What is the maximum data rate supported by a GSM system?

- The maximum data rate supported by a GSM system is 9.6 kbps.
- However there are extensions to GSM standard to improve throughput.
- GPRS is one of the extended GSM service.
- The extended standards of GSM allows theoretical data rates on the order of 114 Kbit/s, but with throughput closer to 40Kbit/s in practice. 

Explain the services offered by GSM ?

- The services offered by GSM are ISDN compatible
- GSM allows synchronous data and asynchronous data to be transported as bearer service, one of the telecommunication services offered by GSM, and forms ISDN terminal
- The data could be either transparent service or nontransparent service
- Telephony is one of the services offered by GSM, which an emergency and the service provider is notified by dialing 3 digits
- By using appropriate fax adaptor, G3 fax service is supported
- One of the features of GSM is Short Messaging Service
- Certain services, namely supplementary services are provided on top of teleservices or bearer services by GSM, such as, caller identification, call forwarding, multiparty conversations, barring outgoing calls and call waiting. 

What is GSM?

- Short form of Global System for Mobile Communications, is a wireless network system
- A standard for digital cellular mobile communications
- International roaming arrangements are enabled among mobile network operators, by providing the subscribers to use their personal mobile phones anywhere in the world.
- GSM is considered as second generation mobile, as signaling and speech channels are digital
- The carriers can be replaced without replacing mobile phones.
- The ubiquity of GSM implementations is also enabling the switching between network operators, who can choose equipment from many GSM equipment vendors.
- GSM pioneered low cost SMS implementation
- The GSM standard includes a worldwide emergency telephone number feature.

Explain the following type of hand off in CDMA system (Softer handoff) ?

Softer handoff

- Softer handover is a significant soft handover in which the added and removed links belong to the same node
- Macro diversity with maximum ratio combining could be performed in the same node
- The movement of handoff, when a user can be served in another cell more efficiently (less power emission, less interference), is the most obvious cause for better performance.

Explain the following type of hand off in CDMA system ( Soft handoff) ?

Soft handoff

- Soft handoff is a feature in which a cellular phone is simultaneously connected to two or more cellular phones during a single call
- It is he overlapping of repeater coverage ones, which enables every cell phone set is always well within the range of a specific repeater.
- More than one repeater can send and receive signals to transmit signals to and from mobiles.
- All repeaters are used with the same frequency channel for each mobile phone set.
- Practically no dead zones and as result, the connections seldom interrupted or dropped.

Explain Sync. Channel ?

Sync. Channel

- A base station transmits a Sync-Channel that spreads with Walsh code 32.
- The frame of synch channel is 80/3ms long with frame boundary is aligned to the pilot.
- Sync channel transmits a single message continually, called Sync Channel Message.
- The Sync Channel Message contains network information, including the PN offset that is used by the Base Station sector.
- The length and content of the message is dependent on the P_REV.
- The message transmission rate is 32 bits / frame.
- The message is encoded to 128 symbols
- The message yielding rate is 1200 bits / s.

What is Pilot Channel ?

Pilot Channel

- A forward link channel which is a base to mobile that modulates only by the pilot PN. It spreads common codes to all signals transmitted from a given base station.
- Several critical important functions are provided by the pilot channel for forward links in IS-95 systems
- The pilot channel modulation facilitates the process of time synchronized replica generation at the receiver of the PN spreading sequences. These are utilized at the transmitter for modulating the synchronization, paging and traffic channels. These are transmitted from the same base station.

Which of them (CDMA and GPRS) is better?

- W-CDMA technology is faster than GPRS, since the user cares about the technology that is applied for air interface.
- Average latency on GPRS is around 1.3 seconds, where as on CDMA is around 400 milli second
- GPRS supports only User Datagram Protocol, where as CDMA supports both UDP and TCP
- GPRS relies on Network Address Translation and a private IP address is assigned to it. On the other hand CDMA assigns a public IP address CDMA is better because:
- E-mail is pretty light, until you enter MS-Office.
- Pocket PC’s support for office documents with similar functionality which can be had on Palm OS and Symbian
- Upon availability of APIs, a software developer could write various applications, like voice transfer, data transfer to client’s account, integrating billing amount etc.
- Web services could be utilized.

What is the difference between CDMA and GPRS?

- CDMA is one of the types of mobile connections for making calls where as GPRS is a technology for internet connections through a mobile phone.
- GPRS enables to surf the internet from a mobile phone. GPRS technology is used in other gadgets apart from mobile phones.

