3rd Generation Wireless, or 3G, is the generic term used for the next generation of mobile communications systems. 3G systems aim to provide enhanced voice, text and data services to user. The main benefit of the 3G technologies will be substantially enhanced capacity, quality and data rates than are currently available. This will enable the provision of advanced services transparently to the end user (irrespective of the underlying network and technology, by means of seamless roaming between different networks) and will bridge the gap between the wireless world and the computing/Internet world, making inter-operation apparently seamless. The third generation networks should be in a position to support real-time video, high-speed multimedia and mobile Internet access. All this should be possible by means of highly evolved air interfaces, packet core networks, and increased availability of spectrum. Although ability to provide high-speed data is one of the key features of third generation networks, the real strength of these networks will be providing enhanced capacity for high quality voice services. The need for landline quality voice capacity is increasing more rapidly than the current 2nd generation networks will be able to support. High data capacities will open new revenue sources for the operators and bring the Internet more closer to the mobile customer. The use of all-ATM or all-IP based communications between the network elements will also bring down the operational costs of handling both voice and data, in addition to adding flexibility.
On The Way To 3G
As reflected in the introduction above, the drive for 3G mobile wireless communication is the need for higher capacities and higher data rates. Whereas higher capacities can basically be obtained by having a greater chunk of spectrum or by using new evolved air interfaces, the data requirements can be served to a certain extent by overlaying 2.5G technologies on the existing networks. In many cases it is possible to provide higher speed packet data by adding few network elements and a software upgrade.
A Look At GPRS, HCSD, and EDGE
Technologies like GPRS (General Packet Radio Service), High Speed Circuit Switched Data (HSCSD) and EDGE fulfill the requirements for packet data service and increased data rates in the existing GSM/TDMA networks. I’ll talk about EDGE separately under the section “Migration To 3G“. GPRS is actually an overlay over the existing GSM network, providing packet data sevices using the same air interface by the addition of two new network elements, the SGSN and GGSN, and a software upgrade. Although GPRS was basically designed for GSM networks, the IS-136 Time Division Multiple Access (TDMA) standard, popular in North and South America, will also support GPRS. This follows an agreement to follow the same evolution path towards third generation mobile phone networks concluded in early 1999 by the industry associations that support these two network types.
The General Packet Radio Service (GPRS)
The General Packet Radio Service (GPRS) is a wireless service that is designed to provide a foundation for a number of data services based on packet transmission. Customers will only be charged for the communication resources they use. The operator’s most valuable resource, the radio spectrum, can be leveraged over multiple users simultaneously because it can support many more data users. Additionally more than one time slots can be used by a user to get higher data rates.
GPRS introduces two new major network nodes in the GSM PLMN:
Serving GPRS Support Node (SGSN)
The SGSN is the same hierarchical level as an MSC. The SGSN tracks packet capable mobile locations, performs security functions and access control. The SGSN is connected to the BSS via Frame Relay.
Gateway GPRS Support Node (GGSN)
The GGSN interfaces with external packet data networks (PDNs) to provide the routing destination for data to be delivered to the MS and to send mobile originated data to its intended destination. The GGSN is designed to provide inter-working with external packet switched networks, and is connected with SGSNs via an IP based GPRS backbone network.
A packet control unit is also required which may be placed at the BTS or at the BSC. A number of new interfaces have been defined between the existing network elements and the new elements and between the new network elements. Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about three times as fast as the data transmission speeds possible over today’s fixed telecommunications networks and ten times as fast as current Circuit Switched Data services on GSM networks. Actually we may not see speeds greater than 64 kbps however it would be much higher than the speeds possible in any 2G network. Also, another advantage is the fact that the user is always connected and is charged only for the amount of data transferred and not for the time he is connected to the network.
Packet switching means that GPRS radio resources are used only when users are actually sending or receiving data. Rather than dedicating a radio channel to a mobile data user for a fixed period of time, the available radio resource can be concurrently shared between several users. This efficient use of scarce radio resources means that large numbers of GPRS users can potentially share the same bandwidth and be served from a single cell. The actual number of users supported depends on the application being used and how much data is being transferred. Because of the spectrum efficiency of GPRS, there is less need to build in idle capacity that is only used in peak hours.
Already many field trials and also some commercial GPRS implementations have taken place. GPRS is the evolution step that almost all GSM operators are considering. Also, coupled with other technologies like WAP, GPRS can act as a stepping stone towards convergence of cellular service providers and the internet service providers.
