• 한국인터넷방송통신학회논문지
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• 제17권1호
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• pp.33-39
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• 2017

차량 네트워크, 분산 로봇과 사이버 물리 시스템 등 mission-critical 환경에서 동작하는 서비스들은 기존 서비스에 비해 latency에 대한 요구사항이 훨씬 엄격하다. 그 중 자율주행 차량 간 통신은 급격히 부상하고 있는 애플리케이션 영역으로 수 ms 수준의 엄격한 latency 요구사항을 가진다. 802.11p나 LTE-direct standards를 이용하는 현재 시스템은 이러한 수준의 ultra-low latency를 만족하지 못한다. 현재, 전체 latency의 상당부분을 medium access가 차지하기 때문에, 이 부분의 해결을 위해서는 Layer2를 수정할 필요가 있다. 따라서 본 논문에서는 MAC layer에 초점을 맞추어 coordinator에 의한 scheduling 없이 join/leave가 자유로운 Autonomous TDMA(ATDMA)를 고안하여 scalable하면서 latency가 보장되는 MAC을 구현하였다. 또한 WAVE 프로토콜과의 비교를 통해 알고리즘의 성능을 평가하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권5호
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• pp.1412-1430
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• 2024

The soft cancellation list (SCANL) decoding algorithm for polar codes runs L soft cancellation (SCAN) decoders with different decoding factor graphs. Although it can achieve better decoding performance than SCAN algorithm, it has high latency. In this paper, a fast simplified SCANL (Fast-SSCANL) algorithm that runs L independent Fast-SSCAN decoders is proposed. In Fast-SSCANL decoder, special nodes in each factor graph is identified, and corresponding low-latency decoding approaches for each special node is propose first. Then, syndrome check aided Fast-SSCANL (SC-Fast-SSCANL) algorithm is further put forward. The ordinary nodes satisfied the syndrome check will execute hard decision directly without traversing the factor graph, thereby reducing the decoding latency further. Simulation results show that Fast-SSCANL and SC-Fast-SSCANL algorithms can achieve the same BER performance as the SCANL algorithm with lower latency. Fast-SSCANL algorithm can reduce latency by more than 83% compared with SCANL, and SC-Fast-SSCANL algorithm can reduce more than 85% latency compared with SCANL regardless of code length and code rate.

• Journal of Information Processing Systems
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• 제4권4호
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• pp.133-144
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• 2008

Clusters have become a popular alternative for building high-performance parallel computing systems. Today's high-performance system area network (SAN) protocols such as VIA and IBA significantly reduce user-to-user communication latency by implementing protocol stacks outside of operating system kernel. However, emerging parallel applications require a significant improvement in communication latency. Since the time required for transferring data between host memory and network interface (NI) make up a large portion of overall communication latency, the reduction of data transfer time is crucial for achieving low-latency communication. In this paper, Eager Data Transfer (EDT) mechanism is proposed to reduce the time for data transfers between the host and network interface. The EDT employs cache coherence interface hardware to directly transfer data between the host and NI. An EDT-based network interface was modeled and simulated on the Linux-based, complete system simulation environment, Linux/SimOS. Our simulation results show that the EDT approach significantly reduces the data transfer time compared to DMA-based approaches. The EDTbased NI attains 17% to 38% reduction in user-to-user message time compared to the cache-coherent DMA-based NIs for a range of message sizes (64 bytes${\sim}$4 Kbytes) in a SAN environment.

• ETRI Journal
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• 제27권5호
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• pp.525-532
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• 2005

In this paper, we propose and present implementation results of a high-speed turbo decoding algorithm. The latency caused by (de)interleaving and iterative decoding in a conventional maximum a posteriori turbo decoder can be dramatically reduced with the proposed design. The source of the latency reduction is from the combination of the radix-4, center to top, parallel decoding, and early-stop algorithms. This reduced latency enables the use of the turbo decoder as a forward error correction scheme in real-time wireless communication services. The proposed scheme results in a slight degradation in bit error rate performance for large block sizes because the effective interleaver size in a radix-4 implementation is reduced to half, relative to the conventional method. To prove the latency reduction, we implemented the proposed scheme on a field-programmable gate array and compared its decoding speed with that of a conventional decoder. The results show an improvement of at least five fold for a single iteration of turbo decoding.

