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A Distributed Approach to Interference Alignment in OFDM-based Two-tiered Networks
, 2014
"... Abstract—In this contribution, we consider a two-tiered network and focus on the coexistence between the two tiers at physical layer. We target our efforts on a long term evolution advanced (LTE-A) orthogonal frequency division multiple access (OFDMA) macro-cell sharing the spectrum with a randomly ..."
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Cited by 5 (1 self)
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Abstract—In this contribution, we consider a two-tiered network and focus on the coexistence between the two tiers at physical layer. We target our efforts on a long term evolution advanced (LTE-A) orthogonal frequency division multiple access (OFDMA) macro-cell sharing the spectrum with a randomly deployed second tier of small-cells. In such networks, high levels of co-channel interference between the macro and small base stations (MBS/SBS) may largely limit the potential spectral efficiency gains provided by the frequency reuse 1. To address this issue, we propose a novel cognitive interference alignment based scheme to protect the macro-cell from the cross-tier interference, while mitigating the co-tier interference in the second tier. Remarkably, only local channel state information (CSI) and autonomous operations are required in the second tier, resulting in a completely self-organizing approach for the SBSs. The optimal precoder that maximizes the spectral efficiency of the link between each SBS and its served user equipment is found by means of a distributed one-shot strategy. Numerical findings reveal non-negligible spectral efficiency enhancements with respect to traditional time division multiple access approaches at any signal to noise (SNR) regime. Additionally, the proposed technique exhibits significant robustness to channel estimation errors, achieving remarkable results for the imperfect CSI case and yielding consistent performance enhancements to the network. Index Terms—Interference alignment, self-organizing networks, overlay cognitive network, two-tiered network I.
L.: Cognitive interference alignment for OFDM two-tiered networks
- In: IEEE 13th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC
, 2012
"... In this contribution, we introduce an interference align-ment scheme that allows the coexistence of an orthogonal frequency division multiplexing (OFDM) macro-cell and a cognitive small-cell, deployed in a two-tiered structure and transmitting over the same bandwidth. We derive the opti-mal linear s ..."
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Cited by 3 (2 self)
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In this contribution, we introduce an interference align-ment scheme that allows the coexistence of an orthogonal frequency division multiplexing (OFDM) macro-cell and a cognitive small-cell, deployed in a two-tiered structure and transmitting over the same bandwidth. We derive the opti-mal linear strategy for the single antenna secondary base sta-tion, maximizing the spectral efficiency of the opportunistic link, accounting for both signal sub-space structure and power loading strategy. Our analytical and numerical findings prove that the precoder structure proposed is optimal for the consid-ered scenario in the face of Rayleigh and exponential decay-ing channels. 1.
EDITORIAL Open Access Cooperative MIMO multicell networks
"... Recently, the pressing desire to provide cost-effective solutions aimed at supporting high-throughput broadband wireless access with large-scale coverage has significantly changed the notion of the traditional cellular systems. Physical layer cooperation serves as an enabling technology for such a c ..."
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Recently, the pressing desire to provide cost-effective solutions aimed at supporting high-throughput broadband wireless access with large-scale coverage has significantly changed the notion of the traditional cellular systems. Physical layer cooperation serves as an enabling technology for such a change. In latest cellular networks, neighboring infrastructure stations, such as base stations (BSs) or relay stations (RSs), share their communication resources to create virtual multiple-input multiple-output (MIMO) systems by means of distributed transmission and signal processing. Cooperative processing at the BSs promises to exceed the limits on spectral efficiency imposed by inter-cell interference, thereby allowing ever more aggressive frequency reuse patterns. On the other hand, cooperation between BSs and RSs, as
Cognitive Orthogonal Precoder for Two-tiered Networks Deployment 1
, 2014
"... In this work, we consider a two-tiered network, where a tier of cognitive small base stations is deployed inside the coverage area of a preexisting macro-cell. The cross-tier interference caused by a complete bandwidth sharing is managed by introducing a new orthogonal precoder based mechanism, impl ..."
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In this work, we consider a two-tiered network, where a tier of cognitive small base stations is deployed inside the coverage area of a preexisting macro-cell. The cross-tier interference caused by a complete bandwidth sharing is managed by introducing a new orthogonal precoder based mechanism, implemented by the small base stations. This technique, called multi-user Vandermonde-subspace division multiplexing (MU-VFDM), allows to cancel the interference generated by several cognitive small base stations towards legacy macro cell receivers, without any cooperation between the two tiers. The achievable sum rate of the small-cell network, satisfying the interference cancelation requirement, is evaluated for perfect/imperfect channel state information at the transmitter (CSIT). Simulation results for MU-VFDM show a comparable performance to that of state-of-the-art dirty paper coding technique, for the case of a dense cellular layout. Finally, we propose a comparison between MU-VFDM and a standard spectrum partitioning strategy, and show promising gains in terms of achievable rate for the two-tiered network w.r.t. the traditional bandwidth management approach.