HSCSD (High speed circuit swiched data)
This is the evolution of circuit switched data within the GSM environment. HSCSD will enable the transmission of data over a GSM link at speeds of up to 57.6kbit/s. This is achieved by cocatenating, i.e. adding together, consecutive GSM timeslots, each of which is capable of supporting 14.4kbit/s. Up to four GSM timeslots are needed for the transmission of HSCSD. This allows theoretical speeds of up to 57.6 kbps. This is broadly equivalent to providing the same transmission rate as that available over one ISDN B-Channel. HSCSD is part of the planned evolution of the GSM specification and is included in the GSM Phase 2 development. In using HSCSD a permanent connection is established between the called and calling parties for the exchange of data. As it is circuit switched, HSCSD is more suited to applications such as video conferencing and multimedia than ‘bursty’ type applications such as email, which is more suited to packet switched data. In networks where High Speed Circuit Switched Data (HSCSD) is deployed, GPRS may only be assigned third priority, after voice as number one priority and HSCSD as number two. In theory, HSCSD can be preempted by voice calls- such that HSCSD calls can be reduced to one channel if voice calls are seeking to occupy these channels. HSCSD does not disrupt voice service availability, but it does affect GPRS. Even given preemption, it is difficult to see how HSCSD can be deployed in busy networks and still confer an agreeable user experience, i.e. continuously high data rate. HSCSD is therefore more likely to be deployed in start up networks or those with plenty of spare capacity since it is relatively inexpensive to deploy and can turn some spare channels into revenue streams.
An advantage for HSCSD could be the fact that while GPRS is complementary for communicating with other packet-based networks such as the Internet, HSCSD could be the best way of communicating with other circuit switched communications media such as the PSTN and ISDN. But one potential technical difficulty with High Speed Circuit Switched Data (HSCSD) arises because in a multi-timeslot environment, dynamic call transfer between different cells on a mobile network (called “handover”) is complicated unless the same slots are available end-to-end throughout the duration of the Circuit Switched Data call.
Because of the way these technologies are evolving, the market need for high speed circuit switched data and the market response to GPRS, the mobile infrastructure vendors are not as committed to High Speed Circuit Switched Data (HSCSD) as they are to General Packet Radio Service (GPRS). So, we may only see HSCSD in isolated networks around the world. HSCSD may be used by operators with enough capacity to offer it at lower prices, such as Orange.  believes that every GSM operator in Europe will deploy GPRS, and by 2005 GPRS users will almost match the number of voice only users. Right now there are 300 million wireless phones in the world. By 2005 we expect one billion.
Before I proceed, a quick look at the table below would help you appreciate and understand clearly the technology characterizations as 2nd generation, 2.5 generation and 3G. We have looked into 2G and some 2.5G technologies so far.
Destination: Third Generation
Standardization of 3G mobile systems is based on ITU (International Telecom Union) recommendations for IMT 2000. IMT 2000 specifies a set of requirements that must be achieved 100% for a network to be called 3G. By providing multimedia capacities and higher data rates, these systems will enhance the range and quality of services provided by 2G systems. The main contenders for 3G systems are wideband CDMA (W-CDMA) and cdma2000. The ETSI/ GSM players including infrastructure vendors such as Nokia and Ericsson backed W-CDMA. cdma2000 was backed by the North American CDMA community, led by the CDMA Development Group (CDG) including infrastructure vendors such as Qualcomm and Lucent Technologies. Universal Mobile Telephone System (UMTS) is the widely used European name for 3G.
The proposed IMT-2000 standard for third generation mobile networks globally is a CDMA-based standard that encompasses THREE OPTIONAL modes of operation, each of which should be able to work over both GSM MAP and IS-41 network architectures. The three modes are shown in the following table.
|1||Direct Sequence FDD (Frequency Division Duplex)||Based on the first operational mode of ETSI’s UTRA (UMTS Terrestrial Radio Access) RTT proposal.||Japan’s ARIB and GSM network operators and vendors.|
|2||Multi-Carrier FDD (Frequency Division Duplex)||Based on the cdma2000 RTT proposal from the US Telecommunications Industry Association (TIA).||cdmaOne operators and members of the CDMA Development Group (CDG).|
|3||Time Division Duplex (TDD)||The second operational mode of ETSI’s UTRA (UMTS Terrestrial Radio Access) RTT proposal. An unpaired band solution to better facilitate indoor cordless communications.||Harmonized with China’s TD-SCDMA RTT proposal.|
UMTS is the European designation for 3G systems. The UMTS frequency bands selected by the ITU are 1,885 MHz – 2,025 MHz (Tx) and 2,110 MHz – 2,2,20 MHz (Rx). Higher frequency bands could be added in future if need be, for stationary data. There is still some confusion about all the frequency options as FCC has not given clear indications so far. The following table should briefly give an idea about the 3G system specifications.
