Karim Rabie No Comments

Mobile Broadband… You might have heard this term before, possibly in an ISP environment. The term has always represented a name of a department within a mobile operator or a vendor organization. It is always there in profile description for telecom professionals. It is everywhere actually when it comes to a certain ecosystem or framework that delivers Internet Service using Mobile Network.

Let me bring the Wikipedia definition followed with a small note …

Mobile broadband is the marketing term for wireless Internet access through a portable modem, mobile phone, USB wireless modem, tablet or other mobile devices.

Definition is true but the note here is that you can’t rely solely on google to understand the MBB related technologies (EDGE, UMTS, 4G/LTE, etc.) because what is in google is mainly the marketing articles and the vendor specific publications which is fine but as a lesson learned, one need always to understand the technology concept decoupled from vendors influence.

The good thing is that the whole knowledge, principles, & Service descriptions for Mobile Broadband is there in the standards. Mainly the 3GPP which is freely accessible. So I’d clearly say that the “debate” that it is hard to get the knowledge of the MBB is “debatable“!

http://www.3gpp.org/specifications/79-specification-numbering

3GPP_TM_RD

One just need to know how to get the information? Which 3GPP standard Specifications? Which 3GPP Release? Throughout this article, I am going to talk about the Mobile broadband evolution and the related standardization specifications which will enable the audience to see the big picture of the MBB and the plan is that by the end of the Five articles series, readers will be on the Mobile Broadband Track.

The Mobile Systems in general are classified into generations (2G, 3G, 4G, 5G) and for every generation, there are a set of standards specifications that describe the related service descriptions, interfaces, protocols, Call flows, etc.

1G

That was the first generation of Analogue Mobile systems firstly launched by NTT Docomo in 1979 and then that was followed by commercial deployments in the Nordics and the US in the early 1980’s.

It was more like Direct Dialling rather a network architecture controlled by the Operator. FDMA, Frequency Division Multiple Access technique was used by the Analogue Technology to serve Voice Calls.

No Data Service were offered by 1G.

2G

GSM (Global System for Mobile Communication) was a standard developed by ETSI, European Telecommunications Standards Institute to realize the 2G digital Cellular Network.

With the first Commercial deployment in Finland (Radiolinja) in July 1991. GSM had the target to deliver a Digital Circuit Switching network that is capable to deliver voice services.

One can conclude that the 2G GSM technology is a pure circuit switching network delivering voice service with no data service offered. This understanding will help us to understand the evolution of GPRS and Edge Technologies.

From the standardization perspective, the early GSM releases were called GSM Phase 1 & GSM Phase 2.

The logical architecture of 2G Network that was introduced by this release is shown below

Blank Flowchart - GSM Phase 1%2F2

The Yellow Highlighted Network Elements are representing the RAN (Radio Access Network) Domain and can be called BSS (Base Station Subsystem) in some other contexts while the green highlighted network elements are representing the CN (Core Network)

  • BTS: Base Transceiver Station
  • BSC: Base Station Controller
  • MSC: Mobile Switching Center
  • GMSC: Gateway MSC
  • ISC: International Switching Center
  • HLR: Home Location Register
  • VLR: Visited Location Register
  • EIR: Equipment Identity Register

The diagram is simple just to give an overview of the 2G architecture. The function for every Network Element will be illustrated in next articles.

The Catch here is that the early 2G didn’t provide a framework for Data Service and the network is solely serving CS Services. All Core Interfaces were based on Legacy SS7 interfaces. The term Circuit Switched was very dominant in a way there there were no IP Interfaces, No Data Services, and no Supporting handsets by that time.

Post releases are named GSM Phase 2+ (R96, R97, & R98).

Starting from GSM Phase 2+ (Release 96), There were some attempts to allow the network to deliver Data Services in addition to Voice.

The R96 specs are referring to 14.4 Kb/s User data based on High Speed Circuit Switched Data so still the enhancements were provided on Circuit Switched Network.

Release 97 brought some good news for Data Services where it introduced GPRS (General Packet Radio Services) on both Radio Part and Network Part and thus, the Network architecture has shifted to the below architecture to provide the PS Core Network (Packet Switched Core Network)

R97 Architecture - R97 Updated

  • SGSN: Serving GPRS Support Node
  • GGSN: Gateway GPRS Support Node

The two main network elements of PS Core Network (SGSN & GGSN) were introduced in 3GPP Release 97. The Protocol used between SGSN & GGSN over the Gn/Gp Interface is GTP, GPRS Tunneling Protocol (Over UDP/IP) and that was the first IP interface introduced by that time together with the Gi Interface which is a transparent IP interface to Internet.

GPRS typically reached speeds of 40Kbps in the downlink and 14Kbps in the uplink.

At this stage, technically and theoretically we are still at 2G but because of the introduction of the Data service and for an efficient marketing of the new service; vendors and Operators introduced a new Marketing term which is the 2.5 G.

So, here is a catch; The marketing term 2.5 G refers to R97 introduction of GPRS over the GSM network.

Screen Shot 2016-07-01 at 8.18.40 PM

Evolution continued on R98, and EDGE technology was introduced at the radio side achieving 384 Kbps data rate (almost 3G) but that was not accompanied with any change in the Core Network.

Again, the evolution was labeled 2.75G by industry operators so that’s another marketing term referring to EDGE technology.

You might have seen the letter “E” for Edge on your mobile phone while being covered by 2G coverage.

