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The Effect of Channel Parameters on the Degrees of Freedom Regions of the Interference Channels

Johnny, Milad | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51133 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Aref, Mohammad Reza
  7. Abstract:
  8. In the research area of network information theory, except in some cases, finding the exact capacity of different communication channels has always been a challenge. In the high-signal to noise ratios, the capacity of all Gaussian channels can be calculated within a low difference. Therefore, a parameter called the degree of freedom is introduced that describes the behaviour of the capacity of different networks at high signal-to-noise ratios. In other words, the DoF region is used as a tool to determine the capacity of interference channels at high $ \mathrm{SNR}$ values. In almost all interference networks, the idea of interference alignment can be used to achieve the maximum available sum DoF. In this method, all interferers can be modeled as an interferer ( in the case of perfect IA ) or the lower number of interference signals (in the case of imperfect IA). For example, it has been proven that in a channel with $K$ different users, the sum DoF cannot be greater than $ \frac{ K}{2} $ and it can be achieved using the interference alignment method. In this case, there are a lot of impractical assumptions, including very long precoder length, which makes this method far from an applicable method. We will show that in some cases the length of the precoders can be reduced by $10^7$ times. Unfortunately, it is not clear if the channel parameters are not available what is the maximum achievable sum DoF . In this thesis, it will be shown that b y accessing to half of the interference channel coefficients in the network for the $ K-$ user interference channel, we can achieve the maximum sum DoF $ \frac{ K}{2} $ . For a more efficient state using MBM\footnote{Media Based Modulation} antenna structure at the receiver , we show that without access to channel state information at transmitters, one can achieve the sum DoF of $ \frac{\sqrt {K}} {2}$. Furthermore using this structure, we show that we can follow the DoF region of interference channel at low $\mathrm{SNR}$ values
  9. Keywords:
  10. Interference Channel ; Freedom Region Degrees ; Interference Alignment ; Blind Interference Aignment ; Channel State Information (CSI) ; Reconfigurable Antenna

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