9:50 PM

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Explain 2G (GSM) optimization principles lect1

GSM optimization principles 

first in 2G optimization and the first  behavior we must study is  the IDLE Mode
the Main tasks for Mobile Station (MS) in idle Mode are :
1- PLMN selection.
2-Cell selection
3-Cell re-selection.
4- location updating.
5- Monitor the incoming page .
========================================================================

First : PLMN selection :

When the mobile is switched on it will select the registered PLMN in the mobile if there exists one. 
when you put the SIM card in the MS the MS will read the IMSI(The International Mobile Subscriber Identity) which already identified for the SIM card .
the IMSI = MCC+MNC+MSIN
MCC: mobile country code .
MNC: mobile network code .
MSIN: mobile subscriber identity .
EX: 602 + 02+ ******** 
Vodafone in Egypt MCC = 602 , and MNC =02 
every cell in the network has CGI(Cell Global identity) 
the CGI= MCC+MNC+LAC+CI
LAC: location area code 
CI: cell identity
- when the MS is powered on it will search in all frequencies about his HOME PLMN 
it will read the MCC and MNC and compare them with the stored before on the SIM card and also after camping on it the MS will compare the LAC currently with the old one which stored before deactivation .
                                 ---------------------------------------------------------------------------------------------
A MS need to make a PLMN selection in two cases :
1- it is the first time that the MS is powered on 
2- there is no coverage for its HOME PLMN 
                               -----------------------------------------------------------------------------------------------
there are two ways to do PLMN selection 
1- Manual PLMN selection Mode : 
In the manual mode the mobile will try to connect to the Home PLMN first. If it is unsuccessful then it will provide a list of available PLMN and ask the user to choose one. If the second chosen PLMN is not successful then the mobile will make an indication to the user to select another PLMN. Until the users selects another network a message “No Access” will be displayed. If there is no GSM or DCS coverage at all then a message “No Network” will be displayed 

 The  MS do frequency scan and search about a frequency which  belong to its HOME PLMN 
and if you chose another network this network will reject you .




2- Automatic PLMN selection Mode :
The priority will be :
-The last network on which you were registered
- Home PLMN
- Each PLMN stored in the SIM card in priority order
 -Other PLMN with signal level above -85 dBm in random order

- All other PLMN in decreasing signal strength
each PLMN stored in the SIM card with its priority order
the MS will Compare all MCC and MNC and will chose the frequency which belong to its HOME PLMN  




in automatic PLMN selection the MS scan all frequencies and chose the Frequency with 
SS(signal strength) > -85db  
so in the air ports and Hotels when you traveled to another country the other network try to make its frequencies better than -85db , but the MS will camp on the network which has agreements with its SIM card.

in the same country we called it National Roaming and the MCC will be the same but the different here is the MNC .
and if the MS camp on another PLMN due to bad coverage or any cause there is a timer = 30 minutes when it count the MS back again to search about its HOME PLMN

T= default = 30 minutes 
will be continue ( cell selection and re selection criteria)

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5:59 PM

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شرح كورس الGSM للمهندس وليد الصافوري بالعربي

شرح كورس ال GSM  للمهندس وليد الصافوري 
حمل شرح كورس المهندس وليد الصافوري بالعربي , شرح الكورس من السليدات بتاعة المهندس وليد الصافوري


الشرح زي ما كان بيتكلم المهندس وليد في الكورس بالظابط 

من افضل واروع الشخصيات :) وتقدر تستفيد منه في كل كلمة بيقولها وكفاية انك تحضر الكورس معاه وتقراه وتبقي تماام  
10:40 AM

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SIMPLE EXPLAIN OF THE LTE STRUCTURE








System Architecture Evolution (SAE) is the network architecture and designed to simplify the network to other IP based communications network. SAE uses an eNB and Access Gateway (aGW) and removes the RNC and SGSN from the equivalent 3G network architecture, to make a simpler mobile network. This allows the network to be built as an “All-IP” based network architecture. SAE also includes entities to allow full inter-working with other related wireless technology (WCDMA, WiMAX, WLAN, etc.)
In LTE the architecture is differente from 3G network architecture :
E-NB ----------> BTS+BSC (IN 2G)
           ----------> RNC + NODE-B (IN 3G)
HSS-------------> HLR+AUC
P-GW------------> GMSC+GGSN
S-GW ------------->MSC+SGSN
MME-----------------> VLR

NOTE THAT : cs and ps components be in one component based on(( OVER IP TECHNOLOGY )).

