This paper proposes a practical application of Massive MIMO technology, Massive Antenna Systems for Wireless Entrance (MAS-WE), and along with related inter-user interference cancellation (IUIC) and scheduling techniques. MAS-WE, in which the entrance base station (EBS) employs a large number of antennas, can effectively provide high capacity wireless entrance links to a large number of access points (APs) distributed over a wide coverage area. The proposed techniques are simplified to practical implementation; EBS side uses around 100 antenna elements to spatially multiplex more than 16 signal streams. SIR performance is evaluated by system level simulations that consider imperfect channel state information (CSI). The results show that MAS-WE with the proposed techniques can reliably achieve high spectral efficiency with high level space division multiplexing.

This paper proposes a sector base station antenna for mobile wireless communication systems employing multiple woodpile metamaterial reflectors and a multiband radiator that establishes the same beamwidth in the horizontal plane for more than two frequency bands. Electromagnetic Band Gap (EBG) characteristics of each metamaterial reflector can be controlled through structural parameters of the woodpile reflector, e.g., the rod width and rod spacing. As an example of the proposed antenna, a design for a triple-frequency-band antenna that radiates at 800 MHz, 2,GHz, and 4,GHz is shown. The algorithm used to adjust the beamwidth of the proposed antenna is newly introduced and adjusts the beamwidth to be the same for each band using the rod width of the woodpile. A prototype of the proposed antenna has the approximately 90$^{circ}$ beamwidth in the horizontal plane at the three frequencies, and the measurement results agree well with the electromagnetic field simulation results.

In this letter, we present a low-complexity residual symbol timing offset (STO) estimation scheme in a long term evolution (LTE) downlink system. The proposed scheme is designed to estimate STO without a priori knowledge of cell-specific reference signals, which reduces the arithmetic complexity while maintaining a similar performance to the conventional algorithm.

This letter proposes a monopole multi-sector antenna with dielectric cylinder, and shows some results of simulations that examined the antenna characteristics. The dependency of radiation characteristics on relative permittivity εr shows the lens effect with increase of εr. Furthermore, the characteristics of the proposed antenna are improved by optimizing the termination conditions at the quiescent antennas. The backlobe level is lower than -10 dB. Also, the vertical HPBW and the conical HPBW are around 70.5° and 63.4°, respectively. The optimization improved the actual gain by 2 dB. It is found that the diameter of the proposed antenna is 1/3rd that of the conventional one.

Cognitive radio is an emerging technology to further improve the efficiency of spectrum use. Due to the nature of the technology, it has many facets, including its enabling technologies, its implementation issues and its regulatory implications. In ITU-R (International Telecommunications Union – Radiocommunication sector), cognitive radio systems are currently being studied so that ITU-R can have a clear picture on this new technology and its potential regulatory implications, from a viewpoint of global spectrum management. This paper introduces the recent results of the ITU-R studies on cognitive radio on both regulatory and technical aspects. This paper represents a personal opinion of the author, but not an official view of the ITU-R.

This paper presents a newly developed small-sized shaped beam base station antenna in order to reduce inter-sector interference for next generation high speed wireless data communication systems. The developed antenna realizes polarization diversity as a single small-sized antenna without decreasing the 3 dB main beamwidth compared with the conventional antenna by applying a newly designed beam shaping method. Furthermore, side sub-reflectors are newly installed in the radome to reduce the antenna beam gain in the direction toward the edge region neighboring the other sectors of the horizontal antenna pattern. By adopting this type of reflector, the diameter of the radome can be minimized at 0.65 λ, which is slightly longer than that of the conventional antenna. Both a computer simulation and a field measurement test based on an actual cellular network were conducted for the purpose of clarifying the validity of the shaped beam antenna. In the results, the CINR at the service area by the shaped beam antenna was 1 dB and 3.5 dB better than that of the conventional antenna at the median and 10% of CDF, respectively. The developed antenna will be expected to contribute to the enhancement of the quality of cellular radio systems in the future.

