• ETRI Journal
• /
• v.33 no.1
• /
• pp.1-5
• /
• 2011

Downlink transmit power allocation schemes are proposed for soft fractional frequency reuse (FFR) in loose and tightly coordinated systems. The transmit powers are allocated so that the loss of spectral efficiency from the soft FFR is minimized, and the required cell edge user throughput is guaranteed. The effect of the soft FFR on spectral efficiency is evaluated depending on the power allocation schemes and the number of subbands. Results show that the loss of spectral efficiency from the soft FFR can be reduced by configuring an appropriate number of subbands in the loosely coordinated systems. In tightly coordinated systems, results show that the loss of spectral efficiency can be minimized regardless of the number of subbands due to its fast coordination.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.4A
• /
• pp.316-323
• /
• 2009

Power allocation of soft frequency reuse(SFR) to increase cell edge user throughput by reducing inter-cell interference is proposed for coordinated cellular systems. SFR is the effective technique to increase cell edge user throughput, however, it costs the degradation of total system throughput. The cost increases when SFR operated in distributed resource controlled systems fails to be fast adaptive in the change of user distribution. The proposed scheme enables coordinated cells to control transmit power adaptively depending on user distribution so that it minimizes the loss of system throughput introduced from SFR while it guarantees enhancement of cell edge user throughput. Through system level simulation considering neighboring two cells, evaluation result for adaptive power allocation is shown compared with static power allocation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37A no.10
• /
• pp.885-894
• /
• 2012

Currently, Demand of data traffic has rapidly increased by popular of smart device. It is very difficult to accommodate demand of data traffic by limited resource of base station (BS). To solve this problem, method has proposed that the Device-to-Device (D2D) reduce frequency overload of the BS and all of the user equipment (UE) inside the BS and neighbor BS don't allow communicating directly to BS. However, in LTE-Advance system cellular link and sharing radio resources of D2D link, the strong interference of the cellular network is still high. So we need to eliminate or mitigate the interference. In this paper, we use the transmission power control method and Soft Frequency Reuse (SFR) resource allocation method to mitigate the interference of the cellular link and D2D link. Simulation results show that the proposed scheme has high performance in terms of Signal to Noise Ratio (SINR) and system average throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.1
• /
• pp.186-205
• /
• 2019

Intercell interference coordination (ICIC) is considered as a promising technique to increase the spectral efficiency of OFDMA cellular systems. The soft frequency reuse (SFR) and fractional frequency reuse (FFR) are representative and efficient management techniques for ICIC. Herein, to enhance the performance of the SFR scheme, we propose a call admission (CAC) scheme. In this CAC scheme, called Spectrum handoff-SFR(S-SFR), the spectrum handoff technique is applied to the user equipment (UE) located near the cell center. We derive the traffic analysis model to describe the S-SFR. In addition, a two-dimensional (2-D) Markov chain and an outage analysis are used in our analytical model. From the traffic analysis, the significant performance measures are the outage probability, call blocking probability, system throughput and resource utilization. Based on those, the outage probability and system throughput are obtained using resource utilization as an interference pattern. The analytical results are verified with computer simulation results. Finally, we compare our proposed scheme with other ICI schemes.

• ETRI Journal
• /
• v.36 no.4
• /
• pp.554-563
• /
• 2014

The burgeoning growth of real-time applications, such as interactive video and VoIP, places a heavy demand for a high data rate and guarantee of QoS from a network. This is being addressed by fourth generation networks such as Long-Term Evolution (LTE). But, the mobility of user equipment that needs to be handed over to a new evolved node base-station (eNB) while maintaining connectivity with high data rates poses a significant challenge that needs to be addressed. Handover (HO) normally takes place at cell borders, which normally suffers high interference. This inter-cell interference (ICI) can affect HO procedures, as well as reduce throughput. In this paper, soft frequency reuse (SFR) and multiple preparations (MP), so-called SFRAMP, are proposed to provide a seamless and fast handover with high throughput by keeping the ICI low. Simulation results using LTE-Sim show that the outage probability and delay are reduced by 24.4% and 11.9%, respectively, over the hard handover method - quite a significant result.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.49 no.8
• /
• pp.481-490
• /
• 2000

