COMMUNICATION ACCESS
Mobile computing has grown exponentially in the last few years due to several factors including the growth of service work in Western society and the need for co-operation between many parties in the work force . These factors require increased use of information technology and physical interaction thus leading to the need for mobile computing.
Mobile computing devices are a common and it is more common than not to have internet access available on these devices via a wide variety of connection methods. This paper presents the different connection methods, how they work and gives examples of where the various connections can best be used. The next section classifies mobile computer systems and section three discusses various connection methods and how they operate. This report then concludes in section four.
Mobile Computer Systems
Mobile computer systems are computing devices that are portable and not limited to use at a single location. The advantages of using mobile computing systems include portability, increased productivity since devices can be used while you move, use of the devices for entertainment as well as access to cloud computing. Mobile cloud computing is an especially significant game changer because it removes the limitation of hardware which caused mobile devices to consistently come second when compared to PCs .
Disadvantages of using mobile computing systems include frequent need to recharge the devices due to high battery power consumption, low quality of connection when compared to other systems, higher device costs and security concerns. Mobile cloud computing is one solution to prolong battery life and reduce device costs since less hardware is required .
According to Barnatt, , mobile computers can be divided into several categories including laptops, ultra-books, netbooks, tablet computers, E-book readers, smart phones, media players/ games consoles and ambient computing devices while Nosrati in categorizes the devices as personal digital assistant, smart phone, tablet computer, ultra-mobile PC and wearable computers. We briefly discuss the different categories below.
Laptops – these generally can be considered as portable desktop computers which have similar hardware to desktops and can run the same applications. There are various laptop manufacturers available including HP and Dell.
Ultrabook - these are a lightweight and thinner version of a laptop meet specific Intel requirements for example they should be less than 21mm thick and have at least five hours of battery life. Examples of ultra-books are Aspire S7 and Aspire M from Acer.
Netbooks – these are smaller low powered laptops with a less than full size keyboard but generally run the same software applications as a laptop, an example of this device was the Eee PC.
E-book readers – these are generally tablets used for reading electronic documents such as books, magazines and newspapers. An example is the Kindle Paperwhite reader .
Smart phones – these are mobile phones combined with internet connectivity, coming in many different shapes and sizes e.g. Samsung Galaxy series of smart phones .
Media players/mobile game consoles - these are portable music, video and game consoles used for entertainment e.g. Play Station Portable consoles .
Ambient computing devices – these devices display and deliver information discreetly in your environment through the use of pre-attentive processing e.g. the Ambient Energy Orb monitors energy use in homes allowing users to know when to consume or save energy.
Personal Digital Assistant (PDA) – these are now largely obsolete due to the adoption of smart phones but were initially used to function as a personal information manager and contained an electronic visual display and ability to access the internet. An example of a PDAs is HP’s iPAQ Pocket PDA
Wearable computers – these are electronic devices that are worn under, with or on top of clothing . These devices have constant interaction for monitoring various parameters with the user and examples of such devices are fitness products such as Fitbit .
As technology continues to change, there will be changes in the categories of mobile devices as some become obsolete and other new technologies are introduced to society. However the key common thread linking these devices remains portability and mobile connectivity. We discuss various mobile internet connectivity methods in the next section.
Internet Connectivity
There are several organizations lead in developing standards for mobile communications and these include the European Telecommunications Standards Institute (ETSI) which created the Global System for Mobile Communications (GSM) standard, International Telecommunications Union (ITU) which is a UN ICT specialized agency and 3rd Generation Partnership Project 3GPP which is the standards body behind UMTS. These agencies ensure that complete system specifications for wireless technologies developed and documented. There are various methods of connecting to the internet from mobile devices including GPRS, 3G, LTE and Wi-Fi and we discuss these next.
General Packet Radio Service (GPRS)
General Packet Radio Service (GPRS) was the first technology to allow delivery data on mobile handsets . Downlink speeds were typically 40Kbps while uplink speeds were approximately 14Kbps in Release 97 however enhancements made in Releases R’98 and R’99 improved these speeds. GPRS utilizes the telecommunications operator’s GSM network however it is packet switched rather than circuit switched.
GPRS makes use of the idle radio capacity which is not being used for calls in the GSM network and utilizes this capacity to establish a data network only using radio resources when data is being sent or received. However since the radio capacity is shared by voice calls and data, if there are many ongoing voice calls in the network, the data speeds and transmission is decreased.
In GSM, each radio channel has 8 time slots and whenever a timeslot is not being used for a voice call, it can be used to transmit data packets. In addition data is transmitted as packets through the network and can take multiple paths through the GSM network to reach the final destination.
In order to support GPRS, a few new nodes were added to the GSM network including the Serving GPRS Support node (SGSN), the Gateway GPRS Support node (GGSN) and the Packet Control Unit (PCU). The SGSN establishes and manages the data connections between the mobile device and the destination network as well as monitors and tracks the mobile device while the GGSN connects the GPRS domain to the external data networks such as the Internet . Each external network such as the Internet or other Intranets, is given an APN (Access Point Name) which is unique and is used by the mobile device to establish the connection to the required destination network. The Packet Control Unit is part of the Base Station Subsystem to support packet mode of operation.
Three important operations must be performed in order to connect to the Internet via the GPRS network: service subscription, GPRS attach and PDP context activation . The mobile device must be subscribed for the GPRS service in the HLR (Home Location Register) of the telecom operator. The device must first attach to the GPRS network by sending an attach request message containing its identity, device capabilities and location. On receiving this request, the SGSN contacts the HLR to update the location of the device and confirm the user has subscribed for GPRS services. For data transfer to be possible, the device then needs to activate a Packet Data Protocol (PDP) Context i.e. logon to the destination network. When the device tries to logon, the APN and other information is sent to the SGSN which checks the devices subscription record and if valid, forwards the request to the relevant GGSN which opens a tunnel to the required network and data transfer can now take place. A more detailed description of the GPRS service operation is available at the ETSI website .
