2. Current Technical Possibilities
In this chapter we will discuss the most important technical possibilities that should make mobile internet possible, though at an extremely low transfer rate. However, they have layed the foundation for new emerging technologies that are being build on top of the current industry standards (GSM and GPRS) and it is expected that those new technologies are well capable of providing mobile internet connections at a convenient transfer rate in the nearby future.
2.1 GSM
[http://www.irius-technologies.com/gsm_technology.htm]The most widely accepted standard for mobile communication is the GSM-network. GSM stands for Global System for Mobile communications and uses a dedicated two-way radio infrastructure for cellular telephony and also data applications. The GSM technology is based on TDMA (Time Division Multiple Access) which allows for very large numbers of subscribers on a cellular and micro-cellular approach. The GSM standard allows for both voice, messaging and data services. The pre-decessor of GSM is AMPS, Advanced Mobile Phone System. We will not discuss this technology extensively in this study, but from a point of completeness, it is included in figure 2.1.
In figure 2.1, you'll see that AMPS (once widely used in North-America) is said to be the first generation of mobile communication technologies. This technology existed around 1980. From 1982, the GSM technology was being developed en around 1992 it was introduced to the big crowd. The "2.5"-th generation, as some people call GPRS, as well as the third generation (UMTS) will be discussed in the next chapter.
The frequency range in which the GSM-network operates, are the following [http://www.gsmworld.com]:
| GSM-type | Pair 1 (Mhz) | Pair 2 (Mhz) |
| GSM 400 | 450.4 - 457.6 | 460.4 - 467.6 |
| 478.8 - 486 | 488.8 - 496 | |
| GSM 900 | 880 - 915 | 925 - 960 |
| GSM 1800 | 1710 - 1785 | 1805 - 1880 |
| GSM 1900 | 1850 - 1910 | 1930 - 1990 |
The most common GSM-types today are the GSM 900 and 1800 Mhz. Launched in 1992, the GSM represents approximately 135 million users world-wide in 100 countries with over 200 operators and represents 62% of the global digital cellular market. GSM has a disadvantage in speed when it is used for sending and receiving data (like internet). Whereas internet traffic through cable can reach up to several megabits per second, people don't accept the extremely slow 9.6 kbps (kilobits per second) that GSM offers. It is barely possible to read e-mail, let alone photo's, sound (music) or video's.
Another large disadvantage for GSM to facilitate internet traffic at a large scale is that GSM uses a circuit switched network. This means that the customer has to pay a certain amount of money per timeframe. This is not the case with e.g. GPRS, which will be discussed next. Future communication technologies (GPRS, EDGE, UMTS) will have the possibility of billing per package of data that is sent. So when you don't send any information over the network, you simply don't pay. In this case, a person can stay on-line without the huge telephone costs involved.
2.2 GPRS
GPRS stands for General Packet Radio Services and it is a technology that is built on top op GSM, allowing traffic to be sent and received at a speed of approximately 170 Kbps (kilobit per second). This is a whole lot faster than the current GSM possibilities but only time will learn if it will be enough. GPRS supports Packet Swichted networks. 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. GPRS therefore lets network operators maximize the use of their network resources in a dynamic and flexible way, along with user access to resources and revenues.
GPRS should improve the peak time capacity of a GSM network since it simultaneously:
allocates scarce radio resources more efficiently by supporting virtual connectivity
imigrates traffic that was previously sent using Circuit Switched Data to GPRS instead, and reduces SMS Center and signalling channel loading by migrating some traffic that previously was sent using SMS to GPRS instead using the GPRS/ SMS interconnect that is supported by the GPRS standards.
