Compound Multiple Access Channel Research Articles

Universal Classical-Quantum Superposition Coding and Universal Classical-Quantum Multiple Access Channel Coding

We derive universal classical-quantum superposition coding and universal classical-quantum multiple access channel code by using generalized packing lemmas for the type method. Using our classical-quantum universal superposition code, we establish the capacity region of a classical-quantum compound broadcast channel with degraded message sets. Our universal classical-quantum multiple access channel codes have two types of codes. One is a code with joint decoding and the other is a code with separate decoding. The former universally achieves corner points of the capacity region and the latter universally achieves general points of the capacity region. Combining the latter universal code with the existing result by Quantum Inf Process. 18, 246 (2019), we establish a single-letterized formula for the capacity region of a classical-quantum compound multiple access channel.

Secret communication over compound multiple access channel

The general gaussian numerous entrance wire-tap channel(GGMAC-WT) and the guassiantwoway wire-tap channel(GTW-WT) are considered. In this paper, we learn about the mystery correspondence between the correspondence channels with exacerbate various access channel(CMAC). Secret messages are exchanged with consummate mystery. In this channel the messages sent by one channel can be decoded by its relating recipient and kept mystery from other beneficiary. A MAC is considered and the messages from the encoders ae secret. By and large, our outcomes demonstrate that in various access situation, clients can help each other to on the whole accomplish positive mystery rates. At the end of the day, collaboration among clients can be priceless for accomplishing mystery for the framework.

Imperfect and Perfect Secrecy in Compound Multiple Access Channel With Confidential Message

In this paper, we study the problem of secret communication over a compound Multiple Access Channel (MAC). In this channel, we assume that one of the transmitted messages is confidential, which is only decoded by its corresponding receiver and kept secret from the other receiver. We call this proposed setting the compound MAC with a confidential message. For this model, we derive general inner and outer bounds for both imperfect and perfect secrecy conditions for the second receiver. Also, as examples, we investigate less noisy and Gaussian versions of this channel, and extend the results of the discrete memoryless version to these cases. Moreover, providing numerical examples for the Gaussian case, we illustrate the comparison between achievable rate regions of compound MAC and compound MAC with a confidential message. In addition, for the Gaussian case, we show that using cooperative jamming strategy can increase the achievable secrecy rate between the legitimate transmitter and the receiver.

Polar Codes in Network Quantum Information Theory

Polar coding is a method for communication over noisy classical channels which is provably capacity-achieving and has an efficient encoding and decoding. Recently, this method has been generalized to the realm of quantum information processing, for tasks such as classical communication, private classical communication, and quantum communication. In the present work, we apply the polar coding method to network quantum information theory, by making use of recent advances for related classical tasks. In particular, we consider problems such as the compound multiple access channel and the quantum interference channel. The main result of our work is that it is possible to achieve the best known inner bounds on the achievable rate regions for these tasks, without requiring a so-called quantum simultaneous decoder. Thus, our work paves the way for developing network quantum information theory further without requiring a quantum simultaneous decoder.

Multiple access channel with common message and secrecy constraint

The authors study the problem of secret communication over a multiple-access channel with a common message. Here, the authors assume that two transmitters have confidential messages, which must be kept secret from the wiretapper (the second receiver), and both of them have access to a common message which can be decoded by the two receivers. The authors call this setting as multiple-access wiretap channel with common message (MAWC-CM). For this setting, the authors derive general inner and outer bounds on the secrecy capacity region for the discrete memoryless case and show that these bounds meet each other for a special case called the switch channel. As well, for a Gaussian version of MAWC-CM, the authors derive inner and outer bounds on the secrecy capacity region. Providing numerical results for the Gaussian case, the authors illustrate the comparison between the derived achievable rate region and the outer bound for the considered model and the capacity region of compound multiple access channel.

Gaussian doubly dirty compound multiple‐access channel with partial side information at the transmitters

In this study, the authors study a two-user Gaussian doubly dirty compound multiple-access channel with partial side information (GDD-CMAC-PSI) where two independent additive interference signals are considered, each one known non-causally and partially to one of the encoders but unknown to either of the receivers. This channel, first, can model two users communicating with two base stations suffering from interference, and second, includes many previously studied channels as its special cases. For such a communication scenario, first, a general capacity outer bound is derived. Depending on the values of cross link gains, they classify the channel into three classes: weak, strong and mixed GDD-CMAC-PSI. Next, assuming that the interference signals have infinite variances, they obtain capacity outer bounds for these classes. Then, an achievable sum-rate is derived for the GDD-CMAC-PSI using Costa's strategy and thereby, they show that when both interference signals have infinite variances, this achievable sum-rate vanishes. Later, by utilising the lattice strategies and deriving achievable rate regions, independent of the interference powers, they show that in contrast with Costa's strategy, lattice-strategies can achieve positive rates. Finally, depending on signal-to-noise ratio gaps at receivers, various achievable rates are obtained.

