Sharif Digital Repository

We present two compact analytic formulae for calculating the channel number in graphene nanoribbons (GNRs), in terms of GNRs' width and Fermi energy. Numerical data obtained from these analytic formulae fit those obtained numerically from the exact formula, with accuracies within 1%. Using appropriate fit parameters, the compact formulae are valid for zigzag, armchair-metallic, and armchair-semiconducting GNRs, at room, liquid nitrogen, and liquid helium temperatures (i.e. 300, 77 and 4.2 K)  

The Partially Cooperative Relay-Broadcast Channel (PC-RBC) is a generalization of Relay Channel in which the relay node decodes its own private message. In this paper, we introduce a class of parallel PC-RBCs with three unmatched subchannels, in which the first component of the channel is assumed to be degraded, the second to be orthogonal and the third to be deterministic. We characterize the capacity region of this channel for the case where the source sends a private message for each of the users. We also investigate a class of parallel relay channels with three unmatched subchannels, in which the first component of the channel is degraded, the second is orthogonal and the third is... 

Two-user Multiple Access Channel with a Wire- Tapper (MAC-WT) is considered. A general outer bound for the secrecy capacity region is given. Also, we have defined the Deterministic MAC-WT, where the channel input of each user is a deterministic function of the channel output and the channel input of the other user. For this network single-letter inner and outer bounds for the secrecy capacity region are given. Furthermore, it is shown that in the Deterministic MAC-WT, if the wiretapper channel is a degraded version of the main channel, inner and outer bounds meet and the secrecy capacity region is characterized  

A secret key agreement framework involving three users is considered in which each of the users 1 and 2 intends to share a secret key with user 3 and users 1 and 2 are eavesdroppers with respect to each other. There is a generalized discrete memoryless multiple access channel (GDMMAC) from users 1 and 2 to user 3 where the three users receive outputs from the channel. Furthermore, there is a feedback channel from user 3 to users 1 and 2 through which user 3 sends information extracted from the received output from the GDMMAC to increase the key rates. We consider both noiseless and noisy feedback. In the case of noiseless feedback, a public channel of unlimited capacity from user 3 to users... 

In this paper, which is an extended version of our work at LVA/ICA 2010 [1], the problem of Inter Symbol Interface (ISI) Sparse channel estimation and equalization will be investigated. We firstly propose an adaptive method based on the idea of Least Mean Square (LMS) algorithm and the concept of smoothed l0 (SL0) norm presented in [2] for estimation of sparse ISI channels. Afterwards, a new non-adaptive fast channel estimation method based on SL0 sparse signal representation is proposed. ISI channel estimation will have a direct effect on the performance of the ISI equalizer at the receiver. So, in this paper we investigate this effect in the case of optimal Maximum Likelihood... 

In this paper, capacity inner and outer bounds are established for multiuser channels with Channel State Information (CSI) known non-causally at the transmitters: The Multiple Access Channel (MAC), the Broadcast Channel (BC) with common information, and the Relay Channel (RC). For each channel, the actual capacity region is also derived in some special cases. Specifically, it is shown that for some deterministic models with non-causal CSI at the transmitters, similar to Costa's Gaussian channel, the availability of CSI at the deterministic receivers does not affect the capacity region  

In this paper, the impact of a small variations in the channel gains on the secrecy rate of the wiretap channel is studied, in which it is assumed that the imperfect channel knowledge is available at the transmitter. First, we consider general additive noise model for both legitimate and eavesdropper channels in the wiretap channel, and compute the variation of the secrecy rate resulting from the small variations in the channel gains. Then, we focus on the Gaussian wiretap channel, as a special case and calculate the sensitivity of the secrecy capacity to the channel gains with imperfect channel knowledge. Interestingly, it is shown that in some situations the effect of the channel variation... 

In this paper we prove a new capacity upper bound for a class of relay channels known as Relay-With-Delay channels. The proposed bound is general and holds for any arbitrary amount of delay. We have shown that the previously introduced bounds can be considered as special cases of our proposed upper bound. The new introduced bound is, in some cases, tighter than the previously established bounds. It is also notable that the proposed bound coincides with the previously known capacity of "Relay-With-Delay" channels. © 2009 IEEE  

We introduce the concept of quasi-inverse of quantum and classical channels, prove general properties of these inverses and determine them for a large class of channels acting in an arbitrary finite dimension. Thereforewe extend the previous results of Karimipour et al (2020 Phys. Rev. A 101 032109) to arbitrary dimensional channels and to the classical domain. We demonstrate how application of the proposed scheme can increase on the average the fidelity between a given random pure state and its image transformed by the quantum channel followed by its quasi-inversion. © 2021 The Author(s)  

