CellularSystems

CellularSystems - 4. Cellular Systems: Multiple Access and...

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Unformatted text preview: 4. Cellular Systems: Multiple Access and Interference Management 1 4. Cellular Systems: Multiple Access and Interference Management Fundamentals of Wireless Communication, Tse&Viswanath 4. Cellular Systems: Multiple Access and Interference Management 2 Cellular Systems • So far we have focused on point-to-point communication. • In a cellular system, additional issues come into forefront: – Multiple access – Inter-cell interference management 4. Cellular Systems: Multiple Access and Interference Management 3 Some History • Cellular concept (Bell Labs, early 70’s) • AMPS (analog, early 80’s) • GSM (digital, narrowband, late 80’s) • IS-95 (digital, wideband, early 90’s) • 3G/4G systems 4. Cellular Systems: Multiple Access and Interference Management 4 Four Systems • Narrowband (GSM) • Wideband system: CDMA (IS-95) • Wideband system: OFDM (Flash OFDM) • Opportunistic Communication (1x EV-DO) (later) 4. Cellular Systems: Multiple Access and Interference Management 5 Narrowband (GSM) • The total bandwidth is divided into many narrowband channels. (200 kHz in GSM) • Users are given time slots in a narrowband channel (8 users) • Multiple access is orthogonal: users within the cell never interfere with each other. • Interference between users on the same channel in different cells is minimized by reusing the same channel only in cells far apart. • Users operate at high SINR regime • The price to pay is in reducing the overall available degrees of freedom. 4. Cellular Systems: Multiple Access and Interference Management 6 Frequency Reuse Frequency reuse is poor in narrowband systems because of lack of interference averaging. 4. Cellular Systems: Multiple Access and Interference Management 7 Wideband System: CDMA • Universal frequency reuse: all the users in all cells share the same bandwidth (1.25 MHz in IS-95 and 1x) • Main advantages: – Maximizes the degrees of freedom usage – Allows interference averaging across many users....
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This note was uploaded on 10/02/2011 for the course ECE 5670 taught by Professor Scaglione during the Spring '11 term at Cornell.

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CellularSystems - 4. Cellular Systems: Multiple Access and...

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