| 1. |
- Bianco, A., et al.
(författare)
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OpenFlow driven ethernet traffic analysis
- 2014
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Ingår i: 2014 IEEE International Conference on Communications, ICC 2014. - : IEEE Computer Society. - 9781479920037 ; , s. 3001-3006
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Konferensbidrag (refereegranskat)abstract
- Software Defined Networking (SDN) is a new networking paradigm that permits to slice network infrastructures. An example of SDN is the OpenFlow framework, where the control plane runs on a separate device, called controller, that manages data forwarding switches. The OpenFlow protocol ensures communications between OpenFlow switches and the OpenFlow controller. Before widely deploying OpenFlow based networks, scalability and performance of such networks should be studied and better understood. In this paper, the scalability of NOX, one of the most popular OpenFlow controller, is analyzed through both simulation and lab measurements. We perform an Ethernet trace analysis on the controller by defining flow characteristics as would be seen by an OpenFlow controller. We study the potential trace impact on an OpenFlow controller, analyzing among others, the number of flows, flow inter arrival times, traffic volumes and flow size distribution. Our results permit to discuss the feasibility of running OpenFlow networks with a single commodity PC as the controller in a mid-size campus network. © 2014 IEEE.
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| 2. |
- Bing, L., et al.
(författare)
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Spectrally-efficient FDMA-CPM systems
- 2014
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Ingår i: 2014 IEEE International Conference on Communications, ICC 2014. - 9781479920037 ; , s. 5215-5220
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Konferensbidrag (refereegranskat)abstract
- This paper concerns with the design of spectrally-efficient Frequency-Division-Multiple-Access (FDMA) multiuser systems based on Continuous-Phase-Modulation (CPM). A class of FDMA-CPM is proposed to accommodate multiple users in a subchannel and therefore admits significantly improved spectral-efficiency. Phase spacing is incorporated into the system to improve the Euclidean distance property, especially for FDMA-CPM systems with small frequency spacing. The impacts of the phase spacing and frequency spacing are then evaluated in terms of the distance property, which shows that the proposed FDMA-CPM systems have a comparable error performance to the single user systems. The proposed strategy is exemplified by systems having spectral-efficiency varying from 1.67 bits/s/Hz to 12 bits/s/Hz, which shows significantly improved spectral efficiency is obtained comparing with existing systems given the same signal to noise ratio.
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| 3. |
- Gan, M., et al.
(författare)
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Calibration of indoor UWB sub-band divided ray tracing using multiobjective simulated annealing
- 2014
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Ingår i: 2014 IEEE International Conference on Communications, ICC 2014. - 9781479920037 ; , s. 4844-4849
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Konferensbidrag (refereegranskat)abstract
- Sub-band divided ray tracing (RT) has been widely used to reproduce as reliably as possible the ultra-wideband (UWB) radio wave propagation channel in realistic indoor environments. However, its accuracy is strictly limited by the available description of the environment. Moreover, its computational complexity scales with the number of selected subbands and the number of propagation paths. In the present work, our RT tool considers not only deterministic propagation paths but also diffuse scattering components. Based on a low-complexity sub-band divided RT implementation, we propose a calibration method for indoor UWB sub-band divided RT. The method estimates the optimal material parameters, including the dielectric parameters and the scattering parameters, using channel measurements and multiobjective simulated annealing (MOSA). This calibration can improve the accuracy of sub-band divided RT in terms of the power delay profile (PDP) and the root mean square (RMS) delay spread for all test locations including those not considered by the calibration. A measurement campaign is used to verify the calibration technique. © 2014 IEEE.
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| 4. |
- Gerami, Majid, et al.
(författare)
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Exact optimized-cost repair in multi-hop distributed storage networks
- 2014
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Ingår i: 2014 IEEE International Conference on Communications, ICC. - : IEEE Computer Society. - 9781479920037 ; , s. 4120-4124
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Konferensbidrag (refereegranskat)abstract
- The problem of exact repair of a failed node in multi-hop networked distributed storage systems is considered. Contrary to the most of the current studies which model the repair process by the direct links from surviving nodes to the new node, the repair is modeled by considering the multi-hop network structure, and taking into account that there might not exist direct links from all the surviving nodes to the new node. In the repair problem of these systems, surviving nodes may cooperate to transmit the repair traffic to the new node. In this setting, we define the total number of packets transmitted between nodes as repair-cost. A lower bound of the repair-cost can thus be found by cut-set bound analysis. In this paper, we show that the lower bound of the repair-cost is achievable for the exact repair of MDS codes in tandem and grid networks, thus resulting in the minimum-cost exact MDS codes. Further, two suboptimal (achievable) bounds for the large scale grid networks are proposed.
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| 5. |
- Häger, Christian, 1986, et al.
(författare)
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Optimized Bit Mappings for Spatially Coupled LDPC Codes over Parallel Binary Erasure Channels
- 2014
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Ingår i: Proc. 1st IEEE International Conference on Communications (ICC). - 9781479920037 ; , s. 2064-2069
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Konferensbidrag (refereegranskat)abstract
- In many practical communication systems, one binary encoder/decoder pair is used to communicate over a set of parallel channels. Examples of this setup include multi-carrier transmission, rate-compatible puncturing of turbo-like codes, and bit-interleaved coded modulation (BICM). A bit mapper is commonly employed to determine how the coded bits are allocated to the channels. In this paper, we study spatially coupled low-density parity check codes over parallel channels and optimize the bit mapper using BICM as the driving example. For simplicity, the parallel bit channels that arise in BICM are replaced by independent binary erasure channels (BECs). For two parallel BECs modeled according to a 4-PAM constellation labeled by the binary reflected Gray code, the optimization results show that the decoding threshold can be improved over a uniform random bit mapper, or, alternatively, the spatial chain length of the code can be reduced for a given gap to capacity. It is also shown that for rate-loss free, circular (tail-biting) ensembles, a decoding wave effect can be initiated using only an optimized bit mapper.
