HD-Voice for cellular communication - Khariton, Dmitry, Vladimir, Oleg, Irina, Glory!

We enabled HD-Voice on the Beeline network in Moscow. Below are sound recordings before and after, as well as technical details.

The HD-voice mode is based on AMR-WB technology (Adaptive Multi Rate Rate Wadeband) - a broadband adaptive coding with variable speed, also this codec is known as the G.722.22 standard. In theory, a person can hear sounds in the range of 20 Hz - 20 kHz, but in practice it is enough to transmit sound in a much narrower range. When encoding speech in AMR-WB, a frequency band of 50Hz-7kHz is used, which is absolutely enough for full voice transmission. For example, the AMR codec uses a range of 300-3 kHz. The method can be used in 2G and 3G networks.

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Simply put, now the human voice will sound more natural , because it will cease to “squeeze” into a rather narrow band, the need of which was once dictated by the limitations of infrastructure. In addition, with HD coding, ambient noise has less of an effect on speech intelligibility.

How did we get to HD-Voice, and how does it work?

A person is able to hear a certain band of sound frequencies, usually it is assumed to be equal to 20Hz-20kHz. Transmitting the entire spectrum over wireless communication channels without compression is difficult, so the voice without cutting the band is transmitted only in wired systems. For speech compression, voice codecs or vocoders are used. Their side effect is the distortion of the transmitted voice by limiting the frequency band of the voice message.

The very first voice codec used in mobile networks was “Full Rate” - FR. Simultaneously with the FR, the Half Rate codec was introduced, the only purpose of which is to increase the number of simultaneously served subscribers, and, as its name implies, it occupies half of the FR codec band in the radio channel. However, the voice quality after transcoding to FR was not very high, and for some countries (for example, Arabic, where speech speed is high and many high-frequency sounds), it is completely unacceptable. Therefore, the FR codec has been reworked, and the “Enhanced Full Rate” appeared, providing significantly better voice quality, with a lower bitrate being created.

With the increasing penetration of mobile networks, the requirements for the quality of voice services began to grow, and a problem appeared with the deterioration of voice quality, with a low radio signal level from the base station. To solve this problem, a new codec was developed - “Adaptive Multi Rate”, which used the same frequency range for analysis and compression, but the algorithm was implemented in such a way that the codec bitrate dynamically changed, depending on the quality of the received signal. Due to this, an opportunity to provide excellent voice quality under good radio conditions, and for bad ones, to keep the conversation even where FR / EFR codecs could not work at all.

All 3G networks work only with the use of the AMR codec or its subsequent implementations, for example AMR-WB. But since the network remains a large number of subscribers using phones that support only work with EFR / HR codecs, the 2G network continues to work with all codecs (FR / EFR / HR / AMR FR / AMR HR) at once, providing voice to any phone.

Currently, voice quality requirements in mobile networks continue to grow, and the time has come to use AMR-WB technology. All the codecs described above use the frequency range up to 200Hz-3.4kHz for compression, while AMR-WB uses the voice message band at 50Hz-7kHz for coding. AMR-WB allows you to transmit twice the bandwidth, which gives an increase in the quality and saturation of the high and low frequencies of the transmitted voice.

Some characteristics of codecs are listed in the table:

Codec	Standard	Year of creation	Compressible frequency range	Generated bitrate
Full Rate - FR	GSM 06.10	1990	200-3400 Hz	13 kbit / s
Half Rate - HR	GSM 06.20	1990	200-3400 Hz	5.6 kbit / s
Enhanced Full Rate - EFR	GSM 06.60	1995	200-3400 Hz	12.2 kbit / s
Adaptive Multi Rate - AMR	3GPP TS 26.071	1999	200-3400 Hz	4.75 - 12.20 kbit / s
Adaptive Multi Rate - WideBand - AMR-WB	3GPP TS 26.190	2001	50-7000 Hz	6.60 - 23.85 kbit / s
Adaptive Multi Rate-WideBand + - AMR-WB +	3GPP TS 26.290	2004	50-7000 Hz	6 - 36 kbit / s (mono) 7 - 48 kbit / s (stereo)

Hint for curious programmers: a sample of the implementation of the AMR codec in the C language is available in the 3GPP TS 26.073 standard (you can easily find it, download it and try to implement it).

In the diagram below you can see a comparison of voice quality, according to the MOS (Mean Opinion Score) scale, depending on the codec used. The MOS scale is a subjective assessment of voice quality from 0 to 5, where 0 is a total lack of audibility, and 5 is live speech. G.711 codec is used in wired telephony, that is, this is the quality that you should hear from your landline phone (if it is, of course, not transferred to the IP channel, but this is a completely different topic).

Update: The comments rightly indicated that the average MOS score for the G.711 codec is about 4.1, this picture distorts reality a little.

As can be seen from the diagram (and taking into account the information from the Update), the AMR-WB codec provides, under good radio conditions, the voice quality is similar to the one we are used to when using a wired home phone.

