• Journal of Korea Society of Industrial Information Systems
• /
• v.17 no.7
• /
• pp.1-8
• /
• 2012

In this paper, we consider an efficient protocol for the multi-hop relay transmission on a sensor network which can be utilized in a ubiquitous environment. More specifically, we propose an efficient relaying protocol for the distance and position recognition on the proposed sensor network which performs with the differentially bi-orthogonal chirp spread spectrum (DBO-CSS) in the industrial, scientific and medical (ISM) bands. For an efficient networking access, we design and implement four different packet structures, zone information packet, hop information packet, tag information packet, and application serial packet. Additionally, we also propose an efficient position recognition algorithm. Finally, for verification of our proposed protocol's efficiency, we build the testbed system which consists of $15m{\times}15m$ multi-cell and 10 hops in the network.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.9
• /
• pp.4446-4462
• /
• 2019

In this paper, we focus on interference cancellation for three-hop cognitive radio networks (CRNs) over Rayleigh fading channels. In CRNs, secondary users (SUs) are allowed to opportunistically utilize the licensed spectrum during the idle time of primary users (PUs) to achieve spectrum sharing. However, the SUs maybe power constrained to avoid interference and cover a very short transmission range. We here propose an interference cancellation scheme (ICS) for three-hop CRNs to prolong the transmission range of SUs and improve their transmission efficiency. In the proposed scheme, a flexible transmission protocol is adopted to cancel the interference at both secondary relays and destinations at the same time. And a closed-form expression for the secondary outage probability over Rayleigh fading channels is derived to measure the system performance. Simulation results show that the proposed scheme can significantly reduce the secondary outage probability and increase the secondary diversity in comparison with the traditional cases.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.9
• /
• pp.809-819
• /
• 2004

In this paper, in order to exclude the expansion of M/W relay frequency or its new frequency assignment possibly, we analyzed a possibility of substituting M/W system by B-WLL or optical fiber network regarding service quality and economical points. To define the target of service quality, pre-condition and analysis method for the selected media have been derived to compare each other. E1 transmission with BER 10$^{-1}$ was chosen as a reference capacity, and service distance was calculated f3r the selected media as a function of availability. Also from the economical point we considered 3 systems such as optical fiber, M/W, and B-WLL based upon basic system structure, and analyzed them for various line configurations of fiber optic and B-WLL according to service period, system capacity, transmission distance, and data rate. It was confirmed that B-WLL can provide quality of service with 99.999 % availability within 1.6 km cell radius, and for optical fiber substitution, the leased fiber conduit on an electric pole is more economical than M/W system irrespective of service period, but in case of directly digging for underground conduit, it turned out ineffective regardless of cabling duct types.

• Journal of electromagnetic engineering and science
• /
• v.10 no.3
• /
• pp.190-198
• /
• 2010

This paper evaluates the performance of two methods of spectrum sensing: the linear combining method and the selection combining method which is based on maximum SNR of sensing channel. We proposed a rule for global detection for the purpose of combating hidden terminal problems in spectrum sensing. Our analysis considers a situation when sensing channels experience the non-identically, independently distributed(n.i.d) Rayleigh fading. The average probabilities of global detection in these methods are derived and compared. In the scope of this paper, the reporting channels are assumed to be the AWGN channel with invariant and identical gain during the system's operation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2004.05b
• /
• pp.112-115
• /
• 2004

본 논문에서는 M/W 방송중계용 주파수 공유방안에 관한 기초연구로써 디지털 방송중계용 STL/TTL 링크 무선전송 시스템을 모델링하고 다중경로 페이딩 채널 환경에서 시스템 특성 및 성능 분석이 가능한 M/W대 디지털 방송중계용 STL/TTL 링크 무선전송 시스템 시뮬레이터를 GUI 환경으로 구현하였다. 국내 방송 중계용의 경우 디지털화 진행이 추진되고 있는바, 본 연구에서 구현한 디지털 STL/TTL 링크 무선전송 시스템 시뮬레이터를 이용하여 향후 M/W 대역 방송중계용 주파수 재배치를 위한 채널 성능 및 간섭평가를 수행함으로써 국내 방송중계용 표준화에 기초 자료로 활용하고자 한다.

