Techniques are described for efficiently estimating and compensating for the effects of a communication channel in a multi-carrier wireless communication system. The techniques exploit the fact that the transmitted symbols are drawn from a finite-alphabet to efficiently estimate the propagation channel for multi-carrier communication systems, such systems using OFDM modulation. A transmitter transmits data through a communication channel according to the modulation format. A receiver includes a demodulator to demodulate the data and an estimator to estimate the channel based on the demodulated data. The channel estimator applies a power-law operation to the demodulated data to identify the channel. The techniques can be used in both blind and semi-blind modes of channel estimation.

Channel estimation for wireless ofdm systems

This chapter contains sections titled: Introduction Overview of Multicarrier CDMA Systems Channel Model Performance of MC-CDMA System Performance of Overlapping Multicarrier DS-CDMA Systems Performance of Multicarrier DS-CDMA-I Systems Performance of AMC DS-CDMA Systems Performance of SFH/MC DS-CDMA Systems Chapter Summary and Conclusion 
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Overview of Multicarrier CDMA

Methods and systems for transmitting uplink control information and feedback are disclosed for carrier aggregation systems. A user equipment device may be configured to transmit uplink control information and other feedback for several downlink component carriers using one or more uplink component carriers. The user equipment device may be configured to transmit such data using a physical uplink control channel rather than a physical uplink shared channel. The user equipment device may be configured to determine the uplink control information and feedback data that is to be transmitted, the physical uplink control channel resources to be used to transmit the uplink control information and feedback data, and how the uplink control information and feedback data may be transmitted over the physical uplink control channel.

Uplink control data transmission

A method and apparatus for allocating subcarriers in an orthogonal frequency division multiple access (OFDMA) system is described. In one embodiment, the method comprises allocating at least one diversity cluster of subcarriers to a first subscriber and allocating at least one coherence cluster to a second subscriber.

Ofdma with adaptive subcarrier-cluster configuration and selective loading

This overview portrays the evolution of orthogonal frequency division multiplexing (OFDM) research. The amelioration of powerful multicarrier OFDM arrangements with multiple-input multiple-output (MIMO) systems has numerous benefits, which are detailed in this treatise. We continue by highlighting the limitations of conventional detection and channel estimation techniques designed for multiuser MIMO OFDM systems in the so-called rank-deficient scenarios, where the number of users supported or the number of transmit antennas employed exceeds the number of receiver antennas. This is often encountered in practice, unless we limit the number of users granted access in the base station's or radio port's coverage area. Following a historical perspective on the associated design problems and their state-of-the-art solutions, the second half of this treatise details a range of classic multiuser detectors (MUDs) designed for MIMO-OFDM systems and characterizes their achievable performance. A further section aims for identifying novel cutting-edge genetic algorithm (GA)-aided detector solutions, which have found numerous applications in wireless communications in recent years. In an effort to stimulate the cross pollination of ideas across the machine learning, optimization, signal processing, and wireless communications research communities, we will review the broadly applicable principles of various GA-assisted optimization techniques, which were recently proposed also for employment in multiuser MIMO OFDM. In order to stimulate new research, we demonstrate that the family of GA-aided MUDs is capable of achieving a near-optimum performance at the cost of a significantly lower computational complexity than that imposed by their optimum maximum-likelihood (ML) MUD aided counterparts. The paper is concluded by outlining a range of future research options that may find their way into next-generation wireless systems.

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Multiuser MIMO-OFDM for Next-Generation Wireless Systems

A method of transmitting data across an electronic data communication system comprising a plurality of terminals that can send and receive data in the form of electromagnetic waves to and from at least one of the terminals, which method comprises the steps of: (a) identifying at least one control terminal, at least one target terminal and at least two relaying terminals from the plurality of terminals; and (b) using the control terminal to instruct the at least two relaying terminals to receive and relay data intended for the at least one target terminal, so that the at least one target terminal can receive data directly from at least one terminal and from the at least two relaying terminals, thereby increasing capacity of the system.

Virtual antenna array

Electronic data communication system

Spatial diversity is a widely applied technique for enhancing wireless system performance since it greatly reduces the detrimental effects of multipath fading. Space-time block codes have been considered the best choice for transmit diversity in narrowband environments, but their use in broadband channels is questionable due to their inability to pick up multipath diversity. However, when used in conjunction with an MC-CDMA system, they achieve not only full spatial but also variable multipath diversity depending on the employed spreading. In comparison, cyclic delay diversity is an attractive approach to achieve spatial and multipath diversity. Its simplicity and conformability with current standards makes it desirable for multicarrier systems. Previous studies suggest that CDD is only advantageous with an outer channel code for OFDM systems. In this article, we compare STBCs and CDD applied to an MC-CDMA system in terms of complexity and performance. It is shown that for an MC-CDMA system, CDD benefits from spreading and channel coding that makes it very competitive with STBCs, particularly since it is applicable to any number of transmit antennas with no loss in rate.

Performance comparison of space-time block coded and cyclic delay diversity MC-CDMA systems

A method of operating a cellular communications system comprising at least one macro cell having a macro cell base station and at least one micro cell having a micro cell base station, at least part of the micro cell being located within an area served by the macro cell base station, which method comprises the steps of: (I) receiving an electronic indication representative of the quality of service at one or more cellular communications devices served by the macro cell base station; (2) electronically processing the or each electronic indication to obtain a comparison with a predetermined threshold for said quality of service; and (3) electronically controlling signals emitted from the micro cell base station in response to said comparison such that the quality of service of any cellular communication device(s) served by the macro cell base station that are within a predetermined range of the micro cell base station exceeds said predetermined threshold so as to permit the transmission and reception of data in the micro and macro cells on substantially the same frequency band(s).

Cellular communications systems

In this paper we have done performance comparisons of mobile ad hoc network's protocol with its quality of service factors. It is seen that mobile ad hoc networks will be an integral part of next generation networks because of its flexibility, infrastructure less nature, ease of maintenance, auto configuration, self administration capabilities, and costs effectiveness. This research paper shows comparison within mobile ad hoc networks' routing protocols from reactive, proactive and hybrid categories. We comprehensively analyzed the results of simulation for

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Fatin Said

Papers

Virtual antenna array

Electronic data communication system

Performance comparison of space-time block coded and cyclic delay diversity MC-CDMA systems

Cellular communications systems

Mobile Ad Hoc Networks Simulations Using Routing Protocols for Performance Comparisons