• Journal of information and communication convergence engineering
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• 제6권3호
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• pp.245-248
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• 2008

Everytime a node moves out of its area, the connection to the node encounters a handover which may cause much latency. NetLMM(Network based Localized Mobility Management) supports the mobility management for such nodes and improves handover latency using MIH(Media Independent Handover) function. In this paper, we add some messages to NetLMM procedure to improve handover latency and analyze its effects through a scenario based approach

• International Journal of Internet, Broadcasting and Communication
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• 제13권1호
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• pp.69-81
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• 2021

While the fifth generation (5G) and beyond 5G (B5G) mobile communication networks are being rolled over the globe, several world-wide companies have already started to prepare the sixth generation (6G). Such 6G mobile networks targets ultra-reliable low-latency communication (URLLC). In this paper, we challenge to reduce the inherent latency of existing non-orthogonal multiple access (NOMA) in 5G networks of massive connectivity. First, we propose the novel unipodal binary pulse amplitude modulation (2PAM) NOMA, especially without SIC, which greatly reduce the latency in existing NOMA. Then, the achievable data rates for the unipodal 2PAM NOMA are derived. It is shown that for unequal gain channels, the sum rate of the unipodal 2PAM NOMA is comparable to that of the standard 2PAM NOMA, whereas for equal gain channels, the sum rate of the unipodal 2PAM NOMA is superior to that of the standard 2PAM NOMA. In result, the unipodal 2PAM could be a promising modulation scheme for NOMA systems toward 6G.

• 전자통신동향분석
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• 제34권3호
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• pp.93-105
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• 2019

This study emphasizes the importance of the newly added Ultra-Reliable and Low-Latency Communications (URLLC) service as an important evolutionary step for 5G mobile communication, and proposes a remedial application. We analyze the requirements for the application of 5G mobile communication technology in high-precision vertical industries and applications, introduce the 5G URLLC design principles and standards of 3GPP, and summarize the current state of applied artificial intelligence technology in wireless communication. Additionally, we summarize the current state of research on ultra-reliable and low-latency machine learning-based wireless communication technology for application in ultra-high-precision vertical industries and applications. Furthermore, we discuss the technological direction of artificial intelligence technology for URLLC wireless communication.

• ETRI Journal
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• 제38권5호
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• pp.885-895
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• 2016

The lowest power mode (passive-standby mode) was proposed for reducing the power consumption of set-top boxes in a standby state when not receiving content. However, low-power set-top boxes equipped with the lowest power mode have been rarely commercialized because of their low-quality user experience. In the lowest power mode, they deactivates almost all of operational modules and processes, and thus require dozens of seconds for activation latency (that is, the latency for activating all modules of the set-top boxes in a standby state). They are not even updated in a standby state because they deactivate their network interfaces in a standby state. This paper proposes an adaptive standby mode scheduling method for improving the user experience of such boxes. Set-top boxes using the proposed method can analyze the activation pattern and find the frequently used time period (that is, when the set-top boxes are frequently activated). They prepare for their activation during this frequently used time period, thereby reducing the activation latency and enabling their update in a standby state.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2008년도 추계학술발표대회
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• pp.1387-1390
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• 2008

In a wireless network, handover latency is very important in supporting user mobility with the required quality of service (QoS). In view of this many schemes have been developed which aim to reduce the handover latency. The Hierarchical Mobile IPv6 (HMIPv6) approach is one such scheme which reduces the high handover latency that arises when mobile nodes perform frequent handover in Mobile IPv6 wireless networks. Although HMIPv6 reduces handoff latency, failures in the mobility anchor point (MAP) results in severe disruption or total disconnection that can seriously affect user satisfaction in ongoing sessions between the mobile and its correspondent nodes. HMIPv6 can avoid this situation by using more than one mobility anchor point for each link. In [3], an improved Robust Hierarchical Mobile IPv6 (RH-MIPv6) scheme is presented which enhances the HMIPv6 method by providing a fault-tolerant mobile service using two different MAPs (Primary and Secondary). It has been shown that the RH-MIPv6 scheme can achieve approximately 60% faster recovery times compared with the standard HMIPv6 approach. However, if mobile nodes perform frequent handover in RH-MIPv6, these changes incur a high communication overhead which is configured by two local binding update units (LBUs) as to two MAPs. To reduce this communication overhead, a new cost-reduced binding update scheme is proposed here, which reduces the communication overhead compared to previous schemes, by using an increased number of MAP switches. Using this new proposed method, it is shown that there is a 19.6% performance improvement in terms of the total handover latency.

• 한국인터넷방송통신학회논문지
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• 제23권3호
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• pp.59-64
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• 2023

화재 재난방송 시스템에서는 아날로그, 디지털, 네트워크 디지털 전관 방송 시스템으로 나뉘며, 네트워크 디지털 전광 방송 시스템에서 중요한 사양은 낮은 대기 시간(Low-latency), 높은 샘플링 레이트, 다채널 입출력이다. 기존에 데이터링크 층의 MAC 주소 기반으로 구별하는 AoE(Audio over Ethernet) 방법을 널리 사용하고 있다. 그러나 이 방법은 복잡성과 비용이 증가하는 문제가 있다. 이에 본 제안은 AoIP(Audio over Internet Protocol)/UDP 방식으로 별도의 중복적인 네트워크가 필요 없이 IP(Internet Protocol) 주소로 손쉽게 구별하는 통신을 할 수 있어 네트워크를 자유롭게 사용 구성하고 복잡도를 낮추어 비용을 낮출 수 있도록 제안한다. AoIP/UDP 방식으로 구현 후 실험결과 2.66ms 대기 시간 성능으로 동등한 성능으로 비용의 개선함을 보였다.