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Wireless Communication Systems Using Phased Array Antennas

Thu, 02/14/2013 - 3:31pm
Dr. John Howard, President & CEO of Electromagnetic Technologies Industries, Inc. (ETI)

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Once bandwidth is used up in an area, no other system utilizing the same frequency bands can coexist and hence data speeds are limited.

Figure 1: Typical Cell Site using 3 separate frequency channels, F1, F2, F3.There are many factors that contribute to the limitations of wireless systems, of which arguably the most important are frequency bandwidth (spectrum availability) and frequency efficiency.  Though efficiency may be increased by higher modulation rates, more sensitive receivers and more accurate bit error detection/correction methods, wireless telecommunication systems are built around the frequency bandwidth or spectrum limitations that are set by governing authorities.  Consequently, once bandwidth is used up in an area, no other system utilizing the same frequency bands can coexist and hence data speeds are limited.

Due to this fact, the current technologies of wireless systems have limited data and user capacity.  For example, a typical GSM cell site has three sectors in 360° and uses three frequency channels (see figure 1).  Within a sparsely populated area this may be acceptable; however, networks covering dense urban areas often require hundreds of such cell sites.  Such a large number of sites incur high costs associated with the cell equipment, site management and site rental.  In addition, with every new site, RF planning becomes more complex.

The same difficulties and high costs apply to all wireless systems such as, WiMAX, LTE and 3G.  In the case of 3G even if each of the three (or six) sectors employs the same band (frequency reuse of 1 - see figure 2) there will be a reduction of codes per sector due to interference between sectors.

Apart from the above limitations, wireless systems can also suffer from signal cancellations due to multiple reflections, known also as multipath, as well as from losses due to absorption from building materials, precipitation and vegetation.

In order to minimize the limitations mentioned above, equipment manufacturers devised various equipment improvements ranging from increased modulation rates, the use of MIMO, and software beam forming. E.T. Industries' antenna systems, however, solve the aforementioned problems by increasing the available bandwidth for an area. To achieve this, our systems have been designed to produce up to 48 sectors around a single cell site while using only four physical antennas. Additional sectors yield more data and user capacity. We can offer up to 16 times the user capacity and data rate of a typical 3-sectored wireless system.

In addition, whereas all sectors around a single base station in traditional systems use different frequencies, our multi-beam antennas are able to reuse the same frequencies around the base station by spatially optimizing frequency usage. By using interference rejection technology, site interference between sectors is kept to a minimum. The ability to reuse frequency bands in the same area facilitates a substantial increase in the throughput. In fact, it is a Virtual FiberTM (VFIBERTM).

Figure 2: Typical 3G cell site repeating the same frequency in each cell-reuse of 1.E.T. Industries' systems achieve a high number of sectors by employing a smart antenna multiple times. A single 90° sectored smart antenna system can produce up to 12 individual beams in multiple directions within that area. Each beam is accurately spatially aligned by a beam-forming network (BFN) while a beam-shaping network (BSN) shapes the radiation pattern envelope (RPE) of each lobe. Essentially the BFN focuses each beam in a specified direction and the BSN minimizes any possibility of interference between beams using the same frequency band. The result produced is many exclusive high gain lobes radiating from one antenna in a 90° sectored area.

Because of the narrow focusing of the BFN, the accurate shaping of the BSN, and the resulting individual beam spatial isolation, our wireless systems are able to reuse frequency bands multiple times within the 90° area.

Figure 3: Beam Array diagram of four E.T. Industries' 6-beam antennas using three frequency channels, F1, F2, and F3. Frequency reuse ratio of 8:1.MIMO (Multiple Input Multiple Output2) is a technique employed to improve communication between the base station and the subscriber.  It is based on the old diversity techniques used in troposcattering communications in order to improve the fading (loss) of signals in a link between two sites.

NIMO is a novel approach of a phased array antenna and beamforming system that can be used to overcome bandwidth and capacity limitations on dense wireless networks.  It is a hardware based fully passive beamforming system.  It combines beamforming technology with MIMO and beam shaping techniques and supports transparent integration with any telecommunication system.  NIMO provides multiple simultaneous narrow beams (see figure 6) using a single phased array antenna and provides improved characteristics compared to conventional beamforming techniques.  Up to 48 beams may be employed in a 360 degree angle; however, for mobile systems up to 12 beams is recommended.  NIMO's multibeam phased array antenna system increases spectral efficiency and

Figure 4: Beam Array diagram of four E.T. Industries' 2-beam antennas using four frequency channels, F1, F2, F3, and F4. Frequency reuse ratio of 2:1.While all of the methods described herein (increased modulation rates, use of MIMO, software beam forming, and NIMO) have improved the performance of wireless networks only ETI’s antenna systems can provide frequency reuse.  By increasing an operator’s existing spectrum an operator will substantially increase their capacity, provide higher data rates, cover greater area (which in turn reduces the number of total sites needed in any given cell, which will reduce CAPEX and OPEX).

Our antenna systems incorporate only passive components ensuring that our antennas can integrate into the network infrastructure of any vendor. We offer a simple solution to scaling up throughput and capacity while ensuring the flexibility to work with other vendors and to operate on any standard. Our systems are optimized to work at multiple frequency bands.

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