Question and Answer Test: Computers and the Mobile Phone

Questions

1. Data packets have priority over voice signals over the network.

2. Data packets are inserted in the idle time between the voice segments on the existing cellular channels.

3. CDPD technology does not allow sending of data across channels used for voice segment transmission.

Q2. What does mobility mean in Data Communications?

1. The user can move around with his/her computer while transmitting/receiving data.

2. A connection to the cellular network can be made in any cell , but once the connection is established, the user must stay within that cell.

3. A connection to the cellular network can only be made in the "home" cell of the user.

Q3. In terms of Security , which technology is considered to be the best?

1. Cellular Digital Packet Data (CDPD).

2. Circuit Switched Cellular.

3. Propietary Wireless Data Networks.

Q4. What feature of the Reed-Solomon forward error correcting code makes it most suitable for ensuring CDPD network reliability?

1. It is based on group of bits (bytes)rather than individual bits.

2. It is mapping from a vector space of dimension m over a finite field K into a vector space of higher dimension over the same field.

3. It is repeating each information(data) bit 5 times.

Q5. Which CDPD network database stores information relating each subscriber to its network?

1. The Authentication Centre (AUC).

2. The Visitor Location Register (VLR).

3. The Home Location Register (HLR).

Q6. How many air-link channels does a Mobile data base station create between itself and a mobile end-user in order for a data transmission to take place?

1. One.

2. Two.

3. Three.

Q7. What is the scanning receiver, used to detect idle time, known as?

1. Sniffer.

2. Environmental Signal Power tracker.

3. Snoopy.

Q8. What is the speed of the actual throughput for a CDPD network?

1. 19.2 kbps.

2. 32.2 kbps.

3. 9.6 kbps.

Q9. How do Intermediate Systems (IS) handle mobility of end users?

1. They don't handle mobility.

2. They keep records of movements of all end users in a database held in each Intermediate System.

3. They use data held in MDBS data logs on end users currently in their domain to track end users.

Q10. Why is CDPD advantageous?

1. Very little new equipment is required to implement CDPD.

2. Existing voice channels performance is not affected by the addition of the CDPD technology.

3. CDPD is much more practical for people on the move.

4. CDPD is a very cost effective solution.

5. All of the above.

Answers

Back to Question 1.

A2. The answer is 2 : A connection to the cellular network can be made in any cell , but once the connection is established, the user must stay within that cell.
Reason:
During hand over between cells, the line is lost for about 400ms. If it is voice telecommunications this is undetectable but for data communication not only is detectable but delay is caused since the message will have to be sent again.

Back to Question 2.

A3. The answer is 1 : Cellular Digital Packet Data (CDPD).
Reason:
This is because CDPD uses Reed-Solomon forward error correcting-code which is very efficient and very reliable. Also the continuous checking from network databases on :

makes CDPD the most secure technology.

Back to Question 3.

A4. The answer is 1 : It is based on group of bits (bytes)rather than individual bits.
Reason:
Reed-Solomon is a coding system based on groups of bits--such as bytes-- rather than individual 0s and 1s. That feature makes Reed-Solomon codes particularly good at dealing with "bursts" of errors:Six consecutive bit errors, for example, can affect at most two bytes. Thus, even a double-error-correction version of a Reed-Solomon code can provide a comfortable safety factor. (Current implementations of Reed-Solomon codes in CD technology are able to cope with error bursts as long as 4000 consecutive bits.)

Back to Question 4.

A5. The answer is 3 : The Home Location Register (HLR).
Reason:
The Home Location Register (HLR) stores information relating the subscriber to its network. This includes information for each subscriber on subscription levels , supplementary services and the current or most recently used network and location area. The Authentication Centre (AUC) provides the information to authenticate subscribers using the network , in order to guard against possible fraud , stolen subsciber cards , or unpaid bills. The Visitor Location Register (VLR) stores information about subscription levels , supplementary services and location for a subscriber who is currently in, or has very recently been ,in that area. It may also record whether a subscriber is currently active , thus avoiding delay and unnecessary use of the network in trying to call a switched off terminal.

Back to Question 5.

A7. The answer is 2 : Two.
Reason:
In order to implement bi-directional communication ie: transmission and reception, two air link channels are required. The forward link channel is unique to each end user whereas the reverse channel is shared by a number of end users.

Back to Question 6.

A7. The answer is 1 : Sniffer.
Reason:
Your guess is as good as ours!!

Back to Question 7.

A8. The answer is 3 : 9.6 kbps.
Reason:
Although CDPD transmits digital packet data at 19.2 Kbps, the actual throughput is only 9.6 Kbps. This is due to the extra redundant data required in order to implement error checking, as well as sender/reciever addressing data (and packet number if using Datagram switching) required for each data packet.

Back to Question 8.

A9. The answer is 1 : They don't handle mobility.
Reason:
All mobility issues are handled by the Mobile Data Intermediate Systems and lower levels of the network hierarchy.

Back to Question 9.

A10. The answer is 5 : All of the above.
Reason:
See "Cellular Digital Packet Data: The answer to all mobile business individuals' problems?" article by Omar Iqbal.

Back to Question 10.

References

Vasilis Koudounas' 1st article named "Why Mobile Computing? Where can it be used?"

Omar Iqbal's 1st article named "Cellular Digital Packet Data (CDPD) : The answer to all mobile business individuals' problems?"

Vasilis Koudounas' 2nd article named "Cellular Digital Packet Data (CDPD) : What makes it reliable?"

Omar Iqbal's 2nd article named "Warning : Cellular communication may damage your health."