CS8601 MOBILE COMPUTING
ANSWER KEY
Part A
1) Application of mobile computing
Web or Internet access.
Global Position System (GPS).
Emergency services.
Entertainment services.
Educational services.
2) strategy to address hidden terminal problem
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
Dynamic Time Slot Allocation
Spatial Reuse
Dynamic Channel Assignment
Use of RTS/CTS Mechanism
3) various functionality of mobility mangement layer in GSM
Location Update
Cell Reselection
Handover Management
Subscriber Authentication
Temporary Mobile Subscriber Identity (TMSI) Management
4) IEEE 802.3 frame format
+-----------+------------+------------+--------+---------+----------+---------+-------------+
| Preamble | SFD (Start| Destination| Source | Length/ | Data | FCS | IFG |
| (7 bytes) | Frame | Address | Address| Type | (46-1500)| (4 bytes)| (12 bytes) |
| | Delimiter)| | | | | | |
+-----------+------------+------------+--------+---------+----------+---------+-------------+
5) Difference between foreign agent COA and colocated COA
Foreign agent care-of address (FACoA): The mobile node receives the same CoA as
the foreign agent. All mobile nodes in the foreign network are given the same CoA.
Co-located care-of address: Each mobile node in the foreign network is assigned its
own CoA, usually by a DHCP server.
6) How ad hoc networks differ from cellular network
A cellular network is an asymmetric radio network which is made up of fixed
transceivers or nodes, maintain the signal while the mobile transceiver which is using
the network is in the vicinity of the node. An ad-hoc network is a local area network
(LAN) that is built spontaneously as devices connect.
7) Benefit of Wireless application protocol
WAP is a very fast-paced technology.
It is an open-source technology and completely free of cost.
It can be implemented on multiple platforms.
It is independent of network standards.
It provides higher controlling options.
It is implemented near to Internet model.
8) Draw the basic transaction of wtp class 0
9) what is microkernel operating system
A microkernel is a minimal computer operating system kernel which, in its purest
form, provides no operating system services at all, only the mechanisms needed to
implement such services, such as low-level address space management, thread
management, and inter-process communication (IPC).
10) List the constraints of mobile operating system
The main constraints are memory, battery life, ability to adapt to different screen sizes
and orientations, security, and network bandwidth.
Part B
11) a)GSM Architecture and explanation
10marks
Discuss how worldwide automatic worldwide localization in GSM
The fundamental feature of the GSM system is the automatic, worldwide localization of users
for which, the system performs periodic location updates. The HLR always contains
information about the current location and the VLR currently responsible for the MS informs
the HLR about the location changes. 3Marks
11) b) Various multiplexing technique 10 marks
Frequency-division multiplexing (FDM). ...
Wavelength-division multiplexing (WDM). ...
Time-division multiplexing (TDM). ...
Code-division multiplexing (CDM). ...
Space-division multiplexing (SDM). ...
Pros and cons with other technique (3 marks)
12) a) compare FHSS and DSSS (13 marks)
Category FHSS DSSS
FHSS is Frequency-Hopping Spread DSSS is Direct-Sequence
Abbreviation
Spectrum Spread Spectrum
DSSS is a type of spread
FHSS is a type of spread spectrum
spectrum technology in
technology in which the frequency of
which the transmitted signal
the transmitted signal changes according
is spread across multiple
Definition to a specific pattern.
frequency bands.
In DSSS, the data
In FHSS, the data transmission is transmission is encoded and
encoded and decoded using a specific decoded using a pseudo-
pattern called hopset. random binary sequence
Pattern
or chip code.
FHSS transmits data using a narrowband
Frequency DSSS transmits data using a
carrier that hops among different
band wider frequency band.
frequency channels.
FHSS is more resistant to interference
DSSS is more vulnerable to
because it uses frequency hopping,
Interference interference because it uses a
which makes it difficult to intercept the
resistant wider frequency band.
signal.
FHSS is less susceptible to multipath
fading, it is a phenomenon in which the DSSS is more susceptible to
transmitted signal arrives at the receiver multipath fading because it
via multiple paths, resulting in a loss of uses a wider frequency band.
Susceptibility
signal quality.
Transmission FHSS has low transmission rates (up to DSSS has high transmission
speed 3 Mbps). rates (up to 11 Mbps).
Modulation Multilevel Frequency Shift Keying BPSK (Binary Phase-Shift
techniques used (FSK) was used. Keying) was used.
