LTE fundamentals

The fundamentals of the LTE Radio interface and get an overview of the evolution of 4G telecommunication. This 19 minutes video is presented by Ericsson expert Sven-Anders Sturesson.

The tutorial gives an overview of the fundamental technology of Long Term Evolution (LTE). You will learn the basics of the LTE radio interface, including multiple input, multiple outputs (MIMO), OFDM, uplink and downlink, SIMO, TDD, FDD, channel coding and GSA.

 

http://www.ericsson.com/ourportfolio/ericsson-academy/online-tutorials/lte_fundamentals_module/player.html



Source: Ericsson

What is Citrix ?

Citrix facilitates real-time access to shared applications over networks and the Internet. Remote access to Citrix-enabled applications can be over DSL, T1, ISDN, or dial-up. Citrix MetaFrame enables multiple users to run shared applications simultaneously. Communication between Citrix clients and servers consists of exchange of user inputs (keyboard/mouse) and screen shots. Citrix MetaFrame runs on Windows NT 4.0 (Terminal Server Edition) and Windows 2000, with Terminal Services installed.

Citrix products include:

• Citrix Access Essentials
• Citrix Access Gateway
• Citrix Access Suite
• Citrix Application Gateway
• Citrix GoToAssist
• Citrix GoToMeeting
• Citrix GoToMyPC
• Citrix NetScaler
• Citrix Password Manager
• Citrix Presentation Server

For technical support and questions regarding Citrix MetaFrame, go to http://support.citrix.com

Multimedia Broadcast Multicast Service, MBMS

Multimedia Broadcast Multicast Service, MBMS

A new service introduced in 3GPP Release 6 specifications is Multimedia Broadcast Multicast Service (MBMS). There are two high level modes of operation in MBMS, as given

 

1.       Broadcast mode, which allows sending audio and video. The already existing Cell Broadcast Service (CBS) is intended for messaging only. The broadcast mode is expected to be a service without charging and there are no specific activation requirements for this mode.

2.        Multicast mode allows sending multimedia data for the end users that are part of a multicast subscription group. End users need to monitor service announcements regarding service availability, and then they can join the currently active service. From the network point of view, the same content can be provided in a point-to-point fashion if there are not enough users to justify the high power transmission. A typical example in 3GPP has been the sport results service where, for example, ice hockey results would be available as well as video clips of the key events in different games of the day. Charging is expected to be applied for the multicast mode.

 

From the radio point of view, MBMS is considered an application independent way to deliver the MBMS User Services, which are intended to deliver to multiple users simultaneously. The MBMS User Services can be classified into three groups as follows

1. Streaming services, where a basic example is audio and video stream;

2. File downloads services;

3. Carousel service, which can be considered as a combination of streaming and file download. In this kind of service, an end user may have an application which is provided data repetitively and updates are then broadcast when there are changes in the content.

 

For MBMS User Services, an operator controls the distribution of the data. Unlike CBS, the end user needs first to join the service and only users that have joined the service can see the content. The charging can then be based on the subscription or based on the keys which enable an end user to access the data. The MBMS content can be created by the operator itself or by a third party and, as such, all the details of what an MBMS service should look like will not be specified by 3GPP, but left for operators and service providers. One possible MBMS high level architecture is shown in Figure, where the IP multicast network refers here to any server providing MBMS content over the Internet.

 

 

 

 

 

Push-to-Talk over Cellular (PoC)

Push-to-talk over cellular (PoC) service is instant in the sense that the voice connection is established by simply pushing a single button and the receiving user hears the speech without even having to answer the call. While ordinary voice is bi-directional, the PoC service is a one directional service. The basic PoC application may hence be described as a walkie-talkie application over the packet switched domain of the cellular network. In addition to the basic voice communication functionality, the PoC application provides the end user with complementary features like, for example:

      ·         Ad hoc and predefined communication groups;

·         Access control so that a user may define who is allowed to make calls to him/her;

·         ‘Do-not-disturb’ in case immediate reception of audio is not desirable.

