Benefits of Wireless Communications with MVPN (Mobile Virtual Private Network)

For wireless operators deploying latest-generation cellular systems based on packet-switched data such as GPRS and CDMA2000, and especially those targeting business customers for significant portion of their revenue stream, the importance of services based on MVPN technologies is hard to underestimate. For operators, MVPN is not only one of the required technologies for business customers' private network access but also a foundation for other services requiring interaction with private networks such as m-commerce, virtual presence and gaming applications, and multimedia applications (which includes Voice over IP-based services).

The benefits of deploying Mobile VPNs for businesses and institutions include:

• Uninterrupted, media and location-independent connectivity to private networks

• Seamless private network access mobility

• Connectivity to a particular Internet service provider (ISP) or application service provider (ASP)

• Mobile remote access outsourcing possibilities

• Secure m-commerce enabler

• Constant remote-workers reachability

• Higher cost-effectiveness

As a result, businesses, which already had a positive experience with wireline VPN services, are now looking to wireless operators for extending these services into wireless environments. In our view, during the next few years as the latest generations of cellular systems and other wireless technologies take off, an enormous market opportunity awaits wireless carriers who can meet demands for services requiring private network access.

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What is 3G or Wideband Digital Cellular System

The 3rd generation wireless requirements are defined in the International Mobile Telecommunications “IMT-2000” project developed by the International Telecommunication Union (ITU). The IMT-2000 project that defined requirements for high-speed data transmission, Internet Protocol (IP)-based services, global roaming, and multimedia communications. After many communication proposals were reviewed, two global systems are emerging; wideband code division multiple access (WCDMA) and CDMA2000.

Wideband Code Division Multiple Access (WCDMA)

WCDMA is a 3rd generation digital cellular system that uses radio channels that have a wider bandwidth than 2nd generation digital cellular systems such as GSM or IS-95 CDMA. WCDMA is normally deployed in a 5 MHz channel plan.

The Third Generation Partnership Project (3GPP) oversees the creation of industry standards for the 3rd generation of mobile wireless communication systems (WCDMA). The key members of the 3GPP include standards agencies from Japan, Europe, Korea, China and the United States. The 3GPP technology, also known as the Universal Mobile Telecommunications System (UMTS), is based on an evolved GSM core network that contains 2.5G elements, namely GPRS switching nodes. This concept allows a GSM network operator to migrate to WCDMA by adding the necessary 3G radio elements to their existing network, thus creating ‘islands’ of 3G coverage when the networks first launch.

A large number of GSM operators have secured spectrum for WCDMA and many network launches are imminent, with live networks presently in Japan, the United Kingdom and Italy.

Code Division Multiple Access 2000 (CDMA2000)

CDMA2000 is a family of standards that represent an evolution from the IS- 95 code division multiple access (CDMA) system that offer enhanced packet transmission protocols to provide for advanced high-speed data services. The CDMA2000 technologies operate in the same 1.25 MHz radio channels as used by IS-95 and offer backward compatibility with IS-95.

The CDMA2000 system is overseen by the Third Generation Partnership Project 2 (3GPP2). The 3GPP2 is a standards setting project that is focused on developing global specifications for 3rd generation systems that use ANSI/TIA/EIA-41 Cellular Radio Intersystem Signaling.

Time Division Synchronous CDMA (TD-SCDMA)

On a global basis it likely that WCDMA and CDMA2000^TM will dominate the 3G market, however in China there is growing support for a homegrown standard known as Time Division Synchronous CDMA (TD-SCDMA). TDSCDMA offers voice services and data services, both circuit-switched and packet-switched, at rates up to 2 Mbps. It uses a Time Division Duplex (TDD) technique in which transmit and receive signals are sent on the same frequency but at different times. The timeslots on the radio carrier can either be allocated symmetrically for services such as speech or asymmetrically for data services where the bit rates in the two directions of transmission may differ significantly.

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Upgraded Digital Cellular System (Generation 2.5)

The types of upgraded 2nd generation digital cellular systems (generation 2.5) include GPRS, EDGE, and CDMA2000^TM , 1xRTT.