Efficiency FHSS is generally more efficient than DSSS is less efficient
Category FHSS DSSS
because it uses a wider
DSSS in terms of bandwidth utilization.
frequency band.
It is widely used in a variety of It is well-suited for particular
applications, including wireless applications where the signal
networking like Bluetooth, mobile must travel over long
Application
communications, and military distances like GPS, and
areas
communications. WIFI.
12)b) Different phases in hiperlan1 (13 marks)
Discovery and Association Phase
Authentication Phase
Association Phase
Synchronization Phase
Configuration Phase
Data Transfer Phase
Power-Save Phase
Handover Phase
13)a) Working principle of GRE
Encapsulation Process (3 marks)
Routing and Transmission (3 marks)
GRE Header (3 marks)
Delivery of Payload (2 marks)
Transporting Multicast Traffic (2 marks)
13)b) justify your answer why it is not possible to adapt the traditional tcp environment
in mobile wireless networks
Adapting the traditional TCP (Transmission Control Protocol) environment directly to mobile
wireless networks can face challenges due to the unique characteristics and constraints of
mobile environments. Here are several reasons why it may not be straightforward to apply
traditional TCP in mobile wireless networks:
High mobility
Variable Bandwidth and Link Quality:
Packet Loss Sensitivity
Round-Trip Time Estimation
Energy Efficiency
TCP Slow Start
Need for Cross-Layer Optimization (10 marks)
The main drawback of I-TCP is the segmentation of the single TCP connection into two TCP
connections, which loses the original end-to-end TCP semantic. A new enhancement, which
leaves the TCP connection intact and is completely transparent, is Snooping TCP. (3 marks)
14) a) DHCP operation (10 marks)
Benefits of DHCP (3 marks)
Reliable IP address configuration. DHCP minimizes configuration errors caused by manual
IP address configuration, such as typographical errors, or address conflicts caused by the
assignment of an IP address to more than one computer at the same time.
Reduced network administration.
14)b) Difference of WML compared to HTML (6 Marks)
Characteristics WML HTML
Stands for Wireless Markup Language Hyper Text Markup Language
WML is hardly used It is employed as a structuring
Definition frequently and only serves as language for papers and webpages
a secondary page. that will be displayed online.
Communication It is wireless communication It is wired communication
Variables WML uses the variables HTML doesn’t use the variables
Scripts are stored in the JavaScript is embedded in the same
Script
separate file html file
Case Sensitive Not a case sensitive It is a case sensitive
WML script to design a page for online food ordering (7 marks)
<?xml version="1.0"?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.3//EN"
"http://www.wapforum.org/DTD/wml13.dtd">
<wml>
<card id="main" title="Online Food Ordering">
<p align="center">
Welcome to our Online Food Ordering Service!
</p>
<p>
Choose your favorite food items and place your order.
</p>
<do type="accept" label="Menu">
<go href="#menu"/>
</do>
</card>
<card id="menu" title="Food Menu">
<p>
<b>Menu:</b>
</p>
<select name="foodItems">
<option value="pizza">Pizza</option>
<option value="burger">Burger</option>
<option value="pasta">Pasta</option>
<!-- Add more food items as needed -->
</select>
<p>
<b>Quantity:</b>
</p>
<input name="quantity" type="text" title="Quantity"/>
<do type="accept" label="Order">
<!-- Assuming you have a server-side script to handle the order -->
<go href="submit_order.php?foodItem=$(foodItems)&quantity=$(quantity)"/>
</do>
<do type="prev" label="Back">
<go href="#main"/>
</do>
</card>
</wml>
15) a) Monolithic structure of OS (10 Marks)
Compare with microkernel design (3 Marks)
Robustness
Flexibility
Performance
15)b) Three popular mobile OS with protocol stack (13 marks)
Apple macOS, Microsoft Windows, Google's Android OS, Linux Operating System, and
Apple iOS.
Each protocol stack carries 4 marks
Part C
16)a) Reactive routing protocol (15 Marks)
Reactive routing protocols (8 marks)
Proactive routing protocols (7 marks)
16)b) proxy based design for mobile service access (15 marks)
Design (11 marks)
Benefits of proxy based service access models (4 marks)
Traffic Management and QoS
Load Balancing for Scalability
Enhanced Security and Privacy
Protocol Translation for Interoperability
Caching for Improved Performance
