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Monday, January 31, 2011

Difference between WCDMA(UMTS/HSPA) and GSM,GPRS,EDGE

Carrier spacing5 MHz200 kHz
Downlink modulationQPSK, 16QAM, 64QAMGMSK, 8PSK
Network ArchitectureFlat in HSPA (2), 4 in convenstional 4
Packet Scheduling and
Power Control 
Upto 1500HzUpto 2Hz
Frequency reuse factor11 to 18
Frequency DiversityMultipath diversity
with rake receiver
Frequency Hopping with Frequency diversity

Best programming practice(C/C++):How to do you decide whether to have a variable as class member or static class member

Simple but people often do mistakes!
I have seen people writing code, where some of variables does not fit to be class member still used as class members. If a variable not required during the life of class instance then it is not required to have it as class member. Remember static class members are per class not per instance.

Best practise in Embedded Programming (C/C++):Interrupt Service Routine - ISR

Thumb rule for ISR is : It should be short and sweet.
1) Will not have any parameters or return values.
2) Should avoid performance hit operations like floating point operations.
3) Should not contain non-entrant functions.
If somebody gives you an example code to identify the problems in the ISR routine, these points should be considered to identify the faults.

Throughput in 3GPP WCDMA Release including HSPA, GPRS, EDGE


ThroughputFamilyRaw data/
Radio Block
CS19.05  GMSK

Saturday, January 22, 2011

Cellular Wireless networks

• 1G
– Analog speech communications.
– Analog FDMA.
– Technology: AMPS
• 2G
– Digital modulation of speech communications.
– Advanced security and roaming.
– TDMA and narrowband CDMA.
– Technology: GSM, PDC and IS-95 (cdmaOne)
• 3G
– Global harmonization and roaming.
– Wideband CDMA
– Technology: UMTS, cdma2000 and TD-SCDMA

Friday, January 21, 2011

AMR: Discontinuous TX (DTX)

Mobile Battery life will be prolonged or a smaller battery could be used for a given operational duration. From the network point of view, the average required bit rate is reduced, leading to a lower interference level and, hence, increased capacity.

How to acheive DTX in AMR?
- Voice Activity Detector on TX side
- Evaluation of the background acoustic noise on the TX side
- Transmission of comfort noise information to the RX side using SID at regular intervals
- Generation of comfort noise on the RX side during periods when no normal speech frames are received.

Tuesday, January 18, 2011

LTE as an all IP architecture,endorsed by many leading vendors

LTE (Long term evolution) is the latest standard for mobile network technology, specifications are available in the 3GPP standard. LTE is also an all IP architecture supported by major vendors like AT&T, T-Mobile, Verizon and more. Best part of the technology is that it also provides the inter-working for non 3GPP systems like 3GPP2 (CDMA)and WiFi, WiMax etc. Non 3GPP system are divided into trusted and non-trusted, based on that architecture will change. It is also called as 4G technology in mobile network industry. 3GPP release 8 and above specification talks about adapting to LTE. LTE started as a technology which support packet data network, later to support voice over the packet data network.
What is more fascinate about LTE?
- All IP Architecture
- Signaling and Data path separated out using MME and S-GW where PS Core and CS core is merged into single core network
- High data rates
- Decreased latency
- Better spectrum efficiency
- Scalable bandwidth
- Support for paired and unpaired spectrum
- Inter-working with 3GPP and non 3GPP systems

Below is reference architecture and inter-working with existing 3GPP systems (Reference 3GPP specifications:

Concerns operators shall have could be
- Cost effective evolution of IMS and LTE
- Spectrum efficiency
- Service quality
- Coverage performance

Target would be to address these concerns. However lot depends on the approaches that would be considered by operators for the architecture. Most of them probably consider overlay architecture and gradual transition.

If you have any questions please try to post the same. I would try to answer the same.

Monday, January 3, 2011

Best practice for Singleton pattern

Best practice for the singleton class to avoid the mis-usage.

1) Make the constructor as private.
2) Hide the copy constructor
3) Hide the = operator
4) Return the reference of the instance instead of pointer in the instance() method

Below is the example:

class Singleton


     * @brief Method to retrieve the object (singleton pattern)
    static Singleton & instance();

     * @brief Destructor
    virtual ~Singleton();


     * @brief constructor, which can only be accessed by instance() method

     * @brief Hide the copy constructor.
    Singleton(const Singleton & p_singleton);

     * @brief Hide the operator '='.
    Singleton & operator =(const Singleton & p_rhs);

     * @brief singleton, can only be accessed by instance()
    static Singleton* c_pInstance;