Sharif Digital Repository

Many applications in wireless networks impose locally distributed traffic on the network. We consider the effect of traffic localization on throughput of large wireless networks in the scaling sense. We show that by careful exploitation of traffic localization, one can enhance the throughput of various schemes in wireless networks. Also, the important case of Small World traffic distribution in wireless networks is addressed. In this type of traffic, in addition to the local traffic, a non-negligible amount of global traffic should be handled by the network. It is shown that a non-negligible amount of network-wide traffic can be tolerated by network without any performance degradation in the... 

We consider one-hop communication in wireless networks with random connections. In the random connection model, the channel powers between different nodes are drawn from a common distribution in an i.i.d. manner. In a wireless network with n nodes, a simple one-hop scheme achieving the throughput scaling of order n 1/3-δ, for any arbitrarily small δ > 0, is proposed. This scheme is based on maximizing the number of successful concurrent transmissions. Such achievable throughput, along with the order n 1/3 upper bound derived by Cui et al., characterizes the throughput of one-hop schemes for the class of connection models with distribution having finite mean and variance  

This paper presents an analytical study of the stable throughput for multiple broadcast sessions in a multi-hop wireless tandem network with random access. Intermediate nodes leverage on the broadcast nature of wireless medium access to perform inter-session network coding among different flows. This problem is challenging due to the interaction among nodes, and has been addressed so far only in the saturated mode where all nodes always have packet to send, which results in infinite packet delay. In this paper, we provide a novel model based on multi-class queueing networks to investigate the problem in unsaturated mode. We devise a theoretical framework for computing maximum stable... 

Designing proper spectrum decision schemes for cognitive radios (CRs) improves spectral usage efficiency as well as CR network throughput. One of the key effecting factors of the CR network throughput is the spectrum sensing sequences of the secondary users (SUs). In this paper, the SUs throughput maximization through appropriately selecting the sensing sequences of the SUs, called sensing matrix (SM), is investigated. More specifically, first the average throughput of the CR network is evaluated for a given SM in the case of error-free channel sensing. Then, an optimization problem is formulated with the aim to maximize the network throughput by finding the optimal SM. In order to avoid... 

Latency-insensitive design (LID) is a correct by-construction methodology for system on chip design that prevents multiple iterations in synchronous system design. However, one problem in the LID is system throughput reduction. In this study, a protocol is proposed to increase the throughput of internal cores in the latency-insensitive systems when there are several repetitive structures. The validation of the protocol is checked for latency equivalency in various system graphs. A shell wrapper to implement the protocol is described and superimposed logic gates for the shell wrapper are formulated. Simulation is performed for 12 randomly generated systems and four actual systems. The... 

In this paper, we propose a new packet routing scheme, i.e., a combined digital and analog network coding scheme (DNC-ANC) suitable for multiple unicast scenario. In this respect, we consider a random access WLAN comprised of single and multi-hop unicast sessions. Then we modify the MAC scheme in order to enable ANC. In order to evaluate the effect of the proposed DNC-ANC scheme analytically, we employ an open queueing network and map the details of MAC as well as routing schemes onto its suitable parameters. By writing the corresponding traffic equations and applying the stability condition, we are able to find the maximum stable throughput for the considered scenario. Finally, we will show... 

The widespread growth of Big Data and the evolution of Internet of Things (IoT) technologies enable cities to obtain valuable intelligence from a large amount of real-time produced data. In a Smart City, various IoT devices generate streams of data continuously which need to be analyzed within a short period of time; using some Big Data technique. Distributed stream processing frameworks (DSPFs) have the capacity to handle real-time data processing for Smart Cities. In this paper, we examine the applicability of employing distributed stream processing frameworks at the data processing layer of Smart City and appraising the current state of their adoption and maturity among the IoT... 

In this paper, we investigate the secrecy throughput for a full-duplex wireless powered communication network. A multi-antenna base station (BS) transmits energy towards nodes all the time and each node harvests energy prior to its transmission time slot. Nodes sequentially transmit their confidential information to the BS in presence of other nodes which are considered as potential eavesdroppers. We derive the secrecy rate and formulate the sum secrecy throughput optimization of all nodes. The optimization variables are the time slot duration and the BS beamforming during different transmission phases. The problem is non-convex and non-trivial. We propose a suboptimal approach in which the... 

Since DCF is the main protocol of accessing other mobile stations in ad hoc networks such as IEEE 802.11 WLANs, a self-controlling method for each station is necessary, called the backoff algorithm. An exponential backoff method has been used in WLANs and significant efforts have been made to analyze its throughput and other important properties such as delay and jitter. In this article, we propose a new backoff algorithm and model it with a discrete-time Markov chain; measuring its saturation throughput under several conditions and several set of parameters which are to be adjusted according to the network condition, with the aim of approaching maximum throughput when stations are... 

In this paper, we propose an analytical framework in order to compute the throughput capacity of a multi-hop ad hoc network with a finite number of mobile wireless nodes. The proposed framework consists of two related queueing networks; a closed BCMP queueing network to represent the mobility model of the wireless nodes and an open BCMP queueing network comprising symmetric M/G/l nodes to represent the multi-hop packet routing process from sources to destinations. In this respect, we consider very simple MAC and routing schemes and then map the related parameters onto several components of the queueing network. By solving the linear traffic equations corresponding to concerned queueing... 

