Throughput-Guaranteed Resource-Allocation Algorithms for Relay-Aided Cellular OFDMA System 1 Megumi Kaneko, 2 Petar Popovski, and 1 Kazunori Hayashi 1 Graduate School of Informatics, Department of Systems Science, Kyoto University ( ), Japan 2 Department of Electronic Systems, Aalborg University ( ), Denmark Outline Introduction System model Goal Proposed Resource-Allocation Algorithms Single-Relay Case: FTD and ATD Multiple-Relay Case: MRPA and MRAA Performance Conclusion Introduction Installing relay stations in strategic positions in a cell higher data rates can be provided in remote or shadowed areas of the cell low-cost devices that can easily be deployed BS RS MS Direct link Relayed link Introduction This paper investigates the problem of resource allocation for a relay-aided cellular system based on OFDMA. This paper focuses on the downlink (DL) transmission from a BS to mobile stations (MSs) or RS in a single cell. BS-Subframe (T BS ) BSMS or BSRS RS-Subframe (T RS ) RSMS TFTF Time Freq. System model Relay station stores the received packets decodes the received packets re-modulates the received packets Assume that packets sent to the RS in a frame cannot immediately be forwarded due to hardware limitations The data for relayed users takes two frames to be delivered. The data for direct users takes one frame. System model MSs feed back to the BS their CSI on every subchannel. CSI = Channel-State Information Assumption that BS knows the achievable rate r k,n for each user k on subchannel n Path Selection A user is linked to the RS only if r k RS-MS 2 r k BS-MS ; Otherwise, it is linked to the BS. Goal The BS-subframe is shared between the direct users and BS-RS links If the BS forwarded all the packets for the relayed users as they arrive in the BS queue, there will be less resource that is available for the direct users. BS-Subframe (T BS ) BSMS AND BSRS RS-Subframe (T RS ) RSMS Time Freq. relayed users direct users Goal The target of this work is to design an algorithms with good throughput and outage performance. Single-Relay Case Multiple-Relay Case RS BS MS 1 MS 2 r 1 > r 2 Outage ! r1r1 r2r2 Proposed Resource-Allocation Algorithms RS makes its own initial allocation to minimize the outage. BS optimizes the final allocation to improve the overall throughput. Single-Relay Case: FTD and ATD Multiple-Relay Case: MRPA and MRAA BS-Subframe (T BS ) BSMS or BSRS RS-Subframe (T RS ) RSMS T F /2 Single-Relay Case: FTD Fixed Time-Division Algorithm RS makes its own initial allocation to minimize the outage. r k,n : achievable rate on subchannel n for user k k (t1) : previous average rate for user k R : the minimum data rate requirement for user k BS-Subframe (T BS ) BSMS or BSRS RS-Subframe (T RS ) RSMS T F /2 Average rates are higher than their required rates Single-Relay Case: FTD Fixed Time-Division Algorithm RS makes its own initial allocation to minimize the outage. r k,n : achievable rate on subchannel n for user k k (t1) : previous average rate for user k R : the minimum data rate requirement for user k BS-Subframe (T BS ) BSMS or BSRS RS-Subframe (T RS ) RSMS T F /2 Average rates are lower than their required rates Single-Relay Case: FTD Fixed Time-Division Algorithm If user k has the higher and its packets are queued at the RS, the user k is serviced first by RS. If user k has the higher than the allocated one but its packets are not queued at the RS, RS sends a Request Message to the BS. User k set U Req max : The maximum value of for user in U Req BS-Subframe (T BS ) BSMS or BSRS RS-Subframe (T RS ) RSMS T F /2 Single-Relay Case: FTD Fixed Time-Division Algorithm BS RS MS 1 MS 2 MS 3 MS 4 DL Queue: MS 1, MS 2 1 = 500 2 = 600 3 = 900 4 = 400 DL Queue: MS 3, MS 7 max min 33 U Req Single-Relay Case: FTD Fixed Time-Division Algorithm BS optimizes the final allocation to improve the overall throughput. BS calculates the number of sub-channels n BR that are required to send all the packets that are queued at the BS of the users in U Req. The metric of the direct user is compared with max, and the sub-channel n is allocated to the link with the highest value. RS-Subframe (T RS ) RSMS T F /2 BS-Subframe (T BS ) BSMS or BSRS max direct user RS BS (950) (400) U Req ( max ) Single-Relay Case: FTD Fixed Time-Division Algorithm Channel utilization: Number of allocated time slots for user k Number of allocated packets for user k BM / RM BS-Subframe (T BS ) BSMS (BM) or BSRS RS-Subframe (T RS ) RSMS (RM) TFTF Single-Relay Case: FTD Fixed Time-Division Algorithm Throughput: Number of allocated time slots for user k 1 or 0 Single-Relay Case: ATD Adaptive Time-Division Algorithm Starting from the allocation by the FTD algorithm for T BS = T RS = T F /2, time division can be adapted to increase the overall throughput. BS-Subframe (T BS ) BSMS or BSRS RS-Subframe (T RS ) RSMS T F /2 Multiple-Relay Case: MRPA Multiple-RS Parallel with Activation Algorithm Path Selection (user k is on direct or relayed link) User id linked to the RS only if ; otherwise, it is linked to the BS. Due to The data for relayed users takes at least two frames to be delivered. The data for direct users takes only one frame. Direct link Relayed link BS-Subframe (T BS ) BSMS or BSRS RS-Subframe (T RS ) RSMS T F /2 BS RS MS Direct link Relayed link Multiple-Relay Case: MRPA Multiple-RS Parallel with Activation Algorithm If the number I of relays is an even number, there are I/2 relay pairs by regrouping the diametrically opposed relays. Frequency reuse because of minimized interference. FTD-based resource allocation. BS RS1 RS6 RS5 RS4 RS3 RS2 Direct link Relayed link Multiple-Relay Case: MRPA Multiple-RS Parallel with Activation Algorithm If the number I of relays is an even number, there are I/2 relay pairs by regrouping the diametrically opposed relays. Frequency reuse because of minimized interference. FTD-based resource allocation. BS RS1 RS6 RS5 RS4 RS3 RS2 Direct link Relayed link Multiple-Relay Case: MRAA Multiple-RS Adaptive Activation Algorithm Without assuming frequency reuse. RS j with the worst throughput is removed, and the RS j -subframe is reallocated to the BS-subframe. For higher throughput performance ATD-like resource allocation BS RS6 RS4 RS3 RS2 Performance BS Cell : 1000m radius Relay placed in 800m away from BS BS/RS Power: 20/5 W Subchannels : 12 Frame duration : 12 ms Packet arrive at BS : Poisson process Performance Single-Relay Case Upper Bound All Fwd: Relays selected in random w/o U Req PFS: Proportional Fair Scheduling w/o considering R and w/o Relays Upper / Lower Bound Packets from BS through RS to MS is in the same frame Performance Single-Relay Case Lower Bound All Fwd: Relays selected in random w/o U Req PFS: Proportional Fair Scheduling w/o considering R and w/o Relays Upper Bound (throughput) Performance Multiple-Relay Case Upper Bound PFS: Proportional Fair Scheduling w/o considering R and w/o Relays Performance Multiple-Relay Case Lower Bound PFS: Proportional Fair Scheduling w/o considering R and w/o Relays Conclusion This paper investigated the problem of resource allocation for a relay-aided cellular system based on OFDMA. Design FTD, ATD, MRPA and MRAA algorithms for good throughput and outage performance. The End THANK YOU