smart phone

<1> Guide to smartphone hardware (3/7): Memory and Storage [Mar 12, 2012] -

System On a Chip (SoC)

RAM -

Size -512MB is pretty enough.  Speed - smartphone SoCs mostly use LPDDR2, where the “LP” stands for low-power. LPDDR2 is mostly similar to standard DDR2 except that it uses less power (hence the name) which does degrade performance. DDR3 interfacing capabilities will be introduced in upcoming smartphone SoCs.  Channel - Memory channels do little in real-world performance to improve the speed of a RAM set-up.

The iPhone 4S has 512 MB of LPDDR2 embedded inside the A5 SoC. 

Internal storage and ROM - internal storage is critical to a smartphone's operation; without any place to store the operating system and critical files there would be nothing for the phone to do. Even if a phone has no storage accessible to the user, there will also be some form of internal storage that stores the operating system.

multiple storage chips : (1) ROM - stores the system files; (2) Others - stores applications, for cache, etc.

classification of the internal storage: (1) user accessible ; (2) non-user-accessible, for system files and (non-movable? not allow to delete/uninstall?) applications.

Some devices, such as the Samsung Galaxy S, have a multi-ROM set-up. One memory chip is smaller around 512 MB, but faster, and stores the main system files, cache and application data in separate partitions. The second chip is larger, and is usually a 1-2 GB partition of the user storage that is slower but allows for storage of applications.

Other devices such as the Apple iPhone 4S and Motorola Droid Razr prefer to include just one storage chip that sits, in terms of performance, between the two chips used in a multi-chip set-up. The phone may be stated to include 16 GB of internal storage, but after a 1-2 GB system partition and (in the case of the Razr) a 4 GB application partition the user accessible storage may end up as low as 8 GB. 

Performance of internal storage chips are, generally speaking, better than you would achieve with external microSD cards.

User removable storage

Out of the three major smartphone operating systems (iOS, Android and WP7), Android is the only one that really supports removable storage. 

When it comes to Android there are two implementations of user removable storage: it’s either the only user accessible storage or it complements the internal user accessible storage. If it complements what is already available, there will be a separate system partition for the external card such as /sd-ext or /mmc that some applications, such as music and video players, can access. Often applications that download data to the “SD card” will actually download to the internal storage in situations where there are both available (unless there is an option). [tsiu: so not really only to SD card but download to both internal storage and the card.]

SDXC cards are not supported in most new smartphones, meaning the maximum expansion of storage rests at 32 GB.

With the right combination of a device with 64 GB of internal storage with a microSD card slot, such as the Samsung Galaxy Tab 7.7, you could potentially have 96 GB of user accessible storage if you added in a 32 GB microSD card.

src

My Note:
<1> RAM on smartphone = RAM on PC.  Internal storage on smartphone = C drive on PC.  On PC, 4GB RAM is minimum; and 128GB SSD is comfortable for Win 7.  My another PC which uses an only 40GB SSD as the OS drive is handicapped. 
<2> Suggestion:  buy Redmi Note 2 Prime (32GB internal storage).      


<2>

Cloud Storage

To overcome the problem of reduced internal storage space, several high-end smartphones are sold with free cloud storage accounts. This could be 10, 20 or even 50GB. Whilst this is a nice extra, bear in mind that not all data and files can be saved to cloud storage (apps for example). You will also be unable to access files stored in the cloud if you do not have a Wi-Fi or mobile data connection.   src


<3> my_xiaomi.htm

Redmi Note 2 :

MediaTek Helio X10 octa-core 64-bit processor

2GB RAM

16GB Flash

SIM slots

3060mAh battery

Full Spec: <1>    Review: <1>

MEMORY Card slot microSD, up to 32 GB - Chinese version only
Internal 16 GB, 2 GB RAM - Redmi Note 2
32 GB, 2 GB RAM - Redmi Note 2 Prime

Redmi Note 3 (MediaTek):

Full Spec: <1> - 3GB RAM

LAUNCH Announced 2015, November
Status Available. Released 2015, November
BODY Dimensions 150 x 76 x 8.7 mm (5.91 x 2.99 x 0.34 in)
Weight 164 g (5.78 oz)
SIM Dual SIM (Micro-SIM, dual stand-by)
DISPLAY Type IPS LCD capacitive touchscreen, 16M colors
Size 5.5 inches (~72.4% screen-to-body ratio)
Resolution 1080 x 1920 pixels (~403 ppi pixel density)
Multitouch Yes
  - MIUI 7.0
PLATFORM OS Android OS, v5.0.2 (Lollipop)
Chipset Mediatek MT6795 Helio X10
CPU Octa-core 2.0 GHz Cortex-A53
GPU PowerVR G6200
MEMORY Card slot No
Internal 16 GB, 2 GB RAM
32 GB, 3 GB RAM