3rd Generation Initiatives
3GPP (Third Generation Partnership Project) and 3GPP2 are the two alliances working towards the specification for the 3G systems. 3GPP partners are ETSI, TTC, ARIB, TTA, T1 and the 3GPP2 includes TIA, TTC, ARIB, TTA. Although both have chosen CDMA as the technology behind the 3G systems, the systems advocated by these two groups are different. The 3GPP organizational partners have agreed to co-operate for the production of Technical Specifications for a 3rd Generation Mobile System based on the evolved GSM core networks and the radio access technologies that the Organizational Partners support (i.e. UTRA both FDD and TDD modes). 3GPP2 provides global specifications for ANSI/TIA/EIA-41 network evolution to 3G and global specifications for the RTTs (Radio transmission technologies) supported by ANSI/TIA/EIA-41. Yet another group, the Operators Harmonization Group, is dedicated to achieving the maximum possible level of commonality of technologies to maximize interworking of different versions. It was as a result of pushing by OHG that led to ITU’s mixed solution to 3G air interfaces with ANSI-41 and GSM MAP networking.
The 3G Market
Wireless internet access is high on the priority lists of major wireless carriers. NTT DoCoMo’s iMode service in Japan, launched just two years ago, is expected to double the number of subscribers to 10 million by the end of 2000. It is important to understand that wireline data technologies are advancing very fast and will support very high data rates at very low costs that would be prohibitive with foreseeable wireless technology. 3G aim is high data rates, but the focus is mobility!
According to a market report 3G Wireless: Market Expectations, by the Philips Group, we should see 3G wireless subscribers growing from 1.7 million in 2002 to around 38 million in 2007. Whereas consumers account for 80% of the overall wireless market, they are expected to be only 20% of the 3G wireless market. Similarly, business-vertical subscribers, estimated to be about 6 percent of the overall wireless market, are assumed to be 42 percent of the 3G market initially, and business-horizontal, 38 percent. The penetration of 3G subscribers relative to total wireless subscribers is expected to grow from 1.3 percent in 2002 to 23 percent in 2007. Consumer penetration, even by the end of the period, is assumed to have grown to only 9 percent, while business-vertical has reached 91 percent, and business-horizontal, 68 percent. Wireless operator revenue opportunity should also grow from $4.3 billion to $63 billion in the same time. Infrastructure opportunities should also grow from $4 billion to $34 billion.
The actual deployment of 3G will not be a homogeneous occurrence. Japan will lead with the service in early 2001, followed by Western Europe in mid to late 2003. U.S. is expected to wait for some time at 2.5G and 2.75G before going in to true 3G. As I have mentioned earlier, with TDMA based networks like GSM and IS-136, increased capacity will be the initial driving factors. Therefore these networks will take a comparatively longer time to true 3G.
Evolving Today’s Networks Towards 3G
The 3rd Generation Mobile System will most likely grow out of the convergence of enhanced 2nd generation mobile systems with greater data transfer speed and capacity and 1st generation satellite mobile systems. Evolution to the current generation mobile networks to 3G doesn’t necessarily mean seamless upgradation to the existing infrastructure to the 3G. Evolution should also be seen in context of coexistence of the 2G and 3G networks for some time, with users able to roam across the new and the old networks, able to access 3G services wherever 3G coverage is available. As mentioned before, a 3G network can have one of the 3 optional air interfaces supporting one of the two GSM MAP and IS-41 network architectures. This results in a range of choices for the existing networks to evolve/migrate towards 3G. Possible convergence of TDMA and GSM networks with EDGE adds another variable to the overall migration paths. Another variable that adds complexity to this already complex list of options is the time frames involved. By the time some of the 2.5 or 2.75G technologies go to field, we may see the emergence of 3G technologies also. So, a lot of thought regarding the costs involved, and/or the viability of 2.5G technologies like EDGE could be questioned. The same is true about the time frames of the so called “4G”.
