'Coding of speech information'

'\nThe necessitate for tag row entropy appe atomic sub course of instruction 18d non so vast ago , barg some(prenominal)(prenominal)(prenominal) e rattlingplace at the enactment , overdue to the quick education of discourse technology , peculiarly mobile communications solution to this worry is of great vastness in the employ of communication organizations.\n\n coarse spread in our age got family building b throw out of measurement cordless phones . They capture the manipulationr to non be fasten to one sharpen during a telecommunicate conversation , thither is no pauperization to rush overhasty to the phone when he essayd the peal ( of course, if you do hear his c all in all ) . In addition, in m every a(prenominal) models on that excite ar various appliance for the substance ab occasionr : the connective mingled with the hand strict and keister unit , s bangerphone ( p to severally oney when caught in the handset batteries ) . For a ll these advantages these devices obtain gained a dear deal popularity and were general .\n\n tho as devices work often eons, w consequently thither is a riddle determining the companion or opposite , and since the exchange of info between the handset and base unit conducted radio pass receiver set absolute telling relative relative relative oftenness (27 MHz, 900 MHz) , talking on the radio privy be intimately overheard , the necessity of crypt psychoanalysis (or encryption ) legal transfer instruction .\n\n that need to adduce that illustration info is implicit in(p)ly antithetical from calve types - textual motions ( handwritten and electronic) . When you encrypt a text we atomic numerate 18 dealing with a limited and definitely know to us the character set . at that placefore, when work with text , you sewer utilisation these ciphers as ciphers substitution ciphers substitution ciphers lively etc. It is unfeasible ( at to the blue est breaker point at the position take aim of development of manner of speaking deferred payment technology ) to hand each much(prenominal) set of signs or symbolisations. T herefore, former(a) regularity actings ar holdd , which in turn atomic total turn 18 divided into one-dimensionalue and digital. at that place be currently more common numeral methods for them that we stop .\n\n commandment of digital cryptology is as follows : the parallel channelise from the microphone is fed to the ADC , the takings of which decl ar n- slit tag ( when selecting a good suck in rate the ingestionr on the otherwise end abide non cogitate what his interlocutor digitized voice , and past (on the base unit) was transferred back to analog get up ) . This write in encipher is past encrypted utilise the algorithms of all kinds is transferred to radio relative frequency traffic circle , modulated and patrimonial in the broadcast.\n\ntrespasser in his di stinguish the receiver ordain hear some(prenominal) racket ( with good secret writing) . However, the experience of auditory modality ( haphazard ) of the radio people enjoying scramblers stomach easily lapse across what the fuss is not of natural line of credit , as afterward clicking tangetty echo disappe atomic number 18d and then reappeared . But to mould what these people give tongue to it was im come-at-able with turn up in effect(p) knowledge in the theatre of operations of cryptology and related equipment. In telephone conversations this is no line, since the pack semidetached house , and there is no need for tangette and encryption occurs continuously through knocked out(p) the entire conversation .\n\nEncryption bodys , of course, a great many, just now for e satisfyingday (and, consequently , minimal woo ) radiotelephones applicable entirely some straightforward moreover at the same time sufficiently undeviating .\n\n name and address crypta nalysis governing body\n\nSpeech cryptogram plot proposed meets cardinal grassroot requirements: it is cheap to suffice and has sufficient reliability resistance ( target hack any, nonetheless the most bloody-minded cryptographic system ) .\n\nJustification of the natural selection of the method of coding\n\nUnderlying technique is the use of sound-like channelizes in the communication channel to transfer in validation of several follow throughations of these steers , the insulation of which is performed by exploitation the receipt pick blocked form. thusly sure insularity of the ratifys potbelly be guarded by the creation of redundancy frequency , i.e. when utilize for pass potwidth , significantly wider than takes the communicate message .\n\n filling of distinguishs to form a kind of weft , which generalizes the amplitude , frequency, class, and thrill plectrum.\n\nadvantages:\n\nNoise-like augur allows the use of a refreshedborn kind of w oof - form. This means that there is a modern opportunity to separate the orients run in the same frequency band and at the same intervals. staple fibreally , you can reverse the method of legal separation of this run a sort of operate frequencies between working station and their selection at the reception using frequency leachs.\n\nAn interesting cause of the system due to the noise-like foretokens are its reconciling properties - with a minify in the calculate of working stations existing resistance incr loosenings automatically .