Don't Buy.  Instead, buy Redmi Note 2 Prime or Redmi 3 (has a microSD slot for up to 128GB of additional storage; a 5in HD screen).  But Redmi 3 uses Non-removable Li-Ion 4100 mAh battery.  So my preference is:

 Redmi Note 2 Prime > Redmi 3 > Redmi Note 3.  How about Redmi 2?


NETWORK Redmi Note 3 Redmi 3 Redmi Note 2 / Prime
NETWORK Technology GSM / HSPA / LTE GSM / CDMA / HSPA / EVDO / LTE GSM / HSPA / LTE
2G bands GSM 900 / 1800 / 1900 - SIM 1 & SIM 2 GSM 900 / 1800 / 1900 - SIM 1 & SIM 2 GSM 900 / 1800 / 1900 - SIM 1 & SIM 2
  CDMA 800 / 1900
3G Network HSDPA 850 / 900 / 1900 / 2100 HSDPA 850 / 1900 / 2100 HSDPA 850 / 900 / 1900 / 2100
  TD-SCDMA TD-SCDMA TD-SCDMA
  CDMA2000 1xEV-DO
4G Network LTE band 1(2100), 3(1800), 7(2600), 38(2600), 39(1900), 40(2300), 41(2500) LTE band 1(2100), 3(1800), 7(2600), 38(2600), 39(1900), 40(2300), 41(2500) LTE band 1(2100), 3(1800), 7(2600), 38(2600), 39(1900), 40(2300), 41(2500)
Speed HSPA, LTE HSPA, LTE, EV-DO Rev.A 3.1 Mbps HSPA, LTE Cat4 150/50 Mbps
GPRS Yes Yes Yes
EDGE Yes Yes Yes
LAUNCH Announced 2015, November 2016, January 2015, August
Status Available. Released 2015, November Available. Released 2016, January Available. Released 2015, August
BODY Dimensions 150 x 76 x 8.7 mm (5.91 x 2.99 x 0.34 in) 139.3 x 69.6 x 8.5 mm (5.48 x 2.74 x 0.33 in) 152 x 76 x 8.3 mm (5.98 x 2.99 x 0.33 in)
Weight 164 g (5.78 oz) 144 g (5.08 oz) 160 g (5.64 oz)
SIM Dual SIM (Micro-SIM, dual stand-by) Dual SIM (Micro-SIM/Nano-SIM, dual stand-by) Dual SIM (Micro-SIM, dual stand-by)
DISPLAY Type IPS LCD capacitive touchscreen, 16M colors IPS LCD capacitive touchscreen, 16M colors IPS LCD capacitive touchscreen, 16M colors
Size 5.5 inches (~72.4% screen-to-body ratio) 5.0 inches (~71.1% screen-to-body ratio) 5.5 inches (~71.5% screen-to-body ratio)
Resolution 1080 x 1920 pixels (~403 ppi pixel density) 720 x 1280 pixels (~294 ppi pixel density) 1080 x 1920 pixels (~403 ppi pixel density)
Multitouch Yes Yes Yes
  - MIUI 7.0 - MIUI 7.0 - MIUI 7.0
PLATFORM OS Android OS, v5.0.2 (Lollipop) Android OS, v5.1 (Lollipop) Android OS, v5.0 (Lollipop)
Chipset Mediatek MT6795 Helio X10 Qualcomm MSM8939v2 Snapdragon 616 Mediatek MT6795 Helio X10
CPU Octa-core 2.0 GHz Cortex-A53 Quad-core 1.5 GHz Cortex-A53 & quad-core 1.2 GHz Cortex-A53 Octa-core 2.0 GHz Cortex-A53 - Redmi Note 2
Octa-core 2.2 GHz Cortex-A53 - Redmi Note 2 Prime
GPU PowerVR G6200 Adreno 405 PowerVR G6200
MEMORY Card slot No microSD, up to 128 GB (uses SIM 2 slot) microSD, up to 32 GB - Chinese version only
Internal 16 GB, 2 GB RAM
32 GB, 3 GB RAM
16 GB, 2 GB RAM 16 GB, 2 GB RAM - Redmi Note 2
32 GB, 2 GB RAM - Redmi Note 2 Prime
CAMERA Primary 13 MP, f/2.2, phase detection autofocus, dual-LED (dual tone) flash 13 MP, f/2.0, phase detection autofocus, LED flash 13 MP, f/2.2, phase detection autofocus, LED flash
