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FBMC-OQAM Modulation.pptx
- 2. “Modulation” “Someone I know” definition: Convert bits of information into an electromagnetic wave Digital modulations here Modulation 0,1,1,0,1 … 2
- 3. OFDM leakage 33 - 𝑇 2 𝑇 2 𝑔 𝑡 𝑡 |𝐺 𝜔 | = |sinc 𝜔𝑇 | +∞ ∫ 𝜔2 𝐺 𝜔 −∞ 2𝑑𝜔 = ∞ +∞ ∫ 𝑡2 𝑔 𝑡 −∞ 2𝑑𝑡 ≤ 𝜉 𝑇 Δ𝑡 = 𝑇, Δ𝑓 = 1 and complex orthogonality (easy to show) < 𝑔𝑚,𝑙 , 𝑔𝑚 ,𝑙 0 0 𝑡 𝑚0,𝑙0 > = ∫𝑔𝑚,𝑙(𝑡)𝑔∗ (𝑡)𝑑𝑡 = 𝛿𝑚−𝑚 ,𝑙−𝑙 0 0 Wi-Fi, DSL, LTE, WiMAX, DVB… Spectral leakage
- 4. Spectral leakage leads to interference 34 U1 U2 Frequency Overlapping U1 Synchronisation required to keep orthogonality U2
- 5. Time-frequency lattice of CP-OFDM 𝑚=0 𝑙=−∞ 2𝑀−1 +∞ 𝑠 𝑛 = ∑ ∑ 𝑑𝑚,𝑙 𝑔𝑚,𝑙[𝑛] Undersampled lattice, loss in throughput rate 1 𝑇 𝑇 + 𝑇𝐶𝑃 𝑡 𝑓 35 ≈ ~ 𝑇 𝑇 10 4 Wi-Fi, DSL, LTE, WiMAX, DVB… 𝑇 + 𝑇𝐶𝑃 1 𝑇 1 𝑇 𝑇 + 𝑇𝐶𝑃 = < 1
- 6. FBMC-OQAM principle We want: • Good time-frequency localization •Full spectral efficiency But how? Balian-Low… Use staggered lattices to circumvent the Balian-Low theorem Idea used by FBMC-OQAM modulations [Chang, 66], [Saltzberg, 67] Link to Wilson bases. 6
- 8. FBMC-OQAM lattice 1 𝑇 𝑡 𝑓 𝑇 2 𝑇 1 1 Lattice density Δ𝑡Δ𝑓 = 𝑇 1/𝑇 = 2 real symbols per second per Hertz 2 Orthogonality satisfied only in the real domain Real symbol 8 Imag. symbol
- 10. No need for synchronization of the users USER 1 USER 2 Frequency USER 1 10 USER 2 No overlapping
- 11. FBMC-OQAM transmission model Transmitted signal 𝑠 𝑛 = ∑ 𝑚=0 𝑙=−∞ 2𝑀−1 +∞ ∑ 𝑑𝑚,𝑙 𝑔𝑚,𝑙 𝑛 𝒍+𝒎 𝑗2𝜋 𝑚𝑛 with 𝑔𝑚,𝑙 𝑛 = 𝒋 𝑔 𝑛 − 𝒍𝑴 𝑒2𝑀 . Assume ideal channel, i.e., 𝑟 𝑛 = 𝑠[𝑛]. The demodulated signal is 𝑑^𝑚0,𝑙0 = ℜ < 𝑠 𝑛 , 𝑔𝑚0,𝑙0 𝑛 > 𝑙 =−∞ = ∑2𝑀−1 ∑+∞ 𝑑𝑚,𝑙 ℜ < 𝑔𝑚,𝑙 𝑛 , 𝑔𝑚 ,𝑙 0 0 𝑛 > 𝑚=0 = 𝑑𝑚0,𝑙0 if, ℜ < 𝑔𝑚,𝑙 𝑛 , 𝑔𝑚0,𝑙0 Purely real now ! ℜ-ℑ pattern Interference from symbol 𝑑𝑚,𝑙 𝑛 > = 𝛿𝑚−𝑚0,𝑙−𝑙0 ∀𝑚, 𝑚0, 𝑙, 𝑙0. −𝑙2𝑀 symbols are closer in time 11
- 12. FBMC-OQAM lattice 1 𝑇 𝑇 𝑡 𝑓 𝑇 2 𝑑𝑚0,𝑙0 𝑑𝑚,𝑙 ℜ < 𝑔𝑚,𝑙 𝑛 , 𝑔𝑚0,𝑙0 𝑛 > 12
- 13. Real orthogonality conditions < 𝑔𝑚,𝑙 𝑛 , 𝑔𝑚0,𝑙0 𝑛 > = 𝑗Δ𝑚+Δ 𝑙 ∑𝑛 𝑔 𝑛 − 𝑙𝑀 𝑔 𝑛 − 𝑙0𝑀 𝑒2𝑀 𝑗2𝜋 Δm𝑛 … (simple math. manipulations) = 𝑗 −1 Δ𝑚+Δ𝑙+Δ𝑙Δ𝑚 Δ𝑚𝑙0 𝑛 ∑ 𝑔 𝑛 − 𝑔 𝑛 + Δ𝑙𝑀 Δ𝑙𝑀 2 2 𝑒2𝑀 𝑗2𝜋Δm𝑛 ℜ < 𝑔𝑚,𝑙 𝑛 , 𝑔𝑚0,𝑙0 𝑛 > 0 mod 2, which only occurs when Δ𝑚 = Δ𝑙 = 0 mod 2. Hence, 𝑔[𝑛] should be designed to cancel those terms. “Ambiguity function”: real for real and even pulse 𝑔[𝑛] is only non zero if Δ𝑚 + Δ𝑙 + Δ𝑙Δ𝑚 = Δ𝑚 = 𝑚 − 𝑚0, Δ𝑙 = 𝑙 − 𝑙0 13
