• Title/Summary/Keyword: FH-OFDMA

Search Result 6, Processing Time 0.036 seconds

Maritime Wireless Data Communications of Predictive Frequency Hopping Technique

  • Bae, Sang-Hyun;Lee, Kwang-Ok;Jang, Bong-Seog
    • Journal of Integrative Natural Science
    • /
    • v.5 no.3
    • /
    • pp.182-185
    • /
    • 2012
  • In this paper, For 4th generation wireless communication systems, we propose a method to predict FH patterns in FH-OFDMA systems. OFDM is recognized as a promising modulation technique. Multi-user allocation in OFDM system can use FH that provides the spectrum-spread techniques. If one can generate more predictable FH sequences, then performance of the system can be easily improved. Current random FH and simple adaptive FH methods, however, are not considering predicting FH sequences. In this paper we show that the sampling of the wireless faded signal is not realized as a certain probability nature. With this regard, the proposed predictive FH allocation method is designed to embed the unknown probability models. Simulation study shows that the predictive FH method is more accurately predict FH sequences than the random or simple adaptive FH methods. We will further improve this proposed method to apply QoS control and MAC function development in OFDMA based wireless physical structures, especially maritime wireless data communications.

Robust Frequency Offset Estimation with a Single Symbol for FH-OFDMA (단일 심볼을 이용한 FH-OFDMA의 주파수 옵셋 추정)

  • Yoon Dae jung;Han Dong seog
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.30 no.4A
    • /
    • pp.250-258
    • /
    • 2005
  • An initial carrier frequency offset estimation algorithm is proposed for a multi-user frequency bowing orthogonal frequency division modulation-frequency division multiple access (FH-OFDMA) system with a single preamble symbol. To mitigate the effect of the frequency offset, every mobile station needs to accurately and rapidly acquire synchronization. The proposed algorithm uses only one preamble symbol in which two kinds of subcarriers are designed for coarse and fine frequency offset estimation. The non-data aided estimation using the energy spectrum is exploited for fine offset estimation, and maximum likelihood estimation using correlation for coarse offset estimation. By combining the two estimation results, an accurate frequency offset can be estimated with a single symbol. Through simulations, the performance of the proposed algorithm is evaluated by comparing estimation error variance with a conventional method.

Statistical Multiplexing Based RFH-OfDMA System for Improving Downlink User Capacity (하향링크 사용자 용량 개선을 위한 통계적 다중화기반의 RFH-OFDMA)

  • Jung, Bang-Chul;Lee, Hyung-Jin;Sung, Dan-Ken
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.30 no.7A
    • /
    • pp.578-586
    • /
    • 2005
  • We propose a random frequency hopping orthogonal frequency division multiple access (RFH-OFDMA) system based on statistical multiplexing for improving downlink user capacity. User capacity is defined as the maximum number of users served with a given basic data-rate in a cell. We compare the downlink user capacity of the proposed RFH-OFDMA system with that of the conventional frequency hopping OFDMA (FH-OFDMA) systems in the worst case where all users are located at the cell boundary. User capacity is limited by either the number of subcarriers or other-cell interference (OCI). Simulation results show that the proposed RFH-OFDMA system can accommodate 262 users in a 3-sectored cell, while the conventional FH-OFDMA systems can accommodate 51 users, when the user channel activity and the required Eb/I0 are 0.1 and 6 dB, respectively, and all users are assumed to be located at the cell boundary.

Frequency and Subcarrier Reuse Partitioning for FH-OFDMA Cellular Systems

  • Lee, Yeonwoo;Kim, Kyung-Ho
    • Journal of Korea Multimedia Society
    • /
    • v.16 no.5
    • /
    • pp.601-609
    • /
    • 2013
  • One of the most serious factors constraining the next generation cellular mobile consumer communication systems will be the severe co-channel interference experienced at the cell edge. Such a capacity-degrading impairment combined with the limited available spectrum resource makes it essential to develop more spectrally efficient solutions to enhance the system performance and enrich the mobile user's application services. This paper proposes a unique hybrid method of frequency hopping (FH) and subcarrier-reuse-partitioning that can maximize the system capacity by efficiently utilizing the available spectrum while at the same time reduce the co-channel interference effect. The main feature of the proposed method is that it applies an optimal combination of different frequency reuse factors (FRF) and FH-subcarrier allocation patterns into the partitioned cell regions. From the simulation results, it is shown that the proposed method can achieve the optimum number of subcarrier subsets according to the frequency-reuse distance and results in better performance than the fixed FRF methods, for a given partitioning arrangement. The results are presented in the context of both blocking probability and BER performances. It will also be shown how the proposed scheme is well suited to FH-OFDMA based cellular systems aiming at low co-channel interference performance and optimized number of subcarriers.

Packet Scheduling Algorithms for Throughput Fairness and Coverage Enhancement in TDD-OFDMA Downlink Network (TDD-OFDMA 하향 링크에서의 수율 공평성과 서비스 커버리지 보장을 위한 패킷 스케줄링 알고리즘 연구)

  • Ki, Young-Min;Kim, Dong-Ku
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.30 no.7A
    • /
    • pp.611-619
    • /
    • 2005
  • The present paper proposes two different packet scheduling algorithms in the IEEE 802.16e type TDD-OFDMA downlink, which are the weighted fair scheduling(WFS) and the throughput guarantee scheduling(TGS). The performance of proposed scheduling algorithms are compared to some of conventional schedulers such as round robin(RR), proportional fair(PF), fast fair throughput(FFTH), and fair throughput(FH) in terms of service coverage, effective throughput and fairness at 64 kbps and 128 kbps minimum user throughput requirements. For a relatively smaller throughput(64 kbps) requirement, the proposed algorithms provide higher improvement in the number of users per sector within 95$\%$ service coverage while satisfying the lxEV-DV fairness criterion. For a relatively larger throughput(128 kbps) requirement, the proposed algorithms provide higher coverage enhancement while maintaining the same effective aggregate throughput over PF scheduler.