For example, two fragments of a musical composition, which were compressed by AMR and AMR-WB codecs, you can compare the sound quality yourself and visually assess the difference in the sound picture created by different codecs.

AMR coded top track

Bottom track encoded in AMR-WB

Tests

We are not the first to launch this technology in Russia, so some developments have already been made. Our first part of the network with HD-Voice was built within the Moscow Ring Road, on the equipment of Ericsson. Activating AMR-WB took a long time: first, it was tested on one controller (with numerous drive tests to measure speech quality). And even after everything was tested on one controller, the subsequent activation proceeded in stages, controller by controller. The whole activation process took almost half a year.

Here are the sample samples from the final tests , which were evaluated by hardware using accurate measurements at different times.

Does it already work?

Yes, now the technology is implemented in the 3G network for Moscow. In order to use the mode, you do not need to make additional settings, it is activated itself, if both subscribers are in the 3G network and both their phones support the work of the codec.

The diagram shows the conditions that are necessary for the operation of AMR-WB. Now, as mentioned above, the codec is running on the 3G network, the next stage is to ensure the codec works between the 2G and 3G networks, then between the networks and between the operators.

What devices are supported?

List. Carefully, under the spoiler a lot of letters.

Alcatel One Touch 903

Alcatel One Touch 916 / 916D

Alcatel One Touch 918

Alcatel One Touch 983

Alcatel One Touch 985 / 985D

Alcatel One Touch 991 / 991D / 991T

Alcatel One Touch 992D

Alcatel One Touch 993 / 993D

Alcatel One Touch 995/996

Alcatel One Touch Idol

Alcatel One Touch Idol Ultra

Alcatel One Touch Scribe Easy

Alcatel One Touch Scribe HD

Alcatel One Touch Star

Alcatel One Touch Tribe

Alcatel One X'POP

Apple iPhone 5

Apple iPhone 5S

Apple iPhone 5C

Blackberry q10

Blackberry q5

BlackBerry Torch 9810

Blackberry z10

Blackberry z30

HTC Desire 500

HTC ChaCha

HTC Desire C

HTC Desire HD

HTC Desire S

HTC Desire X

HTC Desire Z

HTC EVO 3D

HTC Incredible

HTC One

HTC One mini

HTC One S

HTC One SV

HTC One V

HTC One X

HTC One X +

HTC One XL

HTC One (M8)

HTC Radar

HTC Raider

HTC Rhyme

HTC Sensation

HTC Sensation XE

HTC Sensation XL

HTC Titan

HTC Touch HD

HTC Wildfire S

HTC Windows Phone 8X

HTC Windows Phone 8S

Huawei Ascend D Quad

Huawei Ascend D2 LTE (VoLTE)

Huawei Ascend G510

Huawei Ascend G740

Huawei Ascend P1 U9200

Huawei Ascend P2

Huawei Ascend P6

Huawei Boulder U8350

LG A310

LG Nexus 4 E960

LG Nexus 5

LG Optimus 3D

LG Optimus G

LG Optimus G Pro

LG Optimus L4 II

LG Optimus L5

LG Optimus L5 II

LG Optimus L7

LG Optimus L7 II

LG Optimus L9

LG Optimus LTE2 F160LV (VoLTE)

LG Optimus F7

LG Optimus F180S (VoLTE)

LG Optimus Vu2 F200 (K, L, S) (VoLTE)

LG Optimus Vu3 F300 (K, L, S) (VoLTE)

LG Optimus GX F310L (VoLTE)

LG Optimus G2 F320S (VoLTE)

LG Optimus G Pro F240S (VoLTE)

LG Optimus LTE III F260S (VoLTE)

LG Optimus G Flex F340S (VoLTE)

LG Optimus 3D Max (P720)

LG Optimus 3D (P920)

LG Optimus 4X HD (P880)

LG Prada (P940)

LG Prada 3.0

Motorola quench

Motorola RAZR (XT910)

Motorola RAZR i (XT890)

