Mobile Computing Technologies - Essay Example

Mobile Computing Technologies Part A1 You are required to design a mobile communication link between 2 points in Sheffield city centre approximately 1.5km apart. The link must be capable of providing audio transmission. Systems based on analogue and digital modulation techniques (AM,FM) and (FHSS,DSSS) respectively have been proposed and you have been asked to research and evaluate the following: (you must clearly state any assumptions you have made when answering) 1. Which is the best modulation and why? FM is the best modulation. This is because the FM modulation does not fall prey to interference and noise like AM does. The sound quality of FM is greater as compared to AM. This betterment of sound quality is owing to availability of higher bandwidth as compared to that of AM. 2. Which system would provide the optimum quality audio transmission? The FHSS is expected to provide the optimum quality of audio transmission. The capability of FHSS to resist any interference from false RF signals is supposed to be quite a number of times better than the capability of DSSS. The implementation of FSSS system is easier. A lower power density is used by DSSS. This makes the detection of DSSS harder. Another reason why DSSS is not preferred is that in order to ensure reception it sends redundant copies of encoded data. 3. Assuming normal UK licensing restrictions - propose a suitable frequency bands for each of the systems and state any implications this may have. The suitable frequency bands would be between 275GHz to 275.25GHz for uplink and 275.35GHz to 275.60GHz for downlink. This is because this part is not allocated to any other cellular company. One of the implications that may be associated in this case is that the assignment would have to be within the standards set by ITU. The maximum limit of allocation cannot exceed 300GHz in accordance with the set limits as shown in the Figure 2: (Roke Manor Research, n.d.) Figure 2: UK Spectrum (Roke Manor Research, n.d.) Part A2 1. Assuming the system is point to point fixed link is required investigate a suitable types of antennae and propose a suitable design. The Suitable antennas may be: 1. Yagi Antennas, 2. Directional Radio antenna 3. Backfire antenna 2. The receiver system to be used is based on the Superhtrodyne design. Briefly explain the principle of operation of the Superhetrodyne and discuss any potential issues which may be of concern with this type of receiver design and receiver systems in general. The way Superhetrodyne receives is that it uses frequency mixing and converts its received signal into a fixed Intermediate Frequency. An If or an Intermediate Frequency are much conveniently processed than the conventional radio carrier frequency. One concern with Superhetrodyne is that along with the wanted signal it also generates an unwanted signal which is referred to as image frequency. This is a problem because it is a false response. The only way this response can be prevented by incorporating a filter that would restrict the image frequency from reaching the mixer. Another problem is local oscillator radiation. Part A3 It has been decided that the cost of implementing a bespoke communication link is too expensive and the existing cellular infrastructure will be used. The GSM mobile unit 1.5km away is receiving a signal from the Vodafone base station transmitter on top of the Owen Building (post code S1 1WB). 1. Estimate, using an appropriate model, the path loss between the base and the mobile As height of transmission and receiving antenna is not given. We will use free space propagation model according to that L(p ) = 32.5 +20 log ( d) +20 log (f ) Where L(p) is Path loss, d is distance and f is frequency. As Vodafone operate on 900 MHz for audio link and the distance is 1.5 km L(p)=32.5+3.52+59 L(p) = 95.5 dB 2. Suggest alternative models that could be used to model the path loss Suggested alternate models: 1. Okumara Model 2. Hata Model 3. If road traffic passes between the base station and the mobile how will this affect the signal? When signals collided with road traffic they can cause diffraction, absorption and multipath fading. When signals collides with a material it can lose its strength and its path can be reflected and refracted thus causing delay in receiving of signal which result in Multipath fading. 4. Find the received signal power by calculating the link budget for the system. Received Power (dBm) = Tx Power (dBm) + Tx Antenna Gain (dBi) + Rx Antenna Gain (dBi) – FSPL (dB) Let gain for Parabolic antenna be 2.14 dBi so the transmitted power is calculated to be 56.3 dBm Hence Received Power (dBm) = 56.3+2.14+2.14-95.5 = -34.92 dBm 5. Find the overall noise temperature of the receive system if it consists of: an antenna of 5dB gain in the direction of the mobile a cable with 2dB loss a receiver with a noise figure of 0.7dB and a gain of 40dB Overall noise temperature is calculated to be 0.025K 6. Find out the modulation scheme used in GSM and so work out the bit error rate for the link between the base and the mobile. It uses GMSK modulation scheme.BER for GMSK for 1.5 km link is 2. Part A4 The cell in which the system operates has 48 channels and monitoring of usage suggests that each user is likely to make 4 calls per hour and with duration of 7minutes. If a Grade of Service (GOS) of 