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. 

TRANSMISSION CODES in Telecom

All data communication codes are based on the binary system (1s and 0s). A message can be encoded into a meaningful string of 1s and 0s that can be transmitted along a data line and decoded by a receiver. The string of 1s and 0s is meaningful because it is defined by a code that is known to both the source and the receiver. Code is limited by the number of bits (binary digits) it contains, e.g. one-bit code means that we can have 2 characters so that we can encode the letter A by '0' and B by '1'. Similarly, a 2 bit code will enable us to handle 4 characters. Thus, a n-bit code enables us to handle 2ⁿ characters. 

Some commonly used codes are :

1.             Baudot code

2.             ASCII code

3.             BCDIC code

4.             EBCDIC Code

ASCII Code (American Standard Code for Information Interchange)

It is an eight-bit code which consists of seven information bits and one bit for parity checking. This is most widely used data code. Seven information bits gives us 128 combinations, which allows us to encode a full keyboard of the computer.

-          52 alphabets (capital and small).

-          0-9 (10 numbers).

-          Punctuation marks

-          Additional graphic and control characters.

BCDIC (Binary Code Decimal Interchange Code)

It is a six-bit code that is used as an internal code by some computers. With 6 information bits, we can have 2⁶ = 64 possible code combinations. For data transmission, code is implemented as 7-bit code containing 6 information bits and one parity bit.

EBCDIC (Extended Binary Coded Decimal Interchange Code)

It is a 8-bit code in which all the 8-bits are used for information (unlike ASCII), giving 256 possible code combinations. EBCDIC is used as an internal machine code in some of the computers. 

TEMS CELLPLANNER UNIVERSAL

TEMS CellPlanner Universal is Ericsson´s tool for mobile radio network planning. It is a highly graphical, easy-to-use, PC-based tool for design, realization, and optimization of mobile radio networks. TEMS CellPlanner Universal helps the user to roll out and expand mobile radio networks, and optimize radio network regarding service availability and service quality. It assists the user in a number of complex tasks, including network dimensioning, traffic planning, site configuration, and frequency planning. TEMS CellPlanner Universal is the key to successfully competing in the market place.

TEMS CellPlanner Universal provides support for WCDMA, GSM 850, GSM 900, GSM 1800, GSM 1900, iDEN, CDMA, CDMA2000 1xRTT, TDMA/AMPS, NMT 450, NMT 900, TACS, and E-TACS. TEMS CellPlanner Universal also provides support for GPRS and EGPRS (EDGE), implemented in GSM system

The modular platform makes it possible to customize TEMS CellPlanner Universal to meet the needs of every customer. TEMS CellPlanner Universal can be used in all phases of a radio networks life cycle, from early planning to the most complex optimization. The combination of the modular platform and a modern programming language also make it possible to add new functionality in a fast and easy way. In addition, open interfaces enable connection to external data sources for easy exchange of data.

TEMS CellPlanner Universal incorporates the following major features:

·         User-friendly, intuitive menu structure and guided work flows.

·         TEMS CellPlanner Universal uses an Ericsson-developed GIS Engine specially developed to fit the needs of a demanding RF planning tool. TEMS CellPlanner Universal can read several map data formats natively, and it also handles multiple resolutions.

·         Propagation prediction modeling and calculation of signal coverage and interference.

·         Allows real network deployment scenarios such as layered network architectures, distributed antennas, repeaters, and macro-/micro cells. It supports both Baseband and Synthesized Frequency hopping with MAIO management.

·         Efficient and sophisticated radio propagation in urban and rural environments including automatic model tuning

·         Direct import of TEMS™ logfiles to tune propagation models or analyze network performance

·         True Multi-technology support.

·         TEMS CellPlanner Universal 5.0 was designed to be a multi standard/multi-technology RF planning tool. All technologies can co-exist in the same session. Each technology follows the same flow, making it easier for the user to understand the tool.

·         Generic import interface

TRANSMISSION in telecommunication

For understanding the data communication following terminology is discussed: -

·         Communication lines

The medium that carries the message in a data communication system, example of  A 2W telephone line.

  Communication Channel

A channel is defined as a means of one way transmission.

It can carry information in either direction but in only one direction at a time, e.g. A hose pipe. It can carry water in either direction, but the direction of flow depends on which end of pipe is connected to the water tap.

 Simplex Transmission

1.     Message always flows in one direction only.

2.     An input Terminal can only receive and never transmit.

3.     An O/P Terminal can only transmit and never receive.

Half Duplex Transmission

-         A half duplex channel can transmit and receive but not simultaneously.

-         Transmission flow must halt each time and direction is to be reversed.

-         This halt is called the turn-around time and is typically 8 to 10 ms in the case of leased circuits and 50-500 ms in case of 2W telephone line through Public Switched Telephone Network (PSTN). 

Full-duplex Transmission

It is both way communications. If we set up a communication line with two channels, we have the capability of sending information in both directions at the same time. This is called full duplex transmission system. 

