| 1. |
- Atzeni, Italo, et al.
(författare)
-
Low-Resolution Massive MIMO Under Hardware Power Consumption Constraints
- 2021
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781665458283 ; 2021-October
-
Konferensbidrag (refereegranskat)abstract
- We consider a fully digital massive multipleinput multiple-output architecture with low-resolution analogto-digital/digital-to-analog converters (ADCs/DACs) at the base station (BS) and analyze the performance trade-off between the number of BS antennas, the resolution of the ADCs/DACs, and the bandwidth. Assuming a hardware power consumption constraint, we determine the relationship between these design parameters by using a realistic model for the power consumption of the ADCs/DACs and the radio frequency chains. Considering uplink pilot-aided channel estimation, we build on the Bussgang decomposition to derive tractable expressions for uplink and downlink ergodic achievable sum rates. Numerical results show that the ergodic performance is boosted when many BS antennas with very low resolution (i.e., 2 to 3 bits) are adopted in both the uplink and the downlink.
|
|
| 2. |
- Fedorov, Aleksei, et al.
(författare)
-
Implementation of spatially consistent channel models for real-time full stack C-ITS V2X simulations
- 2021
-
Ingår i: 55th Asilomar Conference on Signals, Systems and Computers, ACSSC 2021. - 1058-6393. - 9781665458283 ; 2021-October, s. 67-71
-
Konferensbidrag (refereegranskat)abstract
- Vehicle-to-everything (V2X) wireless communication is expected to play a key role in enabling complex Advanced Driving Assistance Applications, including the support of emerging autonomous vehicles. The development of V2X applications, especially safety-related, requires rigorous verification. Field trials, though, have to be supplemented with less expensive and more repeatable methods. Thorough V2X modeling could be an efficient approach to boost V2X development. However, to be helpful, V2X modeling has to be realistic and properly capture the signal propagation in a complex V2X environment. To this end, Geometry Based Stochastic Models (GSCM) have been derived to account for the influence of the environment as well as small yet critical details, where we typically lack information about their physical and geometrical properties. In this paper, we present an implementation of a GSCM in the Unity3D game engine. Due to extensive signal path search in a 3D environment with ray-tracing, the GSCM computation has to be further optimized to enable real-time V2X simulations. Thus, we also propose the approach for GSCM computation optimization and explain the practicalities of its implementation. The results show that optimization can accelerate the simulation framework up to a few thousand times without losing the precision in modeling channel characteristics.
|
|
| 3. |
- Ferreira, Lucas, et al.
(författare)
-
Energy-Efficient Application-Specific Instruction-Set Processor for Feature Extraction in Smart Vision Systems
- 2021
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781665458283 ; 2021-October, s. 324-328
-
Konferensbidrag (refereegranskat)abstract
- Smart vision sensor systems enable many computer vision applications such as autonomous drones and wearable devices. These battery-powered gadgets have very stringent power consumption requirements. Close-to-sensor feature extraction compressing the full image into descriptive keypoints, is crucial as it allows for several design optimizations. First, the amount of necessary on-chip memory can be lessened. Second, the volume of data that needs to be exchanged between nodes in Internet of Things (IoT) applications can also be reduced. This work explores the usage of an Application Specific Instruction Set Processor (ASIP) tailored to perform energy-efficient feature extraction in real-time. The ASIP features a Very Long Instruction Word (VLIW) central core comprising one RV32I RISCV and three vector slots. The on-chip memory sub-system implements parallel multi-bank memories with near-memory data shuffling to enable single-cycle multi-pattern vector access. As a case study, Oriented FAST and Rotated BRIEF (ORB) is used to evaluate the proposed architecture. We show that the architecture supports VGA-resolution images at 140 Frames-Per-Second (FPS), for one scale, reducing the number of memory accesses by 2 orders of magnitude comparing to other embedded general-purpose architectures.
|
|
| 4. |
- Marti, Gian, et al.
(författare)
-
Hybrid Jammer Mitigation for All-Digital mmWave Massive MU-MIMO
- 2021
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781665458283 ; 2021-October
-
Konferensbidrag (refereegranskat)abstract
- Low-resolution analog-to-digital converters (ADCs) simplify the design of millimeter-wave (mmWave) massive multi-user multiple-input multiple-output (MU-MIMO) base-stations, but increase vulnerability to jamming attacks. As a remedy, we propose HERMIT (short for Hybrid jammER MITigation), a method that combines a hardware-friendly adaptive analog transform with a corresponding digital equalizer: The analog transform removes most of the jammer’s energy prior to data conversion; the digital equalizer suppresses jammer residues while detecting the legitimate transmit data. We provide theoretical results that establish the optimal analog transform as a function of the user equipments' and the jammer’s channels. Using simulations with mmWave channel models, we demonstrate the superiority of HERMIT compared both to purely digital jammer mitigation as well as to a recent hybrid method that mitigates jammer interference with a nonadaptive analog transform.
|
|
| 5. |
- Ngo, Khac-Hoang, 1992, et al.
(författare)
-
Age of Information in Prioritized Random Access
- 2021
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781665458283 ; 2021-October
-
Konferensbidrag (refereegranskat)abstract
- Age of information (AoI) is a performance metric that captures the freshness of status updates. While AoI has been studied thoroughly for point-to-point links, the impact of modern random-access protocols on this metric is still unclear. In this paper, we extend the recent results by Munari to prioritized random access where devices are divided into different classes according to different AoI requirements. We consider the irregular repetition slotted ALOHA protocol and analyze the AoI evolution by means of a Markovian analysis following similar lines as in Munari (2021). We aim to design the protocol to satisfy the AoI requirements for each class while minimizing the power consumption. To this end, we optimize the update probability and the degree distributions of each class, such that the probability that their AoI exceeds a given threshold lies below a given target and the average number of transmitted packets is minimized.
|
|
| 6. |
- Aabel, Lise, 1992, et al.