2% must be achieved what is the maximum number of user that the cell could support. To increase the capacity of the area and or cell what techniques could be used. You should consider physical/hardware possibilities and channel allocation strategies. The techniques that can be used are: 1. Cell splitting 2. Sectoring 3. Repeater for range extensions 4. Microcell can be introduced Introduction to 4G The evolution of mobile networks began around three decades back. It has been since then that their progress towards betterment began. The original initiation can be traced back to the mid of the earlier century: "The US Federal Communications Commission (FCC) approved the first commercial car-borne telephony service in 1946, operated by AT&T." (Dahlman et al., 2011, p. 2) The very first mobile phone communications spread internationally were in the early 1980s. The digital technologies used to develop second generation of mobile communication standards came round about the same time frame. This advancement improved not only the quality of the voice transmission but also enabled development of true mobile devices that were much more developed. The term 4G represents fourth generation wireless standard for cellular systems. The requirements specifications of 4G standard are named as IMT-Advanced (International Mobile Telecommunications Advanced). It was in early 2008 when ITU-R (International Telecommunications Union-Radio communications sector) laid down this set of requirements. 4G standard is a planned and well thought off continuation of its predecessor i.e. 3G standard. According to ITU-R, for a highly mobile wireless connection (such as a moving object like car or train) the max speed requirements for this standard are 100 megabits per second while for stationary or low mobility wireless connections it is 1 gigabit per second. "An integral part of this architecture is a streaming proxy, which acts on both the service and transport levels. It is flexible enough to deal with different operator requirements and that it can provide high-quality streaming services in a mobile application environment." (Tanvar, Singh, Gour, 2010, p.695) Almost all of the packet switched technologies can be utilized by 4G owing to the fact that it is a multi-use and adaptable technology. Both OFDM (Orthogonal Frequency Division Multiplexing) and OFDMA (Orthogonal Frequency Division Multiple Access)can be used by 4G. The intervention among channels associated for data streaming and symbols can very well be minimized by 4G. MIMO or the Multiple Input/ Multiple Output Technology can also be used by 4G. MIMO is an antenna technology by virtue of which data speed if optimized and errors within the networks are reduced. 4G covers UMTS as well. UMTS (Universal Mobile Telecommunication Service) carries voice, video, text and other types of multimedia data at speeds of 2Mb in the form of packets or frames. This facility helps 4G by enabling International roaming on mobile phone via GSM. "4G networks make it possible for completely new classes of mobile applications to be developed to take advantage of such high data rates, and a framework describing such applications is highly desirable." (Yang, 2012, p. 354) Yang (2012) also researches that it is the possibility of expansion of 4G that would eventually lay the basis of cloud based mobile telecommunications. Fundamental Concepts of WiMax and LTE: The ITU-R under the guidelines and requirements chalked out in IMT-Advanced, sought proposals regarding implementation of 4G standard from communication standards organizations. The proposals received were primarily wrapped up around two technologies that were, WiMax and LTE. The text appended below reviews both in detail under the perspective of adoption of 4G standard. WiMAX: WiMAX is an abbreviation of “Worldwide Interoperability for Microwave Access”. It is a wireless broadband communication technology that is based on IP. WiMax standard was developed by IEEE initially as 802.16 - 2004 for stationary access and then superseded by 802.16e – 2005 (WiMax Mobile) for both stationary and mobile accessibility. IEEE submitted a proposal to ITU-R in late 2009. This proposal was based on IEEE 802.16m standard in order to meet the requirements penned down in IMT-Advanced. WiMax is designed for MAN (Metropolitan Area Networks). It can provide wireless broadband access up to the radius of 50 km or 30 miles for stationary locations and 5 – 15 km (i.e. 3 -10 miles) for mobile stations. WiMAX works on both frequencies that are licensed and non-licensed. The key advantages of using WiMAX are cost optimization and uniform adoption of advanced features of radio technology. LTE: The cellular standards of High Speed Packet Access eventually evolved into the LTE standard of 3GPP. Since the 3GPP standard comprised of international standardization bodies from several countries, its official LTE standard became to be known officially as "document 3GPP Release 8". Since this release 8 was all in compliance with the requirements of IMT advanced it was also commonly being referred to as 3.9G. Eventually by September 2009 'document 3GPP Release 10' was finally proposed. (Abichar, Chang, Hsu, n.d., p. 29) Roaming Internet Access via cellular phones and devices that were handheld is supported mainly by a broadband technology termed as the LTE (Long Term Evolution). Several