Author Archives: Mohit Kumar

EPS – The Network Architecture

Posted on by
EPS_SAE_LTE_NETWORK_ARCHITECTURE_KUMARMOHIT.COM
EPS NETWORK ARCHITECTURE

Nodes Description

Evolved UTRAN

The evolved RAN for LTE consists of a single node, i.e., the eNodeB (eNB) that interfaces with the UE.  The eNB hosts the PHYsical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers that include the functionality of user-plane header-compression and encryption. It also offers Radio Resource Control (RRC) functionality corresponding to the control plane. It performs many functions including radio resource management, admission control, scheduling, enforcement of negotiated UL QoS, cell information broadcast, ciphering/deciphering of user and control plane data, and compression/decompression of DL/UL user plane packet headers.

 

Serving Gateway (SGW) The SGW routes and forwards user data packets, while also acting as the mobility anchor for the user plane during inter-eNB handovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and PDN GW). For idle state UEs, the SGW terminates the DL data path and triggers paging when DL data arrives for the UE. It manages and stores UE contexts, e.g. parameters of the IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception.

Mobility Management Entity (MME)

The MME is the key control-node for the LTE access-network. It is responsible for idle mode UE tracking and paging procedure including retransmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the SGW for a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN)
node relocation. It is responsible for authenticating the user (by interacting with the HSS). The Non-Access Stratum (NAS) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to UEs. It checks the authorization of the UE to camp on the service provider’s Public Land Mobile Network (PLMN) and enforces UE roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles the security key management. Lawful interception of signaling is also supported by the MME. The MME also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME from the SGSN. The MME also terminates the S6a interface towards the home HSS for roaming UEs.

Packet Data Network Gateway (PDN GW)
The PDN GW provides connectivity to the UE to external packet data networks by being the point of exit and entry of traffic for the UE. A UE may have simultaneous connectivity with more than one PDN GW for accessing multiple PDNs. The PDN GW performs policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screening. Another key role of the PDN GW is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA 1X and EvDO).

PCRF - Policy and Charging Rules Function

Policy and Charging Rules Function (PCRF) is the software node designated in real-time to determine policy rules in a multimedia network. This particular component of LTE is responsible for supporting the detection of service data flow, the charging system based on this data flow, and policy enforcement.Unlike earlier policy engines that were added on to an existing network to enforce policy, the PCRF is a software component that operates at the network core and accesses subscriber databases and other specialized functions, such as a charging system, in a centralized manner.Because it operates in real time, the PCRF has an increased strategic significance and broader potential role than traditional policy engines. This has led to a proliferation of PCRF products since 2008.

India and the Naxalites

Posted on by

I just watched this video and soon as I watched this I was compelled to write about it. Indians are very ignorant, and I am one of them. There is an ongoing battle between Indian Government and Naxalites that will play an important role in India’s future of integrity and development.

What I learnt after watching the video and reading fellow articles is summarized as follows.

There is a tremendous increase in millionaires in India in past decade. Is this because of the growth of Indian Inc? If that would be the case then the Indian middle class and lower class would be in quite better position. Most of these millionaires belong to the field involving natural resources like Real Estate, Minerals, Coal, Silver, Energy and rest are from service sector. How, these industrialists are able to tap such a huge amount of resources, which infact belong to the People of India and turn profit from it. Naxalism is the by -product of such practices only.

Naxalism

Naxalism is a wound in Indian State and will be effecting its integrity if not dealt properly.It is an immediate result of the Corruption and Ignorance of Indian Government , which prioritized profit of Private firms over the land and social respect of the native people. The problem could be resolved with much more mutual respect for each other. There is a foul smell of corruption in the allotment of the mineral-rich lands to the private organisations.

The term ‘Naxal’ derives from the name of the village Naxalbari in the state of West Bengal, India, where the movement had its origin. The Naxals are considered far-left radical communists, supportive of Maoist political sentiment and ideology. Their origin can be traced to the split in 1967 of the Communist Party of India (Marxist), leading to the formation of the Communist Party of India (Marxist–Leninist). Initially the movement had its centre in West Bengal. In later years, it spread into less developed areas of rural central and eastern India, such as Chhattisgarh, Orissa and Andhra Pradesh through the activities of underground groups like the Communist Party of India (Maoist).

For the past 10 years, it has grown mostly from displaced tribals and natives who are fighting against exploitation from major Indian corporations and local officials whom they believe to be corrupt.

Naxalism is an movement for a good cause, done wrong. It a lost cause now where the way of achieving thing has become much more important than the cause itself.

