Develop of CFO in High Mobility Environments for OFDM-DMWT Based Mobile Wireless Applications

An “Orthogonal Frequency division Multiplexing (OFDM)” systems are sensitive to “service Frequency Offset (CFO)” mistakes. OFDM- “Discrete Multi-wavelet remodel (DMWT)” based totally cellular wireless with a sender, a provider Frequency Offset errors turns into similarly tough for cellular applications in view that power postpone outline of the channel may trade quick because of the sporadic start and dying of the channel paths. We discover analytical expressions for channel estimation mistakes inside the existence of CFO mistakes and excessive mobility. We display that the sensitivity of the channel estimator be capable of still be exploited to increase CFO in high mobility environments. A comparative have a look at amongst extraordinary techniques of service frequency offset estimation in OFDM systems is offered. We keep in mind strategies in frequency area are considered, namely; training image approach and Pilot tone technique. Mean square blunders (MSE) is the evaluation criteria used within the look at. Simulation consequences display that the CFO estimation strategies the schooling image technique outperforms the pilot tone approach with the aid of about 2dB. The contrast results are considered at MSE of 10-4 and normalized CFO of 0.2. Keywords— CFO, ICI, BER, SNR, OFDM, DMWT, MSE, Frequency domain. DOI: 10.7176/NCS/10-04 Publication date:July 31st 201

On bounds and algorithms for frequency synchronization for collaborative communication systems

Cooperative diversity systems are wireless communication systems designed to exploit cooperation among users to mitigate the effects of multipath fading. In fairly general conditions, it has been shown that these systems can achieve the diversity order of an equivalent MISO channel and, if the node geometry permits, virtually the same outage probability can be achieved as that of the equivalent MISO channel for a wide range of applicable SNR. However, much of the prior analysis has been performed under the assumption of perfect timing and frequency offset synchronization. In this paper, we derive the estimation bounds and associated maximum likelihood estimators for frequency offset estimation in a cooperative communication system. We show the benefit of adaptively tuning the frequency of the relay node in order to reduce estimation error at the destination. We also derive an efficient estimation algorithm, based on the correlation sequence of the data, which has mean squared error close to the Cramer-Rao Bound.Comment: Submitted to IEEE Transaction on Signal Processin

Timing synchronization in decode-and-forward cooperative communication systems

Cooperative communication systems have attracted much attention recently due to their desirable performance gain while using single antenna terminals. This paper addresses the joint timing and channel estimation problem, and furthermore the resynchronization of multiple timing offsets in a cooperative relay system. The estimations of timing and channel are conducted in two phases and the associated Cramér-Rao bounds (CRB) are derived for both phases. It is demonstrated that the conventional CRB is not valid for timing parameters under fading conditions, and a new bound called Weighted Bayesian CRB is proposed. With the timing and channel estimates, a general framework of the resynchronization filter design is developed in order to compensate the multiple timing offsets at the destination. The proposed methods are applied to different scenarios with varying degrees of timing misalignment and are numerically shown to provide excellent performances that approach the perfectly synchronized case. © 2009 IEEE.published_or_final_versio

Combined distributed turbo coding and space frequency block coding techniques

The distributed space-time (frequency) coding and distributed channel turbo coding used independently represent two cooperative techniques that can provide increased throughput and spectral efficiency at an imposed maximum Bit Error Rate (BER) and delay required from the new generation of cellular networks. This paper proposes two cooperative algorithms that employ jointly the two types of techniques, analyzes their BER and spectral efficiency performances versus the qualities of the channels involved, and presents some conclusions regarding the adaptive employment of these algorithms. © 2010 V. Bota et al.FP7/ICT/2007/21547

Combined distributed turbo coding and space frequency block coding techniques

The distributed space-time (frequency) coding and distributed channel turbo coding used independently represent two cooperative techniques that can provide increased throughput and spectral efficiency at an imposed maximum Bit Error Rate (BER) and delay required from the new generation of cellular networks. This paper proposes two cooperative algorithms that employ jointly the two types of techniques, analyzes their BER and spectral efficiency performances versus the qualities of the channels involved, and presents some conclusions regarding the adaptive employment of these algorithms. © 2010 V. Bota et al.FP7/ICT/2007/21547

Single and multiple antenna relay-assisted techniques for uplink and downlink OFDM systems

In this paper we propose and assess the performance of relay-assisted schemes designed for both the uplink and downlink OFDM based systems, using efficient distributed space-frequency block coding protocols. We consider the use of an antenna array at the base station and a single antenna at the user terminal. At the relay node we consider either single antenna or an antenna array. We assume that some of the user terminals deployed in a certain area could act as relaying-able terminals for the communication of other users. Two types of relay-assisted protocols are considered: equalize-and-forward and decode-and-forward. The optimal maximum ratio combining coefficients are derived for the proposed relay-assisted schemes. The performance of these cooperative schemes is evaluated under realistic scenarios, considering typical pedestrian scenarios based on WiMAX specifications and using channel convolutional turbo code. The proposed schemes are also compared against the non-cooperative OFDM based systems. +umerical results show that the availability of antenna arrays at the relays significantly improves the cooperative systems performance, which outperform the non-cooperative ones in most studied scenarios

SourceSync: A Distributed Wireless Architecture for Exploiting Sender Diversity

Diversity is an intrinsic property of wireless networks. Recent years have witnessed the emergence of many distributed protocols like ExOR, MORE, SOAR, SOFT, and MIXIT that exploit receiver diversity in 802.11-like networks. In contrast, the dual of receiver diversity, sender diversity, has remained largely elusive to such networks. This paper presents SourceSync, a distributed architecture for harnessing sender diversity. SourceSync enables concurrent senders to synchronize their transmissions to symbol boundaries, and cooperate to forward packets at higher data rates than they could have achieved by transmitting separately. The paper shows that SourceSync improves the performance of opportunistic routing protocols. Specifically, SourceSync allows all nodes that overhear a packet in a wireless mesh to simultaneously transmit it to their nexthops, in contrast to existing opportunistic routing protocols that are forced to pick a single forwarder from among the overhearing nodes. Such simultaneous transmission reduces bit errors and improves throughput. The paper also shows that SourceSync increases the throughput of 802.11 last hop diversity protocols by allowing multiple APs to transmit simultaneously to a client, thereby harnessing sender diversity. We have implemented SourceSync on the FPGA of an 802.11-like radio platform. We have also evaluated our system in an indoor wireless testbed, empirically showing its benefits.National Science Foundation (U.S.) (Award CNS-0831660)United States. Defense Advanced Research Projects Agency. Information Theory for Mobile Ad-Hoc Networks Progra