| 1. |
- Carpenter, Sona, et al.
(författare)
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A Fully integrated D-band Direct-Conversion I/Q Transmitter and Receiver Chipset in SiGe BiCMOS Technology
- 2021
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Ingår i: Journal of Communications and Networks. - 1976-5541 .- 1229-2370. ; 23:2, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents design and characterization of single-chip 110-170 GHz (D-band) direct conversion in-phase/quadrature-phase (I/Q) transmitter and receiver monolithic microwave integrated circuits (MMICs), realized in a 130 nm SiGe BiCMOS process with ft/fmax of 250 GHz/370 GHz. The chipset is suitable for low power wideband communication and can be used in both homodyne and heterodyne architectures. The Transmitter chip consists of a six-stage power amplifier, an I/Q modulator, and a LO multiplier chain. The LO multiplier chain consists of frequency sixtupler followed by a two-stage amplifier. It exhibits a single sideband conversion gain of 23 dB and saturated output power of 0 dBm. The 3 dB RF bandwidth is 31 GHz from 114 to 145 GHz. The receiver includes a low noise amplifier, I/Q demodulator and x6 multiplier chain at the LO port. The receiver provides a conversion gain of 27 dB and has a noise figure of 10 dB. It has 3 dB RF bandwidth of 28 GHz from 112-140 GHz. The transmitter and receiver have dc power consumption of 240 mW and 280 mW, respectively. The chip area of each transmitter and receiver circuit is 1.4 mm x 1.1 mm.
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| 2. |
- Fan, Yijia, et al.
(författare)
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High capacity relay protocols for wireless networks
- 2009
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Ingår i: Journal of Communications and Networks. - 1229-2370 .- 1976-5541. ; 11:2, s. 196-206
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Tidskriftsartikel (refereegranskat)abstract
- Over the last five years, relaying or multihop techniques have been intensively researched as means for potentially improving link performance of wireless networks. However, the data rates of relays are often limited because they cannot transmit and receive on the same frequency simultaneously. This limitation has come to the attention of researchers, and recently a number of relay techniques have been proposed specifically to improve the data efficiency of relaying protocols. This paper surveys transmission protocols that employ first single relays, then multiple relays and finally multiple antenna relays. A common feature of these techniques is that novel signal processing techniques are required in the relay network to support increased data rates. This paper presents results and discussion that highlight the advantages of these approaches.
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| 3. |
- Fountoulakis, Emmanouil, et al.
(författare)
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Information Freshness and Packet Drop Rate Interplay in a Two-User Multi-Access Channel
- 2022
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Ingår i: Journal of Communications and Networks. - : Korean Institute of Communication Sciences. - 1229-2370 .- 1976-5541. ; 24:3, s. 357-364
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we combine the two notions of timely delivery of information to study their interplay; namely, deadline -constrained packet delivery due to latency constraints and freshness of information. More specifically, we consider a two -user multiple access setup with random access, in which user 1 is a wireless device with a buffer and has external bursty traffic which is deadline-constrained, while user 2 monitors a sensor and transmits status updates to the destination. We provide analytical expressions for the throughput and drop probability of user 1. For user 2, we derive in closed form the age of information distribution, the average age of information (AoI), and the probability the AoI to be larger than a certain value for each time slot. The relations reveal a trade-off between the average AoI of user 2 and the drop rate of user 1: the lower the average AoI, the higher the drop rate, and vice versa. Simulations corroborate the validity of our theoretical results.
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| 4. |
- Huang, Song, et al.
(författare)
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Bandwidth Partition and Allocation for Efficient Spectrum Utilization in Cognitive Communications
- 2019
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Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 21:4, s. 353-364
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Tidskriftsartikel (refereegranskat)abstract
- Conventional cognitive communications rely heavily on the smartness of secondary (unlicensed) users (SUs) to achieve high spectrum utilization, which involves the optimization of the SUs policies and behaviors for dynamic spectrum access, power allocation among multiple channels, etc. Due to the inherent randomness of the primary users (PUs) transmission, those efforts inevitably increase the implementation complexity and sensing overheads of the SUs, and in turn lower the spectrum utilization efficiency. In this paper, we try to change the focus from SU to PU. A cooperative traffic allocation strategy for PU, together with the non-uniform bandwidth partition, is employed to regularize the PUs resource occupancy pattern without compromising its performance, and to maximize the spare bandwidth for the SU at the same time. We first study the capacity based optimization problem (COP) together with the fully polynomial time approximation scheme (FPTAS) for an approximation guarantee of the global optimum. Then we analyze the subcarrier based optimization problem as the surrogate problem of COP, which can be solved by a greedy algorithm exactly. Both the theoretical analysis and the numerical simulations demonstrate the effectiveness of those methods to achieve the performance that almost identical to that of the global optimum solution.
