December 2010 - Telecommunications Blog

A blog for mobile communications systems GSM , UMTS and LTE

Recomended

Friday, December 31, 2010

Explaining HSDPA

12/31/2010 09:04:00 PM 1
Explaining HSDPA
     High-Speed Downlink Packet Access (HSDPA) is also known as High-Speed Downlink Protocol Access. HSDPA is a protocol for mobile telephones. It is a third-generation (3G) High-Speed Packet Access technology designed to speed up network capacity and data transmission rate of cellular phones.


HSDPA is associated with various Universal Mobile Telecommunications System (UMTS) networks. These include the Global System for Mobile (GSM) Communications.

     

An intro to GPS

12/31/2010 08:24:00 PM 0
An intro to GPS
First , What's the meaning of GPS ?
  It's meaning Global Positioning System .



    This system is based on a system of satellites ,Revolves around the Earth and works on solar energy and the spin rate of two complete cycles per day.The orbits are arranged so you can see 4 satellites in the sky at any time and from any point on Earth's surface.

     GPS receiver determine the location of these satellites and calculate the distance between them and the earth, and take advantage of these data to infer the site of the future and thus determine your coordinates on the surface of the earth. 

    

4G LTE Network Elements

12/31/2010 07:57:00 PM 3
4G LTE Network Elements
We will speak about the LTE Network Elements .
LTE network comprises of two main segments.
       1. LTE EUTRAN
       2. LTE Evolved Packet Core.


LTE EUTRAN: -


EUTRAN consists of eNB.

    EUTRAN is responsible for complete radio management in LTE. When UE comes up eNB is responsible for Radio Resource Management, i.e it shall do the radio bearer control, radio admission control, allocation of uplink and downlink to UE etc. When a packet from UE arrives to eNB, eNB shall compress the IP header and encrypt the data stream. It is also responsible for adding a GTP-U header to the payload and sending it to the SGW. Before the data is actually transmitted the control plane has to be established. eNB is responsible for choosing a MME using MME selection function.
    As the eNB is only entity on radio side, the whole QoS is taken care by it. It shall mark the packets in uplink, i.e Diffserv based on QCI, and also schedule the data.

    Other functionalities include scheduling and transmission of paging messages, broadcast messages, and bearer level rate enforcements based on UE-AMBR and MBR etc.



LTE Interfaces and Protocols

12/31/2010 07:46:00 PM 2
LTE Interfaces and Protocols
   The picture shows main network elements, interfaces and the protocols used in LTE.
The main interfaces in LTE are Uu, S1-MME, X2, S1-U, S11 and S5.

LTE Uu : -
    This is the air interface between UE and eNB. LTE layer 1 is dealt with later. RRC is the protocol that is used for communication between UE and eNB. Above RRC there is a NAS layer in UE. This NAS layer terminates at MME and eNB shall silently pass the NAS messages to MME.

LTE S1-MME: -

    eNB and MME communicate using this IP interface. S1-AP is application layer interface. The transport protocols used here is SCTP. (Stream control transmission protocol).


Evolution of the CDMA Standards

12/31/2010 07:29:00 PM 0
Evolution of the CDMA Standards
    The evolution process of the CDMA standards is roughly divided into the following stages :

   CdmaOne namely, IS-95A and IS-95B It mainly supports the voice service, belonging to 2G communications.

   cdma2000 1X: It can support both voice and data services. The max. Data rate can reach 153 kbps, belonging to 3G mobile communications.

   cdma2000 1xEV-DO: As the enhanced version of cdma2000 1X at stage 1, it supports data services, with max. forward rate being up to 2.4 Mbps.

   cdma2000 1xEV-DV: As the enhanced version of cdma2000 1X at stage 2, it supports both voice and data services, with max. data rate being up to 4 Mbps, and even higher.

   

Hello everybody

12/31/2010 02:32:00 PM 2
Hello everybody
Hello ,
My name is mahmoud . A communications engineer .I'd like to share all things that i know with you .This blog will discuss all things about Communications engineering and Communications networks as cellular ( GSM , UMTS and LTE ) and networks ( WiFi - WiMAX ).
I wish that i can help each one who needing help or searching for any information .
Thanks ,
Mahmoud