17-01-2012, 09:15 PM
I WANT COMPLETE ABSTRACT N PPT OF THIS PROJECT
17-01-2012, 09:15 PM
I WANT COMPLETE ABSTRACT N PPT OF THIS PROJECT
18-01-2012, 10:06 AM
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11-08-2012, 04:45 PM
Smart Antenna
smartantennafullreport.doc (Size: 1.13 MB / Downloads: 84) ABSTRACT One of the most rapidly developing areas of communications is “Smart Antenna” systems. This paper deals with the principle and working of smart antennas and the elegance of their applications in various fields such a 4G telephony system, best suitability of multi carrier modulations such as OFDMA etc.., This paper mainly concentrates on use of smart antennas in mobile communications that enhances the capabilities of the mobile and cellular system such a faster bit rate, multi use interference, space division multiplexing (SDMA),increase in range, Multi path Mitigation, reduction of errors due to multi path fading and with one great advantage that is a very high security. The signal that is been transmitted by a smart antenna cannot tracked or received any other antenna thus ensuring a very high security of the data transmitted. This paper also deals the required algorithms that are need for the beam forming in the antenna patters. The applications of smart antennas such as in WI-FI transmitter, Discrete Multi Tone modulation (DMT), OFDMA and TD-SCDMA is already in real world use is also incorporated in this paper. INTRODUCTION: What is a smart antenna? A smart antenna is an array of antenna elements connected to a digital signal processor. Such a configuration dramatically enhances the capacity of a wireless link through a combination of diversity gain, array gain, and interference suppression. Increased capacity translates to higher data rates for a given number of users or more users for a given data rate per user. Multipath paths of propagation are created by reflections and scattering. Also, interference signals such as that produced by the microwave oven in the picture, are superimposed on the desired signals. Measurements suggest that each path is really a bundle or cluster of paths, resulting from surface roughness or irregularities. The random gain of the bundle is called Multipath fading. PRINCPLE OF WORKING: The smart antenna works as follows. Each antenna element "sees" each propagation path differently, enabling the collection of elements to distinguish individual paths to within a certain resolution. As a consequence, smart antenna transmitters can encode independent streams of data onto different paths or linear combinations of paths, thereby increasing the data rate, or they can encode data redundantly onto paths that fade independently to protect the receiver from catastrophic signal fades, thereby providing diversity gain. A smart antenna receiver can decode the data from a smart antenna transmitter this is the highest-performing configuration or it can simply provide array gain o Applications in Mobile Communications: A space-time processor (’smart ‘antenna’) is capable of forming transmit/receive beams towards the mobile of interest. At the same time it is possible to place spatial nulls in the direction of unwanted interferences. This capability can be used to improve the performance of a mobile communication system Increased antenna gain The ’smart’ antenna forms transmit and receive beams. Therefore, the ’smart’ antenna has a higher gain than a conventional omni-directional antenna. The higher gain can be used to either increase the effective coverage, or to increase the receiver sensitivity, which in turn can be exploited to reduce transmit power and electromagnetic radiation in the network. Decreased inter-symbol-interference (ISI) Multipath propagation in mobile radio environments leads to ISI. Using transmit and receive beams that are directed towards the mobile of interest reduces the amount of Multipath and ISI. Decreased co-channel-interference (CCI) ’Smart’ antenna transmitters emit less interference by only sending RF power in the desired directions. Furthermore, ’smart’ antenna receivers can reject interference by looking only in the direction of the desired source. Consequently ’smart’ antennas are capable of decreasing CCI. A significantly reduced CCI can be taken advantage of by Spatial Division Multiple Access (SDMA) o The same frequency band can be re-used in more cells, i.e. the so called frequency re-use distance can be decreased. This technique is called Channel Re-use via Spatial Separation. Spatial Structure Methods: As mentioned before, spatial structure methods exploit the information in the steering vector ..»._¼. The spatial structure is used to estimate the direction of arrivals (DOAs) of the signals impinging on the sensor array. The estimated directions of arrivals are then used to determine the weights in the pattern forming network. This is called beam forming. Spatial structure methods only exploit spatial structure and training signals and the temporal structure of the signals is ignored. In the following an overview will be given about the three main spatial structure methods, namely conventional beam forming methods, maximum likelihood estimation and the so-called subspace-based methods. For simplicity, the vector channel model used here (and everywhere in the array processing literature for spatial structure methods) is a spatial-only vector channel. Future applications are based on “Bearer Services”: Real-time applications like voice, video conferencing or other multimedia applications require minimum delay during the transmission and generate symmetric traffic. This type of communication is nowadays carried via circuit switching systems. For non real-time applications like e-mail, Internet and Intranet access timing constraints are less strict. In addition, the generated traffic is asymmetric. This type of communication is relayed via packet switched systems. Future pattern of use will show a mix of real-time and non real-time services at the same time and same user terminal. Based on the TDD principle, with adaptive switching point between uplink and downlink, TD-SCDMA is equally adept at handling both symmetric and asymmetric traffic. Wireless Multi Media requires high data rates. With data rates of up to 2 Mbit/s TD-SCDMA offers sufficient data throughput to handle the traffic for Multi Media and Internet applications. With their inherent flexibility in asymmetry traffic and data rate TD-SCDMA-based systems offer 3G services in a very efficient way. Although it is optimally suited for Mobile Internet and Multi Media applications, TD-SCDMA covers all application scenarios: voice and data services, packet and circuit switched transmissions for symmetric and asymmetric traffic, pico, micro and macro coverage for pedestrian and high mobility users. CONCLUSION: In conclusion to this paper “Smart Antenna” systems are the antennas with intelligence and the radiation pattern can be varied without being mechanically changed. With appropriate adaptive algorithms such as Recursive Least Square Algorithm (RLS) the beam forming can be obtained. As the system uses a DSP processor the signals can be processed digitally and the performance is with a high data rate transmission and good reduction of mutual signal interference. |
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