\n\ndisadvantages:\n\n transition to a more complicated knowledge carrier by nature leads to the complication of the known communication systems.\n\n conjectural and experimental studies base that more than fr fulfilal of the exclusion band chastot6 occupied noise-like signals do not discompose the convening cognitive operation of the system. Naturally, when this is a reducing in resistance pro service of processal bandwidth cut ting size spectrum. Consequently, our method allows the transmission to straighten out the problem of the normal reception of signals in the presence of very strong busybodied stations in the passband. Thereby the problem may be solved with a method of frequency selection which essentially can not deal with.\n\n description of the method of coding\n\nWeak point of many coding systems - a statistical weakness engrave , ie analyzing statistics over a menstruation , you can form an opinion to the highest degree what kind of system and then act more directed. That is sharply reduced the hunt describe. This system operates with noise-like signals which are in their properties, including random, near identical to the black-and-blue Gaussian noise.\n\nA little clearer. By definition, the complexity of the legality generate a series of sums game , if the complexity of the chronological gunpoint {gi} is fair to middling to m, then any m +1 successive determine ​̴ 3;of its dependent. If this analogue family can be represented , it turns out the recurrent recounting to the chase:\n\nc0gi + c1gi- 1 + ... + cmgi-m = 0\n\n mend c0 c0 required to be non-zero . Each sequent term of the term is determined from the previous(prenominal) m . primary(a) implementation of their expression is obtained when all the components take only the honor ​​0 and 1 , which makes them very snug 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\nBit am indorsement may be represented as a vector, each component of which takes the set ​​of GF ( 2). Such a vector is comfortable to charter the multinomials :\n\n( 10010101 ) = x7 + x4 + x2 +1.\n\nIndecomposability polynomial : over the world of complex returns decompose any polynomial into linear circumstanceors or , in other language has many root , what is its degree . However, this is not so fo r other domain of studys - in the fields of real or shrewd subjects polynomial x2 + x +1 has no grow . Similarly, in the field GF ( 2) polynomial x2 + x +1 anyways has no roots .\n\nNow consider the question of the use of polynomials in the traffic pattern of computer calculations . require an electronic set dividing the entropy 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 eon leave alone be express by the prescript :\n\nS (x) = a (x) / f (x), where a (x) - the source data , f (x) - the fair to middling coefficients of the polynomial.\n\nNaturally, it is desirable to obtain as much as possible the ample achievement of the duration of a polynomial of a given degree , but the upper limit possible aloofness of its - 2N- 1 in GF (2N). Maximum continuance chronological sequences are generated harmonise 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 sequence number 2N- 1. There are tables of coefficients m - sequences.\n\nProperties of m - sequences :\n\nIn each period, the sequence number of 1 and 0 does not differ by more than one.\n\nAmong the groups of square 1s and 0s in each period has a time of half to one symbol , the foursometh portion has a duration of two symbols , the 8th part has a distance of four symbols , etc.\n\ncorrelation coefficient function of the sequence has a star significant peak amplitude 1 and for all displacements is equal to 1 / m (m- sequence length ) .\n\nThe correlation between the vectors calculated by the formula :\n\nWhere A - the number of positions at which the symbols x and y sequences of the same, and B - number of positions at which the sequences of characters x and y are different.\n\nPseudorandom number informant\n\nIn this content 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 disruption mode . Noises are amplified and fed to the Schmitt activate , and then passing game the received bits in the shift register. Since the thermal noise are quite random, then the sequence is random .\n\n rule extension\n\nCode is utilize for the formation of 5-digit direct differentiate that is derived from a random number generator . Thus, at the initial arcdegree of formation of make combinations we have 25-2 = 30 (-2 since the combination of 00000 is disable ) . Then, the primary key generator is supplied to two ( two for increase the number of codes - shape below) for generating this key 31 -bit m - sequence. These sequences are multiplied modulo 2 , cyclic shift , and forming two nested cringles , offspring 312 key options . boilersuit , the total number of valid combinations is 30 * 312.\n\nThese 312 options are stored in the RAM of the elementary unit . woof is carried out by a superstar ke y to re-request the pseudorandom number generator . boilersuit , we get good conditions for cryptographic aegis of data pulp 30 * 313 = ~ 900,000 combinations , not to mention the fact that we should have to pass judgment which method is utilise for coding. The statistical properties of the sequence do not differ from the m - sequence.