Outage-Optimal Power Allocation for Hybrid ARQ with Incremental Redundancy

We consider the optimization of power in incremental redundancy (IR) based hybrid automatic repeat request (HARQ) schemes when the maximum number of (re)transmissions is fixed. We formulate two optimization problems: (i) minimizing the packet drop probability (PDP) under a total average transmit power constraint, and (ii) minimizing the average transmit power under a fixed PDP constraint. We consider in detail the special case of only two allowed transmissions, and we prove that the two optimization problems are equivalent. For this special case, we also provide a sub-optimal root-finding solution and compare its performance with the optimal solution obtained through an exhaustive search. The results show that the optimal power allocation can provide significant gains over the equal power solution in terms of average transmit power spent. The performance of the proposed root-finding solution is practically the same as that of the optimal solution.

[1]  Chung-Ju Chang,et al.  Q-Learning-based Hybrid ARQ for High Speed Downlink Packet Access in UMTS , 2007, 2007 IEEE 65th Vehicular Technology Conference - VTC2007-Spring.

[2]  Seung-Hoon Hwang,et al.  A hybrid ARQ scheme with power ramping , 2001, IEEE 54th Vehicular Technology Conference. VTC Fall 2001. Proceedings (Cat. No.01CH37211).

[3]  Stephen P. Boyd,et al.  Convex Optimization , 2004, Algorithms and Theory of Computation Handbook.

[4]  Giuseppe Caire,et al.  The throughput of hybrid-ARQ protocols for the Gaussian collision channel , 2001, IEEE Trans. Inf. Theory.

[5]  Weifeng Su,et al.  The Optimal Transmission Power Per Round for Hybrid-ARQ Rayleigh Fading Links , 2010, 2010 IEEE International Conference on Communications.

[6]  Nihar Jindal,et al.  Performance of hybrid-ARQ in block-fading channels: A fixed outage probability analysis , 2010, IEEE Transactions on Communications.

[7]  Giuseppe Caire,et al.  Incremental redundancy hybrid ARQ schemes based on low-density parity-check codes , 2004, IEEE Transactions on Communications.

[8]  Narayan B. Mandayam,et al.  Optimal Power Allocation for Type II H-ARQ via Geometric Programming , 2005 .

[9]  Vincent K. N. Lau,et al.  Combined cross-layer design and HARQ for multiuser systems with outdated channel state information at transmitter (CSIT) in slow fading channels , 2008, IEEE Transactions on Wireless Communications.

[10]  Mohamed-Slim Alouini,et al.  Product of shifted exponential variates and outage capacity of multicarrier systems , 2009, 2009 European Wireless Conference.

[11]  Xiaoxin Qiu,et al.  On the performance of adaptive modulation in cellular systems , 1999, IEEE Trans. Commun..

[12]  Shu Lin,et al.  Automatic-repeat-request error-control schemes , 1984, IEEE Communications Magazine.