- 14. FBMC-OQAM lattice 1 𝑇 𝑡 𝑓 𝑇 2 Real symbol Imag. symbol 𝑇 Purely imaginary interference, eliminated directly when 𝑔[𝑛] is even and real Remaining interference, eliminated by filter design Δ𝑚 = Δ𝑙 = 0 mod 2 14
- 15. Pros and cons 48 Advantages of MC systems: easy channel equalization… High data rate Filter well time-frequency localized: Higher complexity… especially in certain scenarios. Need for more investigation, many open issues. Wait… Good for us ! We like complex things ! That means that there is still a lot to do ! Pros and Pros “Le beurre et l’argent du beurre”
- 16. Evolution of telecommunication standards 2010… 2030 2020… 2040 4G modulation format might not be the best to address 5G challenges 2
- 17. Flexible spectrum utilization in 5G Fragmented spectrum 2 MHz 20 MHz 5 MHz 150 KHz 840MHz 1285MHz 20 MHz 602MHz 604MHz 820MHz 1280MHz 1700MHz 1680MHz 17
- 18. REFERENCES [1] Ericsson, “More than 50 Billion Connected Devices,” White Paper, http://www.ericsson.com/res/docs/whitepapers/wp-50-billions.pdf, Feb. 2011. [2] A. Osseiran, F. Boccardi, V. Braun, K. Kusume, P. Marsch, M. Maternia, O. Queseth, M. Schellmann, H. Schotten, H. Taoka, H. Tullberg, M. Uusitalo, B. Timus, and M. Fallgren, “Scenarios for 5G mobile and wireless communications: the vision of the METIS project,” IEEE Communications Magazine, vol. 52, no. 5, pp. 26–35, May 2014. [3] M. Schellmann, Z. Zhao, H. Lin, P. Siohan, N. Rajatheva, V. Luecken, and A. Ishaque, “FBMC-based air interface for 5G Mobile: Challenges and proposed solutions,” in Proc. of the International Conference on Cognitive Radio Oriented Wireless Networks (Crowncom), Oulu, Finland, June 2014. [4] METIS, Mobile and Wireless Communications Enablers for the Twenty- Twenty Information Society, EU 7th Framework Programme project, http://www.metis2020.com. [5] P. Siohan, M. Gharba, and R. Legouable, “An alternative multiple access scheme for the uplink 3GPP/LTE based on OFDM/OQAM,” in Proc. Of the IEEE Int. Symp. Wireless Commun. Syst. (ISWCS), Barcelona, Sep. 2010, pp. 941–945.