The Capacity of the Quantum Multiple Access Channel

We define classical-quantum multiway channels for transmission of classical information, after recent work by Allahverdyan and Saakian. Bounds on the capacity region are derived in a uniform way, which are analogous to the classically known ones, simply replacing Shannon entropy with von Neumann entropy. For the single receiver case (multiple access channel) the exact capacity region is determined. These results are applied to the case of noisy channels, with arbitrary input signal states. A second issue of this work is the presentation of a calculus of quantum information quantities, based on the algebraic formulation of quantum theory.Comment: 7 pages, requires IEEEtran2e.cl

Byzantine Multiple Access Channels -- Part II: Communication With Adversary Identification

We introduce the problem of determining the identity of a byzantine user (internal adversary) in a communication system. We consider a two-user discrete memoryless multiple access channel where either user may deviate from the prescribed behaviour. Owing to the noisy nature of the channel, it may be overly restrictive to attempt to detect all deviations. In our formulation, we only require detecting deviations which impede the decoding of the non-deviating user's message. When neither user deviates, correct decoding is required. When one user deviates, the decoder must either output a pair of messages of which the message of the non-deviating user is correct or identify the deviating user. The users and the receiver do not share any randomness. The results include a characterization of the set of channels where communication is feasible, and an inner and outer bound on the capacity region. We also show that whenever the rate region has non-empty interior, the capacity region is same as the capacity region under randomized encoding, where each user shares independent randomness with the receiver. We also give an outer bound for this randomized coding capacity region.Comment: arXiv admin note: substantial text overlap with arXiv:2105.0338

Achievable Rate and Optimal Physical Layer Rate Allocation in Interference-Free Wireless Networks

We analyze the achievable rate in interference-free wireless networks with physical layer fading channels and orthogonal multiple access. As a starting point, the point-to-point channel is considered. We find the optimal physical and network layer rate trade-off which maximizes the achievable overall rate for both a fixed rate transmission scheme and an improved scheme based on multiple virtual users and superposition coding. These initial results are extended to the network setting, where, based on a cut-set formulation, the achievable rate at each node and its upper bound are derived. We propose a distributed optimization algorithm which allows to jointly determine the maximum achievable rate, the optimal physical layer rates on each network link, and an opportunistic back-pressure-type routing strategy on the network layer. This inherently justifies the layered architecture in existing wireless networks. Finally, we show that the proposed layered optimization approach can achieve almost all of the ergodic network capacity in high SNR.Comment: 5 pages, to appear in Proc. IEEE ISIT, July 200

Radio resource allocation in OFDMA system

In this thesis, orthogonal frequency division multiple access (OFDMA) system is considered. Assuming perfect knowledge of instantaneous channel conditions for all users, we propose resource allocation algorithms to minimize the total transmission power subject to the constraints of the requirements of each user’s data rate and bit error rate (BER) which is referred to as margin adaptive (MA) problem, or to maximize the overall spectral efficiency while simultaneously satisfying the requirements of each user’s d ata rate, BER and base station (BS)’s transmission power constraint which is referred to as rate adaptive (RA) problem. By converting the above problems into linear integer programming problems, a branch-and-bound method based optimal algorithm and a fast suboptimal algorithm are proposed. The proposed branch-and- bound method based optimal algorithm offers the same optimal performance as full-search algorithm with remarkably reduced computational complexity. The proposed suboptimal algorithm , which is based on the formulation with constraints considered and greedy approach, can be used to solve both MA and RA optimization problems by satisfying the constraints one by one without any bit loading or transmission power distribution assumptions. Compared with other suboptimal methods, the performance of this suboptimal algorithm is close to the optimal one with even lower computational complexity. Index Terms-adaptive modulation, frequency selective fading channel, multi-access communication, multiuser channel, channel capacity, orthogonal frequency division multiple access (OFDMA), power control, resource management