1Cognitive Orthogonal Precoder for Two-tiered Networks Deployment
"... In this work, we consider a two-tiered network, where a tier of cognitive small base stations is deployed inside the coverage area of a preexisting macro-cell. The cross-tier interference caused by a complete bandwidth sharing is managed by introducing a new orthogonal precoder based mechanism, impl ..."
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In this work, we consider a two-tiered network, where a tier of cognitive small base stations is deployed inside the coverage area of a preexisting macro-cell. The cross-tier interference caused by a complete bandwidth sharing is managed by introducing a new orthogonal precoder based mechanism, implemented by the small base stations. This technique, called multi-user Vandermonde-subspace divi-sion multiplexing (MU-VFDM), allows to cancel the interference generated by several cognitive small base stations towards legacy macro cell receivers, without any cooperation between the two tiers. The achievable sum rate of the small-cell network, satisfying the interference cancelation requirement, is evaluated for perfect/imperfect channel state information at the transmitter (CSIT). Simulation results for MU-VFDM show a comparable performance to that of state-of-the-art dirty paper coding technique, for the case of a dense cellular layout. Finally, we propose a comparison between MU-VFDM and a standard spectrum partitioning strategy, and show promising gains in terms of achievable rate for the two-tiered network w.r.t. the traditional bandwidth management approach.
1A Distributed Approach to Interference Alignment in OFDM-based Two-tiered Networks
"... Abstract—In this contribution, we consider a two-tiered net-work and focus on the coexistence between the two tiers at physical layer. We target our efforts on a long term evolution advanced (LTE-A) orthogonal frequency division multiple access (OFDMA) macro-cell sharing the spectrum with a randomly ..."
Abstract
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Abstract—In this contribution, we consider a two-tiered net-work and focus on the coexistence between the two tiers at physical layer. We target our efforts on a long term evolution advanced (LTE-A) orthogonal frequency division multiple access (OFDMA) macro-cell sharing the spectrum with a randomly deployed second tier of small-cells. In such networks, high levels of co-channel interference between the macro and small base stations (MBS/SBS) may largely limit the potential spectral efficiency gains provided by the frequency reuse 1. To address this issue, we propose a novel cognitive interference alignment based scheme to protect the macro-cell from the cross-tier interference, while mitigating the co-tier interference in the second tier. Remarkably, only local channel state information (CSI) and autonomous operations are required in the second tier, resulting in a completely self-organizing approach for the SBSs. The optimal precoder that maximizes the spectral efficiency of the link between each SBS and its served user equipment is found by means of a distributed one-shot strategy. Numerical findings reveal non-negligible spectral efficiency enhancements with respect to traditional time division multiple access ap-proaches at any signal to noise (SNR) regime. Additionally, the proposed technique exhibits significant robustness to channel estimation errors, achieving remarkable results for the imperfect CSI case and yielding consistent performance enhancements to the network. Index Terms—Interference alignment, self-organizing net-works, overlay cognitive network, two-tiered network I.
Invited Article On the Practical Implementation of VFDM-based Opportunistic Systems: Issues and Challenges
, 2012
"... Abstract – Vandermonde-subspace frequency division multiplexing (VFDM) is a physical layer technique for cognitive two-tiered networks, allowing for the coexistence of an orthogonal frequency division multiplexing (OFDM) legacy system and a cognitive secondary system in a time division duplex mode. ..."
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Abstract – Vandermonde-subspace frequency division multiplexing (VFDM) is a physical layer technique for cognitive two-tiered networks, allowing for the coexistence of an orthogonal frequency division multiplexing (OFDM) legacy system and a cognitive secondary system in a time division duplex mode. It consists of a linear null-space precoder used by the secondary transmitter to effectively cancel the interference towards one or more primary receivers, while guaranteeing a non-negligible rate to a served secondary receiver. In this work, we propose an implementation of an experimental test-bed using the new SDR4All platform developed at the Alcatel-Lucent Chair on Flexible Radio (SUPELEC) to take a step towards a proof of concept of a VFDM-based system. We focus on the secondary link, where an opportunistic transmitter/receiver pair communicates over moderately frequency selective channels, characterized by very short root mean square (r.m.s.) delay spreads and non uniform power delay profiles (PDP). The obtained results show the practical feasibility of a VFDM transmission over a secondary link. However, a significant bit error rate (BER) loss with respect to the previously shown achievable theoretical performance is evident. A thorough analysis of the structure of the VFDM precoder is carried out and the impact of the channel characteristics on the performance of the opportunistic system is discussed. Numerical findings demonstrate that the potential BER drop can be addressed by designing a suitable flexible receiver able to deal with the