Final Exam Study Guide

Question 1

What year was bluetooth version 1 released?

Answer 1

Bluetooth version 1 was released in 1999.

Question 2

What is the name of the organization that founded bluetooth, currently owns the bluetooth trademark, controls bluetooth research and development, and licenses marketing?

Answer 2

Bluetooth Special Interest Group (SIG)

Question 3

What Band frequency (i.e., GHz) does bluetooth operate?

Answer 3

2.4 GHz

Question 4

What ways can you avoid interference with Wi-Fi?

Answer 4

1) Time Division Multiplexing (TDM)

2) Use 5GHz Wi-Fi

Question 5

Which frequency-shift keying filter algorithm does bluetooth use?

Answer 5

Gaussian filter

Differential filter

Question 6

What is Edge Computing?

Answer 6

Edge computing is a distributed computing paradigm which brings computer data storage closer to the location where it is needed. Computation is largely or completely performed on distributed device nodes. Edge computing pushes applications, data and computing power (services) away from centralized points to locations closer to the user.

Question 7

Describe some problems with and challenges associated with Edge computing.

Answer 7

Programmability
Current solutions custom made
Need frameworks
Naming
No current standard for name edge devices
Hard for edge devices to be found
Privacy and Security
Hackers can gather info from IoT devices with poor security
Need to ensure encryption of data on network and edge devices

Question 8

Functionalities of each layer in TCP/IP

Example Protocols for Each Layer

Answer 8

application: supporting network applications
FTP, SMTP, HTTP
transport: process-process data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
Ethernet, 802.111 (WiFi), PPP
physical: bits “on the wire”

Question 9

Describe Go-back-N transport protocol

Answer 9

the sender can have up to N unacked packets in pipeline
receiver only sends cumulative ack
doesn’t ack packet if there’s a gap
sender has timer for oldest unacked packet
when the timer expires, retransmit all unacked packets

Question 10

Describe Selective Repeat Protocol

Answer 10

sender can have up to N unack’ed packets in pipeline
rcvr sends individual ack for each packet

sender maintains timer for each unacked packet
when timer expires, retransmit only that unacked packet

Question 11

Describe Stop and Wait Protocol

Answer 11

“stop-n-wait” (sometimes known as “positive acknowledgement with retransmission”) is the fundamental technique to provide reliable transfer under unreliable packet delivery system.

NORMAL OPERATION
After transmitting one packet, the sender waits for an acknowledgment (ACK) from the receiver before transmitting the next one. In this way, the sender can recognize that the previous packet is transmitted successfuly and we could say “stop-n-wait” guarantees reliable transfer between nodes.
To support this feature, the sender keeps a record of each packet it sends.
Also, to avoid confusion caused by delayed or duplicated ACKs, “stop-n-wait” sends each packets with unique sequence numbers and receives that numbers in each ACKs.

TIMEOUT
If the sender doesn’t receive ACK for previous sent packet after a certain period of time, the sender times out and retransmits that packet again. There are two cases when the sender doesn’t receive ACK; One is when the ACK is lost and the other is when the frame itself is not transmitted.
To support this feature, the sender keeps timer per each packet.

Question 12

What are some challenges of RF communications underwater?

Answer 12

Radio Waves
Propagate at long distances through conductive sea water only at extra low frequencies (30-300Hz)
large antennae and high transmission power
(e.g., Berkeley MICA motes  transmission range of 120 cm in UW at 433Mhz)
Optical Waves
No high such attenuation but scattering problem
High precision in pointing the narrow laser beams
Links in Underwater Networks 
Acoustic wireless communications

Question 13

Describe the Ethernet Header (802.3)

Answer 13

PREAMBLE 7 BYTES
SFD 1 BYTE
DESTINATION ADDRESS 6 BYTES
SOURCE ADDRESS 6 BYTES
LENGTH 2 BYTES
DATA 46-1500 BYTES
CRC 4 BYTES

Question 14

Describe Parity Bit

Answer 14

Parity bit is padded with the data
If data contains even number of 1’s – Parity bit will be 0
If data contains odd number of 1’s – Parity bit will be 1

Question 15

What is CRC

Answer 15

Cyclic redundancy check

Question 16

What are some security concerns with 5G?

Answer 16

Authentication
Requires more authentication between service providers
Authentication needs to be fast
Requires low latency and high data rates
Unlike 4G, can’t be based solely on symmetric key
Integrity: prevent manipulation when modifying data
Availability: cell reception, signal scrambling, DoS
Confidentiality: vehicle routing data, health monitoring data

Question 17

Proposed solutions for increased security on 5G

Answer 17

Cyclic Redundancy Check (CRC) authentication
Detects malicious activity and errors without increasing bandwidth
Dual authentication

Question 18

Why do you think that spectrum sharing between wifi and DSRC on the 5.9 GHz band would be a bad thing?

Answer 18

DSRC using the same 5.9 GHz band as dual-band Wi-fi
Rise in IoT devices
Influence reliability
Influence accuracy

Question 19

What is the application layer responsible for?

Answer 19

The application layer is responsible for supporting network applications.

Protocols are FTP, HTTP, SMTP

Question 20

What is the transport layer responsible for?

Answer 20

The transport layer is responsible for process data transfer.

Protocols are TCP and UDP

Question 21

What is the Network layer responsible for?

Answer 21

The network layer is responsible for routing datagrams from source to destination

Protocols are IP

Question 22

What is the link layer responsible for?

Answer 22

The link layer is responsible for data transfer between neighboring network events.

Protocols are Ethernet and 802.111

Question 23

What is the physical layer?

Answer 23

The physical layer is the “bits on the wire”

Question 24

What is the hidden terminal problem?

Answer 24

In wireless networking, the hidden node problem or hidden terminal problem occurs when a node is visible from a wireless access point (AP), but not from other nodes communicating with said AP. This leads to difficulties in media access control.

Question 25

Why is edge computing important for the Internet of Things?

Answer 25

Data generated by IoT devices is processed by the cloud; however, the physical distance between these devices and the cloud can cause latency. Edge computing allows some application processing to be performed by a small edge server positioned between the cloud and the user. Usually located closer to the user. Removes some of the workloads from the cloud and the user’s device causing a low latency communication.