• Journal of Broadcast Engineering
• /
• v.15 no.1
• /
• pp.89-98
• /
• 2010

In this paper, the technical analyzing methodology has been suggested to preserve the same transmission quality of a M/W system used for FM broadcasting link after the frequency reallocation. The simulation was also performed for the actual M/W system operating in each frequency band, and its results were evaluated in terms of an availability based upon a fade margin. It was confirmed that only if the relative fade margin of more than 2.6 dB at 1700 MHz is provided, the equivalent service quality may be obtained regardless of the frequency reallocation. The suggested method will be expected to be widely used for accessing service quality of the M/W system concerned with the frequency reallocation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.3A
• /
• pp.229-234
• /
• 2009

In this paper, we propose a decision scheme of amount of required resources in wireless multi-hop systems which can reuse radio resources adaptively among relay stations (RSs). Base stations (BSs) can allocate resources dynamically based on amount of required resources of each RS. Moreover using resource reuse with this allocation method can increase amount of available resources in multi-hop systems. Generally, BSs allocate same amount of resources for RSs which share and reuses same resources for each other. Since amount of required resources are different among these RSs, a decision scheme of a specific value which can represent various required resources of RSs is needed. We propose this scheme which can decide the representative value of required resources of RSs adaptively based on the amount of required resources and the buffer state of each RS. Our simulation results show that the proposed scheme can increase performance of a multi-hop system. System capacity with the proposed adaptive scheme is increased by twice as large as one with a fixed representation value.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.7 no.9
• /
• pp.2081-2100
• /
• 2013

In this paper, we propose a cooperative hybrid spectrum sharing protocol by jointly considering interweave (opportunistic) and underlay schemes. In the proposed protocol, secondary users can access the licensed spectrum along with the primary system. Our network scenario comprises a single primary transmitter-receiver (PTx-PRx) pair and a group of M secondary transmitter-receiver (STx-SRx) pairs within the transmission range of the primary system. Secondary transmitters are divided into two groups: active and inactive. A secondary transmitter that gets an opportunity to access the secondary spectrum is called "active". One of the idle or inactive secondary transmitters that achieves the primary request target rate $R_{PT}$ will be selected as a best decode-and-forward (DF) relay (Re) to forward the primary information when the data rate of the direct link between PTx and PRx falls below $R_{PT}$. We investigate the ergodic capacity and outage probability of the primary system with cooperative relaying and outage probability of the secondary system. Our theoretical and simulation results show that both the primary and secondary systems are able to achieve performance improvement in terms of outage probability. It is also shown that ergodic capacity and outage probability improve when the active secondary transmitter is located farther away from the PRx.

• Journal of Broadcast Engineering
• /
• v.15 no.1
• /
• pp.99-111
• /
• 2010

In this paper as a follow-up to Paper I, the required fade margin derived in Paper I to preserve the same service quality has been examined by analyzing system and propagation characteristics as well as measured data. The comparison of the fade margin between simulated and measured results is also performed for the actual operating line-of-sight(LOS) and non-LOS links, and practical usefulness as an analysis tool is revealed by checking service quality of M/W system relevant to frequency reallocation. According to simulated and measured results, there was a little difference for LOS link between Mt. Moodung and Mt. Mangun, but a fairly good agreement was reached for non-LOS link between Andong KBS and transmitter site.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.5
• /
• pp.489-498
• /
• 2003

Recently to introduce new services of ultra-high speed wireless access and systems beyond the 3rd generation mobile communication, 5 GHz band has been highly interested. As a way of getting the required frequency, it is considered that microwave relay bands below 6 GHz, which shows a slow decrease in demand and less cost-effectiveness, should be moved to other bands above 6 GHz. In this paper, as a tool for analyzing microwave link design and its service quality, the outage prediction based upon Vigants & Barnett＇s model is reviewed. To show outage and availability calculation, simulations are performed for the operating 4 GHz radio sites, and some results and features regarding frequency movement to 6.7 as well as 8 GHz are also discussed in terms of diversity techniques, bit error rate, and availability As the results, it is confirmed that only the diversity techniques of space or space and frequency can satisfy the annual objective of availability irrespective of frequency movement.