General Packet Radio Service (GPRS)

General Packet Radio Service (GPRS) is a portion of the GSM specification that allows packet radio service on the GSM system. The GPRS system adds (defines) new packet channels and switching nodes within the GSM system. The GPRS system provides for theoretical data transmission rates up to 172 kbps.

Enhanced Data Rates for Global Evolution (EDGE)

Enhanced Data Rates for global Evolution (EDGE) is an evolved version of the global system for mobile (GSM) radio channel that uses new phase modulation and packet transmission to provide for advanced high-speed data services. The EDGE system uses 8 levels Phase Shift Keying (8PSK) to allow one symbol change to represent 3 bits of information. This is 3 times the amount of information that is transferred by a standard 2 level Gaussian Minimum Shift Keying (GMSK) signal used by the first generation of GSM system. This results in a radio channel data transmission rate of 604.8 kbps and a net maximum delivered theoretical data transmission rate of 384 kbps. The advanced packet transmission control system allows for constantly varying data transmission rates in either direction between mobile radios.

CDMA2000™, 1xRTT

CDMA2000^TM is a 3G standard that allows operators to evolve from their existing IS-95 networks to offer 3G services. The original CDMA2000^TM proposal contained two distinct evolutionary phases, the first known as 1xRTT used the same 1.25 MHz channels as IS-95 but delivered increased capacity and data rates compared to IS-95. The second phase was known as 3xRTT that uses three times the spectrum of IS-95, that is 3.75 MHz. The 3xRTT concept would deliver data rates up to 2 Mbps, a requirement for any 3G technologies. However recent evolutions of 1xRTT are offering data rates in excess of this and therefore it is unlikely that 3xRTT is required.

By the middle of 2003 there were a total of 60 commercial 1xRTT networks offering service.

Evolution Data Only (1xEVDO)

The evolution of existing systems for data only (1xEVDO) is an evolved version of the CDMA2000^TM 1xRTT system. The 1xEVDO system uses the same 1.25 MHz radio channel bandwidth as the existing IS-95 system that provides for multiple voice channels and medium rate data services. The 1xEVDO version changes the modulation technology to allow for data transmission rates up to 2.5 Mbps. The 1xEVDO system has an upgraded packet data transmission control system that is allows for bursty data transmission rather than for more continuous voice data transmission.

Evolution Data and Voice (1xEVDV)

The evolution of existing systems for data and voice (1xEVDV) is an evolved version of the CDMA2000^TM 1xRTT system that can be used for data and voice service. The 1xEVDV system provides for both voice and high-speed data transmission services in the same 1.25 MHz radio channel bandwidth as the existing IS-95 system. The 1xEVDV Vision allows for a maximum data transmission rate of approximately 2.7 Mbps.

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What is Code Division Multiple Access (IS-95 CDMA)

Code Division Multiple Access (CDMA) system (IS 95) is a digital cellular system that uses CDMA access technology. IS-95 technology was initially developed by Qualcomm in the late 1980’s. CDMA cellular service began testing in the United States in San Diego, California during 1991. In 1995, IS-95 CDMA commercial service began in Hong Kong and now many CDMA systems are operating throughout the world, including a 1.9 GHz all-digital system in the USA that has been operating since November 1996 (Fig. 1).

Fig. 1: CDMA Tower

Spread spectrum radio technology has been used for many years in military applications. CDMA is a particular form of spread spectrum radio technology. In 1989, CDMA spread spectrum technology was presented to the industry standards committee but it did not meet with immediate approval. The standards committee had just resolved a two-year debate between TDMA and FDMA and was not eager to consider another access technology.

The IS-95 CDMA system allows for voice or data communications on either a 30 kHz AMPS radio channel (when used on the 800 MHz cellular band) or a new 1.25 MHz CDMA radio channel. The IS-95 CDMA radio channel allows multiple mobile telephones to communicate on the same frequency at the same time by special coding of their radio signals.

