Network Microwave Link

Network Microwave Link Microwave Communications Link Design And Implementation Gert Brits AbstractInternet and network access from any location is a requirement in most businesses around the world today. This paper outlines the procedure necessary to plan, install and commission a 5.8 GHz un-licensed point-to-point microwave link. The link will serve as a connection between two office buildings to provide internet and network access to the employees. The planning stages of the project presents the various environmental influences on a microwave link, as well as the considerations that must be made to select the appropriate sites, hardware and configuration settings for the link. These parameters are used to calculate the expected performance data and install a microwave link that would operate reliably at five nines (99.999%) of availability. Index Termsattenuation, losses, fading, line-of-site, received signal level, Introduction DIGITAL microwave systems are used all over the world for a wide variety of applications. The majority is point-to-point systems; a single link connecting two sites together. For most businesses, having access to the local area network and the internet is essential. The challenge for many is the occupation of more than one office building and how multiple buildings can gain access to the same network. Harris Stratex Networks (HSTX) in San Jose, California occupies an office building in San Jose as well as an equipment warehouse in Milpitas, two miles from the office building. Since the company manufactures digital point-to-point microwave radios and has access to such equipment, an effective method was researched to utilize a point-to-point radio link as a connection between the two buildings. The purpose of this paper is to demonstrate how a digital point-to-point microwave link can be used to link two office buildings together, in this case the main office building of HSTX in San Jose and the warehouse in Milpitas, and provide internet and local area network access to the employees at the warehouse. The various aspects involved in the design, installation and commissioning of a digital point-to-point microwave system is described to highlight the procedures and planning required from microwave engineering before, during and after a microwave link is installed. attenuating influences on a microwave link Almost all components involved in a microwave link will cause the signal to be attenuated at some stage during transmission. In microwave engineering, attenuation plays a major role in the design and planning of such a link to ensure reliability and availability regardless of the surrounding conditions. Whether its in the cables, connectors, antennas or free space; attenuation on a link can not be avoided and provision needs to be made, during the design stage, for the degree of expected attenuation to occur. Propagation losses Propagation losses such as attenuation caused by reflection, free space losses, attenuation caused by rain and by atmospheric gasses have a negative influence on a microwave link. Reflection Line-of-Sight Microwave links are designed to have enough clearance over any object or terrain along the path to avoid the signal grazing or scraping across obstacles. The Fresnel zone is known as the area around the visual line-of-sight that radio waves spread out into after they leave the antenna [1] and where obstacles would cause in phase or out of phase reflection of the radio wave. This area must be clear of any obstructions to avoid an undesired affect on signal strength. Fig. 1 illustrates the typical Fresnel zones associated with a microwave link. Microwave signals which are reflected or refracted could lead to multiple copies of the same transmitted signal to arrive at the receiving antenna at different times and out of phase. The reflected and refracted signals will experience differences in attenuation, delay and phase shifts which will result in either constructive (amplifying the signal) or destructive (attenuating the signal) interference. There are an infinite number of Fresnel zones. Obstacles in the first Fresnel zone will create signals that will be 0 to 90 degrees out of phase. The second Fresnel zone will cause signals to be 90 to 270 degrees out of phase. In the third, the signals will be 270 to 450 degrees out of phase and so forth. Odd numbered zones (1, 3, 5 etc.) have a negative effect on the signal power while even numbered zones have a positive effect since these signals actually add to the signal power. The phase canceling effect is strongest in zone 1 and decreases in each successive zone, hence the need to eliminate as many obstacles from the first zone as possible. These clearance requirements also include the sides of the path and not only the top and bottom. Free space loss Free space loss is defined as the loss that would obtain between two isotropic