LAPD protocol

All messages sent on the A-bis interface use the LAPD protocol that enables reliable transmission of information. LAPD provides two kinds of transfer modes: Unacknowledged info transfer with no guarantee that the information frame is successfully delivered to the addressee, and acknowledged information transfer, where each signal is acknowledged, and the system makes sure that the frame has reached the destination successfully. Only measurement reports use unacknowledged information transfer.
Frame Structure and Data Links
A flag, 01111110 (h'7E), delimits a frame. The one flag is enough between consecutive frames. The receiving entity looks for the flag 01111110 to synchronize on the start of a frame.

TEI and SAPI are used to access the right entity and right function at the receiving end.
SAPI
is the address used to access different functions, such as TRXC, CF and Layer 2 management procedures, within one physical entity. The CF (Central Function) link is used in RBS 2000 for common management functions for the TG, for example BTS software download.



TEI
is the address used to access different physical entities such as an individual TRX for radio signaling.

Two data link types are defined for each TEI. The data link types and their corresponding SAPI are:
SAPI=0
is used for the Radio Signaling Link (RSL). This link is used for supporting traffic management procedures mainly for circuit switched traffic. Signalling on Packet Data Channels (PDCH) is not carried by the RSL link. One link is required per TRX defined.

SAPI=62
is used for the Operations & Maintenance Link (OML). This link is used for supporting network TRXC management procedures.

The physical entities (TRX) that BSC communicates with at the BTS, via data links, are referred to as Terminal Equipment. A TEI/SAPI pair, unique within each physical connection identifies each data link. Each physical connection can support a number of data links.
Each TRX have one OML and one RSL signaling link. Additionally there is a CF signalling link to the DX function in the RBS2000. These links use the LAPD protocol:
  • The CF link is identified by the TEI value (configurable) and SAPI=62.
  • The OML link is identified by the TEI value for the TRX and SAPI=62.
  • The RSL link is identified by the TEI value for the TRX and SAPI=0.
  • The TRX TEI value is defined by the TRX position in the RBS cabinet.
The LAPD concentrator receives messages from several TRXs and sends these messages on one 64 kbit/s Abis time slot to BSC. The LAPD concentrator also receives messages on this Abis time slot from the BSC and distributes them to the TRXs.
Without LAPD Concentration and LAPD Multiplexing each 64 Kbits/s A-bis time slot can support signalling for only one TRX.
With LAPD Concentration each 64 Kbits/s A-bis time slot can support signalling for up to four TRXs. The allocation of bandwidth between the different TRXs sharing a 64 kbit/s A-bis time slot is dynamic: the concentration is implemented as separately addressed messages which are sent over the common path. This means both transmission delays are minimized - LAPD Concentration is superior to LAPD Multiplexing when it comes to delays and thoughput performance.


GSM PHASES


In the late 1980s, the groups involved in developing the GSM standard realized that within the given time-frame they could not complete the specifications for the entire range of GSM services and features as originally planned. Because of this, it was decided that GSM would be released in phases with phase 1 consisting of a limited set of services and features. Each new phase builds on the services offered by existing phases.


Phase 1
Phase 1 contains the most common services including:
·         Voice telephony
·         International roaming
·         Basic fax/data services (up to 9.6 kbits/s)
·         Call forwarding
·         Call barring
·         Short Message Service (SMS)
Phase 1 also incorporated features such as ciphering and Subscriber Identity Module (SIM) cards. Phase 1 specifications were then closed and cannot be modified.

Phase 2
Additional features were introduced in GSM phase 2 including:
·         Advice of charge
·         Calling line identification
·         Call waiting
·         Call hold
·         Conference calling
·         Closed user groups
·         Additional data communications capabilities

Phase 2+
The standardization groups have already defined the next phase, 2+. This program covers multiple subscriber numbers and a variety of business oriented features. Some of the enhancements offered by Phase 2+ include:

·         Multiple service profiles
·         Private numbering plans
·         Access to Centrex services
·         Interworking with GSM 1800, GSM 1900 and the Digital

Enhanced Cordless Telecommunications (DECT) standard Priorities and time schedules for new features and functions depend primarily on the interest shown by operating companies and manufacturers and technical developments in related areas.

Phase 2++ This phase includes sophisticated enhancements to the radio interface including:

·         Enhanced Datarates for Global Evolution (EDGE), a new modulation method which increases capacity on the air interface.
·         Customized Application for Mobile Enhanced Logic (CAMEL), a standard, governing IN service access while roaming internationally.
·         High Speed Circuit Switched Data (HSCSD), a method of delivering higher data rates per subscriber by allocating an increased number of time-slots per call.

Types of Alarm

TGC FAULT No active TGC application exists in the Transceiver Group.

