• 제목/요약/키워드: Spectrum Coexistence

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Narrowband Listen-Before-Talk under Coexistence with Wideband Systems in Unlicensed Spectrum (비면허대역에서 광대역 시스템과 공존을 위한 협대역 Listen-Before-Talk 기법 연구)

  • Murti, Wisnu;Yun, Ji-Hoon
    • Journal of IKEEE
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    • v.23 no.1
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    • pp.91-98
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    • 2019
  • LTE's extension for unlicensed spectrum called Licensed Assisted Access (LAA) is equipped with Listen-Before-Talk (LBT) designed similar with the backoff mechanism of Wi-Fi for coexistence. However, Wi-Fi's backoff mechanism has not evolved from its old design for compatibility with legacy devices, thus LAA's LBT is not efficient either in utilizing spectrum. If LAA operates with no Wi-Fi systems in proximity, it can run more efficient LBT. In this paper, we propose Narrowband Clear Channel Assessment (NCCA) for narrowband transmission. In NCCA, an LAA node performs LBT in either wide or each narrow bandwidth segment. This allows multiple LAA nodes to perform simultaneous transmissions in orthogonal bandwidth segments in the same time slot. We design four variants of NCCA implementation and model their performance using a mathematical model. The coexistence performance of NCCA with conventional wideband nodes and the accuracy of the model are shown via simulation.

Interference Avoidance Technology Using Cognitive UWB in Ultra Wideband Systems (Cognitive UWB 기술을 이용한 UWB 시스템에서의 간섭 회피 기술)

  • Hwang, Jae-Ho;Sohn, Sung-Hwan;Lee, Sung-Jun;Kim, Jae-Moung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.8A
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    • pp.836-846
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    • 2007
  • Wireless Communication is playing a key role in implementing the ubiquitous society. However, due to the increasing wireless and mobile devices occupying the spectrum, the frequency resources are believed to become more and more limited. In order to deal with the problem, coexistence is considered to be a effective method to improve the efficiency of spectrum utilization between several different systems. Here, we utilize the UWB system to realize the coexistence, because it is an ultra wide band system which can co-exist with other narrow band systems. On the other hand, Cognitive Radio technology is an intelligent technology which can sense the spectrum environment and adaptively adjust the parameters for wireless transmission. In this paper, by using Cognitive UWB, the spectrum efficiency of the transmission channels is largely improved; Furthermore, the interference to other systems can be effectively avoided.

On the Interference of Ultra Wide Band Systems on Point to Point Links and Fixed Wireless Access Systems

  • Giuliano, Romeo;Guidoni, Gianluca;Mazzenga, Franco
    • Journal of Communications and Networks
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    • v.6 no.2
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    • pp.163-172
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    • 2004
  • Ultra Wide Bandwidth (UWB) spread-spectrum techniques will playa key role in short range wireless connectivity supporting high bit rates availability and low power consumption. UWB can be used in the design of wireless local and personal area networks providing advanced integrated multimedia services to nomadic users within hot-spot areas. Thus the assessment of the possible interference caused by UWB devices on already existing narrowband and wideband systems is fundamental to ensure nonconflicting coexistence and, therefore, to guarantee acceptance of UWB technology worldwide. In this paper, we study the coexistence issues between an indoor UWB-based system (hot-spot) and outdoor point to point (PP) links and Fixed Wireless Access (FWA) systems operating in the 3.5 - 5.0 GHz frequency range. We consider a realistic UWB master/slave system architecture and we show through computer simulation, that in all practical cases UWB system can coexist with PP and FWA without causing any dangerous interference.

Spectrum Sharing SDMA with Limited Feedback: Throughput Analysis

  • Jo, Han-Shin
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.12
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    • pp.3237-3256
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    • 2012
  • In the context of effective usage of a scarce spectrum resource, emerging wireless communication standards will demand spectrum sharing with existing systems as well as multiple access with higher spectral efficiency. We mathematically analyze the sum throughput of a spectrum sharing space-division multiple access (SDMA) system, which forms a transmit null in the direction of other coexisting systems while satisfying orthogonal beamforming constraints. For a large number of users N, the SDMA throughput scales as log N at high signal-to-noise ratio (SNR) ((J-1) loglog N at normal SNR), where J is the number of transmit antennas. This indicates that multiplexing gain of the spectrum sharing SDMA is $\frac{J-1}{J}$ times less than that of the non-spectrum sharing SDMA only using orthogonal beamforming, whereas no loss in multiuser diversity gain. Although the spectrum sharing SDMA always has lower throughput compared to the non-spectrum sharing SDMA in the non-coexistence scenario, it offers an intriguing opportunity to reuse spectrum already allocated to other coexisting systems.

The Coexistence of OFDM-Based Systems Beyond 3G with Fixed Service Microwave Systems

  • Jo Han-Shin;Yoon Hyun-Goo;Lim Jae-Woo;Chung Woo-Ghee;Yook Jong-Gwan;Park Han-Kyu
    • Journal of Communications and Networks
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    • v.8 no.2
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    • pp.187-193
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    • 2006
  • In this paper, we study the coexistence of orthogonal frequency division multiplexing (OFDM)-based systems beyond 3G (B3G) and point-to-point (P-P) fixed service (FS) microwave systems. The advanced general analytical model derived via a power spectral density (PSD) analysis proposed in this paper has two advantages in comparison with the conventional minimum coupling loss (MCL) method. First, the interfering signal power that appears in the band of a victim system can be easily assessed without a spectrum emission mask. Second, when transmit power is not allocated to some subcarriers overlapping the band of the victim system in order to mitigate B3G OFDM-based systems interference with other systems, the general analytical model can successfully assess the interference from the B3G systems into FS systems, whereas the MCL method incorporating the spectrum emission mask cannot be applied in the presence of the same interference condition. The proposed model can be derived in a closed form and is simply implemented with the help of simulation, and thus the solution can be obtained in significantly reduced time. Through application of the proposed model, coexistence results are analyzed in a co-channel and adjacent channel with respect to guard band and minimum separation distance.