Differentiate between CDMA and TDMA ?

b.) CDMA and TDMA

CDMA

- Power limited system
- While people talking, random noise band playing occurs
- Conversation need to be extracted from the background din
- GP is high when people speak different languages, which is easier to distinguish individual speakers
- It is difficult for distinguishing individuals, when GP is low.
- The system performance will be degraded for every user when the number of users increases.
- Fading would be reduced with wide frequency spectrum
- Need to have separate multipath signals with different delays by “chip” unit.

TDMA

- Receiving or transmission is allowed for only one user in a given slot
- All slots are assigned cyclically
- The transmission is non-continuous
- It is essential to use digital data and modulation
- Data rate overhead is between 20% – 30%
- Overhead tradeoffs are size of data payload and latency
- Multiple users are shared with single carrier frequency
- Handoff is made simpler by using non-continuous transmission
- All slots are assigned on demand
- Due to reduced inter user interference, the power control is less stringent.

Differentiate between CDMA and FDMA ?

a.) CDMA and FDMA 

CDMA

- Same frequency is used by every user and simultaneous transmission occurs
- Every narrowband signal is multiplied by wideband spreading signal, usually known as codeword
- Every user has a separate pseudo-codeword, i.e., orthogonal to others
- Only the desired codeword is detected by the receivers and others appear as noise
- It is mandatory for the receivers to know about the transmitter’s codeword

FDMA

- When the channel is not in use, it sits simply idle
- Bandwidth of Channel is relatively narrow (30 KHz), known as narrowband system
- Little or no equalization is needed for spreading symbol time
- Analog links are suitable for FDMA
- Framing or synchronization bits are not needed for continuous transmission
- Tight filtering is needed to minimize interference
- Combined with FDD for duplexing

What is the importance of CDMA in today’s cellular world?

- The transition to digital radio through the process of defining standards is implementing about 90% in the cellular industry.
- Smooth transition to digital standards is involved in CDMA technology.
- Most often, it can be viewed as improved and replacement technology of TDMA
- Moving towards 4G technology is compatible with CDMA technology.

What is the difference between CDMA and GSM?

The important differences are:

Data Transfer Speed:

- CDMA is faster than GSM.
- CDMA2000 downstream rate is 2 megabits / second, through EVDO, where GSM downstream rate is up to 384 kilobits / second, through EDGE technology

Subscriber Identity Module (SIM) cards:

- SIM is tied to the network, rather than the actual phone. Phones with card-enabled can be used with any carrier of GSM
- Proprietary handsets are linked to one carrier only and not card-enabled in CDMA

Roaming:

- GSM carriers have wider coverage of more rural areas, where as CDMA may not cover rural areas compared to GSM carriers

International Roaming:

- GSM has facility to offer more international roaming, as the number of connections in world market dominate GSM network.
- CDMA phones do not have the capacity; however, there are more countries that use CDMA networks.

What is EV-DO/ EVDO ?

- EVDO stands for Evolution Data Optimized - EVDO is a 3G broadband technology used by Verizon, Spring, Alltel - It provides typical download speeds of 600 to 1400 KBPS - A personal broadband service for wide range of customers - It is always On - EVDO utilizes CDMA signals - Users can be connected remotely for using email, downloading large files, spreadsheets etc. - EVDO is relatively low cost with high capacity - Allows rich web browsing and application usage - Seamless roaming, internal internet connectivity without relying on other’s connection, accessibility to the corporate Virtual Private Network by customers are some of the advantages over WiFi.

What is EDGE ?

- EDGE is an acronym for Enhanced Data GSM Environment
- An improved wireless technology over GSM
- A 2nd generation cell phone technology
- EDGE is used for wireless data transfer via mobile phone connection
- Data transfer rates up to 4 times more than GSM networks
- With the advent of Blackberry and iPhone, faster data transfer is sought
- Using more sophisticated coding, usually without high end hardware, wireless carrier’s base stations are supported for data transfer speeds up to 384 KBPS
- EDGE is an alternative to replacing wireless technology, such as GPRS
- EDGE will eventually be replaced by 3G technology such as WCDMA.

What is CDMA2000 ?

- Also known as IMT Multi-Carrier, a family of 3G mobile technology standards.
- Used for sending voice, data and signaling between cell sites and mobile pones
- The standards such as CDMA2000 1X, CDMA2000 EV-DO Rev. 0, are approved radio interfaces for ITU IMT-2000
- CDMA 2000 is backward compatible with its previous 2G iteration IS-95

Evolution of 2G ?