Features Geo-tagging, touch focus, face/smile detection, HDR, panorama Geo-tagging, touch focus, face/smile detection, HDR, panorama Geo-tagging, touch focus, face/smile detection, HDR, panorama
Video 1080p@30fps 1080p@30fps 1080p@30fps
Secondary 5 MP, f/2.0, 1080p 5 MP, f/2.2, 1080p@30fps 5 MP, f/2.0, 720p
SOUND Alert types Vibration; MP3, WAV ringtones Vibration; MP3, WAV ringtones Vibration; MP3, WAV ringtones
Loudspeaker Yes Yes Yes
3.5mm jack Yes Yes Yes
COMMS WLAN Wi-Fi 802.11 a/b/g/n/ac, dual-band, WiFi Direct, hotspot Wi-Fi 802.11 b/g/n, Wi-Fi Direct, hotspot Wi-Fi 802.11 a/b/g/n/ac, dual-band, WiFi Direct, hotspot
Bluetooth v4.1, A2DP, LE v4.1, A2DP v4.0, A2DP, LE
GPS Yes, with A-GPS, GLONASS, BDS Yes, with A-GPS, GLONASS, BDS Yes, with A-GPS, GLONASS, BDS
Infrared port Yes Yes Yes
Radio Stereo FM radio; recording FM radio Stereo FM radio
USB microUSB v2.0, USB On-The-Go microUSB v2.0 microUSB v2.0, USB On-The-Go
FEATURES Sensors Fingerprint, accelerometer, gyro, proximity, compass Accelerometer, gyro, proximity, compass Accelerometer, gyro, proximity, compass
Messaging SMS(threaded view), MMS, Email, Push Mail, IM SMS(threaded view), MMS, Email, Push Mail, IM SMS(threaded view), MMS, Email, Push Mail, IM
Browser HTML5 HTML5 HTML5
Java No No No
  - Fast battery charging
- Active noise cancellation with dedicated mic
- XviD/MP4/H.265 player
- MP3/WAV/eAAC+/Flac player
- Photo/video editor
- Document viewer
- Fast battery charging
- Active noise cancellation with dedicated mic
- DivX/Xvid/MP4/H.264 player
- MP3/WAV/eAAC+/FLAC player
- Photo/video editor
- Document viewer
- Fast battery charging
- Active noise cancellation with dedicated mic
- MP4/H.264 player
- MP3/WAV/eAAC+ player
- Photo/video editor
- Document viewer
BATTERY   Non-removable Li-Po 4000 mAh battery Non-removable Li-Ion 4100 mAh battery Removable Li-Po 3060 mAh battery
Stand-by Up to 264 h (3G) Up to 144 h (3G)
Talk time Up to 11 h 30 min (3G)
Music play Up to 60 h Up to 46 h
MISC
Colors Silver, Gray, Gold Gold, Dark Gray, Silver, Classic Gold White, blue, yellow, pink, mint green
Price group 4/10 4/10 4/10
TESTS Performance Basemark OS II: 956 / Basemark OS II 2.0: 1018
Basemark X: 8540
Basemark OS II: 930 / Basemark OS II 2.0: 1063
Basemark X: 8518
Display Contrast ratio: 953 (nominal), 2.249 (sunlight) Contrast ratio: 953 (nominal), 2.166 (sunlight)
Camera Compare PHOTO / Compare VIDEO
Loudspeaker Voice 66dB, noise 66dB, ring 75dB Voice 66dB, noise 66dB, ring 76dB
Audio quality Noise -94.2dB / Crosstalk -93.7dB Noise -96.1dB / Crosstalk -94.8dB
Battery life 72h endurance rating 49h endurance rating


Src: http://www.gsmarena.com/compare.php3?idPhone1=7769&idPhone2=7862&sSearch3=&idPhone3=6992


4G LTE

4G LTE is the most advanced in terms of speed. The general claim is that 4G LTE networks can download data at speeds between 5 and 12 megabits per second.