This paper analyzes interference power, Erlang capacity, the number of handoff occurrences, and call blocking probability with respect to the cell radius, the soft handoff region, and the mobile's velocity in a CDMA hierarchical cellular system. The microcell cellular system has the higher Erlang capacity than the macrocell cellular system. However, the microcell cellular system, which has a high system capacity through frequency reuse has the call blocking probability higher than macrocell cellular system. Also the interference power and the call blocking probability are decreased with the operation of soft handoff. Therefore, this paper presents the optimization of soft handoff region so as to maximize system's Erlang capacity with the low the call blocking probability according to mobile's velocity in the CDMA hierarchial cellular system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.12A
• /
• pp.1191-1199
• /
• 2008

We propose the Staggered-zone Resource Allocation (SRA) in order to relax throughput decrease problems by the co-channel interference of the cell boundary users at the cellular OFDMA system using frequency reuse factor K=1 and analyze the throughput improvement. The proposed algorithm allocates the resources to the users in compliance with resource allocation rule which is planned in order to minimize co-channel interference between cells without any additional information. The resource allocation method in the SRA lines up the users in pathloss order as descending series, and then allocates from pre-determined resource allocation region where decides differently in each cell. This algorithm prevents the co-channel interferences of the cell boundary user to be caused by using same resource simultaneously and equalizes interference to the users in the cell.

• Journal of dental hygiene science
• /
• v.9 no.1
• /
• pp.121-127
• /
• 2009

A comparative analysis was conducted through this study on tooth brushing and a use of auxiliary oral hygiene devices for oral hygiene for 287 S Health College students some of whom major dental hygiene and some of whom don't relate to the department, and then has drawn out the results as below. 1. Relating to the frequency of tooth brushing, 2-3 times a day was the utmost case in both departments(p < 0.05). 2. In use of toothbrush bristle, the students of dental hygiene department used medium bristle(51.2%), while the student of other department used soft bristle(51.5%)(p > 0.05). 3. In the term of tooth brush used, 2~5 months was the utmost case in both departments(p > 0.05). 4. In tooth- brushing method, all the student of both departments said they knew how to do it(p > 0.05). 5. In the acquisition of tooth brushing methods, the students of dental hygiene acquired it from dentistry 44.4%, and the students of other department from TV or Radio 47.5% (p > 0.05)which was a quite high rate. 6. In reference to recognition level on auxiliary oral hygiene devices, dental hygiene students said Yes 79.8%, and the other side students said No 63.9%(p < 0.05). In reuse of auxiliary oral hygiene devices, a great number of students of both departments said No (p < 0.05). 8. In reference to the chance to use auxiliary oral hygiene devices, 58.1% of dental hygiene students chose them with their own judgement, and 37.8% of other department students recommended by dentist's offices(p < 0.05). 9. Relating to the reason for not using auxiliary oral hygiene devices, 38.9% of the dental hygiene students said it's bothersome, and 56.7% of the other department students said they didn't know about these things(p < 0.05). 10. In the recognition level of dental floss, in knowing the way to use it, whether or not of using it, the students of both department showed a significant difference (p < 0.05). 11. In the recognition level of floss holder and the yes or not of using it, there was an insignificant difference(p > 0.05), while in understanding of it, there was a significant difference(p < 0.05). 12. Relating to the recognition level of electric tooth brush, yes or no of using it, there wasn't a significant difference(p > 0.05). 13. In the cognition level of rubber stimulator, yes or no of using it, there wasn't much difference, while in understanding to use it, there was a significant difference(p < 0.05). 14. In the understanding level of water pik, yes or not of using it, there wasn't a great deal of difference(p < 0.05), but in inquiry of whether or not of using it, there was no difference (p > 0.05), 15. In the understanding level of tongue scraper, whether or not of using it, there wasn't much difference(p > 0.05), but in understanding to use it, there was a great deal of difference(p < 0.05). 16. In the recognition of garglin, understanding of it, and whether or not of using it, the two departments didn't show a significant difference(p < 0.05).