‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها

من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

GSM
1- Explain how to make a call from one cell phone to another (Yomna
wants to call Sara), and the hand off from one cell to another.
At first, we identify where the first and the second cell phone BS are according
to their locations, next the MSC connects the two callers to communicate. When
one of the callers changes its location, it moves to another BS and the MSC still
can connect the two callers together and that’s what we call Handoff.
Handoff: enables a call to proceed uninterrupted when the user moves from
one cell to another

2- What are the cellular Telephone system components?

A basic cellular system consists of
1- Mobile stations (MS)
2- Base stations (BS)
3- Mobile switching center (MSC) or telephone switching office (MTSO).
3- Explain adaptive power control?
As cellular mobile moves power seen at Bs changed so we use adaptive power
control to maintain it.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

4- Compare among cellular generations?

Generation 1G 2G 3G 4G 5G

Deployment 1970 1980 1990 2000 2020+

Bandwidth 2Kbps 14-64 Kbps 2 Mbps 200 Mbps 1Gbps+

Multiplexing FDMA TDMA/CDMA W-CDMA OFDMA OFDMA /

SDMA
Technologies Analog Digital Digital Digital Digital
Types of
System

Handoff Horizontal Horizontal Horizontal Horizontal / Horizontal /

Vertical Vertical
Internet service No- Narrowband Broadband Ultra- Wireless
Internet Broadband World Wide
Web
Applications Voice calls Voice calls Video High speed IOT
Only conferencing applications
short messages remote
mobile TV Dynamic control of
Information cars
GPS Access
Robots

medical
process
5- what are the cell types and explain cell splitting?
-Cell Types are:
1-Macro cell
2-Micro cell
3-Pico Cell
-Cell Splitting: as traffic Load increases in a cell to increase cannels designer
Tend to split Cell into smaller cells.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

‫?‪6- Explain the Channel allocation Techniques‬‬

‫)‪-fixed channel assignment Technique (less Ts‬‬
‫)‪-dynamic channel assignment Technique (largest Ts‬‬
‫)‪- Hybrid channel assignment Technique (improved‬‬

‫لو عايز تفهم السؤال ده‬

‫ھنفرض ان عندنا ‪ cluster‬فيه ‪cells 3‬والباند كله عبارة عن ‪9‬ترددات بس تعالوا نشوف‬
‫المقترحات لتوزيع الترددات دى على ال ‪cells‬واية المستخدم فعال فيهم‪....‬‬
‫(ال ‪cluster‬بيبقى فيه كل الترددات الى فى النظام بالكامل والترددات دى بتتوزع‬
‫على ال ‪cells‬الموجودة فى ال ‪cluster‬ده )‬
‫‪: Fixed Channel Assignment Teq‬اول اقتراح‬
‫وھو ان نقوم بتوزيع الترددات بالتساوى على ال‪ cells‬اى ان تكون لكل ‪cell‬الترددات الخاصة بها‬
‫ولكن المشكلة ھنا اذا حدث ضغط على ‪cell‬من ال ‪cells‬الثالثة ‪ .‬ھيبقى عندى ترددات غير‬
‫مستخدمة مع انى محتاج ليها‬
‫‪: Dynamic Channel Assignment Teq‬تانى اقتراح‬
‫وھو جعل الترددات جميعها متاحة الى ‪cell‬تحتاجها وھو حل رائع‬
‫ولكنه سيسبب طول فى مدة اجراء المكالمة ‪-‬ن النظام سوف يقوم بالبحث عن الترددات الشاغرة‬
‫العطاءھا للمتصل‬
‫‪: Hybrid Channel Assignment Teq‬ثالث اقترح‬
‫وھنا اخذنا مزايا ا‪-‬قتراحين معا فسوف نوزع بعض الترددات على ال ‪cells‬وجعلها ثابتة وسوف‬
‫نترك بعض الترددات متاحة للجميع‬
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

7- Explain the multipath fading? and how to overcome it?