In comparison, the realistic download speeds for 4G networks can range anywhere from 3 to 8 megabits per second, depending on congestion, the wireless carrier and the specific technology the company has used for its data network. The older 3G networks can typically download data around 800 to 950 kilobits per second.  src


The different LTE frequencies and bands used in different countries will mean that only multi-band phones will be able to use LTE in all countries where it is supported.   wiki

Redmi 2 - supports 4G, and in particular LTE bands 3, 7 and 8 on the FDD LTE standard. This means the phone will be able to use 4G in markets such as UK and Australia but not in the US.


http://www.pcmag.com/article2/0,2817,2498615,00.asp  FEBRUARY 1, 2016

US Mobile, which uses T-Mobile's network, is selling, servicing, and supporting a few Xiaomi and Meizu phones as of last night.

The phones going on sale include the Xiaomi Redmi 2 for $119, the Xiaomi Mi 3 for $135, the Meizu Note 2 for $149, and the Xiaomi Mi 4 for $219. 

There are some down sides to these new phones. Most notably, the phones can't get LTE in the U.S. They just weren't designed for our networks, and they don't have U.S.-compatible 4G bands.

[Tsiu : It doesn't matter.  In US, mostly I use WiFi.  And I can still use 3G.  So no 4G is bearable.  In HK, I probably only use 3G service too.]


http://www.androidcentral.com/unlocked-phones-europe  (June 2015)

As mentioned in the article, in the USA, for a phone to just be unlocked is not sufficient due to the many different LTE bands used by the different carriers, often exclusively so.

A good example are devices sold by Verizon, the largest of all the US carriers. ALL of Verizon's LTE devices are unlocked (regardless of whether they are purchased under contract or not). However, a typical Verizon device might not work well on the other 3 nationwide carriers as most Verizon devices lack bands to support those other carriers. So, a typical Verizon phone used on SEE BELOW will not support the following:

AT&T (missing bands 17, 29 and 30; will support bands 2, 4 and 5)
T-Mobile (missing band 12; will support bands 2 and 4)
Sprint (missing bands 25, 26 and 41, will not support any of Sprint's current LTE bands)

Tsiu: 

A typical Verizon unlocked phone might get AT&T service if the service is of bands 2, 4 and 5.  If your area is of bands 17, 29 and 30, then no AT&T signal.  

A typical Verizon unlocked phone might get T-Mobile service if the service is of bands 2 and 4.  If your area is of bands 12, then no T-mobile signal. 

When Winnie switches from T-Mobile to TracFone, go to the web site to make sure the T-Mobile Prism II is supported by TracFone in the area.


Does XIAOMI REDMI Note 3 32GB 4G Phablet works with ATT LTE Network?
ATT LTE network band is 1900 and 1700 MHZ and according to GSMARENA Xiaomi REDMI Note 3 4G phablet support the following bands,
LTE band 1(2100), 3(1800), 7(2600), 38(2600), 39(1900), 40(2300), 41(2500)
in the above list you can see the 1900 band support Xiaomi REDMI Note 3 so the answer is yes, XIAOMI REDMI Note 3 32GB 4G Phablet  works with ATT LTE Network.
Do the latest Xiaomi phones work with 4G or LTE networks in the USA?

The Xiaomi Note supports the following 4G bands

Network                                            Bands
4G FDD-LTE,TDD-LTE         B1 / B3 / B7 /B40
 Source: Mi Note - Ahead of the curve 

None of the US carriers support these bands.  Source: Cheat Sheet: US Wireless Carrier Bands for Unlocked Phones | Droid Life


= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
it is the latest xiaomi- xiaomi note
2G:GSM 850/900/1800/1900
3G:TD-SCDMA B34/39
3G:WCDMA B1/2/5
4G:TD-LTE B38/39/40/41
4G:FDD-LTE B3/7MHz
you could compare it with your carrier.

