| 1. |
- Wang, Chao, et al.
(författare)
-
On the Degrees of Freedom of Parallel Relay Networks
- 2010
-
Ingår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010. - 1930-529X. - 9781424456383 - 9781424456369
-
Konferensbidrag (refereegranskat)abstract
- We study the degrees of freedom (DOF) of a single-antenna M-user time-varying parallel relay network, where the communications between M pairs of unconnected sources and destinations are provided by a large number of half-duplex decode-and-forward (DF) relays. Unlike the conventional relaying strategy which demands all the relays to simultaneously assist the sources, we divide the relays into two clusters and permit them to take turns forwarding the source messages. With appropriate interference alignment design, it is proved that the M-user time-varying relay network has M DOF, provided that the number of relays is infinitely large.
|
|
| 2. |
- Stala, Michal, et al.
(författare)
-
Hardware Implementation of an Iterative Sampling Rate Converter for Wireless Communication
- 2010
-
Ingår i: IEEE Global Telecommunications Conference (Globecom). - 1930-529X. - 9781424456383
-
Konferensbidrag (refereegranskat)abstract
- Abstract in Undetermined This paper presents a new technique for fractional sample rate conversion based on an iterative Sinc (ISRC) method. The proposed algorithm was evaluated against the Farrow re-sampler, and performance simulation targeting different signal-to-noise ratios show the ISRC qualifies for application in reconfigurable terminals. The architecture was implemented in 65nm CMOS technology, and synthesis results show that the ISRC requires at least 23% less silicon area, compared to a Farrow filter with similar performance. The generic nature of the architecture enables further area reduction by time-multiplexing.
|
|
| 3. |
- Beygi, Lotfollah, 1977, et al.
(författare)
-
A novel multilevel coded modulation scheme for fiber optical channel with nonlinear phase noise
- 2010
-
Ingår i: Proc. Global Communications Conference, Miami, FL. - 9781424456383
-
Konferensbidrag (refereegranskat)abstract
- A multilevel coded modulation (MLCM) system in the presence of nonlinear phase noise for fiber optical communication is introduced. The proposed scheme exploits a 16-point ring constellation with nonlinear post compensation of the self phase modulation produced via the Kerr effect. A new set partitioning based on the Ungerboeck approach is introduced to maintain unequal error protection in amplitude and phase direction. The rate allocation for the MLCM component codes for different fiber lengths and transmit powers are done numerically. Simulation results show that the proposed MLCM system provides up to 2 dB gain over a forward error correcting scheme for a block error rates around 10-9, with the same overhead (7%) and complexity. ©2010 IEEE.
|
|
| 4. |
- Björnson, Emil, 1983-, et al.
(författare)
-
Optimality Properties and Low-Complexity Solutions to Coordinated Multicell Transmission
- 2010
-
Ingår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010. - : IEEE. - 9781424456383 ; , s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- Base station cooperation can theoretically improve the throughput of multicell systems by coordinating interference and serving cell edge terminals through multiple base stations. In practice, the extent of cooperation is limited by the increase in backhaul signaling and computational demands. To address these concerns, we propose a novel distributed cooperation structure where each base station has responsibility for the interference towards a set of terminals, while only serving a subset of them with data. Weighted sum rate maximization is considered, and conditions for beamforming optimality and the optimal transmission structure are derived using Lagrange duality theory. This leads to distributed low-complexity transmission strategies, which are evaluated on measured multiantenna channels in a typical urban multicell environment.
|
|
| 5. |
- Caceres, M.A., et al.
(författare)
-
Hybrid GNSS-terrestrial cooperative positioning via distributed belief propagation
- 2010
-
Ingår i: GLOBECOM - IEEE Global Telecommunications Conference. - 9781424456383
-
Konferensbidrag (refereegranskat)abstract
- Cooperative positioning algorithms have been recently introduced to overcome the limitations of traditional methods, relying on GNSS or other terrestrial infrastructure. In particular, SPAWN (Sum-Product Algorithm over a Wireless Network) was shown to provide accurate position estimate even in challenged indoor environments, thanks to exchange of local information among peers based on terrestrial ranging. In this paper we extend the SPAWN framework by considering a hybrid scenario, where agents combine satellite and peer-to-peer terrestrial measurements. The novel hybrid SPAWN (H-SPAWN) approach allows increased availability and robustness compared to GNSS-only positioning in light and deep indoor scenarios, while keeping the advantages of a distributed implementation of the original SPAWN. A parametric message representation is proposed to reduce the communication overhead, and to improve the estimation accuracy. Simulation results show that the proposed solution outperforms traditional algorithms such as cooperative least squares and the extended Kalman filter.
|
|
| 6. |
- de Kerret, Paul, et al.