2G networks were built mainly for voice services and slow data transmission (defined in IMT-2000 specification documents), but are considered by the general public^[who?] to be 2.5G or 2.75G services because they are several times slower than present-day 3G service.

Advantage of 2G ?

Advantage of 2G :

While digital calls tend to be free of static and background noise, the lossy compression they use reduces their quality, meaning that the range of sound that they convey is reduced. Talking on a digital cell phone, a caller hears less of the tonality of someone's voice.

Disadvantages of 2G ?

Disadvantages of 2G:

• In less populous areas, the weaker digital signal transmitted by a cellular phone may not be sufficient to reach a cell tower. This tends to be a particular problem on 2G systems deployed on higher frequencies, but is mostly not a problem on 2G systems deployed on lower frequencies. National regulations differ greatly among countries which dictate where 2G can be deployed.

• Analog has a smooth decay curve, but digital has a jagged steppy one. This can be both an advantage and a disadvantage. Under good conditions, digital will sound better. Under slightly worse conditions, analog will experience static, while digital has occasional dropouts. As conditions worsen, though, digital will start to completely fail, by dropping calls or being unintelligible, while analog slowly gets worse, generally holding a call longer and allowing at least some of the audio transmitted to be understood.

2G Data Transmission capacity ?

• With GPRS (General Packet Radio Service), you have a theoretical transfer speed of max. 50 kbit/s (40 kbit/s in practice).
• With EDGE (Enhanced Data Rates for GSM Evolution), you have a theoretical transfer speed of max. 1 Mbit/s (500 kbit/s in practice).

Benefits of 2G Network ?

 Three primary benefits of 2G networks over their predecessors were that :

•  phone conversations were digitally encrypted
• 2G systems were significantly more efficient on the spectrum allowing for far greater mobile phone penetration levels
•  and 2G introduced data services for mobile, starting with SMStext messages.

What is HLR (Home Location Register) ?

HLR (Home Location Register) :

a. For GSM and CDMA wireless networks
b. It’s responsibility is to authenticate and authorize subscribers and their services

Explain the following techniques in GSM( Sectorization of a cell)?

Sectorization of a cell:

- Sectorization is a process to cut down equipment costs in a cellular network. It influences in traffic load and cell size
- Sectorization reduces co-channel interference, when applied to clusters of cells
- The maximum traffic capacity of sectored antennas is more than omnidirectional antennas.

What is GSM (Global System for Mobile Communications) ?

 GSM (Global System for Mobile Communications): 

a. Most popular standard for mobile telephony systems, originated from Groupe Special Mobile
b. The ubiquity of GSM enables the international roaming arrangements among mobile phone operators.
c. Both signaling and speech channels are digital, and thus GSM is considered as 2G mobile phone system.
d. GSM standard benefited customers the ability to roam and switch carriers without replacing the hand sets and network operators.
e. GSM implements low-cost implementation of Short Message Service

What is GPRS ( General Packet Radio Service) ?

GPRS ( General Packet Radio Service) :

a. Packet oriented mobile data service available to the users of 2G cellular systems.
b. It is global system for communicating through mobile phones using GSM as well as in 3G systems.
c. GPRS data transfer is charged per MB of traffic transferred, where as in circuit switching, data transfer is charged per minute of connection time
d. GPRS is better packet switching service, as opposed to circuit switching.
e. 2G cellular systems are combined with GPRS and known as 2.5G.
f. Provides moderate speed data transfer by using unused TDMA channels, such as GSM.

How is 3G different from 2G?

a. Packet data speed is higher in 3G, and it is up to 384 KBPS
b. Voice and sms speed is also 384 KBPS in 3G
c. 2G utilizes different switching techniques for voice and data, where as 3G uses single switching, irrespective of data
d. 3G has at least 2MB of data link of a mobile, where in 2G the data rate is in KBPS
e. 3G has WiMAX facility for faster VOIP and internet
f. 2G uses GSM TDMA technology with narrowband 200Khz.
g. 3G uses CDMA technology with broadband 5Mhz, with same frequency carrier and time.

Disadvantages of 3G ?

a. The cost of cellular infrastructure , upgrading base stations is very high
b. Needs different handsets.
c. Roaming and data/voice work together has not yet been implemented
d. Power consumption is high
e. Requires closer base stations and are expensive
f. Spectrum-license costs, network deployment costs and handset subsidies subscribers are tremendous.

