| 1. |
- Azari, Amin, et al.
(författare)
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RACH Dimensioning for Reliable MTC over Cellular Networks
- 2017
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Ingår i: 2017 IEEE 85th Vehicular Technology Conference (VTC Spring). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509059324
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Konferensbidrag (refereegranskat)abstract
- Successful implementation of massive machine-type communications (MTC) service over cellular networks is an important enabler of Internet of things. As the existing cellular infrastructure has been designed and optimized for moderate traffic, the introduction of MTC in cellular networks results in several key challenges, among them, temporal starvation of initial access resources is of paramount importance. Here, we propose a new traffic model for cellular networks serving machine-type subscribers. This model is subsequently used to derive closed-form expressions for the access rate performance of the system. This closed-form expression are subsequently used for RACH resources planning in the time and frequency domains. Given a target access rate requirement, numerical analysis indicates how and when the required RACH resources in the code/frequency domain, i.e. number of preambles, can be traded with the occurrence frequency of RACH slots in the time domain.
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| 2. |
- Chu, Thi My Chinh, et al.
(författare)
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MAC Protocol for Opportunistic Spectrum Access in Multi-Channel Cognitive Relay Networks
- 2017
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Ingår i: IEEE Vehicular Technology Conference. - : Institute of Electrical and Electronics Engineers Inc.. - 9781509059324
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a medium access control (MAC) protocol for multi-channel cognitive cooperative radio networks (CCRNs). In this protocol, each secondary user (SU) senses for spectrum opportunities within M licensed bands of the primary users (PUs). To enhance the accuracy of spectrum sensing, we employ cooperative sequential spectrum sensing where SUs mutually exchange their sensing results. Moreover, the information obtained from cooperative spectrum sensing at the physical layer is integrated into the channel negotiation process at the MAC layer to alleviate the hidden terminal problem. Finally, the performance of the proposed MAC protocol in terms of aggregate throughput of the CCRNs is analyzed. Numerical results are provided to assess the impact of channel utilization by PUs, number of contenting CCRNs, number of licensed bands, and false alarm probability of SUs on the aggregate throughput. © 2017 IEEE.
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| 3. |
- Gutiérrez Peón, Pablo, et al.
(författare)
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Applying Time Diversity for Improved Reliability in a Real-Time Heterogeneous MAC Protocol
- 2017
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Ingår i: 2017 IEEE 85TH VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING). - 9781509059324
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Konferensbidrag (refereegranskat)abstract
- Supporting real-time applications over wireless networks is challenging for several reasons. The medium access control (MAC) layer has a key role in enabling real-time guarantees by providing bounded access time to the transmission medium. Unfortunately, even when timely access is granted, transmissions can still be compromised, specially in the wireless domain, due to the unreliable transmission medium. A common way to increase the reliability of a communication system is to apply redundancy in the form of time diversity, i.e., transmitting several copies of the same message at different points in time. In this paper we propose a wireless MAC protocol capable of handling traffic with different levels of criticality and where transmissions and retransmissions are tailored to deadlines, so that the reliability of the communication system is increased and real-time guarantees can be provided. We focus on the traffic scheduling problem, and extend an already existing solution, Time-Triggered Ethernet, suitable for real-time traffic over wired multi-hop networks. The extension enables transmission of heterogeneous traffic over hybrid wired-wireless networks, and provides timely retransmissions in the wireless segment, such that the real-time guarantees are met. Further, we are able to schedule traffic to better cope with interference patterns of different duration, frequency and level of persistence. The results show that the MAC protocol can be successfully applied to combat different kinds of interference while meeting real-time deadlines.
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| 4. |
- Harris, Paul, et al.
(författare)
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Temporal Analysis of Measured LOS Massive MIMO Channels with Mobility
- 2017
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Ingår i: 2017 IEEE 85th Vehicular Technology Conference, VTC Spring 2017 - Proceedings. - 9781509059324
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Konferensbidrag (refereegranskat)abstract
- The first measured results for massive multiple-input, multiple-output (MIMO) performance in a line-of-sight (LOS) scenario with moderate mobility are presented, with 8 users served by a 100 antenna base Station (BS) at 3.7 GHz. When such a large number of channels dynamically change, the inherent propagation and processing delay has a critical relationship with the rate of change, as the use of outdated channel information can result in severe detection and precoding inaccuracies. For the downlink (DL) in particular, a time division duplex (TDD) configuration synonymous with massive MIMO deployments could mean only the uplink (UL) is usable in extreme cases. Therefore, it is of great interest to investigate the impact of mobility on massive MIMO performance and consider ways to combat the potential limitations. In a mobile scenario with moving cars and pedestrians, the correlation of the MIMO channel vector over time is inspected for vehicles moving up to 29km/h. For a 100 antenna system, it is found that the channel state information (CSI) update rate requirement may increase by 7 times when compared to an 8 antenna system, whilst the power control update rate could be decreased by at least 5 times relative to a single antenna system.
