Article

# User capacity scaling laws for fading multiple-access channels

Dept. of Electr. & Comput. Eng., Univ. of Manitoba, Winnipeg, MB, Canada
(Impact Factor: 2.5). 10/2009; 8(9):4498 - 4507. DOI: 10.1109/TWC.2009.080399
Source: IEEE Xplore

ABSTRACT In this paper, the maximum number of simultaneous active transmitters (i.e. user capacity) is obtained in the many user case for fading multiple-access channels in which a minimum rate must be maintained for all active users. The results are presented in the form of scaling laws as the number of transmitters increases and three commonly used fading models, namely, Rayleigh, Rician and Nakagami are considered. It is shown that in all three cases, the user capacity scales double logarithmically with the number of users and differs only by constants depending on the distributions. We also show that the scheduling policy maximizing the number of simultaneous active transmitters can be implemented in a distributed fashion.

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Available from: Ravi R. Mazumdar, Jul 04, 2014
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• "Under the assumption of independent Rayleigh fading channels for different users, we show that the maximum number of active receivers is very close to log (P log n) /R min with probability approaching 1, where P denotes the total transmitted power. In [2], the same analysis is extended to multiple-access channels and it is shown that the maximum number of active transmitters also scales double logarithmically with the total number of transmitters in the system. "
##### Article: Maximum Number of Active Links in Wireless Networks with Fading Channels
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ABSTRACT: In this paper, the maximum number of active links supporting a minimum rate is asymptotically obtained in a single-hop wireless network with an arbitrary structure. It is assumed that each source-destination pair communicates through a fading channel; consequently, destinations receive interference from all other active source-destination pairs. Under the assumption of independent Rayleigh fading channels for different source-destination pairs, it is shown that the optimal number of active links is of the order log N with probability approaching one as the total number of nodes, N , tends to infinity. The achievable total throughput is also scales logarithmically with the total number of links/nodes in the network.
• ##### Conference Paper: User Capacity of Fading Multi-User Channels with a Minimum Rate Constraint.
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ABSTRACT: In this paper, a power allocation scheme is proposed to maximize the number of active terminals in fading multi-user channels in which a minimum rate must be maintained for all active users. It is assumed that receivers and transmitters have perfect channel state information. Both uplink and downlink scenarios are considered and under the assumption of independent Rayleigh fading channels for different terminals, the optimal number of active terminals is asymptotically obtained as the total number of users, n, is large enough. For broadcast channels with successive interference cancellation at receivers and multiple- access channels with joint decoding at the receiver, the maximum number of active terminals is shown to be arbitrarily close to In ( Ptotal/sigma2 In n) /Rmin with probability approaching one, where Ptotal and Rmin denote total transmit power and the minimum rate respectively, and sigma2 represents the noise variance.
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• ##### Conference Paper: Effects of channel estimation on the optimal number of active users in multi-user channels with Rayleigh fading
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ABSTRACT: It has already been shown that in rate-constrained multi-user channels, under the assumption of independent Rayleigh fading channels for different terminals, the number of active users (i.e. the user capacity) scales with double logarithmically with the total number of users. However, to achieve the aforementioned result, it is assumed that channel state information (CSI) is perfectly known to the receivers. Due to this fact that the gain channel is time variant, CSI can be estimated by empirical algorithms of the channel estimation like Minimum Mean Square Error (MMSE). Considering the errors stemmed from the channel estimation, this paper intends to assess the role of the channel estimator in the analysis of the number of the active users.
Electrical Engineering (ICEE), 2013 21st Iranian Conference on; 01/2013