Mobile Computing: The Story Of G's

Computing is defined as the use of computers or any such device which works on some program or set of programs. Now as we had already started a discussion on Cloud Computing, these are the techniques on which this computing implicated.

Present day, we would have come across these terms like- GSM, GPRS, CDMA, TDMA, EDGE, 3G, 4G, etc. Now being the “End-User”, we hardly try to know what they are, nor bother to know how these things differ. What we bother about, is that how to use them.

Now where’s the fun in watching a movie when you can’t even remember a scene or a punch dialogue. The same applies in everything we do. Thus, my motive from writing and spreading this article is that we try to know the slightest of details about the various “G’s”.

Now going way back to the past, when inventions of devices like radio, TV, Telephone, W-Phone (Wireless Telephones) were at its work. Now it’s not a joke to convert one form of energy into other, it takes great understanding. Thus, many inventions were combined to achieve what we understand as Wireless communication. The concepts used were the idea behind working of radio and that of a telephone. With this they came to know that sound energy captured from one end can be converted to electrical signals with help of magnets and routed to a desired location in the form of waves through a transmitter. Also it can be received at the other end by a receiver and converted back to electrical coding which can be further converted to sound. All this was possible because of the common factor “frequency” between electricity, magnetism and sound. Now the factor of differentiating signals from one device to other was an issue i.e.: making a device unique. We all are familiar with the quantum theory, and various electromagnetism phenomenons. Now this helped us in relating various factors like speed of light, frequency of signal, bandwidth, wavelength of signal, amplitude of signal etc. Then, a particular electrical coding was assigned to each device which differentiated them from each other.

That was a bit of history of how things began. Now we head straight away to what is this “G”. ‘G’, in computing stands for “Generation”.

It all began with zero-generation mobile systems called the Mobile Radio Telephone System (MRTS).

The image shown above is a MRTS based device, a predecessor of the modern telephone. In MRT System the technologies used were as follows:-
PTT: Push to Talk.
MTS: Mobile Telephone System.
IMTS: Improved Mobile Telephone System.

AMTS: Advanced Mobile Telephone System.

Each of them differed in frequency range i.e.: kept increasing from one technology to other. This MRTS/ 0G, system of communication started as early in 1940’s and ended up by mid 80’s.

During early 80’s researches on the first generation (1G), communication systems had been started up. This was surely the best invention in field of communication technology. Instead of converting a single frequency into electrical signal a packet of data was converted into a particular signal and it was analog in nature. Thus, 1G speed varied between that of a 28k modem (28kbit/s) and 56k modem (56kbit/s), meaning actual download speeds of 2.8KBytes/s to 5.6KBytes/s.

With the beginning of 1G marked the evolution of present day Mobile Cellular Systems. 2G, or the Second Generation system works on a GSM standard. Now GSM stands for Global System for Mobile communication. This is based on TDMA i.e.: Time Division Multiple Access. The only difference between 1G and 2G is the signals were analog then and digital in the later.

TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channels.

GSM uses a narrowband TDMA, which allows eight simultaneous calls on the same radio frequency.

The other standard for 2G system is CDMA or Code Division Multiple Access. This uses a spread- spectrum technique where data is sent in small pieces over a number of discrete frequencies available for use. Each user’s signal is spread over the entire bandwidth by unique spreading code. At the receiver end, the same unique code is used to recover the signal.

Now both of the above techniques i.e. the entire 2G system was built mainly for voice services and slow data transmissions.

Thus there was a need of modification. But the modification though should have been considered as 3G, did not match up to the uplink/downlink speed.

This is nothing but GPRS or General Packet Radio Service. It is used to describe 2G-systems that have implemented a packet-switched domain in addition to the circuit-switched domain. It does not necessarily provide faster services because bundling of timeslots is used for high speed circuit-switched data services (HSCSD) as well. GPRS could provide data rates of 56 kbit/s - 115 kbit/s. It can be used for services such as Wireless Application Protocol (WAP) access, Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access

EDGE is standardized by 3GPP as part of the GSM family and it is an upgrade that provides a potential three-fold increase in capacity of GSM/GPRS networks. The specification achieves higher data-rates (up to 236.8 kbit/s) by switching to more sophisticated methods of coding (8PSK), within existing GSM timeslots. Presently EDGE is known as Enhanced Data rates for Global Evolution.

Mixture of GSM/ GPRS/ EDGE is considered to be the modern day 3G.

LTE or 3GPP in Long Term Evolution is what should be considered as modern day 3G. As it matches the required data rates of 2 Mbit/s for stationary or walking users, and 384 kbit/s in a moving vehicle, but does not actually clearly specify minimum or average rates or what modes of the interfaces qualify as 3G, so various rates are sold as 3G intended to meet customers expectations of broadband data i.e.: 2.5G and 2.75G are used as 3G.

