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Communication and Information Theory (IWCIT), 2013 Iran Workshop on

Date 8-9 May 2013

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Displaying Results 1 - 25 of 31
  • List of authors

    Publication Year: 2013 , Page(s): 1 - 3
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  • 2013 Iran Workshop on Communication and Information Theory [Copyright notice]

    Publication Year: 2013 , Page(s): 1
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  • [Front cover]

    Publication Year: 2013 , Page(s): 1
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  • Key agreement over a state-dependent 3-receiver broadcast channel

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB) |  | HTML iconHTML  

    In this paper, we consider the problem of secret key agreement in state-dependent 3-receiver broadcast channels. In the proposed model, there are two legitimate receivers, an eavesdropper and a transmitter where the channel state information is non-causally available at the transmitter. We consider two setups. In the first setup, the transmitter tries to agree on a common key with the legitimate receivers while keeping it concealed from the eavesdropper. Simultaneously, the transmitter agrees on a private key with each of the legitimate receivers that needs to be kept secret from the other legitimate receiver and the eavesdropper. For this setup, we derive inner and outer bounds on the secret key capacity region. In the second setup, we assume that a backward public channel is available among the receivers and the transmitter. Each legitimate receiver wishes to share a private key with the transmitter. For this setup, an inner bound on the private key capacity region is found. Furthermore, the capacity region of the secret key in the state-dependent wiretap channel can be deduced from our inner and outer bounds. View full abstract»

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  • A network coding-based packet forwarding scheme for unicast random access networks with exponential backoff

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    Exponential backoff is an intrinsic feature of MAC-layer standards of most types of ad hoc networks. It leads to random access channels with memory. In this paper we propose a new network coding-based packet forwarding scheme suitable for multiple unicast scenarios in downlink direction of a wireless network. The wireless nodes as well as the access point attempt to access the channel, based on slotted Aloha with exponential backoff. In the proposed scheme we convert multiple unicast scenario to a combination of several anycast and a multicast scenarios. By proposing an open multiclass queueing network, we are able to derive the maximum stable download throughput of the network. The superiority of the proposed scheme compared to simple forwarding scheme as well as the optimum scheme recently proposed for memoryless channels is shown in different conditions. Simulation results confirm our analytical approach. View full abstract»

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  • Multi-layer Gelfand-Pinsker strategies for the generalized multiple-access channel

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB) |  | HTML iconHTML  

    We study a two-user state-dependent generalized multiple-access channel (GMAC) with correlated states. It is assumed that each encoder noncausally knows partial channel state information. We develop an achievable rate region by employing rate-splitting, block Markov encoding, Gelfand-Pinsker multicoding, superposition coding and jointly typical decoding. In the proposed scheme, the encoders use a partial decoding strategy to collaborate in the next block, and the receiver uses a backward decoding strategy with a joint unique decoding at each stage. Our achievable rate region includes several previously known rate regions proposed in the literature for different scenarios of multiple-access and relay channels. We finally consider a Gaussian GMAC with an additive interference which is known noncausally at both of the encoders and construct a multi-layer Costa precoding scheme that removes completely the effect of the interference. View full abstract»

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  • Perfect secrecy via compressed sensing

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (145 KB) |  | HTML iconHTML  

    In this paper we consider the compressive sensing based encryption and proposed the conditions in which the perfect secrecy is achievable. We prove that when the measurement matrix holds the Restricted Isometry Property (RIP) and the number of measurements is more than two times of the sparsity level, i.e., M ≥ 2k, the Shannon perfect secrecy condition is achievable either i) the cardinality of the message set tends to infinity or ii) the message set does not include the zero message. As an implicit assumption, we suppose that the eavesdropper has not access to the secret key during the transmission. View full abstract»

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  • Interference channel with common message and Slepian-Wolf channel state information

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (281 KB) |  | HTML iconHTML  

    In this paper, the two-user interference channel (IC) with specially correlated sources and channel state information (CSI), both in the sense of Slepian-Wolf (SW) is considered in which channel states are available at the encoders non-causally. In correlation structures in the sense of Slepian-Wolf, two correlated sources are modeled by three independent sources: a common source and two private sources. Therefore, we can call this channel as the IC with common message (ICC) and Slepian-Wolf CSI (ICCSWCSI). We derive an achievable rate region for this channel by using rate splitting technique, superposition coding, binning scheme and jointly decoding; then we show that our rate region subsumes some related rate regions for the IC with or without non-causal CSI as its special cases. View full abstract»

