Technical Program

Paper Detail

Paper Title Capacity per Unit-Energy of Gaussian Many-Access Channels
Paper IdentifierFR2.R8.2
Authors Jithin Ravi, Tobias Koch, Universidad Carlos III de Madrid, Spain
Session Energy Efficient Communications
Location Conseil, Level 5
Session Time Friday, 12 July, 11:40 - 13:00
Presentation Time Friday, 12 July, 12:00 - 12:20
Manuscript  Click here to download the manuscript
Abstract We consider a Gaussian multiple-access channel where the number of transmitters grows with the blocklength $n$. For this setup, the maximum number of bits that can be transmitted reliably per unit-energy is analyzed. We show that if the number of users is of an order strictly above $n/\log n$, then the users cannot achieve any positive rate per unit-energy. In contrast, if the number of users is of order strictly below $n/\log n$, then each user can achieve the single-user capacity per unit-energy $(\log e)/N_0$ (where $N_0/ 2$ is the noise power) by using an orthogonal access scheme such as time division multiple access. We further demonstrate that orthogonal codebooks, which achieve the capacity per unit-energy when the number of users is bounded, can be strictly suboptimal.