• The KIPS Transactions:PartC
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• v.14C no.7
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• pp.597-602
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• 2007

In conventional cooperative communication data rate is 1/2 than non cooperative protocols. In this paper, we propose a full data rate DF (Decode and Forward) cooperative transmission scheme. Proposed scheme is based on time division multiplexing (TDM) channel access. When DF protocol has full data rate, it can not obtain diversity gain under the pairwise error probability (PEP) view point. If it increases time slot to obtain diversity gain, then data rate is reduced. The proposed algorithm uses orthogonal frequency and constellation rotation to obtain both full data rate and diversity order 2. Moreover, performance is analyzed according to distance and optimized components that affect the system performance by using computer simulation. The simulation results revealed that the cooperation can save the network power up to 7dB over direct transmission and 5dB over multi-hop transmission at BER of $10^{-2}$. Besides, it can improve date rate of system compared with the conventional DF protocol.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.4
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• pp.159-167
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• 2018

In this paper, we propose an algorithm to optimize energy efficiency in a multi-user decoupled RF energy harvesting network and experiment on the trend of energy efficiency change assuming users' various geographical distribution scenarios. In the RF energy harvesting network where both wireless data transmission and RF energy harvesting are simultaneously performed, the energy efficiency is a key indicator of network performance, and it is necessary to investigate how various factors can affect the energy efficiency. In order to increase energy efficiency effectively, we can confirm that users' distributions are important factors in the RF energy harvesting network from the simulation results.

• Journal of the Korea Society of Computer and Information
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• v.12 no.5
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• pp.139-144
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• 2007

The mobile terminal's frequent changes to the access point introduce significant network overhead in mobile IP networks. To solve this problem, we introduce a hierarchical structure with consideration given to the dynamic value of neighbor scope in IP regional registration[1]. When a mobile terminal moves within the neighbor given by the scope value, it makes registration locally without registration with its home agent. We analyze the algorithm mathematically and show the numerical results. As a result, optimization of the scope value for the localized registration under the hierarchical structure makes the proposed scheme outperform the standard mobile IP protocol[2]. This can be explained from the fact that there is only local registration for terminal's movement within the scope region. Moreover, as the signaling cost for home agent increases, the proposed scheme becomes more advantageous.