@article{kim_sichitiu_2011, title={Optimal Max-Min Fair Resource Allocation in Multihop Relay-Enhanced WiMAX Networks}, volume={60}, ISSN={["1939-9359"]}, DOI={10.1109/tvt.2011.2163431}, abstractNote={In this paper, an optimal resource allocation scheme is proposed for WiMAX networks that are enhanced with nontransparent relay stations (RSs). We first focus on two-hop relaying networks, because this scenario has the largest throughput gain. Furthermore, several researchers have proposed different resource allocation schemes in two-hop relaying networks, and thus, we can compare the performance of our proposed scheme with the following two well-known schemes in terms of cell throughput, outage rate, and computational time: 1) orthogonal and 2) overlapped . We then explore an extension of the proposed scheme to a general multihop relaying scenario by taking into account spatial reuse in both the access and relay zone periods. The numerical results show that the highest cell throughput can be achieved by the proposed optimal scheme while maintaining the fairness and lower outage performance of the orthogonal scheme at a higher computational cost. Moreover, the cell throughput degradation from increasing the number of hops from two to three hops, under the proposed optimal scheduling scheme, is only 12% and 19% when six and nine RSs are deployed, respectively.}, number={8}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Kim, Yongchul and Sichitiu, Mihail L.}, year={2011}, month={Oct}, pages={3907–3918} }
 @article{kim_sichitiu_2011, title={Optimal Placement of Transparent Relay Stations in 802.16j Mobile Multihop Relay Networks}, volume={E94B}, ISSN={["1745-1345"]}, DOI={10.1587/transcom.e94.b.2582}, abstractNote={WiMAX (IEEE 802.16) has emerged as a promising radio access technology for providing high speed broadband connectivity to subscribers over large geographic regions. New enhancements allow deployments of relay stations (RSs) that can extend the coverage of the base station (BS), increase cell capacity, or both. In this paper, we consider the placement of transparent RSs that maximize the cell capacity. We provide a closed-form approximation for the optimal location of RS inside a cell. A numerical analysis of a number of case studies validates the closed-form approximation. The numerical results show that the closed-form approximation is reasonably accurate. key words: WiMAX, relay networks, optimal placement}, number={9}, journal={IEICE TRANSACTIONS ON COMMUNICATIONS}, author={Kim, Yongchul and Sichitiu, Mihail L.}, year={2011}, month={Sep}, pages={2582–2591} }
 @inproceedings{kim_sichitiu_2011, title={Optimal resource allocation in multihop relay-enhanced WiMAX networks}, DOI={10.1109/wcnc.2011.5779254}, abstractNote={Multihop relaying in WiMAX networks is considered an increasingly attractive technology for providing throughput enhancement, coverage extension, or both. In this paper, we consider deploying non-transparent relay stations (RSs) that transmit on the same carrier frequency as the base station (BS) for the purpose of coverage extension. Since it is possible that the RSs and BS are transmitting/receiving simultaneously to/from the subscriber stations (SSs) during the access zone period, it is challenging to schedule resources optimally for serving SSs in a fair manner. We propose an optimal scheduling scheme that preserves fairness among active SSs, and compare its performance with two different resource allocation schemes, namely, the overlapped and orthogonal in terms of cell throughput and outage performance. Our numerical results show that proposed scheme can achieve more throughput than the orthogonal scheme, while maintaining the fairness and lower outage performance of the orthogonal one.}, booktitle={2011 IEEE Wireless Communications and Networking Conference (WCNC)}, author={Kim, Y. and Sichitiu, Mihail L.}, year={2011}, pages={737–742} }