CDMA radio channels carry control, voice, and data signals simultaneously by dividing a single traffic channel (TCH) into different sub-channels. Each of these channels is identified by a unique code. When operating on a CDMA radio channel, each user is assigned to a code for transmission and reception. Some codes in the TCH transfer control channel information, and some transfer voice channel information.

The control channel that is part of a digital traffic channel on a CDMA system has new advanced features. This digital control channel (DCC) carries system and paging information, and coordinates access similar to the analog control channel (ACC). The DCC has many more capabilities than the ACC such as a precision synchronization signal, extended sleep mode, and others. Because each CDMA radio channel has many codes, more than one control channel can exist on a single CDMA radio channel and the CDMA control channels co-exist with other coded channels that are used for voice.

The IS-95 CDMA cellular system has several key attributes that are different from other cellular systems. The same CDMA radio carrier frequencies may be optionally used in adjacent cell sites, which eliminates the need for frequency planning, the wide-band radio channel provides less severe fading, which the inventors claim results in consistent quality voice transmission under varying radio signal conditions. The CDMA system is compatible with the established access technology, and it allows analog (EIA-553) and dual mode (IS-95) subscribers to use the same analog control channels. Some of the voice channels are replaced by CDMA digital transmissions, allowing several users to be multiplexed (shared) on a single RF channel. As with other digital technologies, CDMA produces capacity expansion by allowing multiple users to share a single digital RF channel.

The IS-95 CDMA radio channel divides the radio spectrum into wide 1.25 MHz digital radio channels. CDMA radio channels differ from those of other technologies in that CDMA multiplies (and therefore spreads the spectrum bandwidth of) each signal with a unique pseudo-random noise (PN) code that identifies each user within a radio channel. CDMA transmits digitized voice and control signals on the same frequency band. Each CDMA radio channel contains the signals of many ongoing calls (voice channels) together with pilot, synchronization, paging, and access (control) channels. Digital mobile telephones select the signal they are receiving by correlating (matching) the received signal with the proper PN sequence. The correlation enhances the power level of the selected signal and leaves others unenhanced.

Each IS-95 CDMA radio channel is divided into 64 separate logical (PN coded) channels. A few of these channels are used for control, and the remainders carry voice information and data. Because CDMA transmits digital information combined with unique codes, each logical channel can transfer data at different rates (e.g. 4800 b/s, 9600 b/s).

CDMA systems use a maximum of 64 coded (logical) traffic channels, but they cannot always use all of these. A CDMA radio channel of 64 traffic channels can transmit at a maximum information throughput rate of approximately 192 kbps [14], so the combined data throughput for all users cannot exceed 192 kbps. To obtain a maximum of 64 communication channels for each CDMA radio channel, the average data rate for each user should approximate 3 kbps. If the average data rate is higher, less than 64 traffic channels can be used. CDMA systems can vary the data rate for each user dependent on voice activity (variable rate speech coding), thereby decreasing the average number of bits per user to about 3.8 kbps [15]). Varying the data rate according to user requirement allows more users to share the radio channel, but with slightly reduced voice quality. This is called soft capacity limit.

In 1997 the CDMA Development Group (CDG) registered the trademark cdmaOne ^TM as a label to identify second-generation digital systems based on the IS-95 standard and related technologies.

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Bangladesh WiMAX First Introduces Augere Brand Name 'Qubee'

Jerry Mobbs, chief executive officer of
Augere, speaks at the launch of the
company's wireless broadband service
in Dhaka yesterday.Photo: Masthead PR

Augere Wireless Broadband Bangladesh Ltd yesterday launched the much-waited wireless broadband service through WiMax in some designated areas in Dhaka.

Augere, one of the two WiMax licensees, is the first company in Bangladesh to launch such service under the brand name 'Qubee'.

Augere is initially offering two packages. Customer will have to pay Tk 3,400 a month for the Qubee 512 kbps package. The monthly charge for the Qubee 1 Mb has been fixed at Tk 6,200, while the modem price for both the packages is Tk 7,000.