PERMANENT FAULT A managed object is classified as being permanently faulty when fault situations have occurred, and have been cleared, a certain number of times within a certain period of time. Manual intervention is required to bring such equipment back into operation.

LOCAL MODE The BTS equipment is in Local Mode or the BTS equipment has changed from Local to Remote Mode and a fault exists in the communication link between the BSC and the BTS. Communication between the BSC and the BTS is not possible.

LMT INTERVENTION Local maintenance activities are being performed in the BTS.

LOOP TEST FAILED Test of the traffic carrying capabilities of the TS has failed.

BTS INTERNAL There is a fault internal to the BTS.

MAINS FAILURE There is a fault in the power supply to the BTS or one or more items of equipment within the BTS. Battery backup (where available) is in use. Escalation may occur if corrective action is not  taken.

BTS EXTERNAL There is a fault external to the BTS.

OML FAULT There is a fault in the communications link between the BSC and BTS.

ABIS PATH UNAVAIL No transmission device exists between the BSC and BTS.

CON QUEUE CONGESTION At least one of the LAPD Concentrator concentration outlet queues has reached an unacceptable filling level.

TS SYNC FAULT Synchronization lost on uplink or downlink TRA or PCU channels.

FORLOPP RELEASE A fault has occurred within the BSC software leading to a Forlopp release. Automatic recovery procedures are taking place. Report to your Ericsson Support Office. Alternatively, this alarm is issued as an advisory following a command ordered Forlopp release of a TG. In either case, the alarm is automatically ceased following successful recovery.

OPERATOR CONDITION A condition has arisen due to operator intervention.

How to calculate Peak Data Rate in LTE


The Peak Data rate of LTE is about 400Mbps?   It’s in a simple way to calculate date rate in LTE.

First: Assume That 20 MHz channel bandwidth, normal CP, 64QAM  and  4x4 MIMO technology are used.

Second: Calculate the number of resource elements (RE) in a subframe with 20 MHz channel bandwidth:
12 subcarriers x 7 OFDMA symbols x 100 resource blocks x 2 slots= 16800 REs per subframe. Each RE can carry a modulation symbol.

Third:  Assume 64 QAM modulation and no coding, one modulation symbol will carry 6 bits.
The total bits in a subframe (1ms) over 20 MHz channel is 16800 modulation symbols x 6 bits / modulation symbol = 100800 bits. So the data rate is 100800 bits / 1 ms = 100.8 Mbps.

Fourth:  with 4x4 MIMO, the Peak Data rate goes up to 100.8 Mbps x 4 = 403 Mbps.


EPG on Juniper

          

Based on the Juniper M320 or M120 router, the EPG supports Physical Interface Cards (PICs) of the following types:
·         EPG services PIC: All EPG application software entities run on the EPG services PIC. These entities consist of Globe Session Controller (GSC), SGW Session Controller (SSC) and PGW Session Controller (PSC) for Control Plane, and Packet Processor (PP) and L2TP Packet Processor (TPP) for User Plane. The EPG services PIC is PB-GGSN3 Services PIC.
·         Network interface PIC: The network interface PIC provides 1GE or 10GE Ethernet connectivity for the EPG.
·         Standard services PIC: the standard services PIC runs platform-generic services, such as encapsulation and decapsulation of user payload into Generic Routing Encapsulation (GRE) or IPsec tunnels.
For EPG on Juniper, the following Network Interface PICs are supported:
·         2-Port Gigabit Ethernet  PIC
·         4-Port Gigabit Ethernet PIC
·         8-Port Gigabit Ethernet PIC
·         10-Port Gigabit Ethernet PIC
·         1-Port 10Gigabit Ethernet PIC
Note: The 10-Port Gigabit Ethernet PIC is only used by the EPG on M320 router.
Both M120 and M320 routers contain 4 and 8 Flexible PIC Concentrators (FPCs) respectively, which are used for the PIU container installation. In addition, two compact FPC (cFPC) slots are available on the M120 router for transport purposes only.
A single FPC or a cFPC slot in the EPG on M120 router has a maximum throughput of 10 Gbps full duplex.  A single FPC slot on the M320 router has a maximum throughput of 16 Gbps or 20 Gbps full duplex. 

EPG- Evolved Packet Gateway


The EPG combines the GGSN, SGW and PGW functions in one physical node. In addition, the evolved platform adaptation layer supports the EPG application running on both operating systems: Junos OS (the OS of Juniper M series routers) and IPOS (the OS of Smart Services Router), 
The EPG is available on different hardware platforms:
·         Juniper (M320, M120)
·         Smart Services Router (SSR 8020)


The EPG based on Juniper hardware is simply called EPG on Juniper and the EPG based on SSR hardware is respectively called EPG on SSR. In the EIN documents, these terms are used to distinguish between these hardware platforms. If the hardware platform does not matter, the EPG term covers all possible EPG configurations.
The EPG on SSR has an increased capacity, up to 10 times greater than the EPG on Juniper. Therefore, the EPG on SSR has a big impact on the PS core network, and this needs to be sustained in terms of capacity from the other PS network elements and transmission systems.