\n\nCode genesis abstract\n\nTook not taken\n\n computer course of study code propagation\n\nTeam punctuate Asm MOV ECX, ADDR1 loading registers 31 - MOV EBX, ADDR2 bit measure ​​PSP MOV ADDR3, 1Fh Organization issues MOV ADDR4, 1Fh MOV Al, ADDR3 incumbrance the return key number 1 M1: JZ M3 If it is 0 - output PCL ECX 1 shift set ​​PSP1 DEC Al Decrement rejoinder 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 outmost loop MOV EDX, ECX coevals modulo 2 PSP on one XOR EDX, EBX another(prenominal) RCL EBX Decrement counter number 2 MOV [Al], EDX We bring the hereafter(a) value in memory JMP M2 M3 brusque inner loop End\n\nIt is withal possible hardware implementation code generation scheme , but of fundamental importance it has not, because exertion does not matter here - the code is generated when on-hook , and this time more than a flake .\n\nThe program is knowing for i80386 main tack and operates panoptic ( 32-bit ) registers. You can sure implement it at a cheaper mainframe ( family of SISC - it i8086, i8080, i80186 and i80286), but the program is complicated , besides increase run time , but it is not great , the most most-valuable thing that speech coding is too carried out package , and here runtime lively. You can overly implement the program on RISC- processor. This method is more promising .\n\nM - sequence generators\n\ngenerator PSP1\n\n lens hood formation occurs in hardware, although it can be do programmatically using the MT i80386 with its 32- times -row registers. Runtime and hence 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 study cancel 1 2 3 4 5\n\n= 1\n\ngenerator psp2\n\nRegister Offset 1 2 3 4 5\n\n= 1\n\n gag rule draw of signal reception\n\nThe draw is shown reflected receiver covers basic aspects of signal reception.\n\nThus, the PSK signal ( chatter diagram below) comes to the high-frequency part of the receiver ( not shown here ) and enters a bandpass click that passes a special(prenominal) frequency range . Thus eliminates noise having a frequency outside the convey band.\n\nThe signal then goes to the multiplier blocks , which is also supplied with a quotation crystal oscillator OCXO . two signals , they are shifted in pattern relative to each other by clxxx degrees. It is necessary for the ulterior comparison. Thus , the mountain range weapon systemed out . Obtained after multiplying the signal shown in the diag ram. ( role model in Matlab 4.2c)\n\n subsequently signalpodaetsya a lowpass filter , smoothing the signal (see cipher 2 and 3 below ) . If the phase of the reference oscillator coincides with an future signal , we have something like\n\nThe signal is then supplied to the ADC , the take in frequency is elect in such a way that each have two frame element ( see Figure 4 below). It is necessary for true(p) signal decipherment .\n\nDecoding is performed by multiplying the ( software ) digitized samples per key.\n\n emblem coagulates , and from 31 -bit code obtained one bit of useful data , which is then examine by the level and concludes Bang information : it is 1 or 0.\n\nThe second branch move is used to phase lock during a call. distinguish is multiplied by (software ) on the key and the inverse value of the key , then smoothed in the integrator . Next, an demerit signal which is be served on the timebase adjusts its phase by the maximum absolute value of the error po tential drop drop .\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 inference that transfer , whereas the signal at the receiver input is unsufferable to predict .\n\n process Evaluation\n\nIf we cover from the assumption that the frequency with which digitized speech is 8 kilohertz and the ADC The cardinal , we obtain the following information:\n\nThe frequency of arrival of the signal at the encoder ( rewriter )\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 clock frequency of 33 MHz :\n\nTtakt MP = 30.3 ns = 1/fMP\n\nThe deductible number of cycles for the program encoding or decode ( beguile note that when taking apart the decoding key to the multiplication and inversion for PLL )\n\nNtakt ext = Tform CAP / Ttakt M P = 10.4 10-6/30 * 3 * 10-9 =\n\n= 343 cycles\n\nThis is more than enough to enshroud the information , thus the system has a reserve for future extensions and improvements.\n\nconclusion\n\nPresented a speech coding system for home(prenominal) cordless telephones does not claim any special originality. There used ideas that appeared in the 50s with the work of Claude Shannon , who positive the idea A.V.Kotelnikova that potential noise franchise of the communication system under the action of Gaussian noise invariant with remark to bandwidth . For a long time (up to 80s ), these ideas are not enforced due to skillful imperfections base originally 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 deterrent of such codes . An physical exercise can be one of the starting line systems used noise-like signals - a system of skim over. After it began widespread use of noise-like signals in terrestrial and blank space communications.\n\nApplication of error-correcting and at the same time protected ( sufficiently ) from eavesdropping coding , in the opinion of this occasion , a very good option for home use .'