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MOTOROLA and the Stylized M Logo are trademarks or registered trademarks of Motorola Trademark Holdings, LLC. All other trademarks are the property of their respective owners. © 2011 Motorola Mobility, Inc. All rights reserved.

Pacific Northwest Section AES June 2011by Scott Mehrens

Inside A Cellular Telephone

Motorola Mobility MM Pacific Northwest Section AES June 2011 2Page

Overview

06/27/2011© 2011 Motorola Mobility, Inc. – General Business Use

•A Brief History of Motorola

•Handset Acoustics (microphone & speaker)

•Voice quality in narrow band audio (8kHz)

•40,000 ft Overview of the Android Audio framework

•Motorola Handset multimedia (Audio)

•Fixed Point Numbers

•40,000 ft overview of cellular RF


A Brief History of Motorola – the Early Days


•1928 - On September 25, 1928, Paul V. Galvin and his brother, Joseph, incorporated Motorola’s founding company—Galvin Manufacturing Corporation—in Chicago, Illinois, USA.•1930 - First Motorola Brand Car Radio linking "motor" (for motorcar) with "ola" (which implied sound). Thus the Motorola brand meant sound in motion.•1958 - Car Phones for AT&T •1968 - Motorola engineers began researching cellular technologies to increase the capacity of mobile phone systems.

•1969 - First Words From the Moon •1973 - World's First Portable Cellular Demonstration Motorola DynaTAC (DYNamic Adaptive Total Area Coverage)•1983 - World's First Commercial Portable Cellular Phone the 28-ounce (794-gram) phone became available to consumers in 1984.


A Brief History of Motorola – Early Cell phones


•1989 - MicroTAC Personal Cellular TelephoneIt weighed 12.3 ounces (349 grams). •1991 - World's First GSM Cellular System•1994 - iDEN Digital Radio •1996 - StarTAC Wearable PhoneIt weighed 3.1 ounces (88 grams) •1999 - iDEN i1000plus Handset world's first to combine a digital phone, two-way radio, alphanumeric pager, Internet microbrowser, email, fax and two-way messaging.


A Brief History of Motorola – Digital Cell Phones


•1999 - Voice Over Internet Protocol Cellular Call Motorola completed a Voice over Internet Protocol (VoIP) cellular phone call using the GSM cellular standard in 1999. The call originated in London, England.•2000 World's First GPRS Cellular SystemIn June 2000, Motorola and Cisco Systems, Inc. supplied the world’s first commercial General Packet Radio Service (GPRS) cellular network to BT Cellnet in the United Kingdom.The system used the world’s first GPRS cellular phone, the Motorola Timeport P7389i model.•2001 Motorola V60 Cellular PhoneMotorola introduced its first metal mobile phone, the Motorola V60, with anodized aluminum housing, Internet access, text-messaging capabilities and voice-activated dialing. In 2002, the phone became available in GSM, TDMA and CDMA technologies, and quickly became a worldwide best seller.


A Brief History of Motorola – 3G & early smartphones


•2002 Motorola's First 3G Nationwide Network In 2002 Motorola launched its first 3G nationwide voice and data network using CDMA 1X technology with KDDI, a large wireless operator in Japan.The technology enabled Internet access at speeds more than double that of existing networks. •2002 Motorola A830 Phone Motorola introduced its first 3G (third-generation) cellular phone,the A830 model, in 2002. The A830 phone allowed users to make voice calls while sending or receiving data, and to capture and send images and short video clips. •2003 A760 Cellular Phone Introduced in 2003, the Motorola A760 cellular phone was the world's first handset to combine a Linux operating system and Java technology with full PDA functionality. •2004 MOTORAZR V3 Cellular Phone In 2004 Motorola introduced the RAZR V3 cellular phone, an ultraslim, metal-clad, quad-band flip phone. The 13.9mm thin phone used aircraft-grade aluminum to achieve several design and engineering innovations, including a nickel-plated keypad.


