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Text of the page (random words):
cations standards institute etsi 1 and is designed to be low cost and easy to use dmr along with p25 phase ii and nxdn are the main competitor technologies in achieving 6 25 khz equivalent bandwidth using the proprietary ambe 2 vocoder dmr and p25 ii both use two slot tdma in a 12 5 khz channel while nxdn uses discrete 6 25 khz channels using frequency division and tetra uses a four slot tdma in a 25 khz channel dmr was designed with three tiers dmr tiers i unlicensed and ii conventional licensed were first published in 2005 and dmr iii trunked version 2 was published in 2012 with manufacturers producing products within a few years of each publication the primary goal of the standard is to specify a digital system with low complexity low cost and interoperability across brands so radio communications purchasers are not locked into a proprietary solution specifications edit the dmr interface is defined by the following etsi standards ts 102 361 1 air interface protocol ts 102 361 2 voice and general services and facilities ts 102 361 3 data protocol ts 102 361 4 trunking protocol the dmr standard operates within the existing 12 5 khz channel spacing used in land mobile frequency bands globally but achieves two voice channels through two slot tdma technology built around a 30 ms structure the modulation is 4 state fsk which creates four possible symbols over the air at a rate of 4 800 symbols s corresponding to 9 600 bit s after overhead forward error correction and splitting into two channels there is 2 450 bit s left for a single voice channel using dmr compared to 4 400 bit s using p25 and 64 000 bit s with traditional telephone circuits the standards are still as of late 2015 under development with revisions being made regularly as more systems are deployed and improvements are discovered 3 it is very likely that further refinements will be made to the standard which will necessitate firmware upgrades to terminals and infrastructure in the future to take advantage of these new improvements with potential incompatibility issues arising if this is not done dmr covers the rf range 30 mhz to 1 ghz there are dmr implementations that operate as low as 66 mhz within the european union in lo band vhf 66 88 mhz 4 dmr tiers edit dmr tier i edit dmr tier i products are for licence free use in the european pmr446 band tier i products are specified for non infrastructure use only meaning without the use of repeaters this part of the standard provides for consumer applications and low power commercial applications using a maximum of 0 5 watts rf power 5 note that a licence free allocation is not present at this frequency outside of europe which means that pmr446 radios including dmr tier i radios can only be used legally in other countries once an appropriate radio licence is obtained by the operator some dmr radios sold by chinese manufacturers most notably baofeng have been mis labelled as dmr tier i a dmr tier i radio would only use the pmr446 licence free frequencies and would have a maximum transmitted power of 0 5 watts as required by law for all pmr446 radios 6 although the dmr standard allows tier i dmr radios to use continuous transmission mode all known tier i radios currently use tdma the same as tier ii this is probably due to the 40 battery savings that come with transmitting only half the time instead of continuously 7 dmr tier ii edit dmr tier ii covers licensed conventional radio systems mobiles and hand portables operating in pmr frequency bands from 66 to 960 mhz the etsi dmr tier ii standard is targeted at those users who need spectral efficiency advanced voice features and integrated ip data services in licensed bands for high power communications a number of manufacturers have dmr tier ii compliant products on the market etsi dmr specifies two slot tdma in 12 5 khz channels for tier ii and iii 8 dmr tier iii edit a portable radio compatible with the dmr tier iii digital radio standard dmr tier iii covers trunking operation in frequency bands 66 960 mhz tier iii supports voice and short messaging handling similar to tetra with built in 128 character status messaging and short messaging with up to 288 bits of data in a variety of formats it also supports packet data service in a variety of formats including support for ipv4 and ipv6 tier iii compliant products were launched in 2012 in april 2013 hytera participated in the completion of the dmr tier iii interoperability iop test 9 dmr association edit in 2005 a memorandum of understanding mou was formed with potential dmr suppliers including tait communications fylde micro selex motorola hytera sanchar communication vertex standard kenwood and icom to establish common standards and interoperability while the dmr standard does not specify the vocoder mou members agreed to use the half rate dvsi advanced multi band excitation ambe vocoder to ensure interoperability in 2009 the mou members set up the