| 1. |
- Chatzinotas, Symeon, et al.
(författare)
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Interference Alignment for Clustered Multicell Joint Decoding
- 2011
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Ingår i: 2011 IEEE Wireless Communications and Networking Conference, WCNC 2011. - : IEEE. - 9781612842547 ; , s. 1966-1971
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Konferensbidrag (refereegranskat)abstract
- Multicell joint processing has been proven to be very efficient in overcoming the interference-limited nature of the cellular paradigm. However, for reasons of practical implementation global multicell joint decoding is not feasible and thus clusters of cooperating Base Stations have to be considered. In this context, intercluster interference has to be mitigated in order to harvest the full potential of multicell joint processing. In this paper, interference alignment is investigated as a means of intercluster interference mitigation and its performance is compared to global multicell joint processing. Both scenarios are modelled and analyzed using the per-cell ergodic sum-rate capacity as a figure of merit. In this process, a number of theorems are derived for analytically expressing the asymptotic eigenvalue distributions of the channel covariance matrices. The analysis is based on principles from Free Probability theory and especially properties in the R and Stieltjes transform domain.
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| 2. |
- Sutic, Davor, et al.
(författare)
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Lower trees with fixed degrees : a recipe for efficient secure hierarchical aggregation in WSNs
- 2011
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Ingår i: 2011 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC). - : IEEE Computer Society. - 9781612842547 ; , s. 659-664
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Konferensbidrag (refereegranskat)abstract
- We propose two strategies to reduce energy consumption for secure data aggregation in wireless sensor networks. While the purpose of data aggregation is to reduce energy consumption, secure data aggregation introduces an overhead making the total energy consumption comparable to naive secure non-aggregation. Another aspect is that the secure data aggregation has higher node congestion than non-aggregation schemes for networks of sizes up to about 100 nodes. Considering a secure data aggregation protocol, our strategies are to reduce the height of the aggregation tree and limit its node degree. The former results in fewer verification messages and a lower total communication load, and the latter reduces node congestion. The most heavily burdened node sends a third of the messages required in the original protocol, which for small networks is lower than with non-aggregation, and the total communication load is lowered compared to non-aggregation.
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| 3. |
- Wilhelmsson, Leif, et al.
(författare)
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Analysis of a novel low complex SNR estimation technique for OFDM systems
- 2011
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Ingår i: IEEE Wireless Communications and Networking Conference (WCNC). - 9781612842547 ; , s. 1646-1651
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Konferensbidrag (refereegranskat)abstract
- Signal-to-noise ratio (SNR) estimation is commonly used in wireless receivers to enhance the performance in different ways. In this paper a novel low complexity SNR estimator for OFDM is proposed. The estimator might be implemented using floating point representation or by using only the sign-bit, and can if desired be effectively implemented by reconfiguring the standard correlator used for time- and frequency estimation. Closed form expressions for the SNR estimate are derived for both the floating point implementation and the sign-bit implementation, and compared to simulation results both for an additive white Gaussian noise (AWGN) channel and for a frequency selective channel showing the feasibility of the proposed algorithm.
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| 4. |
- Zu, L., et al.
(författare)
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Joint optimization in multi-user MIMO-OFDMA relay-enhanced cellular networks
- 2011
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Ingår i: 2011 IEEE Wireless Communications and Networking Conferenc. - : IEEE. - 9781612842547 ; , s. 13-18
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Konferensbidrag (refereegranskat)abstract
- MIMO, OFDMA and cooperative relaying are the key technologies in future wireless communication systems. However, under the usage of these technologies, resource allocation becomes a more crucial and challenging task. In multi-user MIMO-OFDMA relay-enhanced cellular networks, we formulate the optimal instantaneous resource allocation problem including user group selection, path selection, power allocation, and subchannel scheduling to maximize system capacity. We first propose a low-complex resource allocation algorithm named CP-CP under constant uniform power allocation and then use a water-filling method named CP-AP to allocate power among transmitting antennas. Moreover, we solve the original optimization problem efficiently by using the Jensen's inequality and propose a modified iterative water-filling algorithm named AP-CP. Based on AP-CP, the AP-AP algorithm is proposed to allocate power adaptively not only among subchannels but also among multiple transmitting. Finally, we compare the performance of the four schemes. Our results show that allocating power among subchannels is more effective than among transmitting antennas if the average signal-to-noise radio of users is low, and vice versa. Furthermore, the AP-AP algorithm achieves the highest throughout especially for users near the cell edge.
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