Homework SourseWhat is the main difference between the First and the Second
Solution
2.First Generation Networks
These are based on analog cellular networks
The ability to transfer calls from one site to the next as the user travelled between cells during a conversation.
In a cellular system, a signal between a base station (cell site) and a terminal (phone) only need be strong enough to reach between the two, so the same channel can be used simultaneously for separate conversations in different cells.
The system expanded and neared capacity, the ability to reduce transmission power allowed new cells to be added, resulting in more, smaller cells and thus more capacity.
There is no encryption of calls in first generation
Second generation cellular networks
The \'second generation\' (2G) mobile phone systems emerged, primarily using the GSM standard.
These are also known as digital networks.
The introduction of advanced and fast phone-to-network signaling.
The second generation introduced a new variant to communication, as SMS text messaging became possible, initially on GSM networks and eventually on all digital networks.
One benefits of 2G were Digital signals require consume less battery power, so it helps mobile batteries to last long. Digital coding improves the voice clarity and reduces noise in the line. Digital signals are considered environment friendly.
Digital encryption has provided secrecy and safety to the data and voice calls.
It can be used for services such as Wireless Application Protocol (WAP) access, Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access.
3.list types of wireless fading in time and frequency domains
fading in time
Frequency Selective Fading
If the channel possesses a constant-gain and linear phase response over a bandwidth that is
smaller than the bandwidth of transmitted signal, then the channel creates frequency selective
fading on the received signal. Under such conditions, the channel impulse response has a multipath
delay spread which is greater than the reciprocal bandwidth of the transmitted message
waveform.
Flat fading
If the mobile radio channel has a constant gain and linear phase response over a bandwidth
which is greater than the bandwidth of the transmitted signal, then the received signal will
undergo flat fading. This type of fading is historically the most common type of fading described
in the technical literature. In flat fading, the multipath structure of the channel is such that the
spectral characteristics of the transmitted signal are preserved at the receiver. However the
strength of the received signal changes with time, due to fluctuations in the gain of the channel
caused by multipath.
1. Rapid changes in signal strength over a small travel distance or time interval.
2. Random frequency modulation due to varying Doppler shifts on different multipath
signals.
3. Time dispersion or echoes caused by multipath propagation delays.
Frequency domain
Frequency domain is spoken of in the singular, there are a number of different mathematical transforms which are used to analyze time domain functions and are referred to as \"frequency domain\" methods. These are the most common transforms, and the fields in which they are used:
Fourier series have repetitive signals, oscillating systems
Fourier transform have nonrepetitive signals, transients
Laplace transform have electronic circuits and control systems
Z transform have discrete signals, digital signal processing
Wavelet transform have image analysis, data compression