Advantages of 3G ?

Advantages of 3G:

a. Overcrowding is relieved in existing systems with radio spectrum
b. Bandwidth, security and reliability are more
c. Provides interoperability among service providers
d. Availability of fixed and variable rates
e. Support to devices with backward compatibility with existing networks
f. Always online devices – 3G uses IP connectivity which is packet based
g. Rich multi media services are available.

What is 3G ?

3G actually stands for “third generation”, as it is the third type of access technology that has been made widely commercially available for connecting mobile phones.
In the UK, 3G services were launched commercially in 2003 through Hutchinson 3G, now known as Three. Now, all of the mobile network operators in the UK offer 3G services, and all major mobile phone manufacturers offer 3G phones that can access these services; many can be found in the 3 store online. In fact, just about every smartphone and most feature phones support 3G.

What is High Speed Packet Access ?

- HSPA is a combination of 2 mobile telephony protocols – High Speed Downlink Packet Access and High Speed Uplink Packet Access
- HSPA improves the performance of existing WCDMA protocols.
- HSPA provide increased performance by utilizing schemes of modulation and refining the protocols, through which the base stations and handsets communicate
- HSPA is used for better usage of the available bandwidth provided by WCDMA
- HSPA supports data rates of up to 14 MBit / s in the downlink
- HSPA supports data rates of up to 5.8 MBit / s in the uplink
- HSPA reduces the latency and increases up to 5 times more system capacity during downlink and twice more system capacity during uplink
- HSPA uses 16QAM for yielding higher bit rates
- HSPA rollouts are achieved by implementing software upgrades to existing 3G networks. This gives HSPA a head start over WiMax.

What is DECT?

- DECT is one of the wireless technologies, originated in Europe - DECT was designed to interwork with various networks such as PSTN, ISDN, GSM etc. - The initial standard. of DECT focused on developing air interface which is a radio link between cordless telephone and the base stations - This standard plugged into the telephone socket and the standard protocols for handover between several base stations - All these are connected to the same office switchboard, typically a PABX - The first product of its kind was from Olivetti, was a wireless LAN type product, known as NET3.

What is CDMA One ?

- CDMA one refers original ITU IS-95 CDMA wireless interface protocol. It is considered as a 2G mobile wireless technology
- The version IS-95A protocol employs a 1.25 Mhz carrier and data speeds up to 14.4 Kbps
- The version IS-95B support data speeds up to 115 kbps by employing 800 MHz / 1.9 GHz.

What is CDMA? Explain the technology ?

- CDMA stands for Code Division Multiple Access
- CDMA is a wireless technology used in transmission of signal from places with high Security and noise reduction.
- The principle of Spread Spectrum is used to work with CDMA.
- Spread signal is below the noise level noise and has no effect on the signal.
- CDMA does not frequency specific to each user. Instead, every channel uses the full available spectrum.
- Individual conversations are encoded with a pseudo-random digital sequence.
- CDMA always provides better capacity for voice and data communications
- CDMA is a common platform for 3G technologies
- Analog radio transmission technologies like Advanced Mobile Phone System were used in CDMA at the time of its inception
- A unique code is received by all mobile network users and is allowed continuous network access instead of intermittent and timed access.

What is CDMA2000?

- CDMA2000 is a Multi-carrier code-division multiple access version of IMT-2000 standard
- CDMA2000 is a 3G wireless technology.
- World’s first 3G commercial system was launched by SK Telecom of South Korea using CDMA2000 1X
- CDMA 2000 supports mobile data communications at speeds from 144KBPS to 3MBPS
- The versions of CDMA2000 have been developed by Qualcomm and Ericsson
- There were 250,300,000 subscribes world for CDMA by March 2006.

Functions of International Telecommunications Union ?

- Maintaining and extending the international cooperation for the improvement
- Rational usage of telecommunications, for promoting efficient use of technical facilities
- To harmonize the actions of nations.

What is International Telecommunications Union ?

- ITU is an intergovernmental organization
- Telecommunications are developed by using ITU by public and private organizations.
- ITU is responsible for adopting regulations, international treaties and standards that governs telecommunications

What are the benefits of 4G?

The benefits of 4G fall firmly into three categories. These are

• improved download/upload speeds
• reduced latency
• crystal clear voice calls (coming later)

What is 4G ?

4G is the fourth generation of mobile phone technology that follows on from the existing 3G and 2G mobile technology.