The EPG on SSR is not a product designed only for high capacity networks. Its scalable configuration suits it perfectly for small and medium networks with potential for further extensions.
The EPG can be ordered and deployed in the following deployment modes for single and combined functions:
·         GGSN only functionality
·         PGW only functionality
·         SGW only functionality (applicable only to EPG on SSR)
·         Combined SGW and PGW
·         Combined GGSN and SGW and PGW

RAN OSS - Technical Certification

Ericsson - RAN OSS Radio Access Networks - Technical Certification overview
RAN OSS
Knowledge objective, the candidate should be able to identify and describe:
The role of OSS in Ericsson Business Support System, the products, functionalities and features: OSS-RC, ENIQ Event, ENIQ Statistics, SON, ENM, etc. Main advantages/values as well as impact on RAN performance and OPEX reduction.

Importance of OSS
Ericsson Network Manager
Total Network Performance
The Importance of OSS in Self Organizing Networks
Key SON Features for the Mobile Domain
SON Overview
SON detailed functionality
SON based GSM Spectrum Management
OSS Architecture Overview
OSS in Modern Networks  
OSS-RC Overview (WBL)
OSS-RC Applications Overview -
OSS-RC Features and Roadmap (Video)
OSS-RC Functionality for LTE (Centra) 

Ericsson RAN Radio Access Networks - Associate Technical Certification

RAN Fundamentals

Knowledge objective, within this radio technical competence area the candidate should be able to identify and describe the followings:
- The general RAN architecture: Nodes, UE categories, RAN standards, etc.
- Radio design principles: Dimensioning, link budget for radio coverage, multipath propagation, path loss predictions, propagation models and tuning, traffic models, etc
- Air interface principles: Radio channel concept, modulations, spectral efficiency, FDD / TDD, transmission and reception, multiplex access technique principles, mobile technology differences, frequency, voice coding, basic antenna system, dB, dBm, dBi, etc.
- Signaling, protocols and layers: Radio messages, layers, interaction, basic protocols, etc.
- Radio network basic functionalities: mobility, idle mode, call set-up, radio resource mgmt, etc.
- RAN performance: Accessibility, retain ability, integrity, latency and throughput, counter & KPI’s, energy consumption reduction, impact of quality of service, etc.
- RAN lifecycle stages (design, optimization, integration and installation, etc)

     Access Networks an Overview 
     Networking Basics, an Overview 
     Ethernet Standards 
     LTE Fundamentals 
     LTE Radio Interface
     LTE KPIs and Acceptance 
     LTE Network Design Overview 
     LTE Protocols and Procedures 
     LTE Air interface 

LTE  RAN 
Knowledge objective, the candidate should be able to identify and describe:
The fundamental technology and characteristics of LTE RAN, the products & solutions, functionalities and features. Channel structure, bearer concept, network architecture and interfaces, radio planning principles (capacity, limitations, connected users), radio units and their functionality, SW features such as: LTE advanced, voice in LTE, IRAT mobility, QoS handling, etc. LTE introduction in legacy networks FDD vs. TDD. Main advantages/values, as well as impacts on RAN performance.

         LTE Fundamentals 
         LTE/SAE in a Nutshell
         LTE /SAE System Overview
         LTE/EPC Overview 
         LTE Features and Functionality 
          LTE Air Interface 
          LTE Product Strategy 
          Ericsson´s LTE Performance Advantage
          Coverage and Capacity in LTE 
         LTE Shared Network Solutions incl Transport options 
         LTE Multi-Layer Antenna Solutions & Capacity
          LTE RAN Voice Evolution
          LTE Load and Capacity Evolution

WCDMA RAN

Knowledge objective, the candidate should be able to identify and describe:
The fundamental technology and characteristics of WCDMA RAN, the products & solution, functionalities and features. Channel structure, bearer principles, network architecture and interfaces, planning principles (capacity, limitations, interference reduction, robustness, spectrum load), radio units and their functionality, SW features such as: HSPA/MBB functionality, QoS, Smartphone related functionality, and  mobility, etc. Main advantages/values, as well as impacts on RAN performance.
WCDMA Release Overviews 
Mobile Broadband - Enhanced Uplink Evolution 
Secure Smartphone Business 
HSPA Smartphone Capacity Evolution 
High Capacity WCDMA - Flow of users 
Ensuring high performance in high loaded HSPA NW 
Introduction to Service Differentiation and end-to-end QoS 
Uplink Features (

GSM RAN
Knowledge objective, the candidate should be able to identify and describe:
The fundamental technology and characteristics of GSM RAN, the products & solutions, functionalities and features. Channel structure, network architecture and interfaces, planning principles (capacity, limitations, interference reduction, robustness, spectrum load), signal measurements, radio units and their functionality, SW features such as: packet data support, EDGE, VAMOS, HD Voice, etc. Main advantages/values, as well as impacts on RAN performance.

