MSc-IT Study Material
June 2010 Edition

Computer Science Department, University of Cape Town

Portable/Mobile Device Connectivity

The capabilities of portable or mobile computing devices continue to increase despite drastic reductions in their size and weight. Fast connectivity has also become available to these devices. The different classes of portable/mobile devices include:

  1. Cellular Phones: These devices are at the forefront of data connectivity due to the fact that they are already connected to a communication platform (GSM in South Africa). As such their connectivity largely depends on the underlying cellular technology, leading to typically higher costs associated with connecting such devices. However, in Japan the i-mode system has been very popular, mainly due to its low cost and the large time most Japanese spend commuting. (To do: read up about i-mode, why has it not widely spread to the rest of the world?) Some cellular phones are not limited to only connecting using the underlying cellular network technology. Some made use of other medium such as infrared, Bluetooth, and WiFi. (see later.)

    Recently, a group of cellular phones manufacturer has introduced an operating system called Symbian. It is hoped that Symbian will produced a single platform for developing applications for these mobile devices, thus resulting in new ways of using and connecting such devices.

  2. Personal Digital Assistants or PDAs initially offered only basic PIM (Personal Information Manager) functionality, such as management of contacts, calendar and to-do lists. However, these have grown into full-fledged computing platforms. The Pocket PC is one such device.

    Microsoft has taken the step of splitting the windows mobile platform (for Pocket PC) into two classes, although both are based on the same base operating system. One class of Pocket PC is a straight PDA (or more accurately described as portable computer), while the other is a cellular phone with a some what higher processing power than other cellular phones, but still less powerful than its Pocket PC PDA cousins. These devices are still quite new and customers still do not seem to have decided which type of device they want. The two classes of devices reflect the two types of users that might be making use of the devices: those who want to be portable (small) and those who want a larger (implying a bigger screen and easier input method) and more powerful devices.

    Another PDA class of PDAs are the Palm-OS based devices. As with the Pocket PC platform, the Palm-OS trend is to offer devices with cellular phone connectivity as well as standalone PDA functionality.

    There is a prediction that eventually PDA-only devices will die out, leaving behind a class of powerful cellular phones. However, there is still a conflict in the size of the device which consumers will ultimately want, with some (non-voice) tasks remaining difficult to do on a small devices.

  3. Laptops: Laptops and notebooks have existed for a few decades, but have only recently been able to connect wirelessly. Initially, this was achieved with help of cellular phones acting as modems. This provided slow data rates of around 10-25% of the speed achievable by a wired solution at any given time (e.g. During the late 1990s, where 56kbps was a common wired rate, cellular modems were connecting at approximately 9600bps).

    Modern laptops are equipped with Wifi cards for connectivity to Wifi hot spots. Many companies have deployed common wireless solutions throughout their offices for laptops to connect to. In addition to this, other service providers are also offering solutions tailored made for laptops such as 3G, iburst and Sentech MyWireless in South Africa.

  4. Portable Gaming Devices: A new class of connectable devices has recently emerged. The portable entertainment devices have been popularized by the introduction of devices such as the Sony PlayStation Portable (PSP), Nintendo DS and the Nokia N-Gage. These devices support some class of connectivity (WiFi or GSM), usually to other similar devices or the Internet. Since these devices are still new to the market, manufacturers are still exploring different ideas of what the consumer wants to do.

Connectivity Technologies

GPRS, EDGE, 3G and other Cellular phone based protocols

Cellular phone manufacturers have been at the forefront of developing data communication standards over the relevant networks. In particular, the GSM group has been responsible for leading standards in fast connectivity over cellular technology.

In the late 1990s, data transmission over GSM occurred at 9600 bps. The introduction of General Packet Radio Services or GPRS (which runs over GSM networks with no modification) resulted in the increase of data rates to between 56 and 114 kbps. GPRS also gave consumers continuous connectivity. GPRS is a packet-based service, meaning that data packets are only sent and received when necessary and, in theory, this should lead to reduced connectivity costs as many users can share the available bandwidth in an area at any given time. Contrast this to the connection-based model of the previous GSM data connectivity, which meant that users were allocated dedicated bandwidth.

Enhanced Data rates for Global Evolution (EDGE) is improvement to GPRS allowing data rates of up to 384 kbps. EDGE was designed as a technology to be implemented on cellular networks that could not be upgraded to the faster UMTS (Universal Mobile Telephone System) spectrum (discussed later). EDGE allows such network to offer data transmission rates closer to those operators with more modern infrastructure.

Third generation (3G) connectivity technology was originally envisaged by the ITU to be a single world-wide standard, but it has since split into three groups, with the main group being UMTS (W-CDMA). UMTS (Universal Mobile Telephone System) is based on the W-CDMA (Wideband Code Division Multiple Access) which allows the sharing of multiple connections over the same radio spectrum. This configuration is usually found in GSM networks, including the 3G service currently provided in South Africa. The other 3G configuration includes CDMA2000 (which is employed in the USA, Japan and Korea) and TD-SCDMA (used in the People's Republic of China).


Bluetooth is a specification for wireless personal area networks, or PANs. It was designed to be the protocol of choice for the wireless connectivity between devices usually found in the home, such as a computer, printer, scanner, digital camera, mobile phone and PDA. Bluetooth was designed to work in a small area, approximately 10m wide, the size of a typical room or office. However, some specifications allow for larger ranges (such as 100m for class 1 Bluetooth devices).

Due to Bluetooth's somewhat limited range, the specification is not incorporated into many devices other than those mentioned earlier. Bluetooth is also notoriously difficult and tedious to set up and make use of. As WiFi has become more popular, fewer devices are now sold with Bluetooth.

WiFi (Wireless Fidelity)

WiFi is a set of standards based on the IEEE 802.11 specification for WLAN (Wireless Local Area Network). There are also newer standards such as 802.16 (WiMAX) which provides for wider coverage and increased speeds. WiFi was originally intended to work as a wireless version of LAN technologies, but are now employed to connect arbitrary devices to the Internet as well.

One of the advantages of WiFi over standards such as GSM, is that WiFi uses unlicenced radio spectrum and as such can be readily deployed wherever needed. WiFi also allows for easier setup than Bluetooth, and can be treated in a similar way to a LAN. Many layers of security can be employed to prevent unauthorized access to a WiFi network.

Many portable computing devices now come WiFi ready, and the number of WiFi Hotspots (where one can connect via WiFi to the Internet) are increasing, steadily making WiFi more popular. WiFi is also a global standard, meaning that devices can make use of any WLAN in any country. On the down side, WiFi requires a lot of power to operate, making its use very limited. Additionally, WiFi security is regarded to be weak by many.

Exercise 6

Do research into Bluetooth and WiFi technologies. Compare the two and suggest scenarios where each would be more suitable than the other.