wireless


Jennie Learns

What is Wireless broadband?

Jennie: Dad, What is the meaning of wireless ?

Dad : Your cell phone is Wireless(CDMA or GSM). Your Cordless Mouse is Wireless(Bluetooth). Your laptop is connected to the AccessPoint by Wireless( WiFi). And, all of our offices in the city are interconnected by  wireless technique known as WiMAX.  All the above techniques use Radio Waves.

 

 

 

Jennie : What exactly is  the meaning of Broadband?

Dad : Meaning No.1 : BROADBAND is opposite of NARROW BAND. That means,  your Internet  connection can be called as broadband if its speed is high. The minimum speed to consider an Internet connetion as a broadband connection varies company to company. For example, my telecom company considers .......kbps as the minimum speed for a broadband connection.

Meaning No.2 : Broadband is opposite of DIALUP.  DIALUP users gets Internet only when they dial the ISP telephone numbers. But BROADBAND users will have PERMANENT  Internet connection. 

Meaning No. 3 : BROADBAND is opposite of BASEBAND. In BASEBAND,  signals are transmitted digitally,say +5v and -5V. But in BROADBAND, signals are transmitted anolog, say in  MHz.

So, if you combined all these three  meanings,  then BROADBAND is a HIGHSPEED PERMANENT Internet connection  mainly using  WIRELESS techniques.

Jennie: What do you mean by Radio waves?

Dad: Radio waves are Electromagnetic Waves.

Jennie: Dad, Sometime back, you told, Light is Electromagnetic waves.

Dad: Yes.

Jennie: And, when we went to hospital to take x-ray for my mum, you told, x-ray is Electromagnetic waves.

Dad: Yes.

Jennie: Then what is the difference between radio wave, light and  is x-ray?

Dad: Generally speaking,  waves that can transmiited using antenna (and received by tuners) can be called as Radio waves. Waves that are detected by our eyes are called as light . Technically speaking, 300MHz to 300GHz are  Radio waves. See the EM spectrum  given here. 

 

 

Jennie : You tell me some important points about  Bluetooth.

Dad :  1)  There was a king in Denmark around the year 950 whose name is Harald Bluetooth II.

               Don't think he has a blue color tooth. In Denish, blu means DARK SKIN and tan means GREATMAN.

          2) It uses Radio  Frequency of 2.4GHz ISM band

          3) It uses  Gaussian FSK Modulation technique ( in Version.1)

          4) It uses Fast Frequncy-Hopping Spread Spectrum (FastFHSS).

          5) The speed  of version.1 is  1 Mbps. Version 2 has more speed.

          6)  Effective distance is 10 meters.

          7) Data is transmitted in packets during time slots which are of fixed duration.

          8) Security :FHSS allows only the synchronized receivers to receive the data.

              In addition, it uses 128 bit encryption of data.

          9) Using Bluetooth,you can connect a computer to a Printer,Fax,Headset,Mobile phone,Camera,Mouse,etc.

         10. It is Personal Area Network(PAN).

         11) IEEE standard is 802.15

          Let us have a complete discussion on bluetooth  some ther day.

Jennie: What is Uplink and Downlink in wireless network?

Dad : Uplink is from Subscriber Station to Base Station. Downlink is, ofcourse, the reverse.

Jennie: Dad, can you tell something about WiMAX?

Dad : These are the important points you should remember about WiMAX:

1) WiMAX stands for  Worldwide Interoperability for Microwave Access.

2) It is basically a wireless Metropolitan Area network (Wireless MAN).

3. The transmission occurs between Base Station and Subscriber Station

4. The Subscriber Station  can be called as Receiver. The Receiver can be inbuilt in a laptop, It can be a small PCB that can be inserted in the mother of a PC. It is can be a small box.

5. Base station is just like any cellphone base station. One tower can cover upto 50 km.

6) The speed is 2 Mbps to 75 Mbps. Yeah. It is broadband.

6) About IEEE 802.16 :

  •    This is  for Fixed WiMAX
  •    Speed is 32 to 124 Mbps
  •    RF channel bandwidth is 20,25,28 MHz
  •    Cell radius is 1 to 3 miles
  •    Access techniques is   Request/Grant
  •    Modulation is Adaptive from 64QAM to QPSK 

7) IEEE 802.16e for Mobile

8) IEEE 802.16-2004 is for Portable

8) When higher frequencies are used (11 to 66 Ghz), you should use line of sight antennaes.

9) For 2 to 11 GHz you can use non-line-of-sight antennaes.

 

 

When you find time, go through these web pages :

1. What is WiMAX

2. A Powerpoint on Wimax