> Multipath fading occurs in any environment where there is multipath
propagation, and the paths change for some reason.
>To overcome multipath fading, we use:
- Microscopic diversity and combining techniques
1- microscopic diversity techniques
a-Time diversity technique: Time diversity involves
transmitting the same information over multiple time slots or
frames. By transmitting redundant copies of the signal at
different instances in time, the receiver can combine these
copies to reduce the impact of fading or interference.
b-Frequency diversity technique: transmitting redundant
copies of the signal on different frequency bands.
c-Space diversity technique: It involves transmitting multiple
copies of the signal from different antennas or using multiple
receive antennas to capture the signal.
2- combining techniques
a-selective technique: choosing the best signal while receiving
and leaving the weak signal. It’s used in mobile due to simplicity.
b-maximal ratio technique: using micro processor in the mobile to amplify the
weak signal and amplify the good signal even more it’s a complicated technique
and costs but it provides me with the best fading reduction.
c-the equal gain technique: multiplying the received signal in the same
amplitude and amplify it without microprocessor but it’s useless.
- Frequency hopping
the carrier frequency of the transmitted signal is rapidly changed or "hopped"
over a set of predefined frequencies within a frequency band.
- Error correction
- Interleaving technique
The basic idea behind interleaving is to introduce a delay between consecutive
data packets during transmission. Instead of sending packets in a sequential
order, they are grouped and transmitted in a different order.
- adaptive power control
is to dynamically adjust the transmission power of a communication system
based on the common channel conditions.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

8- How to overcome shadow fading problem?

The Solution of this problem by using Macroscopic Diversity By selecting a BS
which is not shadowed when others are.
9- What is doppler shift?
Doppler shift is the change in frequency or wavelength of a wave that happens
when the wave source and the person listening or observing are moving relative
to each other.
10- explain co-channel interference and adjacent channel interference
and how to overcome it using channel management?
Co-channel interference is the interference between the cells that uses the
same frequency.
Adjacent channel interference is the interference that happen between
frequency and the next frequency due to the imperfection of band pass filter

To avoid that problem, we use a technique called channel management which

states that when we allocate the frequencies in the cell we won’t put Two
consecutive frequencies in the same cell.
11- Why Delay Spread (Time dispersion) happen and how to
overcome it?
Due to multipath fading
- To overcome this, we use delay equalizer
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

12- What problem Distance between MS and BS make and how to

overcome it?
- This makes Time alignment Problem
- To overcome this system should respond to this delay
13-Explain by drawing the GSM network architecture?

14-What the graphical representations, definitions, and the functions

of ME. SIM, BTS, BSC, MSC. HLR, VLR, OMC, EIR, AUC, BSC and GMSC
1- Mobile Equipment (ME): This refers to the physical phone itself.
2-Subscriber Identity Module (SIM): The SIM is a small smart card that is
inserted into the phone and carries information specific to the subscriber
3-Base Transceiver Station (BTS): The BTS is the Mobile Station’s access point to
the network.
4-Base Station Controller (BSC): The BSC controls multiple BTS’s. also functions
as a ’funneled”.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

5-Mobile Switching Center (MSC): The MSC is the heart of the GSM network. It
handles call routing, call setup, and basic switching functions.

6-Gateway Mobile Switching Center (GMSC): The GMSC functions as a gateway

between two networks.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

7-Home Location Register (HLR): The HLR is a large database that permanently
stores data about subscribers.
8-Visitor Location Register (VLR): The VLR is a database that contains similar
information as the HLR, but only for subscribers currently in its Location Area.

9-Equipment Identity Register (EIR): The EIR is a database that keeps tracks of
handsets on the network using the IMEI.
10-Authentication Center (AUC): is responsible for generating the necessary
crypto variables encryption on the network.

11-The operations and maintenance center (OMC): is connected to all

equipment in the switching system and to the BSC.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

15- Explain the configuration of Base Station Subsystem (BSS)?

-
Each base station in the cascade connects to another base station, forming a
chain-like structure. This allows for seamless handovers and better signal
distribution across the network.

