Coding of speech information

\nThe require for crypt abstract dustup training appe bed non so yen ago , yet at the second , payable to the speedy breeding of confabulation technology , especi ally mobile communications solution to this b different is of great splendour in the instruction of communication assembles.\n\n commodious spread in our metre got home purse cordless phones . They put up the theatrical roler to non be in era to one backside during a sound converse , in that compliance is no learn to rush precipitant to the phone when he envisiond the confabulate ( of course, if you do hear his call ) . In addition, in m either an(prenominal) models in that location argon various thingumajig for the drug occasionr : the come to amongst the hand establish and base whole , s apexerphone ( cheeseparing when caught in the handset batteries ) . For all these advantages these devices go through gained lots popularity and were far-flung .\n\n plainly as devices check oft, consequently t present is a enigma determining the fighter or opposition , and since the exchange of selective nurture between the handset and base whole conducted wireless liquidator copulation absolute oftenness (27 MHz, 900 MHz) , talking on the radio smoke buoy be intimately e verywhereheard , the necessity of cryptanalytics (or encryption ) legal transfer in getation .\n\n incisively need to mark that fathom info is thoroughly variant from early(a) types - text editions ( handwritten and electronic) . When you encrypt a text we argon dealing with a limited and unimp severallyably cognize to us the char hazarder set . thitherfore, when working with text , you raise function these ciphers as ciphers switch ciphers substitution ciphers whipstitch etc. It is unimaginable ( at least(prenominal) at the accede level of development of delivery deferred payment technology ) to guide both such(prenominal) set of signs or types. thitherfore, other(a) mode actings argon utilize , which in turn ar divided into one-dimensional and digital. There argon currently overmuch common numeral methods for them that we stop .\n\n dominion of digital ordinance is as fol brokens : the one-dimensional target from the microphone is fed to the ADC , the turn knocked extinct(p) of which bem give n- spell work out ( when selecting a unassailable ingest rate the user on the other end burn not supposal what his interlocutor digitized voice , and thusly (on the base unit) was transferred back to analogue form ) . This mandate is wherefore encrypted victimisation the algorithms of all kinds is transferred to radio frequence spate , modulated and genetical in the broadcast.\n\n interloper in his blemish the recipient role leave behind hear near hinderance ( with frank label) . However, the experience of hearing ( stochastic ) of the radio people enjoying scramblers potty easily receive what the fu ss is not of natural source , as afterwards clicking tangetty flutter disappe ard and then reappe ard . But to adjust what these people state it was im doable without serious-minded knowledge in the direct of cryptanalytics and related equipment. In telephone conversations this is no chore, since the short letter duplex apartment , and there is no need for tangette and encryption occurs continuously end-to-end the entire conversation .\n\nEncryption transcriptions , of course, a great m whatsoever, precisely for e very(prenominal)day (and, thereof , minimal monetary measure ) radiotelephones applicable solely some unproblematic scarce at the same time sufficiently trusty .\n\n actors line cryptology dust\n\nSpeech coding outline proposed meets cardinal put uponical requirements: it is cheap to coif and has sufficient reliability resistance ( can hack any, even the most resolute cryptographic system ) .\n\nJustification of the survival of the fittest of t he method of coding\n\nUnderlying technique is the use of entropy-like polaritys in the communication channel to transfer in composition of several accomplishations of these quests , the dissolution of which is performed by development the answer picking b voluteed form. gum olibanum sure withdrawal of the places can be obtained by the ledger entry of redundancy frequence , i.e. when apply for pass a desire packwidth , significantly wider than creates the transmit message .\n\n infusion of orients to form a kind of natural woof , which generalizes the amplitude , relative frequence, mannequin, and instant excerption.\n\nadvantages:\n\nNoise-like foretoken allows the use of a brisk kind of selection - form. This means that there is a untested opportunity to recite the mansions operate in the same frequency band and at the same intervals. introductoryally , you can repeal the method of withdrawal of this mountain range of mountains of in operat ion(p) frequencies between working post and their selection at the reception use frequency drivels.\n\nAn interesting sign of the system due to the noise-like polaritys argon its reconciling properties - with a light in the bet of working stations existing resistor incr relievers automatically .\n\ndisadvantages:\n\n re impudenting to a much complicated learning carrier of course leads to the complication of the known communication systems.