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| 5. |
- Karapantelakis, Athanasios, 1982-, et al.
(författare)
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A Deep-Q Learning Approach to Mobile Operator Collaboration
- 2020
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Ingår i: Journal of Communications and Networks. - Seoul Korea. - 1229-2370 .- 1976-5541. ; 22:6, s. 455-466
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Tidskriftsartikel (refereegranskat)abstract
- Next-generation mobile connectivity services include a large number of devices distributed across vast geographical areas. Mobile network operators will need to collaborate to fulfill service requirements at scale. Existing approaches to multioperator services assume already-established collaborations to fulfill customer service demand with specific quality of service (QoS). In this paper, we propose an agent-based architecture, where establishment of collaboration for a given connectivity service is done proactively, given predictions about future service demand. We build a simulation environment and evaluate our approach with a number of scenarios and in context of a real-world use case, and compare it with existing collaboration approaches. Results show that by learning how to adapt their collaboration strategy, operators can fulfill a greater part of the service requirements than by providing the service independently, or through pre-established, intangible service level agreements.
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| 6. |
- Knutsson, Björn, et al.
(författare)
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Transparent proxy signalling
- 2001
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Ingår i: Journal of Communications and Networks. - 1229-2370 .- 1976-5541. ; 3:2, s. 164-174
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Tidskriftsartikel (refereegranskat)
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| 7. |
- Kosta, Antzela, et al.
(författare)
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Age of Information Performance of Multiaccess Strategies with Packet Management
- 2019
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Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 21:3, s. 244-255
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Tidskriftsartikel (refereegranskat)abstract
- We consider a system consisting of N source nodes communicating with a common receiver. Each source node has a buffer of infinite capacity to store incoming bursty traffic in the form of status updates transmitted in packets, which should maintain the status information at the receiver fresh. Packets waiting for transmission can be discarded to avoid wasting network resources for the transmission of stale information. We investigate the age of information (AoI) performance of the system under scheduled and random access. Moreover, we present analysis of the AoI with and without packet management at the transmission queue of the source nodes, where as packet management we consider the capability to replace unserved packets at the queue whenever newer ones arrive. Finally, we provide simulation results that illustrate the impact of the network operating parameters on the age performance of the different access protocols.
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| 8. |
- Marzetta, Thomas L., et al.
(författare)
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Special issue on Massive MIMO
- 2013
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Ingår i: Journal of Communications and Networks. - : IEEE. - 1229-2370 .- 1976-5541. ; 15:4, s. 333-337
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Demand for wireless communications is projected to grow by more than a factor of forty or more over the next five years. A potential technology for meeting this demand is Massive MIMO (also called Large-Scale Antenna Systems, Large-Scale MIMO, ARGOS, Full-Dimension MIMO, or Hyper-MIMO), a form of multiuser multipleantenna wireless which promises orders-of-magnitude improvements in spectral-efficiency over 4G technology, and accompanying improvements in radiated energy-efficiency. The distinguishing feature of Massive MIMO is that a large number of service-antennas ?? possibly hundreds or even thousands ?? work for a significantly smaller number of active autonomous terminals. Upsetting the traditional parity between service antennas and terminals in this manner is a game-changer: The simplest multiplexing precoding and decoding algorithms can be nearly optimal, expensive ultra-linear forty-Watt power amplifiers are replaced by many low-power units, and the favorable action of the law of large numbers can greatly facilitate power-control and resource-allocation.
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| 9. |
- Pappas, Nikolaos, et al.
