• Journal of Communications and Networks
• /
• 제8권2호
• /
• pp.169-174
• /
• 2006

In this paper, the algorithm of a methodology for the calculation of spectrum requirements was implemented. As well, the influence of traffic distribution ratio among radio access technology groups, spectral efficiency, and flexible spectrum usage (FSU) margin was analyzed in terms of the spectrum requirements, with a view toward for future development of international mobile telecommunication (IMT)-2000 and systems beyond IMT-2000. The calculated spectrum requirement in the maximum spectral efficiency case is reduced by approximately 40% compared to a minimum spectral efficiency case. The effect of the distribution ratio on the required spectrum is smaller than the effect of the spectral efficiency. As the flexible spectrum usage margin increases by 1.0 dB, the total spectrum requirement decreases by 0.9 dB. The required spectrum for the market input parameter, ${\rho}$ = 0.5 is 801.63 MHz, while the required spectrum for ${\rho}$ = 1.0 is 6295.4 MHz. This is equivalent to an increase of 785.32 %.

• Journal of Communications and Networks
• /
• 제8권2호
• /
• pp.163-168
• /
• 2006

This paper presents one possible approach for liberalization of the radio spectrum based around spectrum usage rights (SURs) which are technology and usage neutral. This is challenging technically because of the complexity of defining rights which are flexible and technology-neutral while retaining sufficient safeguards against interference. The work presented here is part of an ongoing process of defining and testing SURs. Of com is currently considering SURs, though is not committed to implementing them at this stage, and will issue further discussion documents on this area in due course.

• 한국전자파학회논문지
• /
• 제17권2호
• /
• pp.110-116
• /
• 2006

본 논문에서는 4세대 이동통신 주파수 소요량 산출 방법론을 구현하고, 주파수 소요량의 변화에 큰 영향을 미치는 RATG간 트래픽 배분을, 주파수 효율성, FSU 이득과 시장 데이터 입력 파라미터 ${\rho}$에 따른 주파수 소요량의 변화를 시뮬레이션 하였다. 트래픽 배분율에 따른 주파수 소요량 변화는 $1\;GHz/20\;\%$정도였으며, 주파수 효율성에 따른 변화는 $5{\sim}9\;GHz$였다. 그리고 FSU 이득이 1 dB 증가하면 주파수 소요량은 약 0.9 dB 정도 감소하였다. 시장 데이터 입력 파라미터 ${\rho}=0.5$ 일 때 주파수 소요량은 801.63 MHz, ${\rho}=1.0$ 일 때는 6295.4 MHz로, 시장 데이터 입력 파라미터가 주파수 소요량에 미치는 영향이 가장 크다.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
• /
• pp.51-56
• /
• 2005

In this paper we implemented the algorithm of methodology for calculation of spectrum requirements and analyzed the influence of traffic distribution ratio among radio access technology groups, spectral efficiency, and flexible spectrum usage margin on spectrum requirements for future development of IMT-2000 and systems beyond IMT-2000

• 한국전자파학회논문지
• /
• 제17권3호
• /
• pp.307-316
• /
• 2006

본 논문에서는 차세대 이동통신 시스템의 간섭을 분석하기 위해 개선된 MCL(Advanced Minimum Coupling Loss) 방법을 제안하고 기존의 MCL 방법과 비교하였다. 제안된 방법은 OFDM(Orthogonal Frequency Division Multiplex) 기반의 차세대 이동통신 시스템의 송신 전력밀도 스펙트럼을 이용하여 간섭전력을 해석적으로 구한다. 또한 개선된 MCL 방법을 이용하여 기존의 MCL에서는 정확히 계산하기가 불가능했던 FSU(Flexible Spectrum Usage)를 사용하는 차세대 이동통신 시스템과 차세대 이동통신 후보 주파수 대역에 존재하는 고정 마이크로파 시스템과의 공유 간섭을 분석하였다. 피간섭원의 수신 안테나에 도착한 간섭 전력을 계산한 결과, 기존 MCL보다 개선된 MCL로 계산한 결과가 보다 정확했으며 그 차이는 최대 4.5 dB였다. 따라서 본 논문에서 제시한 개선된 MCL 방법은 차세대 이동통신 시스템의 공유 분석에 유용하게 사용될 수 있다고 판단된다.

• Journal of electromagnetic engineering and science
• /
• 제10권3호
• /
• pp.104-116
• /
• 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.

• Journal of Communications and Networks
• /
• 제7권2호
• /
• pp.115-125
• /
• 2005

This paper discusses how to effectively design a next-generation wireless communication system that can possibly provide very high data-rate transmissions and versatile quality services. In order to accommodate the sophisticated user requirements and diversified user environments of the next-generation systems, it should be designed to take an efficient and flexible structure for multiple access and resource allocation. In addition, the design should be optimized for cost-effective usage of resources and for efficient operation in a multi-cell environment. As orthogonal frequency division multiple access (OFDMA) has turned out in recent researches to be one of the most promising multiple access techniques that can possibly meet all those requirements through efficient radio spectrum utilization, we take OFDMA as the basic framework in the next-generation wireless communications system design. So, in this paper, we focus on introducing an OFDMA-based downlink system design that employs the techniques of hybrid multiple access (HMA) and frequency group (FG) in conjunction with intra-frequency group averaging (IFGA). The HMA technique combines various multiple access schemes on the basis of OFDMA system, adopting the multiple access scheme that best fits to the given user condition in terms of mobility, service, and environment. The FG concept and IFGA technique help to reduce the feedback overhead of OFDMA system and the other-cell interference (OCI) problem by grouping the sub-carriers based on coherence band-widths and by harmonizing the channel condition and OCI of the grouped sub-carriers.