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Re: Frequency hopping
frequency hopping has two different types the first is the fast frequency hopping (FFH) which is used in spread spectrum tech. but it's usually used in militry application but commercial CDMA uses direct sequence spread spectrum instead, on the otherhand we have the second...
tdd vs tdma
dear pmonon;
TDD stands for time division duplix, which means that the mobile sends it's data in a specific time and recieve the data from the BTS in another time.
TDMA stands for time division multible access, which means that the mobiles share the same resources but in...
detect cell phone when off
Dear steve_rb;
the provided link is showing a trick that can be used to make the mobile work like a spyphone!!!!!????
so i dont think this has any thing to do with normal MS behaviour it's just a silly feature to attract customers not a GSM standard.
maybe it use...
auto registration signal
dear gied;
there is a feature which is called implicity detach which force the mobile to inform the system that it's going to turn off but this is only in of natural turn off so the system knows that the mbile will be out of duty and so it will not send it anymore...
simply WCDMA is the developed version of CDMA in order to be compatible with the requirements of the 3G system (UMTS) the requirements are as follow:
1- wide bandwidth==> increase the spreading bandwidth( 5MHZ) and increase the chip rate ( 3.84 chip per sec)
2-variable bit rate support==>use...
Re: GSM VS GPRS
look my friend here i will assume that you have the minimum knowledge about GSM, any way in GSM we used to have a very low bitrate about 13 kbps and we used a circuit switched tech. but after that user started to need some applications on thier mobiles on their mobiles so we...
ec/n0
we have the signal power=P
the chip rate=W
the user bit rate=R
the noise=PN
the interference= I (interference between users)
Ec=P/W
Io=I/W
N0=(I+PN)/W
Eb=P/R
actually i don't know what is Nt!!!!!
i hope this is what you are looking for
look you can think about it in the following way we have the data as one's and zero's each one of them represent a piece of information so if we lost any one of them we will actually lost important information.
what if we simply represent each piece of information with more than one bit so that...
it's simple if you already understand the nature of the CDMA technique and the fact that CDMA is an interference limited system, if you understand that so we may say that hard-blocking happens when we have no more physical channels free for any more subscribers in other words if all the walsh...
i believe that you are talking about the packet switched and circuit switched techniques and why we use the pcket switched with data and circuit switched in data.
actually in telecommunication the operator is looking for two things first cost and second QoS, and he want to have min. cost with...
I couldnt see your snapshot but if it says that this modem supports different datarates i think it means that the data coding or the data modulation is variable according to the used datarate because it's usual to have a variable datarate modem and as it mentioned in the manual so i think he...
Re: coding method
actually it's a big mistake to say that a specific type of line coding is the best because there is no berfect line coding scheme each one of them is used in a specific cases for example the return to zero is very usefull in VLSI because it has a spectral line at the clock...
Re: Questions about GSM
1.Why the bit rate in EDGE is Asymetric?
because of the fact that each user uses in the uplink time slots less than in the downlink so the uplink bitrate is less than downlink bitrate but if u r asking why they did that because usaualy users download data more than...
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