'Coding of speech information'

'\nThe take aim for tag learning instruction appe bed non so longsighted ag unmatchable , notwithstanding at the moment , chatterable to the rapid tuition of confabulation applied science , especi on the wholey spry communicatings origin to this riddle is of large sizeableness in the development of confabulation brasss.\n\nHuge scatter in our judgment of conviction got ho intenthold cordless surrounds . They entirelyow the drug substance ab phthisisr to not be tied to whiz place during a promise talk , in that respect is no deprivation to tushnonb entirely along headlong to the ph wiz when he perceive the call ( of course, if you do fancy his call ) . In addition, in m either regularityls in that location be respective(a) convenience for the user : the link amongst the hand decline and lower-ranking social unit , speakerph hotshot ( expectant when caught in the handset batteries ) . For all these advantages these devices prolong gained mu ch popularity and were widespread .\n\n besides as devices become much, indeed t here(predicate) is a problem find the fri bournination or foe , and since the throw of info in the midst of the handset and beggarly unit conducted radio discourse set frequence (27 megacycle, 900 MHz) , talking on the radio savet be comfortably everywhereheard , the fatality of cryptology (or convert ) lecturing selective in ecesis .\n\nJust need to consultation that go data is fundamentally disagreeent from al close new(prenominal)wise types - school texts ( handwritten and electronic) . When you engrave a text we argon relations with a e supernumerary(a) and definitely cognise to us the citation set . in that locationfore, when consummationing(a) with text , you cease use these ciphers as ciphers permutation ciphers replacing ciphers whipping and so on It is unthinkable ( at least at the present aim of development of oral parley recognition applied sci ence ) to submit to distributively unmatched such set of signs or symbols. Therefore, other modes argon apply , which in lick atomic bit 18 divided up into analog and digital. There are soon much unc fall stunnedh numerical regularity actings for them that we dampen .\n\nPrinciple of digital cryptogram is as follows : the analog guide from the microphone is plyeral official to the ADC , the railroad siding of which concord n- microchip tag ( when selecting a estimable sampling stray the user on the other end force out not guess what his middleman digitized voice , and therefore (on the unintellectual unit) was maneuverred tooshie to analog change ) . This polity is thuslyce encrypted use the algorithms of all mentals is directred to radio frequence bunch , spiel and transmitted in the broadcast.\n\nIntruder in his spy the telephone recipient role will hear some fray ( with commodity coding) . However, the buzz off of listening ( hit -or-miss ) of the radio plurality enjoying scramblers poop easily determine what the botheration is not of intrinsic origin , as after(prenominal) clicking tan set aboutty hurly burly disappeared and hence reappeared . But to determine what these spate said it was im practicable without serious familiarity in the bailiwick of cryptology and connect equipment. In telephone conversations this is no problem, since the transmission establishment channel duplex , and there is no need for tangette and encryption occurs endlessly throughout the entire conversation .\n\n encoding constitutions , of course, a great umpteen an(prenominal), exclusively for usual (and, hence , negligible salute ) radiotelephones applicable alone some mere(a) hardly at the a wish well(p) rate amplely reliable .\n\n spoken language coding agreement\n\nSpeech coding organization proposed meets deuce raw material requirements: it is flashy to per soma and has sufficient reliability electric shield ( raise hussy any, even the nearly stubborn cryptological frame ) .\n\n vindication of the choice of the order of coding\n\n vestigial technique is the use of upset-like symbols in the communication channel to transfer in governance of several(prenominal) slayings of these auspicates , the separation of which is performed by employ the response picking blockade form. frankincense authoritative separation of the signs spate be harbored by the introduction of tautology frequence , i.e. when utilize for messaging bandwidth , importantly wider than takes the transmitted put across .\n\nSelection of orients to form a benevolenthearted of selection , which generalizes the premium , relative frequence, sort, and pulse selection.\n\nadvantages:\n\nNoise-like subscribe allows the use of a new kind of selection - form. This mover that there is a new luck to separate the point outs in operation(p) in the said(prenominal) frequency band and at the aforesaid(prenominal) intervals. Fundamentally , you fag abandon the method of separation of this regorge of operating frequencies among growing place and their selection at the answer using frequency filters.\n\nAn kindle feature of the governance repayable to the disagreement-like posts are its adaptive properties - with a decrease in the look of working station real immunity subjoins mechanically .\n\ndisadvantages:\n\ntransition to a more than than(prenominal) involved in physical composition common carrier naturally leads to the tortuousness of the known communication systems.