Traffic-aware training and scheduling for the 2-user MISO broadcast channel

Destounis, Apostolos; Assaad, Mohamad; Debbah, Mérouane; Sayadi, Bessem

doi:10.1109/isit.2014.6875058

Cited by 4 publications

(2 citation statements)

References 13 publications

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“…Explicitly, denoting by C N T (x) the average cost obtained over the time duration 0 ≤ t ≤ T under Whittle's index policy conditioned on the initial state x ,we show that C N T (x) tends to C RP,N when N and T scale. The reason behind comparing C RP,N and C N T (x) is that C RP,N is a lower bound of all expected average cost obtained by any policy that resolves the original problem (3). This means that it is sufficient to prove that C N T (x) converges to C RP,N when T and N scale in order to establish the asymptotic optimality of Whittle's index policy.…”

Section: Local Optimalitymentioning

confidence: 99%

Performance analysis of wireless network aided by discrete-phase-shifter IRS

Kriouile¹,

Assaad²,

Larrañaga³

2022

J. Commun. Netw.

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As a new technology to reconfigure wireless communication environment by signal reflection controlled by software, intelligent reflecting surface (IRS) has attracted lots of attention in recent years. Compared with conventional relay system, the relay system aided by IRS can effectively reduce the cost and energy consumption, and significantly enhance the system performance. However, the phase quantization error generated by IRS with discrete phase shifter may degrade the receiving performance of the receiver. To analyze the performance loss caused by IRS phase quantization error, based on the law of large numbers and Rayleigh distribution, the closed-form expressions for the signalto-noise ratio (SNR) performance loss and achievable rate of the IRS-aided amplify-and-forward (AF) relay network, which are related to the number of phase shifter quantization bits, are derived under the line-of-sight (LoS) channels and Rayleigh channels, respectively. Moreover, their approximate performance loss closed-form expressions are also derived based on the Taylor series expansion. Simulation results show that the performance losses of SNR and achievable rate decrease with the number of quantization bits increases gradually. When the number of quantization bits is larger than or equal to 3, the SNR performance loss of the system is smaller than 0.23dB, and the achievable rate loss is less than 0.04bits/s/Hz, regardless of the LoS channels or Rayleigh channels.

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Section: Local Optimalitymentioning

confidence: 99%

Performance analysis of wireless network aided by discrete-phase-shifter IRS

Kriouile¹,

Assaad²,

Larrañaga³

2022

J. Commun. Netw.

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“…Apart from focusing on the receivers and not the precoder at the transmitter, the work in [10] addresses sum rate maximization, so the traffic processes of the users are not taken into account. More in this direction, a recent work [11] showed that feedback policies exploiting the fact that the users know their channel can enlarge the stability region for a two-user system, under the idealized assumption that contention without collisions ispossible.…”

Section: Introductionmentioning

confidence: 99%

A threshold-based approach for joint active user selection and feedback in MISO downlink systems

Destounis

Assaad

Debbah

et al. 2015

2015 IEEE International Conference on Communications (ICC)

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In this paper we study the downlink of a TDD (Time Division Duplex) single cell system where the Base Station (BS) employs multiple antennas to serve the users taking into account the traffic patterns. The BS chooses each slot the users to be active, and serves them using Zero Forcing (ZF) precoding. This requires the knowledge of the users' channels which is assumed to be performed e.g. via uplink training. Due to the channel acquisition overhead, only a subset of users must be active at each timeslot (depending on traffic patterns and channel states). In this paper, we develop an active user selection strategy where the base station sets a given threshold for the channel gain of the users. Then, only the users that have their channel gain higher than the threshold send their training sequence and are then considered to be served. The base station estimates the channel states of these users and, due to channel reciprocity, uses these channel states to transmit data via ZF precoding. With appropriate signaling and threshold selection, which adapt to the queuing behavior of the users, we prove that our proposed method achieves a larger stability region than the baseline centralized policy where the BS selects the users based on channel statistics and queue lengths. The performance of the threshold-based method is illustrated via simulations, where we can observe a tradeoff between the expansion of the stability region and delay performance.

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Queueing stability and CSI probing of a TDD wireless network with interference alignment

Deghel

Assaad

Debbah

et al. 2015

2015 IEEE International Symposium on Information Theory (ISIT)

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This paper characterizes the performance of interference alignment (IA) technique taking into account the dynamic traffic pattern and the probing/feedback cost. We consider a time-division duplex (TDD) system where transmitters acquire their channel state information (CSI) by decoding the pilot sequences sent by the receivers. Since global CSI knowledge is required for IA, the transmitters have also to exchange their estimated CSIs over a backhaul of limited capacity (i.e. imperfect case). Under this setting, we characterize in this paper the stability region of the system under both the imperfect and perfect (i.e. unlimited backhaul) cases, then we examine the gap between these two resulting regions.Further, under each case, we provide a centralized probing algorithm (policy) that achieves the max stability region. These stability regions and scheduling policies are given for the symmetric system where all the path loss coefficients are equal to each other, as well as for the general system. For the symmetric system, we compare the stability region of IA with the one achieved by a time division multiple access (TDMA) system where each transmitter applies a simple singular value decomposition technique (SVD). We then propose a scheduling policy that consists in switching between these two techniques, leading the system, under some conditions, to achieve a bigger stability region. Under the general system, the adopted scheduling policy is of a high computational complexity for moderate number of pairs, consequently we propose an approximate policy that has a reduced complexity but that achieves only a fraction of the system stability region. A characterization of this fraction is provided.

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Traffic-aware training and scheduling for the 2-user MISO broadcast channel

Cited by 4 publications

References 13 publications

Performance analysis of wireless network aided by discrete-phase-shifter IRS

Performance analysis of wireless network aided by discrete-phase-shifter IRS

A threshold-based approach for joint active user selection and feedback in MISO downlink systems

Queueing stability and CSI probing of a TDD wireless network with interference alignment

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