A Brief History of Motorola


•2006 MOTO Q Business PhoneIn 2006 Motorola introduced the MOTO Q with full QWERTY keyboard, a Microsoft Windows mobile software-based smartphone.•2006 Motorola MING Smart PhoneMotorola introduced the MING touch screen smart phone in Asia in 2006. It used advanced handwriting software to recognize more than 10,000 handwritten characters of the Chinese alphabet. •2007 iPhone released on June 2•2009 Motorola Droid released November 6•2011 Motorola becomes two new companies: Motorola Mobility & Motorola Solutions•2011 Atrix first dual-core processor phone & first with 1GB of RAM•2011 Xoom tablet released. First Android 3.0 tablet


Handset Speakers vs. Studio Speakers


Handset Speakers: 14x20x4mm to 9x13x3mm.The responses look like 2nd-order HPF's with corners at around 800Hz - 1.2kHzlevels ranging from 90 - 100 dBSPL @ 5cm when measured at rated voltage, free field.volumes range from 2cc on the large end to <1cc for many applications, i.e. 0.7cc.

Mackie HR824 Studio Monitors: 270x420x290mmLF - 222mm 91 dBSPL (2.83V, 100 cm)Passive Radiator 152mm x 305 mm.Acoustic Response +/- 1.5dB 39 Hz to 20kHz

E398 Frequency Response

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Handset Acoustic Transducers


Handset Mics: 1x3x4mm, MEMS (Micro Electro-Mechanical System), about -40dBV/Pa sensitivity flat as a ruler out until about an octave away from resonance (typically ~ 16kHz - lower for top-mount mics, higher for bottom-mount mics).

Earpieces: 8x15x2.5mm down to 7x11x3mm (or smaller)about 16dBPa/V when mounted in a coupler on a 3.2HL ear, with resonance at or below 400Hz.


Why do we need echo cancellation?


•Echo is a common phenomenon in modern telecommunication systems, and it originates on both network and user equipment

•Echo is an annoying audio artifact for the user, and impairs audio quality

•Echo can not be avoided by changing location

•Acoustic echo is inherently present and is determined by the acoustic housing design, the location, position and isolation between microphone and speaker, and the presence of reflective surfaces in the loudspeaker-enclosure-microphone (LEM) system


Half Duplex Speakerphone (Echo Suppression)


•One side is attenuated. Algorithm compares signal energy to alter gain on uplink or downlink in real-time.

•Originally developed in 1999 for CDMA V270c.

•Upgraded to adaptive echo suppressor in 2001 with better break-in capability.

•Good half-duplex performance

•Used in GSM Triplets (V300, V400, V600) & RAZR (V3)

•Common in phones until early to mid 2000’s


Full Duplex Speakerphone High Level Block Diagram



Full Duplex Speakerphone Motivation & Challenges


•Required by carriers•It is a more natural and convenient way of handsfree voice communication compared to half-duplex speakerphone.•Much higher acoustic echo return due to the high acoustic coupling between speaker and microphone.•More nonlinearity in echo path due to the low power of the amplifier, small speaker, and the maximum loudness requirement.•More near-end noise•Higher Near-end Echo to Speech Ratio due to the relative distance between microphone-speaker and microphone-user.


Full Duplex Speakerphone Performance Challenges


•Low Echo Return Loss (ERL) between downlink/forward and uplink/reverse path • high echo: -6dB (measured PCM level)

•Large Echo to Speech Ratio (ESR) in uplink path • Echo dominating: 6~20 dB

•Echo Path Changing with User’s Movement

•Speakerphone Used in Noisy Environments

•Non-linearity caused by the front-end analog (FEA) and acoustic components such as microphone, speaker, A/D, D/A and amplifier


Full Duplex Speakerphone Example


Downlink Speech

Uplink Echo

Uplink Speech

Uplink Echo


Full Duplex Speakerphone Details


Uplink EchoUplink Echo

Residual Echo Residual Echo

Uplink Speech


Full Duplex Speakerphone Implementation Details


•Uses echo cancellation (Adaptive Filter)

•Noise Suppressor (1 mic- IS127; 2 mic- proprietary, improved non-stationary noise removal)

•Comfort Noise Generator

•Double Talk Detector

•Nonlinear Processor


Full Duplex Speakerphone Performance Details


• High Convergence Rate of over 30 dB/s

• ERL Enhancement obtained from Adaptive Filter 15~30 dB (average)

• Minimal false DBTK detection

• Excellent full-duplex capability, obtained at low ESR

• Excellent Stability observed with user/UE Movement

• Robust Performance in Noisy Environments


Personalized Hearing Profiles


Use Pre-characterized / high percentile and statistical hearing profiles

Avoid needing an Audiologist

Provide an UI on the phone for user to select best profile

Preloaded audio files (MP3) Voice prompts

Automatically adapt the profile to according to mode and ambient noise conditions.