antennas in free space, where there are no ground influences or obstructions [2]; in other words, the loss where no obstacles nearby can cause blocking, refraction, diffraction or absorption. This loss increases with an increase in frequency and distance and the formula for calculating free space loss [3] using the frequency of operation (f) and the distance (in miles) between the two antennas (D) is given by: (1) Attenuation caused by atmospheric gasses Attenuation caused by atmospheric gases is mainly caused by oxygen and water vapor in the air. The small amount of attenuation caused by oxygen stays relatively constant across all operating frequency bands. Attenuation caused by water vapor absorption however is highly dependent on the frequency of operation as well as the density of the water vapor and will have a deep impact on the links operating above 14 GHz. Attenuation caused by rain Furthermore, fading can be the distortion a microwave signal experiences due to changes in the atmosphere or rain. The total amount of rain that falls is not as important as the intensity of the rainfall. For example, an area which gets lite rain for most of the year would be less affected by rain attenuation than an area that gets a storm of rain during the rainy season, even for a short period of time. Microwave links operating below 8 GHz remain largely unaffected by rain attenuation but at 10 GHz and above, rain has a big impact on the networks reliability. Availability for modern day high reliability systems varies. The annual outage objective for high reliability systems could be as little as 0.01% to 0.0001% of the total operating time which translates to 53 minutes of down time per year for 99.99% reliability and only 30 seconds of downtime per year for 99.9999% reliability. Fading can degrade the bit error rate (BER) performance of a microwave link resulting in loss of data. Parameters such as the radio frequency, path length, humidity, temperature, smoothness of the terrain, calmness of the wind, fog and the number of thunderstorms per year can all increase the probability of fading. Branching losses Branching losses are introduced by the hardware used to carry the microwave signal and is generally specified by the equipment manufacturer. Other losses Other losses associated with a microwave link include losses from feeders, connectors, antennas, radomes and TX line losses. These losses are specified by the manufacturers at different frequencies of operation. Microwave link Planning Sufficient microwave path engineering ensures a link performs according to the requirements set by the owner or user. In a perfect world, any microwave beam would travel in a straight line from start to finish. In reality however, everything surrounding the microwave beam and equipment can cause the signal to be attenuated, amplified or interfered with. The challenge for any microwave engineer is to know what these factors are and how to design around it. Site selection An essential part of planning a microwave link is the selection of appropriate sites. The office and warehouse roof of HSTX provided a line of sight which was clear of any surrounding buildings and obstructions that could block or cause the microwave signal to be diffracted. There was no possibility of additional floors being added to either of the two buildings and the absence of other towers and microwave systems in the area, which could interfere with this link, made these sites ideal for the antenna installation. In addition to this, the sites already had access roads, ac power and telephone services which were other requirements considered when choosing the appropriate sites. Frequency and equipment selection Industry standards and licensing for microwave radios are, in the USA, governed by the Federal Communications Commission (FCC). Radios operating in the license-free 2.4 GHz and 5.8 GHz bands are considered un-licensed radios and require no licensing from any governing body. Un-licensed radios, such as the Velox LE 5850 manufactured by Harris Stratex Networks, can be installed and operated without any approval from the FCC. The Velox 5850 series is capable of providing up to 45 Mbps of Ethernet throughput (Full-duplex) which was sufficient for the purpose of this link. The output power of the radio can be software adjusted up to +22 dBm and with a receiver sensitivity of -78 dBm; enough fade margin can be achieved to ensure link availability of 99.999%. The radio hardware is available in a split-mount configuration; a radio frequency unit (RFU) which is connected to a digital unit (DU) using shielded CAT5e cable. The RFU is installed on the tower or mounted below the antenna and the DU is installed inside an equipment building or enclosure. Management software to configure the radio and monitor the performance of the radio link is available for this product. A 4.940-5.580 GHz Grid Antenna (model no GS2-58N), manufactured by mWAVE Industries, LLC was selected for the project. The antenna provided a gain of +27 dBi, a VSWR of 1.5:1, a return loss of 14 dB and could be mounted for horizontal or vertical polarization as illustrated in Fig. 2. Microwave link calculations The microwave link design was started by doing a link budget analysis; a calculation that involves all the gains and losses associated with the antennas, cables, connectors, radio hardware and environment. The link budget was used to determine the expected received signal levels at each end of the link. Once this has been done, minor adjustments were made to the sites and hardware selections to achieve the desired link availability. Path calculations The receiver threshold value is a measure of the lowest possible signal level the radio can receive and still operate at an acceptable level of performance. This level was specified by the equipment manufacturer as -78 dBm. The difference between the received signal level and the receiver threshold indicates the fade margin (the amount of fading a microwave radio can experience before having the signal degraded enough to cause BER errors or framing errors) of the link. To calculate the expected receive signal level and the fade margin, the propagation losses, branching losses and other losses had to be subtracted from the radio output power and antenna gain. The attenuation caused by atmospheric gasses for links below 14 GHz was negligible. The free space loss given by (1) and therefore the total propagation loss was calculated as 114.32 dB. Transmit and receive branching losses associated with the Velox 5850 radio was specified by the equipment manufacturer as 1.5 dB respectively. Other losses, all of which were specified by the various manufacturers, included the TX line losses of 3.72 dB (1.24 dB per 100ft of cable used) for each site and an N-Type connector loss of 0.3 dB per connector (four connectors used). Output Power = + 22 dBm TX Branching Loss = 1.5 dBm Antenna Gain = + 27 dBm Propagation Losses = 114.341 dBm Other Losses = 8.34 dBm Antenna Gain = + 27 dBm RX Branching Los = 1.5 dBm Received Power = 49.68 dBm Receiver Threshold = 78 dBm Fade Margin = + 28.32 dB Fading and interference calculations The amount of attenuation expected on the link due to rain was calculated using the formula in (2)[4], where R0.01% represents the rain rate exceeded 0.01% of the time in mm/hour and D the path length in kilometers. Multiplier a and exponent b are values taken from the North American and ITU-R rain attenuation coefficients chart, while d represents the effective path length in kilometers. The link operating at 5.8 GHz over two miles can thus expect 0.106 dB of additional attenuation during the heaviest rainfall. (2) The possibility of the radio signal being diffracted was investigated by observing the structures surrounding the microwave beam and calculating the first and second Fresnel zones using (3)[5]. The distance from the antenna to any possible obstruction is given by d1 while d2 represents the remaining distance to the other end of the link. (3) Since the Fresnel zones consist of a series of concentric circles, the areas to the side, above and below the microwave beam had to be clear of obstructions. The height of the two buildings where the antennas were to be installed provided enough clearance to ensure no obstructions within the first two Fresnel zones. With a mere 0.106 dB of additional attenuation from rain and no possibility of the signal being diffracted or reflected, only 3 dB of variation on the calculated receive level was expected. The 3 dB of variation is due to component tolerance and is specified by the equipment manufacturer. Microwave link installation The antenna and radio frequency unit were installed on a mounting pole on the roof of both buildings, in accordance with the manufacturers recommended installation procedures. A high quality 5/8 coaxial cable was used to connect the antenna to the RFU. The digital units were installed in 19 racks inside the buildings while Belden 7921A Shielded CAT5e cable was used to connect the DU to the RFU. All the hardware was grounded to the various grounding points at the sites and the recommended impedance of less than one ohm measured on all ground connections. The antennas were aligned using a digital voltmeter connected to the back of each RFU. The DC voltage reading from the voltmeter was compared to the received signal level (RSL) chart shown in Fig. 3 [6] which was supplied by the radio manufacturer. [1] Fresnel Zone http://www.webopedia.com/TERM/F/Fresnel_Zone.htm [16 June 2000] [2], [4]-[5] GTE Lenkurt. 1970. Engineering Considerations for Microwave Communications Systems [3] Harvey Lehpamer. 2004. Microwave Transmission Network:, Planning, Design and Deployment [6] Harris Stratex Networks. July 2004. Velox LE Installation and Operation Manual.