The Maoists’ fight with the Indian government began 50 years ago, just after India became independent. A loose collection of anti-government communist groups – that initially fought for land reform – they are said to be India’s biggest internal security threat. Over time, their focus has expanded to include more fundamental questions about how India is actually governed.

The uprising by Maoist fighters and its suppression by the Indian government, has claimed more than 10,000 lives since 1980, and displaced 12 million people. Many of the victims are not even associated with either side. They are simply caught in the crossfire. And the violence is escalating as both sides mount offensive after counter-offensive.
In this battle the looser are the people residing in that area who become the target of both the Indian Government and the Naxalites.

I am sharing this video, so that you can watch this as well.

5 most entertaining Flash Mobs

Posted on by

flash mob (or flashmob)is a group of people who assemble suddenly in a public place, perform an unusual and seemingly pointless act for a brief time, then quickly disperse, often for the purposes of entertainment, satire, and artistic expression. Let us see some of the most interesting and entertaining flash mobs from around the globe..BTW they are in a random order :P

1. On Nov.13 2010 unsuspecting shoppers got a big surprise while enjoying their lunch. Over 100 participants in this awesome Christmas Flash Mob

2.On August 4th, 2009, dozens of Bollywood dancers suddenly began to dance in the middle of Times Square to support Bollywood Hero, a 3 part mini-series on IFC

3.On 19 Dec, 30 everyday Kiwis melted into Britomart and Aoteo square in the form of Flash mob moving to the song ‘why this Kolaveri de?’ – With a large crowd of tourists watching on, the flash dance lasted around Five minutes – and then melted away again.

4.200 ordinary Mumbaikars (aged 4-60) come together one busy Sunday evening for pure joy. The historic CST station blares ‘Rang De Basanti’ on its speakers while surprised train commuters rush to see whats going on.

5.Birmingham Flash Mob’s Pillow Fight. Near the Bull Ring 12 February 2007

SC-FDMA -Single-carrier FDMA

Posted on by

Single-carrier FDMA (SC-FDMA) is a frequency-division multiple access scheme. It deals with the assignment of multiple users to a shared communication resource. SC-FDMA can be interpreted as a linearly precoded OFDMA scheme, in the sense that it has an additional DFT processing preceding the conventional OFDMA processing.SC-FDMA has drawn great attention as an attractive alternative to OFDMA, especially in the uplink communications where lower PAPR greatly benefits the mobile terminal in terms of transmit power efficiency and terminal costs.

Orthogonal Frequency-Division Multiple Access (OFDMA)

Posted on by

With Orthogonal Frequency-Division Multiple Access (OFDMA) muliple access is achieved by assigning subsets of sub-carriers to individual users. This allows simultaneous low data rate transmission from several users.OFDMA simultaneously supports multiple users by assigning them specific subchannels for intervals of time.So in short,

  • Each terminal occupies a subset of sub-carriers
  • Subset is called an OFDMA traffic channel
  • Each traffic channel is assigned exclusively to one user at any time
  • The IEEE 802.16e/ WiMax use OFDMA as Multiple access technique
  • OFDMA allows different users to transmit over different portions of the broadband spectrum (traffic channel)
  • Simpler Reciever – Only FFT processor is required
  • Bit Error Rate performance is better only in Fading environment

Orthogonal Frequency Division Multiplexing – OFDM

Posted on by

OFDM – Orthogonal Frequency Division Multiplex, the modulation concept being used for many wireless and radio communications radio applications from DAB, DVB, Wi-Fi and Mobile Video.OFDM is a special case of Frequency Division Multiplexing.Orthogonal frequency division multiplexing (OFDM) has been shown to be an effective technique to combat multipath fading in wireless communications.

Concept – Divide and Rule..

  • An OFDM signal consists of a number of closely spaced modulated carriers.
  • When modulation of any form – voice, data, etc. is applied to a carrier, then sidebands spread out either side.
  • It is necessary for a receiver to be able to receive the whole signal to be able to successfully demodulate the data.As a result when signals are transmitted close to one another they must be spaced so that the receiver can separate them using a filter and there must be a guard band between them. This is not the case with OFDM.
  • Although the sidebands from each carrier overlap, they can still be received without the interference that might be expected because they are orthogonal to each another.

Understand.. How it works?

The main concept is orthogonality. 

Area Under a sine wave is always 0
Area Under a sine wave is always 0

You would recall that the functions, sin(nx), cos(nx) : n = 1, 2, 3, … are orthogonal with respect to Riemann integration on the intervals [0, 2π], [-π, π], or any other closed interval of length 2π. This fact is a central one in Fourier series. Corresponding to it the area under a sine(or a cosine) wave will be always 0.