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| 5. |
- Hoang, Le-Nam, 1984-, et al.
(författare)
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Low Complexity Algorithm for Efficient Relay Assignment in Unicast/Broadcast Wireless Networks
- 2017
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Ingår i: 2017 IEEE 85th Vehicular Technology Conference (VTC Spring). - : IEEE. - 9781509059324 - 9781509059331 ; June
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Konferensbidrag (refereegranskat)abstract
- Using relayers in wireless networks enables higher throughput, increased reliability or reduced delay. However, when building networks using commercially available hardware, concurrent transmissions by multiple relayers are generally not possible. Instead one specific relayer needs to be assigned for each transmission instant. If the decision regarding which relayer to assign, i.e., which relayer that has the best opportunity to successfully deliver the packet, can be taken online, just before the transmission is to take place, much can be gained. This is particularly the case in mobile networks, as a frequently changing network topology considerably affects the choice of a suitable relayer. To this end, this paper addresses the problem of online relay assignment by developing a low-complexity algorithm highly likely to find the optimal combination of relaying nodes that minimizes the resulting error probability at the targeted receiver(s) using a mix of simulated annealing and ant colony algorithms, such that relay assignments can be made online also in large networks. The algorithm differs from existing works in that it considers both unicast as well as broadcast and assumes that all nodes can overhear each other, as opposed to separating source nodes, relay nodes and destination nodes into three disjoint sets, which is generally not the case in most wireless networks.
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| 6. |
- Hu, Sha, et al.
(författare)
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The Potential of Using Large Antenna Arrays on Intelligent Surfaces
- 2017
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Ingår i: 2017 IEEE 85th Vehicular Technology Conference (VTC Spring). - 9781509059324
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider capacities of single-antenna terminals communicating to large antenna arrays that are deployed on surfaces. That is, the entire surface is used as an intelligent receiving antenna array. Under the condition that the surface area is sufficiently large, the received signal after matched-filtering (MF) can be well approximated by an intersymbol interference (ISI) channel where channel taps are closely related to a sinc function. Based on such an approximation, we have derived the capacities for both one-dimensional (terminals on a line) and high dimensional (terminals on a plane or in a cube) terminal-deployments. In particular, we analyze the normalized capacity $\bar{\mathcal{C}}$, measured in nats/s/Hz/m$^2$, under the constraint that the transmit power per m$^2$, $\bar{P}$, is fixed. We show that when the user-density increases, the limit of $\bar{\mathcal{C}}$, achieved as the wavelength $\lambda$ approaches 0, is $\bar{P}/(2N_0)$ nats/s/Hz/m$^2$, where $N_0$ is the spatial power spectral density (PSD) of noise. In addition, we also show that the number of signal dimensions is $2/\lambda$ per meter deployed surface for the one-dimensional case, and $\pi/\lambda^2$ per m$^2$ deployed surface for two and three dimensional terminal-deployments.
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| 7. |
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| 8. |
- Rusek, Fredrik, et al.
(författare)
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Multiuser Bandwidth Minimization with Individual Rate Requirements for Non-Orthogonal Multiple Access
- 2017
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Ingår i: IEEE 85th Vehicular Technology Conference : VTC2017-Spring - VTC2017-Spring. - 9781509059324 - 9781509059331
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Konferensbidrag (refereegranskat)abstract
- Non-Orthogonal Multiple Access (NOMA) for a multi-user single- input single-output (SISO) setup is studied in the power and the frequency domains simultaneously. The problem of sum-bandwidth minimization under perfect channel state information is solved for various combinations of rate requirements and user pairings. In this process, an iterative Tabu-search based algorithm is applied to avoid an exhaustive search over all possible user pairing combinations. It is assumed that each constituent user of the pair has a required quality of service and a flat power spectrum. Further, for each user pair, the NOMA operating region is defined by dividing the allocated bandwidth into two non-overlapping Orthogonal Multiple Access (OMA) sub-bands and an overlapping NOMA sub-band. Such an assumption achieves a greater capacity region when compared to the conventional power domain only NOMA. Also for most of the rate requirements, only one of the OMA sub-bands is active in addition to the NOMA sub-band. This simplifies the NOMA user rate expressions and power allocation process. To verify the performance gain, NOMA is compared to an OMA technique.
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