| 1. |
- Ahmad, Suhail, 1992, et al.
(författare)
-
Predictive Resource Allocation Evaluation with Real Channel Measurements
- 2017
-
Ingår i: IEEE International Conference on Communications. - 1550-3607.
-
Konferensbidrag (refereegranskat)abstract
- Mobile services, especially video streaming, has seen a rapid usage increase in recent years. Base stations (BSs) need to employ smarter and efficient resource allocation strategies to maintain high quality of service (QoS) to users at all the times. Predictive resource allocation (PRA), is one such novel scheme, in which BSs seek to anticipate the user demands and offer service to users in advance. As a result, the QoS can be improved, network load can be distributed over time, while at the same time offering efficient utilization of BS power. In location-aware PRA, the BS exploits location information of the users to predict the channel expected variations and adapt the BS resources accordingly. We evaluate PRA strategies based on an empirical study of the radio channel variation from measured location-aided channel radio maps using a smart phone. We observed that gains offered by the PRA scheme are highly dependent on user mobility patterns.
|
|
| 2. |
- Chowdappa, V.P., et al.
(författare)
-
Distributed channel prediction for multi-agent systems
- 2017
-
Ingår i: IEEE International Conference on Communications. - 1550-3607.
-
Konferensbidrag (refereegranskat)abstract
- Multi-agent systems (MAS) communicate over a wireless network to coordinate their actions and to report their mission status. Connectivity and system-level performance can be improved by channel gain prediction. We present a distributed Gaussian process regression (GPR) framework for channel prediction in terms of the received power in MAS. The framework combines a Bayesian committee machine with an average consensus scheme, thus distributing not only the memory, but also computational and communication loads. Through Monte Carlo simulations, we demonstrate the performance of the proposed GPR.
|
|
| 3. |
- Du, Rong, et al.
(författare)
-
Optimal Energy Beamforming and Data Routing for Immortal Wireless Sensor Networks
- 2017
-
Ingår i: IEEE International Conference on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1550-3607. - 9781467389990
-
Konferensbidrag (refereegranskat)abstract
- Wireless sensor networks (WSNs) consist of energy limited sensor nodes, which limits the network lifetime. Such a lifetime can be prolonged by employing the emerging technology of wireless energy transfer (WET). In WET systems, the sensor nodes can harvest wireless energy from wireless charger, which can use energy beamforming to improve the efficiency. In this paper, a scenario where dedicated wireless chargers with multiple antennas use energy beamforming to charge sensor nodes is considered. The energy beamforming is coupled with the energy consumption of sensor nodes in terms of data routing, which is one novelty of the paper. The energy beamforming and the data routing are jointly optimized by a non-convex optimization problem. This problem is transformed into a semidefinite optimization problem, for which strong duality is proved, and thus the optimal solution exists. It is shown that the optimal solution of the semi-definite programming problem allows to derive the optimal solution of the original problem. The analytical and numerical results show that optimal energy beamforming gives two times better monitoring performance than that of WET without using energy beamforming.
|
|
| 4. |
- Hong, Y., et al.
(författare)
-
Cross-tier Handover Analyses in Small Cell Networks: A Stochastic Geometry Approach
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; 2015-September, s. 3429-3434
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we make theoretical analysis on cross-tier handover in Small Cell Networks (SCNs). The cross-tier handover is defined as the handover occurred from a macro cell tier to a small cell tier, or vice versa. Based on stochastic geometry, we first propose a linear approximation approach to study the coverage of small cells. Using the proposed method, we then derive analytical expressions for cross-tier handover rate and sojourn time inside a small cell, which are the key parameters in mobility performance evaluation of an SCN. According to the analysis, we show that the small cell coverage area can be well represented by a biased circle, and the expected value of small cell size is inversely proportional to the square root of the BS density in the macro cell tier. Another important observation is that the handover rate and sojourn time change linearly with the reciprocal of small cell radius. These analytical results could provide fundamental supports for improving mobility management in SCNs.
|
|
| 5. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
High-SNR Capacity of Multiple-Antenna Phase-Noise Channels with Common/Separate RF Oscillators
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; 2015-September, s. 4012-4017
-
Konferensbidrag (refereegranskat)abstract
- In multiple antenna systems, phase noise due to instabilities of the radio-frequency (RF) oscillators, acts differently depending on whether the RF circuitries connected to each antenna are driven by separate (independent) local oscillators (SLO) or by a common local oscillator (CLO). In this paper, we investigate the high-SNR capacity of single-input multiple-output (SIMO) and multiple-output single-input (MISO) phase-noise channels for both the CLO and the SLO configurations.Our results show that the first-order term in the high-SNR capacity expansion is the same for all scenarios (SIMO/MISO and SLO/CLO), and equal to 0.5ln(SNR), where SNR stands for the signal-to-noise ratio. On the contrary, the second-order term, which we refer to as phase-noise number, turns out to be scenario-dependent. For the SIMO case, the SLO configuration provides a diversity gain, resulting in a larger phase-noise number than for the CLO configuration. For the case of Wiener phase noise, a diversity gain of at least 0.5ln(M) can be achieved, where M is the number of receive antennas. For the MISO, the CLO configuration yields a higher phase-noise number than the SLO configuration. This is because with the CLO configuration one can obtain a coherent-combining gain through maximum ratio transmission (a.k.a. conjugate beamforming). This gain is unattainable with the SLO configuration.
|
|
| 6. |
- Kolomvakis, Nikolaos, 1985, et al.
(författare)
-
Downlink Performance of Regularized ZF in Massive MIMO Systems Subject to IQ Imbalance
- 2017
-
Ingår i: IEEE International Conference on Communications. - 1550-3607.
