Mimo ofdm thesis report
Support for QoS involves catering to two types of traffic:. Medium access control protocols and its effect on capacity are important aspects in communication system design for any shared medium like wireless. In multi-hop ad hoc networks that use a distributed and contention based channel access mechanism such as those specified in the IEEE Existing methods in literature attempt to solve this using measurement based approaches. This thesis proposes graph theoretical and real-time approaches to estimate the capacities of individual links in a multi-hop ad hoc network and uses analytical modeling to derive node throughputs and successful transmission probabilities of individual nodes in multi-hop ad hoc networks.
In a contention based system based on the IEEE While the link capacity can be expressed by the number of times it gets activated, it can be more accurately expressed in probabilistic terms.
This is due to the randomness introduced in the channel access procedure in the form of virtual carrier sensing and binary exponential backoff. This thesis proposes centralized and distributed methods to estimate the active time of links. The centralized approaches have the knowledge of the entire network topology and use graph theoretic approaches to derive individual link active times.
The distributed approaches on the other hand only have the partial knowledge of network topology to derive the link active times. This thesis proposes another approach to the link capacity problem using the analytical modeling of multi-hop network for string and grid topologies. The analytical modeling uses Markov models to derive node throughputs and successful transmission probabilities of individual nodes in multi-hop ad hoc networks. The advantages of the estimation methods are topology independent nature of the solution, a wide spectrum of applications using the estimates and real-time applications using the distributed approach.
It also provides insight into the performance evaluation of multi-hop networks. The accuracy of the estimations is validated through simulations and it is observed that there is a difference between the estimated and simulated values only of the order of 10e The values obtained through analytical model too matches the values obtained in simulations to a good degree. The IEEE Enhancements to the standards have been ongoing resulting in various flavors of the standard.
Recent activities have centered around IEEE New CE schemes are proposed by modifying the existing CE schemes to obtain better performance with less computational complexity. This results in a system with a large computational complexity.
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In this thesis, we propose a low complexity time synchronization algorithm and a low complexity spatial detection technique for high-speed WLANs based on the The two major goals of the To achieve the first goal, the proposals for the This necessitates the use of spatial detection techniques at the receiver. The conventional spatial detection techniques exhibit a tradeoff between their complexity and their performance.
Since the To achieve the backward compatibility goal, we have to address two issues. They are the design of a new preamble and the use of protection mechanism to avoid interference from the legacy systems. The protection mechanism can be provided either in the physical PHY layer level or in the medium access control MAC layer level. At the PHY layer, the header which carries the length and rate field is decoded by the non- transmitting stations and they defer the channel access for that duration. To decode the header information of the new preamble successfully, the legacy system should be able to use its existing initial receiver algorithms.
In the first part of the thesis, we propose a low complexity time synchronization algorithm for the legacy stations and for the MIMO-OFDM stations in a typical We first study the different ways of extending the legacy We show that sending the cyclically shifted versions of the legacy preamble from the We show that the proposed coarse timing estimation algorithm in SISO systems performs well for legacy preamble and for the new preambles as compared to the threshold based algorithm.
We compare the performance of this algorithm with the popular correlation based techniques. We evaluate the performance of the proposed fine timing estimation algorithm for all the preamble types under all the channel models. From the simulation results, we have shown that the cyclically shifted preamble with cyclic shift of 8 samples for a 2x2 system seems to be good choice for mixed mode and green field operations. We first review the different spatial detection techniques, their performance, and their complexity requirements. Roman, M.
Enescu and V. By permission. Joint time-domain tracking of channel and frequency offset for OFDM systems. Wireless Personal Communications, Vol.
Roman, S. Visuri and V. Blind frequency synchronization in OFDM via diagonality criterion. Roman and V. Name: isbnX.
- Advanced receiver structures for mobile MIMO multicarrier communication systems.
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Introduction to OFDM | PhD Thesis on OFDM
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Send Feedback. Advanced receiver structures for mobile MIMO multicarrier communication systems. Roman, Timo. Electrical engineering.