Plan:

10 alternatives (MVNOs):  TracFone/Net10, UltraMobile


Xiaomi Redmi Note 2 - Specifications :  http://www.devicespecifications.com/en/model/848e3256

Wi-Fi: n 5GHz, ac, Dual band, Wi-Fi Hotspot, Wi-Fi Direct, Wi-Fi Display


Xiaomi Redmi Note 4X

NETWORK Technology GSM / HSPA / LTE
LAUNCH Announced 2017, February
Status Available. Released 2017, February
BODY Dimensions 151 x 76 x 8.5 mm (5.94 x 2.99 x 0.33 in)
Weight 165 g (5.82 oz)
SIM Dual SIM (Micro-SIM/Nano-SIM, dual stand-by)
DISPLAY Type IPS LCD capacitive touchscreen, 16M colors
Size 5.5 inches (~72.7% screen-to-body ratio)
Resolution 1080 x 1920 pixels (~401 ppi pixel density)
Multitouch Yes
  - MIUI 8.0
PLATFORM OS Android 6.0 (Marshmallow)
Chipset Qualcomm MSM8953 Snapdragon 625
CPU Octa-core 2.0 GHz Cortex-A53
GPU Adreno 506
MEMORY Card slot microSD, up to 256 GB (uses SIM 2 slot)
Internal 32 GB, 3 RAM or 64 GB, 4 GB RAM
CAMERA Primary 13 MP, f/2.0, phase detection autofocus, dual-LED (dual tone) flash
Features 1.12 µm pixel size, geo-tagging, touch focus, face detection, panorama, HDR
Video 1080p@30fps, 720p@120fps
Secondary 5 MP, f/2.0, 1080p
SOUND Alert types Vibration; MP3, WAV ringtones
Loudspeaker Yes
3.5mm jack Yes
  - 24-bit/192kHz audio
- Active noise cancellation with dedicated mic
COMMS WLAN Wi-Fi 802.11 a/b/g/n, Wi-Fi Direct, hotspot
Bluetooth 4.2, A2DP, LE
GPS Yes, with A-GPS, GLONASS, BDS
Infrared port Yes
Radio FM radio
USB microUSB 2.0, USB On-The-Go
FEATURES Sensors Fingerprint (rear-mounted), accelerometer, gyro, proximity, compass
Messaging SMS(threaded view), MMS, Email, Push Mail, IM
Browser HTML5
Java No
  - XviD/MP4/H.265 player
- MP3/WAV/eAAC+/Flac player
- Photo/video editor
- Document viewer
BATTERY   Non-removable Li-Po 4100 mAh battery

Xiaomi Redmi Note 4X: http://www.devicespecifications.com/en/model/9910413e

Wi-Fi: n 5GHz, Dual band, Wi-Fi Hotspot, Wi-Fi Direct, Wi-Fi Display

http://c.mi.com/thread-48836-1-1.html : 100 % working solution for stuck at 2G problem! ... This occurs mostly in MIUI 8. A bug  ...

Winnie tried her new phone with 4G LTE (Access Point Name = fast.tmobile.com).  Internet very fast.  Outgoing call is good because it can go through her data cellular network.  But can't receive incoming call. 

Then trying 2G (EDGE).  All works but Internet slow. 

Then trying 3G with setting APN=epc.tmobile.com.  All good.

T-Mobile APN Settings 2017


Which bands does T-Mobile use?

T-Mobile still supports one 2G band, but like other carriers are primarily focusing on LTE (4G) deployment.

2G bands (EDGE)

3G bands

LTE (4G) bands


TracFone T-mobile compatibility alert:

In order to connect to the TracFone 4G LTE network, your device must operate on Band II, IV or in certain areas, Band 12. For 3G or other 4G service, your device must operate on Band II (1900 MHz) or IV (1700/2100 MHz). GSM devices that do not support these bands may operate at 2G (EDGE) speeds.


https://apn.gishan.net/settings/943_12_t-mobile_apn_settings_for_xiaomi_redmi_note_2.php

歐普瑞斯 紅米 note 4x 手機皮套 手機套 保護殼 支架 紅米note4x 保護套 手機殼 外殼 軌跡系列

http://feebee.com.tw/bid/%E7%B4%85%E7%B1%B3Note%204X%20%E4%BF%9D%E8%AD%B7%E5%A5%97/?page=48&sort=rp&mode=l?page=48&skip=m


Mobal® International Cell Phone


https://www.internationalstudent.com/international-communications/sim-card/

Some companies that offer international cell phone rentals are:

My ideal smartphone (9/2017):

1. One for all - talk/text/Internet.  NYC and Hong Kong.

2. Internet at 4G LTE in both NY & HK.  3G is acceptable.  2G is not desirable.

3. Not expensive.  < US$300.  iPhone is not desirable.

4. Reasonable strong spec:  2GB RAM.  16GB Internal Memory.  Support SD.  Good camera.

Possible Candidates:

C1.  Redmi Note 4X (Winnie's phone)