• Title, Summary, Keyword: uplink channel

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Performance Improvement of Wireless Uplink Channels Using Packet Diversity (패킷 다이버시티를 이용한 무선 상향 링크의 성능 개선)

  • Lee, Goo-Yeon;Kim, Hwa-Jong;Jeong, Choong-Kyo;Lee, Yong
    • Journal of Industrial Technology
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    • v.24 no.B
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    • pp.187-192
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    • 2004
  • In this paper, we introduce a packet diversity scheme to increase uplink channel utilization in a wireless network where forward error correction is used. The packet diversity allows neighbor base stations to receive uplink packets from a mobile terminal in order to increase the utilization of the uplink channel. By allowing multiple base stations to receive the same packets, we can improve the error correction capability in an uplink channel. By incorporating the packet diversity we can reduce the parity overhead of each packet for a given tolerable loss probability, which improves the link efficiency.

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Handover Ranging Power Adjustment Using Uplink Channel Information in IEEE 802.16e/m

  • Kim, Ji-Su;Kim, Jae-Hyun
    • ETRI Journal
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    • v.32 no.5
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    • pp.823-826
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    • 2010
  • This letter proposes a handover ranging power adjustment scheme to improve handover performance. Incorrect ranging power can degrade handover performance due to the increased handover latency; therefore, the proposed scheme exploits the uplink channel information to adjust the uplink handover ranging power. Simulation results demonstrate that the proposed scheme reduces call outage probability by 33% compared to that of the conventional scheme. It also improves the number of users who satisfy the system requirements for handover interruption time.

Concatenated Zigzag(CZZ) Code for Improving Error Performance of Uplink Data in Marine Environment (해상 환경에서의 업링크 데이터의 오류성능 개선을 위한 CZZ 부호화)

  • Yun, Jung-Kug
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.4
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    • pp.648-654
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    • 2011
  • We can model marine uplink channel environment as time-correlated rician fading channel that has direct path and time varying reflected path. In this channel, error performance of uncoded system can be seriously degraded by multipath inteference. In this paper, we propose Concatenated Zigzag(CZZ) coded binary FSK signaling with noncoherent detection to improve error performance of uplink data in marine environment. CZZ code is a kind of channel coding scheme that is fast decodable as well as fast encodable. We have confirmed error performance of uplink data in marine environment can be improved dramatically through applying CZZ code.

Pilot signaling for multi-cell OFDMA uplink systems

  • Ko Jae-Yun;Lee Yong-Hwan
    • Proceedings of the IEEK Conference
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    • pp.27-30
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    • 2004
  • OFDMA is considered as one of the major candidates for broadband wireless access. The OFDMA signal is usually coherently demodulated, requiring the channel estimation which can be estimated using a known pilot signal. In multi-cell environment, the performance of channel estimation is mainly limited by intercell interference. It is desirable to use a pilot signal that can estimate the channel information robust to the intercell interference in the OFDMA uplink system. In this paper, we consider two types of pilot signal applicable to multi-cell OFDMA uplink systems: One is time-multiplexed pilot signal and the other is code­multiplexed pilot signal. Simulation results show that the code-multiplexed pilot is suitable for low mobility environment and time-multiplexed pilot is suitable for high mobility environment.

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Suboptimal Adaptive Handover Method Considering Uplink and Downlink Signals (상.하향 링크 신호를 고려한 준 최적의 적응적 하드 핸드오버 기법)

  • Cho, Young-Bo;Han, Seung-Youp;Bang, Keuk-Joon;Hong, Dae-Sik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.12C
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    • pp.1273-1279
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    • 2006
  • In this paper, we address the design of adaptive handover schemes based on the signal strength measurement for cellular communications systems. Conventional handover algorithms, which are based only on the downlink measurement, cannot guarantee the required uplink quality because uplink channel can differ greatly from downlink channel quality. Therefore, we proposes a new suboptimal adaptive handover algorithm that considers both the uplink and downlink channel quality in order to achieve the best cell selection gains when there is a wide difference between the uplink and downlink signal quality. Simulation results show that the proposed scheme achieves better performance compared to conventional handover schemes.

Channel Estimation and Analog Beam Selection for Uplink Multiuser Hybrid Beamforming System (상향링크 다중사용자 하이브리드 빔포밍 시스템에서 채널 추정과 아날로그 빔 선택 방법)

  • Kim, Myeong-Jin;Ko, Young-Chai
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.3
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    • pp.459-468
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    • 2015
  • In this paper, we consider an uplink multiuser hybrid beamforming system where an access point (AP) communicates with multiple users simultaneously. The performance of the uplink multiuser hybrid beamforming system depends on the effective channel which is given by the product of the channel matrix and the analog beams. Therefore, to maximize the performance, we need to obtain the channel information and then select the analog beams appropriately by using the acquired channel information. In this paper, we propose the channel estimation method and low complexity analog beam selection algorithm for the uplink multiuser hybrid beamforming system. Additionally, our analysis shows that the proposed low complexity analog beam selection algorithm provides much less complexity than the optimum analog beam selection algorithm. From the numerical results, we confirm that the proposed low complexity analog beam selection algorithm has little performance degradation in spite of much less complexity than the optimum analog beam selection algorithm under the equal system configuration.

