Article

# User capacity scaling laws for fading multiple-access channels

Dept. of Electr. & Comput. Eng., Univ. of Manitoba, Winnipeg, MB, Canada

IEEE Transactions on Wireless Communications (Impact Factor: 2.42). 10/2009; DOI: 10.1109/TWC.2009.080399 Source: IEEE Xplore

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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.Proceedings of IEEE International Conference on Communications, ICC 2008, Beijing, China, 19-23 May 2008; 01/2008 - [Show abstract] [Hide abstract]

**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: 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

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