with stacking the bandwidth increases to 440 MHz. The airgap of 10mm is used between the two patches. The gain and directivity has also been increased. The bandwidth has been increased upto 42 % in this design. The application of this design is in WLAN and WIMAX. The simulation is done using CST 2010 software.
However, mobile signals in these environments suffer from multipath fading, penetration and scattering effects and other losses. Many solutions
The available radio spectrum is limited and it is getting crowded day by day as there is increase in the number of wireless devices and applications Cognitive radio technology proposed tempting solution for spectral crowding problem by introducing the opportunistic usage of frequency bands. Which are not heavily occupied by licensed users since they cannot be utilizing by the users other than the licensed owner at moment. Orthogonal Frequency Division Multiplexing (OFDM) is one of the widely used technologies in wireless communication systems which have the potential of fulfilling the requirements of cognitive radios inherently or with minor changes.
In order to allow for multiple calls to be handled by a single base station, multiplexing techniques are used which are ways of combining multiple signals. The four main techniques include: frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and orthogonal frequency division multiplexing (OFDM).
Print. The. Gordon A. Gow, and Richard K. Smith. Mobile and wireless communications: an introduction, McGraw-Hill International, 2006. Print.
Mote to mote communication is the radio communication in Tiny os. This introduces us the interfaces and components in Tiny os which supports the radio communication. And also we learn the basics how to use the message_ t that is a message buffer which is used to send the message buffer to the radio and receives the message buffer from the radio. Tiny os provides us with the interfaces and the components.
The world has gone through a lot of changed as time passes by. With advancements in the technological field people are can communicate with ones from around the world without having to even lift a finger. To make things more efficient and more cost saving industries have made technology wireless. Wireless technology gives people the chance to get up from their stationary computer, or cord phone and able to freely move without restrictions. The IT, or Information Technology has become a standard and very critical part of today’s society. Wireless technology came from the basic just cellular usage to sensors in the medical field. Wires are now a thing of the past in today’s world with forever revitalizing technology.
As wireless communication and multimedia applications are increasing at a rapid pace and there is need to meet the requirements a better standard for communication is developed titled LTE. With the release of various versions over the years shows a continuous enhancement in the framework standard. This paper discusses about the advent of LTE into the mobile and wireless communication universer and the need for it. The various features and technical aspects are also discussed. With features such as closed subscriber group, self-organising networks, location services, enhancement cell ID and Multimedia Broadcast services this is a standard which pretty much became the norm. Technologies such as Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output(MIMO) which were instrumental in the evolution to the LTE-Advanced are also discussed.
In recent years, network coding [1], [2] has been considered as an auspicious information network paradigm for augmenting the throughput of multiple unicast networks [5]. The pioneering researches of network coding were undertaken by R. Ahlswede, N. Cai, S.-Y.R. Li and R.W. Yeung. Their discovery, which was first introduced in [1][2], are considered to be the crucial breakthrough in modern information theory and the time of its appearance, is recognized as the beginning of a new theory-Network Coding theory. In these elegant, succinct articles, within the purview of rigorous mathematics, the glimmering of an optimal network protocol for multiple unicast network was introduced in which the key idea is considering digital information as wave [riis].
In today’s world there is an increasing demand for wireless connectivity. But with the present technology there is an inefficient use of the available. A large part of the spectrum is underutilised as shown in Fig 1. Due to the inefficient use of spectrum by the current spectrum allocation methods there is a need for developing new methods which aids in efficient use of available spectrum.
are widely separated. But we can use the same concept for several antennas assuming all are