This paper proposes a new switched-beam eight-sector antenna for multi-gigabit wireless LAN in the 60-GHz band. Our antenna system introduces access-point (AP) and user-terminal (UT) antennas having the same secθ pattern in the elevation plane so that the received signal power at the receiver is kept constant, independent of the position of the UT. For this system, an eight-sector antenna, a single-pole eight-throw (SP8T) switch, and a beam control unit are integrated as the switched-beam eight-sector antenna. The specifications of the antenna are wide bandwidth ( ≥3 GHz), high-gain ( ≥13 dBi at θ =66), and wide coverage area in both azimuth (0 ≤ φ ≤ 180) and elevation planes (0 ≤ θ ≤ 66). The antenna beam is steered within the specified response time (which is short) by the Media Access Control (MAC). In our antenna, both high gain for a wide elevation angle and wide bandwidth are obtained by using the proposed closely spaced waveguide slot array antenna, which is used as each sector of the eight-sector antenna. The SP8T switch with the beam control unit enables 180 beam scan in the azimuth plane. In a component evaluation, the eight-sector antenna achieves a 10-dB return loss bandwidth of 8 GHz with more than 40-dB port-to-port isolation. Radiation characteristics of the eight-sector antenna indicate that it covers 82% of the entire coverage area at the center frequency and that the coverage rate in the operating frequency band is from 78% to 88%. The performance of the SP8T switch and the beam control unit is verified by measuring the insertion loss at all eight ports and the switching response time. In the antenna system evaluation, measurement by using two prototype antennas as the AP and the UT antennas in the usage condition indicates that the measured received signal power meets the specified constant power for the specified wide elevation angle range, independent of the position of the UT. These experimental results verify the effectiveness of our proposed antenna for multi-gigabit WLAN.

In MIMO systems, the deployment of a multiple antenna technique can enhance the system performance. However, since the cost of RF transmitters is much higher than that of antennas, there is growing interest in techniques that use a larger number of antennas than the number of RF transmitters. These methods rely on selecting the optimal transmitter antennas and connecting them to the respective. In this case, feedback information (FBI) is required to select the optimal transmitter antenna elements. Since FBI is control overhead, the rate of the feedback is limited. This motivates the study of limited feedback techniques where only partial or quantized information from the receiver is conveyed back to the transmitter. However, in MIMO/OFDM systems, it is difficult to develop an effective FBI quantization method for choosing the space-time, space-frequency, or space-time-frequency processing due to the numerous subchannels. Moreover, MIMO/OFDM systems require antenna separation of 5 10 wavelengths to keep the correlation coefficient below 0.7 to achieve a diversity gain. In this case, the base station requires a large space to set up multiple antennas. To reduce these problems, in this paper, we propose the link correlation based transmit sector antenna selection for Alamouti coded OFDM without FBI.

Assume that 2m red points and 2n blue points are given on the lattice Z2 in the plane R2. We show that if they are in general position, that is, if at most one point lies on each vertical line and horizontal line, then there exists a rectangular cut that bisects both red points and blue points. Moreover, if they are not in general position, namely if some vertical and horizontal lines may contain more than one point, then there exists a semi-rectangular cut that bisects both red points and blue points. We also show that these results are best possible in some sense. Moreover, our proof gives O(N log N), N=2m+2n, time algorithm for finding the desired cut.

A cell planning and resource allocation scheme called EBRD (Enhanced Bandwidth and Region Division) is presented for improving channel capacity and for maintaining a proper QoS (Quality of Service) over the downlink OFDMA (Orthogonal Frequency Division Multiple Access) system. Through an optimal combination of sectorization and frequency overlay, the EBRD scheme improves both channel capacity and outage probability. In order to analyze the performance of the proposed algorithm, the outage probability is obtained as a closed numerical form. In the simulation, the EBRD scheme outperforms 3-sectorization in terms of throughput and outage probability.

The time division duplex cellular system can support various downlink and uplink traffic ratios by setting the downlink and uplink transmission periods appropriately. However, it causes severe co-channel interference problem when some cells are active in the downlink while the others are in the uplink [2]. To mitigate this problem, a resource allocation scheme combined with sectorization is proposed for orthogonal frequency division multiple access. Simulations demonstrate that the proposed scheme improves both spectral efficiency and outage performance compared to the conventional allocation schemes.

This paper presents design of an alternating-phase fed single-layer slotted waveguide array for a sector shaped beam in the E-plane radiation pattern. A sector beam pattern is very effective for radar applications for detecting obstacles in a certain angular range without mechanical or electronic scanning. The sector shaped beam with 13 degree beam width is synthesized by a cascade of T-junctions in the feed waveguide which excite the radiating waveguides with a longitudinal shunt slot array. In order to realize the required excitation distribution of the radiating waveguides for the sector shaped beam, 30 T-junctions with symmetrical arrangement are designed by tuning a width of the coupling window, an offset of the window, and a width of the feed waveguide cascaded to the subsequent T-junction, respectively. Design and measurement are performed in 60 GHz band. The prototype antenna assembles easily; the slotted plate is just tacked on the groove feed structure and is fixed by screws at the periphery, which is the key advantage of the alternating-phase fed arrays. The measured sector pattern with low sidelobe level agrees well with the predicted one. Validity of the sector beam design as well as the performance of the alternating-phase fed array is confirmed by the measurement.

