Browsing by Author "Li, Zexian"

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5G URLLC: Design challenges and system concepts
(2018-10-12) Li, Zexian; Shariatmadari, Hamidreza; Singh, Bikramjit; Uusitalo, Mikko
A4 Artikkeli konferenssijulkaisussa
The upcoming fifth generation (5G) wireless communication system is expected to support a broad range of newly emerging applications on top of the regular cellular mobile broadband services. One of the key usage scenarios in the scope of 5G is ultra-reliable and low-latency communications (URLLC). Among the active researchers from both academy and industry, one common view is that URLLC will play an essential role in providing connectivity for the new services and applications from vertical domains, such as factory automation, autonomous driving and so on. The most important key performance indicators (KPIs) related to URLLC are latency, reliability and availability. In this paper, after brief discussion on the design challenges related to URLLC use cases, we present an overview of the available technology components from 3GPP Rel-15 and potential ones from Rel-16. In addition, coordinated multi-cell resource allocation methods are studied. From the system level simulation results in an urban macro environment, it can be observed that effective multi-cell cooperation, more specifically soft combining, can lead to a significant gain in terms of URLLC capacity.
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.
Contention-Based Access for Ultra-Reliable Low Latency Uplink Transmissions
(2018-04) Singh, Bikramjit; Tirkkonen, Olav; Li, Zexian; Uusitalo, Mikko
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We consider sporadic ultra-reliable and low latency communications in the uplink 5G cellular systems. Reliable low latency access for randomly emerging packet transmission needs cannot be guaranteed in current wireless systems. To achieve the goal of low latency and high reliability simultaneously, we propose a contention-based transmission scheme aimed for the users with small payloads. We target to reduce collision probability by considering multiple transmissions for the same packet for reliable reception. We find the optimal number of consecutive multiple transmissions that reduces collisions and achieves target reliability within the latency window. By means of intended frame structure design for the 5G cellular systems, results are drawn and comparisons are made with default multi-channel slotted ALOHA access scheme.
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
Flexible Resource Allocation for Device-to-Device Communication in FDD System for Ultra-Reliable and Low Latency Communications
(2017) Singh, Bikramjit; Li, Zexian; Uusitalo, Mikko
A4 Artikkeli konferenssijulkaisussa
Ultra-reliable and low latency communications is envisioned to enable new services and applications with high reliability, availability and low latency, e.g, factory automation, Tactile Internet. Device-to-device communication is one such mean that allows devices to experience benefits in terms of shorter communication latency. Currently most device-to-device communication in frequency-division duplex system occurs in uplink spectrum. However, due to unbalanced cellular traffic in uplink and downlink bands may result poor spectrum utilization of network resource. In this paper, we investigate resource allocation where network offers reliable communication using normal cellular and device-to-device communications. We consider flexible allocation for device-to-device communication in both uplink and downlink bands in a frequency-division duplex system. The network optimizes resource allocation to improve the network rate with 99.999 % availability target. We demonstrate the usability of the proposed protocol in a factory scenario.
Interference coordination in ultra-reliable and low latency communication networks
(2018) Singh, Bikramjit; Tirkkonen, Olav; Li, Zexian; Uusitalo, Mikko
A4 Artikkeli konferenssijulkaisussa
5th Generation cellular communication is envisioned to enable connectivity for a wide range of new use cases. The focus on mission-critical communications, such as industrial automation and motion control, presses the demand for ultra-reliable communication. High availability, e.g., 99.999 % can be strived to reduce the outage probability. However, in multi-cell networks, interference from neighboring cells can be damaging in the ultra-reliable communication region. This requires a coordination amongst the interfering cells to relieve the interference in order to improve the network availability. In Multiple-Input, Multiple-Output based networks where the interference is colored, multiple base stations can coordinate by precluding the usage of precoders that increases the overall interference strongly. With this, multiple cells can jointly improve the minimum cell rate without inflicting harm to the other cell users, and thereby improve the network availability.
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.
On-off necklace codes for asynchronous mutual discovery
(2018-02-14) Tirkkonen, Olav; Li, Zexian; Wei, Lu; Vinel, Alexey
A4 Artikkeli konferenssijulkaisussa
We consider mutual discovery of asynchronous wireless transceivers with a fixed activity ratio. On-off activity patterns are slotted, and repeat in discovery frames. For discovery it has to be guaranteed that the activity patterns of two transceivers are not overlapping. We design necklace codes determining activity patterns to guarantee discovery within a discovery frame, so that two asynchronous transceivers always have non-overlapping activity patterns. The number of distinct patterns is analyzed as a function of discovery frame length, and on-off activity ratio. As an application example, we consider the discovery problem for vehicle-to-vehicle communication. To guarantee discovery of far-away vehicles, discovery sequences providing processing gain, and necklace coded activity patterns are needed. We find that billions of discovery code identities can be provided with a repetition frequency that is high enough to guarantee a missed discovery probability less than 10-6.