(författare)
-
Distributed Massive MIMO via all-Digital Radio Over Fiber
- 2020
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2020-November, s. 319-323
-
Konferensbidrag (refereegranskat)abstract
- A crucial challenge in the implementation of distributed massive multiple-input multiple-output (MIMO) architectures is to provide phase coherence while, at the same time, limit the complexity of the remote-radio heads (RRHs), which is important for cost-efficient scalability. To address this challenge, we present in this paper a phase-coherent distributed MIMO architecture, based on off-the-shelf, low-cost components. In the proposed architecture, up- and down-conversion are carried out at the central unit (CU). The RRHs are connected to the CU by means of optical fibers carrying oversampled radio-frequency (RF) 1-bit signals. In the downlink, the 1-bit signal is generated via sigma-delta modulation. At the RRH, the RF signal is recovered from the 1-bit signal through a bandpass filter and a power amplifier, and then fed to an antenna. In the uplink, the 1-bit signal is generated by a comparator whose inputs are the low-noise-amplified received RF signal and a suitably designed dither signal. The performance of the proposed architecture is evaluated with satisfactory results both via simulation and measurements from a testbed.
|
|
| 7. |
- Arslan, Mehmet Ali, et al.
(författare)
-
Partitioning and Mapping Dynamic Dataflow Programs
- 2012
-
Ingår i: [Host publication title missing]. - 1058-6393. ; , s. 1452-1456
-
Konferensbidrag (refereegranskat)abstract
- Partitioning and mapping are important design decisions in exploiting the parallelism of programs that are to be run on systems with multiple processing elements. In this paper we introduce a fast, incremental approach for mapping dynamic dataflow programs to multiprocessor systems. We use causation traces and architecture descriptions as input for the mapping process that devises several heuristics for reaching a short makespan for the given trace. We evaluate our approach by comparing our results to two different lower bounds and another algorithm used often in solving mapping problems: simulated annealing.
|
|
| 8. |
- Bai, Jianan, et al.
(författare)
-
Multi-agent Policy Optimization for Pilot Selection in Delay-constrained Grant-free Multiple Access
- 2021
-
Ingår i: 2021 55th Asilomar Conference on Signals, Systems, and Computers. - : IEEE. - 9781665458283 - 9781665458290 - 9781665458276 ; , s. 1477-1481
-
Konferensbidrag (refereegranskat)abstract
- Grant-free multiple access (GFMA) mitigates the uplink handshake overhead to support low-latency communication by transmitting payload data together with the pilot (preamble). However, the channel capacity with random access is limited by the number of available orthogonal pilots and the incoordination among devices. We consider a delay-constrained GFMA system, where each device with randomly generated data traffic needs to deliver its data packets before some pre-determined deadline. The pilot selection problem is formulated to minimize the average packet drop rate of the worst user. A priority-sorting based centralized policy is derived by introducing a fairness promoting function. For decentralization, we propose a multi-agent policy optimization algorithm with improved sample efficiency by exploring the model structure. Simulation results show that our proposed scheme facilitates near-optimal coordination between devices by using only partial state information.
|
|
| 9. |
- Bencheikh Lehocine, Chouaib, 1993, et al.
(författare)
-
Sensitivity analysis of beamforming techniques for periodic broadcast V2V communication
- 2021
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; Volume 2021-October, s. 61-66
-
Konferensbidrag (refereegranskat)abstract
- In this work, we extend the results of two previously proposed transmit beamforming techniques for periodic, broadcast, vehicle-to-vehicle communication with a common fixed broadcast period, to the scenario where vehicular users (VUs) use different, and potentially varying broadcast periods. The two techniques, analog beamforming network (ABN) of phase shifters and antenna switching network (ASN), were previously developed in accordance with a multiple antenna receiver that employs an analog combining network (ACN) of phase shifters. To accommodate the use of multiple broadcast periods, we propose the design of phase shifter parameters of ABN-ACN and ASN-ACN systems using a design period Td. Then, we analytically derive sets of broadcast periods that sustain optimality, in the sense that the sum signal-to-noise ratio (SNR) of Kconsecutive packets for any receiving VU is maximized. Next, we provide guidelines on how to set Td to ensure a sufficient granularity of the sets of optimal broadcast periods. Finally, we investigate using numerical computations the effect of certain design choices on the sensitivity of ABN/ASN-ACN systems to small variations of the broadcast period.
|
|
| 10. |
- Callebaut, Gilles, et al.
(författare)
-
Massive MIMO goes Sub-GHz : Implementation and Experimental Exploration for LPWANs
- 2020
-
Ingår i: Conference Record of the 54th Asilomar Conference on Signals, Systems and Computers, ACSSC 2020. - 1058-6393. - 9780738131269 ; 2020-November, s. 1101-1105
-
Konferensbidrag (refereegranskat)abstract
- Low-Power Wide-Area Networks operating in the unlicensed bands are being deployed to connect a rapidly growing number of Internet-of-Things devices. While the unlicensed sub-GHz band offers favorable propagation for long-range connections, measurements show that the energy consumption of the nodes is still mostly dominated by the wireless transmission affecting their autonomy. We investigate the potential benefits of deploying massive MIMO technology to increase system reliability and at the same time support low-energy devices with good coverage at sub-GHz frequencies. The impact of different antenna configurations and propagation conditions is analyzed. Both actual average experienced array gain and channel hardening are examined. The assessment demonstrates the effect of channel hardening as well as the potential benefits of the experienced array gain. These measurements serve as a first assessment of the channel conditions of massive MIMO at sub-GHz frequencies and are, to the best of our knowledge, the first of its kind.
|
|