The links between base stations form a closed loop, with each base station
connected to multiple neighboring base stations. This loop configuration helps
create redundancy.

all the base stations are directly connected to the central base station, forming a
star topology. This configuration allows for efficient management and control of
the network.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

16-List, in order of importance, the operational requirements of GSM?

1- High audio quality
2- Identical system in all countries
3- High degree of flexibility
4- integration with ISDN
5- Other security features
6- Easy to introduce the system
7- Low-cost infrastructure
17- Why, in actuality, are only 124 or even less channels used instead
of the total available 125 channels?
> Because the first channel is guard.
The bandwidth for the GSM system is 25 MHZ, which provides 125 carriers each
having a bandwidth of 200KHZ due to interference to other systems the first
carrier is not used thus reducing the number of carriers to 124.
18-Why is VLR regarded as a distributed HLR? What particulars about
mobile will you like to keep in the VLR database?
VLR is distributed HLR because it acts as a copy of HLR which contains.
more information about mobile location and used when the user moves from
cell area to another area.
Data stored in VLR are:
• The IMSI.
• The MSISDN
• The TMSI.
• ID of the current MSC.
19- state the main functions of (1) BTS (2) BSC (3) MSC/GMSC (4) OMC
1- Functions of BTS(Base Transceiver Station):
> Encodes, encrypts, multiplexes, modulates, and feeds the RF signals to the
antenna.
> Transcoding and rate adaptation.
> Each BTS serves a single cell.
> Time and frequency synchronization signals transmitted from BTS.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

2- Functions of BSC (Base Station Controller):

> Intercell handover.
> Power management of BTSs
> Controls frequency hopping
> Reallocation of frequencies among BTSs
3- Functions of MSC/GMSC: MOBILESWITCHING CENTER AND GATEWAY
SWITCHING CENTER
> paging
> Gateway to SMS.
> Handover management
> One MSC may interface several BSSs.
4- Functions of OMC: operations and maintenance center
> Supports for maintenance.
> X.25 interface.
> Alarm handling.
> Fault management.
> Performance management.
> Network status.
20- Explain White, black and gray identities with respect to IMEI?
> Whitelist: contains those IMEIs that are known to have been assigned to valid
MSs. (That means if an IMEI is not on the black list or on the gray list, then it is
considered good and is "on the white list".)
> Blacklist: contains IMEIs of mobiles that have been reported stolen.
> gray list: is a list of IMEIs that are to be monitored for suspicious activity.
21- List different logical channels and their associated functions?
Types of logical channel:
1- A- TCHs Channel: are intended to carry either encoded speech or user data.
divided into:
> Full rate TCH → (TCH/F)
> Half rate TCH →(TCH/H)
2- B- Control Channel: are intended to carry signaling or synchronization data.
Control Channel divided into:
> Broadcast Control Channel (BCCH).
> Common Control Channel (CCCH).
> Dedicated Control C channel (DCCM).
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

22- Name different types of Brust signals used in GSM. Justify the
utility of including the training sequence in the middle of the normal
burst. What is the reason for using TB?
Burst signal types:
1- Normal burst.
2-Synchronization burst.
3-Frequency correction burst.
4-Access burst.
5-Dummy burst
> The reason why the training sequence is placed in the middle is that the
channel is constantly changing.
(The training sequence is a known 26-bit pattern used by equalizer to create
channel model.)
> The reason of the tail bits they help the equalizer know the start and stop bit
pattern.
23- What are the limitations of 2G technology?
1- No data traffic
2-Averge rates of the order of Kbps
3-unsuitable for internet (packet switch cct)
4- Multiple standard (US, Europe)
5-Miss for global coverage
24- Discribe the stages for receiving a mobile call from a PSTN?
1-MSC dispatches the request to all base stations
2-mobile identification number is broadcast as a paging message over all FCC
through the service area
3-MS receives the paging message from BTS it is monitoring, it responds by
identifying itself over RCC
4-BTS conveys the handshake to the MSC
5-MSC instructs the BS to move to unused voice channel
6-BTS signals the MS to change over unused voice channel
7-A data message (alert) is transmitted over FVC to instruct the mobile to ring
8- While call in progress, MS calculated the power level MSC adjusting
transmitted power.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