This paper presents sector based flooding (SBF) and adaptive sector-based flooding (ASBF) that are flooding methods for mobile ad hoc networks using position information. SBF, which divides the communication area of a sender node into sectors, allows only the node nearest to a sector representative position in each sector to rebroadcast a packet. SBF is divided into two methods, SBF-1 and SBF-2; the difference is the number of criteria used to decide whether to rebroadcast or to drop the packet. In ASBF, each node selects a flooding method from among SBF-1, SBF-2, and pure flooding, depending on its local node density. The node density is obtained from the distance between the sector representative position and its nearest node. Simulation results show that SBF reduces the number of packet transmissions generated in flooding and ASBF has high packet reachability with few packet transmissions.

Resource management for infrastructure-based two-hop fixed relay systems which are applicable to TDD-FH-OFDMA based cellular systems with sectorization is proposed in this paper. The severe interference problem caused by both inter-sector and inter-cell can be tackled by employing 6-sector directional antennas combined with the resource allocation. The simulation results demonstrate that at the outer-region of the cell, the high data rate service coverage can be extended.

A post-wall waveguide slot array with a three-way power divider on a single-layer substrate is designed to have a H-plane sectoral beam and an E-plane cosecant pattern with null-filling. Experiments in the 26 GHz band confirmed the sectoral beam with a -3 dB beam width of 117 deg and a ripple width of 2 dB in the sector.

This letter develops a practical sectorized antenna array using center-fed half-wavelength dipole antennas that are parallel to and a distance in front of a large ground plane reflector. Each element in the array is designed to provide coverage to isolate each 120sector from adjacent sectors. We derive a closed-form expression for spatial correlation function that can be used as guides in evaluating the effects of array spatial correlation on diversity performance in sectorized cellular communications.

The fiber-optic sectorized remote antenna system by using the radio frequency (RF) optical transmission technique was promising for increasing the number of subscribers in the millimeter-wave broadband wireless access (MMW BWA) networks. To realize the cost-effectiveness of the fiber-optic sectorized remote antenna system covering four areas, we reached the conclusion that the best multiplexing schemes were the sub-carrier division multiplexing (SCM) of the intermediate frequency (IF) signals of 2 GHz for the down link, the coarse wavelength division multiplexing (CWDM) with the IF signals optical transmission for the up link and 1.3/1.55 µm-WDM for multiplexing the down link and the up link. In addition, the target specifications of this SCM-CWDM system were described, and the designs of the carrier to noise ratio (CNR) and the third order intermodulation distortion (IM3) were examined.

This paper presents the analysis of the impedance characteristics of a sectoral cylindrical cavity-backed axial slot antenna excited by a probe. The integral equations are derived based on boundary conditions of the proposed structure and they are expressed in terms of dyadic Green functions and unknown current densities. The dyadic Green functions are obtained by using the eigenfunction expansion method together with application of scattering superposition techniques. The unknown current densities are solved by the Method of Moments. The input impedance is subsequently determined from the unknown electric current density at the probe. Numerical results of input impedance and return loss are demonstrated as functions of frequency for various parameters such as cavity length, cavity radius ratio, slot location in φ direction, slot length and probe length. Calculated results are validated by the measurements. At the operating frequency, it is found that the result is sufficiently accurate. The results from this study are very useful for the design of a sectoral cylindrical cavity-backed axial slot array antenna excited by a probe with omnidirectional beam radiation.

An adaptive array antenna should be applied for suppression of CCI in the spatial domain. However, the adaptive array antenna has some problems as follows. Because the adaptive array antenna takes a long time to converge to the optimum antenna weights, it's hard to track in case of quick varying channel. On the other hand, processing burden increases with the number of elements in the array antenna. To solve these problems, we propose an adaptive array antenna using array antenna as element antennas, the so-called "Layered array antenna." At the 1st layer, sector area are defined. We can change the sector areas according to the DOA distribution, because the sector areas are defined by the antenna weights. At the 2nd layer, MMSE is performed. Interference that couldn't be suppressed at the 1st layer is suppressed at the 2nd layer. By the proposed system, we confirmed higher convergence speed while relieving processing complexity.

Achieving optimal performance with minimal complexity are conflicting problems encountered in constructing receivers. In this paper, to solve the problem, we propose sector beamed space hopping which utilizes a Viterbi equalizing receiver. Reduction of the number of RF circuit sets, system complexity and decreasing the computational burden of the Viterbi equalizer through the use of sector beamed space hopping is presented. This is achieved using a sector beamed antenna which limits the number of paths in the multipath channel environment. This paper describes each key component which comprises the system and discusses the application of FH-SS communication. The channel is assumed to be an industrial indoor propagation channel, such as those found in a factory, where high reliability is required and many complex multipaths exist. We confirm through simulation that Viterbi equalization using less computational complexity can be obtained. It is found that there exists a trade off between system complexity and performance. Through the discussion of power consumption, cost and BER performance, we show that the proposed system achieves acceptable performance while having a low system complexity.