Using Ofdm Transmitter And Receivers

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.

In wireless communication or open space communication there is no requirement of wired. Wireless communication has several advantages over wired communication like there is less requirement of wire as compared to guided structure communication and wireless communication provide it’s user to move from one space to another without causing interface i.e. its provides freedom to its user, but wireless communication limitation of spectrum.

Inter symbol interference (ISI) is avoided by assuming the duration of cyclic long enough and furthermore the channel is assumed to be stationary within one symbol period ( h(k)=hr ).

OFDM or Orthogonal Frequency Division Multiplexing is a transmission scheme that is widely used in broadcast and wireless communication technologies. Some of the applications employing OFDM include Digital Audio Broadcast (DAB), Digital Video Broadcasting Terrestrial (DVB-T2), Wireless-LAN, Worldwide Interoperability for Microwave Access (WiMAX) and 4G Long Term Evolution (LTE) radio technologies [1, 2]. Two of the main reasons to use OFDM are to increase date rates and robustness against frequency-selective fading. In the rest of this document an overview of OFDM transmission theory is given.

The Release 10 of LTE is the version that is approved by the ITU-R as an IMT Advanced technology and so is called LTE-Advanced. Release 10 of the LTE that came out in March 2011 included carrier aggregation, enhanced downlink MIMO, uplink MIMO, enhanced ICIC and advanced relays. Following the Release 10 came the Release 11 that incorporated enhanced carrier aggregation and additional intra-band carrier aggregation. In 2008 the work associated with IMT-Advanced within the ITU-R circulated the detailed requirements and process via a circular letter. For 3GPP, LTE advanced is not a new technology but is an evolutionary step in the ongoing development of LTE. To reach the IMT Advanced standards, wider bandwidth by aggregation of various multiple carriers and evolved use of advanced antenna techniques in both downlink and uplink are the two main phenomenon added in the Release 10 of LTE. The transmission scheme used for this technology is called OFDM (Orthogonal Frequency Division Multiplexing) which is also prevalent in other radio-access technologies like WiMax and DVB broadcasting technologies.

These sub-carriers are orthogonal to each other. It is very much popular scheme used in digital television, audio broadcasting and 4G communications. OFDM has the ability to deal with severe channel fading conditions without complex equalization filters. Due to the longer symbol period and the CP extension, OFDM is more robust against the effect of timing offset and delay spread in multipath fading channels. OFDM also gain higher spectral efficiency due to the overlapping of the subcarrier spectrum which are orthogonal to each other. The major drawback of OFDM is high

During June 2012 summer vacations, I had the opportunity to attend an in-plant training at BSNL REGIONAL TELECOM TRAINING CENTRE AT CHENNAI (BSNL is India's oldest and largest communication service provider). Here I learnt the basics of Digital Communication and Optical Fiber Communication, which helped me, enjoy these subjects and

5. (DSSS), Direct Sequence Spread Spectrum , frequency Hopping Spread Spectrum (FHSS) and Infrared and Orthogonal Frequency Division Multiplexing(OFDM)

By contrast, software defined radio technology provides an efficient and comparatively reasonable solution to this problem [4].

TDM advantage over FDM is that it offers bandwidth saving and there is low interference between the signals that are being multiplexed.

Abstract- In this paper, ordered successive interference cancellation (OSIC) is adopted with minimum mean square error (MMSE) detection to enhance the multiple-input multiple-output (MIMO) system performance. The optimum detection technique increases the system complexity with improved error rate performance. Therefore, MMSE-OSIC detection is used which gives reduced error rate compared to traditional MMSE with a considerable level of complexity. The system performance is analyzed in a composite fading environment which deals with multipath and shadowing, known as Weibull-gamma (WG) fading environment. Along with the composite fading, a composite noise i.e. additive white generalized Gaussian noise (AWGGN) model is taken into account to form various noise scenarios such as impulsive, Gamma, Laplacian, Gaussian and uniform noise. Consequently, generalized Q- function is used to develop such noise scenario. The average symbol error probability (ASEP) of MIMO system is computed for 16-quadrature amplitude modulation (16-QAM) using MMSE-OSIC detection in WG fading with AWGGN. Analytical expressions are evaluated in terms of Fox-H function (FHF). These expressions demonstrate the best fit to simulation results.

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),

Abstract- In multiple-input multiple-output (MIMO) systems, spatial demultiplexing at the receiver is a motivational task. Thus, several detection techniques are investigated in existing literature. There is a tradeoff between computational complexity and optimal performance in many detection techniques. The ordered successive interference cancellation (OSIC) with minimum mean square error (MMSE) is used to improve the error performance. However, maximum likelihood (ML) detection gives optimal performance at the higher complexity level whereas MMSE-OSIC detection is less complex. Therefore, MMSE-OSIC2 detection is suggested as a solution. In this paper, spatial multiplexed (SM) MIMO systems are considered to evaluate error performance with different detection techniques such as MMSE-OSIC, ML and MMSE-OSIC2 in a composite fading i.e. Weibull-gamma (WG) fading environment. In WG distribution, Weibull and gamma distribution represent multipath and shadowing effects respectively. It is shown by simulation results that the MMSE-OSIC2 detection technique gives the improved symbol error performance (SER) which is closely likely ML performance

[1]S. M. Alamouti, describes a simple two-branch transmit diversity scheme. Using two transmit antenna and one receive antenna, the new transmit antenna provides the same diversity order as maximal-ratio receiver combining (MRRC) with one transmit and two receive antennas. The scheme easily be generated to two transmit antenna and M receive antenna to provide a diversity order of 2M. This scheme does not require any bandwidth expansion any feedback from the receiver to the transmitter and its computation complexity is similar to MRRC. This also provide diversity improvement to all the remote units in a wireless system, using two transmit antennas at the base station instead of two receive antenna at all the remote terminals.

Rapid and exponential increases in data communications are continuing to drive the complexity of our computing, networking and sensing systems. Recently OAM has gained much interest in transmission efficiency and spectral efficiency in optical fiber communications with the ability of carrying independent data streams on orthogonal spatial modes. The key factor in the optical fiber communications using OAM is to design and fabrication of the fiber so as to support the the different modes of OAM.while the free space systems can theoretically use an unlimited number of OAM modes. However achieving the full potential of OAM multiplexing requires an efficient and rotation invariant multiplexer and demultiplexer which can be interfaced with single-mode optical components. Fiber based OAM generation and