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Single OVSF code assignment in W-CDMA

Single OVSF code assignment in W-CDMA. 彭瑱瑞. Outline. Introduction Code Assignment Strategy Conclusion My proposal and project Reference. Introduction. Base Station. Dedicated Channel. Dedicated Channel. Code 3. Code 1. Dedicated Channel. Code 2. Voice Terminal (VT).

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Single OVSF code assignment in W-CDMA

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  1. Single OVSF code assignment in W-CDMA 彭瑱瑞

  2. Outline • Introduction • Code Assignment Strategy • Conclusion • My proposal and project • Reference

  3. Introduction Base Station Dedicated Channel Dedicated Channel Code 3 Code 1 Dedicated Channel Code 2 Voice Terminal (VT) Video Terminal (VDT) Data Terminal (DT) Code = Resource e.g. One base station can support only 512x256=131072 codes on Downlink channel

  4. Revolution MC-CDMA High bit rate OVSF-CDMA Internet Video OCSF-CDMA Large file 2G 3G Voice Short message Voice Short message Low bit rate

  5. Why use OVSF? • MC-CDMA requires multiple transceiver units to support higher date rates, thus increased hardware complexity • OVSF-CDMA has several constraints such as code blocking, coarsely quantized data rates and a limitation on the maximum data rate

  6. Basic knowledge bit chip Chip rate= chips / s Maximum chip rate= 3.84M chips/s Maximum SF= 256 chips/bit SF= chips / bit

  7. OVSF code architecture

  8. Code blocking definition • We define OVSF code blocking as the condition that a new call cannot be supported although the system has excess capacity to support the rate requirement of the call • If system have no enough capacity, we call that call blocking

  9. Code blocking example =assigned =blocking Totalcapacity=32 Free capacity=10 Request rate=8 =free C6,1 6 32R 1 5 C5,1 C5,2 16R 1 2 4 C4,1 C4,2 C4,3 C4,4 8R 1 2 3 4 3 4R 1 2 3 4 5 6 7 8 2 2R 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 1 R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

  10. Code assignment strategy • Random • Leftmost • Nonrearrangeable compact assignment • Crowded first • Weight crowded first

  11. Random =assigned =blocking Request 1= 2R Request 2= R Request3 = 2R =free C6,1 6 32R 1 5 C5,1 C5,2 16R 1 2 4 C4,1 C4,2 C4,3 C4,4 8R 1 2 3 4 3 4R 1 2 3 4 5 6 7 8 2 2R 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 1 R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

  12. Leftmost =assigned =blocking Request 1= 2R Request 2= R Request 3= 2R =free C6,1 6 32R 1 5 C5,1 C5,2 16R 1 2 4 C4,1 C4,2 C4,3 C4,4 8R 1 2 3 4 3 4R 1 2 3 4 5 6 7 8 2 2R 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 1 R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

  13. Leftmost • Advantage • Vacant the right-hand tree for high rate service • Make left-hand tree more compact • Disadvantage • Too much proactive reassignment

  14. NCA • Choose the most crowded tree to assign code is better • Compact index • The total number of assignable codes in its different neighborhood

  15. Compact index =assigned =blocking =free C6,1 6 32R 1 5 C5,1 C5,2 16R 1 2 4 C4,1 C4,2 C4,3 C4,4 8R 1 2 3 4 3 3 4R 1 2 3 4 5 6 7 8 8 10 10 2 2R 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 24 24 25 25 27 27 27 27 13 1 R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 C1,1= 1 +2 +4 +8 +9 =24 C1,9= 2 +4 +4 +8 +9 =27 C1,25= 1 +1 +1 +1 +9 =13

  16. NCA • Advantage • Make the code tree more compact without proactive reassignment • Disadvantage • All compact indices need to be recalculated before each code assignment, and it is time consuming

  17. Crowded-first =assigned =blocking =candidate Request 2R 6 32R 1 5 16R 1 2 4 8R 1 2 3 4 4R 3 1 2 3 4 5 6 7 8 2 2R 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 1 R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 2 6 6 0 0 14 2 6

  18. Crowded-first • Advantage • Make the code tree more compact without proactive reassignment and less computation complexity than NCA • Disadvantage • Need to calculate recursively

  19. Weighted crowded-first =assigned =blocking =free C6,1 6 32R 1 C5,1 C5,2 5 16R 1 2 0 C4,2 C4,3 C4,4 4 C4,1 8R 1 2 3 4 1 1 4R 3 1 2 3 4 5 6 7 8 0 2 2 2 2 0 2 2R 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 1 1 3 3 3 3 3 3 3 3 1 1 1 R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

  20. Weighted crowded-first • Advantage • Faster decision than crowded-first • Disadvantage • Little higher code blocking probability than crowded-first

  21. Other • Novel code assignment • Region division code assignment • Dynamic code assignment

  22. Conclusion • Wireless bandwidth is a precious resource ,thus its resource management is important • The main idea is to keep the code tree less fragmented so as to accept more calls

  23. Crowded first Compact index Different Scope =assigned =blocking =free C6,1 6 32R 1 C5,1 C5,2 5 16R 1 2 C4,2 C4,3 C4,4 4 C4,1 8R 1 2 3 4 4R 3 1 2 3 4 5 6 7 8 2 2R 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 20 24 24 24 24 18 19 19 1 R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

  24. Code blocking ? (R,2R,4R,8R)=(40,10,10,40) Call blocking

  25. My project • Simulation Program • Simulate system environment • Implement all code assignment algorithms • Computation code blocking probability • New performance metric

  26. Plot the simulation result

  27. Reference • Leftmost: R. Fantacci and S. Nannicini, “Multiple Access Protocol for Integration of Variable Bit Rate Multimedia Traffic in UMTS/IMT-2000 Based on Wideband CDMA,” IEEE J. Selected Areas in Comm.,vol. 18, no. 8, pp. 1441-1454, Aug. 2000. • Dynamic code assignment: T. Minn and K.-Y. Siu, “Dynamic Assignment of Orthogonal Variable-Spreading-Factor Codes in W-CDMA,” IEEE J. Selected Areas in Comm., vol. 18, no. 8, pp. 1429-1440, Aug. 2000. • NCA: Y. Yang and T.-S.P. Yum, “Nonrearrangeable Compact Assignment of Orthogonal Variable-Spreading-Factor Codes for Multi-Rate Traffic,” Proc. IEEE Vehicular Technology Conf. 2001 Fall,pp. 938-942, 2001. • Crowded-first: Y.-C. Tseng, C.-M. Chao, and S.-L. Wu, “Code placement and replacement strategies for wideband CDMA OVSF code tree management,” in Proc. of IEEE GLOBECOM, vol. 1, pp. 562–566, 2001. • Weighted crowded-first: Angelos N. Rouskas and Dimitrios N. Skoutas, “OVSF Codes Assignment and Reassignment at The Forward Link of W-CDMA 3G System”

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