Sharif Digital Repository

Crosstalk is the major limiting factor in DSL systems in terms of bit-rate or service coverage. Multiuser power control algorithms can be used to combat crosstalk degrading effects. The best ever known distributed power control solution is Iterative Water-filling (IWF). In this paper the performance of IWF in an ADSL system is considered in terms of offered rate-region and convergence speed. Then two novel modifications are proposed to accelerate convergence (usually 100-400%) without any performance loss. Therefore it suits better in practical applications, since each iteration needs re-initialization of the modem. © 2004IEEE  

In this paper the new and improvement approach is suggested for realization of a HF receiver without using equalizer. This approach is based on implementing considerations suggested by [1]. In our approach an HF modem without using equalizer implemented which can communicate over several hundred bits per second with very low bits error rate. This improvement was obtained by changing the framing and the coding structures which has been suggested by [1] and by using the symbol time recovery approach which is proposed by [2]. In this paper, the symbol time recovery approach generalized for multipath fading channels. We implemented our approach on Digital Signal Processor named TMS320F2811.... 

This paper considers the problem of digital data transmission through the Global System for Mobile communications (GSM) for security applications. A data modem is presented that utilizes codebooks of Speech-Like (SL) symbols to transmit data through the GSM Adaptive Multi Rate (AMR) voice codec. Using this codebook of finite alphabet, the continuous vocoder channel is modeled by a Discrete Memory less Channel (DMC). A heuristic optimization algorithm is proposed to select codebook symbols from a database of observed human speech such that the capacity of DMC is maximized. Using the DMC capacity, a lower bound on the capacity of the considered voice channel can be achived. Simulation results... 

This paper considers the problem of digital data transmission through the Global System for Mobile communications (GSM). A data modem is presented that utilizes codebooks of Speech-Like (SL) symbols to transmit data through the GSM Adaptive Multi Rate (AMR) voice codec. Using this codebook of finite alphabet, the continuous vocoder channel is modeled by a Discrete Memory less Channel (DMC). A heuristic optimization algorithm is proposed to select codebook symbols from a database of observed human speech such that the capacity of DMC is maximized. Simulation results show that the proposed data modem achieves higher data rates and lower symbol error rates compared to previously reported... 

The paper aims at investigating the microstructure, failure mode transition, peak load and energy absorption of DP600 dual phase steel during the tensile-shear test. It was found that the welding current has profound effect on the load–displacement characteristics. In the low welding current, welds failed in interfacial failure mode. Increasing welding current resulted in sufficient weld nugget growth to promote double-sided pullout failure mode with improved mechanical properties. Further increase in the welding current caused expulsion and failure mode was changed to single-sided pullout with reduced energy absorption capability. It was found that the fusion zone size is the key parameter... 

The paper aims at investigating the microstructure, failure mode transition, peak load and energy absorption of DP600 dual phase steel during the tensile-shear test. It was found that the welding current has profound effect on the load–displacement characteristics. In the low welding current, welds failed in interfacial failure mode. Increasing welding current resulted in sufficient weld nugget growth to promote double-sided pullout failure mode with improved mechanical properties. Further increase in the welding current caused expulsion and failure mode was changed to single-sided pullout with reduced energy absorption capability. It was found that the fusion zone size is the key parameter... 

In these days, IEEE802.16 protocol is being developed and in the next years, 802.16 modems will be used in every house to connect to the Internet through base-stations in both urban and rural areas. Since user bandwidth for connection to the Internet is limited, a large fraction of each modem's bandwidth is not used. In this paper, we propose an architecture to construct a public peer-to-peer mesh network using the non-utilized bandwidth of independent 802.16 users. The architecture is composed of a routing algorithm, a forwarding incentive mechanism, and a security-resiliency scheme. Design challenges are discussed in each case. © 2009 IEEE