Browsing by Author "Uusitalo, Mikko A."

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  • Asymmetric ACK/NACK Detection for Ultra-Reliable Low-Latency Communications
    (2018-08-20) Shariatmadari, Hamidreza; Duan, Ruifeng; Iraji, Sassan; Jantti, Riku; Li, Zexian; Uusitalo, Mikko A.
     A4 Artikkeli konferenssijulkaisussa
    The fifth generation wireless systems are expected to encounter new services in order to provide connectivity for a wide range of applications. One of the considered services is ultra-reliable low-latency communications (URLLC), which has stringent requirements on availability, reliability, and latency. The communication efficiency of URLLC can be improved by employing error control protocols, such as automatic repeat request (ARQ) and hybrid ARQ (HARQ). However, this requires a reliable feedback channel to carry acknowledgement (ACK) and negative ACK (NACK) signals. Improving the detection reliability of ACK and NACK signals simultaneously entails allocating more resources for the feedback channel. Instead, we propose employing an asymmetric signal detection to provide a better protection for NACK signals compared to the ACK signals, without assigning more resources to the feedback channel. The simulation results show that the asymmetric signal detection can achieve a better resource utilization for URLLC.
  • Communications Survival Strategies for Industrial Wireless Control
    (2022) Khosravirad, Saeed R.; Tirkkonen, Olav; Parts, Ulo; Zhou, Liang; Korpi, Dani; Baracca, Paolo; Uusitalo, Mikko A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Industrial wireless control systems are mainly designed on the premise of time-sensitive ultra-reliable low-latency communications (URLLC). With the introduction of survival time to the quality of service requirements of such systems, the design paradigm has evolved from typical link reliability (i.e., minimizing packet error rate), to service availability, that is, minimizing the chance of burst errors, which can cause loss of communication for longer than survival time. In this article, we address the implications of this evolution and present a set of survival time strategies that are designed to guarantee end-To-end dependable industrial wireless control. To ensure service availability, transmissions are divided into normal and survival modes. The presented strategies include scheduling and link adaptation that are designed to target the differences between these modes of operation, traffic prioritization to enhance service availability for users in survival mode, and more efficient multi-node, multi-path, and multi-carrier communications techniques.
  • Fifth-Generation Control Channel Design: Achieving Ultrareliable Low-Latency Communications
    (2018-06) Shariatmadari, Hamidreza; Iraji, Sassan; Jantti, Riku; Popovski, Petar; Li, Zexian; Uusitalo, Mikko A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Link adaptation design for ultra-reliable communications
    (2016-05-01) Shariatmadari, Hamidreza; Li, Zexian; Uusitalo, Mikko A.; Iraji, Sassan; Jäntti, Riku
     A4 Artikkeli konferenssijulkaisussa
    The fifth generation (5G) of cellular networks is expected to provide connectivity for a wide range of services. This requires the network to encounter novel features. Ultra-reliable communications (URC) is one of the considered features, which provides a certain level of communication service almost all the time. This is essential in order to support mission-critical applications, such as industrial automation, public safety, and vehicular communications. This paper studies link adaptation optimization for URC, considering errors in both data and feedback channels. As the implementation of optimal link adaptation is challenging, particularly, for downlink transmissions due to the limited feedback channel, a simple link adaption scheme is also proposed. Results reveal that the performances of the proposed and optimal link adaptation schemes are close. Hence, the proposed scheme can be utilized to efficiently support URC in cellular networks.
  • Optimized Survival Mode to Guarantee QoS for Time-critical Services
    (2021-07) Tirkkonen, Olav; Khosravirad, Saeed R.; Baracca, Paolo; Zhou, Liang; Parts, Ulo; Korpi, Dani; Uusitalo, Mikko A.
     A4 Artikkeli konferenssijulkaisussa
    We consider time critical transmissions for wireless industrial IoT services, where information should not be older than a survival time in the millisecond order, and extreme service availability is targeted. With non-zero survival time, a feedback based survival mode is possible, where the network incorporates additional robustness if the previous transmission was not received. We consider the tradeoff between reliability of normal mode and survival mode transmission, and analyze the effect of feedback errors on these. We formulate an optimization to minimize average resource usage, guaranteeing time critical quality of service (QoS), and show numerical results in scenarios with typical system assumptions. For a user with a Rayleigh fading channel, average signal-to-noise ratio 10 dB, and control channel error probability 10-3, optimization based on judiciously choosing survival and normal mode reliability targets can reduce resource usage needed to guarantee QoS with a factor of 30.