• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.345-355
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• 2012

The WiMedia Alliance has specified a Distributed Medium Access Control (D-MAC)/WUSB protocol based on UWB for high speed wireless home networks and WPANs. In this paper, we propose a novel SoQ-based cooperative communication protocol adaptive to current UWB link transmission rate and QoS measure. The proposed SoQ-based cooperative communication protocol has compatibility with current WiMedia D-MAC/Wireless USB standard and is executed at each device according to a SoQ-based Relay Node Selection (RNS) criterion.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1397-1405
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• 2012

Cooperative communications play a important role in increasing frame transmission rate at wireless communication networks where frequency resource is strictly limited. In this paper, we did a research on how to select the helper nodes that are very import in cooperative communications. As a prelude study in this research field, we carried out performance comparison of three helper node selection schemes using computer simulation. The system throughput was used as the performance measure and the random way point mobility model, where every communicating nodes move around within the designated communication range, was used.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.5
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• pp.53-58
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• 2011

In this paper, we firstly propose a novel cooperative transmission protocol, which utilizes the advantages of mid-notes in the route from the source to the destination. Taking benefits from balancing between the received packet from the source and acknowledge message from the destination, the mid-node between the source and the destination is firstly considered to be the broadcaster. If its signal is successfully received from the source, it leads to consider the next nodes, which has closer distance to the destination than it. If one of these nodes correctly receives the signal, it performs broadcasting the signal to the destination instead of mid-node. Otherwise, the mid-node directs attention to these nodes being near to the destination. As the result, some nodes are unnecessary to be considered and passed over time. After that, we analyze some published selection relaying schemes based on geographic information to choose the best nodes instead of the instantaneous SNR as before. Finally, simulation results are given to demonstrate the correctness of the performance analyses and show the significant improvement of the selection relaying schemes based geographic information compared to the other ones.

• Journal of Korea Multimedia Society
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• v.14 no.12
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• pp.1559-1571
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• 2011

In wireless ad hoc networks, nodes communicate with each other using multihop routed transmission in which hop-by-hop cooperative diversity can be effectively employed. This paper proposes (i) two cooperation models for per-link cooperation (PLC) and per-node cooperation (PNC) for exploiting cooperative diversity in wireless ad hoc networks and (ii) a cooperative routing algorithm for the above models in which best relays are selected for cooperative transmission. First, two cooperation models for PLC and PNC are introduced and represented as an edge-weighted graph with effective link quality. Then, the proposed models are transformed into a simplified graph and a cooperative routing algorithm with O(n2) time is developed, where n is the number of nodes in the network. The effectiveness of the algorithm is confirmed for the two cooperation models using simulation.

• Journal of Communications and Networks
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• v.12 no.6
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• pp.616-623
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• 2010

In this paper, exact closed-form expressions for outage probability and bit error probability (BEP) are presented for multi-hop decode-and-forward (DF) relaying schemes in conjunction with cooperative diversity, in which selection combining technique is employed at each node. We have shown that the proposed protocol offers remarkable diversity advantage over direct transmission as well as the conventional DF relaying schemes with the same combining technique. We then investigate the system performance when different diversity schemes are employed. It has been observed that the system performance loss due to selection combining relative to maximal ratio combining is not significant. Simulations are performed to confirm our theoretical analysis.

• ETRI Journal
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• v.40 no.2
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• pp.237-245
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• 2018

The Distributed Modulated Wideband Converter (DMWC) is a networking system developed from the Modulated Wideband Converter, which converts all sampling channels into sensing nodes with number variables to implement signal undersampling. When the number of sparse subbands changes, the number of nodes can be adjusted flexibly to improve the reconstruction rate. Owing to the different attenuations of distributed nodes in different locations, it is worthwhile to find out how to select the optimal sensing node as the sampling channel. This paper proposes the spectrum sensing of DMWC based on a Markov random field (MRF) to select the ideal node, which is compared to the image edge segmentation. The attenuation of the candidate nodes is estimated based on the attenuation of the neighboring nodes that have participated in the DMWC system. Theoretical analysis and numerical simulations show that neighboring attenuation plays an important role in determining the node selection, and selecting the node using MRF can avoid serious transmission attenuation. Furthermore, DMWC can greatly improve recovery performance by using a Markov random field compared with random selection.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1390-1405
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• 2014

This paper investigates optimal relay selection and power allocation under an aggregate power constraint for cooperative wireless sensor networks assisted by amplify-and-forward relay nodes. By considering both transmission power and circuit power consumptions, the received signal-to-noise ratio (SNR) at the destination node is calculated, based on which, a relay selection and power allocation scheme is developed. The core idea is to adaptively adjust the selected relays and their transmission power to maximize the received SNR according to the channel state information. The proposed scheme is derived by recasting the optimization problem into a three-layered problem-determining the number of relays to be activated, selecting the active relays, and performing power allocation among the selected relays. Monte Carlo simulation results demonstrate that the proposed scheme provides a higher received SNR and a lower bit error rate as compared to the average power allocation scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.1
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• pp.95-101
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• 2009

Wireless Sensor Network (WSN) has limited power and bandwidth. In order to high data rate and high speed communication systems are required. Cooperative communication system can help to decrease power consumption through spatial diversity. In cooperative transmission, one partner node assists one sensor node to transmit their data to destination. Instead of using M partners for M sensor nodes, we propose 1 partner for M sensor nodes. And we proposed relay selection scheme base on ARQ. Proposed protocol offers higher diversity order as conventional one with much less bandwidth and power. The destination will consider the one packets received from the best relay to reduce the complexity of the system. We verified BER performance for the proposed protocol through Monte-Carlo simulation over Rayleigh fading plus AWGN.

• Advances in Computational Design
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• v.3 no.2
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• pp.191-200
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• 2018

Establishment of an efficient routing technique in multiple-input-multiple-output (MIMO) based mobile ad hoc network (MANET) is a new challenge in wireless communication system to communicate in a complex terrain where permanent infrastructure network implementation is not possible. Due to limited power of mobile nodes, a minimum power consumed routing (MPCR) algorithm is developed which is an integration of cooperative transmission process. This algorithm select relay node and support short distance communication. The performance analysis of proposed routing algorithm increased signal to noise interference ratio (SNIR) resulting effect of cooperative transmission. Finally performance analysis of the proposed algorithm is verified with simulated result.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10A
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• pp.752-759
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• 2009

Cooperative diversity is an effective technique to combat multi-path fading. When this technique is applied to energy-constrained wireless sensor networks, it is a key issue to design appropriate relay selection and power allocation strategies. In this paper, we proposed a new multi-relay selection and power allocation algorithm to maximize network lifetime. The algorithm are composed of two relay selection stages, where the channel condition and residual power of each node were considered in multi-relay selection and the power is fairly allocated proportional to the residual power, satisfies the required SNR at destination and minimizes the total transmit power. In this paper, proposed algorithm is based on AF (amplify and forward) model. We evaluated the proposed algorithm by using extensive simulation and simulation results show that proposed algorithm obtains much longer network lifetime than the conventional algorithm.