25- Explain Frame, Multi-frame. Super-frame, and Hyper-frame for a

GSM network?
1- frame:
-Bit rate of the radio carrier is 270.833 Kbps
-Bit duration =1/270833=3.69 µsec
-One time slot =148 bits+8.25 guard bits=156.25 bits
-Time slot duration =156.25×3.69 µsec= 0.577 msec
-Frame duration=0.577x8= 4.615 msec
1- Multi-frame: Higher order frames called multi-frame consists of 26 frames
and have a duration of 120 ms (26 * 4.615 ms). This muti-frame consist of 26
TDMA frames.
2- Super frame: one super frame consists of 51 traffic multi-frames or 26 control
multi-frames and consist of 51 * 26 TDMA frames with total duration of 6.12 sec
(51 * 120 ms)
3- hyper frame: the highest order frame is called hyper frame and consists of
2.048 super frames or 2.715.648 frames (2048*51*26). The time duration of the
hyper framed is 3 hrs, 28 min and 52.76 sec (2.715.648*4.615 ms).
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

26- define Power control and what is the role of MS and BSC in
handover?
Power control: The BTS will adjust the transmitted power of each mobile
station to ensure that the received power is within a specified window.
-during call, the MS is continuously measuring transmission
quality of neighboring cells and reports these results to the BSC
through the BTS.
-The BSC, being responsible on supervising the cells Is responsible of handover
initiation.
27-Why do we need to make handover?
1- A handover due to transmission measuring results occurs when the signal
strength or Its quality Is too low, or the distance from the mobile station to the
BTS Is too great. The call Is then transferred to a neighboring cell.
2-A handover due to high traffic volume within the cell occurs when the
capacity of the cell Is exhausted, and the call Is transferred into a neighboring
cell which is less busy.
3-When necessary, a handover can be forced by the OMC٠due to maintenance
work in the cell.
28-Explain the types of handover?
1- Intra BSC Handover: When the cell to which the call will be handed over
belongs to the same BSC of the serving cell.
2-Inter BSC/ Intra MSC Handover: When the cell to which the call will be handed
over belongs to the different BSCs but to the same serving MSC.
3- Inter MSC: When the cell to which the call will be handed over belongs to the
different BSC and different MSC.
29-Explain how intra BSC handover happens?
1-The BSC decides from the power measurement reports that the call
must be handed over to another cell
2- The BSC checks the new cell and orders this cell to activate the TCH
3- The BSC orders the serving cell to send a message to the MS telling
the information of new TCH
4- The MS tunes to the new frequency and Sends handover access
burst
5- The new cell detects the handover 'burst and sends information
about the suitable timing advance to the MS
6- The MS sends complete message to the new cell
7- The new cell sends a message to the BSC that the handover is
successful
8- the BSC orders the old cell to release the TCH
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

30-Why do we need to update our location data?

To identify the location of the subscribers within the network so that any
incoming call goes directly to the called subscriber.
31-When do we update our location data?
1-When a mobile customer switches on his/her mobile station.
2-When a mobile customer changes his/her location Area.
3- at regular intervals after a mobile customer has not moved his/her mobile
station for some time
32- Explain with drawing the GSM area classifications?

33- Compare between Macro, Micro. and Pico cells?

 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

34-Explain the process of direct sequence CDMA system?

direct sequence CDMA system can be divided into three processes:
٠Signal Spreading
٠RF Transmission and Reception
٠Signal Recovery

35-Explain with drawing signal spreading?

The incoming digital speech signal is multiplied by a digital pseudo-noise (PN)
code through a process called bit stream multiplication.

35-Explain The key of CDMA?

