L. C. Godara, "Applications of Antenna Arrays to Mobile Communications, Part II: Beam-Forming and Direction-Of-Arrival Considerations," Proceedings of the IEEE, vol. 85, no. 8, pp. 1195--1245, August 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....to make the antenna response to energy emanating from certain directions more sensitive than others. Until recently most of the research on antenna arrays for beamforming has dealt with beamformers at the receiver. Transmit beamformers behave di#erently and require di#erent algorithms and hardware [32]. Methods of beamforming at the receive antenna array currently in use are based on array processing algorithms for signal copy, direction finding and signal separation [32] These include Applebaum Frost beamforming, null steering beamforming, optimal beamforming, beam space Processing, blind ....

....dealt with beamformers at the receiver. Transmit beamformers behave di#erently and require di#erent algorithms and hardware [32] Methods of beamforming at the receive antenna array currently in use are based on array processing algorithms for signal copy, direction finding and signal separation [32]. These include Applebaum Frost beamforming, null steering beamforming, optimal beamforming, beam space Processing, blind beamforming, optimum combining and maximal ratio combining [15, 32, 64, 68, 69, 74, 80] Many of these beamformers require a reference signal and use adaptive algorithms to ....

[Article contains additional citation context not shown here]

L. C. Godara, "Applications of antenna arrays to mobile communications and part i: Performance improvement and feasibility and and system considerations," IEEE Proceedings, vol. 85, no. 7, pp. 1031--1060, July 1997. 181

....In this thesis, we will concentrate on spatial diversity resulting from deployment of multiple antennas. Spatial diversity, at the receiver (multiple antennas at the receiver) or at the transmitter (multiple antennas at the transmitter) can improve link performance in the following ways [31] 1. Improvements in spectrum e#ciency: Multiple antennas can be used to accommodate more than one user in a given spectral bandwidth. 2. Extension of range coverage: Multiple antennas can be used to direct the energy of a signal in a given direction and hence minimize leakage of signal energy. ....

L. C. Godara, "Applications of antenna arrays to mobile communications and part ii: Beamforming and direction-of-arrival considerations," IEEE Proceedings, vol. 85, no. 8, pp. 1195-- 1245, August 1997.

....on each branch of a broadband beamformer before combining. In both cases, various design criteria can be applied to compute the beamformer coecients such as minimization of mean square error, maximization of output SNR, maximization of signal to interference and noise ratio (SINR) etc. [86, 87]. Recently there has been an increasing interest in communication systems with both transmit and receive diversity. It is shown in [88 92] that deploying multiple antennas at either or both ends of the channel increases the capacity in the presence of fading and Gaussian noise. A major conclusion ....

L.C. Godara, \Application of antenna arrays to mobile communications. II. Beam-forming and direction-of-arrival considerations," Proc. IEEE,vol. 85, no. 8, pp. 1195-245, July 1997.

....on each branch of a broadband beamformer before combining. In both cases, various design criteria can be applied to compute the beamformer coecients such as minimization of mean square error, maximization of output SNR, maximization of signal to interference and noise ratio (SINR) etc. [86, 87]. Recently there has been an increasing interest in communication systems with both transmit and receive diversity. It is shown in [88 92] that deploying multiple antennas at either or both ends of the channel increases the capacity in the presence of fading and Gaussian noise. A major conclusion ....

L.C. Godara, \Applications of antenna arrays to mobile communications. I. Performance improvement, feasibility, and system considerations," Proc. IEEE, vol. 85, no. 7, pp. 1031-60, July 1997.

....in the network access points of a system but also in the terminals. Using multiple sensors, linear combinations can be formed 1.3 Parameter Estimation 7 by the receiver to help improve the estimate of the signal transmitted. An operation known as spatial filtering or beamforming [MM80, VB88, KV96, God97, Win98, Tso99, BO01, Tre02] In contrast to the use of only one receive antenna, having access to observations collected in the spatial domain, both spatial and spatio temporal processing approaches can be considered to improve the interference robustness of a receiver. Depending on the known or ....

L. C. Godara. Application of Antenna Arrays to Mobile Communications, Part II: Beamforming and Direction-ofArrival Considerations. Proceedings of the IEEE, August 1997.

