Mobile Communication Systems: Digital vs Analog Systems and GSM Framing Format, Slides of Mobile Communication Systems

Download Mobile Communication Systems: Digital vs Analog Systems and GSM Framing Format and more Slides Mobile Communication Systems in PDF only on Docsity! 1 C O N N E C T I V I T Y Radio System Mobile Communication Systems docsity.com 2 Digital vs Analog Systems • Analog mobile phone systems modulates voice signals without converting them to digital signals • Results  User receives actual voice with all frequencies  Reception includes noise from surroundings ( Normal radio channels )  Error correction was limited and difficult • Digital mobile phone systems converts voice signals to digital signals by using a speech coders and these binary streams are modulated over analog signals • Results  Not all frequencies are transmitted, voice is altered by speech coders  Reception is much better and noise removal is easy as in CDMA discussed  Error detection and correction is feasible to a greater extent as discussed  Bandwidth utilization is better as discussed in CDMA docsity.com GSM900 Digital Worldwide 1992 900 MHz See Developed Section asa 11.3 European standard, has become highly successful GSM1800 Digital Norldwide 1994 1800 MHz Sameas Originated GSM but in the ata United higher Kingdom frequency asa means of breaking the cellular duopoly GSM1900 __— Digital United 1996 1900 MHz Same as States GSM but ata higher e frequency e , docsity.com  Analog or Countries Date of Frequency Key Name digital of use introduction band features Comments DAMPS Digital United Mid 1990s = 800 MHz Direct States replace- ment for AMPS CDMAone _ Digital United Late 1990s 800MHz Only See (previously States and and 1900 system — Section known as Asia-Pacific MHz to use 11.4 18-95) CDMA PDC Digital Japan Mid 1990s = 800 MHz Has not been successful Personal Digital Cellular outside Japan > docsity.com 7 Why so many networks • Actually there are two main branches of mobile phone networks  Digital  Analog • All digital networks works on same patterns the basic structure is similar with few exception same is the case with analog systems • Digital systems vary in terms of frequency they are using e.g. GSM900, GSM1800, GSM1900  A mobile phone capable of working at 900 might not work at 1800 except it is a dual band mobile phone • Different countries impose certain condition for mobile phone operators that’s why they have to limit to certain frequency band • One major reason is that once a system is adopted by one or more operators others have limited room to grow such as GSM vs CDMA  The major reason is a lots of software hardware is available for these devices on the other hand new technologies don’t have this favour • Japan and USA implement their own standards while in most of the case neighbor follow these technologies to facilitate their customers docsity.com Traffic channel of a single user Shs ebetetsteP yet tats} tspeyrte diffs} ays teris ti Bursts for user allocated slot 1 S docsity.com  Slots delafafsfef7yelipelafafsfer7{elafe[sf4a[sfe]7]al a... ¥ Bursts for user A 12131475] 6] 778] 9) tof i) 12] 13fs4] 15] 16} 47] 18) 9] 20] 21] 22] 23]24] 25}o6] 4 allocated slot? = ITT TT) PT] Pty Ut] ate dsp qty ip dtp ytd qty ytd yt Bursts for user B P2131 475] 6] 778 | 9/109 14) 12] 13)44] 15] 16]47] 18] 19] 20] 21] 22] 23] 24] o5}oq] 4 allocated slot 1 TH UTE UT) UTE UTE UTE aT aT aT TT tos docsity.com 12 Slow associated control channel • Each mobile sends speech data and information about its surrounding cells  The capacity required to send information about its surrounding is 1/24 of the capacity required for speech  Out of 25 burst one is reserved for sending information about surrounding • Actually the 13th burst contains information about the surrounding after 13th burst 12 more burst are sent then the cycle is repeated  The burst reserved for sending information about surrounding is termed as control channel  As the traffic channel is used for sending this control information it is termed as associated control channel  As the capacity used by this channel is much smaller as compared to other control channel in GSM it is termed as slow associated channel docsity.com