• Title/Summary/Keyword: Uplink signal

Search Result 139, Processing Time 0.022 seconds

An Enhanced AGC Structure and P-SCH Detection Method for Initial Cell Search in 3GPP LTE FDD/TDD Dual Mode Downlink Receiver (3GPP LTE FDD/TDD 듀얼 모드 하향 링크 수신기의 초기 셀 탐색을 위한 개선된 AGC 구조 및 P-SCH 검출 기법)

  • Chung, Myung-Jin;Jang, Jun-Hee;Choi, Hyung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.35 no.3C
    • /
    • pp.302-313
    • /
    • 2010
  • In this paper, we propose an enhanced AGC (Automatic Gain Control) structure and P-SCH detection method for initial cell search in 3GPP (3rdGenerationPartnershipProject) LTE (Long Term Evolution) FDD(Frequency Division Duplex) / TDD (Time Division Duplex) dual mode system. Since TDD frame structure consists of uplink subframe and downlink subframe, conventional AGC structure causes P-SCH detection performance degradation by increase of AGC variation due to signal power difference between uplink and downlink subframe. Also, P-SCH detection performance is degraded by distortion of P-SCH correlation characteristic in frequency offset and multipath fading channel environments. Therefore, we propose an AGC structure which can minimize P-SCH detection performance degradation with stable operation in 3GPP LTE TDD mode as well as FDD mode. Also we propose a P-SCH detection method which can reduce distortion of correlation chareteristics in frequency offset and multipath fading environments and obtain good P-SCH detection performance. Simulation results show that the proposed AGC structure and P-SCH detection method have stable AGC operation and excellent P-SCH detection performance for 3GPP LTE TDD / FDD dual mode downlink receiver in various channel environments.

Adaptive Multi-Tap Equalization for Removing ICI Caused by Transmitter Power Transient in LTE Uplink System (LTE 상향 링크 시스템에서 송신기의 전력 과도 현상에 의해 발생하는 ICI를 제거하기 위한 적응적 멀티 탭 등화 기법)

  • Chae, Hyuk-Jin;Cho, Il-Nam;Kim, Dong-Ku
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.20 no.8
    • /
    • pp.701-713
    • /
    • 2009
  • This paper studies a method for reducing performance degradation due to losing sub-carrier orthogonality caused by power transient between physical channels in LTE uplink transmission. The pattern of inter-carrier interference(ICI) caused by power transient is different from what has been studied for doppler shift, in that its pattern occurs at front and rear sides of channels in each period of power transient. The reason of ICI's occurrence results from power difference between channels, power transient duration, multi-path channel delay spread, and numbers of sub-carrier. New criterion is proposed to find out number of taps of multi-tap equalizer enough to improve the ICI. The scheme is to determine the number of taps of multi-tap equalizer when a normalized interference or a normalized ICI is greater than a normalized noise. Simulation results show that the number of taps is flexibly adjusted according to SNR(Signal to Noise Ratio) of a received signal to improve Bit Error Rate(BER), while the complexity of the proposed scheme is reduced down to 88 percentage of the classical method.

A Group Search-based Distributed Dynamic Channel Allocation Algorithm in Uplink Cellular System (상향링크 셀룰러 시스템에서 그룹 탐색 기반의 분산동적채널할당 방법)

  • Yoo, Doh-Kyoung;Kim, Dong-Hoi
    • Journal of Broadcast Engineering
    • /
    • v.15 no.3
    • /
    • pp.407-413
    • /
    • 2010
  • In DCA (Dynamic Channel Allocation) scheme of uplink cellular system appling a frequency reuse factor of one, when a new call requests a channel, the new call will be blocked if its SINR (Carrier to Noise and Interference Ratio) is less than the required SINR or there is no available channel. The additional channel allocation for the blocked new call can be performed with channel borrowing in the adjacent cells. The channel borrowing causes the CCI (Co-Channel Interference), thus the SINR of the existing calls is deteriorated and the channel reallocation for the existing calls is required. As a result, the channel borrowing leads to a complex calculation so that it is a NP-hard problem. Therefore, to overcome the problem, we propose a novel Group Search-based DCA scheme which decreases the number of the blocked new calls and then reduces the number of the channel reallocation by the channel borrowing for the blocked new calls. The proposed scheme searches the all channels in a group of the adjacent cells and home cell at the same time in order to minimizes the number of the blocked new calls. The simulation results show that proposed Group Search-based DCA scheme provides better new call blocking probability and system throughput than the existing Single Search-based DCA scheme which searches only the channels in home cell.