(författare)
-
Analytic framework for the mutual information cumulants of different MIMO channels
- 2010
-
Ingår i: 53rd IEEE Global Communications Conference, GLOBECOM 2010; Miami, FL; United States; 6 December 2010 through 10 December 2010. - 9781424456383 ; , s. Art. no. 5683814-
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we present a general analytical framework for the exact mutual information (MI) cumulants of multiple-input multiple-output (MIMO) systems with perfect receiver channel state information (CSI) and no transmitter CSI. Our derivation is based on a recent parameterization of the joint ordered eigenvalue probability density function (PDF) [1], that encompasses both uncorrelated/semi-correlated Rayleigh channels as well as uncorrelated Rician channels. In addition, we extend our framework to account for the cumulants of doubly-correlated Rayleigh channels and also to deduce tractable expressions in the high Signal-to-Noise ratio (SNR) regime. The cumulants are particularly useful to study all high-order statistics (HOS) of the MI; in fact, they can be used to express the MI mean and variance as a finite sum of determinants. Our analytical expressions are then validated via Monte-Carlo simulations with the attained accuracy being excellent in all cases.
|
|
| 7. |
- Dely, Peter, 1982-, et al.
(författare)
-
An Experimental Comparison of Burst Packet Transmission Schemes in IEEE 802.11-based Wireless Mesh Networks
- 2010
-
Ingår i: Proceedings of IEEE Global Telecommunications Conference (GLOBECOM) 2010. - : IEEE. - 9781424456369 ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- Wireless mesh networks (WMNs) are wireless multihop networks comprised of mesh routers, which relay traffic on behalf of clients and other nodes. Using the standard IEEE 802.11 distributed coordination function (DCF) as MAC layer, a node needs to contend for the medium each time it wants to transmit a packet. This creates high overhead in particular for small packets and leads to poor performance for real-time applications such as Voice over IP (VoIP) or online gaming. Burst packet transmission can increase the efficiency. For example, with the Transmission Opportunity limit (TXOPlimit) in IEEE 802.11e, a station may transfer several packets without contending for the channel in between. Similarly, IP packet aggregation combines several IP packets together and sends them as one MAC Service Data Unit. Originally, both schemes have been developed for singlehop networks only. Thus the impact on WMNs is unclear if the packets need to contend over multiple hops. In this paper, we use measurements from a 9-node WMN testbed to compare TXOPs and IP packet aggregation for VoIP in terms of fairness, network capacity and quality of user experience. We show that for low networks loads, both TXOPs and IP packet aggregation increase the VoIP quality compared to IEEE 802.11 DCF. However, in highly loaded networks IP packet aggregation outperforms the other schemes.
|
|
| 8. |
- Di Marco, Piergiuseppe, et al.
(författare)
-
Analytical Modelling of IEEE 802.15.4 for Multi-hop Networks with Heterogeneous Traffic and Hidden Terminals
- 2010
-
Ingår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010. - 9781424456383
-
Konferensbidrag (refereegranskat)abstract
- IEEE 802.15.4 multi-hop wireless networks are an important communication infrastructure for many applications, including industrial control, home automation, and smart grids. Existing analysis of the IEEE 802.15.4 medium access control (MAC) protocol are often based on assumptions of homogeneous traffic and ideal carrier sensing, which are far from the reality when predicting performance for multi-hop networks. In this paper, a generalized analysis of the unslotted IEEE 802.15.4 MAC is presented. The model considers heterogeneous traffic and hidden terminals due to limited carrier sensing capabilities, and allows us to investigate jointly IEEE 802.15.4 MAC and routing algorithms. The analysis is validated via Monte Carlo simulations, which show that routing over multi-hop networks is significantly influenced by the IEEE 802.15.4 MAC performance. Routing decisions based on packet loss probability may lead to an unbalanced distribution of the traffic load across paths, thus motivating the need of a joint optimization of routing and MAC.
|
|
| 9. |
- Eriksson, Kristoffer, et al.
(författare)
-
Globally Optimal Resource Allocation for Achieving Maximum Weighted Sum Rate
- 2010
-
Ingår i: Proceedings of the IEEE Global Communications Conference (GLOBECOM). - 9781424456376 - 9781424456369 ; , s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- We establish a general optimization framework for joint resource allocation and interference mitigation. By utilizing axiomatic interference functions, our problem formulation is very general and includes many problems as special cases. We consider the sum rate maximization problem, which is known to be NP hard. It is shown that due to the structural model of the interference function, the joint optimization of powers and adaptive receive strategies ends up with the optimization solely with respect to powers. This facilitates our formulation of the problem under consideration as a problem of difference of convex functions (DC). Based on this DC representation, we employ a prismatic branch and bound algorithm to find a global optimum.
|
|
| 10. |
- Haghighi, Kasra, 1978, et al.
(författare)
-
Wideband Sequential Spectrum Sensing with Varying Thresholds
- 2010
-
Ingår i: Proceedings IEEE Global Communications Conference, Wireless Communications Symposium, Miami, Florida, USA. - 9781424456383
-
Konferensbidrag (refereegranskat)abstract
- In this contribution, time varying threshold sequentialdetectors are employed for energy detection-based spectrumsensing in low-SNR regimes. Sequential detection is proven to befaster (on average) than any other multi-sample detector for a setof given probabilities of detection and false-alarm. In this report,exact performance of a sequential detector for spectrum sensingis analyzed using the direct method. The theoretical resultspresented herein are verified with Monte-Carlo simulations. Itis shown that for a SNR of −10 dB, among tests with Wald andtriangular thresholds with similar probabilities of mis-detectionand false-alarm, triangular performs 54% faster in terms ofmaximum detection time (90 percentile).
|
|
