• Journal of Information Processing Systems
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• 제13권6호
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• pp.1602-1612
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• 2017

Since rapidly disseminating of Internet of Things (IoT) as the new communication paradigm, a number of studies for various applications is being carried out. Especially, interest in the smart medical system is rising. In the smart medical system, a number of medical devices are distributed in popular area such as station and medical center, and this high density of medical device distribution can cause serious performance degradation of communication, referred to as the coexistence problem. When coexistence problem occurs in smart medical system, reliable transmitting of patient's biological information may not be guaranteed and patient's life can be jeopardized. Therefore, coexistence problem in smart medical system should be resolved. In this paper, we propose a distributed coexistence mitigation scheme for IoT-based smart medical system which can dynamically avoid interference in coexistence situation and can guarantee reliable communication. To evaluate the performance of the proposed scheme, we perform extensive simulations by comparing with IEEE 802.15.4 MAC protocol which is a traditional low-power communication technology.

• Journal of Communications and Networks
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• 제17권6호
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• pp.622-633
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• 2015

The coexistence among different systems is a major problem in communications. Mutual interference between different systems should be analyzed and mitigated before their deployment. The paper focuses on two aspects that have an impact on the system performance. First, the coexistence analysis, i.e. evaluating the mutual interference. Second aspect is the coexistence techniques, i.e. appropriate system modifications that guarantee the simultaneous use of the spectrum by different technologies. In particular, the coexistence problem is analyzed between ultra-wide bandwidth (UWB) and narrow bandwidth (NB) systems emphasizing the role of spectrum sensing to identify and classify the NB interferers that mostly affect the performance of UWB system. A direct sequence (DS)-time hopping (TH) code design technique is used to mitigate the identified NB interference. Due to the severe effect of Narrowband Interference on UWB communications, we propose an UWB transceiver that utilizes spectrum-sensing techniques together with mitigation techniques. The proposed transceiver improves both the UWB and NB systems performance by adaptively reducing the mutual interference. Detection and avoidance method is used where spectrum is sensed every time duration to detect the NB interferer's frequency location and power avoiding it's effect by using the appropriate mitigation technique. Two scenarios are presented to identify, classify, and mitigate NB interferers.

• ETRI Journal
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• 제28권1호
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• pp.91-94
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• 2006

Impulse radio (IR) is a competitive candidate for ultra-wideband (UWB) systems. In this letter, we evaluated the coexistence of an IR-UWB system based on an orthogonal sinusoidal correlation receiver (OSCR) with an IEEE 802.11a WLAN through a detailed simulation. The coexistence performance of the two systems is characterized in terms of the receiver's bit-error rates. Then, some approaches to interference mitigation are discussed.

• Journal of electromagnetic engineering and science
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• 제6권2호
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• pp.117-122
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• 2006

This paper presents the impacts of Ultra-wideband(UWB) applied in the communication applications using frequency band from 3.1 GHz to 10.6 GHz on Broadband Wireless Access(BWA) based on orthogonal frequency division multiplexing(OFDM) using frequency band of 3.5 GHz. It proposes low duty cycle(LDC) for enabling UWB to mitigate strong interference to BWA. The effects of interference mitigation are evaluated and analyzed in the environment of UWB coexistence with BWA. UWB with LDC scheme will be given to bring higher transmit power level corresponding to Federal Communications Commission(FCC) provisional limit for enabling UWB operation at 3.5 GHz bands.

• 인터넷정보학회논문지
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• 제16권3호
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• pp.1-11
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• 2015

인체를 중심으로 동작하는 WBAN(Wireless Body Area Network)은 의료 및 비의료 서비스를 동시에 제공하는 것을 목적으로 하며, 저전력, 다양한 전송률과 높은 데이터 신뢰성을 요구하는 근거리 통신 기술이다. 이러한 요구사항을 만족시킬 수 있는 통신기술 표준 중 IEEE 802.15.4는 WBAN 운영에 높은 호환성을 제공할 수 있어 이를 통한 다양한 연구가 진행되고 있다. 한편, IEEE 802.15.4 기반 다수의 WBAN이 밀집될 경우 발생하는 신호 간섭과 충돌은 데이터의 신뢰성을 저하시키는 주요한 원인되고 있으며, IEEE 802.15.4 표준은 다수의 네트워크가 공존하는 상황을 고려하여 설계되지 않았기 때문에 이에 대한 개선이 필요하다. 이를 해결하기 위해 본 논문에서는 사전 실험을 통해 IEEE 802.15.4 기반의 WBAN 간 공존 상황에서 발생할 수 있는 문제점들을 파악하였고, 실험 결과를 바탕으로 다수의 WBAN이 공존하는 상황에서의 신뢰성 저하를 완화하기 위한 기법을 제안한다. 제안하는 기법의 동작은 크게 두 단계로 구분될 수 있으며, 첫 번째 단계에서는 슈퍼 프레임의 CFP 구간에서의 데이터 전송 방법을 개선하여 WBAN 간 충돌을 회피하며, 두 번째 단계에서는 채널 접근 방식을 전환함으로써 충돌을 완화한다. 제안하는 기법은 표준 기반의 WBAN과 비교 실험을 수행하여 성능을 검증하였다.

• 한국통신학회논문지
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• 제32권1A호
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• pp.34-43
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• 2007

In the IEEE 802.15.3 Medium Access Control (MAC) protocol, Simultaneously Operating Piconets (SOPs) are linked by the parent/child (P/C) or parent/neighbor (P/N) configuration, which work on a Time Division Multiple Access (TDMA) basis. This provides interference mitigation but the overall throughput is limited because the SOPs share the channel time exclusively. The protocol is not efficient for SOPs if we focus on the combination of interference mitigation and high throughput maintenance. In this paper Public Channel Time Allocation (Public CTA) is proposed, which is able to greatly reduce the inter-piconet interference (IPI) and achieve greater throughput without much loss of link success probability (LSP) in the SOPs. The simulation results based on the SOPs of Direct Sequence Ultra Wideband (DS-UWB) system demonstrate that the proposed scheme effectively supports the coexistence of SOPs, and it can not only significantly improve the overall throughput of SOPs but also maintain high LSP.

• ETRI Journal
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• 제32권1호
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• pp.44-52
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• 2010

Ultra-wideband (UWB) systems have witnessed a debate over whether they may cause interference to other existing and future narrowband systems sharing their band of operation. The detect and avoid (DAA) mechanism was developed as a solution to reduce interference to narrowband systems in order to ease regulatory concerns. It works by adaptively reducing the transmitted power at the overlapping bands upon detecting an active narrowband link. However, employing DAA degrades the performance of UWB transmissions. In this paper, we present the Korean UWB regulations as an example of regulations that require DAA in certain bands. We investigate DAA's impact on performance and propose a method to mitigate it, which provides UWB with the more efficient support of the DAA mechanism and enables it to avoid a larger number of narrowband users while sustaining the data rate. Results show significant improvement in performance with the application of our technique compared to conventional performance.