TYPES OF HDLC FRAMES

There are three types of HDLC frames :

·         Information transfer frame (I-Frame)

·         Supervisory frame (S-Frame)

·         Unnumbered frame (U-Frame)

Information Transfer Frame (I-FRAME)

I-Frame is used for transporting user data. It also carries acknowledgement of the received frames. The control field of the I-Frame is as shown in Fig.7. The first bit is 0 which identifies the frame as an I-Frame. The next three bits are the sequence number N(S) of the frame.

The fifth is Poll/Final (P/F) bit. Its use is explained later.

The last three bits are the sequence number N(R) of the acknowledgement (RR) which is piggy backed on the I-Frame. 

Supervisory frame (S-FRAME)

S-Frame does not have data field (Fig.3b) and is used to carry only acknowledgements, requests for retransmission, etc. It is identified by the first two bits of the control field (Fig. 8). These two bits are 10 in an S-Frame. The next two bits (SS) are used to indicate four supervisory states. Receive Ready (RR), Receive Not Ready (RNR), Reject (REJ) and Selective Reject (SREJ).

The fifth bit is Poll/Final bit. The last three bits are the sequence number associated with the supervisory states RR, RNR, REJ and SREJ indicated in the SS-Bits of the control field. Note that an acknowledgement (RR) can be sent either on a supervisory frame or piggybacked on an I-Frame as mentioned earlier. On the other hand RNR, REJ and SREJ are sent only through a supervisory frame.

Unnumbered Frame (U-Frame)

The U-Frames do not have data field as S-Frames. They are used for link establishment, termination, mode setting and other control functions. Controls field of an unnumbered frame is shown in Fig.9.

The first two bits of the control field are 11 which identify an unnumbered frame. The fifth bit is Poll/Final bit. The rest five bits are called modifier bits. They specify the control function. 

High Level Data Link Control (HDLC)

 HDLC was developed by ISO and has become the most widely accepted data link protocol. It offers a high level of flexibility, adaptability, reliability and efficiency of operation for today as well as tomorrow's synchronous data communication needs. ADCCP developed by ANSI is almost similar to HDLC, IBM'S SDLC is a proper subset of HDLC and level 2 of X-25 is a permissible option of HDLC.

In this chapter, we shall study the basic features and operation of HDLC protocol. Certain liberties have been taken in the level of completeness of description so as not to cloud the overall picture with the details.

GENERAL FEATURES of hdlc  

HDLC is a bit oriented data link control protocol which satisfies wide variety of data link control requirements including:

·         Point-to-point and point-to-multipoint links.

·         Two way simultaneous communication over full duplex circuits.

·         Two way alternate operation over half duplex or full duplex circuits.

·         Synchronous and asynchronous communication.

·         Communication between primary stations and between primary and secondary stations.

·         Full data transparency.

Types of Stations

To make HDLC protocol applicable in various possible network configurations, three types of stations have been defined.

·         Primary station

·         Secondary station

·         Combined station

Communication can be between a primary station and one or more secondary stations . The primary station has the responsibility of link management, i.e. activating and disconnecting the communication link. The secondary stations operate under the control of the primary station. The frames sent by a primary station are called commands and the frames sent by secondary station are called responses. as showing in fig.

A combined station can act as a primary as well as secondary station, i.e. it is capable of link management function, sending and receiving both commands and responses. Such a communication situation occurs when it is between two logical equal stations. 

ERROR DETECTION & COORECTION

ERROR DETECTION

When a code word is transmitted, one or more of its bits may be reversed due to signal impairment. The receiver can detect these errors if the received code word is not one of the valid code word of the code set. If the corrupted received word becomes another valid code word, the error cannot be detected.

When error occurs, the distance between the transmitted and received code words is equal to the number of erroneous bits . as showing in given below figure.

TRANSMITTED CODE WORD	RECEIVED CODE WORD	NUMBER OF ERRORS	DISTANCE
11001100	11001110	1	1
10010010	00011010	2	2
10101010	10100100	3	3

In other words the valid code words must be separated by a distance more than 1 else even a single bit error will generate another valid code word and the error will not be detected. The number of errors which can be detected depends on the distance between any two valid code words. For example, if the valid code words are separated by a distance 4, upto three errors in a code word can be detected. By adding certain number of redundant bits and properly choosing the algorithm for generating them, we ensure some minimum distance between any two valid code words and, therefore, the error detection capability.

ERROR CORRECTION

After an error is detected, there are two approaches to correction of errors :

·          Reverse Error Correction (REC).

·          Forward Error Correction (FFC).

In the first approach, the receiver requests for retransmission of the code word. In the second approach, the code set is so designed that it is possible for the receiver to not only detect but correct the errors also without requesting for retransmission. The receiver either locates the errors by analysing the received code word and reverses the erroneous bits. An alternative way is to search the most likely correct code word. When an error is detected, the distances of all the valid code words from the received invalid code word are measured. The nearest valid code word is the most likely correct version of the received word (Fig.3). If the minimum distance between valid code words is D, upto D/2-1 errors can be corrected. More than D/2-1 errors will cause the received code word to be nearer to the wrong valid code word.