(författare)
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Effect of Energy Harvesting on Stable Throughput in Cooperative Relay Systems
- 2016
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Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 18:2, s. 261-269
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the impact of energy constraints on a two hop network with a source, a relay and a destination under random medium access is studied. A collision channel with erasures is considered, and the source and the relay nodes have energy harvesting capabilities and an unlimited battery to store the harvested energy. Additionally, the source and the relay node have external traffic arrivals and the relay forwards a fraction of the source nodes traffic to the destination; the cooperation is performed at the network level. An inner and an outer bound of the stability region for a given transmission probability vector are obtained. Then, the closure of the inner and the outer bound is obtained separately and they turn out to be identical. This work is not only a step in connecting information theory and networking, by studying the maximum stable throughput region metric but also it taps the relatively unexplored and important domain of energy harvesting and assesses the effect of that on this important measure.
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| 10. |
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| 11. |
- Pappas, Nikolaos, 1982-, et al.
(författare)
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Wireless Network-Level Partial Relay Cooperation: A Stable Throughput Analysis
- 2018
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Ingår i: Journal of Communications and Networks. - 1229-2370 .- 1976-5541. ; 20:1, s. 93-101
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we study the benefit of partial relay cooperation. We consider a two-node system consisting of one source and one relay node transmitting information to a common destination. The source and the relay have external traffic and in addition, the relay is equipped with a flow controller to regulate the incoming traffic from the source node. The cooperation is performed at the network level. A collision channel with erasures is considered. We provide an exact characterization of the stability region of the system and we also prove that the system with partial cooperation is always better or at least equal to the system without the flow controller.
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| 12. |
- Ramachandran, Viswanathan
(författare)
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State-Dependent Broadcast Channels with Reversible Input Constraints
- 2024
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Ingår i: Journal of Communications and Networks. - : Institute of Electrical and Electronics Engineers (IEEE). - 1229-2370 .- 1976-5541. ; 26:2, s. 158-165
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Tidskriftsartikel (refereegranskat)abstract
- joint message communication and input reconstruction problem over a two-user state-dependent degraded discrete-memoryless broadcast channel is considered. The state process is assumed to be independent and identically distributed (i.i.d.), and known non-causally at the transmitter as well as the non-degraded receiver. The two receivers have to decode the messages from the transmitter, while the degraded receiver also needs to estimate the channel input codeword to meet a prescribed distortion limit. A complete characterization of the optimal rates versus distortion performance is provided. The tight characterization is also illustrated by means of an example of an additive binary broadcast channel with a Hamming distortion constraint for the input reconstruction at the degraded receiver.
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| 13. |
- Salimnejad, Mehrdad, et al.
(författare)
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State-aware Real-time Tracking and Remote Reconstruction of a Markov Source
- 2023
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Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 25:5, s. 657-669
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Tidskriftsartikel (refereegranskat)abstract
- The problem of real-time remote tracking and reconstruction of a two-state Markov process is considered here. A transmitter sends samples from an observed information source to a remote monitor over an unreliable wireless channel. The receiver, in turn, performs an action according to the state of the reconstructed source. We propose a state-aware randomized stationary sampling and transmission policy which accounts for the importance of different states of the information source, and their impact on the goal of the communication process. We then analyze the performance of the proposed policy, and compare it with existing goal-oriented joint sampling and transmission policies, with respect to a set of performance metrics. Specifically, we study the real-time reconstruction error, the cost of actuation error, the consecutive error, and a new metric, coined importance aware consecutive error. In addition, we formulate and solve a constrained optimization problem that aims to obtain the optimal sampling probabilities that minimize the average cost of actuation error. Our results show that in the scenario of constrained sampling generation, the optimal state-aware randomized stationary policy outperforms all other sampling policies for fast evolving sources, and, under certain conditions, for slowly varying sources. Otherwise, a semantics-aware policy performs better only when the source is slowly varying.
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| 14. |
- Setterqvist, Eric, 1980-, et al.
