Communications In Cellular Systems Research Articles

Enhancing the Throughput of Device-to-Device Communication in Cellular Systems Using Non-orthogonal Transmission

Enhancing the Throughput of Device-to-Device Communication in Cellular Systems Using Non-orthogonal Transmission

Multipoint communication using a fog-robotic coordinated nodal conveying system for wireless networks

Fog computing is a framework that makes use of the features of both cloud and edge devices to provide quality services, support mobility, reduce delay & latency, and to provide other services to the recent technologies. The fog computing is incorporated in wireless networks using coordinated multi-point communication, which helps to in sending raw bits over a physical link that connects network swarm nodes rather than logical data packets. This, inturn improves system performance and service quality. In the physical layer, the multipoint connection between swarm nodes established during communication in cellular systems consistently reveals limitations in signaling cost, energy consumption, delay and latency. These limitations nevertheless define a wireless network that integrates wide-ranging applications, from independent systems to extended reality (XR) to support minimal network infrastructure. In this paper, the proposed Fog-Robotic Coordinated Nodal Conveying System (FCNCS) helps optimize the data transmission and lowers the signaling cost of coordinated multipoint communication in the physical layer of a wireless system. Besides, optimized link utilization helps to lower signaling costs by 14.3% with improved coordinated multi-point communication network performance efficiency by 85.5% in the physical layer of the wireless framework compared to the existing methods.

On signal processing scheme based on network coding in relay-assisted D2D systems

Network coding (NC) can greatly improve a system’s performance on throughput and channel utilization via corresponding signal processing on the relay side. Implementation of NC in relay-assisted device-to-device (RA-D2D) communications is a promising way to further explore the advantages of RA-D2D communications in cellular systems. This paper proposes a signal processing scheme for RA-D2D which jointly takes into account NC and optimal relay selection. First, the optimal relay user equipment (UE) is selected by jointly considering the end-to-end data rate, end-to-end transmission delay, and relay survival time. Then, in the procedure of signal processing, the transmitted useful signal is combined with interference signal for NC operation, and finally, the original useful signal is recovered at the destination node. Simulation results show that the proposed scheme is able to not only eliminate the interference effectively but also has a superior performance on end-to-end transmission delay, reachability, and amount of transmitted information than that without NC. In particular, signal processing via NC is equivalent to encrypting the signal, which further enhances the information security in D2D communications.

Overlay Device-to-Device Communications in Asymmetric Two-Way Cellular Systems With Hybrid Relaying

Device-to-device (D2D) communications in cellular systems have been envisioned as a promising technique to compensate for spectrum scarcity. In this paper, we analyze the performance of overlay D2D communications in two-way cellular systems by employing a three-phase hybrid decode-amplify-forward (3P-HDAF) relaying scheme. Herein, two D2D users provide relay cooperation to the bidirectional cellular transmissions to support certain target rates with the opportunity of sharing same cellular spectrum for their own information exchange. With the proposed 3P-HDAF scheme, one complete round of end-to-end information exchange for both cellular and D2D systems can be accomplished in three time phases, wherein the D2D users can adaptively select either decode-forward or amplify-forward relaying strategy to facilitate the cellular transmissions. For performance analysis of considered setup, we derive the expressions for outage probability (OP) of both cellular and D2D systems by posing asymmetric traffic requirements under Nakagami- m fading. Further, to gain better insights, we obtain the asymptotic OP expressions in a high signal-to-noise ratio (SNR) regime. Hereafter, we deduce some key design parameters such as the critical value of power splitting factor and spectrum sharing region. Moreover, we also obtain an expression of average system throughput to conduct a fair performance comparison with similar existing schemes.

Efficient resource allocation algorithm for overlay D2D communication

Device-to-device (D2D) communication in cellular systems offers an economically viable means of improving the system capacity by allocating multiple D2D links within the same resource block (RB), under appropriate interference-control techniques. In this paper, we propose an efficient resource allocation algorithm that enables maximum spatial reuse in orthogonal frequency division multiple access (OFDMA) systems. Given a set of D2D requests, the proposed algorithm greedily determines the number of RBs required, following the reliability criteria. Simulation results show that, compared to the greedy algorithm (Lee, Choi, and Jeon, 2013), the proposed algorithm could save up to 18.6% RBs, improve the throughput per RB by up to 23.4%, and reduce the computation time by up to 67.9%.

Hybrid Limited Feedback in 5G Cellular Systems With Massive MIMO

Massive multiple input multiple output (MIMO) is one of the promising technologies to address the growing capacity requirement in fifth-generation cellular systems. However, the massive MIMO deployed at base stations (BSs) or relay stations (RSs) brings new challenges on channel state information (CSI) feedback because of its large-scale complex channel matrix. In this paper, we propose a hybrid limited feedback with selective eigenvalue information (HLFSEI), which adopts the individual quantized feedback and the codebook-based feedback jointly. In HLFSEI, we feed back only selective eigenvalue elements for power allocation by individual quantized feedback and the precoding matrix by codebook-based feedback. Furthermore, we study the optimal feedback bit allocation of the aforementioned two feedback methods to minimize the throughput loss with the feedback-link capacity constraint. Specifically, the feedback bits are allocated according to the properties of the throughput loss in high- and low-signal-to-noise regimes. Both the BS–RS communications and the BS/RS–user-equipment communications in cellular systems are taken into consideration. Finally, we evaluate the performance of the proposed HLFSEI strategy by simulation and show its performance gain compared with conventional feedback strategies.