Before I talk about evolution/migration paths of all the existing 2G mobile wireless technologies, let me briefly discuss the 3G network architecture and other technology factors involved in the migration to 3G.
The 3G network will have a layered architecture, which will enable the efficient delivery of voice and data services. A layered network architecture, coupled with standardized open interfaces, will make it possible for the network operators to introduce and roll out new services quickly. These networks will have a connectivity layer at the bottom providing support for high quality voice and data delivery. Using IP or ATM or a combination of both, this layer will handle all data and voice info. The layer consists of the core network equipment like routers, ATM switches and transmission equipment. Other equipment provides support for the core bit stream of voice or data, providing QOS etc. Note that in 3G networks, voice and data will not be treated separately which could lead to a reduction in operational costs of handling data separately from voice. The application layer on top will provide open application service interfaces enabling flexible service creation. This user application layer will contain services for which the end user will be willing to pay. These services will include eCommerce, GPS and other differentiating services. In between the application layer and the connectivity layer, will run the control layer with MSC servers, support servers, HLR etc. These servers are needed to provide any service to a subscriber.
The migration to 3G is not just based on evolving core networks and the radio interface to IMT 2000 compliant systems. Migration towards 3G would also be based on the following steps/technologies:
- Network upgrades in the form of EDGE, GPRS, HSCSD, CDPD, IS-136+, HDR etc. Evolution to 2.5G basically will provide support for high speed packet data. Though these technologies are extensions to 2G rather than precursors to 3G these will have a major impact either by proving (or not) demand for specific services.
- Service trials to test infrastructure, handsets and applications etc.
- Introduction of WAP-based services that bring the web to the wireless phone. In short-term WAP and, in longer term, XML will provide a standard framework for accessing wireless Internet content, enabled by 2.5G/3G.
- The development of mobile web portals
- Development of microbrowsers and operating systems.
- Wide acceptance of short-range wireless connectivity technologies like Bluetooth, HomeRF etc.
EDGE! Will TDMA and GSM ever meet?
EDGE is a new time division multiplexing based radio access technology that gives GSM and TDMA an evolutionary path towards 3G in 400, 800, 900, 1800 and 1900 MHz bands. It was proposed to ETSI in 1997 as an evolution to GSM. Although EDGE reuses GSM carrier bandwidth and time slot structures, it is not restricted to use in GSM cellular systems only. In fact, it can provide a generic air interface for higher data rates. It provides an evolutionary path to 3G. Some call it 2.5G. It can be introduced smoothly into the existing systems without altering the cell planning. But as with GPRS, EDGE doesn’t provide any additional voice capacity. The initial EDGE standard promised mobile data rates of 384 kbps. It allows data transmission speeds of 384 kbps to be achieved when all eight timeslots are used. In fact, EDGE was formerly called GSM384. This means a maximum bit rate of 48 kbps per timeslot. Even higher speeds may be available in good radio conditions. Actual rates will be lower with rates falling as one goes away from the cell site. EDGE can also provide an evolutionary migration path from GPRS to UMTS by implementing now, the changes in modulation that will be necessary for implementing UMTS later. Both High Speed Circuit Switched Data (HSCSD) and GPRS are based on something called Gaussian minimum-shift keying (GMSK) which only yields a moderate increase in data bit rates per time slot. EDGE, on the other hand, is based on a new modulation scheme that allows a much higher bit rate across the air interface. This modulation technique is called eight-phase-shift keying (8 PSK). It automatically adapts to radio circumstances and thereby offers its highest rates in good propagation conditions close to the site of base stations. This shift in modulation from GMSK to 8 PSK is the central change with EDGE which prepares the GSM world (and TDMA in general) for UMTS.
Only one EDGE transceiver unit will need to be added to each cell. With most vendors, it is envisioned that software upgrades to the BSCs and Base Stations can be carried out remotely. The new EDGE-capable transceiver can also handle standard GSM traffic and will automatically switch to EDGE mode when needed. EDGE capable terminals will also be needed – existing GSM terminals do not support the new modulation techniques and will need to be upgraded to use EDGE network functionality.