Harverd Case Roche

Advanced Corporate Finance Final Case: Roche 1 2 Reasons for Roche’s 100% ownership of Genentech Since Roche and Genentech both operate in the pharmaceutical industry, but still have their own specialty, they can benefit from a partnership. Roche owns a majority stake in Genentech since 1990 and since 2007, it owns 56% of Genentech. Genentech was founded in 1976, their focus lies on biotechnology in which they are the second largest firm of the world. Genentech had become an important part of Roche’s business representing 24% of Roche’s pharmaceutical product sales in 2008.In July 2008, Roche made public that they’d want to acquire the remaining 44% of Genentech. For Roche this acquisition beholds several benefits, but of course also several risks. These benefits and risk are stated below. Benefits First of all since Genentech, in terms of revenue, is the second largest firm in biotechnology in 2007, a full acquisition will strengthen the market positions of both companies. Genentech experiences an expanding growth in sales (see exhibit B), so both companies notice more and more direct competition of each other in several U.S. markets. A merger of Roche and Genentech would take away the direct competition and create new opportunities and strengths which would give them the opportunity to excessively work together on a world wide scale. Secondly, the acquisition beholds a great cost reduction. Roche managers believed there was increasing duplication of effort and facilities at the two companies and, thus, opportunities to create value by cutting costs and streamlining operations.They identified that annual savings realizable over five years would be between $750 million and $850 million, most of which would be in manufacturing, General &Administrative and commercial operations. Another benefit of Roche owning 100%, a merge of the two companies would give Roche access to all the intelligence of Genentech. The concerns about property ri ghts blocked the flow of information between researchers at the two companies. By the merge, they can share their intellectual property, which might facilitate product development and research.Thus the constraint between Roche’s and Genentech’s R&D efforts would disappear. Since the R&D pipeline of Genentech grew stronger by the day in the ten years before the announcement (see exhibit A, B and C), a merge would be a big advantage to Roche. Finally, since the beginning of 2007, the free cash flow of Genentech grew largely. Roche could not access Genentech’s cash directly under the present ownership structure. If a merge occurred, Roche would gain full access to the cash of Genentech.Because expectations are that Genentech’s cash flow will remain high, full access to this cash would have many advantages to Roche, like repaying the debt made by the acquisition. Risks Besides the benefits, there are also several risks involved with the takeover. First, the t akeover would cost $44 billion, which partially would have to be loaned. The management wasn’t sure that Roche would be able to raise the required debt funding given the state of the financial markets. In the middle of the financial crisis, banks weren’t very keen in arranging bridge loans to finance such acquisitions.As a result of this, even if they were able to manage in getting a bridge loan, this would be very expensive. Secondly, it is very hard to value the benefits to Roche in taking over Genentech. One of the causes of a misvaluation is that synergies tend to be mispriced. On top of that, Genentech was waiting on test results of their cancer drug Avastin, wich were to be expected in April 2009. If the acquisition would take place before this date, Roche bears the risk that the drug is rejected. Which would result in a drop in value of Genentech.The risk that Roche takes by waiting on the test results is that, if the test results tend to be positive, stock pric e of Genentech would increase, making a deal substantially more expensive and thus making it even harder to finance it. Finally, there is a big chance of losing a lot of the human capital of Genentech. Genentech has become famous for its strong working culture. This is partially because of the fact that most of the minority shareholders are Genentech employees. By taking over Genentech, Roche risks destroying the old culture and as a result, losing the employees to other firms.Acquisition of Genentech by Roche would bring synergies to both companies. The several risks that are involved, are mostly being compensated by the benefits to Roche. The high debt can be repaid by the large amount of cash of Genentech, the risk brought by the uncertainty of the test results can be reduced by letting independent firms estimate Genentech’s stand alone value, and the employees can be compensated for the loss of their share in Genentech in another way, e. g. by developing a strategy which maintains the important current working culture. Both companies would increase in strength

Out of the Dust Essay

In the novel, Out of the dust, Billie Joe experiences conflict with herself, her environment, and others. Additionally, she has great conflicts with her dad. They secretly blame each other wanting the other to know they accidently killed the mom. Billie Joe also has to deal with the dust. The dust kills families and destroys homes. Futhermore, she also has a conflict with herself. She knows she accidently killed her mom, but despite tragedies and conflicts Billie Joe knows that her family loves her and they forgive her by coming together to help each other live in peace. Billie Joe works against herself by blaming and limiting herself. For example, she stops trying to heal her hands. She has an amazing talent of playing the piano, but since she suffered burns on her hands, she limits herself by not practicing. Without her mother’s support, Billie Joe can barely go on in life without thinking of her mother’s death. Billie Joe still has her dad but both stay stuck in the horrible past. She and her dad both move on knowing they love each other and that they can help one another get through the horrible times. Billie Joe encounters nature in a horrible way. He dust causes huge problems for the people living in Oklahoma and all the dust bowl states. The dust comes in as thick clouds, burying houses and sickening families. Billie Joe cannot wait to leave her town along with other families wanting to escape from the dust and drought. She makes a decision to leave Oklahoma on a train. After Billie Joe arrives in California she realizes that the dust defines her and she can’t leave her dad at home to live by himself. In the novel, Out of the Dust, Billie Joe finds herself battling for a relationship with her father. Billie Joe and her father both know they have a part in the mother’s death. They both secretly blame each other wanting the other to have the guilt instead. In the end, Billie Joe and her father come together knowing the both love each other and they can’t afford to lose each other. In the end, Billie Joe still experiences conflicts with herself, her environment, and others. As she goes on in the book, she finds that if she comes together with her father they can help each other move on from the tragedy. As the dust comes into her town, Billie Joe struggles to live her everyday life. She then runs away but decides that the dust defines her and she must go back. Billie Joe then has to deal with not blaming herself about her mother’s death. Billie Joe figures out that if she ultimately accepts her family, she can defeat any battle thrown her way.

Mcdonald s Successful Fast Food Chain - 911 Words

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