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Radio Resource Management for a Two-hop OFDMA Relay System in Downlink

Radio Resource Management for a Two-hop OFDMA Relay System in Downlink. Mi Kyoung Kim and Hwang Soo Lee School of EECS, Division of Electrical Engineering, KAIST, Korea IEEE Symposium on Computers and Communications (ISCC 2007). Outline. Introduction System model Problem formulation

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Radio Resource Management for a Two-hop OFDMA Relay System in Downlink

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  1. Radio Resource Management for a Two-hop OFDMA Relay System in Downlink Mi Kyoung Kim and Hwang Soo Lee School of EECS, Division of Electrical Engineering, KAIST, Korea IEEE Symposium on Computers and Communications (ISCC 2007)

  2. Outline • Introduction • System model • Problem formulation • Simulation results • Conclusions

  3. Introduction • The relay system, with its many merits, is one of the most promising techniques for the future of mobile communications systems. • The resource allocation mechanism of the relay system is divided into the centralized and distributed methods, according to the role of resource manager. • In the centralized method, BS controls all information from BS-MS, BS-RS, RS-RS, and RS-MS links.

  4. Introduction Motivation If more RS is added in the system, BS must control more information and the information collection time and algorithm execution time will be longer.  It generates too much signaling overhead and complexity. Goal To propose methods that have almost the same performance as the centralized method but lower complexity and higher flexibility compared to the centralized method.

  5. BS MS MS MS RS1 RS2 RSM System Model • RS is a fixed station. • (2) The channel state information (CSI) is known • to the transmitter (BS or RS). • (3) There is a protocol to gather CSI and • broadcast the allocation results and • the protocol uses separate control channel. • (4) The mobility velocity of MS is slow so that • the BS-MS or RS-MS connection is not • altered during resource allocation. • (5) One MS can communicate with only one BS • or RS.

  6. Problem formulation BS allocates resources to the directly connected mobile stations and relay stations, first. Separate and Sequential Allocation (SSA): RS uses the assigned subcarriers from BS. Separate and Reuse Allocation (SRA): All system subcarriers independently.

  7. Problem formulation – Inputs and decision variables

  8. Problem formulation – Inputs and decision variables

  9. Problem formulation – Inputs and decision variables

  10. BS MS1 MS2 MS3 MS4 MS5 MS6 MS7 RS1 RS2 Centralized method Overall achievable capacity:

  11. Centralized method C1 is a constraint for the correct value of the subcarrier assignment indicator

  12. Centralized method C2 is a constraint so that subcarrier n is not shared by severalMSs.

  13. Centralized method C3 is the rate requirement for each MS. rk: The achievable data rate of user k. Rk: Minimum data rate requirement of user k.

  14. BS MS MS MS RS Semi-distributed methods Step-I Step-II • SSA • SRA

  15. BS MS MS MS MS MS RS RS Semi-distributed methods - Step-I The reported raterequirement of RS is the sum of the raterequirements of the MSs connected to RS.

  16. Semi-distributed methods - Step-II (SSA) SSA: RS m allocates subcarriers using only assigned Nrm subcarriers from BS. The real number of used subcarriers in RS.

  17. Semi-distributed methods - Step-II (SRA) SRA: RS m allocates all N subcarriers to MSs.

  18. Simulation results

  19. Simulation results

  20. Simulation results

  21. Simulation results

  22. Simulation results

  23. Conclusions • In this paper, they suggest two semi-distributed methods, the SSA and the SRA methods, for an OFDMA relay system. • These methods reduce the large burden of the BS and offer an easy extension of the traditional BS based system.

  24. Thank you!

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