A Study on the SNR Margin Performance of Digital Subscriber Line in Complex Noises Environment (복합 잡음환경에서 디지털 가입자 회선의 SNR 마진 성능에 관한 연구)

  • 김용환;조평동;박상준;강영흥
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.27 no.9C
    • /
    • pp.829-835
    • /
    • 2002
  • DSL(digital subscriber line) transceiver designers have concerned the impulsive noise as well as NEXT(near-end crosstalk) and FEXT(far-end crosstalk) immunities Down as the strongest sources that limit the DSL channel capacity. In these noise environment the analysis on the performance of DSL should be needed. Therefore, in this paper we have estimated and simulated the SNR(signal-to-noise ratio) margin of DMT(discrete multi-tone) signal in Gauss, NEXT, FEXT and impulse noise environment by modeling an Middleton's Class A impulse signal with the test Cook pulses. As a result, it is known that the transmission rate of uplink is limited by noise characteristics rather than by loop length, but that of downlink limited complexly by both of noise characteristics and loop length. In conclusion, these results will be utilized as the threshold of ADSL performance in the complex noise environment including impulse noise.

Outage Probability of the Device-to-Device Communication According to the Interference-to-Signal-Ratio Generated by Cellular Networks (셀룰러 시스템의 간섭에 의한 D2D 시스템의 Outage 확률 분석)

  • Min, Hyun-Kee;Seo, Woo-Hyun;Park, Sung-Soo;Hong, Dae-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
    • /
    • v.48 no.1
    • /
    • pp.55-61
    • /
    • 2011
  • In this paper, the outage probability of device-to-device (D2D) uplink communication underlaying cellular networks is analyzed over Rayleigh fading. We assume that a D2D pair and M cellular user equipments share the same frequency resources. To prevent any harmful interference from a D2D transmitter to the BS, the maximum transmit power of the D2D transmitter is strictly limited. Under these assumptions, the outage probability is represented as a function of the interference-to-signal ratio from M cellular user equipments to a D2D receiver and the number of cellular user equipments, M. In addition, the interference-to-signal ratio is represented as a function of distances among D2D equipments, cellular user equipments and the BS. Simulation results validate these analytical results.

A game theory approach for efficient power control and interference management in two-tier femtocell networks based on local gain

  • Al-Gumaei, Y. A.;Noordin, K. A.;Reza, A. W.;Dimyati, K.
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • v.9 no.7
    • /
    • pp.2530-2547
    • /
    • 2015
  • In the recent years, femtocell technology has received a considerable attention due to the ability to provide an efficient indoor wireless coverage as well as enhanced capacity. However, under the spectrum sharing between femtocell user equipment (FUEs) and the owner of spectrum macrocell user equipment (MUEs), both may experience higher uplink interference to each other. This paper proposes a novel distributed power control algorithm for the interference management in two-tier femtocell networks. Due to the assignment of licensed radio frequency to the outdoor macrocell users, the access priority of MUEs should be higher than FUEs. In addition, the quality of service (QoS) of MUEs that is expressed in the target signal-to-interference-plus-noise ratio (SINR) must always be achieved. On the other hand, we consider an efficient QoS provisioning cost function for the low-tier FUEs. The proposed algorithm requires only local information and converges even in cases where the frontiers of available power serve the target SINRs impossible. The advantage of the algorithm is the ability to implement in a distributed manner. Simulation results show that the proposed algorithm based on our cost function provides effective resource allocation and substantial power saving as compared to the traditional algorithms.

A study on the MAC protocol for an aeronautical mobile data communication (항공용 이동 무선 데이터 통신에 적합한 매체접속제어 프로토콜에 관한 연구)

  • 이은주;박효달
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.22 no.11
    • /
    • pp.2604-2612
    • /
    • 1997
  • Media access control(MAC) protocol that is used between aircraft and ground station now is non-persistent CSMA protocol, but this protocol hs defects to apply in the wireless mobile radio communication environment. In this paper, to solve this Problems, the modified ICMA/CD protocol which ban be applied in the wireless environment was proposed and analyzed. In the modified ICMA/CD protocol, instead of usig special control channel, control signal was inserted into the uplink message. After the analysis, simulation was performed to approve the analysis resutls. As a results, modified ICMA/CD protocol can solve the hidden termined effect of CSMA protocol and packet detection delay time problem of ICMA/CD protocol and acquired the same channel throughput as CSMA/CD protocol. This results shows the modified ICMA/CD protocol can be used in the aeronauical telecommunication.