Most mobile devices that support only GPRS are class B devices which can attach to both the GSM and GPRS networks at the same time but cannot transmit or receive on both simultaneously. Due to the slow speeds of GPRS it is mostly used for downloading emails.
Universal Mobile Telecommunications System (UMTS)
Universal Mobile Telecommunications System (UMTS) is the third generation of mobile communication technologies and was designed to be differentiated from 2G by having significantly higher performance speeds . UMTS was designed to have target data rates of 144 Kbits/s for satellite and rural outdoors, 384 Kbits/s for urban outdoor and 2048 Kbits/s for indoor and low range outdoor scenarios.
The UMTS network is slightly different from the GSM/GPRS network and consists of three domains; the Core Network (CN), radio access network (UMTS Terrestrial Radio Access Network or UTRAN) and the end user equipment. The core network architecture is similar to the GSM/GPRS network with a few modifications to cater for UMTS operation and services. The UTRAN allows over-the-air access for the user equipment and the base station is called the Node B. In order to set up a packet switched call for data transfer the following process is followed.
First of all a Radio Resource Control (RRC) connection to the UTRAN needs to be set up and an Iu connection established to the core network (Iu is the interface between the UTRAN and the core network). The end device then makes an attach request and security procedures are carried out i.e. identification, authentication and setting the security mode. Once the attach process is completed, the device requests for PDP context activation. The RAB’s (Radio Access Bearers) are then set up for the connection and GTP (GPRS Tunneling Protocol) connections are created. The PDP context is created at the GGSN creating a tunnel than can be used for data transfer to the device. If relatively low data rates and ubiquitous connectivity are required then 3G is the connection type to use.
Long Term Evolution (LTE)
Long Term Evolution (LTE) follows UMTS in the development path and was motivated by factors such as demand for higher data rates and quality of service due to the emergence of new applications such as multimedia online gaming, mobile TV and Web 2.0 which all required increased mobile data usage. Other factors motivating the development of LTE include a continued demand for cost reduction and need for an optimized packet switch system . LTE was designed to provide improved performance including low latency, high data rates and high quality of service. Operators with 4G services typically see 4G users consuming double the monthly data when compared with non-4G users mostly due to video streaming .
LTE is also known as 4G however although LTE from 3GPP is called a 4G technology, ITU still considers it an evolution of 3G technology
LTE uses both Frequency Division Duplex (FDD) and Time Division Duplex (TDD). With TDD, the uplink and downlink carrier are the same and only separated by time while in FDD the uplink and downlink use different frequencies. LTE was designed to have more than 100Mbps peak transmission rate on the downlink while using Orthogonal Frequency-Division Multiple Access (OFDMA) and more than 50Mbps peak transmission rate on the uplink while using Single Carrier Frequency Division Multiple Access (SC-FDMA) .
There are three main components in the LTE architecture; the user equipment, the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and the Evolved Packet Core (EPC). The user equipment connects to the E-UTRAN which consists of evolved base stations called eNodeBs which send and receive radio transmissions to all the mobile devices. There is no centralized intelligent controller of the eNodeBs and this distributed intelligence among the eNodeBs reduces handover time and speeds connection setup since for many real time data sessions such as online gaming, data session setup time is critical .
The process of registration, authentication and attaching to the network is then completed and the default EPS (Evolved Packet switched System) bearer setup is done. A dedicated EPS bearer is set up next and the user equipment can now receive data. An EPS bearer here can be considered as a pipeline within the EPS through which data flows. A more detailed LTE call flow is available in and . If high speed data rates are required together with ubiquitous connectivity then LTE is the connection type to use.
WiFi
WiFi is also known as 802.11 networking and there are three versions: 802.11b operates at 2.4 GHz and handles 11 Mbps, 802.11a operates at 5GHz and handles up to 54Mbps and 802.11g operates at 2.4GHz and handles 54Mbps. 802.11a and 802.11g use orthogonal frequency-division multiplexing (OFDM) while 802.11b uses Complementary Code Keying (CCK) for efficient coding.
Connecting via WiFi requires use of a wireless router containing a low power transmitter and receiver to route packets between the mobile device and the internet. The mobile device needs a wireless adaptor to access Wi-Fi and the wireless router may connect to the internet via a physical Ethernet connection to the telecom provider. In a simple explanation of Wi-Fi operation is given using the analogy of communicating using walkie talkies which transmit and receive using radio waves with the walkie talkies converting the radio waves into voice and vice versa.
Security of data is one key issue with WiFi since unencrypted data can easily be detected. Web pages need to use SSL and encryption technologies such as WPA and WPA2 need to be implemented. It is always advisable however never to send/receive sensitive information while using a public unsecured WiFi hotspot. When higher data rates are required but within a specific smaller area which can be covered by a hot spot then WiFi is the connection mode to be used.
Conclusion
There are many different types of mobile devices in use today including laptops, media pads, game consoles and wearable devices each with a different role to play. Access to the internet from these mobile devices is a key requirement and this can be done via a variety of technologies such as UMTS, LTE or WiFi.
Research is ongoing into ways to improve data access and speeds by looking in different aspects like introducing new technologies such as 5G , or proposing a means to enable seamless and robust interworking between the existing technologies so that the users get the best network all the time ,.
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