In-Seok Hwang

Resource Management Scheme Reflecting Relative Utilities in Multi-channel Wireless Systems

This paper proposes a combined resource management and scheduling scheme for multi-channel wireless systems based on the knowledge of the channel quality information. In multi-channel wireless systems, such as MIMO, SDMA, or OFDMA systems, the quality of individual channel changes with time in a fairly independent manner, and is very much user-dependent. Consequently, the overall system performance or capacity heavily depends not only on the time (i.e., the scheduling scheme) but also the way (i. e. the radio resource management scheme) that channels are allocated to users. Unlike the most existing scheduling and/or RRM schemes for wireless systems, our approach employs multiple schedulers, each of which is responsible for allocating a single channel (or a channel group) to different users. In other words, the proposed scheme carries out the RRM and scheduling at the same time. Further, we introduce the notion of request-based scheduling as a way to extend the advantage of opportunistic scheduling to channel axis. Numerical experiments demonstrate that a significant performance improvement can be achieved by the parallel scheduling scheme, and the improvement may even be magnified via request-based scheduling.

Inter-cell coordinated beamforming with opportunistic scheduling

This paper proposes a distributed coordination framework with opportunistic scheduling among the multiple users as opposed to the existing works on the multi-cell cooperative beamforming problem subject to a single active user in each cell. This framework deals with the best throughput trade-off between throughput gain by interference nulling, and opportunistic scheduling gain in a cellular MISO system. In this framework, multi-user scheduling and inter-cell coordination issues are jointly considered for improving the cell-edge throughput performance without compromising the overall system performance. Our simulation results have demonstrated that its performance can reach up to 85% of its upper bound at the cell boundary.

On the Gain of Data Rate Control in OFDMA Systems

Unlike single carrier systems, the primitive allocation unit in OFDMA systems is a sub-channel that is a collection of pre-arranged sub-carriers, and these sub-channels can be divided into two groups depending on the sub-carrier locations-diversity sub-channel and AMC sub-channel. The former consists of scattered sub-carriers over entire band while the latter consists of clustered sub-carriers on specific frequency band. For the case of AMC sub-channels, we can achieve link level SNR gain due to the reduced channel selectivity as well as system level multi-user scheduling gain due to the increased degree of freedom in selecting frequency bands. This paper investigates the performance difference between these two sub-channel types, specifically in terms of average throughputs, cell edge data rate and service outage probability.