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See detailCollaborative Distributed Q-Learning for RACH Congestion Minimization in Cellular IoT Networks
Sharma, Shree Krishna UL; Wang, Xianbin

in IEEE Communications Letters (2019), 23(4), 600-603

Due to infrequent and massive concurrent access requests from the ever-increasing number of machine-type communication (MTC) devices, the existing contention-based random access (RA) protocols, such as ... [more ▼]

Due to infrequent and massive concurrent access requests from the ever-increasing number of machine-type communication (MTC) devices, the existing contention-based random access (RA) protocols, such as slotted ALOHA, suffer from the severe problem of random access channel (RACH) congestion in emerging cellular IoT networks. To address this issue, we propose a novel collaborative distributed Q-learning mechanism for the resource-constrained MTC devices in order to enable them to find unique RA slots for their transmissions so that the number of possible collisions can be significantly reduced. In contrast to the independent Q-learning scheme, the proposed approach utilizes the congestion level of RA slots as the global cost during the learning process and thus can notably lower the learning time for the low-end MTC devices. Our results show that the proposed learning scheme can significantly minimize the RACH congestion in cellular IoT networks. [less ▲]

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See detailNOMA Aided Interference Management for Full-Duplex Self-Backhauling HetNets
Lei, Lei UL; Lagunas, Eva UL; Chatzinotas, Symeon UL et al

in IEEE Communications Letters (2018), 22(8), 1696-1699

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See detailDistributed Caching Enabled Peak Traffic Reduction in Ultra-Dense IoT Networks
Sharma, Shree Krishna UL; Wang, Xianbin

in IEEE Communications Letters (2018), 22(6), 1252-1255

The proliferation of massive machine-type communications devices and their random and intermittent transmissions have brought the new challenge of sporadic access-network congestion in ultra-dense ... [more ▼]

The proliferation of massive machine-type communications devices and their random and intermittent transmissions have brought the new challenge of sporadic access-network congestion in ultra-dense Internet of Things (IoT) networks. To address this issue, we propose an innovative approach of peak traffic reduction within the access network by utilizing distributed cache of IoT devices to coordinate their sporadic transmissions. The proposed technique is realized by employing a novel uplink transmission scheduling based on delay adaptation, in which distributed IoT devices adjust their transmission timings by utilizing embedded caching. An optimization problem is formulated for the minimization of peak data rate demand subject to delay tolerance levels, and is solved for the 3GPP-based traffic models by employing a gradient descent-based algorithm. Our results show that the proposed scheme can significantly reduce the peak data traffic in ultra-dense IoT networks. [less ▲]

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See detailPower Optimization With BLER Constraint for Wireless Fronthauls in C-RAN
Vu, Thang Xuan UL; Nguyen, Thang Van; Quek, Tony Q.S.

in IEEE Communications Letters (2016), 20(3), 602-605

Cloud radio access network (C-RAN) is a novel architecture for future mobile networks to sustain the exponential traffic growth thanks to the exploitation of centralized processing. In C-RAN, one data ... [more ▼]

Cloud radio access network (C-RAN) is a novel architecture for future mobile networks to sustain the exponential traffic growth thanks to the exploitation of centralized processing. In C-RAN, one data processing center or baseband unit (BBU) communicates with users via distributed remote radio heads (RRHs), which are connected to the BBU via high capacity, low latency fronthaul links. In this letter, we study C-RAN with wireless fronthauls due to their flexibility in deployment and management. First, a tight upper bound of the system block error rate (BLER) is derived in closed-form expression via union bound analysis. Based on the derived bound, adaptive transmission schemes are proposed. Particularly, two practical power optimizations based on the BLER and pair-wise error probability (PEP) are proposed to minimize the consumed energy at the RRHs while satisfying the predefined quality of service (QoS) constraint. The premise of the proposed schemes originates from practical scenarios where most applications tolerate a certain QoS, e.g., a nonzero BLER. The effectiveness of the proposed schemes is demonstrated via intensive simulations. [less ▲]

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See detailApproaching the DT Bound Using Linear Codes in the Short Blocklength Regime
Salamanca Mino, Luis UL; Murillo-Fuentes, Juan José; Martinez-Olmos, Pablo et al

in IEEE Communications Letters (2015), 19

The dependence-testing (DT) bound is one of the strongest achievability bounds for the binary erasure channel (BEC) in the finite block length regime. In this paper, we show that maximum likelihood ... [more ▼]

The dependence-testing (DT) bound is one of the strongest achievability bounds for the binary erasure channel (BEC) in the finite block length regime. In this paper, we show that maximum likelihood decoded regular low-density parity-check (LDPC) codes with at least 5 ones per column almost achieve the DT bound. Specifically, using quasi-regular LDPC codes with block length of 256 bits, we achieve a rate that is less than 1% away from the rate predicted by the DT bound for a word error rate below 10^−3. The results also indicate that the maximum-likelihood solution is computationally feasible for decoding block codes over the BEC with several hundred bits. [less ▲]

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See detailGateway Switching in Q/V Band Satellite Feeder Links
Gharanjik, Ahmad UL; Shankar, Bhavani UL; Arapoglou, Pantelis-Daniel UL et al

in IEEE Communications Letters (2013), 17(7), 1384-1387

A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder ... [more ▼]

A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder link to the higher Q/V band, where more spectrum is available. When utilizing the Q/V band, due to heavy rain attenuation, gateway diversity is considered a necessity to ensure the required feeder link availability. Although receive site diversity has been studied in the past for SatCom, there is much less maturity in terms of transmit diversity techniques. In this paper, a modified switch and stay combining scheme is proposed for a Q/V band feeder link, but its performance is also evaluated over an end-to-end satellite link. The proposed scheme is pragmatic and has close to optimal performance with notably lower complexity. [less ▲]

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See detailCapacity limits and multiplexing gains of MIMO channels with transceiver impairments
Bjornson, Emil; Zetterberg, P.; Bengtsson, M. et al

in IEEE Communications Letters (2013), 1(17), 91-94

The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from ... [more ▼]

The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO is at least as large as with ideal transceivers. [less ▲]

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See detailQueue Management Mechanism for 802.11 Base Stations
Kliazovich, Dzmitry UL; Gomes, Pedro Henrique; Granelli, Fabrizio et al

in IEEE Communications Letters (2011), 15(7), 728-730

This paper presents a novel queue management mechanism for base stations in infrastructure IEEE 802.11 networks. The mechanism is transparent to high-level protocols and is compatible with the standard ... [more ▼]

This paper presents a novel queue management mechanism for base stations in infrastructure IEEE 802.11 networks. The mechanism is transparent to high-level protocols and is compatible with the standard. Its effectiveness is illustrated by showing that it can ameliorate the RTT unfairness and the MAC anomaly problems in wired-cum-wireless networks. [less ▲]

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See detailOn the Capacity of Variable Density Cellular Systems under Multicell Decoding
Chatzinotas, Symeon UL; Imran, Muhammad Ali; Tzaras, Costas

in IEEE Communications Letters (2008), 12(7), 496-498

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See detailEnhanced GPSR Routing in Multi-Hop Vehicular Communications through Movement Awareness
Granelli, Fabrizio; Boato, Giulia; Kliazovich, Dzmitry UL et al

in IEEE Communications Letters (2007), 11(10), 781-783

Detailed reference viewed: 49 (1 UL)