.... approach that requires some known transmitted data, typically a preamble, in order to design a well suited filter that recovers the transmitted sequence from the received signal, by a minimization of the Mean Square Error (MSE) between the filtered received signal and the transmitted signal [9]. This yields to a classical Wiener solution when the number of available samples tends to infinity. A recent related paper is [6] where the authors also work with the SMI algorithm with subcarrier grouping in the frequency domain. They analyze the system with coding and propose an adaptive ....

L. Godara, "Application of Antenna Arrays to Mobile Communications, Part II: Beamforming and Direction-of-Arriaval Considerations," Proceedings of IEEE, vol. 85, no. 8, pp. 1195--1245, Aug. 1997.

....considered to be spatially white) As noise and interference is reduced by this method, the range of one access point is increased. Early contributions in the area of antenna arrays for mobile communication are [AMVW91] and [SBEM90] The issue of smart antennas has been overviewed in e.g. God97a, God97b] The special area of beamforming is summarized in [VB88] 3.3.1 Sensor Array Processing To be able to utilize the spatial dimension of the wireless channel, knowledge about the channel is important. Either parametric methods are used to estimate an angle, or statistic methods are used to ....

....the channel to the desired user, the signals transmitted or received on the di#erent antennas elements may be combined to give required gain on the desired signal. In uplink beamforming it possible to estimate the channel via the received signal and thus to have a good channel estimate [God97a, God97b, VB88] The basic method is beamforming, where the weights in the receiver are matched to the estimated channel vector. Zero forcing methods may be used in order to take care of interfering signals, though with high sensitivity of estimation errors and risk of worsening the noise situation. A ....

Lal C. Godara. Application of antenna arrays to mobile communications, part II: Beam-forming and direction-of-arrival consideration. Proceedings of the IEEE, 85(8):1195--1245, August 1997.

....may be considered to be spatially white) As noise and interference is reduced by this method, the range of one access point is increased. Early contributions in the area of antenna arrays for mobile communication are [AMVW91] and [SBEM90] The issue of smart antennas has been overviewed in e.g. God97a, God97b] The special area of beamforming is summarized in [VB88] 3.3.1 Sensor Array Processing To be able to utilize the spatial dimension of the wireless channel, knowledge about the channel is important. Either parametric methods are used to estimate an angle, or statistic methods are used ....

....of the channel to the desired user, the signals transmitted or received on the di#erent antennas elements may be combined to give required gain on the desired signal. In uplink beamforming it possible to estimate the channel via the received signal and thus to have a good channel estimate [God97a, God97b, VB88] The basic method is beamforming, where the weights in the receiver are matched to the estimated channel vector. Zero forcing methods may be used in order to take care of interfering signals, though with high sensitivity of estimation errors and risk of worsening the noise ....

Lal C. Godara. Application of antenna arrays to mobile communications, part I: Performance improvement, feasibility and system considerations. Proceedings of the IEEE, 85(7):1031--1060, July 1997.

....FUNCTIONALITIES A. Adapted MAC Protocol Due to this reason, the slot based beam switching solution has been designed as the most optimal approximation for the convergence of the OBANET scenario and the reference standards. This strategy is based onto the control information replication idea [10]. In this way, the control information would be retransmitted for all the beam positions (also called subsector) in a kind of scanning. As may be seen in figure 2, the use of the channel is shared between the equivalent sub sectors during the time of a frame, as the beam is pointed to the desired ....

....features in the next generation mobile networks is the capacity of evaluate the terminal position and even more to track it with an antenna beam. Traditional tracking algorithms are based in Direction of Arrival (DOA) estimation algorithms performed with digital signal processing techniques [10]. However, digital signal processing techniques are not suitable for BWA networks due to the high frequency of operation and their envisaged high data rate applications. The proposed algorithm is based in pilot tones power measurements in a similar way to the radar mono pulse ranging. The ....

L. Godara, "Applications of antenna arrays to mobile communications, Part II: beam-forming and direction-of-arrival considerations", Proceedings of the IEEE, vol. 85, no. 8, pp. 1195-1245, 1997.