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Presbycusis hearing loss, according to Spoor's Equations

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Otologically Normal


MOS Testing- PESQ is a pest


PESQ (Perceptual Evaluation of Speech Quality ITU standard P.862) is full-reference algorithm and analyzes the speech signal sample-by-sample after a temporal alignment of corresponding excerpts of reference and test signal. PESQ can be applied to provide an end-to-end (E2E) quality assessment for a network, or characterize individual network components.PESQ results principally model mean opinion scores (MOS) that cover a scale from 1 (bad) to 5 (excellent).


Android Multimedia Audio Framework


•AudioFlinger acts like a mixer.•Multiple Player & Recorders are supported by AudioFlinger.


Motorola Android Audio Framework Gingerbread & up


•Gingerbread release includes partial Open SL ES API support.•4 Audio Effects supported: Bass Boost, Equalizer, Reverb, Virtualizer•Future releases will likely include full Open SL ES support to enhance gaming experience, e.g. positional 3D Audio


Motorola Multimedia Audio FX - Overview


•Virtualizer – allow “out of head” sound with headphones. Increase stereo image for closely spaced, side firing speakers. Create virtual home theater 5 channel speaker placement.

•Spectral Enhancer – Manage bass headphones or loudspeaker. Increase loudness of alerts and ringtones.

•Dynamics Processor – Protect loudspeaker from being overdriven. Maximize loudness of audio. Gate noise from microphone. Flexible setup: Gate, Expand, Compress, Limit.


Motorola Multimedia Audio FX - Virtualizer


•Supports stereo or multichannel input (discrete 5 channel)•Uses HRTFs + delay to place virtual sound sources•Headphone use cases: externalize so sound image is outside of your head; create sound sources at specific locations to mimic typical home theater setup center, left, right, surround•Loudspeaker use case: create virtual sound sources to increase apparent separation of phone speakers

Stereo Music Source

Spatial Audio

Extraction

L Spatial Positioning

andRoom

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Motorola Multimedia Audio FX – Spectral Enhancer


•Audio Playback – Graphic Equalizer; User Controlled Variable Bass Boost•Alert/Ringtone – Frequency shape audio to maximize loudness.•Noise Adaptive Ringtone – Record ~1s from microphone during call setup. Use Noise Suppressor to generate 16 frequency band estimate. Dynamically compute filter gains to compensate for background noise. Also include compensation for loudspeaker acoustic response & equal loudness curves.

E398 Frequency Response

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Motorola Multimedia Audio FX – Dynamics Processor


•Alert/Ringtone-Prevent overloading transducer•Speakerphone-Compress & limit downlink to maximize loudness•Microphone-Gate noise




An Operating “Envelope” is defined. The red curve shown here defines the maximum output (at 50 cm) of the transducer, physical and electronic systems. Factors considered to derive this curve included amplifier clipping, acceptable distortion limits, including those

caused by diaphragm breakup and non-linear excursion, Codec filters and analog circuit frequency response, and frequency limitations caused by the physical system. The white area above this curve is beyond the system capability. The blue shaded area below this curve is the operating envelope of the system.




Correction filters were designed for each volume step to smooth and extend frequency response. The red “8 bar”curve shown here is the frequency response of the Codec filters and analog amplifier stages, with no DSP correction. The three other curves combine this response with correction filters

to derive a composite transfer function for each volume step. Each volume step has a gain reduction of 3 dB. Volume steps below the purple “5 bar” curve use the same 5 bar filter shape with a 3 dB reduction in amplitude for each step.




The response of the combined system is dramatically improved at low to mid volume levels. Low frequency response is extended about an octave, and the response is flattened to +/- 1.5 dB from the low frequency cutoff up to the codec filter cutoff at 3300 hz.


Dynamics Processor-Compression to prevent clipping


There is marketing pressure to deliver louder products. If we design in gain sufficient to meet these requirements with nominal signals, we may have clipping or other distortion with loud signals. The graph above shows a 0 dBV peak sine wave limited to -3 dBV by clipping.


