Beam-forming Technique in which the gain pattern of an adaptive array is steered to a desired direction through either beam steering or null steering signal processing algorithms Adaptive beam forming algorithms can provide substantial gains (of Antenna Pattern of 7-element the order of 10log(M) dB, where M uniform equally spaced is number of array elements) circular array.
Adaptive Beam-forming An adaptive beam former is a device that is able to separate signals co-located in the frequency band but separated inthe spatial domain. This providesa means for separating the desired signal from interfering signals. A two element adaptive array for interference suppression
Switched beam Consists of a set of predefined beams. Allows selection of signal from desired user. Beams have narrow main lobe & small side lobes. Signals received from side lobes can be significantly attenuated. Uses a linear RF network called Fixed Beam-forming network that combines M antenna elements to form up-to M directional beams.
Dynamically phased array :Consists of either a number of fixed beams with one beam turned on towards the desired signal or a single beam (formed by phase adjustment only) that is steered toward the desired signal.
Dynamically phased array : A Direction of arrival algorithm(DoA) tracks the user’s signal as he roams within the range of that beam that is tracking him Generalization of switched beam concept where received power is maximized. More efficient than Switched beam system
What is DoA?The goal of direction-of-arrival (DoA) estimation is to use the data received on the downlink at the base-station sensor arrayto estimate the directions of the signals from the desired mobile users as well as the directions of interference signals.
Types of Dynamically phased array Time domain beamformers: Delays the incoming signal from each array element by a certain amount of time & then adds them. Frequency domain beamformers: Different frequencies are separated. Applying different sum & delay to each frequency it is possible to point out the main lobe.
Application Mobile Communication GSM CDMA Wireless Communication Aerospace Application. IS-136 SDMA EDGE
Mobile Communication Improved services. Advanced mobile phone system(AMPS). Advanced TDMA. User friendly services.
GSM (Global system for Mobile Communication) Mainly used in the base station. Full beam adaptation in uplink & downlink. Bit rate of 1% Carrier interference of -14 db.
CDMAFeatures Diversity Cellular Antennas with 800/1900 MHz bands High accuracy GPS receiver Supports UART and/or USB interfacesBenefits Designed for easy internal integration no need of SIM card Provides integrators with a network pre-approved communication device Fleet Management and diagnostics In-dash Internet access General Automotive Aftermarket
Wireless Communication Over come the limitations of omni-directional antenna. Secterized antenna and coverage pattern.
Aerospace Application Smart antenna adapts the electromagnetic condition. Increase of antenna gain Airborne satellite communication. Reliable source of communication.
SDMA Spatial Division Multiple Access Uses an array of antennas to provide control of space Network planning (frequency) is simpler More network management upgrade required
IS-136 TDMA with 3 users per channel 162 symbols/slot 14 symbol synchronization sequence Two receive antennas at base
Smart antennas in generation 3 rd systems: EDGE High data rate ( 384 kbps) service based on GSM, for both Europe and North America BPSK at 270.833 kbps 26 symbol training sequence 3 58 26 58 3 8.25 576.92 s
Advantages of smart antenna Both phased and adaptive arrays provide increased power by providing higher gain for the desired signal. In terms of interference suppression, phased arrays reduce the probability of interference with the narrower beam, and adaptive arrays adjust the beam pattern to suppress interference.
Conclusion The use of smart antennas is not purely a radio transmission issue. It also influences network services such as handover and connection setup. A smart antenna is a digital wireless communications antenna system that takes advantage of diversity effect at the source (transmitter), the destination (receiver), or both.
Reference G. K. Chan, “Effects of Sectorization the Spectrum Efficiency of Cellular Radio systems,” Transaction on Vehicular Technology, pp.217-225, vol.41, no.3, Aug 1992. M. G. Jansen, R. Prasad, “Capacity, Throughput, and Delay Analysis of a Cellular DS CDMA System with Imperfect Power Control and Imperfect Sectorization,” Transaction on Vehicular Technology, pp.67-75, vol.44, no.1, Feb 1995. X. Yang, S. Ghaheriand N. R. Tafazolli, “Sectorization Gain in CDMA Cellular Systems,” First Conference on 3G Mobile Communication Technologies, pp.70-75, 2000.