Uplink channel power control improvement in DS-CDMA system using channel predictions
In cellular systems all Mobile’s Station (MS) signals should arrive to Base Station (BS) at equal power, if not the weaker one will be blocked and the strong signals will interference with each other. The research areas include coding and improving power control for uplink channel schemes in cell...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
2013
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/1921/1/24p%20IBTESAM.%20A.%20OTHMAN.pdf http://eprints.uthm.edu.my/1921/2/IBTESAM.%20A.%20OTHMAN%20WATERMARK.pdf |
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| Summary: | In cellular systems all Mobile’s Station (MS) signals should arrive to Base Station (BS) at
equal power, if not the weaker one will be blocked and the strong signals will
interference with each other. The research areas include coding and improving power
control for uplink channel schemes in cellular systems. Commonly the uplink channel
power control schemes utilizes Signal to Interference Ratio (SIR) to design a Power
Control Command (PCC) to adjust the transmit power of the mobile station in cellular
systems.
Conventional SIR based uplink channel power control schemes updates the
transmitting power based on the current channel state, in the fact the state of channel will
be changed when the transmission is made; the channel is already in its next state. The
state is different from previous one. That causes the SIR to drop or rise drastically and
lead to Near-Far effect interference resulting in power escalation and making the DSCDMA
system
go
unstable.
To
overcome
these
problems,
a
new
approach
method
has
been
developed,
based
on
linear quadratic Gaussian (LQG) control and Extended Kalman filter for channel
prediction, this method dependent on the channel state instead of the current. Using the
proposed method the next state of uplink channel can be predicted and update the power
accordingly. This will give us a more stable SIR behavior and leads to stable DS-CDMA
system.
The simulation of this research is performed using Matlab to show the result of
building a DS-CDMA system link with existing SIR based uplink channel power control
schemes, implementing the predictive approach for uplink channel power control
achieved the signal to interference ratio (SIR) as close as possible to the predefine level
in order to maximize a DS-CDMA systems capacity and performance. That is clearly
shown in the results when compared with the conventional methods. |
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