  • PDF

Two-Tier Interference Elimination for Femtocells Based on Cognitive Radio Centralized Spectrum Management

  • Yi, Leng-Gan;Lu, Yi-Min
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • v.8 no.5
    • /
    • pp.1514-1531
    • /
    • 2014
  • Femtocell provides better coverage and higher spectrum efficiency in areas rarely covered by macrocells. However, serious two-tier interference emerging from randomly deploying femtocells may create dead zones where the service is unavailable for macro-users. In this paper, we present adopting cognitive radio spectrum overlay to avoid intra-tier interference and incorporating spectrum underlay and overlay to coordinate cross-tier interference. It is a novel centralized control strategy appropriate for both uplink and downlink transmission. We introduce the application of proper spectrum sharing strategy plus optimal power allocation to address the issue of OFDM-based femtocells interference-limited downlink transmission, along with, a low-complexity suboptimal solution proposed. Simulation results illustrate the proposed optimal scheme achieves the highest transmission rate on successfully avoiding two-tier interference, and outperforms the traditional spectrum underlay or spectrum overlay, via maximizing the opportunity to transmit. Moreover, the strength of our proposed schemes is further demonstrated by comparison with previous classic power allocation methods, in terms of transmission rate, computational complexity and signal peak-to-average power ratio.

Self-Encoded Spread Spectrum and Turbo Coding

  • Jang, Won-Mee;Nguyen, Lim;Hempel, Michael
    • Journal of Communications and Networks
    • /
    • v.6 no.1
    • /
    • pp.9-18
    • /
    • 2004
  • Self-encoded multiple access (SEMA) is a unique realization of random spread spectrum. As the term implies, the spreading code is obtained from the random digital information source instead of the traditional pseudo noise (PN) code generators. The time-varying random codes can provide additional security in wireless communications. Multi-rate transmissions or multi-level grade of services are also easily implementable in SEMA. In this paper, we analyze the performance of SEMA in additive white Gaussian noise (AWGN) channels and Rayleigh fading channels. Differential encoding eliminates the BER effect of error propagations due to receiver detection errors. The performance of SEMA approaches the random spread spectrum discussed in literature at high signal to noise ratios. For performance improvement, we employ multiuser detection and Turbo coding. We consider a downlink synchronous system such as base station to mobile communication though the analysis can be extended to uplink communications.

A comparative study of low-complexity MMSE signal detection for massive MIMO systems

  • Zhao, Shufeng;Shen, Bin;Hua, Quan
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • v.12 no.4
    • /
    • pp.1504-1526
    • /
    • 2018
  • For uplink multi-user massive MIMO systems, conventional minimum mean square error (MMSE) linear detection method achieves near-optimal performance when the number of antennas at base station is much larger than that of the single-antenna users. However, MMSE detection involves complicated matrix inversion, thus making it cumbersome to be implemented cost-effectively and rapidly. In this paper, we first summarize in detail the state-of-the-art simplified MMSE detection algorithms that circumvent the complicated matrix inversion and hence reduce the computation complexity from ${\mathcal{O}}(K^3)$ to ${\mathcal{O}}(K^2)$ or ${\mathcal{O}}(NK)$ with some certain performance sacrifice. Meanwhile, we divide the simplified algorithms into two categories, namely the matrix inversion approximation and the classical iterative linear equation solving methods, and make comparisons between them in terms of detection performance and computation complexity. In order to further optimize the detection performance of the existing detection algorithms, we propose more proper solutions to set the initial values and relaxation parameters, and present a new way of reconstructing the exact effective noise variance to accelerate the convergence speed. Analysis and simulation results verify that with the help of proper initial values and parameters, the simplified matrix inversion based detection algorithms can achieve detection performance quite close to that of the ideal matrix inversion based MMSE algorithm with only a small number of series expansions or iterations.