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LTE from GSM and UMTS


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E-NB Functions 
No RNC is provided anymore, The evolved Node Bs take over all radio management functionality.
 This will make radio management faster and hopefully the network , architecture simpler
RBS 6201 LTE BS MOTOROLA

-At TX OFDMA modulator
-At RX SC-FDMA demodulator
-channel coding (error correction and detection)
-radio frequency fuctions: 1- power amplifier 2-low noise amplifier
-segmentation
-ciphering and deciphering
-resources assignment
-channel deundancy schedule
-handover
-adaptive frequency function
-broadcatsting information
-paging

 RRM, Radio Bearer Control, Radio Admission Control,Connection Mobility Control, Scheduling for uplink and downlink,IP header compression and encryption of user data stream,Selection of an MME at UE attachment, Routing of user plane data towards SAE Gateway,Scheduling and transmission of paging messages originated from MME,Scheduling and transmission of broadcast information originated
from MME or O&M, Measurement and measurement reporting configuration

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MME FUNCTIONS :
 Distribution of paging messages to eNBs
 Security parameters Control
 Idle state mobility control attach and detach for user
 location area update

 Ciphering and integrity protection of NAS Signaling وThe non-access stratum (NAS) protocol terminated in the MME on the network side and at the UE on the terminal side performs functions such as EPS (evolved packet system) bearer management,authentication and security control
poling mode : this mode to connect all  MME S together 


Mobility Management. Provides the necessary support for subscriber mobility within the network, as well as support for mobility between networks. It keeps track of the current location of all subscribers including the states of their user device.

S-GW FUNCTIONS
serving gate way : serving of subscribers in there location
route users packets in the network and to packet gateway
serving the user in ip assignment
S-GW (Serving Gateway) is responsible for the transport, forwarding and route switch over of  LTE user data.


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PDN -GW FUNCTIONS
packet data network gateway interfaces the network to external networks , responsible ip versions it makes packet filtering .
manages the connection of mobile terminal and external packet data network. It allocates IP address for terminal and is responsible for the egress route of user service data. Besides, it works as the anchor point inside mobile network, and always keeps service continuity. when user moves.
HOME SUBSCRIBER SERVER(HSS)
Centrlal dta base for the home network , generate security parameters, delivery of user information to MME at initial registration ,policy and charging resources function, it manages user subscription and authentication information .


ZTE HSS


FINALLY :

ecns600 core network 

The Enterprise Core Network System 600 (eCNS600) is developed by Huawei for the enterprise Evolved Packet Core (EPC), and it applies only to the Long Term Evolution (LTE)/System Architecture Evolution (SAE) architecture. It integrates the subscriber management functions of the SAE-HSS, the Mobility Management Entity (MME) functions, and the Serving Gateway (S-GW)/PDN Gateway (P-GW) and Policy and Charging Rules Function (PCRF) functions. The eCNS600 is operated and maintained in a centralized manner.




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5:29 PM

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شرح كباين موتورولا للمهندس احمد شوقي