Dynamic Resource Adjustment for Coexistence of LAA and Wi-Fi in 5 GHz Unlicensed Bands

  • Choi, Jihoon;Kim, Eunkyung;Chang, Sungcheol
    • ETRI Journal
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    • v.37 no.5
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    • pp.845-855
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    • 2015
  • To enable the coexistence of Licensed Assisted Access (LAA) and Wi-Fi in 5 GHz unlicensed bands, a new channel access mechanism is proposed. Accounting for the fairness between LAA and Wi-Fi, the proposed mechanism finds the optimal transmission time ratio by adaptively adjusting the transmission durations for LAA and Wi-Fi. In addition, we propose a new analytical model for the distributed coordination function of IEEE 802.11 through some modifications of conventional analytical models for saturation and non-saturation loads. By computing the activity ratio of Wi-Fi, the proposed analytical model is able to control the time ratio between LAA and Wi-Fi, which is required for practical implementation of the proposed access mechanism. Through numerical simulations, the proposed channel access mechanism is compared with conventional methods in terms of throughput and utility.

An Integrated Game Theoretical Approach for Primary and Secondary Users Spectrum Sharing in Cognitive Radio Networks

  • Kim, Jong-Gyu;Nguyen, Khanh-Huy;Lee, Jung-Tae;Hwang, Won-Joo
    • Journal of Korea Multimedia Society
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    • v.14 no.12
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    • pp.1549-1558
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    • 2011
  • In this paper, we address the problem of bandwidth sharing among multiple primary users and multiple secondary users in a cognitive radio network. In cognitive radio networks, effective spectrum assignment for primary and secondary users is a challenge due to the available broad range of radio frequency spectrum as well as the requisition of harmonious coexistence of both users. To handle this problem, firstly, Bertrand game model is used to analyze a spectrum pricing in which multiple primary users emulate with each other to acquire maximal profit. After that, we employ Cournot game to model the spectrum sharing of secondary users to obtain optimal profit for each user also. Simulation results show that our scheme obtains optimal solution at Nash equilibrium.

WLAN CR Coexistence Beacon Protocol for Cognitive Radio-Based WLAN Network (무선인지 기술을 이용한 차세대 WLAN 네트워크에서의 WLAN CR 공존 비콘 프로토콜)

  • Kim, Hyun-Ju;Yoo, Sang-Jo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.12B
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    • pp.790-799
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    • 2007
  • In this paper, we propose WLAN CR coexistence beacon protocol for thenext WLAN network. This method can provide WLAN with high-speed data rate in new WLAN architecture and network platform based on cognitive radio technology. WLAN CR devices that enter the CR network can know UHF channels by listening CR beacon including the coexistence parameter set and start using CR channel fast. During handover of WLAN device in UHF spectrums, WLAN device that lost their channel can change available channel by obtaining the current CR channel information from the CR beacon. In advance relaying coexistence parameter set to entire CR system, WLAN CR system can prepare own candidate channel set that is different with other CR system. In CR beacon and relay delay, we show the results that WLAN CR coexistence beacon protocol supports spectrum handover efficiently and decreases the probability of collision in candidate channel set.

A Study on the Effect of Spectrum Sharing/Overlapping in a Heterogeneous OFDM System with Nonlinear High Power Amplifiers (비선형 고전력 증폭기를 가진 이종 직교주파수분할다중화 시스템에서 스펙트럼 공유/중복 효과에 대한 연구)

  • Lee, Sung-bok;Park, Jaehyun;Park, Jae Cheol;Kang, Kyu-Min
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.12
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    • pp.1707-1714
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    • 2016
  • This paper presents the effect of spectrum sharing/overlapping in a heterogeneous OFDM system with nonlinear High Power Amplifier (HPA). According to the spectrum sharing strategies, the achievable rate performances are analyzed. In the non-orthogonal spectrum sharing, we address how the portion of the overlapped or overlaid spectrum band and the nonlinear properties of HPA affect the system performance and accordingly, propose the optimized spectrum sharing strategies.

On the Coexistence among WiMAX-TDD, TD-LTE, and TD-SCDMA

  • Cho, Bong-Youl;Kim, Jin-Young
    • Journal of electromagnetic engineering and science
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    • v.10 no.3
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    • pp.104-116
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    • 2010
  • With several advantages such as flexible downlink-to-uplink(DL-to-UL) ratio and flexible spectrum usage, Time Division Duplexing(TDD) is emerging as an alternate to Frequency Division Duplexing(FDD), especially in wireless broadband systems. We already have at least four different TDD systems in the industry: Time Division-Synchronous Code Division Multiple Access(TD-SCDMA), IEEE 802.16e-TDD, IEEE 802.16m-TDD, and Time Division-Long Term Evolution(TD-LTE). A disadvantage of TDD is that tight coordination such as time synchronization between adjacent operators is required to prevent interference between the adjacent TDD systems. In this paper, we investigate coexistence scenarios among the above four well-known TDD systems and calculate spectral efficiency(SE) loss in each scenario. Our findings are that SE loss can be significant if TDD ratios of the adjacent operators are considerably different. However, as long as the TDD ratios of the adjacent operators are similar, configurations in the systems permit perfect time synchronization between the two heterogeneous TDD systems, and the resulting SE loss is zero or reasonably low. We believe that the above findings and the configurations of the TDD systems recommended tominimize SE loss will be helpful for operators who deploy TDD systems in system parameter determination and cross-operator coordination.