dmr association to work on interoperability between vendors equipment and to provide information about the dmr standard 10 formal interoperability testing has been taking place since 2010 results are published on the dmr association web site there are approximately 40 members of the dmr association the standard allows dmr manufacturers to implement additional features on top of the standards which has led to practical non interoperability issues between brands in contravention to the dmr mou amateur radio use edit dmr is used on amateur radio vhf and uhf bands with the early adoption network development led by dmr marc around 2010 11 the fcc officially approved the use of dmr by amateurs in the us in 2014 12 in amateur spaces coordinated dmr identification numbers are assigned and managed by radioid inc their coordinated database can be uploaded to dmr radios in order to display the name call sign and location of other operators 13 internet linked systems allow users to communicate with other users around the world via connected repeaters or dmr hotspots often based on the raspberry pi single board computer there are currently more than 5 500 repeaters and 16 000 hotspots linked to the brandmeister system worldwide 14 the low cost and increasing availability of internet linked systems has led to a rise in dmr use on the amateur radio bands 15 some raspberry pi based dmr hotspots often those running the pi star or wpsd software allow users to connect to multiple internet linked dmr networks at the same time 16 dmr hotspots are often based on the open source multimode digital voice modem or mmdvm hardware with firmware developed by jonathan naylor 17 18 examples of organised amateur radio activities conducted using internet linked dmr networks include the world wide check in a weekly international net operating on talk group 91 of the brandmeister network 19 encryption edit encryption was not defined in the initial releases of the dmr standard so each dmr radio manufacturer added its own encryption protocol these early encryption protocols are therefore incompatible with each other for example hytera s basic encrypt encryption is completely incompatible with motorola s basic encrypt encryption the dmra now manages an interoperable voice and data encryption scheme for dmr 40 bit arc4 64 bit des 128 and 256 bit aes options are defined these encryption schemes are interoperable between manufacturers and support voice call late entry multiple keys and with no discernible degradation of voice quality 20 some dmr encryption algorithms have been released such as pc4 released in 2015 with source code available 21 pc4 is a block cipher specifically designed for dmr radio communication systems using 253 rounds and a key size from 8 bits to 2112 bits the block size is 49 bits which is equal to the size of an ambe dmr voice frame a firmware that implements pc4 encryption is available for the tytera md 380 and md 390 radios 22 in motorola basic encryption ambe frames are encrypted by simple xor using one of 255 possible static keys 23 the basic mode from other manufacturers offers 10 32 or 64 character keys to produce a 882 bit fixed string of random characters that is combined via xor with ambe frames the entire superframe rather than each individual ambe frame is xored with this longer static key a superframe contains 18 ambe frames i e 882 bits and it is these 882 bits that will be encrypted with this 882 bit fixed string pc4 encryption mode encrypts an entire 49 bit frame in ecb mode a single bit that differs makes the entire encrypted block completely different for the enhanced arc4 or advanced aes mode each complete superframe is also encrypted with a 32 bit iv initialization vector as a result the encryption is no longer fixed for the same key but changes with each superframe improving security the dmr standard does not leave any room to store this iv so the iv with the addition of an error correcting code for a total of 72 bits replaces 4 low order bits in each 49 bit ambe frame these 4 bits are therefore lost degrading the voice quality which is not the case with fixed ciphers in basic mode the 72 bit encoded iv is thus spread across all 18 ambe frames in the superframe weaknesses in arc4 dmra edit motorola has created its standard so that the 40 bit arc4 alleged rc4 can withstand casual attackers it is supposed to offer 40 bit security where an attacker must test the 2 40 possible keys to find the right one this level of encryption offers no real protection and there is software that allows decoding the key 24 rc4 encryption is a stream cipher that must use an iv initialization vector each time it performs encryption the size of this iv should be large enough so that there is no repetition of this iv during the entire use of the same key rc4 weak iv encryption has already been compromised in the wep wi fi encryption system because the iv size was too short 24 bits motorola has opted to use a slightly longer iv size 32 bit but not that much