| 1. |
- Beygi, Sajjad, et al.
(författare)
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Structured Sparse Approximation via Generalized Regularizers: With Application to V2V Channel Estimation
- 2014
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Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479935116 ; , s. 3013-3018
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider the estimation of a signal that has both group- and element-wise sparsity (joint sparsity); motivated by channel estimation in vehicle-to-vehicle channels. A general approach for the design of separable regularizing functions is proposed to adaptively induce sparsity in the estimation. A joint sparse signal estimation problem is formulated via these regularizers and its optimal solution is computed based on proximity operations. Our optimization results are quite general and they can be applied in the context of hierarchical sparsity models as well. The proposed recovery algorithm is a nested iterative method based on the alternating direction method of multipliers (ADMM). Due to regularizer separability, key operations can be performed in parallel. V2V channels are estimated by exploiting the joint sparsity (group/element-wise) exhibited in the delay-Doppler domain. Simulation results reveal that the proposed method can achieve as much as a 10 dB gain over previously examined methods.
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| 2. |
- Bing, L., et al.
(författare)
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Continuous phase modulated orthogonal multiple access scheme
- 2014
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Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479935116 ; , s. 3886-3891
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on the design and performance analysis of continuous phase modulated orthogonal multiple access systems. The multiuser interference is firstly derived in the context of single user detection, which reveals that the interference is determined by the modulation format. Therefore, the interference can be successfully suppressed by carefully chosen modulation parameters. Based on this observation, a class of orthogonal multiple access schemes is proposed. It is shown that the proposed strategy not only facilitates simple detection at the receiver side but also offers improved sum rate.
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| 3. |
- Bing, L., et al.
(författare)
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Single user detection of continuous phase modulated multiuser systems
- 2014
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Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479935116 ; , s. 4008-4013
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Konferensbidrag (refereegranskat)abstract
- The performance analysis of single user detection of continuous phase modulated multiuser systems is presented in this paper. The discussion is formulated in the context of a mismatched receiver and the performance of single user detection is analyzed in terms of Euclidean distance. Taking the modulation parameters into consideration, a closed-form expression for the performance evaluation is obtained. Principles of designing the transceiver for spectrally-efficient systems are proposed. Numerical and analytical results show that properly designed spectrally efficient multiuser systems can be successfully detected by the presented detector with low complexity.
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| 4. |
- Levorato, M., et al.
(författare)
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Distributed optimization of transmission strategies in reactive cognitive networks
- 2014
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Ingår i: 2014 IEEE Global Communications Conference, GLOBECOM 2014. - 9781479935116 ; , s. 905-910
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Konferensbidrag (refereegranskat)abstract
- A framework for the distributed optimization of reactive cognitive networks with multiple secondary users is presented. The secondary users iteratively locate the policy maximizing their aggregate performance under bounds on the maximum performance loss caused to the primary users. The policy accounts for the impact of interference on the dynamics of the primary users' network due to transmission and channel access protocols. To minimize coordination overhead, it is assumed that the secondary users only coordinate the policy, whereas actions in each slot are independently selected by the individual secondary user based on the agreed policy. The distributed optimization technique proposed herein is based on alternating convex optimization. Numerical results are presented assessing the performance of the obtained transmission policy with respect to the optimal centralized and fully-coordinated policy.
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| 5. |
- Li, Jingya, 1986, et al.
(författare)
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I/Q Imbalance in Two-Way AF Relaying: Performance Analysis and Detection Mode Switch
- 2014
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Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479935116 ; , s. 4001-4007
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Konferensbidrag (refereegranskat)abstract
- This paper studies the impact of in-phase and quadrature-phase imbalance (IQI) in two-way amplify-and-forward (AF) relaying systems. In particular, the effective signal-to-interference-plus-noise ratio (SINR) is derived for each source node, considering four different linear detection schemes, namely, uncompensated (Uncomp) scheme, maximal-ratio-combining (MRC), zero-forcing (ZF) and minimum mean-square error (MMSE) based schemes. For each proposed scheme, the outage probability (OP) is investigated over independent, non-identically distributed Nakagami-m fading channels, and exact closed-form expressions are derived for the first three schemes. Based on the closed-form OP expressions, an adaptive detection mode switching scheme is designed for minimizing the OP of both sources. An important observation is that, regardless of the channel conditions and transmit powers, the ZF-based scheme should always be selected if the target SINR is larger than 3 (4.77 dB), while the MRC-based scheme should be avoided if the target SINR is larger than 0.38 (-4.20 dB).
