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KAUST Digital Communication EE – 242

KAUST Digital Communication EE – 242. Outage Models. Prepared by: Ahmad Dehwah & Emad Al- Hemyari. Outline:. Introduction. Approaches of analyzing the outage. Motivation and previous work System Model. Conclusion. References. Q & A. Definition.

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KAUST Digital Communication EE – 242

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  1. KAUSTDigital Communication EE – 242 Outage Models Prepared by: Ahmad Dehwah & Emad Al-Hemyari

  2. Outline: • Introduction. • Approaches of analyzing the outage. • Motivation and previous work • System Model. • Conclusion. • References. • Q & A.

  3. Definition • Outage models are applied in wireless communication systems, which are subjected to • fading • and other interfering signals to predict their performance. The performance of a given system is considered to be unacceptable when the Signal to Interference plus Noise Ratio (SINR) is below a given threshold. i.e, SINR<z0

  4. Ways of analysis Different analysis ways to approach this problem can be followed depending on the way an outage model is defined:  • The simplest definition introduced before: SINR<z0 • Interference-limited model: SIR Signal power < defined power protection ratio neglecting the receiver background noise and the thermal noise • Noise-Limited model: where noise is treated as co-channel interference. Signal power< the powers of (total interference + noise) by power protection margins • Minimum Signal Power Constraint: signal power< total interference power by a protection ratio and Signal power<minimum power level in the presence of thermal noise.

  5. How is it quantified? • Such reliability study of outage is conducted in terms of error probability given that the SINR is above the given threshold. Pr(Error|SINR>z0)

  6. Motivation The motivation behind this study of outage models: • No closed form expression of the probability of outage for a sum of K multiple interfering signals with different powers of the same distribution. • Previous work either considered limited number of interferers or numerical approximations. • Different communication systems require different conditions on the definition of the outage to achieve certain reliability. • Performance analysis of BPSK system through a Rayleigh fading channel is conducted in terms of Pr(Error|SINR>z0) rather than just studying the probability of outage.

  7. Where does the randomness come from?

  8. System Model • The signal at the receiver front is of the following form: Where • Sk(t): is the kth interfering signal (k=0, 1, …, K). • n(t): is a Gaussian noise of two sided power spectral density N0/Tb. • τ: is a uniform time offset of S(t) over [0,2π].

  9. Randomness • There are three combinations to consider the SINR components according to our system model. • -Signal -Interference - Noise • Each of these parameters can be either deterministic or random.

  10. The Interfering signal form • The kth interfering signal (k=0, 1, …., K) is: Where • Sk: is the average received power • Xk: is the Rayliegh fading level of the kth signal with . • φk: is uniform over [0,2π] and φ0=0. • Xk and φk are mutually independent random variables • Ψ(t): is the shaping waveform

  11. The decision variable Now the decision variable at the output of the correlator is given by: Where • η: is Gaussian Random variable with variance . • Ik: is the multiple access interference component due to the kth signal given by:

  12. Interference component

  13. SINR

  14. Conditional CDF

  15. CDF

  16. Conclusion Q & A

  17. References 1. A. Annamalai, C. Tellambura, and V. K. Bhargava, .Simple and accurate methods for outage analysis in cellular mobile radio systems-a uni_ed approach,. IEEE Trans. Commun., vol. 49, pp. 303-316, Feb. 2001. http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=905889 2. D. Dardari, V. Tralli, and R. Verdone, .On the capacity of slotted Aloha with Rayleigh fading: the role played by the number of interferers,. IEEE Commun. Lett., vol. 4, pp. 155-157, May 2000. http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=846496 3. K. A. Hamdi, . Exact probability of error of BPSK communication links subjected to asynchronous interference in Rayleigh fading environment,. IEEE Trans. Commun., vol. 50, pp. 1577 - 1579, Oct. 2002 http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1044597 4. K. A. Hamdi, On the reliability of outage models http://cat.inist.fr/?aModele=afficheN&cpsidt=18184207

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