Maung Sann Maw

Adaptive usage of polarization and physical carrier sensing in wireless ad hoc networks

The aggregate throughput of a wireless ad hoc network depends on the hidden nodes problem and the usage of same polarized omnidirectional antenna on every node. Hidden node problem can be avoided by using optimal physical carrier sensing range in the wireless ad hoc network to achieve the good aggregate throughput. Moreover, using different polarization might further increase aggregate throughput because of the possible concurrent transmissions in overlapped physical carrier sensing range for different transmitting nodes to different receiving nodes. In this paper, optimal physical carrier sensing range is calculated based on the signal to interference and noise ratio and distance between transmitter and receiver nodes in the ad hoc network to avoid the packet collision in ongoing receiver node. After that, the adaptive usage of polarized antenna will be applied to further increase the aggregate throughput in ad hoc network. The simulation results show that the proposed methods can give the higher aggregate throughput for ad hoc network.

Singular value decomposition based adaptive transmission scheme for misalignment cross polarized MIMO system

In the conventional multi-input multi-output (MIMO) communication systems, only spatially separated uni-polarized antenna elements are mainly considered in a lot of research works, and some researcher consider to use the cross-polarized MIMO system to reduce the channel correlation effect in MIMO channel matrix. By using orthogonal polarized antennas in the MIMO system, the transmitted signal from vertical and horizontal polarized antennas are easily separated in MIMO receiver. However, misalignment between transmitter and receiver sides might be occurred because of rotation of transmit or receive antennas in the system. In this situation cross-polarized discrimination (XPD) ability is no longer reliable in this kind of MIMO system and we proposed the adaptive transmission scheme to improve the bit error rate (BER) performance for misalignment cross-polarized MIMO system. In the proposed scheme, transmission methods are adaptively changed based on the calculation of singular value decomposition (SVD) of channel matrix. Simulation results show that BER performance can be improved under the constraint of target data rate and total transmit power of the MIMO system.