1-Uses unique, digital PN codes to distinguish subscribers on tile same carrier.
2-Produces spread spectrum, noise-like, transmissions.
36-Explain the Strengths of CDMA?
1- increased system capacity
2-Cell sites can be larger
3-Enchanced RF Channel performance
4-Enhanced privacy due to digital coding of CDMA signals
5- Reduced interference from other sources
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

36-Explain Bit stream multiplication concepts?

Is the process where an input bit stream of information called b(t) is multiplied
by a pseudo-noise (PN) code called c(t) to produce a new output signal called
y(t)

37-Explain the channel layout and frequency bands of operation

(spread spectrum) of GSM?
-Band used for the uplink is 890 MHz to 915MHz (from MS to base station)
-for the downlink 935 MHz to 960MHz (from base station to MS)

38-Compare between FDD and TDD?

 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

39-Narate ‫؛‬he distinction between the following service areas: GSM,

PLMN, MSC, LA and cells?
1-Cell: A cell is the smallest radio coverage area in the network.
2-LA: is a group of cells

3-MSC/VLR: is made up of several،LA'S and is covered by one MSC.

4- PLMN: is a public land mobile network it’s a group of MSC/VLR services areas
and it’s the largest geographical service area served by one network operator
5-GSM: is geographic network areas it’s a collection of PLMNs in which you can
use one mobile station.
40-Explain spread spectrum techniques (FHSS and DSSS)?
-Frequency Hopping Spread Spectrum (FHSS): Rata signal is modulated with a
narrowband signal that hops from frequency band to frequency band, over time

-Direct Sequence Spread Spectrum (DSSS): Data signal is multiplied by a

spreading code, and resulting signal occupies a much higher frequency band
Spreading code is a pseudo-random sequence.

41-What are the types of codes used in CDMA?

1-Walsh code: orthogonal codes
2-Short PN code (16 bit): used to identify the BS and hence the cell
3- Long PN code (42-bit code): used to identify the Mobile station on reverse link
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

Problems
1- Find the spectral efficiency in bps/Hz of the GSM system assuming
channel band width BW to be 200 kHz and the channel data rate of
270.833 kbps. What will be the spectral efficiency if the BW is
decreased by 30%?
𝒄𝒉𝒂𝒏𝒏𝒆𝒍 𝒅𝒂𝒕𝒂 𝒓𝒂𝒕𝒆 𝟐𝟕𝟎.𝟖𝟑𝟑𝑲𝒃𝒑𝒔
𝒔𝒑𝒆𝒄𝒕𝒓𝒂𝒍 𝒆𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚 = = = 𝟏. 𝟑𝟓𝟒 𝒃𝒑𝒔/𝑯𝒛
𝒄𝒉𝒂𝒏𝒏𝒆𝒍 𝒃𝒂𝒏𝒅𝒘𝒊𝒅𝒕𝒉 𝟐𝟎𝟎𝑲𝑯𝒁
If the BW decreased by 30%:
𝟑𝟎
BW(New) = BW (old ) – [ BW(oId ) × ]=
𝟏𝟎𝟎
𝟑𝟎
200 KHz – [200 KHz × ] = 140 KHz
𝟏𝟎𝟎
𝟐𝟕𝟎.𝟖𝟑𝟑𝑲𝒃𝒑𝒔
spectral efficiency = = = 𝟏. 𝟗𝟑𝟒 𝒃𝒑𝒔/𝑯𝒛
𝟏𝟒𝟎𝑲𝑯𝒁
2- Find the spectral efficiency in bps/Hz of the GSM system assuming
channel band width BW to be 200 kHz and the channel data rate of
270.833 kbps. What will be the spectral efficiency if the BW is
increased by 50%?
𝒄𝒉𝒂𝒏𝒏𝒆𝒍 𝒅𝒂𝒕𝒂 𝒓𝒂𝒕𝒆 𝟐𝟕𝟎.𝟖𝟑𝟑𝑲𝒃𝒑𝒔
𝒔𝒑𝒆𝒄𝒕𝒓𝒂𝒍 𝒆𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚 = = = 𝟏. 𝟑𝟓𝟒 𝒃𝒑𝒔/𝑯𝒛
𝒄𝒉𝒂𝒏𝒏𝒆𝒍 𝒃𝒂𝒏𝒅𝒘𝒊𝒅𝒕𝒉 𝟐𝟎𝟎𝑲𝑯𝒁
If the BW increased by 50%?
𝟓𝟎
BW(New) = BW (old ) + [ BW(oId ) × ]=
𝟏𝟎𝟎
𝟓𝟎
200 KHz + [200 KHz × ] = 300 KHz
𝟏𝟎𝟎
𝟐𝟕𝟎.𝟖𝟑𝟑𝑲𝒃𝒑𝒔
spectral efficiency = = = 𝟎. 𝟗𝟎𝟐 𝒃𝒑𝒔/𝑯𝒛
𝟑𝟎𝟎𝑲𝑯𝒁
3- Assuming the hopping is at the frame rate in a GSM system,
compute the hopping rate. What happens to signal quality as the
hopping rate is reduced lo half or increased by a factor of Two?
The hopping rate is 216.7 hops/s. which corresponds to l / (frame duration)
= 1/ (4.1615 x 10-3).
> If the hopping rate is reduced to half the signal quality will be improved.
> If the hopping rate increased by factor of two this will be reducing the signal
quality.
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

