Table of Contents Executive Summary 2
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- 2.6 Cellular Technology
2.5 Wireless CommunicationThere are two widely used forms of wireless communication, Bluetooth and 802.11. Bluetooth is generally used to connect two devices together to share information on a secure connection while 802.11 is a broadcasted signal devices use to share large chunks of data. Both have pros and cons that make them useful for some things and not for others. Most commonly used is the 802.11 wireless network. The 802.11 broadcasts in the 2.4, 3.6, and 5 GHz frequency bands and has 4 different protocols. The protocols (labeled a/b/g/n) determine the speed of the connection and its range as well as control over data loss and corruption. Below is table 2.5 Table 1, providing some basic information on the four protocols.
2.5 Table 1: List of wireless protocols and their operating frequencies. Each protocol was developed with certain ideas in mind to improve on the previous one. 802.11a (one of the original WLAN) was developed to have a high data rate. However because of its high frequency band it has issues with range. Its small wavelength has issues passing through objects and walls. 802.11b was developed to have a greater range by placing it on a small frequency. It however doesn’t use the same multiplexing in the physical layer as 802.11a (OFDM) so it’s data rate is much less. 802.11b is also known to have issue with common household appliances that run on the same frequency such as microwaves and ovens. This has been known to drop the data rate of 802.11b down significantly, in some cases as much as 1 Mbps. 802.11g runs in the same frequency as 802.11b but uses the same OFDM as 802.11a. 802.11g has been widely adopted due to its higher data rate and availability. Because of this the frequency has become crowded, reducing data rates. The newest WLAN is the 802.11n. It operates on the same frequency as 802.11b/g (2.4 GHz) but also on the less crowded 5 GHz band. Its data rate is increased by adding more antennas for more I/O connections. This is known as MMO or multiple-input multiple-output. Although 802.11g is more widely used, 802.11n is slowly being adopted as the norm. 802.11n also has a greater range than 802.11a/b/g. Bluetooth also uses the 2.4 GHz frequency band. However, instead of using one channel like 802.11, Bluetooth breaks the data into up to 79 parts and transmits it over the full spectrum of the 2.4 GHz (2.402-2.480). Because of this the transmission of data is much more efficient, using less power to transmit then wireless. However this poses a problem. Because the data is split up it must also be recombined and checked on arrival. This causes a drop its data rate. Originally Bluetooth only obtained a max data rate of 1Mbps. By improving its protocol Bluetooth has reach a max data rate of 24 Mbps. Bluetooth is mostly used for devices that don’t require a lot of data transfer and to conserve power. Depending on the range of the device it can use as much as 100 mW or as little as 1 mW. Bluetooth’s maximum range however is around 300ft. Choosing between wireless 802.11 and Bluetooth depends on your intended use. 802.11 has a much higher data rate with range but uses a lot of power. This makes it useful for applications that require large data transfers at high speeds and not as portable. Bluetooth however uses little power which makes it grate for small hand held applications that need to conserve their power consumption. However, because of its data rate the data being sent is only good for smaller applications such as sound, voice or small packets of data. Based off this research Bluetooth would be the best choice for our handheld umpire’s device. Its power efficient nature will allow the device to run much longer and cheaper than if it was equipped with a 802.11 network card. This also allows for the device to be wireless which makes it easier on the umpire. Because the device will only be sending small pieces of data a larger data transfer rate is not needed. As for the Android tablets the coaches will use they support both 802.11 and Bluetooth. If a central device was used to collect both the umpire’s data and the coach’s data to upload to the server, 802.11 stands out because of the size and speed of data that will need to be transferred. Also, this will allow the tablets more flexibility in their distance from the central device. As far as protocol of the 802.11, g and n are both supported and are the best choices with n being the better of the two. 2.6 Cellular TechnologyCellular technology is another choice for uploading the data to the server. It will also be the main means to which the fans will obtain the data to their devices. The 3G model of the android tablets uses cellular and wireless technology. This will enable the umpire’s device to communicate directly with the tablets and then transmitting to the server without a central device. However, current cellular technology is still very young. The tablets support 3G on the UMTS/HSDPA and GSM/EDGE networks. Their frequencies range from 850-2100 MHz. The average data rate for these networks is about 22 Mbps. This is about half the speed of a wireless 802.11 connection. However, because of its network, cellular technology can easily be taken almost anywhere and still receive the same connection speeds where as 802.11 needs a access point within range of it to transmit and losses data rate the further away it gets. So there is a trade off, speed for flexibility. If an easy solution to a readily available wireless network is found it is the better choice however a cellular connection, although slow, may prove to be the best choice. Also, both networks can be use with wireless 802.11 as the main with 3G as backup. Directory: seniordesign -> fa2010sp2011 seniordesign -> Hvac control and Feedback System 0 Group 2 Steve Jones Mathew Arcuri Elroy Ashtian, Jr seniordesign -> Group 5 Spr-Sum 2011 seniordesign -> Senior Design II paper seniordesign -> Remote Touchscreen-Controlled Defense Turret Senior Design Documentation Courtney Mann, Brad Clymer, Szu-yu Huang Group 11 seniordesign -> Flight Performance Data Logging System seniordesign -> Amphibious vehicle seniordesign -> T-100 Watch Dog (Autonomous Security Vehicle) seniordesign -> Ehvac: Wireless Modular Multi-Zone hvac controller Group b javier Arias Ryan Kastovich Genaro Moore Michael Trampler Download 471.88 Kb. Share with your friends:
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