-
Konferensbidrag (refereegranskat)abstract
- This paper studies the impact of in-phase and quadrature imbalance (IQI) on the downlink of a single-cell multiuser multiple-input multiple-output (MU-MIMO) system with large antenna arrays. Moreover, we consider a time-division duplex (TDD) system where we assume uplink/downlink channel reciprocity in the downlink precoding design and study the impact of uplink/downlink channel mismatch on the downlink rate caused by different IQI on the base station (BS) and users equipment (UEs). A tractable analytical expression to predict the achievable downlink rates is derived for the regularized zero-forcing (RZF) and based on this expression, we prove that, as the number of BS antennas grow large, the achievable downlink rate of each UE is limited either by the RX IQI at the UEs or by the simultaneous presence of the transmit/receive IQI at the BS and TX IQI at the UEs, when there is uplink/downlink channel mismatch.
|
|
| 7. |
- Kolomvakis, Nikolaos, 1985, et al.
(författare)
-
Massive MIMO with IQ Imbalance: Performance analysis and compensation
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; 2015-September, s. 1703-1709
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider the uplink of a single-cell massive multiple-input multiple-output (MIMO) system with inphase and quadrature-phase imbalance (IQI). This scenario is of particular importance in massive MIMO systems, where the deployment of lower-cost, lower-quality components is desirable to make massive MIMO a viable technology. Particularly, we investigate the effect of IQI on the performance of massive MIMO employing maximum-ratio combining (MRC) receivers. In order to study how IQI affects channel estimation, we derive a new channel estimator for the IQI-impaired model and show that IQI can substantially downgrade the performance of MRC receivers. Moreover, a low-complexity IQI compensation scheme, suitable for massive MIMO, is proposed which is based on the IQI coefficients' estimation and it is independent of the channel gain. The performance of the proposed compensation scheme is analytically evaluated by deriving a tractable approximation of the ergodic achievable rate and providing the asymptotic power scaling laws assuming transmission over Rayleigh fading channels with log-normal large-scale fading. Finally, we show that massive MIMO effectively suppresses the residual IQI effects, as long as, the compensation scheme is applied.
|
|
| 8. |
- Kong, C., et al.
(författare)
-
Performance of downlink massive MIMO in ricean fading channels with ZF precoder
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; 2015-September, s. 1776-1782
-
Konferensbidrag (refereegranskat)abstract
- We investigate the achievable sum rate and energy efficiency of zero-forcing precoded downlink massive multipleinput multiple-output systems in Ricean fading channels. A simple and accurate approximation of the average sum rate is presented, which is valid for a system with arbitrary rank channel means. Based on this expression, the optimal power allocation strategy maximizing the average sum rate is derived. Moreover, considering a general power consumption model, the energy efficiency of the system with rank-1 channel means is characterized. Specifically, the impact of key system parameters, such as the number of users N, the number of BS antennas M, Ricean factor K and the signal-to-noise ratio (SNR) ρ are studied, and closed-form expressions for the optimal ρ and M maximizing the energy efficiency are derived. Our findings show that the optimal power allocation scheme follows the water filling principle, and it can substantially enhance the average sum rate in the presence of strong line-of-sight effect in the low SNR regime. In addition, we demonstrate that the Ricean factor K has significant impact on the optimal values of M, N and ρ.
|
|
| 9. |
- Lagkas, T. D., et al.
(författare)
-
The impact of mobility patterns on the efficiency of data forwarding in MANETs
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. ; 2015-September, s. 6037-6042
-
Konferensbidrag (refereegranskat)abstract
- One of the most challenging requirements in cutting-edge Mobile Ad hoc Networks is the need for adaptive and efficient routing. Networks capable of adapting their behavior based on current conditions are often characterized as self-organizing networks, which are lately considered very promising for future applications. This work examines the impact of the different mobility properties on the performance of self-organizing networks. For that purpose, a simulator was developed to model different mobility patterns and study the way they affect the effectiveness of the well-known AODV routing protocol. Particularly, this paper focuses on the effect of the different mobility schemes on network topology and consequently to the overall network performance. The results reveal the tight correlations between node mobility characteristics and network metrics.
|
|
| 10. |
- Li, Jingya, 1986, et al.
(författare)
-
Optimal Design of Energy-Efficient HetNets: Joint Precoding and Load Balancing
- 2015
-
Ingår i: IEEE International Conference on Communications. - : IEEE. - 1550-3607. - 9781467364324 ; 2015-September, s. 4664-4669
-
Konferensbidrag (refereegranskat)abstract
- This paper considers the downlink of a heterogeneous network, where multiple base stations (BSs) can serve the users by non-coherent multiflow beamforming. We assume imperfect channel state information at both BSs and users. The objective is to jointly optimize the precoding, load balancing, and BS operation mode (active or sleep) for improving the energy efficiency of the network. The considered problem is to minimize the weighted total power consumption (both circuit power and dynamic transmit power), while satisfying per-user quality of service constraints and per-BS transmit power constraints. This problem is non-convex, but we prove that for each combination of BS modes, the considered problem has a hidden convexity structure. Thus, the global optimal solution is obtained by an exhaustive search over all possible BS mode combinations. Furthermore, by iterative convex approximations of the non-convex power consumption functions, a heuristic algorithm is proposed to obtain a local optimal solution with low complexity. Simulation results illustrate that our proposed algorithms significantly reduce the total power consumption, compared to the scheme where all BSs are continuously active. This implies that putting a BS into sleep mode by proper load balancing is an important solution for energy savings in heterogeneous networks.
|
|