UMTS or Universal Mobile Telecommunication System is a standard and the higher version of 3G. It is called 3.5G as it doesn’t match up the requirements of 4G but can be appreciably close. It is based on W-CDMA i.e.: Wideband CDMA (increased bandwidth).

Mobile-WiMax also happens to match up the requirements as 4G but the technique used and the data rates are much closer to 3G thus often termed under ‘3.5G’.

HSPA or High Speed Packet Access is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA) that extends and improves the performance of existing WCDMA protocols.

A further 3GPP standard, Evolved HSPA (also known as HSPA+), was released late in 2008 with subsequent worldwide adoption beginning in 2010.

HSPA supports increased peak data rates of up to 14 Mbit/s in the downlink and 5.76 Mbit/s in the uplink. It also reduces latency and provides up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink, reducing the production cost per bit compared to original WCDMA protocols. Many HSPA rollouts can be achieved by a software upgrade to existing 3G networks, giving HSPA a head start over WiMAX, which requires a dedicated network infrastructure.

Evolved HSPA (also known as: HSPA Evolution, HSPA+, I-HSPA or Internet HSPA) is a wireless broadband standard defined in 3GPP release 7 and 8 of the WCDMA specification. Evolved HSPA provides data rates up to 84 Mbit/s in the downlink and 22 Mbit/s in the uplink (per 5 MHz carrier) with multiple input, multiple output (MIMO) technologies and higher order modulation. It utilises multiple base stations to potentially double the channels available utilising MIMO principles.

MIMO or Multiple Input and Multiple Output is the use of multiple antennas at both the transmitter and receiver to improve communication performance. It is one of several forms of smart antenna technology. Note that the terms input and output refer to the radio channel carrying the signal, not to the devices having antennas.

MIMO technology has attracted attention in wireless communications, because it offers significant increases in data throughput and link range without additional bandwidth or increased transmit power. It achieves this by spreading the same total transmit power over the antennas to achieve an array gain that improves the spectral efficiency (more bits per second per hertz of bandwidth) or to achieve a diversity gain that improves the link reliability (reduced fading). Because of these properties, MIMO is an important part of modern wireless communication standards such as IEEE 802.11n (Wifi), 4G, 3GPP Long Term Evolution, WiMAX and HSPA+.

LTE-Advanced is termed as 3.9G. 3.9G because it is closest to 4G but differs in the desired data rates. Also the technology adopted in LTE-Advanced is a combination of W-CDMA, MIMO & Evolved UMTS Terrestrial Radio Access (E-UTRA).

LTE Advanced (Long-term-evolution Advanced) is a candidate for IMT-Advanced standard, formally submitted by the 3GPP organization to ITU-T in the fall 2009, and expected to be released in 2012. The target of 3GPP LTE Advanced is to reach and surpass the ITU requirements. LTE Advanced is essentially an enhancement to LTE. It is not a new technology but rather an improvement on the existing LTE network. This upgrade path makes it more cost effective for vendors to offer LTE and then upgrade to LTE Advanced which is similar to the upgrade from WCDMA to HSPA. LTE and LTE Advanced will also make use of additional spectrum and multiplexing to allow it to achieve higher data speeds. Coordinated Multi-point Transmission will also allow more system capacity to help handle the enhanced data speeds. Release 10 of LTE is expected to achieve the LTE Advanced speeds. Release 8 currently supports up to 300 Mbit/s download speeds which is still short of the IMT-Advanced standards.

Fourth Generation Tele-communication system uses the HSOPA High Speed OFDM Packet Access, i.e.: OFD Multiplexing.

OFDMA or Orthogonal Frequency Division Multiple Access is the latest research field. It is a multi-user version of the popular Orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of sub-carriers to individual users as shown in the illustration below. This allows simultaneous low data rate transmission from several users.

Data speed rate of 4G systems:

Peak Download- 1Gbit/s. Not less than this.

Peak Upload- 500Mbit/s. Not less than this.

Benefits of OFDM:

► Over CDMA/W-CDMA.

•OFDM can combat multipath interference with more robustness and less complexity.

•OFDMA can achieve a higher MIMO spectral efficiency due to providing flatter frequency channels than a CDMA rake receiver can.

•No cell size breathing as more users connect.

► Over TDMA.

•Allows simultaneous low-data-rate transmission from several users.

•Pulsed carrier can be avoided.

•Lower maximum transmission power for low data rate users.

•Shorter delay and constant delay.

•Contention-based multiple access (collision avoidance) is simplified.

•Further improves OFDM robustness to fading and interference.

OFDMA is still a theory, as there has not been any practice of it till now. America claims to run on 4G but in some areas only. That can be considered LTE-A.

That’s not it researches have been started already for “5G”. Something that would give a promising of 750 Mbit/s uplink and a downlink of 1 Gbit/s even when used by someone in a moving vehicle.