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| 6. |
- LINDBERG, CHRISTOPHER, 1988, et al.
(författare)
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Distributed Compressed Sensing for Sensor Networks with Packet Erasures
- 2014
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Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479935116 ; , s. 13-19
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Konferensbidrag (refereegranskat)abstract
- We study two approaches to distributed compressed sensing for in-network data compression and signal reconstruc- tion at a sink. Communication to the sink is considered to be bandwidth-constrained due to the large number of devices. By using distributed compressed sensing for compression of the data in the network, the communication cost (bandwidth usage) to the sink can be decreased at the expense of delay induced by the local communication. We investigate the relation between cost and delay given a certain reconstruction performance requirement when using basis pursuit denoising for reconstruction. Moreover, we analyze and compare the performance degradation due to erased packets sent to the sink.
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| 7. |
- Makki, Behrooz, 1980, et al.
(författare)
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Green communication via Type-I ARQ: Finite block-length analysis
- 2014
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Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479935116 ; , s. 2673-2677
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Konferensbidrag (refereegranskat)abstract
- This paper studies the effect of optimal power allocation on the performance of communication systems utilizing automatic repeat request (ARQ). Considering Type-I ARQ, the problem is cast as the minimization of the outage probability subject to an average power constraint. The analysis is based on some recent results on the achievable rates of finite-length codes and we investigate the effect of codewords length on the performance of ARQ-based systems. We show that the performance of ARQ protocols is (almost) insensitive to the length of the codewords, for codewords of length $\ge 50$ channel uses. Also, optimal power allocation improves the power efficiency of the ARQ-based systems substantially. For instance, consider a Rayleigh fading channel, codewords of rate $1$ nats-per-channel-use and outage probability $10^{-3}.$ Then, with a maximum of 2 and 3 transmissions, the implementation of power-adaptive ARQ reduces the average power, compared to the open-loop communication setup, by 17 and 23 dB, respectively, a result which is (almost) independent of the codewords length. Also, optimal power allocation increases the diversity gain of the ARQ protocols considerably.
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| 8. |
- Park, J., et al.
(författare)
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Asymptotic behavior of ultra-dense cellular networks and its economic impact
- 2014
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Ingår i: 2014 IEEE Global Communications Conference, GLOBECOM 2014. - 9781479935116 ; , s. 4941-4946
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the relationship between base station (BS) density and average spectral efficiency (SE) in the downlink of a cellular network. This relationship has been well known for sparse deployment, i.e. when the number of BSs is small compared to the number of users. In this case the SE is independent of BS density. As BS density grows, on the other hand, it has previously been shown that increasing the BS density increases the SE, but no tractable form for the SE-BS density relationship has yet been derived. In this paper we derive such a closed-form result that reveals the SE is asymptotically a logarithmic function of BS density as the density grows. Further, we study the impact of this result on the network operator's profit when user demand varies, and derive the profit maximizing BS density and the optimal amount of spectrum to be utilized in closed forms. In addition, we provide deployment planning guidelines that will aid the operator in his decision if he should invest in densifying his network or in acquiring more spectrum.
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| 9. |
- Sanguinetti, L., et al.
(författare)
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Optimal linear precoding in multi-user MIMO systems : A large system analysis
- 2014
-
Ingår i: 2014 IEEE Global Communications Conference, GLOBECOM 2014. - : Institute of Electrical and Electronics Engineers Inc.. - 9781479935116 ; , s. 3922-3927
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Konferensbidrag (refereegranskat)abstract
- We consider the downlink of a single-cell multi-user MIMO system in which the base station makes use of N antennas to communicate with K single-antenna user equipments (UEs) randomly positioned in the coverage area. In particular, we focus on the problem of designing the optimal linear precoding for minimizing the total power consumption while satisfying a set of target signal-to-interference-plus-noise ratios (SINRs). To gain insights into the structure of the optimal solution and reduce the computational complexity for its evaluation, we analyze the asymptotic regime where N and K grow large with a given ratio and make use of recent results from large system analysis to compute the asymptotic solution. Then, we concentrate on the asymptotically design of heuristic linear precoding techniques. Interestingly, it turns out that the regularized zero-forcing (RZF) precoder is equivalent to the optimal one when the ratio between the SINR requirement and the average channel attenuation is the same for all UEs. If this condition does not hold true but only the same SINR constraint is imposed for all UEs, then the RZF can be modified to still achieve optimality if statistical information of the UE positions is available at the BS. Numerical results are used to evaluate the performance gap in the finite system regime and to make comparisons among the precoding techniques.
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