بسم الله الرحمن الرحيم 


انا اخوكم المهندس احمد هحاول فى البدايه اقولكم مكونات كباين موتورلا

فى البدايه فى نوعين من الكباين horizon 1 
ودى قديمه جدا ونادر لما بتلاقيها فى سيتات فى منها بس قليل اوى 
والنوع التانى اللى هو horizon 2
وده زى اللى فى الصورة وبيتكون من اللى على اليمين 
كارت اسمه h2sc
وده عباره عن البروسيسور بتاع الكابينه والكارت اللى جمبه ده
 فى الصورة بس فى الغالب بيكون كارت واحد بس فى الكابينه واللى بعده ده كارت الالارمات الداخليه بتاعت الكابينه بتظهر عليه بعد كده فى الكروت اللى بتشيل المكالمات وهى نوعين اول حاجه اسمها
gsm 900
وده زى اللى فى الصورة والنوع التانى
بيكون DCS 1800
وطبعا الاختلاف بيكون فى الباند بتاعتنا وغالبا كل نوع بيكون فى كابينه غير التانيه يعنى ال
gsm 900
فى كابينه مثلا والتانى فى كابينه غيرها فى نفس السيتوهما دول بس النوعين اللى موجودين عندنا مفيش انواع كتيره زى هواوى بعد كده فى اللى تحتهم دى فانات عشان تهوى ع الكروتوا للى على الشمال خالص دول ال
power supply
وفى حاجه اسمها circuit breaker
ودى عباره عن المفاتيح بتاعت البور بتاعت كل الكروت اللى عندنا دى يعنى اللى بتطفيها وتشغلها منهم





دى صورة لدوبلكسرات من فوق من كابينه فى الشكل ده كل راديو متوصل بدوبلكسر بس عاده مش كل راديو بيتوصل بدوبلكسر
وفى كارت اسمه HCU
وده وظيفته انه يوصل اتنين راديو على دوبلكسر واحد يعنى حاجه زى المشترك كده



horizon 2
بس هنا فى الصورة الكابينه من فوقالحاجات اللى على اليمين دى الى مكتوب عليها
tx blocks 



دى عباره عن حاجه اسمها الدوبلكسر  وده بيتوصل بيه الجمبر اللى هو جاى من الفيدر اللى جاى من الانتينا ووظيفه الدوبلكسر ده انه بيختار افضل مسار للاشاره يعنى مثلا بيشوف الراديو
(gsm 900 or dcs 1800)
وعندنا هنا اسمهم راديو بيشوف الراديو الفاضى اللى مش مشغول عشان يتحمل عليه المكالمه وبيتوصل الدوبلكسر ده
بكارت ورا كده اسمه كارت السيرف
ووظيفه الكارت ده انه بيعمل فيلتر للاشاره  بياخد الاشارة يظبطها ويبعتها تانى وبعدين بيتوصل الدوبلكسر بالرداوى بتاعتناوفى حاجه ع الشمال مكان الكارت اللى فى النص اللى فيه فتحات ده
بيكون متوصل مكانه كارته الBIB
وبيتوصل فيها كابل ال BIB
وده اللى بينقل الترافيك
بتاع الكابينه كله لل DDF


اخوكم المهندس أحمد شوقى

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5:21 PM

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CDMA / UMTS RF Interview Questions 4

1. What are the RRC states?
There are 4 RRC States: Cell_DCH, Cell_FACH, URA_PCH and Cell_PCH.

URA = UTRAN Registration Area.
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2. What are transparent mode, acknowledged mode and unacknowledged mode?
· Transparent mode corresponds to the lowest service of the RLC layer, no controls and no
detection of missing data.
· Unacknowledged mode offers the possibility of segment and concatenate of data but no
error correction or retransmission therefore no guarantee of delivery.
· Acknowledged mode offers, in addition to UM mode functions, acknowledgement of
transmission, flow control, error correction and retransmission.

3. Which layer(s) perform ciphering function?
RRC – for acknowledged mode (AM) and unacknowledged mode (UM).
MAC – for transparent mode (TM).

4. What is OVSF?
Orthogonal Variable Spreading Factor.

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5. How many OVSF code spaces are available?
· Total OVSF codes = 256.
· Reserved: 1 SF64 for S-CCPCH, 1 SF256 for CPICH, P-CCPCH, PICH and AICH each.
· Total available code space = 256 – 4 (1 SF64) – 4 (4 SF256) = 248.

6. Can code space limit the cell capacity?
Yes, cell capacity can be hard-limited by code space. Take CS-12.2k for example:
· A CS-12.2k bearer needs 1 SF128 code.
· Total available codes for CS-12.2k = 128 – 2 (1 SF64) – 2 (4 SF256) = 124.
· Consider soft-handover factor of 1.8: 124 / 1.8 = 68 uers/cell.