Initially, the Qubee service is available for businesses and residential customers in Gulshan, Banani, Baridhara, Mirpur and Uttara. Qubee will be available across Bangladesh soon.

WiMax is a technology that provides wireless transmission of data using a variety of transmission modes from point-to-multipoint links to portable and fully mobile internet access. The technology supports peak download rates of up to 46 Mbps and peak uplink rates of up to 14 Mbps.

Jerry Mobbs, chief executive officer of Augere Bangladesh, Russell T Ahmed, chief marketing officer, were present at the launching ceremony.

"We can offer low priced packages, but our goal is to ensure quality first," said Ahmed. "We believe our services will satisfy our customers."

Augere also unveiled a Qubee Flagship Store at Gulshan to provide 24-hour customer services.

Three bidders -- BanglaLion Communication, BRAC BD Mail Network Ltd and Augere Wireless Broadband Bangladesh Ltd -- won the WiMax licences through an auction organised by the Bangladesh Telecommunication Regulatory Commission (BTRC) in September last year. However, BRAC later refused to take the licence.

UK-based Augere Holdings owns 60 percent of Augere Wireless Broadband Bangladesh Ltd along with two local companies. Teleport Bangladesh owns 30 percent and Aamra Resources Ltd owns the remaining 10 percent.

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Global System for Mobile Communication (GSM)

The Global System for Mobile Communications (GSM) system is a global digital radio system that uses Time Division Multiple Access (TDMA) technology. GSM is a digital cellular technology that was initially created to provide a single-standard pan-European cellular system. GSM began development in 1982, and the first commercial GSM digital cellular system was activated in 1991. GSM technology has evolved to be used in a variety of systems and frequencies (900 MHz, 1800 MHz and 1900 MHz) including Personal Communications Services (PCS) in North America and Personal Communications Network (PCN) systems throughout the world. By the middle of 2003, 510 networks in 200 countries offered GSM service (Fig: 1).

Fig 1: GSM Network

The GSM system is a digital-only system and was not designed to be backward-compatible with the established analog systems. The GSM radio band is shared temporarily with analog cellular systems in some European nations.

When communicating in a GSM system, users can operate on the same radio channel simultaneously by sharing time slots. The GSM cellular system allows 8 mobile telephones to share a single 200 kHz bandwidth radio carrier waveform for voice or data communications. To allow duplex operation, GSM voice communication is conducted on two 200 kHz wide carrier frequency waveforms.

The GSM system has several types of control channels that carry system and paging information, and coordinates access like the control channels on analog systems. The GSM digital control channels have many more capabilities than analog control channels such as broadcast message paging, extended sleep mode, and others. Because the GSM control channels use only a portion (one or more slots), they typically co-exist on a single radio channel with other time slots that are used for voice communication.

A GSM carrier transmits at a bit rate of 270 kbps, but a single GSM digital radio channel or time slot is capable of transferring only 1/8th of that, about 33 kbps of information (actually less than that, due to the use of some bit time for non-information purposes such as synchronization bits).

Time intervals on full rate GSM channels are divided into frames with 8 time slots on two different radio frequencies. One frequency is for transmitting from the mobile telephone; the other is for receiving to the mobile telephone. During a voice conversation at the mobile set, one time slot period is dedicated for transmitting, one for receiving, and six remain idle. The mobile telephone uses some of the idle time slots to measure the signal strength of surrounding cell carrier frequencies in preparation for handover.

On the 900 MHz band, GSM digital radio channels transmit on one frequency and receive on another frequency 45 MHz higher, but not at the same time. On the 1.9 GHz band, the difference between transmit and receive frequencies is 80 MHz. The mobile telephone receives a burst of data on one frequency, then transmits a burst on another frequency, and then measures the signal strength of at least one adjacent cell, before repeating the process.

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WiMAX Advantages

The IEEE 802.16 standard is designed for WMAN networks. It provides inter-
operable broadband wireless connectivity to fixed and nomadic users. It
provides up to 50 km of service area and allows the users to get broadband
connectivity without the need of direct line of sight to the base station. It pro-
vides a total data rate of up to 75 Mbps, which is enough to simultaneously
support a lot of business and home requirements. The advantages of WiMAX
are given as follows.

