Ofdm Transmission By Stephen Kiambi

Now the channel response at all data subcarrier are estimated using pilot subcarriers and are denoted as H ̂_k k= (-N)/2,-,0,-,N/2-1 and the received data can then be equalized

Precoding is the process of multi-stream beamforming which process at the transmitter. The main advantage of multi stream beamforming is to increase the received signal input, by making signals emitted from different antennas add up constructively and it is also able to mitigate the multipath fading effect.

Prioritized Quality of Service is expressed in the terms of relative delivery priority, which is used to be within the medium access control data service in the transfer of data frames between peer stations. The values of Quality of Service parameters such as data rate, delay bound, and jitter bound, may be differ in the transfer of data frames, without the need to reserve the required resources by negotiating the Traffic Specification.

frequency offsets in the subcarriers, the orthogonality among the subcarriers breaks and this causes intercarrier interference (ICI). The second drawback, is that

In many countries, the frequency range 57-66 GHz is split into a number of discrete bands with differing requirements and conditions of use and/or licensing. From a global point of view, the use of this spectrum by Fixed Services (FS) is being addressed by the ITU- R in its draft report on Fixed Service use trends in WP5C, which is currently under development. In 2001, the federal Communication Commission (FCC) allocated 7 GHz in the 57-64 GHz for unlicensed use. The allotted spectra in different countries are shown in the figure.

Turbo codes being a capacity approach codes are very popular and these codes are also being used for peak to average power ratio reduction. Three turbo coded OFDM systems for peak to average power ratio reduction were proposed where first using m-sequences for peak to average power ratio reduction and short codes for side information, second uses interleaving and third is combination of first two schemes. A tail-biting turbo coded OFDM system is proposed to generate candidates in a selective mapping scheme, without need of side information protection.

But contemporary communication requires to provide mobile user multimedia service over broadband to enable full function of next generation mobile network based on internet technology. As the 3G core network evolved from the 2G, it is not the optimal system that processing Transmission Control Protocol / Internet Protocol (TCP / IP) packets. Meanwhile, it cannot handle data transmission with containing large images and information either. Therefore, a critical need is to create a new telecommunication network with the optimal transmission of TCP / IP data packet, it would be completely different from the 2G and 3G wireless network

For, FDMA, an allocated bandwidth over the channel is divided among the users connected over that channel. In, TDMA, each of the users take turns to transmito r reciveve data over the same frequency. While in CDMA, each user has a specific code according to which the original information is modified so that it appears as noise to the other users connected over the same channel and hence saves

Various woks have been done on OFDM. In OFDM, as all the carriers are added using an IFFT operation, this may lead to a signal with large peaks and dynamic range in time domain. For an OFDM signal x (t),

In designing base stations, it is very important to have the knowledge about the electromagnetic environment where the system is operated, and the location of the transmitter and receiver. it is difficult to predict indoor radio propagation because of the dense multipath

SDM (space division multiplexing) has been putforth by Savory. SDM is extremely challenging technology, of requiring developments in all areas of Photonics Technology. The optical communication systems are being upgraded every day .There is a rapid development taking place in this field at the global level in the space division multiplexing. Space Division Multiplexing (SDM) is conceptually simple, SDM is extremely challeng technologically, requiring the development of new fibers, amplifiers, multiplexers, digital signal processing circuits, and other components. The multiplexing means the utilization of channel by the

In spatial multiplexing scheme the different stream of data has been transmitted on the same downlink resource block. As there is SU-MIMO (Single user MIMO) and MU-MIMO (Multiuser MIMO) and the data stream could be related to one of these. SU-MIMO is used to achieve higher data rate whereas on the other hand MU-MIMO is

Now a day’s communication is an important factor and requirement high data rate for the communication and also require the error free environment. So for these entire requirements we use OFDM. OFDM is used for both wired and wireless communication. OFDM belongs to a broader class of multicarrier modulation (MCM) in which the data information is carried over many lower rate subcarrier [1]. OFDM is a solution of intersymbol interference (ISI). ISI is caused by dispersive channel.

For that a Software-defined radio SDR receivers matching with good antenna and an efficient software systems are required

This project describes the different types of digital modulation techniques that are implemented in modern communication systems. Currently most of the wireless transmission and radio communication systems adapts digital modulation techniques because of its ability to provide high information capacity, better data encryption, greater noise immunity and easier multiplexing of different forms of inputs/information such as sound, video etc. All the experiments and data collected are obtained using software called Simulink. Digital modulation techniques have the ability to convey more information in the same channel than analog modulation techniques this also implies that same amount of data can be stored in less space. The basic techniques which include Amplitude shift keying, Phase Shift keying, Frequency Shift keying and Quadrature Phase shift keying have been demonstrated by creating a model using the blocks and channels available in the Simulink library. The signal used in all of the experiments which is to be transmitted is a randomly generated sequence of bits and the carrier signal used is a high frequency sinusoidal signal. All of these experiments vary a characteristic (frequency, amplitude and phase) of the carrier sinusoid to represent the signal that is to be transmitted. A separate communication system has been developed which accepts sound as input signal which is digitally modulated and the corresponding output is obtained accordingly.