7. Can a user have OVSF code as “1111”?
No, because “1111…” (256 times) is used by CPICH.

8. What are the symbol rates (bits per symbol) for BPSK, QPSK, 8PSK and 16QAM?
· BPSK: 
.

· QPSK:
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· 8PSK:


· 16QAM: 


9. Briefly describe UMTS frame structure.
· UMTS frame duration = 10ms.
· Each frame is divided into 15 timeslots.
· Each timeslot is divided into 2560 chips.
· Therefore 2560 chips/TS * 15 TS/frame * (1000ms/10ms) frame/sec = 3,840,000
chip/sec.

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10. What is cell selection criterion?
Cell selection is based on:
· Qmean: the average SIR of the target cell.
· Qmin: minimum required SIR.
· Pcompensation: a correction value for difference UE classes.
S = Qmean - Qmin - Pcompensation
· If S>0 then the cell is a valid candidate.
· A UE will camp on the cell with the highest S.

11. Briefly describe Capacity Management and its functions:
Capacity Management is responsible for the control of the load in the cell. It consists of 3
main functions:
· Dedicated Monitored Resource Handling: tracks utilization of critical resources of the
system.
· Admission Control: accepts/refuses admission requests based on the current load on the
dedicated monitored resources and the characteristics of the request
· Congestion Control: detects/resolves overload situations

12. What are the major 4 KPIs in propagation model tuning and typical acceptable values?
The 4 KPIs are standard deviation error, root mean square error, mean error and correlation
coefficient. The typical acceptable values are:
· Standard deviation error: the smaller the better, usually 7 to 9dB.
· Mean error: the smaller the better, usually 2 to3.
· Root mean square error: the smaller the better, usually
· Correlation coefficient: the larger the better, usually 70% to 90%.

13. What is the minimum number of bins required for a certain propagation model?
The more bins the more likely to come up with a good model. Usually a minimum of 2,000
bines is considered acceptable, but sometimes as low as 500 bins may be accepted.
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14. How many scrambling codes are there?
There are 512 scrambling codes in the downlink and 16,777,216 codes in the uplink.

15. How many scrambling code groups are there for downlink?
There are 64 code groups, each group has 8 scrambling codes.

16. Can we assign same scrambling codes to sister sectors (sectors on same site)?
No, because scrambling code on the downlink is used for cell identity. As a requirement,
scrambling codes have to maintain a safe separation to avoid interference.

17. Are scrambling codes orthogonal?
No, scrambling codes are not orthogonal since they are not synchronized at each receiver.
They are pseudo random sequences of codes.

18. Can we assign scrambling codes 1, 2 and 3 to sister sectors?
Yes.

19. In IS-95 we have a PN reuse factor (PN step size) and therefore cannot use all 512 PN
codes, why isn’t it necessary for UMTS scrambling codes?
Because IS-95 is a synchronized network, different PN codes have the same code sequence
with a time shift, therefore we need to maintain a certain PN step size to avoid multi-path
problem. For example, if two sectors in the neighborhood have a small PN separation then
signal arriving from cell A may run into the time domain of cell B, causing interference.
UMTS, on the other hand, is not a synchronized network and all scrambling codes are
mutually orthogonal so no need to maintain a step size.
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20. What are coverage thresholds in your UMTS design and why?
The coverage thresholds are based on UE sensitivity, fading and penetration loss. Assuming
UE sensitivity of -110dBm, fade margin of 5dB:
· Outdoor: -110dBm sensitivity + 5dB fade margin = -105dBm.
· In-vehicle: -110dBm + 5dB + 8dB in-vehicle penetration loss = -97dBm.
· In-building: -110dBm + 5dB + 15dB in-building penetration loss = -90dBm.

21. What is the Ec/Io target in your design?
The Ec/Io target typically is between -12 to -14dB. However, if a network is designed for
data then the Ec/Io target could go higher to around -10dB because server dominance is more
critical for a data network – since there isn’t software in the downlink.