....Systems (MBS) operating in the millimetre wave band, which allow data rates higher than 2 Mbps, are also envisaged to accomplish with the bandwidth demand of future multimedia mobile applications. In parallel, a lot of research has been devoted in the promising field of Smart Antennas (SA) [4 6]. SA are basically antenna arrays which have adaptive capabilities, conforming their radiation pattern to a changing environment to counteract system performance impairments. A wide range of benefits may be obtained from SA capabilities such as network capacity improvement or reduction of ....

L. Godara, "Applications of antenna arrays to mobile communications, part I: performance improvement, feasibility, and system consideration", Proc. of the IEEE, vol. 7, no. 85, pp. 1031-1060, 1997.

....[3] Smart Antennas (SA) are envisaged to counter such impairments . A SA is basically an antenna array with adaptive capabilities, e.g. to conform its radiation pattern. Using these properties a SA may counteract the LoS impairments, cancel system interferences, reduce multipath fading, etc [4]. An SA is usually electronically controlled by means of DSP based or RF IF signal processing. However, the use of these techniques in mm wave BWA is limited because are bandwidth limited, suffer from EMI and beam squint, and bulky hardware is required. Optical technologies have shown very ....

L. C. Godara, "Applications of antenna arrays to mobile communications: part I", Proc. of the IEEE, vol. 85, no. 7, pp. 1031-1060, 1997.

....is possible to specify (L 1) maximas and minimas (nulls) in desired directions, by using constrained optimization techniques when determining the beamforming weights. This flexibility of an L element array to be able to fix the pattern at (L 1) places is known as the degree of freedom of the array [5]. Figure 1 depicts a scenario where beamforming is done using the RLS algorithm to obtain the weights that place a main lobe in the direction of the desired user s signal (arriving at an angle of 60 degrees with respect to linear array) and simultaneously place nulls in the interferers ....

L. C. Godara. Application of Antenna Arrays to Mobile Communications, Part I: Performance Improvement, Feasibility and System Considerations. In Proceedings of the IEEE, volume 85, Jul 1997.

....smart antenna. I. INTRODUCTION Smart antenna technology, which originally was developed in 1980s, is a hot high tech arena these days as wireless communications companies worry how to cope with the prospect of high data demands from broadband applications for both fixed and mobile wireless [1]. Current generation digital mobile wireless technology is based on one big beam of data sent to each of three sectors at a cell site. Next generation technology will create specific beams for each mobile customer, creating less interference from other mobiles and using less power. More ....

L.C. Godara, "Application of Antenna Arrays to Mobile Communications, Part II: Beamforming and Direction-of-Arrival Consideration", Proceedings of the IEEE, Vol. 85, No. 8:1195 1245, August 1997.

....total wired infrastructure, which will typically breakdown completely. WLANs can also allow nomadic type applications. AP APAP Fig. 3. Infrastructure WLAN IV. PROPAGATION IMPAIRMENTS AND SMART ANTENNAS Wireless systems face a number of impairments that limit their performance and capacity [9,11,12,13]. These impairments are path loss and shadowing (large scale fading) multipath fading which is caused by the multiple paths that the transmitted signal can take to reach the receiver, delay spread which causes inter symbol interference (ISI) limiting the maximum usable data rate and co channel ....

L.C. Godara, "Applications of Antenna Arrays to Mobile Communications Part I: Performance Improvement, Feasibility and System Considerations", Proceeding of the IEEE, vol.85, No.7, pp1031-1060, July 1997.

....CDMA system and can cause the near far effect. Advanced signal processing algorithms have been developed to combat these problems. In particular, multiuser detectors have been proposed [1] which exhibit immunity to the near far effect. Another promising method is to employ an tenna arrays [2,3]. In general, the multipath signals arrive at the receiver with different angles of arrival (AOA) allowing an antenna array to exploit this spatial signature and provide increased space diversity to combat deep fades that occur in the wireless channels. By using this extra degree of freedom, MAI ....

.... signal bandwidth is large compared to the propagation time across the array, the complex envelopes of the signals received by different antenna elements from a given path are identical except for phase and amplitude differences that depend on the path AOA, array geometry and the element pattern [3]. The AOA of the lth multipath signal from the mth user is m q and ( m q a is the array response vector (spatial signature vector) to the multipath signal arriving from the direction m q , with T l m A m m a a q q q , 1 = a . We can represent the reverse link baseband complex signal in the ....