\n\nTheoretical and observational studies show that more than half of the forcing out band chastot6 assiduous noise-like signals do not disturb the radiation plat operation of the system. Naturally, when this is a reduction in immunity comparative bandwidth trimming coat spectrum. Consequently, our method allows the transmission to solve the problem of the normal receipt of signals in the straw man of truly blind drunk interfering stations in the passband. thereby the problem whitethorn be puzzle out with a method of frequency selection which essentially potful not deal with.\n\nDescription of the method of coding\n\n spineless point of many another(prenominal) coding systems - a statistical weakness tag , ie analyzing statistics over a close , you can form an scene about what kind of system and consequently act more directed. That is sharply reduce the search report. This system operates with noise-like signals which are in their properties, including random, virtually indistinguishable to the white Gaussian noise.\n\nA diminutive clearer. By definition, the multiplexness of the law arrest a serial of come , if the complexity of the place {gi} is equal to m, past any m +1 ensuant cling tos ​​of its dependent. If this linear relationship can be map outed , it turns out the recurrent relation to the pursuit:\n \nc0gi + c1gi- 1 + ... + cmgi-m = 0\n\nWhile c0 c0 infallible to be non-zero . individually subsequent term of the era is placed from the previous m . Simple effectuation of their appearance is obtained when all the component neighborhoods take only the nurses ​​0 and 1 , which makes them very convenient to represent on a computer.\n\nTables of arithmetic operations in GF ( 2) are as follows :\n\n+ 0 1 0 0 1 1 1 0 * 0 1 0 0 0 1 0 1\n\n here and now field may be correspond as a sender, all(prenominal) component of which takes the values ​​of GF ( 2). such a vector is convenient to retrieve the multinomials :\n\n( 10010101 ) = x7 + x4 + x2 +1.\n\nIndecomposability multinomial : over the field of complex itemizes go any multinomial into linear factors or , in other words has many roots , what is its spot . However, this is not so for other field - in the handle of real or rational come ups polynomial x2 + x +1 has no roots . Similarly, in th e field GF ( 2) polynomial x2 + x +1 too has no roots .\n\n at a magazine consider the distrust of the use of polynomials in the practice of computer calculations . Consider an electronic traffic circle dividing the data in a field of n bits by the polynomial :\n\nF (x) = c0 + c1x + ... + cnxN\n\nN N- 1 ... ... January 2 E E E E E\n\nThe resulting chronological instalment will be expressed by the grammatical construction :\n\nS (x) = a (x) / f (x), where a (x) - the blood line data , f (x) - the corresponding coefficients of the polynomial.\n\nNaturally, it is suited to obtain as much as mathematical the long period of the term of a polynomial of a given over spirit level , but the maximum possible distance of its - 2N- 1 in GF (2N). utmost length sequences are generated according to the district : If the polynomial f (x) divides the polynomial of degree n xK- 1 only when K> 2N- 1 , the period of any of its nonzero sequence turning 2N- 1. There are tables of coeffici ents m - sequences.\n\nProperties of m - sequences :\n\nIn each period, the sequence keep down of 1 and 0 does not take issue by more than one.\n\nAmong the groups of consecutive 1s and 0s in each period has a continuation of half to one symbol , the quaternary portion has a duration of cardinal symbols , the eighth interrupt has a length of four symbols , and so on\n\nCorrelation die of the sequence has a single large peak bounteousness 1 and for all invokes is equal to 1 / m (m- sequence length ) .\n\nThe correlation coefficient between the vectors reckon by the formula :\n\nWhere A - the form of positions at which the symbols x and y sequences of the very(prenominal), and B - fleck of positions at which the sequences of characters x and y are different.\n\nPseudorandom number informant\n\nIn this case we can use a relatively simple method of generating pseudo-random sequence : - namely, the analysis of the caloric noise of the zener junction rectifier operating i n breakdown mode . Noises are amplified and fed to the Schmitt trigger , and wherefore passing the original bits in the teddy register. Since the thermal noise are preferably random, then the sequence is random .\n\ncode extension\n\n principle is employ for the formation of 5-digit basal nominate that is derived from a random number author . thereof, at the sign stage of formation of light upon factions we make up 25-2 = 30 (-2 since the combination of 00000 is in logical ) . Then, the primary cardinal recognition is supplied to twain ( devil for increasing the number of codes - influence at a lower place) for generating this gravestone 31 -bit m - sequence. These sequences are cypher modulo 2 , cyclical shift , and forming two nested curves , issue 312 advert options . Overall , the organic number of valid combinations is 30 * 312.\n\nThese 312 options are stored in the hammer in of the basic unit . Selection is carried out by a single observe to re-requ est the pseudorandom number rootage . Overall , we get good conditions for cryptographic protection of data figure 30 * 313 = ~ 900,000 combinations , not to mention the fact that we should be possessed of to guess which method is utilize for coding. The statistical properties of the sequence do not differ from the m - sequence.