This paper discusses how to effectively design a nextgeneration wireless communication system that can possibly provide very high data-rate transmissions and versatile quality services. In order to accommodate the sophisticated user requirements and diversified user environments of the next-generation systems, it should be designed to take an efficient and flexible structure for multiple access and resource allocation. In addition, the design should be optimized for cost-effective usage of resources and for efficient operation in a multi-cell environment. As orthogonal frequency division multiple access (OFDMA) has turned out in recent researches to be one of the most promising multiple access techniques that can possibly meet all those requirements through efficient radio spectrum utilization, we take OFDMA as the basic framework in the next-generation wireless communications system design.So, in this paper, we focus on introducing an OFDMA-based downlink system design that employs the techniques of hybrid multiple access (HMA) and frequency group (FG) in conjunction with intra-frequency group averaging (IFGA). The HMA technique combines various multiple access schemes on the basis of OFDMA system, adopting the multiple access scheme that best fits to the given user condition in terms of mobility, service, and environment. The FG concept and IFGA technique help to reduce the feedback overhead of OFDMA system and the other-cell interference (OCI) problem by grouping the sub-carriers based on coherence bandwidths and by harmonizing the channel condition and OCI of the grouped sub-carriers.

In this paper, we investigate how to do resource allocation to guarantee a minimum user data rate at low signaling overhead in multi-cell orthogonal frequency division multiple access (OFDMA) wireless systems. We devise dynamic resource allocation (DRA) algorithms that can minimize the QoS violation ratio (i.e., the ratio of the number of users who fail to get the requested data rate to the total number of users in the overall network). We assume an OFDMA system that allows dynamic control of frequency reuse factor (FRF) of each sub-carrier. The proposed DRA algorithms determine the FRFs of the sub-carriers and allocate them to the users adaptively based on inter-cell interference and load distribution. In order to reduce the signaling overhead, we adopt a hierarchical resource allocation architecture which divides the resource allocation decision into the inter-cell coordinator (ICC) and the base station (BS) levels. We limit the information available at the ICC only to the load of each cell, that is, the total number of sub-carriers required for supporting the data rate requirement of all the users. We then present the DRA with limited coordination (DRA-LC) algorithm where the ICC performs load-adaptive inter-cell resource allocation with the limited information while the BS performs intra-cell resource allocation with full information about its own cell. For performance comparison,we design a centralized algorithm called DRA with full coordination (DRA-FC). Simulation results reveal that the DRA-LC algorithm can perform close to the DRA-FC algorithm at very low signaling overhead. In addition, it turns out to improve the QoS performance of the cell-boundary users, and achieve a better fairness among neighboring cells under non-uniform load distribution.Index Terms: Dynamic resource allocation, inter-cell interference, orthogonal frequency division multiple access (OFDMA), quality of service (QoS), signaling overhead.

Takayasu's arteritis (TA) is a nonspecific, chronic and stenotic panarteritis which usually involves the aorta and its major branches. Corticosteroid and immunosuppressants are recommended to manage the acute inflammatory phase, but their long term benefits are uncertain. Blood pressure (BP) control during the chronic phase of TA is essential to preserve renal function, which is associated with the patient's long-term prognosis and survival. Revascularization in organ damaging arterial stenosis with percutaneous angioplasty (PTA)/stenting or bypass surgery have been accepted as established treatment options in chronic complicated phase of TA. We present a case of a 31-year-old female patient with a two-day history of sudden onset oliguria and generalized edema whose acute oliguric renal failure was successfully reversed following PTA and stenting in a solitary functioning kidney with critical renal artery stenosis (RAS) caused by TA.

We propose a new distributed QoS routing scheme called PCSP that uses Pro-Computation based Selective Probing for routing decision. This algorithm pre-computes the cost and QoS metrics respectively for the least cost and the best QoS paths. The pro-computed information enables to strictly limit the set of neighbor nodes involved in the probing process, thereby reducing the message complexity without sacrificing cost optimality. Computer simulation reveals that the PCSP scheme indeed has low message complexity and high success ratio with guaranteed optimal search.

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