Motorola Moto G

Nokia 300

Nokia 301

Nokia 302

Nokia 500

Nokia 515

Nokia 600

Nokia 603

Nokia 700

Nokia 701

Nokia 808 PureView

Nokia 5230

Nokia 5330 Mobile TV Edition

Nokia 5530 XpressMusic

Nokia 5630 XpressMusic

Nokia 5730 XpressMusic

Nokia 6260 Slide

Nokia 6600i slide

Nokia 6700 classic

Nokia 6700 slide

Nokia 6710 Navigator

Nokia 6720 classic

Nokia 6760 slide

Nokia 6790 slide

Nokia 7230

Nokia Asha 300

Nokia Asha 301

Nokia Asha 302

Nokia Asha 303

Nokia Asha 311

Nokia C2-01

Nokia C3-01 Touch and Type

Nokia C5-03

Nokia C5-04

Nokia C6-00

Nokia C6-01

Nokia C7-00

Nokia E5-00

Nokia E52

Nokia E55

Nokia E6-00

Nokia E63

Nokia E7 Communicator

Nokia E7-00

Nokia E71x

Nokia E72

Nokia E73 Mode

Nokia Lumia 510

Nokia Lumia 520

Nokia Lumia 520.2

Nokia Lumia 521

Nokia Lumia 610

Nokia Lumia 610 NFC

Nokia Lumia 620

Nokia Lumia 625

Nokia Lumia 710

Nokia Lumia 720

Nokia Lumia 800

Nokia Lumia 810

Nokia Lumia 820

Nokia Lumia 822

Nokia Lumia 900

Nokia Lumia 920

Nokia Lumia 920T

Nokia Lumia 925

Nokia Lumia 925 Superman Edition

Nokia Lumia 925T

Nokia Lumia 928

Nokia Lumia 929 LTE-A (Cat 4)

Nokia Lumia 1020.2

Nokia Lumia 1020 3G

Nokia Lumia 1020 LTE

Nokia Lumia 1520

Nokia N7

Nokia N8

Nokia N86 8MP

Nokia N9

Nokia N97

Nokia N97 mini

Nokia X3-02

Nokia X5

Nokia X6-00

Nokia X7-00

Samsung Galaxy Star

Samsung Galaxy Light

Samsung Ativ S

Samsung galaxy ace

Samsung Galaxy Ace 2

Samsung Galaxy Express

Samsung Galaxy Fame

Samsung Galaxy Mini

Samsung Galaxy Mini 2

Samsung Galaxy Nexus

Samsung Galaxy Note

Samsung Galaxy Note II

Samsung Galaxy Note 3

Samsung Galaxy Note 10.1

Samsung Galaxy S II

Samsung Galaxy S III

Samsung Galaxy S4

Samsung Galaxy S4 Mini

Samsung Galaxy S5

Samsung Galaxy S Advance

Samsung Galaxy S Plus

Samsung Galaxy W

Samsung Galaxy Y

Samsung Omnia 7

Samsung Omnia Pro B7350

Samsung S5610

Samsung Wave 3

Samsung Trend Plus

Sony Ericsson Elm

Sony Ericsson Hazel

Sony Ericsson Live with Walkman

Sony Ericsson Xperia X8

Sony Ericsson Xperia X10 Mini

Sony Ericsson Xperia X10 mini pro

Sony Ericsson Xperia acro

Sony Ericsson Xperia active

Sony Ericsson Xperia Arc

Sony Ericsson Xperia arc S

Sony Ericsson Xperia mini

Sony Ericsson Xperia Mini Pro

Sony Ericsson Xperia neo

Sony Ericsson Xperia Neo V

Sony Ericsson Xperia Play

Sony Ericsson Xperia ray

Sony Ericsson W995

Sony Xperia A SO-04E

Sony xperia acro s

Sony xperia e

Sony Xperia E dual C1605

Sony Xperia Go (ST27i)

Sony Xperia i1 HSPA + C6902

Sony Xperia i1 LTE

Sony xperia ion

Sony xperia j

Sony xperia l

Sony xperia m

Sony Xperia M35t (VoLTE)

Sony xperia miro

Sony Xperia P

Sony xperia s

Sony xperia sola

Sony Xperia SP

Sony xperia t

Sony xperia tipo

Sony Xperia Tipo Dual

Sony xperia u

Sony xperia v

Sony Xperia Z

Sony Xperia ZL

Sony Xperia ZR

Sony Xperia Z1

Sony Xperia Z1S (T Mobile US only)

Sony Xperia Z1 Compact LTE-A D5503

Sony Xperia Z2 LTE-A D6543 / D6503

TechFaith Wildfire 80

ZTE Blade V880

ZTE Crescent (San Francisco 2 on Orange)

ZTE Era

ZTE F160 Atlanta

ZTE Grand X

ZTE Grand X IN

ZTE Orbit

ZTE R252 / Orange Tara

ZTE Kis Pro / Orange Zali

ZTE Skate (Monte Carlo on Orange)

ZTE Smart Netphone 701

ZTE Tania

ZTE TMN smart A15

Recognition problems

Human speech is such that in the radio and on a narrow band of the audio spectrum, the sounds of “C” and “F” are poorly distinguished. Couples “T” and “P”, “M” and “H” also suffer. Hence the mnemonic system with the names: “I dictate, number two-zero-zero, three Olga, as I understand it, reception?”. From here, things like the assignment of the most critical parts of the call sign to “p” grow up - for example, a sniper who in no case should confuse his call sign will most likely be “thirty-third” because it is very well discernible on air in narrow conditions. stripes.

Voice recognition is also growing with HD-Voice. This is important both for personal communication and for additional voice authentication gaining popularity, for example, in banks.

Source: https://habr.com/ru/post/228231/

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