GSM State of the Business 
Thin Layer GSM 
GSM RAN Key Business Areas – Introduction 
GSM KBA – Drive Cost Efficiency 
GSM KBA –  Increase Coverage and Capacity 
GSM KBA – Increase smart device Business, 
GSM Radio Access Network Overview 
GSM / WCDMA Basics 
GSM System Survey 
Monetize on Voice Efficiency: VAMOS 
GSM RAN SW Licensing 
GSM RAN BSC HW Activation Codes 
SON Based GSM Spectrum Management 
Energy Efficiency Features in GSM RAN 
RAN Modernization 


What is 5G ?

It is a mobile broadband system that will provide higher performance than is available today’s most advanced 4G networks.  These performance improvements will be measurable in terms of speed, latency, reliability, scale and openness.  The 5G system will achieve this higher performance by integrating many new devices over multiple wireless technologies with new management and orchestration systems.  A 5G system will include existing and new technologies such as: LTE, new radio technology, highly variable end devices especially for M2M, virtualized software and management and orchestration systems.  There will be a single global 5G standard to ensure global coverage.  It will be deployed in commercial service by 2020, but components may be ready earlier. 

The main focus is now on research where evolution of existing technologies is on-going in parallel with innovation of new technologies. A lot of research is done in cooperation with universities and partners. By join forces, we can together understand the new use cases and the new requirements that will be put on 5G.
Pre-standardization and technology development will be on-going until 2017. Standardization activities to set the requirements and make 5G a global standard starts at 2017. In parallel, trials and test systems will be up and running. First commercial system will most likely be deployed by 2020.


   Requirements on 5G
The exact performance levels and requirements that systems and equipment will need to meet to label themselves 5G are yet to be defined by the International Telecommunication Union (ITU). This will take place somewhere around 2016-2018.
At this stage, we are using expectations levels that where set in the METIS project*). These expectations are:

·         Handle 1000 times the mobile data traffic of today
·         Billions of connected devices
·         100 times user data rates
·         Latency reduced by up to a factor of 5
·         10 times the battery life
·         Different devices: from mobiles, tablets and wearables, to cars, trucks, bikes, cereal packets… anything
·         Data integrity 

Resignation Letter sample


Samaple -01

Dear Sir,
I submit this letter of resignation and will be leaving my position from XXXX( Engineer/manager) with Company name  effectively on DD-MM-YEAR.
It has been a pleasure working for Company name  . During this past tenure, work has been challenging and productive, and I have thoroughly enjoyed working in your team . Thank you for the opportunities for professional and personal development that you have provided me during the last **months.
Please accept my letter of resignation.

Sincerely,
Employee name
+Mobile number


SIGNAL ENCODING

We can represent bits as digital electrical signals in many ways. Data bits can be coded into following two types of codes :
(a)               Non Return to Zero (NRZ Codes).
(b)               Return to Zero (RZ Codes)

NRZ Codes
In this type of codes, the signal level remains constant during a bit duration. There are 3 types of NRZ codes.
NRZ-L Coding
Bit is represented as a voltage level which remains constant during the bit duration.
NRZ-M Coding
A transition in the beginning of a bit interval whenever there is a 'Mark.
NRZ-S Coding
A transition in the beginning of a bit interval whenever there is a 'Space'. Let us see the following bit stream 10100110 into three different types of NRZ codes 

RZ Codes:
Following are the RZ Codes
(a)        Manchester Coding
(b)        Biphase-M Coding
(c)         Biphase-S Coding
(d)        Differential Manchester Coding.
Manchester Coding
There '1' is represented as the clock pulse itself and '0' as inverted clock pulse. It is widely used in local area networks. Fig.21 shows representation of '1' and '0'.
Bi-phase M Coding


 
There is always a transition in the beginning of a bit interval and binary '1' is having additional transition in the middle of the bit interval.
Bi-phase S Coding
There is a transition at the beginning of a bit interval and binary '0' is having additional transition in the middle of the bit interval.
Differential Manchester Coding

There is always a transition in the middle of the bit interval and Binary '0' has additional transition in the beginning of the bit interval. Let us see Fig.22 in which bit sequence 10100110 has been shown in different RZ codes.