On Modulo-Sum Computation Over an Erasure Multiple-Access Channel

We study modulo-sum computation of two binary source sequences over a two-user erasure multiple access channel. The channel is modeled as a binary-input, erasure multiple access channel, which can be in one of three states-either the channel output is a modulo-sum of the two input symbols, or the channel output equals the input symbol on the first link and an erasure on the second link, or vice versa. The associated state sequence is independent and identically distributed. Unlike previously studied multiple-access channels, the proposed channel is not matched to the modulo-sum function and therefore we expect simple cut-set upper bounds to be far from capacity. In this paper, we establish a new upper bound on the modulo-sum capacity that is tighter than the cut-set bound. The key step in establishing this new bound is to provide suitable side information to the encoders to reduce the setup to a compound multiple-access channel and then capture the tension across multiple receivers required to compute the modulo-sum function. In our lower bound, it suffices to use identical linear codebooks at the two encoders. When a (strictly) causal feedback of the channel state is available to the encoders, we present a simple coding scheme that can achieve a rate larger than our upper bound for the case without feedback. This shows that the modulo-sum capacity is increased with feedback. An extension to the case of lossy reconstruction is also treated briefly.

The Arbitrarily Varying Multiple-Access Channel With Conferencing Encoders

We derive the capacity region of arbitrarily varying multiple-access channels with conferencing encoders for both deterministic and random coding. For a complete description it is sufficient that one conferencing capacity is positive. We obtain a dichotomy: either the channel's deterministic capacity region is zero or it equals the two-dimensional random coding region. We determine exactly when either case holds. We also discuss the benefits of conferencing. We give the example of an AV-MAC which does not achieve any non-zero rate pair without encoder cooperation, but the two-dimensional random coding capacity region if conferencing is possible. Unlike compound multiple-access channels, arbitrarily varying multiple-access channels may exhibit a discontinuous increase of the capacity region when conferencing in at least one direction is enabled.

Coset Codes for Compound Multiple Access Channels With Common Information

Code construction is considered for arbitrary discrete memoryless compound multiple access channels (MACs) with common information. This class of channels includes MACs with/without common messages or with partially cooperating encoders. A construction method of code ensembles based on coset codes is proposed for these channels. Assuming joint maximum likelihood decoding, the performance of the proposed code ensemble is analyzed by deriving a lower bound on error exponents. A condition assuring that codes achieve the capacity region on average is given. It is seen that an elaborate combination of good linear codes gives capacity achieving codes for compound MACs with common messages or with partially cooperating encoders. The use of restricted ensembles with low-density parity check (LDPC) codes as component codes is also discussed. It is shown that a coset code ensemble based on nonbinary regular LDPC codes approaches the random coding exponent, and thus is capacity-achieving.

The Compound Multiple Access Channel With Partially Cooperating Encoders

The goal of this paper is to provide a rigorous information-theoretic analysis of subnetworks of interference networks. We prove two coding theorems for the compound multiple-access channel (MAC) with an arbitrary number of channel states. The channel state information at the transmitters is such that each transmitter has a finite partition of the set of states and knows which element of the partition the actual state belongs to. The receiver may have arbitrary channel state information. The first coding theorem is for the case that both transmitters have a common message and that each has an additional private message. The second coding theorem is for the case where rate-constrained, but noiseless transmitter cooperation is possible. This cooperation may be used to exchange information about channel state information as well as the messages to be transmitted. The cooperation protocol used here generalizes Willems' conferencing. We show how this models base station cooperation in modern wireless cellular networks used for interference coordination and capacity enhancement. In particular, the coding theorem for the cooperative case shows how much cooperation is necessary in order to achieve maximal capacity in the network considered.

