Abstract-In this paper, we propose a dynamic channel assignment (DCA) scheme for distributed antenna networks (DANs). DANs, in which many antennas are distributed in each cell, significantly reduce the transmit power compared to conventional cellular networks (CNs). In DAN, a different group of channels should be assigned for each distributed antenna to avoid the interference. Since DAN can also reduce the interference power due to its low transmit power property, the same channel groups can be reused even within the same cell. Proposed DCA scheme dynamically assigns the channels based on the co-channel interference measurement. Computer simulation results demonstrate that the DAN using proposed DCA achieves higher spectrum efficiency than the conventional CN.

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In order to tackle rapidly increasing traffic, the 5th generation (5G) mobile communication system will introduce small cells using higher frequency bands with wider bandwidth to achieve super high bit rate transmission of several tens Gbps. Massive MIMO beamforming (BF) is one of promising technologies to compensate for larger path-loss in the higher frequency bands. Joint analog fixed BF and digital precoding has been proposed to reduce the cost of a Massive MIMO transceiver. However, the conventional scheme assumes the transmission of a few streams using well-known codebook-based precoding as the digital precoding, and both a selection method of the fixed BF weights and a digital precoder design, which are suitable for the super high bit rate transmission using multiple streams, have not been studied. This paper proposes a joint fixed BF and CSI-based precoding (called FBCP) scheme for the 5G Massive MIMO systems. FBCP first selects the analog fixed BF weights based on maximum total received power criterion, and then it calculates eigenmode (EM) precoding matrix exploiting CSI. This paper targets a 5G system achieving 20 Gbps in 20 GHz band as one example, and throughput performances of the proposed FBCP are evaluated by link level simulation and compared with those of the fixed BF and those of the EM precoding. Keywords-5G; higher frequency bands; Massive MIMO; analog fixed beamforming; eigenmode precoding.I.

By introducing high-purity and low-temperature Ar annealing at 850 °C, atomically flat Si surfaces of silicon-on-insulator (SOI) and shallow-trench-isolation (STI)-patterned wafers were obtained. In the case of the STI-patterned wafer, this low-temperature annealing and subsequent radical oxidation to form a gate oxide film were introduced into the complementary metal oxide semiconductor (CMOS) process with 0.22 µm technology. As a result, a test array circuit for evaluating the electrical characteristics of a very large number (>260,000) of metal oxide semiconductor field effect transistors (MOSFETs) having an atomically flat gate insulator/Si interface was successfully fabricated on a 200-mm-diameter wafer. By evaluating 262,144 nMOSFETs, it was found that not only the gate oxide reliability was improved, but also the noise amplitude of the gate–source voltage related to the random telegraph noise (RTN) was reduced owing to the introduction of the atomically flat gate insulator/Si interface.

Background: The ankle-brachial pressure index (ABI) is widely used as a standard screening method for arterial occlusive lesion above the knee. However, the sensitivity of ABI is low in hemodialysis (HD) patients. Exercise stress (Ex-ABI) may reduce the false negative results. Patients and Methods: After measuring resting ABI and toe-brachial pressure index (TBI), ankle pressure and ABI immediately after walking (Post-AP, Post-ABI) were measured using one-minute treadmill walking in 52 lower limbs of 26 HD patients. The definition of peripheral arterial occlusive disease (PAD) required an ABI value of less than 0.90, TBI value of less than 0.60, and decrease of more than 15% of the Post-ABI value and 20 mmHg of Post-AP in Ex-ABI. Computed tomographic angiography (CTA) was performed in 32 lower limbs of 16 HD patients. PAD is defined as presence of stenosis of more than 75% in the case of lesions from an iliac artery to knee on CTA. Results: The accuracy of Ex-ABI (Sensitivity, 85.7%; Specificity, 77.7%) was higher than those of ABI (Sensitivity, 42.9%; Specificity, 83.3%) or TBI (Sensitivity, 78.6%; Specificity, 61.1%). Conclusion: Ex-ABI with one-minute treadmill walking is the most useful tool for the screening of arterial occlusive lesions above the knee in maintenance HD patients.