2G technology launched in the 1990s and was capable of making digital phone calls and sending texts. Then 3G came along in 2003 which made it possible to browse web pages, make video calls and download music and video on the move.

4G technology builds upon what 3G currently offers, but does everything at a much faster speed.

What is UMTS ?

UMTS ?

a. UMTS stands for Universal Mobile Telecommunications Systems b. One of the emerging mobile technologies for 3G mobile phones. c. The main benefit of UMTS is, undoubtedly, its speed d. Current rates of broadband data transfer is 2MBits / second e. The speed of UMTS makes it possible to stream video that supports movie downloads and video conferencing. f. In a nut shell, UMTS provides almost all the facilities of a home computer system while on the move. g. UMTS combines the technologies like wireless, satellite which provides seamless transitions between Wi-Fi and satellite.

What is i-appli?

i-appli :

a. i-appli is a Java environment based on CLDC.
b. Handsets of NTT DoCoMos are utilizing i-appli
c. It is similar to MIDP, however both APIs are incompatible.

what is iDEN (Integrated Digital Enhanced Network) ?

iDEN (Integrated Digital Enhanced Network) :

a. A wireless technology for Motorola
b. It has the capabilities of digi-cellular phone, 2 way radio, alphanumeric pager and data modem / fax modem in a single network
c. Operational bands are 800 MHz, 900 MHz and 1.5 GHz
d. iDEN is based on TDMA (Time Division Multiple Access) and GSM architecture
e. For voice compression it uses Motorola’s Vector Sum Excited Linear Predictors vocoder
f. For delivering 64KBPS over a 25 KHz channel, it uses QAM modulation.
g. iDEN is designed to serve the mobile user for accessing information quickly without carrying several devices.

Advantages of 1G ?

Advantages :

1G mobile phones used a single, universal network standard, known as the Advanced Mobile Phone System (AMPS). Introduced in 1976, this analog network saw adoption around the world and brought different cell phone service providers together under a single network, allowing for shared cost of network development and maintenance.

Earlier cell phone networks, mostly intended for industrial, military and research applications, used a series of dissimilar networks with very small broadcast areas. The idea of a universal network that started with 1G persists in today's worldwide digital

Disadvantages of 1G ?

Disadvantages :

• The main disadvantages  of 1g technology is that it makes use of analog rather than digital signals.
•  This is a less effective means of transmitting information. 
• It is significanty  slower, and signals can not reach as far in terms of secluded areas and such - 2g and 3g signal is far more widespread. 
• In addition, analogue signals are more likely to suffer interference problems.
•  This can make using a mobile phone with analogsignal more difficult. In all, the newer brands of 2g and 3g technology are more highly recommended.

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History of 1G ?

History :

The first commercially automated cellular network (the 1G generation) was launched in Japan by NTT (Nippon Telegraph and Telephone) in 1979, initially in the metropolitan area of Tokyo. Within five years, the NTT network had been expanded to cover the whole population of Japan and became the first nationwide 1G network.

In 1981, the Nordic Mobile Telephone (NMT) system simultaneously launched in Denmark, Finland, Norway and Sweden. NMT was the first mobile phone network to feature international roaming. In 1983, the first 1G network launched in the USA was Chicago-based Ameritech using the Motorola DynaTAC mobile phone. Several countries then followed in the early to mid-1980s including the UK, Mexico and Canada.

Difference Between 1G & 2G ?

Difference Between 1G & 2G :

The main difference between the two mobile telephone systems (1G and 2G), is that the radio signals used by 1G networks are analog, while 2G networks are digital.

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2.75G (EDGE) ?

2.75G (EDGE) :

 GPRS networks evolved to EDGE networks with the introduction of 8PSK encoding. Enhanced Data rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE was deployed on GSM networks beginning in 2003—initially by AT&T in the United States.

EDGE is standardized by 3GPP as part of the GSM family and it is an upgrade that provides a potential three-fold increase in capacity of GSM/GPRS networks.The 2G digital service provided very useful features, such as caller ID, call forwarding and short messaging.

What is 1G network ?

1G (or 1-G) refers to the first generation of wireless telephone technology (mobile telecommunications). These are the analog telecommunications standards that were introduced in the 1980s and continued until being replaced by 2G digital telecommunications. 

What is 2G ?

2G (or 2-G) is short for second-generation wireless telephone technology. Second generation 2G cellular telecom networks were commercially launched on the GSM standard inFinland by Radiolinja (now part of Elisa Oyj) in 1991