To Vietnam market, the first GMS mobile with simple 2G generation just allows voice calls. Upgrading to GPRS technology in the late 2003 helps users start discovering data applications. In the late 2007, with the application of EGDE, speed peaks around 384kb/s. However, the real speed is rather slow which limits development and explosion of data-based services comparing with telephoning service today.  

In the world, 2 high generations of family GSM have yet been applied in Vietnam market, that is WCDMA – 3G with 2Mbps and HSPA (HSDPA & HSUPA) – 3,5G with transmission capacity of up to 14,4 Mbps. These advanced technologies are applied worldwide with over 200 millions subscribers, on over 220 networks in 94 countries, occupying 2/3 subscribers of 3G globally. (GSA, 6/2008).

According to the information from the biggest suppliers with amount of subscribers and infrastructures in Vietnam, apart from recruitment purpose, mobile operators have been well-prepared every thing to implement 3G as soon as possible: Bidding, installing, trial running, implementing.v.v…. Users in Vietnam will have chance to access this technology, keeping trends with nearly other 100 countries. How does network infrastructure change?

GSM/GPRS/EDGE technologies share the ground basis which is TDMA and FDMS access technique so they work on the same bandwidth (with frequency of 200kHz per each channel. Upgrading is therefore not too complicated.
When upgrading to 3G, WCDMA technology operates on a quite different access technique, which is CDMA, so frequency band must differentiate from GSM (WCDMA frequency band each channel is 5MHz). There will need a new 3G bandwidth in stead of the current one (the purpose of 3G competition is to get the license for this bandwidth). And this also needs one new Base Transceiver Station (BTS) named Node B, going along with a new original base station controller equipment (BSC), called Radio Network Controller (RNC). Inheriting from the upgrade, the current core network system (switching switchboard) is still used to connect with Radio Network (Node B and RNC) of the new WCDMA technology (Picture 1)

Image 1: Sharing core network

On the other hand, to limit impacting on current network system as well as to expand capacity, a new solution used by suppliers is investing a completely new network system. (Image 2)

Image 2: Adding core network

Overtime, all core network and wireless devices will integrate together as shown in Picture 3. All old BTS and BSC devices will depreciate of be moved to remote areas to support GSM/EDGE.

Image 3: Common Integration Method

Seamless development

When looking at Image 2, most of people comment that upgrading to 3G is a pairing a new system and new technology with the existing system. In order for readers to have better understanding about the inheritance and seamlessness when developing to 3G of GSM, please infer to Image 4.

Image 4: Seamless Development

- Apart from the WCDMA radio system (including RNC and Node B) needed to invest a new system, other existing system will be reutilized. Most operators today have their own ways to upgrade core network, transmission, database, operating system….to support both GSM and WCDMA.
So, wherever 3G is covered, 3G broadcasting equipment must be set up in that area (using existing station) and connecting to switchboard. Of course, with over 3000 – 4000 stations for each network in Vietnam, investing in covering 3G nationwide is not easy and expensive.
However, with the investment in WCDMA, upgrading to 3,5G HSPA will become easier because operators only need to upgrade software, similarly to upgrading from GPRS to EDGE, users will access mobile services as well as ADSL

- In spite of being on 2 different equipments, operation of two radio systems including GSM and WCDMA will be managed and transferred continuously between 2 systems. Calls will still exist when changing band and technology, which will happen when users move out of wave coverage area of a technology or be overloaded.

With this continuousness, using band will become more effectively (have distribution among calls on bands), meaning that it will reduce network stuck; equipment will be used effectively (sharing resources for both systems); and investment for WCDMA will not be necessary on the whole network. 

Overview of operation of 3G network

Depending on development of each market and each network, the model of implementation 3G of each operator will be different from each other. Or covering wave on the whole market or covering wave partly on each urban centre and then broadening. At 3G area, there must be GSM, GPRS, EDGE, WCDMA (and even HSPA if already upgraded), depending on your mobile technology you are using, and you can use the correspondent speed. 