older communication standards have been left behind by the significant improvements that LTE is accompanied with. These improvements are often referred by some as 4G (fourth generation) technology and WiMax. The architecture of LTE is based on Internet Protocol. Thus unlike many other older cellular IPs services such as VoIP, browsing of websites and some other IP based services are also supported by Long Term Evolution. Based on experimental trials, downloads at the rate of 300 Mbits per second are born by LTE. The actual bandwidth that reaches an individual LTE user is however very less owing to the sharing of the service provider's network among other subscribers as well. Cox (2012) mentions the initial prospective advances of LTE and compares them with its eventual implementations in the following words: “LTE was required to deliver a peak data rate of 100 Mbps in the downlink and 50 Mbps in the uplink. This requirement was exceeded in the eventual system, which delivers peak data rates of 300 Mbps and 75 Mbps respectively.” (Cox, 2012, p. 89) A current drawback is that the service of LTE is currently available in a restricted number of physical locations only. However, steps are being carried out by telecommunication service providers to expand the services of LTE. Modulation schemes used The 4G WiMAX networks have been deployed earlier than the LTE standards based networks commercially. LTE is intended to use 700 MHz band while WiMAX is deployed in 2.5 GHz BRS band. Along with operating in two dissimilar bands of frequency, both the standards use different protocols as well. However there are some commonalities that both the standards share: Radio Technology: Both utilize MIMO (Multiple Input Multiple Output) antenna technologies and have as a feature OFDM (Orthogonal Frequency Division Multiplexing) modulation. The OFDM is used on both the downlink and the uplink by WiMAX. LTE based networks incorporate OFDM for downlink while the uplink exploits SCFDMA (Single Carrier Frequency Division Multiple Access). Both the standards share adaptive modulation and FEC (Forward Error Correction) coding levels. Greater Reliability and Higher Capacity: As compared to the former 3G systems the bandwidth efficiency is much better with 4G standard based WiMAX and LTE. Moreover the data transmission is proved to be highly reliable. All-IP Core: The difference among the earlier technologies and the present 4G technology is that while the earlier ones were focusing mainly on the handling and transmission of voice the latest technology of 4G is aimed at focusing on both voice and data. This focus of the 4G covers the entire architecture of Internet Protocol. The main aim is to integrate all the earlier media types into a single usability enhanced single form. The achieving of this point would be done by moving further on the already implemented IP Multimedia System Bandwidth Usage and Data Rates "Data rates for wireless services span the gamut from a few bits per second to several gigabit per second, depending on the application." (Molisch, 2005, p.16) The respective bandwidth usage and data rates for both the technologies in order to implement 4G standards are presented in Table 1 (Abichar et al. 2010) below. Real time applications such as voice applications are supported well by the WiMAX and the LTE. This is because the need for latency in their terms little enough to support the said applications. A user often does not recognize a drop in voice quality if a delay of 50 to 200 ms occurs in the voice application. It is therefore said that voice applications can get away with delays of 50 ms - 200 ms. For the mobile broadband standards low latency thus becomes inevitable. Any application that requires intensive bandwidth can also be satisfied by low latency because it often comes in combination with high rates of data transfer. It is these standards and their support of data rates on a move that a user travelling on a high speed train can also get connected to a 4G network. The maximum speed supported so far is 350 km/h. 4G Licensing in UK Ofcom, the British telecom regulator introduced the 4G mobile spectrum for auction for the expected overall revenue between £1.3bn and £4bn. The bids can be made for 2.6 GHz and 800 MHz bands. Despite being 5 – 7 times faster than its predecessor (3G) networks the licensing for 4G is expected to be comparatively cheaper, reports Mathew (2012). The licenses are expected to be bid in January 2013, with its results to be revealed in February 2013. However according to McCarra (2012), Ofcom considerd the November 2011 application of UK’s largest mobile operator namely Everything Everywhere and issued 4G license way before the bidding process. The telecom giant launched 4G using LTE in the mid of September 2012. Coverage An understanding picture regarding the coverage and other issues related to both the networks (that are WiMAX and LTE) in pursuit of implementing the 4G standards based network services is portrayed through table 2 (Abichar et al., 2010). Equipment Costs Technavio (2011) claims that the Europe is expected to witness a growth rate of CAGR 57.3 percent regarding 4G equipment market during the period 2010 – 2014. Technavio (2011) on behalf of the research conducted by its industry analyst also indicates that the TCO (Total Cost of Operation that generally comprise