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Wireless Communications


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Wireless Communications, Technologies and Standards

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Wireless Communications

  1. 1. Yasir Ahmed
  2. 2. <ul><ul><li>Technologies: are the techniques, algorithms and formulas e.g. modulation techniques, channel coding techniques. </li></ul></ul><ul><ul><li>Standards: allow the implementation and integration of the various technologies e.g. GSM standard. </li></ul></ul>
  4. 4. <ul><ul><li>Time Division Multiple Access is a technology that is used by the GSM standard. </li></ul></ul><ul><ul><li>It allows eight GSM users to use the same frequency. </li></ul></ul><ul><ul><li>Each user gets a 0.577msec time slot in a GSM frame. </li></ul></ul>1 2 3 4 5 6 7 8 0.577msec 4.616msec
  5. 5. <ul><ul><li>Code Division Multiple Access is both a technology and a standard. </li></ul></ul><ul><ul><li>CDMA technology is based on the principle of differentiating users based on their unique codes. </li></ul></ul><ul><ul><li>CDMA standards include CDMA2000, WCDMA, EVDO… </li></ul></ul>
  6. 6. <ul><ul><li>Orthogonal Frequency Division Multiplexing is a technique that allows a signal to be transmitted at multiple frequencies. </li></ul></ul><ul><ul><li>So if the signal at one frequency gets corrupted, it would still get transmitted. </li></ul></ul>f1 f2 f3 f4 f5 f6
  7. 7. <ul><ul><li>Multi-Input Multi-Output systems make use of multiple antennas at the transmitter and receiver. </li></ul></ul><ul><ul><li>Using two antennas instead of one (at either end) improves the performance by several dB. </li></ul></ul><ul><ul><li>It is easier to implement multiple antennas at the base-station then in all the mobile devices. </li></ul></ul>
  8. 8. <ul><ul><li>Wi-Fi is a standard that uses both CDMA and OFDM. </li></ul></ul><ul><ul><li>It is also known as IEEE802.11. </li></ul></ul><ul><ul><li>It operates in the unlicensed 2.4GHz band and allows data rates of up to 54Mbps. </li></ul></ul>
  9. 9. <ul><ul><li>Wi-Max is a standard that uses a variant of OFDM. </li></ul></ul><ul><ul><li>Wi-Max operates in the licensed bands. </li></ul></ul><ul><ul><li>It is also known as IEEE802.16. </li></ul></ul><ul><ul><li>It uses a scheduling algorithm to allow access to the users. </li></ul></ul>
  10. 10. CDMA TDMA GSM EVDO UMTS Wi-Max Wi-Fi IEEE802.11 OFDM GPRS IEEE802.16 MIMO Standards Technologies