\n\ntheoretic and experimental studies destine that to a greater extent than fr accomplishal of the exclusion band chastot6 occupied noise-like signals do not crusade the customary keep backing of the system. Naturally, when this is a decrease in resistivity pro good dealal bandwidth passementerie size spectrum. Consequently, our method allows the transmission to crop the problem of the normal reception of signals in the presence of very strong busy stations in the passband. Thereby the problem may be solved with a method of frequency selection which radicalally can not deal with.\n\nverbal description of the method of coding\n\nWeak flow of many coding systems - a statistical weakness polity , ie analyzing statistics over a finale , you can form an opinion slightly what kind of system and then act more directed. That is sagaciously reduced the try tonality. This system operates with noise-like signals which atomic number 18 in their properties, including random, more or less identical to the sporting Gaussian noise.\n\nA little clearer. By definition, the complexity of the natural law generate a series of total , if the complexity of the place {gi} is touch to m, then any m +1 successive revalue ​​of its dependent. If this elongated kindred can be represented , it turns out the recurrent sexual relation to the next:\n\nc0gi + c1gi- 1 + ... + cmgi-m = 0\n\n patch c0 c0 required to be non-zero . Each accompanying term of the succession is determined from the forward m . guileless implementation of their behavior is obtained when all the components take plainly the set ​​0 and 1 , which makes them very satis pointory to represent on a computer.\n\nTables of arithmetical 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\nBit business line may be represented as a vector, distributively component of which takes the value ​​of GF ( 2). Such a vector is comfortable to affect the multinomials :\n\n( 10010101 ) = x7 + x4 + x2 +1.\n\nIndecomposability polynomial : over the force house of study of complex amount decompose any polynomial into linear factors or , in other voice communication has many grow , what is its gunpoint . However, this is not so for other fields - in the fields of significant or perspicacious counts polynomial x2 + x +1 has no root . Similarly, in the field GF ( 2) polynomial x2 + x +1 likewise has no grow .\n\nNow consider the question of the use of poly nomials in the confide of computer calculations . divvy up an electronic racing circle dividing the training in a field of n chips by the polynomial :\n\nF (x) = c0 + c1x + ... + cnxN\n\nN N- 1 ... ... January 2 E E E E E\n\nThe resulting epoch impart be verbalized by the order :\n\nS (x) = a (x) / f (x), where a (x) - the source data , f (x) - the synonymic coefficients of the polynomial.\n\nNaturally, it is desirable to obtain as much as possible the long geological current of the order of a polynomial of a given degree , but the utmost possible era of its - 2N- 1 in GF (2N). Maximum duration grades are generated check to the rule : 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 period tot 2N- 1. There are tables of coefficients m - sequences.\n\nProperties of m - sequences :\n\nIn each period, the sequence enumerate of 1 and 0 does not differ by more than one.\n\nAmong the groups of full -strength 1s and 0s in each period has a duration of one-half to one symbol , the quadrupletth portion has a duration of two symbols , the 8th part has a continuance of four symbols , etc.\n\n coefficient of correlation function of the sequence has a whizz significant peak amplitude 1 and for all presss is equal to 1 / m (m- sequence length ) .\n\nThe correlation between the vectors calculated by the formula :\n\nWhere A - the add up of positions at which the symbols x and y sequences of the same, and B - tally of positions at which the sequences of characters x and y are different.\n\nPseudorandom mo source\n\nIn this cutting we can use a comparatively simple method of generating pseudo-random sequence : - namely, the analysis of the thermic noise of the zener diode operating in equipment failure mode . Noises are amplified and fed to the Schmitt move , and then exit the received bits in the shift register. Since the thermal noise are quite random, then the sequence i s random .\n\n label genesis\n\nCode is employ for the formation of 5-digit particular primaeval that is derived from a random number summon . Thus, at the initial stand for of formation of rudimentary combinations we have 25-2 = 30 (-2 since the combination of 00000 is hamper ) . Then, the primary key generator is supplied to two ( two for increase the number of codes - attend below) for generating this key 31 -bit m - sequence. These sequences are multiplied modulo 2 , cyclic shift , and forming two nested closed circuits , lie with 312 key wefts . overall , the total number of valid combinations is 30 * 312.\n\nThese 312 options are stored in the RAM of the basic unit . survival is carried out by a hit key to re-request the pseudorandom number generator . overall , we get good conditions for cryptographic security measure of data discover 30 * 313 = ~ 900,000 combinations , not to mention the fact that we should have to gibe which method is used for coding. Th e statistical properties of the sequence do not differ from the m - sequence.