1. High Capacity
A single WiMAX main station can serve hundreds of users. It targets a range
of up to 31 miles with target transmission rate exceeding 100 Mbps. By using
higher modulation, bandwidth can further be increased. Through WiMAX
one can transfer data, voice, Internet, video images, pictures, video conferencing, etc., at a very high data rate. So WiMAX can provide sufficient bandwidth to the end users

2. Quality of Service
The MAC layer of the WiMAX architecture is responsible for Qos. Subchannelization and different coding schemes enable end-to-end QoS. High data rate and flexible scheduling can enhance the QoS.

3. Flexible Architecture
The architecture of WiMAX is highly flexible. Depending upon the require-
ment it can connect different stations on point-to-point or point-to-multipoint
basis. Further the range can be increased with the help of directional antennas.

4. Mobility
In WiMAX, the user device can maintain an operating network data service session for real-time application as it moves at vehicular speeds within the network coverage area. It supports optimized handover schemes with latencies less than 50 ms to ensure real-time application such as voice over Internet protocol (VoIP) without service degradation. Flexible key management assures that security is maintained during handover.

5. Improved User Connectivity
The IEEE 802.16 standard keeps more users connected by virtue of its flexible channel bandwidths and adaptive modulation. WiMAX uses channels narrower than the fixed 20 MHz channels used in Wi-Fi. It can serve lower data rate users without wasting bandwidth. Adaptive modulation helps to connect them in the noisy or low-signal strength conditions.

6 Robust Carrier Class Operation
As the number of users accessing the data increases, the aggregate bandwidth is shared because of which the individual throughput starts decreasing linearly. The decrease is lesser than what is experienced under Wi-Fi. So this standard is designed for carrier class operation.

7. Scalability
WiMAX system offers scalability in network architecture as well as in radio access technology. It provides a great deal of flexibility in network deployment options and service offerings. It is designed to work in different forms of channelization from 1.25 to 20 MHz to comply with varied worldwide requirements. It can also fulfill the needs such as providing affordable Internet access in rural areas versus enhancing the capacity of broadband access in metro and suburban areas only.

8. Nonline-of-Sight Connectivity
WiMAX is based on OFDM technology and can handle nonline-of-sight connectivity. This capability helps WiMAX to communicate in a nonline-of-sight environment, which other wireless products cannot. The nonline-of-sight coverage can further be increased by using directional antennas or adaptive modulation .

9. Cost Effectiveness
Mass adoption of the standard and the use of low-cost, mass-produced chipsets can reduce costs dramatically, and the resultant competitive pric-
ing will provide considerable cost saving for service providers and end users.
Further, base stations and base station equipments need not be installed in
totality at the outlet, but can be deployed over a period of time to address
specific market segments or geographical areas of Internet to the operator.

10. Fixed and Nomadic Access
WiMAX can provide both fixed and nomadic access to its users. In fixed
access, the user device is assumed to be fixed in a single geographical area
for the duration of the network subscription. Here the user can connect and
disconnect from the network. It can select the best base station while entering
the network. The user is associated only with the same base station sector or
cell, and any reassociation with other cell is controlled by the network.
In nomadic access, the user device is assumed to be fixed in a geographical
location at least as long as the network data service session is in operation
if the user shifts to a new location in the same wireless network. The user
subscription is recognized, and a new data service session is established. The
user device is associated with the same base station during a data service
session. So WiMAX complements third-generation mobile networks by pro-
viding “nomadic’’ broadband access. Vendors can now compete to sell their
equipment, which benefits the customer base by providing lower costs and
enabling broadband access in emerging markets.

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What do you mean by WiMAX Standard

WiMAX technology is specified by IEEE as IEEE 802.16 standard. The technology extends as IEEE 802.16 a, b, d, and e and they operate in different frequencies band and different data rate. TheIEEE802.16-2004 includes P2P, P2MP and mesh access networks while the IEEE 802.16e-2005 includes mobility. Table 1.1 shows WiMAX Standards.