Transceiver optimization for multi-antenna device-to-device communications

It has been shown that the deployment of device-to-device (D2D) communication in cellular systems can provide better support for local services. However, improper design of the hybrid system may cause severe interference between cellular and D2D links. In this paper, we consider transceiver design for the system employing multiple antennas to mitigate the interference. The precoder and decoder matrices are optimized in terms of sum mean squared error (MSE) and capacity, respectively. For the MSE minimization problem, we present an alternative transceiver optimization algorithm. While for the non-convex capacity maximization problem, we decompose the primal problem into a sequence of standard convex quadratic programs for efficient optimization. The evaluation of our proposed algorithms for performance enhancement of the entire D2D integrated cellular system is carried out through simulations.

Energy Efficient D2D Communications in Dynamic TDD Systems

Device-to-device (D2D) communication is a promising technology for improving the performance of proximity-based services. This paper demonstrates how the integration of D2D communication in cellular systems operating under dynamic time division duplex (TDD) can improve energy efficiency. We perform joint optimization of mode selection, uplink/downlink transmission period, and power allocation to minimize the transmission energy consumption while satisfying a traffic requirement. Solutions are developed for two scenarios: with and without interference among D2D communications. Both formulations are expressed as mixed-integer nonlinear programming problems, which are NP-hard in general. We exploit problem structure to develop efficient solutions for both scenarios. For the interference-free case, we design algorithms that find the optimal solution in polynomial time. When considering interference, we propose a customized solver based on branch-and-bound that reduces the search complexity by taking advantage of the problem-specific proprieties. We complement this solver by a more practical heuristic algorithm. Simulation results demonstrate that D2D communications in dynamic TDD systems can yield significant energy savings and improved spectral efficiency compared with the traditional cellular communication. Furthermore, we give analytical characterizations of the receiver locations relative to a given transmitter where D2D communication is optimal. These regions can be surprisingly large and not necessarily circular.

Interference Mitigation in D2D Communication Underlaying LTE-A Network

The mobile data traffic has risen exponentially in recent days due to the emergence of data intensive applications, such as online gaming and video sharing. It is driving the telecommunication industry as well as the research community to come up with new paradigms that will support such high data rate requirements within the existing wireless access network, in an efficient and effective manner. To respond to this challenge, device-to-device (D2D) communication in cellular networks is viewed as a promising solution, which is expected to operate, either within the coverage area of the existing eNB and under the same cellular spectrum (in-band) or separate spectrum (out-band). D2D provides the opportunity for users located in close proximity of each other to communicate directly, without traversing data traffic through the eNB. It results in several transmission gains, such as improved throughput, energy gain, hop gain, and reuse gain. However, integration of D2D communication in cellular systems at the same time introduces new technical challenges that need to be addressed. Containment of the interference among D2D nodes and cellular users is one of the major problems. D2D transmission radiates in all directions, generating undesirable interference to primary cellular users and other D2D users sharing the same radio resources resulting in severe performance degradation. Efficient interference mitigation schemes are a principal requirement in order to optimize the system performance. This paper presents a comprehensive review of the existing interference mitigation schemes present in the open literature. Based on the subjective and objective analysis of the work available to date, it is also envisaged that adopting a multi-antenna beamforming mechanism with power control, such that the transmit power is maximized toward the direction of the intended D2D receiver node and limited in all other directions will minimize the interference in the network. This could maximize the sum throughput and hence, guarantees the reliability of both the D2D and cellular connections.

Joint Power and Rate Control for Device-to-Device Communications in Cellular Systems

This paper investigates device-to-device (D2D) communication nested in a cellular network, where a pair of D2D users directly exchanges their information using the uplink frequency band of the cellular network. When the D2D user treats the interference from the cellular user as noise, power control at the cellular user is optimal for maximizing the rate of the cellular user while controlling the interference to the D2D user. However, if the D2D user can perform successive interference cancelation (SIC), the cellular user needs to adjust both transmit power and rate to maximize its rate, because the decodability of the interfering signals at the D2D user depends not only on the signal power but also on the rate of the cellular user. To control the interference from the cellular user, we propose a joint transmit power and rate control scheme at the cellular user. Forcing the cellular user to transmit with a reduced data rate compared with the maximum possible rate, given its transmit power, the proposed joint power and rate control scheme efficiently enables SIC at the D2D user. To reduce the computational complexity, we also propose a near-optimal scheme that employs either power control or rate control depending on the channel conditions.

Advances in smart antennas - Network coordination for spectrally efficient communications in cellular systems

In this article we consider network coordination as a means to provide spectrally efficient communications in cellular downlink systems. When network coordination is employed, all base antennas act together as a single network antenna array, and each mobile may receive useful signals from nearby base stations. Furthermore, the antenna outputs are chosen in ways to minimize the out-of-cell interference, and hence to increase the downlink system capacity. When the out-of-cell interference is mitigated, the links can operate in the high signal-to-noise ratio regime. This enables the cellular network to enjoy the great spectral efficiency improvement associated with using multiple antennas