Optimization techniques for nonconvex problems and optimum discrete transmit beamformer design /

Demir, Özlem Tuğfe
In this thesis, transmit beamformer design is investigated for single group multicast scenario. The problem is considered for both discrete and continuous case. The discrete problem is converted to a linear form in which there are both discrete and continuous variables. The resulting mixed integer linear programming problem is optimally solved with much lower computational complexity than brute force search. For practical reasons, robust version of the problem is also elaborated and solved with mixed integer convex programming. Several experiments are carried out in order to show performance gain and computational complexity of the proposed techniques. An important variation of discrete beamforming problem for spectrum sharing based cognitive radio is also considered. Antenna and secondary user selection which are critical in cognitive radio scenario are included into this beamforming problem. An equivalent problem to this joint problem is obtained and solved optimally using mixed integer linear programming. It is shown that antenna selection provides the system with power gain and more user service capability. Finally, a near-optimal continuous broadcast beamforming algorithm based on alternating maximization is developed and its performance is shown to be better than the existing approaches in simulation results.


Optimum discrete transmit beamformer design
DEMİR, ÖZLEM TUĞFE; Tuncer, Temel Engin (2015-01-01)
In this paper, transmit beamformer design problem is considered for single group multicast case. This problem is treated in discrete phase and amplitude and converted to a linear form. The solution of this linear optimization problem is always feasible as long as the total transmit power is above a certain value. The proposed method is guaranteed to find the optimum solution. This new approach is used to design discrete phase-only (DPOB) and discrete phase-amplitude beamformers (DPAB). It is shown that the ...
Improved ADMM-Based Algorithm for Multi-Group Multicast Beamforming in Large-Scale Antenna Systems
Demir, Özlem Tuğfe; Tuncer, Temel Engin (2018-08-07)
In this paper, we consider beamformer design for multi-group multicasting where a common message is transmitted to the users in each group. We propose a novel effective alternating direction method of multipliers (ADMM) formulation in order to reduce the computational complexity of the existing state-of-the-art algorithm for multi-group multicast beamforming with per-antenna power constraints. The proposed approach is advantageous for the scenarios where the dimension of the channel matrix is less than the ...
Optimum Discrete Max-Min Style Broadcast Beamforming Design
Demir, Özlem Tuğfe; Tuncer, Temel Engin (2014-04-25)
In this paper, max-mm style transmit beamformer design for single group multicast (broadcast) scenario is considered. The phase and amplitude values of beamformer vector coefficients are selected from finite discrete sets. With the help of integer variables, original optimization problem is converted to a linear form appropriate for mixed integer linear programming. The solution is always feasible as long as the total power is above a certain value. Branch and cut strategy guarantees the optimum solution. P...
Differential network coding in wireless networks Telsiz aǧlarda farksal aǧ kodlamasi
Özdemir, Özgür; Yılmaz, Ali Özgür (2009-10-29)
In this paper a three-terminal communication scenario where two users exchange information by employing differential binary modulation and network coding via a relay is considered. The transmission is divided into three slots in time where the first and second slots are allocated to the transmission of differential encoded data of the users. After demodulation, the relay broadcasts the bit-wise XOR-ed and differential encoded packet to the users in the third slot. The optimum detector and a simplified decis...
Relay-Assisted Beamforming for Multicast Systems with Energy Harvesting Capability
Demir, Özlem Tuğfe; Tuncer, Temel Engin (2016-05-19)
In this paper, multi-group multicasting scenario is considered where single antenna sources transmit their own information to different groups of users with the help of single antenna relays. Users have energy harvesting capability, i.e., a part of the received signal is used for information decoding while the rest is used for energy harvesting. Beamforming is performed by the relays which use amplify-and-forward protocol. The design of complex relay coefficients and power splitting ratios for the users is ...
Citation Formats
Ö. T. Demir, “Optimization techniques for nonconvex problems and optimum discrete transmit beamformer design /,” M.S. - Master of Science, Middle East Technical University, 2014.