Radio Resource Management Algorithm for Uplink Coordinated Cooperative Spatial Multiplexing (셀 간 협동 CSM에서 상향 링크 용량 개선을 위한 자원 할당 알고리즘)

  • Mun, Cheol;Jo, Han-Shin
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.11
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    • pp.1311-1317
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    • 2010
  • In this paper, for a uplink space division multiple access system named cooperative spatial multiplexing(CSM), radio resource management(RRM) algorithms are proposed based on sharing uplink channel information among a serving base station(BS) and interfering BSs in a uplink coordinated wireless communication system. A constrained maximum transmit power algorithm is proposed for mobile station(MS) to limit uplink inter-cell interference(ICI). And joint scheduling algorithm among coordinated BSs is proposed to enhance uplink capacity through ICI mitigation by using channel information from interfering BSs. It is shown that the proposed RRM algorithm provides a considerable uplink capacity enhancement by effective ICI mitigation only with moderate complexity.

Capacity Optimization of a 802.16e OPDMA/TDD Cellular System using the Joint Allocation Algorithm of Sub-charmel and Transmit Power - Part II : Sub-channel Allocation in the Uplink Using the Channel Sounding and Initial Transmit Power Decision Algorithm According to the User's Throughput (802.16e OFDMA/TDD 셀룰러 시스템의 성능 최적화를 위한 부채널과 전송전력 결합 할당 알고리즘 - Part II : 상향링크에서 Channel Sounding을 통한 부채널 할당 및 사용자의 수율에 따른 초기전송전력 결정 알고리즘)

  • Ko, Sang-Jun;Chang, Kyung-Hi;Kim, Jae-Hyeong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.9A
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    • pp.888-897
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    • 2007
  • In this paper, we propose an uplink dynamic resource allocation algorithm to increase sector throughput and fairness among users in 802.16e OFDMA TDD system. In uplink, we address the difference between uplink and downlink channel state information in 802.16e OFDMA TDD system. The simulation results show that not only an increment of 10% of sector throughput but higher level of fairness is achieved by round-robin using the FLR and the rate / margin adaptive inner closed-loop power control algorithm. The FLR algorithm determines the number of sub-channels to be allocated to the user according to the user's position. Also, we get 31.8% more sector throughput compared with the round-robin using FLR by FASA algorithm using uplink channel state information. User selection, sub-channel allocation, power allocation algorithms and simulation methodology are mentioned in Part I.

Fairness-insured Aggressive Sub-channel Allocation and Efficient Power Allocation Algorithms to Optimize the Capacity of an IEEE 802.16e OFDMA/TDD Cellular System

  • Ko, Sang-Jun;Chang, Kyung-Hi
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.3 no.4
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    • pp.385-398
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    • 2009
  • This paper aims to find a suitable solution to joint allocation of sub-channel and transmit power for multiple users in an IEEE 802.16e OFDMA/TDD cellular system. We propose the FASA (Fairness insured Aggressive Sub-channel Allocation) algorithm, which is a dynamic channel allocation algorithm that considers all of the users' channel state information conditionally in order to maximize throughput while taking into account fairness. A dynamic power allocation algorithm, i.e., an improved CHC algorithm, is also proposed in combination with the FASA algorithm. It collects the extra downlink transmit power and re-allocates it to other potential users. Simulation results show that the joint allocation scheme with the improved CHC power allocation algorithm provides an additional increase of sector throughput while simultaneously enhancing fairness. Four frames of time delay for CQI feedback and scheduling are considered. Furthermore, by addressing the difference between uplink and downlink scheduling in an IEEE 802.16e OFDMA TDD system, we can employ the uplink channel information directly via channel sounding, resulting in more accurate uplink dynamic resource allocation.

Uplink Pilot Signal Design for Mobile Wireless Backhaul (이동무선백홀을 위한 상향링크 파일럿 신호 설계)

  • Choi, Seung Nam;Kim, Ilgyu;Kim, Dae Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.6
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    • pp.1005-1013
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    • 2015
  • In this paper, an uplink pilot signal structure is proposed for millimeter wave(mmWave)-based mobile wireless backhaul. For the transmit diversity of two antenna ports, uplink pilot signals generated from the Zadoff-Chu sequence can be mapped in an interleaved mode or continuous mode on the frequency axis, and channel estimation algorithms are different depending on the pilot signal mapping schemes. Through a simulation under Rayleigh fading channel assuming a subway scenario, the interleaved mapping scheme showed no performance degradation compared to the continuous mapping scheme and the implementation complexity of the uplink channel estimator was reduced due to the interleaved mapping scheme.