Wipro Limited Technical Interviews Question Bank continued from Part-1
Q. What is the difference between authorization and authentication, for example when you enter your card details while net banking?
Ans. A user is first authenticated, i.e. identity of the user is verified (valid bank card details). Then it proceeds to authorization where if the user has access rights then they are allowed to access the resources. For example, there are different account types and not all users are allowed to access all types of accounts.
Q. How is a call processed during roaming?
Ans. The subscriber details are provisioned in local VLR only when the subscriber is ON in that area. While in roaming, the MSC queries the local VLR. When the user details are not available there, it queries the HLR. Wherever the subscriber’s mobile equipment is ON, its sends request to the roaming VLR and the details are registered in that VLR also informing its home HLR about its updated location. So, when the MSC queries the HLR, after knowing its current location it forwards the call to other MSC where the user is already registered with the VLR hence completing the call flow.
Q. Does HLR store the mobile number of the subscribers?
Ans. No.
Q. What details/information is provisioned in HLR?
Ans. HLR contains data related to subscription and identification. For example, IMSI (International Mobile subscriber identity), VLR number, MSC number, NAM (Network Access Mode), subscription restriction, data related to authentication and ciphering like RAND etc.
Q. How is the postpaid and prepaid billing done?
Ans. Prepaid billing is online charging or real time charging. In prepaid charging, as the call is initiated a fixed amount is deducted from the balance (say charge for 3 minutes). If the call is terminated before 3 minutes, then the call is charged according to the plan and the rest amount is credited back in the balance within no time.
But this is not the case with the postpaid billing (offline charging). In postpaid billing, HLR generates CDR (Call Data Record) which contains the essential details of a processed call. The CDR is evaluated at the end of the month and the bill is calculated according to the plan of the user.
Q. What is CDR?
Ans. Call Data Record is a file maintained in HLR which stores the details of a call for example, dialing number, dialed number, duration of the call, time/date of call etc. , which is used in the postpaid billing.
Q. What are the latest technologies you are aware of?
Ans. LTE (Long Term Evolution), SDN (Software Defined Networking), NFV (Network Function Virtualization), Cloud.
Q. What is cloud computing?
Ans. Cloud computing, also on-demand computing, is a kind of Internet-based computing that provides shared resources and data to computers and other devices on demand.
Q. What is SDN?
Ans. Software defined network is managing networks using software in such a way that minimal changes are required to be done in the hardware in case of any fault or while implementing a new technology. It uses software, thus allowing network administrators to manage network services through abstraction of higher-level functionality.
Q. How has speed/data rate increased from 3G to 4G?
Ans. (i) Reduced number of blocks (BTS and BSC merge and become RNC) in the architecture of 4G reduces latency as compared to 3G.
(ii) OFDM is used for downlink which carries data on multiple subcarriers hence increasing the overall data rate.
Q. What is the difference between CDMA and GSM in layman language?
Ans. In case of CDMA, the users cannot switch phone as easily as in the case of GSM. In GSM, the customer information is stored in removable SIM cards, which is not the case with CDMA.