Daniel @ nowhere: Mobile

2009/11/24

Enfin iPhone

des feuilles.Central Park.New York.US

Enfin, j'ai acheté un iPhone à Taiwan. Quand j'étais aux etats-unis, j'utilisais souvent les portables qui sont fabriquées par ma compagnie. Bien que l'on ait bien travaillé sur eux, ils sont encore loins d'être parfaits.

Donc, j'ai décidé d'acheter un iPhone pour moi-même. Pour fabriquer de bons produits, on doit bien savoir les uns des competitors.Bah.... je sais c'est seulement un excuse pour mon achat. :p

l'iPhone est mieux que je le pense: elegant, et rapide.

2009/04/05

Introduction to 3G network

It's a shame not knowing common knowledge of 3G networks while working in a mobile phone manufacturer. Well, Obviously, some people do not think so. Here's the brief outline of radio network change: from first generation to 2G, 2.5G, and 3G. Although 4G is coming on its way, knowing current technologies will help catching up the new ones.

Introduction to 3G network
- History
  - 1G
    - NMT (Nordic Mobile Telephone)
      - NMT-450
      - NMT-900
        International Roaming is possible
      - Scandinavia, Ecntral and Southern Europe
    - TACS (Total Access Communications System)
      - UK standard, based on AMPS
      - 900 MHz
    - AMPS (Advanced Mobile Phone Service)
      - US standard
      - 800 MHz
    - MCS
      - NTT: first cellular network in Japan
  - 2G
    - Feature
      - use digital radio transmission for traffic
      - basic GSM uses 900 MHz
      - 1800 MHz
    - GSM (Global System for Mobile communications)
      - Most successful and widely used 2G system
      - TDMA
    - D-AMPS (digital AMPS)
      - US-TDMA, IS-136, or just TDMA
    - CDMA IS-95 (Code-division Multiple Access)
      - Developed by Qualcomm
      - the only 2G CDMA standard so far
      - IS-95 also called cdmaOne (brand name)
    - PDC (Personal Digital Cellular)
      - Frequency bands
        800 MHz
        1500 MHz
      - Feature
        physical layer: similar to D-AMPS
        protocal stack: resembles GSM
      - Only operated in Japan
    - Digital Cordless systems
      - CT2
      - DECT (Digital Enhanced Cordless Telecommunications)
      - PHS (Personal Handyphone System)
  - 2.5G
    - new technologies
      - HSCSD High-speed Circuit-switched Data)
        allocate 4 time slots for transmisstion (9.6 Kbps or 14.4 x 4)
        summary
        Good: software updates to network, and phone; good for real time apps
        Bad: usage of scarce radio resources
      - GPRS (General Packet Radio Services)
        up to 115 Kbps
        packet switched
        suitable for non real-time apps
        bursty data is well handled
        do not guarantee an absolute maximum delay
      - EDGE (Enhanced Data Rates for Global Evolution)
        3 folds of original GSM speed
        8PSK (eight-phase shift keying)
        + GPRS --> EGPRS
        384 Kbps maximum
    - IS-136 + (GPRS || EDGE) --> 2.5G
    - Qualcomm
      - CDMA2000 1xRTT
        IS-95: 14.4 Kbps, 1xRTT: 64 Kbps
        IS-95 + IS-95B or upgrade CDMA2000 1xRTT -->2.5G
      - HDR (High Data Rate)
        2.4 Mbps
        standardized in IS-856
        1xEV-DO (1x Evolved Data Optimized)
        Add a TDMA component beneath code component
    - PDC-P (NTT DoCoMo)
      - i-mode
- 3G standard proposals
  - UMTS (Universal Mobile Telecommunications System)
    - Done by ETSI SMG (Special Mobile Group)
    - UMTS Forum was created in 1996
  - new technologies
    - WCDMA
      - the bandwidth is 5 MHz or more (144kbps, 384kbps or even 2Mbps
      - network
        Synchronous
        CDMA2000
        compatible with IS-95
        manufacturer: Qualcomm, Lucent, Motorola
        use ANSI-41 core network
        3GPP2 (less support than 3GPP)
        good/not good
        good: effecient radio interface
        bad: expensive H/W
        Asynchronous
        ETSI/ARIB WCDMA
        most popular 3G system
        manufacturer: Ericsson, Nokia, NTT DocoMo
        rename to UTRAN (FDD)
        based on GSM MAP network
        3GPP
      - feature
        fast power control
        vary bit rate, service params on frame by frame basis
    - Advanced TDMA
      - UWC-136 only
    - Hybrid CDMA/TDMA
      - Not supported
      - in fact, it likes UTRAN TDD
    - OFDM
      - spectrum: effecient
      - user: DAB, DVB, 802.11a, 802.11g, ADSL
      - TDMA/CDMA possible
      - good
        bandwidth effecient
        resistance to
        narrow band interference
        multipath interefrence
  - IMT-2000
    - umbrella spec of all 3G systems (origin from ITU)
    - IMT Direct Spread (IMT-DS)
      - UTRA FDD
      - 3GPP
    - IMT Multicarrier (IMT-MC)
      - CDMA2000
      - 3GPP2
    - IMT Time Code (IMT-TC)
      - UTRA-TDD/TD-SCDMA narrowband TDD
      - 3GPP
    - IMT Single Carrier (IMT-SC)
      - UWC-136
    - IMT Frequency Time (IMT-FT)
      - DECT
- 3GPP
  - an org that develops spec for 3g system based on UTRA radio interface
  - partners
    - ETSI
    - ARIB
    - TTA
    - TTC
    - CWTS(china wireless telecommunications Standard
  - ULTRA
    - FDD
      - vocabs
        chip: a bit in a code word
        spreading factor: chip rate / data bit rate
        spreading code: a sequence of chips used to modulate the data bits
      - up/down use separate freq bands
      - chip rate: 3.84 Mcps
    - TDD
      - NOrmal: 3.84 Mcps
      - TD-SCDMA: 1.28 Mcps
    - channels
      - physical (air interface)
      - transport
        between layer 1 and 2
        define how data is sent over the air
      - logical
        within layer 2
        define the type of data to be sent
- 3GPP2
  - should be backward compatible with IS-95

and here's the Introduction to 3G network in tree view for better reading.

2009/11/24

Enfin iPhone

2009/04/05

Introduction to 3G network

乩童警探 一二集

乩童警探一二集