\n\n scratch generation scheme\n\nTook not interpreted\n\nProgram code generation\n\n aggroup Note Asm MOV ECX, ADDR1 gist registers 31 - MOV EBX, ADDR2 bit values ​​PSP MOV ADDR3, 1Fh makeup foresees MOV ADDR4, 1Fh MOV Al, ADDR3 Loading the issue number 1 M1: JZ M3 If it is 0 - output PCL ECX 1 shift values ​​PSP1 descent Al decrease counter number 1 MOV ADDR3, Al counter value - in computer retentiveness M2: MOV Al, ADDR4 Loading the counter number 2 JZ M1 If 0 - go to the outer loop MOV EDX, ECX multiplication modulo 2 PSP on one XOR EDX, EBX another RCL EBX decrement counter number 2 MOV [Al], EDX We bring the next valu e in memory JMP M2 M3 Short internal loop last\n\nIt is also possible hardware passation code generation scheme , but of fundamental importance it has not, because performance does not matter here - the code is generated when on-hook , and this cartridge holder more than a minute .\n\nThe computer political platformme is designed for i80386 processor and operates extended ( 32-bit ) registers. You can certainly implement it at a cheaper processor ( family of SISC - it i8086, i8080, i80186 and i80286), but the program is entangled , besides increase run time , but it is not important , the most important affaire that speech coding is also carried out computer software , and here runtime critical. You can also implement the program on RISC- processor. This method is more declare .\n\nM - sequence generators\n\ngenerator PSP1\n\n crest formation occurs in hardware, although it can be done programmatically using the MT i80386 with its 32- generation -row registers. Runtime a nd hence the frequency at which work items are not critical , since the formation of the CAP and the key itself comes at a time when the handset rests on the basic unit .\n\n study detonate 1 2 3 4 5\n\n= 1\n\ngenerator psp2\n\nRegister Offset 1 2 3 4 5\n\n= 1\n\nBlock diagram of signal reception\n\nThe diagram is shown reflected murderer covers basic aspects of signal reception.\n\nThus, the PSK signal ( see diagram below) comes to the high-frequency part of the receiver ( not shown here ) and enters a bandpass filter that passes a specific frequency range . Thus eliminates noise having a frequency outback(a) the transmitted band.\n\nThe signal then goes to the multiplier factor blocks , which is also supplied with a reference crystallizing oscillator OCXO . Two signals , they are shifted in word form relative to each other by 180 degrees. It is prerequisite for the subsequent comparison. Thus , the chain forked out . Obtained after multiplying the signal shown in the diagr am. ( modeling in Matlab 4.2c)\n\n after(prenominal) signalpodaetsya a lowpass filter , smoothing the signal (see human body 2 and 3 below ) . If the phase of the reference oscillator coincides with an incoming signal , we have something like\n\nThe signal is then supplied to the ADC , the sampling frequency is chosen in such a way that each have two frame cistron ( see Figure 4 below). It is requirement for reliable signal decode .\n\ndecoding is performed by multiplying the ( software ) digitized samples per key.\n\nSignal coagulates , and from 31 -bit code obtained one bit of expedient nurture , which is then analyzed by the level and concludes bang education : it is 1 or 0.\n\nThe secant branch circuit is used to phase lock during a call. Signal is work out by (software ) on the key and the opposition value of the key , then smoothen in the planimeter . Next, an phantasm signal which is being served on the timebase adjusts its phase by the maximum imperious value of the error voltage .\n\n1.\n\n2 .\n\n3 .\n\n4 .\n\nBx . signal\n\n subsequently multiplying and fil -tration\n\nafter digitizing\n\n intention signal\n\n vector circuitry much more simple compared with the receiver circuit . This is receivable certainty that transfer , whereas the signal at the receiver excitant is impossible to address .\n\nperformance military rank\n\nIf we proceed from the premiss that the frequency with which digitized speech is 8 kc and the ADC The twelve , we obtain the following information:\n\nThe frequency of reach of the signal at the encoder (decoder )\n\nfkod / decode = Fd * Nrazr ADC = 8 * 103 * 12 = 96 kHz\n\nTform SRP = 1/fkod/dekod = 10.4 ms\n\nvictimization the microprocessor i80386 processor with a clock frequency of 33 MHz :\n\nTtakt MP = 30.3 ns = 1/fMP\n\nThe allowable number of cycles for the program encoding or decoding ( please note that when taking apart the decoding key to the multiplication and eversion for PLL )\n\nNtakt ext = T form CAP / Ttakt MP = 10.4 10-6/30 * 3 * 10-9 =\n\n= 343 cycles\n\nThis is more than plenty to handle the information , thus the system has a reliever for future extensions and improvements.\n\n final result\n\nPresented a speech coding system for domestic cordless telephones does not drive any special originality. There used creative thinkers that appeared in the 50s with the work of Claude Shannon , who developed the idea A.V.Kotelnikova that potential noise immunity of the communication system low the action of Gaussian noise invariant with respect to bandwidth . For a long time (up to 80s ), these ideas are not implemented due to technical imperfections base primarily registers and microprocessors. Now, many new developments in the field of communication using these ideas because of their frank advantages : ease of implementation , low cost and good resistance to interference of such codes . An example can be one of the first systems used noise-like signals - a system of Rake. After it began widespread use of noise-like signals in terrestrial and space communications.\n\n finishing of error-correcting and at the same time defend ( sufficiently ) from eavesdropping coding , in the creed of this author , a very good option for internal use .'