12. What are the drawbacks of walsh codes?
Walsh codes have the following drawbacks :
1. The codes do not have a single, narrow autocorrelation peak.
2. The spreading is not over the whole bandwidth; instead the energy is spread
over a number of discrete frequency components.
3. Although the full sequence cross correlation is identically zero, this does
not hold for a partial sequence cross correlation function. Thus advantage of
using orthogonal codes is lost.
4. Orthogonality is also affected by channel properties like multi path.
13. Explain radio environment in building.
Building penetration : Building penetration depends on the material used for
construction and architecture used. This varies building to building and is
based on building construction.
Building Height Effect : The signal strength is always higher at top floor and
generally floor gain height is about 2.7dB/floor which is not dependent on
Building Floor Reception : The signal isolation between floors in a multi floor
building is on the average about 20dB. Within a floor of 150 * 150 feet, the
propagation loss due to interior walls, depending on the wall materials is
about 20 dB between the strong and the weak areas.
14. List some advantages of GSM.
Here are some advantages of GSM :
1. GSM is mature, this maturity means a more stable network with robust
2. Less signal deterioration inside buildings.
3. Ability to use repeaters.
4. Talk time is generally higher in GSM phones due to pulse nature of
5. The availability of Subscriber Identity Modules allows users to switch
networks and handset at will.
6. GSM covers virtually all parts of world so international roaming is not a
15. What are the various types of numbers for network identity?
Various types of number for network identity are as follows :
1. MSISDN ( Mobile station ISDN) Number : It is international mobile subscriber
number which is normally called mobile number. It is unique worldwide.
2. MSRN ( Mobile Subscriber Routing Number) : MSRN is used during mobile
terminate trunk call to provide location of mobile subscriber.
3. HON ( Hand Over Number ) : HON is used for providing information required to
transfer call from one B?SC to another BSC or to another MSC.
4. ISMI ( International Mobile Subscriber Identity Number) : Purpose of ISMI is
for location update and authentication.
5. TMSI ( Temporary Mobile Subscriber Identity ) : TMSI is used instead of IMSI
to improve security efficiency of network.
6. IMEI : International Mobile Equipment Identity.