So by using the same concept we can transmit, using a single transmitter, a set of frequency multiplexed signals with the exact minimum frequency spacing, to make them orthogonal so that they do not interfere with each other.In OFDM, the subcarrier frequencies are chosen so that the subcarriers are orthogonal to each other, meaning that crosstalk between the subchannels is eliminated and intercarrier guard bands are not required. This greatly simplifies the design of both the transmitter and the receiver (No Filters and No Guard bands.. well theoretically ). Unlike in conventional FDM, a separate filter for each subchannel is not required.

Data in OFDM

  • The data to be transmitted on an OFDM signal is spread across the carriers of the signal, each carrier taking part of the payload. This reduces the data rate taken by each carrier.
  • The lower data rate has the advantage that interference from reflections is much less critical. This is achieved by adding a guard band time or guard interval into the system. This ensures that the data is only sampled when the signal is stable and no new delayed signals arrive that would alter the timing and phase of the signal.

 

The Home Subscriber Server (HSS)

Posted on by

The Home Subscriber Server, HSS is the master database for a given user. It is called Home, as this server contains all the information of the subscriber of that service area.It contains the subscription-related information to support the network entities actually handling calls/sessions.
A Home Network may contain one or several HSSs (depends on the number of Mobile subscriber, capacity and organisation of n/w)
The HSS is responsible for holding the following user related information:

  • User Identification, Numbering and addressing information;
  • User Security information: Network access control information for authentication and authorization;
  • User Location information at inter-system level: the HSS supports the user registration, and stores inter-system location information, etc.;
  • User profile information.

The HSS also generates User Security information for mutual authentication, communication integrity check and ciphering.

The HSS consists of the following functionalities:

  • IP multimedia functionality to provide support to control functions of the IM subsystem such as the CSCF (Call Session Control Function).
  • The subset of the HLR/AUC functionality required by the PS Domain (GPRS and EPC).
  • The subset of the HLR/AUC functionality required by the CS Domain, if it is desired to enable subscribe access to the CS Domain or to support roaming to legacy GSM/UMTS CS Domain networks.

MME Area

Posted on by

The MME area is the part of the network served by an MME. An MME area consists of one or several Tracking Areas. All cells served by an eNodeB are included in an MME Area. There is no one to one relationship between an MME Area and an MSC/VLR area. Multiple MMEs may have the same MME Area as described in clause “Pool-area”. MME Areas may overlap each other.

Tracking area – TA

Posted on by

A Tracking Area (TA) includes one or several E-UTRAN cells. The network allocates a list with one or more TAs to the UE . In certain operation modes, the UE may move freely in all TAs of the list without updating the MME.

Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)

Posted on by

Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)

So EUTRAN, as the name suggests is a type of Radio Access Technology ( A technology that allows you to access any network remotely,of course when you are authenticated.The word radio specifies the radio waves). It is evolved from its earlier work specification that was termed as 2G and 3G respectively.

LTE E-UTRAN architecture
LTE E-UTRAN architectureLTE E-UTRAN architecture

So we can say , It is a radio access network standard meant to be a replacement of the UMTS, HSDPA and HSUPA technologies specified in 3GPP releases 5 and beyond. Unlike HSPA, LTE’s E-UTRA is an entirely new air interface system, unrelated to and incompatible with W-CDMA.

The evolved RAN for LTE consists of a single node, i.e., the eNodeB (eNB) that interfaces with the UE.

Layers

The eNB hosts the

  • PHYsical (PHY),
  • Medium Access Control (MAC),
  • Radio Link Control (RLC), and
  • Packet Data Control Protocol (PDCP) layers

What does it do? – Functions

  • user-plane header-compression and encryption.
  • Radio Resource Control (RRC) functionality corresponding to the control plane.
  • radio resource management
  • admission control
  • scheduling
  • enforcement of negotiated UL QoS
  • cell information broadcast
  • ciphering/deciphering of user and control plane data
  • compression/decompression of DL/UL user plane packet headers.

Interfaces  –

  • The eNBs are interconnected with each other by means of the X2 interface.

  • The eNBs are connected by means of the S1 interface to the EPC (Evolved Packet Core).

  • The connection to the MME (Mobility Management Entity) is termed as S1-MME and
  • the connection to the Serving Gateway (S-GW) is termed as S1-U.

Protocols

The protocols used by the E-UTRAN are as follows.

User Plane

The user plane is the set of protocols that are utilized to transfer the user data from one interface to the another.The protocols utilized by the user plane are as follows which will be discussed in detail in the post.

PDCP,RLC,MAC,PHY

Control Plane

(RRC) protocol terminations towards the UE