| 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. |
- 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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| 3. |
- 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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| 4. |
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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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