| Author | Khan, Mohammad Enam Ur Rahman |
| Call Number | AIT Thesis no.TC-03-10 |
| Subject(s) | Multiplexing
Discrete-time systems
|
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. TC-03-10 |
| Abstract | The demand for multimedia over wireless link is growing rapidly. Because of its
many advantages, Orthogonal Frequency Division Multiplexing (OFDM) is considered as
a competent candidate for realizing this demand. But, occasional very high Peak to
Average Power Ratio (PAPR) is a serious matter of concern in OFDM systems. To
combat this problem many methods have been proposed by many researchers but to date
no method justifies the ending of search for P APR reduction scheme. One of the best
methods is Partial Transmit Sequences (PTS), proposed by Muller and Huber in 1997.
This method has the drawback that it requires exhaustive search to find optimum
combination of rotation factors giving minimum P APR. Later Cimini and Sollenberger
proposed a suboptimum technique to reduce the number of searches. In the first part of
this thesis, a new criterion has been introduced to decide suboptimum algorithm.
In the second part of the thesis, Parallel Branch Selection (PBS) method is
proposed that can work with arbitrary number of subcarriers without limitation to
modulation schemes and incurs very little overhead. It has the advantage over PTS that at
the receiver there is no need to derotate all the subcarrier phases which means a
considerable saving in computation. Results show that the PBS can produce the same
Complementary Cumulative Distribution Function (CCDF) as exhaustive PTS with 50%
reduction in the number of trials.
There are two drawbacks of PBS method. Firstly, it is difficult to manage the
buffer and secondly, delay is introduced in the system. To handle the buffer underflow or
overflow problem, during formation of a suitable OFDM symbol, a second criterion of
maintaining minimum variance of buffer occupancy distribution is introduced. It is
observed that inclusion of this second criterion gives propitious result. The amount of
delay wholly depends upon initial number of OFDM symbols that is needed to be fed into
buffer for smooth operation of PBS method. |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. TC-03-10 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Ahmed, Kazi M. ; |
| Examination Committee(s) | Erke, Tapio J. ;Teerapat Sanguankotchakorn; |
| Scholarship Donor(s) | Keihin Electric Express Railway Company
Limited (KEIKYU), Japan; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2003 |