It should be noted that the General Packet Radio Service is not only a service designed to be deployed on mobile networks that are based on the GSM digital mobile phone standard. The Time Division Multiple Access (TDMA) standard, popular in North and South America, will also support GPRS. GPRS is an important new enabling mobile data service which offers a major improvement in spectrum efficiency, capability and functionality compared with today's nonvoice mobile services. However, it is important to note that there are some limitations with GPRS, which can be summarized as:
Limited cell capacity for all users
GPRS does impact a network's existing cell capacity. There are only limited radio resources that can be deployed for different uses- use for one purpose precludes simultaneous use for another. For example, voice and GPRS calls both use the same network resources. The extent of the impact depends upon the number of timeslots, if any, that are reserved for exclusive use of GPRS. However, GPRS does dynamically manage channel allocation and allow a reduction in peak time signalling channel loading by sending short messages over GPRS channels instead.
Speeds much lower in reality
Achieving the theoretical maximum GPRS data transmission speed of 172.2 kbps would require a single user taking over all eight timeslots without any error protection. Clearly, it is unlikely that a network operator will allow all timeslots to be used by a single GPRS user. Additionally, the initial GPRS terminals are expected be severely limited- supporting only one, two or three timeslots. The bandwidth available to a GPRS user will therefore be severely limited. As such, the theoretical maximum GPRS speeds should be checked against the reality of constraints in the networks and terminals. The reality is that mobile networks are always likely to have lower data transmission speeds than fixed networks. The result is that relatively high mobile data speeds may not be available to individual mobile users until Enhanced Data rates for GSM Evolution (EDGE, see later in this paper) or Universal Mobile Telephone System (UMTS, again see later in this paper) are introduced.
In the next table you can see in which fase the introduction of GPRS will be at what time.
| Date | Milestone |
|---|---|
| Througout 1999-2000 | Network operators place trial and commercial contracts for GPRS infrastructure. Incorporation of GPRS infrastructure into GSM networks |
| Summer of 2000 | First trial GPRS services become available. Typical single user throughput is likely to be 28 kbps. |
| Start of 2001 | Basic GPRS capable terminals begin to be available in commercial quantities |
| Throughout 2001 | Network operators launch GPRS services commercially and roll out GPRS. Vertical market and executive GPRS early adopters begin using it regularly for nonvoice mobile communications |
| 2001 / 2002 | Typical single user throughput is likely to be 56 kbps. New GPRS specific applications, higher bitrates, greater network capacity solutions, more capable terminals become available, fuelling GPRS usage |
| 2002 | Typical single user throughput is likely to be 112 kbps. GPRS is routinely incorporated into GSM mobile phones and has reached critical mass in terms of usage. |
As we see now at the end of December 2000 the dutch telecom operator KPN has lounced GPRS services in the entire country, for a limited amount of customers. Of course this is still in a test phase, but as you can see by this example GPRS is quite well on schedule.
GPRS does have quite an advantage over GSM and some of these advantages will be briefly discussed below:
Still Images
Still images such as photographs, pictures, postcards, greeting cards and presentations, static web pages can be sent and received over the mobile network as they are across fixed telephone networks. It will be possible with GPRS to post images from a digital camera connected to a GPRS radio device directly to an Internet site, allowing near real-time desktop publishing.
Moving Images
Over time, the nature and form of mobile communication is getting less textual and more visual. The wireless industry is moving from text messages to icons and picture messages to photographs and blueprints to video messages and movie previews being downloaded and on to full blown movie watching via data streaming on a mobile device. Sending moving images in a mobile environment has several vertical market applications including monitoring parking lots or building sites for intruders or thieves, and sending images of patients from an ambulance to a hospital. Videoconferencing applications, in which teams of distributed sales people can have a regular sales meeting without having to go to a particular physical location, is another application for moving images.
Web browsing
Using Circuit Switched Data for web browsing has never been an enduring application for mobile users. Because of the slow speed of Circuit Switched Data, it takes a long time for data to arrive from the Internet server to the browser. Don't even mind the need to call in to get online.Alternatively, users switch off the images and just access the text on the web, and end up with difficult to read text layouts on screens that are difficult to read from. As such, mobile Internet browsing is better suited to GPRS.
