On the Separability of Parallel MISO Broadcast Channels Under Partial CSIT: A Degrees of Freedom Region Perspective

Joudeh, Hamdi; Clerckx, Bruno

doi:10.1109/tit.2019.2962136

Cited by 13 publications

(8 citation statements)

References 55 publications

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“…The recent insights into the fragility of schemes that rely on highly precise CSIT, enabled by AI bounds, have given new vitality to robust schemes that only require coarse channel knowledge, including treating interference as noise, rate-splitting and layered superposition, as seen through a number of studies [7][8][9][10][11]. These works seek to identify operational regimes in which such robust (and simple) schemes are DoF or GDoF optimal in various settings and networks.…”

Section: Introductionmentioning

confidence: 99%

On the Optimality of Treating Inter-Cell Interference as Noise in Uplink Cellular Networks

Joudeh

Clerckx

2019

IEEE Trans. Inform. Theory

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In this work, we study the generalized degrees-of-freedom (GDoF) of downlink and uplink cellular networks, modeled as Gaussian interfering broadcast channels (IBC) and Gaussian interfering multiple access channels (IMAC), respectively. We focus on regimes of low inter-cell interference, where single-cell transmission with power control and treating inter-cell interference as noise (mc-TIN) is GDoF optimal. Recent works have identified two relevant regimes in this context: one in which the GDoF region achieved through mc-TIN for both the IBC and IMAC is a convex polyhedron without the need for time-sharing (mc-CTIN regime), and a smaller (sub)regime where mc-TIN is GDoF optimal for both the IBC and IMAC (mc-TIN regime). In this work, we extend the mc-TIN framework to cellular scenarios where channel state information at the transmitters (CSIT) is limited to finite precision. We show that in this case, the GDoF optimality of mc-TIN extends to the entire mc-CTIN regime, where GDoF benefits due to interference alignment (IA) are lost. Our result constitutes yet another successful application of robust outer bounds based on the aligned images (AI) approach.The authors are with the

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Section: Introductionmentioning

confidence: 99%

On the Optimality of Treating Inter-Cell Interference as Noise in Uplink Cellular Networks

Joudeh

Clerckx

2019

IEEE Trans. Inform. Theory

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“…Different variants of this hybrid PNparallel channel model have been widely adopted in information-theoretic studies focusing on capacity and DoF limits of wireless networks under CSIT imperfections (see e.g. [35]- [38] and references therein).…”

Section: A the Considered Cache-aided Wireless Networkmentioning

confidence: 99%

“…For any P-block and N-block indexed by m (p) and m (n) respectively, the sets of subpackets D (p) m (p) and D (n) m (n) to be delivered are deemed feasible only if their cardinalities satisfy (37) and (38). Hence by keeping the caching realization, demand vector and splitting ratio fixed, the following integer programming problems yields a lower bound on the delivery time:…”

Section: B Integer Program Formulationmentioning

confidence: 99%

Centralized and Decentralized Cache-Aided Interference Management in Heterogeneous Parallel Channels

Piovano

Joudeh

Clerckx

2020

IEEE Trans. Commun.

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We consider the problem of cache-aided interference management in a network consisting of K T single-antenna transmitters and K R single-antenna receivers, where each node is equipped with a cache memory. Transmitters communicate with receivers over two heterogenous parallel subchannels: the Psubchannel for which transmitters have perfect instantaneous knowledge of the channel state, and the N-subchannel for which the transmitters have no knowledge of the instantaneous channel state. Under the assumptions of uncoded placement and separable one-shot linear delivery over the two subchannels, we characterize the optimal degrees-of-freedom (DoF) to within a constant multiplicative factor of 2. We extend the result to a decentralized setting in which no coordination is required for content placement at the receivers. In this case, we characterize the optimal one-shot linear DoF to within a factor of 3.

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“…The finite precision CSIT assumption eliminates the GDoF benefits of schemes that rely on precise CSIT [17], such as IA for the IBC [41], and ZF and DPC for the MISO-BC [19], which naturally gives way to classes of robust schemes based on power control, TIN, rate-splitting and SLS [21][22][23][24][25][26][27][28][29][30][31][32][33][34], which only require coarse CSIT (i.e. channel strength parameters).…”

Section: From Multi-cell Tin To Multi-cell Slsmentioning

confidence: 99%

“…A common theme emerging from these robust characterizations is that GDoF gains due to sophisticated schemes that rely on precise CSIT-as signal-space and signal-scale IA [12,13], zero forcing (ZF) and dirty paper coding (DPC) [18][19][20]-are entirely lost under finite precision CSIT. The new insights into the fragility of those once-promising elegant schemes have brought back to the forefront simple and robust alternatives that require only coarse channel knowledge-as power control and treating interference as noise (TIN) [21][22][23][24][25][26][27][28][29][30], rate-splitting and simple layered superposition (SLS) [31][32][33][34]which, perhaps surprisingly, have turned out to be GDoF optimal in a number of settings.…”

Section: Introductionmentioning

confidence: 99%

Cellular Networks With Finite Precision CSIT: GDoF Optimality of Multi-Cell TIN and Extremal Gains of Multi-Cell Cooperation

Joudeh¹,

Caire²

2020

Preprint

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We study the generalized degrees-of-freedom (GDoF) of cellular networks under finite precision channel state information at the transmitters (CSIT). We consider downlink settings modeled by the interfering broadcast channel (IBC) under no multi-cell cooperation, and the overloaded multiple-input-single-output broadcast channel (MISO-BC) under full multi-cell cooperation. We focus on three regimes of interest: the mc-TIN regime, where a scheme based on treating inter-cell interference as noise (mc-TIN) was shown to be GDoF optimal for the IBC; the mc-CTIN regime, where the GDoF region achievable by mc-TIN is convex without the need for time-sharing; and the mc-SLS regime which extends a previously identified regime, where a simple layered superposition (SLS) scheme is optimal for the 3-transmitter-3-user MISO-BC, to overloaded cellular-type networks with more users than transmitters. We first show that the optimality of mc-TIN for the IBC extends to the entire mc-CTIN regime when CSIT is limited to finite precision. The converse proof of this result relies on a new application of aligned images bounds. We then extend the IBC converse proof to the counterpart overloaded MISO-BC, obtained by enabling full transmitter cooperation. This, in turn, is utilized to show that a multi-cell variant of the SLS scheme is optimal in the mc-SLS regime under full multi-cell cooperation, albeit only for 2-cell networks. The overwhelming combinatorial complexity of the GDoF region stands in the way of extending this result to larger networks. Alternatively, we appeal to extremal network analysis, recently introduced by Chan et al., and study the GDoF gain of multi-cell cooperation over mc-TIN in the three regimes of interest. We show that this extremal GDoF gain is bounded by small constants in the mc-TIN and mc-CTIN regimes, yet scales logarithmically with the number of cells in the mc-SLS regime.

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On the Separability of Parallel MISO Broadcast Channels Under Partial CSIT: A Degrees of Freedom Region Perspective

Cited by 13 publications

References 55 publications

On the Optimality of Treating Inter-Cell Interference as Noise in Uplink Cellular Networks

On the Optimality of Treating Inter-Cell Interference as Noise in Uplink Cellular Networks

Centralized and Decentralized Cache-Aided Interference Management in Heterogeneous Parallel Channels

Cellular Networks With Finite Precision CSIT: GDoF Optimality of Multi-Cell TIN and Extremal Gains of Multi-Cell Cooperation

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