EDGE is currently being developed in two modes: compact and classic. Compact employs a new 200 kHz control channel structure. Synchronized base stations are used to maintain a minimum spectrum deployment of 1 MHz in a 1/3-frequency reuse pattern. EDGE Classic on the other hand employs the traditional GSM 200 kHz control structure with a 4/12 frequency reuse pattern on the first frequency.
How Can GSM and TDMA Converge With EDGE?
While developing the 3G wireless technology for TDMA, the Universal Wireless Communication Consortium (UWCC) proposed the 136 High-Speed (136 H-S) radio interface as a means of satisfying requirements for IMT-200 radio transmission technology (RTT). After evaluating various proposals, UWCC adopted EDGE (Actually EGPS, EDGE+GPRS) as the outdoor component of 136HS to provide 384 kbps data services. Since GSM networks can also have an evolutionary path via EDGE, this presents an interesting opportunity where the air interfaces of TDMA and GSM can converge and then evolve together. EDGE is being developed concurrently in ETSI and UWCC. The phase one of EDGE emphasizes enhanced circuit-switched data (ECSD) and enhanced GPRS (EGPS).
The TDMA terminals that support 30 kHz circuit switched services scan for a 30 kHz control channel (DCCH) according to TIA/EIA 136 procedures. If an acceptable 200 kHz EGPRS carrier exists, a pointer to this system will be available on the DCCH. On finding this, the terminal will leave the 30KHz system and start scanning of the 200 kHz system. When it finds it, it starts behaving as if it is were a GSM/GPRS terminal. To answer a circuit switched page, the mobile suspends packet data traffic and starts looking for a 30 kHz control channel. Mobile terminals that only support 200 kHz carriers immediately start looking for 200 kHz packet data system.
Will This Happen?
While EDGE provides a common air interface for TDMA and GSM to converge, there is one possible problem. GSM operators may decide to skip EDGE altogether in their migration path to 3G. By the time EDGE will be commercially available for GSM systems, 3G will already be in sight with W-CDMA and since W-CDMA will need an entirely new air interface, the additional investments in EDGE, only to be replaced by another system seems a bit unjustified. EDGE has lost favor in Europe with some wireless operators and vendors that are not convinced it will actually be adopted in force once carriers move to GPRS. As described above, the belief is that wireless service providers may be more inclined to move straight to WCDMA from GPRS. On the other hand, some North American operators have taken the position that they may not need to upgrade to WCDMA after EDGE because it doesn’t offer increased speeds in the mobile environment (the ITU/UMTS definition of G3G is 384 Kbps mobile, 2 Mbps low mobility/fixed wireless). This is an especially strong point when one considers that the market demand for high-speed wireless data has yet to be fully proven.
The convergence of TDMA and GSM can’t be ruled out also. Particularly in the US, operators may have more interest in moving on to EDGE to get compatibility with the TDMA networks. According to a study , EDGE should be available in the North American markets by 2002. The study also indicates that initially only the big operators may go in for EDGE first:
“In the end, the decision to upgrade will be made on two points. First, operators will want the technology that will both be available in a suitable time frame and will endure for the longest period of time–GSM and TDMA operators would like to avoid the continuous string of upgrades for the next five years. Second, operators will want the upgrade path that will provide the necessary data services while displacing as little voice traffic spectrum as possible.”
Individual Technology Evolution Paths
A variety of technologies/standards exist and therefore, so do the number of paths that can be taken. The table below briefly summarizes these standards.
GSM and TDMA To 3G
GSM and TDMA systems have more or less the same set of options for migrating to 3G. The path to 3G is not as simple in case of GSM/TDMA as is in the case of CDMA. The main evolutionary standards are GPRS, EDGE and, finally, W-CDMA. Vendors are positioning each of these standards as a step to the next, but operators are not so sure. For an operator moving from GSM to GPRS to EDGE and then to W-CDMA, he’ll have to make investments 3 times which won’t be pleasing to any operator. As  suggests, at this time, there seem to be four basic options that GSM and TDMA operators are considering:
- Install GPRS, then move straight to WCDMA;
- Install EDGE, then move straight to WCDMA;
- Install GPRS, then move to EDGE, then to WCDMA; or
- Install EDGE, skip move to WCDMA, and wait for the next generation (4G).