If your mobile is a GSM (or GPRS, EDGE), your call will still work on the existing band, to GSM wave broadcasting station and following the existing switching switchboard system. Technology of your mobile (GSM/GPRS/EDGE) will help you to have different access speed. 
 
If buying a 3G mobile  (WCDMA or HSPA, or iPhone 3G, for example), your call this time will work on new band, Node B station and run to switchboard. Configuration of mobile 3G can surely work with 2G, that is a multi-functional mobile with GSM/GPRS/EGDE/WCDMA…This is obliged because wave coverage area of 2G and 3G is not identical, if you move out of the wave coverage 3G you will still connect via wave 2G existing. 
With the multi-functional network, switchboard will have 3 types of controlling, providing suitable technology for calls:
- Operators will stipulate on service policies: each type of calls will go with a kind of technology, for example, voice calls will match with GSM and data calls will match with 3G.
- Controlling load balancing between states: for example, when calls on GSM band are overloaded, some subscribers will be moved to WCDMA for calls, or vice versa.
- Packages, user’s subscribers: each subscriber will belong to a group of customers with different priority. Gold subscribers will have priority of using low download or high speed. Usual subscribers only use low speed service or use GSM even in WCDMA coverage. 
To study more about this operation, let’s see a demonstrated image. One person using a multi- functional mobile GSM/WCDMA took a train form city center out to countryside. His subscriber is GSM with EDGE coverage worldwide, in some cities covered with WCDMA.
When the train set up, he called a relation, then he sent a piece of video while calling (WCDAMA allows to make 2 data call and voice call at the same time).
When the train set up, he called a relation, then he sent a piece of video while calling (WCDMA allows making 2 data call and voice call at the same time). When the train was out of the city, and out of the WCDMA coverage, switchboard would move voice calls to GSM network and move video calls to EDGE network. The quality of video call would decrease while the quality of calls was the same.

Model of 3G implementation

Talking about upgrading 3G must mention to model or strategy to implement 3G. There are 3 strategies: (1) Implementing WCDMA on the whole network, (2) Implementing 3G gradually (3) Implementing 3G later.
1. Implementing 3G quickly on the whole network: There are many reasons for operators to follow this strategy: high market competition level; government requirement; high demand of data service from market; stable finance; limited GSM capacity, left rate from network rising; aim of broadening market share and increasing revenue on a subscriber (ARPU).
If coverage 3G everywhere but users do not have any tools to use is meaningless.  Thus, this strategy can succeed only when operators must have a policy of developing subscribers correspondingly: encouraging users to buy new mobile; advertising new tools enclosed with data services…..
 2. Implementing WCDMA gradually: firstly covering WCDMA in urban centers and then broadening in areas around, while investing GSM to upgrade capacity voice service and data service having low speed GPRS. Reasons to choose this strategy are: ability to develop GSM and GPRS; problems in quality and capacity of GSM and GPRS (need investing to serve customers 2G); GSM and subscribers overloaded; lots of 2G mobile existing; new market of mobile data; stable finance. 
End point equipment has multi-functions GSM/GPRS/WCDMA so these will be introduced, advertised gradually depending on demand and capability of customers.
3. Implementing 3G later: When market demand of data service is still low, demand of voice calls is developing, or when government hasn’t given license 3G, operators in the market improving their network to EDGE is enough. Upgrading to WCDMA will be considered in the future. However, when investing network infrastructure GSM or GPRS, operators must consider choosing support system for upgrading WCDMA in the future.
Of three above description, model 2 is suitable to GSM network in Vietnam, developing 3G from urban centers to areas around then. High or low speed depends on potentiality of each operator.

In Conclusion

Upgrading network is necessary for establishing and developing high level mobile service apart from traditional voice services, improving ability and capacity of the system. In addition, continuity and inheritance when upgrading is important because they can take advantage of the existing system, save time for investment, and ensure operation of many technologies in the unique system. Continuity Upgrading to 3G will help investors to deploy and maintain the loyalty and satisfaction of customers, and increase opportunity and revenue for Telecommunication.