(författare)
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Real-Time Communication Systems based on Taut Strings
- 2018
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Ingår i: Journal of Communications and Networks. - : IEEE. - 1229-2370 .- 1976-5541. ; 20:2, s. 207-218
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Tidskriftsartikel (refereegranskat)abstract
- We consider buffered real-time communication over channels with time-dependent capacities which are known in advance. The real-time constraint is imposed in terms of limited transmission time between sender and receiver. For a network consisting of a single channel it is shown that there is a coding rate strategy, geometrically characterized as a taut string, which minimizes the average distortion with respect to all convex distortionrate functions. Utilizing the taut string characterization further, an algorithm that computes the optimal coding rate strategy is provided. We then consider more general networks with several connected channels in parallel or series with intermediate buffers. It is shown that also for these networks there is a coding rate strategy, geometrically characterized as a taut string, which minimizes the average distortion with respect to all convex distortion-rate functions. The optimal offline strategy provides a benchmark for the evaluation of different coding rate strategies. Further, it guides us in the construction of a simple but rather efficient strategy for channels in the online setting which alternates between a good and a bad state.
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| 15. |
- Vilni, Saeid Sadeghi, et al.
(författare)
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AoI Analysis and Optimization in Systems with Computations-Intensive Updates
- 2023
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Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 25:5, s. 585-597
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Tidskriftsartikel (refereegranskat)abstract
- consider a status update system consisting of a sampler, a controller, a processing unit, a transmitter, and a sink. The sampler generates a sample upon receiving a request from the controller and the sample requires further processing before transmission, hence is computation-intensive. This is mathematically modeled by a server called process server. After processing the sample, the status update packet is generated and sent to the transmitter for delivery to the sink. This is mathematically modeled by a server called transmit server. The service time of each packet at the transmit and process servers follow geometric distributions. Moreover, we consider that the servers serve packets under the blocking policy, i.e., whenever a server is busy at the arrival time of a new packet, the new arriving packet is blocked and discarded. We analyze the average age of information (AoI) for two fixed policies, namely, 1) zero-wait-one policy and 2) zero-wait-blocking policy. According to the former policy, the controller requests sampling when there is no packet in the system. According to the zero-waitblocking policy, the controller requests a sample whenever the process server is idle. Furthermore, we develop an optimal control policy to minimize the average AoI using the tools of Markov decision process (MDP). In numerical results, we evaluate the performance of the policies under different system parameters. Moreover, we analyze the structure of the optimal policy.
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| 16. |
- Xing, Weijun, et al.
(författare)
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Multi-Source Network-Coded D2D Cooperative Content Distribution Systems
- 2018
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Ingår i: Journal of Communications and Networks. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370 .- 1976-5541. ; 20:1, s. 69-84
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate the information transmission in a typical 5G device-to-device (D2D) communication application scenario, i.e., a content distribution system with a number of information sources intending to broadcast their messages to multiple destinations in the vicinity. Due to the dynamic nature of wireless signal propagation links, it is hard to guarantee a satisfactory performance by direct source-destination transmissions, especially when the system is operating in a reuse-mode. Relays can be introduced to the system to solve this problem. However, adopting the conventional repetition coding at relays inefficiently utilizes the available resources, for the considered multi-source scenario. Therefore, we investigate applying a class of finite-field network codes at the relays, when potentially three types of relays are deployed to assist the information distribution process. We proposed the algorithms to derive the system outage probability and analyze the trade-off between energy efficiency and spectral efficiency. Our analytical and numerical results clearly demonstrate the potential of exploiting network-coded cooperative communications in future 5G D2D systems.
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| 17. |
- Arikan, Erdal, et al.
(författare)
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Challenges and some new directions in channel coding
- 2015
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Ingår i: Journal of Communications and Networks. - 1229-2370. ; 17:4, s. 328-338
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Tidskriftsartikel (refereegranskat)abstract
- Three areas of ongoing research in channel coding are surveyed, and recent developments are presented in each area: spatially coupled Low-Density Parity-Check (LDPC) codes, non-binary LDPC codes, and polar coding.
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| 18. |
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| 19. |
- Knutsson, B, et al.
(författare)
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Transparent proxy signalling
- 2001
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Ingår i: JOURNAL OF COMMUNICATIONS AND NETWORKS. - : KOREAN INST COMMUNICATIONS SCIENCES (K I C S). - 1229-2370. ; 3:2, s. 164-174
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Tidskriftsartikel (refereegranskat)abstract
- This paper argues that the increasing use of proxies is not a stop-gap measure, but rather, that proxies play a fundamental role in the Internet architecture: They bridge discontinuities between different regions of the Internet, To be effective, however,
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