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| 6. |
- Li, Jingya, 1986, et al.
(författare)
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I/Q Imbalance in Two-Way AF Relaying: Power Allocation and Performance Analysis
- 2014
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Ingår i: IEEE International Conference on Communications, ICC 2014, Sydney, Australia. - 9781479920037 ; , s. 5042-5048
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Konferensbidrag (refereegranskat)abstract
- We investigate the performance of dual-hop two-way amplify-and-forward (AF) relaying in the presence of in-phase and quadrature-phase imbalance (IQI) at the relay node. In particular, the effective signal-to-interference-plus-noise ratio (SINR) at both sources is derived. These SINRs are used to design an instantaneous power allocation scheme, which maximizes the minimum SINR of the two sources under a total transmit power constraint. The solution to this optimization problem is analytically determined and used to analytically investigate the outage probability (OP) of the considered two-way AF relaying system. Both analytical and numerical results show that IQI can create fundamental performance limits on relaying systems, which cannot be avoided by simply improving the channel conditions.
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| 7. |
- Li, J., et al.
(författare)
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One-bit soft forwarding for network coded uplink channels with multiple sources
- 2014
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Ingår i: 2014 IEEE International Conference on Communications, ICC 2014. - : IEEE Computer Society. - 9781479920037 ; , s. 5790-5795
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a threshold-based one-bit soft forwarding (TOB-SF) protocol for a multi-source relaying uplink system with network coding. In the TOB-SF protocol, the relay calculates the log-likelihood ratio (LLR) value of each network coded symbol, compares this LLR value with a pre-optimized threshold, and determines whether to transmit or keep silent. We first derive the bit error rate (BER) expression at the destination, based on which, we optimize the threshold to minimize the BER. Then we theoretically prove that the system can achieve the full diversity gain by using this threshold. Further, we optimize the power allocation at the relay to achieve a higher coding gain. Simulation results show that the proposed TOB-SF protocol outperforms other conventional relaying protocols in terms of error performance.
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| 8. |
- Medeiros, Eduardo, et al.
(författare)
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How Vectoring in G.fast May Cause Neighborhood Wars
- 2014
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Ingår i: [Host publication title missing]. - 9781479920037 ; , s. 3865-3870
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Konferensbidrag (refereegranskat)abstract
- Emerging wireline transmission systems such as G.fast use bands up to around 200 MHz on short cables. A key enabler for achieving the aspired throughput of several hundred Mbit/s is joint processing of transmit signals in downstream direction as well as joint processing of receive signals in upstream direction through techniques referred to as vectoring. A new challenge in such systems are sudden and severe changes in the channel matrix caused by changing terminations on lines outside the vectoring group. Such events can be caused by users disconnecting their modems, turning them on or off, or on-/off- hook events on lines that still support the plain old telephony service. This work presents channel measurements capturing the impact of termination changes caused by modems or handsets. An analysis of the impact of these sudden changes on the signal- to-noise-power-ratio in vectoring systems reveals that throughput and stability can be seriously degraded. The potential of decision- directed channel tracking based on least squares estimation is investigated.
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| 9. |
- Mesodiakaki, Agapi, et al.
(författare)
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Energy-efficient Context-aware User Association for Outdoor Small Cell Heterogeneous Networks
- 2014
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Ingår i: 2014 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781479920037 ; , s. 1614-1619
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Konferensbidrag (refereegranskat)abstract
- To meet the ever-increasing traffic demands, future cellular networks are about to include a plethora of small cells (SCs), with user equipments (UEs) being able of communicating via multiple bands. Given that SCs are expected to be eventually as close as 50 m apart, some of them will not have a direct connection to the core network, and thus will forward their traffic to the neighboring SCs until they reach it. In such architectures, the user association problem becomes challenging with backhaul (BH) energy consumption playing a key role. Thus, in this paper, we study the user association problem aiming at maximizing the network energy efficiency. The problem is formulated as an optimization problem, which is NP-hard. Therefore, we propose a cognitive heuristic algorithm that exploits context-aware information (i.e., UE measurements and requirements, the HetNet architecture knowledge and the available spectrum resources of each base station (BS)) to associate the UEs in an energy-efficient way, while considering both the access and the BH energy consumption. We evaluate the performance of the proposed algorithm under two study-case scenarios and we prove that it achieves significantly higher energy efficiency than the reference algorithms, while maintaining high spectral efficiency.
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| 10. |
- Miridakis, N. I., et al.
(författare)
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Multiuser dual-hop relaying over mixed RF/FSO links
- 2014
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Ingår i: 2014 IEEE International Conference on Communications, ICC 2014. - 9781479920037 ; , s. 3389-3394
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Konferensbidrag (refereegranskat)abstract
- The performance of multiuser dual-hop relaying over mixed radio frequency/free-space optical (RF/FSO) links is investigated. RF links are used for the simultaneous data transmission from m single-antenna sources to the relay, which is equipped with n ≥ m receive antennas and a photo-aperture transmitter. The relay operates under the decode-and-forward protocol and utilizes the popular ordered V-BLAST technique to successively decode each user's transmitted stream. A common norm-based ordering approach is adopted, where the streams are decoded in an ascending order. After the V-BLAST decoding, the relay retransmits the initial information to the destination, which is equipped with a photo-detector, via a point-to-point FSO link in m consecutive timeslots. Analytical expressions for the end-to-end outage probability and average symbol error probability of each user are derived. Some engineering insights are manifested, such as the diversity order, the impact of the pointing error displacement on the FSO link and the severity on the turbulence-induced channel fading.
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