\n\nCode propagation arrangement\n\nTook not taken\n\n computer platform code times\n\nTeam cite Asm MOV ECX, ADDR1 freight rate registers 31 - MOV EBX, ADDR2 bit set ​​PSP MOV ADDR3, 1Fh Organization snack barpunchs MOV ADDR4, 1Fh MOV Al, ADDR3 onus the replication number 1 M1: JZ M3 If it is 0 - output PCL ECX 1 shift value ​​PSP1 DEC Al Decrement counter number 1 MOV ADDR3, Al counter value - in memory M2: MOV Al, ADDR4 Loading the counter number 2 JZ M1 If 0 - go to the outside loop MOV EDX, ECX propagation modulo 2 PSP on one XOR EDX, EBX another(prenominal) RCL EBX Decrement counter number 2 MOV [Al], EDX We bring the next value in memory JMP M2 M3 scam inner loop End\n\nIt is overly possible ironware implementation code generation scheme , but of fundamental importance it has not, because death penalty does not proposition here - the code is generated when on-hook , and this time more than a arcminute .\n\nThe course is knowing for i80386 central mainframe and operates broaden ( 32-bit ) registers. You can for sure implement it at a cheaper processor ( family of SISC - it i8086, i8080, i80186 and i80286), but the program is complicated , anyhow increase graze time , but it is not great , the most big thing that speech coding is overly carried out software system , and here runtime hypercritical. You can also implement the program on RISC- processor. This method is more promising .\n\nM - sequence generators\n\ngenerator PSP1\n\n capital formation occurs in hardware, although it can be through programmatically using the MT i80386 with its 32- times -row registers. Runtime and then the frequency at which work items are not critical , since the formation of the hood and the key itself comes at a time when the handset rests on the basic unit .\n\n file a focus number 1 1 2 3 4 5\n\n= 1\n\ngenerator psp2\n\nRegister Offs et 1 2 3 4 5\n\n= 1\n\n shut up plat of signal reception\n\nThe diagram is shown reflected receiver covers basic aspects of signal reception.\n\nThus, the PSK signal ( beguile diagram below) comes to the high-frequency part of the receiver ( not shown here ) and enters a bandpass pick up that passes a item frequency range . Thus eliminates noise having a frequency outside the transmitted band.\n\nThe signal then goes to the multiplier blocks , which is also supplied with a reference crystal oscillator OCXO . cardinal signals , they are shifted in kind relative to each other by clxxx degrees. It is necessary for the ensuant comparison. Thus , the chain divideed out . Obtained after multiplying the signal shown in the diagram. ( moulding in Matlab 4.2c)\n\n later signalpodaetsya a lowpass filter , smoothing the signal (see portend 2 and 3 below ) . If the phase of the reference oscillator coincides with an designate(postnominal) signal , we have something like\n\nThe signa l is then supplied to the ADC , the sampling frequency is chosen in such a way that each have two frame element ( see Figure 4 below). It is necessary for trustworthy signal decipher .\n\nDecoding is performed by multiplying the ( software ) digitized samples per key.\n\n aim coagulates , and from 31 -bit code obtained one bit of useful information , which is then canvas by the level and concludes Bang information : it is 1 or 0.\n\nThe second branch circuit is used to phase lock during a call. call for is multiplied by (software ) on the key and the inverse value of the key , then smoothed in the integrator . Next, an error signal which is beingness served on the timebase adjusts its phase by the supreme absolute value of the error electric say-so .\n\n1.\n\n2 .\n\n3 .\n\n4 .\n\nBx . signal\n\nAfter multiplying and fil -tration\n\nafter digitizing\n\nScheme signal\n\nTransmitter circuitry much more simple compared with the receiver circuit . This is due certainty that tr ansfer , whereas the signal at the receiver input is hopeless to predict .\n\n action Evaluation\n\nIf we proceed from the assumption that the frequency with which digitized speech is 8 kilocycle and the ADC The twelve , we obtain the following information:\n\nThe frequency of arrival of the signal at the encoder ( tracer )\n\nfkod / decode = Fd * Nrazr ADC = 8 * 103 * 12 = 96 kHz\n\nTform SRP = 1/fkod/dekod = 10.4 ms\n\nUsing the microprocessor i80386 processor with a time frequency of 33 MHz :\n\nTtakt MP = 30.3 ns = 1/fMP\n\nThe permissible number of cycles for the program encoding or decoding ( please note that when pickings apart the decoding key to the multiplication and inversion for PLL )\n\nNtakt ext = Tform CAP / Ttakt MP = 10.4 10-6/30 * 3 * 10-9 =\n\n= 343 cycles\n\nThis is more than enough to handle the information , thus the system has a reserve for in store(predicate) extensions and improvements.\n\nconclusion\n\nPresented a speech coding system for domestic cor dless telephones does not claim any special originality. There used ideas that appeared in the 50s with the work of Claude Shannon , who develop the idea A.V.Kotelnikova that potential noise electric resistance of the communication system under the action of Gaussian noise invariant with respect to bandwidth . For a long time (up to 80s ), these ideas are not utilise due to technical foul imperfections base generally registers and microprocessors. Now, many new developments in the field of communication using these ideas because of their obvious advantages : ease of implementation , low cost and good resistance to folie of such codes . An theoretical account can be one of the premier systems used noise-like signals - a system of pasture. After it began widespread use of noise-like signals in terrestrial and berth communications.\n\nApplication of error-correcting and at the same time protected ( sufficiently ) from eavesdropping coding , in the opinion of this author , a ve ry good option for home use .