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  • On dimension bounds for quantum systems

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    Expressions of several capacity regions in quantum information theory involve an optimization over auxiliary quantum registers. Evaluating such expressions requires bounds on the dimension of the Hilbert space of these auxiliary registers, for which no non-trivial technique is known; we lack a quantum analog of the Caratheodory theorem. We argue in this paper that developing a quantum analog of the Caratheodory theorem requires a better understanding of “quantum convexification.” We then proceed by proving a few results about quantum convexification. To prove one of these results, we develop a new non-Caratheodory-type tool which might be useful for bounding the dimension of quantum registers as well as the cardinality of auxiliary classical random variables. View full abstract»

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  • Mathematical modeling of nonlinearity impairments in optical OFDM communication systems using multiple optical phase conjugate

    Publication Year: 2013 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (242 KB) |  | HTML iconHTML  

    In this paper, we present a mathematical model for the idea of using more than one optical phase conjugate (OPC) module for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems in long-haul fiber optic channels. The four-wave mixing (FWM) formulation is derived for three different scenarios in which different numbers of OPC modules are used. The simulation results reveal that using more than one OPC modules leads to a much better BER performance operating on a typical OFDM system. View full abstract»

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  • Optimal power and rate allocation in the degraded Gaussian relay channel with energy harvesting nodes

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    Energy Harvesting (EH) is a novel technique to prolong the lifetime of the wireless networks such as wireless sensor networks or Ad-Hoc networks, by providing an unlimited source of energy for their nodes. In this sense, it has emerged as a promising technique for Green Communications, recently. On the other hand, cooperative communication with the help of relay nodes improves the performance of wireless communication networks by increasing the system throughput or the reliability as well as the range and efficient energy utilization. In order to investigate the cooperation in EH nodes, in this paper, we consider the problem of optimal power and rate allocation in the degraded full-duplex Gaussian relay channel in which source and relay can harvest energy from their environments. We consider the general stochastic energy arrivals at the source and the relay with known EH times and amounts at the transmitters before the start of transmission. This problem has a min-max optimization form that along with the constraints is not easy to solve. We propose a method based on a mathematical theorem proposed by Terkelsen [1] to transform it to a solvable convex optimization form. Also, we consider some special cases for the harvesting profile of the source and the relay nodes and find their solutions efficiently. View full abstract»

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  • Towards optimization of toeplitz matrices for compressed sensing

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (382 KB) |  | HTML iconHTML  

    Compressed sensing is a new theory that samples a signal below the Nyquist rate. While Gaussian and Bernoulli random measurements perform quite well on the average, structured matrices such as Toeplitz are mostly used in practice due to their simplicity. However, the signal compression performance may not be acceptable. In this paper, we propose to optimize the Toeplitz matrices to improve its compression performance to recover sparse signals. We establish the optimization on minimizing the coherence of the measurement matrix by an intelligent optimization method called Particle Swarm Optimization. Our simulation results show that the optimized Toeplitz matrix outperforms the non-optimized one in reconstructing sparse signals in terms of quality and sampling rate. View full abstract»

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  • Channel coding adoption versus increasing sensing time in secondary service to manage the effect of imperfect spectrum sensing in cognitive radio networks

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    In this paper we consider an overlay cognitive network in which to guarantee a Quality of Service (QoS) for the primary users, a maximum probability of collision is enforced to secondary service. When collision, caused by imperfect spectrum sensing, happens, it results in increasing error rate in both primary and secondary systems. While such degradation in primary service conforms with QoS requirements of that service, this may not be acceptable from secondary user perspective. Such degradation can be dealt with in secondary service either by employing channel coding techniques at the expense of effective rate reduction or increasing the sensing time to reduce the collision probability. This results in the reduction of the data transmission time which also results in the reduction of effective data rate for secondary users. In this paper, we compare these two cases and show that using rate-compatible Low-Density Parity-Check codes, the effective data rate for the coded case can be significantly more than that of the case without channel coding while exhibiting a considerably better performance. View full abstract»

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  • An achievable rate region for interfering multiple access channel and broadcast channel with a cognitive transmitter