longer than the wep s 24 bit iv motorola calls this iv the mi message indicator motorola reported that the dmr standard did not define a method for transporting encryption parameters its solution embeds a 32 bit initialization vector together with error protection data by replacing selected least significant bits in the dmr vocoder frames these bits were selected to minimize degradation of the received voice audio 25 according to the author of the dsd fme software a dmr specialist according to whom this claim is false because there is the possibility of creating custom dmr frames such a frame could therefore have contained a large iv 128 bits for example 26 some users discovered that anytone radios such as the anytone 878 using arc4 had the iv constant 0x12345678 at the beginning of each transmission 27 this flaw was fixed in anytone d878uvii firmware update v3 03 2023 12 18 5 modify the firmware to make the aes encryption have a variable vector iv instead of fixed 12345678 the motorola arc4 dmra should by design provide at least 4 billion different ivs so there should be 4 billion superframes with a different iv 2 32 bits possible ivs but one user discovered that motorola uses a non primitive lfsr for the arc4 to generate the ivs instead of 4 billion different ivs there are only 294 903 different ivs so instead of a 32 bit iv you get an 18 bit iv which is much shorter than the 24 bit wep wi fi iv 28 according to cryptologist eric filiol it is likely that all exported products with a key length of more than 56 bits have a backdoor as this is a legal requirement due to the wassenaar arrangement 29 30 see also edit dpmr d star references edit etsi dmr standard overview pdf etsi archived from the original pdf on 2018 11 10 retrieved 22 march 2012 benefits and features of dmr white paper pdf dmr association p 15 retrieved 5 april 2024 dmr association press release oct 27 2015 stating revision to standard archived 2015 11 08 at the wayback machine digital mobile radio association the dmr standards developed by etsi www dmrassociation org retrieved 2026 07 24 dmr association infrastructure and mobile terminals archived from the original on 2015 02 04 retrieved 2015 01 12 a guide to the new pmr446 license free radio frequencies following ecc decision 15 05 pdf kenwood retrieved 7 february 2018 two way radios and battery life hytera europe retrieved 19 october 2020 etsi ts 102 361 1 dmr air interface protocol pdf dmr association announces completion of three interoperability testing sessions pdf www dmrassociation org april 3 2013 dmr association dmr marc network dmr marc net archived from the original on 2026 07 18 retrieved 2026 07 24 trynor don fcc officially gives the green light to dmr for us hams va3xpr net archived from the original on 2014 06 16 radioid home www radioid net retrieved 2021 02 25 dashboard brandmeister brandmeister network retrieved 2023 01 27 about us bridgecom systems inc retrieved 2021 02 25 hotspots dmr for dummies retrieved 14 june 2022 naylor jonathan g4klx jonathan naylor github retrieved 14 june 2022 mmdvm multi mode digital voice modem vk3fs vk3fs retrieved 14 june 2022 the world wide check in netfinder radio retrieved 15 june 2026 bohn tom march 30 2023 dmr association dmr feature evolution pdf dmr_association_dmr_feature_evolution archived from the original pdf on aug 5 2024 retrieved aug 5 2024 pc4 encryption cipher source code pastebin com voice crypt firmware archive org 2018 motorola basic encryption s analysis github 2021 dmr arc4 key finder us8422679b2 chowdhary dipendra m belmonte john p wiatrowski david g method and device for sending encryption parameters issued 2013 04 16 create ivs without using voice frames radioreference com 2023 constant iv with the anytone 878 in rc4 and aes radioreference com 2017 non primitive lfsr in arc4 dmra radioreference com 2023 interview with cryptologist eric filiol theregister com 2017 backdoors analysis pdf blackhat com 2017 fcc modifies amateur service testing and emission rules federal communications commission 2015 12 10 retrieved 2022 07 05 external links edit dmr association mndmr minnesota s first in house dmr repeater network system radio id inc coordinated dmr identification numbers for amateur radio v t e digital two way radio standards fdma tetrapol dpmr nxdn p25 phase 1 d star tdma tetra dmr p25 phase 2 v t e trunked radio systems central controller motorola systems type i type ii type iii hybrid type ii smartzone type ii smartzone omnilink iden other apco project 16 apco project 25 edacs edacs provoice mpt 1327 opensky tetra tetrapol gota dpmr mode 3 nxdn dmr tier iii pdt scan based distributed control general electric mobile radio ge marc v logic trunked radio ltr standard ltr passport ltr standard and passport ltr multinet ltr net retrieved from https en wikipedia org w index php title digital_mobile_radio oldid 1378115687 categories etsi mobile telecommunications standards wireless communication systems 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