L. C. Godara, "Application of Antenna Arrays to Mobile Communications, Part II: Beamforming and Direction of Arrival Considerations", Proceedings of IEEE, pp.1031-1060, Aug. 1997.

....isotropic transmit antennas, and one or several receiver antennas are used. Only applying space time coding does not allow to target transmit power spatially. If the receiver is using a single isotropic antenna, then only a superposition of the transmitted signal is possible. Smart antennas [7] [8] combine multiple signals to receive or transmit with multiple antenna elements in an intelligent way, using an adaptive antenna processor. The transmitted signals are sent using an antenna beam aimed at the best known direction for the receiver. The transmission power used is multiplexed ....

L. C. Godara, "Application of antenna arrays to mobile communications. Part II: Beam-forming and direction-of-arrival considerations," Proceedings of the IEEE, vol. 85, no. 8, pp. 1195--1245, August 1997.

....two isotropic transmit antennas, and one or several receiver antennas are used. Only applying space time coding does not allow to target transmit power spatially. If the receiver is using a single isotropic antenna, then only a superposition of the transmitted signal is possible. Smart antennas [7], 8] combine multiple signals to receive or transmit with multiple antenna elements in an intelligent way, using an adaptive antenna processor. The transmitted signals are sent using an antenna beam aimed at the best known direction for the receiver. The transmission power used is multiplexed ....

L. C. Godara, "Application of antenna arrays to mobile communications. Part I: Performance improvement, feasibility, and system considerations, " Proceedings of the IEEE, vol. 85, no. 7, pp. 1031--1060, July 1997.

....the desired output and the actual array output. This principle has its roots in the traditional beamforming employed in sonar and radar systems. Adaptive implementation of the theoretical minimum MSE (MMSE) beamforming solution can readily be realized using temporal reference techniques [2] [4], 12] 15] Specifically, block based beamformer weight adaptation can be achieved for example using the so called sample matrix inversion (SMI) algorithm [12] 13] while sample by sample adaptation can be carried out using the least mean square (LMS) algorithm [14] 15] The authors are with ....

L. C. Godara, "Applications of antenna arrays to mobile communications, Part I: Performance improvement, feasibility, and system considerations," Proc. IEEE, Vol.85, No.7, pp.1031--1060, 1997.

....mobile communication capacity has motivated the necessity for new technologies, such as space division multiple access, to improve spectrum utilization. One approach that has shown real promise for substantial capacity enhancement is the use of spatial processing with adaptive antenna arrays [1] [2]. Beamforming is capable of separating signals transmitted on the same carrier frequency, provided that they are separated in the spatial domain. The beamforming processing appropriately combines the signals received by the different elements of an antenna array to form a single output. ....

L. C. Godara, "Applications of antenna arrays to mobile communications, Part I: Performance improvement, feasibility, and system considerations," Proc. IEEE, Vol.85, No.7, pp.1031--1060, 1997.

....through SIC is poor in this case. Hence, the main theme of this paper is the combination of SIC with multiple BS antennas in the context of SDMA TDMA systems, where more substantial performance improvement is envisioned. SDMA has been investigated for single carrier wireless communication systems [7, 8, 9]. However, in these studies SDMA was not combined with SIC. It should be noted that V BLAST uses a similar approach to the one proposed here, however it is computationally expensive owing to the use of signal ordering based upon the pseudoinverse of the vector channel transfer function [10, 11] ....

L.C. Godara, "Applications of antenna arrays to mobile communications, Part I: Performance improvement, feasibility, and system considerations", Proc. IEEE, Vol. 85, July 1997, pp. 1031-1060

....weighting the antenna outputs and combining them to make the antenna response to certain directions more sensitive than others. Most of the research on antenna arrays for beamforming has mostly been on receivers. Transmit beamforming is different and requires different algorithms and hardware [28]. Different kinds of beamforming at the recieve antenna array currently in use are based on array processing algorithms such as signal copy, direction finding and signal separation algorithms [28] that include conventional beamforming, Null steering beamforming, Optimal beamforming, Beam Space ....

