Beamsteering and nullsteering in interference aware wireless networks with point to point beamforming
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The concept of beamforming and beamsteering has been gathering immense popularity since the idea's inception. Many in the field of Wireless Communication and in the defense community have tried and succeeded in utilizing the benefits of beamforming and beamsteering with directional antennas. With the increasing popularity of decentralized adhoc networks, it only becomes necessary that the concept of beamsteering be formulated with respect to the network that is being studied. In relation to RF Engineering, the idea of beamsteering has been studied and explored diversely, by proposing beamsteering/ nullsteering algorithms pertaining to Digital Signal Processing. We however, make an attempt to understand beamsteering and nullsteering from the perspective of the physical layer of an Ad hoc network. Hence, it becomes essential that several network parameters like Signal to Interference Ratio, and contention in between individual connections be considered along with the RF parameters like antenna beamwidth, mainlobe and sidelobe gains, Relationship between sidelobes and nulls, Positions of sidelobes and nulls with change in the beamwidth and the number of elements in the directional antenna array. All these different parameters generate a sequence of combinations of results and change the performance of the network accordingly. The crux of this thesis is the antenna pattern model that is consistent with a practical directional antenna pattern, with a mainlobe, several sidelobes and nulls. This antenna pattern is able to derive a network that is much more efficient than its predecessor models that did not use the nulls and sidelobes in their antenna patterns. An algorithm implemented in this thesis shows the vast improvement in the network efficiency, when the different network entities use beamsteering and the alignment of nulls along interfering nodes. It is noticeable that the performance of the network improves by a factor of almost 30 percent due to the implementation of beamsteering as compared to only alignment of nulls along interfering nodes; and by a factor of 37 percent when compared to a model where no Sidelobes and nulls are considered.
Table of Contents
Introduction -- Ad hoc network with different types of antenna models -- Network model - "sidelobes and nulls" model -- Beamsteering -- Algorithm -- Network simulation -- Results and discussion -- Conclusions and future work