3G

The UMTS (Universal Mobile Telecommunications System) was introduced as part of 3GPP Release 99 together with EDGE enhancements. New Interfaces has been added and new Network Elements as well such as Node-B & RNC that resembles the BTS & BSC in 2G.

The logical architecture of 3G Network introduced by R99 release is shown below

R97 Architecture - R99

Theoretical rates refer to 2 Mbps for both Uplink and Downlink however, actual rates by that time were 384 Kbps.

The Network has become more ready to welcome the “All-IP” Interfaces that is introduced in the following release (Release 4). The concept of All IP Network has been introduced in 3GPP Release 4 where the SS7 legacy interfaces have been standardized for a Sigtran deployment (SS7 over IP).

3GPP Release 4 is a popular release for CS Core Network where the Split of Control Plane & User Plane was achieved by introducing the Media Gateway handling the UP and dedicate the MSC for handling the CP. There was no change in the PS Core Network architecture of R99.

In R5, The major enhancement was on the air interface introducing HSDPA (High Speed Downlink Packet Access) reaching theoretical rates of 14.4 Mbps and also this release has introduced the IMS (IP Multimedia System).

R6 added the HSUPA (High Speed Uplink Packet Access) evolution that achieves 5.76 Mbps on the Uplink.

Note : In Mobile Broadband, Downlink is the direction from Network to MS and Uplink is the direction from MS to Network.

R7 Introduced the evolved HSPA (HSPA+) with typical speeds of 42 Mbps. The 3GPP Release 7 is a well know release in the PS Core domain because it introduced a very well established and deployed Architectural feature which is the Direct Tunnel giving the option that user plane is established directly between RNC and GGSN bypassing SGSN.

Screen Shot 2016-07-02 at 1.29.22 AM

Same like Edge 2.75G, The HSPA technology has been marketed by some marketing terms such as 3.5G & 3.75G.

you should see the “3G”, “H”, or “H+” signs on your mobile according to the technology deployed by your carrier.

LTE (A step towards 4G)

3GPP Release 8 is one of the main Evolutionary stages when the 3GPP community decided to use IP (Internet Protocol) as the key protocol to transport all services.

A new Core Network Architecture was introduced as an evolution for the Packet switched Core in GPRS/UMTS under name EPC (Evolved Packet Core) with a direction to not have a circuit-switched domain in the sense that the new EPC would deliver both Data and Voice services.

In old release, the RAN needed to integrate to both CS & PS network where in LTE the eNodeB is only integrated to EPC. The logical architecture of LTE/EPC is shown below

Picture1

  • eNB: Evolved Node-B
  • MME: Mobility Management Entity
  • SGW: Serving Gateway
  • PGW: PDN Gateway
  • HSS: Home Subscriber Server
  • OCS: Online Charging System
  • PCRF: Policy and Charging Rules Function

That was the innovative LTE, Long Term Evolution that most of the operators of the world started to adopt with serious momentum towards 5G.

The diagram below shown the difference between the main Packet Core reference architecture (R6, R7, & R8)

Blank Flowchart - Releases (1)

Scandinavian TeliaSonera deployed the first commercial LTE Network in June 2009. Theoretical Data rates were 300 Mbps but never reached more than 100 – 150 Mbps at this pilot stage (2009 – 2010).

Here comes a well known confusion.. LTE is 4G or it is not? Does the evolutionary 3GGP R8 cover the 4G requirements?

The answer is always the same … search for marketing! LTE was introduced and marketed by the term 4G although in the reality, it is not. From the standards perspective the 4G requirements are covered by LTE Advanced which is standardized in 3GPP R10 but however introducing the new ecosystem under name “3G” would have been misinterpreted.

These 4G requirements are defined by ITU, International Telecommunications Union. Please have a look on the below link for more insights about the 4G (LTE-A) requirements.

http://www.etsi.org/deliver/etsi_tr/136900_136999/136913/08.00.01_60/

The confusion is still on going with LTE-Advanced being marketed as 4.5 G while it is 4G as per the standards evolution.

3GPP Release 8 provide a mean to have voice services over CS Network via CS Fallback as an alternative for Voice over LTE. That’s justified because the Voice over LTE solution was not mature enough by the time of R8 being released and operators were not ready to migrate all voice services from CS network to LTE/EPC Network.

Moving beyond R8, there is no big change in the Core Architecture. 3GPP R9 continued the enhancement of LTE radio side with some enhancement on the CSFB, & the Femto Cell.

3GPP R10 introduced the standardization of LTE-Advanced and is thought to be the standard 4G deployment.

3GPP R11 continued the enhancement of the radio Physical Layer, enhancements on the MTC, Machine Type Communications, Introduced the SaMOG enabling the integration between Trusted Non 3GPP Access (WiFi) to the EPC.

3GPP R12 and that’s the current “Frozen” release has made enhancements to the physical radio layer, Small Cells, & MIMO and Introduced the Device-to-Device proximity service.

3GPP R13 & R14 are still in “Open” state and some topics related to 5G are already discussed while the expected date for 3GPP 5G standardization release is June 2018.

There are a lot of details and bits & bytes that I’d like to discuss but I believe that this is sufficient for a first article in a 5 articles row. I hope that it gave an overview on the Mobile Broadband ecosystem and the corresponding standardization releases. I am going to build on that and start publishing a weekly article from the below List.

  • Article (2) – The Core Network Architecture (2G & 3G)
  • Article (3) – Mobile Broadband Essential Terms & Concepts
  • Article (4) – Getting the Service in 3G (under the hood)
  • Article (5) – Introduction to LTE

Thanks and waiting for your insights in the comment box below.

 
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