Ergodic Fading Interference Channels: Sum-Capacity and Separability

The sum-capacity for specific sub-classes of ergodic fading Gaussian two-user interference channels (IFCs) is developed under the assumption of perfect channel state information at all transmitters and receivers. For the sub-classes of uniformly strong (every fading state is strong) and ergodic very strong two-sided IFCs (a mix of strong and weak fading states satisfying specific fading averaged conditions) the optimality of completely decoding the interference, i.e., converting the IFC to a compound multiple access channel (C-MAC), is proved. It is also shown that this capacity-achieving scheme requires encoding and decoding jointly across all fading states. As an achievable scheme and also as a topic of independent interest, the capacity region and the corresponding optimal power policies for an ergodic fading C-MAC are developed. For the sub-class of uniformly weak IFCs (every fading state is weak), genie-aided outer bounds are developed. The bounds are shown to be achieved by treating interference as noise and by separable coding for one-sided fading IFCs. Finally, for the sub-class of one-sided hybrid IFCs (a mix of weak and strong states that do not satisfy ergodic very strong conditions), an achievable scheme involving rate splitting and joint coding across all fading states is developed and is shown to perform at least as well as a separable coding scheme.

Multiple Multicasts With the Help of a Relay

The problem of simultaneous multicasting of multiple messages with the help of a relay terminal is considered. In particular, a model is studied in which a relay station simultaneously assists two transmitters in multicasting their independent messages to two receivers. The relay may also have an independent message of its own to multicast. As a first step to address this general model, referred to as the compound multiple access channel with a relay (cMACr), the capacity region of the multiple access channel with a “cognitive” relay is characterized, including the cases of partial and rate-limited cognition. Then, achievable rate regions for the cMACr model are presented based on decode-and-forward (DF) and compress-and-forward (CF) relaying strategies. Moreover, an outer bound is derived for the special case, called the cMACr without cross-reception, in which each transmitter has a direct link to one of the receivers while the connection to the other receiver is enabled only through the relay terminal. The capacity region is characterized for a binary modulo additive cMACr without cross-reception, showing the optimality of binary linear block codes, and thus highlighting the benefits of physical layer network coding and structured codes. Results are extended to the Gaussian channel model as well, providing achievable rate regions for DF and CF, as well as for a structured code design based on lattice codes. It is shown that the performance with lattice codes approaches the upper bound for increasing power, surpassing the rates achieved by the considered random coding-based techniques.

Source and Channel Coding for Correlated Sources Over Multiuser Channels

Source and channel coding over multiuser channels in which receivers have access to correlated source side information are considered. For several multiuser channel models necessary and sufficient conditions for optimal separation of the source and channel codes are obtained. In particular, the multiple-access channel, the compound multiple-access channel, the interference channel, and the two-way channel with correlated sources and correlated receiver side information are considered, and the optimality of separation is shown to hold for certain source and side information structures. Interestingly, the optimal separate source and channel codes identified for these models are not necessarily the optimal codes for the underlying source coding or the channel coding problems. In other words, while separation of the source and channel codes is optimal, the nature of these optimal codes is impacted by the joint design criterion.

Compound Multiple-Access Channels With Partial Cooperation

A two-user discrete memoryless compound multiple-access channel (MAC) with a common message and conferencing decoders is considered. The capacity region is characterized in the special cases of physically degraded channels and unidirectional cooperation, and achievable rate regions are provided for the general case. The results are then extended to the corresponding Gaussian model. In the Gaussian setup, the provided achievable rates are shown to lie within some constant number of bits from the boundary of the capacity region in several special cases. An alternative model, in which the encoders are connected by conferencing links rather than having a common message, is studied as well, and the capacity region for this model is also determined for the cases of physically degraded channels and unidirectional cooperation. Numerical results are also provided to obtain insights about the potential gains of conferencing at the decoders and encoders.

Capacity of Interference Channels With Partial Transmitter Cooperation

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Capacity regions are established for several two-sender, two-receiver channels with partial transmitter cooperation. First, the capacity regions are determined for compound multiple- access channels (MACs) with common information and compound MACs with conferencing. Next, two interference channel models are considered: an interference channel with common information (ICCI) and an interference channel with unidirectional cooperation (ICUC) in which the message sent by one of the encoders is known to the other encoder. The capacity regions of both of these channels are determined when there is strong interference, i.e., the interference is such that both receivers can decode all messages with no rate penalty. The resulting capacity regions coincide with the capacity region of the compound MAC with common information. </para>