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History of Mobile Cellular System

First Generation(1G)

The 1G period began in the late 1970s and lasted through the 1980s. These systems featured the first true mobile phone systems, known at first as "cellular mobile radio telephone." These networks used analog voice signaling, and were little more sophisticated than the repeater networks used by amateur radio operators.
Second Generation (2G)
The 2G phase began in the 1990s and much of this technology is still in use. The 2G cell phone features digital voice encoding. Examples include CDMA and GSM. Since its inception, 2G technology has steadily improved, with increased bandwidth, packet routing, and the introduction of multimedia.

Third Generation (3G)
3G refers to the third generation of developments in wireless technology, especially mobile communications. The third generation, as its name suggests, follows the first generation (1G) and second generation (2G) in wireless communications.
3G includes capabilities and features such as:
• Enhanced multimedia (voice, data, video, and remote control).
• Usability on all popular modes (cellular telephone, e-mail, paging, fax, videoconferencing, and Web browsing).
• Broad bandwidth and high speed (upwards of 2 Mbps).
• Roaming capability throughout Europe, Japan, and North America.

3G offers the potential to keep people connected at all times and in all places. Researchers, engineers, and marketers are faced with the challenge of accurately predicting how much technology consumers will actually be willing to pay for. Another challenge faced by 3G services is competition from other high-speed wireless technologies, especially mobile WiMAX, and ability to roam between different kinds of wireless networks.
The current status of mobile wireless communications, as of July 2007, is a mix of 2nd and 3rd generation technologies.

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WiMAX, How do WiMAX Works?

Worldwide interoperability for microwave access (WiMAX), based on the
Institution of Electrical & Electronics Engineering (IEEE) 802.16 standards,
enables wireless broadband access anywhere, anytime, and on virtually
any device. When users want broadband service today, they are generally
restricted to a T1, digital subscriber loop (DSL), or cable modem-based con-
nection. However, these wireline infrastructures can be considerably more
expensive and time-consuming to deploy than a wireless system. In addi-
tion, rural areas and developing countries lack optical fiber or copper wire
infrastructure for broadband services, and service providers are unwilling
to install the necessary equipments in these areas because of little profit and
potential. WiMAX is an ideal technology for backhaul applications because
it eliminates expansive leased line or fiber alternative. WiMAX promises to
deliver high data rates over large areas to a large number of users (Shows Fig w).
It can provide broadband access to locations in the world’s rural and developing areas
where broadband is currently unavailable.

Fig w: WiMAX network

WiMAX has numerous advantages, such as improved performance and
robustness, end-to-end internet protocol (IP)-based network, secure mobility,
and broadband speeds for voice, data, and video. It is a wireless metropolitan
area network (WMAN) technology that provides interoperable broadband
wireless connectivity to fixed, portable, and nomadic users within 50 km of
service area. It allows the users to get broadband connectivity without the
need of direct line-of-sight communication to the base station and provides
total data rates up to 75 Mbps with sufficient bandwidth to simultaneously
support hundreds of residential and business areas with a single base station.
In fact WiMAX is not a technology, but rather a configuration mark, or
“stamp of approval’’ given to equipments that meet certain conformity and
interoperability tests for the IEEE 802.16 family of standards. A similar con-
fusion surrounds the term Wi-Fi (wireless fidelity), which like WiMAX, is
a certification mark for equipments based on a different set of IEEE stan-
dard from the 802.11 working group for wireless local area network (WLAN).
Neither WiMAX nor Wi-Fi is a technology but their names have been adopted
in popular usage to denote the technologies behind them. This is due to the
difficulty of using terms like IEEE 802.11 in common speech and writing.
WiMAX is a term coined to describe standard, interoperable implementation
of IEEE 802.16 wireless networks in a way similar to Wi-Fi being interopera-
ble of the 802.11 WLAN standards. However, the working of WiMAX is very
different from Wi-Fi.

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