We consider the effect of caching in wireless networks where fading is the dominant channel effect. First, we propose a one-hop transmission strategy for cache-enabled wireless networks, which is based on exploiting multi-user diversity gain. Then, we derive a closed-form result for throughput scaling of the proposed scheme in large networks, which reveals the inherent trade-off between cache memory size and network throughput. Our results show that substantial throughput improvements are achievable in networks with sources equipped with large cache size. We also verify our analytical result through simulations  

In this paper, a novel hard-output detection algorithm for the complex multiple-input multiple-output (MIMO) detectors is proposed, which results in a significant throughput enhancement, a near-ML performance, and an SNR-independent fixed-throughput. Moreover, a high-throughput VLSI implementation is proposed, which is based on a novel method of the node generation and sorting scheme. The proposed design achieves the throughput of 10Gbps in a 0.13 μ CMOS process, which is the highest throughput reported in the literature for both the real and the complex domains. Synthesis results in 90nm CMOS also show that the proposed scheme can achieve the throughput of up to 15Gbps. Moreover, the FPGA... 

Multiplication is an essential operation in cryptographic computations. One of the important finite fields for such computations is the binary extension field. High-throughput low-complexity multiplication architectures lead to more efficient cryptosystems. In this paper, a high-throughput low-complexity unified multiplier for triangular and dual bases is presented, and is referred to as basic architecture. This multiplier enjoys slightly simpler and more regular structure due to use of the mentioned bases. Additionally, structurally improved architectures have been proposed, which have smaller time complexity than basic ones. This is achieved by the use of parallel processing method.... 

In this paper, we evaluate the effect of power randomization on the saturation throughput of a WLAN comprised of four classes of users, corresponding to four access categories (ACs) of IEEE 802.11e EDCA. To this end, we consider a specific number of power levels for all users. By some simplifications, we find the probability distributions for the power levels at each class in order to optimize the saturation throughput of a specific class. We evaluate the effect of such optimization onto the saturation throughput of other ACs as well as the saturation throughput of the whole network. Finally, we present some numerical results to show the effect of our optimization in different conditions  

Cryptographic computation exploits finite field arithmetic and, in particular, multiplication. Lightweight and fast implementations of such arithmetic are necessary for many sensitive applications. This brief proposed a low-complexity systolic Montgomery multiplication over GF(2m). Our complexity analysis shows that the area complexity of the proposed architecture is reduced compared with the previous work. This has also been confirmed through our application-specific integrated circuit area and time equivalent estimations and implementations. Hence, the proposed architecture appears to be very well suited for high-throughput low-complexity cryptographic applications  

In this paper, we evaluate the effect of energy constraints on the performance of a simple network comprised of wireless nodes with energy harvesting capability. In this scenario, wireless nodes contend with each other based on slotted Aloha protocol in order to transmit a packet. Packet transmission occurs provided that enough energy exists in the energy buffer. We propose an analytical model based on a closed queueing network (QN) to include details of data and energy buffers as well as random access MAC protocol. We show how energy limitation affects the MAC design parameters, e.g., contention window size, in order to optimize the performance of the network. Moreover, we evaluate the... 

This paper studies the energy-limited performance of multi-relay networks. Taking the properties of the power amplifiers (PAs) into account, we derive closed-form expressions for the optimal power allocation, the outage probability and the throughput in the cases with a sum consumed energy constraint. Moreover, we analyze the diversity and the multiplexing gains of the PA-aware systems. Finally, we investigate the performance of large-scale multi-relay networks and develop efficient multi-relay systems with low cooperation overhead. The numerical and the analytical results show that the inefficiency of the PAs affects the outage probability and the throughput of the multi-relay systems... 

The use of Spread-Time CDMA for ultrawideband (UWB) wireless communication is proposed and its capability for supporting many high data rate users is investigated. Furthermore we will study a hybrid technique, namely, Spread-Time/Time-Hopping to increase the capacity of the above mentioned technique and simultaneously minimizing the effect of near-far in a typical CDMA system  

In this paper, the TCP retransmission timer adjustment mechanism is approached from the system's theoretic point of view. TCP uses a simple recursive system identification algorithm to capture both time variant and time invariant Internet behavior and provides a dynamic Round-Trip Time (RTT) predictor. Based on real Internet data collection, it is observed that when the retransmission timer is adjusted by using the proposed predictor instead of the traditional RTT estimator, its performance increases significantly  

Interference control is one of the fundamental challenges in resource allocation of femtocell networks that use orthogonal frequency-division multiple access (OFDMA). In this paper, a method is proposed that reduces the interference between femtocells. This method is implemented by the femtocells in a self organizing manner and increases frequency reuse factor. Thus, the network throughput will increase and the fairness between femtocells remains reasonable we also propose a mechanism that can be applied increase the frequency resources assigned to each femtocell. These new frequencies can be used when femtocells require more frequency resources to carry higher traffic loads. Results of...