TRANSMISSION ERRORS

Errors are introduced in the data bits during their transmission across a sub network. These errors can be categorised into :

·          Content errors

·          Flow integrity errors

Content errors are the errors in the content or a message, e.g. a "1" may be received as "0". This type of errors gets introduced due to impairment of the electrical signal in the transmission media.

Flow integrity errors refer to missing blocks of data. For example, a data block may be lost in the sub-network due to its having been delivered to a wrong destination.

In voice communication, the listener can tolerate a good deal of signal corruption during transmission. But data is very sensitive to errors. Measures are, therefore, built into a data communication system to counteract the effect of errors. These measures include:

·                     Introduction of additional check bits in the data bits to detect and correct content errors.

·                     Establishing procedures of data exchange which enable recovery of corrupted/lost messages.

BIT ERROR RATE (BER)

In analog transmission, signal quality is specified in terms of Signal to Noise ratio (S/N) which is usually expressed in decibels. In digital transmission, the quality of received digital signal is expressed in terms of Bit Error Rate (BER) which is number of errors in a fixed number of transmitted bits. A typical error rate on a high quality leased telephone line is as low as 1 error in 10⁶ bits or simply 1 x 10^-6.

OSI REFERENCE MODEL

The International Organization introduced the OSI layer for Standardization (ISO) in 1984 in order to provide a reference model to make sure products of different vendors would interoperate in networks. OSI is short for Open System Interconnection.

The OSI layer shows WHAT needs to be done to send data from an application on one computer, trough a network, to an application on another computer, not HOW it should be done.  A layer in the OSI model communicates with three other layers: the layer above it, the layer below it, and the same layer at its communication partner. Data transmitted between software programs passes all 7 OSI layers. The Application, Presentation and Session layers are also known as the Upper Layers.

The Data Link and Physical layers are often implemented together to define LAN and WAN specifications. 

Application Layer (Layer 7)

Application Layer provides network services directly to applications. Type of software programs vary a lot: from groupware and web browser to Tactical Ops (video game). Software programs itself are not part of the OSI model. It determines the identity and availability of communication partners, and determines if sufficient resources are available to start program-to-program communication. This layer is closest to the user. Gateways operate at this layer. Following are the examples of Application layer protocols:

i)                 Telnet

ii)               SMTP

iii)             FTP

iv)             SNMP

v)               NCP

vi)             SMB

Presentation Layer (Layer 6)

Presentation Layer defines coding and conversion functions. It ensures that information sent from the application layer of one system is readable by the application layer of another system. It includes common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes, common examples of these formats and schemes are:

i)          MPEG, QuickTime

ii)        ASCII, EBCDIC

iii)      GIF, TIFF, JPEG

Gateways operate at this layer. It transmits data to lower layers.

Session Layer (Layer 5)

The session layer establishes, manages, maintains and terminates communication channels between software programs on network nodes. It provides error reporting for the Application and Presentation layer. Examples of Session layer protocols are:

i)                 NFS

ii)               SQL

iii)             RPC

iv)             Zone Information Protocol (ZIP)

Gateways operate at this layer. It transmits data to lower layers.

Transport Layer (Layer 4)

The main purpose of this layers is making sure that the data is delivered error-free and in the correct sequence. It establishes, maintains and terminates virtual circuits. It provides error detection and recovery. It is concerned with reliable and unreliable transport. When using a connection-oriented, reliable transport protocol, such as TCP, acknowledgments is send back to the sender to confirm that the data has been received. It provides Flow Control and Windowing. It provides multiplexing; the support of different flows of data to different applications on the same host. Examples of Transport layer protocols are:

i)                 TCP (connection-oriented, reliable, provides guaranteed delivery.)

ii)               UDP (connectionless, unreliable, less overhead, reliability can be provided by the Application layer)

iii)             SPX

Gateways operate at this layer. It transmits data to lower layers.

Network Layer (Layer 3)

This layer defines logical addressing for nodes and networks/segments. It enables internetworking, passing data from one network to another. It defines the logical network layout so routers can determine how to forward packets trough an internet-work. Routing occurs at this layer, hence Routed and Routing protocols reside on this layer. Routed protocols are used to encapsulate data into packets. The header added by the Network layer contains a network address so it can be routed trough an internet-work. Examples of Network layer Routed protocols are:

i)        IP

ii)      IPX

iii)    AppleTalk

Routing protocols are used to create routing tables; routing tables are used to determine the best path / route. Routing protocols provide periodic communication between routers in an Internet work to maintain information on network links in a routing table. It transmits Packets. Routers operate at this layer. Examples of Network layer Routing protocols are:

i)                 OSPF

ii)               IGRP/EIGRP

iii)             RIP

iv)             BGP

v)               NLSP

Data Link Layer (Layer 2)

It defines psychical addressing, network topology, and is also concerned with error notification, sequencing of frames and flow control. Examples of network topologies are:

i)                 Star

ii)               Bus

iii)             Ring 

Physical Layer (Layer 1)

The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. It transmits and receives bits (bit stream) to transmission media. Physical layer specifications define characteristics such as:

• Voltage levels
• Timing of voltage changes
• Physical data rates
• Maximum transmission distances
• Physical connectors