....been on receivers. Transmit beamforming is different and requires different algorithms and hardware [28] Different kinds of beamforming at the recieve antenna array currently in use are based on array processing algorithms such as signal copy, direction finding and signal separation algorithms [28] that include conventional beamforming, Null steering beamforming, Optimal beamforming, Beam Space Processing, Blind Beamforming, Optimum Combining and Maximal Ratio combining [28, 41, 57, 2, 58, 53, 71] Some of the beamformers require a reference signal and use adaptive algorithms like LMS to ....

[Article contains additional citation context not shown here]

L. C. Godara, "Applications of antenna arrays to mobile communications, part i: Performance improvement, feasibility, and system considerations," IEEE Proceedings, vol. 85, no. 7, pp. 1031--1060, July 1997.

....WANs, satellite links, digital dispatch networks, one way and two way paging networks, diffuse infrared, laser based communications, keyless car entry, the Global Positioning System, mobile communications, indoor radio and more. There is such a wide variety of research in antennas that in future [27] we can expect a hand held terminal the size of a wristwatch capable of steering beams toward a satellite. The system would also consist of many radiating elements fabricated by microstrip technology, each with its own phase shifting network, power amplifier, and so on with other required ....

....and the receiver which is not always feasible. In this thesis, we will concentrate on spatial diversity offered with multiple antennas. Spatial diversity, receive (multiple antennas in the receiver) and transmit (multiple antennas at the transmitter) helps in improving system performance by [27] 1. Improving spectrum efficiency: Using multiple antennas we can accomodate more than one user in a given spectral bandwidth. 2. Extending range coverage: Multiple antennas can be used to direct the energy of a signal in a given direction and hence minimize unnecessary transmission of signal ....

L. C. Godara, "Applications of antenna arrays to mobile communications, part ii: Beamforming and direction-of-arrival considerations," IEEE Proceedings, vol. 85, no. 8, pp. 1195-- 1245, August 1997.

....in the choice of constraints and can be extended to be robust to channel perturbations. 1 Introduction The use of antenna arrays brings new possibilities in the design of mobile communications systems. It is well known that the system capacity is more limited in the downlink than in the uplink [7, 22]. Yet, the literature on beamforming for transmission is relatively small, compared to the well investigated topic of beamforming for a receiving antenna array. Some results on downlink beamforming can be found in [8, 11, 12, 15, 21, 22] The simplest transmit strategy is to use standard ....

Lal C. Godara. Applications of antenna arrays to mobile communications. I. Performance improvement, feasibility, and system considerations. Proceedings of IEEE, 85(7):1031-- 1060, July 1997.

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L. C. Godara, "Applications of Antenna Arrays to Mobile Communications, Part II: Beam-Forming and Direction-Of-Arrival Considerations," Proceedings of the IEEE, vol. 85, no. 8, pp. 1195--1245, August 1997.

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L. C. Godara, "Application of antenna arrays to mobile communications, part II: Beam-forming and direction-of-arrival considerations," Proc. IEEE, vol. 85, pp. 1195--1245, Aug. 1997.

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L. Godara, "Application of Antenna Arrays to Mobile Communications, Part II: Beam-forming and Angle-of-Arrival Considerations," IEEE Proceedings, vol. 85, no. 8, pp. 1195--1245, 1997.

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L. Godara, "Application of Antenna Arrays to Mobile Communications, Part II: Beam-forming and Angle-of-Arrival Considerations," IEEE Proceedings, vol. 85, no. 8, pp. 1195--1245, 1997.

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L. C. Godara, "Application of antenna arrays to mobile communications. II. Beam-forming and direction-of-arrival considerations, " Proc. IEEE, vol. 85, no. 8, pp. 1195--1245, 1997.

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L. C. Godara, Applications of antenna arrays to mobile communications. i. performance improvement, feasibility, and system considerations, Proc. the IEEE, vol. 85, no. 7, pp. 103160, 1997.

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L. Godara, "Applications of antenna arrays to mobile communications, part II: Beam forming and direction of arrival considerations," Proc. IEEE, vol. 85, pp. 1195--1245, Aug. 1997.

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L. Godara "Applications of Antenna Arrays to Mobile Communications, Part II: Beam-Forming and Direction of Arrival Considerations" Proceedings of the IEEE, Vol. 85, No. 85, August 1997.