Dynamics Processor-Compression to maximize loudness


Here the same speech sample is shown at a nominal level (Average 20 dB below clipping, peaks 8 dB below) on the left side of the graph. The right side shows the same sample after compression and amplitude shift. The average level is 8 dB louder. The term “compression” comes from the fact that the dynamic range is compressed, as the soft sounds are now closer in level to the loud sounds than before. With a small speakerphone this greatly improves the intelligibility of softer sounds in a noisy environment, while preventing clipping for loud signals.


Fixed Point Numbers


Resolution determines smallest non-zero magnituderesolution=1/2qf32; Accuracy is the magnitude of the maximum difference between a real value and it's representation.accuracy=resolution/2; Range is the difference between the most negative and most positive number; range32=[-2qi32; (2qi32-2-qf32)];range32_dB=20*log10(range32(:,2));

% Decimal places is based on accuracy. Similar to significant digits (assuming inputs have proper significant digits)decimal_places=floor(-log10(accuracy));


Fixed Point Numbers 16bit (single precision)


8Q7 format:Resolution: 0.0078125Accuracy: 0.00390625Decimal Places: 2Range: -256 <= x <=255.9921875







15Q0 format:Resolution: 1Accuracy: 0.5Decimal Places: 0Range: -32768 <= x <=32767

0Q15 format:Resolution: 3.0517578125e-005Accuracy: 1.52587890625e-005Decimal Places: 4Range: -1 <= x <=0.999969482422

1Q14 format:Resolution: 6.103515625e-005Accuracy: 3.0517578125e-005Decimal Places: 4Range: -2 <= x <=1.99993896484

2Q13 format:Resolution: 0.0001220703125Accuracy: 6.103515625e-005Decimal Places: 4Range: -4 <= x <=3.99987792969







Fixed Point Numbers-How to compute a square root?


/* SQRT 0132 from Computer Approximations 5.08 digits of accuracy Range 0.5 <= x =< 1.0 P00 = +0.22906994529 P01 = +1.3006690496 P02 = -0.90932104982 P03 = +0.50104207633 P04 = -0.12146838249 To cover range & resolution use 1Q30 coefficients P(x) = P04*x^4+P03*x^3+P02*x^2+P01*x+P00*/ int32 P00 = 0x0EA914FD; int32 P01 = 0x533E2966; int32 P02 = 0xC5CDAF15; int32 P03 = 0x201112C9; int32 P04 = 0xF839DCAD;

L_temp = L_mpy_ll(P04,L_SqrtIn); L_temp = L_add(L_temp,P03); L_temp = L_mpy_ll(L_temp,L_SqrtIn); L_temp = L_add(L_temp,P02); L_temp = L_mpy_ll(L_temp,L_SqrtIn); L_temp = L_add(L_temp,P01); L_temp = L_mpy_ll(L_temp,L_SqrtIn); L_temp = L_add(P00,L_temp); /* Scale final result 1Q30 -> 0Q31 */ L_temp = L_shl(L_temp,1); /* Round Q31 -> Q15 */ swSqrtOut = dsp_round(L_temp); /* return output */ /* ------------- */ return (swSqrtOut);


Fixed Point Numbers-How to compute a square root?



GSM Overview


MT/TE – Mobile Terminal/Terminal EquipmentSIM – Subscriber Identity ModuleBTS – Base Transceiver StationBSC – Base Station ControllerPCU – Packet Control UnitMSC/VLR – Mobile Switiching Center/Visitors Location RegisterPSTN – Public Switched Telephone NetworkHLR/AUC – Home Location Register/Authentication CenterGPRS – Global Packet Radio SystemSGSN – Serving GPRS Support NodeGGSN – Gateway GPRS Support Node


GSM Overview


TCH – Traffic ChannelCCH – Control ChannelTDMA – Time Division Multiple AccessBurst – one channel timeslotFrame – 8 timeslots (4.615 ms ~= 217 Hz a.k.a. GSM Buzz)Multiframe – 26 TCH frames or 51 CCH framesSuperframe – 51 TCH Multiframes or 26 CCH MultiframesHyperframe – 2048 Superframes


Questions?


Scott MehrensEmail: [email protected]

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