The problem of dephasing channel discrimination is addressed for finite-dimensional systems. In particular, the optimization with respect to input states without energy constraint is solved analytically for qubit, qutrit and ququart. Additionally, it is shown that resorting to side entanglement assisted strategy is completely useless in this case. © 2022 IOP Publishing Ltd  

In this paper, we study two important transmission strategies in full-duplex two-way relaying in the presence of channel estimation errors. In analog network coding (ANC), the relay transmits the combined signals that were received from both sources, with the aim of achieving better spectral efficiency. However, due to imperfect channel-state information (CSI), sources cannot perfectly cancel their own data in the relayed signal. We derive an achievable information rate for ANC in imperfect-CSI conditions and show how the ANC performance can significantly be degraded as a result. Moreover, we derive cut-set bounds with channel estimation errors for traditional routing (TR), in which time... 

The interference channel with a cognitive relay is a variation of the classical two-user interference channel in which a relay aids the transmission among the users. The relay is assumed to have genie-aided cognition: that is it has full, a-priori, knowledge of the messages to be transmitted. We obtain a new outer bound for this channel model and prove capacity for a class of channels in which the transmissions of the two users are non interfering. This capacity result improves on a previous result for the Gaussian case in which the capacity was proved to within a gap of 3 bits/s/Hz  

In this paper, lattice based coding is used over two-user Gaussian state-dependent multiple access channel with common message for two channel models. First, it is assumed that the additive channel interference is noncausally known at both encoders. Exploiting a lattice encoding and decoding scheme, the effect of the interference is completely removed and the capacity region is achieved. Then, the multiple access channel with two additive interferences is considered in the case, where each interference is known noncausally to the associated transmitter. A pure lattice based encoding and decoding structure is proposed and an inner bound on the capacity region is derived which is valid for the... 

In this paper, the Two-Way Channel (TWC) with noncausal Channel State Information (CSI) is investigated. For the discrete memoryless channel an achievable rate region is derived. Then by extending the result to the Gaussian TWC with additive interference noise, it is shown that the capacity region of the latter channel is the same as the capacity when there is no interference, i.e., a two-way version of Costa's writing on dirty paper problem is established  

The authors propose a new technique to model the arriving energy's knowledge (AEK) in the energy harvesting (EH) communication systems. They consider a batteryless EH transmitter with the AEK non-causally provided to it. They show that the capacity of the authors' model in general case, that is, discrete memoryless channel, can be derived through a binning scheme. This resembles a Gelfand-Pinsker type capacity formula which intuitively is the result of treating the energy as a channel state. Moreover, they investigate two especial cases of binary and Gaussian channels with the EH transmitters. In the binary symmetric channel with EH transmitter (BSCEH), their coding scheme leads to achieve... 

A pipelined architecture is developed for a Sequential Monte Carlo (SMC) receiver that performs joint channel estimation and data detection. The promising feature of the proposed SMC receiver is achieving the near-bound performance in fading channels without using any decision feedback, training or pilot symbols. The proposed architecture exploits the parallelism intrinsic to the algorithm and consists of three blocks, i.e., the SMC core, weight calculator, and resampler. Hardware efficient/parallel architectures for each functional block including the resampling block is developed. The novel feature of the proposed architecture is that makes the execution time of the resampling independent... 

The authors consider 'partially' and 'fully cooperative' state-dependent relay broadcast channels (RBCs), where partial channel state information (CSI) is available at the nodes causally. First, the authors derive an achievable rate region for general discrete memoryless partially cooperative RBC (PC-RBC) with partial causal CSI, by exploiting superposition coding at the source, decode-and-forward scheme at the relay and Shannon's strategy at the source and the relay. Then, they establish the capacity region of the discrete memoryless physically degraded PC-RBC with partial causal CSI. They also characterise the capacity region of discrete memoryless PC-RBC with feedback and partial causal... 

In this letter, we consider two problems of sending a bivariate Gaussian source through a two-user Gaussian non-orthogonal multiple-access channel. We provide a new distortion outer bound for the considered joint source-channel coding problems, which significantly reduces the gap between inner and outer bounds of the distortion for correlation coefficients below a threshold. Furthermore, numerical results show, that under some conditions, our proposed outer bound matches with the inner bound obtained via the separate source-channel coding scheme, which proves the optimality of this scheme. © 1997-2012 IEEE