CDMA To 3G
While GSM and TDMA operators have multiple choices ahead for progressing to the next-generation networks, CDMA operators have a single path that truly builds upon itself . Currently all North American CDMA networks are based on IS-95 (cdmaOne) which can be setup to provide data rates upto 14.4 kbps. The next step is to have a software upgrade from IS-95A to IS-95B which provides additional voice efficiencies giving additional capacity, and allows for up to 84-Kbps packet data. (We might not see 84kbps but instead 64kbps, initially.) While this migration does not need any additional hardware but as brought out by  most operators may decide not to move to IS-95B because of two reasons.
1. IS-95A in itself is relatively new and carriers have just launched their IS-95A data services.
2. By the time IS-95B becomes available, 1XRTT will be ready.
What Are The Costs?
In the shorter term, TDMA and GSM have a much more cost-effective upgrade option by means of moving to GPRS to be in a position to provide data services. As mentioned earlier, an upgrade to GPRS doesn’t require substantial investments and existing GSM/ TDMA service providers can upgrade to GPRS at around 28% cost of their initial 2G investments. The IS-95 upgrade path to 1xRTT is comparatively costly at around 40% investments on the existing 2G networks. It should also be noted that IS-95A in itself has also not been in existence for long. However, in the final run to truly 3G networks, GSM/TDMA operators may have to incur much higher investments as shown in the figure below. The cost equations for TDMA or GSM may vary depending on the exact path taken (EDGE or no EDGE or only EDGE). CDMA has the unique advantage of having the same air interface in 2G as in 3G (same underlying technology).
Therefore, it is very probable that most CDMA carriers in North America will move straight to 1XRTT. 1XRTT is the first step in moving to the full ITU/UMTS-defined 3G standard. It has many features that make it completely different from IS-95B. It will provide more than double the data speeds available from IS-95B (153 Kbps vs. 64 Kbps); but, more importantly, in the spectrum-constrained market of North America, 1X will almost double the voice capacity. Additionally, the software and chip boards necessary for 1X are also an essential step to continue the upgrade to 3XRTT, which is also called G3G-MC-3X, but is also more popularly known by the trade name of cdma2000 (307 Kbps). However, cdma2000 is expected to provide only moderate voice capacity gains over 1X, and as such, 1X is the primary concern of carriers for the immediate future. Besides 1X and 3X paths to the ITU/UMTS-sanctioned G3G standards, there is also the Qualcomm-defined offshoot of CDMA–High Data Rate (HDR). This standard, which is proprietary to Qualcomm, sets aside a standard 1.25-MHz CDMA carrier specifically for data, and offers rates of up to 2.4 Mbps in a mobile environment. Though this standard achieves the data rates required for 3G, it is not considered a 3G standard because it is a data-only standard and has not been opened up for the approval of any standards bodies.
They’re Already Talking About 4G!
Several new standards have been proposed which don’t fit into this classification of 2, 2.5 or 3G. These standards either provide only data services and/or provide much higher data rates than those specified by 3G systems. Examples are 1Xplus and 1XTREME. Since they use a single CDMA carrier they may be called 2.5G but then they provide much higher data rates than 3G. According to Motorola, 1XTREME will not require additional antennas as HDR will, and it will also keep data on the same spectrum as the voice services, meaning carriers won’t have to devote any spectrum specifically to data services. 1XTREME is proposed to deliver the same voice capacity increases as standard 1X, and provide data rates approaching 1.4 Mbps. The second iteration, expected to be in trials by the first quarter of 2001, is expected to deliver data rates as high as 5.2 Mbps. Motorola expects 1XTREME to be market-ready in the same time frame as HDR: by the end of 2001 to the first half of 2002.
Another interesting thing is that these so called 4G technologies may start appearing almost at the same time when 3G comes. It is not very clear as to how these developments will influence an already very complex set of equations.
Mobile communications are really poised to see major improvements in terms of capabilities of mobile networks. The next generation of wireless services, besides improving the overall capacity, will create new demand and usage patterns, which will in turn, drive the development and continuos evolution of services and infrastructure. While development of 3G networks will continue and pick up pace in the near future, the 2nd generation networks will keep evolving in terms of continuous enhancements and towards convergence of existing 2G standards. The initial 3G solutions should coexist with the 2G networks while slowly evolving to all 3G networks. While 3G in its true sense should have transparent roaming across all networks through out the world, given the penetration and the investments in the 2nd generation, true roaming (consistent service availability, across networks, independent of networks) looks to be to a very distant proposition!