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L. Godara "Applications of Antenna Arrays to Mobile Communications, Part I: Performance Improvement, Feasibility and System Considerations" Proceedings of the IEEE, Vol. 85, No. 7, July 1997.

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L.C.Godara, "Application of Antenna Arrays to Mobile Communications, Part I: Performance improvement, Feasibility and System Considerations", Proceedings of the IEEE, Vol. 85, No.7, July 1997

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Godara, "Application of Antenna Arrays to Mobile Communications, Part II: BeamFormaing and Direction-of-Arrival Considerations," vol. 85, no. 8, pp. 1195-1245 August 1997.

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Godara, "Applications of Antenna Arrays to Mobile Communications, Part 1: Performance Improvement, Feasibility, and system Considerations," vol. 85, no. 7, pp. 1031-1060 July 1997.

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L. C. Godara, "Application of antenna arrays to mobile communications part II: Beamforming and direction-of-arrival considerations," Proceedings of the IEEE, vol. 85, pp. 1195--1245, Aug. 1998.

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L. C. Godara, "Application of antenna arrays to mobile communications part I: Performance improvement, feasibility and system considerations," Proceedings of the IEEE, vol. 85, pp. 1031--1060, July 1998.

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L. Godara, "Application of antenna arrays to mobile communications, Part II: Beamforming and direction-of-arriaval considerations," Proc. IEEE, vol. 85, pp. 1195--1245, Aug. 1997.

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L.C. Godara, "Applications of Antenna Arrays to Mobile Communications, Part 2: Performance Improvement, Feasibility, and System Considerations", Proceedings of IEEE, August 1997, pp. 1195-1245

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L.C. Godara, "Applications of Antenna Arrays to Mobile Communications, Part 1: Performance Improvement, Feasibility, and System Considerations", Proceedings of IEEE, July 1997, pp. 1031-1060

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L. C. Godara, "Application of antenna arrays to mobile communications part I: Performance improvement, feasibility and system considerations," Proc. IEEE, vol. 85, pp. 1031--1060, July 1998.

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L.C. Godara, "Applications of Antenna Arrays to Mobile Commu nications, Part I: Performance Improvement, Feasibility, and System Considerations," Proceedings of the IEEE, vol. 85, no. 7, pp. 1031--1060, Ju ly 1997.

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L.C. Godara, "Application of Antenna Arrays to Mobile Communications, Part II: Beam-forming and Direction-of-Arrivel Considerations", Proceedings of the IEEE,Vol. 85, No. 8, pp. 1195-1245, August 1997.

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L. C. Godara, "Application of antenna arrays to mobile communications, Part II: beam-forming and directionof -arrival considerations," Proceedings of the IEEE, vol. 85, pp. 1193-1245, August 1997.

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L. C. Godara. Application of antenna arrays to mobile communications II: Beam-forming and direction-of-arrival considerations. Proceedings of the IEEE, 85:1195--1245, August 1997.

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L. C. Godara. Application of Antenna Arrays to Mobile Communications, Part II: Beam-Forming and Direction-of-Arrival Estimation. Proceedings of the IEEE, 85(8):1195--1245, August 1997.

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L. C. Godara, "Applications of antenna arrays to mobile communications, Part II: Beam-forming and direction-of-arrival considerations," Proc. IEEE, Vol.85, No.8, pp.1193--1245, 1997.

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L. C. Godara, "Applications of antenna arrays to mobile communications, Part I: Performance improvement, feasibility, and system considerations, " Proc. IEEE, Vol.85, No.7, pp.1031--1060, 1997.

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L. C. Godara, Application of Antenna Arrays to Mobile Communications: Part 1, Proc. IEEE, Vol 85, No. 7. pp 1031-1060, July 97 72 ISSCC 2000, DSP Tutorial. Ingrid Verbauwhede, Chris Nicol References (cont)

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L. C. Godara, "Application of Antenna Arrays to Mobile Communications: Part 1", Proc. IEEE, Vol 85, No. 7. pp 1031-1060, July 97 28 55 ISLPED 2000, Tutorial. Ingrid Verbauwhede, Dave Garrett References (cont)

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