Friday, March 30, 2012

CDMA, HSDPA, UMTS, GSM, WCDMA, HSUPA

What HSDPA & HSUPA?




HSDPA vs HSUPA
HSPA (High Speed Packet Access), commonly referred to as 3.5G, is an upgrade to WCDMA networks that allows for much higher data speeds for internet connectivity. There are two aspects to this technology and each is more or less independent of the other. HSDPA (High Speed Downlink Packet Access) is the one that improves the downlink of the data transmission while HSUPA (High Speed Uplink Packet Access) is the one that improves the uplink or transmission from the mobile device to the network.
Common practices that would be affected by having HSDPA include watching online videos, browsing sites, downloading files, and a lot more. If you usually send emails with large attachments, upload files to sites, or seed files in a file sharing network, then HSUPA would improve the speed at which you do your tasks.

CDMA /WCDMA
CDMA (code-division multiple access) refers to any of several protocols used in so-called second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.

GSM
Radio spectrum is very limited, that�s why we have only 10-25MHz dedicated to wireless communication. Such narrow bandwidth allows 100-400 channels of reasonable quality, which is not rational and commercially not profitable to develop network for such small number of mobile subscribers. Genius idea lead to division of the whole geographical area to relatively small cells, and each cell may reuse the same frequencies by reducing power of transmission. Each cell has its own antenna (base station), and all base stations are interconnected using microwave or cable communication.



History 

Once upon a time there was analog cellular communication that didn�t support encryption, compression, and ISDN compatibility; in addition each country (company) developed its own system, which was incompatible with everyone else�s in equipment and operation.
So, in early 80s Europeans realized that pan-European public mobile system should be developed. The new system had to meet certain criteria:
  • Good subjective speech quality
  • Low terminal and service cost
  • International roaming
  • ISDN compatibility
  • Digital

GSM Network Architecture

UMTS

UMTS is one of the Third Generation (3G) mobile systems being developed within the ITU's IMT-2000 framework. It is a realisation of a new generation of broadband multi-media mobile telecommunications technology. The coverage area of service provision is to be world wide in the form of FLMTS (Future Land Mobile Telecommunications Services and now called IMT2000). The coverage will be provided by a combination of cell sizes ranging from 'in building' Pico Cells to Global Cells provided by satellite, giving service to the remote regions of the world. The UMTS is not a replacement of 2nd generation technologies (e.g. GSM, DCS1800, CDMA, DECT etc.), which will continue to evolve to their full potential.



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