Mobile Communication Systems
Content
signal processing in gsm - r528
speech coder
mcom imp
module 1: fdma, tdma, sdma difference, frequency reuse, channel assessment str
ategies, s/I ratio nd cluster size n, umbrella cell concept, cell dragging nd
dwell time, nd numericals(imp.)
modules 2: gsm architecture, gsm channels, authentication in gsm, services nd
features, signal processing in gsm nd interleaving, gprs architecture, forward
wcdma channels
module 3: imt 2000/ umts architecture, handoff in 1g nd 3g, power control in 3g
module 4 nd module 5 just basic concept need to study.
module 6: factors effecting small scale fading, rake receivee, doppler spread (
numerical) , 2 ray ground refraction model, knife diffraction model, numericals
( jitne bhi hai utne imp. hai) .
Code Division Multiple Access (CDMA) uses different digital codes on the same fr
equency. Like a comb with teeth missing, only the matching teeth missing comb wi
ll receive signals. This way many users can use the same frequency simultaneousl
y. Doesn't extent forever because too many signals make it look like noise, even
to a correct receiver.
Frequency Division Multiple Access (FDMA) is used on analog phones where every p
hone needs a channel for no interference. It is also used on CDMA & TDMA service
s to get more users service. This is why digital is so popular; More users per c
hannel.
Time Division Multiple Access (TDMA) uses time slots in a given channel for diff
erent users. All start counting at the start pulse, and use either the first, se
cond, third etc. time slot for their service. When all the time slots are in use
, the phone is directed to a different frequency (FDMA) to get a time slot there
.
Space Division Multiple Access (SDMA) is how cell phones actually work. Small ce
lls are set up, according to predicted use, and certain frequencies are assigned
to that cell. Surrounding cells are assigned different frequencies. When you ge
t a couple of cells away from the same frequency cell, that set of channels can
be used again. This way, a frequency can be used over and over. The problems occ
ur when two many customers are using cell phones and enter a cell from different
directions. When the cell tries to find a new frequency to switch to, sometimes
there anen't any available, and the call is dropped.
speech coder
mcom imp
module 1: fdma, tdma, sdma difference, frequency reuse, channel assessment str
ategies, s/I ratio nd cluster size n, umbrella cell concept, cell dragging nd
dwell time, nd numericals(imp.)
modules 2: gsm architecture, gsm channels, authentication in gsm, services nd
features, signal processing in gsm nd interleaving, gprs architecture, forward
wcdma channels
module 3: imt 2000/ umts architecture, handoff in 1g nd 3g, power control in 3g
module 4 nd module 5 just basic concept need to study.
module 6: factors effecting small scale fading, rake receivee, doppler spread (
numerical) , 2 ray ground refraction model, knife diffraction model, numericals
( jitne bhi hai utne imp. hai) .
Code Division Multiple Access (CDMA) uses different digital codes on the same fr
equency. Like a comb with teeth missing, only the matching teeth missing comb wi
ll receive signals. This way many users can use the same frequency simultaneousl
y. Doesn't extent forever because too many signals make it look like noise, even
to a correct receiver.
Frequency Division Multiple Access (FDMA) is used on analog phones where every p
hone needs a channel for no interference. It is also used on CDMA & TDMA service
s to get more users service. This is why digital is so popular; More users per c
hannel.
Time Division Multiple Access (TDMA) uses time slots in a given channel for diff
erent users. All start counting at the start pulse, and use either the first, se
cond, third etc. time slot for their service. When all the time slots are in use
, the phone is directed to a different frequency (FDMA) to get a time slot there
.
Space Division Multiple Access (SDMA) is how cell phones actually work. Small ce
lls are set up, according to predicted use, and certain frequencies are assigned
to that cell. Surrounding cells are assigned different frequencies. When you ge
t a couple of cells away from the same frequency cell, that set of channels can
be used again. This way, a frequency can be used over and over. The problems occ
ur when two many customers are using cell phones and enter a cell from different
directions. When the cell tries to find a new frequency to switch to, sometimes
there anen't any available, and the call is dropped.