With ordinary voice calls a bi-directional communication channel is reserved between the end users throughout the duration of the call. In PoC, the channel is only set up to transfer a short speech burst from one to possibly multiple users. Once this speech burst has been transferred, the packet switched communication channel can be released. This difference is highlighted in Figure.

 

 

The speech packets are in the PoC solution carried from the sending mobile station to the server by the OPRS/UMTS network. The server then forwards the packets to the receiving mobile stations. In the case of a one-to-many connection, the server multiplies the packets to all the receiving mobile stations. This is illustrated in Figure  The PoC service is independent of the underlying radio access network.

 

 

 

SNG

HNG

Differences between WCDMA and Second Generation Air Interfaces

Main differences between the third and second generation air interfaces are described. GSM and IS-95 (the standard for cdmaOne systems) are the second generation air interfaces considered here. Other second generation air interfaces are PDC in Japan and US-TDMA mainly in the Americas; these are based on TDMA (time division multiple access) and have more similarities with GSM than with IS-95. The second generation systems were built mainly to provide speech services in macro cells. To understand the background to the differences between second and third generation systems, we need to look at the new requirements of the third generation systems which are listed below:

       ·         Bit rates up to 2 Mbps;

·         Variable bit rate to offer bandwidth on demand;

·         Multiplexing of services with different quality requirements on a single connection, e.g. speech, video and packet data;

·         Delay requirements from delay-sensitive real time traffic to flexible best-effort packet data;

·         Quality requirements from 10 % frame error rate to 10_6 bit error rate;

·         Co-existence of second and third generation systems and inter-system handovers for coverage enhancements and load balancing;

·         Support of asymmetric uplink and downlink traffic, e.g. web browsing causes more loading to downlink than to uplink;

·         High spectrum efficiency;

·         Co-existence of FDD and TDD modes.

GSM also covers services and core network aspects, and this GSM platform will be used together with the WCDMA air interface: see the next section regarding core networks.

 

 

 

 

 

 

What is Bluetooth ?

Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from 2400–2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Created by telecoms vendor Ericsson in 1994,[1] it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization.

To understand any kind of communication technology, you should be able to answer to several basic questions about it. In other words, if you can answer the following questions, I would say you already have some general understanding on it.

• Is it wired communication? or Wireless communication ?
• If it is wireless communication, what kind of wave length (frequency) range it uses ?
• What is the typical range of communication? (How far it can go) ?
• What is the typical data rate you can transmit and receive ?
• What is the typical connection topology ? (Is it one-to-one connection ? or one-to-many connection ? etc)

Can you find the answers to these questions from the wikipedia definition that I quoted above?

Let's tackle each of the questions one by one.

• Is it wired communication? or Wireless communication ? ==> It is 'wireless Communication'.
• If it is wireless communication, what kind of wave length (frequency) range it uses? ==> It is 2400~2800 Mhz frequency Range called ISM (Industrial Science Medical) band.
• What is the typical range of communication ? (How far it can go) ? ==> It is usually a couple meter range (The wikipedia definition does not explictely say about the range though)
• What is the typical data rate you can transmit and receive ? ==> At the beginning, it started with the max data rate of 1 Mbp and now mostly 2,3 Mbps (EDR). Recent specification defines the technology for even higher data rate.

• What is the typical connection topology ? (Is it one-to-one connection ? or one-to-many connection ? etc) ==> It support both one-to-one and one-to-many connection.

 Typical Bluetooth Application

Headset

Hands-free Automotive

Dial-up Networking

Ad-hoc File Transfer

PC-Peripherals,

Printing

Stereo Audio

Image

Home Automation

Music Player Synch

Video Transfer

Smart Remotes

Convert Latitude/Longitude to Decimal

Degrees, Minutes, Seconds to/from Decimal Degrees

The form below allows you to convert Latitude and Longitude information between decimal format and degree/minute/second (DMS) format. This is useful when finding distances. Here's the basic equation:

     Decimal Degrees = Degrees + minutes/60 + seconds/3600

Decimal Lat Long

Deg Min Sec Lat N S Long E W

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.