of CAPEX (Capital Expenditure) and OPEX (Operational Expenditure) required for deployment of 4G standard based networks is four to seven times lesser than of 3G network equipment. Moreover the LTE based implementation of 4G standard requires smaller number of access nodes with a flat RAN (Radio Access Network) which in turn reduces the OPEX and CAPEX more. The cellular operators do not mention the pricing details when there is time to the going live of the service. It is very probable that the 4G data usage would be a part of the mobile contract in the same manner that 3G data usage is part of mobile contracts today. Every new technology is usually introduced at a Premium price. It is therefore expected that the cost of the 4G based contracts would be slightly higher than the current contracts being offered. The deployment of 4G would probably take each company billions of pounds. The last thing that these companies would want is that the technology in which they are financing would not receive a whole hearted response. After the launch of 4G it would take them a while to cover their costs incurred. The infrastructure upgrades would probably be the reason for the actual money making of the service providing companies. It is thought that the updates would most probably be sent out for being sold at cheap rates in order to promote the sales. The eventual pricing of the 4G data services would however be within the limits of the EU wholesale pricing guidelines for data. (Woods, 2012) Proposed deployment(s) within UK The table below titled Figure 1 (Lomas, 2013) demonstrates the current view of the spectrum holdings within UK. The table shows that only two spectrums have a spectrum which is liberalized. These spectrums are EE and Three (H3G) respectively. The table also demonstrates that how EE became as a result of the merger of Orange and T-Mobile. This way it became possible for EE to be able to use the existing spectrum for 4G. It may be seen in the table below that while EE possesses a large spectrum (2 x 45 MHz) the rest of the carriers could not try their hands at a spectrum of similar length: The major carriers in UK want to acquire new spectrum within the 800MHz and 2.6 GHz bands. It is for this reason that they are placing bids. The resultant would be the launching of new 4G networks by the rivals of EE. It is a realistic fact that rivals of EE would not be able to launch 4G if not provided with broader spectrum. Conclusion LTE can be preferred over WiMAX owing to the preference of uplink signal it makes. The choice of LTE makes it preserve the sanctity of performance and system flexibility and still manage to save power. It is imperative to mention here that both LTE and WiMAX use the same means for down-linking that is OFDMA (orthogonal frequency-division multiple access). The use of the same means would be inefficient in terms of power efficiency. This is compromised upon by WiMAX while not by LTE. REFERENCES: Abichar, Z, Chang, J, & Hsu, C n.d., 'WiMAX vs. LTE: Who Will Lead the Broadband Mobile Internet?', It Professional, 12, 3, pp. 26-32, Science Citation Index, EBSCOhost, viewed 10 February 2013. Cox, C 2012, 'An introduction to LTE : LTE, LTE-advanced, SAE, and 4G mobile communications', Books24x7, EBSCOhost, viewed 10 February 2013. Dahlman, E., Parkvall, S., & Sköld, J. (2011). 4G LTE/LTE-Advanced for mobile broadband. Amsterdam, Elsevier/Academic Press. Jaloun, M, & Guennoun, Z 2010, 'Wireless Mobile Evolution to 4G Network', Engineering, 2, 4, pp. 309-317, Academic Search Complete, EBSCOhost, viewed 10 February 2013. Mathew, J. 2012. UK's 4G Licensing Fees to Fall Well Below 3G Rates. Available: http://www.ibtimes.co.uk/articles/404319/20121113/4g-3g-ofcom-ee-vodafone-o2-three.htm. Last accessed 10th Feb 2013. McCarra, D. 2012. Everything Everywhere to offer 4G in UK as early as next month. Molisch, A. F. 2005. Wireless communications. Chichester, England, John Wiley & Sons. Roke Manor Research. (2013) The UK Frequency Allocations.. [online] Available at: http://www.onlineconversion.com/downloads/uk_frequency_allocations_chart.pdf [Accessed: 11 Feb 2013]. Tanwar, G, Singh, G, & Gour, V 2010, 'Multimedia Streaming Technology n 4G Mobile Communication Systems', International Journal On Computer Science & Engineering, 1, 3, pp. 695-699, Academic Search Complete, EBSCOhost, viewed 10 February 2013. TechCrunch. 2011. From 3G To 4G: U.K. Telecoms Regulator Consults On Liberalising All Spectrum Licences In 900 MHz, 1,800 MHz, 2,100 MHz Bands | TechCrunch. [online] Available at: http://techcrunch.com/2013/02/01/from-3g-to-4g-u-k-telecoms-regulator-consults-on-liberalising-all-spectrum-licences-in-900-mhz-1800-mhz-2100-mhz-bands/ [Accessed: 11 Feb 2013]. Technavio.com. 2011. 4G Equipment Offers Low Cost Benefits | TechNavio. [online] Available at: http://www.technavio.com/content/4g-equipment-offers-low-cost-benefits [Accessed: 11 Feb 2013]. Woods, B. 2012. 4G in the UK: What it is, when it's coming and what it means for you | ZDNet. [online] Available at: http://www.zdnet.com/uk/4g-in-the-uk-what-is-it-when-its-coming-and-what-this-means-for-you-7000001819/ [Accessed: 11 Feb 2013]. Yang, SC 2012, 'Mobile applications and 4G wireless networks: a framework for analysis', Campus -- Wide Information Systems, 29, 5, pp. 344-357, Academic Search Complete, EBSCOhost, viewed 10 February 2013. Read More