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Thursday, July 11, 2013

What properties are common between WDMA and GSM channel access protocols?

About Wavelength Division Multiplexing Access(WDMA)
- Wavelength division multiplexing access or WDMA is a concept of fiber optics communications that is all about multiplexing the number of optical carrier signals in to one optical fiber. 
- This is done by using a number of different wavelengths or colors of the LASER lights. 
- This technique has made it possible to make bidirectional communications through one fiber strand and multiplication of capacity.
- The frequency division multiplexing is applied to radio carrier whereas this WDMA is used in the optical fibers. 
- An inverse relationship ties the frequency and wavelength together since the same concept is described by the two terms. 
- WDMA is classified under channel access methods and is based on wavelength division multiplexing. 
- A system using the WDM consists of a multiplexer at the transmitting end for joining the signals together. 
- Similarly, a de-multiplexer is installed at the receiver’s end.
- The de-multiplexer is used for splitting the joined signal apart.
- It is possible to make a device using the right kind of fiber that can do both multiplexing and de-multiplexing simultaneously as well as an optical add – drop multiplexer.

About Global System for Mobile Communications(GSM)
- Global system for mobile communications is an ETSI (European telecommunications standards institute) developed standard set for describing the protocols for 2G i.e., second generation mobile networks. 
- This standard set now rules the market with around 80 percent of the total market share. 
- GSM describes a digital network operating on circuit switching and that has been optimized for full duplex voice telephony. 
- GSM means a cellular network. 
- For connecting to this network, the cell phone searches for other cells in its surrounding. 
- GSM network offers 5 types of different cell sizes namely:
  1. Macro
  2. Micro
  3. Pico
  4. Femto
  5. Umbrella cells
- The extent of the area covered by each of the cells varies depending on the environment in which they are being implemented. 
- The base antenna is installed in the macro cells as a mast.
- In the micro cells, the height of the antenna is at the average level of the roof top. 
- Pico cells have a coverage diameter of only few meters.
- Femto cells find use in the small business and residential environments. 
- They are used for connecting to the ISP’s network. 
- Shadowed regions of the cells which are small are covered by the umbrella cells.

Common Properties and Differences between WDMS and GSM

Usually there are a number of differences between GSM and WDMA but they share some common properties also. 
- The base station of the GSM system and that of the WDMA both are connected to the core network of the GSM system in order to facilitate radio connectivity in the handsets. 
- Therefore, the same core network is shared by both the technologies. 
Principles of the cellular radio system form the basis for the two technologies. 
There exists a correspondence between the WDMA radio network controller i.e., RNC and the GSM base station controller or BSC. 
- The RBS (radio base station) of GSM system corresponds to the RBS of the WDMA. 
- The basis for developing the lu – interface of WDMA was provided by the A-interface of the GSM technology. 
- The only difference is of the new additional services that are offered by the WDMA. 
- GSM makes use of time division multiplexing along with the radio functionality for the management of the time slots. 
- On the other hand, WDMA makes use of the code division multiplexing for the same. 
- This implies that the control as well as the hardware functions of both are different

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