‫‪4-‬‬

‫‪5-‬‬

‫‪6-‬‬
 ‫الي باللون االخضر امتحان ساعات واالصفر الميدترم بتاعنا واللبني اتكرر في ساعات وعندنا والرصاصي دي انا كتباها من‬
‫محاضرات ممكن تيجي وممكن ال والباقي اتكرر في امتحانات قديمة وكويزات وريبورتات‬

7-Consider global system for mobile which is a TDMA/FDD system

that uses 25 MHZ for the forward link which is broken into radio
channels of 200KHZ. If 8 speech channels are supported on a single
radio channel and if no guard band is assumed find the number of
simultaneous users that can be accommodated in GSM.
Solution: the number of simultaneous users that can be accommodated in GSM
is given as 25MHZ
𝟐𝟓𝑴𝑯𝒛
𝑵= = 𝟏𝟎𝟎𝟎
𝟐𝟎𝟎𝒌𝑯𝒛
𝟖
Thus, GSM can accommodate 1000 simultaneous users.
8- GSM System uses a TDMA/FDD system. The GSM system uses a
frame structure where each fram consist of 1 time slots and each time
slot contains 156.25 bits and data is transmitted at 270.833 Kbps in
the channel. Find:
1. Time duration of a hit
2. Time duration of a slot
3. Time duration of a frame and
4. How long must a user occupying a single slot wait between two
simultaneous transmissions?
Solution: The time duration of bit
𝟏 𝟏
𝑻𝒃 = = = 𝟑. 𝟔𝟗𝟐𝝁𝒔
𝑩𝒊𝒕𝑹𝒂𝒕𝒆 𝟐𝟕𝟎. 𝟖𝟑𝟑 × 𝟏𝟎𝟑
The time duration of a slot Tslot = 156.25× Tb = 0.577 ms
The time duration of frame Tf = 8 × Tslot = 4.615 ms
A user has to wait 4.615 ms, the arrival time of a new frame, for its next
transmission
9- If a normal GSM timeslot consists of 6 trailing bits 8.25 guard bits, 26 training
bits, and 2 traffic bursts of 58 bits of data, find: frame efficiency
A time slot has 6 + 8.25 + 26 + 2/58 – 156.25 bits.
A frame has 8 * 156.25 = 1250 bits/frame
The number of overhead bits per frame is given by
bOH= 8(6) + 8(8.25) + 8(26) = 322 bits
(1250- 322)
(𝟏𝟐𝟓𝟎−𝟑𝟐𝟐)
Frame efficiency𝜼𝒇 = = 𝟕𝟒. 𝟐𝟒%
𝟏𝟐𝟓𝟎