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (190 KB) |  | HTML iconHTML  

    We consider the inter-cluster cognitive behavior of two dissimilar interfering clusters, where the first cluster (i.e. primary cluster) consists of a single multiple access channel (MAC) with two senders and one receiver and the second cluster (i.e. cognitive cluster) is a broadcast channel (BC) which has a single sender and two receivers. The BC is assumed to have cognitive transmitter, who knows the messages transmitted by the other non-cognitive multiple access transmitters, in a non-causal manner. A Gel'fand-Pinsker coding-like technique is used to mitigate inter-cluster interference. An achievable rate region for this model is derived based on the Marton region with common message for the general BC and using a result of Slepian-Wolf rate region for the MAC. View full abstract»

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  • On the performance of 1-level LDPC lattices

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    The low-density parity-check (LDPC) lattices perform very well in high dimensions under generalized min-sum iterative decoding algorithm. In this work, we focus on 1-level LDPC lattices. We show that these lattices are the same as lattices constructed based on Construction A and low-density lattice-code (LDLC) lattices. In spite of having slightly lower coding gain, 1level regular LDPC lattices have remarkable performances. The lower complexity nature of the decoding algorithm for these type of lattices allows us to run it for higher dimensions easily. Our simulation results show that a 1-level LDPC lattice of size 10000 can work as close as 1.1 dB at normalized error probability (NEP) of 10-5.This can also be reported as 0.6 dB at symbol error rate (SER) of 10-5 with sum-product algorithm. View full abstract»

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  • Alamouti coding scheme for cooperative relay networks with full duplex relaying

    Publication Year: 2013 , Page(s): 1 - 4
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    In this paper we propose a distributed Alamouti coding scheme for cooperative network in full-duplex (FD) mode as an application of well-known Alamouti code. The proposed scheme benefits from linear decoding complexity and due to the FD mode, has increase in system rate in comparison with using half-duplex (ED) mode. The residual loop interference signal come from the relay's transmitter is added to the signal received from source in the relay's receiver. This unwanted signal because of participating several fading can be consider as a noise term in the destination. So the Alamouti code is constructed in the destination due to an acceptable approximation. Finally simulation results will approve the accuracy and capability of the proposed scheme while it is compared with previous distributed Alamouti code in ED mode. View full abstract»

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  • Delay analysis and buffer management for random access in cognitive radio networks

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (159 KB) |  | HTML iconHTML  

    In this paper, we consider a cognitive radio network in which multiple Secondary Users (SUs) contend to access primary network's channels with a random access scheme. Our goal is to analyze SUs' queuing delay performance in terms of mean queue lengths and find a minimum buffer space for which the overflow probability is less than a desired threshold. In general, the considered network can be modeled as a multidimensional Markov chain. However, the enormous state space makes the numerical analysis intractable. Nevertheless, the state space can be reduced to a two-dimensional Markov chain in the symmetric channel condition. By this approach, the optimal contention probability that minimizes mean queue lengths is obtained. Besides, we find the minimum buffer space to meet the desired overflow probability. Average queue lengths from simulations are compared with expected queue lengths obtained by analysis. Simulation results show that these two quantities are close to each other for different packet arrival rates and we can meet the overflow probability condition by the proposed buffer space. View full abstract»

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  • On the performance of polar codes for lossy compression of Gaussian sources

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (161 KB) |  | HTML iconHTML  

    In this work, we study the lossy source coding of a Gaussian source with polar codes. We show through two distributions on discrete alphabet, quantized approach as well as Central Limit Theorem (CLT) approach, when the alphabet size grows to infinity, polar codes can achieve the rate distortion bound for a Gaussian source. By comparing the rate of convergence on two distributions, we show that the quantized approach have a better convergence rate than the CLT approach. View full abstract»

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  • Network delay analysis of a (σ, ρ) - Regular traffic stream over multiple paths in a network of fair-queuing servers

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    In this paper, we analyze the worst-case delay performance of a network of fair queuing servers in case of multiple-paths between source-destination pairs. In order to develop worst-case delay analysis for the multiple-path scenario, two challenging events should be addressed: merging different sub-streams of a session as well as distributing a traffic stream among different paths (traffic partitioning). Specifically, we propose to merge incoming sub-streams of a session to a node according to a limited rate Fair Queuing (FQ) scheme. Although the merged stream is treated as a unity, this approach results in a guaranteed level of service to each sub-stream. In addition, an algorithm is proposed for partitioning of a traffic stream into multiple sub-streams. Upon presented algorithms in this paper and their performance analysis, an equivalent worst-case service curve is concluded for the paths between a source-destination pair. According to the achieved service curve, an integrated upper bound on the end to end delay of a (σ, ρ)-regular traffic stream is derived in case of multi-path routing scenario. View full abstract»

