Mobile Computing and Smartphones: Complete Exam Notes

The correct answer is A, Long Term Evolution. LTE is the radio access technology of fourth generation mobile networks, standardised by the Third Generation Partnership Project. The name records the intention of the standard bodies to let the existing GSM and UMTS networks evolve over the long term towards an all-IP system rather than be replaced overnight, and voice over LTE later brought ordinary calls on to the same data network. Option B, Last Time Evolution, is not a term used anywhere in telecommunications. Option C, Least Time Evolution, is likewise invented and has no technical meaning. Option D, Long Time Evolution, is the commonest wrong choice because it differs from the right answer by a single word, but the standard uses the word term, not time. Candidates should remember LTE with 4G and New Radio with 5G.

The correct answer is B, duplexing. A telephone conversation requires both parties to speak and listen at the same time, so a mobile link must carry traffic in both directions together. That arrangement is called duplexing, and cellular systems achieve it either by using two separate frequency bands, known as frequency division duplex, or by alternating very rapidly between sending and receiving on one band, known as time division duplex. Option A, triplexing, is not a recognised mode of mobile communication. Option C is wrong because the correct term for one-way communication is simplex, not simplexing, and a simplex link such as a broadcast cannot support a phone call. Option D, quadraplexing, is not a term in mobile standards at all. Only duplex and its two forms appear in the syllabus of cellular communication.

The correct answer is A, Subscriber Identity Module. The SIM is a small smart card issued by the operator that stores the subscriber identity, the authentication keys used to prove that identity to the network, and a limited amount of contact and message data. Because the identity lives on the card, a subscriber can move the number to another handset simply by moving the card. Option B, Single Identity Module, resembles the right answer but is not the standard expansion. Option C, Subscriber Internet Module, is wrong because the card is not tied to internet service; it authenticates voice, message and data service alike. Option D, Secure Identity Memory, is invented, although the card is indeed a secure element. Note the contrast with the IMEI, which identifies the handset rather than the subscriber.

The correct answer is C, 15. The International Mobile Equipment Identity is a fifteen-digit number assigned to every handset, made up of a code identifying the type approval of the model, a serial part and a final check digit. It can usually be displayed by dialling a short code and is printed under the battery or on the box. Because it identifies the device rather than the subscriber, it is the number quoted when a lost phone is reported so that the network can bar the handset. Option A, ten digits, is the length of an Indian mobile telephone number, which is why it is the commonest wrong answer. Option B, twelve digits, is the length of the Aadhaar number. Option D, twenty digits, matches the longer identifier printed on some SIM cards, not the IMEI.

The correct answer is B, Linux. Android uses a modified Linux kernel at its lowest layer to manage memory, processes, power and device drivers, and builds its own runtime, libraries, application framework and user interface above it. The project began at a company called Android Inc., which Google acquired in 2005, and the first Android handset reached buyers in 2008. Option A is wrong because the Windows NT kernel underlies desktop Windows and the discontinued Windows Mobile line, not Android. Option C is wrong because kernels derived from Unix and BSD underlie Apple macOS and iOS, which are Android competitors rather than its base. Option D is wrong because Symbian was a complete mobile operating system of the era before Android, used mainly by Nokia, and it was never a kernel for Android.

The correct answer is B, Global System for Mobile Communications. GSM is the European-born digital standard that replaced the analogue first generation networks; it introduced the removable SIM card, digital encryption of the radio link, international roaming and the short message service, on which a plain text message is limited to one hundred and sixty characters. Option A, General Switching Mode, is not a telecommunications standard and simply borrows two technical-sounding words. Option C, Generic Signal Modulation, is invented, although modulation is indeed part of how GSM encodes a signal. Option D, Global Satellite Messaging, is wrong because GSM is a terrestrial cellular standard that works through ground base stations, not through satellites. Keep GSM with 2G, UMTS with 3G and LTE with 4G, and remember that CDMA, or Code Division Multiple Access, was the rival second generation family in which every call was spread across the band under its own code rather than given a separate time slot.

The correct answer is A, a few centimetres. NFC is deliberately designed for extremely short range, so the two devices must be touching or nearly touching before any data passes. This limitation is itself the security feature that makes the technology suitable for contactless card payments, tap-to-pay on phones, transit tickets and identity tags, since an attacker cannot read the exchange from across a room. Option B, about ten metres, is the usual working range of Bluetooth, which is the commonest confusion in this question. Option C, about one hundred metres, is closer to the range of a Wi-Fi access point in open conditions. Option D, several kilometres, describes a cellular link to a base station or a long-range radio system, far beyond anything NFC attempts.

The correct answer is C, the accelerometer. An accelerometer measures acceleration along three axes, which includes the constant pull of gravity, so the phone can work out which way is down and therefore how it is being held. The system uses that reading to rotate the screen, to count steps and to detect shaking. Option A is wrong because the proximity sensor detects an object close to the top of the screen and blanks the display when the phone is lifted to the ear during a call. Option B is wrong because the ambient light sensor measures the brightness of the surroundings and adjusts screen brightness automatically. Option D is wrong because the magnetometer senses the earth magnetic field and serves as the compass for map applications. A gyroscope refines rotation sensing but the basic orientation switch belongs to the accelerometer.

The correct answer is C, IEEE 802.15. The 802.15 family covers wireless personal area networks, the very short-range links meant to join the devices a single person carries, and Bluetooth was standardised within it as IEEE 802.15.1. Its working range is about ten metres in the common low-power class, which suits earphones, speakers, keyboards and file transfer. Option A is wrong because IEEE 802.3 is the Ethernet standard for wired local area networks. Option B is wrong because IEEE 802.11 is the Wi-Fi family for wireless local area networks, which is the usual distractor since both are wireless. Option D is wrong because IEEE 802.16 is WiMAX, a broadband wireless access standard designed for metropolitan area coverage. Learning the four together, 802.3, 802.11, 802.15 and 802.16, settles a whole family of questions.

The correct answer is A, Navigation with Indian Constellation. NavIC is the operational name of the system formally called the Indian Regional Navigation Satellite System, built by ISRO so that the country would not depend on a foreign constellation for positioning in a crisis. It gives position, velocity and timing over India and a surrounding region rather than over the whole earth, which is why it is described as regional and not global. Option B, National Vehicle Information Centre, is invented and belongs to no space programme. Option C, Navigation Indian Communication, mixes the right words in the wrong order and omits the key idea of a constellation. Option D, National Integrated Coordination, has no connection with satellite navigation. The American system is GPS, the Russian one GLONASS, the European one Galileo and the Chinese one BeiDou.

The correct answer is B, the National Payments Corporation of India. UPI was launched by NPCI in 2016 as a system that lets a user link several bank accounts to one mobile application and transfer money instantly using a virtual payment address or a QR code, without sharing account numbers. NPCI is the umbrella organisation for retail payments in the country and also runs RuPay, IMPS and the national automated clearing house. Option A is wrong because the Securities and Exchange Board of India regulates the securities market. Option C is wrong because the Telecom Regulatory Authority of India regulates telecom services and tariffs, not payment systems, even though UPI runs on phones. Option D is wrong because the Unique Identification Authority of India issues Aadhaar, which supports payments but does not operate UPI.