1. Capacity & Interference in 3G

2. © Tallal Elshabrawy 2 SINR in CDMA Systems: Base Station-to-Mobile (Forward Link) MT 1 MT 2 MT j MT K Single cell with K active Mobile Terminals d2d2 djdj dKdK d1d1 Effective SINR because of Codes Cross- Correlation (Pseudo-Random Codes) G is called the processing gain (T symbol /T chip ), reflects the decline in perceived interference due to spreading and de-spreading The term Noise reflects noise power in the spreaded bandwidth Effective SINR because of Codes Cross- Correlation (Orothgonal Codes)

3. © Tallal Elshabrawy 3 SINR in CDMA Systems: Mobile-to-Base Station (Reverse Link) MT 1 MT 2 MT j MT K Single cell with K active Mobile Terminals d2d2 djdj dKdK d1d1 Effective SINR because of Codes Cross- Correlation (Pseudo-Random Codes) G is called the processing gain (T symbol /T chip ), reflects the decline in perceived interference due to spreading and de-spreading The term Noise reflects noise power in the spreaded bandwidth Effective SINR because of Codes Cross- Correlation (Orothgonal Codes)

4. © Tallal Elshabrawy 4 The Near-Far Effect MT 1 MT 2 d1d1 d2d2 The Near-Far Effect SINR 2 | eff is much worse than SINR 1 | eff The strongest received mobile signal may capture the demodulator at the base station The Near-Far effect is the resultant of multiple users using the same transmit power level to communicate with the base station over the same frequency and in the same time within the same cell. Mobile-to-Base Station Communication (Uplink or Reverse Link)

5. © Tallal Elshabrawy 5 Strength-Based Power Control To address the Near-Far Effect Control the transmission power of each mobile terminal such that it is received at the base station at an equal level S Mobile-to-Base Station Communication (Uplink or Reverse Link) Strength-Based Power Control MT 1 MT 2 MT j MT K d2d2 djdj dKdK d1d1

6. © Tallal Elshabrawy 6 Capacity of CDMA Cellular Systems Assume interference from first tier (ring) of co-channel interferers X R D D D D D D D i : interfering distance from i th co-channel interference N B No. of co-channel interfering sites Assume Forward Link and Ignore Noise

7. © Tallal Elshabrawy 7 Diversity in 2G/3G CDMA Systems Multi-Path resistant RAKE Receiver can collect energy spread by the small-scale channel Suitable for bursty applications No need for frequency planning (frequency reuse of one) Soft blocking and soft handoff