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The correspondence cited in the title [1] derived ergodic capacity of the coherent multiple-input multiple-output (MIMO) channel in independent and identically distributed (IID) Rayleigh fading. While the theoretical results are correct, several plots in the paper are incorrect. In this correspondence, we correct the plots. More importantly, the corrected plots present an interesting and compelling contrast between performances of the coherent MIMO systems with and without channel state information at the transmitter; whereas this view is somewhat limited in [1] because of flaws in the capacity curves.

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IEEE Transactions on Information Theory

Comments and Corrections to “Capacity of Multiple-Antenna Systems With Both Receiver and Transmitter Channel State Information”

In a coherent time-varying MIMO multiple access channel (MAC), the ergodic sum-capacity can be achieved by suitable power control, which adapts the transmit covariance matrices based on the available channel state information (CSI). We consider a MIMO-MAC model where each transmitter is only aware of its own fading realization. For this distributed MAC, we propose decentralized power control schemes. First, some key structural properties on the optimal power control laws are derived, followed by an upper bound on the sum-capacity. Numerical results show that the proposed power control schemes closely characterize the sum-capacity in several regimes of interest.

IEEE International Symposium on Information Theory - Proceedings

On Decentralized Power Control for Ergodic MIMO Multiple Access Channels

We consider the decentralized power optimization problem for Gaussian fast-fading multiple access channel (MAC) so that the average sum throughput is maximized. In our MAC setup, each transmitter has access to only its own fading coefficient or channel state information (CSI), while the receiver has full CSI available at all instants. Unlike centralized MAC (full CSIT MAC) where the optimal powers are known explicitly, the analytical solution for optimal decentralized powers does not seem feasible. In this letter, we specialize the alternating-maximization (AM) method for numerically computing the optimal powers and ergodic capacity of the decentralized MAC for general fading statistics and average power constraints. For illustration, we apply our AM method to compute the capacity of MAC channels with fading distributions such as Rayleigh and Rician.

IEEE Communications Letters

Optimal Power Control in Decentralized Gaussian Multiple Access Channels

We consider a fast fading AWGN multiple-access channel (MAC) with full receiver CSI and distributed CSI at the transmitters. The objective is to evaluate the ergodic sum-capacity of this decentralized model, under identical average powers and channel statistics across users. While an optimal water-filling solution can be found for centralized MACs with full CSI at all terminals, such an explicit solution is not considered feasible in distributed CSI models. Our main contribution is an upper-bound on the ergodic sum-capacity when each transmitter is aware only of its own fading coefficients. Interestingly, our techniques also suggest an appropriate lower bound. These bounds are shown to be very close to each other, suggesting the tight nature of the results.

On the Ergodic Sum-Capacity of Decentralized Multiple Access Channels

We consider decentralized power control in fading multiple-access channels (MAC). When compared to a centralized MAC, solving the optimal power control for a decentralized system is difficult even for moderate number of users. Good thumb-rules for decentralized power control are available in literature, which are also asymptotically tight in the number of users. In this paper, we first derive a structural property that any optimal decentralized power control scheme must follow and use this property to suggest a modified power control scheme. Numerical results suggest that the scheme we propose outperforms the existing ones.

2015 21st National Conference on Communications, NCC 2015

Decentralized power adaptation in ergodic fading multiple access channels

In this paper, we evaluate and compare the performances of Viterbi decoding schemes based on soft decision and hard decisions, with results applicable to the Digital Video Broadcast-Terrrestial (DVB-T) standard. The standard suggests that the BER ≤ 2 × 10-4 at the decoder output is good enough for the quasi error-free condition. We assume that the channel state information (CSI) of all sub-carriers are available at the receiver at all times. The multipath fading is assumed to be Rayleigh type. Simulation results confirm the advantage of using soft-decision decoding over the hard-decision type. Approximate Eb/N0 gains in the range 3-4.5 dB are reported for the different choices of code rates and OFDM transmission modes available in the standard.

11th IEEE India Conference: Emerging Trends and Innovation in Technology, INDICON 2014

A simulation study of performance of joint soft demapping-viterbi decoding in DVB-T system

We consider a two-user binary multiple access setup suitable for pulse based communications. The link from each user to the receiver is modeled by independent time-varying Z-channel. We consider the cross-over probabilities of the Z-channels as the state of the process. Each user has access only to its own state process and is unaware of the other user's states. The receiver observes the superposition of the symbols from the links. Assuming a block fading state process, we propose adaptive communication schemes, which also ensure outage-free communication in any transmission block. Furthermore, the proposed strategies turn out to be throughput optimal for highly dispersive systems. {\textcopyright} 2014 IEEE.

2014 20th National Conference on Communications, NCC 2014

MAC channel with states for pulse-based communication systems

We consider a distributed MAC setting with block-wise flat fading links and full receiver CSI (channel state information). Of the L transmitters, a subset is assumed to have knowledge of the global CSI vector in each block, whereas the remaining users have access only to their respective link qualities, i.e. each one in the latter set is unaware of the quality of other links. Outage is not allowed in any communication block. We propose efficient power-allocation and rate-adaptation strategies which are sum-rate optimal when users in each subset observe identical fading distributions chosen from a class, which includes the popular Rayleigh, Ricean etc. {\textcopyright} 2013 IEEE.