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  • Finite-SNR diversity-multiplexing tradeoff in multi-relay channels

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (314 KB) |  | HTML iconHTML  

    In this paper, we investigate the diversity-multiplexing tradeoff (DMT) for multi-relay channels in finite-SNR regime. In our analysis, we consider the decode and forward (DF) relaying strategy and a line of sight path from source to destination. First, we determine the outage probability in a multi-relay scenario and obtain its exact analytical expressions. Then, the outage probability of a multi-relay channel with relay selection is calculated and provided as a closed-form expression. Based on these results, we determine the DMT in finite-SNR regime. Finally, using simulation results, we show that our analysis has accurate results which coincides with that of obtained from Monte-Carlo simulation. View full abstract»

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  • Degrees of freedom in a three-user cognitive interference channel

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (309 KB) |  | HTML iconHTML  

    We study the degrees of freedom of the three-user Gaussian interference channel under the circumstance where one or more transmitters are non-causally cognitive, meaning they are aware of the messages of one or more transmitters in a non-causal manner. Our focus is on the total degrees of freedom of the three-user cognitive interference channel. Our first case is when only one of the transmitters is fully cognitive and knows the messages of the other users. We prove that using interference alignment and interference cancellation, the achievable total degrees of freedom is 116 and does not coincide with the calculated total degrees of freedom upper bound which is 2. In the second and third cases, while one transmitter is fully cognitive, another one is partially cognitive and only knows the message of one other user and one user is non-cognitive. We prove that the achievable total degrees of freedom in both of these channels is 2, using a linear combination of messages in the transmitters, which results in interference alignment and interference cancellation in the receivers. In the second case, our calculated upper bound for total degrees of freedom coincides with the achievable total degrees of freedom but in the third case the upper bound is 3. View full abstract»

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  • Secure noisy network coding

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB) |  | HTML iconHTML  

    In this paper we use the Output Statistics of Random Binning (ORSB) framework to extend the noisy network coding of Lim et to. to include an eavesdropper. View full abstract»

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  • On the secrecy capacity of cooperative wiretap channel

    Publication Year: 2013 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (226 KB) |  | HTML iconHTML  

    Secure communications using physical layer characteristics has attracted many attentions in recent years. Secrecy capacity of communication systems can be increased by using multiple-antenna nodes. In this paper, we concentrate on the cooperative wiretap channel in which confidential messages are sent from a source to a legitimate receiver with the help of a relay in the presence of an eavesdropper. We study the secrecy capacity of Amplify and Forward (AF) relaying under peak power constraint at the relay node. To this end, we first evaluate an achievable secrecy rate for Gaussian input by solving a nonconvex optimization problem. Then, we prove the converse by using the secrecy capacity of genie-aided channel as an upper bound of the secrecy capacity of interested channel. We show that this upper bound is achievable and equal to achievable secrecy rate of Gaussian input. View full abstract»

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  • On expected capacity of multicarrier frequency hopping systems

    Publication Year: 2013 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (223 KB) |  | HTML iconHTML  

    Multicarrier frequency hopping (MCFH) modulation is a multicarrier modulation technique, which unlike orthogonal frequency division multiplexing (OFDM), does not require centralized frequency assignment. In a MCFH system, the available bandwidth is divided into subbands, which respectively are divided into subchannels. The transmitter randomly selects one subchannel from each subband, and simultaneously transmits data over the chosen subchannels. In this paper we study the uplink performance of multicarrier frequency hopping systems over slow fading channels. We model users spatial distribution by a homogeneous Poisson point process (PPP), and study the expected capacity of such systems. Through our numerical simulations, we show how optimizing the system parameters such as the number of subbands can increase the systems throughput. View full abstract»

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  • Extended polar codes perform better in terms of compound rate and scaling behavior

    Publication Year: 2013 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (345 KB) |  | HTML iconHTML  

    Polar codes provably achieve the capacity of a wide array of channels under successive decoding. However, in terms of some practical aspects, these codes do not perform optimally and need further improvement. In this paper, we consider two such aspects: universality and finite-length scaling. We argue analytically that for extensions of polar codes that are based on ℓ × ℓ matrices, these aspects become optimal as ℓ grows large. View full abstract»

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